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Liver and Muscle Contribute Differently to the Plasma Acylcarnitine Pool During Fasting and Exercise in Humans
G Xu1, J S Hansen1, X J Zhao1
1Key Laboratory of Separation Science for Analytical Chemistry (G.X., X.J.Z., X.L.W.), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China; Department of Clinical Biochemistry (J.S.H., P.P.), Rigshospitalet, Copenhagen, Denmark; The Centre of Inflammation and Metabolism and the Centre for Physical Activity Research (J.S.H., B.K.P., P.P.), Department of Infectious Diseases and CMRC, Rigshospitalet, Copenhagen, Denmark; Department of General Surgery and Laboratory of General Surgery (S.C.), Xinhua Hospital, affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China; Institute of Biliary Tract Diseases Research (S.C.), Shanghai Jiao Tong University School of Medicine, Shanghai, China; Division of Endocrinology (M.H., H.U.H., R.L., C.W.), Diabetology, Angiology, Nephrology, Pathobiochemistry and Clinical Chemistry, Department of Internal Medicine IV, University Tuebingen, Germany; Department of Hepatology (J.O.C.), Rigshospitalet, Copenhagen, Denmark; Department of Anaesthesiology (N.H.S.), The Copenhagen Muscle Research Centre, Rigshospitalet, Copenhagen, Denmark; Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Zentrum München at the University of Tuebingen (H.U.H., R.L., C.W.), Tuebingen, Germany; and German Center for Diabetes Research (H.U.H., R.L., C.W.), Germany.
Plasma acylcarnitine levels change with fasting and exercise. The liver releases short-chain acylcarnitines, while muscles release medium-chain acylcarnitines during exercise, contributing to systemic levels.
Area of Science:
- Metabolic Biochemistry
- Human Physiology
Background:
- Plasma acylcarnitine levels are influenced by physiological states like fasting and exercise.
- Elevated acylcarnitine levels are also observed in metabolic conditions such as insulin resistance and obesity.
Purpose of the Study:
- To investigate the specific contributions of the liver and skeletal muscle to plasma acylcarnitine levels.
- To understand these contributions during both fasting and acute exercise in humans.
Main Methods:
- Two studies involved young healthy males undergoing overnight fasting and acute exercise.
- Measurements included skeletal muscle biopsies and arterial-venous plasma differences in exercising/resting legs.
- Hepato-splanchnic bed flux was also assessed.
Main Results:
- During fasting, the liver released short-chain acylcarnitines (C2, C3), while legs took up free carnitine.
- Exercise increased liver release of C3-carnitine and leg uptake of free carnitine.
- Muscles released medium-chain acylcarnitines (C8-C12) during exercise, while the liver took up various medium- and long-chain acylcarnitines.
Conclusions:
- The liver significantly contributes to systemic short-chain acylcarnitines.
- Skeletal muscle releases medium-chain acylcarnitines during exercise.
- These findings highlight organ-specific roles in acylcarnitine metabolism and systemic level regulation.
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