Effect of Sleeve Gastrectomy on Ghrelin, GLP-1, PYY, and GIP Gut Hormones A Systematic Review and Meta-analysis

Objective: To perform a structured systematic review and meta-analysis to evaluate changes in ghrelin, glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and gastric inhibitory peptide (GIP) gut hormone levels in patients after sleeve gastrectomy. Background: Despite sleeve gastrectomy becoming the most common surgical weight loss procedure, weight loss mechanisms remain less clear. Methods: Searches of PubMed, EMBASE, Web of Science, and Cochrane Library databases were performed through April 1, 2019, in accordance with PRISMA and MOOSE guidelines. Randomized controlled trials and prospective observational studies evaluating pre and post-procedure hormones fasting ghrelin, postprandial GLP-1, postprandial PYY, and fasting GIP levels were included. Hedge g with random-effects models were used to determine pooled effect size and corresponding 95% confidence intervals (CIs). Results: A total of 28 studies (n ¼ 653; 29.56% male) were included. Mean age was 42.00 ± 5.48 years, with average follow-up of 11.70 ± 11.38 months. Pre-procedure body mass index (BMI) was 46.01 ± 4.07 kg/m² with a post-sleeve gastrectomy BMI of 34.07 ± 3.73 kg/m², representing total body weight loss of 25.13 ± 4.44% and excess weight loss of 57.48 ± 9.64% (P < 0.001). Ghrelin decreased (Hedge g -1.486, 95% CI -1.884 to -1.089, I² ¼ 91.95%), whereas GLP-1 and PYY increased post-procedure (Hedge g 1.095, 95% CI 0.509 to 1.642, I² ¼ 84.38%; and Hedge g 1.396, 95% CI 0.781 to 2.011, I² ¼ 84.02%, respectively). GIP did not significantly change (Hedge g -0.213, 95% CI -1.019 to 0.592, I² ¼ 79.65%). Conclusions: Fasting ghrelin levels decreased, whereas postprandial GLP-1 and PYY increased after sleeve gastrectomy. Fasting GIP levels remained unchanged. Future studies are needed to assess the role of these gut hormones and relationship to weight loss and metabolic outcomes.