More than one glycan is needed for ER glucosidase II to allow entry of glycoproteins into the calnexin/calreticulin cycle

Nascent and newly synthesized glycoproteins enter the calnexin (Cnx)/calreticulin (Crt) cycle when two out of three glucoses in the core N-linked glycans have been trimmed sequentially by endoplasmic reticulum (ER) glucosidases I (GI) and II (GII). By analyzing arrested glycopeptides in microsomes, we found that GI removed the outermost glucose immediately after glycan addition. However, although GII associated with singly glycosylated nascent chains, trimming of the second glucose only occurred efficiently when a second glycan was present in the chain. Consistent with a requirement for multiple glycans to activate GII, pancreatic RNase in live cells needed more than one glycan to enter the Cnx/Crt cycle. Thus, whereas GI trimming occurs as an automatic extension of glycosylation, trimming by GII is a regulated process. By adjusting the number and location of glycans, glycoproteins can instruct the cell to engage them in an individually determined folding and quality control pathway.     

Conservative management of pregnancy in diabetic women.

In 1979 the obstetric management of pregnancies in diabetic women in Cardiff was changed from elective delivery at 37-38 weeks to delivery at term. This change was facilitated by home monitoring of blood glucose concentrations and improved techniques for assessing fetal wellbeing. There were 35 pregnancies in insulin dependent diabetics in 1972-8 and 45 in 1979-82. The quality of diabetic control during pregnancy was equally good in both periods. The average gestation at final admission to hospital increased from 30 to 37 weeks. Amniocentesis to assess fetal pulmonary maturity was necessary in 26 patients (74%) in the first period of study and in only four (9%) in the second. Gestational age at delivery increased from 37.4 to 39.4 weeks after the change in policy. The proportion of mothers entering spontaneous term labour and delivering vaginally increased from 14.3% to 37.8%. The mean birth weight of live born, singleton infants increased from 3090 g to 3650 g, the feeding pattern improved, and respiratory problems were less common. Morbidity was reduced and perinatal mortality was not increased with conservative management of pregnancy in diabetic women.     

Outcomes of pregnancy in insulin dependent diabetic women: results of a five year population cohort study.

OBJECTIVE: To monitor pregnancies in women with pre-existent insulin dependent diabetes for pregnancy loss, congenital malformations, and fetal growth in a geographically defined area of north west England. DESIGN: Population cohort study. SETTING: 10 maternity units in Cheshire, Lancashire, and Merseyside which had no regional guidelines for the management of pregnancy in diabetic women. SUBJECTS: 462 pregnancies in 355 women with insulin dependent diabetes from the 10 centres over five years (1990-4 inclusive). MAIN OUTCOME MEASURES: Numbers and rates of miscarriages, stillbirths, and neonatal and postneonatal deaths; prevalence of congenital malformations; birth weight in relation to gestational age. RESULTS: Among 462 pregnancies, 351 (76%) resulted in a liveborn infant, 78 (17%) aborted spontaneously, nine (2%) resulted in stillbirth, and 24 (5%) were terminated. Of the terminations, nine were for congenital malformation. The stillbirth rate was 25.0/1000 total births (95% confidence interval 8.9 to 41.1) compared with a population rate of 5.0/1000, and infant mortality was 19.9/1000 live births (5.3 to 34.6) compared with 6.8/1000. The prevalence of congenital malformations was 94.0/1000 live births (63.5 to 124.5) compared with 9.7/1000 in the general population. When corrected for gestational age, mean birth weight in the sample was 1.3 standard deviations greater than that of infants of non-diabetic mothers. Infants with congenital malformations weighed less than those without. CONCLUSION: In an unselected population the infants of women with pre-existent insulin dependent diabetes mellitus have a 10-fold greater risk of a congenital malformation and a fivefold greater risk of being stillborn than infants in the general population. Further improvements in the management of pregnancy in diabetic women are needed if target of the St Vincent declaration of 1989 is to be met.     

Genetic control of diabetes and insulitis in the nonobese diabetic mouse. Pedigree analysis of a diabetic H-2nod/b heterozygote

The development of autoimmune type 1 diabetes mellitus in man and the nonobese diabetic (NOD) mouse is greatly influenced by a gene linked to the MHC. Although homozygosity at the NOD MHC is required for a high prevalence of disease, during backcross studies we have found a small number of diabetic H-2nod/b MHC heterozygotes. These diabetic heterozygotes could either represent a crossover event between the MHC and a putative MHC-linked diabetogenic gene or, alternatively, they could indicate that there is a dominant MHC-linked diabetic gene that has low penetrance in the heterozygous state. Pedigree analysis of a diabetic H-2nod/b MHC heterozygote favors the latter hypothesis.     

