DiaPep277 peptide therapy in the context of other immune intervention trials in type 1 diabetes

Introduction: Type 1 diabetes (T1D) is characterized by the autoimmune destruction of pancreatic β-cells. The aim of immune intervention is to arrest this autoimmune attack. DiaPep277, a major T-cell epitope of heat shock protein 60 (hsp60), has been shown to be effective in the modulation of the immune response in recent onset T1D and is the main focus of this review in the context of other ongoing trials using different approaches.

Areas covered: The authors performed a literature search of Pubmed listed publications (from the last 10 years) and a website search of the company licensing DiaPep277. DiaPep277 has been investigated in Phase I – III trials in humans. Phase II trials showed a significant preservation of β-cell function in adult T1D patients (but not children) with an absence of adverse effects and not accompanied by lower glycosylated haemoglobin (HbA1c) levels or reduced daily insulin requirement compared with placebo-treated patients.

Expert opinion: Administration of DiaPep277 is safe and represents a promising therapeutic strategy in patients with recent-onset T1D. The results of two large Phase III trials will tell us whether this therapy may change our current approach to treating T1D patients at diagnosis.     

Efficacy and Safety of Linagliptin in Subjects With Long-standing Type 2 Diabetes Mellitus (>10 Years): Evidence From Pooled Data of Randomized,Double-blind,Placebo-controlled,Phase III Trials

PurposeLong duration of type 2 diabetes mellitus (T2DM) is associated with progressive β-cell loss and may pose a challenge to maintenance of good glycemic control. This study aimed to assess the efficacy and safety of the dipeptidyl peptidase-4 inhibitor linagliptin in an understudied population of patients with long-standing T2DM.MethodsData from 202 individuals with T2DM for >10 years were pooled from 2 randomized, placebo-controlled, Phase III trials. Participants received either linagliptin 5 mg once daily (n = 122) or placebo (n = 80) for 24 weeks as an add-on to their current glucose-lowering therapy.FindingsLong-standing T2DM was associated with older age (mean [SD], 69.1 [10.0] years) and a high prevalence of diabetes-related complications (78% with diabetic kidney disease and 83% with macrovascular disease). The mean baseline glycosylated hemoglobin (HbA_1c) level was 8.22% (1.08%), and mean baseline fasting plasma glucose level was 161.8 (49.2) mg/dL. Linagliptin significantly improved glycemic control after 24 weeks, with a placebo-adjusted mean change in HbA_1c from baseline of −0.66% (95% CI, −0.95 to −0.38; P < 0.0001). This change was accompanied by a significant reduction in fasting plasma glucose, with a placebo-adjusted mean change from baseline of −15.5 mg/dL (95% CI, −29.6 to −1.3; P = 0.0323) at week 24. Overall, linagliptin was well tolerated, with drug-related adverse events in 21.3% and 16.3% of the linagliptin and placebo groups, respectively. Investigator-reported hypoglycemia occurred more often with linagliptin (25.4%) compared with placebo (12.5%). However, no severe hypoglycemic events were reported with linagliptin. Moreover, in patients not receiving concomitant sulfonylureas, the incidence of hypoglycemia with linagliptin (12.5%) was similar to that with placebo (12.2%). Patients’ mean weight remained unchanged in both groups.ImplicationsThis pooled analysis found that linagliptin was well tolerated and significantly improved hyperglycemia in a clinically challenging population of patients with long-standing T2DM (>10 years). Although T2DM is commonly associated with diminished β-cell function, the extent of glucose lowering was similar to that in linagliptin trials, which largely included patients in earlier stages of the disease. Thus, this observation supports the hypothesis that regulation of glucagon release from pancreatic α cells may be of particular relevance for improving hyperglycemia in patients with long-term T2DM (NCT01194830 and NCT01084005).     

