Hypertension and kidney disease: A deadly connection

Ocular manifestations in renal diseases

The eyes and kidneys are the targets for end-organ damage in multiple pathologies. Both these organs develop during the same embryonic stage around the fourth to sixth week of gestation, thus sharing a strong correlation between both eye and kidney diseases. Both the eyes and kidneys can be the target of the systemic disease process; however, the eyes can also be affected as a consequence of renal disease or its treatment. Risk factors such as diabetes, hypertension, and smoking are commonly shared between kidney and eye diseases. Ocular manifestations can be predictive of renal disease, and/or patients with renal disease are at higher risk for developing ocular manifestations. Various congenital anomalies of the eyes and kidneys can also present as an oculorenal syndrome. This article summarizes the ocular pathology, which can be seen in renal diseases.

Does the Composition of Gut Microbiota Affect Hypertension? Molecular Mechanisms Involved in Increasing Blood Pressure

Arterial hypertension is a chronic disease which is very prevalent contemporarily. The aim of this review was to investigate the impact of gut microbiota on the development and potential treatment of hypertension, taking into consideration underlying molecular mechanisms. The bacteria present in the intestines have the ability to secrete different metabolites, which might play a significant role in the regulation of blood pressure. The most important include short-chain fatty acids (SCFAs), vasoactive hormones, trimethylamine (TMA) and trimethylamine N-oxide (TMAO) and uremic toxins, such as indoxyl sulfate (IS) and p-cresyl sulfate (PCS). Their action in regulating blood pressure is mainly based on their pro- or anti-inflammatory function. The use of specifically formulated probiotics to modify the composition of gut microbiota might be a beneficial way of supportive treatment of hypertension; however, further research on this topic is needed to choose the species of bacteria that could induce the hypotensive pattern.

Trimethylamine, a gut bacteria metabolite and air pollutant, increases blood pressure and markers of kidney damage including proteinuria and KIM-1 in rats

Background

Trimethylamine oxide (TMAO) is a biomarker in cardiovascular and renal diseases. TMAO originates from the oxidation of trimethylamine (TMA), a product of gut microbiota and manufacturing industries-derived pollutant, by flavin monooxygenases (FMOs). The effect of chronic exposure to TMA on cardiovascular and renal systems is undetermined.

Methods

Metabolic, hemodynamic, echocardiographic, biochemical and histopathological evaluations were performed in 12-week-old male SPRD rats receiving water (controls) or TMA (200 or 500 µM/day) in water for 18 weeks. TMA and TMAO levels, the expression of FMOs and renin-angiotensin system (RAS) genes were evaluated in various tissues.

Results

In comparison to controls, rats receiving high dose of TMA had significantly increased arterial systolic blood pressure (126.3 ± 11.4 vs 151.2 ± 19.9 mmHg; P = 0.01), urine protein to creatinine ratio (1.6 (1.5; 2.8) vs 3.4 (3.3; 4.2); P = 0.01), urine KIM-1 levels (2338.3 ± 732.0 vs. 3519.0 ± 953.0 pg/mL; P = 0.01), and hypertrophy of the tunica media of arteries and arterioles (36.61 ± 0.15 vs 45.05 ± 2.90 µm, P = 0.001 and 18.44 ± 0.62 vs 23.79 ± 2.60 µm, P = 0.006; respectively). Mild degeneration of renal bodies with glomerulosclerosis was also observed. There was no significant difference between the three groups in body weight, water-electrolyte balance, echocardiographic parameters and RAS expression. TMA groups had marginally increased 24 h TMA urine excretion, whereas serum levels and 24 h TMAO urine excretion were increased up to 24-fold, and significantly increased TMAO levels in the liver, kidneys and heart. TMA groups had lower FMOs expression in the kidneys.

Conclusions

Chronic exposure to TMA increases blood pressure and increases markers of kidney damage, including proteinuria and KIM-1. TMA is rapidly oxidized to TMAO in rats, which may limit the toxic effects of TMA on other organs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03687-y.

Risk of Kidney Dysfunction from Polypharmacy among Older Patients: A Nested Case-Control Study of the South Korean Senior Cohort

