Brain Dopamine Receptor System is Not Altered in Obesity: Bayesian and Frequentist Meta-Analyses

Abstract

ABSTRACTBackgroundFeeding induces dopamine release in the striatum, and a dysfunction of the dopaminergic reward system can lead to overeating, and obesity. Studies have reported inconsistent findings of dopamine receptor (DR) positron emission tomography (PET) scans in obesity. Here we investigated the association between DR availability and overweight/obesity using Bayesian and frequentist meta-analysis.MethodsWe performed a systematic search of Embase, Medline, Scopus and Web of Science for studies which compared striatal DR availability between lean subjects and overweight/obese subjects. The standardized mean difference (Hedge’s g) of DR availability was calculated after extraction of data from each study. Studies were divided into two groups according to the definition of overweight/obese subjects (BMI cutoff of 25 and 30kg/m2). Both Bayesian and conventional meta-analysis was done in R Statistical Software version 4.2.2 (The R Foundation for Statistical Computing).ResultsNine studies were eligible for inclusion in this study. Three studies with C11-raclopride, one with C11-PNHO, two with F18-fallypride, one with I123-IBZM, one with C11-NMB and one with both C11-raclopride and C11-PNHO were included. In Bayesian meta-analysis, the standardized mean difference of DR availability between lean and overweight/obese subjects markedly overlapped with zero regardless of BMI cutoff for obesity. In frequentist meta-analysis the pooled standardized mean difference of DR availability did not show the significant difference between lean and overweight/obese subjects. There was an effect of the radiopharmaceutical on the standardized mean difference of DR availability in meta-analysis of BMI cutoff of 25 kg/m2.ConclusionsBrain DR availability is not different between lean and overweight/obese subjects. However, the effect is dependent on the radiopharmaceutical and the degree of obesity. Further studies with multi-radiopharmaceutical in the same individuals are need to understand the association between DR and obesity.