24-h blood pressure and autonomic function is related to albumin excretion within the normoalbuminuric range in IDDM patients

Summary Significant changes in both blood pressure, autonomic function and kidney ultrastructure are observed in insulin-dependent diabetic (IDDM) patients with microalbuminuria. Intervention strategies are evaluated at even earlier stages of disease. Identification of patients at risk of developing microalbuminuria must be based on a thorough knowledge of the relations between key pathophysiological parameters in patients with normoalbuminuria. The aim of the present study was to characterize the interactions of urinary albumin excretion (UAE), 24-h ambulatory blood pressure (AMBP), and sympathovagal balance in a large group of normoalbuminuric IDDM patients. In 117 normoalbuminuric (UAE < 20 μg/min) patients we performed 24-h AMBP (Spacelabs 90 207), with assessment of diurnal blood pressure and heart rate (HR) variation, and short-term (three times 5 min) power spectral analysis of RR interval oscillations, as well as cardiovascular reflex tests (HR variation to deep breathing, postural HR and blood pressure response). Patients with UAE above the median (4.2 μg/min) had significantly higher 24-h systolic and diastolic AMBP (125 ± 10.1/76 ± 7.2 mmHg) compared to the low normoalbuminuric group (120 ± 8.4/74 ± 5.1 mmHg), p < 0.01 and 0.02, respectively. Patients with UAE above the median had significantly reduced short-term RR interval variability including both the high frequency component (5.47 ± 1.36 vs 6.10 ± 1.43 ln ms²), and low frequency component (5.48 ± 1.18 ln ms² compared to 5.80 ± 1.41 ln ms²), p < 0.02 and p = 0.04 (ANOVA). In addition, patients with high-normal UAE had reduced mean RR level (faster heart rates) 916 ± 108 compared to 963 ± 140 ms, p < 0.04. These differences were not explained by age, duration of diabetes, gender, level of physical activity, or cigarette smoking. HbA_{1 c} was significantly higher (8.6 ± 1.2 vs 8.2 ± 1.0 %, p = 0.03) in the group with high normal UAE. Comparing normoalbuminuric IDDM patients with UAE above and below the median value, we found significantly higher AMBP in combination with significant differences in sympathovagal balance and significantly poorer glycaemic control in the group with high-normal albumin excretion. Our data demonstrate interactions between albumin excretion, blood pressure, autonomic function, and glycaemic status, already present in the normoalbuminuric range and may describe a syndrome indicative of later complications. [Diabetologia (1997) 40: 718–725] Received: 9 January 1997 and in revised form: 12 March 1997     

Serum sialic acid concentration is elevated in IDDM especially in early diabetic nephropathy

Abstract. Objectives. Elevated serum sialic acid concentration is a strong predictor of cardiovascular mortality in non-diabetic subjects. Because patients with insulin-dependent diabetes mellitus (IDDM) and albuminuria have a highly increased cardiovascular morbidity and mortality, we hypothesized that IDDM patients with albuminuria would have an increased concentration of serum sialic acid. Design. Cross-sectional study. Setting. Outpatient clinic at Steno Diabetes Centre, Gentofte, Denmark. Subjects. Twenty-six non-diabetic controls and 74 IDDM patients with normoalbuminuria (urinary albumin excretion [UAE] < 30 mg 24 h^?1; n = 37), incipient nephropathy (UAE 30–300 mg 24 h^?1; n = 20) and clinical nephropathy (UAE > 300 mg 24 h^?1; n = 17), matched for sex, age and body mass index (BMI). Main outcome measures. Serum sialic acid concentration, concurrent fasting blood glucose, glycated haemoglobin (HbA1c), serum creatinine, plasma fibrinogen and erythrocyte sedimentation rate. Results. Normoalbuminuric patients had a higher serum sialic acid concentration (mmol L^?1) than non-diabetic controls (1.83 ± 0.24 vs. 1.67 ± 0.26; P < 0.02). Serum sialic acid concentration was further increased in patients with incipient nephropathy (2.02 ± 0.37; P < 0.03) and in patients with clinical nephropathy (2.13 ± 0.33; P < 0.002) compared with normoalbuminuric IDDM patients. Serum sialic acid correlated strongly with plasma fibrinogen (r = 0.78; P < 0.0001) and erythrocyte sedimentation rate (r = 0.62; P < 0.0001). In a multiple regression analysis including UAE, retinopathy status, fasting blood glucose, HbA1c, mean blood pressure, serum creatinine, age, BMI, duration and smoking, UAE and fasting blood glucose were the independent variables which correlated significantly with serum sialic acid concentration (P < 0.0001 and P < 0.05, respectively). Conclusion. Serum sialic acid is elevated in IDDM especially in albuminuric patients. Whether elevated serum sialic acid is predictive for early diabetic nephropathy and cardiovascular disease in IDDM has to be shown in the future.     

