Rapid changes in chromatographically determined haemoglobin A1c induced by short-term changes in glucose concentration

Comparability of different methods of glycated hemoglobin measurement for samples of patients with variant and non-variant hemoglobin

BACKGROUND

Glycated hemoglobin (e.g., HbA_1c) is measured to monitor patients with diabetes. However, the measurement results can vary according to the analysis method and presence of variant hemoglobin. Thus, we compared HbA_1c results between liquid chromatography-tandem mass spectrometry (LC-MS/MS) as the reference method and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS).

METHODS

%HbA_1c were measured using the 2 methods in 45 non-variant and 73 heterozygous variant samples. Precision was calculated; the results were compared using Passing-Bablok regression and the concordance correlation coefficient (CCC). The average bias between methods was compared with the lowest bias of 2.3% for biological variation.

RESULTS

The precision of the 2methods was <2%. The R² for the non-variant samples were 0.986 and the CCC was 0.99. Based on α- and β-chain, the variant samples were divided into 4 groups: α-chain, α-chain negligible, β-chain, and β-chain negligible variants. The R² between the 2 methods of the 4 groups were ＞0.95; However, the average biases of α-chain and β-chain variants were above the minimum bias.

CONCLUSION

LC-MS/MS and MALDI-TOF MS had good comparability in the measurement of HbA_1c in non-variant samples, but the existence of variant hemoglobin caused discrepancies.

A labile form of hemoglobin A1c is higher in African-American youth with type 1 diabetes compared to Caucasian patients at similar glucose levels

BACKGROUND

Hemoglobin A1c (HbA1c) levels are higher in African-American (AA) individuals compared to Caucasians (EA) even after adjustment for blood glucose levels. To better understand the mechanism of this disparity we examined the relationship of an unstable (labile) form of HbA1c (L-HbA1c) with race and glucose.

METHODS

Samples for HbA1c were collected from pediatric patients self-identified as either AA (15F, 12M, age 13.4 ± 3.5 years) or EA (22F, 30M, age 14.6 ± 3.4 years) with type 1 diabetes at the time of a clinic visit. Clinic HbA1c (HbA1c) was performed by immunoassay. L-HbA1c equaled the difference in the HbA1c fraction by dynamic capillary isoelectric focusing before and after incubation in a low pH buffer. A capillary glucose (Clinic-BG) was measured at clinic visit. Mean blood glucose (MBG) was calculated from the last 30 days of the patient's glucose meter data. The influence of race on L-HbA1c was assessed in a multiple variable regression model adjusted for Clinic-BG.

RESULTS

The groups were similar for age and duration of diabetes. L-HbA1c was correlated with Clinic-BG, MBG, and HbA1c. The mean levels of L-HbA1c, HbA1c, MBG, but not Clinic-BG were higher in AA patients compared to EA. After adjustment for Clinic-BG, L-HbA1c was still higher in AA (2.8 ± 0.7% AA vs 2.1 ± 0.7% EA, P < .0001).

CONCLUSIONS

L-HbA1c is correlated with Clinic-BG. At any given level of Clinic-BG, AA patients have higher levels of L-HbA1c than EA. This preliminary study suggests that early factors prior to the formation of stable HbA1c may contribute to the observed glucose-independent racial disparity.

Skeletal muscle adaptations to physical training in type II (non-insulin-dependent) diabetes mellitus

Seven middle-aged men with manifest type II diabetes mellitus underwent an endurance training programme for 10-15 weeks. The maximal aerobic capacity, as well as the endurance capacity, was improved by 10% (p less than 0.05). The intramuscular glycogen store increased by more than 80% (p less than 0.05) from 350 mumol/g dw (dry weight), and the activities of citrate synthase and 3-hydroxy-acyl-CoA dehydrogenase increased by more than 50% (p less than 0.05) and 30% (p less than 0.05). The activity of glycogen synthase was decreased by approximately 20% (p less than 0.05), whereas lactate dehydrogenase remained unchanged. Capillaries/fibre and fibre area increased by more than 50% (p less than 0.05) and 30% (p less than 0.05) leaving the area of supply constant. Training did not influence fasting blood lipids and glucose, glycosylated hemoglobin, oral glucose tolerance, and insulin response to an oral glucose load measured 72 hours post-exercise. It is concluded that patients with manifest type II diabetes, as normoglycaemic individuals, adapt to physical training. However, no persistent effect on glucohomeostasis and lipaemia is produced by short-term training in the diabetic patients.

Clinical outcome of using insulin at 40 IU/ml and 100 IU/ml in pump treatment. Results of a controlled multi-center trial

In three different diabetes centers the use of insulin at a strength of 40 IU/ml (U40) and 100 IU/ml (U100) in continuous subcutaneous insulin infusion (CSII) treatment of insulin dependent (Type I) diabetic patients was compared in a randomized cross-over design. Forty-six Type I diabetic patients, all previously treated with CSII for at least one year, completed consecutively two 13-week periods of treatment with U40 and U100. Body weight and insulin requirements were identical at the end of the two periods. Slightly higher levels of glycemia were recorded during U40 when compared to U100 treatment: mean blood glucose was 142 +/- 34 (SD) vs. 133 +/- 34 mg/dl (2 p less than 0.01). The same tendency was observed in the mean glycosylated hemoglobin value (6.84 +/- 1.35 vs. 6.65 +/- 1.13%, 2 p greater than 0.1). There were no significant differences between U40 and U100 in the number of catheters used and the number of catheter blockages reported, while the development of subcutaneous nodules at the insertion sites was significantly more frequent during U40 treatment. It is concluded that the implementation of insulin in the strength of 100 IU/ml is as effective as the use of insulin in the strength of 40 IU/ml for CSII therapy, and might even be associated with slightly improved glycemic control and less subcutaneous side-effects.

Incidence of nocturnal hypoglycaemia in insulin-dependent diabetic patients on intensive therapy

The frequency of nocturnal hypoglycaemia, i.e. blood glucose concentration (BG) less than 3.0 mmol/l, was evaluated in consecutively selected insulin-dependent patients on multiple insulin injections (MII), n = 23, or continuous subcutaneous insulin infusions (CSII), n = 25. Blood was sampled hourly from 23.00 to 07.00. Seven patients (30%) on MII had at least one BG less than 3.0 mmol/l during the night. Eleven patients (44%) on CSII had hypoglycaemia (NS). The total number of BGs less than 3.0 mmol/l was higher on CSII, 42 of 225, versus 16 of 207 on MII (p less than 0.025). The duration of hypoglycaemia was 2 hours (range 1-6) on MII and 4 hours (range 1-7) on CSII with a maximal prevalence at 4 hours and between 5 and 7 hours, respectively (p = less than 0.05). The frequency of nocturnal hypoglycaemia is high in patients on intensified insulin regimens. Nocturnal hypoglycaemia occurs later in the night and is of longer duration on CSII than on MII. HbA1c, BG before bedtime and in the morning might be useful in the evaluation of nocturnal hypoglycaemia.

