Identification of Ppy-lineage cells as a novel origin of pancreatic ductal adenocarcinoma.

The Ppy gene encodes pancreatic polypeptide (PP) secreted by PP- or γ-cells, which are a subtype of endocrine cells localised mainly in the islet periphery. For a detailed characterisation of PP cells, we aimed to establish PP cell lines. To this end, we generated a mouse model harbouring the SV40 large T antigen (TAg) in the Rosa26 locus, which is expressed upon Ppy-promoter-mediated Cre-loxP recombination. Whereas Insulin1-CreERT-mediated TAg expression in beta cells resulted in insulinoma, surprisingly, Ppy-Cre-mediated TAg expression resulted in the malignant transformation of Ppy-lineage cells. These mice showed distorted islet structural integrity at 5 days of age compared with normal islets. CK19+ duct-like lesions contiguous with the islets were observed at 2 weeks of age, and mice developed aggressive pancreatic ductal adenocarcinoma (PDAC) at 4 weeks of age, suggesting that PDAC can originate from the islet/endocrine pancreas. This was unexpected as PDAC is believed to originate from the exocrine pancreas. RNA-sequencing analysis of Ppy-lineage islet cells from 7-day-old TAg+ mice showed a downregulation and an upregulation of endocrine and exocrine genes, respectively, in addition to the upregulation of genes and pathways associated with PDAC. These results suggest that the expression of an oncogene in Ppy-lineage cells induces a switch from endocrine cell fate to PDAC. Our findings demonstrate that Ppy-lineage cells may be an origin of PDAC and may provide novel insights into the pathogenesis of pancreatic cancer, as well as possible therapeutic strategies. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Novel time-resolved reporter mouse reveals spatial and transcriptional heterogeneity during alpha cell differentiation.

AIMS/HYPOTHESIS: Glucagon-expressing pancreatic alpha cells have attracted much attention for their plasticity to transdifferentiate into insulin-producing beta cells; however, it remains unclear precisely when, and from where, alpha cells emerge and what regulates alpha cell fate. We therefore explored the spatial and transcriptional heterogeneity of alpha cell differentiation using a novel time-resolved reporter system. METHODS: We established the mouse model, 'Gcg-Timer', in which newly generated alpha cells can be distinguished from more-differentiated cells by their fluorescence. Fluorescence imaging and transcriptome analysis were performed with Gcg-Timer mice during the embryonic and postnatal stages. RESULTS: Fluorescence imaging and flow cytometry demonstrated that green fluorescence-dominant cells were present in Gcg-Timer mice at the embryonic and neonatal stages but not after 1 week of age, suggesting that alpha cell neogenesis occurs during embryogenesis and early neonatal stages under physiological conditions. Transcriptome analysis of Gcg-Timer embryos revealed that the mRNAs related to angiogenesis were enriched in newly generated alpha cells. Histological analysis revealed that some alpha cells arise close to the pancreatic ducts, whereas the others arise away from the ducts and adjacent to the blood vessels. Notably, when the glucagon signal was suppressed by genetic ablation or by chemicals, such as neutralising glucagon antibody, green-dominant cells emerged again in adult mice. CONCLUSIONS/INTERPRETATION: Novel time-resolved analysis with Gcg-Timer reporter mice uncovered spatiotemporal features of alpha cell neogenesis that will enhance our understanding of cellular identity and plasticity within the islets. DATA AVAILABILITY: Raw and processed RNA sequencing data for this study has been deposited in the Gene Expression Omnibus under accession number GSE229090.

Overexpression of Pdx1, reduction of p53, or deletion of CHOP attenuates pancreas hypoplasia in mice with pancreas-specific O-GlcNAc transferase deletion.

