Role of Shp2 in forebrain neurons in regulating metabolic and cardiovascular functions and responses to leptin

OBJECTIVE: We examined whether deficiency of Shp2 signaling in forebrain neurons alters metabolic and cardiovascular regulation under various conditions and if it attenuates the anorexic and cardiovascular effects of leptin. We also tested whether forebrain Shp2 deficiency alters blood pressure (BP) and heart rate (HR) responses to acute stress. DESIGN: Forebrain Shp2(-/-) mice were generated by crossing Shp2(flox/flox) mice with CamKIIα-cre mice. At 22 to 24 weeks of age, mice were instrumented for telemetry for measurement of BP, HR and body temperature (BT). Oxygen consumption (VO2), energy expenditure and motor activity were monitored by indirect calorimetry. RESULTS: Shp2/CamKIIα-cre mice were heavier (46±3 vs 32±1 g), hyperglycemic, hyperleptinemic, hyperinsulinemic, and hyperphagic compared to Shp2(flox/flox) control mice. Shp2/CamKIIα-cre mice exhibited reduced food intake responses to fasting/refeeding and impaired regulation of BT when exposed to 15°C and 30°C ambient temperatures. Despite being obese and having many features of metabolic syndrome, Shp2/CamKIIα-cre mice had similar daily average BP and HR compared to Shp2(flox/flox) mice (112±2 vs 113±1 mmHg and 595±34 vs 650±40 bpm), but exhibited increased BP and HR responses to cold exposure and acute air-jet stress test. Leptin's ability to reduce food intake and to raise BP were markedly attenuated in Shp2/CamKIIα-cre mice. CONCLUSION: These results suggest that forebrain Shp2 signaling regulates food intake, appetite responses to caloric deprivation, and thermogenic control of body temperature during variations in ambient temperature. Deficiency of Shp2 signaling in the forebrain is associated with augmented cardiovascular responses to cold and acute stress but attenuated BP responses to leptin.