HbA1c and the diagnosis of diabetes mellitus

To evaluate the usefulness of haemoglobin A1c (HBA1C) determinations in the diagnosis of diabetes mellitus, the outcome of a standard oral glucose tolerance test (OGTT) and HbA1c values were compared in 178 consecutive subjects referred for a diagnostic OGTT. The subjects were mainly in age groups in which non-symptomatic diabetes mellitus predominates. The prevalences of elevated fasting plasma glucose and abnormal OGTT were found to increase with increasing age. One third of the total series had impaired or diabetic OGTT. In the group with normal OGTT, 16% had fasting plasma glucose concentrations above the upper normal limit, but the range of HbA1c values did not differ from that of healthy controls. In the group with impaired OGTTs (n = 20), elevated HbA1c values were found only in subjects with elevated fasting plasma glucose and the highest two-hour OGTT values (n = 4). In the group with diabetic OGTT, 86-94% had HbA1c values above the upper normal limit, and HbA1c was elevated in all subjects with a fasting plasma glucose higher than 10.5 mmol/l or a 2-hour OGTT glucose value above 14.4 mmol/l. Using the results of the OGTT as the true diagnosis, HbA1c had a diagnostic specificity of 0.78 and sensitivity of 0.96. Only subjects with a substantially reduced glucose tolerance may be diagnosed by HbA1c determinations.

Elevated third-trimester haemoglobin A 1c predicts preterm delivery in type 1 diabetes

The prevalence of preterm delivery is considerably elevated in women with type 1 diabetes. The aim of the study was to evaluate haemoglobin A(1c) (HbA(1c)) as a predictor of preterm delivery. Two hundred thirteen consecutive pregnant women with type 1 diabetes and normal urinary albumin excretion were included prospectively. HbA(1c) was analyzed at 10, 20 and 28 weeks of gestation. Seventy-one women (33%) delivered pre term and 142 at term. At 10 weeks of gestation, HbA(1c) was 7.3% (S.D. 1.0) vs. 6.9% (S.D. 0.9) (P<.01), at 20 weeks of gestation 6.6% (S.D. 0.7) vs. 6.1% (S.D. 0.7) (P<.001) and at 28 weeks of gestation 6.7% (S.D. 0.8) vs. 6.1% (S.D. 0.7) (P<.001). When comparing HbA(1c) at 10, 20 and 28 weeks of gestation, HbA(1c) at 28 weeks of gestation (P<.001) was the best predictor of preterm delivery. The adjusted odds ratio per 1% increment in HbA(1c) at 28 weeks of gestation was 2.8 (95% CI 1.7-4.4). HbA(1c) at 28 weeks of gestation was a clinical significant predictor of preterm delivery in type 1 diabetes.

Progression of nephropathy in type 2 diabetic patients

BACKGROUND

Nephropathy in type 2 diabetes is the single most common cause of end-stage renal disease (ESRD), but the decline in kidney function varies considerably between individuals, and determinants of renal function loss, early in the course of renal disease, have not been clearly identified.

METHODS

In a prospective observational study, we followed 227 (60 female) Caucasian type 2 diabetic patients with nephropathy for 6.5 (range 3 to 17) years from a baseline glomerular filtration rate (GFR) of 83 (SD30) mL/min/1.73m(2) with 7 (range 3 to 22) measurements of GFR ((51)Cr-EDTA) per patient. We evaluated determinants of (1) rate of decline in GFR, (2) risk of doubling in serum creatinine or ESRD, and (3) mortality using potential risk factors at baseline and during follow-up.

RESULTS

The mean (SD) rate of decline in GFR was 5.2 (4.1) mL/min/year. In multivariate regression analysis, higher baseline albuminuria, systolic blood pressure (SBP), hemoglobin A1c, GFR, age, and degree of diabetic retinopathy were significantly associated with increased rate of decline in GFR (R(2) (adj) 0.24). During follow-up, elevated mean albuminuria, SBP, hemoglobin A1c, and lower hemoglobin, heavy smoking, and presence of diabetic retinopathy were significantly associated with increased decline in GFR (R(2) (adj) 0.26). During follow-up, 63 patients had a doubling in serum creatinine or developed ESRD, and 79 patients died, primarily due to cardiovascular disease. In Cox regression analysis, higher baseline albuminuria, hemoglobin A1c, and SBP, together with lower GFR and hemoglobin, were significantly associated with shorter time to doubling of serum creatinine or ESRD. Higher baseline albuminuria, hemoglobin A1c, SBP, and age were significantly associated with increased mortality.

CONCLUSION

Our long-term prospective study of type 2 diabetic patients with nephropathy has revealed several modifiable risk factors of enhanced progression in kidney disease and increased mortality.

Release of endothelium-associated proteins into blood by injection of heparin in normal subjects and in patients with Type 1 diabetes

AIMS

Disturbances in heparan sulphate proteoglycans in patients with diabetic nephropathy might contribute to the pathogenesis of vascular disease in these patients. To investigate this possible link, we measured the heparin-induced, immediate release of eight proteins with heparan sulphate binding properties in patients with nephropathy.

METHODS

We studied three groups, Type 1 diabetic patients with (n = 10) or without (n = 15) albuminuria and matched controls (n = 12). Blood samples were obtained before and 5 min after the injection of 40 anti-Xa IU low molecular weight heparin/kg body weight.

RESULTS

Lipoprotein lipase increased more in diabetic patients without albuminuria than in controls and patients with albuminuria [261 (170-293) vs. 177 (103-438), P < 0.05 and 203 (159-280) mU/ml, P < 0.05]. Total tissue factor pathway inhibitor increased more in the diabetic patients [284 (198-449) and 275 (243-399)] than in the controls [221 (169-289) ng/ml, P < 0.005]. Vitronectin increased significantly only in the diabetic patients with albuminuria. The remaining proteins did not increase significantly (antithrombin, von Willebrand factor, fibronectin) or increased equally in the three investigated groups (extracellular superoxid dismutase and platelet factor 4).

CONCLUSIONS

The different release of lipoprotein lipase and vitronectin in diabetic subjects with and without albuminuria may reflect novel aspects of vascular derangement in patients with albuminuria.

Audit on stillbirths in women with pregestational type 1 diabetes

OBJECTIVE

To audit stillbirth cases in women with type 1 diabetes to search for specific characteristics in order to improve antenatal care and treatment.

RESEARCH DESIGN AND METHODS

Retrospectively identified cases of stillbirths in women with type 1 diabetes during 1990-2000 were analyzed regarding characteristics of the mother, the pregnancy, glycemic control, and the stillborn. The cause of stillbirth was categorized as explainable, likely, or without obvious cause.

RESULTS

We found 22 women with 25 stillbirths among 1,361 singleton births by women with type 1 diabetes. In seven stillbirths the cause was categorized as explainable and in six as likely. In 12 cases no obvious cause was found; however, glycemic control was suboptimal in 9 of these cases. A total of 14 women reported daily smoking, and 10 of 19 with low education were unemployed.

CONCLUSIONS

Women experiencing stillbirth were characterized by a high incidence of suboptimal glycemic control, diabetic nephropathy, smoking, and low social status.

Decreasing incidence of severe diabetic microangiopathy in type 1 diabetes

OBJECTIVE

Conflicting evidence of a decline in incidence of microvascular complications in type 1 diabetes during the last decades has been reported. To assess recent trends in the cumulative incidence of diabetic microangiopathy in type 1 diabetes, we analyzed data from long-term prospective observational studies lasting >/=20 years.

RESEARCH DESIGN AND METHODS

A total of 600 Caucasian patients with onset of type 1 diabetes between 1965 and 1984 were followed until death or until the year 2000. Patients were divided into four groups based on the year of diabetes onset: group A, 1965-1969 (n = 113); group B, 1970-1974 (n = 130); group C, 1975-1979 (n = 113); and group D, 1979-1984 (n = 244). Group A, B, and C are prevalence cohorts identified in 1984; group D is an inception cohort.

