DICER is downregulated in mouse adipose tissue during high-fat diet feeding
The adipose tissue plays an important role in controlling whole-body energy balance, and proper regulation of adipose tissue function is essential for metabolic health. In response to energy surplus, the adipose tissue needs to expand, which may lead to local areas of hypoxia within the tissue. This is thought to promote whole-body insulin resistance. Here we report that DICER, a key enzyme in the maturation of miRNAs and a potential marker of adipocyte health, is profoundly downregulated in mouse adipose tissue within the first week of high-fat diet (HFD) feeding, and this effect is sustained in response to long-term HFD feeding. The downregulation of DICER protein occurs in both mature adipocytes and in the stromal vascular cells. Mechanistically, we provide evidence that hypoxia and hypoxia-inducible factor 1-a (HIF1a) facilitate ubiquitination of DICER to target it for autophagy-mediated degradation, and we show that DICER and HIF1a interact in adipose tissue after HFD feeding, which may signal for DICER degradation. Finally, despite reductions in DICER protein, we were not able to detect any differences in global miRNA levels in subcutaneous adipose tissue of mice after one or three weeks of HFD-feeding. In conclusion, the nutritional challenge of HFD feeding in mice leads to a large reduction in adipose tissue DICER protein, which is induced by hypoxia during tissue expansion and mediated through an interaction with HIF1a. Overall design: miRNA sequencing of subcutaneous adipose tissue from mice having been on either a control diet or a high-fat diet for 1 day, 1 week or 3 weeks.