PLASMA-GLUCOSE, INSULIN, AND GLUCAGON BEFORE AND AFTER LONG-TERM OVERFEEDING IN IDENTICAL-TWINS

Plasma glucose, insulin, and glucagon levels were measured before and after long-term overfeeding (4.2 MJ/d during a 100-day period) in 24 l ean adults (12 pairs of monozygotic twins). Pasting plasma glucose, in sulin, and glucagon were significantly increased by overfeeding. Durin g a 75-g oral glucose tolerance test (OGTT), no major alteration in gl ucose tolerance was observed and insulin area under the curve was incr eased. During a meal test, insulin and glucagon areas under the curve were increased. The pre-overfeeding values for glucose, insulin, and g lucagon (fasting and areas) were not correlated with the gains in body weight and in fat mass. However, fasting glucagon before overfeeding was positively correlated with the gains in abdominal visceral fat and in femoral fat. The changes with overfeeding in insulin area during t he OGTT were positively correlated with the changes in total subcutane ous fat, even after adjustment for total body fat gain. Significant tw in intrapair similarity was observed for fasting plasma glucagon befor e overfeeding and for the changes in fasting insulin and glucagon with overfeeding. These results indicate that (1) in response to long-term overfeeding, both fasting insulin and glucagon are increased; (2) ini tial levels of glucose, insulin, and glucagon do not predict the gains in body weight and total body fat during overfeeding, but are related to changes in indicators of fat topography; (3) the changes in total subcutaneous fat represent an important correlate of insulin changes w ith overfeeding; and (4) the genotype could be an important determinan t of insulin and glucagon responses to a prolonged positive-energy-bal ance period. Copyright (C) 1995 by W.B. Saunders Company