Relationship of matrix Gla protein and vitamin K with vascular calcification in hemodialysis patients.

Objective: This study evaluated associations of serum matrix Gla protein (MGP), plasma vitamin K1, and plasma vitamin K2 with coronary artery calcium score (CACS) and cardiovascular disease (CVD) in maintenance hemodialysis (MHD) patients. Methods: Subjects comprised 112 MHD patients aged 30-60 years and 40 age-matched healthy subjects. Total MGP, vitamin K1, vitamin K2, and lipid profile were examined in all subjects; other clinical data, medication use, and CACS were assessed only in MHD patients. Determinants of MGP in all subjects were identified by regression analysis. Factors associated with CACS and CVD in MHD patients were identified by regression analysis and logistic analysis, respectively. Results: Lower plasma levels of vitamin K1 corrected for triglycerides [0.39 (0.24-0.70) vs. 0.77 (0.48-1.34) ng/mg, p < 0.001], higher frequency of plasma vitamin K2 ≤ 0.05 ng/ml (p = 0.23), and higher serum total MGP (288.4 ± 44.2 vs. 159.7 ± 40.6 ng/ml, p < 0.0001) were observed in MHD patients than in healthy controls. Total MGP level was significantly associated with levels of vitamin K1 corrected for triglycerides (p <0 .001) and vitamin K2 ≤ 0.05 ng/ml (p < 0.05) in all subjects. Total MGP level was significantly associated with presence of CVD (p <0 .05), but not CACS, in MHD patients. Conclusion: The end-stage renal disease on hemodialysis is a deficiency state of vitamin K. Total MGP was significantly higher in MHD patients compared to healthy subjects and total MGP was associated with the presence of CVD, but not CACS, in MHD patients.

Hypomagnesemia is not an independent risk factor for mortality in Japanese maintenance hemodialysis patients.

PURPOSE: It is unclear whether hypomagnesemia is an independent risk factor or innocent bystander for mortality in maintenance hemodialysis (MHD) patients. Thus, we studied associations between hypomagnesemia and all-cause as well as cardiovascular (CV) mortality in MHD patients. METHODS: Baseline clinical characteristics and coronary artery calcium score (CACS) of 353 Japanese MHD patients were reviewed. Three-year survival rate and mortality risk factors were assessed. RESULTS: Median (interquartile range) age, dialysis vintage, serum magnesium (Mg), serum albumin and CACS of the subjects were 68 (60-78) years, 75 (32-151) months, 2.4 (2.2-2.7) mg/dl, 3.6 (3.3-3.8) g/dl, and 1181 (278-3190), respectively. During the 3-year period, 91 patients died. Kaplan-Meier overall 3-year survival rates were 59.0% in in patients with Mg < 2.4 mg/dl (n = 136) and 82.3% in patients with Mg ≥ 2.4 mg/dl (n = 217), (P < 0.0001). In Cox regression models not incorporating serum albumin, Mg < 2.4 mg/dl was significantly associated with 3-year all-cause death, independent of age, dialysis vintage, average ultrafiltration, Log (CACS + 1), warfarin use, serum potassium, high-sensitivity C-reactive protein (hsCRP), phosphate, uric acid, and intact parathyroid hormone [Hazard ratio (HR) 95% confidence interval (CI): 2.82 (1.31-6.29), P = 0.0078], and CV death, independent of age, dialysis vintage, Log (CACS + 1), warfarin use, serum hsCRP, and uric acid [HR (95% CI): 4.47 (1.45-16.76), P = 0.0086]. Nevertheless, associations of Mg < 2.4 mg/dl with all-cause and CV mortality were all absent in models that included serum albumin. CONCLUSIONS: Hypomagnesemia is not an independent risk factor for mortality but is associated with malnutrition in MHD patients.

A case report of plasmapheresis in paraneoplastic cerebellar ataxia associated with anti-Tr antibody.

