Kazue Honma

The regulation of jejunal induction of the maltase-glucoamylase gene by a high-starch/low-fat diet in mice

Maltase and glucoamylase are derived from the same mRNA and are responsible for digestion of starch in the small intestine. Their jejunal activities in rodents are induced by a high-starch/low-fat (HS)-diet. However, it is unknown whether jejunal expression of the maltase-glucoamylase (Mgam) gene is enhanced by the HS-diet. In this study, we found that jejunal Mgam mRNA was increased by a HS-diet in mice. We showed that the HS-diet increased acetylation of histones, bindings of a coactivator, Creb binding protein (CREBBP), and the transcriptional factors caudal type homeobox 2 (CDX2) and HNF1 homeobox (HNF1) in the promoter/enhancer and transcriptional regions of Mgam gene. This suggests that the increase in the jejunal activity of maltase and glucoamylase caused by a HS-diet in mice is regulated at the mRNA level through histone acetylation and binding of CREBBP, CDX2 and HNF1 in the promoter/enhancer and transcriptional regions of Mgam gene.

Inductions of histone H3 acetylation at lysine 9 on SGLT1 gene and its expression by feeding mice a high carbohydrate/fat ratio diet

OBJECTIVE We examined in this study whether histone H3 acetylations on jejunal NA(+)/glucose transport-1 (SGLT1) gene are associated with induction of its gene by feeding mice a high carbohydrate/fat ratio diet. METHODS The chromatin immunoprecipitation (ChIP) assays using antibodies of acetylated histone H3 were performed in jejunum of mice fed a high carbohydrate/fat ratio diet or a low carbohydrate/fat ratio for 7 d. RESULTS The acetylations of histone H3 of lysine 9/14 were highly detected on the SGLT1 gene and the levels were enhanced by feeding mice a high carbohydrate/fat ratio diet. Histone H3 acetylation at lysine 9 was enhanced by feeding a high carbohydrate/fat ratio diet, whereas that at lysine 14 was not enhanced significantly. CONCLUSION These observations indicate that induction of SGLT1 gene expression by feeding a high carbohydrate/fat ratio diet is associated with acetylation of histone H3 at lysine 9 on the SGLT1 gene.

Loss of circadian rhythm of circulating insulin concentration induced by high-fat diet intake is associated with disrupted rhythmic expression of circadian clock genes in the liver

OBJECTIVE Peripheral clock genes show a circadian rhythm is correlated with the timing of feeding in peripheral tissues. It was reported that these clock genes are strongly regulated by insulin action and that a high-fat diet (HFD) intake in C57BL/6J mice for 21days induced insulin secretion during the dark phase and reduced the circadian rhythm of clock genes. In this study, we examined the circadian expression patterns of these clock genes in insulin-resistant animal models with excess secretion of insulin during the day. MATERIALS/METHODS We examined whether insulin resistance induced by a HFD intake for 80days altered blood parameters (glucose and insulin concentrations) and expression of mRNA and proteins encoded by clock and functional genes in the liver using male ICR mice. RESULTS Serum insulin concentrations were continuously higher during the day in mice fed a HFD than control mice. Expression of lipogenesis-related genes (Fas and Accβ) and the transcription factor Chrebp peaked at zeitgeber time (ZT)24 in the liver of control mice. A HFD intake reduced the expression of these genes at ZT24 and disrupted the circadian rhythm. Expression of Bmal1 and Clock, transcription factors that compose the core feedback loop, showed circadian variation and were synchronously associated with Fas gene expression in control mice, but not in those fed a HFD. CONCLUSIONS These results indicate that the disruption of the circadian rhythm of insulin secretion by HFD intake is closely associated with the disappearance of circadian expression of lipogenic and clock genes in the liver of mice.

Induction by Fructose Force-Feeding of Histone H3 and H4 Acetylation at Their Lysine Residues around the Slc2a5 Gene and Its Expression in Mice

It has been reported that fructose force-feeding rapidly induced jejunal Slc2a5 gene expression in rodents. We demonstrate in this study that acetylation at lysine (K) 9 of histone H3 and acetylation at K5 and K16 of histone H4 were more enhanced in the promoter/enhancer to transcribed regions of the Slc2a5 gene in fructose force-fed mice than in glucose force-fed mice. However, fructose force-feeding did not induce acetylation at K14 of histone H3, or at K8 and K12 of histone H4 around the Slc2a5 gene. These results suggest that fructose force-feeding induced selective histone acetylation, particularly of H3 and H4, around the jejunal Slc2a5 gene in mice.

Relationship between epigenetic regulation, dietary habits, and the developmental origins of health and disease theory

Environmental stressors during developmental stages are hypothesized to increase the risk of developing metabolic diseases such as obesity, type 2 diabetes, hypertension, and psychiatric diseases during later life. This theory is known as the Developmental Origins of Health and Disease (DOHaD). Recent studies suggest that accumulation of environmental stress, including those during developmental stages, is internalized as acquired information designated as “epigenetic memory.” This epigenetic memory is generally indicated as DNA methylation and histone modifications in the chromatin. In general, the demethylation of CpG islands induces histone acetylation and associated changes from heterochromatin to euchromatin, and enhances transcriptional activation. These changes are induced by the binding of transcriptional factors to cis‐elements located on promoter and enhancer regions and the associated binding of histone acetyl‐transferase and the transcription initiation complex. Recent studies have demonstrated novel epigenetic modifications that regulate transcription elongation steps by activating histone acetylation and bromodomain‐containing protein 4, which contains two bromodomains to bind acetylated histones, on the gene body (transcribed region). Gene expression alterations induced by carbohydrate signals and by changes in energy balance in the body are regulated by this model. In addition, induction of many metabolic genes, which are induced or reduced in adulthood by malnutrition during developmental stages, by intake of major nutrients, or development of lifestyle diseases in adulthood, are targeted by these novel epigenetic changes. In the present review, we introduce epigenetic regulations and the relationship with nutrient intake, and discuss links between epigenetic regulation and the development of metabolic diseases according to DOHaD.

