hide
Free keywords:
Agouti-Related Protein/genetics/metabolism
Animals
Body Composition/genetics
Body Weight/genetics
Disease Models, Animal
Eating/genetics
Electrophoretic Mobility Shift Assay
Enzyme-Linked Immunosorbent Assay/methods
Feedback/physiology
Gene Expression Regulation/drug effects/genetics
Glucose Tolerance Test
Green Fluorescent Proteins/genetics
Hypothalamus/pathology
In Vitro Techniques
Insulin/*metabolism
Insulin Resistance/genetics
Leptin/*metabolism
Leukemia Inhibitory Factor/pharmacology
Membrane Proteins/genetics/*metabolism
Mice
Mice, Transgenic
Neural Inhibition/drug effects/genetics/*physiology
Neurons/*physiology
Neuropeptide Y/genetics/metabolism
Obesity/genetics/metabolism/*physiopathology
Patch-Clamp Techniques/methods
Phosphatidylinositol 3-Kinases/metabolism
Pro-Opiomelanocortin/*metabolism
Signal Transduction/genetics
Suppressor of Cytokine Signaling Proteins/genetics/metabolism
Transfection
Abstract:
Leptin-stimulated Stat3 activation in proopiomelanocortin (POMC)-expressing neurons of the hypothalamus plays an important role in maintenance of energy homeostasis. While Stat3 activation in POMC neurons is required for POMC expression, the role of elevated basal Stat3 activation as present in the development of obesity has not been directly addressed. Here, we have generated and characterized mice expressing a constitutively active version of Stat3 (Stat3-C) in POMC neurons (Stat3-C(POMC) mice). On normal chow diet, these animals develop obesity as a result of hyperphagia and decreased POMC expression accompanied by central leptin and insulin resistance. This unexpected finding coincides with POMC-cell-specific, Stat3-mediated upregulation of SOCS3 expression inhibiting both leptin and insulin signaling as insulin-stimulated PIP(3) (phosphatidylinositol-3,4,5 triphosphate) formation and protein kinase B (AKT) activation in POMC neurons as well as with the fact that insulin's ability to hyperpolarize POMC neurons is largely reduced in POMC cells of Stat3-C(POMC) mice. These data indicate that constitutive Stat3 activation is not sufficient to promote POMC expression but requires simultaneous PI3K (phosphoinositide 3-kinase)-dependent release of FOXO1 repression. In contrast, upon exposure to a high-fat diet, food intake and body weight were unaltered in Stat3-C(POMC) mice compared with control mice. Taken together, these experiments directly demonstrate that enhanced basal Stat3 activation in POMC neurons as present in control mice upon high-fat feeding contributes to the development of hypothalamic leptin and insulin resistance.