Assessment of baroreceptor-cardiac reflex sensitivity using time domain analysis in patients with IDDM and the relation to left ventricular mass index

Summary Autonomic dysfunction in insulin-dependent diabetic (IDDM) patients has been associated with abnormalities of left ventricular function and an increased risk of sudden death. A group of 30 patients with IDDM and 30 age, sex and blood pressure matched control subjects underwent traditional tests of autonomic function. In addition, baroreceptor-cardiac reflex sensitivity (BRS) was assessed using time domain (sequence) analysis of systolic blood pressure and pulse interval data recorded non-invasively using the Finapres beat-to-beat blood pressure recording system. ’Up BRS' sequences–increases in systolic blood pressure associated with lengthening of R-R interval, and ’down BRS' sequences–decreases in systolic blood pressure associated with shortening of R-R interval were identified and BRS calculated from the regression of systolic blood pressure on R-R interval for all sequences. We also assessed heart rate variability using power spectral analysis and, after expressing components of the spectrum in normalised units, assessed sympathovagal balance from the ratio of low to high frequency powers. IDDM subjects underwent 2-D echocardiography to assess left ventricular mass index. Standard tests of autonomic function revealed no differences between IDDM patients and control subjects, but dramatic reductions in baroreceptor-cardiac reflex sensitivity were detected in IDDM patients. ’Up BRS' when supine was 11.2 ± 1.5 ms/mmHg (mean ± SEM) compared with 20.4 ± 1.95 in control subjects (p < 0.003) and when standing was 4.1 ± 1.9 vs 7.6 ± 2.7 ms/mmHg (p < 0.001). Down BRS when supine was 11.5 ± 1.2 vs 22 ± 2.6 (p < 0.001) and standing was 4.4 ± 1.9 vs 7.3 ± 2.5 ms/mmHg (p < 0.003). There were significant relations between impairment of the baroreflex and duration of diabetes (p < 0.001) and poor glycaemic control (p < 0.001). From a fast Fourier transformation of supine heart rate data and using a band width of 0.05–0.15 Hz as low-frequency and 0.2–0.35 Hz as high frequency total spectral power of R-R interval variability was significantly reduced in the IDDM group for both low-frequency (473 ± 62.8 vs 746.6 ± 77.6 ms² p = 0.002) and high frequency bands 125.2 ± 12.9 vs 459.3 ± 89.8 ms² p < 0.0001. When the absolute powers were expressed in normalised units the ratio of low frequency to high frequency power (a measure of sympathovagal balance) was significantly increased in the IDDM group (2.9 ± 0.53 vs 4.6 ± 0.55, p < 0.002 supine: 3.8 ± 0.49 vs 6.6 ± 0.55, p < 0.001 standing). Thus, time domain analysis of baroreceptor-cardiac reflex sensitivity detects autonomic dysfunction more frequently in IDDM patients than conventional tests. Impaired BRS is associated with an increased left ventricular mass index and this abnormality may have a role in the increased incidence of sudden death seen in young IDDM patients. [Diabetologia (1996) 39: 1385–1391] Received: 9 April 1996 and in revised form: 19 July 1996     

Premature cell ageing and evolution of diabetic nephropathy

Summary The rate of development and progression of renal disease varies greatly in insulin-dependent diabetic (IDDM) patients. The cellular and molecular reasons for this difference are largely unknown but could be related to early cell differentiation, a phenomenon recently reported in IDDM patients with nephropathy. In this study we compared cell differentiation and cell volume between IDDM patients with and without nephropathy and investigated the cell ageing characteristics in relation to the rate of evolution of renal disease in the IDDM patients with diabetic nephropathy. Cell volume was larger and the percentage of post-mitotic fibrocytes was higher in skin fibroblasts derived from IDDM patients with diabetic nephropathy compared to those from IDDM patients without kidney disease (mean ± SD in arbitrary units 817.3 ± 25.7 vs 760 ± 32.8; p = 0.005; and mean ± SD % 33.6 ± 11.8 vs 20.8 ± 10; p = 0.02 respectively). Analysis of the interaction of the time to proteinuria (TTP) and the rate of change of glomerular filtration rate (GFR) with glycaemic control, arterial blood pressure and cell volume and the state of cell differentiation showed that glycated haemoglobin and the percentage of post-mitotic fibrocytes were negatively correlated to TTP (r = – 0.68; p = 0.008; r = – 0.52; p = 0.05 respectively) and positively associated with the rate of change of GFR (r = 0.76; p = 0.03; r = 0.56; p = 0.037 respectively). Cell volume was negatively correlated to TTP (r = – 0.53; p = 0.05). Diastolic blood pressure was also related to the rate of GFR change (r = 0.56; p = 0.039). In a multiple linear regression analysis glycated haemoglobin maintained its significant independent relationship with TTP at the 1 % level, while the strength of the association between the percentage of post-mitotic cells and cell volume was reduced to the 11 and 9 % level, respectively. Cultured skin fibroblasts from IDDM patients with nephropathy show signs of early differentiation. Glycaemic control is a key factor in the rate of onset of proteinuria and different rates of cell ageing appear to contribute to the rate of development and progression of diabetic nephropathy. Their interaction may be responsible for the severity of renal involvement in susceptible IDDM patients. [Diabetologia (1997) 40: 244–246] Received: 30 September 1996 and in revised form: 15 November 1996     

