Genetic basis of nondiabetic end-stage renal disease

Non-diabetic end-stage renal disease in Saudis associated with polymorphism of MYH9 gene but not UMOD gene

The prevalence of risk factors of chronic kidney disease in Saudi Arabia has augmented an already serious public health problem, therefore, determination of genetic variants associated with the risk of the disease presents potential screening tools that help reducing the incidence rates and promote effective disease management.The aim of the present study is to determine the association of UMOD and MYH9 genetic variants with the risk of non-diabetic end-stage renal disease (ESRD) in the Saudi population.Two single nucleotide polymorphisms (SNP), rs12917707 in gene UMOD and rs4821480 in gene MYH9 were genotyped in 154 non-diabetic ESRD Saudi patients and 123 age-matched healthy controls using Primers and Polymerase chain reaction conditions (PCR), Sanger sequencing, and TaqMan Pre-designed SNP Genotyping Assay. The association of these genetic variants with the risk of the disease and other renal function determinants was assessed using statistical tools such as logistic regression and One-way Analysis of Variance tests.The genotypic frequency of the two SNPs showed no deviation from Hardy-Weinberg equilibrium, the minor allele frequency of UMOD SNP was 0.13 and MYH9 SNP was 0.08. rs4821480 in MYH9 was significantly associated with the risk of non-diabetic ESRD (OR = 3.86; 95%CI: 1.38-10.82, P value .010), while, rs12917707 showed lack of significant association with the disease, P value .380. and neither of the 2 SNPs showed any association with the renal function determinants, serum albumin, and alkaline phosphatase enzyme.

Genetic characterization of early renal changes in a novel mouse model of diabetic kidney disease

Genetic factors influence susceptibility to diabetic kidney disease. Here we mapped genes mediating renal hypertrophic changes in response to diabetes. A survey of 15 mouse strains identified variation in diabetic kidney hypertrophy. Strains with greater (FVB/N(FVB)) and lesser (C57BL/6 (B6)) responses were crossed and diabetic F2 progeny were characterized. Kidney weights of diabetic F2 mice were broadly distributed. Quantitative trait locus analyses revealed diabetic mice with kidney weights in the upper quartile shared alleles on chromosomes (chr) 6 and 12; these loci were designated as Diabetic kidney hypertrophy (Dkh)-1 and -2. To confirm these loci, reciprocal congenic mice were generated with defined FVB chromosome segments on the B6 strain background (B6.Dkh1/2f) or vice versa (FVB.Dkh1/2b). Diabetic mice of the B6.Dkh1/2f congenic strain developed diabetic kidney hypertrophy, while the reciprocal FVB.Dkh1/2b congenic strain was protected. The chr6 locus contained the candidate gene; Ark1b3, coding aldose reductase; the FVB allele has a missense mutation in this gene. Microarray analysis identified differentially expressed genes between diabetic B6 and FVB mice. Thus, since the two loci identified by quantitative trait locus mapping are syntenic with regions identified for human diabetic kidney disease, the congenic strains we describe provide a valuable new resource to study diabetic kidney disease and test agents that may prevent it.

Past Decline Versus Current eGFR and Subsequent ESRD Risk

eGFR is a robust predictor of ESRD risk. However, the prognostic information gained from the past trajectory (slope) beyond that of the current eGFR is unclear. We examined 22 cohorts to determine the association of past slopes and current eGFR level with subsequent ESRD. We modeled hazard ratios as a spline function of slopes, adjusting for demographic variables, eGFR, and comorbidities. We used random effects meta-analyses to combine results across studies stratified by cohort type. We calculated the absolute risk of ESRD at 5 years after the last eGFR using the weighted average baseline risk. Overall, 1,080,223 participants experienced 5163 ESRD events during a mean follow-up of 2.0 years. In CKD cohorts, a slope of -6 versus 0 ml/min per 1.73 m(2) per year over the previous 3 years (a decline of 18 ml/min per 1.73 m(2) versus no decline) associated with an adjusted hazard ratio of ESRD of 2.28 (95% confidence interval, 1.88 to 2.76). In contrast, a current eGFR of 30 versus 50 ml/min per 1.73 m(2) (a difference of 20 ml/min per 1.73 m(2)) associated with an adjusted hazard ratio of 19.9 (95% confidence interval, 13.6 to 29.1). Past decline contributed more to the absolute risk of ESRD at lower than higher levels of current eGFR. In conclusion, during a follow-up of 2 years, current eGFR associates more strongly with future ESRD risk than the magnitude of past eGFR decline, but both contribute substantially to the risk of ESRD, especially at eGFR<30 ml/min per 1.73 m(2).

