Normal Urinary Albumin Excretion Rate Research Articles

Histological Manifestations of Diabetic Kidney Disease and its Relationship with Insulin Resistance.

Histological manifestations of diabetic kidney disease (DKD) include mesangiolysis, mesangial matrix expansion, mesangial cell proliferation, thickening of the glomerular basement membrane, podocyte loss and foot process effacement, hyalinosis of the glomerular arterioles, interstitial fibrosis and tubular atrophy. Glomerulomegaly is a typical finding. Histological features of DKD may occur in the absence of clinical manifestations, having been documented in patients with normal urinary albumin excretion and normal glomerular filtration rate. Furthermore, the histological picture progresses over time while clinical data may remain normal. Conversely, histological lesions of DKD improve with metabolic normalization, following effective pancreas transplantation. Insulin resistance has been associated with the clinical manifestations of DKD (nephromegaly, glomerular hyperfiltration, albuminuria, and kidney failure). Likewise, insulin resistance may underlie the histological manifestations of DKD. Morphological changes of DKD are absent in newly diagnosed type 1 diabetes patients (with no insulin resistance), but appear afterwards when insulin resistance develops. In contrast, structural lesions of DKD are typically present before the clinical diagnosis of type 2 diabetes. Several heterogeneous conditions that share the occurrence of insulin resistance, such as aging, obesity, acromegaly, lipodystrophy, cystic fibrosis, insulin receptor dysfunction, and Alström syndrome, also share both clinical and structural manifestations of kidney disease, including glomerulomegaly and other features of DKD, focal segmental glomerulosclerosis, and C3 glomerulopathy, which might be ascribed to reduction in the synthesis of factor H binding sites (such as heparan sulfate) that leads to uncontrolled complement activation. Alström syndrome patients show systemic interstitial fibrosis markedly similar to that present in diabetes.

Impact of type 1 diabetes on maternal long-term risk of hospitalisation and mortality: a nationwide combined clinical and register-based cohort study (The EPICOM study).

The aims of this study were to examine long-term mortality and morbidity rates in mothers with type 1 diabetes, both overall and according to the level of albuminuria prior to pregnancy, the presence of hypertension, pre-eclampsia and periconceptional HbA1c. This study was a part of the EPICOM (Environmental Versus Genetic and Epigenetic Influences on Growth, Metabolism and Cognitive Function in Offspring of Mothers with Type 1 Diabetes) study, which is a prospective follow-up study focusing on pregnancies complicated by maternal type 1 diabetes. We carried out a nationwide combined clinical and register-based cohort study of mortality rates and hospital admissions in mothers with diabetes (n = 986) who gave birth between 1992 and 2000. Control mothers (n = 91,441) were women from the background population, matched according to age and year of childbirth. Age at follow-up was 32-66years. Mortality rate was increased threefold in mothers with diabetes compared with control mothers (HR 3.41 [95% CI 2.42, 4.81]; p < 0.0001), and was also increased with pre-gestational kidney dysfunction (normoalbuminuria, HR 2.17 [95% CI 1.28, 3.68]; microalbuminuria, HR 3.36 [95% CI 0.82, 13.8]; macroalbuminuria, HR 12.9 [95% CI 5.45, 30.7]). Moreover, the presence of hypertension prior to or at any time during pregnancy and of pre-eclampsia also increased mortality rate (hypertension, HR 4.34 [95% CI 2.13, 8.84]; pre-eclampsia, HR 5.55 [95% CI 2.71, 11.4]). Mortality rate also increased with higher levels of HbA1c in early pregnancy (HbA1c ≤75mmol/mol [≤9%], HR 2.15 [95% CI 1.31, 3.53]; HbA1c >75mmol/mol [>9%], HR 6.10 [95% CI 2.67, 14.0]). However, in mothers with diabetes and HbA1c <64mmol/mol (<8%) in the first trimester and normal pre-gestational urinary albumin excretion rate (n = 517), mortality rate was comparable with that of control mothers. Among mothers with diabetes, mortality rate was associated with HbA1c level: per 11mmol/mol (1 percentage point) increase in HbA1c, HR was 1.52 (95% CI 1.19, 1.94; p = 0.001). In mothers with diabetes, the overall incidence of hospital admissions was more than double (incidence rate ratio [IRR] 2.69 [95% CI 2.59, 2.80]; p < 0.0001) that of control mothers, as were admissions with various diagnoses from 14 out of 19 ICD-10 chapters. Among mothers with diabetes, the IRR for hospital admissions increased with the level of HbA1c: per 11mmol/mol (1 percentage point) increase in HbA1c, HR was 1.07 (95% CI 1.04, 1.10; p < 0.0001). Overall, mothers with type 1 diabetes have a two- to threefold increase in mortality and morbidity rates. HbA1c levels, level of albuminuria around the time of conception, and the presence of hypertension and pre-eclampsia are important risk factors for mortality/morbidity in this cohort. However, it is reassuring that mothers with type 1 diabetes without kidney complications and with HbA1c <64mmol/mol (<8%) in early pregnancy have a similar survival potential during the period where they are raising their children to that of control mothers from the background population.

