Impaired development of pancreatic beta-cell mass is a primary event during the progression to diabetes in the GK rat

Summary In the endocrine pancreas of the GK rat, a genetic model of non-insulin-dependent diabetes mellitus (NIDDM), it is not clear whether the histopathological changes reported up to now are related to the pathogenesis of hyperglycaemia or whether they occur secondarily to metabolic alterations. Using GK rats from the Paris colony, our study chronicles for the first time the pathophysiologic changes that occur in the GK pancreas from the late fetal period (day 21.5) until adult age (18 weeks). As compared to Wistar controls, GK fetuses exhibited higher plasma glucose level, lower plasma insulin level and normal plasma glucagon level. Their pancreatic insulin content and the relative volume and the total mass of their beta cells were sharply decreased, representing only 23, 38 and 23 % of control values, respectively. During the period from 4 days to 14 days after birth, GK neonates exhibited normal basal plasma glucose and glucagon levels despite decreased plasma insulin level. Their pancreatic insulin content represented only 31–40 % of values found in the age-related control pancreases and their total beta-cell mass was only 35 % on day 4, 30 % on day 7 and 37 % on day 14. The adult diabetic GK rats exhibited higher basal plasma glucose and insulin levels while their basal plasma glucagon level remained normal. Their pancreatic insulin content and the total beta-cell mass remained decreased, representing only 32 % and 47 % of control values, respectively. Moreover, the adult GK pancreases exhibited noticeable alteration in the architecture of the large islet sub-population which displayed considerable fibrosis with clusters of beta cells widely separated from each other by strands of connective tissue. Concerning the development of alpha cells in the GK rats, their relative volume was found to be normal during fetal and early neonatal periods. It was found to be moderately decreased (representing 64–67 % of corresponding control values) in 14-day-old neonates and adult GK rats. Our findings demonstrate that in the GK rat, the deficit of total beta-cell mass as observed in the adult animal is related to impaired beta-cell development. The restriction of the beta-cell mass must be considered as a primary and crucial event in the sequence leading to overt diabetes in this NIDDM model. [Diabetologia (1997) 40: 916–925] Received: 6 February 1997 and in revised form: 21 April 1997     

Hyperglycaemia as an inducer as well as a consequence of impaired islet cell function and insulin resistance: implications for the management of diabetes

Summary It is postulated that hyperglycaemia influences the natural history of Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetes mellitus. Hyperglycaemia, even when mild, can attenuate the secretory response of pancreatic and cells to increments in glucose and can impair insulin-mediated glucose transport, thus impeding its own correction and initiating a cycle of progressive self-exacerbation and metabolic deterioration. Both reduced islet function and insulin action may be the consequence of a generalized down-regulation and/or occupation of glucose transporters by hyperglycaemia so that the islets respond less to further increments in glycaemia. The postulated hyperglycaemic cycle can be initiated by any environmental perturbation that increases insulin demand in previously normoglycaemic patients in whom insulin secretion has already reached a maximum level of compensation for peripheral insulin resistance (as in obese pre-Type 2 diabetes) or for a reduced -cell mass (as in pre-Type 1 diabetes). Elimination of hyperglycaemia by any means can halt this cycle of progressive metabolic deterioration and may restore transiently metabolic recompensation both in Type 1 and Type 2 diabetes. There is experimental evidence that long-standing severe hyperglycaemia may irreversibly damage cells.     