Polypharmacy, the concurrent use of multiple medicines, could increase the risk of kidney dysfunction among older adults because it likely burdens the aging kidneys to excrete multiple pharmaceutical ingredients and their metabolites. This study aimed to examine the relation between polypharmacy and kidney dysfunction among older patients. A nested case-control study was conducted using the National Health Insurance Service - Senior Cohort (NHIS-SC, 2009-2013), representative of the Korean senior population. It consisted of all health insurance claims linked to records of mandatory health examination. Kidney dysfunction was defined as having an eGFR lower than 60, with a decline rate of 10% or more compared to the baseline eGFR. Polypharmacy was defined based on daily counts of pharmaceutical ingredients during one year prior to the case's event date. It was classified into polypharmacy (five to 10 ingredients) and excessive polypharmacy (10 or more ingredients). After matching case and control groups based on a range of potential confounders, conditional logistic regression was performed incorporating adjustments on disease-specific, medication-specific, and lifestyle-related risk factors. The matching resulted in 14,577 pairs of cases and controls. Exposure to polypharmacy was significantly associated with increase in the risk of kidney dysfunction; i.e., crude model (polypharmacy: OR = 1.572, 95% CI = 1.492-1.656; excessive polypharmacy: OR = 2.069, 95% CI = 1.876-2.283) and risk adjustment model (polypharmacy: OR = 1.213, 95% CI = 1.139-1.292; excessive polypharmacy: OR = 1.461, 95% CI = 1.303-1.639). The significant associations were robust across different definitions of kidney dysfunction. These findings inform healthcare providers and policy makers of the importance of polypharmacy prevention to protect older adults from kidney dysfunction.

Five-year follow-up after live donor nephrectomy - cross-sectional and longitudinal analysis of a prospective cohort within the era of extended donor eligibility criteria

To establish the outcome of live kidney donors 5 years after donation, we investigated the risk for progressive renal function decline and quality of life (QoL). Data on estimated glomerular filtration rate (eGFR), creatinine, hypertension, QoL and survival were assessed in a prospective cohort of 190 donors, who donated between 2008 and 2010. Data were available for >90%. The mean age predonation was 52.8 ± 11.5 years, 30 donors having pre-existent hypertension. The mean follow-up was 5.1 ± 0.9 years. Eight donors had died due to non-donation-related causes. After 5 years, the mean eGFR was 60.2 (95% CI 58.7-62.7) ml/min/1.73 m² , with a median serum creatinine of 105.1 (95% CI 102.5-107.8) μmol/l. eGFR decreased to 33.6% and was longitudinally lower among men than women and declining with age (P < 0.001), without any association on QoL. Donors with pre-existent and new-onset hypertension demonstrated no progressive decline of renal function overtime compared to nonhypertensives. No donors were found with proteinuria, microalbuminuria or at risk for end-stage renal disease. After an initial decline postdonation, renal function remained unchanged overtime. Men and ageing seem to affect renal function overtime, while decreased renal function did not affect QoL. These data support further stimulation of living kidney donation programmes as seen from the perspective of donor safety.

Relationship between CYP17A1 Genetic Polymorphism and Essential Hypertension in a Chinese Population

The relationship between CYP17A1 genetic polymorphisms and essential hypertension (EH) remains unclear. The aim of this study was to investigate the association of CYP17A1 genetic polymorphisms with EH in Han and Uighur populations in China. A Han population including 558 people (270 EH patients and 288 controls) and a Uighur population including 473 people (181 EH patients and 292 controls) were selected. Five single-nucleotide polymorphisms (SNPs) (rs4919686, rs1004467, rs4919687, rs10786712, and rs2486758) were genotyped using real-time PCR (TaqMan). In the Uighur population, for the total and the men, rs4919686, rs4919687 and rs10786712 were found to be associated with EH (rs4919686: P≤0.02, rs4919687: P≤0.002, rs10786712: P≤0.004, respectively). The difference remained statistically significant after the multivariate adjustment (all P<0.05). The overall distributions of the haplotypes established by SNP1-SNP3, SNP1-SNP4, SNP1-SNP3-SNP5 and SNP1-SNP4-SNP5 were significantly different between the EH patients and the control subjects (for the total: P=0.013, P=0.008, P=0.032, P=0.010, for men: P<0.001, P=0.001, P=0.010, P=0.00). In the Han population, for men, rs2486758 was found to be associated with EH in a recessive model (P=0.007); the significant difference was not retained after the adjustment for the covariates (date not shown). The A allele of rs4919686 could be a susceptible genetic marker, and the T allele of rs10786712 could be a protective genetic marker of EH. The AC genotype of rs4919686, the AG genotype of rs4919687 and the TT genotype of rs10786712 could be protective genetic markers of EH.

The giraffe kidney tolerates high arterial blood pressure by high renal interstitial pressure and low glomerular filtration rate

BACKGROUND

The tallest animal on earth, the giraffe (Giraffa camelopardalis) is endowed with a mean arterial blood pressure (MAP) twice that of other mammals. The kidneys reside at heart level and show no sign of hypertension-related damage. We hypothesized that a species-specific evolutionary adaption in the giraffe kidney allows normal for size renal haemodynamics and glomerular filtration rate (GFR) despite a MAP double that of other mammals.

METHODS

Fourteen anaesthetized giraffes were instrumented with vascular and bladder catheters to measure glomerular filtration rate (GFR) and effective renal plasma flow (ERPF). Renal interstitial hydrostatic pressure (RIHP) was assessed by inserting a needle into the medullary parenchyma. Doppler ultrasound measurements provided renal artery resistive index (RI). Hormone concentrations as well as biomechanical, structural and histological characteristics of vascular and renal tissues were determined.

