Plamen Dimitrov

Is the incidence of Balkan endemic nephropathy decreasing

Balkan Endemic Nephropathy (BEN) is a non-inflammatory, slowly progressing, familial, primarily tubulo-interstitial, bilateral renal disease that affects rural populations in several Balkan countries. Our study describes a time trend of the incidence of BEN in eight villages of Vratza District, Bulgaria, for the period 1965-1987, based on three various data sets. The data suggest that after the initial peak between 1967 and 1970, the incidence remained quite stable for the period 1970-1984, and declined after 1984. However, the study also demonstrates under-recording of BEN cases and less complete case identification, especially after 1979. Migration of population might also have contributed to an apparent decline in registered cases. We detected cases of BEN in villages that previously were BEN-free. We recommended a rigorous monitoring of BEN in all afflicted countries, before concluding that the incidence of BEN is decreasing.

Consensus statement on screening, diagnosis, classification and treatment of endemic (Balkan) nephropathy

Currently used diagnostic criteria in different endemic (Balkan) nephropathy (EN) centers involve different combinations of parameters, various cut-off values and many of them are not in agreement with proposed international guidelines. Leaders of EN centers began to address these problems at scientific meetings, and this paper is the outgrowth of those discussions. The main aim is to provide recommendations for clinical work on current knowledge and expertise. This document is developed for use by general physicians, nephrologists, urologist, public health experts and epidemiologist, and it is hoped that it will be adopted by responsible institutions in countries harboring EN. National medical providers should cover costs of screening and diagnostic procedures and treatment of EN patients with or without upper urothelial cancers.

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

BackgroundThe 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.MethodsIn 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.ResultsWe 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 β2-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.ConclusionThe 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.

Balkan endemic nephropathy in Vratza, Bulgaria, 1964-1987: An epidemiologic analysis of population-based disease registers

Balkan Endemic Nephropathy (BEN), first described in 1956 in Vratza region, Bulgaria, may result from prolonged, chronic exposure to environmental toxicants, but the underlying etiologic factors remain elusive. There has been no recent systematic characterization of the epidemiology of this disease. Recently, it has been suggested that the incidence of the disease is decreasing. We therefore abstracted data from registers of patients in 21 affected villages and the town of Vratza, Bulgaria maintained from 1964 through 1987. In 1964, the prevalence of BEN was 6.0 per 1000 inhabitants; among residents of the affected villages, the prevalence was 12.3 per 1000. From 1965 to 1975 the incidence rate was 0.7 per 1000 person-years, and from 1976 to 1987 the incidence rate was 0.3 per 1000 person-years (rate ratio 0.43; p < 0.001). Incidence was much lower in Vratza town; among residents of affected villages, the period-specific rates were 1.7 and 0.8 per 1000 per year, respectively (rate ratio 0.47; p < 0.01). These trends were consistent across all villages for which registers were maintained. Median survival following registration increased from 2.0 to 5.0 years over the same period (p < 0.001). BEN appears to be decreasing in incidence in this region.

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

AbstractBackgroundBalkan 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.MethodsWe 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.ResultsUsing 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.ConclusionOur data propose a new hypothesis that immunologic dysregulation has a place in BEN etiopathogenesis.

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

BackgroundDespite the characteristic extensive tubulointerstitial fibrosis, Balkan Endemic Nephropathy (BEN) is usually considered a non-inflammatory disease.MethodsWe 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.ResultsCompared 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.ConclusionEarly 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.

Increased blood pressure in adult offspring of families with Balkan Endemic Nephropathy: a prospective study

BackgroundPrevious 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.Methods102 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.ResultsIn 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.ConclusionIn 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.

Ochratoxin A and β2-microglobulin in BEN patients and controls.

Ochratoxin A (OTA) is a mycotoxin naturally occurring in different foods. OTA is arguably a risk factor for Balkan endemic nephropathy (BEN). The aims of this study are to (1) test the OTA-BEN association in BEN-groups and controls and (2) determine whether urine β2-microglobulin, a marker of impaired ability of the kidneys to re-absorb, is related to OTA. BEN patients had significantly higher OTA serum levels. Within the offspring, OTA was significantly related to higher β2-microglobulin excretion. OTA (2005/2006) was related to a higher incidence of BEN after 2008, providing further evidence that OTA is a risk factor for BEN.

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 ≥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.

Genetic, Genomic and Epigenomic Studies of Balkan Endemic Nephropathy (Ben)

Abstract BEN is a primary, chronic tubulointerstitial nephritis characterized with chronic anemia, absence of edema, xantoderma, normal blood pressure and normal findings on the fundus oculi. The disease is distributed in restricted areas in Bulgaria, Romania, Croatia, Bosnia, Former Yugoslavia. Despite numerous studies on genetic and environmental factors and their possible involvement in BEN, its etiopathogenesis still remains elusive. Our recent study aim to elucidate the possible epigenetic component in BEN development. Whole genome DNA array methylation analysis was applied to compare the methylation profiles of male and female BEN patients from endemic regions in Bulgaria and Serbia and healthy controls. All three most prominent candidate genes with aberrations in the epigenetic profile discovered with this study are involved in the inflammatory/immune processes and oncogenesis. These data are in concordance with the reported pathological alterations in BEN. This research supports the role of epigenetic changes in BEN pathology. Exome sequencing of 22.000 genes with Illumina Nextera Exome Enrichment Kit revealed three mutant genes (CELA1, HSPG2, and KCNK5) in BEN patients which encode proteins involved in basement membrane/extracellular matrix and vascular tone, tightly connected to process of angiogenesis. We suggest that an abnormal process of angiogenesis plays a key role in the molecular pathogenesis of BEN. Abstract Балканската ендемска нефропатија (БЕН) е примарен, хроничен тубулоинтерстицијален неф- ритис што се карактеризира со хронична анеми- ја, отсуство на едем, ксантодерма, нормален крвен притисок и нормални наоди на фундус окули. Болеста е дистрибуирана во ограничени области во Бугарија, Романија, во поранешна Југослави- ја - Хрватска, Босна и Херцеговина. И покрај бројните студии за генетски и еколошки факто- ри и нивната можна вклученост во БЕН, нејзи- ната етиопатогенеза останува нејасна. Нашата скорешна студија има цел да ја расветли можната епигенетска компонента во раз- војот на БЕН. Беше применета анализа на мети- лациониот статус на геномот на ДНК да се спо- редат метилациските профили на машки и на женски пациенти со БЕН од ендемските региони во Бугарија и во Србија и здрави контроли. Сите три најзначајни гени-кандидати со аберации во епигенетскиот профил откриени со ова истражување се вклучени во воспалителни- те/имунолошките процеси и онкогенезата. Овие податоци се во согласност со соопштените пато- лошки нарушувања кај БЕН. Ова истражување ја поддржува улогата на епигенетските промени во патологијата на БЕН. Егзом секвенционирањето на 22.000 гени со Illumina Nextera Exome Enrichment Kit откри три мутантни гени (CELA1, HSPG2 и KCNK5) кај пациентите со БЕН кои кодираат протеини вклу- чени во базалната мембрана/екстрацелуларниот матрикс и васкуларниот тонус, тесно поврзан со процесот на ангиогенеза. Ние укажуваме на тоа дека абнормалниот процес на ангиогенеза игра клучна улога во молекуларната патогенеза на БЕН.