Abstract

Myostatin (Mstn) is a secreted growth factor expressed in skeletal muscle and adipose tissue that negatively regulates skeletal muscle mass. Mstn mice have a dramatic increase in muscle mass, reduction in fat mass, and resistance to diet-induced and genetic obesity.

To determine how Mstn deletion causes reduced adiposity and resistance to obesity, we analyzed substrate utilization and insulin sensitivity in Mstn mice fed a standard chow. Despite reduced lipid oxidation in skeletal muscle, Mstn mice had no change in the rate of whole body lipid oxidation. In contrast, Mstn mice had increased glucose utilization and insulin sensitivity as measured by indirect calorimetry, glucose and insulin tolerance tests, and hyperinsulinemic-euglycemic clamp. To determine whether these metabolic effects were due primarily to the loss of myostatin signaling in muscle or adipose tissue, we compared two transgenic mouse lines carrying a dominant negative activin IIB receptor expressed specifically in adipocytes or skeletal muscle. We found that inhibition of myostatin signaling in adipose tissue had no effect on body composition, weight gain, or glucose and insulin tolerance in mice fed a standard diet or a high-fat diet. In contrast, inhibition of myostatin signaling in skeletal muscle, like Mstn deletion, resulted in increased lean mass, decreased fat mass, improved glucose metabolism on standard and high-fat diets, and resistance to diet-induced obesity.

Our results demonstrate that Mstn mice have an increase in insulin sensitivity and glucose uptake, and that the reduction in adipose tissue mass in Mstn mice is an indirect result of metabolic changes in skeletal muscle. These data suggest that increasing muscle mass by administration of myostatin antagonists may be a promising therapeutic target for treating patients with obesity or diabetes.

Citation: Guo T, Jou W, Chanturiya T, Portas J, Gavrilova O, et al. (2009) Myostatin Inhibition in Muscle, but Not Adipose Tissue, Decreases Fat Mass and Improves Insulin Sensitivity. PLoS ONE 4(3): e4937. doi:10.1371/journal.pone.0004937

Inhibiting a growth factor that keeps muscles from getting too big may optimize recovery of injured soldiers, researchers say. They are studying two myostatin inhibitors in mice with limb injuries, first to see which works best and then to identify the best delivery mechanism, says Dr. Mark Hamrick, one biologist in the Medical College of Georgia Schools of Graduate Studies and Medicine.

“Fifty to 60 percent of the injuries occurring in Iraq are to the limbs, and the average injury requires five surgeries,” Dr. Hamrick says. “Myostatin inhibitors are known to improve muscle regeneration and we have evidence that they also increase bone formation. We believe these inhibitors will result in a stronger, more rapid recovery for these soldiers and other victims of traumatic limb injuries.”

A $1.2 million grant from the Office of Naval Research to Dr. Hamrick is enabling laboratory studies of two experimental myostatin inhibitors: a decoy receptor and a binding protein, both developed by MetaMorphix, Inc. of Beltsville, Md. Both inhibitors have been shown effective in muscle regeneration, but this is the first trial that looks at their impact on bone.

Two delivery mechanisms also will be studied. “Is the best approach a single injection bolus that circulates everywhere or just localized delivery?” Dr. Hamrick says.

Study collaborators include Dr. Li Liang of the life sciences company MetaMorphix, who will oversee development of the inhibitors; Dr. Xuejun Wen, bioengineer at Clemson University in Clemson, S.C.; and David Immel, radiographic imaging expert at Savannah River National Laboratory in Aiken, S.C., who will provide three-dimensional, high-resolution computerized tomography scans of injured limbs before and after treatment.

Myostatin is primarily produced by muscle cells. Females tend to produce more myostatin receptors, which helps explain why men tend to have greater muscle mass. Dr. Hamrick’s lab also has found the receptor on bone-derived stem cells – needed to help repair an injury – and others have found it in healing fractures. “When you take it away, the healed callus that forms at the fracture site has more bone in it,” says Dr. Hamrick. “Myostatin also increases fibrosis and scarring within tissue so part of what you are doing is blocking that.”

Bone and muscle healing typically go hand in hand. Muscle provides blood, growth factors and potentially stem cells for a healing callus. It’s not yet known how well bones reciprocate. “If you can improve muscle healing, you can improve bone healing,” Dr. Hamrick says. “Young people have a tremendous potential to heal that can be improved with better approaches to preventing infection and to healing soft tissue and bone in an integrated manner.”

Researchers hope to move to clinical trials in two to three years, Dr. Hamrick says. “If we find the primary role of myostatin is very early in the healing process and see a big jump in expression early in a fracture callus, it may be that a single injection bolus immediately after injury is the best time for treatment rather than continued treatment over a period of time.”

Myostatin is most highly expressed during development, but adults have some as well, so blocking it still facilitates muscle growth and development, primarily in response to exercise. Myostatin expression also tends to rise following an injury, apparently to control proliferation of new and regenerating cells, Dr. Hamrick says. Although there is no FDA-approved myostatin inhibitor, body builders often take supplements that claim to reduce myostatin function and help build muscle.

