Time in range: A best practice guide for UK diabetes healthcare professionals in the context of the COVID-19 global pandemic

The emergence of continuous glucose monitoring has driven improvements in glycaemic control and quality of life for people with diabetes. Recent changes in access to continuous glucose monitoring systems within UK health services have increased the number of people able to benefit from these technologies. The COVID-19 pandemic has created an opportunity for diabetes healthcare professionals to use continuous glucose monitoring technology to remotely deliver diabetes services to support people with diabetes. This opportunity can be maximized with improved application and interpretation of continuous glucose monitoring-generated data. Amongst the diverse measures of glycaemic control, time in range is considered to be of high value in routine clinical care because it is actionable and is visibly responsive to changes in diabetes management. Importantly, it is also been linked to the risk of developing complications associated with diabetes and can be understood by people with diabetes and healthcare professionals alike. The 2019 International Consensus on Time in Range has established a series of target glucose ranges and recommendations for time spent within these ranges that is consistent with optimal glycaemic control. The recommendations cover people with type 1 or type 2 diabetes, with separate targets indicated for elderly people or those at higher risk from hypoglycaemia, as well as for women with type 1 diabetes during pregnancy. The aim of this best practice guide was to clarify the intent and purpose of these international consensus recommendations and to provide practical insights into their implementation in UK diabetes care.

Approaches to screening for hyperglycaemia in pregnant women during and after the COVID-19 pandemic

AIM

To evaluate the diagnostic and prognostic performance of alternative diagnostic strategies to oral glucose tolerance tests, including random plasma glucose, fasting plasma glucose and HbA_1c , during the COVID-19 pandemic.

METHODS

Retrospective service data (Cambridge, UK; 17 736 consecutive singleton pregnancies, 2004-2008; 826 consecutive gestational diabetes pregnancies, 2014-2019) and 361 women with ≥1 gestational diabetes risk factor (OPHELIA prospective observational study, UK) were included. Pregnancy outcomes included gestational diabetes (National Institute of Health and Clinical Excellence or International Association of Diabetes and Pregnancy Study Groups criteria), diabetes in pregnancy (WHO criteria), Caesarean section, large-for-gestational age infant, neonatal hypoglycaemia and neonatal intensive care unit admission. Receiver-operating characteristic curves and unadjusted logistic regression were used to compare random plasma glucose, fasting plasma glucose and HbA_1c performance.

RESULTS

Gestational diabetes diagnosis was significantly associated with random plasma glucose at 12 weeks [area under the receiver-operating characteristic curve for both criteria 0.81 (95% CI 0.79-0.83)], fasting plasma glucose [National Institute of Health and Clinical Excellence: area under the receiver-operating characteristic curve 0.75 (95% CI 0.65-0.85); International Association of Diabetes and Pregnancy Study Groups: area under the receiver-operating characteristic curve 0.92 (95% CI 0.85-0.98)] and HbA_1c at 28 weeks' gestation [National Institute of Health and Clinical Excellence: 0.83 (95% CI 0.75-0.90); International Association of Diabetes and Pregnancy Study Groups: 0.84 (95% CI 0.77-0.91)]. Each measure predicts some, but not all, pregnancy outcomes studied. At 12 weeks, ~5% of women would be identified using random plasma glucose ≥8.5 mmol/l (sensitivity 42%; specificity 96%) and at 28 weeks using HbA_1c ≥39 mmol/mol (sensitivity 26%; specificity 96%) or fasting plasma glucose ≥5.2-5.4 mmol/l (sensitivity 18-41%; specificity 97-98%).

CONCLUSIONS

Random plasma glucose at 12 weeks, and fasting plasma glucose or HbA_1c at 28 weeks identify women with hyperglycaemia at risk of suboptimal pregnancy outcomes. These opportunistic laboratory tests perform adequately for risk stratification when oral glucose tolerance testing is not available.

Dietary intakes of women with Type 1 diabetes before and during pregnancy: a pre-specified secondary subgroup analysis among CONCEPTT participants

AIM

To describe the dietary intakes of women with Type 1 diabetes before and during pregnancy.

METHODS

This was a pre-specified subgroup analysis of CONCEPTT involving 63 women planning pregnancy and 93 pregnant women from 14 sites in England, Scotland and Ireland. Two hundred and forty-six 3-day food diaries (104 planning pregnancy, 142 pregnant) were matched to data source and food reference codes, and analysed using dietary software. Participants were informed that food diaries would be de-identified and used only for research purposes.

RESULTS

Mean (sd) daily energy intake was 1588 (346) kcal and 1673 (384) kcal in women planning pregnancy and pregnant women respectively. Total carbohydrate intake was consistent with dietary guideline recommendations [180 (52) g planning pregnancy, 198 (54) g pregnant], but non-recommended sources (e.g. sugars, preserves, confectionery, biscuits, cakes) contributed to 46% of total daily carbohydrate intake. Fat consumption exceeded guideline recommendations [70 (21) g planning pregnancy, 72 (21) g pregnant]. Fibre [15.5 (5.3) g planning pregnancy, 15.4 (5.1) g pregnant], fruit and vegetable intakes [3.5 (2.2) and 3.1 (1.8) serves/day] were inadequate. Twelve women planning pregnancy (19%) and 24 pregnant women (26%) did not meet micronutrient requirements.

CONCLUSIONS

The diets of pregnant women from England, Scotland and Ireland are characterized by high fat, low fibre and poor-quality carbohydrate intakes. Fruit and vegetable consumption is inadequate, with one in four women at risk of micronutrient deficiencies. Further research is needed to optimize maternal nutrition for glycaemic control and for maternal and offspring health.

A qualitative study of clinician attitudes towards closed-loop systems in mainstream diabetes care in England

AIM

Clinicians mediate access to new technologies. Consequently, their views on specific devices may influence user access to diabetes technology in mainstream care. As yet, little is known about clinicians' views about closed-loop systems. This qualitative study explored clinicians' views on the likely impacts of future closed-loop systems in mainstream diabetes care in England.

METHODS

We conducted interviews with 36 clinicians from a range of professional backgrounds in five hospital outpatient clinics (two adult, two pregnancy, one paediatric) in England to explore possible consequences of closed-loop systems for users and clinicians. Data analysis utilized a framework approach.

RESULTS

Clinicians reported a range of expected benefits for future users, including improved glucose control and quality of life. Expected burdens included continued need for manual input and the risk of losing basic self-care skills. In terms of future clinical workloads, three clinicians emphasized only positive impacts, seven emphasized both positive and negative impacts, and 17 mentioned only negative impacts. Our most prominent finding, expressed by 24 clinicians, was that closed-loop systems would generate initial challenges due to the need for staff training, user education and support, and new analytical capacities, alongside existing intra-clinic variations in technological experience.

