Dopamine receptors in obesity: a meta-analysis

The brain plays a major role in controlling the desire to eat. This meta-analysis aimed to assess the association between dopamine receptor (DR) availability, measured using positron emission tomography, and obesity. We performed a systematic search of MEDLINE (from inception to June 2019) and EMBASE (from inception to June 2019) for articles published in English using the keywords "dopamine receptor," "obesity," and "neuroimaging." Fitting a locally weighted estimated scatterplot smoothing curve for binding potential (BPND) of the ventral striatum measured by 11C-raclopride was performed. Five studies involving 119 subjects were included in this analysis. 11C-raclopride was used in four studies, regardless of the ROIs included. The curve of BPND of the ventral striatum went up and down at BMI of 20-30 kg/m2 and became flat after a BMI of >40 kg/m2. Linear regression analysis was performed with BPND of the striatum from two studies (n = 20). The BPND of the striatum was negatively associated with BMI. In conclusion, dopamine plays a major role in the reward system with regard to obesity. Compared to normal-weight subjects, overweight and obese subjects had decreased DR availability. However, this tendency should be interpreted carefully with regard to radiopharmaceuticals and ROIs.