Diabetes-linked zinc transporter ZnT8 is a homodimeric protein expressed by distinct rodent endocrine cell types in the pancreas and other glands

Background and aimsZinc is abundant in pancreas, being required by endocrine islet cells for hormone secretion and by exocrine acinar cells as pancreatic juice component. ZnT8 is a member of the SLC30A family of zinc transporters whose overexpression in cultured pancreatic β cells leads to increased insulin secretion in response to glucose, suggesting a possible role in regulating glycemia. ZnT8 was therefore proposed as a therapeutic target for diabetes, and recent genome-wide association studies identified polymorphisms in the ZNT8 gene conferring increased type 2 diabetes risk.Methods and resultsAs limited information was available on the biochemical properties of ZnT8 and on its endogenous expression, we have raised a specific polyclonal antibody and immunostained protein extracts, cell lines and tissue sections. We show that ZnT8 forms a very stable dimer that requires biological membranes to properly assemble. We demonstrate localization of murine ZnT8 to the secretory granules in pancreatic β and α islet cells. Moreover, we show that ZnT8 is also expressed in other secretory cell types, namely the cubical epithelium that lines thyroid follicles and the cortex of the adrenal gland, suggesting a more widespread role in endocrine secretion.ConclusionWe provide novel insights into the features of the ZnT8 transporter, of special relevance in light of its proposed role as therapeutical target for diabetes treatment.     

Non-esterified fatty acids are deleterious for human pancreatic islet function at physiological glucose concentration

Aims/hypothesis Whether excess glucose (glucotoxicity) and excess non-esterified fatty acids (lipotoxicity) act synergistically or separately to alter beta-cell function on Type 2 diabetes remains controversial. We examined the influence of non-esterified fatty acids, with or without concomitant increased glucose concentrations, on human islet function and on the expression of genes involved in lipid metabolism.Methods Human islets isolated from non-diabetic and non-obese donors were cultured with 5.5, 16 or 30 mmol/l glucose, and when appropriate with 1 or 2 mmol/l non-esterified fatty acids. After 48 h, glucose-stimulated insulin secretion, insulin content, triglyceride content and expression of different genes were evaluated.Results Non-esterified fatty acids decreased glucose-stimulated insulin secretion, insulin content and increased triglyceride content of human isolated islets, independently from the deleterious effect of glucose. Increased glucose concentrations also decreased glucose-stimulated insulin secretion and insulin content, but had no influence on triglyceride content. Glucose-stimulated insulin secretion of islets appeared to be significantly correlated with their triglyceride content. Glucose and non-esterified fatty acids modified the gene expression of carnitine palmitoyltransferase-I, acetyl-CoA carboxylase, acyl-CoA oxidase and uncoupling protein 2.Conclusion/interpretation In our model of isolated human islets, increased glucose and non-esterified fatty acids separately reproduced the two major beta-cell alterations observed in vivo, i.e. loss of glucose-stimulated insulin secretion and reduction in islet insulin content. Our results also suggest that this deleterious effect was, at least in part, mediated by modifications in lipid metabolism gene expression.Abbreviations ACC Acetyl-CoA carboxylase - ACO acyl-CoA oxidase - CPT-I carnitine palmitoyltransferase-I - GSIS glucose-stimulated insulin secretion - PPAR peroxisome proliferator-activated receptor - PDX-1 pancreatic/duodenal homeobox-1 - PPRE peroxisomal proliferator response element - TG triglyceride - UCP-2 uncoupling protein 2     

ZnT8 and type 1 diabetes

Zinc is essential for the proper storage, secretion, and the action of insulin and is transported from cytoplasm to insulin secretory granules in the pancreatic β-cells by SLC30A zinc transporters (ZnT). ZnT8 is specifically expressed in the pancreatic β-cells and has been identified as a novel target autoantigen in patients with type 1 diabetes. Autoantibodies to ZnT8 (ZnT8A) are detected in 50-60% of Japanese patients with acute-onset and 20% with slow-onset type 1 diabetes. Furthermore, humoral autoreactivity to ZnT8 is unique in terms of a key determinant, which is not reported on other islet autoantigens such as insulin, glutamic acid decarboxylase, or the protein tyrosine phosphatase-related molecules IA-2. Type 2 diabetes-associated nonsynonymous single nucleotide polymorphism in SLC30A8 (the gene of ZnT8), rs13266634 (Arg325Trp), modulates ZnT8A specificities thereby indicating that this amino acid substitution has the critical role in antibody binding. The humoral autoreactivity to ZnT8 depends on the clinical phenotype, which may provide clues to understand the role of this protein in the pathogenesis of type 1 diabetes.     

