Differential effects of hunger and satiety on insular cortex and hypothalamic functional connectivity

TLDR

The insula cortex and hypothalamus are key regulators of eating behavior, containing peptide and hormone receptors, and the insula’s subregions exhibit distinct anatomical and functional connectivity patterns. The study sought to determine how fasting versus satiation alters the functional connectivity of the insula and hypothalamus, hypothesizing that these changes would reflect shifts in homeostatic energy balance. Nineteen healthy adults completed two 7‑minute resting‑state fMRI scans—one in a fasted state and one after satiation—to assess connectivity changes. During fasting, left posterior insula and left hypothalamus showed increased connectivity with cerebellum, superior frontal gyrus, and inferior frontal gyrus, whereas during satiation right middle insula and right hypothalamus exhibited stronger links to default‑mode and superior parietal regions; glucose changes explained several of these effects, supporting a lateralized insula‑hypothalamic network that modulates cognitive control of eating.

Abstract

The insula cortex and hypothalamus are implicated in eating behaviour, and contain receptor sites for peptides and hormones controlling energy balance. The insula encompasses multi-functional subregions, which display differential anatomical and functional connectivities with the rest of the brain. This study aimed to analyse the effect of fasting and satiation on the functional connectivity profiles of left and right anterior, middle, and posterior insula, and left and right hypothalamus. It was hypothesized that the profiles would be altered alongside changes in homeostatic energy balance. Nineteen healthy participants underwent two 7-min resting state functional magnetic resonance imaging scans, one when fasted and one when satiated. Functional connectivity between the left posterior insula and cerebellum/superior frontal gyrus, and between left hypothalamus and inferior frontal gyrus was stronger during fasting. Functional connectivity between the right middle insula and default mode structures (left and right posterior parietal cortex, cingulate cortex), and between right hypothalamus and superior parietal cortex was stronger during satiation. Differences in blood glucose levels between the scans accounted for several of the altered functional connectivities. The insula and hypothalamus appear to form a homeostatic energy balance network related to cognitive control of eating; prompting eating and preventing overeating when energy is depleted, and ending feeding or transferring attention away from food upon satiation. This study provides evidence of a lateralized dissociation of neural responses to energy modulations.