Lack of effect of vitamin D administration during pregnancy and early life on diabetes incidence in the non-obese diabetic mouse.

BACKGROUND AND AIMS: Several studies have suggested that vitamin D supplementation in early life may reduce the risk of developing type 1 diabetes in later life. The non-obese diabetic (NOD) mouse is a model of spontaneous type 1 diabetes currently used for testing hypothesis/compounds aimed at disease prevention. In this study, we tested the effect of vitamin D (16 IU by gavage) on diabetes incidence in NOD/Ba mice treated from conception with olive oil containing vitamin D via maternal dosing up to 10 weeks of age and followed up until 32 weeks of age. METHODS: Twelve breeding pairs were administered olive oil containing vitamin D during pregnancy, 15 days following the birth of the pups and for the next 10 weeks subsequently. The same breeding pairs were bred again after a clearance period of 15 days using a control solution to produce a control litter. This control group received a control solution for the same period of time. Diabetes incidence, degree of insulitis, and insulin content in the pancreas were investigated in the two groups. RESULTS: 12 vitamin D-treated NOD mice developed diabetes compared to 15 animals in the control group (Log rank test p = 0.899, NS). There were no significant differences between the groups in diabetes incidence, time of onset of the disease, degree of insulitis, or the insulin content in the pancreas. CONCLUSION: Vitamin D administered in utero and in the early stages of life at the dosage used does not change the incidence of diabetes or modify the disease process that leads to beta cell destruction in the NOD mouse.     

Visceral fat is a determinant of PAI-1 activity in diabetic and non-diabetic overweight and obese women.

Plasminogen activator inhibitor type 1 (PAI-1), an inhibitor of fibrinolysis and an important and independent cardiovascular risk factor, has been shown to be elevated in obesity and type 2 diabetes. Recent study results have suggested that adipose tissue--visceral fat in particular--could play an important role in the fibrinolytic process.In order to assess the specific role of this fat distribution, we measured PAI-1 activity (AU/ml) and visceral fat (CT-scan at level L4-L5) in 2 groups of 30 overweight and obese diabetic and overweight and obese non-diabetic women. Subjects were matched for age, weight, body mass index, fat mass and total abdominal fat. Visceral adipose tissue and PAI-1 were significantly higher in diabetic women (p = 0.022 and p = 0.004 respectively) than in non-diabetic patients. Visceral fat correlated significantly with PAI-1 activity, even after correction for insulin and triglycerides (r = 0.28, p = 0.034). Stepwise regression analysis showed visceral fat as the most important determinant factor for PAI-1 in the whole group and in the non-diabetic group. In the diabetic group, fasting insulin was the most important determinant. These results show that visceral fat is more important than BMI or total body fat in the determination of PAI-1 levels. Furthermore, the increased amount of visceral fat in type 2 diabetics may contribute to the increase of PAI-1 activity levels and the subsequent increased risk for thrombovascular disease, regardless of BMI and total fatness.     

Prospective population based survey of outcome of pregnancy in diabetic women: results of the Northern Diabetic Pregnancy Audit, 1994.

OBJECTIVE: To determine whether the St Vincent declaration (1989) target of diabetic pregnancy outcome approximating non-diabetic pregnancy outcome in near to being achieved. DESIGN: Prospective collection of population based information on pregnancies in women with diabetes from all participating hospitals. SETTING: District general and teaching hospitals of the former Northern region. SUBJECTS: 111 diabetic women booking with pregnancy during 1 January to 31 December 1994. MAIN OUTCOME MEASURES: Diabetic control, perinatal mortality rate, fetal abnormality rate. RESULTS: The perinatal mortality rate was 48/1000 for diabetic pregnancies compared with 8.9/1000 for the background population (odds ratio 5.38; 95% confidence interval 2.27 to 12.70) and the neonatal mortality rate was 59/1000 compared with 3.9/1000 (15.0; 6.77 to 33.10). Two late neonatal deaths were due to congenital heart defects. Six per cent of all fetal losses (6/109 cases) were due to major malformations. The congenital malformation rate was 83/1000 compared with 21.3/1000 (3.76; 2.00 to 7.06) in the background population. CONCLUSIONS: Diabetic pregnancy remains a high risk state with perinatal mortality and fetal malformation rates much higher than in the background population.