The insulin gene in type 1 diabetes

Insulin is a key autoantigen in the autoimmune process leading to the development of type 1 diabetes. Recent studies in both humans and mice have shown that variation in the expression of the insulin gene, in the thymus rather than the pancreas, contributes to disease susceptibility by affecting self-tolerance to insulin. These findings have brought about a paradigm-shift in our understanding of self-tolerance and autoimmunity to molecules with tissue-restricted expression, which are often the target of autoimmune disease.     

Comparison of insulin receptor binding to monocytes and erythrocytes in newly diagnosed type II diabetes mellitus

Insulin binding to circulating monocytes and erythrocytes was studied in 20 healthy volunteers and in 25 obese hyperinsulinemic newly diagnosed type-II diabetics. In type-II diabetics insulin binding to monocytes as well as to erythrocytes was significantly decreased in comparison with healthy individuals. The lowered insulin binding of the diabetics was mainly caused by a loss of receptor number. Individual analysis of the binding data, however, shows a marked discrepancy between receptor binding to circulating monocytes compared with erythrocytes. Since insulin binding to erythrocytes shows a great variation and seems to be influenced by other factors beside insulin concentrations it is suggested that insulin receptors on monocytes should be preferred for evaluation of peripheral insulin sensitivity.     

The role of rapid-acting insulin analogues and inhaled insulin in type 2 diabetes mellitus

sBackground:The availability of rapid-acting insulin analogues and inhaled insulin gives clinicians additional treatmentoptions in the management of patients with diabetes mellitus (DM). Combining rapid-acting insulin analogues with basal insulin can more closely mimic physiologic insulin release to maximize glycemic control.Objective:The objective of this article was to discuss the role of rapid-acting insulin analogues and inhaled insulin inthe treatment of patients with type 2 DM.Methods:Materials for this article were obtained through an online search of MEDLINE/PubMed and Google(1996-2006) using the search terms bolus insulin, postprandial, rapid-acting insulin analogues, titration, hypoglycemia, glycemic control, inhaled insulin, and insulins lispro, aspart, and glulisine.Results:Glycosylated hemoglobin (A1C) levels and number of all hypoglycemic episodes were similar in patients withtype 2 DM taking either mealtime rapid-acting insulin analogues or regular human insulin (RHI). Rapid-acting insulins have been successfully used in basal-bolus regimens with a variety of long- and intermediate-acting insulins, as well as with oral hypoglycemic agents. Injectable rapid-acting insulin analogues markedly decreased postprandial glucose (PPG) levels compared with RHI. Better reduction in PPG levels may be key to achieving target A1C levels in some patients, but long-term outcome studies are needed to assess whether lowering PPG levels decreases cardiovascular risk in patients with type 2 DM. Inhaled insulin may be an option for patients who cannot inject insulin, but route of administration and dosing issues limit its use in many patients. The effect of inhaled insulin on PPG is unclear at this time.Conclusions:Although rapid-acting insulin analogues are effective in the management of patients with type 2 DM, the limited numbers of studies have yet to demonstrate that these agents have any significant long-term advantage compared with RHI. In addition, they cost more than RHI. Further studies are needed to compare the efficacy of the rapid-acting insulin analogues, to compare the different dosing regimens used with mealtime insulin administration, and to ascertain if the decrease in PPG levels seen with the use of rapid-acting insulin analogues translates into improved glycemic control and perhaps even a reduction in cardiovascular risk in patients with type 2 DM. (Insulin. 2007;2:61-67) Copyright 2007 Excerpta Medica, Inc.     

Intravascular insulin gene delivery as potential therapeutic intervention in diabetes mellitus

We assessed therapeutic potential of intravascular insulin gene delivery in a diabetic murine model. The rat proinsulin-1 gene cDNA engineered to harbor furin consensus cleavage sequences was inserted into EBV-based plasmid vectors that contained CAG promoter or multimerized rat insulin promoter (RIP). Normal or streptozotocin (STZ)-induced diabetic mice were given an injection of the plasmids via the tail vein under high pressure. Transfection of the CAG-proinsulin construct markedly improved hyperglycemia of diabetic mice, accompanied by a considerable increase in serum insulin concentrations. Although the RIP-plasmid failed to reduce fasting blood glucose, the glucose tolerance test and RT-PCR analysis revealed that insulin production was regulated in the liver in a blood glucose level-dependent manner. The present results suggest a potential therapeutic means of controlling DM.     