RESULTS

In patients followed for >/=20 years, the cumulative incidence (95% CI) of diabetic nephropathy after 20 years of diabetes (urinary albumin excretion >300 mg/24 h) was reduced in patients with more recent diabetes onset (groups A-D): 31.1% (22.5-39.7) vs. 28.4% (19.8-37.0) vs. 18.9% (10.9-26.9) vs. 13.7% (6.2-21.2) (P = 0.015). Similarly, the cumulative incidence of proliferative retinopathy was as follows: 31.2% (22.2-39.8) vs. 30.3% (22.2-38.4) vs. 19.3% (11.2-27.4) vs. 12.5% (5.2-19.8) (P < 0.01). In the latter groups, antihypertensive treatment was started earlier, blood pressure and HbA(1c) were lower, and fewer patients smoked.

CONCLUSIONS

Our study demonstrates a decrease in the cumulative incidence of diabetic microangiopathy in type 1 diabetes over the past 35 years. Improved glycemic control, lower blood pressure (in part due to early aggressive antihypertensive treatment), and reduced prevalence of smoking rates were associated with the improved prognosis.

Haemoglobin A1c: Analysis and Standardisation

The measurement of glycated haemoglobin has become centrally important in the monitoring of glycaemic control in the patient with diabetes. A number of analytical techniques have been described to measure this important haemoglobin fraction, and the fraction measured depends on the technique used; this has resulted in laboratories reporting different fractions i.e., HbA1, HbA1c and total glycated haemoglobin. This paper outlines methods currently used in clinical laboratories for the measurement of this glycated fraction. It describes the principles behind these methods and goes on to describe the new IFCC reference method, which will be used in the future to standardise methods used in the clinical laboratory. Analytical goals and factors that interfere with methods are also discussed.

Insulin dose during glucocorticoid treatment for fetal lung maturation in diabetic pregnancy: test of an algorithm [correction of analgoritm]

OBJECTIVE

Poor glycemic control is often a serious clinical problem during glucocorticoid treatment for fetal lung maturation in pregnant women with diabetes. An algorithm for improved subcutaneous insulin treatment during glucocorticoid treatment in insulin-dependent diabetic women was developed and tested.

STUDY DESIGN

The sample, divided into two cohorts, consisted of all insulin-dependent diabetic women (n=16) receiving glucocorticoid treatment (betamethasone 12 mg i.m., repeated after 24 h) from 1996 to 1999. In the first cohort the increments of insulin dose were based on the level of blood glucose obtained. Based on the first cohort an algorithm to determine increments of insulin dose was developed. In the second cohort (n = 8) the insulin dose was increased by up to 40%, according to the algorithm, starting immediately after glucocorticoid treatment; prior to a detectable increase in blood glucose.

RESULTS

After betamethasone, the daily insulin dose for the following 5 days was increased by 6, 38, 36, 27 and 17% in the first cohort vs. 27, 45, 40, 31 and 11% in the second cohort. The algorithm was used in the second cohort. The median blood glucose was 6.7, 14.3, 12.3, 7.7 and 7.7 vs. 7.7, 8.2, 9.6, 7.0 and 7.4 mmol/l (p<0.05 for day 2 and 3) in the two cohorts, respectively. None developed ketoacidosis or severe hypoglycemia.

CONCLUSION

An algorithm with an increasing insulin dose of up to 40% shortly after glucocorticoid treatment for fetal lung maturation in diabetic women prevents severe dysregulation of metabolic control.

Pregnancy outcome in type 1 diabetic women with microalbuminuria

OBJECTIVE

To determine the influence of microalbuminuria on pregnancy outcome in women with type 1 diabetes.

RESEARCH DESIGN AND METHODS

This prospective cohort study took place at the Obstetric Clinic at National University Hospital, Copenhagen, from January 1996 to February 2000. All Caucasian women with type 1 diabetes, unselected from the eastern part of Denmark, with a living fetus before 17 weeks of gestation on admission were asked to participate. For women with more than one delivery in the study period, only the first pregnancy was included. Of the remaining 246 women, 240 (98%) entered the study. They were categorized according to their urinary albumin excretion (normal urinary albumin excretion, <30 mg/24 h; microalbuminuria, 30-300 mg/24 h; or diabetic nephropathy, >300 mg/24 h) before pregnancy or in the first trimester.

RESULTS

A total of 203 women (85%) had normal urinary albumin excretion, 26 (11%) had microalbuminuria, and 11 (5%) had diabetic nephropathy. Mean HbA(1c) at 2-6 weeks was 7.5% (SD 1.1), 8.1 (0.9), and 8.8 (1.3) (P < 0.001), respectively. Of all deliveries in women with normal urinary albumin excretion, microalbuminuria, and diabetic nephropathy, 35, 62, and 91% (P < 0.001), respectively, were preterm, and 2, 4, and 45% (P < 0.001), respectively, were small-for-gestational-age infants. Preeclampsia developed in 6, 42, and 64% of the women (P < 0.001), respectively. Category of urinary albumin excretion (P < 0.01) and HbA(1c) at 2-6 weeks (P < 0.05) were independently associated with preterm delivery.

CONCLUSIONS

The prevalence of preterm delivery is considerably increased in women with microalbuminuria, mainly caused by preeclampsia. Classification according to urinary albumin excretion and metabolic control around the time of conception are superior to the White classification in predicting preterm delivery in women with type 1 diabetes.

Progression of diabetic nephropathy

BACKGROUND

Diabetic nephropathy is a major cause of renal failure. The decline in glomerular filtration rate (GFR) is highly variable, ranging from 2 to 20, with a median of 12 mL/min/year. The risk factors of losing filtration power (progression promoters) have not been clearly identified. Furthermore, information on optimal arterial blood pressure, glycemic control, and cholesterol levels are lacking.

METHODS

We measured GFR with (51)Cr-EDTA plasma clearance technique, blood pressure, albuminuria, glycosylated hemoglobin A1c, and serum cholesterol every year for seven years (range 3 to 14 years) in 301 consecutive type 1 diabetic patients with diabetic nephropathy recruited consecutively during 1983 through 1997. Diabetic nephropathy was diagnosed clinically if the following criteria were fulfilled: persistent albuminuria> 200 microg/min, presence of diabetic retinopathy, and no evidence of other kidney or renal tract disease. In total, 271 patients received antihypertensive treatment at the end of the observation period.

RESULTS

Mean arterial blood pressure was 102 +/- 0.4 (SE) mm Hg. The average decline in GFR was 4.0 +/- 0.2 mL/min/year and even lower (1.9 +/- 0.5 mL/min/year) in the 30 persistently normotensive patients, none of whom had ever received antihypertensive treatment (P < 0.01). A multiple linear regression analysis revealed a significant positive correlation between the decline in GFR and mean arterial blood pressure, albuminuria, glycosylated hemoglobin A(1c), and serum cholesterol during follow-up (R(adj)(2) = 0.29, P < or = 0.001). No threshold level for blood pressure, glycosylated hemoglobin A(1c), or serum cholesterol was demonstrated. A two-hit model with mean arterial blood pressure and glycosylated hemoglobin A(1c) below and above the median values (102 mm Hg and 9.2%, respectively) revealed a rate of decline in GFR of only 1.5 mL/min/year in the lowest stratum compared with 6.1 mL/min/year in the highest stratum (P < 0.001).

CONCLUSIONS

The prognosis of diabetic nephropathy has improved during the past decades, predominantly because of effective antihypertensive treatment. Genuine normotensive patients have a slow progression of nephropathy. Several modifiable variables have been identified as progression promoters.

