Prevalence of peripheral arterial disease and associated risk factors in American Indians: the Strong Heart Study.
Studies of peripheral arterial disease (PAD) in minority populations provide researchers with an opportunity to evaluate PAD risk factors and disease severity under different types of conditions. Examination 1 of the Strong Heart Study (1989-1992) provided data on the prevalence of PAD and its risk factors in a sample of American Indians. Participants (N = 4,549) represented 13 tribes located in three geographically diverse centers in the Dakotas, Oklahoma, and Arizona. Participants in this epidemiologic study were aged 45-74 years; 60% were women. Using the single criterion of an ankle brachial index less than 0.9 to define PAD, the prevalence of PAD was approximately 5.3% across centers, with women having slightly higher rates than men. Factors significantly associated with PAD in univariate analyses for both men and women included age, systolic blood pressure, hemoglobin A1c level, albuminuria, fibrinogen level, fasting glucose level, prevalence of diabetes mellitus, and duration of diabetes. Multiple logistic regression analyses were used to predict PAD for women and men combined. Age, systolic blood pressure, current cigarette smoking, pack-years of smoking, albuminuria (micro- and macro-), low density lipoprotein cholesterol level, and fibrinogen level were significantly positively associated with PAD. Current alcohol consumption was significantly negatively associated with PAD. In American Indians, the association of albuminuria with PAD may equal or exceed the association of cigarette smoking with PAD. (+info
Acute haemodynamic and proteinuric effects of prednisolone in patients with a nephrotic syndrome.
BACKGROUND: Administration of prednisolone causes an abrupt rise in proteinuria in patients with a nephrotic syndrome. METHODS: To clarify the mechanisms responsible for this increase in proteinuria we have performed a placebo controlled study in 26 patients with a nephrotic syndrome. Systemic and renal haemodynamics and urinary protein excretion were measured after prednisolone and after placebo. RESULTS: After i.v. administration of 125-150 mg prednisolone total proteinuria increased from 6.66+/-4.42 to 9.37+/-6.07 mg/min (P<0.001). By analysing the excretion of proteins with different charge and weight (albumin, transferrin, IgG, IgG4 and beta2-microglobulin) it became apparent that the increase of proteinuria was the result of a change in size selectivity rather than a change in glomerular charge selectivity or tubular protein reabsorption. Glomerular filtration rate rose from 83+/-34 ml to 95+/-43 ml/min (P<0.001) after 5 h, whereas effective renal plasma flow and endogenous creatinine clearance remained unchanged. As a result filtration fraction was increased, compatible with an increased glomerular pressure, which probably contributes to the size selectivity changes. Since corticosteroids affect both the renin-angiotensin system and renal prostaglandins, we have evaluated the effects of prednisolone on proteinuria after pretreatment with 3 months of the angiotensin-converting enzyme inhibitor lisinopril or after 2 weeks of the prostaglandin synthesis inhibitor indomethacin. Neither drug had any effect on prednisolone-induced increases of proteinuria. CONCLUSIONS: Prednisolone increases proteinuria by changing the size selective barrier of the glomerular capillary. Neither the renin-angiotensin axis nor prostaglandins seem to be involved in these effects of prednisolone on proteinuria. (+info
Increased renal resistive index in patients with essential hypertension: a marker of target organ damage.
