The effect of a limited period of protein-calorie malnutrition in young rats on glucose tolerance, insulin secretory response to glucose, and tissue composition in the adult was studied. Three-week-old rats were weaned onto semisynthetic diets containing either 5% protein (low protein; LP) or 15% protein (control; C) and maintained for 3 wk on their respective diets. At 6 wk of age all rats were returned to a commercial rat chow diet (18% protein). Glucose tolerance, insulin secretory response to glucose, and the protein/DNA ratio in liver, skeletal muscle, heart, kidney, small intestine, and lung were investigated at 3, 6, and 12 wk of age. Rats receiving LP diet failed to gain weight, but growth resumed immediately when they were transferred to commercial rat chow. They did not, however, catch up with C rats. Glucose tolerance and insulin secretory response to glucose remained similar between 3 and 12 wk in C rats. In 6-wk-old LP rats, glucose tolerance was impaired, and the insulin secretory response to glucose was absent. At 12 wk of age the glucose tolerance of the LP rats had normalized, but the insulin secretory response was still blunted. In 6-wk-old LP rats there was an inhibition of the age-dependent increase in cell size, shown by lowered protein/DNA ratios in all tissues studied. This decrease in cell size persisted at 12 wk in liver, skeletal muscle, heart, and lung.
We conclude that protein-calorie malnutrition early in life persistently impairs the insulin secretion. The persistently lowered protein/DNA ratios in many tissues may be related to this lowered capacity for insulin secretion. The individual could have an impaired ability to respond to diabetogenic and nutritional challenges, and it is thus possible that the early malnutrition may predispose for diabetes.