Medial arterial calcification is frequently found in patients with microalbuminuria

The presence of medial arterial calcification (MAC), often referred to as Moncheberg's sclerosis, was sought in patients with long-standing diabetes mellitus. One hundred patients aged 22-50 years were initially divided into two groups, those with neuropathy and those without. As expected, the incidence of MAC was significantly higher in the neuropathy group (40% vs. 20%). When the patients were divided into two groups, those with MAC and those without, it appeared that the incidence of MAC was very high in patients who had microalbuminuria (57% vs. 13%) and particularly when microalbuminuria was combined with neuropathy (40% vs. 7%). It is concluded that microalbuminuria is a strong predicting factor of medial arterial sclerosis independent of neuropathy.

Diagnosis of cystic fibrosis related diabetes: a selective approach in performing the oral glucose tolerance test based on a combination of clinical and biochemical criteria

BACKGROUND

Cystic fibrosis related diabetes (CFRD) has become increasingly common with the increasing longevity of patients with cystic fibrosis. The diagnosis of CFRD is important as its development may lead to a clinical deterioration which may be reversed with treatment. The oral glucose tolerance test (OGTT) is the method of choice in the diagnosis of CFRD, but performing OGTTs on all patients is inconvenient for patients and labour intensive for staff. The aim of this study was to identify a more selective approach in performing OGTTs in the diagnosis of CFRD based on the use of a combination of clinical and biochemical criteria.

METHODS

Clinically stable adult patients with cystic fibrosis not known to be diabetic attending the Royal Brompton Hospital Cystic Fibrosis Clinic for their annual review were invited to return within a month to have an OGTT. The result of the OGTT was compared with the results of tests performed during the annual review. The sensitivities and specificities of various methods used in the screening or diagnosis of CFRD were determined using OGTT as the "gold standard" diagnostic method. The combination of clinical and biochemical criteria which resulted in the highest sensitivity and specificity in the diagnosis of CFRD was determined.

RESULTS

Between August 1996 and May 1997 122 patients became eligible for the study, 91 of whom agreed to take part. The number of patients with normal, impaired, and diabetic glucose tolerance was 58 (64%), 21 (23%), and 12 (13%), respectively. When used alone, abnormal glycosylated haemoglobin (HbA1c) was found to have the highest sensitivity (83%; 95% CI 62 to 100) in the diagnosis of CFRD. The combination of an abnormal random blood glucose and/or abnormal HbA1c and/or symptoms of hyperglycaemia or weight loss was found to have the highest sensitivity (92%; 95% CI 76 to 100) in the diagnosis of CFRD. The specificity of this combination in the diagnosis of CFRD was 79% (95% CI 70 to 88). By selectively performing OGTTs in patients with one or more of the criteria cited above, 11 of the 12 patients with OGTT defined diabetes would have been identified.

CONCLUSIONS

Patients with cystic fibrosis already have to undergo a large number of routine investigations. The selective approach in performing OGTTs described here has the potential to identify the majority of patients with CFRD without the need to perform this investigation on all patients. This approach is likely to be welcomed by patients and will lead to significant savings in terms of time and resources for patients and staff. Further larger studies are warranted to validate this selective approach in the diagnosis of CFRD.

Survey and assessment of the actual state of routine measurement of glycohaemoglobin/GHb by commercial methods: warning to the users and the providers

As the clinical availability of glycohaemoglobin/GHb measurement increases, so does the need for comparable and accurate values among different laboratories and different methods. At least there should be comparability, i.e., commutability or feasibility of providing comparable results from different assays in different laboratories. A clinical joint study on insulin therapy, a survey of the actual inter-laboratory differences in GHb measurement among 41 institutions and an assessment of 11 assay methods for the determination of GHb were performed using commercial calibrators and fresh blood samples. Data on the actual state of inter-laboratory and inter-assay differences of observed values were useful for comparing results among facilities. The recommendation of the Japan Diabetes Society to measure only the stable GHb component and to correct the GHb percentage by two-point calibration with assigned values, was effective but not sufficient. Even after correction, 8 out of 11 methods still remained of little practical use because of their large relative errors. Inter-method differences among 11 available assay methods were great even after correction and depended on not only the methods but the samples used for the determination. The performance of some methods or instruments used are only poor at distinguishing the stable glycated haemoglobin itself. Some alternative measurement system with comparability, commutability and precision should be established. An urgent and worldwide problem to remove inter-laboratory differences in the measurement of GHb needs to be solved. Users in clinical practice must recognize these problems, and, before supply, the providers should check their method and keep records that are readily traceable.

Changes in corneal and lens autofluorescence and blood glucose levels in diabetics: parameters of blood glucose control

PURPOSE

We investigated corneal and lens autofluorescence in patients with proliferative diabetic retinopathy (PDR) to determine a correlation between the two parameters and blood glucose levels and HbA1c.

METHODS

Corneal and lens autofluorescence levels in 17 PDR patients and 8 healthy controls were measured with a fluorophotometer fitted with an anterior segment adapter. We measured the lower blood glucose level (BS1), corneal autofluorescence (CA1), and lens autofluorescence (LA1) simultaneously and the higher blood glucose level (BS2), CA2, and LA2 simultaneously on the same day. We defined parameter changes as: delta BS = BS2 - BS1, delta CA = CA2 - CA1, and delta LA = LA2 - LA1.

RESULTS

Corneal and lens autofluorescence significantly increased in the patients, compared with the controls (p < 0.001). Lens autofluorescence had a significant positive correlation with HbA1c (r = 0.656, p < 0.01) in the patients. delta CA (ngEq/ml) correlated significantly with delta BS (mg/dl) (r = 0.631, P < 0.01).

CONCLUSIONS

Results suggest that lens autofluorescence might represent the long-term control of diabetes, and corneal autofluorescence levels may represent short-term changes in the blood glucose level, because hyperglycemia accelerates with increasing corneal autofluorescence in PDR patients. Corneal and lens autofluorescence may be related to the breakdown of the blood-aqueous barrier.

Specificity of hemoglobin A1c measurement by cation exchange liquid chromatography. Evaluation of a Mono S column method

A method was developed for evaluating the specificity of the ion exchange chromatographic HbA1c method by Pharmacia which uses a Mono S column. To investigate hemoglobin fractions potentially interfering in HbA1c analysis, the chromatographic resolution was enhanced and a peak integration program was used which enables the quantitation of overlapping and even shoulder-like peaks. Hemoglobin was incubated with glucose in vitro and the chromatograms were analyzed before and after incubation. Five minor peaks were detected, close to hemoglobin A1c, which could not be conclusively identified as hemoglobins previously described. Four of these peaks, the stable ones, were included in the fraction of the chromatogram to be measured as HbA1c by the routine method. In practice, these peaks comprise 20%-35% of the routine HbA1c result in diabetic patients and 30%-45% in non-diabetic subjects. Three of these minor peaks were non-dependent on glucose. The chromatography and the peak integration method described can also be used to study hemoglobin adducts other than glycohemoglobin.

Cohort study of predictive value of urinary albumin excretion for atherosclerotic vascular disease in patients with insulin dependent diabetes

OBJECTIVE

To examine whether slightly elevated urinary albumin excretion precedes development of atherosclerotic vascular disease in patients with insulin dependent diabetes independently of conventional atherogenic risk factors and of diabetic nephropathy.

DESIGN

Cohort study with 11 year follow up.

SETTING

Diabetes centre in Denmark.

SUBJECTS

259 patients aged 19-51 with insulin dependent diabetes of 6-34 years' duration and without atherosclerotic vascular disease or diabetic nephropathy at baseline.

MAIN OUTCOME MEASURES

Baseline variables: urinary albumin excretion, blood pressure, smoking habits, and serum concentrations of total cholesterol, high density lipoprotein cholesterol, sialic acid, and von Willebrand factor.

