Low plasma concentrations of diet-derived antioxidants in association with microalbuminuria in Indigenous Australian populations

Nontraditional Risk Factors for Progression Through Chronic Kidney Disease Risk Categories: The Coronary Artery Risk Development in Young Adults Study

BACKGROUND

There may be nontraditional pathways of chronic kidney disease (CKD) progression that are complementary to classical pathways. Therefore, we aimed to examine nontraditional risk factors for incident CKD and its progression.

METHODS

We used the generally healthy population (n = 4382) starting at age 27-41 years in the Coronary Artery Risk Development in Young Adults (CARDIA) cohort, which is an observational longitudinal study. Nontraditional risk factors included forced vital capacity, inflammation, serum urate, and serum carotenoids. CKD risk category was classified using the estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (UACR) measured in 1995-1996 and repeated every 5 years for 20 years: No CKD, low risk, moderate risk, high risk, and very high risk.

RESULTS

At baseline, 84.8% had no CKD (eGFR ≥60 mL/min/1.73 m2 and UACR <10 mg/g), 10.3% were in the low risk (eGFR ≥60 and UACR 10-29), and 4.9% had CKD (eGFR <60 and/or UACR ≥ 30). Nontraditional risk factors were significantly associated with the progression of CKD to higher categories. Hazard ratios per standard deviation of the predictor for incident CKD and its progression from the No CKD and low and moderate risk into CKD were inverse for forced vital capacity and serum carotenoids and positive for serum urate, GlycA, and C-reactive protein, the first 3 even after adjustment for conventional risk factors.

CONCLUSION

Several nontraditional markers were significantly associated with an increased risk of progression to higher CKD categories in generally healthy young to middle-aged adults.

Antioxidant biomarkers and cardiometabolic risk markers in an Aboriginal community in remote Australia: a cross-sectional study

OBJECTIVE

High-quality diets, characterised by nutrient-rich foods, are one of the foundations for health and well-being. Indicators of diet quality, antioxidants, are associated with protection against cardiometabolic diseases. The current study explores relationships between plasma antioxidants and cardiometabolic risk among Aboriginal people in Australia.

DESIGN

As part of a community-driven health promotion programme, we conducted a cross-sectional study including a health-behaviour questionnaire, plasma antioxidants and cardiometabolic risk markers (anthropometric, blood pressure measurements, fasting glucose, glycated Hb (HbA1c), lipids, C-reactive protein and albumin-creatinine-ratio) continuous and categorised into population-specific cut-offs. Antioxidants (β-carotene, β-cryptoxanthin, lycopene, lutein-zeaxanthin, retinol and α-tocopherol measured using HPLC) were applied to a principal component analysis, which aggregated these into a single component. Linear regression models were applied to investigate associations between the antioxidant component and cardiometabolic risk markers.

SETTING

Community in a remote area in Northern Territory, Australia.

PARTICIPANTS

A total of 324 Aboriginal people, mean age 35·5 (range 15-75) years.

RESULTS

Antioxidant component levels were higher among individuals with higher self-reported vegetable intake (P < 0·01), higher among individuals with higher self-reported fruit intake (P = 0·05) and lower among current smokers (P = 0·06). Linear regression revealed an inverse association between the antioxidant component and C-reactive protein (β = -0·01, P < 0·01) after adjusting for confounders.

CONCLUSION

Higher plasma antioxidant levels, indicators of diet quality, were associated with lower levels of high-sensitivity C-reactive protein in this Aboriginal population in remote Australia. This association suggests plasma antioxidants may be protective against inflammation; however, longitudinal studies are needed to examine this potentially protective relationship.

Relations Between Urinary Albumin Excretion and a Dietary Intake of Fruits in Patients With Type 2 Diabetes

Background

It was reported that microalbuminuria and a decline in renal function were associated with cardiovascular disease (CVD) mortality and renal events and prognostic serious complications. Dietary factors and nutrients affecting microalbuminuria in type 2 diabetes remain unclear, and accordingly we conducted a cross-sectional study on the possible relevance of dietary factors to urinary albumin excretion in patients with type 2 diabetes.

Methods

Forty-two patients with type 2 diabetes participated in this study, and these subjects were categorized into patients without microalbuminuria group with urine albumin-to-creatinine ratio (ACR) of less than 30 mg/g Cr (n = 29) and a microalbuminuria group with ACR of 30 - 299 mg/g Cr (n = 13). ACR levels were measured using spot urine samples. At the time of examination, body mass index (BMI) and systolic and diastolic blood pressures were measured and recorded. We performed sampling fasting-blood and spot urine and conducted a food frequency questionnaire based on food groups to examine dietary habits for the past 1 - 2 months.

