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

Glycosuria amount in response to hyperglycaemia and risk for diabetic kidney disease and related events in Type 1 diabetic patients

BACKGROUND

Hyperglycaemia impairs tubulo-glomerular feedback. We tested whether variable tubulo-glomerular feedback during hyperglycaemia contributes to renal risk heterogeneity seen in Type 1 diabetes.

METHODS

During the period 1990-92, we studied the tubulo-glomerular feedback in Type 1 diabetic patients at high or low renal risk [21 of 54 with glomerular hyperfiltration and/or microalbuminuria against 11 of 55 with normal glomerular filtration rate (GFR) and urinary albumin despite uncontrolled diabetes]. The GFR, effective renal plasma flow, mean arterial pressure and fractional reabsorptions of glucose, osmols, sodium and lithium were measured sequentially during normo- and hyperglycaemia. All patients were followed up until 2016 for incident proteinuria, estimated GFR <60 mL/min/1.73 m2, doubling of serum creatinine, end-stage renal disease or all-cause death.

RESULTS

Glycaemia increased from 6.1 ± 1.3 to 15.1 ± 1.9 mmol/L in both high-risk and low-risk patients. Glycosuria was lower in the high- versus low-risk patients: 0.34 ± 0.25 versus 0.64 ± 0.44 mmol/min (P = 0.03). Both groups displayed similar kidney function during normoglycaemia. Hyperglycaemia increased more importantly GFR and fractional reabsorptions, and pre-glomerular vasodilatation in the high- than in the low-risk patients (all P < 0.05). Over 21 years, 31.5% high- versus 12.7% low-risk patients developed endpoints (adjusted P = 0.006). In a multi-adjusted survival analysis of patients having undergone renal tests, each 0.10 mmol/min glycosuria during hyperglycaemia reduced the outcome risk by 0.72 (95% confidence interval 0.49-0.97, P = 0.03).

CONCLUSIONS

Reduced tubulo-glomerular feedback and glycosuria during hyperglycaemia indicate high renal risk for Type 1 diabetic patients. Inter-individual variability in tubulo-glomerular feedback activity determines renal risk in Type 1 diabetes.

Management of diabetic renal disease

Diabetic nephropathy is the leading cause of end stage renal failure (ESRF) worldwide, representing over 50% of patients on renal replacement therapy in some parts of the world. The condition is common in people with type 1 and type 2 diabetes, although the incidence appears to be declining, especially in type 1 diabetes. More than 1 in 3 people with type 2 diabetes have impaired kidney function. Advances in our understanding of the pathogenesis and natural history of the condition have enabled us to consider earlier therapy aimed at renal preservation and reduction in cardiovascular morbidity. Microalbuminuria is now established as the earliest risk marker for nephropathy in type 1 diabetes and cardiovascular disease in type 2 diabetes. This review examines the current concepts in the pathogenesis and management of diabetic nephropathy.

Microalbuminuria as a risk predictor in diabetes: the continuing saga

OBJECTIVE The rationale for this study was to review the data on microalbuminuria (MA), an amount of albumin in the urine of 30-299 mg/day, in patients with diabetes in the context of cardiovascular risk and development of kidney disease. The objective was to review the pathophysiology of MA in patients with diabetes and review the data from trials regarding MA in the context of risk for cardiovascular events or kidney disease progression. RESEARCH DESIGN AND METHODS Data sources were all PubMed-referenced articles in English-language peer-reviewed journals since 1964. Studies selected had to have a minimum 1-year follow-up and be either a randomized trial linking MA to cardiovascular or kidney disease outcome, a meta-analysis/systematic review, or a large observational cohort study. RESULTS The data suggest that MA is a risk marker for cardiovascular events and possibly for kidney disease development. Its presence alone, however, does not indicate established kidney disease, especially if the estimated glomerular filtration rate is >60 mL/min/1.73 m(2). An increase in MA, when blood pressure and other risk factors are controlled, portends a poor prognosis for kidney outcomes over time. Early in the course of diabetes, aggressive risk factor management focused on glycemic and blood pressure goals is important to delay kidney disease development and reduce cardiovascular risk. CONCLUSIONS MA is a marker of cardiovascular disease risk and should be monitored per guidelines once or twice a year for progression to macroalbuminuria and kidney disease development, especially if plasma glucose, lipids, and blood pressure are at guideline goals.

Prevalence and determinants of albuminuria in a cohort of diabetic patients in Lebanon

BACKGROUND AND OBJECTIVES

Few data are available on the extent of albuminuria in diabetic populations in the Middle East generally and in Lebanon specifically. We conducted this study to determine the prevalence of albuminuria and its major risk factors in a cohort of diabetic patients in Lebanon.

PATIENTS AND METHODS

Diabetic patients followed in the outpatient department at the American University of Beirut Medical Center (AUBMC) were included in a prospective observational study. AUBMC is a tertiary referral center and the outpatient department typically handles patients of low socioeconomic status with advanced disease. Patients were classified according to their urinary albumin-to-creatinine ratio (ACR) as having normoalbuminuria (ACR<30 mg/g creatinine), microalbuminuria (ACR=30 to <300 mg/g creatinine), or macroalbuminuria (ACR > or =300 mg/g creatinine). The three groups were compared to analyze the association between albuminuria and its risk factors. In addition, independent predictors of albuminuria were determined using multivariate logistic regression and presented as an odds ratio.

RESULTS

Microalbuminuria and macroalbuminuria were present in 33.3% and 12.7% of 222 patients (mean age 56.4 years, mean deviation of diabetes 8.6 years, 58.7% women, 43.8% obese), respectively. Factors significantly associated with microalbuminuria included glycemic control, insulin use, and total and LDL cholesterol. Those associated with macroalbuminuria included in addition to glycemic control and insulin use, duration of diabetes, hypertension, elevated mean arterial pressure (MAP), and presence of neuropathy, retinopathy and peripheral vascular disease by bivariate analysis. Only glycemic control was an independent risk factor for both in addition to MAP and retinopathy for macroalbuminuria by multivariate analysis.

CONCLUSION

Albuminuria is highly prevalent among this cohort of diabetic patients in Lebanon. Both glycemic control and blood pressure need to be better targeted in its management.

Prevalence and determinants of albuminuria in a cohort of diabetic patients in Lebanon

BACKGROUND AND OBJECTIVES

Few data are available on the extent of albuminuria in diabetic populations in the Middle East generally and in Lebanon specifically. We conducted this study to determine the prevalence of albuminuria and its major risk factors in a cohort of diabetic patients in Lebanon.

PATIENTS AND METHODS

Diabetic patients followed in the outpatient department at the American University of Beirut Medical Center (AUBMC) were included in a prospective observational study. AUBMC is a tertiary referral center and the outpatient department typically handles patients of low socioeconomic status with advanced disease. Patients were classified according to their urinary albumin-to-creatinine ratio (ACR) as having normoalbuminuria (ACR<30 mg/g creatinine), microalbuminuria (ACR=30 to <300 mg/g creatinine), or macroalbuminuria (ACR > or =300 mg/g creatinine). The three groups were compared to analyze the association between albuminuria and its risk factors. In addition, independent predictors of albuminuria were determined using multivariate logistic regression and presented as an odds ratio.

RESULTS

Microalbuminuria and macroalbuminuria were present in 33.3% and 12.7% of 222 patients (mean age 56.4 years, mean deviation of diabetes 8.6 years, 58.7% women, 43.8% obese), respectively. Factors significantly associated with microalbuminuria included glycemic control, insulin use, and total and LDL cholesterol. Those associated with macroalbuminuria included in addition to glycemic control and insulin use, duration of diabetes, hypertension, elevated mean arterial pressure (MAP), and presence of neuropathy, retinopathy and peripheral vascular disease by bivariate analysis. Only glycemic control was an independent risk factor for both in addition to MAP and retinopathy for macroalbuminuria by multivariate analysis.

