The Counterintuitive Catabolic & Pro-Diabetic Effects of Leucine Supplementation in Rodents on Corticosteroids

Not the mice from this study, but still a nice example of the effects of dexamethasone on skeletal muscle (right; Quin. 2012)

"Leucine-laced water + stress = insulin resistance" - This simple equation is the net result of a recent study by Nelo Eidy Zanchi and his colleagues from the Laboratory of Applied Nutrition and Metabolism at the School of Physical Education and Sports of the University of Sao Paulo in Brazil. Inspired by previous research which clearly indicated that leucine does not only have pro-anabolic, but also insulin sensitizing effects, Zanchi et al. speculated that the provision of adequate amounts of leucine would blunt the catabolic and pro-diabetic effects of 7 days of intraperitoneally injections of  dexamethasone, an artificial corticosteroid that's used to treat all sorts of inflammatory diseases.

Remember SuppVersity Rule of Smart Supplementation No. 2? Right. Specificity!

In order to test their hypothesis that leucine supplementation either in low doses in the drinking water or as higher dosed oral gavage would ameliorate the negative side effects of DEXA treatment, the scientists randomized groups of 10 male Wistar rats to six groups receiving either low dose or high dose leucine supplements with and without dexmethasone.

"During  the duration of the experiment, which lasted  seven  days,  DEXA (a synthetic glucocorticoid analogue that does not bind to plasma binding proteins) was given daily (at 9:00 a.m.) through intraperitoneal injection (5 mg/kg/day); control groups received  an equivalent volume of saline (0.9% NaCl). As DEXA was reported to decrease food intake, all groups were  fed the same amount of food (in terms of caloric intake) equal to the DEX group. Thus, differences among groups did not originate from different food intakes. We measured the caloric content of our standard chow (16.32 kJ/g) as well as leucine (25 kJ/g) in a calorimetric bomb (FTT Oxygen Bomb Calorimeter) in  order to avoid differences in the caloric ingestion between experimental groups and observed that the total caloric consumption was not statistically different among groups." (Zanchi. 2012)

The leucine was administered either in dosages of 0.068g/kg body weight per day (low dose) or 1.35 g/kg per day (high-dose) twice daily at 8:00  a.m. and  2:00  p.m. through gavage over seven days. And while the scientists had selected the high dose (LH) "to induce a maximal increase in muscle protein synthesis and insulin plasmatic levels", the dosage in the LL (=low leucine) group was too low to increase either muscle protein synthesis or plasma insulin levels. The third, non-supplemented control group received an NaCl (sodium) placebo, the volume of which was identical to the supplement to make sure that any possible volume-induced effects of oral gavage that could for example be induced by gastric expansion would not skew the study results.

"But leucine has been shown to be anabolic! So it must help."

Aside from the usual basal fasting glucose, insulin, tryacilglycerol (TAG) and HOMA-IR values, the scientists did also assess the motor performance of the animals by the means of two standardized strength and ambulation tests (Kennel. 1996; Anderson. 2004; Viera. 2008).

Figure 1: Effect of 7 days of low (LL) and high (LH) dose leucine supplementation with and with out dexamethasone on total body mass, soleus (slow twitch) and EDL (fast twitch) muscle mass in male Wistar rats (left; values expressed relative to non-supplemented control) and corresponding changes in mean ambulation and grip strength (right; Zanchi. 2012)

As you can see in figure 1 the supplemental leucine failed to reduce the negative side effects of dexamethasone. As far as the total body weight and the fast-twitch muscle mass (EDL) are concerned, you could even argue that the high dose treatment (DEX-LH) did even amplify the catabolic effects of the synthetic corticosteroid:

"Thus, leucine supplementation at both low and high doses did not counteract body weight loss in both food restricted (control groups) and DEXA-treated animals. Soleus muscle mass did not differ among groups. Leucine supplementation at  high doses  attenuated food  restriction-induced EDL muscle loss (CON-LH group) when compared with the CON-NS group  (p < 0.05). All DEXA-treated animals presented reduced EDL muscle mass when compared with the CON-NS group (p < 0.05), and leucine supplementation at both low and high doses of amino acid did not attenuate it." (Zanchi. 2012)

Now, you may well argue that the mere fact that the muscle weight was "statistically significant" reduced, this does not mean that these reductions would be physiologically significant and that the minimal differences between the DEX groups would not matter, anyway. If you just go by the data on the left side of figure 1, this is certainly right, if you do yet also consider the significant reductions in muscle function (figure 1, right) and the fact that all that happened within no more than 7 days, the overall result should actually remind you of the "Three Simple Rules of Smart Supplementation" - and here specifically the 2nd one: Specificity!

Figure 2: Time course of the dexamethasone-induced detoriations in fed serum glucose levels and ameliorative effect of low and high dose leucine supplementation (left) and effects of the treatment on fasting insulin levels and HOMA-IR (index of insulin resistance) at the end of the study (Zanchi. 2012)

In fact, the data in figure 2 only confirms the notion that things that you cannot define "good and bad", "black and white" and "beneficial or detrimental" without a context and the outcome you are expecting. If you are trying to keep the postprandial blood sugar in check, for example he addition of an effective (high dose) of leucine to the diet would appear to be a good idea. If, on the other hand, you are more concerned about insulin resistance, you would be better advised to use minimal amounts of leucine or simply refrain from supplementation altogether.

Figure 3: If the ingestion of bolus amounts of leucine is not helpful, lacing the water of the rodents DEXA treated rodents with leucine turned them into full-blown diabetics (Zanchi. 2012)

As these results clearly demonstrate the provision of additional leucine is not useful to counter the negative side-effects of synthetic corticosteroids. On the contrary, the negative effects on insulin resistance are apparently even augmented and the muscle function is further compromised by the purpotedly anabolic high dose leucine supplement.

And while the overall effects of the bolus administration may still be negligible, the scientists ingenious idea that the provision of similar amounts of leucine in the drinking water in a second follow-up experiment turned out to be "capable of inducing a massive diabetic state" (Zanchi. 2012; see figure 3 for the ensuing surge in fasting blood glucose levels) while decreasing the mass of the fast-twich EDL muscles even further.

Bottom line: Overall these results only confirm the simple, but often neglected truth that inductive reasoning is a futile undertaking in the realms of exercise and nutrition sciences: What is good for an athlete is rarely optimal for an obese person, the same diet that helps the obese lose weight, will make the athlete feel miserable, and lacing the drinking water of rodents on corticosteroids with the exact same amount of leucine that has had highly beneficial effects on the insulin sensitivity of diabetic rodents in previous studies (Guo. 2010) will not only fail to ameliorate the glucocorticoid-induced detoriations in blood glucose, it will even exasperate them.

So, does that mean you should not take your whey protein or BCAAs any longer? No, if you did that you would make the exact same mistake as someone who laces his water with leucine in order to avoid the catabolic effects of the synthetic corticosteroid he is taking for medical reasons. On the other hand, the results of the study at hand should make you re-evaluate the necessity and even benefits of guzzling BCAAs all-day long, at least if the reason for doing so is that you believe that you are so stressed that you would otherwise fall into a catabolic black hole.

