Mutsuko Nagata

Changes in Superoxide Dismutase Activities and Concentrations and Myeloperoxidase Activities in Leukocytes from Patients with Diabetes Mellitus

To investigate whether the two free-radical scavengers, Cu, Zn- and Mn-superoxide dismutase (SOD), are changed in leukocytes of diabetic patients, and the alteration of these enzymes correlates with the diabetic state, we measured the activity and concentration of these enzymes in leukocytes from diabetic patients. Both Cu, Zn-SOD and Mn-SOD activities in neutrophils and lymphocytes were significantly lower in patients with non-insulin-dependent diabetes mellitus than in healthy controls. The concentrations of these enzymes in leukocytes from diabetic patients, however, did not differ from those in controls. Cu, Zn-SOD and Mn-SOD activities in neutrophils inversely correlated with HbA(1c) concentrations. Myeloperoxidase activity in leukocytes was significantly reduced in NIDDM patients. These findings suggest that changes in these enzymes may affect the susceptibility to infection and immunocompetence of patients with diabetes.

Seasonal changes of serum 25-hydroxyvitamin D and intact parathyroid hormone levels in a normal Japanese population

We conducted an observational study in order to assess the prevalence of hypovitaminosis D and its seasonal changes, in the Tokai area (N35.3 E137.0), in 197 normal subjects in Japan. The mean serum 25-hydroxyvitamin D (25-OHD) level measured by direct radioimmunoassay (RIA) was lowest at the end of winter, and highest at the end of summer (15.1 ± 7.1 ng/ml in March; 21.5 ± 5.5 ng/ml in June; 31.6 ± 5.6 ng/ml in September; 23.1 ± 5.3 ng/ml in December; mean ± SD). The prevalence of hypovitaminosis D (<20 ng/ml) was 86.7%, 33.4%, 1.0%, and 26.0% in March, June, September, and December, respectively. Mean plasma intact parathyroid hormone (iPTH) concentration was lowest at the end of summer and highest at the end of winter (28.2 ± 9.3 pg/ml in March; 21.7 ± 7.0 pg/ml in June; 19.8 ± 6.9 pg/ml in September; and 25.7 ± 9.2 pg/ml in December; mean ± SD). Serum 25-OHD was inversely associated with iPTH (coefficient, −0.223; r = 0.251; P < 0.001). Serum 25-OHD levels were higher in men than in women. The serum 25-OHD level was positively associated with age, body weight, and body mass index, but not with body fat content. These results suggest a high prevalence of hypovitaminosis D associated with elevation of iPTH in Japan, in winter, even in a sunny area.

Reduction of activity, but no decrease in concentration, of erythrocyte Cu, Zn-superoxide dismutase by hyperglycaemia in diabetic patients

Cu,Zn‐superoxide dismutase (SOD) activity in erythrocytes is affected by various diseases, including diabetes mellitus (DM). We investigated changes in the Cu,Zn‐SOD activity compared to changes in the Cu,Zn‐SOD concentration in erythrocytes obtained from patients with Type 2 (non‐insulin‐dependent) diabetes mellitus. Cu,Zn‐SOD activity in erythrocytes was significantly lower in Type 2 DM patients than in healthy non‐diabetic subjects. The activity correlated negatively with HbA1c, but not with other indicators of metabolic control, such as fasting blood glucose or plasma cholesterol or triglyceride. However, there was no statistically significant difference in erythrocyte concentration of Cu,Zn‐SOD between diabetic and control samples. Concentration did not correlate with enzymatic activity or HbA1c. These findings indicate that the inactivation of Cu,Zn‐SOD activity in erythrocytes of Type 2 DM patients by hyperglycaemia may be slow, because there is a negative correlation between the enzyme activities and HbA1c levels, but not fasting blood glucose levels. This is consistent with glycosylation of the active site of Cu,Zn‐SOD, without any effect of hyperglycaemia on the concentration of Cu,Zn‐SOD.