CONCLUSION

Albuminuria is highly prevalent among this cohort of diabetic patients in Lebanon. Both glycemic control and blood pressure need to be better targeted in its management.

Proteinuria in diabetic kidney disease: a mechanistic viewpoint

Proteinuria is the hallmark of diabetic kidney disease (DKD) and is an independent risk factor for both renal disease progression, and cardiovascular disease. Although the characteristic pathological changes in DKD include thickening of the glomerular basement membrane and mesangial expansion, these changes per se do not readily explain how patients develop proteinuria. Recent advances in podocyte and glomerular endothelial cell biology have shifted our focus to also include these cells of the glomerular filtration barrier in the development of proteinuria in DKD. This review describes the pathophysiological mechanisms at a cellular level which explain why patients with DKD develop proteinuria.

Effects of high-dose vitamin E supplementation on oxidative stress and microalbuminuria in young adult patients with childhood onset type 1 diabetes mellitus

INTRODUCTION

The aim of this study was to evaluate the effects of high-dose vitamin E supplementation (1200 mg/day) on reducing both microalbuminuria (MA) and oxidative stress in patients with type 1 diabetes mellitus (T1DM) and persistent MA.

METHODS

We performed a 12-month, randomized, placebo-controlled, double-blind cross-over trial in ten Caucasian young adults (7m/3f; mean age 18.87 +/- 2.91 years) with T1DM and persistent MA. At baseline and at end of the treatment period, determination of albumin excretion rate (AER) and HbA(1c) and evaluation of the oxidant/antioxidant status were performed.

RESULTS

At the beginning of the study, AER and HbA(1c) were not significantly different between the vitamin E and placebo group. No differences in terms of oxidant and antioxidant status were found between the two groups. This was associated with no significantly different urinary VEGF and TGF-beta levels. After 6 months, no significant differences in AER were observed between the two groups (p = 0.59). However, plasma and LDL-vitamin E content were significantly higher in the vitamin E group compared to the placebo group (p = 0.0001 and p = 0.004, respectively). This was associated with a significantly longer lag phase (p = 0.002) and lower MDA (p = 0.049). However, no statistically significant differences were detected in terms of VEGF and TGF-beta urinary levels.

CONCLUSION

These data demonstrate that high-dose vitamin E supplementation reduces markers of oxidative stress and improves antioxidant defence in young patients with T1DM. However, although it positively affects the oxidant/antioxidant status, vitamin E supplementation does not reduce AER in patients with T1DM and persistent MA.

Prevention of hypertension and its complications: theoretical basis and guidelines for treatment

Hypertension is a nutritional-hygienic disease. Long-term caloric intake in excess of energy expenditures, chronic supraphysiological intake of dietary sodium, excessive alcohol consumption, and psychosocial stressors all contribute to the development of hypertension throughout the world. Elevated BP, particularly systolic BP, has been linked to multiple adverse clinical outcomes including stroke, heart failure, myocardial infarction, renal insufficiency/failure, peripheral vascular disease, retinopathy, dementia, and premature mortality. These undesirable clinical outcomes are typically, although not invariably, preceded by pressure-related target-organ injury such as left ventricular hypertrophy, renal insufficiency and proteinuria. The relation of BP and CKD and, in turn, the prevention of CKD or forestalling its progression by hypertension treatment, will be the focus of this manuscript. In hypertensive persons with reduced kidney function and/or proteinuria, lowering BP with multidrug therapy that is inclusive of pharmacologic modulators of the renin-angiotensin-aldosterone-kinin system is an effective strategy to forestall the progressive loss of kidney function. The totality of data support low therapeutic BP targets for persons with proteinuria >1 g/d. Nevertheless, in persons with CKD, even those with proteinuria below the dipstick positive level (approximately 300 mg/d or urine protein to creatinine ratio of 0.22), aggressive BP control also may be warranted because of the high risk of nonrenal cardiovascular disease. Multiple antihypertensive drugs will be required in the vast majority of patients with diabetes and/or reduced kidney function to attain BP goal. Renin-angiotensin system (RAS) modulator therapy is indicated among persons with diabetes mellitus and CKD. Available data support the use of angiotensin receptor blockers in persons with type 2 diabetes and overt nephropathy for preservation of kidney function. Among persons with type I diabetes with or without overt nephropathy, type 2 diabetes without overt nephropathy and in nondiabetic CKD, the available clinical data support the use of angiotensin-converting enzyme inhibitors as the RAS modulator of choice. Low therapeutic target BP levels <130/80 mmHg in persons with type 2 diabetes mellitus also appear warranted based on available data mostly for reducing the risk of nonrenal cardiovascular disease and overall mortality.

Ambulatory blood pressure monitoring (ABPM) in normotensive adolescents with type 1 diabetes

OBJECTIVE

To evaluate 24-h ambulatory blood pressure monitoring (ABPM) for early detection of hypertension in adolescents with type 1 diabetes mellitus (DM1).

DESIGN

Patients underwent fundoscopy, albuminuria determinations, two repeated autonomic cardiovascular tests, heart rate (HR) variation during deep breathing and blood pressure (BP) variation during sustained handgrip. Twenty-four hour BP measurements were taken automatically by an oscillometric portable monitor.

SETTING

A specialty pediatric diabetes clinic and subjects' homes.

PARTICIPANTS

Eighteen children aged 10-17 yr with 2+ yr of DM1, without long-term complications, and 34 controls.

RESULTS

Higher ambulatory HR during the day than at night did not differ between DM1 subjects and controls. Mean systolic (s) and diastolic (d) BP in patients during the daytime were not significantly different from the control values. During the night, both sBP and dBP mean values in patients differed from those of controls. Statistical analysis of day and night HR and BP measurements were not different in both groups. The percentage decrease during the night in sBP and dBP was significantly smaller in patients than in controls. There were no differences by gender or duration of diabetes > or < 5 yr or by HbA1 above and below 10%. No difference in nocturnal sBP or dBP decline was observed between patients with or without abnormal autonomic test results.

CONCLUSION

ABPM is more reliable than casual BP measurement in detecting early BP alterations during the night, before the appearance of microalbuminuria, in young patients with DM1.

Smoking cessation does not change urinary albumin excretion in normal subjects

The aim of the study was to examine the effect of smoking cessation on urinary albumin excretion (UAE) in normal subjects. The study consisted of two parts. The first was a randomized 4-week study, in which 182 heavy smokers were asked to quit smoking immediately (n = 69, available for analysis) or to continue smoking for another 4 weeks (n = 70, available for analysis). After 4 weeks, the latter group was also asked to stop smoking. The second part was a non-randomized follow-up study comparing UAE in 33 unsuccessful and 57 successful quitters followed for 26 weeks. Measurements of UAE (ELISA) were taken from 24-h urine samples before smoking cessation, after 4 weeks, and after 26 weeks. After 4 weeks, no statistically significant change in UAE was found within each group or between quitters and smokers. The 95% confidence intervals of the change in log UAE were -7.4 to 9.9% of the initial value in the smoker group and -4.9 to 11.3% in the quitter group. In the second part of the study, after 26 weeks, a 16% increase (95% confidence interval 5.5 to 26.5%) in mean log UAE was found in the group that had stopped smoking (p < 0.003), but no statistically significant difference in UAE between continued smokers and quitters was found after adjusting for the baseline level (ANCOVA). In conclusion, smoking cessation seems to have no effect on UAE within the physiological range in normal subjects over an observation period of 4 weeks, and no sign of a decrease in UAE was seen after 26 weeks of smoking cessation.

