Free Fatty Acids Block Glucose-Induced -Cell Proliferation in Mice by Inducing Cell Cycle Inhibitors p16 and p18

Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
Diabetes (Impact Factor: 8.1). 03/2012; 61(3):632-41. DOI: 10.2337/db11-0991
Source: PubMed


Pancreatic β-cell proliferation is infrequent in adult humans and is not increased in type 2 diabetes despite obesity and insulin resistance, suggesting the existence of inhibitory factors. Free fatty acids (FFAs) may influence proliferation. In order to test whether FFAs restrict β-cell proliferation in vivo, mice were intravenously infused with saline, Liposyn II, glucose, or both, continuously for 4 days. Lipid infusion did not alter basal β-cell proliferation, but blocked glucose-stimulated proliferation, without inducing excess β-cell death. In vitro exposure to FFAs inhibited proliferation in both primary mouse β-cells and in rat insulinoma (INS-1) cells, indicating a direct effect on β-cells. Two of the fatty acids present in Liposyn II, linoleic acid and palmitic acid, both reduced proliferation. FFAs did not interfere with cyclin D2 induction or nuclear localization by glucose, but increased expression of inhibitor of cyclin dependent kinase 4 (INK4) family cell cycle inhibitors p16 and p18. Knockdown of either p16 or p18 rescued the antiproliferative effect of FFAs. These data provide evidence for a novel antiproliferative form of β-cell glucolipotoxicity: FFAs restrain glucose-stimulated β-cell proliferation in vivo and in vitro through cell cycle inhibitors p16 and p18. If FFAs reduce proliferation induced by obesity and insulin resistance, targeting this pathway may lead to new treatment approaches to prevent diabetes.

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    • "In this context, it could be very intriguing to mention that genome-wide association studies revealed an association between SNPs near Cdk2a (the locus encoding p16INK4a) and increased risk of type 2 diabetes (113, 127, 128). It has also been shown that free fatty acids, whose levels were typically increased in type 2 diabetes and that could be responsible for beta-cell damage (129), can induce p16INK4a expression in islets (130). Thus, p16INK4a could represent a potential link between aging, metabolic derangements, and beta-cell failure in type 2 diabets (131). "
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