That said, there may even be implications for the average pre-diabetic inhabitant of the Western hemisphere who is eating his hamburger and French fries on the parking lot of the local fast food restaurant, because he cannot make room to prepare and consume a real meal somewhere in his busy and stressful schedule. I mean, despite the fact that the aforementioned specificity principle does not allow for anything but a still to be verified hypothesis, it does at least appear not to far-fetched that this chronic endogenous stress, despite being very different from the "stress" that's induced by the administration of a synthetic corticosteroid that does not bind to serum proteins, could have similar negative modulatory effects on the purported benefits of chronic leucine supplementation ... but as I've said before, this would be something to investigate in another study. So unless you are actually taking dexamethasone for medical reasons, you are probably not at risk of developing diabetes due to a high amount of leucine in your diet.

In the unfortunate case that you are actually on synthetic corticosteroids, a previous study by the same group of scientists, in the same rodent model does suggests that three workouts with three sets of squats (10 reps each) per week may offer the protection against corticosteroid induced muscle loss decreased skeletal muscle GLUT-4 expression and insulin resistance, leucine does not have to offer.... well, at least as long as you abstain from leucine supplementation, because the latter had the exact same detrimental effects in the 2011 study where it was administered to one of the experimental groups in conjunction with resistance training as it had in these more recent experiments in the absence of any type of workout (Nicastro. 2011). 

References:

• Anderson,  K.D.; Abdul, M.; Steward, O. Quantitative assessment of deficits and recovery of
  forelimb motor function after cervical spinal cord injury in mice.  Exp. Neurol.  2004,  190,
  184–191.
• Kennel,  P.F.; Fonteneau, P.; Martin, E.;  Schmidt,  J.M.; Azzouz, M.; Borg, J.; Guenet,  J.L.;
  Schmalbruch, H.; Warter, J.M.; Poindron, P. Electromyographical and motor performance studies
  in the pmn mouse model of neurodegenerative disease. Neurobiol. Dis. 1996, 3, 137–147.
• Nicastro H, Zanchi NE, da Luz CR, de Moraes WM, Ramona P, de Siqueira Filho MA, Chaves DF, Medeiros A, Brum PC, Dardevet D, Lancha AH Jr. Effects of leucine supplementation and resistance exercise on dexamethasone-induced muscle atrophy and insulin resistance in rats. Nutrition. 2012 Apr;28(4):465-71. Epub 2011 Nov 12.
• Qin J, Du R, Yang YQ, Zhang HQ, Li Q, Liu L, Guan H, Hou J, An XR. Dexamethasone-induced skeletal muscle atrophy was associated with upregulation of myostatin promoter activity. Res Vet Sci. 2012 Aug 29.
• Vieira, N.M.; Bueno,  C.R., Jr.; Brandalise, V.; Moraes,  L.V.; Zucconi, E.; Secco, M.; Suzuki, M.F.; Camargo, M.M.; Bartolini, P.; Brum, P.C.; Vainzof, M.; Zatz, M. SJL dystrophic mice express a significant amount of human muscle proteins following systemic delivery of human adipose-derived stromal cells without immunosuppression.  Stem Cells  2008,  26, 2391–2398.  
• Zanchi NE, Guimarães-Ferreira L, de Siqueira-Filho MA, Felitti V, Nicastro H, Bueno C, Jr, Lira FS, Naimo MA, Campos-Ferraz P, Nunes MT, Seelaender M, de Oliveira Carvalho CR, Blachier F, Lancha AH, Jr. Dose and Latency Effects of Leucine Supplementation in Modulating Glucose Homeostasis: Opposite Effects in Healthy and Glucocorticoid-Induced Insulin-Resistance States. Nutrients. 2012; 4(12):1851-1867.

Whey or Casein? Which Would be the Better "Staple" Protein Source for Your Trip to Desert Island?

Image 1: They are both sourced from cow's milk, but which is the better part? Whey, the byproduct of cheese production, or casein the cheese protein, itself? A recent study would suggest that it's the "waste product" you would have to chose if you could only have one.

"Whey is the way to go!" I suppose even I have had a headline like that in one or even several of the daily news items, here at the SuppVersity - and rightly, so! With it's high content of branched-chain amino acids (BCAAs) this fast-digesting protein source is certainly the #1 choice for anyone whose goal is to build lean muscle tissue. Whey's slow-digesting brother casein, on the other hand, is often hailed as the "muscle-preservative", the 24h-protein source that will prevent muscle catabolism, when for whatever outrageous reason (like sleep, for example) you cannot ingest your bi-hourly protein shake... well, I guess those of you who have been following the Intermittent Thoughts on Intermittent Fasting will already be "rolling on the floor laughing", but hey! Do we really know whether casein or whey would be the better "staple" protein - I mean, if you sipped it throughout the day?

Casein vs. whey - which one to chose if you cannot have both?

While I would not say that one study could provide a definite answer to this question, the results of a recently published paper by Stéphane Walrand et al. (Walrand. 2011) provides further evidence that whey, not casein would be your best choice - regardless of the diminished return that comes with sipping it.

Figure 1: Ingredients of the 6 diets the rats in the Walrand study were fed for 5 months; CAS = casein, WHEY = whey (data adapted from Walrand. 2011)

In their long-term (5 months!) feeding study, the scientists supplied 21 week old male Winstar rats (at the beginning of the study the animals were thus "middle-aged") with one out of 6 experimental diets (cf. figure 1). The composition of the diets differed not only in their total energy and protein content (ad libitum = 440kj/day; energy restricted only 60%, i.e. 264kj/day), but also with regard to the protein content and source (casein vs. whey). In that, it is particularly noteworthy is that the "energy restricted" diet was actually a "high protein" diet. After all, the protein content of the latter was identical to the one of the rats that had free access to  (the group that was "only" energy restricted received was matched to the average protein consumption of the ad-libitum fed rats.

Figure 2: Effect of 5 months of the experimental diets on muscle and fat weight of male Wistar rats (data adapted from Walrand. 2011)

Contrary, to what you may have expected, the "protein deficient" protein & energy restricted diet did yet not lead to profound losses of lean muscle tissue (cf. figure 2). On the contrary, the protein & energy restricted group that received whey protein as their exclusive protein source had 5% and 2% greater soleus and tibialis anterior mass than the ones that received the "high protein" energy restricted diet. Before you start questioning the value of "high" protein intakes when dieting, you should yet better take a look at the impact of the "high" protein content of the non-protein-restricted diet had on the diet induced reductions of the abdominal fat mass. I mean -87% reduced abdominal fat in the energy & protein reduced group is impressive, the neigh complete annihilation of the abdominal fat (-93%) in the non-protein restricted group, on the other hand, is mind-boggling.

Figure 3: Effect of 5 months of the experimental diets on muscle and fat weight of male Wistar rats (data adapted from Walrand. 2011)

If we also consider the nitrogen balance and the absolute rates of muscle protein synthesis (cf. figure 3), it also becomes evident why the rats on the protein & energy reduced diets retained slightly more lean mass (+3%), when they were fed whey protein, instead of casein. The rats who received whey as their main protein source simply had a favorable nitrogen balance and increased muscle protein synthesis.

Image 2: Sardines for diabetes prevention!?

