Effects of short-term exercise on food intake and the expression of appetite-regulating factors in goldfish.

In mammals, growing evidence indicates that exercise affects food intake, metabolism and the expression and blood levels of appetite regulators. In this study, we examined the effects of short-term (30 min, at low and high water flow) exercise on food intake, glucose levels and the expressions of appetite regulators in goldfish hypothalamus (irisin, orexin, CART, leptin), intestine (CCK, PYY, proglucagon/GLP-1), muscle (irisin) and liver (leptin), of brain-derived neurotrophic factor (BDNF) in brain, interleukin-6 (IL6) in muscle and hypothalamus, and major metabolic enzymes, the glycolytic enzyme glucokinase (GCK) and its regulatory protein (GCKR) in liver, the lipolytic enzyme lipoprotein lipase in intestine and muscle, and trypsin in intestine. Fish submitted to high flow exercise had a lower post-exercise food intake compared to control fish but no differences were seen in glucose levels between groups. Exercise induced an increase in hypothalamic expression levels of CART, IL6 and BDNF, but not orexin, irisin, CRF, leptin and NPY. High flow exercise induced an increase in intestine CCK, PYY and GLP-1, and muscle irisin and IL-6 expression levels. Exercise had no effects on expression levels of hepatic leptin or any of the metabolic enzymes examined. Our results suggest that, in goldfish, short-term exercise might decrease feeding in part by affecting the expressions of myokines and peripheral, but not central appetite regulators or metabolic enzyme/hormones.

Effects of potential climate change -induced environmental modifications on food intake and the expression of appetite regulators in goldfish.

Climate changes due to global warming result in part from the release of gases such as carbon dioxide (CO2) and methane into the atmosphere and results in warming and acidification of water bodies, and changes precipitation and wind patterns, which might in turn affect water currents, turbulence and turbidity. These changes might affect feeding and its endocrine control. Feeding is regulated by central and peripheral hormones that either stimulate (e.g. orexin, ghrelin) or inhibit (e.g. irisin, cocaine and amphetamine regulated transcript - CART, cholecystokinin - CCK and peptide YY -PYY) food intake. In this study we examined the effects of four climate change-related environmental factors (i.e. temperature, pH, turbulence and turbidity) on food intake and the hypothalamic and intestinal expressions of appetite regulators in fish, using goldfish as a model. High temperatures increased food intake and the brain expression of orexin, and decrease brain CART 1 and intestinal CCK, PYY and ghrelin. Low pHs decreased feeding and increased the expressions of CART1 and CART2 in the hypothalamus and CCK and PYY in the intestine. Turbulence (waves) induced an increase in food intake and a decrease in mRNA expression levels of both CART1 and CART2 in the hypothalamus and both CCK and PYY in the intestine. Turbidity (low visibility) did not affect food intake but increased locomotion and the time taken to reach satiation, while increasing brain orexin and intestinal PYY expression levels and lowering CART1 hypothalamic expression. The results of this study suggest that environmental stress affects feeding physiology of goldfish and bring new insights on how fish might respond to climate changes.