END POINT

atherosclerotic vascular disease assessed by death certificates, mailed questionnaires, and hospital records.

RESULTS

Thirty patients developed atherosclerotic vascular disease during follow up of 2457 person year. Elevated urinary albumin excretion was significantly predictive of atherosclerotic vascular disease (hazard ratio 1.06 (95% confidence interval 1.02 to 1.18) per 5 mg increase in 24 hour urinary albumin excretion, P = 0.002). Predictive effect was independent of age; sex; blood pressure; smoking; serum concentrations of total cholesterol, high density lipoprotein cholesterol, sialic acid, and von Willebrand factor; level of haemoglobin A(lc); insulin dose, duration of diabetes, and diabetic nephropathy (hazard ratio 1.04 (1.01 to 1.08) per 5 mg increase

The natural course of microalbuminuria in insulin-dependent diabetes: a 10-year prospective study

The purpose of this study was to describe the clinical course in patients followed right from the onset of microalbuminuria to the development of diabetic nephropathy. A 10-year prospective follow-up of 209 consecutive normotensive insulin-dependent diabetic patients with normal urinary albumin excretion (UAE < 30 mg 24 h-1), age 34 (18-50) years and duration of diabetes 17 (10-30) years was performed. Twenty-four-hour urinary albumin excretion was measured every 4 months, glycated haemoglobin and supine blood pressure was measured annually. Two-hundred (96%) patients completed 10 (range 5-10) years follow-up. Twenty-nine (15%) patients developed persistent microalbuminuria (UAE 30-300 mg 24 h-1). Eight of these have progressed to nephropathy and one had died of diabetic nephropathy. Multiple stepwise logistic regression analysis demonstrated baseline urinary albumin excretion (p = 0.0016) and glycated haemoglobin (p = 0.0014) but not blood pressure as predictors of development of microalbuminuria within the following 10 years. The median annual increase in urinary albumin excretion was 27 (range 17-65) % in the 29 patients developing microalbuminuria. The median duration from onset of microalbuminuria to development of nephropathy was 7 years. The prevalence of patients receiving antihypertensive treatment (BP > 140/90 mmHg) increased from 10% at onset of microalbuminuria to 45% 4 years after onset of microalbuminuria. The prevalence of patients with proliferative retinopathy increased from 7% at onset of microalbuminuria to 28% 4 years after onset of microalbuminuria.(ABSTRACT TRUNCATED AT 250 WORDS)

Procoagulant activity and intimal dysfunction in IDDM

The biological activity of thrombin and coagulation factor Xa was assessed in 62 insulin-dependent diabetic patients. A group of non-diabetic subjects of comparable age and urinary albumin excretion rate (< 30 mg/24 h) served as control subjects (group 1, n = 14). The patients were divided into three groups according to urinary albumin excretion rate. In group 2, albumin excretion rate was less than 30 mg/24 h (n = 17), in group 3 albumin excretion rate was in the range 30-300 mg/24 h (n = 20) and in group 4 albumin excretion rate was greater than 300 mg/24 h (n = 25). Compared to non-diabetic control subjects an increase in the biological activity of factor Xa was observed in all groups of diabetic patients (prothrombin fragment 1 + 2 levels were 1.14 +/- 0.38 nmol/l in group 2, p < 0.005; 1.06 +/- 0.45 nmol/l in group 3, p < 0.05 and 1.03 +/- 0.31 nmol/l in group 4, p < 0.05 vs 0.75 +/- 0.34 nmol/l in group 1). No difference in the level of antithrombin III was seen between the groups. We reconfirmed the presence of intimal dysfunction in diabetic nephropathy demonstrated by elevated transcapillary escape rate of albumin in group 4 compared with group 2 (8.9 +/- 2.0% vs 7.0 +/- 1.9%, p < 0.05). An overall positive correlation between transcapillary escape rate and prothrombin fragment 1 + 2 was found (r = 0.36, p < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Microalbuminuria in type 2 diabetic patients: a cross-sectional study of frequency, sex distribution and relation to hypertension

We studied 112 type 2 diabetic patients. Fourteen patients had frank proteinuria, and 37 of the remaining 98 had microalbuminuria which was more frequent in men than in women (P < 0.02). Hypertension was found in 47 of the patients, equally distributed between sexes. Male diabetics with microalbuminuria had higher systolic blood pressure than diabetics without microalbuminuria (P < 0.02). Body mass index was higher in both sexes with hypertension compared to patients without hypertension. In the hypertensive men plasma C-peptide values were higher compared to patients without hypertension (P < 0.01) irrespective of the presence of microalbuminuria. A positive correlation between blood pressure and C-peptide was found (P < 0.01) in the men. We suggest that gender should be taken into account in the analysis and interpretation of microalbuminuria in type 2 diabetes.

Control of non-insulin-dependent diabetes mellitus partially normalizes the increase in hepatic efficacy for urea synthesis

The relation of urea synthesis rate to blood alanine concentration was assessed in seven healthy controls and eight patients with non-insulin-dependent diabetes mellitus (NIDDM) before (hemoglobin A1c [HbA1c] = 9.9% +/- 1.9%, mean +/- SD) and after (HbA1c = 7.9% +/- 0.8%) improvement of metabolic control. Following an overnight fast, alanine was infused at a rate of 2 mmol/(h.kg body weight [BW]). The hourly rate of urea synthesis was determined as the urinary excretion of urea corrected for accumulation of urea in total body water (TBW) and intestinal hydrolysis. The functional hepatic nitrogen clearance (FHNC) was calculated as the slope of the linear relation of urea synthesis rate to blood alanine concentration. The glucagon level was increased by twofold at the first investigation, but was not increased at the second. The insulin level was moderately increased at both investigations. In controls FHNC was 21.8 +/- 4.4 L/h, in poorly controlled patients it was increased to 36.6 +/- 4.3 L/h (P < .01), and following improvement of metabolic control it was not different from control levels at 28.6 +/- 4.3 L/h. By correlation analyses, FHNC was found only to be related to the fasting glucose value, albeit weakly (R2 = .39). In conclusion, hepatic kinetics of urea synthesis in poorly controlled NIDDM patients are changed in favor of increased conversion of alanine N to urea N at any amino acid concentration. This perturbation is partially normalized by improved metabolic control.

Creatinine height index and lean body mass in adult patients with insulin-dependent diabetes mellitus followed for 7 years from onset

The 24-hour urinary creatinine excretion value can be used as an index of protein nutrition; the creatinine height index and lean body mass can be estimated from this value. On the basis of longitudinally measured 24-hour urinary creatinine excretions during the initial 7 years of type 1 diabetes in an incidence cohort of 147 adult patients, we studied creatinine height index and lean body mass and possible relationships to sequential measurements of glycated hemoglobin (HbA1c). The patients were divided into four groups according to their glycemic control during these 7 years: I, HbA1c < 7.4% (n = 37); II, HbA1c 7.4% to 8.2% (n = 37); III, HbA1c 8.3% to 8.9% (n = 38); IV, HbA1c > 8.9% (n = 35). One year after the onset of diabetes, height indices were as follows (% of normal values, median and quartiles): I, 104% (90 to 116); II, 101% (78 to 105); III, 121% (92 to 128); IV, 87% (78 to 109) ([IV] < [I to III]; p < .05). During the following 6 years no significant differences in height index were observed among the four groups of patients at any point in time. Slightly higher calculated lean body mass values were found in the most well-controlled patients, but otherwise no differences were found in lean body mass. It is concluded that, apart from the first year, indices of protein nutrition remain normal during the initial 7 years of type 1 diabetes, even in patients with poor glycemic control.