Increased urine podocyte-associated messenger RNAs in severe obesity are evidence of podocyte injury.

The aim of this study was to correlate different degrees of excess weight with the expression of podocyte-associated messenger RNAs (mRNAs) in urine. The sample comprised 83 patients with overweight or obesity class I, II, or III and 18 healthy controls. The expression of nephrin, podocin, podocalyxin, α-actinin-4, α3β1integrin, vascular endothelial growth factor, and transforming growth factor-beta (TGF-β1 ) mRNA in urine was quantified with the real-time polymerase chain reaction. mRNA expression was correlated with body mass index, the metabolic syndrome, albuminuria, and inflammation. Adults with obesity class III had higher levels of serum lipids, glucose, HbA1C, insulin resistance, and C-reactive protein (P < 0.05), with 85% of the subjects meeting criteria for the metabolic syndrome (P < 0.001 vs. other groups). Urinary podocyte-associated mRNAs were higher in adults with obesity class III than in other groups (P < 0.05). Patients with overweight or obesity class I or II also had higher levels of podocyte mRNAs than controls: nephrin (P = 0.021), α-actinin-4 (P = 0.014), α3β1integrin (P = 0.036), and TGF-β1 (P = 0.005). Metabolic syndrome, hyperinsulinemia, and C-reactive protein were correlated with podocyturia, but only higher insulin levels were related regardless of obesity. Severe obesity and hyperinsulinemia were associated with higher urinary expression of podocyte-associated mRNAs, even at normal urinary albumin excretion rates.

THE ROLE OF A1166C ANGIOTENSIN II TYPE-1 RECEPTOR GENE POLYMORPHISM IN URINARY ALBUMIN EXCRETION RATE ON HYPERTENSIVE SUBJECTS

Background: Expression of angiotensin-II type 1 receptor (AT1R) play a role in angiotensin-II (Ang-II) mechanism of action. Angiotensin-II also have a role on urinary albumin excretion (UAE) incidence in hypertensive subjects. Objective: Understanding the role of A1166C AT1R gene polymorphism on UAE rate in hypertensive subjects. Method: This is an observational study with cross-sectional approach, conducted in 2014 at Dr. Wahidin Sudirohusodo Hospital Makassar. We included both hypertensive and controlled hypertensive subjects, eGFRMDRD ≥60 ml/menit/.73 m2, no evidence of urinary tract infection, no diabetes mellitus, not on period of menstruation or hematuria. Based on ACR, subjects were classified into A1 (ACR <30 mg/g), A2 (ACR 30–300 mg/g) and A3 (ACR >300 mg/g). A1 group was categorized as normal, while A2 and A3 group as abnormal. A1166C AT1R gene polymorphism detected by PCR examination if we found genotype: AT1R 1166AA, AT1R 1166AC and AT1R 1166CC. Non-AA genotype are AT1R 1166AC and AT1R 1166CC, and AA genotype is AT1R 1166AA. Result: From 71 subjects, 20 subjects (28.2%) are non-AA genotype and 51 subjects (71.8%) are AA genotype. From 20 non-AA genotype subjects, 4 subjects (20%) with abnormal UAE rate and 16 subjects (80%) with normal UAE rate. While from 51 subjects with AA genotype, 6 subjects (11,8%) with abnormal UAE rate and 45 subjects (88.2%) with normal UAE rate. The risk of non-AA genotype to have UAE rate increment is 1.9 times compared with AA genotype, but statistically not significant (CI: 0,47–7,51; p = 0.452). Conclusion: We found that C allele of the A1166C AT1R gene polymorphism is not a risk factor for UAE rate increment in hypertensive subjects.

