A polymorphism in the gene for the atrial natriuretic peptide and diabetic nephropathy. Diabetic Nephropathy Study Group.

BACKGROUND: Atrial natriuretic peptide is involved in blood pressure regulation via its vasodilating and natriuretic actions. Since diabetic nephropathy and hypertension are closely related, ANP is a reasonable candidate gene for diabetic nephropathy (DN). METHODS: We genotyped 410 patients with type I diabetes (without DN n = 307; with DN n = 103) and 658 patients with type II diabetes (without DN n = 464; with DN n = 194). In the patients the duration of diabetes was at least 10 years. Diabetic nephropathy was defined as urinary albumin excretion of > or = 30 mg/24 h. The HpaII polymorphism in intron 2 of the ANP gene was determined using PCR amplification followed by restriction digest. Alleles were separated on agarose gels stained with ethidium bromide. RESULTS: We compared genotype distribution and allele frequencies between patients with and without nephropathy. No significant difference was observed either in type I (allele frequency without DN H1, 0.02/H2, 0.98 vs with DN H1, 0.05/H2, 0.95; P = 0.132) or in type II diabetes (allele frequency without DN H1, 0.04/H2, 0.96 vs with DN H1, 0.05/H2, 0.95; P = 0.551). CONCLUSIONS: The polymorphism in the gene for the atrial natriuretic peptide does not seem to play a major role in the development of diabetic nephropathy in either type I or in type II diabetes.

Persistent GAD 65 antibodies in longstanding IDDM are not associated with residual beta-cell function, neuropathy or HLA-DR status.

Persistent humoral autoimmunity to the enzyme glutamic acid decarboxylase (GAD) has been described in a substantial proportion of patients with insulin-dependent diabetes mellitus (IDDM) of long duration. The source of the stimulus for this autoimmune reactivity is still unknown. Because the GAD 65 isoform is mainly expressed in pancreatic beta-cells and in the nervous system we investigated in the present study of the largest number of well characterized patients with longstanding IDDM (n = 105; median duration: 21 years; range: 10-46 years) the presence of autoantibodies to GAD 65 and their relationship to a residual C-peptide response or peripheral and autonomic neuropathy. Additionally we studied the HLA-DR status relative to GAD 65 antibodies in 86 out of the 105 individuals. One hundred healthy control subjects and 100 recent onset IDDM patients were also studied for GAD 65 antibodies. GAD 65 antibodies were detected in a radioligand-binding-assay with recombinant human GAD 65 and were present in 32% of the long-term diabetic patients, 82% of the recent onset IDDM patients and in 3% of the healthy control subjects. A preserved C-peptide response to i.v. glucagon (Hendriksen criteria) was observed in 23% of the long-term IDDM patients. Autonomic neuropathy and peripheral neuropathy was identified using criteria based on both symptoms and formal testing giving a frequency of 67% vs 79%. The HLA specific DR 4/X was observed in 47% and HLA-DR 3/X in 22% of the long-term IDDM patients. Patients who were heterozygous for DR3/DR4 were found in 23% of the cases. GAD 65 antibodies were significantly less frequent in the long-term IDDM patients compared to recent onset IDDM (p < 0.001), and diabetes duration showed a significant negative correlation with GAD 65 antibody index levels (r = 0.22, p < 0.01). Interestingly, GAD 65 antibodies were not significantly correlated either with residual beta-cell function or neuropathy and no particular HLA-DR status was associated with persistent GAD 65 antibodies. In conclusion neither residual beta-cell function nor diabetic neuropathy or a certain HLA-DR specificity are exclusively associated with persistent autoimmunity directed to GAD 65 in longstanding IDDM. The stimulus for the persistent humoral immune response and its significance for the disease process and its complications remain to be established.

Renal findings in patients with short-term type 2 diabetes.

Under semiambulatory conditions, 85 consecutive patients with the diagnosis of Type 2 diabetes of short duration (excluding patients with islet cell antibodies or maturity onset diabetes of the young) were admitted to a self-control training program and were examined in this study. A comprehensive renal assessment was performed, including evaluation of albumin excretion rate (AER), renal hemodynamics, blood pressure (BP) profile, and indicators of genetic risk. AER > or = 30 mg/24 h was found in 13 (15%) of patients; in two of these patients, AER was > or = 300 mg/24 h. By logistic regression, high HbA1, current smoking, and BP parameters were significantly correlated with an increased risk of microalbuminuria (MA). In a multiple linear regression model, accounting for 57% of total variance, HbA1, ERPF, and current smoking were significantly correlated with AER. Median GFR (Cin(inulin clearance) 136 mL/min per 1.73m2; range, 94 to 194) and ERPF (Cpah(para-aminohippuric acid clearance) 733; range, 451 to 1328) were significantly higher in patients than in control subjects (upper 95th percentile, 131 and 706 mL/min per 1.73m2, respectively). In a multiple linear regression model, explaining 27% of total variance, age, AER, gender, and fasting blood glucose were significantly correlated to GFR. According to the criteria of average daytime BP > or = 135/85 mm Hg or 24-h BP > or = 130/80 mm Hg, 60% of patients were hypertensive (HT). Sixty-one percent of all patients (including 50% of the untreated normotensive patients) were "nondippers", i.e., < 15% nighttime decrease of mean arterial pressure. Either HT or nondipping was found in 79% of all patients, so that only 21% had a completely normal blood pressure profile. Ninety-four percent of untreated hypertensive patients had no MA. First-degree relatives of patients with MA compared with patients without MA had more frequent cardiovascular events (69% versus 31%). The risk of MA in diabetic patients with positive family history was amplified by poor glycemic control. MA, but not hypertension, was marginally related to K(m) of Na+/Li+ countertransport. It was concluded that (1) microalbuminuria is found in 15% of patients newly presenting with Type 2 diabetes; (2) a high proportion of patients exhibit hyperfiltration; (3) according to ambulatory BP only, 21% of patients have a completely normal circadian BP profile; (4) a family history of cardiovascular events interacts with glycemic control to increase the risk of MA.

