Brain insulin and leptin resistance in obesity

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DESCRIPTION (provided by applicant): Obesity is recognized as a serious worldwide threat to human health. Evidence indicates that over the course of hours and days caloric intake is closely matched to energy expenditure in normal individuals, such that body weight remains stable over time. This regulation occurs via a classical endocrine feedback loop in which the "adiposity signals" insulin and leptin are secreted in proportion to body fat mass and interact with regulatory neurons found in the hypothalamic arcuate nucleus (ARC). Human obesity and the best animal model thereof, diet-induced obesity (DIO) are fundamentally different, leading to the hypothesis that acquired hypothalamic resistance to the adiporegulatory effects of insulin and leptin results in impaired body fat mass regulation. Previously we have demonstrated that the ability of both insulin and leptin to regulate feeding is dependent upon the activation of phosphatidylinositol 3-kinase (PI3K) in ARC neurons; this pathway is the major mode of insulin action in peripheral tissues and has been identified as a "target" of insulin resistance via accumulation of long chain fatty acyl CoA molecules (LC-CoA). We have generated preliminary data demonstrating both behavioral (food intake) and biochemical (PI3K) hypothalamic insulin and leptin resistance in obese DIO animals and that mechanisms implicated in peripheral insulin resistance may also be responsible for central resistance. We propose: Aim 1: To determine the time-course of central insulin and leptin (vs peripheral) resistance in DIO. Aim 2: To determine if the accumulation of hypothalamic long-chain fatty acyl CoA molecules in DIO coincides with behavioral and/or biochemical resistance. Aim 3: To determine if insulin and leptin regulation of FOXO proteins in hypothalamus is disrupted in DIO. Aim 4: To determine if genetic enhancement of the hypothalamic PI3K pathway enhances insulin and leptin sensitivity and attenuates DIO.