Serum Total Homocysteine and C-Reactive Protein - Ancillary to IDNT

BACKGROUND:

Patients with diabetic nephropathy experience markedly increased rates of morbidity and mortality due to arteriosclerotic cardiovascular disease [CVD]. Established arteriosclerotic risk factors such as age, sex, cigarette smoking, hypertension, and dyslipidemia do not account adequately for this excess CVD risk. Prospective data from general populations, and much more limited findings from both diabetic cohorts. and cohorts with chronic renal disease, have linked elevated levels of total homocysteine (tHcy) and C-reactive protein (CRP) to arteriosclerotic CVD morbidity and mortality. Determination of baseline serum total homocysteine and C-reactive protein concentrations in the Irbesartan Type 2 Diabetic Nephropathy Trial (IDNT) cohort affords a truly unique opportunity to evaluate the potential independent relationship between these putative CVD risk factors and subsequent CVD morbidity and mortality, in this patient population. The IDNT is a multicenter, randomized, double-blind, placebo-controlled trial of 1,715 hypertensive, Type 2 diabetic patients aged 30 to 70 who have overt nephropathy (24 hour urinary protein excretion greater than 900 mg and a serum creatinine of 90 to 265 micromols/L). The IDNT compares the effect of the angiotensin II receptor antagonist irbesartan with placebo and amlodipine on the progression of renal disease and mortality. The IDNT is supported by Bristol-Myers Squibb Company in Princeton, New Jersey and Sanofi-Synthelabo in Paris, France.

The study is in response to an initiative "Ancillary Studies in Heart, Lung, and Blood Disease Trials" released by the National Heart, Lung, and Blood Institute in June 2000.

DESIGN NARRATIVE:

The first specific aim is to conduct longitudinal analyses of the potential "Independent" relationship between baseline concentrations of serum total homocysteine and C-reactive protein in the full IDNT cohort, and subsequent:pooled cardiovascular disease morbidity and mortality (primary analysis). total mortality, (after multivariable -adjustment for the established predictors of cardiovascular disease morbidity/ mortality, and total mortality). The second specific aim is to conduct cross-sectional analyses to assess baseline serum total homocysteine and C-reactive protein concentrations in the full IDNT cohort, in relation to potential baseline determinants of these analytes, including: B-vitamin status; age and gender; renal function indices, i.e. both creatinine-based glomerular filtration rate estimates, and proteinuria; indices of glycemia, prevalent cardiovascular disease (CVD), traditional CVD risk factors (i.e., in particular, smoking, blood pressure, and total cholesterol/HDL cholesterol ratio).