Genetic Polymorphisms in Nitric Oxide Synthase 3 Gene and Implications for Kidney Disease: A Meta-Analysis

Background/Aims: The NOS3 gene is a biological and positional candidate for diabetic nephropathy. However, the relationship between NOS3 polymorphisms and renal disease is inconclusive. This study aimed to clarify the association of NOS3 variants with nephropathy in individuals with type 1 diabetes. Methods:We conducted a case-control study examining all common SNPs in the NOS3 gene by a tag SNP approach. Individuals with type 1 diabetes and persistent proteinuria (cases, n = 718) were compared with individuals with type 1 diabetes but no evidence of renal disease (controls, n = 749). Our replication collection comprised 1,105 individuals with type 1 diabetes recruited to a nephropathy case group and 862 control individuals with normal urinary albumin excretion rates. Meta-analysis was conducted for SNPs where more than three genotype datasets were available. Results: A novel association was identified in the discovery collection (rs1800783, p_genotype = 0.006, p_allele = 0.002, OR = 1.26, 95% CI: 1.08–1.47) and supported by independent replication using a tag SNP (rs4496877, pairwise r² = 0.96 with rs1800783) in the replication collection (p_genotype = 0.002, p_allele = 0.0006, OR = 1.27, 95% CI: 1.10–1.45). Conclusion: The A allele of rs1800783 is a significant risk factor for nephropathy in individuals with type 1 diabetes, and further comprehensive studies are warranted to confirm the definitive functional variant in the NOS3 gene.

Microalbuminuria in Type 1 Diabetes Is Associated With Enhanced Excretion of the Endocytic Multiligand Receptors Megalin and Cubilin

OBJECTIVEProteinuria is the hallmark of diabetic nephropathy; yet, glomerular histology does not fully explain mechanisms contributing to proteinuria. Our objective was to identify proteins in the urine of individuals with type 1 diabetes and microalbuminuria that might implicate a mechanistic pathway operative in proteinuria.RESEARCH DESIGN AND METHODSUsing a GeLC/MS platform proteomics approach, we compared the urine proteome from 12 healthy nondiabetic individuals, 12 subjects with type 1 diabetes yet normal urinary albumin excretion rates, and 12 subjects with type 1 diabetes and microalbuminuria (type 1 diabetes + microalbuminuria).RESULTSThe abundance of megalin and cubilin, two multiligand receptors expressed in kidney proximal tubule cells and involved with the reuptake of filtered albumin and megalin/cubilin ligands, was significantly increased in type 1 diabetes + microalbuminuria urine, compared with both nonalbuminuric groups.CONCLUSIONSAberrant shedding of megalin and cubilin could contribute to albuminuria in diabetes and to deficiency states of important vitamins and hormones.

Early renal changes in type 1 diabetes

The relationships between renal structural abnormalities, metabolic, and hemodynamic changes were studied in 35 type diabetic patients with normal creatinine clearance. Sixteen patients had normal urinary albumin excretion (UAE) rates, 17 were microalbuminuric and 2 had proteinuria (0.68 and 0.8 g/day). Light and electron microscopy revealed the early stages of diffuse glomerulosclerosis, tubular dystrophy and atrophy, intestinal and arteriolar sclerosis in the renal biopsy specimens of the examinees. Increased UAE was associated with the reduced percent of glomerular podocytes, the thickening and fusion of small podocytic processes, the increased thickness of the glomerular and tubular basement membrane, the reduced number of endothelial fenestrae, the increased fractional volume of the mesangium, perioglomerular sclerosis, global sclerosis of some glomeruli, tubular endothelial atrophy, and intestinal and arteriolar sclerosis. Clycemic control, diabetes duration, albumin excretion rate, and blood pressure are the predictors of early renal structural changes.

Change and significance of serum pigment epithelium-derived factor in type 2 diabetic nephropathy

