Kazunari Matsumoto

Glucose tolerance, insulin secretion, and insulin sensitivity in nonobese and obese Japanese subjects.

OBJECTIVE To investigate the relative contributions of insulin secretion and insulin resistance to the development of glucose intolerance in Japanese subjects. RESEARCH DESIGN AND METHODS A cross-sectional study of 756 Japanese subjects (530 nonobese, 226 obese) was performed. A 75-g oral glucose tolerance test (OGTT) was given, and subjects were classified according to the World Health Organization (WHO) criteria (normal glucose tolerance [NGT], impaired glucose tolerance [IGT], and diabetes). Early-phase insulin secretion was assessed by the insulinogenic index (the ratio of the increment of insulin to that of plasma glucose [PG] 30 min after a glucose load [ΔIRI0-30 min/Δ PG0-30 min]). Total insulin secretion was assessed by mean immunoreactive insulin (IRI) during the OGTT, and insulin resistance was assessed by use of the homeostasis model [HOMA(R)]. RESULTS Early-phase insulin secretion was significantly decreased in IGT, compared with patients with NGT, in both the nonobese and obese subjects (0.70 ± 0.05 vs. 0.37 ± 0.03, P < 0.01 and 1.36 ± 0.19 vs. 0.73 ± 0.08, P < 0.01, respectively). However, mean IRI and HOMA(R) in both nonobese and obese subjects with IGT and NGT were not statistically different. Subjects with diabetes showed a significant decline in early-phase and total insulin secretion and a significantly higher level of insulin resistance than did subjects with IGT. When the fasting glucose (FPG) exceeded 100 mg/dl, early-phase insulin decreased progressively. The graphed relationship between FPG and mean IRI did not show an inverted U-shape, and mean IRI decreased progressively when FPG exceeded 100–130 mg/dl. The pattern of changes in insulin secretion and insulin resistance associated with the progression of glucose intolerance was similar in both the nonobese and obese subjects. CONCLUSIONS The worsening from NGT to IGT in Japanese subjects may be associated with a decrease in early-phase insulin secretion in nonobese as well as in obese subjects. Hyperinsulinemia in IGT is not common. We suggest that impaired early-phase insulin secretion may be the initial abnormality in the development of glucose intolerance in Japanese people. Insulin resistance may be a consequence of hyperglycemia and/or obesity.

Significance of Glutathione Depletion and Oxidative Stress in Early Embryogenesis in Glucose-Induced Rat Embryo Culture

Recent studies have demonstrated the protective effects of supplementing free oxygen radical scavenging enzymes against hyperglycemia-induced embryonic malformations. In this study, the glutathione (GSH)-dependent protection system in hyperglycemia-induced embryopathy was investigated. Rat embryos at the early head-fold stage (day 9.5) cultured in 66.7 mmol/l glucose for 48 h showed significant growth retardation and an increase in the frequency of malformations. The concentration of GSH and activity of the rate-limiting GSH-synthesizing enzyme, γ-glutamylcysteine synthetase (γ-GCS), significantly decreased in embryos exposed to hyperglycemia compared with controls (7.9 ± 0.6 vs. 12.5 ± 0.9 nmol/mg protein, P < 0.01 and 13.3 ± 1.9 vs. 22.6 ± 1.1 μU/mg protein, P < 0.01, respectively). Decreased activity of γ-GCS in embryos exposed to hyperglycemia was associated with decreased expression of γ-GCS mRNA levels. However, the activities of superoxide dismutase and glutathione peroxidase did not significantly change in these embryos. Extracellular and intracellular free oxygen radical formations estimated by Lucigenin-dependent chemoluminescence and flow cytometric analysis using 2′,7′-dichlorofluorescein diacetate increased in isolated embryonic cells taken from embryos cultured under hyperglycemia. Supplementation of 2 mmol/l GSH ester into the hyperglycemic culture nearly restored GSH concentration in these embryos (11.9 ± 0.5 vs. 12.5 ± 0.9 nmol/mg protein) and reduced the formation of free oxygen radical species leading to almost complete normalization of growth retardation and embryonic dysmorphogenesis. These results indicate that the GSHdependent protection system has a central role against oxidative stress in embryos cultured under hyperglycemia and that GSH depletion in embryonic cells during the critical periods of organogenesis plays a role in hyperglycemia-induced embryopathy.

