Research Update #9

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:
Attenuating the decline in ATP arrests the exercise training-induced increases in muscle GLUT4 protein and citrate synthase activity.

Researchers:
Yaspelkis BB 3rd, Castle AL, Ding Z, Ivy JL
Department of Kinesiology, The University of Texas at Austin, 78712, USA.

Source:
Acta Physiol Scand 1999 Jan;165(1):71-9

Summary:
Thirty-two rats were assigned to one of four groups: control (CON); exercise training (TR); exercise training + clenbuterol treatment (0.8 mg/kg/day ) (TR + CL) or exercise training + clenbuterol treatment + 2% beta-guanidinoproprionic acid diet (TR + CL + beta) to examine whether alterations in the ATP levels within the muscle mediates exercise training-induced increases in skeletal muscle GLUT4 protein concentration and citrate synthase activity. Exercise training consisted of running the rats 5 d week(-1) for 8 weeks on a motor-driven treadmill (32 m min(-1), 15% grade).

Gastrocnemius GLUT4 protein concentration and citrate synthase activity were significantly elevated in the TR animals, but these adaptations were attenuated in the TR + CL animals. Providing beta-GPA in combination with clenbuterol enabled training to elevate GLUT4 protein concentration and citrate synthase activity, with the increase in GLUT4 being greater than that observed for the TR animals. Skeletal muscle ATP levels were reduced in the TR + CL + beta animals while ATP levels in the TR + CL animals were significantly elevated compared with CON. An acute 40-min bout of electrical stimulation of the sciatic nerve was found to lower skeletal muscle ATP levels by approximately 50% and elevate cAMP levels in all groups. No difference in post-contraction cAMP levels were observed among groups. However, post-contraction ATP levels in the TR + CL animals were significantly greater than the other groups.

Collectively, these findings suggest that exercise training-induced increases in skeletal muscle GLUT4 protein concentration and citrate synthase activity are initiated in response to a reduction in the skeletal muscle ATP concentration.

Discussion:
Adaptation to training involves increased oxidative capacity of muscle cells along with increases in the muscle’s ability to take up glucose. Increases in the oxidative capacity of muscle cells are characterized by increases in Krebs cycle enzymes. Enhanced glucose uptake is accomplished through increased glucose transporter protein (GLUT 4) content in the muscle cell.

The primary function of the Krebs cycle (also called TCA Cycle or Citric Acid Cycle) is to completely oxidize acetyl groups (derived from the breakdown of glucose, fatty acids, some amino acids, & ketones) in a way that results in ATP formation. Oxidation of acetyl CoA accounts for about two thirds of the ATP formation and oxygen consumption in mammals. Citrate synthase is the enzyme which starts the Krebs cycle by combining Acetyl CoA and oxaloacetate to form citrate. By measuring its activity researchers are able to measure increases in oxidative capacity as a result of exercise training.

Glucose uptake in muscle tissue occurs by facilitated diffusion. The term "facilitated" refers to the use of proteins, embedded in the cell membrane, which help the glucose to diffuse across the membrane. These proteins don’t remain in the cell membrane all the time, rather, they are translocated to the cell surface when insulin attaches to its receptor or when muscle contractions occur. The glucose transporter proteins most sensitive to insulin and muscle contraction are called GLUT 4 proteins. With exercise training, increased GLUT 4 content within muscle cells increases the muscle’s ability to take up glucose from the blood both during exercise and in the presents of insulin. This results in a "nutrient partitioning" (there’s a term you haven’t heard in a while) effect by increasing the portion of dietary carbohydrates that are used by the muscles rather than fat cells.

In the study above it was shown that these adaptations that are normally seen with exercise training, are blocked when the animals were on clenbuterol. Clenbuterol, by activating beta receptors, and thus stimulating adenylate cyclase activity, artificially maintains ATP levels within the cell. When this happens, there is no increase in GLUT 4 protein content nor is there an increase in citrate synthase activity. There appears to be a threshold below which ATP concentrations must fall before your muscles begin long term adaptive changes.

What does all this mean for Clenbuterol users? Well, if you are a performance athlete stay away from it during the competitive season. Clen will inhibit the necessary increases in oxidative capacity need for enhanced athletic performance with training. It will also hamper your attempts to replenish glycogen stores as quickly as possible after competitions.

