Research Update #1

by Hypertrophy

As we approach the new millennium we find the science of building muscle progressing faster than ever before. Long gone are the days of simple trial and error when it comes to building muscle. The modern bodybuilder demands more than just "hear say" if they are to adopt a new training routine or nutritional supplement. This column was created to keep today’s bodybuilder on the cutting edge of scientific research that might benefit them in their quest for body perfection.

Title: Skeletal Muscle Injury Repair and Regeneration Enhanced by Muscle Mitogen.

Researchers: M. Li, JX Li, S. Lee, R. Xie, and KM Chan, from the Department of Orthopedics & Traumatology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong.

Source: Med Sci Sport Exer. 1998 May;30(5) Supplement; S1-S1339

Summary: Previous studies suggested that muscle injuries lead to the formation of wound fluid that can stimulate satellite cell proliferation in cell culture. The present studies focused on the identification of the functional role of the "muscle extract" in muscle injury repair and regeneration in vivo. Two groups of rats were subject to excessive exercise-induced muscle injury, and strain-induced massive muscle injury respectively. Muscle extracts were prepared from the red and white muscle tissue of young rats respectively. Three rats of the first group (exercised group) were injected beneath the epidermis of tibialis anterior muscle with 1 mg muscle extract in one leg an hour after exercise. The remaining 3 rats of the first group were injected with an equal amount of bovine serum albumin (BSA) in PBS as control. The injection were repeated daily for 4 days. After two injections, bromodeoxyuridine (BrdU)(3mg/100g body wt.) were injected along with the third and fourth injections of the extract or control solution respectively. [BrdU is used as a marker of cell proliferation.] The treatment for the "strain" group of rats followed the exercised group’s treatment exactly. Rats of the two groups were sacrificed 3 days after the last injection of the muscle extract or control solution. After sacrifice, the tibialis anterior muscle was removed and homogenized for measurement of DNA. For histological examination, the sample of tibialis anterior was processed for paraffin embedding, then proceeded with immunohistochemical staining, and microscope examination. The results were significant, in that the focal muscle injuries induced by excessive exercise were undergoing better focal repair, with increased-number of myonuclei per fiber after injection of muscle extract compared with that in control injected with same amount of BSA. The result derived from strain-induced model was even more significant, in that massive muscle regeneration was observed with little focal fibrosis after injection of muscle extract, in contrast, massive fibrosis was the main feature with little muscle regeneration in control. Present evidences showed that muscle fibers contain a preexisting muscle mitogen. Injury to the fiber, that cause the release of the mitogen normally enclosed in the muscle fibers that can enhance muscle injury repair. However, in normal course of un-interfered healing of muscle injury, fibrous tissue grows faster to replace the inflammatory reaction, although some little regenerating muscle fibers are present, it is far to insufficient. Administration of exogenous muscle mitogen can greatly improve muscle injury repair and regeneration. Therefore, identification and further production of the muscle mitogen are of great significance both clinically and commercially.

Discussion: The role of muscle fiber injury has been an area of interest for some time. It has been speculated that adaptive muscle growth is analogous to other forms of tissue repair in response to injury. The theory is that cell growth, connective tissue matrix deposition, and angiogenesis (development of new blood vessels) are stimulated by NAD+ depletion caused by a burst in lactate generation in the would site. In the study above, it was demonstrated that if there is insufficient "muscle mitogen", exercise induced muscle injury leads to significant inflamation and as a result, an over production of fibrous connective tissue that effectively replaces functional muscle tissue. The exact composition of the muscle extract that was used was not determined. Apparently it contains growth factors that accelerate the rate of muscle fiber regeneration when injected locally at the site of damage. It is probable that this muscle extract used by these investigators contains chemicals (probably proteins) that act as signals for myogenic stem cells, sometimes called satellite cells, to proliferate and even relocate. Although satellite cells have long been established as the providers of myoblastic cells, very little is really known (apart from their anatomical location in relation to muscle fibers and their ability to migrate) about the precise role of satellite cells in myogenesis.

The results of this study indicate that for significant functional muscle growth you must induce some amount of fiber damage during your training. This damage must be sufficient to cause a release of this "muscle mitogen" from within the muscle cells into the surrounding space. The results of this study may also shed light on the fact that as we age, we respond less favorably to muscle damage than when we are young. Tissue response to injury in the aged is characterized by a disproportional increase in fibrous tissue within the muscle similar to that seen in the untreated groups in this study.

 2. The "Zone" put on trial!

Title: Effects of Two Energy Restricted Diets on Fuel Utilization, Blood Chemistry, and Body Composition.

