Normal dopamine uptake ratio on [¹⁸F]FDOPA pet-imaging in obesity

Dopamine plays a key role in motivation and behavioral regulation and may influence eating behavior in obesity. Previous studies indicate altered dopamine receptor availability in obesity, but the role of presynaptic dopaminergic function remains unclear. This study employed [¹⁸F]FDOPA PET imaging to evaluate presynaptic dopamine function in a large cohort of individuals with obesity compared with individuals with normal weight.

Routine [18F]FDOPA PET/CT scans performed for the detection and follow-up of neuroendocrine tumors were reviewed. Striatal-to-occipital uptake ratios were used as an index of presynaptic dopaminergic tracer uptake after six hours of fasting. Individuals with normal weight (BMI ≤ 25) were compared with individuals with obesity (BMI ≥ 30) using multivariable regression analysis adjusted for age and sex. Sensitivity analyses included BMI modeled continuously and exploratory analyses of non-linear associations. A sensitivity analysis was performed in individuals with obesity class II (BMI 35-40).

Median striatal SUV ratios were 2.2 (IQR 0.4, n = 67) in participants with obesity and 2.3 (IQR 0.4, n = 67) in participants with normal weight. No significant differences were observed between groups in the striatum (p = 0.07), putamen (p = 0.17), or caudate nucleus (p = 0.14), including among individuals with BMI ≥ 35 kg/m². Continuous and multivariable analyses yielded consistent results.

This study did not demonstrate significant differences in striatal [¹⁸F]FDOPA uptake ratios between individuals with normal weight and individuals with obesity in the fasting state. Further research is warranted to clarify the role of the reward system in the development and management of obesity.