锌转运体8及其自身抗体

锌是胰岛素储存和分泌机制中的一个重要组分,β细胞需要有效且特异的转运体来累积足够量的锌.锌转运体8(ZnT8)是新近发现的一种1型糖尿病自身抗原,具有高度β细胞特异性,通过影响锌离子浓度而在胰岛素合成和分泌中发挥重要作用.ZnT8自身抗体对自身免疫性糖尿病(尤其对其他自身抗体阴性者)有着重要的诊断与预测价值.ZnT8基因(SLC30A8基因)多态性影响ZnT8自身抗体的特异性.     

Zinc, zinc transporters and diabetes

The role of zinc in islet function has recently achieved new attention as a consequence of the identification of zinc transporter 8 (ZNT8) in islets, and the association of mutations in the gene for this zinc transporter with glucose intolerance and type 2 diabetes. ZNT8 is also an autoantigen associated with the appearance of type 1 diabetes. A number of experimental models have been employed to suggest how ZNT8 and other zinc transporters regulate beta cell insulin processing and possibly secretion. An additional role for the zinc transporters in regulating alpha cell function has been suggested. In this issue of Diabetologia, Wijesekara and colleagues, using a cell-specific Znt8 (also known as Slc30a8) knockout model, demonstrate that beta cell insulin processing and glucose tolerance is negatively affected after beta cell knock out of Znt8, whereas Znt8 knockout in alpha cells seems to have little effect on glucagon secretion or glucose tolerance. Although we are yet to see the therapeutic potential of these new findings, the area represents a field through which manipulation of islet function may eventually be possible.     

Importance of oestrogen receptors to preserve functional β-cell mass in diabetes

Protecting the functional mass of insulin-producing β cells of the pancreas is a major therapeutic challenge in patients with type 1 (T1DM) or type 2 diabetes mellitus (T2DM). The gonadal hormone 17β-oestradiol (E2) is involved in reproductive, bone, cardiovascular and neuronal physiology. In rodent models of T1DM and T2DM, treatment with E2 protects pancreatic β cells against oxidative stress, amyloid polypeptide toxicity, lipotoxicity and apoptosis. Three oestrogen receptors (ERs)--ERα, ERβ and the G protein-coupled ER (GPER)--have been identified in rodent and human β cells. Whereas activation of ERα enhances glucose-stimulated insulin biosynthesis, reduces islet toxic lipid accumulation and promotes β-cell survival from proapoptotic stimuli, activation of ERβ increases glucose-stimulated insulin secretion. However, activation of GPER protects β cells from apoptosis, raises glucose-stimulated insulin secretion and lipid homeostasis without affecting insulin biosynthesis. Oestrogens are also improving islet engraftment in rodent models of pancreatic islet transplantation. This Review describes developments in the role of ERs in islet insulin biosynthesis and secretion, lipid homeostasis and survival. Moreover, we discuss why and how enhancing ER action in β cells without the undesirable effect of general oestrogen therapy is a therapeutic avenue to preserve functional β-cell mass in patients with diabetes mellitus.     

APPL1 potentiates insulin secretion in pancreatic β cells by enhancing protein kinase Akt-dependent expression of SNARE proteins in mice

Insulin resistance and defective insulin secretion are the two major features of type 2 diabetes. The adapter protein APPL1 is an obligatory molecule in regulating peripheral insulin sensitivity, but its role in insulin secretion remains elusive. Here, we show that APPL1 expression in pancreatic β cells is markedly decreased in several mouse models of obesity and diabetes. APPL1 knockout mice exhibit glucose intolerance and impaired glucose-stimulated insulin secretion (GSIS), whereas transgenic expression of APPL1 prevents high-fat diet (HFD)-induced glucose intolerance partly by enhancing GSIS. In both pancreatic islets and rat β cells, APPL1 deficiency causes a marked reduction in expression of the exocytotic machinery SNARE proteins (syntaxin-1, synaptosomal-associated protein 25, and vesicle-associated membrane protein 2) and an obvious decrease in the number of exocytotic events. Such changes are accompanied by diminished insulin-stimulated Akt activation. Furthermore, the defective GSIS and reduced expression of SNARE proteins in APPL1-deficient β cells can be rescued by adenovirus-mediated expression of APPL1 or constitutively active Akt. These findings demonstrate that APPL1 couples insulin-stimulated Akt activation to GSIS by promoting the expression of the core exocytotic machinery involved in exocytosis and also suggest that reduced APPL1 expression in pancreatic islets may serve as a pathological link that couples insulin resistance to β-cell dysfunction in type 2 diabetes.     