RESULTS

GFR averaged 342 ± 99 mL min(-1) and ERPF 1252 ± 305 mL min(-1) . RIHP varied between 45 and 140 mmHg. Renal pelvic pressure was 39 ± 2 mmHg and renal venous pressure 32 ± 4 mmHg. A valve-like structure at the junction of the renal and vena cava generated a pressure drop of 12 ± 2 mmHg. RI was 0.27. The renal capsule was durable with a calculated burst pressure of 600 mmHg. Plasma renin and AngII were 2.6 ± 0.5 mIU L(-1) and 9.1 ± 1.5 pg mL(-1) respectively.

CONCLUSION

In giraffes, GFR, ERPF and RI appear much lower than expected based on body mass. A strong renal capsule supports a RIHP, which is >10-fold that of other mammals effectively reducing the net filtration pressure and protecting against the high MAP.

The association between chronic kidney disease and diabetic retinopathy: the Korea National Health and Nutrition Examination Survey 2008-2010

PURPOSE

To explore the relationship between chronic kidney disease and diabetic retinopathy in a representative population of Korean diabetic adults.

METHODS

We analyzed data from the Korea National Health and Nutrition Examination Surveys (2008-2010). A total of 15,409 individuals (weighted frequency, 32,168,636) aged 19 and over who completed ophthalmologic and renal functional examinations were evaluated. Chronic kidney disease (CKD) was defined as an estimated glomerular filtration rate of < 60 ml/min/1.73 m2 or proteinuria greater than 1+. Seven standard photographs from the Early Treatment for Diabetic Retinopathy Study were obtained from each eye after pharmacological pupil dilatation. Diabetic retinopathy (DR) was defined as the presence of 1 or more retinal microaneurysms or retinal blot hemorrhages with or without more severe lesions. Vision-threatening diabetic retinopathy (VTDR) was defined as the presence of a clinically significant macular edema (CSME) or proliferative diabetic retinopathy.

RESULTS

CKD was significantly associated with DR and VTDR (odds ratio (OR), 95% confidence interval (CI); 2.49(1.43-4.35) and 3.74(1.56-8.95), respectively) in the diabetic population. After controlling for confounders, however, CKD was significantly associated only with DR [adjusted OR (aOR), 95% CI; 2.34(1.04-5.28)]. In the subgroup analysis for CKD, only proteinuria was significantly associated with DR and VTDR (aOR, 95% CI; 4.56(1.51-13.77) and 5.61(1.06-29.87), respectively) in this population.

CONCLUSIONS

Our results show that CKD appears to be associated with DR and VTDR in a Korean diabetic population. In particular, proteinuria, not decreased eGFR, is more significantly associated with DR or VTDR.

Kidney and eye diseases: common risk factors, etiological mechanisms, and pathways

Chronic kidney disease is an emerging health problem worldwide. The eye shares striking structural, developmental, and genetic pathways with the kidney, suggesting that kidney disease and ocular disease may be closely linked. A growing number of studies have found associations of chronic kidney disease with age-related macular degeneration, diabetic retinopathy, glaucoma, and cataract. In addition, retinal microvascular parameters have been shown to be predictive of chronic kidney disease. Chronic kidney disease shares common vascular risk factors including diabetes, hypertension, smoking, and obesity, and pathogenetic mechanisms including inflammation, oxidative stress, endothelial dysfunction, and microvascular dysfunction, with ocular diseases supporting the 'Common Soil Hypothesis.' In this review, we present major epidemiological evidence for these associations and explore underlying pathogenic mechanisms and common risk factors for kidney and ocular disease. Understanding the link between kidney and ocular disease can lead to the development of new treatment and screening strategies for both diseases.

Clinical epidemiology of reduced kidney function among elderly male fishing and agricultural population in Taipei, Taiwan

Purpose. To quantify the prevalence of and associated factors for chronic kidney disease (CKD) among male elderly fishing and agricultural population in Taipei, Taiwan. Methods. Subjects (n = 2,766) aged 65 years and over voluntarily admitted to a teaching hospital for a physical checkup were collected in 2010. CKD was defined as an estimated glomerular filtration rate <60 mL/min/1.73 m². Results. Among these subjects, the over prevalence of chronic kidney disease was 13.6% (95% CI: 12.3–14.9%). The age-specific prevalence of CKD in 65–74 years, 75–84 years, and ≥85 years was 8.2%, 19.1%, and 27.0%, respectively. From the multiple logistic regression, age (OR = 1.05, 95% CI: 1.02–1.09), hyperuricemia (OR = 2.94, 95% CI: 1.90–3.78), central obesity (OR = 1.17, 95% CI: 1.02–1.56), hyperglycemia (OR = 1.23, 95% CI: 1.11–1.67), hypertriglyceridemia (OR = 1.25, 95% CI: 1.08–1.66), and lower HDL-C (OR = 1.61, 95% CI: 1.23–1.92) were statistically significantly related to CKD. The presence of metabolic components (one or two versus none, OR = 1.10, 95% CI: 1.04–1.25; three or more versus none, OR = 2.12, 95% CI: 1.86–2.78) also appeared to be statistically significantly related to CKD after adjustment for other independent factors. Conclusion. Several clinical factors independently affect the development of CKD in the elderly male fishing and agricultural population.