A whole spectrum of naturally occurring genetic variations likely result in minor alterations in myostatin signaling that could help explain why some people are more muscular than others, Dr. Hamrick notes. In a separate study funded by the National Institutes of Health, he is using a genetically engineered ‘mighty mouse,’ which is missing the myostatin gene, to find the best way to optimize bone growth and help young people avoid osteoporosis. German researchers reported in 2004 in the New England Journal of Medicine the case of a child whose muscles already were bulging as a newborn apparently because of a dysfunctional myostatin gene.

Source: Medical College of Georgia

Athletes and bodybuilders use creatine to increase muscle mass , decrease fat free mass and improve exercise performance. The latest creatine research shows people with muscular dystorphies increase strength and reduce fat-free mass taking creatine.

Muscle strength increased by an average of 8.5 percent among people taking creatine, compared to those who did not use the supplement, according to a recent review of studies. Creatine users also gained an average of 1.4 pounds more lean body mass than nonusers.

The evidence from the studies “shows that short- and medium-term creatine treatment improves muscle strength in people with muscular dystrophies and is well-tolerated,” said lead reviewer Dr. Rudolf Kley of Ruhr University Bochum in Germany.

The review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.

Creatine (creatine monohydrate) is used by muscle tissue in the production of creatine phosphate, which forms the source of energy working muscles use called adenosine triphosphate (ATP).[1] [2] Low levels of creatine have been associated with rheumatoid arthritis, chronic circulatory and respiratory diseases, as well as several muscle diseases, like Duchenne muscular dystrophy.[3]

People with muscular dystrophies can have lower-than-normal levels of creatine, along with increasing muscle weakness as their disease progresses. Since some studies suggest that creatine improves muscle performance in healthy people, many researchers have reasoned that it might be helpful in treating muscle disease.

The Cochrane researchers reviewed 12 studies that included 266 people with different types of muscular dystrophy. People in the studies who took creatine supplements used them for three weeks to six months.

In muscular dystrophies, the proteins that make up the muscles themselves are either missing or damaged. In a related group of disorders called metabolic myopathies, the chemicals that help muscles operate go awry.

Although creatine seemed to help many patients with muscular dystrophies, those with metabolic myopathies gained no more muscle strength or lean body mass than patients who did not use the supplement.

The reason for the contrasting results — creatine’s “fairly consistent” effects in muscular dystrophy and lack of effectiveness in metabolic diseases — is “not entirely clear,” Kley said, calling for more research on treatment for metabolic disorders.

The review was supported by the Neuromuscular Center Ruhrgebiet/Kliniken Bergmannsheil, at Ruhr-University Bochum and the Hamilton Health Sciences Corporation, in Canada. Kley and colleagues have each participated in trials of creatine treatment for muscle disorders, although none of the studies was sponsored by a maker of creatine.

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Article adapted by Sandco from original press release.
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FOR MORE INFORMATION
Health Behavior News Service: hbns-editor@cfah.org

Kley RA, Vorgerd M, Tarnopolsky MA. Creatine for treating muscle disorders. Cochrane Database of Systematic Reviews 2007, Issue 1.

The Cochrane Collaboration is an international nonprofit, independent organization that produces and disseminates systematic reviews of health care interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. Visit http://www.cochrane.org for more information.

If you decide to make the choice to begin bodybuilding, it is good to keep in mind not to become too overzealous and burn itself out too quickly, or even worse, injure yourself. Someone beginning bodybuilding should take it as a gradual process that will eventually lead to more experienced exercise routines.

Below are some suggestions and tip’s for bodybuilding beginners if that is what you choose to pursue.

Diet And Bodybuilding

One of the most important aspects for beginning bodybuilders is diet. If you keep eating fast food or other kinds of junk food you cannot have any expectations to be successful at this sport. When it comes to sculpting your body discipline is one of the main necessities. That is why it is recommended by trainers that you start to consume primarily meat, nuts, fish, grain and milk. Foods such as these are low in fat, as well as high in protein that will assist in helping build muscle as well as increase your metabolism.

Your Workout Routine

Concerning your workout regimen, starting off slowly is important for beginners in this sport. Beginners in this activity in the beginning come to the realization that even though they really want to look as if they have the same physique as bodybuilders on the cover of magazines, or on TV, it is a work in progress. Bodybuilding beginners should start with two sets of repetitions with roughly a minute of rest in between.

They should do this for roughly 45 minutes, 4 days a week. After four weeks have passed, after allowing a body and a time to build itself up, at that point the bodybuilder can start to move gradually up to 60 minutes of a workout while doing three sets of repetitions with roughly a minute of rest in between. At approximately this point, their body should slowly start to change, muscle should be gained and fat should be lost.

Along with exercise and diet, rest is equally important with bodybuilding beginners. This is vitally important, as the individuals muscles need to grow during this period. At a minimum six to eight hours of sleep is recommended per night.

Whatever Your Desires and Goals Are

Whether you want to get into bodybuilding for competitive reasons or for your own personal achievement, it is essential for beginners in this sport to be on a gradual process. Making sure that proper rest, diet and exercise are accomplished is important to physical success. At first do not concern yourself about looking like a bodybuilder immediately; focus on a workout plan that will work for your specific body type as well as your specific goals.

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Author Resource:- Listen to Corbin Newlyn as he shares his insights as an expert author and an avid writer in the field of bodybuilding. If you would like to learn more go to Bodybuilding Advice and at Female Bodybuilding tips.

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