Bariatric surgery reverses morbid obesity-induced changes in the composition of circulating immune cells-a prospective cohort study.

Abstract

Background: Morbid obesity is associated with aging of the immune system, a phenomenon known as "inflammaging," characterized by increased numbers of various immune cell subsets.

Objectives: To evaluate the long-term effects of bariatric surgery on immune cell subsets in patients with obesity and to determine the impact of metabolic syndrome on these changes.

Setting: High-volume bariatric center, Netherlands.

Methods: This prospective cohort study included patients with obesity, with and without metabolic syndrome, as well as lean controls. Peripheral blood samples were collected preoperatively (T0) and at various time points up to 18 months postoperatively (T18). Flow cytometry was used to measure absolute numbers of T cells, B cells, natural killer (NK) cells, and monocyte subsets, with adjustments for age and cytomegalovirus (CMV) serostatus.

Results: At T0, patients with obesity had elevated numbers of CD4+ CD31 naïve T cells, CD8+ terminally differentiated effector memory RA T cells, double-negative B cells, plasmablasts, NK cells, and monocytes compared with lean controls. CD8+ central memory T cells were decreased in patients with obesity. While most immune cell subsets gradually normalized by T18, some subsets, including T cells, B cells, and NK cells, that were initially elevated, decreased during follow-up and ultimately ended up lower than those in lean controls at T12 or T18. Metabolic syndrome did not affect these outcomes. COVID-19-related disruptions reduced the number of patients assessed over time.

Conclusions: Bariatric surgery restores the harmful effects of morbid obesity on the composition of innate and adaptive immune cell subsets in the long-term for patients with obesity, both with and without metabolic syndrome.