Immune response to glycated and oxidized LDL in IDDM patients with and without renal disease.

OBJECTIVE: To study autoantibodies to oxidized and glycated LDL in IDDM patients with and without diabetic nephropathy and in nephropathy-related macroangiopathy RESEARCH DESIGN AND METHODS: The study included 101 IDDM patients with a long duration of diabetes and 54 healthy subjects. Patients were divided into two groups according to their median urinary albumin excretion rate (AER); the normoalbuminuric group had AER <20 microg/min and the albuminuric group >200 microg/min. The groups were matched for age and BMI, and the two diabetic groups were matched for duration of diabetes and glycemic control. Antibodies against oxidized LDL (using malondialdehyde-modified LDL as the antigen) and against glycated LDL were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: The mean antibody levels against glycated LDL were higher in IDDM patients (0.305 +/- 0.399) than in healthy subjects (0.166 +/- 0.22 optical density [OD]; P = 0.019), but levels did not differ significantly between normoalbuminuric and albuminuric IDDM patients (0.258 +/- 0.354 vs. 0.388 +/- 0.459, respectively). Among the three groups, antibody levels to oxidized LDL did not differ. IDDM patients showed an inverse correlation between antibodies to oxidized LDL and HbA1 (r = -0.211, P = 0.04). The antibody levels to glycated and oxidized LDL did not differ among albuminuric IDDM patients with or without clinical macroangiopathy. CONCLUSIONS: Antibodies to glycated and oxidized LDL do not seem to associate with diabetic nephropathy or nephropathy-related macroangiopathy.

Urinary transforming growth factor-beta1 and alpha1-microglobulin in children and adolescents with type 1 diabetes.

OBJECTIVE: Transforming growth factor (TGF)-beta1 is an important mediator in the pathogenesis of diabetic nephropathy. Urinary TGF-beta1 reflects TGF-beta1 production in the kidney, and alpha1-microglobulin tubular dysfunction. These 2 markers were studied in the early phases of type 1 diabetes. RESEARCH DESIGN AND METHODS: There were 113 type 1 diabetic children and adolescents (mean +/- SD: age 14.1 +/- 2.9 years, and diabetes duration 7.4 +/- 2.9 years, HbA1c 9.3 +/- 1.5%) and 39 healthy subjects (age 13.8 +/- 2.8 years) who participated in the study. Of the diabetic patients, 105 were normoalbuminuric (2-3 consecutive overnight urinary albumin excretion rates [AERs] <20 microg/min) and 8 had microalbuminuria (at least 2 AERs 20-200 microg/min). Overnight urinary TGF-beta1 and alpha1-microglobulin levels were measured and the results expressed as the ratio to urinary creatinine concentration. RESULTS: Data are medians (range). Diabetic patients had higher urinary TGF-beta1 levels than those of control subjects: 0.9 ng/mg (0.05-122.3) vs. 0.3 ng/mg (0.05-2.2) creatinine, respectively (P = 0.003). Urinary TGF-beta1 levels correlated with urinary glucose (r = 0.2, P = 0.03) and alpha1-microglobulin (r = 0.2, P = 0.02) levels, but not with HbA1c, AER, age, or duration of diabetes. In 43 patients with urinary TGF-beta1 above the control levels, urinary TGF-beta1 levels correlated with urinary glucose (r = 0.6, P < 0.001) and alpha1-microglobulin (r = 0.6, P < 0.001) levels. Diabetic patients had higher urinary alpha1-microglobulin levels than those of control subjects: 4.8 microg/mg (0.6-48.8) vs. 2.7 microg/mg (0.8-11.6) creatinine, respectively (P < 0.001). Alpha1-microglobulin levels correlated with AER (r = 0.2, P = 0.02), HbA1c (r = 0.3, P = 0.001), urinary glucose (r = 0.5, P < 0.001), and urinary TGF-beta1 levels. CONCLUSIONS: An early rise in urinary TGF-beta1 levels was observed in young type 1 diabetic patients. Urinary TGF-beta1 is associated with 2 interrelated tubular markers, alpha1-microglobulin and urinary glucose.