Effects of thyroid hormone on the sorbitol pathway in streptozotocin-induced diabetic rats

Sorbitol accumulation plays an important role in diabetic complications involving the kidney, nerves, retina, lens and cardiac muscle. To investigate the influence of thyroid hormone on the sorbitol pathway, we studied the effects of thyroid hormone on polyol metabolism in normal and diabetic rats. Rats were divided into three groups: controls, streptozotocin (STZ)-induced diabetic euthyroid rats (DM) and STZ-induced diabetic hyperthyroid (thyroxine-injected) rats (DM+HT). The sorbitol (Sor) concentrations in the kidney, liver and sciatic nerve (2.53+/-0.74, 0.97+/-0.16 and 24.0+/-5.1 nmol/mg protein, respectively) of the DM rats were significantly higher than those (1.48+/-0.31, 0.58+/-0.13 and 3. 1+/-0.6 nmol/mg protein) of the control rats. The Sor concentrations in the kidney and sciatic nerve of the DM+HT rats (1.26+/-0.29 and 9. 40+/-1.2 nmol/mg protein) were significantly lower than those in the DM rats. These values were reduced in the liver, unchanged in the kidney, and increased in the sciatic nerve from the hyperthyroid rats without diabetes. Thyroid hormone reduced the aldose reductase (AR) activities in the kidney, liver and sciatic nerve of the DM rats, and similarly reduced AR in the kidney and liver, but not in the sciatic nerve, of the non-diabetic rats. The sorbitol dehydrogenase (SDH) activities were decreased by thyroid hormone in the kidney and liver but not the sciatic nerve of DM rats. In the non-diabetic rats, this enzyme activity was decreased in liver, but not in kidney or sciatic nerve. A positive correlation between the Sor concentration and AR activity was observed in the kidney and liver but not in the sciatic nerve from control, DM and DM+HT rats. A negative correlation was observed between the Sor concentration and SDH activities in the same organs. These data suggest that thyroid hormone affects the sorbitol pathway, but the detailed mechanism whereby this hormone reduces the sorbitol content (especially in diabetic rats) remains to be clarified.

Alteration of Endothelin-1 Concentration in STZ-Induced Diabetic Rat Nephropathy

Background: Recently, an endothelin (ET-1) with a potent vasoconstrictive activity and stimulative activity of vascular muscular cell growth was discovered and blood ET-1 levels were higher in diabetic patients than in healthy subjects, suggesting that high ET-1 levels assist development and progression of diabetic microangiography. Methods: We examined renal function, and serum and tissue ET-1 levels in streptozotocin (STZ)-induced diabetic rats treated with a prostaglandin (PG) I2 derivative to investigate the effect of PGI2 in diabetic vascular disturbance. Results: Renal weight, urinary albumin, urinary N-acetyl-β,D-glucosaminidase (NAG) and serum ET-1 levels increased in STZ-induced diabetic rats, and a tendency to increase in renal tissue ET-1 levels was observed. Furthermore, electron-microscopic findings in the kidneys showed mesangial cell proliferation and mesangial matrix expansion which might be caused by diabetic nephropathy. The PGI2 derivative reduced urinary albumin and NAG levels in STZ-induced rats. It was considered, therefore, that the PGI2 derivative is effective in diabetic nephropathy. As the PGI2 derivative also reduced renal tissue ET-1 levels, improvement of diabetic nephropathy partially was considered to result from the reduction of renal tissue ET-1 levels. Conclusion: In STZ-induced rats, increased serum ET-1 levels and a tendency to increase in renal tissue ET-1 levels were associated with increases in urinary albumin and NAG levels, and these levels were decreased by a PGI2 derivative. These findings suggested that increased ET-1 concentrations assist development and progression of diabetic nephropathy, especially diabetic microangiopathy, and the PGI2 derivative may be effective for inhibition of diabetic microangiopathy mediated by reduction of ET-1 concentrations.

Surface expression and release of soluble forms of CD8 and CD23 in CD40- and IL-4-activated mononuclear cells from patients with Graves' disease (GD).

We investigated the effect of T cell‐dependent B cell activation on the surface expression and release of the soluble forms of CD8 and CD23 by peripheral blood mononuclear cells (PBMC) obtained from patients with GD, versus patients with Hashimotos thyroiditis, and normal controls. Incubating the PBMC with anti‐CD40 MoAbs and IL‐4 increased the soluble CD23 levels in cells from all three groups. An increase in the number of CD23+ cells was observed in the PBMC from the patients with GD, but not in PBMC from Hashimotos thyroiditis or controls. Less soluble CD8 was released from anti‐CD40 antibody and IL‐4‐stimulated PBMC obtained from patients with GD relative to those from the controls. In addition, the number of CD8+ cells was significantly reduced in stimulated PBMC from the GD patients relative to those from controls. Incubation of PBMC with anti‐CD40 antibody plus IL‐4 did not affect the proportions of CD4+, CD20+, Fas+CD4+, and Fas+CD8+ cells. The addition of T3 to cultured PBMC from controls did not reproduce the changes in CD23+ and CD8+ cells noted in the samples from GD patients. Thus, T cell‐dependent B cell activation, mediated by a CD40 pathway, may reduce the number of CD8+ cells, causing exacerbation of GD.

