The Association Between Adiponectin, Serum Uric Acid and Urinary Markers of Renal Damage in the General Population: Cross-Sectional Data from the Tromsø Study.
Uric acid may cause renal damage, whereas adiponectin in some studies has been reported to have renoprotective properties. The renoprotective role of adiponectin under the influence of hyperuricemia has not been explored. We assessed the cross-sectional association between adiponectin, serum uric acid (SUA) and urinary biomarkers of glomerular and tubular damage (albumin-creatinine ratio [ACR] and N-acetyl-ß-D-glucosaminidase-creatinine ratio [NAG-CR]) in a large cohort from a general population.
Three urine specimens from 7062 persons, participating in the Tromsø Study, were collected. The adjusted associations between adiponectin and SUA as independent variables, and ACR =1.13 mg/mmol (albuminuria) and the upper gender specific 15 percentile of NAG-CR (high NAG-CR) as dependent variables, were assessed.
Mean (standard deviation) age of the participants was 63.5 (9.2) years. Adiponectin was positively associated with albuminuria and high NAG-CR. SUA was associated with albuminuria (odds ratio [OR] 1.13; 95% Confidence Interval [CI] 1.05-1.21 per 59 µmol/L increase), but not with NAG-CR. There were no statistically significant interactions between SUA and adiponectin.
Unexpectedly, adiponectin was positively associated with both urinary markers of renal damage. SUA was positively associated with albuminuria only. SUA and adiponectin added little beyond traditional cardiovascular risk factors to predict renal damage and did not interact in their associations with the urinary biomarkers. Longitudinal studies are needed before firm conclusions can be made.
Hypertension is one of the most important causes of end-stage renal disease, but it is unclear whether elevated blood pressure (BP) also accelerates the gradual decline in the glomerular filtration rate (GFR) seen in the general population with increasing age. The reason may be that most studies have considered only baseline BP and not the effects of changes in BP, antihypertensive treatment and other determinants of GFR during follow-up. Additionally, the use of GFR estimated from creatinine or cystatin C instead of measurements of GFR may have biased the results because of influence from non-GFR related confounders. We studied the relationship between BP and GFR decline using time-varying variables in a cohort representative of the general population using measurements of GFR as iohexol clearance.
We included 1594 subjects aged 50 to 62 years without baseline diabetes, kidney-, or cardiovascular disease in the Renal Iohexol-clearance Survey in Tromsø 6 (RENIS-T6). GFR, BP, antihypertensive medication and all adjustment variables were ascertained at baseline, and at follow-up after a median observation time of 5.6 years in 1299 persons (81%). The relationship between GFR decline and BP was analyzed in linear mixed models.
The mean (standard deviation) GFR decline rate was 0.95 (2.23) mL/min/year. The percentage of persons with hypertension (systolic BP?=?140 mmHg, diastolic BP?=?90 mmHg or antihypertensive medication) increased from 42 to 52% between baseline and follow-up. In multivariable adjusted linear mixed models using time-varying independent variables measured at baseline and follow-up, higher systolic and diastolic BP were associated with slower GFR decline rates by 0.10 and 0.20 mL/min/year/10 mmHg, respectively (p?
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Cites: Am J Kidney Dis. 2014 Sep;64(3):411-24 PMID 24840668
Cites: J Am Soc Nephrol. 2015 Jun;26(6):1261-7 PMID 25525178
Hypertension is one of the most important causes of end-stage renal disease, but it is unclear whether elevated blood pressure (BP) also accelerates the gradual decline in the glomerular filtration rate (GFR) seen in the general population with increasing age. The reason may be that most studies have considered only baseline BP and not the effects of changes in BP, antihypertensive treatment and other determinants of GFR during follow-up. Additionally, the use of GFR estimated from creatinine or cystatin C instead of measurements of GFR may have biased the results because of influence from non-GFR related confounders. We studied the relationship between BP and GFR decline using time-varying variables in a cohort representative of the general population using measurements of GFR as iohexol clearance.