Patterns of renal injury in NIDDM patients with microalbuminuria

Summary Microalbuminuria predicts overt nephropathy in non-insulin-dependent diabetic (NIDDM) patients; however, the structural basis for this functional abnormality is unknown. In this study we evaluated renal structure and function in a cohort of 34 unselected microalbuminuric NIDDM patients (26 male/8 female, age: 58 ± 7 years, known diabetes duration: 11 ± 6 years, HbA_{1 c}: 8.5 ± 1.6 %). Systemic hypertension was present in all but 3. Glomerular filtration rate (GFR) was 101 ± 27 ml · min^–1· 1.73 m^–2 and albumin excretion rate (AER) 44 (20–199) μg/min. Light microscopic slides were categorized as: C I) normal or near normal renal structure; C II) changes “typical” of diabetic nephropathology in insulin-dependent diabetes (IDDM) (glomerular, tubulo-interstitial and arteriolar changes occurring in parallel); C III) “atypical” patterns of injury, with absent or only mild diabetic glomerular changes associated with disproportionately severe renal structural changes including: important tubulo-interstitial with or without arteriolar hyalinosis with or without global glomerular sclerosis. Ten patients (29.4 %) were classified as C I, 10 as C II (29.4 %) and 14 as C III (41.2 %); none of these patients had any definable non-diabetic renal disease. GFR, AER and blood pressure were similar in the three groups, while HbA_{1 c} was higher in C II and C III than in C I patients. Diabetic retinopathy was present in all C II patients (background in 50 % and proliferative in 50 %). None of the patients in C I and C III had proliferative retinopathy, while background retinopathy was observed in 50 % of C I and 57 % of C III patients. In summary, microalbuminuric NIDDM patients are structurally heterogeneous with less than one third having “typical” diabetic nephropathology. The presence of both “typical” and “atypical” patterns of renal pathology was associated with worse metabolic control, suggesting that hyperglycaemia may cause different patterns of renal injury in older NIDDM compared to younger IDDM patients. [Diabetologia (1996) 39: 1569–1576]     

High prevalence of risk factors for cardiovascular disease in parents of IDDM patients with albuminuria

Summary Life expectancy is shorter in the subset of insulin-dependent diabetic (IDDM) patients who are susceptible to kidney disease. Familial factors may be important. In this study the prevalence of cardiovascular disease mortality and morbidity and of risk factors for cardiovascular disease was compared in the parents of 31 IDDM patients with elevated albumin excretion rate (AER > 45 μg/min; group A) with that of parents of 31 insulin-dependent diabetic patients with normoalbuminuria (AER < 20 μg/min; group B). The two diabetic patient groups were matched for age and duration of disease. Information on deceased parents was obtained from death certificates and clinical records and morbidity for cardiovascular disease was ascertained using the World Health Organization questionnaire and Minnesota coded ECG. Hyperlipidaemia was defined as serum cholesterol higher than 6 mmol/l and/or plasma triglycerides higher than 2.3 mmol/l and/or lipid lowering therapy; arterial hypertension as systolic blood pressure higher than 140 mmHg and/or diastolic blood pressure higher than 90 mmHg and/or antihypertensive treatment. The percentage of dead parents was similar in the two groups (26 vs 20 % for parents of group A vs group B, respectively), but the parents of the diabetic patients with elevated AER had died at a younger age (58 ± 10 vs 70 ± 14 years; p < 0.05). Parents of diabetic patients with nephropathy had a more than three times greater frequency of combined mortality and morbidity for cardiovascular disease than that of the parents of diabetic patients without nephropathy (26 vs 8 %; odds ratio 3.96, 95 % CI 1.3 to 12.2; p < 0.02). Living parents of group A had a higher prevalence of arterial hypertension (42 vs 14 % p < 0.01) and hyperlipidaemia (49 vs 26 % p < 0.05) as well as higher levels of lipoprotein (a) [median (range) 27.2 (1–107) vs 15.6 (0.2–98) mg/dl; p < 0.05]. They also had reduced insulin sensitivity [insulin tolerance test: median (range) K_itt index: 3.7 (0.7–6.2) vs 4.8 (0.7–6.7)% per min; p < 0.05]. In the families of IDDM patients with elevated AER there was a higher frequency of risk factors for cardiovascular disease as well as a predisposition to cardiovascular disease events. This may help explain, in part, the high prevalence of cardiovascular disease mortality and morbidity in those IDDM patients who develop nephropathy. [Diabetologia (1997) 40: 1191–1196] Received: 4 March 1997 and in revised form: 9 May 1997     

Angiotensin converting enzyme inhibiting therapy is associated with lower vitreous vascular endothelial growth factor concentrations in patients with proliferative diabetic retinopathy

Aims/hypothesis: Vascular endothelial growth factor (VEGF) is thought to be instrumental in the progression of diabetic retinopathy. Indications exist that the renin-angiotensin system is involved in VEGF overexpression. We assessed the vitreous VEGF concentrations in patients and related them to anti-hypertensive treatment, with special interest in the use of ACE-inhibitors. Methods: Samples of vitreous fluid (10–80 μl) were obtained from 39 patients both with Type I (insulin-dependent) and Type II (non-insulin-dependent) diabetes mellitus and 11 non-diabetic patients undergoing intra-ocular surgery. The VEGF-A concentrations were assessed by immunoassay. Results: Control patients and patients without proliferative diabetic retinopathy (n = 8) had low and comparable VEGF concentrations (medians < 50 pg/ml). In contrast, patients with proliferative diabetic retinopathy (n = 31) had high vitreous VEGF concentrations (median 1134 pg/ml), which showed a negative correlation with the use of ACE inhibiting medication (Spearman rank-R = – 0.54; p = 0.002, n = 13). Diastolic and systolic blood pressure did not differ significantly between the two subgroups with proliferative diabetic retinopathy, i. e. those patients receiving ACE-inhibition (medians 88/160 mm Hg, respectively) and the others (90/160). For the mostly used ACE-inhibitor in the proliferative diabetic retinopathy group, i. e. enalapril (n = 8), a linear dose-effect relation was observed (–20 ± 4 pg · ml^–1· mg^–1· day^–1; p = 0.024; coefficient ± SEM). Conclusion/interpretation: Treatment with ACE-inhibitors attenuates retinal overexpression of VEGF-A in patients with proliferative diabetic retinopathy, probably by interference with a local effect of angiotensin II. [Diabetologia (2002) 45: 203–209] Received: 25 June 2001 and in revised form: 25 October 2001     

