Endocrine Abstracts

As part of the Transregional Collaborative Research Centre TR-SFB134 we study central insulin effects on hedonic food processing across the life-span. So far, 48 younger participants across a wide weight-range (BMI: 18–38) were investigated with functional magnetic resonance imaging (fMRI) during a hedonic food processing task after receiving intranasal insulin (160UI) or placebo in a cross-over design after an overnight fast. Imaging results during the placebo session reveal a robust activation pattern of homeostatic (ventral hypothalamus) and reward-related (ventral tegmental area, ventral striatum, amygdala, ventromedial and orbitofrontal cortex) neurocircuits. Behaviorally, insulin application reduced food liking only in participants with normal insulin-sensitivity, as indicated by an insulin resistance index HOMA-IR of ≤ 2 (N=28). Only in participants with an increased HOMA-IR > 2 (N=20), plasma insulin levels during placebo predicted food liking, i.e. participants with a moderate endogenous insulin level demonstrated reduced food liking while elevated levels were related to high food liking scores. On the neural level, behavioral insulin effects were paralleled by activation changes in the hypothalamus and regions of the reward system. In our ongoing analyses we are now focusing on group- and insulin-effects on connectivity patterns between homeostatic and dopaminergic brain regions as well as on non-linear insulin effects on behavior and brain function. Given recent animal data on differential central insulin action in different areas of the dopaminergic reward system, our approach might be useful to translate and extend current hypotheses to the human brain.