Transcapillary escape rate of albumin in hypertensive patients with Type 1 (insulin-dependent) diabetes mellitus

Summary Diabetic patients with elevated urinary albumin excretion rate (incipient or clinical nephropathy) also have an increased transcapillary escape rate of albumin. This study was designed to clarify whether this is caused by a general vascular dysfunction or by elevated systemic blood pressure. The systemic blood pressure and the transcapillary escape rate of albumin were measured in the following groups after 4 weeks without antihypertensive treatment: Group 1 — eleven healthy control subjects. Group 2 — ten Type 1 (insulin-dependent) diabetic patients with incipient nephropathy (urinary albumin excretion rate: 30–300 mg/24 h) and normal blood pressure. Group 3 — eleven non-diabetic patients with essential hypertension. Group 4 — nine Type 1 diabetic patients with hypertension but normal urinary albumin excretion (<30 mg/24 h). Group 5 — eleven Type 1 diabetic patients with nephropathy (urinary albumin excretion rate > 300 mg/24 h) and hypertension. Systolic and diastolic blood pressure were similar in the three hypertensive groups: group 3, 148±8/95±6; group 4, 150±12/94±8 and group 5; 152±12/92±7mmHg, but significantly elevated (p<0.001) compared to control group 1,117±12/74±9 and group 2, 128±7/82±4 mm Hg. The transcapillary escape rate of albumin was similar in the control subjects (5.2±2.7%) and the subjects in the normoalbuminuric groups 3 and 4 (6.2±1.9 and 5.1±1.4 %, respectively) and significantly lower (p<0.001) than in patients with elevated urinary albumin excretion without or with hypertension group 2, 10.1±2.8 and group 5, 11.4±5.7 %. The increased transcapillary escape rate of albumin in patients with elevated urinary albumin excretion is unrelated to moderate systemic hypertension and may therefore be caused by alterations in the properties of the capillary walls.     

Acute reduction of arterial blood pressure reduces urinary albumin excretion in Type 1 (insulin-dependent) diabetic patients with incipient nephropathy

Summary The effect of an acute reduction in arterial blood pressure upon kidney function was studied in 12 patients with Type 1 (insulin-dependent) diabetes and incipient nephropathy (persistent microalbuminuria). Renal function was assessed by measurement of the glomerular filtration rate (single bolus ⁵¹Cr-EDTA technique) and by the urinary albumin excretion rate (radioimmunoassay). The study was performed twice within 2 weeks, with the patients receiving a slow intravenous injection of either clonidine (225 g) or saline (154 mmol/l) in random order. Clonidine reduced arterial blood pressure from 125/79±13/8 to 104/68±9/7 mmHg (p < 0.01), urinary albumin excretion rate from 68 (31–369) to 46 (6–200) g/min (median and range) (p<0.01), and fractional clearance of albumin in all patients (median 29%) (p < 0.01). Glomerular filtration rate was 110±11 before and 106±13 ml/min/1.73 m² after clonidine injection. The blood glucose concentration was 15±4mmol/l before and 14±5 mmol/l after clonidine injection. In agreement with findings in animal studies, our results suggest that microalbuminuria is to a large extent pressure-dependent, probably because of glomerular hypertension, and that autoregulation of glomerular filtration rate is normal in most patients with incipient diabetic nephropathy.     

Leucocyte Na+/H+ antiport activity in Type 1 (insulin-dependent) diabetic patients with nephropathy