Autoantibodies to glutamic acid decarboxylase in patients with IDDM and autoimmune thyroid disease

Autoantibodies to glutamic acid decarboxylase (GAD), previously reported to be the 64,000-Mr (64K) islet cell protein, were measured by a radioimmunoassay using purified pig brain GAD in 29 insulin-dependent diabetes mellitus (IDDM) patients with autoimmune thyroid disease (AITD) and in 29 sex- and disease duration-matched IDDM patients without AITD. Islet cell antibodies (ICAs) and 64K antibodies were also determined. In IDDM patients with short-duration diabetes (<1 year), the prevalence and levels of GAD antibodies were 100% (8 of 8) and 609 ± 166 U (means ± SE), respectively, in IDDM patients with AITD and 81.8% (9 of 11) and 90 ± 51 U, respectively, in patients without AITD. In patients with long-standing IDDM (3–22 years), the prevalence and levels of GAD antibodies were 76.2% (16 of 21) and 193 ± 66 U, respectively, in patients with AITD and 50.0% (9 of 18) and 36 ± 14 U, respectively, in patients without AITD. For up to 6 years after the onset of IDDM, the levels of GAD antibodies in IDDM patients with AITD were significantly higher than in IDDM patients without AITD. A close and significant correlation was found between GAD antibodies and ICA or 64K antibodies in IDDM patients with AITD. Our results demonstrate that high levels of GAD antibodies were present in IDDM patients with AITD. The observed differences in GAD immunoreactivity between IDDM patients with and without AITD might help evaluate the role of GAD antibodies in IDDM.

Effects of voglibose on glycemic excursions, insulin secretion, and insulin sensitivity in non-insulin-treated NIDDM patients

OBJECTIVE To investigate the effects of voglibose, an α-glucosidase inhibitor, on daily glycemic excursions, insulin secretion, and insulin sensitivity in non-insulin-treated NIDDM patients. RESEARCH DESIGN AND METHODS An open prospective study was conducted in 27 NIDDM patients receiving diet therapy alone or treatment with a sulfonylurea drug. Of the study subjects, 14 patients were treated with voglibose; the remaining 13 patients served as the control group. The metabolic parameters were evaluated before treatment and at week 4 of treatment as follows: glycemic excursions by M-value and 1,5-anhydro-D-glucitol (1,5-AG), insulin secretion by area under the curve of daily serum insulin (AUCinsulin), and insulin sensitivity by the K index of the insulin tolerance test (KITT). RESULTS After the study treatment, HbA1c and plasma glucose in the patients who had received voglibose were comparable to those of patients in the control group. M-value was lower in the patients treated with voglibose than in the control subjects (5.7 ± 0.9 vs. 9.8 ± 1.2, P < 0.05). 1,5-AG was higher in the patients treated with voglibose than in the control subjects (12.2 ± 1.0 vs. 8.2 ± 0.7 μg/ml, P < 0.01). A statistically significant decrease in AUCinsuiin occurred after treatment with voglibose (2,223.5 ± 390.6 to 1,546.7 ± 303.4 pmol · l−1 · h, P < 0.05), but no change occurred in the control group (2,364.5 ± 315.4 to 2,464.2 ± 269.3 pmol · l−1 · h, P = 0.60). Insulin sensitivity (KITT) was improved to a statistically significant level in both the patients treated with voglibose and the patients in the control group. KITT in the patients after voglibose treatment was comparable to that of the control group (3.18 ± 0.30 vs. 3.21 ± 0.23%/min, P = 0.94). CONCLUSIONS The results suggest that voglibose lowers the daily glycemic excursions and inhibits overwork of the pancreatic β-cells but has little effect on insulin sensitivity in NIDDM patients.

Serum concentrations of soluble adhesion molecules are related to degree of hyperglycemia and insulin resistance in patients with type 2 diabetes mellitus

To investigate the relationships between serum concentrations of soluble adhesion molecules and hyperglycemia, insulin resistance, or other conventional risk factors in type 2 diabetes, we measured soluble intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), E-selectin (sE-selectin), insulin sensitivity, and conventional risk factors in 150 Japanese type 2 diabetic patients without apparent diabetic macroangiopathy. High serum concentrations of sVCAM-1 and sE-selectin were observed in patients with type 2 diabetes. Serum concentrations of soluble adhesion molecules were not significantly influenced by sex, hypertension, dyslipidemia, or microangiopathy. Spearman correlation showed that sVCAM-1 concentrations correlated significantly with fasting plasma glucose (FPG), fasting C-peptide, and insulin sensitivity [K index of the insulin tolerance test (K(ITT))] (rho=0.19,0.23, and -0.23, respectively). Soluble E-selectin concentrations correlated significantly with body mass index (BMI), FPG, fasting C-peptide, insulin sensitivity, and triglyceride (rho=0.33,0.42,0.26,-0.48, and 0.29, respectively). Multiple regression analysis showed that FPG, fasting C-peptide, and total cholesterol were independent factors that correlated with sVCAM-1 levels. BMI, FPG, and insulin sensitivity were independent factors that correlated with sE-selectin levels. Serum concentrations of sE-selectin significantly increased associated with clustering of conventional risk factors those obesity, hypertension, dyslipidemia, and current smoking (P<0.01). Thus, sVCAM-1 and sE-selectin levels are related to both hyperglycemia and insulin resistance. Soluble E-selectin levels may be related to obesity, hyperglycemia, and insulin resistance and may reflect the presence of a multiple risk factor clustering syndrome.