Angiotensinogen gene M235T polymorphism is not associated with diabetic nephropathy. The Diabetic Nephropathy Study Group.

BACKGROUND: There is agreement that a family history of hypertension (HT), is a predictor for the risk of diabetic nephropathy (DN) in patients with type 2 diabetes, and possibly also type 1 diabetes. It follows that genes related to the risk of hypertension must also be considered candidate genes for DN. The 235T allele of the angiotensinogen gene was found to be related to primary HT. METHODS: To examine whether it is predictive for DN as well, we examined the angiotensinogen gene polymorphism in 230 healthy local controls, 423 patients with type 1 diabetes (n = 180 with DN; n = 243 without DN) and 663 patients with type 2 diabetes (n = 310 with DN; n = 353 without DN). The angiotensinogen gene M235T polymorphism was determined using PCR amplification. RESULTS: The following results were obtained (i) no significant difference of genotype distribution (type 1: MM/MT/TT (%) 27.6/57.2/15.2 vs 27.2/56.1/16.7 (P = 0.92); type 2; MM/MT/TT (%) 31.7/48.2/2/20.1 vs. 32.9/46.8/20.3 (P = 0.93) or allele frequencies (type 1: M 0.56 vs. 0.55 (P = 0.795); type 2; M 0.56 vs. 0.56 (P = 0.86)) was found, between diabetic patients with or without DN, (ii) no difference was found between normotensive and hypertensive diabetic patients. CONCLUSION: The data argue against a role of the angiotensinogen gene M235T polymorphism in the manifestation of diabetic nephropathy or hypertension in diabetic patients.

Plasma thrombomodulin: a marker for microvascular complications in diabetes mellitus.

Thrombomodulin (TM), a marker of endothelial cell damage was studied in 183 patients with diabetes mellitus and different stages of complications. Thrombomodulin plasma levels correlated with duration of diabetes in patients with type I and type II diabetes. Thrombomodulin levels were higher in patients with increasing numbers of complications (nephropathy, retinopathy, arterio-occlusive disease, neuropathy). Neither the presence of retinopathy, nor neuropathy alone significantly increased plasma thrombomodulin in patients with similar urinary albumin concentration. The plasma level of thrombomodulin was more prominent in hypertensive than normotensive patients. Multivariate analysis showed that albuminuria is the factor which influences the most the increase of thrombomodulin in serum of diabetic patients.

Nephropathy of type II diabetes mellitus.

In recent years there has been a dramatic increase of almost epidemic proportions in the incidence of patients with type II diabetes mellitus who reach end-stage renal failure and enter renal replacement programmes. This is mainly due to the greater prevalence and better survival of patients with type II diabetes and diabetic nephropathy. Against this background measures to prevent the appearance and progression of diabetic nephropathy are of immense interest. Apart from the undoubted role of hyperglycaemia, the importance of genetic determinants of nephropathy has recently been recognized. Factors of proven or suspected efficacy in attenuating progression include: hypertension, hyperglycaemia, smoking and proteinuria. The role of dietary protein intake is less well documented. Nephropathy in type II diabetes has become the single most common cause of end-stage renal failure in Germany and is today a major challenge to clinical nephrology.

[Thrombomodulin is a marker of microvascular, but not for macrovascular endothelial cell damage]. / Thrombomodulin ist ein Marker für mikrovaskuläre, aber nicht für makrovaskuläre Endothelzellschädigung.

UNLABELLED: Plasma levels of thrombomodulin are increased in diseases associated with microangiopathia. The target of this study was to examine whether plasma thrombomodulin is also influenced by macroangiopathia. There was no variation of plasma thrombomodulin in a sample of 183 diabetic patients with or without peripheral arterio-occlusive disease of the lower limbs. In a second sample of 33 patients with peripheral arteriosclerosis of the lower limbs, without any indication of diabetes, plasma levels of thrombomodulin were not significantly increased compared to a control group. Since thrombomodulin is also found in thrombocytes, we analysed whether plasma thrombomodulin levels were influenced by platelet activation. Neither platelet activation after hyperthermal limb perfusion not the PGE1-treatment showed any effect on plasma thrombomodulin level. CONCLUSION: Thrombomodulin is a marker for microvascular but not for macrovascular endothelial cell damage.

Renal involvement in type II diabetes.

The incidence and prevalence of renal failure from type II diabetes have been seriously underestimated in the past. Currently, the incidence of uremia in patients with type II diabetes has increased continuously in Europe and the United States, mainly because of better patient survival (ie, they now live until nephropathy develops) and possibly because of a rising prevalence of type II diabetes in the general population (ie, more patients are at risk of developing nephropathy). Generally, renal hemodynamics and glomerular lesions are similar in type I and type II diabetes, but glomerular histology is more diverse in type II diabetes. Given the high prevalence of diabetes and renal failure from various causes in the elderly, coexistence of the two (even in the absence of glomerulosclerosis) occurs in approximately 20% of uremic type II diabetic patients. The development of nephropathy is controlled by strong genetic determinants, but these have not been further characterized.