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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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Hyperinsulinemic-euglycemic clamps.Third intracerebroventricular leptin treatment (black bars) significantly improved hepatic insulin sensitivity and glucose disposal during hyperinsulinemic-euglycemic clamps in male MKR mice relative to artificial cerebrospinal fluid (ACSF) vehicle treated controls (open bars) and pair fed, ACSF treated male MKR mice (hatched bars). A. Glucose infusion rate (GIR) during the clamp, B. peripheral glucose disappearance rate (Rd), hepatic glucose production (GP) under basal conditions (C) or hyperinsulinemia (D). All data presented as means ± SEM. N = 5–6/group. Different superscript letters indicate significant differences at p<0.05.
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pone-0017058-g005: Hyperinsulinemic-euglycemic clamps.Third intracerebroventricular leptin treatment (black bars) significantly improved hepatic insulin sensitivity and glucose disposal during hyperinsulinemic-euglycemic clamps in male MKR mice relative to artificial cerebrospinal fluid (ACSF) vehicle treated controls (open bars) and pair fed, ACSF treated male MKR mice (hatched bars). A. Glucose infusion rate (GIR) during the clamp, B. peripheral glucose disappearance rate (Rd), hepatic glucose production (GP) under basal conditions (C) or hyperinsulinemia (D). All data presented as means ± SEM. N = 5–6/group. Different superscript letters indicate significant differences at p<0.05.

Mentions: Glucose infusion rate (GIR) and the rate of glucose disappearance (Rd) during hyperinsulinemic-euglycemic clamps were significantly increased in central leptin treated-MKR mice relative to ACSF and ACSF, pair fed mice (Figure 5 A–B). Leptin also produced a small but significant reduction in basal glucose production (Figure 5C). However, endogenous glucose production during the clamp was greatly reduced in mice receiving central leptin infusion relative to both control groups (Figure 5C). Pair feeding alone significantly increased GIR and Rd and decreased glucose production during the clamps, although not to the degree elicited by central leptin infusions (Figure 5 A,B,D).


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)

Hyperinsulinemic-euglycemic clamps.Third intracerebroventricular leptin treatment (black bars) significantly improved hepatic insulin sensitivity and glucose disposal during hyperinsulinemic-euglycemic clamps in male MKR mice relative to artificial cerebrospinal fluid (ACSF) vehicle treated controls (open bars) and pair fed, ACSF treated male MKR mice (hatched bars). A. Glucose infusion rate (GIR) during the clamp, B. peripheral glucose disappearance rate (Rd), hepatic glucose production (GP) under basal conditions (C) or hyperinsulinemia (D). All data presented as means ± SEM. N = 5–6/group. Different superscript letters indicate significant differences at p<0.05.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0017058-g005: Hyperinsulinemic-euglycemic clamps.Third intracerebroventricular leptin treatment (black bars) significantly improved hepatic insulin sensitivity and glucose disposal during hyperinsulinemic-euglycemic clamps in male MKR mice relative to artificial cerebrospinal fluid (ACSF) vehicle treated controls (open bars) and pair fed, ACSF treated male MKR mice (hatched bars). A. Glucose infusion rate (GIR) during the clamp, B. peripheral glucose disappearance rate (Rd), hepatic glucose production (GP) under basal conditions (C) or hyperinsulinemia (D). All data presented as means ± SEM. N = 5–6/group. Different superscript letters indicate significant differences at p<0.05.
Mentions: Glucose infusion rate (GIR) and the rate of glucose disappearance (Rd) during hyperinsulinemic-euglycemic clamps were significantly increased in central leptin treated-MKR mice relative to ACSF and ACSF, pair fed mice (Figure 5 A–B). Leptin also produced a small but significant reduction in basal glucose production (Figure 5C). However, endogenous glucose production during the clamp was greatly reduced in mice receiving central leptin infusion relative to both control groups (Figure 5C). Pair feeding alone significantly increased GIR and Rd and decreased glucose production during the clamps, although not to the degree elicited by central leptin infusions (Figure 5 A,B,D).

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