Summary The development of proteinuria in Type 1 (insulin-dependent) diabetic patients may depend on predisposition to essential hypertension in addition to poor glycaemic control. Previous work has shown increased leucocyte Na^–/H⁺ antiport activity in essential hypertension and increased erythrocyte Li⁺/Na⁺ exchange in Type 1 diabetic patients with proteinuria. To test whether susceptibility to nephropathy in Type 1 diabetes was linked to abnormalities of leucocyte Na⁺/H⁺ antiport activity, we measured the intracellular pH and kinetics of the Na⁺/H⁺ antiport in 19 Type 1 diabetic subjects with, and 15 diabetic subjects without albuminuria and compared them to 25 matched normal control subjects. Intracellular pH (mean ±SD 7.59 ± 0.14) and maximal transport capacity of the antiport (V_max 87.7 ±24.9 mmol· 1^–1·min^–1) were higher in diabetic subjects with albuminuria compared to normotensive control subjects (pH 7.44±0.09; V_max 55.6±10.3 mmol·1^–1min^–1; p <0.001 for both), similar to the defect described in essential hypertension. These differences were not seen in diabetic subjects with normal urinary albumin/creatinine ratios (pH 7.46 ±0.09; V_max 61.0 ±13.6mmol·1^–1min^–1). Buffering characteristics of the leucocytes at different pH in the Type 1 diabetic subjects with albuminuria differed from normal control subjects and diabetic subjects with normal urinary albumin/creatinine ratios. We conclude that increased leucocyte Na⁺/H⁺ antiport activity, a known marker of essential hypertension, is usually associated with nephropathy in Type 1 diabetes.     

Early glomerular hyperfiltration and the development of late nephropathy in Type 1 (insulin-dependent) diabetes mellitus

Summary We performed a follow-up study of the glomerular function in a series of 29 Type 1 (insulin-dependent) diabetic patients who had been studied 18 years previously. Initial median duration of diabetes was 2 years (range 0–9) and at follow-up 21 (17–27) years. At follow-up, 8 diabetic patients exhibited increased urinary albumin excretion rate 515 (32-3234) g/min with glomerular filtration rates significantly lower than 21 diabetic patients with normal urinary albumin excretion (85 vs 126ml/min/1.73 m²; p<0.01). The patients with increased urinary albumin excretion rate also had higher arterial blood pressure (145/90 vs 120/80) mm Hg; p<0.02) and increased frequency of proliferative retinopathy (7 out of 8 vs 2 out of 21; p = 0.0001) as compared to the group with normal urinary albumin excretion. However, we found no association of increased urinary albumin excretion rate (incipient or overt nephropathy) to early glomerular hyperfiltration as median initial glomerular filtration rate was 142 ml/min/1.73 m² in the diabetic patients with increased urinary albumin excretion and 147 ml/min/1.73 m² in the patients with normal excretion rate (p>0.05)     

Impaired autoregulation of glomerular filtration rate in Type 1 (insulin-dependent) diabetic patients with nephropathy

Summary The effect of acute lowering of arterial blood pressure upon kidney function in nephropathy was studied in 13 patients with long-term Type 1 (insulin-dependent) diabetes. Ten normal subjects (six normotensive and four hypertensive) and five short-term Type 1 diabetic patients without nephropathy served as controls. Renal function was assessed by glomerular filtration rate (single bolus ⁵¹Cr-EDTA technique) and urinary albumin excretion rate (radial immunodiffusion). The study was performed twice within 2 weeks, with the subjects receiving an intravenous injection of either clonidine (225 g) or saline (0.154 mmol/l). The arterial blood pressure was similar in the diabetic patients with nephropathy (mean 136±11 mmHg) and in the non-diabetic control subjects 88±5 (mean 140±25 mmHg). The clonidine injection induced sim- 92±15 ilar reductions in mean arterial blood pressure in all three groups (16–18 mmHg). While glomerular filtration rate and urinary albumin excretion rate remained unchanged in both control groups after clonidine injection, glomerular filtration rate dimished from 78 to 71 ml/min per 1.73 m² (p<0.01), and urinary albumin excretion declined from 1707 to 938 g/min (p<0.01) in the patients with diabetic nephropathy. Our results suggest that an intrinsic vascular (arteriolar) mechanism underlying the normal autoregulation of glomerular filtration rate, i. e. the relative constancy of glomerular filtration rate that occurs in response to rather wide variations in perfusion pressure, is defective in diabetic nephropathy.     

