One of the overall goals of this proposal is to understand the role of PKA signaling in the neuronal pathways that regulate feeding and energy expenditure. Mouse genetic techniques allow us to investigate this problem in a physiological setting and also provide us with novel tools for defining regulation at the molecular level. We propose to use a mouse genetic approach to detect and quantities neuron-specific mRNA regulation in regions of the hypothalamus known to be involved in body weight regulation and the response to the adipose derived hormone, leptin. In addition to detecting changes in transcription we will examine the potential role of translational control of pre-existing mRNAs. Recent work has continued to challenge and expand our views on the neural control of body weight. Leptin receptors have been shown to engage multiple signaling pathways in a neuron specific pattern and the crosstalk between these signaling systems, including the cAMP/PKA pathway, is a new avenue that needs to be explored more comprehensively. The RII2 KO mouse line is lean and resistant to diet-induced obesity and our recent results indicate that this is because of an increase in leptin sensitivity in the brain.
The specific aims of this proposal are: (1) Identify the hypothalamic neurons in which PKA activity plays a role in leptin sensitivity and body weight regulation (2) Assay changes in polysome-associated mRNAs in specific hypothalamic neurons in response to diet and leptin (3) Determine the mechanism of increased leptin sensitivity in RII2 KO mice. The sensitivity of the hypothalamic response network to leptin is one of the ultimate determinants of how much energy is stored as fat and leptin resistance is one of the defining features of obesity.
The regulation of feeding and energy balance is coordinated by neurons in the hypothalamic region of the brain. We have demonstrated that intracellular signaling through the cAMP/Protein Kinase A system can regulate this neuronal pathway and prevent diet-induced obesity in mice. In this project, we will study this mechanism for regulating energy balance and hope to reveal novel therapeutic targets for future clinical applications.
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