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

Glomerular permeability and trauma: a correlation between microalbuminuria and Injury Severity Score

OBJECTIVE

To determine if there is a correlation between an increase in glomerular permeability, the magnitude of trauma, and the severity of illness.

DESIGN

Prospective study.

SETTING

Two university hospital intensive care units.

PATIENTS

Forty consecutive critically ill trauma patients admitted directly to the intensive care unit within 120 mins of their injuries.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

For each patient, urine was collected from the time of admission until 7 am the next day. Within 48 hrs, only one sample of all urine collected (5 mL) was examined for microalbuminuria and urinary creatinine. Results were expressed as the microalbuminuria/urinary creatinine ratio (MACR). The mortality rate in the intensive care unit, Injury Severity Score at the moment of admission, Acute Physiology and Chronic Health Evaluation III score, and Simplified Acute Physiology Score in the first 24 hrs were calculated for each patient. The data were analyzed using the Pearson test for linear regression and Student's t-test. During the first 24 hrs after trauma, there was an increase of MACR (6.9 +/- 0.6 mg/mmol) above normal (reference range, <3 mg/mmol) that was positively correlated with Injury Severity Score (31.4 +/- 1.9; r2 = .73, p < .05). However, there was no correlation between MACR, Acute Physiology and Chronic Health Evaluation III score, Simplified Acute Physiology Score, and mortality rate.

CONCLUSIONS

Patients with trauma show an increase in glomerular permeability during the first 24 hrs after injury. The magnitude of this increase is correlated with the extent of trauma but does not seem significant enough to be predictive of severity of illness and/or outcome.

Microalbuminuria and transcapillary albumin leakage in essential hypertension

Microalbuminuria (an increased urinary albumin excretion that is not detectable by the usual dipstick methods for macroproteinuria) predicts cardiovascular events in essential hypertensive patients. A possible reason for this behavior is that albumin leaks through exaggeratedly permeant glomeruli exposed to the damaging impact of subclinical atherogenesis. To evaluate this possibility, the transcapillary escape rate of albumin (TER(alb), the 1-hour decline rate of intravenous (125)I-albumin), a parameter that estimates the integrity of systemic capillary permeability, albuminuria, blood pressure, echocardiographic left ventricular mass, lipids, and body mass index were measured in 73 uncomplicated, glucose-tolerant men with essential hypertension and normal renal function; 53 were normoalbuminuric, and 20 were microalbuminuric. Twenty-one normotensive age-matched male subjects were the controls. TER(alb) was higher in hypertensives, a behavior explained in part by a positive correlation with blood pressure values, although body mass index, lipids, and left ventricular mass showed no association. Transcapillary albumin leakage values did not differ between normoalbuminuric and microalbuminuric patients and were unrelated to albuminuria. Blood pressure, particularly systolic, and cardiac mass were higher in microalbuminuric patients in whom albuminuria correlated with both cardiovascular variables and indicated the influence of the hemodynamic load on urinary albumin levels. Thus, TER(alb), a parameter influenced by the permeability surface area product for macromolecules and the filtration power across the vascular wall, is altered in essential hypertensives. However, this abnormality is dissociated from the amount of albuminuria, which is contrary to the hypothesis that a higher albumin excretion reflects a greater degree of systemic microvascular damage in essential hypertension.

The impact of hypoalbuminemia in kidney-pancreas transplant recipients

BACKGROUND

Hypoalbuminemia is associated with poorer outcomes in renal transplantation. Diabetes can compound hypoalbuminemia's detrimental effects. Kidney-pancreas transplantation alters the diabetic milieu; yet, some patients continue to be hypoalbuminemic.

METHODS

We retrospectively analyzed 232 patients who underwent simultaneous kidney-pancreas transplantation (SPK) between 1993 and 1997 to determine the incidence and clinical correlates of hypoalbuminemia in SPK recipients. Post-SPK hypoalbuminemia was defined as a serum albumin level < or =3.5 g/dl. Univariate analyses were performed to determine whether post-SPK hypoalbuminemia was associated with pre-SPK variables. The effect of albumin level and hypoalbuminemia on the risk of post-SPK events (cardiac events, cytomegalovirus [CMV] infection, rejection, readmission, kidney and pancreas graft failure, and death) was examined with a Cox proportional hazards model.

RESULTS

The study population consisted of 149 men and 83 women. Average follow-up was 2.0+/-1.3 years. Hypoalbuminemia (serum albumin level < or =3.5 g/dL) was most common early after SPK (3 months: 44% of evaluable patients were hypoalbuminemic; 12 months: 15.3%; 36 months: 8.3%). Acute rejection episodes and readmission were the most common adverse events after SPK transplantation. There were 24 episodes of renal allograft loss and only 5 cardiac events. Ten SPK recipients died during the study time period. SPK-related hypoalbuminemia was associated with an increased risk for CMV infection (risk ratio [RR] 2.5; P<0.02), renal graft failure (RR 2.41; P=0.05), pancreas graft failure (RR 3.66; P=0.01), and a trend toward an increased risk for death (RR 2.8; P=0.19).

CONCLUSIONS

Post-SPK hypoalbuminemia resolves over time in many patients. Persistent post-SPK hypoalbuminemia is associated with an increased risk for CMV infection, graft loss, and a trend toward decreased survival. Efforts to improve nutrition, as it may affect hypoalbuminemia in SPK recipients, may be one strategy for improving SPK outcomes.

Pronatriodilatin gene polymorphisms, microvascular permeability, and diabetic nephropathy in type 1 diabetes mellitus

Approximately 30% of diabetic patients develop nephropathy, the appearance of which is partially under genetic control. Atrial natriuretic peptide (ANP) has associated physiologic effects on the kidney. This study was conducted to examine the relationship between a newly identified and known polymorphism at the pronatriodilatin (PND) gene locus and renal involvement in type 1 diabetic subjects. Of 454 type 1 diabetic patients (219 men, 235 women), 323 showed no sign of nephropathy, 79 had incipient renal involvement, and 52 established nephropathy; 58 healthy control subjects were examined for comparison. Allele frequencies (C708 versus T708) were: 0.95 and 0.05 in normoalbuminuric patients, respectively; 0.88 and 0.12 in microalbuminuric patients; 0.96 and 0.04 both in those with overt nephropathy and in healthy control subjects (P = 0.011). Patients with incipient nephropathy were in disequilibrium compared with the total diabetic cohort (P = 0.02). In the same populations, an additional genotype for ScaI polymorphism of the PND gene was tested. The A1 and A2 allele frequencies were: 0.21 and 0.79 in normoalbuminuric patients; 0. 13 and 0.87 in microalbuminuric patients; 0.06 and 0.94 in type 1 diabetic subjects with overt nephropathy; and 0.20 and 0.80 in healthy control subjects, respectively (P < 0.0001). A subset of 55 normotensive patients with type 1 diabetes, well matched for clinical features, plasma ANP levels, and microvascular permeability to macromolecules, was investigated on the basis of the C708/T and A2/A1 polymorphisms. Both transcapillary escape rate of albumin (TERalb) and plasma ANP levels were significantly lower in patients with the T708 than with C708 allele, as well as in the A1 than in A2 allele (TERalb: T708 versus C708: 5.5+/-1.7 versus 7.8+/-2.0%/h, P = 0.0001; plasma ANP levels: 8.3+/-3.9 versus 15.3+/-7.7 pg/ml, P = 0.0003; A1 versus A2: 6.05+/-2.2 versus 7.3+/-2.1%/h, P = 0.044; 8.53+/-4.6 versus 14.5+/-7.4 pg/ml, P = 0.0024, respectively). Thus, in a large ethnically homogeneous cohort of diabetic subjects, our data show: (1) a significant association of C708/T polymorphism with microalbuminuria in long-term diabetes and with both lower plasma ANP levels and widespread albumin leakage; and (2) a strong association between ScaI polymorphism and both diabetic nephropathy and plasma ANP concentrations. These results suggest a possible role of PND gene in conferring protection from nephropathy and microvascular damage in type 1 diabetes.

