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Background: A reduced heparan sulphate (HS) expression in the glomerular basement membrane of patients with overt diabetic nephropathy is associated with an increased glomerular heparanase expression. We investigated the possible association of urinary heparanase activity with the development of proteinuria in patients with Type 1 diabetes (T1D), Type 2 diabetes (T2D), or membranous glomerulopathy (MGP) as non-diabetic disease controls., Methods: Heparanase activity, albumin, HS and creatinine were measured in the urine of patients with T1D (n=58) or T2D (n=31), in patients with MGP (n=52) and in healthy controls (n=10). Heparanase messenger RNA (mRNA) expression in leukocytes was determined in a subgroup of patients with T1D (n=19)., Results: Urinary heparanase activity was increased in patients with T1D and T2D, which was more prominent in patients with macroalbuminuria, whereas no activity could be detected in healthy controls. Albuminuria levels were associated with increased urinary heparanase activity in diabetic patients (r=0.20; P<0.05) but not in patients with MGP (r=0.11; P=0.43). A lower urinary heparanase activity was observed in diabetic patients treated with inhibitors of the renin-angiotensin-aldosterone system (RAAS), when compared to diabetic patients treated with other anti-hypertensives. Additionally, urinary heparanase activity was associated with age in T1D and MGP. In MGP, heparanase activity and β2-microglobulin excretion correlated. In patients with T1D, no differences in heparanase mRNA expression in leukocytes could be observed., Conclusions: Urinary heparanase activity is increased in diabetic patients with proteinuria. However, whether increased heparanase activity is a cause or consequence of proteinuria requires additional research.

Hypoglycemia unawareness has been linked to desensitization of the beta2-adrenergic receptor. Desensitization of the beta2-adrenergic receptor (ADRB2) is genetically determined by the Arg16Gly variant of this receptor. We tested the hypothesis that hypoglycemia unawareness is more common among patients homozygous for the Gly16 variant. We performed genotyping of the A265G (Arg16Gly) polymorphism in the ADRB2 gene in 85 patients with type 1 diabetes and classified them according to hypoglycemia awareness status. A total of 45 patients (53%) were homozygous for Gly16, 32 patients (38%) were heterozygous and eight patients (9%) were homozygous for Arg16. Hypoglycemia unawareness was 3.4-fold more common among patients homozygous for Gly16 than among patients with other variants of the Arg16Gly polymorphism (P=0.014). We conclude that patients with type 1 diabetes who carry two alleles of the Gly16 variant of ADRB2 are at increased risk of developing hypoglycemia unawareness. Future studies are required to confirm these results in larger, independent populations.

Introduction: Elevated plasma levels of total homocysteine are related to the development of vascular complications. Patients with diabetes mellitus are particularly at risk for the development of these complications. Several factors determine plasma total homocysteine including renal function., Aims: As early Type 1 diabetes is characterized by a relative glomerular hyperfiltration, increased renal clearance could contribute to decreased levels of homocysteine as observed in Type 1 diabetes mellitus. Therefore we investigated the relationship between plasma total homocysteine and the glomerular filtration rate (GFR)., Methods: In 92 Type 1 diabetes patients and 44 control subjects, we measured GFR and effective renal plasma flow (ERPF) by means of continuous infusion of inulin and p-aminohippurate. Fasting plasma total homocysteine was measured using high performance liquid chromatography., Results: GFR (121 +/- 21 resp. 104 +/- 14 ml/min; P < 0.001) and ERPF (563 +/- 127 resp. 516 +/- 121 ml/min; P = 0.05) were significantly higher in Type 1 diabetes patients as compared with control subjects. Plasma total homocysteine was reduced in Type 1 diabetes patients as compared with control subjects (11.0 +/- 4.5 resp. 13.4 +/- 7 micromol/l; P = 0.01). Plasma total homocysteine was strongly correlated with GFR (Type 1 diabetes patients: r = -0.43, P < 0.001; control subjects: r = -0.39, P = 0.01)., Conclusion: GFR is a major determinant of plasma total homocysteine levels in Type 1 diabetes patients as well as control subjects. The reduced plasma total homocysteine levels in diabetes patients can be explained by an increased GFR.

Rationale: L-NMMA is widely used in venous occlusion plethysmography studies to determine baseline NO production. Studies using L-NMMA indicate that endothelial dysfunction is present early in the course of diabetic microvascular complications. However, the optimal dose to maximally inhibit NO-production is unknown., Objective: To determine the L-NMMA-dose that maximally reduces basal forearm blood flow (FBF). To investigate whether there are any differences in the response to L-NMMA between non-complicated type 1 diabetes patients and control subjects., Methods: In eight non-complicated type 1 diabetes patients and nine healthy subjects FBF-responses to intra-arterial infusion of increasing doses of L-NMMA (0.01-1.6 mg/min/dL forearm volume [FAV]) were measured using the perfused forearm technique., Results: Infusion of 0.8 mg/min/dL maximally reduced FBF. The dose of 1.6 mg/min/dL did not additionally reduce FBF. No differences existed between non-complicated type 1 diabetes patients and controls with regard to EC50 (0.017 +/- 0.02 resp. 0.22 +/- 0.02 mg L-NMMA/min/dL) or maximal vasoconstrictive response (Delta FBF: 1.13 +/- 0.4 resp. 0.97 +/- 0.4 mL/min/dL). Throughout the study blood pressure increased significantly in both groups, possibly reflecting a systemic vasoconstrictive effect of L-NMMA., Conclusions: The maximal vasoconstrictive dose was 0.8 mg/min/dL in type 1 diabetes patients as well as the control subjects. There were no significant differences between non-complicated type 1 diabetes subjects and controls with regard to the pharmacodynamics of L-NMMA. At high dosages of L-NMMA a systemic effect can not be ruled out.

Type 1 diabetes is a T-cell-mediated chronic disease characterized by the autoimmune destruction of pancreatic insulin-producing beta cells and complete insulin deficiency. It is the result of a complex interrelation of genetic and environmental factors, most of which have yet to be identified. Simultaneous identification of these genetic factors, through use of unphased genotype data, has received increasing attention in the past few years. Several approaches have been described, such as the modified transmission/disequilibrium test procedure, the conditional extended transmission/disequilibrium test, and the stepwise logistic-regression procedure. These approaches are limited either by being restricted to family data or by ignoring so-called "haplotype interactions" between alleles. To overcome this limit, the present study provides a general method to identify, on the basis of unphased genotype data, the haplotype blocks that interact to define the risk for a complex disease. The principle underpinning the proposal is minimal entropy. The performance of our procedure is illustrated for both simulated and real data. In particular, for a set of Dutch type 1 diabetes data, our procedure suggests some novel evidence of the interactions between and within haplotype blocks that are across chromosomes 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 15, 16, 17, 19, and 21. The results demonstrate that, by considering interactions between potential disease haplotype blocks, we may succeed in identifying disease-predisposing genetic variants that might otherwise have remained undetected.