Results

There were no significant differences in sex, age, duration, BMI, blood pressures, biochemical data, and the median of daily intakes of energy and macronutrients between patients without microalbuminuria and microalbuminuria groups. In the intake of 17 food groups per day, fruits were significantly lower in the microalbuminuria group than in patients without microalbuminuria group (the median was 38 g vs. 120 g/day, P < 0.05), but intakes of other food groups were not significantly different between the two groups. Moreover, we examined a model of partial correlation between ACR to the intake of fruits, adjusted by age, sex, glycated hemoglobin and BMI. This partial correlation was insignificantly seen but close to a significant level (partial correlation coefficient: -0.270, P = 0.102).

Conclusions

These results suggest that the intake of fruits may be inversely associated with microalbuminuria in Japanese type 2 diabetic patients. It would be necessary to investigate the exact types and amounts of fruits to be consumed to address microalbuminuria.

Serum xanthophyll carotenoids are associated with estimated glomerular filtration rate in an aged cohort

Progressive renal decline is associated with increasing oxidative stress. However, the majority of studies have investigated endogenous antioxidants in predominantly advanced stages of kidney disease. Many traditional risk factors associated with renal dysfunction have been linked with cognitive decline as the kidneys and brain share comparable anatomic and haemodynamic characteristics that leave them susceptible to common pathogenic mechanisms. The objective of this study was to examine serum dietary antioxidants and their association with renal function characterised by estimated glomerular filtration rate (eGFR) in a cross-sectional analysis of 570 participants. High performance liquid chromatography quantified serum levels of retinol, α-tocopherol, γ-tocopherol and six carotenoids (α-carotene, β-carotene, β-cryptoxanthin, lutein, lycopene and zeaxanthin) in participants. Multiple regression analyses were used to evaluate associations while adjusting for potential confounders. A sensitivity analysis was performed in cognitively-intact participants only. Serum levels of the xanthophyll carotenoid lutein were positively associated with eGFR in analyses adjusted for age (years), gender, smoking, APOE4 status and Alzheimer’s disease. Retinol was inversely associated with eGFR, although was no longer significant in the smaller sensitivity analysis. Our findings identify significant associations between the xanthophyll carotenoids and eGFR. Further investigations are required to confirm these findings.

Systemic Redox Imbalance in Chronic Kidney Disease: A Systematic Review

Patients with chronic kidney disease (CKD) experience imbalance between oxygen reactive species (ROS) production and antioxidant defenses leading to cell and tissue damage. However, it remains unclear at which stage of renal insufficiency the redox imbalance becomes more profound. The aim of this systematic review was to provide an update on recent advances in our understanding of how the redox status changes in the progression of renal disease from predialysis stages 1 to 4 to end stage 5 and whether the various treatments and dialysis modalities influence the redox balance. A systematic review was conducted searching PubMed and Scopus by using the Cochrane and PRISMA guidelines. In total, thirty-nine studies met the inclusion criteria and were reviewed. Even from an early stage, imbalance in redox status is evident and as the kidney function worsens it becomes more profound. Hemodialysis therapy per se seems to negatively influence the redox status by the elevation of lipid peroxidation markers, protein carbonylation, and impairing erythrocyte antioxidant defense. However, other dialysis modalities do not so far appear to confer advantages. Supplementation with antioxidants might assist and should be considered as an early intervention to halt premature atherogenesis development at an early stage of CKD.

Nutritional predictors of chronic disease in a Central Australian Aboriginal cohort: A multi-mixture modelling analysis

BACKGROUND AND AIMS

Chronic diseases (including diabetes, cardiovascular disease, hypertension and chronic kidney disease) are major contributors to the total burden of disease for Aboriginal people. Here we used novel epidemiological modelling to investigate nutritional profiles at a population level associated with chronic disease.

