Hiromichi Gotoh

Increased serum endogenous secretory receptor for advanced glycation end-product (esRAGE) levels in type 2 diabetic patients with decreased renal function.

BACKGROUND The binding of advanced glycation end-products (AGEs) to their receptor for AGEs (RAGE) may play an important role in the development of diabetic vascular complications. Recently, soluble RAGE (sRAGE) has been identified as an alternative splicing form of RAGE. Furthermore, administration of sRAGE improved atherosclerosis in type 2 diabetic mice. OBJECTIVE The objective of the present study is to investigate the role of endogenous secretory RAGE (esRAGE) as a biological marker for type 2 diabetic nephropathy, and also to determine whether serum esRAGE levels are associated with serum AGEs [including Nepsilon-(carboxymethyl) lysine-protein adducts (CML) and pentosidine] levels. MATERIALS AND METHODS Serum esRAGE levels were examined in 107 type 2 diabetic patients including those on hemodialysis (HD). Diabetic patients were divided into three groups as follows: Group A [patients without nephropathy, i.e. normoalbuminuric stage (AER<30microg/mg creatinine)], Group B [patients with nephropathy (AER>30microg/mg creatinine) but excluding HD patients], and Group C (HD patients). RESULTS Serum esRAGE and AGEs (including CML and pentosidine) levels in Group C were significantly higher than in Group A or B. In single linear univariate correlation, serum esRAGE levels were correlated using body mass index (BMI), duration of diabetes, and serum creatinine, high-density lipoprotein (HDL)-cholesterol and AGEs (including CML and pentosidine) levels. Furthermore, in stepwise multivariate regression analysis, the levels of serum creatinine and duration of diabetes were independently associated with serum esRAGE levels. CONCLUSION Serum esRAGE levels are associated with the severity of renal dysfunction and duration of diabetes in type 2 diabetic patients.

Relationship between Abdominal Fat Accumulation and Insulin Resistance in Hemodialysis Patients

It is well known that obesity and insulin resistance are closely related to the development of type 2 diabetes. However, the exact pathogenic mechanism underlying the insulin resistance in renal disease has not been clarified. The purpose of the present study was to clarify the contribution of abdominal (visceral and subcutaneous) fat accumulation to insulin resistance and various clinical parameters, including C-reactive protein (CRP), in hemodialysis (HD) patients. Visceral and subcutaneous fat areas (VFA and SFA) were evaluated at the umbilical level by CT. Insulin resistance was estimated by the homeostasis model assessment−insulin resistance index (HOMA-IR) in 80 HD patients. Insulin resistance and CRP seemed to be closely correlated with fat-related parameters such as body mass index (BMI), VFA and SFA. HOMA-IR was positively correlated with BMI, VFA, SFA, triglycerides (TG), remnant-like particle (RLP)-cholesterol and CRP in simple regression analysis. In multiple stepwise regression analysis, SFA and RLP-cholesterol were predominant determinants of HOMA-IR in HD patients. Furthermore, CRP was positively correlated with BMI, VFA, SFA, TG, high-density lipoprotein (HDL)-cholesterol, atherosclerosis index (AI), immunoreactive insulin (IRI) and HOMA-IR in simple regression analysis. In multiple stepwise regression analysis, VFA and HDL-cholesterol were predominant determinants of CRP in HD patients. In conclusion, insulin resistance and CRP were related to fat-related parameters such as BMI, VFA and SFA in HD patients. Furthermore, the contribution of SFA to insulin resistance was much higher than that of VFA, while the opposite relation was recognized for CRP. (Hypertens Res 2008; 31: 83−88)

Oral Vitamin C Supplementation in Hemodialysis Patients and Its Effect on the Plasma Level of Oxidized Ascorbic Acid and Cu/Zn Superoxide Dismutase, an Oxidative Stress Marker