Deletion of O-GlcNAc transferase (Ogt) in pancreatic epithelial progenitor cells results in pancreatic hypoplasia at birth, partly due to increased apoptosis during embryonic development. Constitutive loss of Ogt in ß-cells results in increased ER stress and apoptosis, and in the Ogt-deficient pancreas, transcriptomic data previously revealed both tumor suppressor protein p53 and pancreatic duodenal homeobox 1 (Pdx1), key cell survival proteins in the developing pancreas, as upstream regulators of differentially expressed genes. However, the specific roles of these genes in pancreatic hypoplasia are unclear. In this study, we explored the independent roles of p53, ER stress protein CHOP, and Pdx1 in pancreas development and their use in the functional rescue of pancreatic hypoplasia in the context of Ogt loss. Using in vivo genetic manipulation and morphometric analysis, we show that Ogt plays a key regulatory role in pancreas development. Heterozygous, but not homozygous, loss of pancreatic p53 afforded a partial rescue of ß-cell, α-cell, and exocrine cell masses, while whole body loss of CHOP afforded a partial rescue in pancreas weight and a full rescue in exocrine cell mass. However, neither was sufficient to fully mitigate pancreatic hypoplasia at birth in the Ogt-deficient pancreas. Furthermore, overexpression of Pdx1 in the pancreatic epithelium resulted in partial rescues in pancreas weight and ß-cell mass in the Ogt loss background. These findings highlight the requirement of Ogt in pancreas development by targeting multiple proteins such as transcription factor Pdx1 and p53 in the developing pancreas.

Cumulative autophagy insufficiency in mice leads to progression of ß-cell failure.

Autophagy is known to play a pivotal role in ß-cell function. While the lifelong inhibition of autophagy through Atg7 deletion in ß cells has been demonstrated to lead to impaired glucose tolerance together with ß-cell dysfunction, the temporal association between autophagy inhibition and ß-cell dysfunction remains unclear. To address such questions, inducible ß-cell-specific Atg7-knockout (ißAtg7KO) mice were generated, and autophagy inhibition was induced for two different time durations. Whereas 2 weeks of Atg7 ablation was sufficient to induce autophagy deficiency, confirmed by the accumulation of p62, ißAtg7KO mice exhibited normal glucose tolerance. In contrast, prolonged autophagy deficiency for 6 weeks resulted in glucose intolerance together with impaired insulin secretion. Direct mRNA sequencing and pathway analysis revealed that the gene set associated with insulin secretion was downregulated only after the 6-week prolonged autophagy inhibition. Furthermore, we identified a novel gene, Sprr1a, which was expressed at more than 50-fold higher levels during both the 2-week and 6-week autophagy inhibition. These findings suggest that autophagy insufficiency cumulatively leads to ß-cell failure after a certain interval, accompanied by stepwise alterations of gene expression patterns.

Characterisation of Ppy-lineage cells clarifies the functional heterogeneity of pancreatic beta cells in mice.

AIMS/HYPOTHESIS: Pancreatic polypeptide (PP) cells, which secrete PP (encoded by the Ppy gene), are a minor population of pancreatic endocrine cells. Although it has been reported that the loss of beta cell identity might be associated with beta-to-PP cell-fate conversion, at present, little is known regarding the characteristics of Ppy-lineage cells. METHODS: We used Ppy-Cre driver mice and a PP-specific monoclonal antibody to investigate the association between Ppy-lineage cells and beta cells. The molecular profiles of endocrine cells were investigated by single-cell transcriptome analysis and the glucose responsiveness of beta cells was assessed by Ca2+ imaging. Diabetic conditions were experimentally induced in mice by either streptozotocin or diphtheria toxin. RESULTS: Ppy-lineage cells were found to contribute to the four major types of endocrine cells, including beta cells. Ppy-lineage beta cells are a minor subpopulation, accounting for 12-15% of total beta cells, and are mostly (81.2%) localised at the islet periphery. Unbiased single-cell analysis with a Ppy-lineage tracer demonstrated that beta cells are composed of seven clusters, which are categorised into two groups (i.e. Ppy-lineage and non-Ppy-lineage beta cells). These subpopulations of beta cells demonstrated distinct characteristics regarding their functionality and gene expression profiles. Ppy-lineage beta cells had a reduced glucose-stimulated Ca2+ signalling response and were increased in number in experimental diabetes models. CONCLUSIONS/INTERPRETATION: Our results indicate that an unexpected degree of beta cell heterogeneity is defined by Ppy gene activation, providing valuable insight into the homeostatic regulation of pancreatic islets and future therapeutic strategies against diabetes. DATA AVAILABILITY: The single-cell RNA sequence (scRNA-seq) analysis datasets generated in this study have been deposited in the Gene Expression Omnibus (GEO) under the accession number GSE166164 ( www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE166164 ).