To investigate the change of pigment epithelium-derived factor (PEDF) in type 2 diabetic nephropathy, and to explore the significance of PEDF in the development of diabetic nephropathy. ELISA was used to detect the serum PEDF and immunoturbidimetry was used to measure the urinary albumin excretion (UAE) in 49 healthy controls and 132 type 2 diabetic patients, including 48 with normal urinary albumin excretion rate (NA group), 50 with microalbuminuria (MA group), and 34 with overt diabetic nephropathy (PR group). HbA1c, triglyceride (TG), total cholesterol, high density lipoprotein cholesterol (HDL-c), and highly sensitive C-reactive protein (hs-CRP) were simultaneously determined. The serum PEDF levels of the NA, MA, and PR groups were (3.7 +/- 2.2) mg/L, (4.7 +/- 2.9) mg/L, and (5.7 +/- 2.8) mg/L respectively, all significantly higher than that of the control group (2.7 +/- 1.3) mg/L. P < 0.05, 0.01, and 0.01 respectively). The serum PEDF levels of the MA and PR groups were significantly higher than that of the NA group (both P < 0.01), and that of the PR group was significantly higher than that of the MA group (P < 0.05). Correlation analysis demonstrated that serum PEDF level was positively correlated with HbA1c (r = 0.198, P < 0.01), FPG (r = 0.231, P < 0.01), TG (r = 0.302, P < 0.01), hs-CRP (r = 0.214, P < 0.01), and urinary albumin excretion rate (UAER) (r = 0.169, P < 0.05), significantly, but negatively correlated with HDL-c (r = -0.237, P < 0.01). Stepwise multiple linear regression analysis showed that TG (beta = 0.314, P < 0.01), hs-CRP (beta = 0.260, P < 0.01), and UAER (beta = 0.148, P < 0.05) were significant independent determinants for serum PEDF. Serum PEDF level significantly increases in type 2 diabetic patients, and the magnitude of PEDF is related to the severity of diabetic nephropathy. TG, hs-CR and UAER are significant independent determinant for serum PEDF. The increase of PEDF may involve in the development of diabetic nephropathy.

Prevention and Treatment of Diabetic Renal Disease in Type 2 Diabetes

Diabetic nephropathy (DN) is the leading cause of end-stage renal failure in Western countries and carries an increased risk for cardiovascular mortality. Studies have identified a number of factors that play a part in the development of DN. Among them, hypertension and proteinuria are the most important. In the early stages of DN, when albumin is present in the urine in very low quantities (microalbuminuria) and an increase is seen in BP, there is no loss of filtrate and patients respond well to prophylactic measures. Microalbuminuria is considered an early marker of DN. Prevention of the onset of microalbuminuria, therefore, could be considered as the primary means of preventing DN. The Bergamo Nephrologic Diabetes Complication Trial (BENEDICT) was a prospective, randomized, double-blind, parallel-group study that was organized in two phases. Phase A included 1204 patients and was aimed at assessing the efficacy of the angiotensin-converting enzyme (ACE) inhibitor trandolapril, the non-dihydropyridine calcium channel blocker verapamil, and the trandolapril plus verapamil combination as compared with placebo in prevention of microalbuminuria in hypertensive patients with type 2 diabetes and normal urinary albumin excretion rate. Phase B was aimed at assessing the efficacy of the combination as compared with trandolapril alone in prevention of macroalbuminuria in patients with microalbuminuria. The BENEDICT Phase A study showed that DN can be prevented by ACE inhibitor therapy. The beneficial effect of ACE inhibition is not enhanced by combined non-dihydropyridine calcium channel blocker therapy. The apparent advantage of ACE inhibitors over other agents includes a protective effect on the kidney against the development of microalbuminuria, which is a major risk factor for cardiovascular events and death in this population.

Putative role of polymorphisms in UCP1-3 genes for diabetic nephropathy

Increased production of reactive oxygen species (ROS) has been suggested as a cause of diabetic complications. Uncoupling proteins (UCPs) have been ascribed a role in reducing the formation of ROS, and genetic variation in genes encoding for UCPs could thus be putative candidate genes for diabetic nephropathy. To test this hypothesis we searched for association between the A→G (−3862) variant in UCP1, the insertion/deletion (I/D) polymorphism in exon 8 in UCP2, and the C→T (−55) polymorphism in UCP3 and diabetic nephropathy in 218 diabetic patients with normal urinary albumin excretion rate (AER), 216 with micro- or macroalbuminuria, and in 106 control subjects without a family history of diabetes. We did not find any association between the different polymorphisms and diabetic nephropathy, nor did we observe any difference in AER among carriers of different UCP1–3 genotypes. We could, however, confirm the reported association between BMI and the UCP3 −55 C→T polymorphism; patients carrying the T allele had higher BMI than patients homozygous for the C allele (26.4±4.2 vs. 25.3±4.3 kg/m 2; P=.01). We conclude that studied polymorphisms in the UCP1–3 genes do not play a major role in the development of micro- or macroalbuminuria in Scandinavian diabetic patients.

C-reactive protein and soluble vascular cell adhesion molecule-1 are associated with elevated urinary albumin excretion but do not explain its link with cardiovascular risk.