Sitagliptin Attenuates the Progression of Carotid Intima-Media Thickening in Insulin-Treated Patients With Type 2 Diabetes: The Sitagliptin Preventive Study of Intima-Media Thickness Evaluation (SPIKE): A Randomized Controlled Trial.

OBJECTIVE The effect of additional treatment with oral hypoglycemic agents on the progression of atherosclerosis remains unknown in insulin-treated patients with type 2 diabetes mellitus (T2DM). We assessed the effects of sitagliptin, a dipeptidyl peptidase 4 inhibitor, on carotid intima-media thickness (IMT) in T2DM. RESEARCH DESIGN AND METHODS This prospective, randomized, open-label, blinded end point, multicenter, parallel-group, comparative study included 282 insulin-treated patients with T2DM free of a history of apparent cardiovascular diseases who were recruited at 12 clinical units and randomly allocated to either the sitagliptin group (n = 142) or the control group (n = 140). The primary outcomes were changes in mean and maximum IMT of the common carotid artery measured by echography at the end of a 104-week treatment period. RESULTS Sitagliptin had a more potent glucose-lowering effect compared with the conventional treatment (−0.5 ± 1.0% vs. −0.2 ± 0.9%; P = 0.004), without increasing hypoglycemic episodes or body weight. Changes in the mean and left maximum IMT, but not right maximum IMT, of the common carotid arteries were significantly greater after sitagliptin treatment compared with conventional treatment (−0.029 [SE 0.013] vs. 0.024 [0.013] mm [P = 0.005]; −0.065 [0.027] vs. 0.022 [0.026] mm [P = 0.021]; −0.007 [0.031] vs. 0.027 [0.031] mm [P = 0.45], respectively). Over 104 weeks, sitagliptin, but not conventional treatment, significantly reduced the mean IMT and left maximum IMT of common carotid arteries relative to the baseline. CONCLUSIONS Sitagliptin attenuated the progression of carotid IMT in insulin-treated patients with T2DM free of apparent cardiovascular disease compared with conventional treatment.

Inflammation and insulin resistance are independently related to all-cause of death and cardiovascular events in Japanese patients with type 2 diabetes mellitus.

Insulin resistance (IR)/hyperinsulinemia and low-grade inflammation (high-sensitivity C-reactive protein [hs-CRP]) can predict cardiovascular disease. However, because IR and inflammation (IF) have not been evaluated simultaneously, it is not known whether IR and IF are independently related to cardiovascular disease. Furthermore, the combined effect of IR and IF on the prediction of cardiovascular disease is presently unknown. Thus, we measured insulin sensitivity (K index of the insulin tolerance test; KITT) and hs-CRP in 350 Japanese patients with type 2 diabetes, and followed them for 1-7 years (mean, 4.5 years). During the follow-up, 33 patients died and 53 patients developed non-fatal coronary artery disease or stroke (endpoint). Age, systolic blood pressure, current smoking, past history of cardiovascular disease, KITT, and hs-CRP independently and significantly correlated with endpoint. One-S.D. difference was associated with a significant increase of relative risk in KITT (1.45; 95% CI 1.09-1.91) and hs-CRP (1.30; 1.04-1.67). When patients were subdivided to tertile, the relative risk in the highest tertile of KITT was 1.76 (95% CI 1.01-3.11) and hs-CRP was 2.00 (1.03-3.85) compared with the patients with lowest tertile. The relative risk in the highest tertile of both KITT and hs-CRP was 5.32 (1.18-24.0) compared with the lowest tertile of both values. In conclusion, low-grade IF and IR are independently related to all-cause of death and cardiovascular disease in Japanese patients with type 2 diabetes. Coexistence of low-grade IF and IR amplify this effect.

Does the production of nitric oxide contribute to the early improvement after a single low-density lipoprotein apheresis in patients with peripheral arterial obstructive disease?

