Glucagon regulates Hepatic Kisspeptin1 to Impair Insulin Secretion in Diabetes Mellitus
ABSTRACT: Glucagon and insulin are counter-regulatory pancreatic hormones that precisely control blood glucose homeostasis1. Type 2 diabetes mellitus (T2DM) is characterized by inappropriately elevated blood glucagon2-5 levels as well as insufficient glucose stimulated insulin secretion (GSIS) by pancreatic ß-cells6. Early in the pathogenesis of T2DM, hyperglucagonemia is observable antecedent to ß-cell dysfunction7-9; and in mice, liver-specific activation of glucagon receptor-dependent signaling results in impaired GSIS10. However, the mechanistic relationship between hyperglucagonemia, hepatic glucagon action, and ß-cell dysfunction remains poorly understood. Here we show that glucagon action stimulates hepatic production of the neuropeptide kisspeptin1, which acts in an endocrine manner on ß-cells to suppress GSIS. In vivo glucagon administration acutely stimulates hepatic kisspeptin1 production, and kisspeptin1 is increased in livers from humans with T2DM and from mouse models of diabetes mellitus. Synthetic kisspeptin1 potently suppresses GSIS in vivo and in vitro from normal isolated islets, which express the kisspeptin1 receptor Kiss1R. Administration of a Kiss1R antagonist in diabetic Leprdb/db mice potently augments GSIS and reduces glycemia. Our observations indicate in the pathogenesis of T2DM an endocrine mechanism sequentially linking hyperglucagonemia via hepatic kisspeptin1 production to impaired insulin secretion. In addition, our findings suggest Kiss1R antagonism as a therapeutic avenue to improve ß-cell function in T2DM. Total RNA from L-Δprkar1a KO mice compared to control D-glucose mice
Project description:The ability to isolate pure pancreatic ß-cells would greatly aid multiple areas of diabetes research. We developed an exendin-4-like neopeptide conjugate for the rapid purification and isolation of functional pancreatic ß-cells. By targeting the glucagon-like peptide-1 receptor, ß-cells were isolated within an hour and were >99% pure. These studies were confirmed by immunostaining, confocal microscopy and microarray analysis on isolated cells. Gene expression profiling studies of the cytofluorometrically sorted ß-cells provided new insights into the genetic programs at play of different ages and stages during type-1 diabetes development. The described isolation method should have broad applicability to the ß-cell field. Microarray profile of beta cells from isolated islets from 4 and 12 week old NOD mice. Cells were stained with 50 nM Ex4+ probe and sorted on FACS ARIA. DAPI and CD45+ cells were excluded.
Project description:Gamma-secretase inhibitors (GSIs), which block the activation of NOTCH receptors, are being tested in the treatment of T-cell acute lymphoblastic leukemia (T-ALL). Thus far, limited antileukemic cytotoxicity and severe gastrointestinal toxicity have restricted the clinical application of these targeted drugs. Here we show that combination therapy with GSIs plus glucocorticoids can improve the antileukemic effects of GSIs and reduce their gut toxicity in vivo. Inhibition of NOTCH1 signaling in glucocorticoid-resistant T-ALL restored glucocorticoid receptor auto-up-regulation and induced apoptotic cell death through induction of BIM expression. Additionally, cotreatment with glucocorticoids induced Ccnd2 upregulation in the gut which protected mice from the intestinal secretory metaplasia typically induced by loss of NOTCH signaling. These results support a role for glucocorticoids plus GSIs in the treatment of glucocorticoid-resistant T-ALL. Experiment Overall Design: Experiments analyzing the interacition of dexamethasone and the gamma-secretase inhibitor DBZ were carried out in 6-week-old C57/Black6 female mice (Jackson Laboratory). In these studies we treated mice with vehicle (DMSO) (n=2), dexamethasone (15 mg/kg) (n=2), DBZ (10 micromol/kg) (n=2) and dexamethasone (15 mg/kg) plus DBZ (10 micromol/kg) (n=2) daily by intraperitoneal injection for 5 days. At the end of the treatment, animals were euthanized and segments of the small intestine were collected and processed for RNA extraction, histological and immunohistochemical analysis.
