Takuhito Shoji

Plasma Level of Endogenous Secretory RAGE Is Associated With Components of the Metabolic Syndrome and Atherosclerosis

Objective—Advanced glycation endproducts, AGEs, and its specific receptor, RAGE, are involved in diabetic vascular complications. Endogenous secretory RAGE, esRAGE, has been identified as an alternatively spliced form of RAGE, and shown to act as a decoy receptor for AGE. Here, we measured plasma esRAGE level with a recently developed enzyme-linked immunosorbent assay (ELISA) and examined its association with atherosclerosis in age- and gender-matched 203 type 2 diabetic and 134 nondiabetic subjects. Methods and Results—Plasma esRAGE was inversely associated with carotid or femoral atherosclerosis, as quantitatively measured as intimal-medial thickness (IMT) by arterial ultrasound. Stepwise regression analyses revealed that plasma esRAGE was the third strongest and independent factor associated with carotid IMT, following age and systolic blood pressure. Plasma esRAGE was significantly lower in diabetic patients (0.176±0.092 ng/mL) than nondiabetic controls (0.253±0.111). Of note, in all, diabetic or nondiabetic group, plasma esRAGE was significantly and inversely correlated with components of the metabolic syndrome including body mass index, blood pressure, triglyceride, HbA1c, or an insulin resistance index. Stepwise regression analyses showed that body mass index or insulin resistance index was the major factor determining plasma esRAGE in all, nondiabetic or diabetic population. Conclusions—esRAGE is a novel and potential protective factor for the metabolic syndrome and atherosclerosis.

Platelet P-Selectin Expression Is Associated With Atherosclerotic Wall Thickness in Carotid Artery in Humans

Background—Recent genetic animal models reveal important roles of platelet P-selectin on progression of atherosclerosis. In the present study, we examine the relation between platelet P-selectin expression and atherosclerotic parameters in 517 subjects. Methods and Results—Unrelated subjects (n=517; 235 male and 282 female), including 187 with type 2 diabetes, 184 with hypertension, and 366 with hyperlipidemia, were enrolled in the study. P-selectin expression was determined by whole-blood flow cytometry. Arterial stiffness (stiffness index &bgr;) and arterial wall thickness (intima-media thickness [IMT]) were determined by carotid ultrasound. P-selectin expression was significantly and positively correlated with carotid IMT and stiffness index &bgr;. Multiple regression analyses showed that the association of the percentage of P-selectin–positive platelets with carotid IMT was independent of other clinical factors. Moreover, the percentage of P-selectin–positive platelets was higher in subjects with carotid plaque and was an independent factor associated with occurrence of carotid plaque analyzed by multiple logistic regression analysis. Finally, the percentage of P-selectin–positive platelets was positively associated with age, body mass index, systolic and diastolic blood pressure, and HbA1c and inversely associated with HDL cholesterol. Conclusions—Platelet P-selectin is independently associated with atherosclerotic arterial wall changes in human subjects.

Receptor for Advanced Glycation End Products Is Involved in Impaired Angiogenic Response in Diabetes

Angiogenic response is impaired in diabetes. Here, we examined the involvement of receptor for advanced glycation end products (RAGE) in diabetes-related impairment of angiogenesis in vivo. Angiogenesis was determined in reconstituted basement membrane protein (matrigel) plugs containing vascular endothelial growth factor (VEGF) implanted into nondiabetic or insulin-deficient diabetic wild-type or RAGE−/− mice. The total, endothelial, and smooth muscle (or pericytes) cells in the matrigel were significantly decreased in diabetes, with the regulation dependent on RAGE. In the matrigel, proangiogenic VEGF expression was decreased, while antiangiogenic thrombospondin-1 was upregulated in diabetic mice, regardless of the presence of RAGE. In wild-type mice, proliferating cell nuclear antigen (PCNA)-positive cells in the matrigel were significantly less in diabetic than in nondiabetic mice, while the numbers of transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells were significantly higher. This alteration in PCNA- and TUNEL-positive cells in diabetes was not observed in RAGE−/− mice. Similarly, the percentage of nuclear factor κB–activated cells is enhanced in diabetes, with the regulation dependent on the presence of RAGE. Importantly, adenovirus-mediated overexpression of endogenous secretory RAGE, a decoy receptor for RAGE, restores diabetes-associated impairment of angiogenic response in vivo. Thus, RAGE appears to be involved in impairment of angiogenesis in diabetes, and blockade of RAGE might be a potential therapeutic target.

