Branched-chain and aromatic amino acids, insulin resistance and liver specific ectopic fat storage in overweight to obese subjects

• In overweight individuals circulating branched-chain amino acids predict whole body- and hepatic insulin resistance.
• Dietary intake of amino acids has a minor effect on circulating amino acid concentrations.
• Plasma branched-chain amino acids concentration are related to organ-specific fat storage.

Background & aimsAmino acids may interfere with insulin action, particularly in obese individuals. We hypothesized that increased circulating branched-chain and aromatic amino acids herald insulin resistance and ectopic fat storage, particularly hepatic fat accumulation.Methods and resultsWe measured fasting branched-chain and aromatic amino acids (tryptophan, tyrosine, and phenylalanine) by mass spectrometry in 111 overweight to obese subjects. We applied abdominal magnetic resonance imaging and spectroscopy to assess adipose tissue distribution and ectopic fat storage, respectively. Plasma branched-chain amino acids concentrations were related to insulin sensitivity and intrahepatic fat independent from adiposity, age and gender, but not to abdominal adipose tissue or intramyocellular fat.ConclusionsIn weight stable overweight and obese individuals, branched-chain amino acid concentrations are specifically associated with hepatic fat storage and insulin resistance.