Beta cell-specific Znt8 deletion in mice causes marked defects in insulin processing, crystallisation and secretion

Aims/hypothesis  

Zinc is highly concentrated in pancreatic beta cells, is critical for normal insulin storage and may regulate glucagon secretion from alpha cells. Zinc transport family member 8 (ZnT8) is a zinc efflux transporter that is highly abundant in beta cells. Polymorphisms of ZnT8 (also known as SLC30A8) gene in man are associated with increased risk of type 2 diabetes. While global Znt8 knockout (Znt8KO) mice have been characterised, ZnT8 is also present in other islet cell types and extra-pancreatic tissues. Therefore, it is important to find ways of understanding the role of ZnT8 in beta and alpha cells without the difficulties caused by the confounding effects of ZnT8 in these other tissues.     

Zinc, a regulator of islet function and glucose homeostasis

It is well known that zinc is required in pancreatic β-cells in the process of insulin biosynthesis and the maturation of insulin secretory granules. In fact, the zinc level in pancreatic islets is amongst the highest in the body and reduction in its levels in the pancreas has been associated with diabetes. High concentrations of zinc can also be toxic because of enhanced oxidative damage. The link between zinc, diabetes and islet dysfunction has recently been reiterated by genomewide association studies that identified an islet cell membrane zinc transporter, SLC30A8 (ZnT8), as one of the risk loci for type 2 diabetes. Here we explore the importance of both zinc and ZnT8 to islet biology and whole body glucose homeostasis.     

Attenuated insulin release and storage in fetal sheep pancreatic islets with intrauterine growth restriction

We determined in vivo and in vitro pancreatic islet insulin secretion and glucose metabolism in fetuses with intrauterine growth restriction (IUGR) caused by chronic placental insufficiency to identify functional deficits in the fetal pancreas that might be caused by nutrient restriction. Plasma insulin concentrations in the IUGR fetuses were 69% lower at baseline and 76% lower after glucose-stimulated insulin secretion (GSIS). Similar deficits were observed with arginine-stimulated insulin secretion. Fetal islets, immunopositive for insulin and glucagon, secreted insulin in response to increasing glucose and KCl concentrations. Insulin release as a fraction of total insulin content was greater in glucose-stimulated IUGR islets, but the mass of insulin released per IUGR islet was lower because of their 82% lower insulin content. A deficiency in islet glucose metabolism was found in the rate of islet glucose oxidation at maximal stimulatory glucose concentrations (11 mmol/liter). Thus, pancreatic islets from nutritionally deprived IUGR fetuses caused by chronic placental insufficiency have impaired insulin secretion caused by reduced glucose-stimulated glucose oxidation rates, insulin biosynthesis, and insulin content. This impaired GSIS occurs despite an increased fractional rate of insulin release that results from a greater proportion of releasable insulin as a result of lower insulin stores. Because this animal model recapitulates the human pathology of chronic placental insufficiency and IUGR, the beta-cell GSIS dysfunction in this model might indicate mechanisms that are developmentally adaptive for fetal survival but in later life might predispose offspring to adult-onset diabetes that has been previously associated with IUGR.     

Stevioside Counteracts Beta-Cell Lipotoxicity without Affecting Acetyl CoA Carboxylase