Before you now throw away your eggs, your cheese, your beef and whatever else, I want to briefly introduce you to the results of two other recently published studies, which would indicate that rotating in some sardines or sheep meat could produce even more favorable results than living on whey alone. While Madani et al. found that sardine protein ameliorated fructose-induced hyperglycemia, insulin resistance, hyperlipidemia and inflammation (vs. casein) in a 2-months rodent study (Madani. 2011), Feng et al. report that the consumption of sheep meat instead of casein lead to increases in free T3 (thyroid hormone) and statistically significant increases in energy expenditure in Sprague-Dawley rats that were fed otherwise identical diets (Feng. 2011).

Despite these and the results of previous studies, most of which would suggest that if you had to chose just one protein source, whey or casein, whey should be the protein of choice, I hope that I do not have to tell you, as a diligent student of the SuppVersity that imbalances are the root cause of many, if not most modern diseases. So, getting all your protein from whey and nothing but whey should not be something you should even remotely take into consideration. And in case you forgot about that: Milk has both of them and a ton of other vital nutrients ;-)

Green Tea for Muscle Protection? GTE Increases Satellite Cell Proliferation & Differentiation, Slows Disuse-Related Atrophy, Does not Promote Hypertrophy in Aged Rodents

Green tea as a magical muscle preservative for injured athletes?

"GTE increased satellite cell proliferation and differentiation, decreased oxidative stress and the abundance of Bax, a proapoptotic protein" (Alway. 2014) - that's the initially exciting result of a recent study from the West Virginia University School of Medicine and Abbott Laboratories. What is not exactly as exciting, though, is how the sentence continues, i.e. "yet this did not further improve muscle recovery in reloaded muscles" (Alway. 2014).

Sounds contradictory, right? Well, before we get deeper into the discussion of the results, let's briefly recap how Alway et al. arrived at these insights, i.e. how exactly the experiment looked like and which experimental evidence it generated.

The scientists from the West Virginia University School of Medicine tested the hypothesis that green tea extract (GTE) would improve muscle recovery after reloading following disuse. In men and women "muscle disuse" would equal lying around in bed or on the sofa all day. In rodents it was simulated by an initial 14-day period of hindlimb suspension (HLS) and a subsequent period of reloading (recovery).

You can learn more about tea at the SuppVersity

Use Roiboos for Stress & Virus Control

Tired? Theacrine Will Get You Goin' in Minutes

Milk, Tea and Honey Don't Belong Together?!

Theacrine or Caffeine for Brain Power?

Aluminum, Lead & Arsenic & MORE in Your Tea

Will Drinking Tea Solve Your Sugar Problem?

The subjects the researchers use were Fischer 344 Brown Norway rats who were randomly assigned to receive either 14 days of hindlimb suspension (HLS) or 14 days of HLS, followed by normal ambulatory function for 14 days (recovery). Additional animals served as cage controls.

Figure 1: Muscle wet weight. Muscle wet weight was obtained in hindlimb muscles of cage control animals, after 14 days of hindlimb suspension group (HLS), or after 14 days of hindlimb suspension followed by 14 days of reloading (Recovery). And Ex vivo isometric force. A. Maximal tetanic force obtained at a frequency of 100Hz, or B. Peak twitch force (PT) of the plantaris muscle was measured in cage control rats, after 14 days of hindlimb suspension (HLS) or after 14 days of hindlimb suspension followed by 14 days of reloading (Recovery | Alway. 2014).

Both active treatment groups were given green tea extracts at a dosage of 50 mg/kg body weight - that's roughly 600-750mg of green tea extract per day. The control group received pure water, instead.
As you can see in Figure 1, the animals that received the green tea supplement exhibited a significantly attenuated loss of hindlimb plantaris muscle mass and tetanic force during.

In addition, compared to the vehicle treatment, GTE attenuated muscle fiber cross sectional area loss in both plantaris (-39.9% vs. -23.9%, p<0.05) and soleus (-37.2% vs. -17.6%) after HLS. This green tea-induced difference was not transient but it was maintained over the reloading period.

Increased muscle retention = increased fat loss!?

That's particularly interesting in view of the fact that the changes in body weight did not differ between the green tea and water group (see Figure 2).

Figure 3: Relative reductions in total body body weight in the two groups (Alway. 2014)

Why? Well it signifies that there is a significantly reduced negative impact on the body composition, with green tea. That does not change, though, that "GTE failed to further improve recovery of muscle function or mass as compared to vehicle treatment" (Alway. 2014)

This begs the question - would you recommend GTE? As a muscle preserver during periods, where you cannot workout, yes. The way it conserved the muscle mass in the study at hand should help help you to get back to the grind after a debilitating exercise, even if the recovery in the study at hand seemed to be identical in both groups. The green tea induced increase in satellite cell proliferation and differentiation, as well as the decreased oxidative stress and the abundance of the catabolic protien Bax, on the other hand, is probably not going to have a significant effect as long as you are still able to move, because exercise alone will induce more pronounced benefits in these domains.

Figure 4: Changes in body composition in a study w/ obese subjects comparing GTE to resistance training and a combination of both green tea extract and resistance training on body comp. (Cardoso. 2013)

Plus: We should not forget that the effects were observed in old rats and thus in a model of a population group that appears to benefit from antioxidant supplementation more than young(er) people. If you don't belong to the corresponding group of human beings whose muscles are particular prone to oxidative damage and suffer from a reduced ability to adapt to exercise induced stress, the effects remain questionable. In obese individuals green tea has yet been shown to promote the beneficial effects of exercie on body composition (Cardoso. 2013) - the risk that it a low dose of GTE does anything but good, does thus appear to be very small; and that's true for the benefits for athletes, too - at least according to previously reported results | Comment on Facebook!

References:

• Alway et al. "Green tea extract attenuates muscle loss and improves muscle function during disuse, but fails to improve muscle recovery following unloading in aged rats." Journal of Applied Physiology (2014). Ahead of print.
• Cardoso, Gabrielle Aparecida, et al. "The effects of green tea consumption and resistance training on body composition and resting metabolic rate in overweight or obese women." Journal of medicinal food 16.2 (2013): 120-127.

HMB Exhibits Differential Effects on ATP and Glycogen Content of Fast & Slow Twitch Fibers and Maximizes Tetanic Force Development in Rodent Study

Image 1: This is where HMB could actually make a difference, the two more reps, the one more sprint, which after weeks and months of training can decide over victory or defeat.

Sometimes, or I should say, time and again (!), it amazes me how the same people who are willing to invest hundreds of bucks in a supplement, which (according to the patent holder) "has been shown in scientitfic studies" (which were conducted by the researcher and a buddy of his at a remote lab, only to file the patent) to "increase testosterone by up to 147.34%", keep telling me that they "would never waste their hard earned money on supplements like HMB..." hello? Am I missing something, here? I mean, right; HMB does not produce the steroid-like effects the same sort of shady businessmen who are now promoting a new natural testosterone booster as legal alternative to Anavar on a monthly base once claimed it would have, but in all  honesty, the scientific research on HMB is by far more promising than the mostly non-existent research on 99% of the "legal anabolics" out there.

