Hisayo Yokoyama

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.

Association of serum fetuin-A with carotid arterial stiffness

Objective   Fetuin‐A is a circulating glycoprotein which is well characterized as an inhibitor of ectopic calcification. Vascular calcification commonly found in chronic kidney disease (CKD) patients is a predictor of cardiovascular death. Recently, several groups have demonstrated that low fetuin‐A levels are associated with mortality in uraemic patients, possibly through regulation of vascular calcification. However, the physiological significance of fetuin‐A in atherosclerosis remains unknown, except in specific conditions, such as vascular calcification in CKD patients. The objective of this study was to investigate the association between serum fetuin‐A levels and arterial stiffness, a functional property of atherosclerosis, in healthy subjects.

Effects of pioglitazone on serum fetuin-A levels in patients with type 2 diabetes mellitus

Fetuin-A (alpha2-Heremans-Schmid glycoprotein), a circulating glycoprotein, can inhibit insulin signaling both in vivo and in vitro. Recently, we and another independent group have shown that fetuin-A is positively associated with insulin resistance in humans. Furthermore, it has been reported that higher fetuin-A levels are associated with metabolic syndrome and atherogenic lipid profiles. These data suggest that fetuin-A might be a regulator of insulin resistance and/or metabolic syndrome. However, it is not clear how fetuin-A levels are regulated. To address this, we investigated the effects of representative insulin-sensitizing therapies such as pioglitazone, metformin, and aerobic exercise on fetuin-A levels. Twenty-seven patients with type 2 diabetes mellitus were divided into pioglitazone-treated (Pio), metformin-treated (Met), and exercise-treated (Ex) groups. Ten patients in the Pio group and 9 patients in the Met group took 15 or 30 mg/d pioglitazone or 500 or 750 mg/d metformin, respectively, for 6 months. Eight patients in the Ex group underwent a 3-month aerobic exercise program. Serum fetuin-A levels were measured before and after each intervention. Intervention significantly decreased hemoglobin A(1c) in all groups. After treatment, serum fetuin-A levels significantly decreased in the Pio group (291.2 +/- 57.7 to 253.1 +/- 43.9 microg/mL, P = .006), whereas there were no changes in serum fetuin-A after intervention in either the Met or the Ex groups. We hypothesize that pioglitazone could partially ameliorate insulin resistance via modulating fetuin-A levels.

Glimepiride increases high-density lipoprotein cholesterol via increasing adiponectin levels in type 2 diabetes mellitus

The aims of the present study are to investigate the effect of glimepiride 1 mg/d on plasma adiponectin and to assess the contribution of adiponectin in changing high-density lipoprotein cholesterol (HDL-c) levels after glimepiride treatment. Forty patients with type 2 diabetes mellitus were included. Plasma adiponectin, fasting plasma glucose, insulin, hemoglobin A(1c), and cholesterol were measured at study entry and after 3 months of treatment with glimepiride. Both plasma adiponectin level (7.5 +/- 4.5 vs 8.3 +/- 4.5 microg/mL, P = .040) and HDL-c level increased significantly (50 +/- 11 vs 53 +/- 10 mg/dL, P = .041) in the all-subjects group. In the low-adiponectin group (initial plasma adiponectin level <6 microg/mL), both plasma adiponectin level (4.5 +/- 0.9 vs 5.9 +/- 2.0 microg/mL, P = .004) and HDL-c level increased significantly (44 +/- 8 vs 49 +/- 9 mg/dL, P = .011). There was no significant change in the high-adiponectin group (initial plasma adiponectin level >or=6 microg/mL). Change in plasma adiponectin level was an independent factor for change in HDL-c level after adjustment for other factors (beta = .574, P = .009, R(2) = 0.524, P = .036). In conclusion, glimepiride improved plasma adiponectin level, especially in the subjects with type 2 diabetes mellitus with low adiponectin level before treatment, and may directly contribute to improving HDL-c level.

