Endstage renal disease owing to diabetic nephropathy in Mississippi: an examination of factors influencing renal survival in a population prone to late referral

Sex-related differences in diabetic kidney disease: A review on the mechanisms and potential therapeutic implications

Sexual dimorphism may play a key role in the pathogenesis of diabetic kidney disease (DKD) and explain differences observed in disease phenotypes, responses to interventions, and disease progression between men and women with diabetes. Therefore, omitting the consideration of sex as a biological factor may result in delayed diagnoses and suboptimal therapies. This review will summarize the effects of sexual dimorphism on putative metabolic and molecular mechanisms underlying DKD, and the potential implications of these differences on therapeutic interventions. To successfully implement precision medicine, we require a better understanding of sexual dimorphism in the pathophysiologic progression of DKD. Such insights can unveil sex-specific therapeutic targets that have the potential to maximize efficacy while minimizing adverse events.

Non-muscle myosin heavy chain 9 gene MYH9 associations in African Americans with clinically diagnosed type 2 diabetes mellitus-associated ESRD

BACKGROUND

Although MYH9 is strongly associated with biopsy-proven idiopathic and HIV-associated focal segmental glomerulosclerosis (FSGS) and clinically diagnosed 'hypertension-associated' end-stage renal disease (ESRD) in African Americans, its role in type 2 diabetes mellitus (T2DM)-associated ESRD is unclear.

METHODS

To assess whether MYH9 was associated with T2DM-ESRD, 751 African Americans with T2DM-ESRD, 227 with T2DM lacking nephropathy and 925 non-diabetic non-nephropathy controls were genotyped for 14 MYH9 SNPs. Association analyses used SNPGWA and Dandelion.

RESULTS

Comparing T2DM-ESRD cases with non-diabetic controls, single SNP associations were detected with 8 of 14 SNPs, gender- and admixture-adjusted P-values 0.047-0.005 [recessive model, odds ratio (OR) range 1.30-1.55]. The previously associated MYH9 E1 and L1 haplotypes were associated with T2DM-ESRD (E1: OR 1.27, 95% CI 1.04-1.56, P = 0.021 recessive and L1: OR 1.43, 95% CI 1.09-1.87, P = 0.009 dominant). Contrasting the 751 T2DM-ESRD cases with 227 T2DM non-nephropathy controls revealed that E1 haplotype SNPs rs4821480, rs2032487 and rs4821481 were associated with kidney failure (OR 1.38-1.40 recessive, all P < 0.048). Among E1 and L1 risk homozygotes, respectively, mean (SD) diabetes duration prior to renal replacement therapy was 16.6 (9.7) and 16.4 (10.0) years, and 65% had diabetic retinopathy.

CONCLUSIONS

Genetic dissection of T2DM-associated ESRD reveals that MYH9 underlies a portion of this clinically diagnosed disorder in African Americans. It is likely that a subset of African Americans with T2DM and coincident nephropathy have primary MYH9-related kidney disease (e.g. FSGS or global glomerulosclerosis), although renal biopsy studies need to be performed.

The natural course of microalbuminuria among African Americans with type 2 diabetes: a 3-year study

BACKGROUND

The natural course of microalbuminuria in African Americans (AA) with type 2 diabetes is not well established.

METHOD

Longitudinal analysis of 186 African Americans with type 2 diabetes enrolled in Project Sugar, a randomized controlled trial of primary care-based interventions to improve diabetes control.

RESULTS

Mean age was 59.4 years and 85% were female. Mean estimated glomerular filtration rate and urinary albumin-to-creatinine ratio were 75.90 mL/min/1.73 m(2) and 1.62, respectively. Thirty-nine patients had macroalbuminuria and significantly higher systolic blood pressure compared with those with microalbuminuria (P=.01). Sixty patients had microalbuminuria, 19 progressed to macroalbuminuria, and none regressed. Progression was associated significantly with systolic blood pressure >or=115 mm Hg and requirement for blood pressure medication in the univariate model. In the multivariate model, the degree of albumin-to-creatinine ratio (odds ratio 35.51, 95% confidence interval, 2.21-571.65) and need for blood pressure medication (odds ratio 8.96, 95% confidence interval, 1.35-59.70) were independently associated with progression. No association was observed with the use of specific antihypertensive agent.