BACKGROUND: Increased renal resistance detected by ultrasound (US) Doppler has been reported in severe essential hypertension (EH) and recently was shown to correlate with the degree of renal impairment in hypertensive patients with chronic renal failure. However, the pathophysiological significance of this finding is still controversial. METHODS: In a group of 211 untreated patients with EH, we evaluated renal resistive index (RI) by US Doppler of interlobar arteries and early signs of target organ damage (TOD). Albuminuria was measured as the albumin to creatinine ratio (ACR) in three non-consecutive first morning urine samples. Left ventricular mass was evaluated by M-B mode echocardiography, and carotid wall thickness (IMT) by high resolution US scan. RESULTS: RI was positively correlated with age (r=0.25, P=0.003) and systolic blood pressure (SBP) (r=0.2, P=0.02) and with signs of early TOD, namely ACR (r=0.22, P=0.01) and IMT (r=0.17, P<0.05), and inversely correlated with renal volume (r=-0.22, P=0.01) and diastolic blood pressure (r=-0.23, P=0.006). Multiple linear regression analysis demonstrated that age, gender, ACR and SBP independently influence RI and together account for approximately 20% of its variations (F=8.153, P<0.0001). When clinical data were analysed according to the degree of RI, the patients in the top quartile were found to be older (P<0.05) and with higher SBP (P<0.05) as well as early signs of TOD, namely increased ACR (P<0.002) and IMT (P<0.005 by ANOVA), despite similar body mass index, uric acid, fasting blood glucose, lipid profile and duration of hypertension. Furthermore, patients with higher RI showed a significantly higher prevalence of microalbuminuria (13 vs 12 vs 3 vs 33% chi2=11.72, P=0.008) and left ventricular hypertrophy (40 vs 43 vs 32 vs 60%, chi2=9.25, P<0.05). CONCLUSIONS: Increased RI is associated with early signs of TOD in EH and could be a marker of intrarenal atherosclerosis. (+info
Cardiovascular, endocrine, and renal effects of urodilatin in normal humans.
Effects of urodilatin (5, 10, 20, and 40 ng. kg-1. min-1) infused over 2 h on separate study days were studied in eight normal subjects with use of a randomized, double-blind protocol. All doses decreased renal plasma flow (hippurate clearance, 13-37%) and increased fractional Li+ clearance (7-22%) and urinary Na+ excretion (by 30, 76, 136, and 99% at 5, 10, 20, and 40 ng. kg-1. min-1, respectively). Glomerular filtration rate did not increase significantly with any dose. The two lowest doses decreased cardiac output (7 and 16%) and stroke volume (10 and 20%) without changing mean arterial blood pressure and heart rate. The two highest doses elicited larger decreases in stroke volume (17 and 21%) but also decreased blood pressure (6 and 14%) and increased heart rate (15 and 38%), such that cardiac output remained unchanged. Hematocrit and plasma protein concentration increased with the three highest doses. The renin-angiotensin-aldosterone system was inhibited by the three lowest doses but activated by the hypotensive dose of 40 ng. kg-1. min-1. Plasma vasopressin increased by factors of up to 5 during infusion of the three highest doses. Atrial natriuretic peptide immunoreactivity (including urodilatin) and plasma cGMP increased dose dependently. The urinary excretion rate of albumin was elevated up to 15-fold (37 +/- 17 micrograms/min). Use of a newly developed assay revealed that baseline urinary urodilatin excretion rate was low (<10 pg/min) and that fractional excretion of urodilatin remained below 0.1%. The results indicate that even moderately natriuretic doses of urodilatin exert protracted effects on systemic hemodynamic, endocrine, and renal functions, including decreases in cardiac output and renal blood flow, without changes in arterial pressure or glomerular filtration rate, and that filtered urodilatin is almost completely removed by the renal tubules. (+info
Microalbuminuria and peripheral arterial disease are independent predictors of cardiovascular and all-cause mortality, especially among hypertensive subjects: five-year follow-up of the Hoorn Study.
