Mechanisms of Low Temperature-induced GH Resistance via TRPA1 Channel Activation in Male Nile Tilapia.

Abstract

Low temperatures significantly impact growth in ectothermic vertebrates, though the underlying mechanisms remain poorly understood. This study investigates the role of transient receptor potential ankyrin 1 (TRPA1) channels in mediating low-temperature effects on growth performance and GH resistance in Nile tilapia (Oreochromis niloticus). Prolonged exposure to low temperature (16 °C for 35 days) impaired growth performance and induced GH resistance, characterized by elevated serum GH levels and decreased IGF-1 levels. Molecular analysis revealed tissue-specific upregulation of TRPA1 expression in the pituitary and liver under low-temperature conditions, concurrent with alterations in GH/IGF-1 axis-related gene expression. Pharmacological modulation of TRPA1 using an agonist mimicked low-temperature effects on the GH/IGF-1 axis, while an antagonist reversed cold-induced hormonal changes. In vitro experiments with tilapia hepatocytes demonstrated that TRPA1 activation decreased IGF-1 expression through calcium ion/calmodulin-dependent pathways and disrupted GH-induced JAK2/STAT5 signaling. Additionally, TRPA1 activation induced GH receptor degradation primarily through lysosomal pathways, with partial involvement of proteasomal mechanisms. This study is the first to reveal that TRPA1 channels play a crucial role in mediating the effects of low temperature on GH resistance in fish, providing new insights into temperature regulation of endocrine function. The evolutionary conservation of TRPA1 and the GH/IGF-1 axis suggests potential relevance to stress-induced endocrine dysfunction in other vertebrates, including mammals.