METHODS AND RESULTS

Multi-mixture modelling, was used to group members of a Central Australian Aboriginal population (n = 444) based on their nutritional profile from a risk factor prevalence survey in 1995. Multi-mixture modelling assigned % membership to four classes; Class 1 (young, low adiposity and lipids, low dietary antioxidants; n = 171.7); Class 2 (older, greater adiposity and lipids; n = 22.6); Class 3 (predominantly female, greater adiposity and antioxidants, low smoking; n = 134.3) and Class 4 (predominantly male, greater lipids and adiposity, low antioxidants, high smoking prevalence; n = 115.4). For persons free of chronic disease (n = 285), incident chronic disease for classes 1, 3 and 4 was determined using follow up hospital, primary health care and death records collected in 2004/05. Fifty-four percent of Class 4 had incident chronic disease, an excess of 3355 events per 100,000 person years relative to Class 1. Incident CVD, hypertension, or CKD was highest for Class 4 and incident diabetes highest for Class 3.

CONCLUSION

Multi-mixture modelling appears useful in identifying population subgroups of an Aboriginal population at risk of chronic conditions.

Nutritional predictors of successful chronic disease prevention for a community cohort in Central Australia

OBJECTIVE

To investigate biomarkers of nutrition associated with chronic disease absence for an Aboriginal cohort.

DESIGN

Screening for nutritional biomarkers was completed at baseline (1995). Evidence of chronic disease (diabetes, CVD, chronic kidney disease or hypertension) was sought from primary health-care clinics, hospitals and death records over 10 years of follow-up. Principal components analysis was used to group baseline nutritional biomarkers and logistic regression modelling used to investigate associations between the principal components and chronic disease absence.

SETTING

Three Central Australian Aboriginal communities.

SUBJECTS

Aboriginal people (n 444, 286 of whom were without chronic disease at baseline) aged 15-82 years.

RESULTS

Principal components analysis grouped twelve nutritional biomarkers into four components: 'lipids'; 'adiposity'; 'dietary quality'; and 'habitus with inverse quality diet'. For the 286 individuals free of chronic disease at baseline, lower adiposity, lower lipids and better dietary quality components were each associated with the absence at follow-up of most chronic diseases examined, with the exception of chronic kidney disease. Low 'adiposity' component was associated with absence of diabetes, hypertension and CVD at follow-up. Low 'lipid' component was associated with absence of hypertension and CVD, and high 'dietary quality' component was associated with absence of CVD at follow-up.

CONCLUSIONS

Lowering or maintenance of the factors related to 'adiposity' and 'lipids' to healthy thresholds and increasing access to a healthy diet appear useful targets for chronic disease prevention for Aboriginal people in Central Australia.

Association of serum carotenoid levels with urinary albumin excretion in a general Japanese population: the Yakumo study

Background

Albuminuria is a risk factor for not only nephropathy progression but also cardiovascular disease. Oxidative stress may have a role in the positive association between albuminuria and cardiovascular disease.

Methods

This cross-sectional study investigated the associations of serum levels of carotenoids, which are dietary antioxidants, with albuminuria among 501 Japanese adults (198 men, mean age ± SD: 66.4 ± 10.0 years; 303 women, mean age ± SD: 65.4 ± 9.8 years) who attended a health examination. Serum levels of carotenoids were determined by high-performance liquid chromatography. Logistic regression analysis was used to estimate odds ratios (ORs) with 95% CIs for albuminuria after adjustment for age, body mass index, smoking habits, drinking habits, hypertension, diabetes mellitus, and dyslipidemia.

Results

Prevalence of albuminuria was 15.4% among men and 18.1% among women. Among women with albuminuria, geometric mean serum levels of canthaxanthin, lycopene, β-carotene, total carotenes, and provitamin A were significantly lower than those of normoalbuminuric women. Adjusted ORs for albuminuria among women in the highest tertiles of serum β-carotene (OR, 0.45; 95% CI, 0.20–0.98) and provitamin A (OR, 0.45; 95% CI, 0.20–0.97) were significantly lower as compared with those for women in the lowest tertile. There were no associations between serum carotenoids and albuminuria in men.

Conclusions

An increased level of serum provitamin A, especially serum β-carotene, was independently associated with lower risk of albuminuria among Japanese women.

Relationship between dietary intake and microalbuminuria: findings from the Takahata study

BACKGROUND

Although several studies have investigated the relationship between dietary nutrient intake and microalbuminuria, no study of an Asian population has been reported. The present study investigates the relationship between dietary intake and microalbuminuria in a general Japanese population.

METHODS

We analyzed 675 men and 924 women who did not have diabetes. Participants who had a urinary albumin-to-creatinine ratio (UACR) ≥300 mg/g, who did not complete a questionnaire regarding food frequency and who did not provide complete urine measurements were excluded. Nutrient intake was assessed by validated food frequency questionnaire. Microalbuminuria was defined as UACR ≥30 mg/g. The relationship between dietary nutrient intake and microalbuminuria was examined using a multiple logistic regression model adjusted for age, total energy intake, body mass index, smoking status, systolic blood pressure and use of antihypertensive medication.