CONCLUSION

This study suggests that African Americans with type 2 diabetes and microalbuminuria experience irreversible disease that not infrequently progresses to overt proteinuria. The degree of microalbuminuria and blood pressure are key determinants in this process and should be primary targets in treating this population regardless of the antihypertensive class used.

Geographical patterns of end-stage renal disease incidence and risk factors in rural and urban areas of South Carolina

To assess the geographical patterns of end-stage renal disease (ESRD) incidence and to identify the risk factors on the regional differences, the authors conducted an ecological study on incidence of ESRD and related risk factors in the 46 counties of South Carolina (SC). Age and gender adjusted, race specific incidence rates for each county in SC were calculated for the 11,346 ESRD patients of all ages who registered in the United States Renal Data Systems Network 6 from 1990 to 1999. County level exposure measures on population physician density, hospitalization rates of diabetes and hypertension, per capita income, percent college degree, and percent below poverty were evaluated. There was a significant increase in mean incidence rates of ESRD from 1990 to 1999 in SC (p<0.0001). The incidence rates were consistently higher in rural than in urban counties. Population physician density (relative risk (RR) 0.49, 95% confidence interval (95%Cl, 0.41-0.58) and rural residence (adjusted RR 1.66, 95%Cl 1.59-1.74) were significantly associated with ESRD incidence. The strong relationship between ESRD and physician density suggests that access to adequate treatment of diabetes and hypertension is of paramount importance for ESRD prevention, and has important public policy implications.

Health disparities in transplantation: focus on the complexity and challenge of renal transplantation in African Americans

The field of renal transplantation has grown exponentially as a result of a greater understanding of the immune system and the advent of numerous immunosuppressive agents. Although African Americans and whites have benefited from these advances, equivalent long-term success eludes African Americans who are disadvantaged in gaining access to renal transplantation. This review summarizes the obstacles for African Americans to end-stage renal disease(ESRD) care, focusing on transplantation. Factors that predispose African Americans for ESRD, impede this ethnic group from timely transplantation, and negatively influence graft survival are examined. Possible solutions to these persistent problems are offered.

Hepatitis C is a predictor of poorer renal survival in diabetic patients

OBJECTIVE

Hepatitis C virus (HCV) is highly prevalent in the U.S. and worsens renal survival in some kidney diseases. We examined the effects of HCV on renal survival in diabetic patients with renal disease.

RESEARCH DESIGN AND METHODS

HCV and diabetes status were noted in patients seen in our nephrology clinic in 2001 and 2002. Charts of diabetic patients were reviewed for demographics, blood pressure, renal function, medicines, the presence of HCV, and other factors at the initial visit and over follow-up. The effect of HCV on renal survival was determined by Cox proportional hazards, using end-stage renal disease (ESRD) as an end point.

RESULTS

Of 1,127 patients, prevalence rates for HCV were higher in African Americans than non-African Americans (8.09 vs. 3.93%, respectively, P = 0.06), with African-American men having the highest prevalence rates (12.7%). The charts of 312 diabetic patients were reviewed. Over 80% were African American, as were 23 of 24 patients with HCV. Compared with non-HCV patients, HCV patients were younger, had higher diastolic blood pressure, and had lower BMI. HCV patients had significantly worse cumulative renal survival by Kaplan-Meier. On Cox proportional hazards analysis, HCV was a significant predictor of reaching ESRD independent of initial renal function, proteinuria, blood pressure, sex, race, presence of diabetic nephropathy, age, or duration of diabetes (odds ratio 3.49, 95% CI 1.27-9.57, P = 0.015).

CONCLUSIONS

HCV is common in African Americans with diabetes and renal disease and is an independent risk factor for renal survival in this population. Prospective studies are necessary to confirm these observations.

Autocrine activation of the local insulin-like growth factor I system is up-regulated by estrogen receptor (ER)-independent estrogen actions and accounts for decreased ER expression in type 2 diabetic mesangial cells