Uptake mechanisms for ascorbate and dehydroascorbate in lymphoblasts from diabetic nephropathy and hypertensive patients

Summary In diabetic nephropathy and hypertension, a major cause of mortality is from cardiovascular disease. Since low levels of antioxidants such as vitamin C have been associated with such complications, we have examined the uptake mechanisms for ascorbic acid (AA) and dehydroascorbic acid (DHA) in lymphoblasts from normal control subjects (CON), normoalbuminuric insulin-dependent diabetic (IDDM) patients (DCON), patients with IDDM and nephropathy (DN) and hypertensive patients (HT) using mass assays of uptake and measuring AA using high-performance liquid chromatography. Precautions were taken to prevent oxidation of AA and to take into account the instability of DHA in buffers. DHA uptake was the major mechanism in all four groups of subjects, and the V_max (maximal uptake rate) was significantly lower in the DN cells (24.7 ± 1.0 nmol [95 % confidence intervals CI 22.5, 26.3] 10⁶ cells^–1 h^–1) compared to CON and DCON cells (33.9 ± 2.1 [95 % CI 29.4, 38.4] and 37.0 ± 2.2 [95 % CI 32.2, 41.8] nmol 10⁶ cells^–1 h^–1, respectively, p < 0.001 for both). DHA V_max was also lower in the HT group (23.2 ± 1.1 [95 % CI 20.7, 25.7] nmol 10⁶ cells^–1 h^–1) compared to the CON group (p < 0.001). There were no significant differences in the K_m or passive membrane permeability for DHA or the AA uptake. DHA uptake showed a negative correlation to systolic blood pressure (r _s = –0.49, p < 0.001). These findings suggest that impaired DHA uptake may be one component of the phenotype expressed by DN cells that may persist in culture. Impaired DHA uptake in vivo, especially in the presence of hyperglycaemia, leads to impaired regeneration of AA and depletion of anti-oxidant defences, exposing such individuals to increased risk of cardiovascular disease. [Diabetologia (1998) 41: 435–442] Received: 10 July 1997 and in final revised form: 24 November 1997     

Glomerular size-and charge selectivity in Type 2 (non-insulin-dependent) diabetic patients with diabetic nephropathy

Summary In an attempt to evaluate the mechanisms of proteinuria in diabetic kidney disease, we measured the renal clearances of albumin, total IgG, and IgG4 in 20 male Type 2 (non-insulin-dependent) diabetic patients with diabetic glomerulosclerosis (biopsy proven), in 10 male Type 2 diabetic patients without nephropathy (urinary albumin excretion rate ≤ 30 mg/24 h), and in 10 healthy male subjects. The fractional clearance of albumin was increased in patients with nephropathy: 659 (42–4355) · 10^–6 (median (range)), compared to 2.6 (0.2–14.2) · 10^–6 in patients without nephropathy, and 2.3 (0.4–4.2) · 10^–6 in healthy subjects. The fractional clearance of total IgG (neutral) and of IgG4 (anionic) was 40–50 times higher in patients with nephropathy compared to the two other groups. The IgG/IgG4 selectivity index was not significantly different in the three groups, being: 1.12 (0.06–5.65), 1.16 (0.45–3.72) and 1.35 (0.65–3.34) in patients with nephropathy, patients without nephropathy, and healthy subjects, respectively. The IgG/albumin selectivity index was decreased in patients with nephropathy: 0.27 (0.01–1.26) compared to 1.29 (0.07–2.67) (p<0.05) and 1.23 (0.76–7.84) (p<0.001) in patients without nephropathy and healthy subjects, respectively. No significant change in IgG/albumin selectivity index was observed between patients without nephropathy and healthy subjects. The systolic blood pressure was elevated in the patients with nephropathy: 164±21 mm Hg (mean ± SD) compared to patients without nephropathy: 145±20 mm Hg (p<0.05) and to healthy subjects: 133±19 mm Hg (p<0.005). The diastolic blood pressure was higher in patients with and without nephropathy: 92±7 vs 90±10 mm Hg compared to 79±8 mm Hg (p<0.005) in healthy subjects. Our cross-sectional study suggests that impaired barrier size selectivity, probably due to an increase in large pore area (“shunt pathway”) in the glomerular capillary wall and systemic hypertension are the major pathogenic mechanisms of proteinuria in Type 2 diabetic patients with diabetic nephropathy. [Diabetologia (1994) 37: 195–201] Received: 7 June 1993 and in revised form: 25 August 1993     

Prevalence of left ventricular hypertrophy in Type I diabetic patients with diabetic nephropathy