We included 1594 subjects aged 50 to 62 years without baseline diabetes, kidney-, or cardiovascular disease in the Renal Iohexol-clearance Survey in Tromsø 6 (RENIS-T6). GFR, BP, antihypertensive medication and all adjustment variables were ascertained at baseline, and at follow-up after a median observation time of 5.6 years in 1299 persons (81%). The relationship between GFR decline and BP was analyzed in linear mixed models.
The mean (standard deviation) GFR decline rate was 0.95 (2.23) mL/min/year. The percentage of persons with hypertension (systolic BP?=?140 mmHg, diastolic BP?=?90 mmHg or antihypertensive medication) increased from 42 to 52% between baseline and follow-up. In multivariable adjusted linear mixed models using time-varying independent variables measured at baseline and follow-up, higher systolic and diastolic BP were associated with slower GFR decline rates by 0.10 and 0.20 mL/min/year/10 mmHg, respectively (p?
Notes
Cites: Am J Kidney Dis. 2014 Sep;64(3):411-2424840668
Cites: J Am Soc Nephrol. 2015 Jun;26(6):1261-725525178
Increased urinary albumin-excretion (UAE) predicts cardiovascular events and clusters with the metabolic syndrome. The aim of this population-based, prospective study was to assess the relationship between baseline and longitudinal changes in cardiovascular risk-factors and 7 years' increase in UAE. Three thousand and four hundred non-diabetic participants (1838 men, 1562 women) of the Tromsø studies in 1994/1995 and 2001/2002 were included. In each survey, first-void spot-urine-samples were collected, and albumin-creatinine ratio (ACR) was calculated. Change in ACR (DeltaACR) was dichotomized into upper vs. the three lower quartiles. Median UAE in the population did not increase during follow-up. Baseline predictors for DeltaACR in the upper quartile were: age (OR 1.32 per 5 years, 95% CI 1.22-1.43), HbA1c (OR 1.43 per %, 95% CI 1.08-1.91) and waist circumference (OR 1.11 per 5 cm, 95% CI 1.04-1.19) in men, and age (OR 1.14 per 5 years, 95% CI 1.04-1.25) and current smoking (OR 1.71, 95% CI 1.27-2.30) in women. Systolic blood pressure and estimated glomerular filtration rate were predictors without gender-specificity. Clustering of three or more metabolic traits did not predict ACR increase independently. Protective factors against ACR increase were initiation of antihypertensive treatment in women (OR 0.59, 95% CI 0.39-0.87) and hard physical activity in men (OR 0.70, 95% CI 0.51-0.96). In summary, cardiovascular risk-factors at baseline predicted ACR increase, but initiation of antihypertensive therapy (women) and physical activity (men) seemed to protect from ACR increase during follow-up. Endpoint-data are needed to explore the clinical significance of low-grade UAE increase.
Although hypertension is a risk factor for end-stage renal disease, this complication develops in only a minority of hypertensive patients. Whether non-malignant hypertension itself is sufficient to cause reduced glomerular filtration rate (GFR) is unclear. Therefore, we investigated whether elevated blood pressure (BP) was associated with accelerated GFR decline in the general population. The study was based on the Renal Iohexol Clearance Survey in Tromsø 6 (RENIS-T6), which included a representative sample of 1594 individuals aged 50 to 62 years from the general population without baseline diabetes or kidney or cardiovascular disease. GFR was measured as iohexol clearance at baseline and follow-up after a median observation time of 5.6 years. BP was measured according to a standardized procedure. The mean (SD) GFR decline rate was 0.95 (2.23) ml/min/yr. In multivariable adjusted linear mixed regressions with either baseline systolic or diastolic BP as the independent variable, there were no statistically significant associations with GFR decline. Thus, elevated BP is not associated with accelerated mean GFR decline in the general middle-aged population. Hence, additional genetic and environmental factors are probably necessary for elevated BP to develop manifest chronic kidney disease in some individuals.
Estimated glomerular filtration rate (eGFR) is used extensively in epidemiological research. Validations of eGFR have demonstrated acceptable performance, but the dependence of creatinine and cystatin C on non-GFR factors could confound associations with disease. Few studies have investigated this issue in direct comparison with measured GFR (mGFR). We compared the associations between eGFR and mGFR and retinal vasculopathy, a marker of systemic microvasculopathy.