CONCLUSIONS

Clinicians recognize the value of closed-loop systems in terms of health benefits, but also identify a range of concerns for both users and healthcare staff, which could impact negatively on user access. Future implementation efforts should address these concerns by providing training and support for healthcare teams, taking varied technological expertise into account.

Seasonal variations in incidence and maternal-fetal outcomes of gestational diabetes

AIMS

To determine whether the neonatal and delivery outcomes of gestational diabetes vary seasonally in the context of a relatively cool temperate climate.

METHODS

A retrospect cohort of 23 735 women consecutively delivering singleton, live-born term infants in a single tertiary obstetrics centre in the UK (2004-2008) was identified. A total of 985 (4.1%) met the diagnostic criteria for gestational diabetes. Additive dynamic regression models, adjusted for maternal age, BMI, parity and ethnicity, were used to compare gestational diabetes incidence and outcomes over annual cycles. Outcomes included: random plasma glucose at booking; gestational diabetes diagnosis; birth weight centile; and delivery mode.

RESULTS

The incidence of gestational diabetes varied by 30% from peak incidence (October births) to lowest incidence (March births; P=0.031). Ambient temperature at time of testing (28 weeks) was strongly positively associated with diagnosis (P<0.001). Significant seasonal variation was evident in birth weight in gestational diabetes-affected pregnancies (average 54^th centile June to September; average 60^th centile December to March; P=0.027). Emergency Caesarean rates also showed significant seasonal variation of up to 50% (P=0.038), which was closely temporally correlated with increased birth weights.

CONCLUSIONS

There is substantial seasonal variation in gestational diabetes incidence and maternal-fetal outcomes, even in a relatively cool temperate climate. The highest average birth weight and greatest risk of emergency Caesarean delivery occurs in women delivering during the spring months. Recognizing seasonal variation in neonatal and delivery outcomes provides new opportunity for individualizing approaches to managing gestational diabetes.

Modelling potential cost savings from use of real-time continuous glucose monitoring in pregnant women with Type 1 diabetes

AIM

To investigate potential cost savings associated with the use of real-time continuous glucose monitoring (RT-CGM) throughout pregnancy in women with Type 1 diabetes.

METHODS

A budget impact model was developed to estimate, from the perspective of National Health Service England, the total costs of managing pregnancy and delivery in women with Type 1 diabetes using self-monitoring of blood glucose (SMBG) with and without RT-CGM. It was assumed that the entire modelled cohort (n = 1441) would use RT-CGM from 10 to 38 weeks' gestation (7 months). Data on pregnancy and neonatal complication rates and related costs were derived from published literature, national tariffs, and device manufacturers.

RESULTS

The cost of glucose monitoring was £588 with SMBG alone and £1820 with RT-CGM. The total annual costs of managing pregnancy and delivery in women with Type 1 diabetes were £23 725 648 with SMBG alone, and £14 165 187 with SMBG and RT-CGM; indicating potential cost savings of approximately £9 560 461 from using RT-CGM. The principal drivers of cost savings were the daily cost of neonatal intensive care unit (NICU) admissions (£3743) and the shorter duration of NICU stay (mean 6.6 vs. 9.1 days respectively). Sensitivity analyses showed that RT-CGM remained cost saving, albeit to lesser extents, across a range of NICU costs and durations of hospital stay, and with varying numbers of daily SMBG measurements.

CONCLUSIONS

Routine use of RT-CGM by pregnant women with Type 1 diabetes, would result in substantial cost savings, mainly through reductions in NICU admissions and shorter duration of NICU care.

The effect of hypoglycaemia during hospital admission on health-related outcomes for people with diabetes: a systematic review and meta-analysis

AIM

To assess the health-related outcomes of hypoglycaemia for people with diabetes admitted to hospital; specifically, hospital length of stay and mortality.

METHODS

We conducted a systematic review and meta-analysis of studies relating to hypoglycaemia (< 4 mmol/l) for hospitalized adults (≥ 16 years) with diabetes reporting the primary outcomes of interest, hospital length of stay or mortality. Final papers for inclusion were reviewed in duplicate and the adjusted results of each were pooled, using a random effects model then undergoing further prespecified subgroup analysis.

RESULTS

In total, 15 studies were included in the meta-analysis. The pooled mean difference in length of stay for ward-based inpatients exposed to hypoglycaemia was 4.1 days longer [95% confidence interval (CI) 2.36 to 5.79; I² = 99%] compared with those without hypoglycaemia. This association remained robust across the pre-specified subgroup analyses. The pooled relative risk (RR) of in-hospital mortality was greater for those exposed to hypoglycaemia (RR 2.09, 95% CI 1.64 to 2.67; I² = 94%, n = 7 studies) but not in intensive care unit mortality (RR 0.75, 95% CI 0.49 to 1.16; I² =0%, n = 2 studies).

CONCLUSION

There is an association between inpatient hypoglycaemia and longer length of stay and greater in-hospital mortality. Studies examining this association were heterogenous in terms of both clinical populations and effect size, but the overall direction of the association was consistent. Therefore, glucose concentration should be considered a potential tool to aid the identification of inpatients at risk of poor health-related outcomes.

Maternal glycaemic control and risk of neonatal hypoglycaemia in Type 1 diabetes pregnancy: a secondary analysis of the CONCEPTT trial

AIMS

To examine the relationship between maternal glycaemic control and risk of neonatal hypoglycaemia using conventional and continuous glucose monitoring metrics in the Continuous Glucose Monitoring in Type 1 Diabetes Pregnancy Trial (CONCEPTT) participants.

METHODS

A secondary analysis of CONCEPTT involving 225 pregnant women and their liveborn infants. Antenatal glycaemia was assessed at 12, 24 and 34 weeks gestation. Intrapartum glycaemia was assessed by continuous glucose monitoring measures 24 hours prior to delivery. The primary outcome was neonatal hypoglycaemia defined as glucose concentration < 2.6 mmol/l and requiring intravenous dextrose.