Prevention and slowing down the progression of the diabetic nephropathy through antihypertensive therapy

Diabetic nephropathy is the major cause of illness and premature death in people with diabetes, largely through accompanying cardiovascular disease and end-stage renal failure. Diabetic patients are several times as prone to kidney disease as nondiabetic people and the accumulative risk of diabetic nephropathy in insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM) is about 30%-50% after 25 years of disease. Diabetic nephropathy is a progressive disease that takes several years to develop, ending in chronic renal insufficiency. Proteinuria heralds the onset of diabetic nephropathy, and the worsening of proteinuria parallels the progression of renal disease. The main risk factors for the frequency, severity, and progression of diabetic nephropathy are the degree of hyperglycemia and associated metabolic disturbances, hypertension, protein overload, cigarette smoking, as well as the duration of diabetes. Interventional strategies for primary, secondary, and tertiary prevention of diabetic nephropathy therefore include meticulous glycemic control, appropriate treatment of associated lipid abnormalities, rigorous control of the blood pressure, reduction in dietary protein intake, in particular animal protein, and of fat intake, and stopping cigarette smoking. Randomized clinical trials indicate that antihypertensive therapy is beneficial in preventing and slowing down the progression of diabetic nephropathy. There is now increasing evidence that angiotensin-converting enzyme inhibitors and certain calcium antagonists produce a more beneficial effect on diabetic nephropathy in terms of reducing proteinuria and slowing the progression to diabetic renal failure. These drugs are attributed nephroprotective capacity beyond their blood pressure lowering capacity and initial clinical trials with combinations have revealed even additive protective effects on end organs.

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.

Microalbuminuria: prognostic and therapeutic implications in diabetic and hypertensive pregnancy

Microalbuminuria is defined as urinary excretion of albumin that is persistently above normal, although below the sensitivity of conventional semiquantative test strips. Several studies have reported that Type 1 diabetic patients with microalbuminuria are apparently more likely to develop diabetic nephropathy eventually progressing to renal failure. Microalbuminuria is also a strong predictor of mortality in Type 2 diabetes, and is correlated with increased blood pressure in patients with benign essential hypertension. Radioimmunoassay revealed a significantly higher urinary albumin excretion rate in normal pregnant women in the third trimester of pregnancy, compared to the second and first, and compared to non-pregnant women. Microalbuminuria was found in 30% of women who had a record of gestational diabetes mellitus. Published results are controversial regarding the assumption that microalbuminuria is an early predictor of pregnancy-induced hypertensive complications.

Is a random urinary albumin concentration a useful screening test in insulin-treated diabetic patients?

The debate continues on how to screen for microalbuminuria in clinical practice in patients with insulin-dependent diabetes mellitus. Our study assesses the value of a spot morning urine specimen obtained at a clinic visit. In 1984, as part of a randomised survey of our diabetes clinic, 43 of 249 patients with insulin treated diabetes mellitus, were found to have microalbuminuria (urinary albumin concentration 35-300 ug ml-1) on a spot morning urine sample. These subjects were compared with an age-matched control group from the 1984 cohort who did not have microalbuminuria. Eight years later, in the group with microalbuminuria, 10 had died compared to six in the control group (p = 0.17) with 62.5% of all deaths being from cardiovascular disease. In the group with microalbuminuria, 10 of 27 still had incipient nephropathy while five had progressed to nephropathy. In the group without microalbuminuria only three of 33 patients had progressed to microalbuminuria while none had progressed to nephropathy. In conclusion a spot morning urine sample is a useful screening test to identify patients at risk of progression to nephropathy.

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.

Persistent microalbuminuria in adolescents with type I (insulin-dependent) diabetes mellitus is associated to early rather than late puberty. Results of a prospective longitudinal study

Microalbuminuria is generally accepted to be highly predictive of overt diabetic nephropathy which is the leading cause of end-stage renal failure and, consequently, of death in patients with type 1 (insulin-dependent) diabetes mellitus (IDDM). Its early identification and therapy are exceedingly important. We studied prospectively the occurrence of microalbuminuria (MA) in relation to puberty and its pubertal stages in 164 children and adolescent patients (83 girls and 81 boys) with IDDM. Analysing 100 healthy subjects, normal values for albumin excretion (range: 0-10.1 micrograms/min/1.73 m2) according to sex and the different pubertal stages were defined. No significant difference between the groups were noted and, therefore, 20 micrograms/min per 1.73 m2 (3 SD above the mean) was generally defined as cutoff for MA. Of the patients with IDDM studied, 20% (20 females and 12 males) developed persistent MA (22.1-448.2 micrograms/min/1.73 m2) during the study period of 8 years. The first manifestation of persistent MA was in 69% (13 females and 9 males) during stages of early and midpuberty; and in 28% (6 females and 3 males) at a late pubertal stage or at the end of puberty. The only child who developed MA before the onset of puberty (range: 23.5-157.4 micrograms/min/1.73 m2) was found to have dystopic kidney. Therefore, all patients with IDDM should be screened for MA regardless of diabetes duration, sex and level of diabetes control beginning at the very first stage of puberty and neither earlier nor after puberty as suggested by the American Diabetes Association.

Cardiovascular and hormonal responses to cold pressor test in insulin-dependent diabetic adolescents with microalbuminuria

Cardiovascular responses to cold pressor test and associated changes in blood concentrations of renin, aldosterone, and catecholamines were measured in 11 type I diabetic patients with microalbuminuria; 11 type I diabetic patients with normoalbuminuria matched for age, duration of diabetes, metabolic control; and in nine normal control subjects. Heart rate, renin, aldosterone, and catecholamines concentrations in diabetic patients and controls at baseline were similar, but higher mean blood pressure was evident in microalbuminuric than normoalbuminuric patients (p < 0.01) and controls (p < 0.05). Heart rate and mean blood pressure during cold pressor test in control subjects and type I diabetic patients increased significantly but similarly, regardless of the presence of microalbuminuria. Catecholamines, but not renin-aldosterone release, was associated to blood pressure modifications during the test. Peak values of mean blood pressure induced by cold test were positively correlated to baseline values in control subjects (r = 0.658, p < 0.05) and normoalbuminuric (r = 0.725, p < 0.01), but not microalbuminuric diabetics. These data suggest that the higher blood-pressure values at rest observed in microalbuminuric than normoalbuminuric diabetics are not associated with a higher cardiovascular response to cold hypertensive stimulus.

Juxtaglomerular body abnormalities in youth-onset diabetic subjects

Abnormal microalbuminuria in insulin-dependent diabetic subjects (IDDS) is significantly associated with pre-clinical nephropathy. In youth-onset IDDS declining plasma renin activity is significantly associated with improved albumin excretion, while persistently elevated renin activity is associated with continued abnormal microalbuminuria. To determine if these changes are reflected in changes in cell count in the juxtaglomerular body and if biopsy findings correlate with abnormal microalbuminuria, renal tissue of 20 IDDS (Study IDDS) ages 16 to 31 years, evaluated concurrently for plasma renin activity and microalbuminuria, were examined by light microscopy. Biopsy or autopsy specimens from 21 normal subjects and 32 IDDS (Non-Study IDDS), ages 2 to 25, were also examined. Specimens from the majority of prepubertal and all pubertal and postpubertal Non-Study IDDS and all Study IDDS independently of status of microalbuminuria had morphologic abnormalities. Normal or mesangially expanded glomeruli were found in association with expanded juxta-glomerular bodies and increased cell number, or with sclerotic bodies and decreased cell number. Sclerosis of juxtaglomerular bodies occurred independently of glomerular sclerosis. The highest percentage of glomeruli with expanded juxtaglomerular bodies and high cell count was present in specimens of Study IDDS with the most abnormal levels of microalbuminuria. T lymphocytes, noted within juxtaglomerular bodies, were present in specimens of 62% of the 52 Study and Non-Study IDDS. Abnormalities of the juxtaglomerular body are distinctive features of renal pathology in IDDS. T lymphocytes in the endocrine juxtaglomerular body suggest the presence of an autoimmune process. Confirmatory studies are necessary.