HMB works, we just don't know exactly how and for whom

As Dr. Connelly pointed out on the last BodyRX Show (highly recommended, especially for Layne's intellectual exchange with Dr. Jeff Volek), it stands out of question that HMB works. There are in fact more than a dozen of studies which show that supplementation with adequate amounts of this leucine metabolite has anti-catabolic effects in various conditions of skeletal muscle atrophy (Nissen. 2003; Smith. 2005). What  is still debatable, though is whether and to which extent athletes, in general, and bodybuilders, in particular can benefit from these effects. In view of the increasing awareness of the importance of leucine, the metabolic precursor of b-hydroxy-b-methylbutyrate (HMB), most athletes in this subgroup probably consume somwhere between 20-30g of leucine from the 300g of protein they are feeding themselves in the form of protein shakes and lean meats alone (with reference to the data that is presented in figure 1 it is noteworthy that the comparison Nissen made is not "fair", because the many of the HMB studies were conducted with "sick" people, while the majority of studies on protein supplements used either healthy people or athletes). With an average conversion rate of ~5% (of dietary leucine), we would have to estimate their daily HMB "production" to roughly 1.0-1.5g, which is interestingly at the lower range of what has been shown to ameliorate muscle wasting in cancer cachexia studies (Eley. 2007; Kovarik. 2010).

Figure 1: Calculated effect sizes of creatine, HMB, chromium, androstendione, DHEA and protein supplements on strength and lean mass gains (adapted from meta-review by Nissen et al.; Nissen. 2003)

And even if we discard the question of whether or not additional HMB is really necessary on a high protein diet and whether or not respective dietary differences could explain the negative results from some, yet by no means all, trials with professional athletes, we must still admit that even in those cases where it does work, we (i.e. scientists) do not really understand how HMB does its anti-proteolytic magic. The results of a recently published study from scientists from the Institute of Biomedical Science at the University of Sao Paulo, could thusly be of particular importance, as this is - at least to my mind - the first study to investigate the effects HMB supplementation had on ATP and glycogen levels, citrate synthase and changes in the contractive properties of individual muscle fibers (Pinheiro. 2011).

Figure 2: Changes (vs. placebo) in ATP and glycogen content, as well as citrate synthesis in red and white portion of rat gastrocnemius muscle after 4 week supplementation with 320mg/kg HMB (data adapted from Pinheiro. 2011)

The data in figure 2 shows, that after 4 weeks of daily supplementation with 320mg/kg HMB (in the study the usual calcium salt, you can buy in bulk on the Internet was used), the ATP and glycogen levels in the gastrocnemius muscle of the rats were profoundly elevated. In that, it is particularly interesting that the leucine metabolite had differential effects on the slow-twitch oxidative red portion of the muscle and the fast-twitch glycolytic white portion: In the slow twitch fibers the increase in ATP is 10x higher than it is in the fast twitch fibers, where the +400% increase in glycogen content should yet provide a similarly extensive buffer of readily (yet not immediately) available energy. Moreover, the increase in citrate synthesis (+67%) in the slow twitch fibers suggests that part of this effect was mediated by an "increased lipid availability due to increased lipolysis", or, put simply, by an increased oxidation of fatty acids to generate more ATP.

Figure 3: Tetanic force production (normalized to muscle weight) in rats receiving 320mg/kg HMB or placebo for 4-weeks; successive tetanic contractions were evoked at 100 Hz each 10 s of interval (data adapted from Pinheiro. 2011)

These increase in both readily available energy stores and the ability to replenish the former via fatty acid oxidation, is - according to Pinheiro et al. - also the underlying reason for the "increase in resistance to fatique" the scientists observed when they subjected the rat muscle to electrical stimulation in order to evaluate the tetanic (=constantly contracting) force production (cf. figure 3). Contrary to the twitch force, which was identical in supplemented and non-supplemented rats, the tetanic force production (normalized for either muscle weight or muscle cross-sectional area) increased by +17% (p<0.05; meaning that the chance that this was mere coincidence is <5%).

Fine!? Now, tell me: Is HMB worth it?

In view of the fact that neither the muscle size (cross-sectional area) nor the lean mass of the rodents in the HMB group differed from their placebo supplemented peers (btw. the animals were not "trained" in the course of the 4-week study), we must conclude that the effects of HMB, similar to those of creatine, are not what you would call "immediately anabolic". In a real world training scenario the metabolic advantage (increased ATP stores, increased glycogen stores and increased oxidative capacity) the rats in the HMB group gained over the 4-week study period, would allow trainees to do those 1-2 reps more which in weeks and months would then translate into this one additional pound of muscle or the 10th of a second that can make the difference between victory or defeat - whether those 1-2 reps are worth the roughly 64$ it would cost to copy the supplementation regimen used in the study (320mg/kg in rats would equate to 53mg/kg per day for humans), does yet depend on who you are, what you want to achieve and how much money you have to spend... and if you do not have your regular diet and training in check, don't even think of HMB (let alone one of those "test boosters" ;-)

Intermittent Thoughts on Intermittent Fasting - The Switch: Introducing the AMPK vs. mTOR Metabolic Seesaw

Figure 1: The mTOR - AMPK "cycle" can become a vicious one, as soon as its natural balance becomes disturbed by external, mostly nutritional and/or exercise related factors. Intermittent fasting could help you restore the balance.

Before we prematurely(?) break the fast and get to the nitty gritty of the feeding window, I want to briefly recapitulate the results of the last installment, which - as it will turn out - are of particular importance in view of today's discussion, as well. It were the thoughts on the health and possibly life-extending effects of intermittent fasting in the last installment of this series that brought up the involvement of 5'-adenosine monophospate (AMP)-activated protein kinase (AMPK) in both the weight, or we should say, fat loss and possible life-extending and anti-cancer effects of (intermittent) fasting. Now, before we even delve into a more detailed discussion of its relation to its "antagonist", the mammalian target of rapamyacin (mTOR), it would appear prudent to begin today's 6th installment of the Intermittent Thoughts on Intermittent Fasting series with a brief review of AMPK's effect(s) on protein synthesis, adipose tissue metabolism and apoptosis.

We already know that both fasting and exercise trigger increases in AMPK enzyme expression, which in and out of itself acts as an intracellular sensor that registers elevated AMP/adenosie tri-phospate (ATP) and inorganic phospate(Pi)/phosphocreatine (PCr) ratios - in short, it registers when you are running out of fuel. It is thus obvious that the main function of AMPK within muscle cells is to maintain energy stores at homeostatic levels. In order to achieve that, the 5’-adenosine monophosphate (AMP)-activated protein kinase enzyme upregulates catabolic processes and downregulates anabolic processes. The (entailing) overall effects the phosphorylation, i.e. the activation, of AMPK has on your metabolism are yet more complex than this dichotomous distinction would suggest - its tissue specific effects are illustrated in figure 2:

Figure 2: Downstream effects the "activation" of AMPK has on liver, muscle, and fat tissue.

In terms of the thought-after gain/retention of lean muscle mass, you must thusly consider AMPK as one of your worst enemies - an enemy which has conclusively been shown to respond to decreasing muscle glycogen content, both at rest and during exercise (Wojtaszewski. 2003) and inhibits overload-induced hypertrophy in fast-twitch muscle fibers.