An elevated urinary albumin excretion rate (UAER) is associated with an increased risk of cardiovascular mortality, but the pathophysiological mechanism underlying this association is poorly understood. To investigate the role of endothelial dysfunction, leukocyte adhesion, and low-grade inflammation (1) in the development of elevated UAER (study I) and (2) in linking elevated UAER with risk of cardiovascular mortality (study II), we performed a prospective study in an age-, sex-, and glucose tolerance- stratified sample of a population-based cohort aged 50 to 75 years. High levels of von Willebrand factor, soluble vascular cell adhesion molecule-1 (sVCAM-1), and C-reactive protein (CRP) were used as markers of endothelial dysfunction, leukocyte adhesion, and low-grade inflammation, respectively. For study I, subjects who had normal UAER at baseline (n=316 subjects, 66 with type 2 diabetes) were reexamined after a mean follow-up of 6.1 years. The development of elevated UAER was defined as a mean albumin-to-creatinine ratio >2.0 mg/mmol at follow-up. Age-, sex-, and glucose tolerance- adjusted logistic regression analyses showed the development of elevated UAER to be significantly associated with levels of sVCAM-1 and CRP (odds ratio 1.14 [95% CI 1.02 to 1.27] per 10% increase of sVCAM-1 and odds ratio 1.17 [95% CI 1.04 to 1.32] per 50% increase of CRP). The results were not materially different after additional adjustment for hypertension, body mass index, cardiovascular disease, and creatinine clearance or stratification by the presence of diabetes. For study II, the vital status of all subjects (n= 575) was determined after a mean follow-up of 6.6 years. Eighty-one of 575 subjects died (30 died of cardiovascular disease). The presence of elevated UAER at baseline was associated with a 4.1-fold (1.94 to 8.73) increased risk of cardiovascular death after adjustment for age, sex, and glucose tolerance status. Adjustment for levels of von Willebrand factor, sVCAM-1, or CRP did not materially affect the results, nor did additional adjustment for the presence of hypertension, retinopathy, and cardiovascular disease and for levels of homocysteine, triglycerides, and high density lipoprotein cholesterol. Leukocyte adhesion (sVCAM-1) and low-grade inflammation (CRP) are determinants of the development of elevated UAER. However, these determinants do not explain the association between elevated UAER and cardiovascular mortality.

Orosomucoid in urine predicts cardiovascular and over-all mortality in patients with Type II diabetes.

Urinary orosomucoid excretion rate is increased in a substantial proportion of patients with Type II (non-insulin-dependent) diabetes mellitus and normal urinary albumin excretion rate. The aim of this study was to determine whether increased urinary orosomucoid excretion rate is predictive of increased mortality in patients with Type II diabetes. In a cohort study including 430 patients with Type II diabetes, baseline urinary samples were analysed for orosomucoid and albumin. Mean follow-up was 2.4 years. We found that 188 (44 %) patients had normal and 242 (56 %) patients had increased urinary orosomucoid excretion rates. During the study period 41 patients died; out of these 23 patients died of cardiovascular diseases. Odds ratio for all-cause mortality was 2.50 (95 % CI 1.00-6.22) and odds ratio for cardiovascular mortality was 9.81 (1.31-73.6) having increased urinary orosomucoid excretion rate at baseline (odds ratios adjusted for age, sex, duration of diabetes, cardiovascular diseases, weight, medication, HbA1 c, plasma creatinine and urinary albumin excretion rate). Urinary albumin excretion rate was an independent predictor of all-cause mortality when urinary orosomucoid excretion rate was not included in the analysis. Subgroup analysis revealed that 39 % of the patients with normal urinary albumin excretion rate (n = 251) had increased urinary orosomucoid excretion rates and that these patients had a higher cardiovascular mortality (p = 0.007) than patients with normal urinary albumin excretion rate and normal urinary orosomucoid excretion rates. We found that urinary orosomucoid excretion rate predicted all-cause and cardiovascular mortality in patients with Type II diabetes independently from other risk factors.

Increased urinary transferrin excretion predicts microalbuminuria in patients with type 2 diabetes.

