Oxytocin Signaling Regulates the Homeostatic Response to Cold Stress in Poikilothermic Vertebrates

Abstract

When exposed to low temperature, homeothermic vertebrates maintain internal body temperature by activating thermogenesis and by altered metabolism, synchronized by neuroendocrine responses. Although such physiological responses also occur in poikilothermic vertebrates, the prevailing notion is that their reactions are passive. Here, we explored molecular hypothalamic and physiological responses to cold stress in the tropical poikilotherm Nile tilapia (Oreochromis niloticus). We show that cold exposed tilapia exhibit complex homeostatic responses, including increased hypothalamic oxytocin, plasma glucose and cortisol concomitant with reduced plasma lactate and metabolic rate. Pharmacological or genetic blockage of oxytocin signaling further affected metabolic rate in two cold-exposed poikilothermic models. This indicates that oxytocin, a known thermoregulator in homeotherms, actively regulates temperature-related homeostasis in poikilotherms. Overall, our findings show that the brain of poikilotherms actively responds to cold temperature by regulating metabolic physiology. Moreover, we identify oxytocin signaling as an adaptive and evolutionarily conserved metabolic regulator of temperature-related homeostasis.

Taxonomy of introns, their evolution, and the role of minor introns in stress response

“…7) . While cold stress has previously been shown to result in alternative splicing and changes in gene expression (36, 63, 64), our data indicates that it disproportionally affects the splicing of minor introns and expression of MIGs. The mechanism by which this specificity is achieved remains elusive and warrants further research.…”

“…Endotherms respond to environmental shifts in temperature by internally maintaining their core body temperature, while ectotherms such as fish and plants are susceptible to shifts in temperature. To test whether minor intron splicing is affected by environmental stresses such as cold exposure, we exposed the tropical poikilotherm Nile tilapia ( Oreochromis niloticus ) to acute cold stress by reducing the water temperature from 25°C to 14°C, at a rate of −1°C/h (36). RNAseq of the hypothalamus, a crucial thermoregulation center in the brain, revealed that over 20% of all minor introns were mis-spliced upon cold exposure, while only a small number of minor-like, hybrid and major-like introns were affected (Fig.…”

Cell-based homologous expression system for in-vitro characterization of environmental effects on transmembrane peptide transport in fish

“…Although capacity is reduced at low temperatures, the integrity of the Mozambique tilapia PepT2 activity is maintained. It had been shown that tilapia actively lowering their metabolism levels in response to cold challenges ( Segev-Hadar et al, 2021 ). Our results indicate that peptide transport at low temperature is feasible and can continuously supply nutrients to support metabolic function.…”