Oncodevelopmental alpha-fetoprotein acts as a selective proangiogenic factor on endothelial cell from the fetomaternal unit

The molecular coordination between angiogenesis and vascular remodeling is a critical step for the development of a functional vasculature in the placenta and the uterus during pregnancy. The oncodevelopmental albumin homolog alpha-fetoprotein (AFP) is mainly synthesized in the developing fetus, and its expression has been found to be associated with highly vascularized tumors in the adult. In this study, we investigated the angiogenic activity of AFP and its possible role in the fetomaternal unit. Immunohistochemical studies revealed that the AFP-binding protein(s) is expressed in blood vessels of chorionic villi from placentae of the second and the third but not of the first trimester during pregnancy. At low concentrations, AFP directly stimulates or enhances, respectively, vascular endothelial growth factor-induced proliferation and sprout formation of endothelial cells isolated from the placenta and the uterus possibly by a MAPK-dependent pathway. Furthermore, AFP enhances blood vessel formation in a chick chorioallantoic membrane assay in vivo. Interestingly, AFP has no proliferative or migratory effects on endothelial cells isolated from the umbilical vein in the absence of vascular endothelial growth factor. These data indicate that AFP may act as a specific proangiogenic factor of endothelial cells within the fetomaternal unit during advanced stages in pregnancy.     

Attenuation of the pancreatic beta cell response to a meal following hypoglycaemia in man

Summary The plasma concentration of C-peptide, insulin (IRI) and glucose was measured in 9 healthy subjects during insulin-induced hypoglycaemia followed by a meal. Identical observations were made in the same subjects after an equivalent period of fasting without hypoglycaemia (control study). Endogenous secretion of insulin was suppressed following administration of exogenous insulin and this persisted long after the blood glucose concentration had returned to normal. After the meal the mean blood glucose rose to a peak of 8.4±0.3 mmol/l (mean ± SEM) at 60 min and was still raised at 7.5±0.3 mmol/l at 120 min, compared with a peak value of only 5.1±0.2 mmol/l at 30 min after the meal in the control study. Following hypoglycaemia the mean plasma IRI rose from 8.3±1.3 mU/l to a delayed peak of 81.6±12.7 mU/l at 60 min and was 123.5±14 mU/l at 120 min post-prandially, compared with a peak of 72.4±0.5 mU/l at 30 min after the meal in the control study. Acute hypoglycaemia may thus induce an abnormal pattern of insulin secretion in response to a meal, with impaired carbohydrate tolerance in normal subjects.     

Insulin secretion is regulated by the glucose-dependent production of islet β cell macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF), originally identified as a cytokine secreted by T lymphocytes, was found recently to be both a pituitary hormone and a mediator released by immune cells in response to glucocorticoid stimulation. We report here that the insulin-secreting β cell of the islets of Langerhans expresses MIF and that its production is regulated by glucose in a time- and concentration-dependent manner. MIF and insulin colocalize by immunocytochemistry within the secretory granules of the pancreatic islet β cells, and once released, MIF appears to regulate insulin release in an autocrine fashion. In perifusion studies performed with isolated rat islets, immunoneutralization of MIF reduced the first and second phase of the glucose-induced insulin secretion response by 39% and 31%, respectively. Conversely, exogenously added recombinant MIF was found to potentiate insulin release. Constitutive expression of MIF antisense RNA in the insulin-secreting INS-1 cell line inhibited MIF protein synthesis and decreased significantly glucose-induced insulin release. MIF is therefore a glucose-dependent, islet cell product that regulates insulin secretion in a positive manner and may play an important role in carbohydrate metabolism.     

Failure to establish islet amyloid polypeptide (amylin) as a circulating beta cell inhibiting hormone in man

Summary The presence of islet amyloid polypeptide in amyloid within pancreatic islet cells in Type 2 (non-insulin-dependent) diabetes, and its reported inhibition of glucose uptake by skeletal muscle in vitro, has prompted speculation concerning its role in the pathogenesis of diabetes. We investigated the effect of infused synthetic amidated human islet amyloid polypeptide (mol. wt. 3904, confirmed by mass spectroscopy) on intravenous glucose tolerance. Seven healthy, non-obese volunteers (age±SD, 27±4 years) were infused over 50 min with normal (0.9%) saline or islet amyloid polypeptide at 50 pmol·kg^–1·min^–1. After 20 min, a bolus of 0.5 g/kg glucose was given within 1 min and blood sampling continued for up to 60 min. Circulating concentrations of islet amyloid polypeptide reached at steady state were 1130±90 pmol/l. The calculated half-life was 11.8±0.9 min, metabolic clearance rate 5.7±0.6 ml·kg^–1·min^–1 and apparent distribution space therefore 94±12 ml/kg. However, islet amyloid polypeptide was found to have no effect on the peak value reached, or the total area under the curve for plasma glucose, insulin or glucagon following intravenous glucose. This study suggests circulating islet amyloid polypeptide may not be an important influence on intravenous glucose tolerance in man.     