Leukotriene A4 hydrolase deficiency protects mice from diet-induced obesity by increasing energy expenditure through neuroendocrine axis.

Obesity is a health problem worldwide, and brown adipose tissue (BAT) is important for energy expenditure. Here, we explored the role of leukotriene A4 hydrolase (LTA4 H), a key enzyme in the synthesis of the lipid mediator leukotriene B4 (LTB4 ), in diet-induced obesity. LTA4 H-deficient (LTA4 H-KO) mice fed a high-fat diet (HFD) showed a lean phenotype, and bone-marrow transplantation studies revealed that LTA4 H-deficiency in non-hematopoietic cells was responsible for this lean phenotype. LTA4 H-KO mice exhibited greater energy expenditure, but similar food intake and fecal energy loss. LTA4 H-KO BAT showed higher expression of thermogenesis-related genes. In addition, the plasma thyroid-stimulating hormone and thyroid hormone concentrations, as well as HFD-induced catecholamine secretion, were higher in LTA4 H-KO mice. In contrast, LTB4 receptor (BLT1)-deficient mice did not show a lean phenotype, implying that the phenotype of LTA4 H-KO mice is independent of the LTB4 /BLT1 axis. These results indicate that LTA4 H mediates the diet-induced obesity by reducing catecholamine and thyroid hormone secretion.

Golgi membrane-associated degradation pathway in yeast and mammals.

Autophagy is a cellular process that degrades subcellular constituents, and is conserved from yeast to mammals. Although autophagy is believed to be essential for living cells, cells lacking Atg5 or Atg7 are healthy, suggesting that a non-canonical degradation pathway exists to compensate for the lack of autophagy. In this study, we show that the budding yeast Saccharomyces cerevisiae, which lacks Atg5, undergoes bulk protein degradation using Golgi-mediated structures to compensate for autophagy when treated with amphotericin B1, a polyene antifungal drug. We named this mechanism Golgi membrane-associated degradation (GOMED) pathway. This process is driven by the disruption of PI(4)P-dependent anterograde trafficking from the Golgi, and it also exists in Atg5-deficient mammalian cells. Biologically, when an Atg5-deficient ß-cell line and Atg7-deficient ß-cells were cultured in glucose-deprived medium, a disruption in the secretion of insulin granules from the Golgi occurred, and GOMED was induced to digest these (pro)insulin granules. In conclusion, GOMED is activated by the disruption of PI(4)P-dependent anterograde trafficking in autophagy-deficient yeast and mammalian cells.

Rubicon in pancreatic beta cells plays a limited role in maintaining glucose homeostasis following increased insulin resistance.

Autophagy has been reported to play a crucial role in the maintenance of intracellular homeostasis, including in pancreatic beta cells. Rubicon, which interacts with the phosphoinositide 3-kinase (PI3K) complex, through autophagy-related 14 (ATG14), is among the few autophagy regulators that have been reported to inhibit autophagic flux to date and the deletion of Rubicon has been shown to increase autophagic flux. Based on previous results showing a causal relationship between autophagic dysfunction and pancreatic beta-cell impairment, we hypothesized that the deletion of Rubicon in pancreatic beta cells would improve cell integrity and confer protective effects. To test this hypothesis, we first confirmed that Rubicon knockdown (KD) promoted autophagic flux in ßTC3 pancreatic beta-cell line. Next, we generated pancreatic beta-cell-specific Rubicon knockout (ßKO) mice, by administering tamoxifen to Rubiconflox/flox:MIP-Cre-ERT mice, which showed normal glucose tolerance and insulin secretion under a normal chow diet, despite successful gene recombination. We also attempted to increase insulin resistance by feeding the mice with a high-fat diet for an additional 2 months to find little differences among the parameters evaluated for glucose metabolism. Finally, severe insulin resistance was induced with insulin receptor antagonist treatment, which resulted in comparable glucose homeostasis measurements between Rubicon ßKO and control mice. In summary, these results suggest that in pancreatic beta cells, Rubicon plays a limited role in the maintenance of systemic glucose homeostasis.