Insulin allergy; desensitization with crystalline zinc-insulin and steroid tapering

The insulin analogues, aspart and lispro, have been considered safe alternatives for patients with insulin allergy, because of their decreased immunogenicity. However, recent several reports showed that neither of them was completely free from allergic reactions. We also experienced a patient with insulin allergy not only to human regular insulin but also to both of the insulin analogues. Interestingly, the insulin analogues, which readily dissociate from polymer to monomer, induced the most severe allergic reaction among several types of human insulin reagents in the present case. Allergy to crystalline zinc-insulin, the three-dimensional structure of which results in delayed dissociation and absorption, was negative on intradermal tests. However, its large subcutaneous injection caused local allergic reaction. These results suggested that the allergic reaction might depend on the rapidity of insulin monomerization and absorption, and thus that the immunogenic residue of insulin is concealed when insulin is polymerized. Based on the intradermal tests, we speculated that the antigenic epitope might be B30-Thr in the present case. We also report here the modified method of insulin desensitization using crystalline zinc-insulin with prednisolone tapering. This might be a simple and useful treatment for insulin allergy.

Significance of intima-media thickness in femoral artery in the determination of calcaneus osteo-sono index but not of lumbar spine bone mass in healthy Japanese people

The aim of this cross-sectional study was to investigate whether physical activity and local arterial thickening may affect bone metabolism. To analyze the effects of physical activity and atherosclerosis on bone in healthy Japanese people, health-related quality of life (HRQL) and local arterial thickening were assessed by means of the MedicalOutcomes Study 36-item Short Form (SF-36), and intimal-medial thickness (IMT) in common carotid artery (CA) and femoral artery (FA), respectively. Bone mineral density (BMD) in lumbar spine was measured by dual X-ray absorptiometry and the osteo-sono assessment index (OSI) of the calcaneus by ultrasound. Healthy subjects (106 male and 154 female) were recruited from those who participated in a local health check program at the Osaka City University Hospital. A significant correlation existed between lumbar spine BMD and calcaneus OSI (r=0.551, P<0.0001). Among various scores in SF-36, only physical functioning score correlated weakly but significantly in a positive manner with lumbar spine BMD (ρ=0.156, P=0.0147) and calcaneus OSI (ρ=0.190, P=0.0024). Lumbar spine BMD correlated negatively with FA IMT (ρ=−0.191, P=0.0027) whereas calcaneus OSI with FA IMT (ρ=−0.199, P=0.0014). Multiple regression analyses revealed a significant association between FA IMT and calcaneus OSI, whereas lumbar spine BMD did not correlate significantly with FA or CA IMT. When subjects were restricted to female, FA IMT, but not CA IMT, still showed tendency against independent factors negatively associated with calcaneus OSI. Furthermore, lumbar spine BMD, but not calcaneus OSI, was weakly but significantly associated with increased physical functioning score independently. In conclusion, it was suggested that physical activity may affect bone strength in lumbar spine and calcaneus and that FA IMT might be a significant determinant of bone strength in calcaneus, but not in lumbar spine, in healthy Japanese subjects.

Non‐oxidative glucose disposal is reduced in type 2 diabetes, but can be restored by aerobic exercise