Now, it would be paradigmatically short-sighted to draw the bro-scientific conclusion that you, as a physical culturist, should do everything in your power to avoid the phosphorylation of the 5’-adenosine monophosphate (AMP)-activated protein kinase enzyme to harness the power of permanent mTOR-activation. As mentioned in the last installment, AMPK and mTOR, i.e. the mammalian target or rapamycin, are antagonist - yet not in the sense of a switch with two mutually exclusive positions, but rather like two kids on a seesaw: where one can only go up, when the other is going down.

Proteine kinase seesawing for beginners

Image 1: Seesawing ain't working if you are trying to do it with someone who does not allow AMPK to come into it's own (img perceptasmile)

There is however more to this analogy than it may appear at first sight. If you think about your childhood, did you ever try to seesaw with an adult or another kid that was much heavier than you were? I assume if you have, you will remember that this was not very funny, because it constantly disrupted the natural (and fun) rythm of up and down... if you are asking yourself now, where this stupid physicist is heading with his seesaw example, think of your counterpart on the other side of the seesaw as being a sedentary, obese, carboholic diabetic who is constantly stuffing candy, chips, burgers and French fries down his pie-hole in a futile effort to satisfy his insatiable craving for a constant supply of readily available energy. This guy will be so heavy that seesawing is absolutely impossible. The rhythmicity of the game, is yet not the only thing that is disrupted, the natural and vital rythm of anabolic and catabolic or I should say production and recycling of your opponent is broken, as well.

With the constant abundance of readily available energy and, consequently, a low AMP:ATP (~used to usable energy source) ratio, the AMPK-related phosphorylation TSC2 and RAPTOR (cf. figure 5), which in turn would inhibit mTOR activity is absent. Now, what sounds as if it was taken right from a body builders well-spray-tanned dreams, is in fact as unhealthy as it is unnatural. Not only does it block all the beneficial effects of AMPK, i.e.

• increased glucose uptake in liver and muscle,
• increased fatty acid oxidation, 
• reduced glucose and fatty acid synthesis, and
• autophagy

the presence of which in figure 1 you may not even have noticed, when you heard the dreaded word "catabolic". Of these, the latter, i.e. autophagy, may have the least cosmetic value (and some of you may even not know what exactly it is) is of paramount importance for your health - after all, these cellular degradation processes allow your body to constantly rebuild itself, to sort out degenerate cells and make good use (recycle) what would otherwise pile up in form of messy metabolic junk or - even worse - uncontrollably proliferating tissue, i.e. cancer!

AMPK vs. mTOR in energy regulation, health and disease

The seesaw analogy should have made it quite clear that not mTOR or AMPK, but mTOR and AMPK and their interplay constitute the fundamental backbone of an energy sensing and growth regulating system, we have inherited from our earliest, eukaryote ancestors. And with many (if not all) of the major health problems of the Western society being related to a profound disturbance in energy regulation, it is by no means surprising that the chronic (over-)expression of the mTOR pathway (as exemplified by our overweight seesawer from image 1) that is so characteristic of our world of nutritional abundance has recently been implicated in all sorts of...

[...] disease states, where growth is deregulated and homeostasis is compromised, namely cancer, metabolic diseases and ageing (Zoncu. 2010).

Assuming that you have read all previous installments of this series, this should make you sit up: Cancer, metabolic disease (obesity, diabetes, hyperlipidemia,...), even aging (cf. figure 3)... in the past Intermittent Thoughts you have not only read about all of these, but you have also seen that intermittent fasting, in the form of either alternate-day-fasting, or Ramadan fasting was able to ameliorate or even partly reverse all these ailments of an obesity-stricken society, which is about to drown in fructose-corn-syrup and partially hydrogenated vegetable oils.

Figure 3: The contribution of a chronic overactivation of the mTOR pathway on aging
(based on a review of the literature by Zoncu. 2010)

The fast (regardless of whether its background is a religious one or not) breaks the vicious cycle of chronic mTOR (over-)expression and allows the body to start necessary and beneficial catabolic breakdown processes to rebuild, repair and recycle what got damaged and patched together raggedly in the course of the "anabolic" phase. Now, just as even someone with the repair-skills of Bob the Builder ("I can fix it!"), would obviously - at some point - be unable to make up for the wear and tear the furnishings in his house are exposed to, the well oiled cellular repair-machinery of our bodies will also hit a wall, when all the debris is cleared and the excess energy that had been stored away in times of nutritional abundance is either running short or cannot be accessed fast enough to satisfy acute energy demands (specifically of the brain). Yet, while the latter would obviously be much more likely, when after the "magical" ~16h, after which the glucose stores in our livers begin to dwindle (cf. Intermittent Thoughts - Myth 2), the undesirable result of the energy shortage, i.e. catabolism, would always be the same.

Image 2: Do you too have a question related to AMPK, mTOR or Intermittent Fasting, in general? Don't be shy and send it in! Questions, comments and suggestions for future installments of this series can be posted either at the Suppversity Facebook wall, via Twitter or right in the comment-area at the bottom of this page.

Does mTOR make you fat? It may be of interest to some of you (I know someone asked, but forgot who - shame on me) what the effect of the "anabolic" mTOR pathway on adipose, i.e. fat, tissue is. Well, if you look at the obese seesawer in image 1, the question appears unnecessary... if we delve a little deeper into the complicated interactions that are taking place here, we will yet notice that it ain't the mTOR signal per se that is fattening, but the way it sets the stage for increased adiposity by inhibiting the expression of adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) (Chakrabarti. 2010), so that stored triglycerides cannot be broken down and released into the blood stream to be subsequently burned as fuel, and, at the same time, by ramping up lipogenesis and thus increasing the lipid accumulation in white adipose tissue (and, in severe overfeeding scenarios, liver and muscle, as well). Without the presence of a chronical overabundance of energy and the consequent over-expression of mTOR in the presence of readily available substrates for fatty acid synthethase, fat storage would however not be a concern. Moreover, if the AMPK-mTOR cycle is intact, the excess energy that is not used for protein synthesis, but stored during the anabolic phase, will come handy to fuel the repair processes when (during a "fast") AMPK takes the reign.

A chronic overexpression of AMPK and consequent catabolism of metablically active tissue (muscle and organ tissue) is unquestionable as undesirable as the fattening, cancer-promoting and life-shortening effects of chronic activation of the mammalian target of rapamycin (mTOR).

Figure 4: Merely illustrative sketch of the interplay of mTOR and AMPK as a function of time [in h] with feeding / fasting periods at the indicated time points.

The sketchy graphical illustration (it should be obvious that neither the sinosodial nor the linear parts are based on actual observational data) of the interplay of AMPK and mTOR and their relation to feeding, and thus energy availability in figure 4 goes provides some clues about how the large fasting window, allows enough time for an acute, yet temporary energy shortage to occur in the course of the postprandial /-absorptive phase, where the constant influx of nutrients which keeps the anabolic mTOR pathway humming runs out and AMPK eventually takes charge, as its activation consequent to the rise in AMP:ATP ratio (=energy shortage) subsequently decativates the mTOR pathway via phosphorylation of tuberous sclerosis protein 1+2 (TSC1+TSC2, cf. figure 5) and their inhibiting effect on GTP-binding protein Rheb, which is the central governor in the regulation of growth and cell cycle progression.