Summary The increased mortality of patients with diabetic nephropathy is mainly due to cardiovascular disease and end stage renal failure. Left ventricular hypertrophy is an independent risk factor for myocardial ischaemia and sudden death. The aim of our cross-sectional study was to evaluate left ventricular structure and function in Type I (insulin-dependent) diabetic patients with diabetic nephropathy. M-mode and Doppler echocardiography were done on 105 Type I diabetic patients with diabetic nephropathy [61 men, age (means ± SD) 44 ± 9 years, and albuminuria [median(range)] 567(10–8188) mg/24 h, serum creatinine 109 (53–558) μmol/l], and 140 Type I diabetic patients with persistent normoalbuminuria [79 men, 47 ± 10 years, urinary albumin excretion rate 8 (0–30) mg/24 h, and serum creatinine 81 (55–121) μmol/l]. Patients with and without nephropathy were comparable with respect to sex, body mass index, and duration of diabetes. Arterial blood pressure was slightly higher in patients with nephropathy: 140/79 ± 17/9 mm Hg vs 134/78 ± 15/8 mm Hg, p < 0.01, and the majority of proteinuric patients received antihypertensive drugs, 84 vs 17 %, respectively, p < 0.001. Left ventricular mass index was increased in the nephropathic group (means ± SD) 100.6 ± 23.9 g/m² compared with the normoalbuminuric group 91.4 ± 21.9 g/m², p = 0.002. Left ventricular hypertrophy was found more often in patients with nephropathy 23 (14–31)% compared with patients with normoalbuminuria 9 (5–14)%, p < 0.005. Diastolic function, assessed by the ratio between the peak diastolic velocity and the peak atrial systolic velocity (E/A ratio) and isovolumic relaxation time, was reduced in patients with vs without nephropathy: 1.17 ± 0.29 vs 1.34 ± 0.32, and 81.7 ± 16.5 vs 74.6 ± 14.5, p < 0.001 and p = 0.002, respectively. Systolic function was about the same and normal in both groups. Our study suggests that an increase in left ventricular mass index and a decrease in diastolic function occurs early in the course of diabetic nephropathy. [Diabetologia (1999) 42: 76–80] Received: 16 April 1998 and in final revised form: 5 August 1998     

Transcapillary escape rate and albuminuria in Type II diabetes. Effects of short-term treatment with low-molecular weight heparin (Short Communication)

Summary The relation between urinary albumin excretion rate (UAE), transcapillary escape rate of albumin (TER_alb), haemostatic factors, ambulatory blood pressure, and metabolic variables was investigated in 45 Type II (non-insulin-dependent) diabetic patients without overt nephropathy or uncontrolled blood pressure. We enrolled 44 patients in a placebo controlled study to test the effects of 3 week long treatment with low-molecular weight heparin (tinzaparin) on the same variables. BMI, 24 h systolic and diastolic blood pressure, plasma concentrations of triglycerides, fasting glucose, factor VIII, von Willebrand factor (vWf), fibrinogen, α-2 macroglobulin, and fibronectin were notably higher in patients with increased albuminuria compared with normoalbuminuric patients, whereas the TER_alb was similar in the two groups. TER_alb correlated with fasting plasma glucose. UAE correlated more closely than TER_alb with 24 h ambulatory blood pressure, vWf, and factor VIII. Urinary albumin excretion rate was unchanged during tinzaparin [28.9 ± 5.6 vs 28.1 ± 6.0 μg/min (geometric mean (antilog SD)] vs placebo (18.0 ± 5.4 vs 17.6 ± 5.3 μg/min), and no change was found in TER_alb [6.3 ± 1.6 vs 6.0 ± 1.5 %/h (means ± SD), and 6.3 ± 1.5 vs 5.6 ± 1.8 %/h; tinzaparin versus placebo, respectively]. Only minor changes were observed in blood pressure, lipids, glycaemic control and haemostatic factors. This study shows no correlation between albuminuria and transcapillary escape rate in Type II diabetic patients without overt nephropathy or uncontrolled blood pressure. UAE is related to markers of atherosclerosis, endothelial injury and dysfunction, and haemostatic factors. Moreover, UAE correlates much more than TER_alb with 24 h ambulatory blood pressure, von Willebrand factor, and factor VIII. Finally, short-term treatment with tinzaparin does not change the transvascular or glomerular leakage of albumin. These results indicate that TER_alb is not a sensitive marker of microvascular dysfunction in such patients and that factors other than abnormal glycosaminoglycan metabolism may contribute to the vascular damage of these patients. [Diabetalogia (1999) 42: 60–67] Received: 2 February 1998 and in final revised form: 1 September 1998     

Diurnal blood pressure variations in normoalbuminuric type 1 diabetic patients

Abstract. Objective. To test the hypothesis that normoal-buminuric type 1 diabetic patients segregate into groups with normal and elevated ambulatory blood pressure. To evaluate diurnal variation of blood pressure assessed by individual or fixed night-time periods. Design. Cross-sectional study. Setting. Tertiary referral centre. Subjects. Inclusion criteria for type 1 diabetic patients (n = 33): normal urinary albumin excretion (UAE age < 45 < 20 μg min^?1), diabetes duration ≤ 20 years, age 45 years. Healthy controls (n = 33) were matched for sex and age. Main outcome measure. Twenty-four hour, day-time, night-time and night/day ratio of ambulatory blood pressure. Results. Twenty-four-hour blood pressure in diabetic patients did not differ significantly from a normal distribution. The 24-h systolic blood pressure was higher in diabetic patients than in healthy controls (difference: 6 mmHg, 95% confidence interval (CI) from 1 to 10 mmHg, P < 0.05), while no significant differences were found for diastolic values. The 24-h systolic blood pressure in diabetic patients with UAE above the median value (5.8 μg min^?1) was higher than for those with lower UAE (difference: 7 mmHg, 95% CI from 0.5 to 13 mmHg, P < 0.05). The night/day ratio of diastolic blood pressure based on individual informations of the night period was (mean ± SD) 80 ± 6% in diabetic patients and 78 ± 8% in controls (difference: 2%, 95% CI from ?1 to 5%, not significant [NS]). This ratio increase significantly (P < 0.00001) to 90 ± 5% in diabetes and to 84 ± 7% in controls if a fixed night period from 22.30 hours to 06.30 hours was assumed. Conclusions. It was not possible to identify a well-separated group of normoalbuminuric type 1 diabetic patients with elevated ambulatory blood pressure. Values of UAE above the median in diabetic patients are associated with higher ambulatory blood pressure. Assessment of the night/day variation from fixed time-points should be abandoned because this leads to a serious underestimation of the nocturnal reduction in blood pressure.     

