Increased urinary albumin excretion is a marker of risk for retinopathy and coronary heart disease in patients with type 2 diabetes mellitus

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Abstract

The prevalence of increased urinary albumin excretion (UAE) (micro- and macroalbuminuria) and its association with diabetic retinopathy (DR) (evaluated by fluorescent angiography), coronary heart disease (CHD), and various related risk factors were studied in 320 type 2 diabetic patients. In this subsample of type 2 diabetic patients, microalbuminuria was present in 15% of the patients; macroalbuminuria in 4.8%, CHD in 9.9%, DR in 53.4%, and arterial hypertension in 46%. UAE was independently related to CHD (P<0.05), retinopathy (P<0.001), hypertension (P<0.001), and triglycerides (P<0.02). We conclude that increased UAE is associated to a greater frequency of retinopathy and CHD in type 2 diabetic patients.

Introduction

The natural history of diabetic nephropathy seems to differ substantially between type 1 and type 2 diabetes mellitus 1, 2, 3, 4, 5. In particular, the presence of microalbuminuria in type 2 diabetes mellitus has acquired a different significance compared to that in type 1 diabetes mellitus because of its greater association with an increased mortality risk for coronary heart disease (CHD). Indeed, the evolution towards renal failure appears to be quite infrequent in type 2 diabetic patients with urinary albumin excretion 3, 6, whereas CHD seems to be the most frequent cause of death in these patients 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. Conversely, the presence of microalbuminuria in patients with type 1 diabetes mellitus mainly represents a marker of renal damage and an important risk factor for retinopathy 16, 17, 18. It is still not clear how the increased urinary excretion of albumin determines risk of coronaropathy, whether the risk is higher in patients with macroalbuminuria compared with those with microalbuminuria, or whether it represents a risk factor independent of or associated to other risk factors for CHD.

The aim of the present study was to evaluate the prevalence of micro- and macroalbuminuria, their association with microangiopathy (shown by the presence of diabetic retinopathy), CHD, and other relative risk factors, such as degree of hyperglycaemia, alterations of lipid profile, and hypertension in type 2 diabetic patients.

Section snippets

Materials and methods

We studied 320 patients with type 2 diabetes mellitus according to the National Diabetes Data Group criteria [19](154 males and 166 females), randomly recruited among patients with age <70 years and disease duration more than 5 years, who attended the Diabetes Center of the University of Catania during a 3-month period. In total, 580 type 2 diabetic patients attended the center during this period and of these 320 met the selection criteria and participated in the study. Their mean age was

Results

Microalbuminuria was present in 47 patients (15%), macroalbuminuria in 15 (4.8%), diabetic retinopathy (DR) in 167 (53.4%), CHD in 31 (9.9%), and arterial hypertension (AH) in 144 (46%). On the basis of values of UAE, patients were divided into three categories: normoalbuminurics, microalbuminurics, and macroalbuminurics. In normoalbuminurics, mean UAE was 4.1 mg/24 h (95% C.I.: 0–11.5); in microalbuminurics 195 mg/24 h (95% C.I.: 60–285); in macroalbuminurics 751 mg/24 h (95% C.I.: 405–1022) (

Discussion

The epidemiologic data related to the diabetic nephropathy in type 2 diabetes are not well defined: they report a prevalence of microalbuminuria ranging from 15% to 59% and of clinical proteinuria ranges between 3% and 16% 6, 22. The prevalence we found in this study (14.69% and 4.69%, respectively) agrees with the lowest values previously reported. We attempted to evaluate the correlation between the increased UAE and vascular involvement, but the low number of patients, especially in the

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