Microalbuminuria in young Sudanese patients with type 1 diabetes

Overnight urinary albumin excretion (UAE) was measured in 51 patients, nine to 18 years old, with type 1 (insulin-dependent) diabetes mellitus and in 22 healthy subjects using radioimmunoassay. Thirteen diabetic patients (25.5%) had microalbuminuria defined as UAE rate between 20 and 200 microg/min. Eleven of these patients were over 13 years of age. This gives a frequency of microalbuminuria of 42% (11/26) in the diabetic children and adolescents in the age group 14-18 years. UAE rate was positively correlated with both age at diagnosis and duration of diabetes. Arterial blood pressure, systolic and diastolic, glycosylated hemoglobin (HbA1c) and insulin dosage U.kg- 1.day-1 were significantly higher (P<0.001) in the diabetic patients with microalbuminuria compared to the diabetic patients with normal UAE rate. Retinal changes were also more common in the microalbuminuric diabetic patients than in the diabetic patients without microalbuminuria (P<0.01). This study has revealed a high prevalence of microalbuminuria in young Sudanese patients with type 1 (insulin-dependent) diabetes mellitus and emphasized the importance of routine screening of diabetic children after the age of 12 years.

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.

Isradipine decreases exercise-induced albuminuria in patients with essential hypertension

The aim of our study was to investigate the effects of exercise on albuminuria and blood pressure in patients with essential hypertension, and the short-term effect of the calcium channel blocker isradipine on exercise-induced albuminuria (UAE) and blood pressure in the same patients. Ten patients (7 males, 3 females) with essential hypertension were admitted to the study. The mean age was 54 +/- 2.7 years and the mean body mass index was 27 +/- 1 kg/m2. Patients performed two physical exercise tests on a cycloergometer. Workload was increased by 30 watts every 2 min until 90% of the theoretical maximal heart rate was achieved. This workload was maintained for 5 min. Samples for albuminuria assay were collected at the end of exercise and 1 h after exercise. The first physical exercise test was performed after 15 days of placebo washout; the second exercise was performed after 10 days of therapy with isradipine 5 mg once daily p.o. After 10 days of therapy with isradipine, UAE immediately after (31 +/- 8.3 micrograms/min) and 1 h after exercise (31.5 +/- 7.3 micrograms/min) were significantly (p < 0.05) lower as compared to the values found after placebo (37.1 +/- 9.3 micrograms/min; 43.5 +/- 9.9 micrograms/min). Our data show that short-term administration of the calcium channel blocker isradipine is able to cause a concomitant significant decrease in exercise-induced pressor and albuminuric response in patients with essential hypertension. The finding that short-term calcium channel blockade can reduce exercise-induced albuminuria in essential hypertensive patients suggests that progression of nephropathy in this early phase could be slowed by isradipine in these patients.

The relationship between the development and progression of microalbuminuria and arterial blood pressure in type 1 (insulin-dependent) diabetes mellitus

OBJECTIVE

to investigate the association between urinary albumin excretion and arterial blood pressure in type 1 (insulin-dependent) diabetes.

RESEARCH DESIGN AND METHODS

urinary albumin excretion and blood pressures were followed prospectively for a mean period of 26 months (range 18-29 months) in 46 young type 1 (insulin-dependent) diabetic subjects without overt nephropathy. Supine blood pressures (BP) were measured by a single observer using a random zero sphygmomanometer. Albumin excretion was assessed at baseline by a timed clinic excretion rate (AER; microalbuminuria = AER greater than 33 micrograms/min), and at follow-up in at least two urine specimens by the albumin/creatinine (A/Cr) ratio (micro-albuminuria = A/Cr greater than 3.7 mg/mmol).

RESULTS

39 subjects initially had normal AERs. Seven had developed microalbuminuria at follow-up: their mean BP rose from 114 +/- 13/62 +/- 13 to 119 +/- 7/77 +/- 5 mmHg (for diastolic BP, P less than 0.05), while there was no change in the mean BP in the remaining 32 patients. A rise in diastolic BP of greater than 10 mmHg occurred in five of the seven subjects who developed microalbuminuria, and in only seven of 32 who did not (P = 0.02). In the seven patients in whom microalbuminuria persisted (n = 3) or progressed to overt proteinuria (n = 4), BP increased from 123 +/- 12/70 +/- 14 to 139 +/- 12/88 +/- 10 mmHg (P less than 0.02 for both).

CONCLUSIONS

this study has shown that BP is normal before the onset of microalbuminuria, and that a rise in diastolic BP accompanies the development or progression of microalbuminuria. The rate of rise in BP may be more important than the absolute level in defining 'hypertension' in young diabetic patients with microalbuminuria.

Plasma lipoproteins and renal function during simvastatin treatment in diabetic nephropathy

The aim of this study was to assess the effect of simvastatin on plasma lipoproteins and renal function in hypercholesterolaemic Type 1 (insulin-dependent) diabetic patients with diabetic nephropathy. Twenty-six hypercholesterolaemic (total cholesterol greater than or equal to 5.5 mmol/l) Type 1 diabetic patients with nephropathy were enrolled in a double-blind randomized placebo-controlled study for 12 weeks. The active treatment group (n = 14) received simvastatin (10-20 mg/day) for 12 weeks while the remaining 12 patients received treatment with placebo. The results during simvastatin treatment (baseline vs 12 weeks): total cholesterol 6.6 vs 4.8 mmol/l (p less than 0.01), LDL-cholesterol 4.25 vs 2.57 mmol/l (p less than 0.01) and apolipoprotein B 1.37 vs 1.06 mmol/l (p less than 0.01). HDL-cholesterol, and apolipoprotein A-I remained unchanged. Total cholesterol, LDL-cholesterol, HDL-cholesterol, apolipoprotein A-I, apolipoprotein B remained unchanged during placebo treatment. Albuminuria measured during the simvastatin and the placebo treatment (baseline vs 12 weeks) (the data are logarithmically transformed before analysis because of their positively skewed transformation; geometric mean (x/divided by antilog SE) is indicated) was 458 (x/divided by 1.58) vs 393 (x/divided by 1.61) and 481 (x/divided by 1.62) vs 368 (x/divided by 1.78 micrograms/min (NS). Glomerular filtration rate during simvastatin and placebo treatment (baseline vs 12 weeks) was 64 vs 63 and 72 vs 74 ml.min-1.1.73 m-2, respectively. Two patients receiving simvastatin treatment were withdrawn, one due to gastrointestinal side effects and one due to myalgia.(ABSTRACT TRUNCATED AT 250 WORDS)

Enalapril. A reappraisal of its pharmacology and therapeutic use in hypertension

Enalapril, an angiotensin converting enzyme (ACE) inhibitor usually administered orally once daily, decreases blood pressure by lowering peripheral vascular resistance without increasing heart rate or output. It is effective in lowering blood pressure in all grades of essential and renovascular hypertension. Patients not responding adequately to enalapril monotherapy usually respond with the addition of a thiazide diuretic (or a calcium antagonist or beta-blocker), and rarely require a third antihypertensive agent. Enalapril is at least as effective as other established and newer ACE inhibitors, and members of other antihypertensive drug classes including diuretics, beta-blockers, calcium antagonists and alpha-blockers, but therapy with enalapril may be less frequently limited by serious adverse effects or treatment contraindications than with other drug classes. The most frequent adverse effect limiting all ACE inhibitor therapy in clinical practice is cough. This favourable profile of efficacy and tolerability, and the substantial weight of clinical experience, explain the increasing acceptance of enalapril as a major antihypertensive treatment and supports its use as logical first-line therapeutic option.

Renal protective effect of enalapril in diabetic nephropathy

OBJECTIVE

To determine whether inhibition of angiotensin converting enzyme can reduce the rate of decline in kidney function more than reducing blood pressure with other antihypertensive treatment.

DESIGN

Prospective, open randomised study lasting a mean of 2.2 years in patients with diabetic nephropathy.

SETTING

Three outpatient nephrology clinics.

PATIENTS

40 patients with insulin dependent diabetes and diabetic nephropathy with reduced renal function.

