Showing papers in "Hormone and Metabolic Research in 1998"

Aerobic endurance exercise or circuit-type resistance training for individuals with impaired glucose tolerance?

Abstract: The role of physical activity in the prevention of non-insulin-dependent diabetes mellitus (NIDDM) is of utmost importance. The aim of the present study was to evaluate the metabolic effects of aerobic endurance exercise and circuit-type resistance training in subjects with impaired glucose tolerance (IGT). Twenty-two individuals participated in the study. Fourteen subjects were enrolled in the aerobic endurance exercise part of the study; seven exercised regularly for six months, while seven served as controls. Maximal aerobic capacity (VO2max) was measured and insulin sensitivity and insulin secretion were assessed by a frequently sampled intravenous glucose tolerance test (FSIVGTT). Eight subjects participated in a circuit-type resistance training program for three months. Insulin sensitivity and substrate oxidation were then assessed using the euglycemic insulin clamp technique combined with indirect calorimetry. The aerobic endurance exercise program caused in increase in VO2max (21.6 +/- 1.9 to 25.4 +/- 2.4 ml/kg.min; p < 0.05) and HDL-cholesterol (1.14 +/- 0.06 to 1.23 +/- 0.08 mmol/l; p < 0.05), but no change in insulin sensitivity nor insulin secretion occurred. However, comparing the changes between the intervention and control group, the differences disappeared. Circuit-type resistance training increased insulin sensitivity (glucose disposal) by 23% (p < 0.05), primarily due to a 27% increase in non-oxidative glucose metabolism. Both circuit-type resistance training and aerobic endurance exercise seem to have beneficial effects in subjects with impaired glucose tolerance. However, by improving insulin sensitivity, circuit-type resistance training may postpone the manifestations of NIDDM in these high-risk individuals and should therefore be included in an exercise program for IGT subjects.

Hyperglycemia-induced circulating ICAM-1 increase in diabetes mellitus: the possible role of oxidative stress.

Abstract: ICAM-1 is one of the most important intercellular adhesion molecules involved in atherogenesis. Previous studies reported increased circulating ICAM-1 plasma levels in NIDDM patients with or without vascular complications. It has been suggested that an acute increase of plasma glucose may produce an oxidative stress in man, and in vitro studies have demonstrated that high glucose and free radicals induce cellular expression of ICAM-1. In this study, three different experiments were performed in nine NIDDM patients and in seven matched healthy controls: oral glucose tolerance test, antioxidant glutathione i.v. administration for two h, oral glucose tolerance test plus glutathione i.v. administration. Blood samples were drawn at -15 min and every 30 min from 0 to 180 min. During the oral glucose tolerance test, circulating ICAM-1 plasma levels significantly increased in both diabetic and normal subjects. Glutathione administration during the oral glucose tolerance test abolished this phenomenon. Glutathione administered alone significantly decreased circulating ICAM-1 plasma levels in diabetic patients, while no effect was observed in the normal subjects. These data suggest that hyperglycemia may induce an increase of circulating ICAM-1 plasma levels through an oxidative stress, and that the antioxidant glutathione counterbalances this effect. These data support the hypothesis of a causal relationship linking hyperglycemia, oxidative stress and atherogenesis in diabetes mellitus.

Influence of paroxetine, branched-chain amino acids and tyrosine on neuroendocrine system responses and fatigue in humans.

Abstract: Effects of a serotonin re-uptake inhibitor and oral amino acid supplementations on physical and mental performance as well as neuroendocrine variables were investigated. 10 male subjects cycled in four trials until exhaustion. Participants ingested a placebo in trial (T) I, 20 mg paroxetine in T II, 21 g branched-chain amino acids (BCAA) in T III and 20g tyrosine (TYR) in T IV. Heart rate, capillary lactate, plasma insulin, free fatty acids, glucose, serotonin and beta-endorphin did not differ in trials. Plasma ammonia increments during exercise were higher in T III. Plasma BCAA in T III and plasma TYR in T IV were increased after 30 min of exercise according to the supplemented substances. In contrast to all other trials, the ratio of plasma free TRP/BCAA did not increase in T III. Plasma TYR/BCAA was augmented in T IV and decreased in T III after 30 min of exercise, whereas it did not change in T I and II. Plasma prolactin (PRL), growth hormone, cortisol, adrenocorticotropic hormone, norepinephrine and epinephrine increased during all trials. Plasma PRL increments were higher in T IV. Exhaustion was reached earlier in T II. No significant differences were found between other trials. Drive during psychometric testing subsequent to exercise was improved in T III and IV. The results indicate that fatigue during endurance exercise was increased by pharmacological augmentation of the brain serotonergic activity. However, a reduction of 5-HT synthesis via BCAA supplementation did not affect physical fatigue. TYR administration did not alter physical performance either although plasma PRL increments suggest that changes in the monoaminergic system were induced. Precaution is necessary before assuming an ergogenic value of amino acids.

Clinical and genetic analysis of primary bilateral adrenal diseases (micro- and macronodular disease) leading to Cushing syndrome.

