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Am J Physiol Endocrinol Metab. 2015 Aug 15;309(4):E311-9. doi: 10.1152/ajpendo.00161.2015. Epub 2015 Jun 9.

Cross-talk between branched-chain amino acids and hepatic mitochondria is compromised in nonalcoholic fatty liver disease.

Author information

1
Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, and nishanth.sunny@medicine.ufl.edu.
2
Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, and.
3
Department of Pathology, University of Florida, Gainesville, Florida;
4
Department of Integrative Biology, University of California, Berkeley, California.
5
Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, and Division of Endocrinology, Diabetes, and Metabolism, Malcom Randall Veterans Administration Medical Center (VAMC), Gainesville, Florida; Division of Diabetes, University of Texas Health Science Center at San Antonio, and Division of Diabetes, Audie L. Murphy VAMC, San Antonio, Texas; and.

Abstract

Elevated plasma branched-chain amino acids (BCAA) in the setting of insulin resistance have been relevant in predicting type 2 diabetes mellitus (T2DM) onset, but their role in the etiology of hepatic insulin resistance remains uncertain. We determined the link between BCAA and dysfunctional hepatic tricarboxylic acid (TCA) cycle, which is a central feature of hepatic insulin resistance and nonalcoholic fatty liver disease (NAFLD). Plasma metabolites under basal fasting and euglycemic hyperinsulinemic clamps (insulin stimulation) were measured in 94 human subjects with varying degrees of insulin sensitivity to identify their relationships with insulin resistance. Furthermore, the impact of elevated BCAA on hepatic TCA cycle was determined in a diet-induced mouse model of NAFLD, utilizing targeted metabolomics and nuclear magnetic resonance (NMR)-based metabolic flux analysis. Insulin stimulation revealed robust relationships between human plasma BCAA and indices of insulin resistance, indicating chronic metabolic overload from BCAA. Human plasma BCAA and long-chain acylcarnitines also showed a positive correlation, suggesting modulation of mitochondrial metabolism by BCAA. Concurrently, mice with NAFLD failed to optimally induce hepatic mTORC1, plasma ketones, and hepatic long-chain acylcarnitines, following acute elevation of plasma BCAA. Furthermore, elevated BCAA failed to induce multiple fluxes through hepatic TCA cycle in mice with NAFLD. Our data suggest that BCAA are essential to mediate efficient channeling of carbon substrates for oxidation through mitochondrial TCA cycle. Impairment of BCAA-mediated upregulation of the TCA cycle could be a significant contributor to mitochondrial dysfunction in NAFLD.

KEYWORDS:

branched chain amino acids; insulin resistance; mitochondrial metabolism; nonalcoholic fatty liver disease

PMID:
26058864
PMCID:
PMC4537921
DOI:
10.1152/ajpendo.00161.2015
[Indexed for MEDLINE]
Free PMC Article

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