Sustained reduction of proteinuria in Type 2 (non-insulin-dependent) diabetes following diet-induced reduction of hyperglycaemia

Summary To determine whether sustained control of hyperglycaemia in Type 2 (non-insulin-dependent) diabetic patients would diminish proteinuria, the effect of hypocaloric diet therapy (500 kcal/day) on proteinuria was assessed in obese, Type 2 diabetic patients (n=24) and compared with results obtained for obese subjects with normal glucose tolerance (n=7) and impaired glucose tolerance (n=6). Diet therapy of similar mean duration resulted in similar percentage weight loss (mean percentage of original weight ±SEM) in diabetic (13.6±1.6%), glucose intolerant (16.4±3.3%) and obese nondiabetic (11.0±1.0%) subjects. Following therapy, plasma glucose concentrations 2h after an oral glucose load declined in the diabetic (18.34±0.81 to 10.67±0.50 mmol/1, mean ±SEM; p<0.001) and in the glucose intolerant subjects (10.2±0.3 to 7.3±0.4 mmol/l, p<0.01) while remaining unchanged in the obese non-diabetic subjects (7.09±0.23 to 6.77±0.32 mmol/l, NS). Concentrations of total protein of plasma origin and albumin in 24-h urine collections were quantified by a sensitive immunonephelometric assay using specific antisera. Initially, 24-h excretion of total protein and albumin were elevated in the diabetic [mg protein/24 h; (median±95% confidence limits): 63 (42–138), p<0.05; albumin: 26 (14–56), p<0.05] and glucose intolerant subjects [protein:52 (13–92), NS; albumin: 24 (3–61), NS] compared with the non-diabetic subjects [protein: 20 (5–38); albumin: 6.2 (3.5–9.5)]. Following diet therapy, both total protein and albumin excretion were reduced significantly in diabetic subjects (p<0.001) and similar decreases were observed in clearance rates of protein and albumin. Initially, 11 out of the 24 diabetic subjects had 24-h albumin excretion in the subclinical range (>30, < 500 mg/24h), whereas following diet therapy, only three out of the 11 had subclinical albuminuria. For all subjects, the decrease in albumin excretion following diet therapy was significantly correlated with the initial albumin excretion (r=0.63, p<0.0001). In one diabetic subject, whose glucose tolerance and albumin excretion were sequentially monitored for 14 months, the decreases in glycaemia and proteinuria observed in the first month of therapy persisted after discontinuation of diet therapy. Thus, metabolic control of Type2 diabetes by a hypocaloric diet produced significant sustained reductions in proteinuria. The question remains whether or not this retards the development of clinical nephropathy or end stage renal disease.     

Apolipoprotein(a) and cardiovascular disease in Type 2 (non-insulin-dependent) diabetic patients with and without diabetic nephropathy

Summary The relative mortality from cardiovascular disease is on average increased five-fold in Type 2 (non-insulin-dependent) diabetic patients with diabetic nephropathy compared to non-diabetic subjects. We assessed the possible contribution of dyslipidaemia in general and elevated serum apolipoprotein(a) (apo(a)) in particular. Type 2 diabetic patients with normo-, micro- and macroalbuminuria were compared with healthy subjects. Each group consisted of 37 subjects matched for age, sex and diabetes duration. Serum creatinine in the nephropathy group was 105 (54–740) mol/l. The prevalence of ischaemic heart disease (resting ECG, Minnesota, Rating Scale) was 57, 35, 19 and 2% in macro-, micro- and normoalbuminuric diabetic patients and healthy subjects, respectively. The prevalence of ischaemic heart disease was higher in all diabetic groups as compared to healthy subjects (p<0.05), and higher in macroalbuminuric as compared to normoalbuminuric diabetic patients (p<0.01). There was no significant difference between apo(a) in the four groups: 161 (10–1370), 191 (10–2080), 147 (10–942), 102 (10–1440) U/l (median (range)) in macro-, micro- and normoalbuminuric groups and healthy subjects. Serum total-cholesterol, HDL-cholesterol and LDL-cholesterol were not significantly different when comparing healthy subjects and each diabetic group. Apolipoprotein A-I was lower (p<0.05) in all diabetic groups as compared to healthy subjects (nephropathy vs healthy subjects): 1.50±0.25 vs 1.69±0.32 g/l (mean ± SD). Triglyceride was higher (p<0.05) in patients with nephropathy and microalbuminuria as compared to healthy subjects (nephropathy vs healthy subjects): 2.01 (0.66–14.7) vs 1.09 (0.41–2.75) mmol/l (median (range)). Apolipoprotein B was higher (p<0.02) in patients with nephropathy as compared to the other three groups (nephropathy vs healthy subjects): 1.54±0.47 vs 1.33±0.30 g/l. In conclusion, our case-control study has confirmed that Type 2 diabetic patients with increased urinary albumin excretion frequently suffer from dyslipidaemia and cardiovascular disease. However, our study revealed no significant elevation in serum concentration of apo(a) in patients with diabetic nephropathy, but numbers were small.     