Project description:We have characterized the global program of transcription in SRC-2-depleted MCF-7 breast cancer cells using short-hairpin RNA technology, and in MCF-7 cells exposed to PKA activating agents. In order to identify genes that may be regulated through PKA-induced downregulation of SRC-2, overlapping transcriptional targets in response to the respective treatments were characterized. MCF-7 human breast cancer cells transduced with shRNA targeting SRC-2 (SRC-2 shRNA) or infected with control shRNA vector (Ctr shRNA) were seeded in 9,2 cm petri dishes, 2,0 x106 cells in each dishes, in DMEM supplemented with 5% charcoaled stripped FBS and 10 nM 17b-estradiol. After 48 hours a selection of the Ctr shRNA cells were treated with cAMP analog (8-CPT-cAMP, 150 µM) and cAMP elevating agents (Forskolin (10 µM) and IBMX (50 µM)) The cells were then incubated for another 24 hour in the cell incubator. Cells were harvested by washing them twice with 8 ml PBS (37 oC), before adding 1,5 ml 0,25 % trypzine. The trypzine reaction was stopped after 5 minutes by adding 2,5 ml DMEM to the cells. Trypzine and cell medium was removed by centrifugating the cell suspensions at 1000 rpm for 3 minutes. The cells were then washed with 400 µl PBS, before addition of 350 µl RLT buffer to the cell pellets. The cells were then homogenized by vortexing for 1 minute and then freezed in -80 oC.
Project description:TCF7L2 is one of the strongest type 2 diabetes (T2DM) candidate genes to emerge from GWAS studies, but the mechanisms by which it regulates the pathways which are important in the pathogenesis of type 2 diabetes are unknown. Previous in vitro and in vivo studies have focused on the link between TCF7L2 and insulin secretion as an explanation for the association between TCF7L2 and T2DM. However, TCF7L2 and the Wnt/β-catenin pathway are important for metabolic zonation in the liver. This raises the interesting possibility that TCF7L2 may influence glucose homeostasis by regulating hepatic glucose production (HGP). To examine this question, we utilized the H4IIE cell as a model of HGP. Inhibition of HGP in H4IIE cells from lactate and pyruvate was highly sensitive to physiological concentrations of insulin and metformin. Silencing of TCF7L2 protein expression induced a 5-fold increase in basal HGP (P<0.0001), and this was accompanied by marked increase in the expression of several key gluconeogenic genes. FBPase, PEPCK and G6Pase mRNA were up-regulated 2.5-fold (P<0.0001), 1.4-fold (P<0.01) and 2.3-fold (P<0.0001), respectively, compared to scramble siRNA. Compared to their respective baseline values, insulin and metformin suppressed HGP equally in the scramble and TCF7L2 siRNA cells, but HGP remained elevated in TCF7L2 silenced cells due to the increased baseline HGP. Using chromatin immunoprecipitation sequencing (ChIP-Seq), we investigated the direct transcriptional targets of TCF7L2 in hepatocytes. A total of 2119 ChIP peaks were detected, of which 36% were located inside gene boundaries and, overall, a total of 65% of all binding events were within 50 Kb of a gene. De novo motif analysis revealed remarkable conservation of the long and short TCF7L2 consensus binding sites in the rat hepatocytes. Pathway analysis showed that the top two disease categories over-represented in our dataset were “non-insulin dependent diabetes” (155 genes; P = 1.63 x 10-10) and “diabetes mellitus” (245 genes; P = 7.4 x 10-12). Inspection of genes in these categories revealed that TCF7L2 directly binds to multiple genes important in the regulation of glucose metabolism in the liver, including PEPCK, FBP1, IRS1, IRS2, AKT2 ADIPOR1, PDK4 and CPT1A. Our findings suggest a novel mechanism for the regulation of HGP by TCF7L2, and provide a possible explanation for the association of TCF7L2 polymorphisms with the incidence of T2DM. two samples: TCF7L2 ChIP-Seq and Input DNA
Project description:Type 1 diabetes mellitus (T1DM) results from immune mediated destruction of pancreatic beta cells. However, clinical and immunologic phenotypes of T1DM are variable. Several auto-antibodies including GADA, IA-2A, and ZnT8A, were identified in T1DM, but the prevalence of these auto-antibodies varied for a broad spectrum of T1DM. Here, we systemically profiled auto-antibodies from serum samples of 16 T1DM, 16 type 2 diabetes (T2DM) patients, and 27 healthy controls with normal glucose tolerance (NGT) using protein microarrays containing 9,480 proteins. Among 9,480 different proteins on the array, we identified novel auto-antibody candidates (EEF1A1-AAb and UBE2L3-AAb) by M-test coupled with PLS-DA. These auto-antibodies were highly present in T1DM than controls and detected in 40% of T1DM without GADA. Furthermore, these auto-antibodies might help to differentiate subtype of T1DM when combined with GADA. These novel auto-antibodies provide new diagnostic information of T1DM, as well as new insights into the pathogenesis of T1DM. Auto-antibodies from serum samples were profiled using a high-density, fluorescence-based protein microarray containing duplicate spots of 9,480 human proteins derived from the Ultimate ORF collection The cohort of patients and controls consisted of 16 T1DM, 16 T2DM patients, and 27 healthy controls with NGT. This cohort was used to screen candidate auto-antibodies using protein microarrays (ProtoArray platform version 5.0, Invitrogen Corp., Carlsbad, CA). Serum samples were drawn from T1DM patients who have 1) fasting C-peptide level <0.3 nmol/L or serum C-peptide <0.6 nmol/L after glucagon loading, 2) initiation of insulin treatment within six months after diagnosis, and 3) duration of diabetes ≤12 months. Mean age of T1DM in the first cohort was 42 ± 16 years. The control serum samples were obtained from T2DM patients who were treated only with oral anti-diabetic drug at least 5 years and from NGTs who had no history of diabetes, no first-degree relatives with diabetes, a fasting plasma glucose concentration of <6.1 mmol/l, and a HbA1c value of <5.8%.
