Michiyo Seno

Erythrocyte Sodium-Lithium Countertransport Activity as a Marker of Predisposition to Hypertension and Diabetic Nephropathy in NIDDM

OBJECTIVE To evaluate the potentiality of erythrocyte sodium-lithium countertransport activity (SLC) as a marker of predisposition to hypertension and diabetic nephropathy in non-insulin-dependent diabetes mellitus (NIDDM). RESEARCH DESIGN AND METHODS We examined 96 patients with NIDDM and 26 healthy control subjects. SLC and other data were compared among subgroups of the patients classified on the basis of hypertension, family history of hypertension, and stages of nephropathy. Data were also analyzed by stepwise multiple regression analyses. RESULTS SLC was significantly higher in patients with hypertension than in those with normotension and significantly higher in patients with a positive family history of hypertension than in the negative group. Further analysis revealed that a family history of hypertension has independent influence on SLC, but hypertension itself does not. SLC was significantly higher in patients with macroalbuminuria than with microalbuminuria and higher in patients with microalbuminuria than with nor-moalbuminuria. In stepwise multiple regression analyses, a family history of hypertension was the most important determinant of SLC, and SLC was the most important determinant of nephropathy. CONCLUSIONS These data suggest that SLC strongly reflects a predisposition to hypertension and that it can be a useful marker of diabetic nephropathy in NIDDM.

Elevated erythrocyte sodium-lithium countertransport activity correlates with increased intracellular sodium and free calcium-ion concentration in type 2 diabetes.

To explore the mechanism by which elevated sodium–lithium countertransport activity (SLC) associates with both predisposition to hypertension and diabetic nephropathy, we investigated the interrelationships among SLC, intracellular sodium concentration ([Na]i), intracellular free calcium‐ion concentration ([Ca2+]i), diabetic nephropathy, hypertension, family history of hypertension, and other factors in 48 patients with Type 2 diabetes and 24 healthy controls. There was a significant correlation between SLC and [Na]i (r = 0.36, p < 0.05), [Na]i and [Ca2+]i (r = 0.47, p < 0.01), SLC and [Ca2+]i (r = 0.46, p < 0.01), and between HbA1c and [Ca2+]i (r = 0.38, p < 0.01). Both [Na]i and [Ca2+]i were significantly higher in the patients with elevated SLC than in those with normal SLC (p < 0.01 and p < 0.05, respectively). In stepwise multivariate regression analysis, [Na]i, HbA1c, and SLC appeared as independent determinants of [Ca2+]i. These data suggest a significant correlation of elevated SLC with increased [Na]i and [Ca2+]i. This may be a possible mechanism underlying the close association of elevated SLC with both predisposition to hypertension and diabetic nephropathy.

Effects of naloxone on basal and vagus nerve-induced secretions of GRP, gastrin, and somatostatin from the isolated perfused rat stomach

The effects of naloxone, an opiate antagonist, on basal and vagus nerve-induced secretions of GRP, gastrin, and somatostatin were examined using the isolated perfused rat stomach prepared with vagal innervation. Naloxone (10(-6) M) significantly inhibited basal somatostatin secretion in the presence and absence of atropine and of hexamethonium, whereas basal GRP and gastrin secretion was not affected by naloxone. Electrical stimulation (10 Hz, lms duration, 10V) of the distal end of the subdiaphragmatic vagal trunks elicited a significant increase in both GRP and gastrin but a decrease in somatostatin. Naloxone (10(-6) M) failed to affect these responses in the presence or absence of atropine. On the other hand, when hexamethonium was infused, naloxone significantly inhibited both the GRP and gastrin responses to electrical vagal stimulation. Somatostatin secretion was unchanged by vagal stimulation during the infusion of hexamethonium with or without naloxone. These findings suggest that basal somatostatin secretion is under the control of an opiate neuron and that opioid peptides might be involved in vagal regulation of GRP and gastrin secretion.