Semicarbazide-sensitive amine oxidase and kidney disease

With better understanding of the molecular mechanisms underpinning chronic kidney disease, the roles of inflammation and fibrosis are becoming increasingly inseparable. The progression of renal disease is characterized by pathomorphological changes that consist of early inflammatory responses followed by tubulointerstitial fibrosis, tubular atrophy, and glomerular and vascular sclerosis. Currently available therapies that reduce hypertension, proteinuria, hyperglycemia, and interruption of the renin-angiotensin-aldosterone system are at best only partially effective. Hence, there remains a need to explore agents targeting nonrenin-angiotensin-aldosterone system pathways. In this review, we discuss mechanistic aspects in the physiological and pathological role of semicarbazide-sensitive amine oxidase, a protein enzyme involved in cellular trafficking and inflammation, with respect to the kidney. We explore the evidence for the use of semicarbazide-sensitive amine oxidase inhibitors as potential agents in renal fibrosis to delay the onset and progression of chronic kidney disease.

Ethnic differences in the association between blood pressure components and chronic kidney disease in middle aged and older Asian adults

Background

Chronic kidney disease (CKD) is an emerging public health problem worldwide. Previous studies have shown an association between blood pressure (BP) and CKD. However, it is not clear if there are ethnic differences in this association. We examined the association between BP and CKD in a multi-ethnic Asian population in Singapore.

Methods

We analysed data from three large population-based studies conducted between 2004–2011, (n=3,167 Chinese, 3,082 Malays and 3,228 Indians) aged 40–80 years. CKD was defined as an estimated glomerular filtration rate <60 mL/min/1.73m² from serum creatinine. Hypertension was defined as a self-reported current use of antihypertensive medication or systolic BP ≥140 mm Hg or diastolic BP ≥90 mm Hg. We also analysed the association of CKD with individual BP components.

Results

The prevalence of both hypertension and CKD was higher among Malays (68.6, 21%) compared to Chinese (57.9, 5.9%) and Indians (56.0, 7.4%), but treatment for hypertension was lower among Malays (53.4%) compared to Chinese (89.8%) and Indians (83.1%). Hypertension was associated with CKD in all three ethnic groups (OR [95% CI] = 2.71 [1.59-4.63], 2.08 [1.62-2.68], 2.43 [1.66-3.57] in Chinese, Malays and Indians). Among the BP components, both systolic and diastolic BP were associated with CKD in Malays whereas, systolic BP was not significantly associated with CKD, and diastolic BP showed an inverse association which was explained by anti-hypertensive medication use in Chinese and Indians.

Conclusions

Hypertension was associated with CKD in Chinese, Malays and Indians. However, the BP components were associated with CKD only in Malays.

Hypertension and the development of new onset chronic kidney disease over a 10 year period: a retrospective cohort study in a primary care setting in Malaysia

BACKGROUND

Little is known about the rate of progression to chronic kidney disease (CKD) among hypertensive patients, particularly at the primary care level. This study aims to examine risk factors associated with new onset CKD among hypertensive patients attending a primary care clinic.

METHODS

This is a 10-year retrospective cohort study of 460 patients with hypertension who were on treatment. Patient information was collected from patient records. CKD was defined as a glomerular filtration rate <60 ml/min per 1.73 m2 (Cockcroft-Gault equation). Multiple logistic regression statistics was used to test the association in newly diagnosed CKD.

RESULTS

The incidence of new CKD was 30.9% (n = 142) with an annual rate of 3%. In multivariate logistic regression analysis, factors associated with development of new onset of CKD among hypertensive patients were older age (odds ratio [OR] 1.123, 95% confidence interval [CI] 1.078-1.169), presence of diabetes (OR 2.621, 95% CI 1.490-4.608), lower baseline eGFR (OR 1.041, 95% CI 0.943-0.979) and baseline hyperuricaemia (OR 1.004, 95% CI 1.001-1.007).

CONCLUSIONS

The progression to new onset CKD is high among urban multiethnic hypertensive patients in a primary care population. Hence every effort is needed to detect the presence of new onset CKD earlier. Hypertensive patients who are older, with underlying diabetes, hyperuricaemia and lower baseline eGFR are associated with the development of CKD in this population.