Diabetic nephropathy is associated with low-grade inflammation in Type 1 diabetic patients

Aims/hypothesis Increased concentrations of C-reactive protein and interleukin-6, a finding suggestive of the presence of inflammation, have been observed in Type 2 diabetes. In such patients, C-reactive protein was predictive of diabetic nephropathy. Studies on low-grade inflammatory markers and nephropathy in Type 1 diabetic patients have shown conflicting results. Therefore we studied whether low-grade inflammation is associated with diabetic nephropathy in Type 1 diabetic patients.Methods We divided 194 Type 1 diabetic patients into three groups from the Finnish Diabetic Nephropathy Study based upon their albumin excretion rate. Patients with normoalbuminuria (n=67) had no antihypertensive medication or signs of cardiovascular disease, while patients with microalbuminuria (n=64) or macroalbuminuria (n=63) were all treated with an angiotensin-converting enzyme inhibitor, a drug that could attenuate low-grade inflammation. As a measure of insulin sensitivity we used estimated glucose disposal rate. C-reactive protein was measured by radioimmunoassay and interleukin-6 by high sensitivity enzyme immunoassay.Results C-reactive protein was higher in micro- and macroalbuminuric patients compared to normoalbuminuric patients (normoalbuminuria 2.0±1.7, microalbuminuria 2.6±1.7, macroalbuminuria 2.9±2.5 mg/l; p=0.016), while interleukin-6 increased in parallel with the severity of the renal disease (1.9±1.5, 2.9±3.3, 3.6±3.1 ng/l; p<0.0001). In multiple regression analysis albumin excretion rate was the only variable independently associated with C-reactive protein (p=0.03), whereas albumin excretion rate (p=0.0003), HDL-cholesterol (p=0.0135) and duration of diabetes (p=0.0176) were independently associated with interleukin-6.Conclusions/interpretation Low-grade inflammatory markers are associated with diabetic nephropathy in Type 1 diabetic patients. The predictive value needs to be assessed.Abbreviations DN diabetic nephropathy - CRP C-reactive protein - eGDR estimated glucose disposal rate - FinnDiane finnish diabetic nephropathy study - MDRD modification of diet in renal disease     

Kidney function in newly diagnosed Type 2 (non-insulin-dependent) diabetic patients, before and during treatment