We studied whether increased urinary transferrin excretion rates (TERs) (urinary transferrin-to-urinary creatinine ratio > or = 107 micrograms/mmol, which is the sum of an average and 2 SDs in 431 healthy nondiabetic individuals) would predict the development of microalbuminuria (urinary albumin-to-urinary creatinine ratio > or = 2.8 mg/mmol) in patients with type 2 diabetes and normal urinary albumin excretion rates (AERs) (albumin-to-creatinine ratio < 2.8 mg/mmol). We also studied the influence of blood pressure, glycemic control, and serum levels of lipids and apolipoproteins on the later development of microalbuminuria. In 77 diabetic patients with normal AER, AER and TER were measured at baseline and after 24 months of follow-up. Blood pressure, glycemic control, and serum levels of lipids and apolipoproteins were measured at 1- to 2-month intervals during the follow-up period. Of the 16 patients who initially had increased TER, 5 (31%) developed microalbuminuria. In contrast, of the 61 who initially had normal TER, 4 (7%) developed microalbuminuria (P = 0.016). At baseline, no difference was found in age, sex, diabetes duration, diabetic medications, prevalence of hypertension, blood pressure, HbA1c levels, or serum lipid and apolipoprotein concentrations between the two group of patients with normal and increased TER. There was also no difference in duration of hypertension and prevalence of users of ACE inhibitors between two subgroups of hypertensive patients with normal and increased TER. During the 24 month follow-up period, those whose condition progressed to microalbuminuria had increased serum levels of triglycerides (1.87 +/- 0.49 vs. 1.29 +/- 0.64 mmol/l, P = 0.003) and apolipoprotein B (114 +/- 20 vs. 102 +/- 24 mg/dl, P = 0.05) and tended to have increased HbA1c levels (7.7 +/- 1.0 vs. 7.1 +/- 1.1%, P = 0.10) compared with those in whom microalbuminuria did not develop. Blood pressure, however, did not differ. In multivariate stepwise logistic regression analysis, the association between increased TER at baseline and subsequent development of microalbuminuria was significant (odds ratio 7.04 [95% CI 1.02-48.5], P = 0.04). In patients with type 2 diabetes and normal AER, increased TER may predict the development of microalbuminuria and abnormalities in triglyceride-rich lipoprotein metabolism, and poor glycemic control may be associated with this progression.

Is diabetic nephropathy inherited? Studies of glomerular structure in type 1 diabetic sibling pairs.

Only a minority of patients with type 1 diabetes develop diabetic nephropathy (DN). Poor glycemic control cannot fully explain DN risk, and family studies suggest genetic susceptibility factors. To understand familial DN concordance, we evaluated glomerular structure in families with type 1 diabetic sibling pairs. Kidney function and biopsy studies were performed in 21 probands (P) (first to develop diabetes) and 21 siblings (S) (second to develop diabetes), most with normal urinary albumin excretion rates (UAER). Glomerular structure was measured by morphometry. Intrafamilial correlation was estimated by one-way random-effects ANOVA and by mixed-effects ANOVA, adjusting for age and duration of diabetes. Diabetes duration was, by definition, longer in P than in S, while age and sex were similar. HbA1c over 5 years and blood pressure were not different in P and S and were without familial effect. UAER was greater in P than in S (P < 0.05), with strong familial effect (P = 0.03). A strong concordance among siblings for mesangial fractional volume (P < or = 0.01) remained significant after adjustment for diabetes duration and age (P = 0.04). Results were similar for mesangial cell (P = 0.01; adjusted P = 0.04) and mesangial matrix fractional volumes (P < 0.01; adjusted P = 0.06). There was also clustering of the patterns of glomerular lesions. For example, if P had relatively marked glomerular basement membrane thickening compared with mesangial matrix expansion, S had a similar pattern (chi2, P < 0.025). Strong concordance in severity and patterns of glomerular lesions in type 1 diabetic siblings, despite lack of concordance in glycemia, supports an important role for genetic factors in DN risk.

Lipid peroxidation and activities of antioxidant enzymes in erythrocytes of patients with non-insulin dependent diabetes with or without diabetic nephropathy.

Diabetes is known to involve oxidative stress. However, data on oxidative stress in diabetic nephropathy is scant. The aim of this study was to examine lipid peroxidation and activities of key antioxidant enzymes in non-insulin dependent diabetes (NIDDM) without nephropathy and in those with diabetic nephropathy. Twenty-one NIDDM outpatients with obvious diabetic nephropathy (persistent proteinuria, over 0.5 g/day and albumin excretion over 200 microg/min), 14 NIDDM outpatients with a long diabetic history but without hypertension and with normal urinary albumin excretion rate (<20 microg/min) and 19 healthy persons were studied. Malondialdehyde (MDA) content of erythrocytes was quantified by HPLC according to Young et al. In erythrocytes, superoxide dismutase (SOD) activity was determined by the adrenaline method of Misra and Fridovich and catalase was estimated according to Beers and Sizer. MDA content was significantly elevated in erythrocytes of NIDDM patients without nephropathy vs the control group and even higher in erythrocytes of NIDDM patients with diabetic nephropathy. SOD and catalase activities were lower in erythrocytes of NIDDM patients without nephropathy than in the control group and lowest in erythrocytes of NIDDM patients with nephropathy. These results confirm oxidative stress in erythrocytes of NIDDM patients with nephropathy. The intensity of oxidative stress appeared to be greater than in NIDDM patients without nephropathy.