Researchers: M. Kern, V. Schuab, and D. Harris, from the Department of Kinesiology, San Francisco State University, SF, CA.

Source: Med Sci Sport Exer. 1998 May;30(5) Supplement; S1-S1339

Summary: Researchers from the Department of Kinesiology from San Francisco State University recently put the "Zone" diet to the test. The purpose of the study was to determine the effect of two energy restricted diets on fuel utilization during exercise, body composition and fasting blood parameters. The two diets that were compared were a typical high carb diet consisting of 65% carbohydrate, 20% protein, and 15% fat, and a second diet which was similar to the "Sears Zone Diet" that was made up of 40% carbohydrate, 30% protein, and 30% fat.

*indicates significance (p£0.05) between pre and post with the same group.

Similar trends in blood lipid changes resulted from following either diet, though Triglycerides and TC/HDL ratio only significantly decreased on the "Zone" diet. Respiratory Exchange Ratio (RER) was not different between or within groups. Most importantly, there was no loss of Fat Free Mass on the "Zone" diet, unlike the "high carb/low fat" diet.

Discussion: Before any conclusions are drawn, attention should be paid to the relatively small sample size used in this study. Any time you use so few people in a study, the statistical "power" of the results are diminished. Inter-individual differences and "unaccounted for" variables can greatly effect the outcome when so few subjects are used. This aside, once again it appears that the phobia about fat is probably unfounded. Weight loss is a matter of burning more calories than one consumes. The difference between these two diets was not in the amount of calories but in the composition of those calories. The "Zone" diet contains 30% of calories from fat, whereas the high carbohydrate diet used in this study contained only 15% of calories from fat.

It is possible that the additional fat content of the "ZONE" diet provided more fuel for muscle and organs, thereby lowering the demand for amino acids (and thus muscle catabolism) as gluconeogenic precursors. It would appear that when the body is given the opportunity to adjust its metabolism towards utilizing fat for fuel instead of sugar, a muscle sparing effect is observed due to a decrease in gluconeogenesis. This theory might seem unlikely if you only look at the RER as these authors did. The RER only measures the Vco2/Vo2 at the lungs and is not an accurate indication of substrate utilization at the cellular levels. Perhaps a more telling measurement would have been the Respiratory Quotient (RQ) which measures the amount of O2 consumed and the amount of CO2 produced at the cellular level. This would provide a more accurate picture of substrate utilization by the tissues. Finally, a favorable change in serum triglycerides and TC/HDL was only evident in the "Zone" group.

Before you go announcing these results to your local dietician, understand that they are firmly indoctrinated in the "food pyramid" view of the universe. As a result, they find it very difficult to stray from the ways of their upbringing. You must also consider the fact that in order for them to acknowledge the value of moderate fat diets, they must in essence, admit to being wrong for the last two decades. This kind of paradigm shift will only happen with time.

3. Keeping cortisol in check with carb drinks could lead to greater muscle growth in only 12 weeks!

Title: Influence of Weight Training Exercise and Modification of Hormonal Response on Skeletal Muscle Growth

Researchers: Tarpenning KM, Wiswell RA, Marcell TJ, Hawkins SA from the University of Southern California, Los Angeles, and the Charles Sturt University, Bathurst NSW, Australia

Source: Med Sci Sport Exer. 1998 May;30(5) Supplement; S1-S1339

Summary: Skeletal muscle growth is influenced by a number of physiological factors such as hormonal action, nutrient supply, and level of contractile activity. Previous research has demonstrated that the consumption of a carbohydrate (CHO) solution during weight lifting exercise can modify the response of several hormones known to regulate protein metabolism. The purpose of this study was to determine if the chronic supplementation of a CHO solution and the resultant alteration of hormone levels, would positively effect the hypertrophic response to resistance exercise. Two groups of young men (21.3±1.5-y) engaged in 12 weeks of progressive resistance weight training exercise. Training for one group included the ingestion of a non-caloric placebo beverage (Ex+P1f), and the other, a 6% CHO solution (Ex+CHO) - each at a quantity of 8.5-ml-kg body wt. The hormonal response to exercise was monitored during weeks 1, 6, and 12, as determined by RIA, while muscle growth was determined from differences in pre and post training muscle fiber area as calculated from biopsy samples obtained from the vastus lateralis. Throughout the twelve weeks of training, the Ex+CHO treatment group continued to display a non-significant change in cortisol concentration (pre to post to exercise). This is in contrast to significantly elevated levels (post exercise) observed for the Ex+Pl control group. Corresponding with these response patterns were differences in muscle growth. Weight training exercise with CHO ingestion resulted in significantly greater gains in both type I and type II muscle fiber area than weight training exercise alone. The differences in cortisol release accounted for 73.5% of the variance in change of type I muscle fiber area, and 52.3% of the variance in change of type II muscle fiber area. The results of this study suggest that the modification of the hormonal response associated with CHO ingestion can positively impact exercise induced muscle hypertrophy in young men.