INTERVENTION

Antihypertensive treatment with enalapril or metoprolol, usually combined with frusemide.

MAIN OUTCOME MEASURE

Rate of decline in glomerular filtration rate measured as chromium-51 edetic acid clearance.

RESULTS

Glomerular filtration rate declined a mean of 2.0 (SD 3.2) ml/min/year in the group given enalapril and 5.6 (5.9) ml/min/year in the control group. The mean arterial blood pressure during the study was 102 (5) mm Hg in the patients given enalapril and 103 (5) mm Hg in the patients given metoprolol. Urinary albumin excretion during treatment with enalapril was 60% lower than during treatment with metoprolol.

CONCLUSIONS

Enalapril has an antiproteinuric effect independent of the effect on systemic blood pressure. Treatment with enalapril can reduce the rate of decline in kidney function in patients with diabetic nephropathy more than equally effective antihypertensive treatment with metoprolol. This points to a specific renal protective effect of angiotensin converting enzyme inhibitors in diabetic nephropathy.

Regression of microalbuminuria in type II diabetic, hypertensive patients after long-term indapamide treatment

The influence of hypertension on the progression of persistent microalbuminuria in type II diabetes has not yet been clarified. We have studied the effects of 36 months of indapamide treatment (2.5 mg once daily) on blood pressure (BP), albumin excretion rate (AER), urinary immunoglobulin G4 (IgG4), and glomerular filtration rate (GFR) in 10 patients who were mildly hypertensive and had type II microalbuminuric diabetes (AER greater than 30 mg/24 hours and less than 300 mg/24 hours). BP, AER, and IgG4 significantly decreased after 6 months until the end of the study. Mean GFR was 94.4 +/- 7.5 ml/min/1.73 m2 in the baseline and did not change significantly throughout the course of the antihypertensive therapy. AER and IgG4 were directly related (r = 0.57; p less than 0.004), whereas BP did not relate to GFR, AER, or IgG4. The nephropathy index (45.5 +/- 4 in the baseline) significantly decreased at 12 months (38.7 +/- 2.1), 24 months (35.4 +/- 1.6), and 36 months (36.5 +/- 1.5) (at least p less than 0.01). Long-term indapamide treatment reduced BP and urinary protein loss without affecting GFR. These results indicate a potential role of this drug in the long-term renal protection of patients with type II diabetes, mild hypertension, and microalbuminuria.

Efficacy of captopril in postponing nephropathy in normotensive insulin dependent diabetic patients with microalbuminuria

OBJECTIVE

To assess the effectiveness of angiotensin converting enzyme inhibition in preventing the development of diabetic nephropathy (albuminuria greater than 300 mg/24h).

DESIGN

Open randomised controlled study of four years' duration.

SETTING

Outpatient diabetic clinic in tertiary referral centre.

PATIENTS

44 normotensive (mean blood pressure 127/78 (SD 12/10) mm Hg) insulin dependent diabetic patients with persistent microalbuminuria (30-300 mg/24h).

INTERVENTIONS

The treatment group (n = 21) was initially given captopril (25 mg/24 h). The dose was increased to 100 mg/24 h during the first 16 months and thiazide was added after 30 months. The remaining 23 patients were left untreated.

MAIN OUTCOME MEASURES

Albuminuria, kidney function, development of diabetic nephropathy (albuminuria greater than 300 mg/24 h), and arterial blood pressure.

RESULTS

Clinical and laboratory variables were comparable at baseline. Urinary excretion of albumin was gradually reduced from 82 (66-106) to 57 (39-85) mg/24 h (geometric mean (95% confidence interval)) in the captopril treated group, whereas an increase from 105(77-153) to 166 (83-323) mg/24 h occurred in the control group (p less than 0.05). Seven of the untreated patients progressed to diabetic nephropathy, whereas none of the captopril treated patients developed clinical overt diabetic nephropathy (p less than 0.05). Systemic blood pressure, glomerular filtration rate, haemoglobin A1c concentration, and urinary excretion of sodium and urea remained practically unchanged in the two groups.

CONCLUSIONS

The findings suggest that angiotensin converting enzyme inhibition postpones the development of clinical overt diabetic nephropathy in normotensive insulin dependent diabetic patients with persistent microalbuminuria.

A double-blind crossover study of oral xamoterol in postural hypotension due to diabetic autonomic neuropathy

Recent reports have suggested that xamoterol, a beta 1 adrenoceptor partial agonist with 43% intrinsic sympathomimetic activity improves symptomatic postural hypotension in patients with primary autonomic failure. To evaluate the use of xamoterol in eleven insulin dependent patients with diabetes mellitus who had postural hypotension (over 20 mmHg systolic blood pressure) secondary to autonomic neuropathy, we performed a double-blind, randomized, placebo controlled crossover study with xamoterol (200 mg bd orally) for 1 month. Treatment with xamoterol raised supine systolic blood pressure by 11 mmHg but a reduced standing systolic blood pressure by 11 mmHg with an increase in the standing-supine systolic blood pressure difference. No significant differences were observed in symptom score, HbA1 or plasma glucose. We conclude that oral xamoterol raises supine systolic blood pressure but paradoxically lowers standing systolic blood pressure further in insulin dependent diabetes mellitus. Xamoterol is unlikely to be of value in the management of postural hypotension in diabetic patients with autonomic neuropathy.

Renal disease in noninsulin-dependent diabetes mellitus

Diabetic nephropathy now accounts for approximately one-third of all patients who develop end-stage renal disease. The estimated cost to supply renal replacement therapy for this population now exceeds $750 million. The relatively recent realization that half of these individuals suffer from noninsulin-dependent diabetes mellitus has sparked increased interest in attempts to understand the pathologic processes involved and how they may be similar or different from those alterations seen in insulin-dependent diabetes mellitus. Basic and clinical investigation continues in an attempt to solve the puzzle of pathogenesis, as well as answer questions about the clinical usefulness of microalbuminuria and the appropriate management of hypertension in this population.

Enalapril reduces microalbuminuria in young normotensive type 1 (insulin-dependent) diabetic patients irrespective of its hypotensive effect

The effect of enalapril on albumin excretion rate was studied in two groups of age- and sex-matched Type 1 (insulin-dependent) diabetic patients, aged 15-20 years, with persistent microalbuminuria greater than 20 micrograms/min. Group 1 contained six patients with systolic blood pressure greater than or equal to 75th percentile for age and sex, group 2 six normotensive patients. Enalapril (10-20 mg/day) was given for six months. Albumin excretion rate, glomerular filtration rate, renal plasma flow, blood pressure at rest and during exercise, and angiotensin converting enzyme activity were measured before, after three weeks' and six months' treatment and six months after treatment withdrawal. Albumin excretion rate decreased in all patients after three weeks' (mean decreases 55% in group 1, 65% in group 2) and six months' treatment (35% in group 1, 61% in group 2). Systolic blood pressure remained unchanged in both groups. Diastolic pressure was reduced after three weeks in group 1 (p = 0.001). No reduction in increment in systolic pressure during exercise test occurred in any group during treatment. Angiotensin converting enzyme activity decreased in all patients after three weeks (p = 0.001) and six months (p = 0.003). This correlated to the decrease in albumin excretion rate after three weeks (r = 0.79, p = 0.05) and six months (r = 0.59, p = 0.04). HbA1c, mean blood glucose and glomerular filtration rate remained unchanged during the study in both groups. Renal plasma flow tended to increase after three weeks' and six months' treatment in group 2 (p = 0.06, respectively) but not in group 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of antihypertensive treatment with indapamide in patients with noninsulin-dependent diabetes and persistent microalbuminuria

In patients with insulin-dependent diabetes, antihypertensive treatment has a beneficial effect on the rate of progression toward uremia of overt diabetic nephropathy (albumin excretion rate [AER] greater than 300 mg/24 hour). The influence of hypertension on the progression of "incipient" nephropathy (AER ranging between 30 and 300 mg/24 hours) is not well defined, particularly in patients with noninsulin-dependent diabetes. In this study, 21 patients with noninsulin-dependent diabetes and hypertension (11 with normoalbuminuria and 10 with microalbuminuria), who were comparable for age, duration of diabetes and hypertension, were treated with indapamide, 2.5 mg once daily, and followed up for 24 months. Blood pressure, glomerular filtration rate (GFR), albumin excretion rate and subclass 4 of urinary immunoglobulin G (IgG4) were indicated. In normoalbuminuric patients, blood pressure was significantly reduced, whereas AER, IgG4 and GFR did not show any variation throughout the study. In microalbuminuric patients, blood pressure, AER and IgG4 were significantly reduced, and GFR remained unchanged. In patients with noninsulin-dependent diabetes, antihypertensive treatment, which is begun during incipient diabetic nephropathy, may have a beneficial effect on the progression of the disease, although a long-term follow-up study is needed to confirm this.