Epitope-specific glutamic acid decarboxylase-65 autoantibodies in intravenous immunoglobulin preparations

Intravenous immunoglobulin (IVIG) has been used to treat many autoimmune disorders including Stiff-Man Syndrome (SMS). SMS is a neurological disorder associated with an immune-mediated deficiency of gamma-aminobutyric acid (GABA) due to autoantibodies against the GABA synthesizing enzyme glutamic acid decarboxylase-65 (GAD65). GAD65 autoantibodies are present among 1-2% of healthy individuals. It can therefore not be excluded that GAD65 autoantibodies may be present in IVIG, which is prepared from multiple blood donors. We report here that GAD65 but not IA-2 autoantibodies were present in commercial IVIG preparations. The presence of autoantibodies may affect the outcome of IVIG treatment and screening commercial preparations of IVIG for GAD65 autoantibodies is therefore recommended before treating patients.     

Tmem27 is upregulated by vitamin D in INS-1 cells and its serum concentrations are low in patients with autoimmune diabetes

Abstract

Transmembrane protein 27 (Tmem27), which is expressed in pancreatic β-cells, plays an important role in insulin secretion and pancreatic β-cell proliferation. Analysis of the INS-1 cell proteome using stable isotope labeling by amino acids in cell culture (SILAC) in combination with LC-MS identified Tmem27 as the one of most robustly (up to seven-fold) upregulated proteins after treatment with the active metabolite of vitamin D, 1,25-(OH)₂D₃. Furthermore, we report that Tmem27 which is cleaved and released from, i.e. pancreatic β-cells, is present in human serum and its levels are significantly lower in subjects with autoimmune diabetes as compared to healthy individuals (13% of the levels). Additionally, Tmem27 correlated positively (0.70) with C-peptide serum levels in healthy subjects. Our data indicate that Tmem27 could be of potential value as a serum marker for the pathogenesis of diabetes and as such may warrant the development of measurement methods with lower limit of detection for its further validation.     

Clarifying the role of incretin-based therapies in the treatment of type 2 diabetes mellitus

BackgroundGlucose homeostasis is the result of a complex interaction of a spectrum of hormones, including insulin, glucagon, amylin, and the incretins. Incretins are released by enteroendocrine cells in the intestine in response to a meal. Incretin dysfunction, along with a number of other defects, has been implicated in contributing to the pathogenesis of type 2 diabetes mellitus (T2DM). Therapies that restore incretin activity may reduce the pathophysiologic consequences of diabetes.ObjectivesThe aim of this article was to review incretin physiology and studies of incretin therapy with glucagon-like peptide-1 (GLP-1) receptor agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors that were developed to specifically address the blunted incretin response in patients with T2DM.MethodsRelevant English-language publications between 1995 and 2010 were identified through a search of the MEDLINE and EMBASE databases using the search terms incretin, type 2 diabetes mellitus, GLP-1, glucose-dependent insulinotropic polypeptide, and DPP-4. Review articles and preclinical and clinical trials that described relevant details of the epidemiology of diabetes and incretin physiology in health and in T2DM were selected for review and inclusion. Clinical trials were used to describe the clinical efficacy and safety of the GLP-1 receptor agonists and DPP-4 inhibitors in patients with T2DM. An occasional systematic review article and/or meta-analysis summarizing numerous clinical trials of a particular agent was selected for summarizing key data.ResultsPharmacologic modulation of incretin pathophysiology by GLP-1 receptor agonists and DPP-4 inhibitors significantly improved glycemic control, benefited β-cell function, improved dyslipidemia, and lowered the risk of hypoglycemia compared with insulin and sulfonylureas. Unlike the DPP-4 inhibitors, GLP-1 receptor agonist therapy also produced weight loss, an important consideration given the close association among T2DM, overweight/obesity, and cardiovascular disease. The most common adverse events with GLP-1 receptor agonist therapy included nausea (28%–44%), vomiting (13%–17%), and diarrhea (11%–17%), which generally reduced in incidence and severity with continued therapy. The tolerability profile of the DPP-4 inhibitors was very good, with the incidence of adverse events similar to that of placebo. There was a suggestion of an increased incidence of nasopharyngitis versus placebo (5%–6% vs 3%–4%) with sitagliptin and urinary tract infection (6.8% vs 6.1% with placebo) and headache with saxagliptin (6.5% vs 5.9% with placebo).ConclusionThe 2 incretin drug classes provided effective and consistent glycemic control with a good tolerability profile. These agents might also improve long-term β-cell function and either reduce body weight or be weight neutral. Their role in the therapeutic armamentarium of T2DM is evolving as their potential strengths and weaknesses become better defined.     

