Meta-Analysis of the Relationship Between Obestatin and Ghrelin Levels and the Ghrelin/Obestatin Ratio With Respect to Obesity

Introduction: The association between gastrointestinal hormones, obestatin and ghrelin, and obesity are controversial. Here, the authors summarize results of published works in this field by using meta-analysis. Methods: Studies that evaluated these hormones and were published before December 2009 were collected from PubMed, HighWire Press and ProQuest Health and Medical Complete. Software Review Manager 4.2 was used (Cochrane Collaboration, Oxford, England). Differences between obese and normal weight (NW) groups were compared using fixed or random effects models based on heterogeneity. Results: In obestatin group, 9 studies with 566 participants were included and had significant heterogeneity (I-2 = 98.6%, P < 0.01). Obestatin of NW groups was 64.19 pg/mL [95% confidence interval (CI) = 36.11-92.26, P < 0.01] higher than those of obese groups. In total ghrelin group, 21 studies with 1187 participants were included and had significant heterogeneity (I-2 = 97.9%, P < 0.01). Total ghrelin of NW groups was 145.53 pg/mL (95% CI = 109.59-181.47, P < 0.01) higher than those of obese groups. In active ghrelin group, 6 studies with 265 participants were included and had significant heterogeneity (I-2 = 98.10%, P < 0.01). Active ghrelin in NW groups was 53.22 pg/mL (95% CI = 25.92-80.53, P < 0.01) higher than those of obese groups. In ghrelin/obestatin group, 5 studies with 259 participants were included and had significant heterogeneity (I-2 = 94.2, P < 0.01). The ratios in NW groups were 2.49 pg/mL (95% CI = 0.03-4.9, P = 0.05) higher than those of obese groups but without significance. Conclusions: Obestatin, total and active ghrelin in NW groups were significantly higher than those of obese groups. Ghrelin/obestatin ratios in NW groups were also higher but without significance.