Effects of heparin on vascular dysfunction in diabetic rats

1. Treatment with heparin has beneficial effects in diabetic nephropathy. The occurrence of increased urinary albumin excretion in diabetic patients reflects general vascular dysfunction, including increased transcapillary permeability of macromolecules. The aim of the present study was to evaluate the effects of heparin on vascular dysfunction in diabetic rats. 2. Male Sprague-Dawley rats were used in two studies. Diabetes was induced by 65 mg/kg, i.v., streptozotocin. In one study, diabetic rats were dosed subcutaneously with different heparin fractions for 8 months and the transcapillary escape rate of albumin (TERalb) was measured in anaesthetized animals. In the other study, heparin was given for 6 weeks, followed by tissue albumin clearance measurements in awake rats. Normal and diabetic rats receiving saline served as controls. 3. Blood glucose did not differ among the diabetic groups and ranged from 22 to 26 mmol/L. The mean (+/- SD) TERalb was increased by diabetes compared with values in normal rats (17.5 +/- 3 vs 14.1 +/- 3.3%/h, respectively). Neither unfractionated nor low molecular weight heparin significantly affected this increase. [131I]-Albumin clearance was significantly increased in diabetic rats in the eye, skin and skeletal muscle tissues compared with normal rats (0.17-0.40 vs 0.1-0.23 microL plasma/g per min). Low molecular weight heparin treatment did not affect the increased organ albumin clearance. 4. In conclusion, heparin treatment does not affect diabetes-induced vascular dysfunction as expressed by increased TERalb and clearance of albumin in rats.

Dealing with diabetic nephropathy

Nephropathy may develop in patients with type 1 diabetes because poor glycemic control produces effects that eventually lead to glomerular scarring and renal failure. The worse and more prolonged the hyperglycemia, the greater the risk of diabetic nephropathy. In patients with type 2 diabetes, hyperglycemia, as well as insulin resistance and generalized vascular disease, is involved in the pathogenesis of nephropathy. The glomerular changes of early diabetic nephropathy can be identified only by renal biopsy or by testing for microalbuminuria. Once macroalbuminuria occurs (albumin excretion rate, > 300 mg/day), usually after type 1 diabetes has been present for 10 to 15 postpubertal years, end-stage renal disease is almost inevitable. However, aggressive control of hypertension in diabetic patients without microalbuminuria helps avoid nephropathy, and tight glycemic control in those with microalbuminuria can avoid or delay its onset. Even when macroalbuminuria is present, treatment can prolong renal function. Aggressive antihypertensive therapy, especially with ACE inhibitors, can reduce renal decline by half. Avoiding circumstances that may damage the kidneys (e.g., use of radiocontrast materials or nephrotoxic drugs, dehydration, hyperlipidemia, urinary tract infection, buildup of AGEs) is critical. Some treatment methods are controversial (dietary protein restriction) or still under investigation (use of injected or oral heparin) but may help delay renal transplantation or dialysis.

Albumin infusion in humans does not model exercise induced hypervolaemia after 24 hours

We rapidly infused 234 +/- 3 mL of 5% human serum albumin in eight men while measuring haematocrit, haemoglobin concentration, plasma volume (PV), albumin concentration, total protein concentration, osmolality, sodium concentration, renin activity, aldosterone concentration, and atrial natriuretic peptide concentration to test the hypotheses that plasma volume expansion and plasma albumin content expansion will not persist for 24 h. Plasma volume and albumin content were expanded for the first 6 h after infusion (44.3 +/- 1.9-47.2 +/- 2.0 mL kg-1 and 1.9 +/- 0.1-2.1 +/- 0.1 g kg-1 at pre-infusion and 1 h, respectively, P < 0.05), but by 24 h plasma volume and albumin content decreased significantly from 1 h post-infusion and were not different from pre-infusion (44.8 +/- 1.9 mL kg-1 and 1.9 +/- 0.1 g kg-1, respectively). Plasma aldosterone concentration showed a significant effect of time over the 24 h after infusion (P < 0.05), and showed a trend to decrease at 2 h after infusion (167.6 +/- 32.5(-1) 06.2 +/- 13.4 pg mL-1, P = 0.07). These data demonstrate that a 6.8% expansion of plasma volume and 10.5% expansion of plasma albumin content by infusion does not remain in the vascular space for 24 h and suggest a redistribution occurs between the intravascular space and interstitial fluid space.

Urinary albumin excretion in hospitalized patients with acute myocardial infarction. Prevalence of microalbuminuria and correlation to left ventricle wall thickness

Microalbuminuria, a subclinical rise in the urinary albumin excretion, is a risk indicator of atherosclerotic cardiovascular disease. The aim of this study was to measure the urinary albumin excretion in patients with acute myocardial infarction, and to correlate this with known atherosclerotic risk factors. One-hundred-and-twenty-six patients and 56 healthy controls matched for age and sex were studied. The albumin/creatinine concentration ratio in morning urine specimens was calculated as an index of the albumin excretion. Microalbuminuria was defined as a urinary albumin/creatinine concentration ratio above 1 mg/mmol. Urinary albumin excretion (0.88 [95% confidence interval 0.69-1.11] versus 0.51 [0.40-0.63] mg/mmol; p = 0.001) and frequency of microalbuminuria (33 [95% confidence interval 25-41] versus 16 [9-23]%; p = 0.03) were higher in patients than controls. This difference was independent of blood pressure, body weight, smoking, diabetes mellitus, renal disease, and thrombolytic treatment. There was a positive correlation between urinary albumin excretion and thickness of the left ventricle wall (R = 0.28; p = 0.001) which was independent of blood pressure. Follow-up examination of the patients will reveal whether microalbuminuria increases the risk for recurrence of acute myocardial infarction.

Microalbuminuria: a marker to increased renal and cardiovascular risk in diabetes mellitus

The presence of persistent microalbuminuria in IDDM is strongly predictive of the future development of end stage renal failure and of cardiovascular disease to a lesser extent. Screening for microalbuminuria is an essential component of modern diabetes practice, as effective antihypertensive therapy, and particularly, the use of angiotensin converting enzyme inhibitors is of proven benefit in retarding progression of renal disease. Cost benefit analysis justifies the expense of microalbuminuria screening programmes and early intervention. It has been estimated that the use of angiotensin converting enzyme inhibitors in microalbuminuric IDDM will save 5200 Pounds-11,000 Pounds per year of life saved. Angiotensin converting enzyme inhibitors are not free of side-effects, and it is therefore essential, given the intrinsic variability of the albumin excretion rate, and the regression to normoalbuminuria of a significant proportion of patients, to confirm the diagnosis of microalbuminuria by repeated measurements prior to the commencement of treatment. The value of intensive glycaemic control is unproven, and further prospective studies are required. There are no proven therapies for the prevention of macrovascular disease in IDDM, although the value of cessation of smoking and aggressive blood pressure control are undoubted in the non-diabetic population. Controversy persists about the value of lipid lowering therapy, especially in young patients, although even in this group there is an increased risk of cardiovascular disease. Microalbuminuria is the strongest known predictor of cardiovascular disease in NIDDM; in contrast to the situation in the non-diabetic population, active lipid lowering therapy is not of proven cardiac benefit, but intervention seems justifiable when taken in the context of the very high prevalence of cardiovascular disease. Microalbuminuria is also predictive of end stage renal disease in NIDDM. Although intervention with angiotensin converting enzyme inhibitors has not been proven to prevent end stage renal disease, stabilisation of albumin excretion rate and creatinine clearance have been demonstrated in normotensive NIDDM, and it seems likely that longer term follow-up studies will confirm the benefit of angiotensin converting enzyme inhibitors in the prevention of end-stage renal disease. The observed predictive power of microalbuminuria as regards both cardiac and renal risk in NIDDM when considered in conjunction with the preliminary results of the benefits of angiotensin converting enzyme inhibition lend further support to the employment of microalbuminuria screening in NIDDM.