TCF7L2基因rs7903146位点多态性与2型糖尿病胰岛β细胞早相功能的相关性

目的探讨TCF7L2基因rs7903146位点单核苷酸多态性与青岛2型糖尿病病人胰岛β细胞早相功能的相关性。方法应用限制性片段长度多态性（RFLP）方法,对213例青岛及周边地区汉族人（其中2型糖尿病病人99例、正常对照114例）的TCF7L2基因rs7903146位点进行基因分型;用左旋精氨酸兴奋实验测定胰岛β细胞早相功能。结果 2型糖尿病组rs7903146位点的CT基因型和T基因频率均明显高于正常对照组（χ2=4.678、4.507,P〈0.05）,其中有家族史的2型糖尿病病人的CT基因型和T基因频率明显高于正常对照组（χ2=4.896、4.739,P〈0.05）,而无家族史组和正常对照组比较差异无显著性（P〉0.05）,有家族史和无家族史组之间比较也无统计学差异（P〉0.05）;CT比CC基因型患2型糖尿病的危险度显著增加（OR=3.28,95%CI为1.026~10.459,P〈0.05）。rs7903146位点CC和CT基因型的胰岛β细胞早相功能差异无显著性（P〉0.05）。结论 TCF7L2基因rs7903146位点多态性与2型糖尿病发病风险有关,该位点多态性与胰岛β细胞早相分泌功能关联性不强。     

Cell therapy for type 1 diabetes

ABSTRACT

Introduction

Type 1 diabetes (T1D) is a lifelong condition resulting from autoimmune destruction of insulin-producing β-cells. Islet or whole-pancreas transplantation is limited by the shortage of donors and need for chronic immune suppression. Novel strategies are needed to prevent β-cell loss and to rescue production of endogenous insulin.     

Otelixizumab: a novel agent for the prevention of type 1 diabetes mellitus

Introduction: Type 1 diabetes mellitus is a chronic, progressive autoimmune disorder linked to numerous genetic and environmental factors. Insulin is the only treatment and preventative strategies do not currently exist. An obvious need exists to develop a safe regimen that suppresses the progression of the disease.

Areas covered: A MEDLINE search (1966–June 2011) was conducted for English-language articles using the terms ‘otelixizumab’, ‘anti-CD3 antibody’ and ‘prevention of type 1 diabetes mellitus’. Relevant literature on otelixizumab, an anti-CD3 monoclonal antibody, currently in Phase III clinical trials for prevention of T1DM is discussed.

Expert opinion: Studies suggest that a monoclonal antibody directed against CD3 mitigates the deterioration in insulin production and decreases the rise in insulin requirement in recent onset T1DM for up to five years. The benefit was most pronounced in younger patients and in those with higher initial β-cell function. Adverse effects were significant but transient. Otelixizumab shows great promise but leaves room for improvement. Results of ongoing trials will help define its role in the prevention of T1DM.     