RESULTS

Neonatal hypoglycaemia occurred in 57/225 (25.3%) infants, 21 (15%) term and 36 (40%) preterm neonates. During the second and third trimesters, mothers of infants with neonatal hypoglycaemia had higher HbA_1c [48 ± 7 (6.6 ± 0.6) vs. 45 ± 7 (6.2 ± 0.6); P = 0.0009 and 50 ± 7 (6.7 ± 0.6) vs. 46 ± 7 (6.3 ± 0.6); P = 0.0001] and lower continuous glucose monitoring time-in-range (46% vs. 53%; P = 0.004 and 60% vs. 66%; P = 0.03). Neonates with hypoglycaemia had higher cord blood C-peptide concentrations [1416 (834, 2757) vs. 662 (417, 1086) pmol/l; P < 0.00001], birthweight > 97.7th centile (63% vs. 34%; P < 0.0001) and skinfold thickness (P ≤ 0.02). Intrapartum continuous glucose monitoring was available for 33 participants, with no differences between mothers of neonates with and without hypoglycaemia.

CONCLUSIONS

Modest increments in continuous glucose monitoring time-in-target (5-7% increase) during the second and third trimesters are associated with reduced risk for neonatal hypoglycaemia. While more intrapartum continuous glucose monitoring data are needed, the higher birthweight and skinfold measures associated with neonatal hypoglycaemia suggest that risk is related to fetal hyperinsulinemia preceding the immediate intrapartum period.

Improving outcomes in gestational diabetes: does gestational weight gain matter?

AIM

Excessive gestational weight gain increases risk of gestational diabetes mellitus (GDM) but it remains unclear whether weight control after GDM diagnosis improves outcomes. We assessed whether: (1) total gestational weight gain during pregnancy (0-36 weeks); (2) early gestational weight gain (0-28 weeks, before GDM diagnosis); or (3) late gestational weight gain (28-36 weeks, after diagnosis) are associated with maternal-fetal outcomes.

METHODS

Some 546 women with GDM who delivered viable singleton infants at a single UK obstetric centre (October 2014 to March 2017) were included in this retrospective observational study.

RESULTS

Higher total gestational weight gain was associated with Caesarean section [n = 376; odds ratio (OR) 1.05; confidence intervals (CI) 1.02-1.08, P < 0.001] and large for gestational age (OR 1.08; CI 1.03-1.12, P < 0.001). Higher late gestational weight gain (28-36 weeks; n = 144) was associated with large for gestational age (OR 1.17; CI 1.01-1.37, P < 0.05), instrumental deliveries (OR 1.26; CI 1.03-1.55, P < 0.01), higher total daily insulin doses (36 weeks; beta coefficient 4.37; CI 1.92-6.82, P < 0.001), and higher post-partum 2-h oral glucose tolerance test concentrations (beta coefficient 0.12; CI 0.01-0.22, P < 0.05). Women who avoided substantial weight gain after GDM diagnosis had 0.7 mmol/l lower postnatal 2-h glucose and needed half the amount of insulin/day at 36 weeks compared with women with substantial weight gain after diagnosis. There were no significant associations between early gestational weight gain (0-28 weeks) and pregnancy outcomes.

CONCLUSIONS

These findings suggest that controlling gestational weight gain should be a priority following GDM diagnosis to optimize pregnancy outcomes and improve maternal postnatal glucose homeostasis. The period after diagnosis of GDM (often 28 weeks gestation) is not too late to offer lifestyle advice or intervention to improve weight management and pregnancy outcomes.

Young people's experiences of managing Type 1 diabetes at university: a national study of UK university students

AIM

Little is known about the challenges of transitioning from school to university for young people with Type 1 diabetes. In a national survey, we investigated the impact of entering and attending university on diabetes self-care in students with Type 1 diabetes in all UK universities.

METHODS

Some 1865 current UK university students aged 18-24 years with Type 1 diabetes, were invited to complete a structured questionnaire. The association between demographic variables and diabetes variables was assessed using logistic regression models.

RESULTS

In total, 584 (31%) students from 64 hospitals and 37 university medical practices completed the questionnaire. Some 62% had maintained routine diabetes care with their home team, whereas 32% moved to the university provider. Since starting university, 63% reported harder diabetes management and 44% reported higher HbA_1c levels than before university. At university, 52% had frequent hypoglycaemia, 9.6% reported one or more episodes of severe hypoglycaemia and 26% experienced diabetes-related hospital admissions. Female students and those who changed healthcare provider were approximately twice as likely to report poor glycaemic control, emergency hospital admissions and frequent hypoglycaemia. Females were more likely than males to report stress [odds ratio (OR) 4.78, 95% confidence interval (CI) 3.19-7.16], illness (OR 3.48, 95% CI 2.06-5.87) and weight management issues (OR 3.19, 95% CI 1.99-5.11) as barriers to self-care. Despite these difficulties, 91% of respondents never or rarely contacted university support services about their diabetes.

CONCLUSION

The study quantifies the high level of risk experienced by students with Type 1 diabetes during the transition to university, in particular, female students and those moving to a new university healthcare provider.

Managing hyperglycaemia during antenatal steroid administration, labour and birth in pregnant women with diabetes

Optimal glycaemic control before and during pregnancy improves both maternal and fetal outcomes. This article summarizes the recently published guidelines on the management of glycaemic control in pregnant women with diabetes on obstetric wards and delivery units produced by the Joint British Diabetes Societies for Inpatient Care and available in full at www.diabetes.org.uk/joint-british-diabetes-society and https://abcd.care/joint-british-diabetes-societies-jbds-inpatient-care-group. Hyperglycaemia following steroid administration can be managed by variable rate intravenous insulin infusion (VRIII) or continuous subcutaneous insulin infusion (CSII) in women who are willing and able to safely self-manage insulin dose adjustment. All women with diabetes should have capillary blood glucose (CBG) measured hourly once they are in established labour. Those who are found to be higher than 7 mmol/l on two consecutive occasions should be started on VRIII. If general anaesthesia is used, CBG should be monitored every 30 min in the theatre. Both the VRIII and CSII rate should be reduced by at least 50% once the placenta is delivered. The insulin dose needed after delivery in insulin-treated Type 2 and Type 1 diabetes is usually 25% less than the doses needed at the end of first trimester. Additional snacks may be needed after delivery especially if breastfeeding. Stop all anti-diabetes medications after delivery in gestational diabetes. Continue to monitor CBG before and 1 h after meals for up to 24 h after delivery to pick up any pre-existing diabetes or new-onset diabetes in pregnancy. Women with Type 2 diabetes on oral treatment can continue to take metformin after birth.