Bile acids induce cyclooxygenase-2 expression via the epidermal growth factor receptor in a human cholangiocarcinoma cell line

BACKGROUND & AIMS: Although bile acids have been implicated in colon cancer development, their role in biliary tract carcinogenesis remains unexplored. Because receptor tyrosine kinases and cyclooxygenase (COX)-2 have been implicated in carcinogenesis, we examined the hypothesis that bile acids modulate these enzymes in KMBC cells, a human cholangiocarcinoma cell line. METHODS: The effect of bile acids on epidermal growth factor receptor (EGFR) stimulation, mitogen-activated protein kinase (MAPK) activation, and COX-2 expression was evaluated. RESULTS: Bile acids both induced EGFR phosphorylation and enhanced COX-2 protein expression. Bile acid-induced EGFR phosphorylation was associated with subsequent activation of MAPK p42/44, p38, and c-Jun-N-terminal kinase (JNK). The MAPK inhibitors, PD098059 for MAP or extracellular signal-regulated kinase 1, SB203580 for p38, and BAY 37-9751 for Raf-1, blocked COX-2 induction by bile acids. However, inhibition of JNK activity did not block bile acid-mediated COX-2 induction. CONCLUSIONS: The results show that EGFR is activated by bile acids and functions to induce COX-2 expression by an MAPK cascade. This induction of COX-2 may participate in the genesis and progression of cholangiocarcinomas.     

Downregulation of orosomucoid 2 acts as a prognostic factor associated with cancer-promoting pathways in liver cancer

BACKGROUND Liver cancer has a high mortality and morbidity rate throughout the world.In clinical practice,the prognosis of liver cancer patients is poor,and the complex reasons contribute to treatment failures,including fibrosis,hepatitis viral infection,drug resistance and metastasis.Thus,screening novel prognostic biomarkers is of great importance for guiding liver cancer therapy.Orosomucoid genes(ORMs)encode acute phase plasma proteins,including orosomucoid 1(ORM1)and ORM2.Previous studies showed their upregulation upon inflammation,but the specific function of ORMs has not yet been determined,especially in the development of liver cancer.AIM To determine the expression of ORMs and their potential function in liver cancer.METHODS Analysis of the expression of ORMs in different human tissues was performed on data from the HPA RNA-seq normal tissues project.The expression ratio of ORMs was determined using the HCCDB database,including the ratio between liver cancer and other cancers,normal liver and other normal tissues,liver cancer and adjacent normal liver tissues.Analysis of ORM expression in different cancer types was performed using The Cancer Genome Atlas and TIMER database.The expression of ORMs in liver tumor tissues and adjacent normal tissues were further confirmed using Gene Expression Omnibus data,including GSE36376 and GSE14520.The 10-year overall survival(OS),progression-free survival(PFS)and relapse-free survival(RFS)rates between high and low ORM expression groups in liver cancer patients were determined using the Kaplan-Meier plotter tool.Gene Set Enrichment Analysis(GSEA)was employed to explore the ORM2-associated signaling network.Correlations between ORM2 expression and tumor purity or the infiltration level of macrophages in liver tumor tissues were determined using the TIMER database.The correlation between ORM2 gene levels,tumor-associated macrophage(TAM)markers(including CD68 and TGFβ1)and T cell immunosuppression(including CTLA4 and PD-1)in liver tumor tissues and liver GTEx was determined using the GEPIA database.RESULTS ORM1 and ORM2 were highly expressed in normal liver and liver tumor tissues.ORM1 and ORM2 expression was significantly decreased in liver tumor tissues compared with adjacent normal tissues,and similar results were also noted in cholangiocarcinoma,esophageal carcinoma,and lung squamous cell carcinoma.Further analysis of the Gene Expression Omnibus Database also confirmed the downregulation of ORM1 and ORM2 in liver tumors.Survival analysis showed that the high ORM2 group had better survival rates in OS,PFS and RFS.ORM1 only represented better performance in PFS,but not in OS or RFS.GSEA analysis of ORM2 from The Cancer Genome Atlas liver cancer data identified that ORM2 positively associated with the G2/M checkpoint,E2F target signaling,as well as Wnt/β-catenin and Hedgehog signaling.Moreover,apoptosis,IFN-αresponses,IFN-γresponses and humoral immune responses were upregulated in the ORM2 high group.ORM2 expression was negatively correlated with the macrophage infiltration level,CD68,TGFβ1,CTLA4 and PD-1 levels.CONCLUSION The results showed that ORM1 and ORM2 were highly expressed specifically in liver tissues,whereas ORM1 and ORM2 were downregulated in liver tumor tissues.ORM2 is a better prognostic factor for liver cancer.Furthermore,ORM2 is closely associated with cancer-promoting pathways.     