Abstract: Primary bilateral adrenocortical diseases are rare entities that have recently been appreciated as potential causes of Cushing syndrome. They include (i) primary pigmented adrenocortical disease (PPNAD), also known as "micronodular adrenal disease", which is a genetic disorder that is often associated with Carney complex, and (ii) massive macronodular adrenocortical disease (MMAD), a rare disorder of unknown etiology that affects older adults. Carney complex is a multiple endocrine neoplasia (MEN) syndrome that affects not only the adrenal cortex, but also the pituitary, thyroid, and gonads. It is associated with pigmentation abnormalities as well as myxomas and other mesenchymal and neural crest neoplasms. The inheritance of the complex is autosomal dominant, and genetic mapping has shown that at least two loci are involved in its pathogenesis. MMAD appears to be an isolated finding in most cases, and a genetic defect has not yet been defined. Ectopic expression of hormone receptors has been implicated in several cases of MMAD, but an underlying deficit has not been detected. Bilateral adrenocortical hyperplasia has also been described in McCune-Albright syndrome and MEN type-1, but this finding is not always associated with hypercortisolism. The genetic defects for these diseases are known, but their role in adrenal cortex pathophysiology has not been fully elucidated. Identification of the molecular defects responsible for bilateral adrenocortical disorders is expected to shed light on many aspects of early adrenal gland differentiation and tumorigenesis.

Leptin and interleukin-6 in sepsis.

Abstract: Both leptin and interleukin-6 (IL-6) are hypersecreted in acute critical illness, such as sepsis. Leptin is produced by adipocytes, it inhibits appetite and stimulates the sympathetic nervous system, thereby reducing adipose mass. IL-6 is produced by immune cells and adipocytes, it reduces the production of other inflammatory cytokines and stimulates release of acute phase proteins by the liver, participating in the control of inflammation. Leptin inhibits, whereas IL-6 stimulates, the hypothalamic-pituitary-adrenal axis. While high IL-6 levels are associated with poor outcome in critically ill patients, the role of leptin in critical illness and its importance for survival are not known. To examine the relation between IL-6, leptin and cortisol in critical illness, we performed frequent 4 h plasma sampling in eight patients on day 1 of intensive care unit admission for acute sepsis. Sampling was repeated on days 3 and 5 in the five survivors. The levels of all three hormones were markedly elevated; there was a lack of the normal diurnal rhythmicity of leptin and IL-6 and a blunted diurnal rhythmicity of cortisol secretion. A strong negative correlation between mean 24 h plasma IL-6 and leptin was revealed. Although such a relationship could possibly be explained by the negative and positive effects of cortisol hypersecretion on each hormone respectively, a negative correlation between leptin and cortisol was detected, whereas there was no significant correlation between IL-6 and cortisol. Mean IL-6 values were higher (1389.5+/-644.9 vs. 658.8+/-250.5) and leptin levels were lower (2.73+/-1.1 vs. 26.5+/-11.6) in the non-survivors than in the survivors. These findings suggest that IL-6 is not the principal stimulus of leptin hypersecretion in critically ill patients with sepsis. The negative relation between IL-6 and leptin is of potential importance, as high IL-6 levels have been associated with poor outcome in critically ill patients, and relatively low leptin levels may impair sympathetic system and immune functions.

Allopregnanolone in women with premenstrual syndrome.

Abstract: 5Alpha-reduced metabolites of progesterone, especially 3alpha-hydroxy-5alpha-pregnan-20-one (allopregnanolone) are now listed to neurosteroids. Their anesthetic properties can be explained by their allosteric interaction with GABA(A) receptors. A woman's organism is provided with an abundance of progesterone during the luteal phase of the menstrual cycle and its level falls down sharply with the first day of menses. The level of allopregnanolone follows that of progesterone. Many women suffer from so called premenstrual syndrome (PMS) during the luteal phase. In this study we have determined allopregnanolone and progesterone levels and their ratios in order to assess the over-all activity of C21-steroid 5alpha-reductase in these patients and in controls. Significantly lower levels of both progesterone and allopregnanolone than in controls have been found in PMS patients in the follicular phase only.

The long acting human insulin analog HOE 901: characteristics of insulin signalling in comparison to Asp(B10) and regular insulin.

Abstract: HOE 901 is a new biosynthetic long-acting human insulin analog (GLY[A21]ARG[B31]ARG[B32]). We compared HOE 901 with normal human insulin and the insulin analog Asp(B10), which is known to have increased mitogenic activity at least partially mediated through the insulin receptor. We have analyzed receptor binding, insulin-induced receptor autophosphorylation and phosphorylation of receptor substrates in rat-1 fibroblasts overexpressing human insulin receptor isoform A (HIR A) or B (HIR B). In HIR A expressing cells, insulin and its analogs showed no significant differences in receptor association while clearly different dissociation kinetics were observed. In HIR B expressing cells, no significant differences in association and dissociation kinetics were observed. All insulins induced rapid autophosphorylation of the insulin receptor reaching a maximum after 10 min of stimulation. Asp(B10)insulin induced a prolonged phosphorylation state (over 60 minutes) of the 95 kDa receptor beta-subunit and of the substrates IRS-1/IRS-2 and Shc in contrast to normal human insulin and to HOE 901. In addition, we observed an increased and prolonged tyrosine phosphorylation of an unidentified protein with Asp(B10)insulin at about 60 kDa. Insulin-dependent dephosphorylation of the focal adhesion kinase (p125FAK) was equally induced by all these ligands. With respect to [3H]thymidine incorporation into DNA, HOE 901 had similar effects as normal human insulin, while Asp(B10)insulin showed increased [3H]thymidine incorporation. In summary, the data show that the increased mitogenic activity of Asp(B10)insulin may be explained with a prolonged kinetics of tyrosine phosphorylation of the insulin receptor and of insulin signalling elements together with the preferential phosphorylation of an yet unidentified 60 kDa protein. HOE 901 behaves with respect to insulin receptor binding, receptor autophosphorylation, phosphorylation of signalling elements and promotion of mitogenesis like regular human insulin.

