Research reportThe different satiating capacity of CHO and fats can be mediated by different effects on leptin and ghrelin systems

Leptin and ghrelin are known to be the main hormones involved in the control of food intake, with opposite effects. Here we aimed to assess whether changes in leptin and ghrelin systems can be involved in the different satiating capacities of carbohydrates (CHO) and fat. Adult male Wistar rats were studied under 24 h fasting conditions and after 24 h fasting followed by a 12 h re-feeding period with 64 kcal of CHO or fat, consisting of a mixture of wheat starch and sucrose or bacon, respectively. Serum levels of leptin and ghrelin, and mRNA levels of leptin and ObRb in the retroperitoneal and inguinal adipose tissue and of NPY, POMC, ObRb and GSHR in the hypothalamus were measured. CHO re-feeding resulted in higher leptin mRNA expression levels in the retroperitoneal adipose tissue and in higher circulating leptin levels compared with those after fat re-feeding. Moreover, circulating ghrelin levels and ghrelin/leptin ratio were significantly higher after fat re-feeding compared with CHO re-feeding, and hypothalamic expression levels of ghrelin receptor increased after fat, but not after CHO, re-feeding. Hence, expression levels of hypothalamic neuropeptides involved in food intake control and regulated by these hormones, particularly the orexigenic NPY and the anorexigenic pro-opiomelanocortin (POMC)-derived α-melanocyte-stimulating hormone, were also differently affected by CHO and fat re-feeding, resulting in a significantly lower NPY/POMC ratio after CHO re-feeding than after fat re-feeding. In conclusion, different effects on the leptin and ghrelin systems can account, at least in part, for the lower satiating capacity of fat compared to CHO.