Usefulness of microalbuminuria in predicting cardiovascular mortality in treated hypertensive men with and without diabetes mellitus. Risk Factor Intervention Study Group

In the present study we report on the predictive power of microalbuminuria for total and cardiovascular mortality in a prospective study (mean follow up 6.3 years) of treated hypertensive men, aged 50 to 72 years, with (n = 94) and without (n = 345) maturity onset diabetes mellitus. Thirty-three (35.1%) of the hypertensive patients with diabetes mellitus died during the follow-up period compared with 57 patients (16.5%) in the hypertensive group without diabetes mellitus (p <0.0002). In those with diabetes mellitus and hypertension, a log-rank test revealed a lower cardiovascular mortality in the normoalbuminuric group compared with both the microalbuminuric (p = 0.035) and the macroalbuminuric group (p = 0.002). The logarithm of urinary albumin excretion was a predictor of both total (p = 0.009) and cardiovascular (p = 0.001) mortality during the follow-up period using Cox regression analysis. This relation remained significant even after adjustment for other risk factors. HbA1c was also an independent predictor of total and cardiovascular mortality. In patients without diabetes mellitus, the small group of patients with macroalbuminuria had a markedly increased cardiovascular mortality compared with both the microalbuminuric (p <0.0001) and the normoalbuminuric groups (p <0.0001). No difference was observed between the normoalbuminuric and the microalbuminuric groups. Smoking at entry and concomitant cardiovascular disease at entry were independent predictors of cardiovascular mortality in these patients. We conclude that microalbuminuria was an independent predictor for cardiovascular mortality in treated hypertensive men with maturity onset diabetes mellitus. Macroalbuminuria, but not microalbuminuria, predicted cardiovascular mortality in nondiabetic treated hypertensive men.

Advanced glycation end products-driven angiogenesis in vitro. Induction of the growth and tube formation of human microvascular endothelial cells through autocrine vascular endothelial growth factor

This study was undertaken to determine whether and how advanced glycation end products (AGE), senescent macroproteins accumulated in various tissues under hyperglycemic states, cause angiogenesis, the principal vascular derangement in diabetic microangiopathy. We first prepared AGE-bovine serum albumin (BSA) and anti-AGE antiserum using AGE-RNase A. Then AGE-BSA was administered to human skin microvascular endothelial cells in culture, and their growth was examined. The AGE-BSA, but not nonglycated BSA, was found to induce a statistically significant increase in the number of viable endothelial cells as well as their synthesis of DNA. The increase in DNA synthesis by AGE-BSA was abolished by anti-AGE antibodies. AGE-BSA also stimulated the tube formation of endothelial cells on Matrigel. We obtained the following evidence that it is vascular endothelial growth factor (VEGF) that mainly mediates the angiogenic activities of AGE. (1) Quantitative reverse transcription-polymerase chain reaction analysis of poly(A)+ RNA from microvascular endothelial cells revealed that AGE-BSA up-regulated the levels of mRNAs for the secretory forms of VEGF in time- and dose-dependent manners, while endothelial cell expression of the genes encoding the two VEGF receptors, kinase insert domain-containing receptor and fms-like tyrosine kinase 1, remained unchanged by the AGE treatment. Immunoprecipitation analysis revealed that AGE-BSA did increase de novo synthesis of VEGF. (2) Monoclonal antibody against human VEGF completely neutralized both the AGE-induced DNA synthesis and tube formation of the endothelial cells. The results suggest that AGE can elicit angiogenesis through the induction of autocrine vascular VEGF, thereby playing an active part in the development and progression of diabetic microangiopathies.

The acute effect of smoking on systemic haemodynamics, kidney and endothelial functions in insulin-dependent diabetic patients with microalbuminuria

The acute effect of smoking upon arterial blood pressure, urinary albumin excretion rate, glomerular filtration rate and transcapillary escape rate of albumin were investigated in nine normotensive insulin-dependent diabetic patients with microalbuminuria, who had been smoking for 19 (range 4-30) years. In a prospective, open randomized cross-over design, patients were investigated with and without smoking three cigarettes per hour during a 5.5-h period. A rise in systolic blood pressure and heart rate (Takeda TM2420, median (range)) was observed during the smoking day (10(-11 to 14) mmHg and 8 (-1 to 19) beats min-1), compared to the non-smoking day (1 mmHg (-7 to 13) (p = 0.05) and 0 beats min-1 (-2 to 4) (p < 0.01)). Urinary albumin excretion rate (ELISA), glomerular filtration rate (plasma clearance of 51Cr-EDTA) and transcapillary escape rate of albumin (125I-albumin) remained the same with or without smoking. Our study suggests that heavy smoking induces an abrupt rise in systolic blood pressure and heart rate, while vascular leakage of albumin and glomerular filtration rate remain unaltered in normotensive insulin-dependent diabetic patients with microalbuminuria who had been smoking for several years.

Microvascular functional abnormalities in diabetes: the role of the endothelium

The development of techniques for measuring microvascular pressure, flow and permeability in man has allowed the construct of a pathophysiological framework for the development of diabetic microangiopathy. In insulin dependent disease the abnormalities observed conform to the haemodynamic hypothesis with early elevation of capillary pressure playing a primary role. In non insulin dependent diabetes differences are apparent, supporting the concept that changes in microvascular vasodilatory mechanisms may antedate the emergence of diabetes. Given the crucial role played by the endothelium in the regulation of local microvascular haemodynamics it is not surprising that disturbance of this tissue has been implicated in the pathogenetic process, an assertion supported by mounting experimental evidence suggesting that the nitric oxide pathway is crucially involved.

Urinary microalbumin as a marker for intermittent claudication

OBJECTIVE

The urinary microalbumin concentration was analysed in patients with intermittent claudication in order to investigate its usefulness as a marker for intermittent claudication.

MATERIALS AND METHODS

Urinary samples were collected prior to and following exercise in 15 patients with claudication. The patients walked on a treadmill as far as possible until they were stopped by pain. Urinary microalbumin concentration was measured by a latex agglutination system, and the result was considered abnormal when the concentration exceeded 10 mg/g creatinine. The ankle brachial pressure index (ABI) at rest and the time taken for the ankle pressure to return to the resting level following exercise (ABI recovery time) also were measured.

RESULTS

In seven (47%) of the patients, the urinary microalbumin concentration was elevated to more than 10 mg/g creatinine following exercise, while in eight (53%) it remained normal. The ABI recovery time was significantly longer in the patients in whom the microalbumin concentration was elevated, compared to that in patients without an elevated concentration. The urinary microalbumin concentration following exercise was reduced significantly when the walking distance was decreased 50% or 15%. Following vascular bypass surgery, the elevation in urinary microalbumin concentration was reduced.

