Insulin's impact on dopamine an important driver of weight gain, obesity: Study
Germany: Researchers in a new study published in the Journal of Clinical Endocrinology & Metabolism have indicated an important role of the impact of insulin on dopamine levels in eating behavior.
"Central insulin modulates dopaminergic tone in the striatum that may affect regional brain activity and connectivity," Stephanie Kullmann, German Center for Diabetes Research (DZD), Tübingen, Germany, and colleagues wrote in their study. "Our results strengthen the knowledge of the interaction between insulin-dopamine and the complex network that underlies the regulation of whole-body metabolism."
Activity in the brain's dopaminergic pathways is shown to be highly sensitive to body weight and metabolic states. Animal studies show that dopamine neurons are important targets for the metabolic hormone insulin with abolished effects in the insulin-resistant state. This leads to an increase in body weight and food intake. However, in humans, the influence of central acting insulin on dopamine and the effects of their interplay is still elusive.
Against the above background, the researchers looked at the impact of insulin on the specific part of the brain which regulates reward processes, reporting that this relationship could be behind the brain's regulation of glucose metabolism and people's eating habits in a randomized, placebo-controlled, blinded, crossover trial.
The researchers simultaneously performed [11C]-raclopride-PET and resting-state functional MRI using a positron emission tomography (PET)/magnetic resonance imaging (MRI) hybrid scanner in 10 healthy normal-weight men after application of intranasal insulin or placebo on 2 separate days.
Following were the study's key findings:
- In response to central insulin compared with placebo administration, the authors observed greater [11C]-raclopride binding potential in the bilateral ventral and dorsal striatum. This suggests an insulin-induced reduction in synaptic dopamine levels.
- Resting-state striatal activity was lower 15 and 30 minutes after nasal insulin compared with placebo.
- Functional connectivity of the mesocorticolimbic circuitry associated with differences in dopamine levels: individuals with a stronger insulin-induced effect on dopamine levels showed a stronger increase in functional connectivity 45 minutes after intranasal insulin.
"This study indicates that central insulin modulates dopaminergic tone in the striatum, which may affect regional brain activity and connectivity," wrote the authors.
Reference:
Stephanie Kullmann, Dominik Blum, Benjamin Assad Jaghutriz, Christoph Gassenmaier, Benjamin Bender, Hans-Ulrich Häring, Gerald Reischl, Hubert Preissl, Christian la Fougère, Andreas Fritsche, Matthias Reimold, Martin Heni, Central Insulin Modulates Dopamine Signaling in the Human Striatum, The Journal of Clinical Endocrinology & Metabolism, Volume 106, Issue 10, October 2021, Pages 2949–2961, https://doi.org/10.1210/clinem/dgab410