Main risk factors for nephropathy in type 2 diabetes mellitus are plasma cholesterol levels, mean blood pressure, and hyperglycemia.

The control of hyperglycemia is of major importance in the treatment of patients with type 1 diabetes mellitus. However, there is no consensus about the required degree of metabolic control in patients with type 2 diabetes mellitus and about the role of hyperglycemia in diabetic nephropathy and in the development of atherosclerosis in relation to other risk factors. A prospective, long-term follow-up study was conducted on 574 patients, aged 40 to 60 years, with recent onset of type 2 diabetes mellitus. Patients were initially normotensive and had normal renal function and a normal urinary albumin excretion rate (<30 mg/24 h). The patients were followed up for 2 to 9 years (mean +/- SD, 7.8 +/- 0.9 years). Levels of hemoglobin A1c and plasma lipids, mean blood pressure, and body mass index (calculated as the weight in kilograms divided by the square of the height in meters) were determined periodically. Cigarette smoking and socioeconomic status were recorded. Renal status was evaluated by the logarithm of the final urinary albumin excretion rate and by the decline in reciprocal creatinine values. Definite clinical events including death, nonfatal myocardial infarction, angina pectoris, congestive heart failure, and peripheral vascular disease were recorded. At the end of the study the urinary albumin excretion rate remained normal (<30 mg/24 h) in 373 patients (65%), 111 (19%) had microalbuminuria (30-300 mg/24 h), and 90 (16%) had overt albuminuria (>300 mg/24 h). Logistic regression models demonstrated that the correlation between hemoglobin A1c levels and the risk of albuminuria is exponential. Multiple logistic regression analysis indicated that levels of total cholesterol, mean blood pressure, and hemoglobin A1c were the main factors associated with the decrease in renal function and with the increase in albuminuria. The combination of values higher than the 50th percentile of all 3 factors defined a high-risk patient population. These high-risk patients had an odds ratio of 43 (95% confidence interval, 25-106) for microalbuminuria and 15 (95% confidence interval, 9-25) for clinical events related to arteriosclerosis compared with the rest of the group. Low levels of high-density lipoprotein, body mass index, cigarette smoking, low socioeconomic status, and male sex were all significantly associated with diabetic nephropathy, as well as with the manifestations of arteriosclerosis. The combination of blood pressure values in the high-normal range with moderately elevated levels of total cholesterol and hemoglobin A1c defines a high-risk group for the progression to diabetic nephropathy and for clinical events related to arteriosclerotic cardiovascular disease.

Nondipping of nocturnal blood pressure is related to urinary albumin excretion rate in patients with type 2 diabetes mellitus.

Although cardiovascular and cerebrovascular morbidity and mortality in type 2 diabetic patients is closely related to urinary albumin excretion rate (UAER), the causative mechanisms are not yet identified. The aim of our study was to define the circadian variation of blood pressure (BP) in 72 type 2 diabetic patients (mean age 60 years, mean diabetes mellitus duration: 12 years) in comparison with 41 nondiabetic controls with essential hypertension (mean age 58 years) by using ambulatory blood pressure measurement. Thirty diabetic patients had normal UAER (< 30 mg/24 h), 27 had microalbuminuria (30 to 300 mg/24 h), and 15 had persistent proteinuria (> 300 mg/24 h). Systolic blood pressure during both nighttime and daytime was significantly elevated in type 2 diabetic patients with macroalbuminuria compared to controls and patients with normal UAER. During nighttime even type 2 diabetic patients with microalbuminuria had significantly elevated systolic blood pressure compared to controls with essential hypertension. We also observed a correlation of nocturnal blood pressure to UAER (systolic: r = 0.32, P < .007 and diastolic: r = 0.24, P < .04). Nondipping (defined as a reduction of nocturnal BP < 10%) was observed in 80% of the macroalbuminuric, 74% of the microalbuminuric, but only in 43% of the normoalbuminuric type 2 diabetic patients and in 37% of the controls (P < .04). Since a loss of circadian variation of BP is closely related to vascular complications in nondiabetics, our findings may indicate an important relationship between nondipping of BP and the high morbidity and mortality rate in diabetic patients with increased UAER.