Background/Aim: Oxidative stress is known to be enhanced in hemodialysis patients, and one of its useful markers is plasma copper/zinc superoxide dismutase (Cu/Zn-SOD). The increase in plasma Cu/Zn-SOD can be inhibited by orally administered lipid-soluble vitamin E. We examined the antioxidative effects of water-soluble vitamin C administered orally on Cu/Zn-SOD levels in hemodialysis patients. Methods: Vitamin C was orally administered to 16 maintenance hemodialysis patients before each dialysis session. Doses were increased from 200 to 1,000 mg over 3 months. The levels of plasma vitamin C and Cu/Zn-SOD and its mRNA expression in leukocytes were determined 1, 2, and 3 months after the start of vitamin C administration. Furthermore, the levels of oxidized and reduced forms of plasma vitamin C were determined before the start of vitamin C administration and before and after dialysis at 1,000-mg vitamin C doses. Results: Following oral administration, the plasma levels of vitamin C and its oxidized form were increased. However, significant changes in plasma Cu/Zn-SOD or its mRNA expression in leukocytes were not observed. Conclusion: In maintenance hemodialysis patients, vitamin C administration resulted in a significant increase in the postdialysis level of the oxidized form of vitamin C, which suggested an increase in antioxidant effect. However, water-soluble vitamin C did not significantly suppress Cu/Zn-SOD expression enhancement.

Long-term effects of alogliptin benzoate in hemodialysis patients with diabetes: a 2-year study.

Aim: To evaluate the long-term efficacy of monotherapy with the dipeptidase-4 inhibitor alogliptin benzoate in hemodialysis (HD) patients with type 2 diabetes. Methods: Sixteen diabetic HD patients with inadequate glycemic control (hemoglobin A1c (HbA1c) level >6.5% and glycated albumin (GA) level >20%) on diet and exercise participated in the study. No patients were taking other oral antidiabetic drugs or receiving insulin therapy. Alogliptin 6.25 mg was administered to patients once daily. HbA1c, GA levels were obtained before and after 2 years of treatment. Body weight and active glucagon-like peptide-1, blood glucose, insulin, C-peptide immunoreactivity, glucagon, albumin, hemoglobin, and total cholesterol levels were also examined before and after treatment. Results: Both HbA1c and GA levels decreased after starting alogliptin administration. As compared to the pretreatment levels, HbA1c and GA levels significantly decreased at 3 and 18 months, respectively, after starting alogliptin administration. HbA1c and GA levels decreased from 7.1 ± 0.2 to 5.8 ± 1.6% and from 22.5 ± 0.7 to 19.6 ± 0.6%, respectively, 24 months after beginning treatment. Glucagon-like peptide-1 levels (8.9 ± 5.7 pmol/l before treatment) doubled after treatment. Body weight and blood glucose, insulin, C-peptide immunoreactivity, glucagon, albumin, hemoglobin, and total cholesterol levels did not change with treatment. Only one significant adverse effect, a drug-related rash, was seen in 1 patient. Conclusion: Long-term (2-year) effects of alogliptin benzoate monotherapy suggest its efficacy as a new treatment strategy in diabetic HD patients.

Anti-inflammatory effects of linagliptin in hemodialysis patients with diabetes

Inflammation and glycemic control are important prognosis‐related factors for hemodialysis (HD) patients; moreover, inflammation affects insulin secretion. Here, we evaluated the anti‐inflammatory effects of monotherapy with linagliptin—a dipeptidase‐4 inhibitor—in HD patients with type 2 diabetes. We examined 21 diabetic HD patients who were not receiving oral diabetes drugs or insulin therapy and with poor glycemic control (glycated albumin [GA] level, >20%). Linagliptin (5 mg) was administered to the patients daily. The levels of prostaglandin E2 (PGE2), interleukin‐6 (IL‐6), high‐sensitivity C‐reactive protein, GA, blood glucose, and active glucagon‐like peptide‐1 were determined before and 6 months after treatment. Body weight and serum levels of albumin, hemoglobin, total cholesterol, and low‐density lipoprotein cholesterol were also recorded before and after treatment. The levels of PGE2 and GA were significantly decreased 1 month after starting linagliptin therapy, whereas the IL‐6 levels were significantly decreased 6 months after starting linagliptin therapy. After 6 months of treatment, the PGE2 levels decreased from 188 ± 50 ng/mL to 26 ± 5 ng/mL; IL‐6 levels, from 1.5 ± 0.4 pg/mL to 0.6 ± 0.1 pg/mL; and GA levels, from 21.3% ± 0.6% to 18.0% ± 0.6%. Glucagon‐like peptide‐1 levels increased 2.5‐fold during the treatment. Over the 6‐month treatment period, body weight and levels of high‐sensitivity C‐reactive protein, blood glucose, albumin, hemoglobin, and cholesterol did not change; none of the patients exhibited hypoglycemia. The anti‐inflammatory effects of linagliptin monotherapy indicate that it may serve as a useful glucose control strategy for HD patients with diabetes.