Summary Glomerular filtration rate, kidney volume, and urinary albumin excretion rate were studied in otherwise healthy newly diagnosed Type 2 (non-insulin-dependent) diabetic patients, untreated at diagnosis, after short-term treatment and after 3 months treatment. In 10 patients (Group A) glomerular filtration rate (measured by the plasma clearance of 51-Cr-EDTA) decreased from the time of diagnosis 106.2±14.6 ml·min^–1·1.73m^2–1 (mean±SD) to 95.9±13.7 ml·min^–1·1.73m^2–1 after 3 months treatment (p=0.049). At the same time, mean plasma glucose was reduced from 13.3±3.2 mmol/l to 6.5±1.1 mmol/l. The fall in mean plasma glucose was correlated to the reduction in glomerular filtration rate, r=0.76, p=0.011. Kidney volume as measured by ultrasonic scanning was reduced from 264.0±33.7 ml/l.73m² to 210.8±23.8 ml/l.73 m² (p<0.005). The relative decline in urinary albumin excretion rate was correlated to the fall in glomerular filtration rate, r=0.69, p=0.026. In 15 patients (Group B) 24-h urine collections were made during 9.5±3.2 days, urinary albumin excretion rate fell from the first to the last day in hospital from 14.0×/÷3.0 g/min (geometric mean ×/÷ tolerance factor) to 7.0×/÷2.7 g/min p=0.015. The relative decline was correlated to the change in mean plasma glucose, r=0.65, p=0.032.Thus, kidney function in Type 2 diabetic patients is influenced by metabolic control, although to a lesser extent than is seen in Type 1 (insulin-dependent) diabetic patients with comparable glycaemic control. Urinary albumin excretion is reduced by improvement in glycaemic control, to which it is significantly correlated. Long-term consequences of reduction in urinary albumin excretion on the development of diabetic nephropathy and on survival remains to be elucidated.     

Magnetic resonance imaging of the kidney in Type 1 (insulin-dependent) diabetes mellitus

Summary Reductions in the physiological cortical to medullary signal intensity ratio are found in magnetic resonance scans of the kidney in non-diabetic glomerular disease. Whether this abnormality can also characterise patients with Type 1 (insulin-dependent) diabetes mellitus and nephropathy is not known. We measured the cortical to medullary signal intensity ratio in magnetic resonance images of the kidney in 34 patients with Type 1 diabetes (ten with either clinical proteinuria or raised serum creatinine or both, nine with microalbuminuria, seven with normal urinary albumin excretion and long duration of diabetes and eight with Type 1 diabetes of short duration). The cortical to medullary signal intensity ratio showed a trend to cluster at lower values in the normoalbuminuric patients with normal serum creatinine rather than in the nine healthy individuals, independent of Type 1 diabetes duration (1.47 ± 0.06 and 1.41 ± 0.13 vs 1.63 ± 0.16; five groups-Scheffé F-test p = 0.05–0.1). Among the Type 1 diabetic patients, significant reductions in the cortical to medullary signal intensity ratio characterised overt nephropathy (1.19 ± 0.15, p <0.05 vs all groups), but not microalbuminuria (1.47 ± 0.13, p = NS), concomitantly with low glomerular filtration rate and elevated fractional excretion of uric acid, but independent of glycaemic control. The determinants of the renal cortical to medullary signal intensity ratio in Type 1 diabetes are uncertain. Reductions in the cortical to medullary signal intensity ratio may be a late finding in diabetic nephropathy, and parallel the accompanying impairment in kidney haemodynamics. Magnetic resonance imaging of the kidney may not offer clues in the early diagnosis of diabetic nephropathy.     

Transcapillary escape rate and relative metabolic clearance of glycated and non-glycated albumin in Type 1 (insulin-dependent) diabetes mellitus

Summary The transcapillary escape rate and relative plasma disappearance of glycated and non-glycated albumin were measured in 25 male Type 1 (insulin-dependent) diabetic patients using a double tracer technique. The patients were divided into three groups on the basis of their urinary albumin excretion: group 1, normal albumin excretion (<30 mg/24h) (n=8); group 2, microalbuminuria (30–300 mg/24 h) (n=9); and group 3, clinical nephropathy (>300 mg/24 h) (n=8). Six male age-matched non-diabetic persons served as control subjects. The transcapillary escape rate of glycated albumin was similar in group 1 and control subjects (4.7±2.1 versus 5.1±1.7%), but significantly increased in group2 (7.0±1.7%,p<0.05) and in group 3 (7.9±3.1%,p<0.05). The transcapillary escape rate of glycated albumin was slightly lower than that of non-glycated albumin in all groups, but significant only in normal control subjects. No difference in the catabolic rate of glycated and non-glycated albumin was found. We conclude that the in vivo effects of glycation on the clearance and transcapillary passage of albumin are small and not likely to play any significant role in the development of late diabetic microvascular complications.     