Insulin resistance is a risk factor for progression to Type 1 diabetes

Aims/hypothesis Glucose homeostasis is determined by an interplay between insulin secretion and insulin action. In Type 1 diabetes, autoimmune destruction of pancreatic beta cells leads to impaired insulin secretion. However, the contribution of impaired insulin action (insulin resistance) to the development of Type 1 diabetes has received little attention. We investigated whether insulin resistance was a risk factor for progression to Type 1 diabetes.Methods Islet-antibody-positive first-degree relatives of Type 1 diabetes probands were followed for 4.0 years (median). Insulin secretion was measured as first-phase insulin response (FPIR) to intravenous glucose. Insulin resistance was estimated by homeostasis model assessment of insulin resistance (HOMA-R). We compared subjects who progressed (n=43) and subjects who did not progress (n=61) to diabetes, including 21 pairs matched for age, sex, islet antibodies and FPIR.Results Progressors had higher insulin resistance relative to insulin secretion at baseline (median HOMA-R : FPIR 0.033 vs 0.013, p<0.0001). According to Cox proportional hazards analysis, islet antibody number, FPIR, fasting plasma glucose, fasting serum insulin, HOMA-R and log(HOMA-R : FPIR) were each predictive of progression to diabetes. However, log(HOMA-R : FPIR) (hazard ratio 2.57 per doubling, p<0.001) was the only metabolic variable independently associated with progression. In the matched comparison, progressors had higher fasting glucose, fasting insulin, HOMA-R and HOMA-R : FPIR, both at baseline and during the follow-up pre-clinical phase.Conclusions/interpretation Relatives positive for islet antibodies who progress most rapidly to diabetes have a subtle disturbance of insulin–glucose homeostasis years before the onset of symptoms, distinguished by greater insulin resistance for their level of insulin secretion. Taking steps to reduce this insulin resistance could therefore delay the development of Type 1 diabetes.An erratum to this article can be found at     

Bone morphogenetic protein-2 acts upstream of myocyte-specific enhancer factor 2a to control embryonic cardiac contractility

