title: Glucagon-like peptide-1 receptor knockout mice are protected from high-fat diet-induced insulin resistance.
abstract: Glucagon-like peptide-1 augments nutrient-stimulated insulin secretion. Chow-fed mice lacking the glucagon-like peptide-1 receptor (Glp1r) exhibit enhanced insulin-stimulated muscle glucose uptake but impaired suppression of endogenous glucose appearance (endoRa). This proposes a novel role for the Glp1r to regulate the balance of glucose disposal in muscle and liver by modulating insulin action. Whether this is maintained in an insulin-resistant state is unknown. The present studies tested the hypothesis that disruption of Glp1r expression overcomes high-fat (HF) diet-induced muscle insulin resistance and exacerbates HF diet-induced hepatic insulin resistance. Mice with a functional disruption of the Glp1r (Glp1r-/-) were compared with wild-type littermates (Glp1r+/+) after 12 wk on a regular chow diet or a HF diet. Arterial and venous catheters were implanted for sampling and infusions. Hyperinsulinemic-euglycemic clamps were performed on weight-matched male mice. [3-(3)H]glucose was used to determine glucose turnover, and 2[14C]deoxyglucose was used to measure the glucose metabolic index, an indicator of glucose uptake. Glp1r-/- mice exhibited increased glucose disappearance and muscle glucose metabolic index on either diet. This was associated with enhanced activation of muscle Akt and AMP-activated protein kinase and reduced muscle triglycerides in HF-fed Glp1r-/- mice. Chow-fed Glp1r-/- mice exhibited impaired suppression of endoRa and hepatic insulin signaling. In contrast, HF-fed Glp1r-/- mice exhibited improved suppression of endoRa and hepatic Akt activation. This was associated with decreased hepatic triglycerides and impaired activation of sterol regulatory element-binding protein-1. These results show that mice lacking the Glp1r are protected from HF diet-induced muscle and hepatic insulin resistance independent of effects on total fat mass.
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA. jayala@sanfordburnham.org
authors.forename: Julio E
authors.initials: JE
authors.lastname: Ayala
authors.forename: Deanna P
authors.initials: DP
authors.lastname: Bracy
authors.forename: Freyja D
authors.initials: FD
authors.lastname: James
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Burmeister
authors.forename: David H
authors.initials: DH
authors.lastname: Wasserman
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Drucker
mesh_terms: D050154:Adiposity / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D000818:Animals; D004036:Diet, Atherogenic; D004041:Dietary Fats / Q000009:adverse effects*; D005260:Female; D000067757:Glucagon-Like Peptide-1 Receptor; D005947:Glucose / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology; D007333:Insulin Resistance / Q000235:genetics*; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D018027:Receptors, Glucagon / Q000235:genetics*; D012727:Sex Characteristics
chemical_list: D004041:Dietary Fats; C000593834:Glp1r protein, mouse; D000067757:Glucagon-Like Peptide-1 Receptor; D007328:Insulin; D018027:Receptors, Glucagon; D005947:Glucose