BACKGROUND: Physical activity helps maintain a healthy stable body weight. One mechanism underlying this beneficial effect could be the improved coupling between energy intake and expenditure, since hunger and satiety are better regulated in active individuals. Whether this enhancement of appetite control by exercise is reflected in overall adaptations in the gut and gut-brain communication remains poorly defined.
METHODS: We investigated how increased physical activity alters gut morphology, intestinal endocrine function, and central appetite signalling in C57BL/6NRJ male mice fed ad-libitum chow diet. We assessed intestinal growth, L-cell density, and glucose-stimulated endocrine secretion, as well as circulating levels and gene expression of gut derived peptide hormones. Additionally, we quantified neuronal activity in the brainstem dorsal vagal complex following a fasting-refeeding intervention and examined the effects of PYY, CCK, ghrelin, and GLP-1 administration on food intake in sedentary and physically active mice. Depending on the dataset, unpaired or paired Student's t-tests, two-way ANOVA followed by Bonferroni's post hoc test, simple linear regression or a linear mixed-effects model were applied. Statistical significance was set at P < 0.05.
FINDINGS: Physical activity induced a slight growth of the small intestine, increased L-cell density, and enhanced glucose-stimulated GLP-1 secretion. It altered the circulating levels of PYY and ghrelin and increased the dynamic regulation of neuronal activity in the area postrema and nucleus tractus solitarius. Active mice displayed greater sensitivity to gut-derived hormones PYY, CCK, and ghrelin exerting amplified and prolonged effects on food intake, whereas native GLP-1 showed no effect, likely due to its short half-life. Physical activity prevented post-fasting hyperphagia, thereby promoting sustained maintenance of fasting-induced weight loss.
INTERPRETATION: The findings demonstrate that physical activity promotes adaptations in the gut and gut-to-brain communication possibly enhancing the responsiveness to appetite-regulating signals. Such adaptations may strengthen the alignment between energy intake and expenditure to support body weight maintenance.
FUNDING: This study was supported by Novo Nordisk Foundation (0059436) and Trygfonden Centre for Physical Activity Research (101390, 20045, 125132, and 177225). P.S. is supported by Lundbeck Foundation (R380-2021-1300).