OBJECTIVE: Cardiac contractility is regulated tightly as an extrinsic and intrinsic homeostatic mechanism to the heart. The molecular basis of the intrinsic system is largely unknown. Here, we test the hypothesis that bone morphogenetic protein-2 (BMP-2) mediates embryonic cardiac contractility upstream of myocyte-specific enhancer factor 2A (MEF2A). METHODS: The BMP-2 and MEF2A expression pattern was analyzed by RT-PCR, Western blotting, whole-mount in situ hybridization, and an in vivo transgenic approach. The cardiac phenotype of BMP-2 and MEF2A knock-down zebrafish embryos was analysed. Cardiac contractions were recorded with a video camera. Myofibrillar organization was observed with transmission electron microscopy. Gene expression profiles were performed by quantitative real-time PCR analysis. RESULTS: We demonstrate that BMP-2 and MEF2A are co-expressed in embryonic and neonatal cardiac myocytes. Furthermore, we provide evidence that BMP-2 is required for cardiac contractility in vitro and in vivo and that MEF2A expression can be activated by BMP-2 signaling in neonatal cardiomyocytes. BMP-2 is involved in the assembly of the cardiac contractile apparatus. Finally, we find that exogenous MEF2A is sufficient to rescue ventricular contractility defects in the absence of BMP-2 function. CONCLUSIONS: In all, these observations indicate that BMP-2 and MEF2A are key components of a pathway that controls the cardiac ventricular contractility and suggest that the BMP2-MEF2A pathway can offer new opportunities for the treatment of heart failure.     

A checkpoint in the cell cycle progression as a therapeutic target to inhibit HIV replication

Human immunodeficiency virus (HIV) expression is boosted after T lymphocyte stimulation. It is not known, however, in which phase(s) of the cell cycle HIV is maximally expressed. We demonstrate here that cell activation induces limited HIV expression and that progression to cell proliferation is required for optimal HIV replication. We also show that the G1/S cell cycle transition is a critical checkpoint in this process and that limiting progression at this step with antiproliferative drugs suppresses HIV replication. These results identify a specific phase of the cell cycle progression that is critical for HIV expression and suggest a new discrete target for anti-HIV treatment.     

2型糖尿病患者一级亲属正常糖耐量人群胰岛素抵抗与胰岛β细胞功能的研究

探讨2型糖尿病（T2DM）患者一级亲属糖耐量正常人群胰岛素抵抗（IR）与胰岛β细胞功能状态。结果发现，母亲或双亲糖尿病组一级亲属糖耐量正常人群，空腹胰岛素水平和HOMA—IR明显升高，而糖刺激后30min胰岛素与血糖比值（△I30／△G30）明显降低，因此，T2DM患者一级亲属在糖耐量正常阶段已存在IR和早期胰岛素分泌功能受损。     

Expression Analysis of cPLA2 Alpha Interacting TIP60 in Diabetic KKAy and Non-Diabetic C57BL Wild-Type Mice: No Impact of Transient and Stable TIP60 Overexpression on Glucose-Stimulated Insulin Secretion in Pancreatic Beta-Cells

In the present study we investigate the expression levels of cytosolic phospholipase A2 α (cPLA2α) interacting histone acetyl transferase proteins TIP60α and TIP60β in non-diabetic C57BL wild-type mice and obese type 2 diabetic KKAy model mice. The aim was to test our hypothesis that TIP60 plays a regulatory role in glucose-stimulated insulin secretion from pancreatic β-cells. MATERIAL AND METHODS: Ten obese diabetic KKAy mice and ten non-diabetic C57BL mice were fed a standard chow diet. After nine weeks, islet RNA was purified and used to measure TIP60 expression. We investigated the effect of TIP60α and TIP60β on glucose-stimulated insulin secretion by transient and stable overexpression in the pancreatic mouse β-cell line MIN6 and the rat β-cell line INS-1E. RESULTS: We found that non-diabetic C57BL mice and diabetic KKAy mice have the same level of both the α and β splice forms of TIP60. Furthermore, we demonstrated that transient and stable expression of TIP60 in INS-1E cells affects neither glucose-stimulated insulin secretion, insulin output nor cell insulin content. Also susceptibility to developing gluco-toxicity was unaffected. CONCLUSION: TIP60 over-expression does not affect glucose stimulated insulin secretion, insulin content or abnormal β-cell function during glucotoxicity.