Contrasting effects of enalapril and metoprolol on proteinuria in diabetic nephropathy

OBJECTIVE

To assess whether angiotensin converting enzyme inhibition reduces proteinuria in diabetic nephropathy more than blood pressure reduction with other antihypertensive treatment.

DESIGN

Prospective, open randomised study lasting eight weeks in patients with diabetic nephropathy.

SETTING

Outpatient nephrology clinics.

PATIENTS

40 Patients with type I diabetes and diabetic nephropathy with reduced renal function.

INTERVENTION

Antihypertensive treatment with enalapril or metoprolol, usually combined with frusemide.

MAIN OUTCOME MEASURES

Arterial blood pressure and urinary excretion of albumin and protein.

RESULTS

Arterial blood pressure after eight weeks was 135/82 (SD 13/7) mm Hg in the group given enalapril and 136/86 (16/12) mm Hg in the group given metoprolol. Proteinuria and albuminuria were similar in both groups before randomisation. After eight weeks' treatment, the geometric mean albumin excretion was 0.7 (95% confidence interval 0.5 to 1.2) g/24 h in the patients given enalapril and 1.6 (1.1 to 2.5) g/24 h in the patients given metoprolol (p less than 0.02). The proteinuria was 1.1 (0.7 to 1.7) and 2.4 (1.6 to 3.6) g/24 h respectively (p less than 0.02).

CONCLUSIONS

Antihypertensive treatment with enalapril reduced proteinuria in patients with diabetic nephropathy more than an equally effective antihypertensive treatment with metoprolol. This points to a specific antiproteinuric effect of the angiotensin converting enzyme inhibitor independent of the effect on systemic blood pressure.

Albuminuria in type 2 (non-insulin-dependent) diabetes mellitus and impaired glucose tolerance in Pima Indians

The prevalence of abnormal urinary albumin excretion, defined by a urine albumin to creatinine ratio greater than or equal to 30 mg/g (approximately equivalent to an albumin excretion rate of greater than or equal to 30 mg/24 h), was determined in 2728 Pima Indians aged greater than or equal to 15 years from the Gila River Indian Community in Arizona, a population with a high prevalence of Type 2 (non-insulin-dependent) diabetes mellitus. Excessive albumin excretion was present in 8% of subjects with normal glucose tolerance, 15% of those with impaired glucose tolerance, and 47% of subjects with diabetes. The intermediate prevalence of abnormal albuminuria in those with impaired glucose tolerance suggests that hyperglycaemia even at levels below those diagnostic of diabetes is associated with renal abnormalities in some subjects and that these abnormalities may precede the onset of diabetes. Abnormal albuminuria at levels not reliably detected by the usual dipstick methods was commonly observed in Pima Indians with diabetes, even those with diabetes of recent onset. Associations were found with age, duration of diabetes, level of glycaemia, blood pressure, and treatment with insulin.

Treatment of hypertension in diabetic patients

Hypertension, common in diabetic patients, worsens not only the risk of cardiovascular complications, but also that of microangiopathic complications (nephropathy, retinopathy) of diabetes mellitus. It is thus important to ensure the perfect control of even mild hypertension in diabetic patients. However, treatment sometimes becomes difficult given that certain categories of antihypertensive drugs interfere with blood glucose control and/or lipid metabolism, interfere with the symptomatology of hypoglycemia, or promote orthostatic hypotension, a complication of autonomic neuropathy. A study was undertaken to determine the effects of rilmenidine, administered for 16 weeks, in 29 diabetic patients treated with insulin and experiencing mild-to-moderate hypertension (supine diastolic blood pressure, 96.7 +/- 0.5 mmHg). Administered as single-drug therapy, rilmenidine rapidly normalized blood pressure (systolic blood pressure, less than 160 mmHg; diastolic blood pressure, no more than 90 mmHg--supine) in 17 patients; this persisted throughout the trial period. Addition of a diuretic after 12 weeks in the remaining 12 patients led to normalization of blood pressure in nine additional patients. Blood glucose control (evaluated at home by weekly blood glucose measurements and by glycosylated hemoglobin levels) was unaffected by treatment. Plasma levels of cholesterol (total, high-density lipoprotein and low-density lipoprotein), triglycerides and proteinuria (or microalbuminuria) showed no change during the course of the trial. In conclusion, rilmenidine offers an effective and safe treatment for mild-to-moderate hypertension in diabetic patients treated with insulin and does not interfere with their blood glucose control.

The increased proximal tubular reabsorption of sodium and water is maintained in long-term insulin-dependent diabetics with early nephropathy

Proximal tubular reabsorption of sodium and water was investigated in long-term insulin-dependent diabetic patients with normoalbuminuria (group I, n = 19), microalbuminuria (group II, n = 39), diabetic nephropathy (group III, n = 12) and in 13 healthy age-matched subjects. Glomerular filtration rate was measured with the single injection, 51Cr-EDTA technique. The fluid flow rate out of the proximal tubules was assessed by the renal lithium clearance. Although glomerular filtration rate was significantly elevated in the diabetic patients (Group I: 122 +/- 16, Group II: 121 +/- 18, Group III: 110 +/- 17, CONTROLS: 105 +/- 13 ml/min X 1.73 m2), lithium clearance was similar in the four groups (Group I: 19 +/- 6, Group II: 22 +/- 7, Group III: 19 +/- 5, CONTROLS: 23 +/- 4 ml/min X 1.73 m2). Both absolute and fractional proximal reabsorption of sodium and water was enhanced in diabetes. Indices of distal tubular function did not differ between controls and patients with insulin-dependent diabetes. Sodium clearance was about the same in the four groups. Our study suggests that the enhanced proximal reabsorption of sodium and water in insulin-dependent diabetic patients is still observed despite the presence of incipient or overt diabetic nephropathy.

Effects of short-term strict metabolic control on kidney function and extracellular fluid volume in incipient diabetic nephropathy

The effects of strict metabolic control (multiple insulin injections for 1 week) on urinary albumin excretion, glomerular filtration rate and extracellular fluid volume was evaluated in long-term Type 1 diabetic patients with (n = 9) and without (n = 10) incipient nephropathy. Investigations were carried out in poor (blood glucose 15 (interquartile range, 13-18) mmol l-1) and good metabolic control (5 (4-8) mmol l-1). In patients with incipient nephropathy glomerular filtration rate was 125 (SD 26) (poor control) vs 125 (20) ml min-1 (good control), urinary albumin excretion 60 (range 37-247) vs 60 (13-359) mg 24 h-1, fractional albumin clearance 6.1 (0.9-67.6) vs 6.7 (2.1-65.4) x 10(-6), extracellular fluid volume 13.4 (2.3) vs 14.3 (2.8) l (p less than 0.10). Apart from an increase in extracellular fluid volume during improved metabolic control (12.2 (1.6) vs 13.6 (2.5) l, p less than 0.02) all the above mentioned variables remained unchanged in the patients with normal urinary albumin excretion. In conclusion, strict metabolic control for 2-7 days has no effect on urinary albumin excretion and glomerular filtration rate in long-term Type 1 diabetic patients with or without incipient diabetic nephropathy.