Zinc transporter ZIP13 suppresses beige adipocyte biogenesis and energy expenditure by regulating C/EBP-ß expression.

Given the relevance of beige adipocytes in adult humans, a better understanding of the molecular circuits involved in beige adipocyte biogenesis has provided new insight into human brown adipocyte biology. Genetic mutations in SLC39A13/ZIP13, a member of zinc transporter family, are known to reduce adipose tissue mass in humans; however, the underlying mechanisms remains unknown. Here, we demonstrate that the Zip13-deficient mouse shows enhanced beige adipocyte biogenesis and energy expenditure, and shows ameliorated diet-induced obesity and insulin resistance. Both gain- and loss-of-function studies showed that an accumulation of the CCAAT/enhancer binding protein-ß (C/EBP-ß) protein, which cooperates with dominant transcriptional co-regulator PR domain containing 16 (PRDM16) to determine brown/beige adipocyte lineage, is essential for the enhanced adipocyte browning caused by the loss of ZIP13. Furthermore, ZIP13-mediated zinc transport is a prerequisite for degrading the C/EBP-ß protein to inhibit adipocyte browning. Thus, our data reveal an unexpected association between zinc homeostasis and beige adipocyte biogenesis, which may contribute significantly to the development of new therapies for obesity and metabolic syndrome.

Development of monoclonal mouse antibodies that specifically recognize pancreatic polypeptide.

Pancreatic polypeptide (PP) is a 36-amino acid peptide encoded by the Ppy gene, which is produced by a small population of cells located in the periphery of the islets of Langerhans. Owing to the high amino acid sequence similarity among neuropeptide Y family members, antibodies against PP that are currently available are not convincingly specific to PP. Here we report the development of mouse monoclonal antibodies that specifically bind to PP. We generated Ppy knockout (Ppy-KO) mice in which the Ppy-coding region was replaced by Cre recombinase. The Ppy-KO mice were immunized with mouse PP peptide, and stable hybridoma cell lines producing anti-PP antibodies were isolated. Firstly, positive clones were selected in an enzyme-linked immunosorbent assay for reactivity with PP coupled to bovine serum albumin. During the screening, hybridoma clones producing antibodies that cross-react to the peptide YY (PYY) were excluded. In the second screening, hybridoma clones in which their culture media produce no signal in Ppy-KO islets but detect specific cells in the peripheral region of wild-type islets, were selected. Further studies demonstrated that the selected monoclonal antibody (23-2D3) specifically recognizes PP-producing cells, not only in mouse, but also in human and rat islets. The monoclonal antibodies with high binding specificity for PP developed in this study will be fundamental for future studies towards elucidating the expression profiles and the physiological roles of PP.

Heterogeneity of autophagic status in pancreatic ß cells under metabolic stress.

Autophagy in ß cells has been demonstrated to play a pivotal role in cellular homeostasis and the progression of glucose intolerance. Although autophagic activity is affected by metabolic stress both in vivo and in vitro, it remains unclear as to what extent the autophagic status in each ß cell is different from its neighboring cells. To address this question, GFP-LC3 reporter mice, which can visualize the autophagic status of each ß cell as green-fluorescent puncta, were crossed with obese diabetic db/db mice. Imaging of green-fluorescent puncta in the islets of GFP-LC3 mice revealed that ß cells are a heterogeneous population, as the density of GFP-LC3 puncta in each cell was variable. Furthermore, the variability was greater in GFP-LC3; db/db mice than in non-diabetic GFP-LC3; db/+ mice. Furthermore, when GFP-LC3 mice were treated with a low dose of S961, which antagonizes insulin signaling without inducing overt hyperglycemia, the number of ß cells with a high density of GFP puncta was increased, suggesting that insulin resistance affects autophagic status independently of glucose profiles. These results suggest that pancreatic ß cells under metabolic stress are heterogeneous regarding their autophagic status, which provides insights into the cellular dynamics of each ß cell rather than the whole ß-cell population.