Autocrine activation of the IGF-I system in mesangial cells (MC) promotes glomerular scarring in a model of type 1 diabetes. Although estrogens protect against progressive nondiabetic glomerulosclerosis (GS), women with diabetes seem to loose the estrogen-mediated protection against cardiovascular disease. However, little is known about the local IGF-I system and its interactions with estrogens in the pathogenesis of type 2 diabetic GS. Therefore, we examined db/db B6 (db/db) mice, a model of type 2 diabetes and diabetic GS. The IGF-I system was activated in the glomeruli and MC of female diabetic db/db mice, but not in nondiabetic db/+ littermates. We found increased IGF-I receptor (IGFR) expression and activation, including activation of MAPK. Surprisingly, estrogens, via an estrogen receptor (ER)-independent mechanism(s), increased IGFR expression, IGFR and insulin receptor substrate phosphorylation, and extracellular signal-regulated kinase activation in db/db MC. In contrast, ER expression was decreased in MC and glomeruli of db/db mice. Treatment with a neutralizing antibody to IGF-I or the MAPK inhibitor PD98059 increased ER expression and transcriptional activity. This suggests that the local prosclerotic IGF-I system is activated in type 2 diabetes and diminishes ER-mediated protection against GS. Although estrogens may stimulate protective ER signaling, they also activate the IGF-I system via ER-independent mechanisms in db/db MC. The later estrogen effects appear to outweigh the antisclerotic effects of ER activation. This may in part account for loss of estrogen protection against the progression of diabetic GS in women with type 2 diabetes.

Diabetic nephropathy in African-American patients

Diabetic nephropathy (DN) is the number one cause of end-stage renal disease (ESRD) in the United States and is highly prevalent in African Americans. Since 1997, DN has been the number one cause of ESRD in African Americans. In African Americans, almost all DN is due to type 2 diabetes mellitus (T2DM), and nephropathy may affect female more than male patients. African Americans with T2DM are at increased risk for developing and having progression of DN. Glycemic control, development of albuminuria, family history of renal disease, and control of blood pressure are important risk factors for progression of DN. In addition, cigarette smoking, presence of hepatitis C, and use of thiazolinediones has an impact on renal survival in African Americans. Large vessel complications may be less frequent in African Americans with T2DM, when compared with white persons. Yet, cardiovascular disease and other microvascular complications are very common, and both are dependent on control of blood pressure. Achieving the recommended blood pressure of less than 130/80 mm Hg is essential but requires multiple antihypertensive medications, including an inhibitor of the renin-angiotensin system.

Differences between blacks and whites in the incidence of end-stage renal disease and associated risk factors

In the United States, the age-and-gender-adjusted incident rate of end-stage renal disease (ESRD) for blacks has been 4 times higher than that for whites. We analyzed patient information and medical services contained in the Medicare 5% random sample database. White (n = 977,436) and black (n = 77,800) Medicare enrollees who were at least 65 years old on January 1, 1997, were followed from 1999 to 2001. Hierarchical Cox regression models were used to estimate the relative risk of ESRD for blacks (with reference to whites) after adjustment for age and gender, socioeconomic status, special health conditions (anemia, chronic obstructive pulmonary disease, cardiovascular disease), primary causal diseases of ESRD (eg, diabetes, hypertension), diabetes care and preventive care (eg, hemoglobin A1c or lipid testing), and physician visits for primary or specialty care. The relative risk of ESRD for blacks (with reference to whites) was 3.52 (95% confidence interval [CI], 3.25-3.80) after adjustment for age and gender; 2.90 (95% CI, 2.67-3.15) after adjustment for socioeconomic status and special health conditions; and 2.11 (95% CI, 1.94-2.30) after further adjustment for primary causal diseases of ESRD, diabetes care and preventive care, and physician visits. We conclude that a higher prevalence of primary causal diseases of ESRD and lower access to diabetes care, preventive care, and primary physician visits in blacks compared with whites partially accounts for the racial difference in the incidence of ESRD in the elderly Medicare population. Public health policy should focus on improving access to care, which may lower the burden of ESRD in minority and other at-risk populations.

Ethical implications of ethnic disparities in chronic kidney disease and kidney transplantation

Chronic kidney disease (CKD) is a major epidemic in underserved and minority populations largely due to excess rates of hypertensive and diabetic kidney disease. Multiple complex socioeconomic barriers to early diagnosis and optimal therapies as well as delayed referral for kidney transplantation have created disparities in CKD care provided to ethnic minorities. Disparities exist in wait list time and kidney transplant rates for Native Americans and blacks, independent of insurance status. Moreover, independent of genetic matching, long-term transplant outcomes in blacks remain significantly lower than all other ethnic groups, suggesting that poorly understood social factors contribute to these survival differences. The existence of these disparities raises ethical concerns of equity and social justice in terms of the allocation of scarce resources. Although current changes in allocation policies will improve some disparities, more efforts are ultimately needed to improve access to care and the overall health and survival for all individuals at risk for CKD, independent of their race, ethnicity, or socioeconomic status.

