Whole genome methylation array analysis reveals new aspects in Balkan endemic nephropathy etiology.

BACKGROUND: Balkan endemic nephropathy (BEN) represents a chronic progressive interstitial nephritis in striking correlation with uroepithelial tumours of the upper urinary tract. The disease has endemic distribution in the Danube river regions in several Balkan countries.DNA methylation is a primary epigenetic modification that is involved in major processes such as cancer, genomic imprinting, gene silencing, etc. The significance of CpG island methylation status in normal development, cell differentiation and gene expression is widely recognized, although still stays poorly understood. METHODS: We performed whole genome DNA methylation array analysis on DNA pool samples from peripheral blood from 159 affected individuals and 170 healthy individuals. This technique allowed us to determine the methylation status of 27 627 CpG islands throughout the whole genome in healthy controls and BEN patients. Thus we obtained the methylation profile of BEN patients from Bulgarian and Serbian endemic regions. RESULTS: Using specifically developed software we compared the methylation profiles of BEN patients and corresponding controls and revealed the differently methylated regions. We then compared the DMRs between all patient-control pairs to determine common changes in the epigenetic profiles.SEC61G, IL17RA, HDAC11 proved to be differently methylated throughout all patient-control pairs. The CpG islands of all 3 genes were hypomethylated compared to controls. This suggests that dysregulation of these genes involved in immunological response could be a common mechanism in BEN pathogenesis in both endemic regions and in both genders. CONCLUSION: Our data propose a new hypothesis that immunologic dysregulation has a place in BEN etiopathogenesis.

Reduced kidney size in adult offspring of Balkan endemic nephropathy patients and controls: a prospective study.

INTRODUCTION: Reduced kidney size has been proposed as a criterion for clinical diagnosis of Balkan endemic nephropathy (BEN). Some studies suggest that smaller kidneys are found in advanced stages of BEN, whereas others reported them in earlier stages. To investigate the clinical course of kidney sizes in the offspring of BEN and non-BEN parents, we followed up a cohort of adult offspring over 5 years. We hypothesized that parental history affects kidney dimensions. METHODS: Four repeated ultrasound measurements of kidney length and cortex width were conducted in 121 offspring of BEN and 98 offspring of non-BEN parents. Repeated measurements were analyzed using mixed models adjusting for gender and time-dependent information on other kidney diseases, diabetes, age, height and year of follow-up. RESULTS: A reduction of kidney length was associated with maternal BEN (-4 mm, P = 0.001). We detected a parallel decline in kidney length in the various offspring groups. However, kidney cortex width was significantly smaller when both parents or the mother had BEN and offspring age > or =60 years (-1.88 mm, P = 0.0003; -1.03 mm, P = 0.05). In the 5th year of follow-up, 37 participants developed BEN (14 confirmed, 23 suspected). Kidney cortex width at baseline was smaller in offspring who developed BEN (P = 0.0001). CONCLUSIONS: The development of kidney dimensions depends on the parental BEN status and offspring age. In BEN offspring, ultrasound measurements of the kidney cortex width seem to have a prognostic value.

Offspring of parents with Balkan Endemic Nephropathy have higher C-reactive protein levels suggestive of inflammatory processes: a longitudinal study.

BACKGROUND: Despite the characteristic extensive tubulointerstitial fibrosis, Balkan Endemic Nephropathy (BEN) is usually considered a non-inflammatory disease. METHODS: We examined a marker of inflammation, C-reactive protein (CRP), in the offspring of patients with BEN, a population at risk for BEN, prior to development of established disease to determine if an inflammatory process could be identified in the early stages of the disease. In 2003/04, 102 adult offspring whose parents had BEN and a control group of 99 adult offspring of non-BEN patients were enrolled in this prospective study. This cohort was re-examined yearly for four consecutive years. Levels of serum CRP were measured in years 3 and 4 and compared between groups. The data were analyzed with mixed models. RESULTS: Compared to controls, offspring of BEN parents had statistically higher CRP levels in two consecutive years, suggestive of early inflammatory reactivity. Whenever the mother was affected by BEN (both parents, or mother only), serum CRP was significantly increased, but not if only the father had BEN. CRP was inversely related to kidney cortex width but not to markers or renal function. CONCLUSION: Early stages of BEN may involve inflammatory processes. The observation of a maternal involvement supports the concept of fetal programming, which has been implicated in the pathogenesis of other chronic kidney diseases.