Functional innervation of the adrenal cortex by the splanchnic nerve.

Abstract: Secretion of steroid hormones by the adrenal cortex is required to maintain whole body homeostasis; that is the ability to maintain blood pressure and volume, carbohydrate, protein and fat metabolism and immune and nervous system function within normal limits is dependent on adrenocortical hormones. The premise of this report is that autonomic-endocrine interactions occurring in the adrenal cortex are required for normal control of steroid secretion. Under non-stress conditions when reduced steroid secretion is required, splanchnic neural activity appears to be inhibitory, whereas during stress conditions when elevated steroid secretion is necessary, neural activity is excitatory. The capacity for innervation to produce both inhibitory and excitatory effects suggests that neural input must be encoded differentially; encoding could be dependent on the neurotransmitter released or on the intra-adrenal target affected. Neural input could act directly at the adrenal cell to affect steroidogenesis or act indirectly by changing adrenal blood flow. An index of the role of innervation has been obtained by assessing adrenal corticosteroid secretion after splanchnicectomy, severing the thoracic splanchnic nerve which is the major source of innervation of the adrenal gland. This approach has resulted in alterations in corticosteroid secretion under non-stress and stress conditions, but in many cases has demonstrated no profound effect on in vivo steroidogenesis. It is likely that splanchnicectomy results in variable secretory responses in part due to the multiplicity of adrenal neurotransmitter systems that are regulated by the splanchnic nerve. Splanchnicectomy alters multiple neurotransmitters at different adrenal sites. Splanchnic innervation acts as an extra-ACTH mechanism in the control of adrenal corticosteroid secretion, yet further elucidation of the physiological conditions under which splanchnic neural activity affects function is clearly warranted.

The effects of anti-convulsant drugs on adrenal function.

Abstract: Since the adrenal cortex and medulla are intimately interrelated, the effects of anticonvulsant drugs may affect both of these hormonal systems. Anticonvulsants are commonly used long-term for the treatment of epilepsy, chronic pain syndromes and affective disorders. In patients where adrenal function needs to be evaluated, the clinician should be aware of the potential interactions between anticonvulsant medication and the hypothalamo-pituitary-adrenal axis. Carbamazepine, phenytoin and phenobarbitone induce the liver P450 cytochrome enzyme system and stimulate steroid clearance. Therefore, patients investigated for Cushing's syndrome may show a falsely positive dexamethasone suppression test, and patients with adrenal insufficiency on steroid replacement may require increased doses of steroids; furthermore, increased corticosteroid-binding-globulin levels are also associated with chronic anticonvulsant administration. In addition, concomitant treatment with benzodiazepines, probably acting via the GABA pathway, can also alter the ACTH/cortisol response to stressful stimuli. Direct and indirect evidence suggest that benzodiazepines, acetazolamide and magnesium sulphate can also interfere with the renin-angiotensin-aldosterone system. Finally, to our knowledge, no systemic data are yet available in the human on the effect of antiepileptics on the function of the adrenal medulla and/or catecholamine metabolism; however, as the adrenal medulla receives part of its blood supply from the cortex, it is possible that alterations of cortical hormonal composition might affect adrenal medulla function overall.

The influence of ovariectomy on ob gene expression in rats.

Abstract: Ovarian steroid hormones exert major influences on eating behaviour and body weight regulation of female rats. Ovariectomy (OVX) results in an increase in food intake and a concomitant increase in body weight, while estradiol (E2) replacement reverses these effects. In this study, we examined the influence of OVX on obese (ob) gene expression in rat adipose tissues and serum leptin concentration. Female Wistar rats, 10 weeks old, were divided into three groups: sham-operated control rats receiving corn oil (group 1, n = 4), ovariectomized rats receiving corn oil (group 2, n = 5), and ovariectomized rats receiving 17beta-E2 (10 microg/kg/day) replacement (group 3, n = 4). After 4 weeks, the rats and food consumption were weighed and serum E2 and leptin levels were measured by radioimmunoassays. Furthermore, the expression levels of ob mRNA obtained from the bilateral perimetric fat pads were estimated by Northern blot analysis. The mean weight and food consumption in group 2 were significantly (p < 0.01) heavier than those in group 1. But there were no significant differences between group 1 and group 3. The expression levels of ob mRNA in group 2 were lower than those in group 1, however, the levels of group 3 were restored to the level of group 1. On the other hand, no significant differences among the 3 groups as to serum levels of leptin were observed. The data herein clearly indicate that ovarian steroid hormones may be one of the factors involved in the regulation of ob gene.

Direct effects of stress on adrenocortical function.