Chronic exposure to high levels of free fatty acids impairs beta-cell function (lipotoxicity). Then basal insulin secretion (BIS) is increased and glucose-stimulated insulin secretion (GSIS) is inhibited. Acetyl CoA carboxylase (ACC) acts as the sensor for insulin secretion in pancreatic beta-cells in response to glucose and other nutrients. Stevioside (SVS), a diterpene glycoside, has recently been shown to prevent glucotoxic effect by regulating ACC activity. The aim of this study was to investigate whether SVS can alleviate impaired beta-cell function by regulating ACC activity. We exposed isolated rat islets and the clonal beta-cell line, INS-1E, to palmitate concentrations of 1.0 or 0.6 mM, respectively, for a period of 24 h to 120 h. The results showed that lipotoxicity occurred in rat islets after 72 h exposure to 1.0 mM palmitate. The lipotoxicity was counteracted by 10(-6) M SVS (n = 8, p < 0.001). Similar results were obtained in INS-1E cells. Neither SVS nor palmitate had any effect on the gene expression of ACC, insulin 2, and glucose transporter 2 in INS-1E cells. In contrast, palmitate significantly increased the gene expression of carnitine palmitoyl transporter 1 (n = 6, p = 0.003). However, the addition of SVS to palmitate did not counteract this effect (n = 6, p = 1.0). During lipotoxicity, SVS did not alter levels of ACC protein, phosphorylated-ACC, ACC activity or glucose uptake. Our results showed that SVS counteracts the impaired insulin secretion during lipotoxicity in rat islets as well as in INS-1E cells without affecting ACC activity.     

Think zinc: New roles for zinc in the control of insulin secretion

Genome wide association studies have identified the islet-restricted zinc transporter ZnT8 (SLC30A8) as a likely player in the control of insulin secretion and the risk of developing type 2 diabetes. The author's laboratory and others have now developed knockout mouse models for the ZnT8 gene, and have studied the impact of the at-risk R325W polymorphism on the activity of this crucial islet zinc transporter. Whilst there are intriguing differences between the phenotypes of the animal models the new studies provide strong evidence that the polymorphism in the SLC30A8 gene identified by human genetic screens is causal for the increased disease risk. The new results also reinforce the view that this transporter represents an exciting therapeutic target for intervention in type 2 diabetes.     

Role of glucotoxicity and lipotoxicity in the pathophysiology of Type 2 diabetes mellitus and emerging treatment strategies

Type 2 diabetes mellitus is a disease characterized by persistent and progressive deterioration of glucose tolerance. Both insulin resistance and impaired insulin secretion contribute to development of Type 2 diabetes. However, whilst insulin resistance is fully apparent in the pre‐diabetic condition, impairment of insulin secretion worsens over the time, being paralleled by a progressive decline in both pancreatic B‐cell function and B‐cell mass. Intense research has identified a number of genetic variants that may predispose to impaired B‐cell function, but such predisposition can be precipitated and worsened by toxic effects of hyperglycaemia (glucotoxicity) and elevated levels of free fatty acids (lipotoxicity). All these aspects of the pathogenesis of Type 2 diabetes are discussed in this review. Moreover, treatments that target reduction in glucotoxicity or lipotoxicity are outlined, including emerging strategies that target the role of glucagon‐like peptide 1 and sodium glucose co‐transporter 2.     

Endogenous islet uncoupling protein-2 expression and loss of glucose homeostasis in ob/ob mice

We hypothesized that the loss of glucose homeostasis in ob/ob mice is associated with upregulation of islet uncoupling protein-2 (UCP2) expression, leading to impaired glucose-stimulated insulin secretion (GSIS). Changes in glucose homeostasis in lean and ob/ob mice from 5 to 16 weeks were assessed by fasting blood glucose, plasma insulin, oral glucose tolerance, and tissue insulin sensitivity. In vitro GSIS and ATP content were assayed in isolated islets, while UCP2 expression was determined by quantitative real-time PCR and immunoblotting. Short-term reduction of UCP2 expression was achieved through transfection of islets with specific small interfering RNA. Insulin resistance was detected in 5-week-old ob/ob mice, but GSIS and blood glucose levels remained normal. By 8 weeks of age, ob/ob mice displayed fasting hyperglycemia, hyperinsulinemia and glucose intolerance, and also had elevated non-esterified fatty acid concentration in plasma. In vitro, GSIS and ATP generation were impaired in ob/ob islets. Islet UCP2 expression was elevated at 5 and 8 weeks of age. Short-term knockdown of islet UCP2 increased GSIS in islets of lean mice, but had no effect in islets from ob/ob mice. Loss of glucose homeostasis and impairment of insulin secretion from isolated islets at 8 weeks in ob/ob mice is preceded by an increase in UCP2 expression in islets. Moreover, the glucolipotoxic conditions observed are predicted to increase UCP2 activity, contributing to lower islet ATP and GSIS.     

