Endocannabinoid dysregulation in the pancreas and adipose tissue of mice fed with a high-fat diet
Obesity. 2008-03-01; 16(3): 553-565
DOI: 10.1038/oby.2007.106
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Objective: In mice, endocannabinoids (ECs) modulate insulin release from pancreatic β‐cells and adipokine expression in adipocytes through cannabinoid receptors. Their pancreatic and adipose tissue levels are elevated during hyperglycemia and obesity, but the mechanisms underlying these alterations are not understood.Methods and Procedures: We assessed in mice fed for up to 14 weeks with a standard or high‐fat diet (HFD): (i) the expression of cannabinoid receptors and EC biosynthesizing enzymes (N‐acyl‐phosphatidyl‐ethanolamine‐selective phospholipase D (NAPE‐PLD) and DAGLα) and degrading enzymes (fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL)) in pancreatic and adipose tissue sections by immunohistochemical staining; (ii) the amounts, measured by liquid chromatography–mass spectrometry, of the ECs, 2‐AG, and anandamide (AEA).Results: Although CB1 receptors and biosynthetic enzymes were found mostly in α‐cells, degrading enzymes were identified in β‐cells. Following HFD, staining for biosynthetic enzymes in β‐cells and lower staining for FAAH were observed together with an increase of EC pancreatic levels. While we observed no diet‐induced change in the intensity of the staining of EC metabolic enzymes in the mesenteric visceral fat, a decrease in EC concentrations was accompanied by lower and higher staining of biosynthesizing enzymes and FAAH, respectively, in the subcutaneous fat. No change in cannabinoid receptor staining was observed following HFD in any of the analyzed tissues.Discussion: We provide unprecedented information on the distribution of EC metabolic enzymes in the pancreas and adipose organ, where their aberrant expression during hyperglycemia and obesity contribute to dysregulated EC levels.