Viviana Vastolo1, Immacolata Cristina Nettore2, Marco Ciccarelli1, Luigi Albano1, Gregory Alexander Raciti1, Michele Longo1, Francesco Beguinot3, Paola Ungaro4. 1. URT Genomics of Diabetes-IEOS, CNR/Department of Translational Medicine, "Federico II" University Medical School of Napoli, via Sergio Pansini 5, 80131 Naples, Italy. 2. Dipartimento di Medicina Clinica e Chirurgia, Unit of Endocrinology, "Federico II" University Medical School of Napoli, via Sergio Pansini 5, 80131 Naples, Italy. 3. URT Genomics of Diabetes-IEOS, CNR/Department of Translational Medicine, "Federico II" University Medical School of Napoli, via Sergio Pansini 5, 80131 Naples, Italy. Electronic address: beguino@unina.it. 4. URT Genomics of Diabetes-IEOS, CNR/Department of Translational Medicine, "Federico II" University Medical School of Napoli, via Sergio Pansini 5, 80131 Naples, Italy. Electronic address: pungaro@ieos.cnr.it.
Abstract
BACKGROUND: The impact of nutrition on the evolution towards type 2 diabetes has recently received increasing attention because of the effect on chromatin structure and gene expression. PURPOSE: Evaluate the effect of high-fat diet on chromatin remodelling and expression of Ped/Pea-15, a gene commonly overexpressed in individuals at risk of type 2 diabetes. METHODS: We used mouse and cell models to investigate Ped/Pea-15 transcriptional regulation by high-fat diet and glucose, respectively. Chromatin structure and histone modification marks were assessed by Micrococcal Nuclease Protection and Chromatin Immunoprecipitation assays. RESULTS: Sixteen-week exposure of C57BL/6J mice to a high-fat diet impaired glucose tolerance and enhanced Ped/Pea-15 expression in their skeletal muscle tissue. This effect was associated with increased chromatin accessibility at specific regulatory sites at the Ped/Pea-15 gene. In particular, the region at -1900 to -1300 bp from Ped/Pea-15 transcription start site was revealed to feature enhancer activity as demonstrated by its function in the luciferase assay, increased p300 recruitment and H3K4me1 and H3K27Ac levels, all marks of functionally active enhancers. Returning mice to a standard chow diet was accompanied by rapid loss of acetylation of K27 on histone H3 and p300 recruitment at Ped/Pea-15. In contrast, the increased H3K4me1, which accompanied the high-fat diet exposure, remained stable. Incubation of muscle cells in culture medium supplemented with 25 mM glucose (HG) increased Ped/Pea-15 mRNA expression and H3K4me1 at the enhancer region. These effects became measurable upon 72 h of exposure to the HG medium and were not rescued upon returning the cells to the 5 mM glucose-containing medium. Interestingly, after 25 mM and sequential 5 mM glucose treatments, re-exposure of the same cells to HG medium further enhanced Ped/Pea-15 expression and increased H3K4me1 above the levels induced by the initial HG challenge already upon 24 h. CONCLUSION: Transient exposure to HFD or HG unveiled the presence of an enhancer element at the Ped/Pea-15 gene. Epigenetic changes imposed at this region by diets, which impair glucose tolerance generate metabolic memory of the nutritional injury and leave Ped/Pea-15 induction in a poised state.
BACKGROUND: The impact of nutrition on the evolution towards type 2 diabetes has recently received increasing attention because of the effect on chromatin structure and gene expression. PURPOSE: Evaluate the effect of high-fat diet on chromatin remodelling and expression of Ped/Pea-15, a gene commonly overexpressed in individuals at risk of type 2 diabetes. METHODS: We used mouse and cell models to investigate Ped/Pea-15 transcriptional regulation by high-fat diet and glucose, respectively. Chromatin structure and histone modification marks were assessed by Micrococcal Nuclease Protection and Chromatin Immunoprecipitation assays. RESULTS: Sixteen-week exposure of C57BL/6J mice to a high-fat diet impaired glucose tolerance and enhanced Ped/Pea-15 expression in their skeletal muscle tissue. This effect was associated with increased chromatin accessibility at specific regulatory sites at the Ped/Pea-15 gene. In particular, the region at -1900 to -1300 bp from Ped/Pea-15 transcription start site was revealed to feature enhancer activity as demonstrated by its function in the luciferase assay, increased p300 recruitment and H3K4me1 and H3K27Ac levels, all marks of functionally active enhancers. Returning mice to a standard chow diet was accompanied by rapid loss of acetylation of K27 on histone H3 and p300 recruitment at Ped/Pea-15. In contrast, the increased H3K4me1, which accompanied the high-fat diet exposure, remained stable. Incubation of muscle cells in culture medium supplemented with 25 mM glucose (HG) increased Ped/Pea-15 mRNA expression and H3K4me1 at the enhancer region. These effects became measurable upon 72 h of exposure to the HG medium and were not rescued upon returning the cells to the 5 mM glucose-containing medium. Interestingly, after 25 mM and sequential 5 mM glucose treatments, re-exposure of the same cells to HG medium further enhanced Ped/Pea-15 expression and increased H3K4me1 above the levels induced by the initial HG challenge already upon 24 h. CONCLUSION: Transient exposure to HFD or HG unveiled the presence of an enhancer element at the Ped/Pea-15 gene. Epigenetic changes imposed at this region by diets, which impair glucose tolerance generate metabolic memory of the nutritional injury and leave Ped/Pea-15 induction in a poised state.