A hybrid reference-guided de novo assembly approach for generating Cyclospora mitochondrion genomes

Cyclospora cayetanensis is a coccidian parasite associated with large and complex foodborne outbreaks worldwide. Linking samples from cyclosporiasis patients during foodborne outbreaks with suspected contaminated food sources, using conventional epidemiological methods, has been a persistent challenge. To address this issue, development of new methods based on potential genomically-derived markers for strain-level identification has been a priority for the food safety research community. The absence of reference genomes to identify nucleotide and structural variants with a high degree of confidence has limited the application of using sequencing data for source tracking during outbreak investigations. In this work, we determined the quality of a high resolution, curated, public mitochondrial genome assembly to be used as a reference genome by applying bioinformatic analyses. Using this reference genome, three new mitochondrial genome assemblies were built starting with metagenomic reads generated by sequencing DNA extracted from oocysts present in stool samples from cyclosporiasis patients. Nucleotide variants were identified in the new and other publicly available genomes in comparison with the mitochondrial reference genome. A consolidated workflow, presented here, to generate new mitochondrion genomes using our reference-guided de novo assembly approach could be useful in facilitating the generation of other mitochondrion sequences, and in their application for subtyping C. cayetanensis strains during foodborne outbreak investigations.

Continuous glucose monitoring in pregnant women with Type 1 diabetes: benefits for mothers, using pumps or pens, and their babies

AIMS

To review the current literature on the use of continuous glucose monitoring during pregnancy in women with Type 1 diabetes.

METHODS

We searched the literature for randomized controlled trials using continuous glucose monitoring during pregnancy in women with Type 1 diabetes.

RESULTS

Three randomized trials were found and discussed in this review. One UK study found a reduction in large-for-gestational-age infants; however, only masked continuous glucose monitoring was used in that study. A Danish study used intermittent real-time continuous glucose monitoring and found no differences. The present authors conducted the CONCEPTT trial, in which pregnant women and women planning pregnancy were randomized to receive continuous glucose monitoring or standard care. We found a greater drop in HbA_1c , more time spent in the target range, and a reduction in some adverse neonatal outcomes in women using continuous glucose monitoring. Numbers-needed-to-treat to prevent a large-for-gestational-age infant, a neonatal intensive care unit admission for >24 h, and a neonatal hypoglycaemia event were low. These findings were seen in both injection and pump users and across all countries. Possible reasons for differences in study findings are discussed. In addition, several issues need further study. Glycaemic variability and differences in dietary intake may also have played a role. Despite excellent glycaemic control, babies continue to be large. More research is needed to understand the role of glucose targets and the dynamic placental processes involved in fetal growth.

CONCLUSIONS

The use of continuous glucose monitoring in women with Type 1 diabetes in pregnancy is associated with improved glycaemic control and neonatal outcomes. Further research examining the glycaemic and non-glycaemic variables involved in fetal growth and the cost-benefit of using continuous glucose monitoring in pregnancy is warranted.

Pregnancy in Diabetes: challenges and opportunities for improving pregnancy outcomes

Our aim was to review the data from the National Pregnancy in Diabetes (NPID) audit, and to identify the challenges and opportunities for improving pregnancy outcomes in women with diabetes. We reviewed three years of NPID data and relevant diabetes and obstetric literature, and found that there has been little change in pregnancy preparation or outcomes over the past 3 years, with substantial clinic-to clinic variations in care. Women with Type 2 diabetes remain less likely to take 5 mg preconception folic acid (22.8% vs. 41.8%; P < 0.05), and more likely to take potentially harmful medications (statin and/or ACE inhibitor 13.0% vs. 1.8%; P < 0.05) than women with Type 1 diabetes. However, women with Type 1 diabetes are less likely to achieve the recommended glucose control target of HbA_1c < 48 mmol/mol (6.5%) (14.9% vs. 38.1%; P < 0.05). The following opportunities for improvement were identified. First, the need to integrate reproductive health into the diabetes care plans of all women with diabetes aged 15-50 years. Second, to develop more innovative approaches to improve uptake of pre-pregnancy care in women with Type 2 diabetes in primary care settings. Third, to integrate insulin pump, continuous glucose monitoring and automated insulin delivery technologies into the pre-pregnancy and antenatal care of women with Type 1 diabetes. Fourth, to improve postnatal care with personalized approaches targeting women with previous pregnancy loss, congenital anomaly and perinatal mortality. A nationwide commitment to delivering integrated reproductive and diabetes healthcare interventions is needed to improve the health outcomes of women with diabetes.

Experiences of closed-loop insulin delivery among pregnant women with Type 1 diabetes

AIMS

To explore the experiences of pregnant women with Type 1 diabetes, and the relationships between perceptions of glucose control, attitudes to technology and glycaemic responses with regard to closed-loop insulin delivery.

METHODS

We recruited 16 pregnant women with Type 1 diabetes [mean ± sd age 34.1 ± 4.6 years, duration of diabetes 23.6 ± 7.2 years, baseline HbA_1c 51±5 mmol/mol (6.8 ± 0.6%)] to a randomized crossover trial of sensor-augmented pump therapy vs automated closed-loop therapy. Questionnaires (Diabetes Technology Questionnaire, Hypoglycaemia Fear Survey) were completed before and after each intervention, with qualitative interviews at baseline and follow-up.

RESULTS

Women described the benefits and burdens of closed-loop systems during pregnancy. Feelings of improved glucose control, excitement and empowerment were counterbalanced by concerns about device visibility, obsessive data checking and diminished attentiveness to hyper- and hypoglycaemia symptoms. Responding to questionnaires, eight participants felt less worry about overnight hypoglycaemia and that diabetes 'did not run their lives'; however, five reported that closed-loop increased time thinking about diabetes, and three felt it made sleep and preventing hyperglycaemia more problematic. Women slightly overestimated their glycaemic response to closed-loop therapy. Most became more positive in their technology attitudes throughout pregnancy. Women with more positive technology attitudes had higher degrees of overestimation, and poorer levels of glycaemic control.

CONCLUSIONS

Women displayed complex psychosocial responses to closed-loop therapy in pregnancy. Perceptions of glycaemic response may diverge from biomedical data.

The management of type 1 and type 2 diabetes in pregnancy

Pregestational diabetes is a common medical complication of pregnancy and preconception planning is an essential component of care for affected women of childbearing age. Once pregnant, structured care in a multidisciplinary team setting is necessary to ensure optimal outcomes. Although significant progress has been made, these women and their offspring remain to have a significantly elevated risk of multiple adverse complications. Structured programmes using information technology and enabling access to novel technologies may facilitate our goal of ensuring an outcome closer to that of a pregnancy unaffected by diabetes.

Plasma C-peptide concentration in women with Type 1 diabetes during early and late pregnancy

AIMS

There are previous suggestions of increased C-peptide concentration in women with Type 1 diabetes during pregnancy. Our aim was to re-evaluate the hypothesis of a pregnancy-induced increase by measuring plasma C-peptide concentration in women with stable blood glucose control under standardized fasting and meal-stimulated conditions.