Metals and kidney markers in adult offspring of endemic nephropathy patients and controls: a two-year follow-up study.

BACKGROUND: The etiology of Balkan Endemic Nephropathy, (BEN), a tubulointerstitial kidney disease, is unknown. Although this disease is endemic in rural areas of Bosnia, Bulgaria, Croatia, Romania, and Serbia, similar manifestations are reported to occur in other regions, for instance Tunisia and Sri Lanka. A number of explanations have been stated including lignites, aristolochic acid, ochratoxin A, metals, and metalloids. Etiologic claims are often based on one or a few studies without sound scientific evidence. In this systematic study, we tested whether exposures to metals (cadmium and lead) and metalloids (arsenic and selenium) are related to Balkan Endemic Nephropathy. METHODS: In 2003/04 we recruited 102 adults whose parents had BEN and who resided in one of three communities (Vratza, Bistretz, or Beli Izvor, Bulgaria). A control group comprised of 99 adults having non-BEN hospitalized parents was enrolled in the study during the same time. We conducted face-to-face interviews, ultrasound kidney measurements, and determined kidney function in two consecutive investigations (2003/04 and 2004/05). Metals and metalloids were measured in urine and blood samples. To assess the agreement between these consecutive measurements, we calculated intraclass correlation coefficients. Repeated measurement data were analyzed using mixed models. RESULTS: We found that cadmium and arsenic were associated with neither kidney size nor function. Lead had a significant but negligible effect on creatinine clearance. Selenium showed a weak but significant negative association with two of the four kidney parameters, namely creatinine clearance and beta2-microglobulin. It was positively related to kidney length. These associations were not restricted to the offspring of BEN patients. Adding credence to these findings are reports showing comparable kidney effects in animals exposed to selenium. CONCLUSION: The findings of this 2-year follow-up study indicate that metals and metalloids do not play a role in the etiology of Balkan Endemic Nephropathy. Against the assumption in the literature, selenium was not protective but a risk factor. Since comparable associations were observed in animals, future studies are needed to explore whether selenium may have adverse renal effects in humans.

Increased blood pressure in adult offspring of families with Balkan endemic nephropathy: a prospective study.

BACKGROUND: Previous studies have linked smaller kidney dimensions to increased blood pressure. However, patients with Balkan Endemic Nephropathy (BEN), whose kidneys shrink during the course of the disease, do not manifest increased blood pressure. The authors evaluated the relationship between kidney cortex width, kidney length, and blood pressure in the offspring of BEN patients and controls. METHODS: 102 offspring of BEN patients and 99 control offspring of non-BEN hospital patients in the Vratza District, Bulgaria, were enrolled in a prospective study and examined twice (2003/04 and 2004/05). Kidney dimensions were determined using ultrasound, blood pressure was measured, and medical information was collected. The parental disease of BEN was categorized into three groups: mother, father, or both parents. Repeated measurements were analyzed with mixed regression models. RESULTS: In all participants, a decrease in minimal kidney cortex width of 1 mm was related to an increase in systolic blood pressure of 1.4 mm Hg (p = 0.005). There was no association between kidney length and blood pressure. A maternal history of BEN was associated with an increase in systolic blood pressure of 6.7 mm Hg (p = 0.03); paternal BEN, +3.2 mm Hg (p = 0.35); or both parents affected, +9.9 mm Hg (p = 0.002). There was a similar relation of kidney cortex width and parental history of BEN with pulse pressure; however, no association with diastolic blood pressure was found. CONCLUSION: In BEN and control offspring, a smaller kidney cortex width predisposed to higher blood pressure. Unexpectedly, a maternal history of BEN was associated with average increased systolic blood pressure in offspring.