CONCLUSIONS

The use of urinary microalbumin as a diagnostic marker for intermittent claudication is limited. However, in cases where the concentration is elevated, it can be used to follow the course of the disease.

Serum albumin and mortality after renal transplantation

The incidence, causes, and consequences of hypoalbuminemia after renal transplantation are not well defined. We examined clinical correlates of serum albumin measured at 3 months, 6 months, 1 year, and annually thereafter in 706 renal transplant recipients who survived at least 6 months with a functioning allograft. Follow-up was 7.0 +/- 4.2 years. Hypoalbuminemia (< or = 3.5 g/dL) was most common at 3 months (31%, n = 692), least common at 1 year (12%, n = 656), and then became increasingly common among survivors, for example, 14% (n = 466) at 4 years, 20% (n = 204) at 8 years, and 29% (n = 77) at 12 years after transplantation. By multiple linear regression, variables that correlated (P < 0.05) with lower serum albumin at 3, 6, 12, and 24 months included age, diabetes, proteinuria, and cytomegalovirus infection. Other independent correlates on at least one of these occasions included renal function and chronic disease (malignancy, liver disease, and cardiovascular disease). Serum albumin, as a time-averaged and time-dependent covariate, was a strong independent risk factor for death using Cox proportional hazards analysis (relative risk for each g/dL increment, 0.26; 95% confidence interval, 0.16 to 0.44 [1.00 = no risk]). The effects of albumin on mortality were independent of age, diabetes, serum lipids, renal function, chronic liver disease, malignancies, and cardiovascular disease. The effects of albumin on mortality were evident even when the analysis was restricted to patients dying several years after albumin was measured. Thus, hypoalbuminemia is common and serum albumin is a strong independent risk factor for all-cause mortality after renal transplantation.

Peri-operative assessment of glomerular permeability

Surgical trauma may provoke an increase in glomerular permeability. Microalbuminuria is a subclinical increase in urinary albumin ranging from 20 to 300 mg..-1. This cannot be measured with routine laboratory tests and is estimated by radioimmunoassay. It has been proposed that microalbuminuria, an expression of increased glomerular permeability, serves to reflect a generalised increase in systemic vascular permeability. In this study the degree of microalbuminuria (expressed as microalbuminuria/creatinine ratio to correct for dilutional changes) has been measured in two groups of patients undergoing either videolaparoscopic surgery (group A) or conventional, open, abdominal surgery (group B). The anaesthetic technique was standardised and the duration of surgery similar in the two groups. A significant increase (p < 0.01) in the microalbuminuria/urinary creatinine ratio occurred in patients undergoing open abdominal surgery (group B). This alteration appeared 2 h after surgery but had disappeared 24 h after the end of the operation. During surgery, there was a direct relationship between glomerular permeability and the severity of the surgical insult.

Renal and systemic transvascular albumin leakage in severe atherosclerosis

Microalbuminuria was recently proposed as a novel atherogenic risk factor. The pathophysiological link between microalbuminuria and atherosclerosis may be mediated through an increased generalized transvascular leakage of albumin. To investigate this hypothesis, urinary albumin excretion and clearance and systemic transvascular albumin leakage (TERalb) were measured in 23 patients with severe clinical atherosclerosis and 25 healthy controls. In addition, renal clearances of three other endogenous plasma proteins (IgG, IgG4, and beta 2-microglobulin) and of creatinine were measured. Measurements of urine and serum proteins were done by enzyme-linked immunosorbent assays. TERalb was measured by the fractional disappearance rate of 125I-albumin from the total intravascular compartment in 1 hour after intravenous injection. Glomerular filtration rate was estimated as creatinine clearance. Urinary albumin excretion (geometric means [95% confidence intervals], 10.5 [6.1 to 18.3] versus 5.7 [4.7 to 6.9] micrograms/min; P < .05), fractional urinary albumin clearance (2.8 [1.6 to 4.8] x 10(-6) versus 1.3 [1.0 to 1.6] x 10(-6); P < .05), and TERalb (6.0 [5.5 to 6.5] versus 5.1 [4.5 to 5.8] %/h; P < .05) were higher in patients than in control subjects. Glomerular charge selectivity (ratio of IgG clearance to IgG4 clearance) was lower in patients than in control subjects (1.5 [1.1 to 2.0] versus 2.3 [2.0 to 2.6]; P < .05). These alterations were independent of blood pressure, glomerular filtration rate, tubular function, and smoking status. It is concluded that atherosclerotic vascular disease is associated with renal and systemic transvascular leakiness for albumin. Theoretically, such leakiness may in addition allow for an increased lipid insudation into the large vessel wall, thereby linking microalbuminuria to atherogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma fluorescein binding and transcapillary fluorescein escape rate in renal failure associated with diabetes

Microvascular damage, often resulting in renal failure, is a common complication of diabetes. Transcapillary fluorescein escape rate (TCFER) as monitored by intravital microscopy has been used as an indicator of the extent of capillary damage in diabetes and to assess improvement in microvascular function after combined kidney-pancreas transplant. However, fluorescein anion binds to plasma albumin, and albumin-ligand binding may be altered in the presence of renal disease. The purpose of this study was to compare fluorescein binding by plasma from diabetics with renal failure with plasma from healthy nondiabetics. Fluorescein binding by plasma from seven type I diabetics awaiting kidney-pancreas transplant and seven healthy adults of similar age and sex was studied using ultrafiltration and dialysis. There was no significant difference in the apparent albumin binding of fluorescein at physiologically relevant fluorescein concentrations, even though the TCFER was significantly increased in the diabetics as compared with the controls. Hippurate, a ligand that accumulates in renal failure, did alter fluorescein binding in a defatted albumin solution but not sufficiently to account for the differences in TCFERs. These data indicate that impaired albumin binding of fluorescein does not contribute significantly to the TCFER in diabetics with renal failure.

Increased transcapillary escape rate of albumin in elderly subjects due to long-term smoking habits

Transcapillary escape rate of albumin (TER) expressed as percentage decrease in specific activity of plasma albumin per hour was measured in 44 healthy male subjects, 10 young non-smokers (median age 24.0 years, range 21-33), 10 young smokers (30.5 years, range 27-36), 10 elderly non-smokers (64.0 years, range 51-75) and 14 elderly smokers (61.5 years, range 54-69). In addition urinary albumin excretion rates were measured in 15 of the elderly subjects. The subjects were investigated after overnight fasting and abstention from tobacco. Median TER was 7.33% (interquartile range 5.82-9.90) in the elderly smoking subjects. This value was significantly elevated as compared to elderly non-smokers, 4.47% (2.93-5.83), young non-smokers, 3.70% (2.24-6.30) and young smokers, 4.25% (2.80-4.44). A statistically non-significant (P = 0.064) tendency of a higher urinary albumin excretion rate was observed in elderly smokers. This agrees with other investigations showing slightly increased albuminuria in smokers compared with non-smokers. The differences were not related to differences in blood pressure, plasma cholesterol, weight, or abuse of alcohol in the elderly subjects. Diabetic subjects with an increased TER to levels comparable with levels in long-term smokers have increased urinary albumin excretion rates, which seems to be greater than in long-term smoking subjects. It is suggested that increased TER in long-term smokers may indicate a vascular dysfunction affecting either capillary permeability or endothelial surface area.