Flow-induced dilatation in isolated resistance arteries from control and streptozotocin-diabetic rats

Summary Acetylcholine-induced vasodilatation is impaired in animal models of insulin-dependent diabetes mellitus (IDDM), and may result from altered nitric oxide synthesis or release. The response to intraluminal flow, a more physiologically relevant stimulus for nitric oxide release, is unknown. This study examined flow-induced responses in isolated resistance arteries from male Sprague-Dawley control and streptozotocin-diabetic (45 mg/kg i.v, 4 week duration) rats. Mesenteric arteries (4–5th order) were dissected and cannulated on a pressure myograph (mean internal diameter ± SEM at 40 mmHg, control 223 ± 8, n = 9 vs diabetic 239 ± 12 μm, n = 8, NS). Arteries were preconstricted with noradrenaline (1 μmol/l) and intraluminal pressure raised and maintained at 80 mmHg. Luminal flow was raised in incremental steps (0–1.27 μl/s). Arteries from control animals dilated to flow while arteries from diabetic animals constricted (% change in internal diameter ± SEM at 0.79 μl/s: control 13.46 ± 6.52, n = 9 vs diabetic –7.44 ± 3.38 %, n = 8; p < 0.005). Incubation with Nω-nitro-l-arginine methyl ester (0.1 mmol/l) abolished flow responses in arteries from controls but not from diabetic rats. In conclusion, impaired flow-induced nitric oxide-mediated vasodilatation may contribute to vascular disease in IDDM. [Diabetologia (1998) 41: 34–39] Received: 18 June 1997 and in final revised form: 12 September 1997     

Studies on the mass action effect of glucose in NIDDM and IDDM: evidence for glucose resistance

Summary The ability of hyperglycaemia to enhance glucose uptake was evaluated in 9 non-insulin-dependent (NIDDM), 7 insulin-dependent (IDDM) diabetic subjects, and in 6 young and 9 older normal volunteers. Following overnight insulin-induced euglycaemia, a sequential three-step hyperglycaemic clamp (+ 2.8 + 5.6, and + 11.2 mmol/l above baseline) was performed with somatostatin plus replacing doses of basal insulin and glucagon, 3-³H-glucose infusion and indirect calorimetry. In the control subjects as a whole, glucose disposal increased at each hyperglycaemic step (13.1 ± 0.6, 15.7 ± 0.7, and 26.3 ± 1.1 μmol/kg · min). In NIDDM (10.5 ± 0.2, 12.1 ± 1.0, and 17.5 ± 1.1 μmol/kg · min), and IDDM (11.2 ± 0.8, 12.9 ± 1.0, and 15.6 ± 1.1 μmol/kg · min) glucose disposal was lower during all three steps (p < 0.05–0.005). Hepatic glucose production declined proportionally to plasma glucose concentration to a similar extent in all four groups of patients. In control subjects, hyperglycaemia stimulated glucose oxidation (+ 4.4 ± 0.7 μmol/kg · min) only at + 11.2 mmol/l (p < 0.05), while non-oxidative glucose metabolism increased at each hyperglycaemic step (+ 3.1 ± 0.7; + 3.5 ± 0.9, and + 10.8 ± 1.7 μmol/kg · min; all p < 0.05). In diabetic patients, no increment in glucose oxidation was elicited even at the highest hyperglycaemic plateau (IDDM = + 0.5 ± 1.5; NIDDM = + 0.2 ± 0.6 μmol/kg · min) and non-oxidative glucose metabolism was hampered (IDDM = + 1.8 ± 1.5, + 3.1 ± 1.7, and + 4.3 ± 1.8; NIDDM = + 0.7 ± 0.6, 2.1 ± 0.9, and + 7.0 ± 0.8 μmol/kg · min; p < 0.05–0.005). Blood lactate concentration increased and plasma non-esterified fatty acid (NEFA) fell in control (p < 0.05) but not in diabetic subjects. The increments in blood lactate were correlated with the increase in non-oxidative glucose disposal and with the decrease in plasma NEFA. In conclusion: 1) the ability of hyperglycaemia to promote glucose disposal is impaired in NIDDM and IDDM; 2) stimulation of glucose oxidation and non-oxidative glucose metabolism accounts for glucose disposal; 3) both pathways of glucose metabolism are impaired in diabetic patients; 4) impaired ability of hyperglycaemia to suppress plasma NEFA is present in these patients. These results suggest that glucose resistance, that is the ability of glucose itself to promote glucose utilization, is impaired in both IDDM and NIDDM patients. [Diabetologia (1997) 40: 687–697] Received: 20 August 1996 and in revised form: 5 March 1997     

Macro-microangiopathy and endothelial dysfunction in NIDDM patients with and without diabetic nephropathy