If you are a bodybuilder Clen is probably going to decrease glycogen storage not only from lower GLUT 4 levels but also from enhanced glycogenolytic activity. It is wrong to assume that ephedrine would be any different. Anything that is going to enhance adenylate cyclase activity such as clenbuterol, ephedrine, or even forskolin, is going to prevent these adaptive processes in response to exercise training. Fortunately, metabolic adaptations are not the key to muscle growth. Nevertheless, increases in oxidative capacity and increased GLUT 4 content are valuable adaptations when trying to train and recover at ever increasing levels.

Scientists uncover key protein in neuromuscular junction formation.

Source:
Regeneron Pharmaceuticals Inc.

Summary:
Researchers at Regeneron Phamaceuticals Inc. are working on developing a drug therapy based on the actions of the protein "Agrin". "What is Agrin" you say? Agrin is a protein released from nerve terminals that works to signal the formation of neuromuscular junctions in developing organisms. The way in which the human body forms these junctions during early development has long been a mystery. Now, several factors have been identified that play a role in neuromuscular junction formation, with agrin being a crucial one.

The neuromuscular junction is the point where the nerve meets the muscle surface. At this junction the nerve is able to initiate a wave of depolarization that travels over the cell membrane leading to contraction.

Here is a brief summary of the steps of muscle contraction.

1. The neuron signal (via acetylcholine release) spreads a wave of depolarization over the membrane of the muscle fiber which travels down into the interior of the fiber via surface invaginations called T-tubules.

2. T-tubule depolarization is linked to calcium ion (Ca2+) release from the sarcoplasmic reticulum

3. The result is a 100 fold increase in calcium ion concentration in the fiber interior.

4. The calcium ions then bind to a protein (troponin) in a thin filament, called actin, in the fiber.

5. The binding of Ca2+ allows protein projections on another filament, called the thick filament or myosin, to bind to actin.

6. When the myosin projections or cross bridges bind to actin, they pull on it and cause the muscle fiber to shorten.

7. The action of millions of cross bridges in many fibers causes the overall muscle to shorten.

8. Finally, the energy to make the myosin cross bridges attach to actin and cause shortening is derived from the hydrolysis of ATP.

This whole process is referred to as "excitation-contraction coupling". The importance of agrin lies in the formation, or clustering, of acetylcholine receptors at the cell surface. Agrin is the signal released by nerve endings that causes the aggregation of acetylcholine receptors on the surface of the muscle fiber. Without this cluster of acetylcholine receptors the nerve could not elicit an action potential sufficient to cause the muscle fiber to contract.

Researchers for Regeneron have been studying the interaction of agrin with its receptor called muscle-specific-receptor kinase, or MuSK If they could come up with a way to enhance or mimic the actions of agrin they could potentially combat disease states where there is a deterioration of the neuromuscular junction such as amyotrophic lateral sclerosis (ALS). ALS is also known as Lou Gehrig's disease. It is a progressive, fatal neurological disease affecting as many as 20,000 Americans with 5,000 new cases occurring in the United States each year. The disorder belongs to a class of disorders known as motor neuron diseases.

It would be interesting to see what role agrin plays in the neuromuscular changes seen with resistance training. It could be that agrin is involved in the enhanced neuromuscular performance typically seen with resistance training. It could be that in the future, these junctions could be enhanced or even increased in number in order to increase strength in athletes.

Title:
Effect of a precompetition bodybuilding diet and training regimen on body composition and blood chemistry.

Researchers:
Too D, Wakayama EJ, Locati LL, Landwer GE

Department of Physical Education and Sport, State University New York, Brockport  14420-2989, USA.

Source:
J Sports Med Phys Fitness 1998 Sep;38(3):245-52

Summary:
One adult male, steroid and drug free, preparing for his first competition, was studied. Average daily dietary intake consisted of 2263 calories (71% protein, 16% carbohydrate, 13% fats), with a protein intake of 5.0 gm.kg-1 body mass (BM).