Melatonin prevents pancreatic β‐cell loss due to glucotoxicity: the relationship between oxidative stress and endoplasmic reticulum stress

Prolonged hyperglycemia results in pancreatic β‐cell dysfunction and apoptosis, referred to as glucotoxicity. Although both oxidative and endoplasmic reticulum (ER) stresses have been implicated as major causative mechanisms of β‐cell glucotoxicity, the reciprocal importance between the two remains to be elucidated. The aim of this study was to evaluate the differential effect of oxidative stress and ER stress on β‐cell glucotoxicity, by employing melatonin which has free radical‐scavenging and antioxidant properties. As expected, in β‐cells exposed to prolonged high glucose levels, cell viability and glucose‐stimulated insulin secretion (GSIS) were significantly impaired. Melatonin treatment markedly attenuated cellular apoptosis by scavenging reactive oxygen species via its plasmalemmal receptor‐independent increase in antioxidant enzyme activity. However, treatments with antioxidants alone were insufficient to recover the impaired GSIS. Interestingly, 4‐phenylbutyric acid (4‐PBA), a chemical chaperone that attenuate ER stress by stabilizing protein structure, alleviated the impaired GSIS, but not apoptosis, suggesting that glucotoxicity induces oxidative and ER stress independently. We found that cotreatment of glucotoxic β‐cells with melatonin and 4‐PBA dramatically improved both their survival and insulin secretion. Taken together, these results suggest that ER stress may be the more critical mechanism for prolonged high‐glucose‐induced GSIS impairment, whereas oxidative stress appears to be more critical for the impaired β‐cell viability. Therefore, combinatorial therapy of melatonin with an ER stress modifier may help recover pancreatic β‐cells under glucotoxic conditions in type 2 diabetes.     

Islet beta cell failure in the 60% pancreatectomised obese hyperlipidaemic Zucker fatty rat: severe dysfunction with altered glycerolipid metabolism without steatosis or a falling beta cell mass

Aims/hypothesis  The Zucker fatty (ZF) rat subjected to 60% pancreatectomy (Px) develops moderate diabetes by 3 weeks. We determined whether a progressive fall in beta cell mass and/or beta cell dysfunction contribute to beta cell failure in this type 2 diabetes model. Methods  Partial (60%) or sham Px was performed in ZF and Zucker lean (ZL) rats. At 3 weeks post-surgery, beta cell mass and proliferation, proinsulin biosynthesis, pancreatic insulin content, insulin secretion, and islet glucose and lipid metabolism were measured. Results  ZL-Px rats maintained normal glycaemia and glucose-stimulated insulin secretion (GSIS) despite incomplete recovery of beta cell mass possibly due to compensatory enhanced islet glucose metabolism and lipolysis. ZF-Px rats developed moderate hyperglycaemia (14 mmol/l), hypertriacylglycerolaemia and relative hypoinsulinaemia. Despite beta cell mass recovery and normal arginine-induced insulin secretion, GSIS and pancreatic insulin content were profoundly lowered in ZF-Px rats. Proinsulin biosynthesis was not reduced. Compensatory increases in islet glucose metabolism above those observed in ZF-Sham rats were not seen in ZF-Px rats. Triacylglycerol content was not increased in ZF-Px islets, possibly due to lipodetoxification by enhanced lipolysis and fatty acid oxidation. Fatty acid accumulation into monoacylglycerol and diacylglycerol was increased in ZF-Px islets together with a 4.5-fold elevation in stearoyl-CoA desaturase mRNA expression. Conclusions/interpretation  Falling beta cell mass, reduced proinsulin biosynthesis and islet steatosis are not implicated in early beta cell failure and glucolipotoxicity in ZF-Px rats. Rather, severe beta cell dysfunction with a specific reduction in GSIS and marked depletion of beta cell insulin stores with altered lipid partitioning underlie beta cell failure in this animal model of type 2 diabetes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users. M. Prentki and J. Leahy contributed equally to this work.     

