LAUSR

Long chain acyl-CoA synthetases (ACSLs) convert fatty acids (FA) to fatty acyl-CoAs that are utilized for various cellular processes, including triglyceride synthesis, activation of transcription factors, signal transduction, and providing energy sources via oxidation. Among 5 isotypes (ACSL1, 3, 4, 5, and 6), ACSL1 is the predominant isotype in adipocytes, and it is known to play important roles in adipocyte physiology, including FA uptake, triglyceride (TG) synthesis, thermogenesis, and FA oxidation. However, the roles of ACSL1 in brown adipocyte differentiation is incompletely understood. During the in vitro differentiation of brown adipocytes from stromal vascular cells (SVC), mRNA expression of ACSL1 was drastically increased. Pharmacological inhibition of ACSLs by triacsin C suppressed the differentiation of brown adipocytes. Interestingly, triacsin C inhibited the expression of uncoupled protein 1 (UCP1), which plays the major role in thermogenesis in mitochondria. Thus, we hypothesize that ACSL1 regulates thermogenesis and energy utilization by regulation of brown adipocyte differentiation. To examine the role of ACSL1 in brown adipose tissue (BAT), we generated BAT specific ACSL1 knockout mice by breeding UCP1-Cre with ACSL1 flox/flox mice (ACSL1 BATKO ). ACSL1 deficiency in BAT reduced the weight gain and glucose intolerance in high fat diet (HFD)-fed mice. ACSL1 BATKO mice were severely cold intolerant. Furthermore, ACSL1 BATKO mice were resistant to beta 3-agonist (CL-316243)-stimulated weight loss. Fat mass in HFD-fed ACSL1 BATKO was lower than HFD-fed wild type mice. These data suggest that ACSL1 in BAT contributes to BAT differentiation, which causes the impairment of FA utilization. However, the mechanisms by which deficiency of ACSL1 in BAT reduces HFD-induced weight gain need to be further investigated. Disclosure G. Ren: None. J. Kim: None. Funding National Institutes of Health (R01HL128695R03AG058078)