Paternal allelic mutation at the Kcnq1 locus reduces pancreatic ß-cell mass by epigenetic modification of Cdkn1c.

Genetic factors are important determinants of the onset and progression of diabetes mellitus. Numerous susceptibility genes for type 2 diabetes, including potassium voltage-gated channel, KQT-like subfamily Q, member1 (KCNQ1), have been identified in humans by genome-wide analyses and other studies. Experiments with genetically modified mice have also implicated various genes in the pathogenesis of diabetes. However, the possible effects of the parent of origin for diabetes susceptibility alleles on disease onset have remained unclear. Here, we show that a mutation at the Kcnq1 locus reduces pancreatic ß-cell mass in mice by epigenetic modulation only when it is inherited from the father. The noncoding RNA KCNQ1 overlapping transcript1 (Kcnq1ot1) is expressed from the Kcnq1 locus and regulates the expression of neighboring genes on the paternal allele. We found that disruption of Kcnq1 results in reduced Kcnq1ot1 expression as well as the increased expression of cyclin-dependent kinase inhibitor 1C (Cdkn1c), an imprinted gene that encodes a cell cycle inhibitor, only when the mutation is on the paternal allele. Furthermore, histone modification at the Cdkn1c promoter region in pancreatic islets was found to contribute to this phenomenon. Our observations suggest that the Kcnq1 genomic region directly regulates pancreatic ß-cell mass and that genomic imprinting may be a determinant of the onset of diabetes mellitus.

Chlorogenic Acid and Caffeine in Coffee Restore Insulin Signaling in Pancreatic Beta Cells.

The incidence of type 2 diabetes is reported to be lower in frequent coffee drinkers than in non-coffee drinkers. To elucidate the mechanism by which coffee prevents the onset of type 2 diabetes, we analyzed how caffeine and chlorogenic acid, which are components of coffee, alter insulin signaling in MIN6 cells, a mouse pancreatic Β cell line. The results showed that caffeine improved insulin signaling under endoplasmic reticulum stress, and chlorogenic acid protected pancreatic Β cells by enhancing the expression of insulin receptor substrate 2 via cAMP response element-binding protein and promoting insulin signaling downstream of insulin receptor substrate 2. In addition, chlorogenic acid was a potent antioxidant for the protection of pancreatic Β cells. Furthermore, in vivo and in vitro analyses revealed that the pancreatic Β cell-protective effect of chlorogenic acid was mediated by the alleviation of endoplasmic reticulum stress. The results suggest that these components of coffee have the potential to reduce the pathogenesis of type 2 diabetes and improve pancreatic Β cell insufficiency.

Dietary, but not topical, alpha-linolenic acid suppresses UVB-induced skin injury in hairless mice when compared with linoleic acids.

Peroxidizability of fatty acids in the air is roughly proportional to the number of double bonds, but in vivo peroxidation proceeds in a more complex manner. Here, we compared the effects of dietary and topically applied oils enriched with linoleic acid (LA, 18:2n-6) or alpha-linolenic acid (ALA, 18:3n-3) on UV-induced skin injury in a strain of hairless mice. The UVB-induced erythema score was significantly lower in mice with topically applied creams containing LA and ALA than in mice with the basal cream; no significant increase in the score was detected in the ALA group compared with the LA group. However, dietary ALA inhibited the increase in erythema score after UVB irradiation compared with LA. The peroxidizability index of the skin total lipids was significantly higher, but UVB-induced prostaglandin E2 (PGE2) production was significantly lower in the group fed an ALA-rich diet compared with the group fed an LA-rich diet. The levels of thiobarbituric acid-reactive substances, estimated in the presence of butylated hydroxytoluene in the assay mixture, were not affected by UVB treatment or by the dietary fatty acids, but the severity of the skin lesion was associated with PGE2 levels. These results indicate that the type of fatty acids, n-6 or n-3, is critical for the suppression of UVB-induced skin lesion when the skin fatty acids are modified by dietary manipulation. Anti-inflammatory activity of dietary flaxseed oil with relatively high ALA and low LA contents was demonstrated in UVB-irradiated hairless mice.