Figure 5: Graphical illustration of the way growth factors, substrate availabilty (amino acids) and energy supply / shortage regulate cell growth and metabolism

The re-constructive yet eventually catabolic reign of AMPK, on the other hand, comes to an abrupt end, as soon as a nutrient-rich meal is ingested and the AMP:ATP ratio decreases. This process will obviously not be as linear as I sketched it in figure 4, but it does stand to reason that the length of the transitional period will be somewhat proportional to the speed at which the intracellular ATP levels are repleted. That being said, a tried and proven way to quickly replenish ATP stores is the ingestion of a relatively large bolus of high glycemic carbs.

Carbing up immediately post workout could help you to make the most of the feeding window

Against that background, even low-carbers may suddenly see some sense in adding a reasonable amount of simple sugar to their post-workout shake, especially if they position their feeding-window right after their training session at the gym (which would then obviously have been performed in the (semi-)fasted state). The fast acting carbohydrate would then not only replete the muscle glycogen stores, they would also allow the amino acids that come with both the post workout shake, as well as the subsequent whole-foods meal(s), and the training and nutritionally induced growth factors to do their anabolic magic by releasing the "catabolic AMPK-break" as fast as possible.

Image 3: To "carb up" after exercise simple dextrose is probably enough. It does not have to be the expensive Vitargo. And certainly not WaxyMaize, which has a profoundly reduced 4-hour glucose and insulin responses compared to maltodextrine / sucrose (Sands. 2009)

Carbohydrate timing: Did you know that a 1988 study by Ivy et al. found that there is a statistically highly significant difference in the rate of muscle glycogen storage depending on when you ingest the carbohydrates? In fact, the rate of glycogen storage was 45% slower if the carbs were ingested 2h after exercise (vs. immediately post) and the amount of glucose that was stored in the vastus lateralis muscle of the 12 healthy subjects after 70 minutes on a cycle ergometer at 65% of their individual VO2Max with two intermittent intervals at 88% of their VO2Max was ~25% greater, when the 2g/kg carbohydrate were consumed immediately post-workout. Overall, clear-cut evidence of the repartitioning effect of exercise that would support the well-known advice to "time your carbs around [for someone on an intermittent fast obviously after] workouts".

Now that we are finally approaching the enjoyable part of intermittent fasting, i.e. the feast after the fast, I got the strange feeling that it is time for me to break my own fast, since the increasingly low glucose levels in my liver appear to impact my ability to hear myself think and thus begin to compromise the quality of the Intermittent Thoughts I am committing to the blogger interface.

I would yet assume that you have ingested more than enough information on funky acronyms and modeled signaling pathways to stimulate the neuro-anabolic lEARNing pathway in your brain, so that the intellectual stimulus would ward off any non-beneficial catabolic effects of acute Intermittent Thought deprivation until the next installment will be available - this, I hope, will happen earlier than you may expect ;-)

Size Does Matter! Mucuna Counters Estrogenic Assaults & Doubles Testosterone. High Hair Cortisol, CVD & Diabetes. Catabolic Laziness. Health & Obesity = Incompatible

While it may be debatable, whether and in which contexts size really matters, 20% of the women in a Dutch study state that they length of the best part of their partner was "important" (Franken.. 2002)

While the debate whether or not "size matters" is probably never going to end, researchers from the Universidad Autónoma del Estado de Mexico have now found that your male offspring could "fall short" if they are exposed to phtalates during pregnancy. For their study, the scientists had collected urine samples of 174 mothers-to-be and analyzed them for phtalate residues. Bustamante-Montes et al. did then correlate the phtalate content of the urine of those mothers who gave birth to male newborns (N=73) to their sons' best parts and found that "prenatal exposure to mono-2-ethylhexyl phthalate exposure was associated with a reduced distance from the anus to anterior base of the penis (-0.2 mm/µg), reduced penile width (-0.04 mm/µg) and a reduced stretched penis length (-0.2 mm/µg).

Now this SuppVersity Figure of the Week certainly sounds pretty funny, but if we go by the maximal phtalate levels in the study at hand, the boys with the highest exposure had a 36% "disadvantage" compared to Joe... ah well, maybe rather Juan Average ;-)

Enough of the saucy science! Let's get to the "serious" stuff!

I have, just as about every week compiled a colorful potpourri of news, but contrary to the last weeks, I am trying to keep things short and simple. I mean "short news" should be short and not shortened versions of the full-articles you're served over the rest of the week, right?

• Will the correlation between heart disease and diabetes risk and cortisol in scalp hair also hold for you? While it seems unlikely that the figures would be identical you can bet that highly elevated hair cortisol and thus chronically elevated systemic cortisol levels are a significant risk factor for cardiovascular disease and diabetes irrespective of a person's age.
  Cortisol in scalp hair provide a pretty accurate image of heart disease and diabetes risk -- If you are trying to elucidate the diabetes risk of your grandma or grandpa a blood-draw may not even be necessary. According to the results of a soon-to-be-published study from the Netherlands, all you'd have to to is go to their bathroom and grab a hair from the brush or comb.
  
  If the cortisol level in the hair is high (>30.6 pg/mg hair), chances your grandparents' heart and pancreas are probably not in the best shape. With a +170% increased risk of cardiovascular disease and +220% increased risk to suffer from / develop type II diabetes, the correlations Manenschijn et al. observed underline the profound negative effects of chronically elevated cortisol levels (Manenschijn. 2013). 

• The anti-catabolic effects of laziness -- At least in the elderly it takes no more than 2 weeks of reduced physical activity to reduce the already inferior (compared to young individuals) rates of myofibrillar protein synthesis.
  
  

  

  Kaatsu may be beneficial for people who don't tolerate hard workouts (learn more), but in a TV chair, it won't work - regardless of your age!

  Leigh Breen and his colleagues from the McMaster University in Hamilton, Ontario (Canada) report in their latest paper that a 75% reduction in daily step count does not only hamper the postprandial insulin sensitivity (-43%) of healthy older adults (72±1 yr), it also increases the levels of TNF-α and CRP by ∼12 and 25%, the total amount of trunk fat by 7% and decreases the lean leg mass by ~4% and the postprandial muscle protein synthesis by a whopping 26% - somehow this reminds me of the good old saying "If you don't use it, you lose it!"

• Healthy but obese? Not really... it's just a question of time until the ugly blubber will make you sick -- You know that I could go off the deep end, whenever I see headlines like "being fat is healthy" or "being fat does not mean that you are sick". A recent paper by a group of Spanish researchers does now clearly indicate that media messages like these are downright dangerous (Soriguer. 2013).
  
  The analysis of data from the Pizarra Study a large scale epidemiological study involving 1051 individuals representative of general population were whose health and body composition was evaluated in ~5 year intervals clearly shows that being "healthy but obese" is just an intermediate state which is associated with a 720% increased risk of developing diabetes within the next 11 years. 