Project description:Insulin resistance and Type 2 Diabetes Mellitus (T2DM) are associated with increased adipocyte size, altered secretory pattern and decreased differentiation of preadipocytes. To identify the underlying molecular processes in preadipocytes of T2DM patients that are a characteristic of the development of T2DM, preadipocyte cell cultures were prepared from subcutaneous fat biopsies of T2DM patients and compared with age- and BMI matched control subjects. Gene expression profiling showed changed expression of transcription factors involved in adipogenesis and in extracellular matrix remodeling, actin cytoskeleton and integrin signaling genes, which indicated decreased capacity to differentiate. Additionally, genes involved in insulin signaling and lipid metabolism were down-regulated, and inflammation/apoptosis was up-regulated in T2DM preadipocytes. The down-regulation of genes involved in differentiation can provide a molecular basis for the reduced adipogenesis of preadipocytes of T2DM subjects, leading to reduced formation of adipocytes in subcutaneous fat depots, and ultimately leading to ectopic fat storage. Overall design: 7 T2DM preadipocyte samples and 9 age- and BMI-matched control samples were hybridized using 70-mer oligonucleotide microarrays. Samples were labeled with either Cy3 or Cy5. A total of 20 arrays were used including dye swop. Per array, a T2DM sample was hybridized with a control sample of the same gender and matched based on age and BMI. To ensure hybridization of two samples with the same gender, three T2DM (5064, 5128, 5395) and one control sample (5616) were used twice and listed as technical replicates.
Project description:Pancreatitis is more frequent in type 2 diabetes (T2DM) although the underlying cause is unknown. We tested the hypothesis that ongoing beta-cell stress and apoptosis in T2DM induces ductal tree proliferation, particularly the pancreatic duct gland (PDG) compartment, and thus potentially obstructs exocrine outflow. PDG replication was increased two-fold in human pancreas from individuals with T2DM (P<0.01), and was associated with increased pancreatic intraepithelial neoplasia (PanINs) (P<0.05), lesions associated with pancreatic inflammation and with the potential to obstruct pancreatic outflow. Increased PDG replication (p<0.05) in the prediabetic HIP rat model of T2DM was concordant with increased beta-cell stress but preceding metabolic derangement. Moreover, the most abundantly expressed chemokines released by the islets in response to beta-cell stress in T2DM, CXCL1, 4 and 10, induced proliferation in human pancreatic ductal epithelium (p<0.05). Also, the diabetes medications that are reported as potential modifiers for the risk of pancreatitis in T2DM modulated PDG proliferation accordingly. We conclude that chronic stimulation and proliferation of the PDG compartment of the pancreas in response to islet inflammation in T2DM is a novel mechanism that serves as a link to the increased risk for pancreatitis in T2DM and may potentially be modified by currently available diabetes therapy. Overall design: HIP rats vs nondiabetic WT rats ( 4 samples total [2 HIP and 2 WT], so 2 replicates)
Project description:Insulin resistance and Type 2 Diabetes Mellitus (T2DM) are associated with increased adipocyte size, altered secretory pattern and decreased differentiation of preadipocytes. To identify the underlying molecular processes in preadipocytes of T2DM patients that are a characteristic of the development of T2DM, preadipocyte cell cultures were prepared from subcutaneous fat biopsies of T2DM patients and compared with age- and BMI matched control subjects. Gene expression profiling showed changed expression of transcription factors involved in adipogenesis and in extracellular matrix remodeling, actin cytoskeleton and integrin signaling genes, which indicated decreased capacity to differentiate. Additionally, genes involved in insulin signaling and lipid metabolism were down-regulated, and inflammation/apoptosis was up-regulated in T2DM preadipocytes. The down-regulation of genes involved in differentiation can provide a molecular basis for the reduced adipogenesis of preadipocytes of T2DM subjects, leading to reduced formation of adipocytes in subcutaneous fat depots, and ultimately leading to ectopic fat storage. 7 T2DM preadipocyte samples and 9 age- and BMI-matched control samples were hybridized using 70-mer oligonucleotide microarrays. Samples were labeled with either Cy3 or Cy5. A total of 20 arrays were used including dye swop. Per array, a T2DM sample was hybridized with a control sample of the same gender and matched based on age and BMI. To ensure hybridization of two samples with the same gender, three T2DM (5064, 5128, 5395) and one control sample (5616) were used twice and listed as technical replicates.
