In vivo stimulation of the insulin receptor kinase in human skeletal muscle. Correlation with insulin-stimulated glucose disposal during euglycemic clamp studies.

To assess the relationship between insulin receptor (IR) kinase activity and insulin action in vivo in humans, we measured glucose disposal rates (GDR) during a series of euglycemic clamp studies. Simultaneously, we measured IR kinase activity in IRs extracted from skeletal muscle obtained by needle biopsy at the end of each clamp. By preserving the phosphorylation state of the receptors as it existed in vivo at the time of biopsy, we could correlate GDR and IR kinase in skeletal muscle. Eight nondiabetic, nonobese male subjects underwent studies at insulin infusion rates of 0, 40, 120, and 1,200 mU/m2 per min. Kinase activity, determined with receptors immobilized on insulin agarose beads, was measured at 0.5 microM ATP, with 1 mg/ml histone, followed by SDS-PAGE. Insulin increased GDR approximately sevenfold with a half-maximal effect at approximately 100 microU/ml insulin and a maximal effect by approximately 400 microU/ml. Insulin also increased IR kinase activity; the half-maximal effect occurred at approximately 500-600 microU/ml insulin with a maximal 10-fold stimulation over basal. Within the physiologic range of insulin concentrations, GDR increased linearly with kinase activation (P less than 0.0006); at supraphysiologic insulin levels, this relationship became curvilinear. Half-maximal and maximal insulin-stimulated GDR occurred at approximately 20 and approximately 50% maximal kinase activation, respectively. These results are consistent with a role of the kinase in insulin action in vivo. Furthermore, they demonstrate the presence of a large amount of "spare kinase" for glucose disposal.

Metabolic effects of new oral hypoglycemic agent CS-045 in NIDDM subjects.

OBJECTIVE: To study the metabolic effects of a new oral antidiabetic agent, CS-045, in subjects with non-insulin-dependent diabetes mellitus (NIDDM). RESEARCH DESIGN AND METHODS: Eleven NIDDM subjects (mean age 59 yr and body mass index 32.3) were treated with 400 mg/day CS-045 for 6-12 wk. Patients were hospitalized before and at the end of the drug-treatment period for metabolic studies, including oral glucose tolerance test (OGTT), meal tolerance test (MTT), euglycemic glucose-clamp studies, and lipid analyses. RESULTS: Eight subjects showed a marked clinical response to the drug, whereas 3 were nonresponders. The data were analyzed both for the total group and for the responders. Fasting plasma glucose (FPG) fell from 12.5 +/- 0.7 to 10.7 +/- 1.0 mM in the total group but fell more dramatically from 12.7 +/- 0.5 to 8.3 +/- 0.6 mM in the responder group. The area under the OGTT glucose curve improved by 17% in the total group and by 29% in the responders. The area under the MTT glucose curve improved by 38 and 52%, respectively. MTT levels of insulin, free fatty acids, and glucagon were significantly lower after treatment. Glucose disposal rates during glucose-clamp studies were increased in all subjects after CS-045 treatment. Mean increases were 63% at 120 mU.m-2.min-1 and 41% at 300 mU.m-2.min-1. Basal hepatic glucose production fell by 17% in the total group and by 28% in the responders. CONCLUSIONS: CS-045 improves insulin resistance, reduces insulinemia, lowers hepatic glucose production, and improves both fasting and postprandial glycemia in NIDDM subjects. CS-045 may represent a new therapeutic option for NIDDM.

[123I-Metaiodobenzylguanidine- (MIBG-) scintigraphy: paradoxical positivity in an oncocytic adrenocortical carcinoma]. / 123I-Methyljodbenzylguanidin- (MIBG-) Szintigraphie: Paradoxe Nuklidspeicherung eines onkozytären Nebennierenrindenkarzinoms.

(123)I-metaiodobenzylguanidine (MIBG), a radio-labeled catecholamine analogue, is used for the imaging of pheochromocytoma based on the selective uptake of MIBG by chromaffin tissues. MIBG scintigraphy displays high sensitivity (90%) and specificity (close to 100%). In contrast, the false-positive uptake of MIBG by adrenal cortical carcinoma is rare. Here, we report a metastatic oncocytic adrenal cortical carcinoma with MIBG uptake used for therapeutic purposes.

Apparent cortisone reductase deficiency: a rare cause of hyperandrogenemia and hypercortisolism.

A 55-year-old woman presented with androgenetic alopecia which had started at age 40. Her clinical history revealed that, unlike her younger sister, she was unable to conceive and was diagnosed as being sterile at age 30. At age 45, 21-hydroxylase deficiency (late-onset CAH) was assumed and glucocorticoid treatment suggested, but not initiated. There was slight hirsutism, but no other sign of virilization. Retesting of plasma steroids revealed elevated 17-OH-progesterone and free testosterone. Treatment with prednisone, cyproterone acetate, and spironolactone was started with significant clinical success. Surprisingly, the analyses of urinary steroid metabolites revealed a pattern that did not support the diagnosis of 21-hydroxylase deficiency (pregnanetriolone absent, pregnanediol, 17-OH-pregnanolone and pregnanetriol not increased). Abdominal CT showed bilateral adrenal hyperplasia and masses in both ovaries. Bilateral adnexectomy was performed, and cystic teratomas were diagnosed. Postoperative urinary steroid analyses showed a decreased tetrahydrocortisol/tetrahydrocortisone ratio (values around 0.08 as compared to age- and sex-matched controls with a ratio of about 0.5-0.8). Plasma cortisol appeared to be repeatedly elevated with exogenous sources excluded. Mass spectrometry showed that, while the tetrahydro metabolites were mainly cortisone-derived, the metabolites not reduced in A ring were mostly cortisol derivatives. This constellation clearly indicates cortisone reductase deficiency, a defect of hepatic 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD1). This enzyme catalyzes the oxidation of cortisol to cortisone and the reduction of cortisone to cortisol. In contrast to the corresponding kidney enzyme (11 beta-HSD2), its primary activity is, however, reductive. Although this is only the fifth reported case of that defect, more attention should be paid to this condition in hyperandrogenic women, even if elevated 17-OH-progesterone and testosterone suggest a more frequent cause.