Association of coronary artery disease and chronic kidney disease in Lebanese population

BACKGROUND

More evidence is emerging on the strong association between chronic kidney disease (CKD) and cardiovascular disease. We assessed the relationship between coronary artery disease (CAD) and renal dysfunction level (RDL) in a group of Lebanese patients.

METHODS

A total of 1268 patients undergoing cardiac catheterization were sequentially enrolled in a multicenter cross sectional study. Angiograms were reviewed and CAD severity scores (CADSS) were determined. Estimated glomerular filtration rate (eGFR) was calculated and clinical and laboratory data were obtained. CKD was defined as eGFR < 60 ml/min. Logistic regression model was performed using multivariate analysis including all traditional risk factors associated with both diseases. ANOVA and the Tukeytestswere used to compare subgroups of patients and to assess the impact of each disease on the severity of the other.

RESULTS

Among the 82% patients who exhibited variable degrees of CAD, 20.6% had an eGFR < 60 ml/min. Logistic regression analysis revealed a bidirectional independent association between CAD and CKD with an OR = 2.01 (P < 0.01) and an OR = 1.99 (P < 0.01) for CAD and CKD frequencies, respectively. We observed a steady increase in the CADSS mean as eGFR declined and a progressive reduction in renal function with the worsening of CAD (P < 0.05). This correlation remained highly significant despite considerable inter-patient variability and was at its highest at the most advanced stages of both diseases.

CONCLUSIONS

Our results show a strong, independent and graded bidirectional relationship between CAD severity and RDL. We propose to add CAD to the list of risk factors for the development and progression of CKD.

Risk Adjustment and the Assessment of Disparities in Dialysis Mortality Outcomes

Standardized mortality ratios (SMRs) reported by Medicare compare mortality at individual dialysis facilities with the national average, and are currently adjusted for race. However, whether the adjustment for race obscures or clarifies disparities in quality of care for minority groups is unknown. Cox model-based SMRs were computed with and without adjustment for patient race for 5920 facilities in the United States during 2010. The study population included virtually all patients treated with dialysis during this period. Without race adjustment, facilities with higher proportions of black patients had better survival outcomes; facilities with the highest percentage of black patients (top 10%) had overall mortality rates approximately 7% lower than expected. After adjusting for within-facility racial differences, facilities with higher proportions of black patients had poorer survival outcomes among black and non-black patients; facilities with the highest percentage of black patients (top 10%) had mortality rates approximately 6% worse than expected. In conclusion, accounting for within-facility racial differences in the computation of SMR helps to clarify disparities in quality of health care among patients with ESRD. The adjustment that accommodates within-facility comparisons is key, because it could also clarify relationships between patient characteristics and health care provider outcomes in other settings.

Agregação familiar da doença renal crônica secundária à hipertensão arterial ou diabetes mellitus: estudo caso-controle

No Brasil, a hipertensão e o diabetes mellitus tipo 2 são responsáveis por 60% dos casos de doença renal crônica terminal em terapia renal substitutiva. Estudos americanos identificaram agregação familiar da doença renal crônica, predominante em afrodescendentes. Um único estudo brasileiro observou agregação familiar entre portadores de doença renal crônica quando comparados a indivíduos internados com função renal normal. O objetivo deste artigo é avaliar se existe agregação familiar da doença renal crônica em familiares de indivíduos em terapia renal substitutiva causada por hipertensão e/ou diabetes mellitus. Estudo caso-controle tendo como casos 336 pacientes em terapia renal substitutiva portadores de diabetes mellitus ou hipertensão há pelo menos 5 anos e controles amostra pareada de indivíduos com hipertensão ou diabetes mellitus e função renal normal (n = 389). Os indivíduos em terapia renal substitutiva (casos) apresentaram razão de chance de 2,35 (IC95% 1,42-3,89; p < 0,001) versus controles de terem familiares com doença renal crônica terminal, independente da raça ou doença de base. Existe agregação familiar da doença renal crônica na amostra estudada e esta predisposição independe da raça e da doença de base (hipertensão ou diabetes mellitus).