Abstract: The adrenal gland plays a pivotal role in the stress response since this response involves the hypothalamic-pituitary-adrenal axis (HPAA) and the sympatho-adrenomedullary system (SAMS) as its two principal components. An important relation between the immune system and the other stress response systems is also centered on the adrenal gland. It is well known that the cortex secretes glucocorticoids while the medulla secretes epinephrine, two of the major effects of the stress response. Some other aspects, however, also deserve special consideration: The paracrine effects of the cortical secretion on the medullary cells through the special irrigation system of the gland and reciprocally the influence of the medulla upon the cortex, either by direct close contact or by local innervation. The influence of vascular events also needs to be considered as well as the existence of some local hormonal axis such as those resulting from the local production of renin or CRH in adrenal cells. Some other cells such as mast cells, macrophages and endothelial cells seem to play a role in the regulation of the adrenal cortex and hence in the tuning of the stress response. Stressors stimulate the release of CRH from the hypothalamic paraventricular nucleus inducing the secretion of ACTH from the pituitary and that of corticosteroids from the adrenal cortex. Through the activation of the sympathetic system the adrenal can be stimulated even before adequate levels of ACTH are reached. In conditions of chronic stress the adrenal cortex undergoes an adaptation that allows the hypersecretion of glucocorticoids to occur even without the increment of ACTH.

Effect of testosterone replacement on whole body glucose utilisation and other cardiovascular risk factors in males with idiopathic hypogonadotrophic hypogonadism

Abstract: BACKGROUND: Excessive testosterone in males or estrogens in females could explain their differences in coronary heart disease event rates. As a contraceptive testosterone is likely to be used at large scale the role of testosterone in increasing the risks of coronary heart disease needs investigation. AIM: To look at the role of testosterone in development of insulin resistance and other cardiovascular risk factors. DESIGN: Prospective, before-after study on ten male subjects with idiopathic hypogonadotrophic hypogonadism pre- and post-testosterone replacement therapy; outcome measures: anthropometry, lipoprotein profile and M value (whole body glucose disposal rates on standard hyperinsulinemic euglycemic clamp; at insulin infusion rate: 40 mU x (m-2)). RESULTS: Pre-treatment serum testosterone was 0.43 (0.515) ng x mL(-1), LH was 1.29 (0.08) IU x L(-1), and FSH was 1.54 (0.08) IU x L(-1). None had glucose intolerance. After replacement testosterone levels increased to 9.4 ng x mL(-1) (p=0.0005); weight increase of 5.0 kg (p=0.140), body mass index increase of 1.2 kg x m(-2) (p=0.28), and the change in waist to hip ratio (p=0.31) were not statistically significant. M-value (mg x kg x min(-1)) did not change after testosterone therapy (5.86 [0.72] vs 5.29 [0.82], p=0.62). Insulin levels (mU x L(-1)) achieved during the clamps were 89.5 (14.2) before and 146 (32.2) after androgen therapy (p=0.127). There was no change in glucose area under curve (mg x min x dL(-1)) (14406 [502.2] vs 12557 [826.5], p=0.312). On testosterone replacement therapy total and LDL cholesterol levels (mg x dL(-1)) declined (122.5 [13.4] vs 91.6 [5.0], p=0.04; 65.9 [9.9] vs 39.4 [7.3], p=0.05); Ratio of total cholesterol to HDL ratio also decreased significantly (p=0.05). Changes of serum triglycerides (p=0.25) and HDL cholesterol (p=0.19) did not attain statistical significance. CONCLUSIONS: Insulin sensitivity does not decrease on testosterone replacement therapy of male subjects with idiopathic hypogonadotrophic hypogonadism. Testosterone replacement was associated with decrease in other cardiovascular risk factors.

Regulation of adrenocortical function by cytokines--relevance for immune-endocrine interaction

Abstract: The importance of the hypothalamic-pituitary-adrenalaxis (HPA) for the regulation of immunological functions has been greatly appreciated in the past (1-3). Activation of the HPA axis due to a given stimulus leads to a stress response which modulates the immune response. The interactions between the immune system and HPA-axis may be characterized by a circuit which includes I) activation of the HPA-axis and initiation of the stress response which, in term, has immune-modulating properties; II) a feedback mechanism derived from the immune system which regulates the HPA-axis. Current concepts on these regulatory circuits mainly favor the action of cytokines as mediators of the immune-endocrine regulation circuits which have been shown to interfere with the endocrine system on all levels of the HPA-axis. Over the past few years, it has become evident that the adrenal gland, itself, as the main effector organ of the HPA-axis, is a major site for both synthesis and action of numerous cytokines. This review summarizes current knowledge on production, action, as well as functional implications of cytokine action within the adrenal gland during development, health and disease.

Serotonergic regulation of adrenocortical function.

Abstract: Serotonin (5-HT) plays a pivotal role in the regulation of the hypothalamo-pituitary-adrenal axis. In particular, 5-HT is involved in the stimulation of ACTH secretion during stress. Recent data indicate that, at the adrenal level, 5-HT acts as a local regulator of corticosteroid secretion. The presence of 5-HT in the adrenal gland has been demonstrated immunohistochemically and biochemically in various species including frog, mouse, rat and human. In the mouse, 5-HT has been detected in nerve fibers while, in the frog and rat, 5-HT appears to be sequestered in chromaffin cells. In man, 5-HT is stored in perivascular mast cells. In vivo and in vitro studies have shown that 5-HT stimulates mineralo- and glucocorticoid secretion from adrenal cells. In rat, the type of receptor involved in the corticotropic effect of 5-HT is still controversial. In the frog and the human, the effect of 5-HT on the adrenal cortex is mediated through a 5-HT4 receptor subtype positively coupled to adenylyl cyclase and calcium influx. Clinical studies indicate that 5-HT4 receptor agonists stimulate aldosterone secretion in healthy volunteers and in patients with aldosterone disorders. The 5-HT4 receptor agonist cisapride and angiotensin II exert additive effects on aldosterone secretion. In contrast, cisapride has no influence on ACTH-induced aldosterone release. Collectively, these findings suggest that intra-adrenal 5-HT stimulates the secretory activity of adrenocortical cells through a paracrine mode of communication involving a 5-HT4 receptor type. Serotonergic control of corticosteroid production may be involved in the physiological control of the activity of the adrenal cortex, in particular during inflammatory stress. 5-HT may also be implicated in the pathophysiology of aldosterone disorders.