• Mucuna pruriens protects male fertility against estrogenic assaults & restores testosterone levels  -- I an interesting rodent experiment researchers from the Division of Endocrinology at the Council for Scientific and Industrial Research-Central Drug Research Institute were able to show that oral supplementation with 300 mg/kg mucuna pruriens or 20 mg/kg BW of l-dopa (Singh. 2013). With the latter being the equivalent of the l-dopa content of Indian mucuna pruriens it is particularly interesting to see that only mucuna, but not l-dopa went far beyond restoring the testosterone levels after 2 weeks on an endocrine disrupting dose of 3mg/kg ethinyl estradiol - it almost tripled them!
  

  

  Figure 1: Testosterone, FSH and LH levels 2 weeks, 4 weeks and 6 weeks into recovery; data expressed relative to non estradiol treated healthy control (Singh. 2013)

  According to the scientists the beneficial effects on sperm quality, LH, FSH and testosterone were brought about or at least accompanied by reductions in ROS level, the restoration of mitochondrial membrane potential, a normalization of apoptotic processes and overall increase in the number of germ cells.
  
  If we assume the effects translate to human beings, a daily dose of 3-4g of mucuna (while this is the HED of the dose used in the study, but probably you'd need lower doses - after all you don't take estrogen, do you?) could protect you against the constant assault of environmental estrogens and come particularly handy, when you "messed up" your endocrine system with other compounds ;-)

---

That's it for today! It's Saturday and time to celebrate that spring is finally there. So after you've checked out the latest SuppVersity Facebook News you better switch off the computer and enjoy whatever spring activities you like best... ;-)

References:

• Breen L, Stokes KA, Churchward-Venne TA, Moore DR, Baker SK, Smith K, Atherton PJ, Phillips SM. Two weeks of reduced activity decreases leg lean mass and induces 'anabolic resistance' of myofibrillar protein synthesis in healthy elderly. J Clin Endocrinol Metab. 2013 Apr 15. [Epub ahead of print]
• Francken AB, van de Wiel HB, van Driel MF, Weijmar Schultz WC. What importance do women attribute to the size of the penis? Eur Urol. 2002 Nov;42(5):426-31.
• Bustamante-Montes LP, Hernandez-Valero MA,  Flores-Pimentel D, Garcıa-Fabila M, Amaya-Chavez A, Barr DB, Borja-Aburto VH. Prenatal exposure to phthalates is associated with decreased anogenital distance and penile size in male newborns. Journal of Developmental Origins of Health and Disease. April 2013 [Epub ahead of print]
• Manenschijn L, Schaap L, van Schoor NM, van der Pas S, Peeters GM, Lips P, Koper JW, van Rossum EF. High Long-Term Cortisol Levels, Measured in Scalp Hair, Are Associated With a History of Cardiovascular Disease. J Clin Endocrinol Metab. 2013 Apr 17. [Epub ahead of print]
• Singh AP, Sarkar S, Tripathi M, Rajender S. Mucuna pruriens and its major constituent L-DOPA recover spermatogenic loss by combating ROS, loss of mitochondrial membrane potential and apoptosis. PLoS One. 2013;8(1):e54655. 
• Soriguer F, Gutiérrez-Repiso C, Rubio-Martín E, García-Fuentes E, Cruz Almaraz M, Colomo N, Esteva de Antonio I, Ruiz de Adana MS, Chaves FJ, Morcillo S, Valdés S, Rojo-Martínez G. Metabolically healthy but obese, a matter of time? Findings from the prospective Pizarra study. J Clin Endocrinol Metab. 2013 Apr 4. [Epub ahead of print]
   

Carnitine as Repartitioning Agent? IGF-1, p-AKT & mTOR Up, Catabolic Proteins Down + 7% Improvement in Lean- to Total Mass Ratio W/ HED of 1-1.5 of Carnitine/Day

It won't spare you the sweat, but carnitine could make it even more worthwhile by ramping up the anabolic and shutting down the catabolic signals.

Until 2006 l-carnitine has been known as a fat-burner, an in-effective fat-burner and an expensive and pretty useless supplement (depending on whom you were asking). Then, in July 2006, Kraemer et al. published a paper (a human study, above all!) in the journal Medicine & Science in Sports and Exercise a consequential paper so to say; a paper in which the authors report that l-carnitine l-tartrate supplementation at a dosage of 2.933g/day (this amount of LCLT contains 2g of pure carnitine) led to a statistically significant increase in androgen receptors in the vastus lateralis after a heavy resistance training protocol in previously strength trained male subjects (Kraemer. 2006).

Still, the evidence has always been inconclusive to say the least

Despite the fact that the concomitantly elevated post-workout luteinizing hormone levels (+19%) Kreamer et al. observed would tell you that the testosterone that would have been necessary to activate those receptors was already on its way, I have never considered this study as convincing evidence of the anabolic prowess of l-carnitine. Plus, let's be honest, differences in whatever serum markers in response to an acute bout of resistance training have failed us way too often, not to look at studies like these with appropriate skepticism.

Do you remember the Ratames study from 2005? The one that showed that high volume training lowers the no. of androgen receptors on the trained muscles? This certainly makes l-carnitine sound like the perfect addition to high volume routines, right? (learn more)

That the same principle of "calm down and don't get too excited over the results of a single trial" does all the more apply to rodent studies should be self-evident and still, science is all about taking each and every experimental result into account to form a theory that can explain all of them, or, alternatively, is able to bust short-comings in previous studies that don't comply with the predictions of the respective theory.

Now, the soon-to-be-published paper by Janine Keller and her colleagues from the University of Giessen (Germany) certainly qualifies as part of the evidence we simply cannot ignore, when we are looking for evidence in support of the theory that l-carnitine could be an overlooked muscle builder or repartitioning agent.

After all, their observation of decreased levels of the proteolytic (=catabolic) MuRF1 protein, as well as the ubiquitin-protein conjugates, which are increased in catabolic states such as starvation and atrophy denervation (cf. Wing. 1995) , alone, would signify that l-carnitine could make a valuable addition to everybody's supplementation regimen.

Lower catabolism + increased anabolism = ???

There is more, however, the addition of 1250 mg L-carnitine/kg to a basally "low carnitine" vegetarian diet also led to significant increases in systemic IGF-1 concentrations in plasma and a local increase in the activity of the PI3K/Akt/FoXO-1 signalling pathway (see figure 1)

Figure 1: IGF-1 mRNA and serum levels, as well as the muscle specific expression and phosphorylation (ph) Akt, mTOR & co after four weeks on the low or high carnitine diets (Keller. 2013)

These results do yet not stand in isolation as the ones by Kraemer et al. still do. Other recent studies by the same research group in Giessen, as well as colleagues from the University of Barcelona have already confirmed the anti-catabolic effects of l-carnitine in piglets and a cancer cachexia model in rodents, respectively (Keller. 2012; Busquets. 2012).

"And you are telling me that works in humans, as well? "

What's the best form of carnitine to take to elicit these effects: I knew you would ask this, so I react to two facebook questions by adding this red box willingly admitting that I just cannot tell you what the best form of carnitine is. There simply is no study that would compare e.g. acetyl-l-carnitine (ALCAR) and l-carnitine l-tartrate (LCLT) in a scenario that would be relevant to the above question. What I can tell you though, is that it appears as if you were better off with LCLT than with ALCAR, if your goal is to top off your intra-muscular carnitine levels. That being said, even normal creatine can do that - you will just have to take more of it. If you are looking for more information you can check out the part of the Amino Acids for Super Humans Series that's dealing with "the carnitines", here.

