Hormonal modulation of food intake in response to low leptin levels induced by hypergravity

A loss in fat mass is a common response to centrifugation and it results in low circulating leptin concentrations. However, rats adapted to hypergravi ty are euphagic. The focus of this study was to examine leptin and other pe ripheral signals of energy balance in the presence of a hypergravity-induce d loss of fat mass and euphagia. Male Sprague-Dawley rats were centrifuged for 14 days at gravity levels of 1.25, 1.5, or 2 G, or they remained statio nary at 1 G. Urinary catecholamines, urinary corticosterone, food intake, a nd body mass were measured on Days 11 to 14. Plasma hormones and epididymal fat pad mass were measured on Day 14. Mean body mass of the 1.26,1.5, and 2 G groups were significantly (P < 0.05) lower than controls, and no differ ences were found in food intake (g/day/100 g body mass) between the hypergr avity groups and controls. Epididymal fat mass was 14%,14%, and 21% lower t han controls in the 1.25, 1.5, and 2.0 G groups, respectively. Plasma lepti n was significantly reduced from controls by 46%, 45%, and 65% in the 1.25, 1.5, and 2 G groups, respectively. Plasma insulin was significantly tower i n the 1.25, 1.5, and 2.0 G groups than controls by 35%,38%, and 33%. No dif ferences were found between controls and hypergravity groups in urinary cor ticosterone. Mean urinary epinephrine was significantly higher in the 1.5 a nd 2.0 G groups than in controls. Mean urinary norepinephrine was significa ntly higher in the 1.25, 1.5 and 2.0 G groups than in controls. Significant correlations were found between G load and body mass, fat mass, leptin, ur inary epinephrine, and norepinephrine. During hypergravity exposure, mainte nance of food intake is the result of a complex relationship between multip le pathways, which abates the importance of leptin as a primary signal.