Iohexol clearance and retinal photography were examined in the Renal Iohexol Clearance Survey in Tromsø 6, which consists of a representative sample of middle-aged persons from the general population. A total of 1,553 persons without self-reported kidney disease, cardiovascular disease or diabetes were investigated. Three eGFR equations based on creatinine and/or cystatin C from the Chronic Kidney Disease Epidemiology Collaboration were studied. Differences between eGFR and mGFR were analyzed with seemingly unrelated regression methods.
mGFR in the lowest quartile was associated with an increased multivariable-adjusted odds ratio of retinopathy (OR 1.86, 95% CI 1.16-2.97), but not with retinal artery or vein diameters. eGFR based on cystatin C (eGFRcys) was consistently biased relative to mGFR in its associations with retinal vessel diameters across different models. eGFR based on creatinine (eGFRcrea) and eGFR based on both creatinine and cystatin C were also biased in several of these models (p
Estimated Glomerular Filtration Rate (eGFR) based on cystatin C was associated with increased risk of hip and proximal humerus fractures in women and decreased risk of hip fracture in men, whereas eGFR based on creatinine was not associated with fracture risk in both sexes: The Tromsø Study.
Patients with end-stage kidney disease have an increased fracture risk. Whether mild to moderate reductions in kidney function is associated with increased fracture risk is uncertain. Results from previous studies may be confounded by muscle mass because of the use of creatinine-based estimates of the glomerular filtration rate (eGFRcre). We tested the hypothesis that lower eGFR within the normal range of kidney function based on serum cystatin C (eGFRcys) or both cystatin C and creatinine (eGFRcrecys) predict fractures better than eGFR based on creatinine (eGFRcre).
In the Tromsø Study 1994-95, a cohort of 3016 women and 2836 men aged 50-84 years had eGFRcre, eGFRcys and eGFRcrecys estimated using the Chronic Kidney Disease Epidemiology Collaboration equations. Hazard ratios (HRs) (95% confidence intervals) for fracture were calculated in Cox's proportional hazards models and adjusted for age, height, body mass index, bone mineral density, diastolic blood pressure, smoking, physical activity, previous fracture, diabetes and cardiovascular disease.
During a median of 14.6 years follow-up, 232, 135 and 394 women and 118, 35 and 65 men suffered incident hip, proximal humerus and wrist fractures. In women, lower eGFRcre did not predict fracture, but the risk for hip and proximal humerus fracture increased per standard deviation (SD) lower eGFRcys (HRs 1.36 (1.16-1.60) and 1.33 (1.08-1.63)) and per SD lower eGFRcrecys (HRs 1.25 (1.08-1.45) and 1.30 (1.07-1.57)). In men, none of the eGFR estimates were related to increased fracture risk. In contrast, eGFRcys and eGFRcrecys were inversely associated with hip fracture risk (HRs 0.85 (0.73-0.99) and 0.82 (0.68-0.98)).
In women, each SD lower eGFRcys and eGFRcrecys increased the risk of hip and proximal humerus fracture by 25-36%, whereas eGFRcre did not. In men, none of the estimates of eGFR were related to increased fracture risk, and each SD lower eGFRcys and eGFRcrecys decreased the risk of hip fracture by 15-18%. The findings particularly apply to a cohort of generally healthy individuals with a normal kidney function. In future studies, the association of measured GFR using the gold standard method of iohexol clearance with fractures risk should be examined for causal inference. More clinical research is needed before robust clinical inferences can be made.
Section of Nephrology, University Hospital of North Norway, Tromsø, Norway; Metabolic and Renal Research Group, UiT The Arctic University of Norway, Tromsø, Norway. Electronic address: marit.solbu@unn.no.
Cardiovascular disease is a common cause of morbidity and mortality, with gender differences in pathophysiology. The endothelial glycocalyx maintains vascular integrity, and glycocalyx shedding reflects endothelial dysfunction and early atherosclerosis. Syndecan-1 and -4 are components of the glycocalyx, and increased serum levels indicate glycocalyx damage. We hypothesised that increased serum syndecan-1 and -4 were independently associated with myocardial infarction (MI), ischaemic stroke and all-cause mortality in men and women from a general population.
