When insulin comes to our mind, the first thing that we think of is diabetes. We are infected by diabetes, when insulin apparently cannot do the crucial function of assisting the body process sugar. But not many know that insulin has another function. Well it is apparently required for muscle growth, increasing blood flow through muscle tissue, encouraging nutrients to scatter from blood vessels and helping as a biochemical signal to improve muscle protein synthesis and cell proliferation.
Lately, experts have identified that loss of sensitivity to insulin may play a key function in the loss of physical strength that may take place as people grow older. Now, University of Texas Medical Branch at Galveston study experts have apparently verified that by rising insulin levels above the standard range in elderly examining participants, they may repair the damaged muscle-building process which may be in charge of age-related physical weakness.
“Insulin is normally secreted during food intake. When you give insulin intravenously and increase the blood insulin levels to the same amount produced after a meal, you see that in young people it stimulates protein synthesis and muscle growth, while in older people it really doesn’t. But when we gave seniors double the insulin they would normally produce after eating, their muscles were stimulated like those of young people,” commented Dr. Elena Volpi, senior author of a paper on the study,
About 14 elderly volunteers were apparently checked by Volpi and her co-authors, postdoctoral fellows Satoshi Fujita and Kyle Timmerman, graduate student Erin Glynn and Professor Blake B. Rasmussen. They were apparently examined for the reaction of thigh muscle to two diverse blood insulin levels, which may be recognized by concoction into the thigh’s major artery. Blood samples were apparently taken from catheters which were supposedly introduced in the femoral artery and vein of each participant. This may facilitate the experts to supposedly analyze blood flow and muscle protein synthesis, and muscle biopsies could let them measure levels of signaling molecules which may be caught up in muscle protein growth.
The complete data apparently illustrated that a blood insulin level double of which may be generated by a typical meal appears to turn back the clock on elderly thigh muscle.
Volpi quoted, “While we had called this ‘insulin resistance’ in the past, we didn’t really have evidence that you can get an elderly person’s muscle to grow if you give it a lot more insulin, which is what we needed to truly say this is insulin resistance. These were older subjects with perfect glucose tolerance. So what we have identified is a novel kind of insulin resistance that’s not related to sugar control.”
Instead, it was mentioned by Volpi that the UTMB experts may credit this novel type of insulin resistance to age-related changes in the vascular system which may mean alterations in the endothelium. It is apparently in charge of blood flow by increasing or reducing the diameter of capillaries, and may adjust the release of oxygen, nutrients, water and other blood-borne cargo through the capillary walls and into muscles and other body tissues.
Volpe remarked, “Having a capillary dilation induced by insulin is important, because it exposes more muscle to the nutrients and hormones and everything flows better and gets stored away better. But in even healthy older people, this dilation response doesn’t work, because they have this endothelial dysfunction.”
The UTMB experts are now examining whether using drugs to expand muscle blood vessels during insulin exposure could enhance muscle growth in older people.
Volpi mentioned, “Preliminary data suggest that this treatment may be effective, but these data are not yet published. On the other hand, in a paper we published two years ago in Diabetes, we showed that a single bout of aerobic exercise — a staple of diabetes treatment — may also improve muscle growth in response to insulin in older nondiabetic people.”
Volpi’s group is apparently performing a bigger, NIH-funded clinical trial to find out if aerobic exercise and nutritional supplementation for around six months may also increase muscle size and function in inactive but otherwise healthy seniors.
This study has been published in the September issue of Diabetologia.