Summary The Steno hypothesis suggests that albuminuria reflects widespread vascular damage (proliferative retinopathy and severe macroangiopathy) due to a generalized vascular (endothelial) dysfunction. We assessed this concept in NIDDM (non-insulin-dependent diabetic) patients with (13 female/39 male, age 60 ± 7 years, group 1) and without (12 female/41 male, age 61 ± 7 years, group 2) diabetic nephropathy compared to matched non-diabetic subjects (7 female/15 male, age 58 ± 8 years, group 3). A 12-lead ECG was recorded and coded blindly using the Minnesota Rating Scale; the World Health Organization cardiovascular questionnaire was used to assess past and present evidence of myocardial infarction, angina pectoris, stroke, and peripheral vascular disease (digital systolic blood pressure determination). The degree of diabetic retinopathy was scored from fundus photography. The following variables were measured: transcapillary escape rate of albumin (initial disappearance of intravenously injected ¹²⁵I-labelled human serum albumin), plasma concentrations of prorenin (radioimmunoassay) and serum concentrations of von Willebrand factor (enzyme-linked immunoadsorbent assay). Prevalence of ischaemic heart disease (ECG reading) (49/20/5)% and peripheral vascular disease as indicated by reduced systolic blood pressure on big toe (69/30/14)% was significantly higher in group 1 vs group 2 (p < 0.01) and in group 2 vs group 3 (p < 0.01), respectively. The prevalence and severity of retinopathy was higher in group 1 vs 2 (p < 0.01). Transcapillary escape rate of albumin (%/h) was elevated in group 1 and 2 as compared to control subjects: 7.9 (4.3–13.7); 7.4 (3.7–16.4) vs 6.0 (3.4–8.7), (p < 0.005), respectively. Plasma prorenin activity (IU/ml) was raised in group 1 and group 2 as compared to group 3: 272 (59–2405); 192 (18–813), and 85 (28–246), p < 0.001, respectively. Serum von Willebrand factor (IU/ml)was elevated in group 1 as compared to group 2 and 3: 2.07 (0.83–4.34); 1.60 (0.30–2.99) and 1.50 (1.00–2.38), p < 0.001, respectively. Our study demonstrated that NIDDM patients with and without albuminuria had increased transcapillary escape of albumin and raised prorenin activity, whereas only those with albuminuria had increased von Willebrand factor. Patients with NIDDM may have abnormal endothelial function in the absence of albuminuria. [Diabetologia (1996) 39: 1590–1597]     

Amelioration of nerve conduction velocity following simultaneous kidney/pancreas transplantation is due to the glycaemic control provided by the pancreas

Summary Diabetic polyneuropathy is a common, disabling chronic complication of diabetes mellitus. Previous studies have suggested that combined pancreas-kidney transplantation can ameliorate nerve conduction. The relative contribution of the correction of hyperglycaemia and uraemia on nerve function is still a matter of debate. Nerve conduction velocity (NCV) was assessed before and after simultaneous pancreas and kidney transplantation, and before and after pancreas graft failure in five insulin-dependent diabetic (IDDM) patients affected by severe diabetic polyneuropathy. Sensory and motor NCV were recorded in five nerves and expressed as a cumulative index for each patient. Metabolic control was evaluated by fasting blood glucose and glycosylated haemoglobin levels. NCV index was below normal values before transplant: –3.8 ± 0.7 (normal value: 0.89), improved 1 and 2 years after transplant: –3.1 ± 1.3 and –2.6 ± 0.9 (p = 0.0019), stabilised until pancreas failure and deteriorated to pre-transplant values 2 years after pancreas graft failure: –3.6 ± 1.0 (p = 0.034). Fasting blood glucose levels worsened after pancreas graft failure. HbA_{1 c} levels, in the normal range during functioning pancreas graft (6.6 ± 0.6 %), deteriorated after its failure (8.0 ± 0.6 %, p = 0.04). Kidney function was preserved. These data support a positive effect of pancreas transplantation per se on NCV in IDDM subjects with diabetic polyneuropathy, thus demonstrating that metabolic control provided by a self-regulated source of insulin not only halts but also ameliorates nerve function, even if polyneuropathy is advanced. [Diabetologia (1997) 40: 1110–1112] Received: 14 May 1997 and in revised form: 12 June 1997     

The JEVIN trial: A population-based survey on the quality of diabetes care in Germany: 1994/1995 compared to 1989/1990

Summary Since 1990 in most Eastern European countries health care systems have been decentralized or are undergoing the processes of decentralization. Increasingly, diabetic patients are no longer treated by diabetologists but by non-specialized physicians. During the same period structured treatment and teaching programmes have been introduced and health care is increasingly influenced by the St. Vincent declaration. To show the effect of these changes on the quality of diabetes care 90 % (n = 244) of all insulin-treated diabetic patients aged 16 to 60 years and living in the city of Jena (100 247 inhabitants) were studied in 1994/1995. The results were compared with the baseline examination of 1989/1990 (n = 190). HbA_1c (HbA_1c/mean normal) in IDDM patients under specialized care was similar in 1994/1995 (1.54 ± 0.27, n = 47) to 1989/1990 (1.52 ± 0.31, n = 131, p = 0.0018), but higher under non-specialized care (1.71 ± 0.38, n = 80, p = 0.0087). In the total group of NIDDM patients there was no significant change in HbA_1c (1994/1995: 1.75 ± 0.4, n = 117, vs 1989/1990: 1.78 ± 0.4, n = 59, p = 0.67), but with a tendency to higher HbA_1c under non-specialized (1.81 ± 0.4, n = 79) compared to specialized care (1.66 ± 0.39, n = 38, p = 0.06). Incidence of severe hypoglycaemia (IDDM 0.13; NIDDM 0.04), ketoacidosis (0.02; 0.01) and the prevalence of nephropathy (21 %; 35 %) and neuropathy (24 %; 38 %) remained unchanged in comparison to 1989/1990, whereas there was an increase in the prevalence of diabetic retinopathy. Specialized care is mandatory for patients with IDDM. [Diabetologia (1997) 40: 1350–1357] Received: 3 April 1997 and in revised form: 18 June 1997     