METHODS

Ten women with Type 1 diabetes; median age 31.1 years, median diabetes duration 19 years, median HbA(1c) 52 mmol/mol (6.9%) were admitted to a clinical research facility for two 24-h visits in early (12-16 weeks) and late (28-32 weeks) pregnancy. Women They ate standardized study meals - 80-g carbohydrate dinner, 60-g carbohydrate breakfast, and fasted between meals and overnight. Closed-loop insulin delivery maintained stable and comparable glycaemic conditions. Paired samples for plasma glucose and C-peptide were obtained.

RESULTS

Plasma glucose levels were comparable in early (median 6.5 mmol/l; interquartile range 5.6-8.6) and late pregnancy (median 7.0 mmol/l; interquartile range 6.1-7.8; P = 0.72). There was no change in fasting or meal-stimulated plasma C-peptide concentration from early to late pregnancy; mean difference 4.0 pmol/l (95% CI -6.0 to 7.0; P = 0.9). Four women had detectable C-peptide; peak (range) early vs. late pregnancy 48.5 (10-115) vs. 40.0 pmol/l (80-105); P = 0.5, which was weakly associated with plasma glucose; R(2) = 0.15, P < 0.0001.

CONCLUSIONS

We found no gestational changes in plasma C-peptide concentration. Previously reported increases may reflect differences in glucose control and/or exogenous insulin doses. This study highlights the importance and challenges of standardizing experimental conditions for accurate plasma C-peptide measurement during Type 1 diabetes pregnancy.

Randomized trial of a diabetes self-management education and family teamwork intervention in adolescents with Type 1 diabetes

AIMS

To evaluate the effectiveness of a family-centred group education programme, in adolescents with Type 1 diabetes.

METHODS

Three hundred and five adolescents with Type 1 diabetes; age 13.1 ± 1.9 years, diabetes duration 5.6 ± 3.3 years, BMI 20.9 ± 3.7 kg/m(2) , HbA(1c) 78 ± 6 mmol/mol (9.3 ± 1.9%) were randomly allocated to the Families and Adolescents Communication and Teamwork Study (FACTS) diabetes education programme; (six 90-min monthly sessions attended by parents and adolescents incorporating skills training and family teamwork) or conventional clinical care. Primary outcome was HbA(1c) at 18 months (12 months post-intervention). Secondary outcomes were HbA(1c) at 9 months, psychosocial outcomes, adolescent quality of life, well-being, family responsibility and insulin dose adjustment behaviours at 12 months (6 months post-intervention) and episodes of severe hypoglycaemia and diabetic ketoacidois during the 12 months post-intervention. All analyses are intention to treat.

RESULTS

Session attendance was poor with 48/158 families (30.4%) not attending any sessions and only 75/158 (47.5%) families attending ≥ 4 group education sessions. All biomedical and psychosocial outcomes were comparable between groups. At 18 months there was no significant difference in HbA(1c) in either group and no between-group differences over time: intervention group 75 mmol/mol (9.0%) to 78 mmol/mol (9.3%), control group 77 mmol/mol (9.2%) to 80 mmol/mol (9.5%). Adolescents perceived no changes in parental input at 12 months.

CONCLUSION

Poor attendance of group education sessions delivered in routine clinics was a major challenge. More personalized educational approaches may be required to support and motivate families who are struggling to integrate the demands of intensive insulin regimens into their daily lives.

Pathophysiology of postprandial hyperglycaemia in women with type 1 diabetes during pregnancy

AIMS/HYPOTHESIS

Although maternal hyperglycaemia is associated with increased risk of adverse pregnancy outcome, the mechanisms of postprandial hyperglycaemia during pregnancy are poorly understood. We aimed to describe glucose turnover in pregnant women with type 1 diabetes, according to stage of gestation (early vs late gestation).

METHODS

The rates of systemic glucose appearance (R(a)) and glucose disposal (R(d)) were measured in ten pregnant women with type 1 diabetes during early (12-16 weeks) and late (28-32 weeks) gestation. Women ate standardised meals--a starch-rich 80 g carbohydrate dinner and a sugar-rich 60 g carbohydrate breakfast--and fasted between meals and overnight. Stable-label isotope tracers ([6,6-(2)H(2)]glucose and [U-(13)C]glucose) were used to determine R(a), R(d) and glucose bioavailability. Closed-loop insulin delivery maintained stable glycaemic conditions.

RESULTS

There were no changes in fasting R(a) (10 ± 2 vs 11 ± 2 μmol kg(-1) min(-1); p = 0.32) or fasting R(d) (11 ± 2 vs 11 ± 1 μmol kg(-1) min(-1); p = 0.77) in early vs late gestation. There was increased hepatic insulin resistance (381 ± 237 vs 540 ± 242 μmol kg(-1) min(-1) × pmol/l; p = 0.04) and decreased peripheral insulin sensitivity (0.09 ± 0.04 vs 0.05 ± 0.02 μmol kg(-1) min(-1) per pmol/l dinner, 0.11 ± 0.05 vs 0.07 ± 0.03 μmol kg(-1) min(-1) per pmol/l breakfast; p = 0.002) in late gestation. It also took longer for insulin levels to reach maximal concentrations (49 [37-55] vs 71 [52-108] min; p = 0.004) with significantly delayed glucose disposal (108 [87-125] vs 135 [110-158] min; p = 0.005) in late gestation.

CONCLUSIONS/INTERPRETATION

Postprandial glucose control is impaired by significantly slower glucose disposal in late gestation. Early prandial insulin dosing may help to accelerate glucose disposal and potentially ameliorate postprandial hyperglycaemia in late pregnancy.

TRIAL REGISTRATION

ISRCTN 62568875

FUNDING

Diabetes UK Project Grant BDA 07/003551. H.R. Murphy is funded by a National Institute for Health Research (NIHR) research fellowship (PDF/08/01/036). Supported also by the Juvenile Diabetes Research Foundation (JDRF), Abbott Diabetes Care (Freestyle Navigator CGM and sensors free of charge), Medical Research Council Centre for Obesity and Related Metabolic Diseases and NIHR Cambridge Biomedical Research Centre.

Obstetric and perinatal outcomes in pregnancies complicated by Type 1 and Type 2 diabetes: influences of glycaemic control, obesity and social disadvantage

AIMS

To compare obstetric and perinatal outcomes in women with Type 1 and Type 2 diabetes and relate these to maternal risk factors.

METHODS

Prospective cohort study of 682 consecutive diabetic pregnancies in East Anglia during 2006-2009. Relationships between congenital malformation, perinatal mortality and perinatal morbidity (large for gestational age, preterm delivery, neonatal care) with maternal age, parity, ethnicity, glycaemic control, obesity and social disadvantage were examined using bivariable and multivariate models.