Pre-mixed insulin delivered by disposable pen in the management of children with diabetes

Pre-mixed insulin preparations are being used increasingly in the management of children with IDDM. Recently this form of insulin has been produced in a disposable insulin pen device. An open randomized 3-month crossover study was conducted to compare glycaemic control on a self-titrating insulin regimen with a pre-mixed (30:70) preparation, both given twice daily. The pre-mixed preparation was delivered by disposable pen. Forty children (age range 7-16 yr) entered the study. Mean +/- SEM glycosylated haemoglobin (HbA1 %) at the start of the study (13.1 +/- 0.6) compared with values at the end of the self-titrating (11.8 +/- 0.5) and pre-mixed periods (12.5 +/- 0.5), as well as blood glucose profiles taken at 3-weekly intervals, showed no significant change. Fourteen of the children were on insulin ratios other than 30:70 (range 10:90 to 50:50) and were unaffected by the switch (HbA1 at the start of the study 12.7 +/- 1; at the end of the self-titrating 11.5 +/- 0.8; and pre-mixed period 12.5 +/- 0.8). Twenty-one children continued on the pen for a further 12 months with no deterioration in control (HbA1 at the beginning and end of this period being 11.9 +/- 0.7 and 11.0 +/- 0.7, respectively). The children (95%) preferred the disposable pen and pre-mixed insulin regimen. Switching to pre-mixed insulin, while not improving, has no detrimental effect on glycaemic control.

Segmental tubular sodium reabsorption in type 1 diabetes

Segmental tubular sodium reabsorption in Type 1 (insulin-dependent) diabetes was measured in 36 patients in a cross-sectional study including one group (n = 13) without significant albuminuria (UalbV < 30 mg 24 h-1), one group (n = 16) with albuminuria in the range from 30 to 300 mg 24 h-1, and a group (n = 7) with nephropathy (UalbV > 300 mg 24 h-1). Lithium clearance was used to measure end proximal delivery. From end proximal delivery, 51Cr-EDTA clearance (GFR) and sodium clearance, segmental tubular reabsorption was calculated. For all patients, GFR was directly correlated with end proximal delivery (r = 0.62, p < 0.0005), while end proximal delivery was inversely correlated to fractional proximal reabsorption (r = -0.71, p < 0.0005). In the subgroup with UalbV less than 30 mg 24 h-1, the direct correlation between GFR and end proximal delivery was also significant (r = 0.77, p < 0.05). In the group with nephropathy (UalbV > 300 mg 24 h-1), mean GFR and end proximal delivery were decreased and fractional proximal reabsorption was increased, but there was still a positive correlation between GFR and end proximal delivery (r = 0.75, p < 0.05) and an inverse correlation between end proximal delivery and fractional proximal reabsorption (r = -0.85, p < 0.05). It is concluded that in these groups of diabetic patients the end proximal delivery is increased while GFR is increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Manipulation of electroosmotic flow in capillary electrophoresis

This paper reports the use of surfactant and polymer-C18 coated capillaries that allow manipulation of electroosmotic flow (EOF). Although this approach to the control of EOF involves the preparation and use of multiple capillaries, all the coatings were prepared by a single procedure. It is shown that the ability to control EOF allows optimization of both separation time and resolution. In the case of proteins, low EOF maximizes resolution whereas high flow gives the shortest analysis time. It should be noted that proteins are a special case and this conclusion may not be true with other molecular species. Through selection of a specific coating, it is possible to complete a separation in the shortest time while maintaining sufficient resolution to give baseline resolution of proteins. The various coated capillaries were examined in capillary zone electrophoresis (CZE) and capillary isoelectric focusing (cIEF) separations of native protein standards and hemoglobin variants. Separation of glycosylated hemoglobin A1 variants was achieved by cIEF within 10 min, including the focusing time. Good run-to-run reproducibility was obtained by flushing the capillary with the coating solution between analyses.

Increased urinary loss of high density lipoproteins in albuminuric insulin-dependent diabetic patients

The pathophysiological mechanisms resulting in hyperlipidaemia in albuminuric insulin-dependent diabetic patients are largely unknown. Increased non-specific hepatic protein synthesis as a response to urinary protein loss, has been proposed. However in that case it is unexplained why the plasma concentration of the high density lipoprotein (HDL) subfraction, in contrast to all other lipoprotein subfractions, is normal or even reduced in albuminuric patients. We studied the urinary excretion of HDL-cholesterol in 26 insulin-dependent diabetic patients matched according to sex and age into three groups. I: normal urinary albumin excretion (< 30 mg 24 h-1; n = 8); II: incipient nephropathy (urinary albumin excretion in the range of 30-300 mg 24 h-1; n = 7); and III: clinical nephropathy (urinary albumin excretion > 300 mg 24 h-1; n = 11). Eight normal subjects served as controls. Lipoproteins in urine were separated by ultracentrifugation, and the daily urinary loss of HDL-cholesterol was 1.30 mumol (0.83-2.21) (median and range) in controls, 1.27 mumol (0.56-2.59) in group I, 1.39 mumol (0.55-1.97) in group II and 4.02 mumol (1.33-42.12) in group III (p < 0.01). More than 95% of cholesterol in urine was found in the HDL-fraction. The plasma concentrations of total cholesterol, very low density lipoprotein cholesterol, low density lipoprotein cholesterol and triglyceride were 21-94% higher in patients with clinical nephropathy compared with normal controls and group I.(ABSTRACT TRUNCATED AT 250 WORDS)

The prevalence of hypercholesterolaemia and its relationship with albuminuria in insulin-dependent diabetic patients: an epidemiological study

To assess the prevalence of hypercholesterolaemia and its relationship with metabolic control and urinary albumin excretion in Type 1 diabetic patients, all 1577 insulin-dependent patients attending the outpatient clinic at the Steno Memorial Hospital were studied. None had previously received lipid-lowering drugs. Hypercholesterolaemia, defined as plasma concentration of cholesterol above 6.4 mmol l-1 was found in 156 patients (10%) (95%) confidence intervals (CI) 8.4-11.5%) compared with 11% in the Danish background population. Compared with the normolipidaemic diabetic patients, the hyperlipidaemic patients were older (42 vs 37 years: p less than 0.001, 95% CI for difference in means 3-7 years), they had a higher glycosylated HbA1C (9.2 vs 8.6%, p less than 0.001, 95% CI for difference in means 0.4-1.3%) and their urinary albumin excretion was 32 vs 12 mg 24 h-1, p less than 0.001. Of the 1577 diabetic patients, 1084 patients (73%) had normal urinary albumin excretion (UAE less than 30 mg 24 h-1), 255 (17%) had microalbuminuria (UAE 30-300 mg 24 h-1) and 136 (9%) had overt clinical nephropathy (UAE greater than 300 mg 24 h-1). The plasma concentration of cholesterol rose significantly with increasing urinary albumin excretion; normoalbuminuric 4.78 mmol l-1 +/- 1.06 (mean +/- SD); microalbuminuric: 5.12 mmol l-1 +/- 1.23 and macroalbuminuric: 4.89 mmol l-1 +/- 1.38 (p less than 0.001). The influence of metabolic control on the plasma level of cholesterol was of only minor clinical importance.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary excretion of retinol-binding protein in type 1 (insulin-dependent) diabetic patients with microalbuminuria and clinical diabetic nephropathy

