Yorihiko Morishita

Congenital generalized lipodystrophy with insulin-resistant diabetes

Hyperglycemia, glucose intolerance, hyperinsulinemia and resistance to exogenous insulin were found in a 10-year-old Japanese boy diagnosed as having congenital generalized lipodystrophy.Studies on insulin receptors of circulating mononuclear leucocytes indicated that insulin-resistant diabetes combined with congenital generalized lipodystrophy may be due to disturbance of insulin binding to membrane receptors. No insulin-binding antibody or antibody that impairs insulin-receptor binding was found.Plasma glucagon showed an exaggerated response to L-arginine before treatment. After treatment with a controlled diet and an oral sulfonylurea (500 mg/day) for 4 weeks, there was improvement in the plasma glucagon response to L-arginine. Improvement in the hyperglycemia, hyperinsulinemia and acanthosis nigricans was also observed.On the other hand, on completion of a 7-day high-fat diet, a marked increase in serum free fatty acids, triglycerides and β-lipoproteins was observed. The total plasma post-heparin lipolytic activity during the high fat diet was within the normal range. However, the level of protamine-inactivated activity was 3 times that of the control.

Platelet glucose-6-phosphatase activity in patients with von Gierke's disease and their parents

The present report describes the results of an assay of platelet glucose-6-phosphatase (G-6-Pase) in patients with von Gierkes disease and their parents. The G-6-Pase activity of the patients was found to be about 10–25% of that of controls, while that of the parents showed an intermediate value between that of the patients and that of the controls, which led to the conclusion that the parents were the heterozygotes of the disease. These results suggest a possible method for the diagnosis of G-6-Pase deficiency as well as for detection of the heterozygotes of the disease by a platelet G-6-Pase assay without making a G-6-Pase assay of liver biopsy materials. As for the separation of platelets, a differential centrifugation was undertaken using Na2 -EDTA as an anticoagulant. In the G-6-Pase assay, universally 14C-labelled glucose 6-phosphate ([U-14C]-G-6-P) was used as a substrate and the enzyme activity was measured by the amount of glucose liberated by the platelet suspension after the reaction. The effect of non-specific phosphatase was estimated by using universally 14C-labelled glucose 1-phosphate ([U-14C] -G -6-P) as substrate. In the diagnosis of von Gierkes disease, as well as the detection of the heterozygotes of the disease by the G-6-Pase assay using platelets as material, the effect of non-specific phosphatase was considered to be negligible.

Functional similarity of yeast and mammalian adenosine 3′,5′-monophosphate-dependent protein kinases*

Summary Although adenosine 3′,5′-monophosphate-dependent protein kinase obtained from Saccharomyces cerevisiae shows different physical and kinetic properties from those isolated from mammalian tissues, the yeast and mammalian enzymes appear to be functionally identical; the enzymes are equally active in the phosphorylation of muscle glycogen phosphorylase kinase and glycogen synthetase, resulting in the activation and inactivation of the respective enzymes.

Glycogen phosphorylase kinase deficiency: A survey of enzymes in phosphorylase activating system

Abstract A four year-old Japanese boy with hepatomegaly and hypoglycemia has low activity of hepatic phosphorylase. A survey of enzymes involved in the phosphorylase activating system has revealed that liver phosphorylase kinase is deficient although adenosine 3′,5′-monophosphate (cyclic AMP)-dependent protein kinase and total phosphorylase measured in a mixture supplemented by rabbit muscle phosphorylase kinase show normal activities. The hormone receptor as well as adenyl cyclase system appears to be normal since cyclic AMP increases immediately after intravenous injection of glucagon. His muscle phosphorylase activating system is normal.

The effect of a high fat diet on pyruvate decarboxylase deficiency without central nervous system involvement

A nine-year-old Japanese boy with low pyruvate decarboxylase activity in fibroblasts showed no central nervous symptoms except for muscle fatigue. The pyruvate decarboxylase activities in fibroblasts of the patient and two control subjects were 0.407 +/- 0.083, 1.029 +/- 0.137 and 1.607 +/- 0.096 mumoles/g protein/30 min, respectively. The Michaelis-Menten constant (Km) was the same in the patient and controls. There was no inhibitor of pyruvate decarboxylase in the patients fibroblasts. A high fat diet has been given to the patient for five years. At present he does not complain of any kind of muscle fatigue, except after severe exercise. Mental and physiological development of the patient are within the normal ranges. However, trials of orally administered thiamine hydrochloride or thiamine hydrochloride combined with lipoamide did not improve his muscle fatigue.

Lymphocyte phosphorylase kinase activities in the sex-linked form of liver phosphorylase kinase deficiency

Lymphocyte phosphorylase kinase activities were measured in normal controls and in patients with the sex-linked form of liver phosphorylase kinase deficiency. The reaction due to phosphorylase kinase activity in normal lymphocytes (2.7×106 in the reaction tube) was found to be linear within 20–60 min at 30° C. The reaction was directly proportional to the concentration of lymphocytes within 1.5×106–9.0×106, at 30° C for 60 min. The phosphorylase kinase activity in normal lymphocytes, which were pre-incubated at 50° C or 95° C for 1 min, decreased to 60% at 50° C and 10% at 95° C of that after pre-incubation at 0° C for 1 min. The activity of normal controls was 125±23.5 U/1010 lymphocytes. Those of the patients with liver phosphorylase kinase deficiency due to the sex-linked form were 43.5 U in case 1, 54.5 U in case 2, and 51.3 U in case 3, respectively and those of the mothers were within the normal range. These results suggest that phosphorylase kinase in lymphocytes might be form intermediate between liver and muscle phosphorylase kinase.