Initial body weight of 76.3 kgf (16% body fat) decreased to 63.4 kgf (4.4% body fat). Blood samples for electrolytes, TP, Alb, bilirubin, LDL-C, TG, UA, and amylase were normal. HDL-C levels increased from 65 to 89 mg.dL-1. Decreased glucose levels (< 50 mg.dL-1), indicated hypoglycemia. Increased Creatine Kinase levels indicated intense training. Increased inorganic phosphorus from 3.7 to 8.2 mg.dL-1 suggested lactic acidosis. Increased BUN levels from 16 to 53 mg.dL-1 and creatinine from 1.1 to 1.8 mg.dL-1 may be attributed to a high protein diet. However, heart muscle enzyme (CK-MB) was not elevated.

Discussion:
It isn’t very often that someone puts up some money to see if bodybuilding diets are as dangerous as the popular press would have you believe. I have personally spent hours and hours over the years listening to so called experts warning other health professionals how dangerous bodybuilding type diets were. It is in situations like these that you can’t really raise your hand and say anything to the contrary. After all, there is an auditorium full of Ph.D.s and M.D.s all in blind agreement with anything said about bodybuilding simply because they have no personal knowledge to the contrary.

The diet used in this study was obviously chosen by the participant, not the investigator. The results show a respectable drop in body fat from ~16% to 4%. Experience using various body composition measurement techniques tells me that either one of those measurements could be off by as much as 5%. Nevertheless, I haven’t seen anyone look too smooth at a true 4%. It would have been interesting to see if alterations in the macronutrient composition of this diet (i.e. more fat) would effect loss of lean tissue. All other blood parameters accept for glucose were normal. This flies in the face of critics complaining about dehydration, electrolyte imbalances and kidney failure from high protein/low carbohydrate diets.

The increase in the popularity of bodybuilding over the last ten years should impact research as some of those young people become researchers themselves. The fields of exercise physiology are also growing in popularity which should increase the amount of research focusing on bodybuilding issues. Until then we will continue with trial and error along with a little intuition thrown in for good measure.

New form of Growth Hormone need only be injected once or twice per month.

Source:
Alkermes, Inc. http://www.alkermes.com/
Genetech http://www.gene.com/

Alkermes, Inc. and Genentech announced that based on the successful completion of a multi-center Phase III clinical trial of Nutropin Depot and the preliminary results, the companies intend to proceed with plans to submit a New Drug Application (NDA) in early 1999 with the United States Food and Drug Administration (FDA). Nutropin Depot is a sustained release formulation of Genentech's somatropin (recombinant human growth hormone or rhGH) based on Alkermes' ProLease® injectable sustained release drug delivery system. In the Phase III clinical trial, Nutropin Depot was administered either once or twice a month.

The Phase III clinical trial was designed to test the safety, tolerability and efficacy of Nutropin Depot in the treatment of children with growth hormone deficiency who had not received any previous treatment with growth hormone. Seventy-four patients were enrolled at twenty-seven centers in the United States from December 1997 through March 1998. Two different dosing regimens were evaluated in the study -- both groups receiving the same total dose of Nutropin Depot. In one group, thirty-six patients received subcutaneous injections of Nutropin Depot once a month for a six month period. In the second group, thirty-eight patients received subcutaneous injections of Nutropin Depot twice a month for a six month period. The primary efficacy endpoint of the trial was linear growth rate at six months, annualized. All patients were given the option of continuing treatment with Nutropin Depot at the completion of the six month study. Nutropin Depot is designed to reduce the frequency of injections by encapsulating the drug in biodegradable microspheres (based on Alkermes' ProLease® injectable sustained release drug delivery system) that, once injected, is intended to slowly release rhGH over a sustained period of time.

The complete analysis of the data from the study is currently underway. Final results are expected to be presented at a scientific meeting in 1999.

Discussion:
The availability of rhGH that need only be injected once or twice per month offers relief to individuals on growth hormone therapy. Children will certainly welcome not having to get so many shots. Athletes juggling multiple injectable "supplements" often feel like human pin cushions. It is common practice to use GH three to four times per day in order to mimic endogenous release patterns. This often causes athletes on heavy cycles to miss out on public or social activities that make taking timeout for several daily injections inconvenient to say the least.

Hormone replacement therapy is becoming more and more acceptable everyday. With the availability of once per month injections, a wider population of individuals that may benefit for GH injections will have a new opportunity for this type of treatment. The elderly, who often must schedule an office visit for hormone therapy, would obviously benefit. It can be assumed that life extensionists groups will also jump at the chance to use and distribute this product. It is unlikely that Nutropin Depot will be any less expensive than other currently available forms of rhGH.