Whole‐body glucose utilization consists of mitochondrial glucose oxidation and non‐oxidative glycogen synthesis. We examined whether reduction of both non‐oxidative glucose disposal and glucose oxidation contributes to insulin resistance in type 2 diabetes. We also examined the effects of exercise on these two components. Whole‐body glucose disposal rate (GDR, mg/kg/min) was evaluated in 37 type 2 diabetic (T2DM) and 17 non‐diabetic (non‐DM) subjects as the mean of glucose infusion rate during steady state in the euglycaemic–hyperinsulinaemic clamp study. Glucose oxidation rates were assessed by indirect calorimetry, and non‐oxidative GDR was calculated by subtracting glucose oxidation rate from GDR. Intramyocellular lipid (IMCL) content of the soleus muscle was measured using 1H‐magnetic resonance spectroscopy. In 10 T2DM subjects, the changes in oxidative and non‐oxidative glucose disposal during clamp were examined after 3‐month exercise intervention. GDR (2.93 ± 1.55 vs. 4.55 ± 1.83, p = 0.001) and non‐oxidative GDR (1.45 ± 1.52 vs. 3.01 ± 1.87, p = 0.002) were significantly lower in T2DM than in non‐DM subjects. Glucose oxidation rate was comparable in the two groups, and inversely correlated with IMCL (n = 15, r =−0.565, p = 0.028). GDR (2.28 ± 1.67 to 4.63 ± 2.42, p = 0.021) and non‐oxidative GDR (0.72 ± 1.27 to 2.26 ± 1.91, p = 0.047) were increased after exercise intervention, although the change in glucose oxidation rate was not significant. In summary, reduction of non‐oxidative glucose disposal may contribute to decreased whole‐body glucose utilization. In addition, exercise improves insulin resistance mainly by increasing non‐oxidative glucose disposal in type 2 diabetes.

Thermoregulatory responses are attenuated after fructose but not glucose intake.

PURPOSE We examined whether plasma hyperosmolality induced by oral monosaccharide intake attenuated thermoregulatory responses and whether the responses were different between fructose and glucose. METHODS Ten healthy young subjects performed three trials in a sitting position in an artificial climate chamber (ambient temperature, 28°C; relative humidity, 40%). After resting for 10 min, the subjects drank 300 mL of water alone (control), or 300 mL of water supplemented with 75 g fructose or 75 g glucose. Twenty minutes later, they were heated passively by immersing the lower legs in water at 42°C for 60 min. Plasma osmolality (Posm), sodium ([Na+]p) and insulin concentrations ([Ins]p), and percent change in plasma volume (%ΔPV) were measured, and esophageal temperature (Tes) thresholds for cutaneous vasodilation (THCVC) and sweating (THSR) at the forearm were determined. RESULTS Posm was significantly increased by fructose and glucose intake compared with water alone, although %ΔPV and [Na+]p were not significantly different among the three trials. [Ins]p was significantly higher after glucose intake than after fructose or water alone. THCVC and THSR were significantly higher after fructose intake than after glucose intake, which showed similar values to water intake. CONCLUSIONS These results suggest that the Tes threshold for thermoregulation is elevated after fructose intake, indicating the attenuation of thermoregulatory responses, whereas it is not attenuated after glucose intake. These results provide a novel insight to better determine the carbohydrate component of oral rehydration fluids for preventing dehydration and/or heat disorders.

Evaluation of Insulin Resistance in Diabetes: Standard Protocol for a Euglycemic-Hyperinsulinemic Clamp Using an Artificial Pancreas

Insulin resistance plays a pivotal pathognomonic role in various pathophysiological states, including diabetes, obesity, and metabolic syndromes. A euglycemic-hyperinsulinemic (EH) clamp, the gold-standard method for evaluating insulin resistance in humans, has been performed according to the original protocol for each hospital or institute, which makes it difficult to compare the findings of different studies. We have established a standard protocol for the EH clamp using an artificial pancreas (AP, models STG-22 and STG-55, Nikkiso Co. Ltd. Tokyo), which has been widely used in Japan since 1987. Among the 351 Japanese subjects, 301 were type 2 diabetics, 12 were impaired glucose tolerance with obesity, and 38 had normal glucose tolerance. In this chapter, the standard protocol using the AP and the insulin resistance data are described in detail. By using an AP for the clamp, stable steady-state euglycemia and glucose infusion rates (GIR, metabolizable glucose [M] value) were achieved with high precision. The insulin resistance index, M/I, in type 2 diabetics was approximately 49 % lower than in patients with normal glucose tolerance and had a strong inverse correlation with body mass index. Furthermore, the validity and clinical implications of insulin resistance were clarified and reported according to the standard protocol for an EH clamp using an AP. In conclusion, a standard protocol for using an AP for an EH clamp would allow us to evaluate insulin resistance in detail and with high precision in various pathological states/diseases.