A 53-year-old-male patient was admitted to the Hiroshima University Hospital in August 2001, with a history of progressive cerebellar ataxia, notable by standing and gait disturbances. Brain computed tomography (CT) and magnetic resonance imaging (MRI) showed no signs of ischemic damage. Two weeks later, left axillary lymphadenopathy developed. The pathological finding was Hodgkin's disease (HD; a classical malignant lymphoma in an early stage). Serum antibodies against Purkinje's cells (anti-Tr antibody) were detected by immunohistochemical study. Thus, we diagnosed this as paraneoplastic cerebellar degeneration (PCD) associated HD. We immediately carried out chemotherapy (ABVD therapy), radiotherapy with 20-30 Gy, steroid pulse and intravenous immunoglobulin (IVIg) without neurologic improvement. The patient was subsequently treated by double filtration plasmapheresis (DFPP), leading to a marked improvement of standing and gait disturbances and to a reduction of autoantibodies, which became undetectable. We conclude that DFPP might be useful in treating patients with cerebellar ataxia, and should be considered as a therapeutic choice for it.

Phosphorylation of beta-catenin by cyclic AMP-dependent protein kinase stabilizes beta-catenin through inhibition of its ubiquitination.

The mechanism of cross talk between the Wnt signaling and cyclic AMP (cAMP)-dependent protein kinase (protein kinase A [PKA]) pathways was studied. Prostaglandin E(1) (PGE(1)), isoproterenol, and dibutyryl cAMP (Bt(2)cAMP), all of which activate PKA, increased the cytoplasmic and nuclear beta-catenin protein level, and these actions were suppressed by a PKA inhibitor and RNA interference for PKA. PGE(1) and Bt(2)cAMP also increased T-cell factor (Tcf)-dependent transcription through beta-catenin. Bt(2)cAMP suppressed degradation of beta-catenin at the protein level. Although PKA did not affect the formation of a complex between glycogen synthase kinase 3beta (GSK-3beta), beta-catenin, and Axin, phosphorylation of beta-catenin by PKA inhibited ubiquitination of beta-catenin in intact cells and in vitro. Ser675 was found to be a site for phosphorylation by PKA, and substitution of this serine residue with alanine in beta-catenin attenuated inhibition of the ubiquitination of beta-catenin by PKA, PKA-induced stabilization of beta-catenin, and PKA-dependent activation of Tcf. These results indicate that PKA inhibits the ubiquitination of beta-catenin by phosphorylating beta-catenin, thereby causing beta-catenin to accumulate and the Wnt signaling pathway to be activated.

Studies on post-transplant dyslipidemia in kidney transplant patients.

This study was performed to retrospectively compare changes in the levels of total cholesterol, non-HDL cholesterol, triglycerides, and immunosuppressive drugs, cyclosporine A and steroids in patients with living-relation renal transplants with those from non-heart-beating donors. We experienced 11 cases of kidney transplants from non-heart-beating donors during the period from April 1995 to May 2003. We evaluated 13 cases of kidney transplants from living-relation donors during the same period. The immunosuppressants used included mainly cyclosporine A as well as mycophenolate mofetil or azathioprine, steroid and ALG, or basiliximab. Over-night fasting lipids (total cholesterol, triglycerides and HDL cholesterol) were studied before renal transplantation and repeated after renal transplantation at 1, 3, 6 and 12 months. The levels of total cholesterol and triglycerides remained in the normal range before transplantation. However, the levels of total cholesterol increased siginificantly 1 and 3 months after transplantation from non-heart-beating donors and remained at higher levels up to 12 months after transplantation. A similar pattern in the levels of triglycerides was observed. The levels of HDL cholesterol remained unchanged and stayed in the normal range before and 1, 3, 6, and 12 months after transplantation from non-heart-beating donors. On the other hand, significant increases in non-HDL cholesterol were observed 3 and 6 months after transplantation from non-heart-beating donors. After transplantation from living-relation donors, levels of total cholesterol, triglycerides, and non-HDL cholesterol remained unchanged and remained in the normal range up to 12 months after transplantation. Although there were no significant differences in the total dosage of cyclosporine A between the patients with living-relation donors and those with non-heart-beating donors, a significant increase in the total dosage of methylprednisolone was observed in patients with non-heart-beating donors compared with those in the patients with living-relation donors. Renal function recovery in patients with living-relation donors was better than in those with non-heart-beating donors. These results may suggest that significant increases in total cholesterol, especially non-HDL cholesterol and triglycerides, were probably partly due to an increased use of immunosuppressants, steroids. It is necessary to aggressively control post-transplant hyperlipidemia and important to reduce or withdraw steroids in the selected, low-risk recipients as early as possible from the viewpoint of preventing post-transplant hyperlipidemia.

Angiotensin II induces thrombospondin-1 production in human mesangial cells via p38 MAPK and JNK: a mechanism for activation of latent TGF-beta1.

