In the presence of dietary lipids, both apolipoprotein A-IV (ApoA-IV) production and brown adipose tissue (BAT) thermogenesis are increased. The effect of dietary lipid-induced AproA-IV on BAT thermogenesis and energy expenditure remains unknown. In the present study, we hypothesized that ApoA-IV knockout (ApoA-IV-KO) mice exhibited decreased BAT thermogenesis to affect energy homeostasis. To test this hypothesis, BAT thermogenesis in wildtype (WT) and ApoA-IV-KO mice fed either a standard low-fat chow diet or a high-fat diet (HFD) was investigated. When fed a chow diet, energy expenditure and food intake were comparable between WT and ApoA-IV-KO mice. After 1 week of HFD consumption, ApoA-IV-KO mice had comparable energy intake but produced lower energy expenditure relative to their WT controls in the dark phase. After an acute feeding of dietary lipids or 1-week HFD feeding, ApoA-IV-KO mice produced lower levels of uncoupling protein 1 (UCP1) and exhibited reduced expression of thermogenic genes in the BAT compared with WT controls. In response to cold exposure, however, ApoA-IV-KO mice had comparable energy expenditure and BAT temperature relative to WT mice. Thus, ApoA-IV-KO mice exhibited reduced diet-induced BAT thermogenesis and energy expenditure.
Keywords: brown adipose tissue; cold exposure; dietary lipids; energy homeostasis; food intake; high-fat diet; tyrosine hydroxylase; uncoupling protein 1; white adipose tissue.