RESULTS

There were 408 (59.8%) Type 1 and 274 (40.2%) Type 2 diabetes pregnancies. Women with Type 2 diabetes were older (P < 0.001), heavier (P < 0.0001), more frequently multiparous (P < 0.001), more ethnically diverse (p < 0.0001) and more socially disadvantaged (P = 0.0004). Although women with Type 2 diabetes had shorter duration of diabetes (P < 0.0001) and better pre-conception glycaemic control [HbA(1c) 52 mmol/mol (6.9%) Type 2 diabetes vs. 63 mmol/l (7.9%) Type 1 diabetes; p < 0.0001), rates of congenital malformation and perinatal mortality were comparable. Women with Type 2 diabetes had fewer large-for-gestational-age infants (37.6 vs. 52.9%, P < 0.0008), fewer preterm deliveries (17.5 vs. 37.1%, P < 0.0001) and their offspring had fewer neonatal care admissions (29.8 vs. 43.2%, P = 0.001). Third trimester HbA(1c) (OR 1.35, 95% CI 1.09-1.67, P = 0.006) and social disadvantage (OR 0.80, 95% CI 0.67-0.98; P = 0.03) were risk factors for large for gestational age.

CONCLUSIONS

Despite increased age, parity, obesity and social disadvantage, women with Type 2 diabetes had better glycaemic control, fewer large-for-gestational-age infants, fewer preterm deliveries and fewer neonatal care admissions. Better tools are needed to improve glycaemic control and reduce the rates of large for gestational age, particularly in Type 1 diabetes.

Development and evaluation of a standardized registry for diabetes in pregnancy using data from the Northern, North West and East Anglia regional audits

OBJECTIVES

To develop and evaluate a standardized data set for measuring pregnancy outcomes in women with Type 1 and Type 2 diabetes and to compare recent outcomes with those of the 2002-2003 Confidential Enquiry into Maternal and Child Health.

METHODS

Existing regional, national and international data sets were compared for content, consistency and validity to develop a standardized data set for diabetes in pregnancy of 46 key clinical items. The data set was tested retrospectively using data from 2007-2008 pregnancies included in three regional audits (Northern, North West and East Anglia). Obstetric and neonatal outcomes of pregnancies resulting in a stillbirth or live birth were compared with those from the same regions during 2002-2003.

RESULTS

Details of 1381 pregnancies, 812 (58.9%) in women with Type 1 diabetes and 556 (40.3%) in women with Type 2 diabetes, were available to test the proposed standardized data set. Of the 46 data items proposed, only 16 (34.8%), predominantly the delivery and neonatal items, achieved ≥ 85% completeness. Ethnic group data were available for 746 (54.0%) pregnancies and BMI for 627 (46.5%) pregnancies. Glycaemic control data were most complete-available for 1217 pregnancies (88.1%), during the first trimester. Only 239 women (19.9%) had adequate pregnancy preparation, defined as pre-conception folic acid and first trimester HbA(1c) ≤ 7% (≤ 53 mmol/mol). Serious adverse outcome rates (major malformation and perinatal mortality) were 55/1000 and had not improved since 2002-2003.

CONCLUSIONS

A standardized data set for diabetes in pregnancy may improve consistency of data collection and allow for more meaningful evaluation of pregnancy outcomes in women with pregestational diabetes.

Cord blood telomere length, telomerase activity and inflammatory markers in pregnancies in women with diabetes or gestational diabetes

AIMS

We tested the hypothesis that diabetes during pregnancy leads to chromosomal DNA damage and telomere attrition in the feto placental unit and cord blood, and provides evidence for intrauterine programming towards a senescent phenotype in the offspring.

METHODS

We obtained cord blood from pregnant women with pregestational Type 1 diabetes (n=26), Type 2 diabetes (n=20) or gestational diabetes (n=71), and control subjects without diabetes (n=45, n=76 and n=81, respectively) matched for maternal and gestational age. We measured cord blood mononuclear cell telomere length, telomerase activity (a reverse transcriptase that limits telomere attrition), and concentrations of insulin, high-sensitivity C-reactive protein (hs-CRP) and soluble intercellular adhesion molecule-1 (sICAM-1).

RESULTS

We found no significant differences between groups in cord blood telomere length in any nucleated cell type, or in hs-CRP or sICAM-1 concentrations, but telomerase activity was higher in cord blood from Type 1 (P<0.05) and gestational diabetes pregnancies (P<0.05), but not in Type 2 diabetes pregnancies. There were no significant relationships between glycaemic control, cord blood telomere length, telomerase activity or inflammatory markers in any group.

CONCLUSIONS

We found no difference in cord blood telomere length in pregnancies of women with diabetes compared with control subjects, but higher cord blood telomerase activity in Type 1 and gestational diabetes. This may reflect upregulated telomere reverse transcriptase in response to in utero oxidative DNA and telomere damage. These observations are relevant to the hypothesis that diabetes during pregnancy leads to in utero preprogramming towards senescence in the offspring.

Personal experiences of women with diabetes who do not attend pre-pregnancy care

AIMS

To explore the views of women who did not attend pre-pregnancy care (PPC), in particular their accounts of contraception, previous pregnancies and the influence of healthcare advice.

METHODS

We conducted semi-structured interviews with 29 pregnant women (21 with Type 1 diabetes, eight with Type 2 diabetes) at three UK specialist diabetes antenatal clinics. Interviews explored women's journeys to becoming pregnant, including use of contraception, their views regarding diabetes and pregnancy and the factors which encouraged and discouraged them from attending PPC.

RESULTS

All women had some understanding of the issues concerning diabetes during pregnancy, predominantly regarding the benefits of PPC (90%) and optimal glycaemic control (80%) and risks of malformation (48%) and macrosomia (35%). Most were not regularly using contraception (70%), having stopped deliberately (45%), become unintentionally less rigorous (28%) or experienced side effects/contraindications (14%). Knowledge concerning the risks of pregnancy (90%) and past pre-conception counselling (38%) did not encourage women to attend PPC, and neither did personal experience of miscarriage, malformation or stillbirth in women with previous poor pregnancy outcome (41%). Barriers included conceiving faster than anticipated (45%), fertility concerns (31%), negative experiences with health professionals (21%), desire for a 'normal' pregnancy (17%) and the logistics of attending (10%).

CONCLUSIONS

More integrated diabetes and reproductive health/contraceptive advice, increased awareness of the potentially short time between stopping contraception and conception and more intensive support between pregnancies are required, particularly for women with previously poor outcomes. Research is also needed into how communication between health professionals and women with diabetes can be improved.

