The involvement of circulating CD69(+) CD56(bright) natural killer cells in weight loss before bariatric surgery: A retrospective cohort study

As the impact of the immune system on weight loss prior to bariatric surgery has never been proven, we elucidated the clinical utility of the immune system as an indicator of preoperative weight loss before bariatric surgery. We examined the relationships between preoperative weight loss and biochemical and clinical data at the initial visit in 34 obese patients. Patients were divided according to preoperative weight loss, and peripheral blood mononuclear cells were compared using flowcytometry. The Δpreoperative excess weight loss [Δpre-EWL: pre-EWL (%)/period of preoperative weight loss (days)] showed negative correlations with total and subcutaneous fat area (P = .02, r = −0.41, P = .02, r = −0.42 respectively). The Δpre-EWL and Δpreoperative total weight loss (Δpre-TWL) were negatively correlated with white blood cell count, lymphocyte count, and C-reactive protein (CRP) levels at the initial visit (Δpre-EWL; P = .02, r = −0.37, P = .01, r = −0.41, P = .008, r = −0.45, Δpre-TWL; P = .01, r = −0.40, P = .01, r = −0.42, P = .01, r = −0.42, respectively). Multivariate regression modeling showed that both Δpre-EWL and Δpre-TWL were significantly associated with lymphocyte count (Δpre-EWL; P = .01, Δpre-TWL; P = .01). A comparison between the high (Δ pre-EWL > 0.098) and low weight loss group (Δ pre-EWL < 0.098) demonstrated a significant difference in the expression of the activation marker CD69 on CD56(bright) Natural killer (NK) cells (P = .01), whereas there was no difference in the frequency of T cells, Natural killer T cells, or NK cells. Additionally, high CRP levels were associated with CD69 expression in CD56(bright) NK cells (P = .01, R = 0.57). Peripheral lymphocytes, especially CD69-positive CD56(bright) NK cells, are involved in preoperative weight loss after bariatric surgery, and systemic inflammation may inhibit weight loss before surgery.