Factors associated with microalbuminuria in type 1 diabetes mellitus: a cross-sectional study

Prevalence of abnormal urinary albumin excretion in a population-based study in Spain: results from the HERMEX Study

BACKGROUND

HERMEX is a population-based study which try to evaluate the relative weight of cardiovascular risk factors in the population of Extremadura. This report provides the data obtained about microalbuminuria in a large Spanish population.

DESIGN AND METHODS

Observational, cross-sectional, population-based study. A total of 3402 subjects were randomly selected from the Health Care System of Extremadura. The final sample included 2813 subjects (mean age 51·2 years, 53·5% female). Urinary albumin excretion rate (UAER) in first morning urine sample was analysed. Microalbuminuria was diagnosed when UAER was ≥ 22 in men or ≥ 31 mg/g in women.

RESULTS

Prevalence of abnormal UAER in general population was 5·5% (microalbuminuria: 4·7%; proteinuria 0·8%). Microalbuminuria grew slightly in patients between 65 and 74 years and showed a dramatic increase in subject older than 75 years (P < 0·001). Men showed a high prevalence of microalbuminuria (5·8% vs. women 3·6%; P = 0·006 chi-squared test). Increased UAER was more common in obese subjects (6·7% vs. 2·3%, P < 0·001), hypertensive patients (8·3% vs. 2·3%, P < 0·001) and diabetic ones (10·9% vs. 3·7%, P < 0·001). The multivariate analysis showed a positive correlation of abnormal UAER with body mass index (BMI), systolic blood pressure, plasma creatinine and triglyceride levels.

CONCLUSIONS

A low frequency of abnormal UAER was detected in a randomly selected sample of Spanish general population. This finding agreed with the low rates of cardiovascular mortality and morbidity observed in Spain in spite of a high prevalence of classic cardiovascular risk factors.

What is the mechanism of microalbuminuria in diabetes: a role for the glomerular endothelium?

Microalbuminuria is an important risk factor for cardiovascular disease and progressive renal impairment. This holds true in the general population and particularly in those with diabetes, in whom it is common and marks out those likely to develop macrovascular disease and progressive renal impairment. Understanding the pathophysiological mechanisms through which microalbuminuria occurs holds the key to designing therapies to arrest its development and prevent these later manifestations. Microalbuminuria arises from the increased passage of albumin through the glomerular filtration barrier. This requires ultrastructural changes rather than alterations in glomerular pressure or filtration rate alone. Compromise of selective glomerular permeability can be confirmed in early diabetic nephropathy but does not correlate well with reported glomerular structural changes. The loss of systemic endothelial glycocalyx--a protein-rich surface layer on the endothelium--in diabetes suggests that damage to this layer represents this missing link. The epidemiology of microalbuminuria reveals a close association with systemic endothelial dysfunction and with vascular disease, also implicating glomerular endothelial dysfunction in microalbuminuria. Our understanding of the metabolic and hormonal sequelae of hyperglycaemia is increasing, and we consider these in the context of damage to the glomerular filtration barrier. Reactive oxygen species, inflammatory cytokines and growth factors are key players in this respect. Taken together with the above observations and the presence of generalised endothelial dysfunction, these considerations lead to the conclusion that glomerular endothelial dysfunction, and in particular damage to its glycocalyx, represents the most likely initiating step in diabetic microalbuminuria.

Microalbuminuria en pacientes diabéticos y en pacientes con hipertensión arterial: estudio de una cohorte de 979 pacientes

BACKGROUND AND OBJECTIVE

Microalbuminuria is a known complication of diabetes mellitus but it is also a cardiovascular risk factor commonly present among hypertensive (non diabetic) population. The prevalence of microalbuminuria is variable and it has been never estimated in our region. The aim of this study has been to determine the prevalence of microalbuminuria in hypertensive (non diabetic) and diabetic population in Extremadura (Spain).

PATIENTS AND METHOD

The study included diabetic patients and non-diabetic hypertensive ones randomly selected. Microalbuminuria was measured in every patient using albumin/creatinin reactive stick in fasting first morning urine. Whenever possible microalbuminuria was confirmed in laboratory by microalbuminuria/creatinina coefficient in first morning urine samples.

RESULTS

A total of 979 patients (mean age [SD], 67.9 [10.8] years; 409 men and 570 women, 505 diabetics) were studied. The presence of microalbuminuria was found in 12.4% of hypertensive patients and in 21.4% of diabetic patients (p < 0.001). Hypertensives and normotensive diabetics showed a similar prevalence of microalbuminuria (13.3%, not significant), but it tripled in hypertensive diabetics (33.8; p < 0.01). Glicemic control was not different for microalbuminuric diabetic patients and non microalbuminuric ones. The patients receiving rennin-angiotensin axis blocking drugs do not showed less prevalence of microalbuminuria (hypertensives 10.5%, diabetics 23.5%). Microalbuminuria was confirmed in 65.4% of patients.

CONCLUSIONS

The prevalence of microalbuminuria in Extremadura seems to be high either in diabetics or non diabetic hypertensive patients. The finding of microalbuminuria in diabetics patients correlates with hypertension but do not with glicemic control. The prevalence of microalbuminuria is high in spite of using rennin-angiotensin axis blocking drugs.

Prevalence of retinopathy and microalbuminuria in pediatric type 2 diabetes mellitus

BACKGROUND

There has been a dramatic rise of type 2 diabetes mellitus (DM2) in the US pediatric population, yet the presence of retinopathy and microalbuminuria in this cohort has not yet been described.

AIM

To assess the presence of retinopathy and microalbuminuria in a cohort of predominantly minority adolescents (African American and Caribbean Hispanic) with DM2.