Antioxidant status and lipid peroxidation in type II diabetes mellitus

Diabetes Mellitus (DM), a state of chronic hyperglycaemia, is a common disease affecting over 124 million individuals worldwide. In this study, erythrocyte glutathione levels, lipid peroxidation, superoxide dismutase, catalase, and glutathione peroxidase and some extracellular antioxidant protein levels of patients with type II diabetes mellitus and healthy controls were investigated. Thirty-eight patients (21 males; with age of mean +/- SD, 53.1+/-9.7 years) and 18 clinically healthy subjects (10 males; with age of mean +/- SD, 49.3+/-15.2 years) were included in the study. Levels of erythrocyte lipid peroxidation, serum ceruloplasmin and glucose levels, HbA1C levels, and erythrocyte catalase activity were significantly increased, whereas serum albumin and transferrin levels, erythrocyte glutathione levels, and glutathione peroxidase activity were significantly decreased compared to those of controls. There was no significant difference in superoxide dismutase activity compared to controls. The results suggest that the antioxidant deficiency and excessive peroxide-mediated damage may appear in non-insulin dependent diabetes mellitus.     

Pathogenesis of hyperglycemia in diabetes mellitus type II (insulin-independent)

The most important causes of hyperglycaemia in the course of diabetes mellitus type 2 are discussed. Those include: insulin secretion disorders, resistance to the insulin and overproduction of glucose in the liver. Affected secretory function of B cells in the pancreatic islets results, first of all, from the primary genetic error and secondary regulatory disorders, chiefly hyperglycaemia. Resistance to the insulin caused by decreased insulin activity in the muscle tissue and adipose tissue includes so-called receptor and postreceptor defects. Mechanism of these disorders is partially explained. Overproduction of glucose in the liver is probably secondary to the above metabolic disturbances and decides on the basic hyperglycaemia. Pathogenetic aspects of the insulin independent diabetes mellitus therapy with particular reference to the role of sulfonylurea derivatives are also discussed.     

The prevalence of type II diabetes mellitus is haptoglobin phenotype-independent

Haptoglobin (Hp) phenotype distribution and the association between Hp polymorphism and type II diabetes mellitus was investigated in a Jordanian sample population consisting of 618 nondiabetics and 265 diabetics. In nondiabetics, Hp 2-2 was the most predominant type occurring at a frequency of 0.529 followed by Hp 2-1 occurring at a frequency of 0.387. In diabetics, the Hp 2-2 frequency was 0.540 while that of Hp 2-1 was 0.381. No statistically significant variation was detected in Hp type distribution between the two groups. The Hp2 allele occurred at a frequency of 0.722 in nondiabetics and 0.730 in diabetics. In both groups, the Hp type distribution was in agreement with the Hardy-Weinberg equilibrium calculations. These results suggest that type II diabetes mellitus is Hp phenotype-independent.     

Prevalence of vitamin D receptor gene polymorphism in a Uruguayan population and its relation to type 1 diabetes mellitus

Vitamin D has important immuno-modulatory properties and it influences insulin secretion. It acts through a vitamin D receptor (VDR), for which several gene polymorphisms have been described. The Uruguayan population presents several epidemiological characteristics that make it different from that of other counties, including other Latin-American countries. It went through miscegenation processes, with a tri-hybrid European, Amerindian and African origin, with no contribution from isolated Amerindian communities. Such differences have important consequences for the relationship between frequencies of several genes in the general population and their association with the diabetes mellitus. We examined the prevalence of VDR gene polymorphisms in the general population and their relation to type 1 diabetes in a parent-case design. One hundred unrelated individuals from the general population and 45 parent-patient triads with a child affected with type 1 diabetes were genotyped for FokI, BsmI and TaqI VDR gene polymorphisms by RFLP-PCR. We used a transmission disequilibrium test to assess preferential transmission of parents to affected offspring. The prevalence of the three VDR polymorphisms was: allele F = 48%, B = 35%, T = 64%. The f, b, T alleles and heterozygous genotypes were found at a high frequency in this population. Among 36 informative heterozygous parental genotypes, 30 transmitted the F allele (probability of transmission = 83%). The other two polymorphisms did not show significant transmission. We suggest that FokI polymorphism indicates susceptibility to type 1 diabetes mellitus in the Uruguayan population.     

DNA polymorphisms of the insulin receptor gene in Japanese subjects with non-insulin-dependent diabetes mellitus

Genotypes identified by two restriction fragment length polymorphisms (RFLPs) of the insulin receptor gene (IRG) with the restriction endonuclease Sst-1 were determined in a Japanese group comprising 51 patients with non-insulin-dependent diabetes mellitus (NIDDM) and 50 control subjects. Southern hybridization using a probe for the beta subunit of the human IRG identifies 4 alleles, termed S1(+) (5.3 kb), S1(-) (5.8 kb), S2(+) (7.0 and 2.4 kb) and S2(-) (9.4 kb). The frequencies of genotypes possessing the S1(-) allele in Japanese controls and Japanese NIDDM patients were 0.11 and 0.16, respectively. Unlike the previously reported association of the S1(-) allele with NIDDM found in Caucasians there was no significant difference in the frequency of the S1(-) allele between non-diabetic and NIDDM Japanese patients. There was a significant difference in the frequency of the S2(+) allele between Caucasian control subjects (0.14) and Japanese controls (0.0) and NIDDM patients (0.02).     