ANG II induces secretion and activation of transforming growth factor-beta (TGF-beta) by glomerular mesangial cells. However, the mechanisms that operate this are unclear. Thrombospondin-1 (TSP-1), which is produced by mesangial cells in damaged glomeruli, is one of several molecules known to activate the latent TGF-beta1 complex. Therefore, we examined whether the ANG II-induced activation of latent TGF-beta1 in human mesangial cells (HMC) operates via TSP-1. The addition of ANG II (1-100 nM) to HMC significantly increased TSP-1 mRNA within 6 h, followed by an increase in TSP-1 protein production as shown by Western blot analysis of cells and immunoassay of the culture supernatant. Production of ANG II-induced TSP-1 mRNA and protein was completely inhibited by an ANG II type 1 (AT1)-receptor antagonist but was unaffected by an AT2-receptor antagonist. Use of a TSP-1-specific blocking peptide demonstrated that the ANG II-induced activation of latent TGF-beta1 operates via TSP-1. Next, we investigated the role of ERK1/2, p38 MAPK, and JNK in ANG II-induced TSP-1 production in HMC. The addition of the upstream ERK1/2 inhibitor PD-98059 did not affect ANG II-induced TSP-1 production, whereas addition of either the p38 MAPK inhibitor SB-203580 or the JNK inhibitor SP-600125 significantly reduced TSP-1 production. In conclusion, this study has demonstrated that ANG II-induced activation of latent TGF-beta1 in HMC operates via TSP-1. Furthermore, ANG II-induced TSP-1 production is dependent on p38 MAPK and JNK signaling.

Bone mineral density may be related to atherosclerosis in hemodialysis patients.

Biological interactions between the bone and the blood vessels are gradually being clarified. To investigate the relationship between bone mineral density and atherosclerosis in hemodialysis patients, we examined the bone mineral density and the intima-media thickness of the carotid artery in 83 dialysis patients with non-diabetic nephropathy (44 men and 39 women) aged from 23 to 83 years. The duration of hemodialysis ranged from 2 to 344 months. The bone mineral density of the radius was measured by dual-energy X-ray adsorptiometry, and the ratio of this value to the standard value for the same age and gender was calculated ( Z-score). As an index of atherosclerosis, the intima-media thickness of the carotid artery was measured by high resolution B-mode ultrasonography. Then the relationship between the Z-score and various factors was examined using Spearman's rank correlation analysis and multiple regression analysis. The Z-score showed a negative correlation with the duration of hemodialysis, the carotid intima-media thickness, and the levels of alkaline phosphatase, intact parathyroid hormone, and low-density lipoprotein cholesterol by Spearman's rank correlation analysis. In addition, the Z-score showed a positive correlation with the lipoprotein (a) level and a negative correlation with the duration of hemodialysis, intima-media thickness, intact parathyroid hormone, and low-density lipoprotein cholesterol by multiple regression analysis. These findings suggest that the decrease of bone mineral density in hemodialysis patients is correlated with secondary hyperparathyroidism and hyperlipidemia, which are factors known to promote atherosclerosis, and thus bone density changes might be related to the progression of atherosclerosis, or vice versa.

A-kinase anchoring protein AKAP220 binds to glycogen synthase kinase-3beta (GSK-3beta ) and mediates protein kinase A-dependent inhibition of GSK-3beta.

Glycogen synthase kinase-3 (GSK-3) is regulated by various extracellular ligands and phosphorylates many substrates, thereby regulating cellular functions. Using yeast two-hybrid screening, we found that GSK-3beta binds to AKAP220, which is known to act as an A-kinase anchoring protein. GSK-3beta formed a complex with AKAP220 in intact cells at the endogenous level. Cyclic AMP-dependent protein kinase (PKA) and type 1 protein phosphatase (PP1) were also detected in this complex, suggesting that AKAP220, GSK-3beta, PKA, and PP1 form a quaternary complex. It has been reported that PKA phosphorylates GSK-3beta, thereby decreasing its activity. When COS cells were treated with dibutyryl cyclic AMP to activate PKA, the activity of GSK-3beta bound to AKAP220 decreased more markedly than the total GSK-3beta activity. Calyculin A, a protein phosphatase inhibitor, also inhibited the activity of GSK-3beta bound to AKAP220 more strongly than the total GSK-3beta activity. These results suggest that PKA and PP1 regulate the activity of GSK-3beta efficiently by forming a complex with AKAP220.