Discussion: During exercise, cortisol accelerates lipolysis, ketogenesis, and proteolysis (protein breakdown). This happens in order to provide additional fuel substrates for continued exercise. The effects of cortisol may also be necessary to provide an amino acid pool from which the muscle can rebuild new contractile proteins. This ensures that some degree of adaptation can occur regardless of the availability of food. Over time however, if this process is not balanced with additional dietary protein the net effect will be only a maintenance or even a decrease in functional muscle tissue, as is evident during periods of starvation or prolonged dieting. From the study above we see that there was only a non-significant rise in cortisol levels when carbohydrates were consumed during exercise. The net effect was a more rapid increase in the cross sectional area of the muscle fibers with the greatest effect seen in type-II fibers.

This may be a less expensive option for those who can not afford the use of phosphatidylserine. In this case, carbohydrate administration appears to down regulate the hypothalamic-pituitary-adrenal axis. This would, in effect, greatly reduce the bodies catabolic response to exercise stress. All good news for bodybuilders.

4. Does supplementing with Glutamine cause insulin resistance?

Title: The effect of Oral Glutamine Supplementation in the Development of Insulin Resistance in Rat’s Muscles

Researchers: L.A. Swada, A.S. Costa, M.L. Marquezi, L.O. Pereira, L.F.B.P. Costa Rosa, & A.H. Lancha Jr., from the School of Physical Education and Sport, Laboratory of Nutrition, Metabolism and Applied Exercise, University of Sao Paulo, Brazil.

Source: Med Sci Sport Exer. 1998 May;30(5) Supplement; S1-S1339

Summary: Insulin resistance to glucose uptake is a metabolic state that seems to be related to some pathological disorders such as obesity and diabetes. One of the mechanisms of the development of insulin resistance could be associated with the impairment of glucose transporter (GLUT 4) translocation to the cellular membrane, which might be related to some defect in one of the steps after insulin receptor activation. Recently, some proteins that mediate the insulin signalizing process have been described, GLUT4 translocation and the activity of these proteins were also subjected to the influence of amino acids. Females Wistar rats, weighting 200-250 g. received 0.4 g/kg of glutamine (200 mM) daily for 10 days, by gavage. The soleus muscle was incubated with labeled glucose C14 with or without glutamine to study glucose uptake. The results showed a decrease in glucose uptake of 40% in the supplemented group compared to the control group (1,099 mM/h). When adding glutamine during incubation, the supplemented group showed a reduction in glucose uptake of 42% and 54% in the control group. Although the oral administration did not increase the plasma glutamine concentration, there was a raise of 15% in plasmatic glutamate. We conclude that the chronic glutamine supplementation decreases glucose uptake in skeletal muscle probably due to the increase in palmitic glutamate which is converted into glutamine in some tissues, such as muscle of liver.

Discussion: Glutamine is an essential amino acid to rapidly proliferating cells such as immune system cells and enterocytes. Although a few studies have demonstrated an increase in glutamine plasma concentration due to high oral supplementation, most of them emphasize that this oral administration of glutamine does not raise plasma concentrations because the enterocytes metabolize most all the glutamine. The role of glutamine in the development of insulin resistance has been described as a consequence of the hexosamine pathway whose product, glucosamine, then prevents GLUT4 translocation in part by induction of protein kinase C (PKC). In muscle cells, glutamine stimulates the hexosamine pathway producing glucosamine, which then leads to insulin resistance. This hypothesis is reinforced considering the glucose uptake reduction when glutamine was added during incubation, even in the control group.

Considering the popularity of glutamine supplementation, this should be food for thought for many of you. The authors point out that although most studies show that oral glutamine supplementation seldom results in significant serum "glutamine" concentrations, it is plasmatic glutamate that showed an 15% increase and eventually leads to an increase in intracellular glutamine. It may be that using a glutamine supplement may not be desirable during high calorie "bulking" phases. It should be mentioned that an acute dose of glutamine only produces acute (temporary) effects on glucose transport, however, chronic supplementation has been shown to reduce the number of GLUT-4 transporters under basal conditions. In other words, overuse of glutamine supplements may lead to chronic insulin resistance and hyperglycaemic effects.