Adipose tissue distribution in relation to insulin resistance in type 2 diabetes mellitus

Insulin resistance (IR) is typically more severe in obese individuals with type 2 diabetes (T2DM) than in similarly obese non-diabetics but whether there are group differences in body composition and whether such differences contribute to the more severe IR of T2DM is uncertain. DEXA and regional CT imaging were conducted to assess adipose tissue (AT) distribution and fat content in liver and muscle in 67 participants with T2DM (F39/M28, age 60 +/- 7 yr, BMI 34 +/- 3 kg/m(2)) and in 35 similarly obese, non-DM volunteers (F20/M15, age 55 +/- 8 yr, BMI 33 +/- 2 kg/m(2)). A biopsy of subcutaneous abdominal AT was done to measure adipocyte size. A glucose clamp was performed at an insulin infusion of 80 mU x min(-1) x m(-2). There was more severe IR in T2DM (6.1 +/- 2.3 vs. 9.9 +/- 3.3 mg x min(-1) x kg FFM(-1); P < 0.01). Group comparisons of body composition parameters was performed after adjusting for the effect of age, gender, race, height and total fat mass (FM). T2DM was associated with less leg FM (-1.2 +/- 0.4 kg, P < 0.01), more trunk FM (+1.1 +/- 0.4 kg, P < 0.05), greater hepatic fat (P < 0.05), and more subfascial adipose tissue around skeletal muscle (P < 0.05). There was a significant group x sex interaction for VAT (P < 0.01), with greater VAT in women with T2DM (P < 0.01). Mean adipocyte size (AS) did not significantly differ across groups, and smaller AS was associated with increased leg FM, whereas larger AS was related to more trunk FM (both P < 0.05). Group differences in IR were less after adjusting for group differences in leg FM, trunk FM, and hepatic fat, but these adjustments only partially accounted for the greater severity of IR in T2DM. In summary, T2DM, compared with similarly obese nondiabetic men and women, is associated with less leg FM and greater trunk FM and hepatic fat.     

线粒体基因组D-Loop区基因多态性与2型糖尿病的相关性

随机选取199例浙江地区2型糖尿病患者与102例正常对照, 采用聚合酶链反应(Polymerase chain re-action, PCR)、基因片段直接测序来检测线粒体基因组D-Loop区域基因变异情况, 同时分析其与主要临床指标的关系。结果显示: 线粒体基因组D-Loop区域为一高变异区, np73A-G、np263A-G、np16223C-T、np16519T-C为4个高变异位点; 发现29个未见报道的新变异位点; np193A-G、np234A-G、np16108C-T等变异与糖尿病家族史有关。这表明浙江籍汉族人线粒体基因组D-Loop区存在大量基因多态性现象, 此区域的某些变异可能与糖尿病的发生发展等具有一定相关性。     

Generation of a floxed allele of the mouse BMP type II receptor gene

Bone morphogenetic proteins (BMPs) regulate a wide range of cellular functions that contribute to embryonic development from mesoderm formation to organogenesis. BMP type II receptor (BMPR-II) transduces BMP signals by forming heteromeric complexes with and phosphorylating BMP type I receptors. Heterozygous germline mutations of BMPR-II gene have been identified in patients with familial and sporadic primary pulmonary hypertension, indicating that BMPR-II may contribute to the maintenance of normal pulmonary vascular structure and function. Since embryos homozygous for a null BMPR-II allele died during gastrulation, precluding further studies of BMPR-II function in organ formation and in adult tissues, we generated mice carrying a conditional mutant BMPR-II allele in which exons 4 and 5 were flanked by loxP sequences. We anticipate that studies of mice carrying a floxed BMPR-II allele and a Cre transgene (under the control of a tissue-specific promoter) will enable characterization of the role of BMPR-II in specific cell types during development and in the pathogenesis of cardiovascular diseases.     

Magnesium metabolism in type 2 diabetes mellitus, metabolic syndrome and insulin resistance

Type 2 diabetes is characterized by cellular and extracellular Mg depletion. Epidemiologic studies showed a high prevalence of hypomagnesaemia and lower intracellular Mg concentrations in diabetic subjects. Insulin and glucose are important regulators of Mg metabolism. Intracellular Mg plays a key role in regulating insulin action, insulin-mediated-glucose uptake and vascular tone. Reduced intracellular Mg concentrations result in a defective tyrosine-kinase activity, post-receptorial impairment in insulin action, and worsening of insulin resistance in diabetic patients. Mg deficit has been proposed as a possible underlying common mechanism of the "insulin resistance" of different metabolic conditions. Low dietary Mg intake is also related to the development of type 2 diabetes. Benefits of Mg supplementation on metabolic profile in diabetic subjects have been found in most, but not all clinical studies, and larger prospective studies are needed to support the potential role of dietary Mg supplementation as a possible public health strategy in diabetes risk.