mRNA Study on Cu/Zn Superoxide Dismutase Induction by Hemodialysis Treatment

Background/Aims: There is little or no controversy about the increased oxidative stress of hemodialysis (HD) patients. Several reports show that the activity of superoxide dismutase (SOD), one of the major endogenous antioxidant enzymes, in plasma is elevated among HD patients. It is still unclear, however, whether this elevation is due to the promotion of SOD production or a decrease in renal excretion of SOD. This study was designed to investigate the cause of the SOD activation in HD patients, and we examined the expression of SOD mRNA levels in leukocytes of patients with chronic renal failure. Methods: The total plasma SOD activity was determined by the nitroblue tetrazolium method, plasma SOD contents by ELISA, and SOD mRNA levels in leukocytes by RT-PCR. Results: Our results demonstrated that contents and mRNA levels of Cu/Zn SOD in HD patients are 4.4 times and 2.0 times, respectively, as large as those in healthy controls. Furthermore, in contrast to nondialyzed chronic renal failure patients, we observed higher concentrations of Cu/Zn SOD in plasma and a more enhanced mRNA expression of Cu/Zn SOD in leukocytes of HD patients. Conclusion: Increased Cu/Zn SOD mRNA reflects enhanced antioxidant capacity of leukocytes and can be a promising oxidative stress marker in HD patients.

Contribution of subcutaneous fat accumulation to insulin resistance and atherosclerosis in haemodialysis patients

BACKGROUND Whereas visceral fat accumulation (VFA) is related to insulin resistance and atherosclerosis in both haemodialysis (HD) patients and the general population, little is known about the role of subcutaneous fat accumulation (SFA). The purpose of the present study was to examine and confirm the relationship between abdominal fat accumulation (AFA) and various clinical parameters in HD patients. METHODS Two hundred and thirty-three HD patients were recruited, including 120 with type 2 diabetes. Abdominal fat distribution was evaluated by computed tomography (CT) scans. Systemic atherosclerosis was assessed by intima-media thickness (IMT) using high-resolution B-mode ultrasonography. The insulin resistance was estimated by the homeostasis model assessment-insulin resistance (HOMA-IR). RESULTS Spearmans analysis revealed that both VFA and SFA showed a significant relationship with HOMA-IR and also that SFA was correlated significantly with IMT in all HD patients. SFA was an independent risk factor associated with HOMA-IR and IMT in multiple regression analysis. Neither body mass index (BMI) nor VFA was a predominant determinant of HOMA-IR and IMT. IMT in HD patients with high SFA/low BMI groups was significantly higher than in the low SFA/high BMI groups. CONCLUSION It appears that there is a close relationship between SFA and insulin resistance or atherosclerosis in HD patients. It was suggested that SFA plays important roles related to carbohydrate or lipid metabolism in HD patients.

Comparison of Effect of Vitamin E-Coated Dialyzer and Oral Vitamin E on Hemodialysis-Induced Cu/Zn-Superoxide Dismutase

Background: We reported earlier that production of Cu/Zn-superoxide dismutase (SOD) increases markedly in hemodialysis patients but not in non-dialyzed chronic renal failure (CRF) patients. In this study, we compared the antioxidant effects of oral vitamin E supplementation (VE-PO) and vitamin E coating of a dialyzer (VE-BMD) by measuring increased Cu/Zn-SOD in hemodialysis patients. Methods: 31 hemodialysis patients were divided into two groups: 16 hemodialysis patients underwent usual dialysis with vitamin E supplementation 600 mg/day while 15 others were dialyzed using vitamin E-coated membrane for 6 months. Total plasma SOD activity was determined by NBT method, plasma Cu/Zn-SOD contents by ELISA and Cu/Zn-SOD mRNA in leukocytes by RT-PCR. Results: VE-PO and VE-BMD showed almost comparable effects on Cu/Zn-SOD contents and its mRNA levels in hemodialysis patients. VE-PO resulted in a progressive decrease of Cu/Zn-SOD content (p < 0.001). A comparable progressive decrease was observed also in VE-BMD (p < 0.0001). Both VE-PO and VE-BMD resulted in a progressive decrease of Cu/Zn-SOD mRNA (p < 0.01), which reached the level of non-dialyzed CRF patients.