Thrombomodulin levels in insulin-dependent diabetic patients with microalbuminuria

Thrombomodulin (TM) plays an important role in the regulation of blood coagulation at the endothelial surface. TM is also present in plasma, where an increase of its level seems to reflect endothelial damage. Since microalbuminuria is associated with an increased atherothrombotic risk and is considered an expression of widespread vascular damage, we evaluated plasma thrombomodulin levels, blood pressure, and plasma lipid values in Type 1 diabetic patients with micro- and normoalbuminuria. Thrombomodulin was measured in 12 microalbuminuric (albumin excretion rate 20-200 micrograms min-1 in 2 of 3 overnight urine collections) and in 12 normoalbuminuric (albumin excretion rate < 20 micrograms min-1) Type 1 diabetic patients matched for age, sex, body mass index, smoking habits, diabetes duration, and glycated haemoglobin. Mean thrombomodulin was significantly higher in micro- than in normalbuminuric group (59.34 +/- 3.58 vs 43.56 +/- 3.52 ng ml-1 p < 0.01). Systolic and diastolic blood pressure were significantly higher in micro- than in normoalbuminuric group (p < 0.05). There was a positive correlation between plasma thrombomodulin and albumin excretion rate (p = 0.013, r = 0.49), and between thrombomodulin and diastolic blood pressure (p = 0.023, r = 0.46) in diabetic patients as a whole but not in the individual groups. These findings suggest the presence of an endothelial injury in microalbuminuric patients.

Management of early nephropathy in diabetic patients

Diabetic patients go through several stages of renal disease, moving from normo- to micro- to macroalbuminuria. Good metabolic control can prevent or postpone the development of microalbuminuria, the earliest sign of diabetic renal disease. Thus, efforts should focus on obtaining the best possible control before the onset of microalbuninuria. In patients with microalbuminuria, blood pressure starts to increase, and early antihypertensive treatment becomes important. Good glycemic control may be difficult to achieve. With overt nephropathy, defined as clinical proteinuria, a relentless decline in glomerular filtration rate (GFR) occurs unless patients are carefully treated with antihypertensive agents. Protein restriction may also be necessary, but a clear beneficial effect of optimized diabetes care is difficult to document. Early screening is recommended, with an emphasis on testing for albuminuria, including microalbuminuria, along with careful control of blood pressure.

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)

Tubular damage in microalbuminuric patients with primary glomerulonephritis and diabetic nephropathy

Tubular damage as suggested by enzymuria and tubular proteinuria is a recognized feature of glomerulonephritis (GN) with clinical proteinuria and both incipient and overt diabetic nephropathy (DN). However, little is known about the presence of tubulopathy in patients with primary GN, microalbuminuria [albumin excretion (AER) 30-300 mg/d] and microhematuria. Three groups were studied. The GN group comprised 17 (2 F) patients with biopsy-proven GN with microalbuminuria. The DN group comprised 35 (14 F) patients with incipient diabetic nephropathy with AER 30-300 mg/d, and controls comprised 38 (15 F) normal subjects with normal AER < 30 mg/d. Serum creatinine, albuminurinuria, transferrinuria, and markers of tubular damage such as urinary excretion of N-acetyl-glucosaminidase (NAG), leucine aminopeptidase (LAP), gamma-glutamyl transferase (gGT), and retinol binding protein (RBP) were measured. GN and DN had comparable degrees of albuminuria, transferrinuria, and LAP excretion, and these were significantly higher than controls. Serum creatinine was significantly higher in GN than DN and controls. DN had significantly higher NAG and RBP, and lower gGT than GN and controls. In both GN and DN groups, both glomerular proteins correlated with each other and NAG correlated significantly to LAP and gGT. Albuminuria correlated to tubular enzymuria in GN group but not in patients with DN. The results suggest that tubular damage is less marked in microalbuminuric patients with GN than those with DN despite similar degree of glomerular proteinuria. The pattern of tubulopathy is also different in the two groups, indicating differences in the pathogenesis of tubular damage in these two clinical settings.

Indications of reduced pulmonary function in type 1 (insulin-dependent) diabetes mellitus

Abnormalities of pulmonary function tests have been described in type 1 (insulin-dependent) diabetes mellitus (IDDM). To better characterise such abnormalities and to verify whether these latter are associated with the presence of diabetic microvascular disease we compared 23 non-smoking patients who had IDDM with 24 non-smoking healthy control subjects strictly matched for sex, age, and body mass index. Compared with controls, diabetic patients had a reduced forced vital capacity (FVC) (87.5 +/- 13.1% vs. 96.4 +/- 13.6% of the predicted; P = 0.03) and forced expiratory volume in 1 s (FEV1) (90.5 +/- 17.7% vs. 101.2 +/- 13.2% of the predicted; P = 0.02). While within the group of patients the presence of retinopathy and autonomic neuropathy were not associated with modifications of pulmonary function tests, those with altered urinary albumin excretion rate (AER > or = 20 micrograms/min; range 21-589) (n = 7) had a significantly lower pulmonary diffusion capacity (DLCO) than the 16 normoalbuminuric subjects (62.6 +/- 7.2% vs. 88.7 +/- 20.1% of the predicted; P = 0.01). Moreover, in the group of patients, DLCO was inversely related with AER (r = -0.43; P = 0.04). In conclusion, IDDM is characterised by reduced FVC and FEV1, while a significant decrease in DLCO may be considered as selectively associated with renal disease.

Microalbuminuria: an important diagnostic tool

The concept of microalbuminuria is reviewed. Measuring the urinary albumin excretion rate and testing for microalbuminuria is well established in the control and treatment of patients with insulin-dependent diabetes mellitus. Microalbuminuria predicts nephropathy and early cardiovascular death. In the presence of microalbuminuria frequent examinations are warranted for early detection of retinopathy, blood-pressure rise, and for optimizing the glycemic control. In patients with non-insulin-dependent diabetes, the independent value of microalbuminuria as a cardiovascular risk factor is not yet clarified. The urinary albumin excretion rate should be measured at diagnosis, because the indications are that presence of microalbuminuria reinforces the urge to intervene against other well-documented cardiovascular risk factors (hypertension, dyslipidemia, tobacco, and obesity). In the nondiabetic population, there is accumulating evidence that an elevated urinary albumin excretion rate is associated with early cardiovascular morbidity and mortality. Large scale cross-sectional and prospective studies are needed in order to clarify further the role of microalbuminuria as an independent risk factor in the background population.

Insulin treatment improves microalbuminuria and other cardiovascular risk factors in patients with type 2 diabetes mellitus

OBJECTIVES

Insulin treatment of patients with type 2 diabetes causes hyperinsulinaemia and improves glycaemic control. We have studied how this affects risk factors for cardiovascular disease.

DESIGN

Patients with secondary failure to oral hypoglycaemic agents were studied whilst still taking oral agents and after insulin treatment for 8 weeks in an open study.

SETTING

Department of Internal Medicine, University Hospital, Linköping.

SUBJECTS

Ten consecutive patients with type 2 diabetes and secondary failure to oral hypoglycaemic agents.

INTERVENTIONS

Switching oral treatment to insulin treatment.

MAIN OUTCOME MEASURES

Effect on several cardiovascular risk factors.

RESULTS

Fasting and postprandial plasma insulin concentrations were increased by insulin treatment whereas C-peptide concentrations were lowered. HbA1c was reduced from 8.9 +/- 0.3% (mean +/- SEM) to 6.3 +/- 0.2% after 8 weeks. There was a weight gain of 2.8 +/- 0.7 kg. Plasma concentrations of total- and very-low-density-lipoprotein (VLDL) cholesterol, VLDL-, low density lipoprotein and high-density-lipoprotein triglycerides were all reduced. The plasma concentration of apolipoprotein B was also lowered. Tissue plasminogen activator antigen measured after venous occlusion showed a significant reduction whilst plasminogen activator inhibitor 1 activity was 26.0 +/- 9.8 IU ml-1 on oral treatment and 18.2 +/- 4.7 IU ml-1 on insulin treatment (NS). Albumin excretion in the urine was reduced and the percentage reduction correlated with the percentage lowering of the tissue plasminogen activator antigen concentration after venous occlusion but not with the percentage change of basal tissue plasminogen activator antigen concentration.