Potentiation of glucose-induced insulin secretion by fagomine, a pseudo-sugar isolated from mulberry leaves.

Abstract: The mechanisms of potentiation by fagomine, an N-containing pseudo-sugar derived from mulberry leaves, of insulin secretion from isolated rat pancreatic islets in response to glucose was studied. Fagomine at more than 1 mmol/L significantly potentiated insulin secretion induced by 10 mmol/L glucose. The pseudo-sugar, however, did not affect the basal insulin secretion assessed at a glucose concentration of 3.5 mmol/L. The effects of fagomine on 10 mmol/L and 20 mmol/L glucose-induced insulin secretion were not significantly different. Fagomine (4 mmol/L) also potentiated glyceraldehyde-induced insulin secretion, but not the leucine-induced type. Glycolysis assessed by lactate production from glucose was significantly enhanced. The amounts of all intermediates (from glucose 6-phosphate to glyceraldehyde 3-phosphate) of the upper part of the glycolytic pathway in islets incubated with 20 mmol/L glucose were not affected by 4 mmol/L fagomine. The rise in the ATP/ADP ratio through both the glycolytic pathway and the citric acid cycle is believed to be pivotal in glucose- and glyceraldehyde-induced insulin secretion; whereas the ATP/ADP ratio rise through the citric acid cycle via the formation of acetyl-CoA is involved in leucine-induced insulin secretion. Our findings, together with these considerations, suggest that fagomine potentiates glucose-induced insulin secretion through acceleration of some step(s) after the formation of glyceraldehyde 3-phosphate in the glycolytic pathway.

Application of a Bioassay with CHO Cells for the Routine Detection of Stimulating and Blocking Autoantibodies to the TSH-Receptor

Abstract: The importance of bioassays measuring stimulating and blocking autoantibodies to the TSH-receptor (TSH-R) by their effect on cAMP production in CHO cells transfected with the recombinant TSH-R is increasingly recognized. The standard technique for this bioassay is cumbersome, as it involves purification of serum IgG with polyethylene glycol (PEG) and resuspension in hypotonic buffer. We have therefore established a simpler approach for the detection of stimulating and blocking autoantibodies using JP09 CHO cells and unfractionated human serum. The cAMP concentration was measured by a highly sensitive commercial radioimmuno assay. Thyroid stimulating autoantibodies (TSAb) were present in 107 out of 126 patients with Graves' disease (85%) and in 4 out of 40 patients with Hashimoto's thyroiditis (10%). Specificity was confirmed by the fact that only 1 patient with insulin dependent diabetes mellitus (IDDM) out of 64 patients with different non-thyroid autoimmune disorders (46 with IDDM, 10 with stiff man syndrome and 8 with rheumatoid arthritis) and 2 out of 100 healthy controls (2%) were positive in this assay. In the subgroup of hyperthyroid Graves' disease patients 76 out of 83 (92%) had TSAb and the same number had TSH binding inhibiting immunoglobulin (TBII), as assessed by the commercial TRAK assay. Although both antibody types showed only a weak correlation (r = 0.30), a combination of TSAb and TBII detected 98% of all Graves' patients and 99% of the hyperthyroid subgroup. Thyroid blocking autoantibodies (TBAb) were measured in 4 out of 24 TSAb negative patients with Graves' disease (17%), who were hypothyroid and positive for TBII. A comparison of our bioassay with the standard bioassay using PEG precipitation showed a good correlation (r = 0.76,p < 0.001), demonstrating the feasibility of the simplified assay for the routine detection of TSAb and TBAb in Graves' disease.

Regulation of adrenocortical function by vasopressin.

Abstract: Accumulating data obtained from various animal species indicate that vasopressin (AVP) participates in the regulation of adrenocortical function. AVP doubled aldosterone and cortisol secretion but did not affect corticosterone secretion. Pharmacological studies indicate that the AVP receptors in the cortex belong to the V1 a subtype. Activation of V1 a receptors induces breakdown of membrane phosphoinositides, with subsequent accumulation of inositol phosphates and diacylglycerol. These effects occur after receptor binding, G-protein activation and coupling to a specific phospholipase C. Inositol trisphosphate, transiently produced, induces a rapid release of Ca2+ from intracellular stores. Diacylglycerol activates protein kinase C, which, together with calcium, is responsible for steroid secretion. The early events of AVP action are mediated by two types of G-proteins. One is coupled to phospholipase C, and insensitive to pertussis toxin (probably Gq/11) and a second one, which is inactivated by pertussis toxin (Gi protein), is involved in the stimulation of calcium influx. This Ca2+ influx pathway is very important, as no steroidogenic effect of AVP could be observed when experiments were performed in a calcium-free medium or in pertussis toxin-treated cells. Besides the pituitary, the adrenal is also a source for AVP production. Indeed, AVP is synthesized and secreted by chromaffin cells either present in the medulla or scattered throughout the cortex with a more prominent concentration in zona glomerulosa. AVP receptors are also present on chromaffin cells. However, in contrast to AVP receptors in the cortex, these mainly belong to the V1 b subtype, although V1 a receptors are also detected. The results summarized in this review conclusively indicate that AVP is one of the regulators of both cortex and medulla, an influence which may be mediated in part via pituitary AVP and in part via local production of AVP.

