Brown adipose tissue regulates glucose homeostasis and insulin sensitivity

TLDR

Brown adipose tissue dissipates chemical energy and modulates energy balance. The study tests whether BAT regulates glucose homeostasis by transplanting BAT from male donor mice into age‑ and sex‑matched recipients. BAT was transplanted into the visceral cavity of recipient mice. BAT transplantation improved glucose tolerance, insulin sensitivity, reduced body weight and fat mass, reversed high‑fat diet–induced insulin resistance, increased insulin‑stimulated glucose uptake in BAT, white adipose tissue, and heart but not skeletal muscle, and these effects required BAT‑derived IL‑6.

Abstract

Brown adipose tissue (BAT) is known to function in the dissipation of chemical energy in response to cold or excess feeding, and also has the capacity to modulate energy balance. To test the hypothesis that BAT is fundamental to the regulation of glucose homeostasis, we transplanted BAT from male donor mice into the visceral cavity of age- and sex-matched recipient mice. By 8–12 weeks following transplantation, recipient mice had improved glucose tolerance, increased insulin sensitivity, lower body weight, decreased fat mass, and a complete reversal of high-fat diet–induced insulin resistance. Increasing the quantity of BAT transplanted into recipient mice further improved the metabolic effects of transplantation. BAT transplantation increased insulin-stimulated glucose uptake in vivo into endogenous BAT, white adipose tissue (WAT), and heart muscle but, surprisingly, not skeletal muscle. The improved metabolic profile was lost when the BAT used for transplantation was obtained from Il6–knockout mice, demonstrating that BAT-derived IL-6 is required for the profound effects of BAT transplantation on glucose homeostasis and insulin sensitivity. These findings reveal a previously under-appreciated role for BAT in glucose metabolism.