Normal pancreatic ß-cell function in mice with RIP-Cre-mediated inactivation of p62/SQSTM1.

Recent studies have suggested that decreased pancreatic ß-cell function and mass are common features of patients with type 2 diabetes mellitus. Pancreatic ß-cell homeostasis is regulated by various types of signaling molecules and stress responses. Sequestosome 1/p62 (SQSTM1, hereafter referred to as p62) is a ubiquitin-binding adaptor protein involved in cell signaling, oxidative stress, and autophagy. Because p62 appears to play an important role in maintaining mitochondrial quality control, it is possible that the loss of p62 in pancreatic ß cells contributes to mitochondrial dysfunction, and thus leading to impaired glucose tolerance. In this study we investigated the physiological roles of p62 by inactivating p62 in a ß-cell specific manner. We found that firstly, rat insulin-2 promoter-Cre (RIP-Cre)-mediated p62 inactivation did not cause body weight gain, although ubiquitous inactivation of p62 was previously shown to result in severe obesity. Secondly, we found no gross structural disorganization of the islets of p62-deficient mice. Consistent with normal islet morphology, no impairment in glucose tolerance was observed in mice with RIP-Cre-mediated p62 deletion. These results suggest that p62 is dispensable for normal islet organization and ß-cell function.

Effects of linagliptin monotherapy compared with voglibose on postprandial lipid profiles in Japanese patients with type 2 diabetes: linagliptin study of effects on postprandial blood glucose (L-STEP) sub-study 1.

Recently, we reported that linagliptin had equivalent efficacy to voglibose in reducing postprandial blood glucose levels in drug-naïve patients with type 2 diabetes (L-STEP Study). As a sub-study of the L-STEP Study we examined the effect of linagliptin on postprandial lipids profile. Between October 2012 and April 2014, the study enrolled patients with type 2 diabetes mellitus who had inadequate glycemic control. Patients were randomly assigned to either the linagliptin group (5 mg once daily, n = 85) or the voglibose group (0.2 mg/meal thrice daily, n = 71). Meal tolerance tests were performed at baseline (week 0) and endpoint (week 12). The increments in 4-h postprandial triglyceride, remnant lipoprotein cholesterol (RLP-C), and apolipoprotein B48 (ApoB48) from baseline to endpoint in the linagliptin group were lower (p < 0.001, p = 0.025 and p < 0.001). 4-h postprandial ApoB48 at endpoint was lower in the linagliptin group (p = 0.007), and positive correlation was detected between change of ApoB48 and changes in both triglyceride (r = 0.67, p < 0.001) and RLP-C (r = 0.73, p < 0.001) at 4 h. This study revealed that in drug-naïve Japanese patients with relatively mild type 2 diabetes mellitus, linagliptin improves not only postprandial blood glucose level but also levels of lipids such as TG and RLP-C by reducing the ApoB48 level compared with voglibose.

Effects of linagliptin versus voglibose on treatment-related quality of life in patients with type 2 diabetes: sub-analysis of the L-STEP study.

Treatment-related quality of life (QOL) is an important aspect of diabetes management. However, no studies have compared the influence of dipeptidyl peptidase-4 inhibitors versus alpha-glucosidase inhibitors on treatment-related QOL. This prespecified sub-analysis of the Linagliptin Study of Effects on Postprandial blood glucose (L-STEP) compared the effects of linagliptin (5 mg once daily) and voglibose (0.2 mg/meal thrice daily) on treatment-related QOL in Japanese patients with type 2 diabetes (T2DM) inadequately controlled with diet and exercise therapy. Among 366 subjects in the original study, 182 in the linagliptin group and 173 in the voglibose group were included in this analysis. The outcome of this study was change in QOL as assessed by the Diabetes Therapy-Related Quality of Life 17 (DTR-QOL17) questionnaire from baseline to week 12. Compared with baseline data, total DTR-QOL17 scores were significantly higher after 12 weeks of linagliptin and voglibose treatment. The change in the total DTR-QOL17 score and the score of one domain, burden on social activities and daily activities, was significantly greater in the linagliptin group than in the voglibose group. In addition, only linagliptin treatment was identified as a factor associated with an increased total DTR-QOL17 score. Linagliptin is superior to voglibose in terms of improving treatment-related QOL in Japanese patients with T2DM.

