Adaptive Thermogenesis and Lipid Metabolism Modulation in Inguinal and Perirenal Adipose Tissues of Hezuo Pigs in Response to Low-Temperature Exposure

In mammals, exposure to low temperatures induces white adipose tissue (WAT) browning and alters lipid metabolism to promote thermogenesis, thereby maintaining body temperature. However, this response varies across different adipose depots. In this study, <i>Hezuo pigs</i> were exposed to either room temperature (23 ± 2 °C) or low temperature (-15 ± 2 °C) for periods of 12 h, 24 h, 48 h, 5 d, 10 d, and 15 d. Inguinal fat (IF) and perirenal fat (PF) were collected and analyzed using hematoxylin and eosin (HE) staining, transmission electron microscopy, RT-qPCR, and RNA-seq. Following cryoexposure, our results demonstrated a significant increase in adipocyte number and a corresponding decrease in cross-sectional area in both IF and PF groups from 24 h to 10 d. While adipocyte numbers were elevated at 12 h and 15 d, these changes were not statistically significant. Moreover, lipid droplets and mitochondria were more abundant, and the mRNA expression levels of thermogenic genes <i>UCP3</i> and <i>PGC-1α</i> were significantly higher compared to the control group during the 24 h-10 d cold exposure period. No significant changes were observed in the other groups. RNA-seq data indicated that the lipid metabolism of IF and PF peaked on day 5 of low-temperature treatment. In IF tissue, lipid metabolism is mainly regulated by genes such as <i>FABP4</i>, <i>WNT10B</i>, <i>PCK1</i>, <i>PLIN1</i>, <i>LEPR</i>, and <i>ADIPOQ</i>. These genes are involved in the classical lipid metabolism pathway and provide energy for cold adaptation. In contrast, in PF tissue, genes like <i>ATP5F1A</i>, <i>ATP5PO</i>, <i>SDHB</i>, <i>NDUFS8</i>, <i>SDHA</i>, and <i>COX5A</i> play roles within the neurodegenerative disease pathway, and PF tissue has a positive impact on the process related to degenerative diseases. Further investigation is needed to clarify the functions of these candidate genes in lipid metabolism in <i>Hezuo pigs</i> and to explore the genetic mechanisms underlying the cold-resistance traits in local pig populations.