Immune intervention for type 1 diabetes mellitus

The major form of type 1 diabetes (T1D) is characterised by immune-mediated pancreatic islet β-cell destruction, and has also been called type 1A diabetes to distinguish it from idiopathic forms of islet β-cell loss. Since the first demonstration of islet cell antibodies in 1974, the concept has been that this form of diabetes is autoimmune in nature. The commonly accepted concept is that antibodies (representing the humoral arm of the immune system) do not mediate the β-cell destruction but rather serve as markers of that destruction, while the cellular arm of the immune system, specifically T-lymphocytes, mediate the β-cell destruction. Yet, the T-lymphocytes do not act alone. They receive help in initiating the response from antigen-presenting cells such as dendritic cells and macrophages, and appear to receive help also from B-lymphocytes. In addition, the initial immune response engenders secondary and tertiary responses - involving the whole immunological army - which collectively result in impairment of β-cell function, progressive destruction of β-cells, and consequent development of type 1A diabetes. The process is insidious and may evolve over many years, with the overt expression of clinical symptoms becoming apparent only when most β-cells have been destroyed. Yet, the process clearly evolves at different speeds - much more rapidly in young children, much more slowly in older individuals. And, although it has been thought that ultimately there is complete β-cell destruction, several studies have now demonstrated some degree of persistent β-cell function or existence (at autopsy) in long-standing T1D. A major focus of investigation in T1D is the preservation of β-cell function (and, it is hoped, of β-cells themselves), in the expectation that continuing endogenous insulin secretion will contribute towards better glycaemic control, reduce episodes of severe hypoglycaemia, and slow the development of complications such as retinopathy and nephropathy. Thus, there have been many studies designed to interdict the T1D disease process, mostly by altering the immune system, both during the stage of evolution of the disease and at the time of disease onset. This chapter of the Yearbook of Advanced Technology and Treatments in Diabetes reviews the key papers that have appeared in this field between July 2009 and June 2010. Articles selected were confined to studies in human beings. All immune intervention studies reported in this time frame were included. In addition, the author selected other relevant articles dealing with mechanisms, markers, triggers, and pathology of human type 1 diabetes.     

短期胰岛素强化治疗诱导初诊2型糖尿病患者血糖长期良好控制的临床研究

目的分析短期应用胰岛素进行强化治疗对于2型糖尿病（T2DM）患者的胰岛β细胞功能以及血糖控制水平的影响。方法收集初诊T2DM患者46例,以胰岛素泵进行治疗2周以后,测定患者治疗前后的血糖以及胰岛素变化情况,并计算患者的胰岛β细胞功能指数（HOMA-β）以及胰岛素抵抗指数（HOMA-IR）,并观察血糖控制情况。结果患者的胰岛素水平、HOMA-β均较治疗前明显提高,HOMA-β以及血糖水平均明显降低（P〈0.05）;16例患者仅依靠运动以及饮食控制便取得了理想的血糖控制效果。结论对初诊T2DM患者实施短期胰岛素泵治疗能够快速控制血糖水平,有效改善其胰岛β细胞功能,并可减轻患者的胰岛素抵抗,值得推广应用。     

Teplizumab therapy for type 1 diabetes

Importance of the field: Type 1 diabetes mellitus (T1D) is a T-cell mediated autoimmune disease with selective destruction of β cells. Immunological interventions are directed at arresting the loss of β-cell function with the promise that this will make it easier for patients to control their glucose levels.

Areas covered in this review: This review provides a summary of the preclinical and clinical research published between 1992 and 2009 using teplizumab and other anti-CD3 antibodies to arrest the loss of β-cell function in new onset T1D. Data from animal and human studies on the probable mechanism of action of teplizumab are also reviewed.

What the reader will gain: A broad perspective on the use of teplizumab in inducing disease specific tolerance.

Take home message: In Phase I/II randomized control trials, in patients with new onset T1D, teplizumab slowed the rate of loss of β-cell function over 2 years of follow-up. Treated patients had better glycemic control and lower insulin requirements. Adverse events so far are mild and of limited duration. Phase III clinical trials are underway to confirm these results and to determine if two courses of drug have greater efficacy in arresting loss of β-cell function.     

Gene variation of the transient receptor potential cation channel,subfamily M,member 2 (TRPM2) and type 2 diabetes mellitus: A case–control study

