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Intracerebroventricular leptin infusion improves glucose homeostasis in lean type 2 diabetic MKR mice via hepatic vagal and non-vagal mechanisms.

Li X, Wu X, Camacho R, Schwartz GJ, LeRoith D - PLoS ONE (2011)

Bottom Line: MKR mice, lacking insulin-like growth factor 1 receptor (IGF-1R) signaling in skeletal muscle, are lean yet hyperlipidemic, hyperinsulinemic, and hyperglycemic, with severe insulin resistance and elevated hepatic and skeletal muscle levels of triglycerides.These reductions were accompanied by increased fat oxidation as measured by indirect calorimetry, as well as increased oxygen consumption.These results demonstrate that central leptin dramatically improves insulin sensitivity independently of its effects on food intake, in a lean mouse model of type 2 diabetes.

View Article: PubMed Central - PubMed

Affiliation: Departments of Medicine and Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States of America.

ABSTRACT
MKR mice, lacking insulin-like growth factor 1 receptor (IGF-1R) signaling in skeletal muscle, are lean yet hyperlipidemic, hyperinsulinemic, and hyperglycemic, with severe insulin resistance and elevated hepatic and skeletal muscle levels of triglycerides. We have previously shown that chronic peripheral administration of the adipokine leptin improves hepatic insulin sensitivity in these mice independently of its effects on food intake. As central leptin signaling has been implicated in the control of peripheral glucose homeostasis, here we examined the ability of central intracerebroventricular leptin administration to affect energy balance and peripheral glucose homeostasis in non-obese diabetic male MKR mice. Central leptin significantly reduced food intake, body weight gain and adiposity, as well as serum glucose, insulin, leptin, free fatty acid and triglyceride levels relative to ACSF treated controls. These reductions were accompanied by increased fat oxidation as measured by indirect calorimetry, as well as increased oxygen consumption. Central leptin also improved glucose tolerance and hepatic insulin sensitivity determined using the euglycemic-hyperinsulinemic clamps relative to pair fed vehicle treated controls, as well as increasing the rate of glucose disappearance. Hepatic vagotomy only partially reversed the ability of central leptin to improve glucose tolerance. These results demonstrate that central leptin dramatically improves insulin sensitivity independently of its effects on food intake, in a lean mouse model of type 2 diabetes. The findings also suggest that: 1) both hepatic vagal and non-vagal pathways contribute to this improvement, and 2) central leptin alters glucose disposal in skeletal muscle in this model.

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Glucose Tolerance Tests In Leptin And Vehicle Treated MKR Mice.Two week intracerebroventricular leptin treatment significantly improved glucose tolerance in male MKR mice relative to artificial cerebrospinal fluid (ACSF) vehicle treated controls and pair fed, ACSF treated MKR mice. A. Intraperitoneal glucose tolerance test (ipGTT, 2 g/kg), B. Area under the curve (AUC) during ipGTT. All data presented as means ± SEM, N = 6–7/group. * p<0.05, ** p<0.01.
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pone-0017058-g004: Glucose Tolerance Tests In Leptin And Vehicle Treated MKR Mice.Two week intracerebroventricular leptin treatment significantly improved glucose tolerance in male MKR mice relative to artificial cerebrospinal fluid (ACSF) vehicle treated controls and pair fed, ACSF treated MKR mice. A. Intraperitoneal glucose tolerance test (ipGTT, 2 g/kg), B. Area under the curve (AUC) during ipGTT. All data presented as means ± SEM, N = 6–7/group. * p<0.05, ** p<0.01.

Mentions: Prior to and immediately following implantation of the infusion pumps, fed blood glucose levels remained in the diabetic range in all MKR mice (between 300–400 mg/dl). ICV leptin significantly lowered fasting blood glucose (BG) beginning 1 week following leptin infusion (98.8±14 mg/dl vs. 222±23 mg/dl, p<0.001), while pair feeding ACSF treated mice to the level of leptin treated controls was without effect (ACSF: BG 222±23 vs. ACSF pair fed: BG 182±13 mg/dl, N.S.). ICV leptin also significantly improved glucose tolerance relative to both ASCF and ASCF-pair fed controls (Figure 4A–B).


