Alterations in plasma protein N-glycosylation after caloric restriction and bariatric surgery.

BACKGROUND: Protein glycosylation is an enzymatic process known to reflect an individual's physiologic state and changes thereof. The impact of metabolic interventions on plasma protein N-glycosylation has only been sparsely investigated. OBJECTIVE: To examine alterations in plasma protein N-glycosylation following changes in caloric intake and bariatric surgery. SETTING: University of Texas Southwestern Medical Center, US and Oxford University Hospitals, UK. METHODS: This study included 2 independent patient cohorts that recruited 10 and 37 individuals with obesity undergoing a period of caloric restriction followed by bariatric surgery. In both cohorts, clinical data were collated, and the composition of plasma protein N-glycome was analyzed chromatographically. Linear mixed models adjusting for age, sex, and multiple testing (false discovery rate <.05) were used to investigate longitudinal changes in glycosylation features and metabolic clinical markers. RESULTS: A low-calorie diet resulted in a decrease in high-branched trigalactosylated and trisialylated plasma N-glycans and a concomitant increase in low-branched N-glycans in both cohorts. Participants from one cohort additionally underwent a washout period during which caloric intake and body weight increased, resulting in reversal of the initial low-calorie diet-related changes in the plasma N-glycome. Immediate postoperative follow-up revealed the same pattern of N-glycosylation changes in both cohorts-an increase in complex, high-branched, antennary fucosylated, extensively galactosylated and sialylated N-glycans and a substantial decline in simpler, low-branched, core fucosylated, bisected, agalactosylated, and asialylated glycans. A 12-month postoperative monitoring in one cohort showed that N-glycan complexity declines while low branching increases. CONCLUSIONS: Plasma protein N-glycosylation undergoes extensive alterations following caloric restriction and bariatric surgery. These comprehensive changes may reflect the varying inflammatory status of the individual following dietary and surgical interventions and subsequent weight loss.

Extensive weight loss reduces glycan age by altering IgG N-glycosylation.

BACKGROUND: Obesity, a major global health problem, is associated with increased cardiometabolic morbidity and mortality. Protein glycosylation is a frequent posttranslational modification, highly responsive to inflammation and ageing. The prospect of biological age reduction, by changing glycosylation patterns through metabolic intervention, opens many possibilities. We have investigated whether weight loss interventions affect inflammation- and ageing-associated IgG glycosylation changes, in a longitudinal cohort of bariatric surgery patients. To support potential findings, BMI-related glycosylation changes were monitored in a longitudinal twins cohort. METHODS: IgG N-glycans were chromatographically profiled in 37 obese patients, subjected to low-calorie diet, followed by bariatric surgery, across multiple timepoints. Similarly, plasma-derived IgG N-glycan traits were longitudinally monitored in 1680 participants from the TwinsUK cohort. RESULTS: Low-calorie diet induced a marked decrease in the levels of IgG N-glycans with bisecting GlcNAc, whose higher levels are usually associated with ageing and inflammatory conditions. Bariatric surgery resulted in extensive alterations of the IgG N-glycome that accompanied progressive weight loss during 1-year follow-up. We observed a significant increase in digalactosylated and sialylated glycans, and a substantial decrease in agalactosylated and core fucosylated IgG N-glycans (adjusted p value range 7.38 × 10-04-3.94 × 10-02). This IgG N-glycan profile is known to be associated with a younger biological age and reflects an enhanced anti-inflammatory IgG potential. Loss of BMI over a 20 year period in the TwinsUK cohort validated a weight loss-associated agalactosylation decrease (adjusted p value 1.79 × 10-02) and an increase in digalactosylation (adjusted p value 5.85 × 10-06). CONCLUSIONS: Altogether, these findings highlight that weight loss substantially affects IgG N-glycosylation, resulting in reduced glycan and biological age.