The urinary excretion of retinol-binding protein (RBP) was studied in 101 insulin-dependent diabetic patients allocated to three groups according to 24-h urinary albumin excretion rate (UAE) (median of three urine collections): group 1 (n = 45), normal UAE less than 30 mg/24 h; group 2 (n = 27), microalbuminuria (UAE 30-300 mg/24 h); and group 3 (n = 29), clinical diabetic nephropathy (UAE greater than 300 mg/24 h). We used 23 healthy subjects as controls. Fractional clearance of RBP (FC-RBP) and its 24-h urinary excretion rate (URBP) were higher in each diabetic group than in healthy subjects, the highest values being found in group 3. Groups 1 and 2 did not differ in URBP and FC-RBP. There was a correlation between FC-RBP and haemoglobin A1c in both the total diabetic cohort (P less than 0.001) and in diabetic patients in groups 1 and 2 with a glomerular filtration rate of more than 90 ml/min (P less than 0.05). No correlation was found between FC-RBP and UAE and/or duration of diabetes in any of the diabetic groups. We conclude that the increased urinary excretion of RBP, indicating proximal tubular dysfunction, is already present in normoalbuminuric insulin-dependent diabetic patients and correlates with metabolic control. Further deterioration in proximal tubular function was not observed in microalbuminuric patients, but is a late event in clinical diabetic nephropathy.

Platelet aggregation and fatty acid composition of platelets in type 1 diabetes mellitus

A raised content of arachidonic acid in platelets from diabetic patients with retinopathy was found without differences in platelet aggregation: platelet aggregability was not related to platelet fatty acid composition. In diabetes, platelet aggregation was inversely correlated to non-esterified fatty acids in plasma and may suggest an inhibiting effect. Mean platelet volume was raised in the diabetic patients, but without hyperaggregability. The findings do not exclude a relationship between platelet fatty acids and platelet aggregability, but suggest that variations in levels of non-esterified fatty acids in plasma might interfere with platelet aggregation.

Dietary supplementation with omega-3-polyunsaturated fatty acids decreases mononuclear cell proliferation and interleukin-1 beta content but not monokine secretion in healthy and insulin-dependent diabetic individuals

The effects of dietary supplementation with omega-3-polyunsaturated fatty acids (omega-3-PUFA) on the proliferative response of PBMC and on the secretion of monokines and arachidonic acid metabolites from PBMC and monocytes (Mo) from healthy subjects and patients with recent-onset insulin-dependent diabetes mellitus (IDDM) were examined. Three groups of eight to nine healthy individuals were randomized to either 2.0 g/day or 4.0 g/day of omega-3-PUFA devoid of vitamins A and D, or an isocaloric amount of placebo. Furthermore, eight patients with recent-onset IDDM received 4.0 g/day of omega-3-PUFA. IL-1 beta production and TNF-alpha secretion was determined before and after 7 weeks of treatment, and 10 weeks after withdrawal of treatment. Significant increases in platelet and PBMC membrane eicosapentaenoic acid was found in omega-3-PUFA-treated individuals. omega-3-PUFA treatment significantly reduced the content of IL-1 beta in lysates of PBMC, but did not affect PBMC or Mo secretion of IL-1 beta, TNF-alpha or prostaglandin E2 (PGE2) or PBMC leukotriene B4 (LTB4) secretion in healthy subjects or in IDDM patients. A significant inhibition of the PHA-stimulated, but not the spontaneous or PPD-stimulated, proliferative response of PBMC was observed in healthy and diabetic subjects treated with omega-3-PUFA. No correlation was found between PHA-stimulated PBMC proliferation and PBMC secretion of TNF-alpha and IL-1 beta. There were no significant differences in the spontaneous or the PPD- or PHA-stimulated proliferative responses of PBMC between diabetic and healthy individuals at entry. We conclude that although dietary supplementation with 4.0 g/day of omega-3-PUFA inhibits the proliferation of PBMC and reduces IL-1 beta immunoreactivity in PBMC and Mo, it does not alter monokine, PGE2 or LTB4, secretion in healthy or IDDM subjects.

Impaired left-ventricular function in insulin-dependent diabetic patients with increased urinary albumin excretion

Cardiac function was studied in 30 patients with insulin-dependent diabetes mellitus. Three groups, matched for age and diabetes duration, were defined as: group I (n = 10), normal urinary albumin excretion less than 30 mg 24 h-1; group II (n = 10), incipient diabetic nephropathy (urinary albumin excretion in the range of 30-300 mg 24 h-1); and group III (n = 10), clinical diabetic nephropathy (urinary albumin excretion greater than 300 mg 24 h-1). Ten non-diabetic subjects matched for sex and age served as controls. The left-ventricular end-diastolic volume measured by radionuclide cardiography was, at rest and during exercise, lower in group II and III compared with controls (p less than 0.05), while intermediate values were found in group I. The cardiac output was similar in the control group and group I; it was reduced, but not significantly so (p = 0.10), in group III and was significantly lower in group II (p less than 0.05). Stroke volume was also lower in group II and III than in controls (p less than 0.05), but not so in group I. These differences could not be explained by differences in metabolic control, blood pressure, blood volume status, degree of autonomic neuropathy or frequency of coronary heart disease. Our results might suggest that insulin-dependent diabetic patients with slightly but persistently elevated urinary albumin excretion have reduced diastolic compliance of the left-ventricle leading to impaired cardiac performance.(ABSTRACT TRUNCATED AT 250 WORDS)

The significance of the products of the Maillard (browning) reaction in diabetes

The accumulation of the products of the Maillard reaction leads to structural and functional modifications of tissue proteins. In normoglycaemia, these modifications result in slow age-related accumulation of AGE-proteins. Hyperglycaemia accelerates formation of the Maillard products. The increased rate of Amadori products formation in poorly controlled diabetes leads to the impairment of the function of susceptible short-lived proteins and accelerates the formation of AGE on proteins with a long half-life. AGE accumulation increases protein crosslinking and leads to changes in the mechanical and biological properties of the affected proteins. AGE-modified proteins covalently bind other molecules. This may contribute to the formation of pathological tissue deposits and to the in situ formation of immune complexes. AGE-modified proteins also induce changes in biosynthetic/secretory patterns of macrophages, endothelial cells, and mesangial cells. These data led to the formulation of hypotheses which propose a central role for the Maillard products both in the process of ageing and in the development of the late complications of diabetes. More clinical studies are required to further substantiate these attractive hypotheses.

Effect of improved metabolic control on loss of kidney function in type 1 (insulin-dependent) diabetic patients: an update of the Steno studies

We re-examined 69 of the 70 patients entering the two independent Steno Studies of effects of improved metabolic control on progression of late diabetic complications. They were analysed according to an intent to treat after follow-up for 8 years (Steno Study 1) and 5 years (Steno Study 2). The glycaemic control had improved in the insulin infusion group compared with the conventional treatment group (mean HbA1c) by 2.0 +/- 0.6% vs 0.7 +/- 1.2 in Steno Study 1 and by 1.8 +/- 1.2% vs 0.4 +/- 1.3 (p less than 0.01) in Steno Study 2. In the insulin infusion groups three patients had died during episodes of ketoacidosis. These were not caused by malfunction of the insulin infusion pumps. In the conventional treatment groups, three patients suffered five cardiovascular events causing two deaths. From the sixth month of Steno Study 1 the annual change of the glomerular filtration rate was -3.7 (-5.4 to -2.0) ml.min-1.1.73 m-2 vs -1.0 (-2.1 to -0.1) (conventional vs insulin infusion group, mean (95% confidence interval, p less than 0.01]. The change in urinary albumin excretion was associated with the glycaemic control (n = 69, r = 0.49, p less than 0.0002). No progression was observed among 32 patients with low range microalbuminuria (30 to 99 mg/24 h).(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship between symptomatic and biochemical hypoglycaemia in insulin-dependent diabetic patients

