The role of hypertension, obesity, and diabetes in causing renal vascular disease

Sex, weight status, and chronic kidney disease among African Americans: the Jackson Heart Study

BACKGROUND

Obesity has been shown to have implications for chronic kidney disease (CKD); however, it has received minimal attention from scientists studying CKD among African Americans.

OBJECTIVES

The purpose of this study was to examine the manner in which weight status has implications for CKD among this group through analysis of data drawn from the Jackson Heart Study (JHS).

DESIGN

Cross-sectional analysis of a single-site longitudinal population-based cohort.

PARTICIPANTS

The data for this study were drawn from the baseline examination of the Jackson Heart Study (JHS). The analytic cohort consisted of 3430 African American men and women (21-84 years of age) living in the tricounty area of the Jackson, Mississippi metropolitan areas with complete data to determine CKD status.

MAIN MEASUREMENTS

The primary dependent variable was CKD (defined as the presence of albuminuria or reduced estimated glomerular filtration rate <60 mL/min per 1.73 m(2)). Weight status, the primary predictor, was a 4-category measure based on body mass index.

RESULTS

Associations were explored through bivariable analyses and multivariable logistic regression analyses adjusting for CKD, weight status, diabetes, hypertension, and cardiovascular disease risk factors as well as demographic factors. The prevalence of CKD in the JHS was 20%. The proportion of overweight, class I, and class II obese individuals was 32.5%, 26.9%, and 26.2% respectively. In the pooled model, weight status was not found to be associated with CKD; however, subgroup analysis revealed that class II obesity was associated with CKD among men (odds ratio, 2.37; confidence interval, 1.34-4.19) but not among women (odds ratio, 1.32; confidence interval, 0.88-1.98). The relationship between CKD prevalence and diabetes and CKD prevalence and hypertension varied by sex and differed across weight categories.

CONCLUSIONS

Weight status has implications for CKD among the JHS participants, and this study underscores the need for additional research investigating the relationship between weight status, sex, and CKD among African Americans.

Social environmental stressors, psychological factors, and kidney disease

Kidney disease is one of the most striking examples of health disparities in American public health. Disparities in the prevalence and progression of kidney disease are generally thought to be a function of group differences in the prevalence of kidney disease risk factors such as diabetes, hypertension, and obesity. However, the presence of these comorbidities does not completely explain the elevated rate of progression from chronic kidney disease (CKD) to end-stage renal disease among high-risk populations such as African Americans. We believe that the social environment is an important element in the pathway from CKD risk factors to CKD and end-stage renal disease. This review of the literature draws heavily from social science and social epidemiology to present a conceptual frame specifying how social, economic, and psychosocial factors interact to affect the risks for and the progression of kidney disease.

Peroxisome proliferator-activated receptors in diabetic nephropathy

Diabetic nephropathy is a leading cause of end-stage renal disease, which is increasing in incidence worldwide, despite intensive treatment approaches such as glycemic and blood pressure control in patients with diabetes mellitus. New therapeutic strategies are needed to prevent the onset of diabetic nephropathy. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear transcription factors that play important roles in lipid and glucose homeostases. These agents might prevent the progression of diabetic nephropathy, since PPAR agonists improve dyslipidemia and insulin resistance. Furthermore, data from murine models suggest that PPAR agonists also have independent renoprotective effects by suppressing inflammation, oxidative stress, lipotoxicity, and activation of the renin-angiotensin system. This review summarizes data from clinical and experimental studies regarding the relationship between PPARs and diabetic nephropathy. The therapeutic potential of PPAR agonists in the treatment of diabetic nephropathy is also discussed.

Advances in contrast-enhanced MR angiography of the renal arteries

Renal artery stenosis (RAS) is a potentially curable cause of renovascular hypertension (RVH) and is caused by either atherosclerosis or fibromuscular dysplasia in the vast majority of patients. Although intra-arterial digital subtraction angiography is still considered the standard of reference test for the anatomic diagnosis of RAS, MR angiography and functional renal MR imaging are promising alternatives that also allow for functional characterization of RAS. This article provides an overview of these techniques and discusses their relative merits and shortcomings. Because missing RVH may have serious consequences the most important requirement for an alternative test is that it has high sensitivity. An unresolved issue is the prediction of functional recovery after therapy.

Relationship between carotid artery intima-media thickness and atherosclerotic renal artery stenosis in type 2 diabetes with hypertension

AIM

To assess the relation between intima-media thickness (IMT) of the common carotid artery and atherosclerotic renal artery stenosis (ARAS) > or =50% (one or both renal arteries) in type 2 diabetic patients with hypertension.

METHODS

We performed a retrospective study of type 2 diabetic patients with hypertension who underwent magnetic resonance angiography or digital subtraction angiography for renal artery stenosis at the National Cardiovascular Center or at the Nagasaki Municipal Medical Center between May 1999 and May 2001. Renal artery stenosis was defined as a narrowing of the artery to at least 50% of normal. Thirty type 2 diabetic patients with hypertension (17 men and 13 women, mean age 65.4 +/- 7.6 years) were identified and divided into two groups: those with ARAS in one or both renal arteries (n = 15) and those without ARAS (n = 15). We used high-resolution B-mode ultrasonography to measure the IMT of the common carotid artery.

RESULTS

With and without ARAS were 9 men and 6 women (mean age 65.0 +/- 7.6 years) and 8 men and 7 women (mean age 65.7 +/- 6.8 years), respectively. The IMT of the carotid artery was significantly greater in patients with ARAS than in patients without ARAS (1.07 +/- 0.10 vs. 0.84 +/- 0.12 mm, p < 0.01). However, the only clinical findings that statistically significantly differed were systolic blood pressure and plasma renin activity.

CONCLUSION

Our findings suggest that the measurement of the IMT of the carotid artery may be useful as a noninvasive screening method for the defection of ARAS even in asymptomatic type 2 diabetic patients.

Renal artery stenosis and ischemic nephropathy

Renal artery stenosis (RAS), in its most severe form, can result in diminished renal function and loss of kidney mass. The prevalence of ischemic nephropathy is greatly under-appreciated in the elderly population and is the source of substantial morbidity and mortality. Diagnostic tests for RAS in patients with renal insufficiency are problematic, and medical therapy does little to slow the natural progression of the disease. Renal artery stenting can achieve long-term vessel patency and has been shown to preserve renal function. Proper technique and careful case selection are critical to the success of such procedures. Large-scale trials are needed to clearly identify groups of patients who will benefit most from percutaneous revascularization.