Role of Zinc Homeostasis in the Pathogenesis of Diabetes and Obesity.

Zinc deficiency is a risk factor for obesity and diabetes. However, until recently, the underlying molecular mechanisms remained unclear. The breakthrough discovery that the common polymorphism in zinc transporter SLC30A8/ZnT8 may increase susceptibility to type 2 diabetes provided novel insights into the role of zinc in diabetes. Our group and others showed that altered ZnT8 function may be involved in the pathogenesis of type 2 diabetes, indicating that the precise control of zinc homeostasis is crucial for maintaining health and preventing various diseases, including lifestyle-associated diseases. Recently, the role of the zinc transporter ZIP13 in the regulation of beige adipocyte biogenesis was clarified, which indicated zinc homeostasis regulation as a possible therapeutic target for obesity and metabolic syndrome. Here we review advances in the role of zinc homeostasis in the pathophysiology of diabetes, and propose that inadequate zinc distribution may affect the onset of diabetes and metabolic diseases by regulating various critical biological events.

Transcriptional regulation of pancreas development and ß-cell function [Review].

A small number of cells in the adult pancreas are endocrine cells. They are arranged in clusters called islets of Langerhans. The islets make insulin, glucagon, and other endocrine hormones, and release them into the blood circulation. These hormones help control the level of blood glucose. Therefore, a dysfunction of endocrine cells in the pancreas results in impaired glucose homeostasis, or diabetes mellitus. The pancreas is an organ that originates from the evaginations of pancreatic progenitor cells in the epithelium of the foregut endoderm. Pancreas organogenesis and maturation of the islets of Langerhans occurs via a coordinated and complex interplay of transcriptional networks and signaling molecules, which guide a stepwise and repetitive process of the propagation of progenitor cells and their maturation, eventually resulting in a fully functional organ. Increasing our understanding of the extrinsic, as well as intrinsic mechanisms that control these processes should facilitate the efforts to generate surrogate ß cells from ES or iPS cells, or to reactivate the function of important cell types within pancreatic islets that are lost in diabetes.

SET7/9 Enzyme Regulates Cytokine-induced Expression of Inducible Nitric-oxide Synthase through Methylation of Lysine 4 at Histone 3 in the Islet ß Cell.

SET7/9 is an enzyme that methylates histone 3 at lysine 4 (H3K4) to maintain euchromatin architecture. Although SET7/9 is enriched in islets and contributes to the transactivation of ß cell-specific genes, including Ins1 and Slc2a, SET7/9 has also been reported to bind the p65 subunit of nuclear factor κB in non-ß cells and modify its transcriptional activity. Given that inflammation is a central component of ß cell dysfunction in Type 1 and Type 2 diabetes, the aim of this study was to elucidate the role of SET7/9 in proinflammatory cytokine signaling in ß cells. To induce inflammation, ßTC3 insulinoma cells were treated with IL-1ß, TNF-α, and IFN-γ. Cytokine treatment led to increased expression of inducible nitric-oxide synthase, which was attenuated by the diminution of SET7/9 using RNA interference. Consistent with previous reports, SET7/9 was co-immunoprecipitated with p65 and underwent cytosolic to nuclear translocation in response to cytokines. ChIP analysis demonstrated augmented H3K4 mono- and dimethylation of the proximal Nos2 promoter with cytokine exposure. SET7/9 was found to occupy this same region, whereas SET7/9 knockdown attenuated cytokine-induced histone methylation of the Nos2 gene. To test this relationship further, islets were isolated from SET7/9-deficient and wild-type mice and treated with IL-1ß, TNF-α, and IFN-γ. Cytokine-induced Nos2 expression was reduced in the islets from SET7/9 knock-out mice. Together, our findings suggest that SET7/9 contributes to Nos2 transcription and proinflammatory cytokine signaling in the pancreatic ß cell through activating histone modifications.