Human Recombinant Alpha2-HS Glycoprotein is Produced in Insect Cells as a Full Length Inhibitor of the Insulin Receptor Tyrosine Kinase

Abstract: Human Alpha 2-HS glycoprotein (AHSG), a glycoprotein synthesized by hepatocytes, was expressed in insect cells using the recombinant baculovirus system. The protein was purified from the cell supernatant, and appeared as a single band at about 52 kDa. Western blot using a specific antibody to the B-chain of AHSG indicated that the connecting peptide was present in the protein. When incubated with solubilized insulin receptors, recombinant AHSG inhibited the tyrosine kinase activity of the receptors in a dose-dependent fashion at concentrations in the range of those of the circulating protein. AHSG did not interfere with the binding of insulin to its receptor. These results indicate that human AHSG represents a natural inhibitor of the insulin receptor tyrosine kinase, is active as a single-chain protein and possesses a biological role similar to that of its homologue in rats, pp63, described by Auberger et al. (1).

Effects of hypophosphatemia on glucose tolerance and insulin secretion

Abstract: Phosphate is an active participant in energy metabolism, and its deficiency has been associated with changes in insulin sensitivity and glucose tolerance. In the present study, we have investigated insulin secretion and glucose tolerance in individuals with moderate and acute phosphate deprivation and in patients with chronic hypophosphatemia. The individuals with dietary phosphate deprivation, evidenced by a significant reduction in phosphaturia from 232.3 +/- 37.1 to 56.8 +/- 23.9 mmol/24 hours, but with normal serum levels of inorganic phosphorus, presented circulating glucose and insulin levels similar to those of the pre-dietary period during the oral and intravenous glucose tolerance tests. In contrast, patients with chronic hypophosphatemia (inorganic phosphorus < 0.65 mmol/l) presented in hyperinsulinemia during the postabsorptive state and during the early and late phases of insulin secretion after the oral and intravenous glucose stimulus. The physiological response of a fall in serum phosphate after glucose administration observed in individuals with chronic hypophosphatemia was similar to that of normal individuals. The presence of hyperinsulinemia both basally and after glucose stimulation, with normal glycemia, in phosphate-depleted individuals suggests that this condition is associated with reduced insulin sensitivity. However, severe phosphate deprivation is necessary for the manifestation of this undesirable association. The deviation of phosphate to the intracellular medium occurring after glucose administration in hypophosphatemic individuals is similar to that of normal individuals and explains the occurrence of severe hypophosphatemia in malnourished hypophosphatemic individuals when submitted to parenteral refeeding.

Mutations in adrenocortical tumors.

Abstract: Silent and incidentally detected adrenocortical neoplasms are the most frequent abnormality of the adrenal cortex. The prevalence of these lesions in the general population is around 1%, increases with age and reaches 6% in the seventh decade of life. Primary adrenocortical carcinoma, on the other hand, a highly malignant tumor, is rare with an incidence of 1.7 cases per million per year. Recent progress has been achieved in the understanding of adrenocortical tumorigenesis by mapping and identification of genes responsible for hereditary tumor syndromes like the Li-Fraumeni syndrome, Beckwith-Wiedemann syndrome, Carney complex and the Multiple Endocrine Neoplasia Type I. Investigation of the clonal composition of adrenal tumors demonstrates that adrenal carcinomas are generally monoclonal, whereas adrenal adenoma may be polyclonal in approximately 25% of cases. These adenomas may have a multicellular origin under the putative action of extra-adrenal and local growth factors. Oncogenes and tumor suppressor genes involved in adrenal carcinomas include mutations in the p53 tumor suppressor gene and rearrangements of the chromosomal locus 11 p15.5 associated with IGF II hyperexpression. Constitutive activation of the ACTH receptor-G protein-cAMP signal cascade does not play a role in adrenal tumor formation. Conversely, deletions of the ACTH receptor gene have been recently found in undifferentiated adenomas and in aggressive adrenocortical carcinomas. This indicates that the signaling pathways responsible for adrenocortical tumor formation are different from that of other endocrine neoplasms like pituitary and thyroid adenomas.

Growth hormone improves weight velocity and height velocity in prepubertal children with cystic fibrosis.

Abstract: We undertook this study to determine if growth hormone treatment of prepubertal children with cystic fibrosis could improve their height and weight. Nine prepubertal children with cystic fibrosis were treated with human recombinant growth hormone for one year. Results obtained during this year were compared to similar measurements made for each patient for the one year prior to the treatment year. Anthropometric data including: height, height velocity, weight, weight velocity and skin fold thickness were measured at three month intervals. Pulmonary function and skeletal muscle strength were measured at three month intervals. Glucose tolerance was evaluated by HbAlc and by fasting blood glucose and insulin levels every three months. Our results demonstrate that growth hormone treatment resulted in significant improvement in height velocity and height Z scores. Weight increased in all subjects, with a significant increase in weight velocity (year prior to treatment = 1.7+/-1.0 kg/yr, treatment year = 3.8+/-1.6 kg/yr; p=0.03). Measurements of skin fold thickness suggests that lean body mass improved with growth hormone treatment. Pulmonary function improved in all but two patients, whose pulmonary function remained the same and muscle strength improved in all subjects. These results suggest that growth hormone used in prepubertal children with cystic fibrosis can improve height and weight and may improve lean body mass.

