PANCREATIC-ISLET CELLS IN PREOBESE YELLOW A(VY) - MICE - RELATION TO ADULT HYPERINSULINEMIA AND OBESITY/

Plasma insulin levels in yellow A(vy)/- mice begin to increase before the animals are overtly obese. Are the elevated insulin levels in yell ow mice primary or secondary to the subsequent obesity? Elevated blood insulin levels in young preobese mice, due to synthesis and release o f insulin by increased number of beta cells, would stimulate lipogenes is, resulting in excess lipid deposition and subsequent peripheral ins ulin resistance. Examination of this possibility was the objective of this study. The beta, alpha, and delta cells in the pancreata of 7-, 1 4-, and 21-day-old male yellow A(vy)/A and agouti Ala (BALB/c x VY)F-1 hybrid mice were counted with immunohistochemical/ morphometric techn iques. The insulin and glucagon concentrations in pancreata from male and female mice of the same ages and genotypes were also assayed. In t he 21-day-old male mice, the mean number of beta cells/pancreas was si gnificantly greater in the yellow mice than in the agouti mice; howeve r, insulin content and body weight were the same. This suggests that i ncreased beta cell proliferation in yellow mice precedes any detectabl e genotype-specific increase in pancreatic insulin content or body wei ght.