Low Circulating Endogenous Secretory Receptor for AGEs Predicts Cardiovascular Mortality in Patients With End-Stage Renal Disease

Objective—Receptor for advanced glycation end-products (RAGE) is involved in diabetic vascular complications. We have recently shown that plasma endogenously secretory RAGE (esRAGE), an alternatively spliced form of RAGE, is closely associated with metabolic syndrome and atherosclerosis. Here, we evaluated if plasma esRAGE is a predictor of cardiovascular mortality in a cohort of 206 (171 nondiabetic) patients with end-stage renal diseases (ESRD). Methods and Results—The cohort was followed for a median of 111 months, and 74 deaths including 34 cardiovascular deaths were recorded. Plasma esRAGE was measured at baseline. Cumulative incidence of cardiovascular death by Kaplan-Meier estimation was significantly higher in subjects in the lowest tertile of plasma esRAGE than those in the middle or the highest tertile both in all and nondiabetic subjects alone. In all subjects, as compared with the lowest tertile of plasma esRAGE, the hazards ratios for the highest and middle tertile were 0.40 (95% CI, 0.18 to 0.89) and 0.26 (0.10 to 0.66), respectively. The higher risk for lower esRAGE was still significant even after adjusted either with body mass index, hypertension, dyslipidemia and vascular complications, but was confounded by age and diabetes. Conclusions—Low circulating esRAGE is a predictor for cardiovascular mortality in ESRD patients.

Different risk factors for peripheral vascular calcification between diabetic and non-diabetic haemodialysis patients – importance of glycaemic control

Abstract Aim/hypothesis. Although derangements of calcium and phosphate control have been emphasized as important risk factors for vascular calcification in non-diabetic haemodialysis patients, similar risk factors for diabetic haemodialysis patients are not known. We compared factors affecting peripheral vascular calcification between haemodialysis patients with and without diabetes. Methods. We examined 421 patients on maintenance haemodialysis. There were 89 patients with Type II (non-insulin-dependent) diabetes mellitus (53 men and 36 women, 62±10 years old) and 332 patients without diabetes (192 men and 140 women, 59±13 years old). Hand roentgenography was carried out, and visible vascular calcification of the hand arteries was evaluated. Results. There were 42 diabetic patients and 45 non-diabetic patients with vascular calcification. The prevalence of vascular calcification in diabetic patients (47.1%) was higher than in non-diabetic patients (13.6%) (p<0.001). In multivariate logistic regression, the main factors affecting vascular calcification in non-diabetic patients were advanced age, longer duration of haemodialysis, increased phosphate concentrations, male gender, and lower predialysis diastolic pressure. In diabetic patients, predictors for vascular calcification were higher values of HbA1C and longer duration of haemodialysis. In diabetic patients, a 1% increase in HbA1C increased the risk of calcification by 2.1-fold (95% CI 1.282–3.575, p=0.0029). Conclusion/interpretation. We have shown that poor glycaemic control, rather than calcium and phosphate concentrations, is a predictor of peripheral vascular calcification in diabetic patients on haemodialysis. This study emphasizes that glycaemic control remains critical even in diabetic patients with end-stage renal disease.

Renal function and insulin resistance as determinants of plasma leptin levels in patients with NIDDM.

Summary Plasma leptin level is known to correlate with the degree of obesity. To determine the influences of renal fuction and insulin resistance on plasma leptin concentrations, we measured plasma leptin concentrations and performed the euglycaemic hyperinsulinaemic clamp studies in 57 patients with non-insulin-dependent diabetes mellitus with a wide range of renal function. In simple regression analyses, plasma leptin concentration showed significant positive correlations with percentage of body fat measured by dual energy X-ray absorptiometry, body mass index, waist to hip ratio and fasting plasma insulin. Leptin level was higher in females than males. Multiple regression analyses indicated that percent body fat, waist to hip ratio, plasma insulin, gender and renal function (1/creatinine), but not insulin sensitivity, were significant and independent determinants of plasma leptin level. These results suggest that plasma leptin level is regulated or affected by multiple factors including renal function. Insulin resistance appeared to increase leptin levels indirectly by raising plasma insulin. [Diabetologia (1997) 40: 676–679]

Receptor for advanced glycation end products regulates adipocyte hypertrophy and insulin sensitivity in mice: involvement of Toll-like receptor 2.

Receptor for advanced glycation end products (RAGE) has been shown to be involved in adiposity as well as atherosclerosis even in nondiabetic conditions. In this study, we examined mechanisms underlying how RAGE regulates adiposity and insulin sensitivity. RAGE overexpression in 3T3-L1 preadipocytes using adenoviral gene transfer accelerated adipocyte hypertrophy, whereas inhibitions of RAGE by small interfering RNA significantly decrease adipocyte hypertrophy. Furthermore, double knockdown of high mobility group box-1 and S100b, both of which are RAGE ligands endogenously expressed in 3T3-L1 cells, also canceled RAGE-medicated adipocyte hypertrophy, implicating a fundamental role of ligands–RAGE ligation. Adipocyte hypertrophy induced by RAGE overexpression is associated with suppression of glucose transporter type 4 and adiponectin mRNA expression, attenuated insulin-stimulated glucose uptake, and insulin-stimulated signaling. Toll-like receptor (Tlr)2 mRNA, but not Tlr4 mRNA, is rapidly upregulated by RAGE overexpression, and inhibition of Tlr2 almost completely abrogates RAGE-mediated adipocyte hypertrophy. Finally, RAGE−/− mice exhibited significantly less body weight, epididymal fat weight, epididymal adipocyte size, higher serum adiponectin levels, and higher insulin sensitivity than wild-type mice. RAGE deficiency is associated with early suppression of Tlr2 mRNA expression in adipose tissues. Thus, RAGE appears to be involved in mouse adipocyte hypertrophy and insulin sensitivity, whereas Tlr2 regulation may partly play a role.