Comparative effect of somatostatin-14 and somatostatin-28 on glucagon-induced glycogenolysis from the perfused rat liver

The effect of somatostatin (SS)-14 and SS-28 on glycogenolysis was studied, using a rat liver perfusion technique. Livers from nonfasted rats were perfused with 5.5 mmol/L glucose or perfusate without the glucose addition. Glucagon-induced glucose output was lower in the presence of 5.5 mmol/L glucose than in glucose free perfusate at every concentration of glucagon. Under glucose free conditions, SS-14 given at five minutes prior to the glucagon addition reduced the glucagon-induced glucose output dose-dependently. SS-14 given 15 minutes after glucagon addition also inhibited glucagon-induced glucose output significantly. However, various concentrations of SS-28 failed to affect glucose output. On the other hand, in the presence of 5.5 mmol/L glucose, neither SS-14 nor SS-28 affected glucagon-induced glucose output. It is suggested, therefore, that glycogenolysis induced by glucagon from the liver is reduced by SS-14, but not by SS-28, only under glucose free conditions.

Effect of DG5128 on epinephrine and glucagon induced glucose output from the isolated perfused rat liver

The effect of a specific alpha 2-adrenergic antagonist 2-[2-(4,5-dihydro-1.H-imidazol-2-yl)-1-phenyl-ethyl] pyridine dihydrochloride sesquihydrate (DG5128), on the glucose output by epinephrine and/or glucagon was studied using the perfused rat liver. The administration of DG5128 alone did not affect the glucose output. However, DG5128 produced a significant inhibition of the increased glucose output when induced by 10(-6) M epinephrine alone or 10(-6) M epinephrine plus 1.4 x 10(-10) M glucagon. There were no significant changes of the glucose output by 1.4 x 10(-10) M or 7.0 x 10(-11) M glucagon alone. On the other hand, addition of 1 mU/ml insulin to the perfusate suppressed the 7.0 x 10(-11) M glucagon-induced glucose output, but failed to decrease the 1.4 x 10(-10) M glucagon effect. DG5128 suppressed further the glucagon (7.0 x 10(-11) M)-induced increase of glucose output in the presence of insulin. These results suggest that DG5128 produces a hypoglycemic effect partly through an inhibition of the increased hepatic glucose output elicited by epinephrine and glucagon.

Effect of antithyroid autoantibodies on pancreatic islet-cell function

SummaryInsulin-dependent diabetes mellitus is frequently associated with organ-specific autoimmune diseases and/or high titers of organ-specific autoantibodies. The effects of thyroid autoantibodies on islet-cell function were examined in the present study. Islet cell surface antibody (ICSAb) was detected in sera from 6 of 40 patients with autoimmune thyroid disease (AITD) who were positive for thyroid microsomal autoantibodies (TMA). Furthermore, all of the ICSAb-positive patients had high TMA titers.In vitro study using isolated rat pancreatic islets revealed that TMA positive sera significantly suppressed glucose-induced insulin release. Only one of 19 (5%) AITD patients showed complement-dependent antibody-mediated cytotoxicity and only one of 6 AITD patients (17%) was positive for antibody-dependent cellular cytotoxicity. These results suggest that TMA has an effect on an antigen of the islet cell membrane in which insulin releasing mechanism might be involved.

Detection of Antibodies against Wheat Germ Agglutinin Bound Glycoproteins on the Islet-cell Membrane

An attempt was made to detect islet cell surface antibodies (ICSAb) using solubilized islet‐cell glycoproteins as antigens. Isolated rat islets were labelled with 125l‐wheat germ agglutinin (WGA) and solubilized by Nonidet P‐40 with sonication. 125l‐WGA‐bound islet‐cell proteins were incubated with test sera, and bound antibodies were precipitated with anti‐human IgG or IgM immunobeads. Serum which had a bound percent beyond the mean plus 2SD of control sera was defined as antibody‐positive. Results obtained by this method correlated well with those by the immunofluorescence method of detecting ICSAb. Prevalences of antibodies were 21/114 (18%) for IgG antibodies and 9/114 (8%) for IgM antibodies in patients with insulin‐dependent diabetes mellitus (IDDM). The prevalence was highest for both IgG and IgM antibodies in patients within a year of the onset of disease (38 and 25%, respectively), and decreased thereafter. The prevalence of IgM antibodies was lower than that of IgG antibodies at all stages. In NIDDM patients, the prevalence of antibodies was 5/72 (7%) for both IgG and IgM antibodies. If these preliminary results are confirmed, this radioassay may be developed to detect antibodies against islet cell membrane proteins on a large scale.