CONCLUSIONS

Insulin treatment of patients with type 2 diabetes and secondary failure to oral hypoglycaemic agents causes hyperinsulinaemia and improves or has no unfavourable effect on several cardiovascular risk factors.

Aminoguanidine reduces regional albumin clearance but not urinary albumin excretion in streptozotocin-diabetic rats

Advanced glycation end-product-formation is thought to play a role in the development of diabetic angiopathy. By altering the structure of different extracellular matrix components advanced glycation end-products might affect vascular and glomerular permeability. In this study we investigated the effect of treatment with an inhibitor of advanced glycation end-product-formation, aminoguanidine, on vascular permeability and the development of albuminuria in streptozotocin-induced diabetic rats. Male Wistar Rp rats were randomized into a control group, a diabetic group, and an aminoguanidine-treated diabetic group. After 8 weeks, 24-h urine collections were taken and rats were implanted with an arterial and a venous catheter. mean arterial blood pressure was determined by intra-arterial measurement. Regional albumin clearances were assessed in the eye, ileum, lung, skeletal muscle and skin using an isotope technique. Mean arterial pressure in the diabetic group was significantly lower in the control and aminoguanidine-treated groups (p < 0.02). Regional albumin clearances were significantly increased in all tissues of diabetic rats compared to control rats (p < 0.05). Aminoguanidine treatment of diabetic rats resulted in a significant decrease of regional albumin clearance in all tissues except the lung (p < 0.05, lung p = 0.07). The development of albuminuria in diabetic rats however, was not affected by aminoguanidine.

Insulin resistance in insulin-dependent diabetic patients with microalbuminuria

In insulin-dependent diabetes, microalbuminuria increases the risk of cardiovascular and renal disease. By means of a euglycaemic hyperinsulinaemic clamp method, we measured total-body glucose utilisation rate and studied the interaction of this measure of insulin sensitivity with known risk factors for cardiovascular disease in 14 diabetic patients with microalbuminuria and 14 with normal albumin excretion (median albumin excretion rate [AER] 56.2 [range 39.2-80.6] vs 8.8 [7.4-10.7] micrograms per min). The two groups were of similar age, duration of diabetes, and body-mass index. Total-body glucose disposal rate was significantly lower in the patients with microalbuminuria than in those without (mean 7.86 [SD 1.40] vs 9.04 [0.90] mg/kg per min; p < 0.05). There were also significant differences between the groups in the daily insulin dose needed for equivalent glucose control (0.76 [0.20] vs 0.65 [0.10] U/kg, p < 0.05), mean systolic blood pressure over 24 h ambulatory monitoring (134 [7] vs 127 [7] mm Hg; p < 0.05), and various plasma lipid concentrations, contributing to a more atherogenic profile in the microalbuminuric group. Total-body glucose disposal rate was inversely correlated with body-mass index and log10 AER. The insulin sensitivity of the microalbuminuric group remained impaired after adjustment for blood pressure and body-mass index. Impaired insulin sensitivity is a feature of insulin-dependent diabetic patients with microalbuminuria, which adds, with other factors, to the increased risks of renal and cardiovascular disease in these patients.

Aminoguanidine treatment increases elasticity and decreases fluid filtration of large arteries from diabetic rats

The accumulation of advanced glycosylation end-products (AGEs) on collagen and the subsequent stiffening of this matrix protein in diabetes has been described many years ago. Structural modification of collagen in the arterial wall might have important effects on arterial elasticity. Aminoguanidine is known to decrease the formation of AGEs. In this study we evaluated the effects of aminoguanidine treatment on different parameters reflecting arterial wall elasticity in diabetic rats. We demonstrated that treatment of diabetic rats with aminoguanidine resulted in a significant increase in carotid static compliance (+39%, P < 0.01 under control conditions, and +27%, P < 0.01 after abolition of vascular tone by KCN), and a decrease in characteristic aortic input impedance (-40%, P < 0.01). The arterial pulse pressure in aminoguanidine-treated rats was decreased (-15%, P < 0.05) and the pulsatile component of left ventricular power output was relatively diminished (-35%, P < 0.05). In addition, we observed a lower fluid filtration across the carotid wall. These results indicate an increased vascular elasticity, an improved left ventricular-arterial coupling, and a decreased vascular permeability in diabetic rats after aminoguanidine treatment, suggesting that AGE-accumulation on collagen negatively affects arterial wall properties in experimental diabetes.

Inhibition of angiotensin-converting enzyme reduces urinary albumin excretion but not regional albumin clearance in experimental diabetes

Albuminuria and increased regional albumin clearance are known to develop concomitantly in diabetes. The anti-proteinuric effect of angiotensin-converting enzyme inhibitor therapy is well established. We studied whether angiotensin-converting enzyme inhibitor therapy with perindoprilat in comparison with conventional antihypertensive treatment could influence the development of increased regional albumin clearance as well as albuminuria in experimental diabetes. Rats with streptozotocin-induced diabetes were randomized into a saline group (n = 7), a perindoprilat (1 mg/kg per day) group (n = 8), and a hydralazine (3 mg/kg per day) group (n = 6); six rats served as non-diabetic controls. After 6-8 weeks, blood pressure was equally reduced in the perindoprilat- and hydralazine-treated groups (P < 0.01). Twenty-four-hour urinary protein and albumin excretion were increased in diabetic rats compared to control rats (P < 0.001). Hydralazine did not reduce 24 h protein or albumin excretion, whereas perindoprilat treatment reduced both (P < 0.001) to levels comparable to those of control rats. Regional albumin clearance, assessed in the eye, ileum, lung, skeletal muscle and skin, was clearly elevated in diabetic rats compared to control rats; however, neither drug therapy had an effect on albumin clearance.

Glomerular filtration and tubular reabsorption of albumin in preproteinuric and proteinuric diabetic rats

Microalbuminuria (26-250 mg/d) is considered to be an indicator of incipient diabetic nephropathy in humans in insulin-dependent diabetes (IDD). However, before microalbuminuria is observed, glomerular alterations, such as glycosylation of the glomerular basement membrane and glomerular hyperfiltration, in IDD may result in increased filtration of albumin before any observed increase in albumin excretion. Glomerular and tubular albumin kinetics were examined in streptozotocin (65 mg/kg body wt, i.v.) diabetic, Munich-Wistar rats at 7-10 (untreated) and 50-70 d (poorly controlled with small doses of insulin) after the onset of diabetes and compared with nondiabetic controls. Additional rats in each condition received acute lysine treatment to prevent tubular protein reabsorption. Urinary albumin excretion and nonvascular albumin distribution volumes were measured in the renal cortex and compared with morphometric measurements of interstitial space and the proximal tubule to assess intracellular uptake of albumin in the proximal tubule. Urinary albumin excretion under anesthesia was not different in 7-10-d IDD versus controls (19 +/- 3 vs. 20 +/- 3 micrograms/min) but increased in the 50-70-d IDD (118 +/- 13 micrograms/min, P < 0.05). Lysine treatment resulted in increased albumin excretion compared with respective nontreatment in 7-10-d IDD (67 +/- 10 micrograms/min, P < 0.05) but not in controls (30 +/- 6 micrograms/min) or in 50-70-d IDD (126 +/- 11 micrograms/min). Glomerular filtration rate was increased both in 7-10-d IDD (2.7 +/- 0.1 ml/min, P < 0.05) and in 50-70-d IDD (2.6 +/- 0.1 ml/min, P < 0.05) compared with control (2.2 +/- 0.1 ml/min). Calculated urinary space albumin concentrations increased early in IDD with 2.5 +/- 0.4 mg% in 7-10-d IDD and 4.9 +/- 0.6 mg% in 50-70-d IDD compared with control (1.4 +/- 0.3 mg%). The increase in filtration of albumin is in excess of that attributable to hyperfiltration before increased albumin excretion early in diabetes. In 50-70-d IDD, absolute tubular reabsorption of albumin is decreased, correlating to the decrease in brush border height of the proximal tubule.

