P. E. De Jong

Microalbuminuria is common, also in a nondiabetic, nonhypertensive population, and an independent indicator of cardiovascular risk factors and cardiovascular morbidity

Abstract. Hillege HL, Janssen WMT, Bak AAA, Diercks GFH, Grobbee DE, Crijns HJGM, van Gilst WH, de Zeeuw D, de Jong PE for the PREVEND Study group (University of Groningen and University Hospital Groningen, Groningen; University Medical centre, Utrecht, the Netherlands). Microalbuminuria is common, also in a nondiabetic, nonhypertensive population, and an independent indicator of cardiovascular risk factors and cardiovascular morbidity. J Intern Med 2001; 249: 519–526.

Sodium intake affects urinary albumin excretion especially in overweight subjects

Objectives.  To examine the relationship between sodium intake and urinary albumin excretion, being an established risk marker for later cardiovascular morbidity and mortality.

Obesity and target organ damage : the kidney

Obesity is a risk marker for progressive renal function loss in patients with known renal disease. There is, however, increasing evidence that obesity may also damage the kidney in otherwise healthy subjects. There appears to be an intriguing parallel between the renal effects of obesity and those of diabetes. First, an increased renal blood flow and glomerular filtration rate has been described in obesity and, second, microalbuminuria is found to be related to obesity. These two events are known to predict future loss of renal function in diabetes. The mechanism responsible for the renal damage in obesity has not been established but there is evidence suggesting that this might be related to both hormonal changes as well as low-grade inflammation.

Association between angiotensin-converting-enzyme gene polymorphism and failure of renoprotective therapy

BACKGROUND Polymorphism in the gene for angiotensin-converting enzyme (ACE), especially the DD genotype, is associated with risk for cardiovascular disease. Glomerulosclerosis has similarities to atherosclerosis, and we looked at ACE gene polymorphism in patients with kidney disease who were in a trial of long-term therapy with an ACE inhibitor or a beta-blocker. METHODS 81 patients with non-diabetic renal disease had been entered into a randomised comparison of oral atenolol or enalapril to prevent progressive decline in renal function. The dose was titrated to a goal diastolic blood pressure of 10 mm Hg below baseline and/or below 95 mm Hg. The mean (SE) age was 50 (1) years, and the group included 49 men. Their renal function had been monitored over 3-4 years. We have looked at their ACE genotype, which we assessed with PCR. FINDINGS 27 patients had the II genotype, 37 were ID, and 17 were DD. 11 patients were lost to follow-up over 1-3 years. The decline of glomerular filtration rate over the years was significantly steeper in the DD group than in the ID and the II groups (p = 0.02; means -3.79, -1.37, and -1.12 mL/min per year, respectively). The DD patients treated with enalapril fared as equally a bad course as the DD patients treated with atenolol. Neither drug lowered the degree of proteinuria in the DD group. INTERPRETATION Our data show that patients with the DD genotype are resistant to commonly advocated renoprotective therapy.

Telomere length loss due to smoking and metabolic traits

Human age‐dependent telomere attrition and telomere shortening are associated with several age‐associated diseases and poorer overall survival. The aim of this study was to determine longitudinal leucocyte telomere length dynamics and identify factors associated with temporal changes in telomere length.

Antihypertensive effect of a 5-day infusion of atrial natriuretic factor in humans.

Atrial natriuretic factor was infused in a low dose (0.2 μg/min) during 5 days in six patients with essential hypertension. Atrial natriuretic factor infusion caused plasma levels of atrial natriuretic factor to increase from 49±10 to 106±19 pg/ml. Within 4 hours after the start of the atrial natriuretic factor infusion, urinary sodium excretion increased hi all subjects. Sodium balance was regained after 24 hours with a net loss of 72.3±14.6 mmol. However, systolic as well as diastolic blood pressure started to decrease gradually in all subjects only after 12 hours of atrial natriuretic factor infusion, reaching a stable level after 36 hours with a decrease of 11.5±1.5% and 10.3±0.8%, respectively. Heart rate increased in parallel by 12.6±3.1%. Hematocrit rose 7.1±2.3%. After cessation of atrial natriuretic factor infusion, plasma atrial natriuretic factor levels, sodium balance, and hematocrit returned to baseline within 24 hours, whereas blood pressure slowly returned toward baseline values over 3 days. These data show that chronic atrial natriuretic factor infusion in patients with essential hypertension causes a negative sodium balance and a rise in hematocrit, followed by a smooth decrease in blood pressure with a rise in heart rate until a new equilibrium is reached after approximately 2 days. Thus, atrial natriuretic factor in low doses appears intimately involved in the regulation of sodium balance and blood pressure in humans. Moreover, these data suggest that atrial natriuretic factor-like substances will eventually become useful antihypertensive drugs.

The reliability of different formulae to predict creatinine clearance

Abstract.  Verhave JC, Baljé‐Volkers CP, Hillege HL, de Zeeuw D, de Jong PE (University Medical Center Groningen, Groningen University, Institute of Drug Exploration, Groningen, the Netherlands). The reliability of different formulae to predict creatinine clearance. J Intern Med 2003; 253: 563–573.

Urinary albumin excretion is related to cardiovascular risk indicators, not to flow-mediated vasodilation, in apparently healthy subjects.