Electrophysiological assessment of visual function in newlydiagnosed IDDM patients

Summary Electrophysiological tests (electroretinogram, oscillatory potentials, visual evoked potentials, in the basal condition and after photostress) reveal an abnormal function of the visual system in insulin-dependent diabetic (IDDM) patients. The aim of our work was to assess whether electrophysiological abnormalities in visual function exist in newly-diagnosed diabetic patients free of any fluorangiographic signs of retinopathy. Ten control subjects (age 28.7 ± 2.44 years) and ten IDDM patients (age 25.2 ± 6.78 years; disease duration 5.3 ± 3.5 months) in stable metabolic control (HbA_{1 C} 7.5 ± 1.1 %) were evaluated. Flash-electroretinograms and oscillatory potentials were similar in both groups. Visual evoked potentials (VEP) recorded under basal conditions showed that P100 latency was significantly increased in the diabetic patients compared to control subjects (p < 0.01), while N75-P100 amplitude was similar in both groups. The recovery time of VEP after photostress was equivalent in diabetic patients and control subjects. The impaired basal VEPs suggest an early involvement of the nervous conduction in the optic nerve. However, the preserved flash-electroretinogram and the normal recovery time after photostress indicate that a short disease duration does not induce physiopathological changes in the outer retinal layers or in the macular function. [Diabetologia (1995) 38: 804–808] Received: 8 July 1994 and in revised form: 23 December 1994     

Reduced capillary hydraulic conductivity in skeletal muscle and skin in Type I diabetes: a possible cause for reduced transcapillary fluid absorption during hypovolaemia

Aims/hypothesis. Patients with Type I (insulin-dependent) diabetes mellitus have a reduced transcapillary fluid absorption from skeletal muscle and skin and thus defective plasma volume regulation during hypovolaemia. Our aim was to find whether a defective capillary filtration coefficient or impaired transcapillary driving force are aetiologic factors for this reduction. Methods. We investigated 11 diabetic patients (diabetes duration 6.9 ± 1.1 years, age 26 ± 1 years), without complications and 12 control subjects (26 ± 1 years). Their capillary filtration coefficient was measured in the upper arm using a volumetric technique at rest and during lower body negative pressure (LBNP). We calculated the driving force for transcapillary fluid transfer. Results. The increase in heart rate and the decrease in systolic blood pressure during lower body negative pressure were similar in diabetic and control subjects. The resting capillary filtration coefficient was decreased in the diabetic subjects, 0.033 ± 0.003 vs 0.051 ± 0.007 ml · 100 ml^–1· min^–1· mmHg^–1 (p < 0.05). During lower body negative pressure, the capillary filtration coefficient increased 35 % in both groups compared with resting capillary filtration coefficient and was still decreased in diabetes; 0.046 ± 0.004 compared with 0.069 ± 0.006 ml · 100ml^–1· min^–1· mmHg^–1 (p < 0.01). The established driving force during lower body negative pressure was 1.37 ± 0.11 vs 1.30 ± 0.15 mmHg (NS) in diabetic and control subjects, respectively. Conclusions/interpretation. Our study indicates that a reduced capillary filtration coefficient rather than defective regulation of transcapillary driving force, is the reason for the reduced transcapillary fluid absorption during hypovolaemic circulatory stress found in Type I diabetic patients. [Diabetologia (2000) 43: 1178–1184] Received: 28 January 2000 and in revised form: 8 May 2000     

Antioxidant treatment of experimental diabetic retinopathy in rats with nicanartine

Summary In order to study the contribution of oxidant stress to the pathogenesis of experimental diabetic retinopathy, male streptozotocin diabetic Lewis rats were treated with the antioxidant and lipid-lowering compound nicanartine (80 mg/kg; n = 8, blood glucose level 16.7 ± 3.9 mmol/l; HbA₁ 11.8 ± 1.6 %) by oral supplementation for 6 months and compared with untreated diabetic (n = 6; blood glucose 18.1 ± 1.4 mmol/l; HbA₁ 11.5 ± 1.5 %) and untreated, non-diabetic rats (n = 8; blood glucose 4.0 ± 0.6 mmol/l; HbA₁ 4.8 ± 0.9 %). Diabetic retinopathy was evaluated by computer-assisted quantitative morphometry including measurement of autofluorescent advanced glycated end-products and immunohistochemistry for heme oxygenase I. Antioxidant treatment did not inhibit the 3.1-fold increase of retinal advanced glycation end products, while the expression of heme oxygenase I in both vascular and glial structures was markedly reduced. Chronic hyperglycaemia led to a 37.3 % increase in endothelial cells (p < 0.001 vs normal controls) and a 26.6 % reduction in pericyte numbers (p < 0.001 vs controls). Both abnormalities were significantly ameliorated by nicanartine (p < 0.001 vs diabetic controls). No effect was observed on the formation of acellular capillaries or microaneurysms. These data indicate that antioxidant therapy with nicanartine is of limited benefit in diabetic retinopathy, at least in the rodent model of streptozotocin-induced diabetes. [Diabetologia (1997) 40: 629–634] Received: 19 December 1996 and in revised form: 20 February 1997