RESULTS

No significant association was observed among the men. The multiple adjusted odds ratios (95% confidence interval) of having microalbuminuria per 1 standard deviation increase in total protein (%kcal), animal protein (%kcal), animal protein (g/day), animal fat, niacin, carbohydrate and β-cryptoxanthin among the women were 1.33 (1.07-1.66), 1.35 (1.09-1.66), 1.42 (1.08-1.88), 1.29 (1.05-1.59), 1.28 (1.04-1.57), 0.73 (0.58-0.92) and 0.76 (0.59-0.996), respectively. The multiple adjusted odds ratio (95% confidence interval) of having microalbuminuria in the highest quintile of n-3 polyunsaturated fatty acids compared with the lowest was 2.16 (1.03-4.54).

CONCLUSION

Less animal protein and more β-cryptoxanthin in the diet might help to prevent microalbuminuria. Prospective studies including controlled trials are required to confirm this conclusion.

Plasma carotenoids are associated with socioeconomic status in an urban Indigenous population: an observational study

Background

Indigenous Australians experience poorer health than other Australians. Poor diet may contribute to this, and be related to their generally lower socioeconomic status (SES). Even within Indigenous populations, SES may be important. Our aim was to identify factors associated with plasma carotenoids as a marker of fruit and vegetable intake among urban dwelling Indigenous Australians, with a particular focus on SES.

Methods

Cross sectional study in urban dwelling Indigenous Australians participating in the DRUID (Darwin Region Urban Indigenous Diabetes) Study. An SES score, based on education, employment, household size, home ownership and income was computed and plasma carotenoids measured by high performance liquid chromatography in 897 men and women aged 15 - 81 years (mean 36, standard deviation 15). Linear regression analysis was used to determine the relationship between SES and plasma carotenoids, adjusting for demographic, health and lifestyle variables, including frequency of intakes of food groups (fruit, vegetables, takeaway foods, snacks and fruit/vegetable juice).

Results

SES was positively associated with plasma concentrations of lutein/zeaxanthin (p trend <0.001), lycopene (p trend = 0.001), α- and ß-carotene (p trend = 0.019 and 0.026 respectively), after adjusting for age, sex, glucose tolerance status, smoking, alcohol use, hypercholesterolemia, dyslipidemia, self-reported health, waist to hip ratio and body mass index. These associations remained after adjustment for self-reported frequency of intake of fruit, vegetables, takeaway foods and fruit juice, which all showed some association with plasma carotenoids. Even in the highest SES quintile, concentrations of all carotenoids (except lycopene) were lower than the mean concentrations in a non-Indigenous population.

Conclusions

Even within urban Indigenous Australians, higher SES was associated with higher concentrations of plasma carotenoids. Low plasma carotenoids have been linked with poor health outcomes; increasing accessibility of fruit and vegetables, as well as reducing smoking rates could increase concentrations and otherwise improve health, but our results suggest there may be additional factors contributing to lower carotenoid concentrations in Indigenous Australians.

Rosiglitazone reduces microalbuminuria and blood pressure independently of glycemia in type 2 diabetes patients with microalbuminuria

OBJECTIVE

To test the hypothesis that rosiglitazone combined with metformin provides a greater reduction in microalbuminuria and blood pressure than metformin and glyburide at comparable levels of glycemic control.

METHODS

In a double-blind, parallel-group design 389 participants with type 2 diabetes were followed for 32 weeks.

RESULTS

Urinary albumin: creatinine ratio was significantly reduced at 32 weeks compared with baseline in the rosiglitazone plus metformin group (-22.7%; P < 0.01) but not in the glyburide plus metformin comparator group (-7.1%; P = 0.32). Patients who completed the study (81.5%) demonstrated a treatment difference of -19.5% (P = 0.03), favoring the rosiglitazone group. Rosiglitazone plus metformin reduced both mean 24-h systolic (-3.4 mmHg; P = 0.01) and diastolic (-2.5 mmHg; P < 0.01) ambulatory blood pressure compared with glyburide plus metformin. Addition of rosiglitazone to metformin also reduced levels of plasminogen activator inhibitor-1 antigen and activity, C-reactive protein, von Willebrand factor and fibrinogen compared with addition of glyburide.