Associations of common variants at APLN and hypertension in Chinese subjects with and without diabetes

Background. Apelin, the endogenous ligand for the APJ receptor, has a potent hypotensive effect via a nitric oxide-dependent mechanism in vivo. The aim of the study was to investigate the association between the common variants of apelin gene (APLN) and hypertension, which was reported recently in a Chinese Han population with and without diabetes. Methods. Three single nucleotide polymorphisms (SNPs) on APLN were genotyped in 3156 diabetic patients and 3736 nondiabetic individuals. For non-diabetic subjects, 1779 were enrolled in stage 1 and 1757 were recruited for validation. A meta-analysis combining the two stages was carried out to obtain the overall effect. Results. In diabetic patients, no significant associations of the three SNPs with hypertension were observed. In contrast, we found that rs2235306 was associated with hypertension in non-diabetic males after adjusting for covariates (OR = 1.19, P = 0.039) while rs2235307 and rs3115759 displayed no evidence of association in both genders. One haplotype, C-C-A, also showed an association with hypertension (OR = 1.47, P = 0.032) only in men. However, analysis in stage 2 and meta-analysis did not support these findings. Conclusions. We conclude that common variants on APLN are not associated with the prevalence of hypertension in the Chinese.

Association of high blood pressure with renal insufficiency: role of albuminuria, from NHANES, 1999-2006

BACKGROUND

The relationship between hypertension and kidney disease is complicated. Clinical trials found intense blood pressure control was not associated with alterations in glomerular filtration rate (GFR) in all patients but did slow the rate of GFR decline among those with a higher baseline proteinuria. However, the underlying mechanism has been unclear.

METHODS

We tested the hypothesis that the association between high blood pressure and renal function is modified by albuminuria status by conducting analyses in a cross-sectional study with 12,440 adult participants without known kidney diseases, diabetes or cardiovascular diseases, participating in the National Health and Nutrition Examination Survey (NHANES) 1999-2006.

RESULTS

1226 out of 12440 were found to have unknown high blood pressure and 4494 were found to have reduced renal function. Overall, a moderate association was found between high blood pressure and renal function insufficiency in all participants analyzed. However, among participants with albuminuria, the prevalence of moderate-severe renal insufficiency substantially and progressively increased from normal subjects to prehypertensive and undiagnosed hypertensive subjects (1.43%, 3.44%, 10.96%, respectively, P for trend<0.0001); on the other hand, the prevalence of undiagnosed hypertension was also significantly higher among subjects with moderate-severe renal insufficiency than those with mild renal insufficiency (35.54% Vs 19.09%, P value <0.05), supporting an association between hypertension and renal function damage. In contrast, no association between hypertension and renal insufficiency was observed among those without albuminuria in this population. Similar findings were observed when the CKD-EPI equation was used.

CONCLUSIONS

The association between high blood pressure and reduced renal function could be dependent upon the albuminuria status. This finding may provide a possible explanation for results observed in clinical trials of intensive blood pressure control. Further studies are warranted to confirm our findings.

A common genetic variant of FCN3/CD164L2 is associated with essential hypertension in a Chinese population

Ficolin-3, encoded by FCN3, is the predominant recognition molecule of lectin pathway for the activation of complement component 3 (C3), which is an important risk factor for the development of hypertension. In our previous study, we found the complement system including ficolin-3 was overrepresented in the serum of type 2 diabetic patients. Since type 2 diabetes shares some pathogenic components, including excessive serum C3, with hypertension, this study aims to test the hypothesis that common variants at FCN3 might be associated with essential hypertension in our Chinese population. A total of 1797 subjects were recruited. Of them, 573 were with essential hypertension. Based on HapMap data, three tagging single nucleotide polymorphisms (rs2504778, rs10794501, and rs3813800) in FCN3/CD164L2 region were selected for genotyping by using MassARRAY. Logistic regression analysis was performed to evaluate the genetic effects on the prevalence of hypertension after adjusting for covariates. rs2504778, which locates in the upstream of FCN3 and in the intron of CD164L2, was found to be significantly associated with hypertension after adjusting for covariates (OR = 1.28, 95% CI: 1.05, 1.55, P = .015). Correction for multiple testing did not remarkably attenuate the significance (empirical P = .042 with 10 000 permutations). rs2504778 also showed a nominal association with systolic blood pressure (P = .044) in the quantitative trait analysis. No evidence of correlation with hypertension and blood pressure was observed for rs10794501 and rs3813800. We found that a common variant of FCN3/CD164L2 is associated with hypertension in our Chinese population. More studies with larger sample size are needed to confirm this finding.