Approaches to integrating paediatric diabetes care and structured education: experiences from the Families, Adolescents, and Children's Teamwork Study (FACTS)

AIMS

The Families, Adolescents and Children's Teamwork Study (FACTS) is a family-centred structured education programme for children and adolescents with Type 1 diabetes. It aims to integrate group-based diabetes education into routine care, enhance parental responsibility for self management and improve glycaemic control.

METHODS

A randomized wait-list control group study allocated participants to either the immediate (four educational sessions during year 1) or delayed intervention (four educational sessions during year 2). In both groups, glycated haemoglobin (HbA1c) was measured 3-monthly and participants completed the Paediatric Quality of Life Inventory (PedsQL), Problem Areas in Diabetes Scale (PAID) and Diabetes Family Responsibility Questionnaire (DFRQ) before and after the intervention.

RESULTS

Intention-to-treat analysis showed no significant difference in HbA1c or parental responsibility between participants randomized to the immediate or delayed programme. However, during 12 months' follow-up, families who attended > or = 2 sessions reported increased parental involvement (P = 0.01), and in children/adolescents who attended > or = 2 sessions HbA1c fell by 0.29% compared with an increase of 0.11% in non-attenders (P = 0.04).

CONCLUSION

This family-centred education programme has been integrated into paediatric diabetes care with potential benefits on parental involvement and glycaemic control, but further study is warranted before routine application into clinical care.

Glycaemic control throughout pregnancy and risk of pre-eclampsia in women with type I diabetes

The aim of this study was to examine the influence of pre-pregnancy care and its effect on early glycaemic control and also the effect of glycaemic control in later pregnancy on risk of pre-eclampsia in women with type I diabetes. A prospective cohort study of 290 consecutive nonselected pregnancies in women with type I diabetes was performed from 1991 to 2002. We examined the relationship of monthly glycosylated haemoglobin (HbA1c) level, pre-pregnancy care, parity, diabetes duration, microvascular complications, maternal age, weight and smoking with risk of pre-eclampsia. Pre-eclampsia developed in 31/243 singleton births (12.8%). HbA1c level at 24 weeks was significantly increased in women with pre-eclampsia compared with women without pre-eclampsia (6.0 versus 5.6%, P= 0.017) and was, after nulliparity, the strongest independent predictor of increased risk (OR 1.65 for each 1% increase in HbA1c; P= 0.01). In contrast, there was no relationship between pre-pregnancy care or HbA1c level at booking and risk of pre-eclampsia.

Psycho-educational interventions for children and young people with Type 1 diabetes

BACKGROUND

A systematic review of the literature in 2000 revealed numerous methodological shortcomings in education research, but in recent years progress has been made in the quantity and quality of psycho-educational intervention studies.

SUMMARY OF CONTENTS

This review focuses on diabetes education programmes developed for children, young people and their families in the past 5 years. A comprehensive review of the literature identified 27 articles describing the evaluation of 24 psycho-educational interventions. Data summary tables compare the key features of these, and comparisons are made between individual, group and family-based interventions. Effect sizes are calculated for nine of the randomized studies. Three research questions are posed: firstly has the recent literature addressed the problems highlighted in the previous review; secondly is there sufficient evidence to recommend adaptation of a particular programme; and, finally, what do we still need to do?

CONCLUSIONS

Progress in the quality and quantity of educational research has not resulted in improved effectiveness of interventions. There is still insufficient evidence to recommend adaptation of a particular educational programme and no programme that has been proven effective in randomized studies for those with poor glycaemic control. To develop a range of effective educational interventions, further research involving larger sample sizes with multicentre collaboration is required.

The pregnancies of women with Type 2 diabetes: poor outcomes but opportunities for improvement

AIM

To compare the outcomes of Type 1 and Type 2 diabetic pregnancies and identify risk factors for poor outcome of Type 2 pregnancies

METHODS

The data from all (389 Type 1 and 146 Type 2) pre-gestational diabetic pregnancies from 10 UK hospitals were collected prospectively.

RESULTS

The Type 2 mothers were less likely to have documented pre-pregnancy counselling (28.7 vs. 40.5%; P<0.05) or be taking folic acid at conception (21.9 vs. 36.4%; P<0.001) than Type 1 mothers. The percentage of pregnancies having a serious adverse outcome was higher in Type 2 patients (16.4 vs. 6.4%; P=0.002). Congenital abnormalities (12.3% in Type 2 vs. 4.4% in Type 1; P=0.002) accounted for most of this difference. The HbA1c of the Type 2 patients was similar to that of the Type 1 with mean first trimester HbA1c of 7.22 and 7.35%, respectively (P=0.5). Treatment with oral hypoglycaemic agents [odds ratio (OR), 1.8; 95% confidence interval (CI), 1.0-3.3; P=0.04], body mass index (OR, 1.09; 95% CI, 1.01-1.18; P=0.02) and folic acid supplementation (OR, 0.3; 95% CI, 0.09-1.0; P=0.04) were all independently associated with congenital malformation.

CONCLUSION

Type 2 diabetic pregnancies are characterized by poor pre-pregnancy planning, inadequate folic acid supplementation and treatment with oral hypoglycaemic agents, all of which may contribute to the serious adverse outcomes affecting one in six Type 2 diabetic pregnancies. These remediable aspects of the pre-pregnancy care of women with Type 2 diabetes provide opportunities for improving the outcome towards that of women with Type 1 diabetes.

An unusual case of Turcot’s syndrome associated with ileal adenocarcinoma, intestinal non-Hodgkin’s lymphoma, and duodenal adenocarcinoma. Review of the classification and genetic basis of Turcot’s syndrome

A 38-year-old man with a history of colonic and small bowel polyposis and glioblastoma was investigated for dyspepsia. Upper GI endoscopy identified an abnormal area in the duodenum, confirmed by histology as high grade non-Hodgkin's B cell MALT lymphoma. Although cases of Turcot's syndrome (TS) (colonic polyposis and primary brain tumour occurring in the same patient) have been previously described, association with haematological malignancy is rare. This is the first report of intestinal lymphoma occurring in an adult with TS.

