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White adipose tissue (WAT) is a complex and dynamic endocrine organ that is most commonly recognized for its energy storage capacity. Brown adipose tissue (BAT) functions to dissipate stored energy in the form of heat through a process known as nonshivering thermogenesis. This process is aided by the mitochondrial matrix protein, uncoupling protein 1 (UCP1), which creates a proton leak across the inner mitochondrial membrane causing chemical energy to be released as heat. More recently, clusters of brown-like or “beige” adipocytes have also been identified in WAT. These adipocytes have the capacity to interconvert between the two phenotypes, in part, through increasing their expression of UCP1. This “beiging” is dependent on environmental and chemical conditions present within the cell. Growth hormone (GH), a protein secreted from the anterior pituitary, has been positively correlated with increased BAT mass. However, this evidence is controversial, and the effects of GH on BAT and WAT beiging are not well defined. Bovine growth hormone transgenic (bGH) mice have increased GH action, are giant and lean, yet develop insulin resistance and have shortened lifespans compared to their wild-type (WT) littermates. The purpose of the current study was to compare the expression of beiging-associated factors at both the RNA and protein levels in bGH mice and WT littermate controls. To accomplish this, several different methods were used to measure expression of beiging-associated gene expression in the WAT and BAT depots of these mice. A previously collected RNA-Seq dataset revealed significant genotype and depot differences, with the greatest number of expression changes detected between genotype in the subcutaneous depot and between depot in the bGH mice. Additionally, qPCR, Western blot analysis, and immunohistochemistry with confocal imaging revealed that UCP1 RNA and protein expression were undetectable in the WAT depots of these mice. No significant differences in UCP1 expression were observed between genotype or age in BAT depots. Basal oxygen consumption rate (OCR) in subcutaneous WAT, but not BAT, exhibited a significant effect of genotype and age. Our results indicate that, at a basal level, GH may affect the expression of certain beiging-associated genes and OCR in a depot-dependent manner, but does not appear to have a direct effect on UCP1 expression. |
