Having appreciated the role of pro-inflammatory IKK?/NF-?B pathway in the hypothalamic mechanism of obesity, the objective of this research is to study how hypothalamic neurons and astrocytes are programmatically involved. Through recent studies including preliminary experiments on mice with hypothalamic astrocytic IKK?/NF-?B activation or inhibition, supportive evidence was obtained to suggest that astrocytes in the mediobasal hypothalamus (MBH) have multiple programs through IKK?/NF-?B for being responsible for metabolic imbalance. Hence, the hypothesis of this proposal is, sustained activation of astrocytic IKK?/NF-?B in the MBH under chronic high-fat diet feeding leads to altered astrocyte-neuron relationships in the MBH, at least due to an impairment in astrocyte-dependent GABA clearance and also an enhancement in astrocytic cytokine production ? which employ GABA and cytokine receptor signaling to influence the responsible neurons, resulting in multiple forms of neuronal dysregulation on metabolic balance which underlie obesity and pre-diabetic development.
Three Aims are designed to study (1) astrocytic IKK?/NF-?B?autophagy axis in linking hypothalamic neurons to metabolic dysregulation, (2) IKK?/NF-?B- dependent astrocytic clearance of GABA in linking POMC neuronal inhibition to obesity, and (3) IKK?/NF-?B- driven astrocytic cytokines in linking other responsive hypothalamic neurons to disease development. A combination of cellular, molecular, genetic, physiological and pharmacological approaches will be used to analyze astrocytic biology and functions, the overall and local influences on neurons, and their mechanistic roles for obesity and pre-diabetes. Successful completion of this project will be important for understanding the hypothalamic basis of obesity and diabetes and provide new paradigms in designing interventional strategies.
The mechanism of diet-induced obesity is significantly attributed to the induction of a pro-inflammatory molecular pathway in the hypothalamus leading to the hypothalamic dysregulation of metabolic balance, but the underlying cellular mechanism is still unclear. This project is to study how astrocytes are altered in response to this pro-inflammatory signaling and how these cells engage various hypothalamic neurons to programmatically induce metabolic dysregulations and ultimately obesity and pre-diabetes. Successful completion of this project will help understand the brain mechanism of obesity and diabetes and possibly provide new paradigms in addressing these diseases.