The Impact of Bariatric Surgery on Glutathione Synthesis in Individuals with Severe Obesity

Abstract

Glycine is deficient in individuals with obesity but improves following bariatric surgery. Glycine deficiency could impair glutathione (GSH) synthesis and worsen oxidative stress. We examined the impact of obesity-associated glycine deficiency and bariatric surgery on GSH synthesis. Twenty-one participants with severe obesity and twenty-one healthy weight controls were recruited. [1,2-¹³C₂] glycine was infused to measure the erythrocyte (RBC) GSH synthesis rate. Participants with obesity underwent bariatric surgery, and 19 were restudied six months post-surgery. Compared to healthy weight controls, individuals with obesity had significantly lower concentrations of RBC GSH (2.43 ± 0.23 vs. 2.63 ± 0.26 mmol/L, p < 0.01). However, there were no differences in GSH fractional synthesis rate [78.0 (51.4-123.7) vs. 76.9 (49.3-110.1) % pool/day, p = 0.58] or absolute synthesis rate [1.85 (1.25-3.32) vs. 1.92 (1.43-3.03) mmol/L RBC/day, p = 0.97]. Despite a post-surgery increase in glycine concentration, no statistically significant changes in RBC GSH concentration or synthesis rates were detected. Further, the significant correlation between plasma glycine and RBC GSH concentration at baseline (r = 0.46, p < 0.01) was also lost following bariatric surgery. GSH concentration was significantly lower in participants with obesity, but bariatric surgery did not significantly increase GSH concentrations or synthesis rates.

Keywords: bariatric surgery; glutathione synthesis; glycine deficiency; severe obesity.

Figure 1

Glutathione concentrations, (A) fractional synthesis rates (B), and absolute synthesis rates (C) in participants with a healthy weight and severe obesity. The between-group difference in GSH concentrations was determined using the unpaired t-test, while the differences in GSH synthesis rates were tested using the Mann–Whitney test.

Figure 2

Glutathione concentrations, (A) fractional synthesis rates (B), and absolute synthesis rates (C) in participants with class III obesity before and after bariatric surgery. The significance of post-surgery changes in GSH concentrations was tested using a paired t-test, while the Wilcoxon signed-rank test was used for GSH synthesis rates.

Figure 3

Correlation between plasma glycine and RBC GSH concentrations in all participants at baseline (A) and in participants with severe obesity post-surgery (B).