GHS-R in brown fat potentiates differential thermogenic responses under metabolic and thermal stresses

PLoS One. 2021 Apr 1;16(4):e0249420. doi: 10.1371/journal.pone.0249420. eCollection 2021.

Abstract

In response to cold or diet, fatty acids are dissipated into heat through uncoupling protein 1 (UCP1) in brown adipose tissue (BAT). This process is termed non-shivering thermogenesis, which is important for body temperature maintenance and contributes to obesity pathogenesis. Thermogenic enhancement has been considered a promising anti-obesity strategy. Ghrelin and its receptor Growth Hormone Secretagogue Receptor (GHS-R) have critical roles in energy intake, nutrient sensing, and lipid metabolism. We previously reported that global Ghsr-knockout mice have increased energy expenditure due to enhanced thermogenesis. To determine the site of action for GHS-R mediated thermogenesis, we generated brown adipocyte-specific Ghsr knockout mice (UCP1-CreER/Ghsrf/f) and assessed thermogenic responses under regular diet (RD) fed homeostatic metabolic state or high-fat diet (HFD) fed metabolically-impaired obese state, under normal or cold housing environment. Under a RD-feeding, UCP1-CreER/Ghsrf/f mice showed increased body fat and a slightly elevated core body temperature under cold but not under normal temperature. Consistently, the expression of thermogenic genes in BAT of RD-fed UCP1-CreER/Ghsrf/f mice was increased in reposes to cold. Under HFD feeding, HFD-fed UCP1-CreER/Ghsrf/f mice showed no difference in body fat or body temperature under either normal or cold exposure. Interestingly, the expression of thermogenic genes in BAT of HFD-fed UCP1-CreER/Ghsrf/f mice was upregulated under normal temperature but downregulated under cold exposure. Overall, our data show that GHS-R has cell-autonomous effect in brown adipocytes, and GHS-R regulates BAT thermogenic activity in a temperature- and metabolic state-dependent manner. The thermogenic effect of GHS-R in BAT is more pronounced in cold environment and differentially variable based on metabolic state; under cold exposure, GHS-R inhibition in BAT activates thermogenesis under homeostatic state but suppresses thermogenesis under obese state. Our finding collectively suggests that GHS-R in BAT, acting as a "metabolic thermostat", differentially regulates thermogenesis in response to different metabolic and thermal stimuli.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adipose Tissue, Brown / metabolism*
  • Animals
  • Body Weight
  • Cold Temperature
  • Diet, High-Fat
  • Mice
  • Mice, Knockout
  • Receptors, Adrenergic, beta-3 / genetics
  • Receptors, Adrenergic, beta-3 / metabolism
  • Receptors, Ghrelin / deficiency
  • Receptors, Ghrelin / genetics*
  • Thermogenesis / physiology*
  • Transcriptome

Substances

  • Adrb3 protein, mouse
  • Receptors, Adrenergic, beta-3
  • Receptors, Ghrelin