Short term effect of captopril on microalbuminuria induced by exercise in normotensive diabetics

OBJECTIVE

To investigate whether captopril has any effect on microalbuminuria induced by exercise in normotensive diabetic patients with early stage nephropathy.

DESIGN

Randomised, double blind, crossover trial.

SETTING

Outpatient department.

PATIENTS

22 diabetics with stage II nephropathy (urinary albumin excretion rate less than 20 micrograms/min; 15 with type I diabetes and seven with type II), 32 patients with stage III nephropathy (urinary albumin excretion rate 20-200 micrograms/min; 14 with type I diabetes and 18 with type II), and 10 normal subjects.

INTERVENTIONS

Four exercise tests on a cycle ergometer: the first two under basal conditions and the third and fourth after subjects had received captopril (two 25 mg doses in 24 hours) or placebo (two tablets in 24 hours).

END POINT

Exercised until 90% of maximum heart rate achieved.

MEASUREMENTS AND MAIN RESULTS

Mean urinary excretion one hour after the first two exercise tests was 21 micrograms/min in normal subjects, 101 micrograms/min in diabetic patients with stage II nephropathy, and 333 micrograms/min in those with stage III nephropathy. Similar results were obtained after placebo. After captopril the urinary excretion rate one hour after exercise was significantly decreased in diabetics with stage II (36 micrograms/min) and stage III (107 micrograms/min) disease compared with placebo but not in normal subjects. Systolic and diastolic pressures were similar in the three groups after placebo and captopril had been given.

CONCLUSIONS

Captopril significantly reduces microalbuminuria induced by exercise in normotensive diabetics without affecting systemic blood pressure. Captopril may reduce renal intracapillary pressure.

Nephropathy in non-insulin-dependent diabetes mellitus

End-stage renal disease develops in about 5 percent of patients with non-insulin-dependent diabetes mellitus (NIDDM). The large majority of diabetic patients have this form of the disease. Thus, end-stage renal disease is an important clinical problem in patients with NIDDM. Moreover, hypertension and its macrovascular sequelae are significant problems in patients with NIDDM and may be linked with renal disease. A review of the problem of nephropathy in NIDDM is attempted, pointing out, where data are available, the clinical and pathophysiologic differences from its presentation in insulin-dependent diabetes. The need for further studies of the impact of renal disease in this maturity onset form of diabetes is emphasized.

Prevention of diabetic nephropathy with enalapril in normotensive diabetics with microalbuminuria

STUDY OBJECTIVE

To assess the effectiveness of inhibition of angiotensin converting enzyme in preventing diabetic nephropathy.

DESIGN

Randomised follow up study of normotensive diabetics with persistent microalbuminuria (30-300 mg/24 hours) treated with enalapril or its matched placebo for one year. Double blind for first six months, single blind for last six months.

SETTING

Diabetic clinic in tertiary referral centre.

PATIENTS

Treatment group and placebo group each comprised 10 normotensive diabetics with persistent microalbuminuria.

INTERVENTIONS

Treatment group was given enalapril 20 mg daily and controls matched placebo. Patients were given antihypertensive treatment after one year.

END POINT

Albumin excretion, arterial pressure, and renal function.

MAIN RESULTS

In last three months of trial three of 10 patients taking placebo had diabetic nephropathy (albumin excretion greater than 300 mg/24 hours). No patients taking enalapril developed nephropathy and five showed normal albumin excretion (less than 30 mg/24 hours) (p = 0.005, Mann-Whitney test). Mean arterial pressure was reduced by enalapril throughout study (p less than 0.005) but increased linearly with placebo (p less than 0.05). Albumin excretion decreased linearly with enalapril but not placebo. An increase in albumin excretion with placebo was positively related to the increase in mean arterial pressure (r = 0.709, p less than 0.05, Spearman's rank test). With enalapril total renal resistances and fractional albumin clearances improved progressively (time effect, p = 0.0001).

CONCLUSION

Inhibition of angiotensin converting enzyme prevents development of nephropathy in normotensive diabetics with persistent microalbuminuria. This may be due to reduction in intraglomerular pressure and to prevention of increased systemic blood pressure. Future studies should compare long term effects of inhibitors of converting enzyme with other antihypertensive drugs.

Rational drug treatment of the hypertensive diabetic with nephropathy

Development of hypertension in Type I diabetics parallels evolution of nephropathy. In Type II diabetics, excessive prevalence of hypertension prior to the appearance of proteinuria suggests that factors other than nephropathy are operative in its pathogenesis. On the other hand, the risk of nephropathy in Type II diabetics is higher than previously appreciated. Recent evidence suggests that angiotensin II plays an important role in the induction and progression of diabetic nephropathy. This provides a rationale for antihypertensive therapy with converting enzyme inhibitors in nephropathic diabetics in whom they have been shown to lower blood pressure and diminish proteinuria. Furthermore, in a retrospective study of patients with various renal diseases (including diabetic nephropathy), the authors found suggestive evidence that converting enzyme inhibitors may also attenuate progression of renal failure to a greater extent than other antihypertensive drugs.

[The renin-angiotensin system in diabetic patients]

We review available data on the activity of the renin-angiotensin system (RAS), responsiveness to angiotensin II (ANG II), ANG II receptor number, and effects of inhibition of the RAS by angiotensin I converting enzyme (ACE) inhibitors in patients with diabetes mellitus. Most authors, including ourselves, observed a normal or enhanced activity of the RAS in metabolically stable diabetics. Increased but also reduced activity of the RAS was described in nephropathic diabetes. This is in contrast to the common suggestion that the RAS of diabetics is generally suppressed and functionally inactive. The last assumption was mainly based on the finding of reduced ANG II receptor numbers in anorectic, severely hyperglycemic rats. These findings could not be reproduced in man, and a higher ANG II receptor concentration on platelets of diabetics goes in parallel with the frequent finding of an enhanced pressor response to infused ANG II in diabetes. This increased responsiveness is most probably of functional importance since the RAS is not suppressed - as one would expect - in the face of a supranormal body sodium content. A number of data also indicate that renal resistance vessels display increased responsiveness to ANG II in diabetics. This may be a reason for hyperfiltration. This notion is further supported by the reduction of albuminuria which is usually observed following inhibition of the RAS with ACE inhibitors, and which may be an index of reduction of glomerular capillary pressure in human diabetes.

Comparative renal pathophysiology relevant to IDDM and NIDDM patients

Hyperfiltration is a very characteristic feature in insulin-dependent diabetes. Hyperfiltration is to some extent associated with long-term glycemic control but the correlation is not very strong. Long-term hyperfiltration may play a role in the genesis of late diabetic nephropathy, but it is difficult to distinguish effects of hyperfiltration per se from effects of poor metabolic control. Long-term hyperfiltration without diabetes does not produce nephropathy. It is hypothesized that IDDM patients who do not show considerable hyperfiltration in spite of poor metabolic control may be those who are to some extent protected against late diabetic nephropathy, but other mechanisms may also be involved in the renal protection of these patients, who survive long-term diabetes without nephropathy. On the other hand, those with poor metabolic control combined with hyperfiltration are likely to develop nephropathy. In addition, it is suggested that the metabolic aberrations in diabetes, with the subsequent changes in the biochemistry of the glomerular wall, are permissive and absolutely required for the development of diabetic nephropathy. Of note, diabetic glomerulopathy in NIDDM occurs without significant hyperfiltration and extreme hyperfiltration in the one-kidney-model (without diabetes) does not produce nephropathy. Nonglycemic modalities of intervention, resulting in reduced hyperfiltration, e.g., low-protein diet or administration of somatostatin analogues, deserves interest as new potential ways of preventing or postponing diabetic nephropathy. Also intervention with aldose-reductase inhibitors may be an important therapeutic modality for those patients in whom good metabolic control is not obtainable. It is now well-established that antihypertensive treatment, including ACE-inhibition, reduces rate of decline in GFR in patients with already established nephropathy. In addition, protein excretion is diminished in IDDM patients with incipient diabetic nephropathy by antihypertensive treatment where GFR is well-preserved during treatment. No data are available for NIDDM.