Vascular-derived connective tissue growth factor (Ctgf) is critical for pregnancy-induced β cell hyperplasia in adult mice

During pregnancy, maternal β cells undergo compensatory changes including hypertrophy, hyperplasia, and increased glucose-stimulated insulin secretion (GSIS). Failure of these adaptations to occur can result in gestational diabetes mellitus. The secreted protein, Connective tissue growth factor (Ctgf), is critical for normal β cell development and promotes regeneration after partial β cell ablation. During embryogenesis, Ctgf is expressed in pancreatic ducts, vasculature, and β cells. In the adult pancreas, Ctgf is expressed only in the vasculature. Here, we report that pregnant mice with global Ctgf haploinsufficiency (Ctgf^LacZ/+) have an impairment in maternal β cell proliferation, while β cell proliferation in virgin Ctgf^LacZ/+ females is unaffected. Additionally, α-cell proliferation, β cell size, and GSIS were unaffected in Ctgf^LacZ/+ mice, suggesting that vascular-derived Ctgf has a specific role in islet compensation during pregnancy.     

胰岛B细胞特异性锌转运蛋白与1型糖尿病

1型糖尿病（T1DM）是胰岛呈进行性破坏的自身免疫性疾病,以表达于胰岛B细胞的分子靶点作为抗原参与自身免疫反应为特征。其中阳离子外流锌转运蛋白8（ZnT8,SLC30A8）是人类T1DM的主要自身抗原之一,T1DM患者中SLC30A8基因位点上氨基酸325的多态性决定了其自身抗体多肽的特异性。ZnT8自身抗体可以在新发T1DM和糖尿病前期患者血清中检测出,在T1DM患者血清中其他自身抗体（谷氨酸脱羧酶抗体、抗酪氨酸磷酸酶抗体、抗胰岛素抗体和抗胰岛细胞抗体）阴性时ZnT8抗体仍有26％的阳性率。对自身抗体ZnT8的检测有助于在人群中筛查糖尿病前期患者,因此检测ZnT8抗体对评估T1DM的发生发展是必要的,ZnT8（SLC30A8）是T1DM的一个重要并独立的预测因子。     

An islet in distress: β cell failure in type 2 diabetes

Over 200 million people worldwide suffer from diabetes, a disorder of glucose homeostasis. The majority of these individuals are diagnosed with type 2 diabetes. It has traditionally been thought that tissue resistance to the action of insulin is the primary defect in type 2 diabetes. However, recent longitudinal and genome‐wide association studies have shown that insulin resistance is more likely to be a precondition, and that the failure of the pancreatic β cell to meet the increased insulin requirements is the triggering factor in the development of type 2 diabetes. A major emphasis in diabetes research has therefore shifted to understanding the causes of β cell failure. Collectively, these studies have implicated a complex network of triggers, which activate intersecting execution pathways leading to β cell dysfunction and death. In the present review, we discuss these triggers (glucotoxicity, lipotoxicity, amyloid and cytokines) with respect to the pathways they activate (oxidative stress, inflammation and endoplasmic reticulum stress) and propose a model for understanding β cell failure in type 2 diabetes. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00021.x, 2010)     

游离脂肪酸对βTc6细胞PDX-1表达及胰岛素分泌能力的影响

目的 探讨游离脂肪酸对胰岛β细胞胰-十二指肠同源盒因子-1(PDX-1)的表达及相应的β细胞增殖活性和胰岛素分泌功能变化的影响.方法 0.25～1.00 mmol/L游离脂肪酸干预小鼠胰岛素瘤细胞系βTc6细胞24～48 h,应用RT-PCR法检测转录因子PDX-1 mRNA表达,四甲基偶氮唑盐法检测细胞的增殖活性,放射免疫法检测葡萄糖刺激的胰岛素分泌水平,并观察细胞形态变化.结果 经0.25～1.00 mmol/L游离脂肪酸干预24 h,βTc6细胞PDX-1 mRNA的转录逐步增加,但随着干预时间进一步延长至48 h,PDX-1 mRNA的转录逐渐回落,特别是用1.00 mmoL/L游离脂肪酸干预48 h后,βTc6细胞PDX-1 mRNA的表达低于空白对照组.经过0.50～1.00 mmol/L游离脂肪酸24～48 h的干预之后,βTc6细胞形态学上呈现凋亡趋势,细胞增殖活力以及葡萄糖刺激的胰岛素分泌功能降低,而0.25 mmol/L游离脂肪酸24 h的干预未见此类现象.结论 短时间低浓度的游离脂肪酸干预可介导β细胞转录因子PDX-1的表达上调,对β细胞的增殖活性和胰岛素分泌能力无明显影响;而长时间高浓度的游离脂肪酸干预则将导致PDX-1 mRNA的表达下调,并使β细胞的增殖活性和胰岛素分泌能力受损.