Circulating TNF Receptors 1 and 2 Predict Mortality in Patients with End-stage Renal Disease Undergoing Dialysis

Relatively high circulating levels of soluble tumor necrosis factor (TNF) receptors (TNFRs: TNFR1, TNFR2) have been associated with not only progression to end-stage renal disease but also mortality in patients with diabetes. It remains unknown whether elevated TNFR levels in haemodialysis patients are associated with mortality. We studied 319 patients receiving maintenance haemodialysis who were followed for a median of 53 months. Circulating markers of TNF pathway (TNFα and TNFRs) were measured with immunoassay. Strong positive correlations between TNFR1 and TNFR2 were observed (r = 0.81, P < 0.0001). During follow-up, 88 (27.6%) patients died of any cause (40 [45.5%] died of cardiovascular disease). In the Cox multivariate model, either TNFR but not TNFα remained a significant independent predictor of all-cause mortality (TNFR1: hazard ratio [HR] 2.34, 95% confidence interval [CI], 1.50–3.64; TNFR2: HR 2.13, 95% CI 1.38–3.29) after adjustment for age, prior cardiovascular disease, predialysis systolic blood pressure, and large systolic blood pressure decline during dialysis session. For cardiovascular mortality, significance was only observed in TNFR1 (TNFR1: HR 2.15, 95% CI 1.13–4.10). Elevated TNFRs levels were associated with the risk of cardiovascular and/or all-cause mortality independent of all relevant covariates in patients undergoing haemodialysis.

Sitagliptin Inhibits the Lipopolysaccharide-Induced Inflammation

Sitagliptin Inhibits the Lipopolysaccharide-Induced Inflammation Abstract Objective: Sitagliptin is an anti-diabetic Dipeptidyl peptidase-4 (DPP-4) inhibitor; used worldwide with a well-established evidence base as an effective anti-diabetic therapy and the lowest cost of all DPP-4 inhibitors. Atherosclerosis and inflammation are more common in diabetic patients than in nondiabetic patients, and progression of atherosclerosis contributes to this inflammation. Therefore, anti-inflammatory therapy is important for the prognosis of diabetic patients. Although several reports have investigated the anti-inflammatory mechanisms of sitagliptin in vitro, none of these studies has described its effects on mitogenactivated protein kinase (MAPK) in human umbilical vein endothelial cells (HUVECs) stimulated with lipopolysaccharide (LPS). We assessed the MAPK-dependent anti-inflammatory effects of sitagliptin in HUVECs. Methods: HUVECs (1–2 × 105 cell/mL) were either pretreated with different doses of sitagliptin for 1 h or left untreated. Subsequently, HUVECs were either incubated with lipopolysaccharide (LPS) together with sitagliptin (after treatment) or left untreated. Five hours post incubation, the culture medium was sampled for interleukin (IL)-6. Additionally, intranuclear p65 levels were measured 5 h after simultaneous treatment with LPS and sitagliptin. p38 MAPK levels and PKC activity were measured in the cytosolic fractions 30 min after simultaneous treatment with LPS and sitagliptin. Results: Treatment with LPS alone induced significant IL-6 production compared with untreated control cells. Pretreatment of cells with sitagliptin at all concentrations tested significantly reduced LPS-stimulated IL-6 production. However, after treatment of cells with sitagliptin at any concentration did not inhibit LPS-stimulated IL-6 production. Compared to untreated cells, treatment with 5 nM sitagliptin significantly inhibited LPS-stimulated intranuclear p65 expression, and p38 MAPK phosphorylation. There was no significant difference in PKC activity with LPS or sitagliptin. Conclusion: In HUVECs, sitagliptin elicits its anti-inflammatory effects through MAPK-dependent mechanisms.