Mechanism of the diabetogenic action of cyclosporin A.

Abstract: To investigate the mechanism of diabetogenic action of cyclosporin A (CsA), 7 male Wistar albino rats received 10 mg/kg/day of the drug for 4 weeks (CsA). The results were compared with controls (C); blood CsA levels measured weekly remained stable throughout the experiment (mean +/- SEM) (X = 2657.9+/-155.1 ng/ml). Intravenous glucose load (0.75 g/kg) performed after 2 weeks of CsA therapy showed glucose intolerance in treated animals as evaluated by the glucose area under the curve (CsA = 409.2+/-17.8 vs. C = 313.3+/-12.6 umol x ml(-1) x min(-1)) (p < 0.05) with insulin levels being similar in the two groups (CsA = 8603.9+/-1645.5 vs. C = 9571.9+/-828.5 pmol x ml(-1) x min(-1)). After 4 weeks of CsA administration, glucose intolerance was maintained (CsA = 398.6+/-35.6 vs. C = 301.7+/-23.0 umol x ml(-1) x min(-1)) (p < 0.05) associated with a significant decrease in insulin secretion (CsA = 4404.9+/-2392.0 vs. C = 10075.9+/-2861.0 pmol x ml(-1) x min(-1) (p < 0.05). These results suggest that CsA induced a state of insulin resistance preceding the failure of insulin secretion. After 4 weeks, the pancreatic insulin content was also decreased (CsA = 0.7+/-0.1 vs. C = 1.4+/-0.5 mU/mg) (p < 0.05). Maximal insulin binding to isolated adipocytes was not affected by CsA (CsA = 7.4+/-2.6 vs. C = 6.4+/-2.0%), although glucose transport and oxidation decreased after CsA treatment (p < 0.05). In conclusion, glucose intolerance induced by CsA in Wistar albino rats is due to decreased insulin production and impaired insulin action by a post-binding mechanism.

Molecular and cellular mechanisms used in the acute phase of stimulated steroidogenesis.

Abstract: Steroidogenic tissue can respond almost immediately to a stimulatory hormonal stimuli. Recent findings are shedding light on the molecular and cellular mechanisms that are used to synthesize and export steroid hormones in the acute phase of stimulation. In addition to utilising the cAMP intracellular messenger system to convey a stimulatory message, steroidogenic cells may employ the protein kinase C, arachidonic acid, tyrosine phosphate and nitrous oxide systems. It has been proposed that cholesterol laden vesicles travel along a network of intermediate filaments to reach the mitochondria. Cholesterol may then translocate from the outer mitochondrial membrane to the inner via sites of contact between the two membranes. These contact sites may be composed of protein bridges which include the constituents, porin, the benzodiazepine receptor and GTP binding proteins. Cholesterol is transported through the contact sites to the inner membrane and on reaching cytochrome P450 side chain cleavage (P450scc), cholesterol is converted to pregnenolone. Pregnenolone is in turn converted to a range of steroid hormones via enzyme casades. GTP binding proteins may regulate the contact site between the inner and outer membranes and thereby modulate cholesterol flux to P450 scc. In the adrenal and gonads the rate that cholesterol traverses the contact point to reach the inner membrane is accelerated by the Steroidogenic acute regulatory protein. Newly synthesized steroid hormones are transported to the cell periphery for export via a mechanism that may utilise an ion exchange protein.

Ym268 increases the glucose uptake, cell differentiation, and mrna expression of glucose transporter in 3t3-l1 adipocytes

Abstract: The purpose of this study was to examine the effects of bis[4-[2,4-dioxo-5-thiazolidinyl)methyl]phenyl]methane (YM-268), a thiazolidinedione derivative, on glucose uptake, adipocyte differentiation through peroxisome proliferator-activated receptor gamma(PPARgamma), and phosphatidylinositol 3-kinase (PI 3-kinase) activity in cultured cells. YM268 and pioglitazone dose-dependently increased the 2-deoxyglucose uptake in 3T3-L1 cells. YM268 facilitated the insulin-stimulated triglyceride accumulation in 3T3-L1 adipocytes and increased the mRNA expression of fatty acid-binding protein. YM268, with and without insulin, increased the mRNA expression of glucose transporter isoforms such as GLUT1 and GLUT4, indicating enhancement of adipocyte differentiation. Additionally, YM268 and pioglitazone showed activity of the PPARgamma ligand, a member of the nuclear receptor superfamily responsible for adipogenesis. To examine the possible involvement of the increased activity of PI 3-kinase in YM268-stimulated glucose uptake, the enzyme activity was estimated by measuring the phosphatidylinositol-3,4,5-trisphosphate (PI-3,4,5-P3) concentration in human monocytic cells. Insulin dose-dependently increased the PI-3,4,5-P3 production but YM268 had no significant effect on the insulin-dependent and -independent PI 3-kinase activation. These results indicate that the mechanism by which YM268 increased glucose uptake, may be accounted for in part by the enhancement of GLUT1 and GLUT4 expression through PPARgamma activation.