Effects of indomethacin on kidney function in Type 1 (insulin-dependent) diabetic patients with nephropathy

Summary We investigated whether the glomerular synthesis of prostaglandins modulates the glomerular filtration rate and albumimiria in diabetic nephropathy. The urinary excretion of immunoreactive prostaglandin E₂ (253pg/min) was significantly elevated in eight Type 1 (insulin-dependent) diabetic women with nephropathy as compared with nine normoalbuminuric Type 1 diabetic women (95pg/min) and 11 non-diabetic women (132 pg/min), respectively (p<0.01). Glomerular filtration rate (single bolus ⁵¹Cr-EDTA technique) and albuminuria (radioimmunoassay) were measured twice within two weeks in the eight Type 1 diabetic women with nephropathy. All eight patients were on a diabetic diet without sodium restriction. The study was performed as a randomized doubleblind trial, with the patients receiving either indomethacin (150mg/day) or placebo for three days prior to the kidney function studies. Indomethacin treatment induced a significant reduction in urinary prostaglandin E₂ excretion (73%, p<0.01), glomerular filtration rate diminished from 120±18 to 106±17ml/min/1.73m² (p<0.05), albuminuria declined from 148 to 69 g/min (median and range) (p<0.05) and fractional clearance of albumin diminished 42% (p<0.05). Blood glucose concentrations were comparable during the placebo and indomethacin treatment, 13.4±4 versus 14.2±3 mmol/l, respectively. Our results suggest that glomerular filtration rate in early diabetic nephropathy is dependent on the enhanced glomerular synthesis of vasodilating prostaglandins.     

Abnormalities in plasmas concentrations of lipoproteins and fibrinogen in Type 1 (insulin-dependent) diabetic patients with increased urinary albumin excretion

Summary Type 1 (insulin-dependent) diabetic patients with clinical nephropathy have a more than ten-fold increase in mortality of cardiovascular diseases compared with diabetic patients without nephropathy. The risk factors for cardiovascular disease, plasma concentrations of lipoproteins and fibrinogen, were investigated in 74 long-term diabetic patients: 37 with normal urinary albumin excretion, 20 with incipient nephropathy and 17 with overt clinical nephropathy based on urinary albumin excretion. The groups were matched according to sex, age and diabetes duration. The concentration of plasma cholesterol, very low density lipoprotein cholesterol, low density lipoprotein cholesterol, triglyceride and fibrinogen rose with increasing urinary albumin excretion. The plasma concentrations of these lipoproteins and fibrinogen were 11–14% higher in the patients with incipient nephropathy and 26–87% higher in the patients with overt clinical ne phropathy compared with the patients without nephropathy. The plasma concentration of high density lipoprotein cholesterol was unaffected by albuminuria. Patients with normal urinary albumin excretion and HbA_1c>8.0% had significantly higher very low density lipoprotein- and lower high density lipoprotein cholesterol concentrations compared with patients with HbA_1c<8.0%. Simple addition of the described risk factors can only account for a minor part of the greatly increased cardiovascular mortality in patients with diabetic nephropathy. An additional and possibly more decisive factor might be a change in the arterial wall, a change which promotes lipid accumulation and/or facilitates thrombus formation.     