Intracerebroventricular leptin infusion improves glucose homeostasis in lean type 2 diabetic MKR mice via hepatic vagal and non-vagal mechanisms.

Li X, Wu X, Camacho R, Schwartz GJ, LeRoith D - PLoS ONE (2011)

Glucose Tolerance Tests In Leptin And Vehicle Treated MKR Mice.Two week intracerebroventricular leptin treatment significantly improved glucose tolerance in male MKR mice relative to artificial cerebrospinal fluid (ACSF) vehicle treated controls and pair fed, ACSF treated MKR mice. A. Intraperitoneal glucose tolerance test (ipGTT, 2 g/kg), B. Area under the curve (AUC) during ipGTT. All data presented as means ± SEM, N = 6–7/group. * p<0.05, ** p<0.01.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3040739&req=5

pone-0017058-g004: Glucose Tolerance Tests In Leptin And Vehicle Treated MKR Mice.Two week intracerebroventricular leptin treatment significantly improved glucose tolerance in male MKR mice relative to artificial cerebrospinal fluid (ACSF) vehicle treated controls and pair fed, ACSF treated MKR mice. A. Intraperitoneal glucose tolerance test (ipGTT, 2 g/kg), B. Area under the curve (AUC) during ipGTT. All data presented as means ± SEM, N = 6–7/group. * p<0.05, ** p<0.01.
Mentions: Prior to and immediately following implantation of the infusion pumps, fed blood glucose levels remained in the diabetic range in all MKR mice (between 300–400 mg/dl). ICV leptin significantly lowered fasting blood glucose (BG) beginning 1 week following leptin infusion (98.8±14 mg/dl vs. 222±23 mg/dl, p<0.001), while pair feeding ACSF treated mice to the level of leptin treated controls was without effect (ACSF: BG 222±23 vs. ACSF pair fed: BG 182±13 mg/dl, N.S.). ICV leptin also significantly improved glucose tolerance relative to both ASCF and ASCF-pair fed controls (Figure 4A–B).

Bottom Line: MKR mice, lacking insulin-like growth factor 1 receptor (IGF-1R) signaling in skeletal muscle, are lean yet hyperlipidemic, hyperinsulinemic, and hyperglycemic, with severe insulin resistance and elevated hepatic and skeletal muscle levels of triglycerides.These reductions were accompanied by increased fat oxidation as measured by indirect calorimetry, as well as increased oxygen consumption.These results demonstrate that central leptin dramatically improves insulin sensitivity independently of its effects on food intake, in a lean mouse model of type 2 diabetes.

View Article: PubMed Central - PubMed

Affiliation: Departments of Medicine and Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States of America.

ABSTRACT
MKR mice, lacking insulin-like growth factor 1 receptor (IGF-1R) signaling in skeletal muscle, are lean yet hyperlipidemic, hyperinsulinemic, and hyperglycemic, with severe insulin resistance and elevated hepatic and skeletal muscle levels of triglycerides. We have previously shown that chronic peripheral administration of the adipokine leptin improves hepatic insulin sensitivity in these mice independently of its effects on food intake. As central leptin signaling has been implicated in the control of peripheral glucose homeostasis, here we examined the ability of central intracerebroventricular leptin administration to affect energy balance and peripheral glucose homeostasis in non-obese diabetic male MKR mice. Central leptin significantly reduced food intake, body weight gain and adiposity, as well as serum glucose, insulin, leptin, free fatty acid and triglyceride levels relative to ACSF treated controls. These reductions were accompanied by increased fat oxidation as measured by indirect calorimetry, as well as increased oxygen consumption. Central leptin also improved glucose tolerance and hepatic insulin sensitivity determined using the euglycemic-hyperinsulinemic clamps relative to pair fed vehicle treated controls, as well as increasing the rate of glucose disappearance. Hepatic vagotomy only partially reversed the ability of central leptin to improve glucose tolerance. These results demonstrate that central leptin dramatically improves insulin sensitivity independently of its effects on food intake, in a lean mouse model of type 2 diabetes. The findings also suggest that: 1) both hepatic vagal and non-vagal pathways contribute to this improvement, and 2) central leptin alters glucose disposal in skeletal muscle in this model.

Show MeSH
Related in: MedlinePlus