Associations of serum amino acids with insulin resistance among people with and without overweight or obesity: A prospective study in Japan

Abstract

Background & aims: Limited evidence exists regarding the prospective associations between amino acids and insulin resistance. In addition, amino acids have been suggested to promote insulin resistance with the requirement of obesity in animal studies, but the interaction between amino acids and obesity on the development of insulin resistance has not been examined in epidemiological studies. We aimed to investigate the differences in the prospective associations of serum amino acids with insulin resistance among adults with and without overweight or obesity.

Methods: Fasting serum concentrations of 25 amino acids were quantified in 1131 non-diabetic Japanese workers aged 22-71 years at baseline. The homeostasis model assessment of insulin resistance (HOMA-IR) was estimated at baseline and the 3-year follow-up. Generalized linear models were used to assess the associations between amino acids at baseline and HOMA-IR at follow-up with adjustment for potential confounding factors. A Bonferroni-corrected threshold of p = 0.001 was considered significant for multiple tests.

Results: The associations for the following amino acids with HOMA-IR at the 3-year follow-up significantly varied by obesity status: isoleucine, valine, tyrosine, alanine, and methionine (all p for interaction <0.05). Higher concentrations of serum isoleucine, valine, tyrosine, and alanine (per 1SD) were significantly associated with higher HOMA-IR levels in overweight/obese participants (multivariable-adjusted β coefficients ranging from 0.09 to 0.12; all p < 0.001), but no association was observed in the underweight/normal-weight participants. The associations for serum methionine were direct among overweight/obese participants, but inverse among underweight/normal-weight participants (all p < 0.001).

Conclusions: This study demonstrated the prospective associations of different individual serum amino acids with insulin resistance, with most pronounced associations being for overweight/obese adults. Our findings support the possibility of heterogeneous effects of individual amino acids, as well as their interplay with obesity in the progression of insulin resistance.

Keywords: Amino acids; Insulin resistance; Obesity; Prospective study.