Angiotensin-Converting Enzyme Genotype in Blacks with Diabetic Nephropathy: Effects on Risk of Diabetes and Its Complications

Objective

Among blacks, we have observed that diabetic nephropathy (DN) is a more frequent primary cause of end-stage renal disease (ESRD) in women (∼ 50%) than in men (< 20%). In this study, we consider the role of the angiotensin-converting enzyme (ACE) polymorphism in determining this gender discrepancy and its role in the course of DN.

Methods

ACE genotype (I = insertion, D = deletion) was determined in consecutive consenting patients with type 2 diabetes mellitus and DN. Charts were subsequently reviewed for renal survival and its determinants (end point: time to ESRD from first clinic visit).

Results

Fifty-four patients (46 blacks) who had DN and were pre-ESRD consented: II = 6, ID = 31, and DD = 17. The allele frequency for D was ∼. 61 versus .39 for the I allele and did not differ by gender. Renal disease at presentation to the renal clinic was significantly worse in II. Twenty-one patients reached ESRD (II = 4, ID = 13, DD = 4; χ2 not significant), but ACE genotype had no significant effect on renal survival. Initial serum creatinine and blood pressure over follow-up independently predicted renal survival. Among blacks reaching ESRD, the presence of the D allele was associated with higher blood pressures. Patients without a family history of diabetes (χ2, p = .01) or diabetic retinopathy (χ2, p = .02) were more likely to have the DD genotype.

Conclusions

The gender discrepancy observed in rates of ESRD owing to DN in blacks is not likely dependent on ACE genotype. The effects of ACE genotype on renal disease progression were not significant; however, patients with diabetic nephropathy and DD genotype were less likely to have traditional risk factors for diabetes or diabetic nephropathy.

Are low target blood pressure goals justified in persons with diabetes mellitus?

Hypertension is common in patients with diabetes and is a major risk factor for development and progression of the macro- and microvascular complications seen in diabetes. The Joint National Committee VI recommendation for goal blood pressure is less than 130/85 mm Hg in diabetics--a more aggressive target than in nondiabetic patients. Data over the past decade support these aggressive goals, especially for cardiovascular and renal outcomes and overall mortality. In addition, in diabetics, blood pressure appears to be a continuous risk factor for these outcomes without evidence of a J-point effect. While these goals are rarely obtained in diabetic patients, studies demonstrate that they are achievable with attention to detail and use of multiple antihypertensive agents.

African Americans and renal transplantation: disproportionate need, limited access, and impaired outcomes

BACKGROUND

Renal transplantation is the therapy of choice for patients with end-stage renal disease (ESRD). However, African Americans' (AA) access to this modality is not commensurate with that of other races. This imbalance, coupled with AA disproportionately representing those with ESRD, has kept AA disadvantaged compared with other races, especially whites.

METHODS

We reviewed published reports that examined the connection between race and the incidence of chronic renal failure, access to optimal therapy, and outcomes of renal transplantation.

RESULTS

The incidence of ESRD in AA is 4 times greater than in whites, but AA remain less likely than whites to be referred for or undergo renal transplantation. Also, AA are at greater risk than whites to experience premature graft failure.

CONCLUSIONS

ESRD management has improved dramatically with the advent of successful renal transplantation. However, AA remain significantly disadvantaged in both access and outcomes compared with whites. Further evaluation of underlying causes and development of specific remedies is warranted.

Diabetic renal disease in African Americans

Diabetic nephropathy (DN) is the No. 1 cause of end-stage renal disease in the United States and is highly prevalent in African Americans. Almost all DN in African Americans is caused by type 2 diabetes. Glycemic control and control of blood pressure are essential to prolong renal survival and to protect against cardiovascular events. Among African Americans, diabetic nephropathy seems to affect women more than men, which may be related to increased rates of obesity and diabetes in African American women. In addition to gender, the development of albuminuria, family history, and possibly birth weight are factors that predict progression of renal disease in African Americans with DN. The impact of glycemic control, appropriate antihypertensives, and the optimal level of blood pressure control in African Americans with advanced DN require further study. This article will review the clinical characteristics, risk factors, predictors of disease progression, and treatment of diabetic nephropathy in African Americans.