Global Analysis of Plasma Lipids Identifies Liver-Derived Acylcarnitines as a Fuel Source for Brown Fat Thermogenesis

• DOI: 10.1016/j.cmet.2017.08.006
• Publication Date: 2017-09-05T16:02:26Z
• Authors: Judith Simcox; Gisela Geoghegan; John Alan Maschek; Claire L. Bensard; Marzia Pasquali; Ren Miao; Sanghoon Lee; Lei Jiang; Ian Huck; Erin E. Kershaw; Anthony J. Donato; Udayan Apte; Nicola Longo; Jared Rutter; Renate Schreiber; Rudolf Zechner; James Cox; Claudio J. Villan...
• Keywords: Aging; Time Factors; Carnitine O-Palmitoyltransferase; Lipolysis; Citric Acid Cycle; Fatty Acids; Thermogenesis; Lipids; Body Temperature; 3. Good health; Cold Temperature; Mice; Phenotype; Adipose Tissue, Brown; Gene Expression Regulation; Hepatocyte Nuclear Factor 4; Liver; Carnitine; Gene Knockdown Techniques; Animals

Cold-induced thermogenesis is an energy-demanding process that protects endotherms against a reduction in ambient temperature. Using non-targeted liquid chromatography-mass spectrometry-based lipidomics, we identified elevated levels of plasma acylcarnitines in response to the cold. We found that the liver undergoes a metabolic switch to provide fuel for brown fat thermogenesis by producing acylcarnitines. Cold stimulates white adipocytes to release free fatty acids that activate the nuclear receptor HNF4α, which is required for acylcarnitine production in the liver and adaptive thermogenesis. Once in circulation, acylcarnitines are transported to brown adipose tissue, while uptake into white adipose tissue and liver is blocked. Finally, a bolus of L-carnitine or palmitoylcarnitine rescues the cold sensitivity seen with aging. Our data highlight an elegant mechanism whereby white adipose tissue provides long-chain fatty acids for hepatic carnitilation to generate plasma acylcarnitines as a fuel source for peripheral tissues in mice.