PATIENTS AND METHODS

Forty pediatric patients with DM2 were examined between July, 2001 and June, 2003 for the presence of retinopathy. Data were also collected regarding microalbuminuria, body mass index, HbA1c, and family history of DM.

RESULTS

Of the 40 patients examined, one patient (2.5%) had retinopathy, whereas nine (27.3%) had microalbuminuria.

CONCLUSIONS

In young predominantly minority adolescents with DM2, retinopathy is rare, while microalbuminuria is common.

Proteinuria in Diabetic Patients – Is It Always Diabetic Nephropathy?

BACKGROUND

Diabetic nephropathy (dNP) is a consequence of type 1 and type 2 diabetes, typically occurring between 5 and 15 years after diabetes has been diagnosed. The coincidence of dNP and diabetic retinopathy (dRP) is well known. In this study we correlated the histological findings of the kidney biopsy with the clinically expected diagnosis of dNP.

PATIENTS AND METHODS

Over a 4-year period with a total of 326 kidney biopsies, 85 biopsies were performed on patients with diabetes. In all of these patients we had information about duration of diabetes and ophthalmological status. Additionally, data about proteinuria, urine sediment and autoantibodies were available. The nephrologist had to give the suspected diagnosis before the biopsy was performed, using the clinical data available.

RESULTS

In 57 patients (67%) dNP was predicted clinically before biopsy. In 28 patients we expected a different kind of kidney disease. Only 43 patients had dNP histologically. In 16 out of 19 patients with dRP we also found dNP. 26 patients with dNP did not have dRP. So dRP was very specific but not sensitive to predict dNP. On the other hand, all patients without dRP but acanthocytes in urine sediment had non-diabetic kidney disease (NDKD). In the case of patients with neither dRP nor acanthocytes, it was very difficult to distinguish between dNP and NDKD. Acanthocytes and antineutrophil cytoplasmatic antibodies with positive antibodies for proteinase 3 or myeloperoxidase were found only in NDKD, but ANAs were detected in a wide titer range in dNP and NDKD. The known duration of the diabetes ranged from 1 to 40 years. There were no additional parameters to differentiate this group.

CONCLUSIONS

Diabetic patients with dRP and proteinuria frequently have dNP. In patients without typical retinal findings dNP is less likely, thus a kidney biopsy is necessary to confirm the diagnosis. Additional knowledge about urine sediment and autoantibodies is helpful, but is not sufficient to differentiate NDKD from dNP in the majority of patients.

Higher levels of HDL cholesterol are associated with a decreased likelihood of albuminuria in patients with long-standing type 1 diabetes

OBJECTIVE

The objective of this study was to determine whether high levels of HDL cholesterol are associated with a lower prevalence of albuminuria

RESEARCH DESIGN AND METHODS

We analyzed the lipid profiles of patients with type 1 diabetes of > or = 20 years duration in 42 patients with albuminuria (28 microalbuminuria and 14 macroalbuminuria) and 65 patients without increased albumin excretion before any interventions with either statins or ACE inhibitors.

RESULTS

Several characteristics were similar in the two groups: sex, age, duration of diabetes, total cholesterol, LDL cholesterol, and triglycerides. By univariate analysis, significant differences (P < 0.01) were found in HDL cholesterol (albuminuria 1.42 mg/dl, no albuminuria 1.71 mg/dl, P < 0.01), HbA1c (A1C) (albuminuria 8.5%, no albuminuria 7.5%), and proportions with no, background, and proliferative retinopathy (albuminuria 2.4, 16.7, and 81%; no albuminuria 24.6, 52.3, and 23.1%, respectively). When adjusted for age and sex, a 0.26-mmol/l (10-mg/dl) increase in HDL cholesterol is associated with an odds ratio (OR) of 0.70 (95% CI 0.54-0.90) for having albuminuria. In a multivariate model that adjusted for age, sex, diabetes duration, and A1C, for every 0.54-mmol/l (21-mg/dl) increase in HDL cholesterol, patients are approximately half (OR 0.51 [95% CI 0.30-0.86]) as likely to have albuminuria, even after controlling for A1C.

CONCLUSIONS

Higher HDL cholesterol levels may be protective against the development of albuminuria in patients with type 1 diabetes. Whether this is due to the HDL cholesterol levels or whether they serve as a marker for some other mechanism remains to be determined.

Does microalbuminuria predict diabetic nephropathy?

OBJECTIVE

To describe risk factors associated with microalbuminuria (MA) in subjects with diabetes, investigate the predictive value of MA as a marker of risk for diabetic nephropathy (DN), and define risk factors associated with the development and progression of MA.

RESEARCH DESIGN AND METHODS

We conducted a prospective longitudinal study of 23 diabetic subjects with persistent MA and 209 diabetic subjects without MA who attended diabetes clinics at the University of Michigan Medical Center in 1989 and 1990. Both groups were examined at baseline and after 7 years. At baseline, urinary albumin-to-creatinine ratios were studied in random, first morning, and 24-h urine samples. At follow-up, a 12-h overnight urine sample was collected and analyzed for albumin and creatinine. At baseline, MA was defined by at least two separate urine specimens with albumin-to-creatinine ratios between 30 and 299 microg albumin per milligram of creatinine.

RESULTS

MA regressed in 56% of subjects with baseline MA without systematic application of corrective measures and developed in 16% of subjects without baseline MA. The predictive value positive of MA as a marker of risk for DN was 43%, and the predictive value negative was 77%. In the combined cohort, the incidence and progression of MA were significantly associated with poor glycemic control and duration of diabetes between 10 and 14 years.

CONCLUSIONS

MA may not be as sensitive and specific a predictor of DN as previously suggested. Other markers of risk for DN are needed for optimal clinical management.