Microalbuminuria (MA) is associated with increased cardiovascular and all-cause mortality. It has been proposed that MA reflects generalized atherosclerosis and may thus predict mortality. To investigate this hypothesis, we studied the associations between, on the one hand, MA and peripheral arterial disease (PAD), a generally accepted marker of generalized atherosclerosis, and, on the other hand, cardiovascular and all-cause mortality in an age-, sex-, and glucose tolerance-stratified sample (n=631) of a population-based cohort aged 50 to 75 years followed prospectively for 5 years. At baseline, the albumin-to-creatinine ratio (ACR) was measured in an overnight spot urine sample; MA was defined as ACR >2.0 mg/mmol. PAD was defined as an ankle-brachial pressure index below 0.90 and/or a history of a peripheral arterial bypass or amputation. After 5 years of follow-up, 58 subjects had died (24 of cardiovascular causes). Both MA and PAD were associated with a 4-fold increase in cardiovascular mortality. After adjusting for age, sex, diabetes mellitus, hypertension, levels of total and HDL-cholesterol and triglyceride, body mass index, smoking habits, and preexistent ischemic heart disease, the relative risks (RR) (95% confidence intervals) were 3.2 (1.3 to 8.1) for MA and 2.4 (0.9 to 6.1) for PAD. When both MA and PAD were included in the multivariate analysis, the RRs were 2.9 (1.1 to 7.3) for MA and 2.0 (0.7 to 5.7) for PAD. MA and PAD were both associated with an about 2-fold increase in all-cause mortality. The RRs of all-cause mortality associated with MA and PAD were about 4 times higher among hypertensive than among normotensive subjects. We conclude that both MA and PAD are associated with an increased risk of cardiovascular mortality. MA and PAD are mutually independent risk indicators. The associations of MA and PAD with all-cause mortality are somewhat weaker. They are more pronounced in the presence of hypertension than in its absence. These data suggest that MA affects mortality risk through a mechanism different from generalized atherosclerosis. (+info
Chronic bradykinin infusion and receptor blockade in angiotensin II hypertension in rats.
The influence of endogenous bradykinin(BK) on the control of arterial pressure and the development of cardiac hypertrophy was assessed in chronically angiotensin II(Ang II)-infused rats (200 ng. kg-1. min-1) through the effects of concomitant infusion of 3 doses of BK (15 ng. kg-1. d-1, 100 ng. kg-1. d-1 and 100 ng. kg-1. min-1 ie, 144 000 ng. kg-1. d-1) or BK-blockade by Hoe140 (300 microg. kg-1. d-1) for 10 days. In Ang II-infused rats, tail-cuff pressure increased from 124+/-3 to 174+/-6 mm Hg (P<0.001). The pressor effect of Ang II was not affected by simultaneous infusion of BK or Hoe140. At the end of the experiments, cardiac mass was higher in rats infused with Ang II alone (3.56+/-0.10 versus 2.89+/-0.05 mg/g in untreated controls, P<0.01) and the development of cardiac hypertrophy was not modified by administration of the 3 doses of BK or Hoe140. In addition, the fall in cardiac output associated with Ang II was prevented only by the moderate and high doses of BK, mainly through an increase in stroke volume and a decrease in total peripheral resistance. In the same way, the renal vasoconstrictor effect of Ang II was abolished by the medium and high dose of BK. Hoe140 did not affect cardiac output or renal blood flow in this model. No influence of BK or Hoe140 on the increase in albuminuria induced by Ang II was detected. In conclusion, exogenous BK may oppose the effect of Ang II on vascular tone, but it cannot prevent hypertension and target-organ damage associated with this experimental model of hypertension, even at a very high dose. (+info
Cyclosporine nephrotoxicity in type 1 diabetic patients. A 7-year follow-up study.