CONCLUSIONS

Rosiglitazone added to background therapy with metformin provides greater reductions in microalbuminuria and blood pressure as compared with glyburide. These additional improvements in microalbuminuria, blood pressure and cardiovascular biomarkers were observed despite comparable improvements in glycemic control in both groups and may be related to the anti-inflammatory properties of rosiglitazone.

Homocysteine, renal disease and cardiovascular disease in a remote Australian Aboriginal community

BACKGROUND

Rates of renal and cardiovascular disease are high among Aboriginal Australians living in remote communities. Nutritional problems, in particular low folate levels, are also common. This suggests that increased homocysteine concentrations might be widespread, and a possible contributor to the high rates of cardiovascular disease.

AIMS

To examine homocysteine concentrations, and their relationships to folate levels, and to markers of renal disease and cardiovascular disease in a remote Aboriginal Australian community

METHODS

As part of a cross-sectional survey among adults in one community, homocysteine concentrations, concentrations of the crucial determinants (red blood cell (RBC) folate, vitamin B(12) and the C677T methylene tetrahydrofolate reductase polymorphism) and cardiovascular risk factors were examined.

RESULTS

Among 221 people, geometric mean homocysteine concentration was 11.8 micromol/L (range: 11.1-12.5 micromol/L), with 57/221 (26%) values > or =15.0 micromol/L. Higher concentrations were associated with older age, male gender, lower RBC folate and lower vitamin B(12) concentrations and homozygosity for C677T. Homocysteine concentrations were not related to the presence of albuminuria, other than over the overt albuminuria range. Homocysteine concentrations were inversely correlated with calculated glomerular filtration rate (GFR). Carotid intima-media thickness, however, was not related to homocysteine concentration. In multivariate analyses, age, male gender, lower RBC folate concentrations, lower vitamin B(12) concentrations, lower calculated GFR and the C677T polymorphism were all associated with homocysteine concentrations.

CONCLUSIONS

Homocysteine concentrations were consistent with previous limited reports in Aboriginal communities. Although superficially they are similar to reports from non-Aboriginal settings, the younger age of this cohort and the association of homocysteine concentrations with age suggest that age-specific concentrations are higher among Aboriginal Australians. In addition to dietary determinants, the high prevalence of apparently reduced renal function renal disease appears to be an important determinant of homocysteine concentrations in remote Aboriginal communities. The role of homocysteine concentrations as a potential mediator of the high rates of cardiovascular disease remains to be determined.

Interfaces between cardiovascular and kidney disease among Aboriginal Australians

Rates of kidney disease among several indigenous groups have been shown to be substantially higher than corresponding non-indigenous groups. This excess has been clearly shown among Aboriginal Australians with respect to both end-stage kidney disease and early kidney disease. Rates of cardiovascular disease among Aboriginal Australians are also very high, as are rates of diabetes, smoking, and possibly overweight and obesity. These factors have been traditionally linked with cardiovascular and renal disease as part of a broader "metabolic syndrome." However, the links and interfaces between cardiovascular and kidney disease in this environment extend beyond these "traditional" factors. The factors associated with atherosclerosis have expanded in recent years to include markers of inflammation, some infection, antioxidants, and other "non-traditional" risk factors. Given the high rates of acute infection and poor living conditions endured by many indigenous people, one might expect these "non-traditional" risk factors to be highly prevalent. In this review, we explore the relationships between markers of inflammation, some serological markers of infection, and other selected markers and both cardiovascular and renal disease. In doing so, we demonstrate links between kidney and cardiovascular disease at a number of levels, beyond the "traditional" cardiovascular/renal risk factors. Many of these factors are beyond the control of the individual or even community; addressing these issues a broader focus and biopsychosocial model.

Reduced renal ClC-5 Cl− channel expression in spontaneously hypertensive rats with microalbuminuria

Mutations in a renal-specific Cl(-) channel, ClC-5, result in low-molecular-weight proteinuria. Herein we studied ClC-5 expression in the kidneys of spontaneously hypertensive rats (SHR) to identify possible causes of their increased urinary excretion of albumin. The amount of ClC-5 protein was significantly reduced in 3-month-old SHR as compared with normotensive Wistar/Kyoto (WKY) rats. The ClC-5 protein level was partially restored by short term administration of perindopril, an inhibitor of angiotensin-converting enzyme. Corresponding to the increase in ClC-5 expression, the albuminuria in SHR improved to the control level. These results implicate the ClC-5 Cl(-) channel reduction in the development of albuminuria in the early stage of essential hypertension.