Receptor for advanced glycation end-products (RAGE) regulation of adiposity and adiponectin is associated with atherogenesis in apoE-deficient mouse

OBJECTIVE Receptor for advanced glycation end-products (RAGE) has been shown to be involved in cardiovascular diseases. We examined the involvement of RAGE in atherosclerosis under non-diabetic status, and its relation to the effect on adiposity. METHODS Apolipoprotein E (apoE)(-/-)RAGE(+/+) or apoE(-/-)RAGE(-/-) mice were fed with an atherogenic diet or the standard chow diet. Adiposity was determined by weight of epididymal adipose tissue, adipocyte size and serum adiponectin. Aortic atherosclerosis was morphometrically determined. RESULTS ApoE(-/-)RAGE(-/-) mice exhibited significantly less total aortic plaque area than apoE(-/-)RAGE(+/+) mice. Body weight, epididymal fat weight, and epididymal adipocyte size were also significantly less in apoE(-/-)RAGE(-/-) mice than apoE(-/-)RAGE(+/+) mice. Serum adiponectin, but not tumor necrosis factor-alpha, was significantly higher in apoE(-/-)RAGE(-/-) mice than apoE(-/-)RAGE(+/+) mice. Simple regression analysis revealed that the total aortic plaque area was positively associated with epididymal fat weight, epididymal adipocyte size, and negatively with serum adiponectin levels. Multiple regression analyses revealed that RAGE genotype and serum adiponectin were mutually interrelated in determining aortic atherosclerosis. Finally, immunohistochemical and real-time RT-PCR analyses revealed that RAGE was indeed expressed in both adipocytes and endothelial cells in epididymal adipose tissue. CONCLUSION RAGE-mediated regulation of adiposity in non-diabetic status could be attributable to the progression of atherosclerosis.

Advanced glycation end products, carotid atherosclerosis, and circulating endothelial progenitor cells in patients with end-stage renal disease.

Numbers of endothelial progenitor cells (EPCs) have been shown to be decreased in subjects with end-stage renal disease (ESRD), the mechanism of which remained poorly understood. In this study, mutual association among circulating EPC levels, carotid atherosclerosis, serum pentosidine, and skin autofluorescence, a recently established noninvasive measure of advanced glycation end products accumulation, was examined in 212 ESRD subjects undergoing hemodialysis. Numbers of circulating EPCs were measured as CD34+ CD133+ CD45(low) VEGFR2+ cells and progenitor cells as CD34+ CD133+ CD45(low) fraction by flow cytometry. Skin autofluorescence was assessed by the autofluorescence reader; and serum pentosidine, by enzyme-linked immunosorbent assay. Carotid atherosclerosis was determined as intimal-medial thickness (IMT) measured by ultrasound. Circulating EPCs were significantly and inversely correlated with skin autofluorescence in ESRD subjects (R = -0.216, P = .002), but not with serum pentosidine (R = -0.079, P = .25). Circulating EPCs tended to be inversely associated with IMT (R = -0.125, P = .069). Intimal-medial thickness was also tended to be correlated positively with skin autofluorescence (R = 0.133, P = .054) and significantly with serum pentosidine (R = 0.159, P = .019). Stepwise multiple regression analyses reveal that skin autofluorescence, but not serum pentosidine and IMT, was independently associated with low circulating EPCs. Of note, skin autofluorescence was also inversely and independently associated with circulating progenitor cells. Thus, tissue accumulated, but not circulating, advanced glycation end products may be a determinant of a decrease in circulating EPCs in ESRD subjects.

Biochemistry of uridine in plasma.

Uridine is a pyrimidine nucleoside that plays a crucial role in synthesis of RNA, glycogen, and biomembrane. In humans, uridine is present in plasma in considerably higher quantities than other purine and pyrimidine nucleosides, thus it may be utilized for endogenous pyrimidine synthesis. Uridine has a number of biological effects on a variety of organs with or without disease, such as the reproductive organs, central and peripheral nervous systems, and liver. In addition, it is used in clinical situations as a rescue agent to protect against the adverse effects of 5-fluorouracil. Since the biological actions of uridine may be related to its plasma concentration, it is important to examine factors that have effects on that concentration. Factors associated with an increase in plasma concentration of uridine include enhanced ATP consumption, enhanced uridine diphosphate (UDP)-glucose consumption via glycogenesis, inhibited uridine uptake by cells via the nucleoside transport pathway, increased intestinal absorption, and increased 5-phosphribosyl-1-pyrophosphate and urea synthesis. In contrast, factors that decrease the plasma concentration of uridine are associated with accelerated uridine uptake by cells via the nucleoside transport pathway and decreased pyrimidine synthesis.