BackgroundDisordered cellular calcium regulation has been implicated in the pathophysiology of diabetes through mechanisms that remain unresolved. The non-selective calcium channel, transient receptor potential cation channel, subfamily M, member 2 (TRPM2), has been recently reported to play a role in insulin secretion by pancreatic β-cells. We hypothesized that gene variation of TRPM2 may play a role in the pathophysiology of type 2 diabetes mellitus (T2DM).MethodsUsing a case–control study from a community-based population sample of the Boston metropolitan area (all whites: 455 controls and 467 cases), we assessed the relationship of 9 TRPM2 tag-SNPs with (i) diabetes-related intermediate phenotypes and (ii) the presence of T2DM.ResultAll SNPs examined were in Hardy–Weinberg equilibrium. Overall allele, genotype, and haplotype distributions were similar between cases and controls. Three TRPM2 variants (rs2838553, rs2838554 and rs4818917) were associated with homeostasis model assessment of β-cell function (HOMA-%B), but not with HOMA-insulin resistance (HOMA-IR), fasting glucose levels nor hemoglobin A1c levels. Marker-by-marker logistic regression analysis, adjusted for potential risk factors, showed no evidence for an association of any of the tag-SNPs tested with T2DM. Further investigation using an entropy blocker-defined haplotype-based approach showed similar null findings.ConclusionsThe present investigation found no evidence for an association of the variants tested with T2DM, although HOMA-%B was negatively associated with three TRPM2 variants (rs2838553, rs2838554 and rs4818917). More importantly, our present findings require replication/confirmation in future large-scale, prospective investigations.     

Effects of incretin-based therapies on β-cell function in type 1 diabetes mellitus: a systematic review and meta-analysis

AimTo assess the effects of incretin-based therapies on β-cell function in patients with type 1 diabetes mellitus (T1DM).MethodsWe searched the PubMed, Cochrane Library, Embase, and Web of Knowledge databases for eligible randomized clinical trials published up to July 2021. The inclusion criteria were patients with T1DM or latent autoimmune diabetes in adults, patients treated with dipeptidyl peptidase-4 inhibitors or glucagon like peptide-1 receptor agonists, and outcomes included one of the following: fasting plasma glucose, fasting C-peptide, postprandial C-peptide, C-peptide area under the curve (AUC), homeostasis model assessment for β cell function, and insulin resistance. The effects were analyzed using a random effect model with STATA 11.0.ResultsEight trials including 427 participants were included in the final analysis. A pooled analysis found no significant difference in fasting plasma glucose, fasting C-peptide, postprandial C-peptide, or C-peptide AUC between patients treated with incretin-based therapies and placebo. The two trials that reported changes in 2-hour postprandial C-peptide and two of the four trials that reported changes in C-peptide AUC reported increases after incretin-based therapies.ConclusionThis meta-analysis showed that incretin-based therapies did not preserve β-cell function in patients with T1DM.     

DiaPep277 peptide therapy in the context of other immune intervention trials in type 1 diabetes

INTRODUCTION: Type 1 diabetes (T1D) is characterized by the autoimmune destruction of pancreatic β-cells. The aim of immune intervention is to arrest this autoimmune attack. DiaPep277, a major T-cell epitope of heat shock protein 60 (hsp60), has been shown to be effective in the modulation of the immune response in recent onset T1D and is the main focus of this review in the context of other ongoing trials using different approaches. AREAS COVERED: The authors performed a literature search of Pubmed listed publications (from the last 10 years) and a website search of the company licensing DiaPep277. DiaPep277 has been investigated in Phase I - III trials in humans. Phase II trials showed a significant preservation of β-cell function in adult T1D patients (but not children) with an absence of adverse effects and not accompanied by lower glycosylated haemoglobin (HbA1c) levels or reduced daily insulin requirement compared with placebo-treated patients. EXPERT OPINION: Administration of DiaPep277 is safe and represents a promising therapeutic strategy in patients with recent-onset T1D. The results of two large Phase III trials will tell us whether this therapy may change our current approach to treating T1D patients at diagnosis.     