Based on studies in diabetic and hypertensive populations it has been postulated that early endothelial dysfunction is the mechanism responsible for the increased cardiovascular risk in microalbuminuric subjects. We evaluated the relation between microalbuminuria and endothelial dysfunction, assessed as flow-mediated dilation of the brachial artery, in an apparently healthy population. Within the framework of the PREVEND Intervention Trial non-hypertensive and non-hypercholesterolemic subjects were recruited on the basis of reproducible microalbuminuria. Using high-resolution ultrasound, flow-mediated dilation and nitroglycerin-mediated dilation of the brachial artery was assessed to measure endothelium-dependent and endothelium-independent responses, respectively. For the current study subjects with diabetes mellitus, clinical atherosclerosis, and macroalbuminuria were excluded from the analyses. We studied 421 men and 233 women (mean age (SD) 50 (12)). Increasing levels of urinary albumin excretion were accompanied by a significant increase in age, percentage men, systolic and diastolic blood pressure, body mass index, and serum triglycerides, whereas there was no decrease of flow-mediated vasodilation or nitroglycerin-mediated vasodilation. Adjusted for age and sex, urinary albumin excretion was significantly related to systolic (r=0.19, P<0.001) and diastolic (r=0.16, P<0.001) blood pressure, body mass index (r=0.18, P<0.001), and triglycerides (r=0.13, P=0.001), but not to flow-mediated vasodilation (r=-0.01, P=0.8). In contrast to blood pressure, body mass index, and triglycerides, there was no relation between urinary albumin excretion and flow-mediated vasodilation in apparently healthy subjects. These data suggest that the presence of atherogenic risk factors precedes the development of endothelial dysfunction in microalbuminuric, but otherwise healthy subjects.

Sodium status and angiotensin-converting enzyme inhibition: effects on plasma angiotensin-(1-7) in healthy man.

Objective Angiotensin-converting enzyme (ACE) inhibitors provide effective intervention for cardiovascular and renal disease. Changes in angiotensin-(1-7) have been proposed to be involved in the mechanism of action of ACE inhibition (ACEi). In particular, an altered balance between angiotensin II and angiotensin-(1-7) might be involved. A shift in sodium status modifies the activity of the renin–angiotensin–aldosterone system and the effects of ACEi, but its effects on angiotensin-(1-7) are unknown. We therefore studied the effect of a shift in sodium intake on angiotensin-(1-7), during placebo and ACEi. Methods A double-blind, placebo-controlled study was conducted in 17 healthy men. The subjects were studied for two 2-week periods: 20 mg/day enalapril and placebo. The first week of each period they used a 50 mmol Na+ diet [low sodium (LS)], the second week a 200 mmol Na+ diet. Angiotensin levels and blood pressure were measured at the end of each week. Results During placebo, LS intake elicited a three-fold rise in ang-(1-7) that paralleled the rise in other components of the renin–angiotensin system. During ACEi LS did not affect angiotensin II, but did induce a clear-cut rise in angiotensin-(1-7) — to the extent that angiotensin-(1-7) was highest during combination of ACEi and LS. Consequently, during ACEi LS shifted the balance between angiotensin-(1-7) and angiotensin II towards angiotensin-(1-7). Conclusion The sodium status modifies levels of angiotensin-(1-7). During ACEi angiotensin-(1-7) is still subject to stimulation by sodium restriction, and provides opportunity for therapeutic manipulation. Exploration of this opportunity in patient populations may lead to strategies to improve therapeutic benefits of ACEi.

Short-term moderate sodium restriction induces relative hyperfiltration in normotensive normoalbuminuric Type I diabetes mellitus.

Aims/hypothesis. Type I (insulin-dependent) diabetes mellitus is associated with an increased extracellular volume. Sodium restriction might seem a logical form of treatment but data on its renal effects is conflicting. We therefore studied the effects of sodium restriction on renal haemodynamics in uncomplicated Type I diabetes mellitus. Methods. Uncomplicated Type I diabetic patients (n = 24) and matched control subjects (n = 24) were studied twice in random order: after a week of 50 mmol or after 200 mmol sodium intake, respectively. The diabetic patients were studied under normoglycaemic clamp conditions. Glomerular filtration rate and effective renal plasma flow were measured as the clearances of iothalamate and hippuran, respectively. Results. During liberal sodium intake, glomerular filtration, effective renal plasma flow and filtration fraction were similar between the diabetic patients and the control subjects. Sodium restriction decreased the effective renal plasma flow in both groups, whereas glomerular filtration rate only decreased in the control subjects. Consequently, in the diabetic patients, the filtration fraction was increased on low sodium (4.1 ± 8.4 %, p < 0.05 vs liberal sodium). As a consequence, filtration fraction (24.0 ± 2.6 vs 22.1 ± 2.0 %, p < 0.05) and glomerular filtration (119 ± 14 vs 110 ± 13 ml/min, p < 0.05) were higher in the diabetic patients than in the control subjects during sodium restriction. Conclusion/interpretation. Short-term moderate sodium restriction induces relative hyperfiltration in uncomplicated Type I diabetes. This could indicate an increased intraglomerular pressure. Sodium restriction could be an unfavourable preventive approach in diabetes mellitus but its long-term effects are not known. [Diabetologia (2002) 45: ▪–▪]