Evidence of Impaired Glomerular Charge Selectivity in Nondiabetic Subjects With Microalbuminuria

Microalbuminuria is associated with excess cardiovascular morbidity and mortality in diabetic and nondiabetic subjects. Loss of glomerular charge selectivity may explain the development of microalbuminuria in diabetic subjects. The primary population in this cross-sectional study was 124 subjects aged 40 to 75 years without glucose intolerance and with a previous (3 years before the present study) urinary albumin excretion rate (UAE) in the normal (<20 microgram/min) or microalbuminuric (>20 microgram/min) range. The secondary population consisted of 39 offspring aged 15 to 40 years. The main outcome measures included UAE, urinary IgG/IgG4 selectivity index (SI), and the presence of ischemic heart disease as determined by questionnaire or ECG. Among the primary population, a significant inverse correlation was found between SI and UAE (r=-.40, P<.001). Reduction in SI could be demonstrated in subjects with UAE >10 microgram/min. In multiple regression analysis reduction in SI was found with increasing age, independent of UAE. In 20 subjects with clinical cardiovascular disease a reduction in SI was found (1.9+/-0.6 versus 2.6+/-1.3, P=.001) without concomitant elevation in UAE (P=.99). Offspring from parents with microalbuminuria had an SI comparable to offspring from parents with normal UAE (2.7+/-0.7 versus 3.3+/-1.6, P=.17). In nondiabetic subjects the development of microalbuminuria is associated with reduced SI, suggesting impairment of glomerular charge selectivity. SI may offer a more sensitive monitoring of abnormalities in glomerular permselectivity than does measurements of UAE, but the ability of SI to predict development of cardiovascular disease needs to be evaluated prospectively.

Serum Sialic Acid, a Risk Factor for Cardiovascular Disease, Is Increased in IDDM Patients With Microalbuminuria and Clinical Proteinuria

An elevated serum sialic acid concentration has recently been shown to be a potent cardiovascular risk factor in the general population. Because clinical proteinuria is associated with a high frequency of cardiovascular disease, and because microalbuminuria predicts the development of renal and cardiovascular disease in diabetes, we investigated whether serum sialic acid levels are increased in insulin-dependent diabetes mellitus (IDDM) patients with microalbuminuria or clinical proteinuria. We studied 23 patients with IDDM who had a normal urinary albumin excretion rate, 23 patients who had microalbuminuria, and 23 patients with clinical proteinuria. The patients were matched for age, sex, duration of diabetes, GHb levels, and body mass index (BMI). Fasting blood samples were taken for measurement of sialic acid, cholesterol, triglyceride, creatinine, and GHb. Serum sialic acid was significantly higher in the microalbuminuric patients compared with the normoalbuminuric group (mean +/- SD: 1.93 +/- 0.26 vs. 1.76 +/- 0.27 mM, P < 0.01). Moreover, serum sialic acid was also significantly higher in the group with clinical proteinuria compared with the microalbuminuric patients (2.34 +/- 0.24 vs. 1.93 +/- 0.26 mM, P < 0.001). Serum sialic acid was not related independently to age, BMI, diabetes duration, GHb, blood pressure, serum cholesterol, triglyceride, or creatinine concentration in any of the diabetic groups. These observations suggest that the serum sialic acid concentration is raised in IDDM patients with both microalbuminuria and clinical proteinuria and may play a role as a cardiovascular risk factor or disease marker in these conditions.

Diagnostic significance of urinary enzymes for diabetes mellitus and hypertension.

In order to evaluate tubular damage in diabetic patients, the activity of renal proximal tubule derived enzymes excreted in 24-hour urine were recorded in 5 groups as follows: (i) 48 noninsulin-independent diabetic patients with normal renal function and a urinary albumin excretion rate within the normal range; (ii) 45 noninsulin-dependent diabetic patients with normal renal function and a high urinary albumin level; (iii) 26 noninsulin-dependent diabetic patients with renal failure; (iv) 40 patients with essential hypertension and normal renal function, and (v) 48 normal control subjects. Regardless of whether cases were noninsulin-dependent diabetics with normal or high urinary albumin excretion rate or cases with renal dysfunction, urinary dipeptidyl aminopeptidase IV and N-acetyl-beta-D-glucosaminidase excretions were significantly higher than in healthy subjects, and urinary gamma-glutamyl transpeptidase excretion was significantly lower than in healthy subjects. No significant changes in urinary enzyme excretions showed specific variations in the essential hypertensive patients. These results suggest that there is tubular damage in the early stages of noninsulin-dependent diabetic patients with normal renal function and normal urinary albumin excretion rate. Detection of urinary excretion of dipeptidyl aminopeptidase IV, N-acetyl-beta-D-glucosaminidase and gamma-glutamyl transpeptidase may be especially useful for the early diagnosis of diabetic nephropathy.