High maternal iron status, dietary iron intake and iron supplement use in pregnancy and risk of gestational diabetes mellitus: a prospective study and systematic review.

AIM: High iron measured using dietary intake and biomarkers is associated with Type 2 diabetes. It is uncertain whether a similar association exists for gestational diabetes mellitus. The aim of this systematic review was to conduct a cohort study examining first trimester body iron stores and subsequent risk of gestational diabetes, and to include these findings in a systematic review of all studies examining the association between maternal iron status, iron intake (dietary and supplemental) and the risk of gestational diabetes. METHODS: Serum samples from women with first trimester screening were linked to birth and hospital records for data on maternal characteristics and gestational diabetes diagnosis. Blood was analysed for ferritin, soluble transferrin receptor and C-reactive protein. Associations between iron biomarkers and gestational diabetes were assessed using multivariate logistic regression. A systematic review and meta-analysis, registered with PROSPERO (CRD42014013663) included studies of all designs published in English from January 1995 to July 2015 that examined the association between iron and gestational diabetes and included an appropriate comparison group. RESULTS: Of 3776 women, 3.4% subsequently developed gestational diabetes. Adjusted analyses found increased odds of gestational diabetes for ferritin (OR 1.41; 95% CI 1.11, 1.78), but not for soluble transferrin receptor (OR 1.00; 95% CI 0.97, 1.03) per unit increase of the biomarker. Two trials of iron supplementation found no association with gestational diabetes. Increased risk of gestational diabetes was associated with higher levels of ferritin and serum iron and dietary haem iron intakes. CONCLUSIONS: Increased risk of gestational diabetes among women with high serum ferritin and iron levels and dietary haem iron intakes warrants further investigation.

Mortality associated with primary hyperparathyroidism.

561 patients with primary hyperparathyroidism were followed between 1961 and 1994. Relative survival was compared to that of the Australian population studied during the same time interval. Mortality was significantly greater in the hyperparathyroid population (P<0.001). Mortality was not greater in the patients with serum calcium levels >3.00 mmol/L compared to those with a serum calcium levels <3.00 mmol/L. 113 patients did not have parathyroid surgery. Their relative survival was not significantly different from those who had surgery but their mean serum calcium and parathyroid hormone (PTH) levels were significantly lower than those who had surgery. A re-analysis of the 453 patients followed between 1972 and 2011 was carried out and a 20-year survival analysis made of those diagnosed between 1972 and 1981 and those diagnosed between 1982 and 1991. The latter group had significantly worse relative mortality than the former group (P<0.001) but was significantly older at the time of diagnosis (56.94 ± 14.83 vs 52.01 ± 13.58, P<0.001). The serum calcium and serum PTH levels were not significantly different between these two groups.

Does Graves' disease or thyrotoxicosis affect the prognosis of thyroid cancer.

Twenty-one patients who underwent surgical treatment for thyrotoxicosis and who were found at operation to have thyroid cancer are presented. Sixteen had Graves' disease and 5 had toxic nodular goiter. The group with Graves' is compared with 110 euthyroid patients with thyroid cancer who underwent their initial surgery in the same time period and who were of the same age (+/- 1 yr) and sex as the patients with Graves' disease. None of the thyrotoxic patients died during follow-up of 2-24 yr or developed subsequent metastases. The 1 patient with a local lymph node metastasis has not shown evidence of recurrence. Hypoparathyroidism appeared as a complication in only 1 patient. The size of tumors in the patients with Graves' disease was significantly smaller than in the euthyroid group. The course of the disease in both the patients with Graves' disease and the thyrotoxic group as a whole was relatively benign. This series does not support the recent suggestions that thyroid cancer in patients with Graves' disease is more aggressive than in either patients with toxic nodular goiter or euthyroid subjects. Patients with Graves' disease and thyroid cancer should be treated identically to other patients with thyroid cancer. Therapy should consist of total thyroidectomy followed by a postoperative 131I scan. Residual tissue or metastases found on the scan should be ablated with 6 GBq 131I. The patient should receive a suppressive dose of T4.

Medroxyprogesterone induced Cushing's syndrome.

