Disturbed homocysteine and methionine cycle intermediates S-adenosylhomocysteine and S-adenosylmethionine are related to degree of renal insufficiency in type 2 diabetes

BACKGROUND

Diabetic nephropathy is a common complication in patients with type 2 diabetes that may increase atherothrombotic risk. Hyperhomocysteinemia (HHcy) further increases the risk in those patients. We studied concentrations of total homocysteine (tHcy) and its related metabolites S-adenosylmethionine (AdoMet) and S-adenosylhomocysteine (AdoHcy) in relation to B-vitamin status and renal function in patients with type 2 diabetes who developed diabetic nephropathy.

METHODS

The study included 93 patients with renal failure and type 2 diabetes. Chronic kidney disease was classified into four subgroups according to the National Kidney Foundation based on glomerular filtration rate plus pathologic abnormalities or markers of kidney damage.

RESULTS

Serum or plasma concentrations of the metabolites increased significantly with worsening of renal function, whereas serum concentrations of the B vitamins (folate, vitamins B12 and B6) did not differ appreciably between the groups. Moreover, plasma concentrations of AdoHcy and AdoMet were markedly increased in patients with kidney failure compared with those in stage 2 (median AdoHcy, 112.7 vs 10.5 nmol/L; median AdoMet, 162.0 vs 80.0 nmol/L). The AdoMet/AdoHcy ratio was more than 80% lower in patients with renal failure compared with stage 2. Vitamin B12 was a significant determinant of concentrations of AdoMet, tHcy, methylmalonic acid (MMA), and cystathionine.

CONCLUSIONS

Increased plasma concentrations of tHcy and methionine cycle intermediates (AdoMet, AdoHcy) are related to disturbed renal function in patients with type 2 diabetes. Vitamin B12 and/or folate are significant predictors of tHcy, cystathionine, MMA, and AdoMet. The effect of therapeutic doses of the B vitamins on AdoMet, AdoHcy, and their ratio should be tested in renal patients.

[Risk analysis of medical products. Implementation of risk analysis exemplified by the spongiosa cannulated screw]

The Medical Devices Act (Medizinproduktegesetz = MPG) took effect in Germany on 01. 01. 1995, and replaced (with the exception of diagnostic laboratory devices) the previously binding MedGV with a transition period ending on 13. 06. 1998. The new German act is the implementation of the EC directive on active implantable medical devices (90/385/EWG) and the directive on medical devices (93/42/EWG). The EC directive 93/42/EWG on medical devices permits the manufacturer of a medical device to chose the conformity assessment procedure. All medical devices are subject to conformity assessment procedures, and are awarded the EC mark through Appendix II, III, VII or VIII. All these appendices contain information about the need for carrying out assessment and the obligation to provide a written description of the risk analysis for a medical device. Risk analysis is a common method that verifiably ensures that the basic requirements of EC Directive 93/42/EWG on medical devices are met by the product. It is obvious that risk analysis is of central importance to the legal measures for ensuring appropriate device safety. The present paper presents and assesses various methods of risk analysis.

Human T-cell lymphotropic virus type 1 Tax1 activation of NF-kappa B: involvement of the protein kinase C pathway

Human T-cell lymphotropic virus type 1 Tax1 induces the activation and nuclear localization of the cellular transcription factor, NF-kappa B. Treatment of cells with calphostin C, a protein kinase C (PKC) inhibitor, blocked induction of NF-kappa B DNA binding activity in human T-cell lymphotropic virus type 1-transformed C81 cells and Tax1-stimulated murine pre-B cells, suggesting that PKC was an important intermediate in the NF-kappa B induction pathway. We further demonstrate that Tax1 associates with, and activates, PKC. PKC was coimmunoprecipitated with anti- Tax1 sera from Tax1-expressing MT4 extracts and Jurkat extracts in the presence of exogenous Tax1 protein. In addition, the glutathione-S-transferase-Tax1 protein bound specifically to the alpha, delta, and eta PKC isoenzymes synthesized in rabbit reticulocyte lysates. The addition of Tax1 to in vitro kinase reaction mixtures leads to the phosphorylation of Tax1 and an 18-fold increase in the autophosphorylation of PKC. Transfection of Jurkat cells with wild-type Tax1 stimulated membrane translocation of PKC. In contrast, Tax1 mutant M22, which fails to stimulate NF-kappa B-dependent transcription, failed to stimulate membrane translocation of PKC. Tax1 did not directly increase PKC phosphorylation of I kappa B alpha. Our results are consistent with a model in which Tax1 interacts with PKC and stimulates membrane translocation and triggering of the PKC pathway. Subsequent steps in the PKC cascade likely stimulate phosphorylation of I kappa B alpha.

Oxidative damage to DNA in diabetes mellitus

BACKGROUND

Increased production of reactive oxygen species (ROS) and lipid peroxidation may contribute to vascular complications in diabetes. to test whether DNA is also oxidatively damaged in diabetes, we measured 8-hydroxydeoxyguanosine (8-OHdG), an indicator of oxidative damage of DNA, in mononuclear cells.

METHODS

For this laboratory-based study, 12 patients with insulin-dependent diabetes mellitus (IDDM) and 15 patients with non-insulin-dependent diabetes mellitus (NIDDM) were matched by age with ten healthy volunteers each. DNA was extracted from mononuclear cells from whole blood. 8-OHdG was assayed by high-pressure liquid chromatography, and ROS were assayed by chemiluminescence.

FINDINGS

IDDM and NIDDM patients had significantly higher median concentrations (p , 0.001, U test) of 8-OHdG in their mononuclear cells than their corresponding controls (in fmol/micrograms DNA): 128.2 (interquartile range 96.0-223.2) and 95.2 (64.0-133.5) vs 28.2 (21.7-43.4) and 21.9 (18.0-24.4), respectively. ROS generation by mononuclear cells was also significantly greater (p < 0.01) in diabetic patients than in their controls (in mV): 238.0 (107.0-243.0) and 101.3 (66.0-134.0) vs 69.5 (49.8-91.9) and 56.0 (38.8-62.5), respectively.

INTERPRETATION

IDDM and NIDDM patients showed greater oxidative damage to DNA, with increased generation of ROS, than controls. Such changes might contribute to accelerated aging and atherogenesis in diabetes and to the microangiopathic complications of the disease.

The pathobiology of Dupuytren's contracture: effects of prostaglandins on myofibroblasts

The in vitro response of myofibroblasts to prostaglandins F2alpha (a vasoconstrictor) and E2 (a vasodilator) were evaluated in specimens obtained from the Dupuytren's nodules of 12 patients. Fibroblasts from four control samples of palmar fascia were similarly tested. This study demonstrated the ability of prostaglandin F2alpha to induce significant contraction of myofibroblasts. Prostaglandin E2 was noted to cause significant relaxation of myofibroblasts. The contractile/relaxation responses of control fibroblasts to these prostaglandins were minimal.

Certain phosphate compounds in the erythrocytes of patients with primary hyperlipidaemia

The investigations were carried out in 30 patients with primary hyperlipidaemia (hypercholesterolaemia, hypertriglyceridaemia and mixed form). The serum total cholesterol and triglycerides, and in the erythrocytes the levels of AMP, ADP, ATP, ATP complex with Fe, MP, HDP and DGP were determined. Twenty blood donors served as a control group. The obtained results showed a statistically highly significant rise in ADP concentration in all investigated subgroups of hyperlipidaemic subjects, and a non-significant quantitative shift of other determined phosphate compounds.