Increased intramyocellular lipid/impaired insulin sensitivity is associated with altered lipid metabolic genes in muscle of high responders to a high-fat diet.

The accumulation of intramyocellular lipid (IMCL) is recognized as an important determinant of insulin resistance, and is increased by a high-fat diet (HFD). However, the effects of HFD on IMCL and insulin sensitivity are highly variable. The aim of this study was to identify the genes in muscle that are related to this inter-individual variation. Fifty healthy men were recruited for this study. Before and after HFD for 3 days, IMCL levels in the tibialis anterior were measured by (1)H magnetic resonance spectroscopy, and peripheral insulin sensitivity was evaluated by glucose infusion rate (GIR) during the euglycemic-hyperinsulinemic clamp. Subjects who showed a large increase in IMCL and a large decrease in GIR by HFD were classified as high responders (HRs), and subjects who showed a small increase in IMCL and a small decrease in GIR were classified as low responders (LRs). In five subjects from each group, the gene expression profile of the vastus lateralis muscle was analyzed by DNA microarray analysis. Before HFD, gene expression profiles related to lipid metabolism were comparable between the two groups. Gene Set Enrichment Analysis demonstrated that five gene sets related to lipid metabolism were upregulated by HFD in the HR group but not in the LR group. Changes in gene expression patterns were confirmed by qRT-PCR using more samples (LR, n = 9; HR, n = 11). These results suggest that IMCL accumulation/impaired insulin sensitivity after HFD is closely associated with changes in the expression of genes related to lipid metabolism in muscle.

Relationship between dietary patterns and risk factors for cardiovascular disease in patients with type 2 diabetes mellitus: a cross-sectional study.

BACKGROUND: While some dietary patterns are associated with the incidence of type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD), the relationship between dietary pattern and risk factors for CVD in patients with T2DM remains to be clarified. The aim of this study was to identify dietary patterns and investigate the relationship between dietary patterns and potential risk factors for CVD in patients with T2DM. METHODS: The study participants comprised 726 Japanese T2DM outpatients free of history of CVD. Life styles were analyzed using self-reported questionnaires. The relationship between dietary patterns, identified by factor analysis, and potential risk factors for CVD was investigated by linear and logistic regression analyses. RESULTS: Six dietary patterns were identified by factor analysis. Especially, three dietary patterns were associated with risk factors for CVD. The "Seaweeds, Vegetables, Soy products and Mushrooms" pattern, characterized by high consumption of seaweeds, soy products and mushrooms, was associated with lower use of diabetes medication and healthier lifestyles. The "Noodle and Soup" pattern, characterized by high consumption of noodle and soup was associated with higher body mass index, alanine aminotransferase, aspartate aminotransferase, γ-glutamyl transpeptidase and triglyceride levels. The "Fruit, Dairy products and Sweets" pattern was associated with lower γ-glutamyl transpeptidase levels, blood pressure, albuminuria and brachial-ankle pulse wave velocity. CONCLUSIONS: The findings suggested that dietary patterns correlated with risk factors for CVD in T2DM patients.

Serotonin regulates glucose-stimulated insulin secretion from pancreatic ß cells during pregnancy.

In preparation for the metabolic demands of pregnancy, ß cells in the maternal pancreatic islets increase both in number and in glucose-stimulated insulin secretion (GSIS) per cell. Mechanisms have been proposed for the increased ß cell mass, but not for the increased GSIS. Because serotonin production increases dramatically during pregnancy, we tested whether flux through the ionotropic 5-HT3 receptor (Htr3) affects GSIS during pregnancy. Pregnant Htr3a(-/-) mice exhibited impaired glucose tolerance despite normally increased ß cell mass, and their islets lacked the increase in GSIS seen in islets from pregnant wild-type mice. Electrophysiological studies showed that activation of Htr3 decreased the resting membrane potential in ß cells, which increased Ca(2+) uptake and insulin exocytosis in response to glucose. Thus, our data indicate that serotonin, acting in a paracrine/autocrine manner through Htr3, lowers the ß cell threshold for glucose and plays an essential role in the increased GSIS of pregnancy.