BRD4 regulates fructose-inducible lipid accumulation-related genes in the mouse liver

OBJECTIVE Fructose intake induces hepatic steatosis by activating fat synthesis. In this study, we searched for genes that showed acute induction in the livers of mice force-fed with fructose, and examined how this induction is regulated. MATERIALS/METHODS We identified genes induced at 6h after the fructose force-feeding using a microarray and quantitative real-time RT-PCR. Histone acetylation and an acetylated histone binding protein bromodomain containing (BRD)4 binding around the fructose-inducible genes were examined using a chromatin immunoprecipitation assay. We examined whether (+)-JQ1, an inhibitor of the binding between the BRD4 and acetylated histones, inhibited the expressions of fructose-inducible genes, histone acetylation and BRD4 binding around the genes. RESULTS We identified upregulated genes related to lipid accumulation, such as Cyp8b1, Dak and Plin5, in mice force-fed with fructose compared with those force-fed with glucose. Acetylation of histones H3 and H4, and BRD4 binding around the transcribed region of those fructose-inducible genes, were enhanced by fructose force-feeding. Meanwhile, (+)-JQ1 treatment reduced expressions of fructose-inducible genes, histone acetylation and BRD4 binding around these genes. CONCLUSIONS Acute induction of genes related to lipid accumulation in the livers of mice force-fed with fructose is associated with the induction of histone acetylation and BRD4 binding around these genes.

Acute induction of histone acetylation on the jejunal sucrase–isomaltase gene by dietary fructose

We have previously reported that dietary fructose rapidly induces jejunal sucrase-isomaltase (SI) gene expression in rats. In this study, we confirmed in mice that SI mRNA was induced 6 h after force-feeding fructose, but not glucose. Using the chromatin immunoprecipitation assay, we revealed that histones H3 and H4 on the promoter/enhancer regions of the SI gene in mice given fructose were highly acetylated, compared with those given glucose or water. These results suggest that acute induction of SI gene expression by dietary fructose is associated with acetylation of histones H3 and H4 on the SI gene.

Re-feeding rats a high-sucrose diet after 3 days of starvation enhances histone H3 acetylation in transcribed region and expression of jejunal GLUT5 gene

Fasting for 3 days leads to reduction in the expression of GLUT5 and SGLT1 genes in jejunum. Re-feeding a high-sucrose diet in fasted rats enhanced mRNA levels and histone H3 acetylation on transcribed region of GLUT5 gene within 24 h, but not in SGLT1. Responsiveness of jejunal GLUT5 gene is associated with changes in histone H3 acetylation on transcribed region.

Regulation of the circadian rhythmic expression of Sglt1 in the mouse small intestine through histone acetylation and the mRNA elongation factor, BRD4-P-TEFb

Abstract Jejunal sodium/glucose co-transporter (Sglt1) displays circadian expression. The jejunum was collected every 4 h from mice, and we examined histone acetylation and binding of bromodomain-containing protein-4 (BRD4) around of the gene. Histone acetylation increased in the transcribed region of Sglt1 prior to induction of the gene. Furthermore, the binding of mRNA elongation factor around the gene showed circadian rhythm.

Insulin-induced inhibition of gluconeogenesis genes, including glutamic pyruvic transaminase 2, is associated with reduced histone acetylation in a human liver cell line

OBJECTIVES Hepatic glutamic pyruvic transaminase (GPT; also known as alanine aminotransferase) is a gluconeogenesis enzyme that catalyzes conversions between alanine and pyruvic acid. It is also used as a blood biomarker for hepatic damage. In this study, we investigated whether insulin regulates GPT expression, as it does for other gluconeogenesis genes, and if this involves the epigenetic modification of histone acetylation. METHODS Human liver-derived HepG2 cells were cultured with 0.5-100nM insulin for 8h, and the mRNA expression of GPT, glutamic-oxaloacetic transaminase (GOT), γ-glutamyltransferase (GGT), PCK1, G6PC and FBP1 was measured. We also investigated the extent of histone acetylation around these genes. RESULTS Insulin suppressed the mRNA expression of gluconeogenesis genes (GPT2, GOT1, GOT2, GGT1, GGT2, G6PC, and PCK1) in HepG2 cells in a dose-dependent manner. mRNA levels of GPT2, but not GPT1, were decreased by insulin. Histone acetylation was also reduced around GPT2, G6PC, and PCK1 in response to insulin. CONCLUSION The expression of GPT2 and other gluconeogenesis genes such as G6PC and PCK1 was suppressed by insulin, in association with decreases in histone H3 and H4 acetylation surrounding these genes.