DIABETES arises through two etiologically distinct routes.1 Type I diabetes is the result of immunologically mediated destruction of the pancreatic beta cells, and usually requires replacement ther...

Epidemiologic Approach to the Etiology of Type I Diabetes Mellitus and Its Complications

Alterations in placental transport may contribute to accelerated fetal growth in pregnancies complicated by diabetes. We studied the activity of the syncytiotrophoblast amino acid transporter system A and the transport of the essential amino acids leucine, lysine, and taurine. Syncytiotrophoblast microvillous plasma membranes (MVMs) and basal plasma membranes (BMs) were isolated from placentas obtained from normal pregnancies and pregnancies complicated by gestational diabetes mellitus (GDM) and type 1 diabetes, with and without large-for-gestational-age (LGA) fetuses. Amino acid transport was assessed using radio-labeled substrates and rapid filtration techniques. System A activity in MVM was increased (65-80%, P < 0.05) in all groups with diabetes independent of fetal overgrowth. However, MVM system A activity was unaffected in placentas of normal pregnancies with LGA fetuses. MVM leucine transport was increased in the GDM/LGA group. In BMs, amino acid transport was unaffected by diabetes. In conclusion, diabetes in pregnancy is associated with an increased system A activity in MVM, and MVM leucine transport is increased in the GDM/LGA group. We suggest that these changes result in an increased uptake of neutral amino acids across MVM, which may be used in placental metabolism or be delivered to the fetus. The increased MVM leucine uptake in the GDM/LGA group may contribute to accelerated fetal growth in these patients.

https://diabetes.diabetesjournals.org/content/diabetes/51/7/2214.full.pdf

Alterations in the Activity of Placental Amino Acid Transporters in Pregnancies Complicated by Diabetes

Type 1 diabetes (T1D) results from the destruction of pancreatic beta cells. Genetic factors are believed to be a major component for the development of T1D, but the concordance rate for the development of diabetes in identical twins is only about 40%, suggesting that nongenetic factors play an important role in the expression of the disease. Viruses are one environmental factor that is implicated in the pathogenesis of T1D. To date, 14 different viruses have been reported to be associated with the development of T1D in humans and animal models. Viruses may be involved in the pathogenesis of T1D in at least two distinct ways: by inducing beta cell-specific autoimmunity, with or without infection of the beta cells, [e.g. Kilham rat virus (KRV)] and by cytolytic infection and destruction of the beta cells (e.g. encephalomyocarditis virus in mice). With respect to virus-mediated autoimmunity, retrovirus, reovirus, KRV, bovine viral diarrhoea-mucosal disease virus, mumps virus, rubella virus, cytomegalovirus and Epstein-Barr virus (EBV) are discussed. With respect to the destruction of beta cells by cytolytic infection, encephalomyocarditis virus, mengovirus and Coxsackie B viruses are discussed. In addition, a review of transgenic animal models for virus-induced autoimmune diabetes is included, particularly with regard to lymphocytic choriomeningitis virus, influenza viral proteins and the Epstein-Barr viral receptor. Finally, the prevention of autoimmune diabetes by infection of viruses such as lymphocytic choriomeningitis virus is discussed.

A new look at viruses in type 1 diabetes.

Type 1 diabetes results from the destruction of pancreatic beta cells. Genetic factors are believed to be a major component for the development of type 1diabetes, but the concordance rate for the development of diabetes in identical twins is only about 40%, suggesting that non-genetic factors play an important role in the expression of the disease. Viruses are one environmental factor that is implicated in the pathogenesis of type 1 diabetes. To date, 14 different viruses have been reported to be associated with the development of type 1 diabetes in humans and animal models. Viruses may be involved in the pathogenesis of type 1 diabetes in at least two distinct ways: by inducing beta cellspecific autoimmunity, with or without infection of the beta cells, (e.g. Kilham rat virus) and by cytolytic infection and destruction of the beta cells (e.g. encephalomyocarditis virus in mice). With respect to virus-mediated autoimmunity, retrovirus, reovirus, Kilham rat virus, bovine viral diarrhoea-mucosal disease virus, mumps virus, rubella virus, cytomegalovirus and Epstein-Barr virus are discussed. With respect to the destruction of beta cells by cytolytic infection, encephalomyocarditis virus, mengovirus and Coxsackie B viruses are discussed. In addition, a review of transgenic animal models for virus-induced autoimmune diabetes is included, particularly with regard to lymphocytic choriomeningitis virus, influenza viral proteins and the EpsteinBarr viral receptor. Finally, the prevention of autoimmune diabetes by infection of viruses such as lymphocytic choriomeningitis virus is discussed.

/pdf/a-new-look-at-viruses-in-type-1-diabetes-30lasa2z0s.pdf

A New Look at Viruses in Type 1 Diabetes

The activation of the interferon (IFN)-alpha system and its relationship with coxsackievirus B (CVB) infection has been analyzed in 56 patients with insulin-dependent diabetes mellitus (IDDM; 25 children and 31 adults). Elevated levels of IFN-alpha were found in plasma of 70% of patients (39/56), and a positive detection of IFN-alpha mRNA in blood cells by reverse transcriptase-polymerase chain reaction (RT-PCR) was observed in 75% of patients (42/56). Enterovirus (EV) RNA assayed by seminested RT-PCR was detected in the blood of 50% of IFN-alpha-positive patients but not in any IFN-alpha-negative patients. The results of genotype analysis of amplified EV RNA sequences (5 CVB2, 8 CVB3, and 8 CVB4) were concordant with the results of CVB-neutralization tests. The comparison between IFN-alpha, EV RNA, and serology suggested that the proportion of CVB infection associated with IFN-alpha positivity might be higher than is predicted from the investigation of EV RNA. Together, the results suggest that, in a majority of cases, a CVB infection is associated with clinical IDDM.

Increased Level of Interferon-α in Blood of Patients with Insulin-Dependent Diabetes Mellitus: Relationship with Coxsackievirus B Infection

The potential role of antecedent viral infection in the pathogenesis of Type 1 (insulin-dependent) diabetes was investigated by measuring antibody titres to several viruses in serum obtained at the time of diagnosis of diabetes. An outbreak of Coxsackie B4 infection followed by a wave of Coxsackie B3 and B5 infections occurred in Seattle during the time viral serology was obtained in the diabetic patients. Antibody titres to Cocksackie B5 and Influenza A and B viruses were comparable in diabetics and matched control subjects, but antibody titres to Cocksackie B3 and B4 were lower in the diabetics and a low antibody titre to Coxsackie B3/B4 was associated with a significantly increased relative risk of diabetes.

/pdf/reduced-coxsackie-antibody-titres-in-type-1-insulin-1n54xndhrg.pdf

R H Ward

Papers

Reduced Coxsackie antibody titres in type 1 (insulin-dependent) diabetic patients presenting during an outbreak of Coxsackie B3 and B4 infection.