Microvascular investigations in diabetes mellitus

This paper reviews the current literature concerning the different investigative modalities available to assess the microcirculation in diabetic microangiopathy. The advantages and disadvantages of the different invasive and noninvasive methods available are presented objectively. We have concentrated on the tests that provide a quantitative assessment of the microcirculation, including laser Doppler fluxmetry, capillary microscopy, plethysmography, transcutaneous oximetry and radioactive isotope clearance. Some of the invasive methods described are now being replaced by noninvasive equivalents, providing similar information with less discomfort and risk to the patient.

Plasma disappearance of glycated and non-glycated albumin in type 1 (insulin-dependent) diabetes mellitus: evidence for charge dependent alterations of the plasma to lymph pathway

The fractional plasma escape rates of glycated and non-glycated albumin have earlier been measured in groups of Type 1 (insulin-dependent) diabetic patients and control subjects. The escape of non-glycated albumin was similar in control subjects and normoalbuminuric patients, but elevated in patients with micro or macroalbuminuria. In all groups the escape rate of glycated albumin was lower than that of non-glycated albumin. Glycation increases the anionic charge of albumin. To assay for charge-dependent alterations of transport a selectivity index (non-glycated albumin/glycated albumin transport ratio) was determined from the disappearance data. The index was high in control subjects (1.021 +/- 0.0057 (SEM)). This reflects a mean difference between the two escape rates of 2.1% per hour (for comparison the mean of the fractional escape rate of non-glycated albumin of the normal control subjects was 4.7% per hour). The index was numerically even higher in normoalbuminuric patients (1.031 +/- 0.0047 (SEM)), but reached significantly lower levels in patients with microalbuminuria (1.013 +/- 0.0030 (SEM), p < 0.02). Patients with clinical nephropathy had very low levels indicating loss of selectivity (1.002 +/- 0.0068 (SEM), p < 0.001). This pattern accords well with measurements of renal clearance selectivity indices, suggesting a general, progressive deterioration of anionic perivascular barrier components in diabetic microangiopathy. The structural target for these changes is likely to be the glycosaminoglycans of the glomerular basal membrane and the interstitial matrix.

Hypertension in individuals with insulin-dependent diabetes mellitus

Hypertension is known to place the individual with IDDM at high risk for the development of both renal and cardiovascular disease. Recent data suggest that aggressive antihypertensive therapy (angiotensin I converting enzyme inhibitors, prazosin, and calcium channel blockers) have significantly improved overall prognosis and long-term survival for individuals with IDDM. Because in individuals with IDDM the development of both hypertension and renal disease has its roots in childhood, it is important that early and effective antihypertensive treatment begin there.

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

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 +/- 7 mmHg, but significantly elevated (p < 0.001) compared to control group 1, 117 +/- 12/74 +/- 9 and group 2, 128 +/- 7/82 +/- 4 mmHg. 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%.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of endothelium in the pathogenesis of diabetic microangiopathy

Damage caused to the vessel wall by diverse mechanisms may lead to diabetic microangiopathy. Consequently, research work is more and more focusing on the pathophysiology of vascular cells, with particular emphasis on endothelium. This paper reviews the present knowledge on the alterations of small vessel endothelium in diabetes. The most important risk factors for diabetic microangiopathy are the duration of disease and the degree of metabolic control maintained throughout the years. However, genetic factors may also contribute. These are examined first, followed by the presumed roles played by increased protein glycation and the production of Advanced Glycosylation End Products, the "polyol pathway" and free radical generation. Endothelium is a widespread, extremely active organ which regulates complex physiologic functions and its structure and function are discussed in the second section of this review. The third part deals with how diabetes can affect endothelium and describes observations on endothelial metabolism in vitro as well as morphologic and functional alterations in the patients. Unfortunately, the mechanisms leading to progressive degeneration of the microcirculation and organ damage in diabetic patients remain largely unaccounted for.

Cross-sectional study of peripheral microcirculation in diabetic patients with microangiopathy: influence of pancreatic and kidney transplantation

Diabetic vascular lesions and peripheral autonomic neuropathy are both closely linked to long-term metabolic control of diabetes. Transcutaneous oxygen tension (PtcO2) measurements were made to elucidate whether autonomic neuropathy disturbs the cutaneous microcirculatory blood flow, and whether long-term glucose normalization ameliorates such impairment. Twenty-eight type 1 (insulin-dependent) diabetic patients in whom clinically significant macroangiopathy had been excluded by angiography were studied, subdivided into group A (n = 14; before simultaneous pancreas/kidney transplantation (SPKT); mean age 35 years, range 22-51 years; mean duration of diabetes 24 years, (range 15-32) years and group B (n = 14; mean 31 months, range 2-101 months, after successful SPKT; mean age 35 years, range 19-56 years; mean duration of diabetes 22 years, range 14-29 years). On addition there was a group (group C) of age- and sex-matched healthy control subjects (n = 14; mean age 35 years, range 23-62 years). PtcO2 measurements included basal recordings at 44 degrees C on the leg and the foot, functional recordings at 44 degrees C after arterial occlusion of the limb for 4 min, measurements during breathing 5 l oxygen per minute and finally while standing up (stand up dP20/dt). All subjects underwent extensive cardiac autonomic testing. In this cross-sectional study the recordings of basal values and of the functional parameters after arterial occlusion and during breathing oxygen did not differ significantly between groups A, B and C.(ABSTRACT TRUNCATED AT 250 WORDS)

A cross-sectional evaluation of cardiovascular risk factors in coronary heart disease associated with type 1 (insulin-dependent) diabetes mellitus

The contribution from lipoproteins, blood pressure, albuminuria and demographic variables to coronary heart disease in 90 adult subjects with and 172 without Type 1 diabetes mellitus was examined in order to investigate whether risk factors were of equivalent importance in diabetic and non-diabetic coronary heart disease. Coronary heart disease (CHD) was present in roughly 25% of subjects in each group. In Type 1 diabetes those with CHD had significantly higher levels of systolic blood pressure, albumin excretion, serum creatinine, triglycerides, VLDL cholesterol and C-peptide, and reductions in serum concentrations of HDL and HDL2 cholesterol, in comparison to those without. However, the prevalence of smokers, and concentrations of Lp(a), ApoB and fibrinogen were comparable. Blood pressure and HDL cholesterol were higher in the CHD group with Type 1 diabetes in comparison to the nondiabetic group with CHD, although LDL concentrations and the prevalence of Lp(a) concentrations > 200 mg/l were lower. Logistic regression analysis revealed the strongest independent predictors of CHD in Type 1 diabetes were serum triglycerides, systolic blood pressure, age, serum LDL cholesterol, and the daily insulin dosage, whereas in the non-diabetic control group HDL2 cholesterol, Lp(a), ApoA1 and ApoB, total serum cholesterol and body mass index were additional predictors. CHD in Type 1 diabetes appears to be most closely associated with increasing age and levels of blood pressure and total serum lipids. Apolipoproteins and albuminuria did not seem to be important independent predictors of CHD in Type 1 diabetes, whereas the former were more clearly associated with CHD in non-diabetic controls.