Changes in Erythrocyte Sorbitol Concentrations Measured Using an Improved Assay System in Patients With Diabetic Complications and Treated With Aldose Reductase Inhibitor

Gugler E, Tonz O, Zurbriigg RP: Increased risk of diabetes mellitus in beta-thalassemia major due to iron overload. Helv Paediat Ada 34:197-207,1979 5. World Health Organization: Report of WHO Study Group: Prevention of Diabetes Mellitus. Geneva, World Health Org., 1994 (Tech. Rep. Ser., no. 844) 6. National Diabetes Data Group: Classification and diagnosis of diabetes mellitus and other categories of glucose intolerance. Diabetes 28:1039-1057, 1979 7. Holl RW, Wolf A, Thon A, Bemhard M, Buck C, Missel M, Heinze E, von der Hardt H, Teller WM: Insulin resistance with altered secretory kinetics and reduced proinsulin in cystic fibrosis (CF) patients. J Pediatr Gastroenterol Nutr 25:188-193,1997 8. Moran A, Diem R Klein DJ, Levitt MD, Robertson RP: Pancreatic endocrine function in cystic fibrosis. J Pediatr 118:715— 723,1991 9. deLuca F, Arrigo T, diBenedetto A, Tedeschi A, Sferlazzas C, Crisafulli G, diCesare E, Romano G, Magazzu G, Cucinotta D: Four-year follow-up of glucose tolerance and beta-cell function in nondiabetic cystic fibrosis patients. Horm Res 44: 45-50, 1995

Urinary sorbitol measurement and the effect of an aldose reductase inhibitor on its concentration in the diabetic state.

The amounts of sorbitol (SOR) excreted in 24-h urine were determined on two groups, i.e., diabetic and nondiabetic patients, using an improved method in which ion exchange resin column processing was applied, and these levels were compared with SOR levels in whole blood. Urinary SOR concentration was also determined in diabetic and normal rats in the same manner and its relationship to aldose reductase (AR) activity in whole blood was investigated. Changes in SOR levels in urine and whole blood were compared in diabetic rats after administration of an AR inhibitor (ARI). Whole blood SOR levels and urinary SOR excretion were significantly higher in diabetic patients than in nondiabetic patients. The same results were obtained in the animal models. In diabetic rats, the urinary SOR excretion was about five times higher than that in control rats, and the AR activity in whole blood was also significantly higher. The increase in urinary SOR excretion and whole blood SOR levels, as well as AR activity, in blood in the diabetic state was inhibited by ARI administration. The influence of the diabetic state and the efficacy of the ARI were more marked in urinary SOR excretion than in whole blood SOR levels. These data indicate that determinations of urinary SOR excretion and AR activity are easily measurable and of benefit to assessing the diabetic condition.

Thyroglobulin may affect telomerase activity in thyroid follicular cells

Telomerase (TA) activity is known to be present in malignant tumor cells, but not in most somatic differentiated cells. TA shows relatively high activity in thyroid cancer cells, but reports vary. This fact prompted us to elucidate whether cell component inhibitors of TA in the thyroid follicles can modulate its activity. The activity of TA extracted from Hela cells was inhibited by mixing with the supernatant fraction of human thyroid tissue extract. To examine the effect of iodine, thyroid hormones (ℓ-T3 and ℓ-T4) and human thyroglobulin (hTg) contained in the thyroid follicles, ℓ-T3, ℓ-T4 and hTg were added to the TRAP assay system in vitro, using TA from Hela cells. Iodine, ℓ-T3 and ℓ-T4 did not affect TA activity, but hTg inhibited the TA activity in a dose-dependent manner (IC50 of hTg: ca 0.45 μM: inhibiting concentration of hTg was from 0.15 μM to 3.0 μM). The hTg inhibition was not evident in the RT-PCR system, suggesting no effect of hTg on Taq DNA polymerase activity. The hTg inhibition of TA activity was attenuated by dNTP but not significantly by TS primer. These data suggest that hTg contained in thyroid follicular cells of various thyroid diseases may affect the TA activity measured in biopsied thyroid specimens, and that the reduction of the TA activity by hTg may induce slow progression and growth, and low grade malignancy of thyroid cancer, particularly differentiated carcinoma.