Elevated urinary prostaglandin excretion and the effect of indomethacin on renal function in incipient diabetic nephropathy

We investigated whether the glomerular synthesis of prostaglandins modulates the glomerular filtration rate and urinary albumin excretion in incipient diabetic nephropathy (defined as urinary albumin excretion between 30 and 300 mg/24 h (microalbuminuria) in two out of three sterile ketone-free 24-h urine collections in patients having insulin-dependent diabetes mellitus (IDDM) without hypertension or other kidney disease). The urinary excretion of prostaglandin E2 was significantly elevated in 8 insulin-dependent diabetic patients with incipient nephropathy as compared with 9 normoalbuminuric IDDM patients and 11 healthy controls: 317 (182-1273); 95 (67-225); 132 (54-263) pg/min, respectively (2p less than 0.01). Glomerular filtration rate (single bolus 51Cr-EDTA technique) and albuminuria (radioimmunoassay) were measured twice within 2 weeks in 8 females having IDDM with incipient nephropathy. The study design was a randomized double-blind trial with the patients receiving either indomethacin (150 mg/day) or placebo for 3 days prior to the kidney function studies. Indomethacin treatment induced a significant reduction in urinary prostaglandin E2 excretion (73%) (2p less than 0.01), urinary albumin excretion rate diminished from 207 (63-253) to 87 (49-147) mg/24 h (2p less than 0.01), fractional clearance of albumin declined (70%) (2p less than 0.01). Glomerular filtration rate remained stable (108 (88-133) versus 110 (95-142) ml/min). Blood glucose and blood pressure were comparable during the placebo and indomethacin treatment (12.6 +/- 3 versus 13.4 +/- 5 mmol/l and 122/79 +/- 3/9 versus 122/82 +/- 4/10 mmHg, respectively). Our results suggest that enhanced glomerular synthesis of vasodilating prostaglandins may accelerate microalbuminuria in incipient diabetic nephropathy.

Prevalence of microalbuminuria, arterial hypertension, retinopathy and neuropathy in patients with insulin dependent diabetes

Diabetic nephropathy is the main cause of the increased morbidity and mortality in patients with insulin dependent diabetes. The prevalence of microalbuminuria was determined in adults with insulin dependent diabetes of five or more years' duration that had started before the age of 41. All eligible patients (n = 982) attending a diabetes clinic were asked to collect a 24 hour urine sample for analysis of albumin excretion by radioimmunoassay; 957 patients complied. Normoalbuminuria was defined as urinary albumin excretion of less than or equal to 30 mg/24 h (n = 562), microalbuminuria as 31-299 mg/24 h (n = 215), and macroalbuminuria as greater than or equal to 300 mg/24 h (n = 180). The prevalence of microalbuminuria and macroalbuminuria was significantly higher in patients whose diabetes had developed before rather than after the age of 20. The prevalence of arterial hypertension increased with increased albuminuria, being 19%, 30%, and 65% in patients with normoalbuminuria, microalbuminuria, and macroalbuminuria respectively. The prevalence of proliferative retinopathy and blindness rose with increasing albuminuria, being 12% and 1.4%, respectively, in patients with normoalbuminuria, 28% and 5.6% in those with microalbuminuria and 58% and 10.6% in those with macroalbuminuria. An abnormal vibratory perception threshold was more common in patients with microalbuminuria (31%) and macroalbuminuria (50%) than in those with normoalbuminuria (21%). This study found a high prevalence (22%) of microalbuminuria, which is predictive of the later development of diabetic nephropathy. Microalbuminuria is also characterised by an increased prevalence of arterial hypertension, proliferative retinopathy, blindness, and peripheral neuropathy. Thus, urinary excretion of albumin should be monitored routinely in patients with insulin dependent diabetes.

Systemic hypertension, diabetes mellitus and the kidney

Diabetic nephropathy is manifested by albuminuria, hypertension and progressive loss of renal function. Only one-third of patients with insulin-dependent diabetes mellitus of juvenile onset develop nephropathy and the risk of nephropathy does not increase with increasing duration of diabetes. Hypertension occurs almost exclusively in patients with nephropathy. Therefore, there is a subset of patients at risk for both nephropathy and hypertension. It is important to identify the patients destined to develop nephropathy, to define the pathophysiology responsible for the nephropathy in this subset of patients and to develop programs to interrupt the pathophysiology early in its course and hopefully prevent the progression to end-stage renal failure. Potential markers to identify patients who will develop nephropathy include a family history of hypertension, increased glomerular filtration rate and renal mass and presence of significant microalbuminuria. Studies are needed to evaluate various classes of drugs for their efficacy in altering the pathophysiologic hemodynamic changes leading to nephropathy.

A reappraisal of the influence of blood rheology on glomerular filtration and its role in the pathogenesis of diabetic nephropathy

The basic assumptions concerning the mechanisms of normal glomerular filtration are discussed. Attention is drawn to blood rheologic changes that follow glomerular filtration and influence postglomerular blood flow adversely. It is proposed that the blood rheologic changes will increase the resistance to flow in the peritubular plexus commensurate with the dimensions of the capillaries and blood viscosity in accordance with the general principles of the Poiseuille formula, even though blood is a non-Newtonian fluid. For this reason, the conditions of flow in the plexus must be a determinant of intraglomerular capillary pressure. When blood rheology is abnormal, as in insulin-dependent diabetic patients, the abnormality will be amplified by glomerular filtration and it is suggested that the consequences will be manifest as problems of blood flow in the peritubular plexus. As the increase in postglomerular intravascular pressure needed to restore the rate of blood flow to normal necessitates dilation of the afferent arteriole and possibly more proximal vessels, such changes will result in an increase in intraglomerular pressure. The increase in pressure that increases filtration is therefore a direct consequence of abnormal blood rheology. This concept provides a basis for understanding the mechanism of diabetic proteinuria and for other proteinurias associated with abnormal blood rheology. A possible role for altered blood rheology in the pathogenesis of both focal and total glomerulosclerosis is discussed, and the potential benefits of agents that improve blood rheology are outlined.

Converting enzyme inhibition and kidney function in normotensive diabetic patients with persistent microalbuminuria

The effects of a long term reduction in blood pressure on the kidney function of normotensive diabetic patients who had persistent microalbuminuria (30-300 mg albumin/24 hours) were studied in two groups of 10 such patients before and during six months of treatment with either 20 mg enalapril or placebo daily. Treatments were assigned randomly in a double blind fashion. Before treatment both groups had similar clinical characteristics, weight, diet, total glycosylated haemoglobin, median albumin excretion rate (enalapril group 124 mg/24 h, placebo group 81 mg/24 h), and mean arterial pressure (enalapril group 100 (SD 8) mm Hg, placebo group 99 (6) mm Hg). During treatment weight, urinary urea excretion, and total glycosylated haemoglobin remained unchanged. The mean arterial pressure decreased in the enalapril group but not in the placebo group (enalapril group 90 (10) mm Hg, placebo group 98 (8) mm Hg). The median albumin excretion rate also fell in the enalapril group but not in the placebo group (enalapril group 37 mg/24 h, placebo group 183 mg/24 h.) The glomerular filtration rate rose in the enalapril group from 130 (23) ml/min/1.73 m2 to 141 (24) ml/min/1.73 m2, and total renal resistances and fractional albumin clearance decreased while fractional albumin clearance increased in the placebo group. These results show that in patients who have diabetes but not hypertension a reduction in blood pressure by inhibition of converting enzyme for six months can reduce persistent microalbuminuria, perhaps by decreasing the intraglomerular pressure.