Project description:Skeletal muscle mitochondrial dysfunction is secondary to T2DM and can be improved by long-term regular exercise training Mitochondrial dysfunction has long been implicated to play a causative role in development of type 2 diabetes (T2DM). However, a growing number of recent studies provide data that mitochondrial dysfunction is a consequence of T2DM development. The aim of our study is to clarify in further detail the causal role of mitochondrial dysfunction in T2DM by a comprehensive ex vivo analysis of mitochondrial function combined with global gene expression analysis in muscle of pre-diabetic newly diagnosed untreated T2DM subjects and long-standing insulin treated T2DM subjects compared with age- and BMI-matched controls. In addition, we assessed the impact of long-term interval exercise training on physical activity performance, mitochondrial function and glycemic control in long-standing insulin-treated T2DM subjects. Ex vivo mitochondrial density, quality and functioning was comparable between pre-diabetic subjects and matched controls, however, gene expression analysis showed a switch from carbohydrate toward lipids as energy source in pre-diabetes subjects. In contrast, long-term insulin treated T2DM subjects had slightly decreased mitochondrial density and ex vivo function. Expression of Krebs cycle and OXPHOS related genes were decreased, indicating a decreased capacity to use lipids as an energy source. The insulin-treated T2DM subjects had a lower physical activity level than pre-diabetic and normoglycemic subjects. A 52 weeks exercise training of these subjects increased submaximal oxidative efficiency, increased in vivo PCr recovery rate, as well as mildly increased in vitro mitochondrial function. Gene expression of β-oxidation, Krebs cycle and OXPHOS-related genes was increased. Our data demonstrate that mitochondrial dysfunction is rather a consequence than a causative factor in T2DM development as it was only detected in overt diabetes and not in early diabetes. Regular exercise training stabilized exogenous insulin requirement and improved mitochondrial functioning, fatty acid oxidation and general physical work load capacity in long-standing insulin-treated T2DM subjects. As such, the present study shows for the first time that long-term exercise interventions are beneficial in this group of complex diabetes patient and may prevent further metabolic deterioration. Overall design: Insulin-treated T2DM subjects before and after 52 weeks of exercise training (T2DM_0 and T2DM_52), normoglycemic controls (NGT) and pre-diabetes subjects (IGT) and were selected. RNA was extracted from skeletal muscle biopsies and hybridized on Affymetrix microarrays.
Project description:Adipose tissue dysfunction in obese humans is associated with disrupted metabolic homeostasis, insulin resistance, and type 2 diabetes mellitus (T2DM). In a mouse model that has preserved insulin sensitivity despite increased adiposity, we used unbiased three-dimensional integration of proteome profiles, metabolic profiles, and gene regulatory networks to understand adipose tissue proteome-wide changes and their metabolic implications. Multiple-dimensional liquid chromatography tandem mass spectrometry and extended multiplexing TMT labeling (24 biological samples) was used to analyze proteomes of epididymal adipose tissues isolated from wildtype (Csf2+/+) and GM-CSF driven dendritic cell deficient (Csf2-/-) mice that were fed low fat, high fat, or high fat plus cholesterol diets for 8 weeks. The peripheral metabolic health (as measured by body weight, adiposity, plasma fasting glucose, insulin, triglycerides, phospholipids, total cholesterol levels, and glucose and insulin tolerance tests) deteriorated with diet for both genotypes, while mice lacking Csf2 were protected from insulin resistance. Regardless of diet, 30, mostly mitochondrial metabolism proteins participating in amino acid and branched chain amino acid pathways were altered, between Csf2-/- and Csf2+/+ mice. Tissue DHTKD1 levels were >4-fold upregulated and plasma 2-aminoadipoate (2-AA) levels were >2 fold reduced in Csf2-/- mice. GM-CSF driven dendritic cells play a detrimental role in insulin sensitivity via lysine metabolism involving Dhtkd1/2-AA axis.