In this context it does yet also have to be mentioned that the effects of l-carnitine are at least in part species specific. How we know that? Well, in contrast to the said study by Basquets et al. the provision of an carnitine to piglets (Keller. 2012) did not only reduce the MuRF-1 expression, but also the level of its likewise catabolic E3 ligase cousin atrogin-1.

"It has been shown that myofibrillar proteins, like myosin light chain proteins are the main targets of MuRF1for ubiquitination. Thus, carnitine might suppress particularly the degradation of myofibrillar proteins, which under physiological conditions comprise around 60% of total muscle proteins. In contrast to MuRF1, atrogin-1 tags primarily proteins for degradation which are important for controlling protein synthesis and myoblast differentiation, like myogenic factor MyoD, myogenin and the eukaryotic initiation factor of protein synthesis eIF3-f." (Keller. 2013)

With pigs usually being a superior model of the human physiology, this would suggest that the anti-catabolic effects l-carnitine could have on humans are probably more, not less pronounced than those that were observed in previous rodent studies.

Whether the same goes for the IGF-1 response cannot be said, but just like the anticatabolic effects, the pro-anabolic increase in IGF-1 has been observed in previous trials, including a human trial by Di Marzio et al. who observed a significant increase in IGF-1 in HIV patients in response to the provision of 3g/day of acetyl-l-carnitine (Di Marzio. 1999). In the absence of the existing evidence from animal studies, these results would yet have little significance for healthy human beings, whose growth hormone and IGF-1 levels are not rock bottom to begin with (Viganò. 2003).

---

Bottom line: Irrespective of the absence of human data on the IGF-1 boosting effects from non-HIV patients - or even better in training scenarios - it would warrant future studies if an adequate amount of carnitine in the diet can exert beneficial effects in non-obese human beings. For the "sedentary", or let's rather say non-exercised rodents in the study at hand, the latter was a mere fat loss effect - despite the elevations in p-AKT, m-TOR, IGF-1 and the overall more "anabolic" state the rodents were in their lean body mass was not increased compared to their peers on the low carnitine diet.

"Just another set!" ... "I don't know man, we've already pumped away 100,000kg today... do you really believe that's productive, I mean, yeah, we are cuttin', but still" ...learn what this dialog is all about and whether and if / when "another set" is / isn't a good idea (read more)

The lean-to-total mass ratio of the rodents, on the other hand was ~7% higher in the rodents in the high carnitine group. If we do however take into consideration that most of you will not be vegetarians and thus not similarly carnitine deprived as the rodents in the control group on the <1mg/kg carnitine diets, it is highly questionable if the addition of the human equivalent of the 1.25g/kg chow, i.e. 15mg/kg body weight (HED) would actually yield any measurable benefit to non-vegetarians - irrespective of whether they train or not. After all, even the average omnivore human being consumes 100-300mg of carnitine per day (Broquist. 1994), so that the difference between your basal carnitine intake and the supplemental equivalent dose of 1050-1500mg/day is more than 100x lower than the exorbitant difference between the low (if not deficient) carnitine diet in Keller's rodent study at hand (remember: the basal diet had less than 1mg/kg chow; the supplemented diet hat 1250mg/kg diet!).

So what's the verdict then? I guess, I will leave the final words to Burke et al. who reviewed the usefulness of carnitine as an ergogenic aid in one of the first installments of the "A-Z Supplement Review" in the British Journal of Sports Medicine and wrote "future work with l-carnitine may also find some useful outcomes" (Burke. 2009) - needless, to say that the SuppVersity is going to be the place, where you will read about it first ;-)


References:

• Broquist HP. Carnitine. In Shils ME, Olson JA, Shike M (eds): "Modern Nutrition in Health and Disease." Malvern, PA: Lea & Febiger, 1994. 459– 465.
• Burke LM, Castell LM, Stear SJ, Rogers PJ, Blomstrand E, Gurr S, Mitchell N, Stephens FB, Greenhaff PL. BJSM reviews: A-Z of nutritional supplements: dietary supplements, sports nutrition foods and ergogenic aids for health and performance Part 4. Br J Sports Med. 2009 Dec;43(14):1088-90.
• Busquets S, Serpe R, Toledo M, Betancourt A, Marmonti E, Orpí M, Pin F, Capdevila E, Madeddu C, López-Soriano FJ, Mantovani G, Macciò A, Argilés JM:  l-Carnitine: An adequate supplement for a multi-targeted anti-wasting therapy in cancer.  Clin Nutr. 2012;31:889–895.
• Di Marzio L, Moretti S, D'Alò S, Zazzeroni F, Marcellini S, Smacchia C, Alesse E, Cifone MG, De Simone C. Acetyl-L-carnitine administration increases insulin-like growth factor 1 levels in asymptomatic HIV-1-infected subjects: correlation with its suppressive effect on lymphocyte apoptosis and ceramide generation. Clin Immunol. 1999 Jul;92(1):103-10.
• Glass DJ:  Signalling pathways that mediate skeletal muscle hypertrophy and atrophy. Nat Cell Biol. 2003; 5:87–90 .
• Kraemer WJ, Spiering BA, Volek JS, Ratamess NA, Sharman MJ, Rubin MR, French DN, Silvestre R, Hatfield DL, Van Heest JL, Vingren JL, Judelson DA, Deschenes MR, Maresh CM. Androgenic responses to resistance exercise: effects of feeding and L-carnitine. Med Sci Sports Exerc. 2006 Jul;38(7):1288-96.
• Keller J, Ringseis R, Koc A, Lukas I, Kluge H, Eder K:  Supplementation with l-carnitine downregulates genes of the ubiquitin proteasome system in the skeletal muscle and liver of piglets. Animal. 2012;6:70–78.  
• Keller J, Couturie A, Haferkamp M, Most E, Eder K. Supplementation of carnitine leads to an activation of the IGF-1/PI3K/Akt signalling pathway and down regulates the E3 ligase MuRF1 in skeletal muscle of rats. Nutrition & Metabolism. 2013; 10:28. 
• Lösel D, Rehfeldt C. Effects of l-carnitine supplementation to suckling piglets on carcass and meat quality at market age. Animal. 2013 Mar 11:1-8.
• Salama AF, Kasem SM, Tousson E, Elsisy MK. Protective role of L-carnitine and vitamin E on the testis of atherosclerotic rats. Toxicol Ind Health. 2013 Feb 13.
• Viganò A, Mora S, Brambilla P, Schneider L, Merlo M, Monti LD, Manzoni P. Impaired growth hormone secretion correlates with visceral adiposity in highly active antiretroviral treated HIV-infected adolescents. AIDS. 2003 Jul 4;17(10):1435-41.
• Wing SS, Haas AL, Goldberg AL. Increase in ubiquitin-protein conjugates concomitant with the increase in proteolysis in rat skeletal muscle during starvation and atrophy denervation. Biochem J. 1995 May 1;307 ( Pt 3):639-45.