Quality issues of self-report of hypertension: analysis of a population representative sample of older adults in Taiwan

The study was to evaluate the quality of self-report of hypertension and examine the factors associated with under- and over-reporting of hypertension in older Taiwanese. Data for this analysis were from the Social Environment and Biomarkers Study in Taiwan 2000, which involved a national sample of 1021 Taiwanese over 54 years of age. We performed binary classification tests to compare the prevalence rates of self-reported vs. clinically measured hypertension according to World Health Organization (WHO) (blood pressure ≥ 160/95 mm Hg or on hypertension medication) and JNC-6 (140/90 mm Hg or on hypertension medication) definitions. Logistic regression analysis was performed to analyze the potential factors associated with under- or over-reporting of blood pressure status. Results showed the test characteristics of self-reports were: sensitivity 73%, specificity 93%, and kappa = 0.68 (p < 0.001) based on the WHO definition; and sensitivity 51%, specificity 95% and kappa = 0.43 (p < 0.001) based on the JNC-6 definition. Old age was associated with over-reporting whereas having no health checkup during the past 12 months was associated with under-reporting. The relatively low agreement between self-reports and clinically measured hypertension (JNC-6 definition) was mainly due to the lack of a well-defined hypertension practice guideline and the failure of clinicians to clearly inform patients of their diagnoses. The consistency of hypertension practice guidelines and the effectiveness of informing the patients of their diagnoses are two main factors impacting the quality of self-report of hypertension in elderly Taiwanese. Better self-reports of health data can improve the efficiency of public health surveillance efforts.

Serum vitamin D level and prehypertension among subjects free of hypertension

BACKGROUND

Low serum vitamin D levels are associated with high blood pressure (BP). Prehypertension is a preclinical stage where primary prevention efforts have been recommended for delaying or preventing the onset of hypertension. However, the majority of studies examining the association between vitamin D and BP have not accounted for kidney function or systemic inflammation.

METHODS

Participants of the 3rd National Health and Nutrition Examination Survey > 20 years of age and free of hypertension (n = 9,215, 53.5% women) and clinical cardiovascular disease were examined. Serum vitamin D levels were analyzed as quartiles. Prehypertension (n = 3,712) was defined as systolic BP 120-139 mm Hg or diastolic BP 80-89 mm Hg.

RESULTS

Lower serum vitamin D levels were found to be associated with prehypertension independent of potential confounders including body mass index (BMI), serum cholesterol, C-reactive protein and estimated glomerular filtration rate. Compared to the highest quartile of serum vitamin D (referent), the odds ratio (95% confidence interval) of prehypertension associated with the lowest quartile was 1.48 (1.16-1.90; p trend < 0.0001). This association persisted in subgroup analyses by gender, race-ethnicity and BMI.

CONCLUSION

Lower serum vitamin D levels are associated with prehypertension in a representative sample of US adults.

Proteomics in chronic kidney disease: The issues clinical nephrologists need an answer for

A growing number of patients are recognised to have chronic kidney disease (CKD). However, only a minority will progress to end-stage renal disease requiring dialysis or transplantation. Currently available diagnostic and staging tools frequently fail to identify those at higher risk of progression or death. Furthermore within specific disease entities there are shortcomings in the prediction of the need for therapeutic interventions or the response to different forms of therapy. Kidney and urine proteomic biomarkers are considered as promising diagnostic tools to predict CKD progression early in diabetic nephropathy, facilitating timely and selective intervention that may reduce the related health-care expenditures. However, independent groups have not validated these findings and the technique is not currently available for routine clinical care. Furthermore, there are gaps in our understanding of predictors of progression or need for therapy in non-diabetic CKD. Presumably, a combination of tissue and urine biomarkers will be more informative than individual markers. This review identifies clinical questions in need of an answer, summarises current information on proteomic biomarkers and CKD, and describes the European Kidney and Urine Proteomics initiative that has been launched to carry out a clinical study aimed at identifying urinary proteomic biomarkers distinguishing between fast and slow progressors among patients with biopsy-proven primary glomerulopathies.

Hypertension, Hypertension Control, and Chronic Kidney Disease in a Malay Population in Singapore

Studies conducted in Western populations demonstrate that blood pressure (BP) is a major risk factor for chronic kidney disease (CKD). The authors examined the cross-sectional association between BP and CKD in 3280 adults of Malay ethnicity aged 40 to 80 years living in Singapore. CKD was defined as (1) estimated glomerular filtration rate (eGFR) of < 60 mL/min/1.73 m2 and (2) presence of microalbuminuria/macroalbuminuria. They observed a dose-dependent positive association between BP and CKD ( P trend < .0001). In multivariable-adjusted analysis, compared with participants with normal BP, the odds ratio (OR; 95% confidence interval [CI]) of eGFR < 60 mL/min/1.73 m2 was 1.85 (0.95-3.62), 2.95 (1.55-5.64), and 4.96 (2.63-9.37) for prehypertension, and stage 1 and stage 2 hypertension, respectively. Similar results were obtained for microalbuminuria/macroalbuminuria. Stage 2 hypertension had the greatest population-attributable risk of CKD (23%). The strong positive association of hypertension with CKD emphasizes the need to control BP in Asian populations to reduce the burden of kidney disease.