Detection of specific mRNAs in single nephron segments by use of the polymerase chain reaction

We have developed a procedure to detect specific mRNAs in single renal nephron segments. This approach combines microdissection, reverse transcription (RT) of the target mRNA, and amplification of the resulting cDNA using the polymerase chain reaction (PCR). After microdissection, the sample is placed in a tube where it is permeabilized and where all reactions are performed directly without the need for isolation of the RNA. Our model target was the mRNA for aldose reductase. This enzyme catalyzes the conversion of glucose to sorbitol. Its expression is modulated by changes in extracellular osmolality in the renal medulla. RT-PCR of inner medullary collecting duct (1 mm) and glomeruli (6-10) yielded a product of the predicted length (670 base pairs) defined by the PCR primers. Its identity was confirmed by a specific oligonucleotide probe that differed from the primers. RT-PCR of proximal tubules (1 mm) resulted in no aldose reductase-specific amplification product. RT-PCR is generally applicable for measuring specific gene expression in single nephron segments or small numbers of cultured cells. Utility, limitations, and refinements of this approach are discussed.

Molecular cloning of cDNA coding for kidney aldose reductase. Regulation of specific mRNA accumulation by NaCl-mediated osmotic stress

Cells generally respond to long-term hyperosmotic stress by accumulating nonperturbing organic osmolytes. Unlike bacteria, in which molecular mechanisms involved in the increased accumulation of osmolytes have been identified, those in multicellular organisms are virtually unknown. In mammals, during antidiuresis, cells of the renal inner medulla are exposed to high and variable extracellular NaCl. Under these conditions, the cells contain a high level of sorbitol and other osmolytes which help balance the high extracellular osmolality. PAP-HT25 is a continuous line of cells derived from rabbit renal inner medulla. When medium osmolality is increased by raising the NaCl concentration, these cells accumulate sorbitol. The sorbitol is synthesized from glucose in a reaction catalyzed by aldose reductase. When the medium is made hyperosmotic, aldose reductase activity increases because of a larger increase in the amount of enzyme. This increase is produced by the accelerated rate of synthesis of aldose reductase protein. The purpose of the present studies was to examine the mechanism of this increase in aldose reductase protein by measuring the relative abundance of aldose reductase mRNA. A cDNA clone coding for rabbit kidney aldose reductase was isolated. Antisense RNA probes transcribed from this clone hybridized specifically with a 1.5-1.6 kilobase mRNA in Northern blots. Cells grown chronically in hyperosmotic medium had a relative abundance of this specific mRNA which was six times that of cells grown in isoosmotic medium. When cells grown in isoosmotic medium were switched to hyperosmotic medium, the level of aldose reductase mRNA peaked (18-fold) at 18-24 h. The induction of aldose reductase mRNA by osmotic stress was reversible. Our finding of increased abundance of a specific mRNA in direct response to hyperosmotic stress represents the first report of such an effect in animals.

Osmoregulation by slow changes in aldose reductase and rapid changes in sorbitol flux

Renal medullary extracellular NaCl concentration is high during antidiuresis. To compensate, the cells accumulate large amounts of nonperturbing, osmotically active solutes (organic "osmolytes"), including sorbitol. GRB-PAP1 is a continuous line of epithelial cells from rabbit inner medulla. These cells accumulate sorbitol when medium NaCl concentration is elevated. The accumulation involves increase in aldose reductase, which catalyzes production of sorbitol from glucose. The purpose of the present study was to investigate control of cell sorbitol once aldose reductase was induced. We measured cell sorbitol, cell-to-medium sorbitol flux, and aldose reductase in cells grown in medium made hyperosmotic (600 mosmol/kg) with added NaCl and at intervals after medium osmolality was reduced to 300 mosmol/kg. In the hyperosmotic medium, cell sorbitol averaged 990 mmol/kg protein (approximately 260 mM), and its flux into the medium was 740 mmol.kg cell protein-1.day-1 (permeability less than 2 X 10(-9) cm/s). Within 5 min after return to isosmotic medium, sorbitol efflux increased greater than 150-fold. By the end of 1 day, cell sorbitol fell 77% but aldose reductase decreased only 10%. Aldose reductase then fell slowly to low levels over 2 wk. Thus renal medullary cells, chronically adapted to high NaCl, reduced their sorbitol level on return to isosmotic conditions by at least two mechanisms: 1) rapid increase in sorbitol flux into the medium, and 2) slow changes in the amount of aldose reductase.

Improved synthesis and iodination of a cleavable photoactivated probe

J. B. Denny and G. Blobel (1984, Proc, Natl. Acad. Sci. USA 81, 5286-5290) have described the synthesis of a water-soluble novel heterobifunctional 125I-labeled photocrosslinking reagent, N-[4-(p-azido-m-[125I]iodophenylazo)benzoyl]-3-aminopropionyl-N'- oxysulfosuccinimide, which contains a cleavable internal azo bond. We report several modifications of their synthesis which greatly increase the yield of a synthetic intermediate, N-[4-(p-aminophenylazo)benzoyl]-3-aminopropionic acid (compound VII). Evidence is presented that direct iodination of compound VII with chloramine-T produces low yields of 125I-labeled compound VII in a reaction which is difficult to control. Alternatively, the yield of 125I-labeled reagent can be greatly improved if the iodination is performed following the derivatization of N-[4-(p-axidophenylazo)benzoyl]-3-aminopropionyl-N'-oxysulfosuc cinimide (compound IX) to a ligand such as dextran. We have demonstrated the transfer of 125I label from the reagent when derivatized to amino-dextran to proteins in solution after photolysis and cleavage of this 125I-labeled reagent.

Isolation and characterization of specialized regions of toad urinary bladder apical plasma membrane involved in the water permeability response to antidiuretic hormone

Antidiuretic hormone (ADH) increases the apical (external facing) membrane water permeability of granular cells that line the toad urinary bladder. In response to ADH, cytoplasmic vesicles called aggrephores fuse with the apical plasma membrane and insert particle aggregates which are visualized by freeze-fracture electron microscopy. Aggrephores contain particle aggregates within their limiting membranes. It is generally accepted that particle aggregates are or are related to water channels. High rates of transepithelial water flow during ADH stimulation and subsequent hormone removal decrease water permeability and cause the endocytosis of apical membrane and aggrephores which retrieve particle aggregates. We loaded the particle aggregate-rich endocytic vesicles with horseradish peroxidase (HRP) during ADH stimulation and removal. Epithelial cells were isolated and homogenized, and a subcellular fraction was enriched for sequestered HRP obtained. The HRP-enriched membrane fraction was subjected to a density shifting maneuver (Courtoy et al., J. Cell Biol. 98:870, 1984), which yielded a purified membrane fraction containing vesicles with entrapped HRP. The density shifted vesicles were composed of approximately 20 proteins including prominent species of 55, 17 and 7 kD. Proteins of these molecular weights appear on the apical surface of ADH-stimulated bladders, but not the apical surface of control bladders. Therefore, we believe these density shifted vesicles contain proteins involved in the ADH-stimulated water permeability response, possibly components of particle aggregates and/or water channels.