Adaptation to intermittent stress promotes maintenance of beta-cell compensation: comparison with food restriction

Intermittent restraint stress delays hyperglycemia in ZDF rats better than pair feeding. We hypothesized that intermittent stress would preserve beta-cell mass through distinct mechanisms from food restriction. We studied temporal effects of intermittent stress on beta-cell compensation during pre-, early, and late diabetes. Six-week-old obese male ZDF rats were restraint-stressed 1 h/day, 5 days/wk for 0, 3, 6, or 13 wk and compared with age-matched obese ZDF rats that had been food restricted for 13 wk, and 19-wk-old lean ZDF rats. Thirteen weeks of stress and food restriction lowered cumulative food intake 10-15%. Obese islets were fibrotic and disorganized and not improved by stress or food restriction. Obese pancreata had islet hyperplasia and showed evidence of neogenesis, but by 19 wk old beta-cell mass was not increased, and islets had fewer beta-cells that were hypertrophic. Both stress and food restriction partially preserved beta-cell mass at 19 wk old via islet hypertrophy, whereas stress additionally lowered alpha-cell mass. Concomitant with maintenance of insulin responses to glucose, stress delayed the sixfold decline in beta-cell proliferation and reduced beta-cell hypertrophy, translating into 30% more beta-cells per islet after 13 wk. In contrast, food restriction did not improve insulin responses or beta-cell hyperplasia, exacerbated beta-cell hypertrophy, and resulted in fewer beta-cells and greater alpha-cell mass than with stress. Thus, preservation of beta-cell mass with adaptation to intermittent stress is related to beta-cell hyperplasia, maintenance of insulin responses to glucose, and reductions in alpha-cell mass that do not occur with food restriction.