Sweet dopamine: Sucrose preferences relate differentially to striatal D₂ receptor binding and age in obesity

Alterations in dopaminergic circuitry play a critical role in food reward and may contribute to susceptibility to obesity. Ingestion of sweets releases dopamine in striatum, and both sweet preferences and striatal D₂ receptors (D2R) decline with age and may be altered in obesity. Understanding the relationships between these variables and the impact of obesity on these relationships may reveal insight into the neurobiological basis of sweet preferences. We evaluated sucrose preferences, perception of sweetness intensity, and striatal D2R binding potential (D2R BP_ND) using positron emission tomography with a D2R-selective radioligand insensitive to endogenous dopamine, (N-[¹¹C] methyl)benperidol, in 20 subjects without obesity (BMI 22.5 ± 2.4 kg/m²; age 28.3 ± 5.4 years) and 24 subjects with obesity (BMI 40.3 ± 5.0 kg/m²; age 31.2 ± 6.3 years). The groups had similar sucrose preferences, sweetness intensity perception, striatal D2R BP_ND, and age-related D2R BP_ND declines. However, both striatal D2R BP_ND and age correlated with sucrose preferences in subjects without obesity, explaining 52% of their variance in sucrose preference. In contrast, these associations were absent in the obese group. In conclusion, the age-related decline in D2R was not linked to the age-related decline in sweetness preferences, suggesting that other, as-yet-unknown mechanisms play a role and that these mechanisms are disrupted in obesity.