Posttransplant hypertension: multipathogenic disease process

Arterial hypertension is prevalent among kidney transplant recipients. The multifactorial pathogenesis involves the interaction of the donor and the recipient's genetic backgrounds with several environmental parameters that may precede or follow the transplant procedure (eg, the nature of the renal disease, the duration of the chronic kidney disease phase and maintenance dialytic therapy, the commonly associated cardiovascular disease with atherosclerosis and arteriosclerosis, the renal mass at implantation, the immunosuppressive regimen used, life of the graft, and de novo medical and surgical complications that may occur after a transplant). Among calcineurin inhibitors, tacrolimus seems to have a better cardiovascular profile. Steroid-free protocols and calcineurin inhibitor-free regimens seem to be associated with better blood pressure control. Posttransplant hypertension is a major amplifier of the chronic kidney disease-cardiovascular disease continuum. Despite the adverse effects of hypertension on graft and patient survival, blood pressure control remains poor because of the high cardiovascular risk profile of the donor-recipient pair. Although the optimal blood pressure level remains unknown, it is recommended to maintain the blood pressure at < 130/80 mm Hg and < 125/75 mm Hg in the absence or presence of proteinuria.

Survival advantage in black versus white men with CKD: effect of estimated GFR and case mix

BACKGROUND

Black dialysis patients have significantly lower mortality compared with white patients, in contradistinction to the higher mortality seen in blacks in the general population. It is unclear whether a similar paradox exists in patients with non-dialysis-dependent chronic kidney disease (CKD), and if it does, what its underlying reasons are.

STUDY DESIGN

Historical cohort.

SETTING & PARTICIPANTS

518,406 white and 52,402 black male US veterans with non-dialysis-dependent CKD stages 3-5.

PREDICTOR

Black race.

OUTCOMES & MEASUREMENTS

We examined overall and CKD stage-specific all-cause mortality using parametric survival models. The effect of sociodemographic characteristics, comorbid conditions, and laboratory characteristics on the observed differences was explored in multivariable models.

RESULTS

During a median follow-up of 4.7 years, 172,093 patients died (mortality rate, 71.0 [95% CI, 70.6-71.3] per 1,000 patient-years). Black race was associated with significantly lower crude mortality (HR, 0.95; 95% CI, 0.94-0.97; P < 0.001). The survival advantage was attenuated after adjustment for age (HR, 1.14; 95% CI, 1.12-1.16), but was magnified after full multivariable adjustment (HR, 0.72; 95% CI, 0.70-0.73; P < 0.001). The unadjusted survival advantage of blacks was more prominent in those with more advanced stages of CKD, but CKD stage-specific differences were attenuated by multivariable adjustment.

LIMITATIONS

Exclusively male patients.

CONCLUSIONS

Black patients with CKD have lower mortality compared with white patients. The survival advantage seen in blacks is accentuated in patients with more advanced stages of CKD, which may be explained by changes in case-mix and laboratory characteristics occurring during the course of kidney disease.

Poverty and racial disparities in kidney disease: the REGARDS study

There are pronounced disparities among black compared to white Americans for risk of end-stage renal disease. This study examines whether similar relationships exist between poverty and racial disparities in chronic kidney disease (CKD) prevalence.

METHODS

We studied 22,538 participants in the REasons for Geographic And Racial Differences in Stroke (REGARDS) cohort study. We defined individual poverty as family income below USD 15,000 and a neighborhood as poor if 25% or more of the households were below the federal poverty level.

RESULTS

As the estimated glomerular filtration rate (GFR) declined from 50-59 to 10-19 ml/min/ 1.73 m2, the black:white odds ratio (OR) for impaired kidney function increased from 0.74 (95% CI 0.66, 0.84) to 2.96 (95% CI 1.96, 5.57). Controlling for individual income below poverty, community poverty, demographic and comorbid characteristics attenuated the black:white prevalence to an OR of 0.65 (95% CI 0.57, 0.74) among individuals with a GFR of 59-50 ml/min/1.73 m2 and an OR of 2.21 (95% CI 1.25, 3.93) among individuals with a GFR between 10 and 19 ml/min/ 1.73 m2.

CONCLUSION

Household, but not community poverty, was independently associated with CKD and attenuated but did not fully account for differences in CKD prevalence between whites and blacks.