The relationship between symptomatic (subjective feelings) and biochemical (blood glucose concentration less than 3 mmol l-1) hypoglycaemia was studied in 66 randomly selected insulin-dependent diabetic out-patients under normal conditions of daily life with conventional insulin injection regimens. The patients (a) collected 7-point diurnal blood glucose profiles at home on three consecutive days and then once weekly for 3 weeks, (b) indicated whether they felt hypoglycaemic at sampling times, and (c) collected extra samples if they felt hypoglycaemic at any time during the study period. The weekly frequencies of symptomatic and biochemical hypoglycaemia were 0.99 and 1.75 per patient, respectively. Biochemical hypoglycaemia was present in 29% of the symptomatic episodes, and symptomatic hypoglycaemia accompanied 16% of the biochemical episodes. Symptomatic hypoglycaemia was experienced at a median blood glucose concentration of 3.4 mmol l-1 (range 1.4-14.9 mmol l-1). Fifty per cent of both symptomatic and biochemical episodes occurred before lunch, while the remainder were evenly distributed throughout the day. The occurrence of biochemical hypoglycaemia, but not of symptomatic hypoglycaemia, was inversely correlated with HbA1c and median blood glucose concentration. Thus symptomatic hypoglycaemia is an unreliable indicator of biochemical hypoglycaemia and of the degree of glycaemic control. Blood glucose measurements are a prerequisite for the diagnosis of hypoglycaemia.

Monocyte function in IDDM patients and healthy individuals

Interleukin 1 beta (IL-1 beta) and tumour necrosis factor alpha (TNF-alpha) may be pathogenetically important in insulin-dependent diabetes mellitus (IDDM), which is associated with genes of the HLA region. Since a regulatory role of HLA region genes on monokine production may exist, we looked for an association between the monokine and prostaglandin E2 (PGE2) responses of monocytes (Mo) from 20 healthy males (18-50 years) with HLA-DR types relevant for IDDM susceptibility and resistance (DR1,2, DR1,3, DR1,4, DR3,4). Monokine assays were established and evaluated and the secretions of IL-1 beta, TNF-alpha, and PGE2 measured in Mo cultures (2h, 6h, 20h) prepared by endotoxin-free techniques and stimulated by low-dose E. coli lipopolysaccharides (LPS). There were no significant associations between Mo responses and HLA-DR phenotype. Likewise, Mo from DR2 (n = 5) and DR4 (n = 5) homozygous healthy males demonstrated no significant differences in monokine and PGE2 responses of Mo. In the HLA class III region a diallelic TNF-beta gene NcoI polymorphism consisting of alleles of 5.5 kb and 10.5 kb was recently described and associated with susceptibility to autoimmune diseases including IDDM. We report that IL-1 beta and TNF-alpha responses of Mo from TNF-beta 10.5 kb homozygous healthy individuals were significantly higher than for TNF-beta 5.5/10.5 kb heterozygotes. IL-1 beta and TNF-alpha responses of Mo from males (18-35 years) with newly diagnosed (n = 10) and long-standing IDDM (n = 10) and from age- and HLA-DR-matched healthy males (n = 10) were studied. LPS, gamma interferon (IFN), and TNF-alpha-stimulated Mo cultures were investigated. No significant differences were found between Mo responses of IDDM patients and controls. IFN (1000 U/ml) in the presence of LPS significantly potentiated LPS-stimulated Mo TNF-alpha secretion and reduced the levels of IL-1 beta immunoreactivity in Mo lysates. IFN and TNF-alpha did not have any effects on LPS-stimulated Mo secretion of IL-1 beta immunoreactivity. We conclude that Mo IL-1 beta and TNF-alpha production is normal in patients with recent-onset and long-standing IDDM. The interindividual differences in monokine responses may be accounted for by the diallelic human TNF-beta gene polymorphism rather than by HLA class II genes. This observation may be important for understanding the association of certain HLA haplotypes with autoimmune phenomena and disease.

Application of high-performance liquid chromatography in establishing an accurate index of blood glucose control

A chromatographic method utilizing a carboxymethylated poly(vinyl alcohol) resin for a more accurate determination of stable haemoglobin A1c (St-A1c) has been developed. The complete separation between St-A1c, labile HbA1c (L-A1c) and HbF was achieved by gradient elution with sodium chloride in phosphate buffer. This high resolution permits accurate quantitation of St-A1c, even in the presence of high levels of HbF or L-A1c. In 142 subjects with normal fasting plasma glucose and normal response to a 75-g oral glucose tolerance test, the reference interval of St-A1c was 2.80-3.98%.

Nephrotoxicity of cyclosporin A in patients with newly diagnosed type 1 diabetes mellitus

Renal function was studied in 18 patients with Type 1 diabetes mellitus. All were participating in the Canadian-European randomized placebo-controlled cyclosporin trial in newly diagnosed Type 1 diabetic patients, nine being randomized to placebo, and nine to cyclosporin A. During treatment for 12 to 18 months, cyclosporin A caused significant reductions in the glomerular filtration rate (before drug withdrawal, cyclosporin 97 +/- 18 vs placebo 125 +/- 16 ml min-1 1.73-m-2, p less than 0.05), renal plasma flow (454 +/- 83 vs 536 +/- 70 ml min-1 1.73-m-2, p less than 0.05), and lithium clearance (17 +/- 3 vs 28 +/- 5 ml min-1 1.73-m-2, p less than 0.05). The fractional proximal reabsorption was increased (0.82 +/- 0.03 vs 0.78 +/- 0.03, p less than 0.05), and the fractional distal sodium reabsorption reduced (0.88 +/- 0.03 vs 0.94 +/- 0.02, p less than 0.05). These results are in accordance with the hypothesis that the nephrotoxic effect of cyclosporin A results from a preferential constriction of afferent glomerular vessels. One year after withdrawal of the drug, all variables were similar in the two groups, except for blood glucose control which was worse in the cyclosporin A treated group. When corrected for differences in blood glucose control it appeared that in three out of nine patients glomerular filtration rate had not completely returned to the reference range of the placebo group. We conclude that the nephrotoxic side-effects of cyclosporin A treatment for 1 year are reversible. There are, however, signs of minor and perhaps chronic renal injury.

Polymorphism in 5' flanking region of human insulin gene. Relationships with atherosclerosis, lipid levels, and age in three samples from Denmark

Variations in the DNA sequence flanking the 5' region of the human insulin gene (U- and L-alleles) were studied in relation to atherosclerosis, lipid levels, and age in three groups of atherosclerotic individuals and in nonatherosclerotic controls. The atherosclerotic groups comprised a postmyocardial infarction group with a mean age of 48 years, a group of individuals operated on for carotid stenosis with a mean age of 62 years, and a group of 85-year-olds with clinical coronary disease, peripheral arterial disease, or both. All 331 individuals were unrelated Caucasians of Danish ancestry. There were no significant differences (p greater than 0.05) in genotype distribution or allele frequencies between atherosclerotic and nonatherosclerotic individuals, but in the 85-year-olds, there was evidence (p less than 0.10) for a lower U-allele frequency in nonatherosclerotic women compared to atherosclerotic women. In nonatherosclerotic women, there was a significant decrease in U-allele frequency with age (60 to 85 years). This decrease does not prove conclusively, but is compatible with, the hypothesis that the U-allele predisposes to, or the L-allele protects against, atherosclerosis. The possible effect of the U-allele on the development of atherosclerosis does not seem to be mediated through conventional risk factors.