A 74-year old female taking medroxyprogesterone acetate (MPA) presented with Cushing's syndrome together with low serum cortisol and plasma ACTH and an impaired response to synthetic ACTH (Synacthen, CIBA). When the medroxyprogesterone therapy was ceased the cushingoid features resolved and serum cortisol, ACTH and ACTH responsiveness all returned to normal. The MPA was acting as an exogenous glucocorticoid causing Cushing's syndrome.

Insulin sensitizes a cultured rat osteogenic sarcoma cell line to hormones which activate adenylate cyclase.

Pretreatment of the osteogenic sarcoma cell line UMR-106-01 with insulin results in sensitization to both parathyroid hormone (PTH) and isoproterenol. In insulin-pretreated cells, the two hormones cause a significantly greater cyclic AMP (cAMP) accumulation than in noninsulin-treated cells. In the presence of cholera toxin, which enhances cAMP production by these cells in both the basal and PTH-stimulated state, the effect of insulin is maintained. In the presence of pertussis toxin, which has no effect on basal cAMP accumulation but enhances both PTH and isoproterenol stimulation, insulin sensitization for both hormones is abolished. These data suggest that insulin sensitizes these cells to subsequent hormone stimulation by lessening the action of an inhibitory guanine nucleotide regulatory protein, possibly Gi.

Insulin promotes growth of the cultured rat osteosarcoma cell line UMR-106-01: an osteoblast-like cell.

The rat osteogenic sarcoma subclone UMR-106-01 is a cell type with osteoblast-like properties. This cell line has been shown to process specific receptors for insulin and insulin-like growth factor I (IGF-I), but not IGF-II. Insulin at physiological concentrations (1-5 ng/ml) in serum-free medium can maintain cell growth, as assessed by protein accumulation, thymidine uptake, and an increase in cell number. IGF-I is less potent than insulin, but, based on relative binding affinities for the insulin receptor, possibly acts via its own receptor. Insulin also enhances PTH-stimulated cAMP accumulation in these cells both by increasing cell number and an effect independent of cell number. Insulin may have a role in bone homeostasis.

A 6-hour human parathyroid hormone (1-34) infusion protocol: studies in normal and hypoparathyroid subjects.

Parathyroid hormone (PTH)-resistant states are usually diagnosed by the failure of an acute PTH injection to elicit a rise in urinary cAMP and phosphate or, less commonly, by the failure of repeated PTH injections to raise serum calcium. We have established a 6 hour infusion of human PTH (1-34) which identifies PTH-resistant hypoparathyroid subjects on the basis of serum 1,25-dihydroxyvitamin D (1,25(OH)2D) and calcium responses. 1,25-Dihydroxyvitamin D levels increased by at least 58 pmol/liter and serum calcium by at least 0.1 mmol/liter in PTH-responsive hypoparathyroid subjects (n = 6), whereas in pseudohypoparathyroid subjects (n = 5) these levels rose by less than 22 pmol/liter and 0.06 mmol/liter respectively. The responsiveness of urinary phosphate excretion, expressed as the renal threshold phosphate concentration (TmPO4/GFR), to PTH also clearly separated the pseudohypoparathyroid patients from the other subjects. Differences in urinary calcium responses were observed though this parameter was less reliable in the identification of individual PTH-resistant or PTH-sensitive hypoparathyroid patients. Nephrogenous cAMP did not discriminate between groups when this protocol was used. This test has the potential to facilitate and extend the classification of PTH-resistant states.

The human growth hormone receptor of cultured human lymphocytes. Structural characteristics and glycosylation properties.

The structural characteristics and glycoprotein nature of the human growth hormone (hGH) receptor in cultured lymphocytes (IM-9 cell line) were studied with the use of a bifunctional reagent (disuccinimidyl suberate) to couple 125I-hGH covalently to intact cells. After cross-linking, the hormone-receptor complexes were analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. A single band of Mr 140,000 was identified under reducing conditions. The labelling of this band was blocked by unlabelled hGH but not by insulin, ovine prolactin, bovine or ovine growth hormones. The Mr 140,000 band was immunoprecipitated by either anti-hGH antibody or by a monoclonal antibody against rat liver growth hormone receptor. In the absence of reductant two major bands of Mr 270,000 and 140,000 were found. On two-dimensional gel electrophoresis, with the first dimension in the absence of reductant and the second in its presence, the Mr 270,000 complex generated the Mr 140,000 band. The nature of the oligosaccharide chains of the receptor was studied by treatment with different glycosidases. The electrophoretic mobility of the Mr 140,000 receptor complex was markedly increased after digestion with endoglycosidase F but showed no or little change after digestion with endoglycosidase H. The Mr 140,000 band was also sensitive to neuraminidase treatment. In addition the 125I-hGH-receptor complex was adsorbed by immobilized wheat germ agglutinin and to a smaller extent by immobilized concanavalin A, lentil lectin, ricin I and ricin II. In conclusion, taking into account that hGH is a Mr 22,000 polypeptide, the binding subunit of the GH receptor in human IM-9 lymphocytes has an Mr of approx. 120,000. The native receptor may exist as a homodimer of the binding subunit formed by disulphide bonds. Furthermore, the GH receptor subunit contains asparagine N-linked type of oligosaccharide chains. Most, if not all, of these chains are of the complex type and appear to be sialylated whereas no high-mannose type chains are detectable in the mature form of the receptor.