Low-density lipoprotein (LDL) adsorption using a dextran sulfate cellulose (DSC) column is commonly performed for extracorporeal removal of LDL in hypercholesterolemic patients with peripheral arterial obstructive disease. We investigated whether the use of heparin or nafamostat mesilate as anticoagulants in a single LDL apheresis produced different clinical effects, or brought about the production of bradykinin and endogenous nitric oxide (NO) in these patients. LDL apheresis was performed in ten patients with peripheral arterial obstructive disease. We measured plasma levels of bradykinin, NO and nitrosylhemoglobin as well as skin temperature. Plasma levels of bradykinin increased 12-fold during LDL apheresis with heparin, but did not increase during LDL apheresis with nafamostat mesilate. LDL adsorption resulted in an immediate rise in skin temperatures (1-2 degrees C) of the lower ischemic legs irrespective of the type of anticoagulant used, and this persisted after the end of LDL apheresis for up to 60 min. There was a progressive and significant increase in plasma NO after the commencement of single LDL apheresis in both groups (heparin group: 64.0 +/- 17.3 micromol/l at baseline, 73.3 +/- 15.2 micromol/l 60 min after apheresis, P<0.005; nafamostat mesilate group: 65.0 +/- 18.8 micromol/l at baseline, 75.5 +/- 17.5 micromol/l 60 min after apheresis, P<0.001). On the other hand, levels of nitrosylhemoglobin increased significantly after 1000 ml of plasma treatment but the level decreased thereafter, although it was significantly higher than baseline 60 min after LDL apheresis. Our results suggest that a single LDL apheresis enhanced peripheral microcirculation, probably as a result of increased production of NO, irrespective of changes in bradykinin release.

Insulin Resistance and Arteriosclerosis Obliterans in Patients With NIDDM

OBJECTIVE To investigate the risk factors for arteriosclerosis obliterans (ASO) in NIDDM, we measured insulin sensitivity and other risk factors including lipoprotein(a) [Lp(a)] in NIDDM patients with and without ASO. RESEARCH DESIGN AND METHODS A case-control study in 100 patients with NIDDM, 35 with and 65 without ASO, was performed. Insulin sensitivity was assessed by the short insulin tolerance tests K index (KITT). Duration of diabetes, a history of smoking, prevalence of hypertension, prevalence of coronary artery disease (CAD), serum C-peptide, 24-h urinary C-peptide, serum lipids, and Lp(a) were compared in the two groups. RESULTS Age, BMI, HbA1c, and fasting plasma glucose were comparable in the two groups. Patients with ASO were significantly more insulin resistant than patients without ASO (KITT 2.16 ± 0.16 vs. 3.00 ± 0.13%/min, P < 0.0001, respectively), had a longer duration of diabetes (10.3 ± 1.2 vs. 7.5 ± 0.8 years, P < 0.05), included a greater number of smokers (68.6 vs. 40.0%, P < 0.01), had a higher prevalence of CAD (60.0 vs. 16.9%, P < 0.01), and had a greater percentage of insulin therapy (48.6 vs. 29.2%, P < 0.05). However, urinary and serum C-peptide levels, serum lipids, and Lp(a) levels were comparable in the two groups. Multiple logistic regression analysis indicated that a history of smoking (odds ratio 3.70, P = 0.011), insulin resistance (odds ratio 3.68, P < 0.001), and an elevated Lp(a) level (odds ratio 1.03, P = 0.020) were independently related to ASO. When patients with CAD were removed from the logistic regression analysis, insulin resistance was most strongly related to ASO (odds ratio 20.9, P < 0.001). CONCLUSIONS Patients with ASO were characterized by a higher prevalence of CAD, a greater percentage of smokers, a greater percentage of insulin therapy, and a higher insulin resistance than were patients without ASO. Insulin resistance, especially, may be the most powerfully related to ASO. Lp(a) may play a minor role in the development of ASO.

Glucose transporter gene expression in rat conceptus during high glucose culture

SummaryWe investigated the expression of glucose transporter genes and protein in embryo and yolk sac during organogenesis and the regulation of glucose transporters during culture in hyperglycaemic media. Erythrocyte-type glucose transporter (GLUT 1) and brain-type glucose transporter (GLUT 3) mRNA were expressed in embryo and yolk sac. The expression of GLUT-1 and GLUT-3 mRNA was abundant on day 9–11 and day 9–10 in the embryo, respectively, and day 9–14 and day 10–11 in the yolk sac, respectively. The levels of GLUT-1 protein in the embryo increased in parallel with the expression of GLUT-1 mRNA during the corresponding period. Immunohistochemical staining of GLUT-1 protein was found principally in the neuroepithelial cells surrounding the neural tube in the embryo on day 10 and appeared in the microvessels surrounding the neural tube after day 12.To test whether the expression of glucose transporter genes and protein was suppressed during hyperglycaemia, conceptuses were cultured in high glucose medium. The abundant expression of GLUT-1 protein was not decreased during culture in high glucose media for 24 h (day 9–10) and was only down-regulated by prolonged exposure to this media for 48 h (day 9–11). We have demonstrated the predominant expression of the high affinity glucose transporter (GLUT 1 and GLUT 3) genes and (GLUT 1) protein in embryo during the early period of organogenesis. The persistently abundant expression of glucose transporter during the critical period of neural tube formation (day 9–10) even in the presence of hyperglycaemia may explain one of the mechanisms of increased glucose flux into the neuroepithelium, which may lead to neural tube defects.