Lithium carbonate therapy is not a risk factor for osteoporosis.

Abstract: Lithium carbonate is a widely used drug for affective disorders. It may effect calcium metabolism and alter parathyroid physiology by causing hypersecretion of parathyroid hormone. Patients treated with this medication might therefore be predisposed to osteoporosis. The purpose of this study was to evaluate the effect of either short- or long-term lithium carbonate therapy on parameters of bone metabolism. Parathyroid function and indices of bone metabolism were assessed in 23 patients treated for affective disorders. 10 patients were treated for 0.4-1.0 year (Group 1), and 13 patients were treated for more than 3 years (Group 2). In all subjects, bone mineral density measurements in the hip and lumbar spine regions were performed using dual energy X-ray absorptiometry. Serum thyroid hormone, PTH, LH, testosterone and urine OH-proline, free cortisol, calcium and phosphate excretion were measured. The two groups were well matched for sex, weight, calcium intake, lithium levels and smoking habits, although Group 2 was slightly older. No differences between the two groups were noted in either bone mineral density or other parameters that were assessed. Urinary OH-proline was elevated similarly in both groups. Our results did not detect any effect on bone density after short- or long-term lithium carbonate therapy, although the data does suggest an increase in bone turnover associated with this treatment. Thus, short- or long-term treatment with lithium is not associated with increased risk for osteoporosis.

The interaction between leptin and the hypothalamic-pituitary-thyroid axis

Abstract: The description of the adipose tissue hormone leptin has led to important discoveries. Leptin plays a role not only in the regulation of metabolic efficiency, energy expenditure, food intake and adiposity, but also contributes greatly to the adaptation of the organism to starvation. Much of the literature has focused on the physiologic roles of leptin-driven processes as diverse as feeding behavior, body weight, defense to starvation and reproduction. The following discussion summarizes knowledge that has accumulated regarding the interaction between leptin and the hypothalamic-pituitary-thyroid axis.

Intravenous methylprednisolone pulse therapy in the treatment of graves ophthalmopathy

Abstract: Graves' ophthalmopathy (GO) is a specific immune-mediated disorder, whose treatment is sometimes difficult. In order to investigate the efficacy of intravenous methylprednisolone (MP) pulse therapy in GO, we studied eight patients with GO, followed up for at least 6 months by clinical patient self-assessment, ophthalmological examination and orbital computed tomography (OCT). A 12.5 mg/kg dose of MP was administered intravenously over a 10 hour period, once every month. Three to six MP pulse administrations were performed in each patient. All patients were outpatients. A 0.5 mg/kg/day oral prednisone dose was given to each patient as interpulse therapy. Clinical assessment of MP pulse therapy showed a good response in 87.5% and no response in 12.5% of patients. The treatment was rapidly efficient, mostly on patient self-assessment, soft tissue inflammation, ophthalmoplegia, corneal involvement, visual acuity and extraocular muscle enlargement on OCT. Post-treatment ophthalmic index was significantly improved (6.75 +/- 3.06 vs. 2.5 +/- 1.41: p < 0.05). MP pulse therapy had less effect on proptosis (22.94 +/- 2.32 mm vs. 21.56 +/- 2.22 mm: p < 0.05). No adverse effects were noted with MP pulse therapy. Patients showed no relapse of eye involvement during a mean follow up of 31.8 months (2-77 months). In conclusion, our results suggest that intravenous MP pulse therapy is a good immunosuppressive therapy for GO. Moreover, in comparison with the previous studies, the MP dose used in our present study appears to be optimal with high efficacy. MP pulse therapy represents a safe and efficient treatment in GO, which can easily be performed in outpatients.

Plasma leptin levels in newborns from normal and diabetic mothers.

Abstract: Leptin can be considered as a peripheral signal which informs the centers about the mass of energy stores. Studies done on the human adult population have demonstrated that degree of adiposity and insulin levels play a major role as determinants of leptin circulating levels. The aim of this study was to evaluate which factors may influence leptin levels at birth. We examined the role played by baby size and by the metabolic environment the fetus was exposed to during pregnancy. We considered 85 newborns from normal (n = 60), gestational (GDM, n = 17) and pregestational (IDDM = 8) diabetes mellitus mothers. At delivery, blood was taken from the umbilical cord vein. Babies from normal and GDM mothers were subdivided into AGA (appropriate for gestational age) and LGA (large for gestational age). There was no difference in leptin levels between babies from normal or GDM mothers belonging to the same weight category, but leptin levels were always higher in LGA than in AGA newborns, and highly correlated with birth weight (r = 0.34, P = 0.001). Moreover, IDDM mothers gave birth to newborns with significantly higher levels of leptin and insulin when compared with normal and GDM mothers. Diabetes of both GDM and IDDM mothers was clinically well controlled (HbA1c was 4.0 and 7.2, respectively). The correlation between leptin and insulin was significant only when newborns from IDDM mothers were included in the regression analysis (r = 0.39, P = 0.0002). Our results suggest that degree of adiposity is one of the main regulators of leptin concentration in the human newborn and that babies exposed to an altered, though clinically controlled, metabolic environment, as in IDDM mothers, have increased levels of leptin.