Identification of a dominant epitope of glutamic acid decarboxylase (GAD-65) recognized by autoantibodies in stiff-man syndrome

Glutamic acid decarboxylase (GAD) is the enzyme that synthesizes the neurotransmitter gamma-aminobutyric acid (GABA) in neurons and in pancreatic beta cells. It is a major target of autoimmunity in Stiff- Man syndrome (SMS), a rare neurological disease, and in insulin- dependent diabetes mellitus. The two GAD isoforms, GAD-65 and GAD-67, are the products of two different genes. GAD-67 and GAD-65 are very similar to each other in amino acid sequence and differ substantially only at their NH2-terminal region. We have investigated the reactivity of autoantibodies of 30 Stiff-Man syndrome patients to GAD. All patient sera contained antibodies that recognize strongly GAD-65, but also GAD- 67, when tested by immunoprecipitation on brain extracts and by immunoprecipitation or immunocytochemistry on cells transfected with either the GAD-65 or the GAD-67 gene. When tested by Western blotting, all patient sera selectively recognized GAD-65. Western blot analysis of deletion mutants of GAD-65 demonstrated that autoantibodies are directed predominantly against two regions of the GAD-65 molecule. All SMS sera strongly recognized a fragment contained between amino acid 475 and the COOH terminus (amino acid 585). Within this region, amino acids 475-484 and 571-585 were required for reactivity. The requirement of these two discontinuous segments implies that the epitope is influenced by conformation. This reactivity is similar to that displayed by the monoclonal antibody GAD 6, suggesting the presence of a single immunodominant epitope (SMS-E1) in this region of GAD-65. In addition, most SMS sera recognized at least one epitope (SMS-E2) in the NH2-terminal domain of GAD-65 (amino acids 1-95). The demonstration in SMS patients of a strikingly homogeneous humoral autoimmune response against GAD and the identification of dominant autoreactive target regions may help to elucidate the molecular mechanisms of GAD processing and presentation involved in GAD autoimmunity. Moreover, the reactivity reported here of GAD autoantibodies in SMS partially differs from the reactivity of GAD autoantibodies in insulin-dependent diabetes mellitus, suggesting a link between the pattern of humoral autoimmunity and the clinical condition.     

Elimination of islet cell antibodies and glutamic acid decarboxylase antibodies II in a patient with newly diagnosed insulin-dependent diabetes mellitus

Islet cell antibodies and glutamic acid decarboxylase II (GAD II) antibodies have been discussed in the autoimmune pathogenesis of insulin-dependent diabetes mellitus (IDDM). Hence, immunosuppressants, intravenous immunoglobulins, and plasmapheresis have been used in an effort to modulate autoimmune activity and thereby prevent the destruction of pancreatic β-cells. We describe the autoantibody (islet cell antibody and GAD II) kinetics and clinical course in a patient with newly diagnosed IDDM treated with a specific immunoglobulin apheresis technique. Five days after the initial diagnosis a 37-year-old patient with IDDM underwent a series of seven immunoglobulin aphereses. Immunoglobulin (IgG, IgA, IgM), islet cell antibody, GAD II, and C-peptide concentrations were monitored for a time course of 74 days. Daily insulin requirements were recorded. One single immunoglobulin apheresis decreased IgG by 66.2 ± 9.1%, IgA by 66.8 ± 8.7%, and IgM by 57.7 ± 12.9%. GAD II antibodies were reduced by 61.9 ± 12.4%. The islet cell antibody titer declined from 1:32 to 1:4 after the treatment series. There were no relevant changes in the safety parameters determined nor were there any clinical side effects. The efficient decrease in islet cell antibodies and glutamic acid decarboxylase II antibodies in a patient with IDDM encourages further investigations into the impact of this treatment on the clinical course of this autoimmune disorder. J. Clin. Apheresis 12:196–199, 1997. © 1997 Wiley-Liss, Inc.     

Glutamic acid decarboxylase 67-reactive T cells: a marker of insulin- dependent diabetes

Glutamic acid decarboxylase (GAD) has been shown to be a target of autoantibodies in insulin-dependent diabetes (IDD). Two forms of GAD, with molecular weights of 67,000 and 65,000, have been cloned from separate genes. As pancreatic islet beta cell destruction DD is an autoimmune process mediated by T cells, we sought to determine if recombinant GAD67 was recognized by T cells in IDD subjects and particularly their first-degree relatives with islet cell antibodies known to be at risk for IDD. The central regions of human islet and brain GAD67 (amino acids 208-404) were cloned as fusion proteins with glutathione-S-transferase (GST). Proliferation of peripheral blood T cells in the presence of recombinant GAD67 was significantly higher in both at-risk relatives and recent-onset IDD subjects than in other autoimmune disease subjects and human histocompatibility leukocyte antigen (HLA)-matched healthy controls. Thus, 12 of 29 (41%) at-risk relatives and 11 of 29 (38%) recent-onset IDD subjects responded to GAD67, compared with 1 of 7 (14%) other autoimmune disease subjects and 1 of 23 (4%) HLA-matched controls. T cell responses to GST alone or to tetanus toxoid were not different between the groups. These findings demonstrate that GAD67 is a target autoantigen of T cells in IDD and suggest the possibility that GAD-reactive T cells may delineate asymptomatic subjects at increased risk for IDD.     