Association study of the elastin microfibril interfacer 1 (EMILIN1) gene in essential hypertension

BACKGROUND

Elastin microfibril interfacer 1 (EMILIN-1) is a negative regulator of the transforming growth factor-beta (TGF-beta) signaling, which is involved in blood pressure (BP) homeostasis. Emilin1 knockout mice display elevated BP. The aim of the present study was to assess the association between the human EMILIN1 gene and essential hypertension (EH) using a haplotype-based case-control study.

METHODS

A total of 287 EH patients and 253 age-matched controls were genotyped for the five single-nucleotide polymorphisms (SNPs) used as genetic markers for the human EMILIN1 gene (rs2289408, rs2289360, rs2011616, rs2304682, and rs4665947). Data were analyzed for three separate groups: the total subjects, men, and women.

RESULTS

For the total, the genotypic distribution of rs2289360, rs2011616, and rs2304682 differed significantly between control and EH (P = 0.010, P = 0.009, and P = 0.008, respectively). For the total and men, there were significant differences noted between the controls and the EH patients for both the dominant model (GG vs. AA+AG) (P = 0.006, P = 0.021, respectively), and the recessive model (AA vs. AG+GG) (P = 0.028, P = 0.038, respectively) of rs2011616. For the total and the men, logistic regression analysis indicated that the AG+GG genotype of rs2011616 was significantly higher in EH patients (P = 0.033, P = 0.043, respectively). The frequency of the G-G-T haplotype (established by rs2536512, rs2016116, rs17881426) was significantly higher in EH men (P = 0.007), and the G-A-T haplotype (established by rs2536512, rs2016116, rs17881426) was significantly higher in control men (P < 0.001).

CONCLUSIONS

We confirmed that rs2289360, rs2011616, and rs2304682 in the human EMILIN1 gene, as well as the haplotype constructed using rs2536512, rs2011616, and rs17881426 are useful genetic markers of EH in Japanese men.

Nut consumption and risk of hypertension in US male physicians

BACKGROUND & AIMS

Hypertension is a risk factor for cardiovascular disease and dietary factors may play an important role in its prevention. We sought to examine the association between nut consumption and incident hypertension.

METHODS

Prospective cohort of 15,966 participants from the Physicians' Health Study I who were free of hypertension at baseline. Nut consumption was assessed using a simple abbreviated food questionnaire and hypertension was self-reported. We used Cox regression to estimate relative risks of hypertension according to nut consumption.

RESULTS

During 237,585 person-years of follow up, 8,423 new cases of hypertension occurred. Compared to subjects who did not consume nuts, multivariable adjusted hazard ratios (95% CI) for hypertension were 0.97 (0.91-1.03), 0.98 (0.92-1.05), 0.96 (0.89-1.03), and 0.82 (0.71-0.94) for nut consumption of 1-2 times per month and 1, 2-6, and > or = 7 times/week, respectively. In a secondary analysis stratified by body mass index, there was an inverse relation between nut intake and hypertension in lean subjects (p for trend 0.0019) but not in overweight or obese subjects (p for interaction 0.0037).

CONCLUSION

Our data suggest that nut consumption is associated with a lower risk of hypertension in US male physicians and that such relation may be influenced by adiposity.

Socioeconomic status and microalbuminuria in an Asian population

BACKGROUND

In studies from developed Western countries, lower socioeconomic status (SES) has been reported to be associated with kidney diseases. However, this hypothesis has not been examined in populations from newly industrialized Asian countries. We evaluated the association between SES and micro/macroalbuminuria in a population-based sample in Singapore.

METHODS

We examined 920 participants of Malay ethnicity aged 40-80 years (49.6% female). SES was defined through education, income and housing type of participants. The main outcome of interest was the presence of micro/macroalbuminuria defined as a urinary albumin-to-creatinine ratio (ACR) >or=17 mg/g for men and >or=25 mg/g for women.

RESULTS

Lower categories of SES were associated with micro/macroalbuminuria; compared to the higher categories of SES, the odds ratio (95% confidence interval) of micro/macroalbuminuria was 1.76 (1.23-2.52) for primary/lower education, 1.64 (1.16-2.31) for income <1000 Singapore dollars (SGD)/retired status, 1.44 (1.01-2.06) for small/medium housing type and 2.37 (1.56-3.60) for the coexistence of all three low SES factors (primary/ below education, income <1000 SGD/retired status and small/medium housing type) compared to <or=1 low SES factor. This pattern of association was consistently present in subgroup analyses by gender and age.

CONCLUSIONS

Lower SES is associated with the presence of micro/macroalbuminuria independent of age, gender, smoking, alcohol intake and body mass index among Malay adults in Singapore.

A haplotype of the CYP4A11 gene associated with essential hypertension in Japanese men

OBJECTIVE

CYP4A11, a member of the cytochrome P450 family, acts mainly as an enzyme that converts arachidonic acid to 20-hydroxyeicosatetraenoic acid, a metabolite involved in blood pressure regulation in humans. Disruption of the murine cyp4a14 and cyp4a10 genes, homologues of human CYP4A11, was reported recently to cause hypertension. The gene-disrupted male mice had higher blood pressure than the gene-disrupted female mice. The present study aimed to assess the association between the human CYP4A11 gene and essential hypertension, using a haplotype-based case-control study including separate analysis of the gender groups.