Using a case-cohort design, we included 1495 participants from the Tromsø Study 2001-02. Syndecan-1 and -4 were measured in serum. Baseline variables also included age, gender, cardiovascular risk factors and urinary albumin-creatinine ratio (ACR). Hazard ratios were assessed using multivariable Cox regression models.
Between baseline in 2001-02 and December 2007 fatal or non-fatal MI was experienced by 328 and ischaemic stroke by 191 subjects, and 423 participants died. Syndecan-4 was independently associated with MI (hazard ratio per 10?ng/mL increase 1.32; 95% confidence interval 1.06-1.63), but not ischaemic stroke and mortality, and the associations were unchanged by adjustment for urinary ACR. Interaction between syndecan-4 and sex was borderline significant, and in gender-specific analysis, syndecan-4 was associated with MI in women only. Syndecan-1 was not associated with any endpoint.
Syndecan-4 was associated with incident MI, and the association was stronger in women than in men. This suggests a link between endothelial glycocalyx shedding and coronary heart disease in women. Use of syndecan-4 as a risk marker in clinical setting needs further investigation.
Population mean GFR is lower in older age, but it is unknown whether healthy aging is associated with preserved rather than lower GFR in some individuals.
We investigated the cross-sectional association between measured GFR, age, and health in persons aged 50-97 years in the general population through a meta-analysis of iohexol clearance measurements in three large European population-based cohorts. We defined a healthy person as having no major chronic disease or risk factors for CKD and all others as unhealthy. We used a generalized additive model to study GFR distribution by age according to health status.
There were 935 (22%) GFR measurements in persons who were healthy and 3274 (78%) in persons who were unhealthy. The mean GFR was lower in older age by -0.72 ml/min per 1.73 m2 per year (95% confidence interval [95% CI], -0.96 to -0.48) for men who were healthy versus -1.03 ml/min per 1.73 m2 per year (95% CI, -1.25 to -0.80) for men who were unhealthy, and by -0.92 ml/min per 1.73 m2 per year (95% CI, -1.14 to -0.70) for women who were healthy versus -1.22 ml/min per 1.73 m2 per year (95% CI, -1.43 to -1.02) for women who were unhealthy. For healthy and unhealthy people of both sexes, both the 97.5th and 2.5th GFR percentiles exhibited a negative linear association with age.
Healthy aging is associated with a higher mean GFR compared with unhealthy aging. However, both the mean and 97.5 percentiles of the GFR distribution are lower in older persons who are healthy than in middle-aged persons who are healthy. This suggests that healthy aging is not associated with preserved GFR in old age.
Department of Medical Biochemistry, University Hospital of North Norway, and the Department of Clinical Medicine, University of Tromsø, Tromsø, Norway. toralf.melsom@unn.no
Increased glomerular filtration rate (GFR), also called hyperfiltration, is a proposed mechanism for renal injury in diabetes. The causes of hyperfiltration in individuals without diabetes are largely unknown, including the possible role of borderline hyperglycemia. We assessed whether impaired fasting glucose (IFG; 5.6-6.9 mmol/L), elevated HbA1c, or hyperinsulinemia are associated with hyperfiltration in the general middle-aged population.
A total of 1,560 individuals, aged 50-62 years without diabetes, were included in the Renal Iohexol Clearance Survey in Tromsø 6 (RENIS-T6). GFR was measured as single-sample plasma iohexol clearance. Hyperfiltration was defined as GFR>90th percentile, adjusted for sex, age, weight, height, and use of renin-angiotensin system inhibitors.
Participants with IFG had a multivariable-adjusted odds ratio of 1.56 (95% CI 1.07-2.25) for hyperfiltration compared with individuals with normal fasting glucose. Odds ratios (95% CI) of hyperfiltration calculated for a 1-unit increase in fasting plasma glucose (FPG) and HbA1c, after multivariable-adjustment, were 1.97 (1.36-2.85) and 2.23 (1.30-3.86). There was no association between fasting insulin levels and hyperfiltration. A nonlinear association between FPG and GFR was observed (df=3, P
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Cites: Kidney Int Suppl. 2003 Feb;(83):S31-712864872