Long-term smoking increases transcapillary escape rate of albumin

Transcapillary escape rate of albumin was measured in 11 young and 10 healthy, elderly male subjects. Approximately half of the subjects were chronic cigarette smokers. Transcapillary escape rate of albumin expressed as percentage of decrease in specific activity of plasma albumin per hour averaged 12.3% in long-term smokers. This value was significantly elevated and twice as high as values measured in young smokers and in young and elderly non-smokers. It is concluded that capillary permeability to albumin is increased in long-term smokers. Further studies are warranted to examine the pathophysiological mechanism and to what extent this abnormality is reversible.

Urinary albumin excretion rate (AER) in newly-diagnosed type 2 Indian diabetic patients is associated with central obesity and hyperglycaemia

Urinary albumin excretion rate (AER) was measured in non-diabetic controls (n = 143) and newly diagnosed impaired glucose tolerant (IGT, n = 64) and non-insulin-dependent (type 2) diabetic patients (n = 146). AER progressively increased from non-diabetic [3.7 (1.1-51.3) micrograms/min, median (5-95th centile)] to IGT [4.8 (1.3-53.7)] and diabetic [7.3 (1.4-91.6)] groups. Eight percent of non-diabetic, 19% of IGT and 23% of type 2 diabetic patients showed 'microalbuminuria' (AER, 20-200 micrograms/min) (non-diabetic vs diabetic P less than 0.01, non-diabetic vs IGT NS, IGT vs diabetic NS). AER was directly related to waist-hip ratio (P less than 0.001) and HbA1 (P less than 0.01) in diabetic patients; 80% of diabetic patients with microalbuminuria were men (P less than 0.06 compared to 'normoalbuminuric' diabetic patients). Association of AER with waist-hip ratio was present in men as well as women. Thus, in the newly diagnosed type 2 Indian diabetic patients AER is associated with central obesity in addition to its well known association with hyperglycaemia. Our findings offer a possible explanation for the increased risk of proteinuria in diabetic men than in women because men are centrally more obese. It could also explain previous reports of higher AER in migrant Asian diabetic patients in the U.K. compared to native white Caucasian diabetic patients because Asians are known to be more centrally obese.

von Willebrand factor and early diabetic retinopathy: no evidence for a relationship in patients with type 1 (insulin-dependent) diabetes mellitus and normal urinary albumin excretion

High plasma levels of von Willebrand factor, an indicator of endothelial cell dysfunction, have been reported in both diabetic retinopathy and nephropathy. It is unclear, however, whether von Willebrand factor is related to diabetic retinopathy in the absence of diabetic nephropathy. The relationship between retinal status and plasma von Willebrand factor concentration was investigated in a cohort of 17 patients with Type 1 (insulin-dependent) diabetes mellitus who were followed-up for a median of 42 months. The patients were examined three times. They were selected for having had normal urinary albumin excretion and no evidence of retinopathy (on fundoscopy) at the first and second examination. They were then divided into two groups, according to absence (Group A; n = 9) or presence (Group B; n = 8) of retinopathy on fundoscopy or fluorescein angiography at the third examination. Urinary albumin excretion remained normal in all patients. Plasma von Willebrand factor levels were similar in both groups: (median) 128 vs 123%, 164 vs 132% and 159 vs 130% (first, second and third examination, respectively). Median changes in plasma von Willebrand factor were also similar: +7 vs +9% and +5 vs +1% (first-second and second-third examination). Patients in whom the plasma von Willebrand factor concentration increased had higher systolic blood pressure at the third examination (150 +/- 30 vs 130 +/- 12 mmHg, p = 0.02) when compared to those in whom plasma von Willebrand factor did not increase, but were of similar age and had similar diabetes duration, retinal status, diastolic blood pressure, glycated haemoglobin and serum cholesterol concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Eight to nine year mortality in known non-insulin dependent diabetics and controls

Microalbuminuria is known to predict mortality in elderly, non-insulin dependent diabetic individuals. To test whether this is also so when studied prospectively and over a longer period, we followed 228 persons with known diabetes mellitus and an age and sex matched, non-diabetic cohort for eight to nine years. Both cohorts were found during a population screening in 1981-1982 of 5292 citizens aged 60 to 74 years. At ascertainment extensive clinical and biochemical examinations including determination of urinary albumin were carried out. At May 15, 1990 111 diabetic and 46 non-diabetics had died (P less than 0.0001). In the diabetic cohort the median value of urinary albumin excretion (UAE) was 17.40 micrograms/min. In the group with values at or above 17.40 micrograms/min 62 died, compared with 40 deaths in the group with values below (P = 0.003). In the non-diabetic cohort the median UAE value was 7.52 micrograms/min. In the upper group 26 died, in the lower 15 (P = 0.05). Cox regression analyses showed coefficients of regression for ln(UAE) of 0.333 (P less than 0.001) for the diabetic group and 0.236 (P = 0.048) for the non-diabetic group. In the Cox model for the diabetics, ischemic heart disease was also of independent significance to mortality. The final model for the non-diabetics included hypertension and sex as significant variables. It is concluded that in a prospective study of elderly diabetics urinary albumin excretion rate is the best prognostic factor for long-term mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Microalbuminuria in systemic sclerosis

A prospective study was performed to determine urinary albumin excretion in a group of 28 patients with systemic sclerosis. At the initial screen one patient had proteinuria and three had microalbuminuria. One year later these abnormalities persisted and in two of of the patients serum creatinine had significantly increased. In addition, a further three patients had developed microalbuminuria. In a control group of 10 patients with primary Raynaud's disease none had microalbuminuria. In a second control group of 16 patients with unrelated skin diseases one patient had microalbuminuria and one proteinuria, but both these patients had a history of hypertension. It is concluded that microalbuminuria is more common in patients with systemic sclerosis than in patients of equivalent age with other dermatological conditions but no vascular disease.

Microalbuminuria and associated cardiovascular risk factors in the community

The prevalence of microalbuminuria and relationship to cardiovascular risk factors was examined in a cross-sectional community survey of cardiovascular risk factors. Microalbuminuria (when classified as albumin concentration greater than 20 micrograms/ml) was present in 6.3% of subjects but in conjunction with an albumin/creatinine ratio greater than 3.5 in only 2.2%. Diastolic blood pressure, prevalence of abnormal electrocardiographs, and to a lesser extent systolic blood pressure and fibrinogen concentration, were greater in those with albuminuria concentrations greater than 20 micrograms/ml. The strongest positive univariate correlates of albumin/creatinine ratios in those with detectable albuminuria were age, fibrinogen, blood pressure, total- and low density lipoprotein-(LDL) cholesterol, apo B and alcohol intake, whereas fasting insulin and insulin resistance were inversely correlated. Multiple regression analysis revealed that age, gender, systolic blood pressure and insulin resistance independently accounted for 37% of the variability in albumin/creatinine ratios. When those 10 subjects with microalbuminuria and albumin/creatinine ratios greater than 3.5 were matched with 20 with normoalbuminuria for age, gender and body mass index, the microalbuminuric subjects had significantly lower LDL cholesterol/apo B ratios and a tendency to lower high density lipoprotein (HDL) cholesterol and HDL cholesterol/apo A1 ratios. Microalbuminuria is uncommon in the general population, and is related to ageing, blood pressure and other vascular risk factors. It may reflect the presence of established cardiovascular disease.