METHODS

The 304 essential hypertension patients and 207 age-matched control individuals were genotyped for three single-nucleotide polymorphisms of the human CYP4A11 gene (rs2269231, rs1126742, rs9333025). Data were assessed for three separate groups: total participants, men and women.

RESULTS

For total participants, the genotypic distribution of rs1126742 differed significantly between the two groups (P = 0.005). For total participants, men and women, the recessive model (CC versus TC + TT) of rs1126742 differed significantly between the two groups (P = 0.007, P = 0.043, and P = 0.045, respectively). Logistic regression analysis showed the TC + TT genotype was significantly higher in essential hypertension patients than in control individuals for total participants and men (P = 0.022 and P = 0.043, respectively). The A-T-G haplotype frequency (established by rs2269231, rs1126742, rs9333025) was significantly higher in essential hypertension men than in control men (P = 0.043).

CONCLUSIONS

Essential hypertension is associated with the TC + TT genotype of rs1126742 in the human CYP4A11 gene. The A-T-G haplotype appears a useful genetic marker of essential hypertension in Japanese men.

Management and treatment of chronic kidney disease

Estimates suggest that 30 million Americans have some degree of chronic kidney disease. By 2030, more than 2.2 million people will require treatment for end-stage renal disease, causing a significant impact on healthcare costs in the United States.

Plasma fatty acid-binding protein 4 increases with renal dysfunction in type 2 diabetic patients without microalbuminuria

BACKGROUND

Fatty acid-binding protein 4 (FABP4) has been linked to metabolic syndrome development, diabetes, and arteriosclerosis, but the role of FABP4 in target organ damage has not been assessed. We evaluated whether plasma FABP4 is associated with renal dysfunction in type 2 diabetic patients.

METHODS

In 263 individuals (161 type 2 diabetic patients and 102 healthy nondiabetic controls), we analyzed the correlation between FABP4 and creatinine or glomerular filtration index (MDRD-GFR) regarding the presence or absence of microalbuminuria. Patients with severe chronic kidney disease (MDRD-GFR <30 mL/min/1.73 m(2)) or albuminuria were not included.

RESULTS

FABP4 concentrations were higher in diabetic patients with MDRD-GFR <60 mL/min/1.73 m(2) (P <0.001). We observed a significant, direct correlation between FABP4 and creatinine (r = 0.446, P <0.001) and an inverse correlation between FABP4 and MDRD-GFR (r = -0.511, P <0.001) in type 2 diabetic patients, but not in nondiabetic individuals. These correlations were sustained when only those patients without microalbuminuria were analyzed (r = 0.414, P <0.001 and r = -0.510, P <0.001, respectively). Type 2 diabetic patients with FABP4 in the highest tertile compared with those in the lower tertiles had increased adjusted odds ratios for moderate renal dysfunction [7.5 (95%CI 1.8-30.7), P = 0.005 and 15.3 (3.1-76.4), P = 0.001; respectively], independent of microalbuminuria.

CONCLUSIONS

High FABP4 plasma concentrations are associated with high plasma creatinine and low MDRD-GFR in patients with type 2 diabetes even in the absence of microalbuminuria or clinically relevant alterations of creatinine and MDRD-GFR values. FABP4 concentrations should be taken into consideration as an early marker of kidney damage in patients with type 2 diabetes.

Mechanical forces in diabetic kidney disease: a trigger for impaired glucose metabolism

Nephropathy is one of the major microvascular complications of diabetes, and both hemodynamic and metabolic stimuli participate in its development and progression toward ESRD. There is now a greater understanding of the molecular pathways that are activated by high glomerular capillary pressure and hyperglycemia and how they interplay to produce kidney pathology. The observation that overexpression of glucose transporter 1 (GLUT-1) in mesangial cells could induce a "diabetic cellular phenotype" has led to the postulation that the expression of GLUT-1 could be upregulated in glomeruli that are exposed to high pressure. This review suggests a mechanism by which mechanical forces may aggravate a metabolic insult by stimulating excessive cellular glucose uptake. Proposed is the existence of a self-maintaining cycle whereby a hemodynamic stimulus on glomerular cells induces GLUT-1 overexpression followed by greater glucose uptake and activation of intracellular glucose metabolic pathways, resulting in excess TGF-beta1 production. TGF-beta1 in turn, maintains overexpression of GLUT-1, perpetuating a signaling sequence that has, as its ultimate effect, increased extracellular matrix synthesis. This mechanical and metabolic coupling suggests a novel pathophysiologic mechanism of injury in the kidney in diabetes and possibly other glomerular diseases.