Novel Considerations on the Antibody/Autoantigen System in Type I (insulin-dependent) Diabetes Mellitus

Insulin dependent diabetes (IDDM) has an autoimmune pathogenesis. Included is the presence of antibodies to pancreatic islet cells. The first identified were islet cell antibodies (ICA), detected by indirect immunofluorescence, and which react with all cells within islets. Importantly, the autoantibodies are found several years prior to disease and although a pathogenic role for the autoantibodies is unclear, they have become useful markers of prediabetes. A number of studies of twins discordant for IDDM and of first degree relatives of IDDM patients have established that there is an increased risk for disease in individuals who have ICA, especially when ICA levels are high. This high predictive value of ICA decreases in the general population where the incidence of IDDM is lower than in first degree relatives, and both ICA and the disease risk associated with ICA, appear to be influenced by a genetic susceptibility. This has been substantiated in a study of patients with endocrine autoimmunity and ICA (Polyendocrine Study) where the predictive value of very high levels of ICA is less than 50% in patients without a first degree relative with IDDM. Hence, there remain a substantial number of patients with ICA who do not develop disease. From these patients, it was demonstrated that ICA include at least two distinct specificities, one of which is beta cell specific and is not associated with a high risk for IDDM.

These data, and an increasing list of new autoantibodies in IDDM, have increased the search for the relevant autoantigens. That of classic ICA is suggested to be a sialoganglioside, and a number of protein autoantigens have been suggested as other potential autoantigens. Of particular importance has been the identification of glutamic acid decarboxylase (GAD), the biosynthesizing enzyme of the neurotransmitter gamma amino butyric acid, as the autoantigen corresponding to the 64K autoantibodies found in the majority of newly diagnosed IDDM patients. Despite the identification of GAD, specific assays developed so far have not detected anti GAD antibodies at high frequencies in newly diagnosed patients. Like ICA, it appears that there may be distinct specificities of autoantibodies to GAD and associated products. Enzyme digestion of the autoantigen yields 50K, 40K and 37K fragments which appear to be derived from distinct polypeptide chains. Patients may have autoantibodies to either the 50K fragment or the 40/37K fragment or all fragments. Importantly, studies in twins and in the polyendocrine patients indicate that autoantibodies to the 37K fragment are more strongly associated with the progression to disease.

In addition to these autoantigens, autoantibodies are detected against the hormone insulin and its precursor proinsulin in up to 40% of newly diagnosed patients. Heat shock protein 65, carboxypeptidase H and glucose transporter have also been reported as autoantigens relevant to IDDM. It is now clear that the autoimmune response associated with IDDM is heterogeneous and against several islet antigens. The search will continue to determine which of these is important in the pathogenesis and which will provide effective markers for prediction which will eventually allow safe intervention therapy for the prevention of IDDM.     

2型糖尿病患者单核/巨噬细胞功能研究

目的 研究2型糖尿病(T2DM)患者单核/巨噬细胞分泌功能.方法 分析T2DM患者及健康者在葡萄糖耐量试验中白细胞介素(IL)-1、IL-6、肿瘤坏死因子(TNF)-α及胰岛素(Ins)的动态变化.结果 T2DM患者IL-1、IL-6、TNF-α、Ins分泌异常,空腹值偏高,服糖后分泌下降(P<0.05).结论 单核/巨噬细胞与胰腺β细胞分泌功能障碍与T2DM发病机制密切相关.