The increase in albuminuria induced by exercise is not associated with preferential excretion of glycated albumin in Type 1 (insulin-dependent) diabetic patients

Summary The increase in urinary albumin excretion induced by acute exercise in Type 1 (insulin-dependent) diabetic patients is associated with the urinary excretion of cationic proteins. To test whether the renal excretion of glycated albumin (more anionic than non-glycated albumin) is affected by exercise, we submitted seven normoalbuminuric (albumin excretion rate < 30 mg/24 h) Type 1 diabetic patients and six well-matched healthy subjects to an exercise test (600 kpm/min for 20 min) on a bicycle ergometer, preceded and followed by a 1-h resting period. The selectivity index (renal clearance of non-glycated/glycated albumin) was not significantly different among the pre-exercise, exercise and post-exercise periods, either in the normal subjects (1.01±0.03 vs 1.08±0.06 vs 1.08±0.05) or in the diabetic patients (1.25±0.09 vs 1.20±0.07 vs 1.20+-0.06), whereas it was significantly higher (p < 0.05) in diabetic patients compared to healthy subjects during pre-exercise. These results are not consistent with the hypothesis that acute exercise may induce a preferential excretion of glycated albumin.     

Increased transcapillary escape rate of albumin in Type 1 (insulin-dependent) diabetic patients with microalbuminuria

Summary The transcapillary escape rate, intravascular mass and outflux of albumin were measured in 75 Type 1 (insulin-dependent) diabetic patients. The groups were defined as: group 1: normal urinary albumin excretion, <30 mg/24 h (n=21); group 2: microalbuminuria, 30–300 mg/24 h (n=36); group 3: diabeticnephropathy, <300 mg/24 h (n=18). Fifteen sex- and age-matched non-diabetic persons served as control subjects. The diabetes duration was: group 1: 20±9 years, group 2: 17±5 years, group 3: 19±7 years. The transcapillary escape rate of albumin was similar in controls and group 1 (5.0±1.8 versus 5.2±1.5%) and was significantly higher in the microalbuminuric group 2 and group 3 (8.1±2.2 versus 8.1±2.3 %). The differences were not explained by differences in metabolic control or blood pressure at the time of investigation. The outflux of albumin was also higher in group 2 than in group 1 and controls (7.1 ± 2.0 versus 5.3±1.5 and 5.1±2.0 g/h × 1.73 m²). It was indistinguishable from controls in group 3 (5.8±1.5 g/h × 1.73 m²) because of a reduced intravascular mass of albumin (p<0.01) in group 3. In conclusion, a universal vascular leakage of albumin is an early event in the development of diabetic nephropathy, with the leakage of albumin being fully developed in the microalbuminuric patient. In contrast, long-term diabetic patients with normal urinary albumin excretion have a normal transcapillary escape rate of albumin.     

Prevalence of microalbuminuria in children with Type 1 (insulin-dependent) diabetes mellitus

Summary The prevalence of microalbuminuria was determined in children aged 7 to 18 years with Type 1 (insulin-dependent) diabetes of more than 2 years' duration. All patients (n =102) attending 2 diabetes clinics were asked to collect 2 overnight timed urine samples for albumin analysis by radioimmunoassay. Complete urine collection was obtained in 97 patients (95%). Overnight urinary albumin excretion rates were also measured in 36 healthy children matched for age and sex. Nineteen of the 97 patients (20%) had microalbuminuria, i. e. overnight urinary albumin excretion rates above the upper normal level (14 g/min) in both urine collections. Microalbuminuria was only demonstrated in patients aged 15 years, prevalence 37% (19/52 patients). Arterial blood pressure was elevated, mean 122/84±11/9mmHg, in the microalbuminuric group (19 patients) compared to the age-matched normoalbuminuric diabetic group (33 patients), mean 117/74±10/10 mm Hg,p < 0.001. The prevalence of simplex retinopathy was identical in these two groups, i. e. 25%. Glycosylated haemoglobin was slightly higher in the microalbuminuric patients,p < 0.10. Our cross-sectional study reveals a high prevalence (37%) of persistent microalbuminuria, a stage highly predictive of later development of diabetic nephropathy, in Type 1 diabetic children aged 15 years.     

