Dr. Yong Xu’s research program focuses on central mechanisms for the regulations of feeding behavior and body weight. Using cutting-edge modern neuroscience technology, Dr. Xu has identified novel hypothalamic circuits, neural messengers and intracellular molecules critical for the regulation of feeding behavior and body weight. His discoveries are highly relevant to common human diseases, especially obesity, diabetes and eating disorders.
Recently, Dr. Xu and his collaborators identified a novel mechanism for human obesity that will guide better diagnosis and treatment for a subset of individuals with obesity. Many genetic variants in humans that affect weight are enriched in the brain, implicating neural dysfunctions in the susceptibility to obesity. Dr. Xu teamed up with physician-scientists to combine human genetics and basic animal neuroendocrinology by using the human/mouse genetic approach to identify HTR2C (encoding serotonin 2C receptor) mutations as the cause of human obesity. These findings indicate that the HTR2C gene should be included in the genetic screening panel for human obesity. In addition, Dr. Xu revealed that the impaired melanocortin signaling in the brain contributes to overeating and weight gain caused by the HTR2C mutations, and therefore suggest that patients with HTR2C deficiency can be treated by an FDA-approved melanocortin agonist (IMCIVREE, also known as setmelanotide).
Dr. Xu has also revealed a potential pathophysiologic basis for anorexia nervosa and provided a mechanistic framework for developing novel therapeutic strategies for this disease. Dr. Xu showed that dopamine (DA) neurons bidirectionally regulate the activity of midbrain 5-HT neurons, with weaker stimulation causing dopamine receptor D2 (DRD2)-dependent inhibition and overeating, and stronger stimulation causing dopamine receptor D1 (DRD1)-dependent activation and anorexia. In a mouse model for anorexia nervosa, DA actions on 5-HT neurons shift from a DRD2-mediated neurotransmission to a DRD1-mediated process, which causes constant activation of 5-HT neurons, resulting in anorexia. These results revealed an interesting DA to 5-HT neurocircuit whose neurotransmission and behavioral outcome are bidirectional, depending on the strength of DA inputs. The findings indicate that an enhanced DRD2 neurotransmission onto 5-HT neurons contributes to development of anorexia nervosa, and further demonstrate the therapeutic potential of DRD1 antagonists in this devastating and life-threatening disease.
In addition, Dr. Xu identified a novel exercise-induced metabolite that reduces food intake and improves glucose balance, which paved the way to develop exercise mimetics as effective anti-obesity and anti-diabetic medicines. Dr. Xu and the team showed that exercise stimulates production of Lac-Phe, a blood-borne signaling metabolite. In diet-induced obese mice, Lac-Phe reduces food intake without affecting movement or energy expenditure. Chronic treatment with Lac-Phe decreases adiposity and body weight and improves glucose homeostasis. Conversely, genetic ablation of Lac-Phe biosynthesis in mice increases their food intake and leads to obesity. These data define a conserved exercise-inducible metabolite that controls food intake and influences systemic energy balance, and resulted in a patent (“Lactoyl amino acids for the treatment of metabolic disease”).