From selection signatures in cattle to functional validation in mice: HSPA12B negatively regulates adipose browning and thermogenesis.

Local cattle breeds have been domesticated and adapted to various climatic environments through natural and artificial selection. However, the molecular mechanisms underlying cold adaptation remain unknown. Adipose tissue browning may play a crucial role in this adaptation. Our analysis of 777K SNP genotyping data from 25 local Chinese cattle breeds revealed that the HSPA12B (heat shock protein A12B) gene underwent positive selection in Chinese northern cold-adapted breeds and Tibetan Plateau breeds. The results of the Western blot experiment showed that HSPA12B was highly expressed in adipose tissues of cattle and mice, with a relatively high expression level in the interscapular brown adipose tissue (iBAT) of mice. Following cold induction, the expression of HSPA12B was upregulated in both the iBAT and subcutaneous white adipose tissue (sWAT) of mice. We generated a Hspa12b knockout mouse model, and qRT-PCR data analysis showed that the deletion of Hspa12b promoted adipose browning thermogenesis by increasing the expression of Elovl3 and Ucp1 (P＜0.05) at low temperature. Protein-protein interaction prediction results showed that interactions exist between HSPA12B and ELOVL3 in both mice and cattle. Furthermore, glucose and insulin tolerance testing experiments showed that the deletion of Hspa12b promoted glucose metabolism and insulin sensitivity (P＜0.05) in mice. Taken together, our results provide compelling evidence that HSPA12B acts as a negative regulator of adipose tissue browning and thermogenesis, and this regulatory effect is mediated through the modulation of ELOVL3 expression. Moreover, HSPA12B is activated by low temperatures, which acts as a homeostatic mechanism to prevent excessive browning of fat and to maintain body temperature. These findings offer new insights into the molecular mechanisms of cold adaptation in animals and may serve as a potential therapeutic target for human obesity and diabetes.