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. The incidence of persistent microalbuminuria in normotensive insulin-dependent diabetic patients is 2% per year, and development of persistent microalbuminuria is a strong predictor of overt nephropathy. Development of hypertension is frequent in the early course of microalbuminuria and treatment modalities for normotensive patients with microalbuminuria are urgently needed.     

Thrombogenic factors are related to urinary albumin excretion rate in Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetic patients

Summary Parameters of haemostasis, endothelial cell markers and lipid peroxide levels were studied in 64 Type 1 (insulin-dependent) and 94 Type 2 (non-insulin-dependent) diabetic patients according to their urinary albumin excretion rate in comparison with age-matched control subjects. We determined plasma levels of fibrinogen (Clauss' method), coagulation factor VII:activity (clotting assay), factor VII antigen, protein C and S antigen, von Willebrand factor antigen,d-dimer concentration (ELISA), and lipid peroxide levels (thiobarbituric acid) in relation to urinary albumin excretion rate (RIA). Significant positive correlations were found between urinary albumin excretion rate and plasma fibrinogen (p<0.005,p<0.02), factor VII activity (p<0.0002,p<0.002), factor VII antigen (p<0.0001,p<0.001), protein C (p<0.003,p<0.05), and lipid peroxides (p<0.02,p<0.004) in Type 1 as well as in Type 2 diabetes. Von Willebrand factor (p<0.001) and protein S (p<0.0005) correlated with albuminuria only in patients with Type 1 diabetes. Although most of the haemostatic abnormalities are already found in normoalbuminuric patients, the significant positive correlations to urinary albumin excretion indicate that endothelial cell damage and coagulation disorders deteriorate with the progression of diabetic nephropathy.     

Relationship of renal size to nephropathy in Type 1 (insulin-dependent) diabetes

Summary Thirty-five patients with Type 1 (insulin-dependent) diabetes mellitus and 90 normal subjects had renal size (renal area index) determined by X-ray and also had examination of renal biopsies by light and electron microscopy. Renal area index of 206±32 cm²/1.73 m² (mean±SD) in the Type 1 diabetic patients exceeded that in the normal subjects (180±25 cm²/1.73 m², p<0.001). In the diabetic patients, the renal area index correlated with creatinine clearance (r=+0.43, p<0.05), but did not correlate with urinary albumin excretion, or the electron microscopic measurements of percentage total mesangium and glomerular basement membrane width. In diabetic patients with clinical nephropathy or severe glomerulopathy on biopsy, the kidneys may remain large. Thus, renal size does not indicate the severity of diabetic renal lesions on biopsy.     

Post-exercise Albuminuria Does Not Predict Microalbuminuria in Type 1 Diabetic Pantients

To investigate whether post-exercise urinary albumin excretion in Type 1 diabetic children and adolescents may prospectively predict the development of microalbuminuria, we have assessed post-exercise urinary albumin excretion before and after 6.2 ± 1.7 years of follow-up in 66 diabetic children and adolescents. Post-exercise urinary albumin excretion rose significantly above the pre-exercise values in diabetic patients by 2.7 (-3.8 to 84.2) μ min^?1 (p < 0.001) and in a group of 9 healthy individuals by 3.9 (-0.7 to 13.7) μg min^?1 (p < 0.02) without significant differences betbeen groups. Post-exercise albuminuria was greater in postpubertal than prepubertal 9.8 vs 4.3 μg min^?1 (p < 0.03) and pubertal 9.8 vs 6.0 μg min^?1 (p < 0.02) patients; post-exercise changes in urinary albumin excretion were also positively related to glycated haemoglobin (r = 0.293; p < 0.05). Eight out of 66 patients developed microalbuminuria at follow-up. Urinary albumin excretion at follow-up was comparable between patients with normal and abnormal post-exercise urinary albumin excretion; moreover post-exercise urinary albumin excretion was within the normal range in 5 out of 8 patients with microalbuminuria at follow-up. In conclusion post-exercise albuminuria does not seem to be a useful predictor of the onset of microalbuminuria in Type 1 diabetic children and adolescents.