N-acetyltransferase-2 polymorphism, smoking and type 1 diabetic nephropathy.

The N-acetyltransferase (NAT2) polymorphism has been suggested to be related to diabetic microvascular complications. To study the distribution of NAT2 genotypes in Caucasian type 1 diabetic patients with and without diabetic nephropathy, 214 adult type 1 diabetic patients and 53 healthy individuals were genotyped by polymerase chain reaction-restriction fragment length polymorphism. In addition, 75 young type 1 diabetic patients were genotyped, and 70 of them also phenotyped by caffeine. Of the adult patients, 83 had normal albumin excretion, 58 had microalbuminuria, and 73 had overt diabetic nephropathy. NAT2 allele frequencies were similarly distributed between the diabetic patients and healthy individuals: 0.29/0.2 5 (NAT2*4), 0.03/0.04 (NAT2*7B), 0.25/0.27 (NAT2*6A), and 0.43/0.44 (NAT2*5B), and within the diabetic subgroups. Because smoking is a known risk factor for diabetic nephropathy, nonsmoking and smoking patients were analysed separately. NAT2 allele frequencies differed significantly between the nonsmoking normoalbuminuric, microalbuminuric and nephropathic patients: 0.18/0.41/0.30 (NAT2*4), 0.04/0.00/0.02 (NAT2*7B), 0.35/0.18/0.17 (NAT2*6A), 0.43/0.41/0.50 (NAT2*5B), P = 0.013. In nonsmoking fast acetylators odds ratio for microalbuminuria and nephropathy was 3.1 (95% confidence interval 1.36-7.05), P = 0.007 by logistic regression. In smokers, a nonsignificant odds ratio was found [0.31 (95% confidence interval 0.08-1.2), P = 0.09]. Smoking is a strong confounding factor in relation to NAT2 analyses and diabetic nephropathy. According to our data, in nonsmoking type 1 diabetic patients fast NAT2 genotype implies an increased risk for diabetic nephropathy.

Increased secretion of TGF-beta1 by peripheral blood mononuclear cells from patients with Type 1 diabetes mellitus with diabetic nephropathy.

AIMS: To study transforming growth factor (TGF)-beta1 secretion by peripheral blood mononuclear cells (PBMC) from Type 1 diabetic patients with and without nephropathy. METHODS: Thirty normoalbuminuric Type 1 diabetic patients (urinary albumin excretion rate (AER) < 20 microg/min), 12 microalbuminuric (AER 20-200 microg/min), 10 nephropathic (AER > 200 microg/min), and 13 non-diabetic individuals were recruited. TGF-beta1 secretion by PBMC was measured by enzyme immunoassay (EIA) after 48 h culture with and without phytohaemagglutinin (PHA) (5 microg/ml). RESULTS: After 48 h culture, the highest TGF-beta1 levels secreted by unstimulated PBMC were found in patients with nephropathy (median 6.2 (range 0.9-20.0) ng/ml) when compared to patients with normal albumin excretion (4.1 (0.2-11.3) ng/ml), microalbuminuria (1.8 (0.2-6.4) ng/ml) and healthy controls (1.0 (0.2-7.0) ng/ml); P = 0.02 for the three diabetic groups and P = 0.006 for all groups. At 48 h, the PHA-stimulated TGF-beta1 levels were 12.4 (2.9-30.0) ng/ml in nephropathic, 7.3 (0.5-21.2) ng/ml in normoalbuminuric, and 5.5 (0.5-27.6) ng/ml in microalbuminuric patients (P = 0.05). A correlation was observed between TGF-beta1 and diastolic blood pressure in the subgroup of patients with incipient and overt nephropathy (r = 0.45, P = 0.04). CONCLUSIONS: Type 1 diabetic patients with overt nephropathy show increased TGF-beta1 secretion by PBMC. Diastolic blood pressure levels correlated with TGF-beta1 secretion in diabetic patients with nephropathy. Increased TGF-beta1 secretion by PBMC may be associated with renal and vascular disease in Type 1 diabetes mellitus.