In research scheduled for presentation at the 11th International Symposium on Amino Acids, to be held in August, 2009 in Vienna, Austria, scientists at Texas A & M University have shown that the amino acid arginine helps reduce fat gain in obese rats, a finding that may prove to be useful against human obesity. The study, which was funded by the American Heart Association, was published in the February, 2009 issue of the Journal of Nutrition.
Texas A & M department of animal science Senior Faculty Fellow Guoyao Wu and associates fed 24 rats a high fat diet and gave 24 a low fat diet starting at 4 weeks of age. After 15 weeks, 8 rats from each group were examined. Animals who received the high fat diet, which provided 40 percent of its calories in the form of fat, experienced 18 percent greater weight gain and 74 percent higher white fat pad weight compared to rats that received the low fat diet, which provided only 10 percent of its calories from fat. (White adipose tissue is the most common form of fat storage in humans, as opposed to brown fat.) The remaining animals in each group were subsequently divided to receive drinking water supplemented with 1.5 percent L-arginine or 2.55 percent L-alanine (as a control) while otherwise maintaining their previous diets.
After twelve-weeks of supplementation, body weight gain in the rats receiving the high fat diet was 40 percent lower among those that received arginine compared with the control group. For rats on the low fat diet, weight gain was 60 percent lower in the arginine group compared with those that received alanine. White fat pad weight increased by 98 percent in animals that received alanine; while in animals that received L-arginine the increase averaged only 35 percent. Arginine supplementation was also associated with lower serum leptin, glucose, triglycerides, urea, glutamine, and branched chain amino acids, as well as improved glucose tolerance.
The researchers concluded that arginine promotes lean tissue growth over fat gain, a finding that was observed in earlier research using pigs. Dr Wu stated that future investigations will involve obese children and adults.
"Given the current epidemic of obesity in the U.S. and worldwide, our finding is very important," stated Dr Wu. "This finding could be directly translated into fighting human obesity. At this time, arginine has not been incorporated into our food (but could in the future)."
Related Health Concern: Obesity
Recent advances in dietary science have highlighted the crucial role of insulin in weight gain. Produced in the pancreas, insulin is a critical hormone for the control of blood sugar (glucose). Its job is to transport glucose into cells, where the glucose is burned as fuel. While this process is necessary for life, abnormalities in the insulin-glucose system caused by aging, lack of exercise and poor diet can cause major health problems. In aging, cells become more resistant to the effects of insulin. As cells become increasingly insulin resistant, the body compensates by increasing the number of insulin receptors on cells and secreting more insulin in an attempt to drive more blood sugar into muscle and liver cells (Fulop 2003).
Insulin resistance is a dangerous condition. Research suggests that adipose tissue (fat) is a source of pro-inflammatory chemicals that have a role in the development of insulin resistance (Sharma AM et al 2005). Insulin resistance is associated with obesity (in particular, abdominal obesity) (Greenfield JR et al. 2004). It is also associated with aging muscle (Nair KS 2005), physical inactivity, and genetics.
This increase in insulin (called hyperinsulinemia) and decreased insulin sensitivity have a number of harmful effects, including contributing to diseases associated with being overweight (Zeman et al 2005; Garveyet al 1998) Over time, high insulin and insulin resistance may lead to type 2 diabetes in susceptible individuals, a major risk factor for heart disease. A study sponsored by the NIH showed that over a 10-year period, hyperinsulinemia was associated with increased all-cause and cardiovascular mortality, independent of other risk factors (NIH 1985).
Controlling insulin levels as we age is essential for overall health, longevity, and weight management. An increasing number of physicians recognize the role of insulin resistance in the current obesity epidemic. The good news is that nonprescription drugs and low-cost dietary supplements that have demonstrated beneficial effects upon insulin action are already available.
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