Regulation of adipose branched-chain amino acid catabolism enzyme expression and cross-adipose amino acid flux in human obesity

American Journal of Physiology - Endocrinology and Metabolism - Tập 304 Số 11 - Trang E1175-E1187 - 2013
Denise E. Lackey1, Christopher J. Lynch2, Kristine C. Olson2, Rouzbeh Mostaedi3, Mohamed Ali3, William H. Smith3, Fredrik Karpe4, Sandy M. Humphreys4, Daniel Bedinger5,6, Tamara N. Dunn7, Anthony P. Thomas7, Pieter J. Oort1, Dorothy A. Kieffer7, Rajesh Amin8, Ahmed Bettaieb7, Fawaz G. Haj7, Paska A. Permana9, Tracy G. Anthony10, Sean H. Adams7,5,1
1Obesity & Metabolism Research Unit, United States Department of Agriculture-Agricultural Research Service Western Human Nutrition Research Center, Davis, California;
2Cellular & Molecular Physiology Department, The Pennsylvania State University, Hershey, Pennsylvania;
3Department of Surgery, University of California Davis School of Medicine, Davis, California;
4Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford and NIHR Oxford Biomedical Research Centre, Oxford University Hospitals Trust, Oxford, United Kingdom;
5Molecular, Cellular & Integrative Physiology Graduate Group, University of California, Davis, Davis, California;
6XOMA, Berkeley, California;
7Graduate Group in Nutritional Biology & Department of Nutrition, University of California, Davis, Davis, California;
8Department of Pharmacal Sciences, Auburn State University, Auburn, Alabam;
9Phoenix Veterans Affairs Health System, Phoenix, Arizona;
10Department of Nutritional Sciences, Rutgers University, Rutgers, New Jersey

Tóm tắt

Elevated blood branched-chain amino acids (BCAA) are often associated with insulin resistance and type 2 diabetes, which might result from a reduced cellular utilization and/or incomplete BCAA oxidation. White adipose tissue (WAT) has become appreciated as a potential player in whole body BCAA metabolism. We tested if expression of the mitochondrial BCAA oxidation checkpoint, branched-chain α-ketoacid dehydrogenase (BCKD) complex, is reduced in obese WAT and regulated by metabolic signals. WAT BCKD protein (E1α subunit) was significantly reduced by 35–50% in various obesity models ( fa/fa rats, db/db mice, diet-induced obese mice), and BCKD component transcripts significantly lower in subcutaneous (SC) adipocytes from obese vs. lean Pima Indians. Treatment of 3T3-L1 adipocytes or mice with peroxisome proliferator-activated receptor-γ agonists increased WAT BCAA catabolism enzyme mRNAs, whereas the nonmetabolizable glucose analog 2-deoxy-d-glucose had the opposite effect. The results support the hypothesis that suboptimal insulin action and/or perturbed metabolic signals in WAT, as would be seen with insulin resistance/type 2 diabetes, could impair WAT BCAA utilization. However, cross-tissue flux studies comparing lean vs. insulin-sensitive or insulin-resistant obese subjects revealed an unexpected negligible uptake of BCAA from human abdominal SC WAT. This suggests that SC WAT may not be an important contributor to blood BCAA phenotypes associated with insulin resistance in the overnight-fasted state. mRNA abundances for BCAA catabolic enzymes were markedly reduced in omental (but not SC) WAT of obese persons with metabolic syndrome compared with weight-matched healthy obese subjects, raising the possibility that visceral WAT contributes to the BCAA metabolic phenotype of metabolically compromised individuals.

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American Journal of Physiology - Endocrinology and Metabolism

Tập 304 Số 11

E1175-E1187

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