OBJECTIVE: To evaluate kidney function 7 years after the end of treatment with cyclosporine A (CsA) (initial dosage of 9.3 tapered off to 7.0 mg.kg-1.day-1) in young patients (mean age 20 years) with newly diagnosed type 1 diabetes participating in a randomized, double-blind, placebo-controlled CsA trial. RESEARCH DESIGN AND METHODS: In this study, 21 patients received CsA for 12.5 +/- 4.0 months (mean +/- SD) and 19 patients received placebo for 14.4 +/- 3.8 months. The two groups were similar with regard to mean arterial blood pressure (BP), urinary albumin excretion rate (UAER), serum creatinine, and estimated glomerular filtration rate (GFR [Cockcroft and Gault]) at initiation of CsA treatment (baseline). HbA1c (mean +/- SEM) during 7 years of follow-up was also the same: 8.7 +/- 0.4 vs. 8.3 +/- 0.4% in the CsA and placebo groups, respectively. RESULTS: During the 7 years after cessation of study medication, two CsA group patients and one control patient were lost to follow-up. One placebo-treated patient developed IgA nephropathy (biopsy proven) and was excluded. Four CsA-treated patients developed persistently elevated UAER > 30 mg/24 h (n = 3 with microalbuminuria), whereas all the 17 placebo-treated patients had normal UAER (< 30 mg/24 h) after 7 years of follow-up. At the end of follow-up, the CsA group had a more pronounced rise in UAER: 2.5-fold (95% CI 1.4-4.5) higher than baseline value vs. 1.1-fold (0.7-1.7) in the placebo-treated group (P < 0.05). Estimated GFR (ml.min-1.1.73 m-2) declined from baseline to end of follow-up (1994) by 6.3 +/- 6.0 in the former CsA group, whereas it rose by 7.4 +/- 5.0 in the placebo group (P = 0.05). In 1994, 24-h blood pressure was nearly the same: 131/77 +/- 4/2 vs. 127/75 +/- 2/2 mmHg (NS) in the CsA and placebo groups, respectively. Five randomly selected CsA-treated patients had a kidney biopsy performed shortly after the CsA treatment was stopped. Interstitial fibrosis/tubular atrophy and/or arteriolopathy were present in two subjects who both subsequently developed persistent microalbuminuria. CONCLUSIONS: The results of our 7-year follow-up study suggested that short-lasting CsA treatment in young, newly diagnosed type 1 diabetic patients accelerated the rate of progression in UAER and tended to induce a loss in kidney function. Longer term follow-up is mandatory to clarify whether CsA-treated patients are at increased risk of developing clinical nephropathy. (+info
Microalbuminuria prevalence varies with age, sex, and puberty in children with type 1 diabetes followed from diagnosis in a longitudinal study. Oxford Regional Prospective Study Group.
OBJECTIVE: The predictive value of microalbuminuria (MA) in children with type 1 diabetes has not been defined. We describe the natural history of MA in a large cohort of children recruited at diagnosis of type 1 diabetes. RESEARCH DESIGN AND METHODS: Between 1985 and 1996, 514 children (279 male) who developed type 1 diabetes before the age of 16 years (91% of those eligible from a region where ascertainment of new cases is 95%) were recruited for a longitudinal study with central annual assessment of HbAlc and albumin excretion (three urine samples). Dropout rates have been < 1% per year, and 287 children have been followed for > 4.5 years. RESULTS: MA (defined as albumin-to-creatinine ratio > or = 3.5 and > or = 4.0 mg/mmol in boys and girls, respectively) developed in 63 (12.8%) and was persistent in 22 (4.8%) of the subjects. The cumulative probability (based on the Kaplan-Meier method) for developing MA was 40% after 11 years. HbAlc was worse in those who developed MA than in others (mean difference +/- SEM: 1.1% +/- 0.2, P < 0.001). In subjects who had been 5-11 years of age when their diabetes was diagnosed, the appearance of MA was delayed until puberty, whereas of those whose age was < 5 years at diagnosis of diabetes, 5 of 11 (45%) developed MA before puberty. The adjusted proportional probability (Cox model) of MA was greater for female subjects (200%), after pubertal onset (310%), and with greater HbAlc (36% increase for every 1% increase in HbAlc). Despite earlier differences based on age at diagnosis of diabetes (< 5, 5-11, and > 11 years), the overall cumulative risks in these groups were similar (38 vs. 29 vs. 39%, respectively) after 10 years' duration of diabetes. CONCLUSIONS: Prepubertal duration of diabetes and prepubertal hyperglycemia contribute to the risk of postpubertal MA. The differences in rates of development of MA relating to HbAlc, sex, and age at diagnosis relative to puberty may have long-term consequences for the risk of subsequent nephropathy and for cardiovascular risk. (+info