Low Energy Diet-induced and Bariatric Surgery-induced Weight Loss Decreases Branched-chain and Aromatic Amino Acids in Plasma and Tissue (P21-078-19)

Abstract

Abstract Objectives Plasma levels of branched-chain amino acids (BCAA) and aromatic amino acids (AAA) phenylalanine (phe) and tyrosine (tyr) have been associated with obesity, insulin resistance and risk of type 2 diabetes. This study aimed to investigate the response of circulating plasma and tissue levels of BCAA and AAA to weight loss, and to correlate the level of these metabolites in plasma and tissue in obese women. Methods 28 obese (mean BMI 46.2 kg/m2) women underwent low energy diet (LED)-induced weight loss (−9.2 ± 4.2 kg) followed by bariatric surgery-induced weight loss (−23.6 ± 2.5 kg). Plasma at baseline (t0), post-LED/pre-surgery (t1) and 6-month post-surgery (t2) as well as biopsies of subcutaneous abdomen adipose tissue (SAfat), superficial thigh adipose tissue (Tfat) and vastus lateralis thigh muscle (Tmuscle) at both t1 and t2 were collected, and profiled using mass spectrometry-based metabolomics approach. Paired t-tests were applied to assess between-timepoint differences, and Pearson correlation used to calculate correlation coefficient of metabolite levels between plasma and tissue. Results Plasma BCAA and AAA were all significantly reduced post-LED at t1 (fold-change of 0.76–0.85 for val, leu, ile, tyr and phe, P < 0.05) and 6-month post-surgery at t2 (fold-change of 0.74–0.85 for val, leu, ile, tyr and phe, P < 0.05) as compared to baseline t0; but not significant between t1 and t2, although trends of decrease were observed. Among the 3 tissue biopsies, only SAfat showed significantly decreased levels of tyr, leu and ile at t2 compared to t1 (fold-change for tyr 0.63, leu 0.66, ile 0.68, P < 0.05). In addition, plasma levels of val and ile were correlated with Tfat levels at both t1 and t2 (r2 = 0.47–0.57), and that of val, ile and leu were correlated with Tmuscle at t1 only (r2 = 0.64–0.67). Conclusions Circulating levels of BCAA and AAA were decreased by weight loss interventions. The decrease following an LED program was sustained after bariatric surgery without further significant decrease. Bariatric surgery also decreased BCAA levels in SAfat; moreover, our data suggested that plasma BCAA levels correlated well with peripheral tissue Tfat and Tmuscle. Funding Sources The New Zealand National Science Challenge High-Value Nutrition program.