Feeding and light cycle disruptions have distinct effects on energy balance and neuroendocrine regulators in goldfish

The synchronization of biological rhythms to environmental cues is essential for maintaining temporal homeostasis. However, the specific neuroendocrine and metabolic effects of circadian misalignment in fish remain poorly understood. This study investigated the effects of chronodisruption on energy homeostasis in goldfish (Carassius auratus). Fish were exposed for 53 days to three conditions: Control (12L:12D photoperiod, feeding at ZT 1); Random Feeding (RF; 12L:12D, feeding at random times) and continuous light (LL, feeding at ZT 1). Feed intake, metabolic rate, and locomotor activity were monitored as indicators of energy input and expenditure. Biometric indices (weight and length gain, growth, nutritional and hepatosomatic indices) were calculated. The expression of feeding and growth regulating genes was also analyzed in hypothalamus (hcrt, npy, crh, pomca, cartpt1, and cartpt2), telencephalon (cnr1), liver (igf1, and lepa1), and intestine (cck1 and ghrl). Plasma and liver metabolites (triglycerides, glycogen, lactate, and glucose) and plasma cortisol levels were analyzed to assess metabolic and stress responses. Both RF and LL groups showed elevated metabolic rate and feed intake, accompanied by changes in the expression of feeding regulators that favored orexigenic signals. However, only RF fish showed increased growth, weight, hepatosomatic index, and plasma glucose, suggesting a positive energy balance. LL fish showed growth similar to controls, likely due to a greater increase in energy expenditure. Overall, our results show that disruption of temporal feeding or light cues alters energy balance, with different physiological outcomes depending on the type of disruption. This study highlights the critical role of circadian alignment in maintaining energy homeostasis in goldfish.