Insulin receptor of human cerebral gliomas. Structure and function.

The insulin receptor from human brain tumors of glial origin was examined for the first time using intact cells (from an established cultured human glioblastoma cell line) and partially purified solubilized membranes (from cultured cells and freshly isolated human brain tumors). The structure of the glial insulin receptor subunits was assessed by affinity cross-linking of 125I-insulin with the alpha-subunit of the receptor, neuraminidase treatment of the cross-linked receptor, behavior of the receptor on lectin columns, and electrophoretic mobility of the phosphorylated beta-subunit. The functions of the insulin receptor were examined by measuring specific 125I-insulin binding (receptor concentration, affinity, specificity, pH-, time-, and temperature dependence), insulin-induced down-regulation of the receptor, insulin-stimulated autophosphorylation of the beta-subunit, and phosphorylation of exogenous substrates as well as insulin-stimulated glucose uptake in glioblastoma cells. All of these properties were typical for the insulin receptor from target tissues for insulin action. The insulin receptor of the normal human brain showed the altered electrophoretic mobility and lack of neuraminidase sensitivity of its alpha-subunit previously reported for the rat brain receptor. There was no difference, however, in the functions of the receptor subunits (binding, phosphorylation) from the normal brain tissue and the eight human gliomal tumors. Since the glial elements compose a majority of the brain cells, the "normal" structure and function of their insulin receptor might provide a key to understanding the role of insulin in the carbohydrate metabolism of the human central nervous system.

Structural difference of the insulin receptors from circulating monocytes and erythrocytes.

We compared insulin receptors obtained from cells widely used in human studies, the circulating monocytes and erythrocytes. Biochemically, these receptors possess both binding (alpha-subunit) and tyrosine kinase (beta-subunit) activities similar to insulin receptors from other sources. Subtle differences in molecular weight, however, were detected between the alpha-subunits of these two cell types when analyzed by NaDodSO4-PAGE. Crosslinked [125I]insulin-labeled alpha-subunit of the monocyte insulin receptor was of higher apparent molecular weight than the alpha-subunit derived from red cells. Neuraminidase treatment of the alpha-subunits from each cell type indicated more sialic acid residues were present on the monocyte than the red cell alpha-subunit. The structural properties of the insulin receptors of human circulating cells are similar but not identical to insulin receptors of other characterized systems.

Polypeptide hormone receptor phosphorylation: is there a role in receptor-mediated endocytosis of human growth hormone?

To determine whether receptor phosphorylation is a critical step in the internalization of polypeptide hormones and their receptors, we have studied a model system wherein insulin stimulates phosphorylation of its receptor and is also internalized. Using insulin as a positive control, we found that it stimulated a partially purified plasma membrane preparation of IM-9 lymphocytes to autophosphorylate its receptor and to catalyze the phosphorylation of a tyrosine-containing substrate. The human GH (hGH) receptor of the IM-9 lymphocytes, when coupled to [125I]iodo-hGH, migrated as a 140,000-dalton protein on polyacrylamide gel electrophoresis. This protein, in contrast to the insulin receptor, was not phosphorylated by the addition of hGH, nor did hGH stimulate this preparation to phosphorylate the tyrosine-containing substrate poly-(GluNa,Tyr)4:1, casein, or histone f2b under a variety of conditions. We conclude that receptor phosphorylation is not a critical intermediate in the receptor-mediated endocytosis of hGH and probably other polypeptide hormones and growth factors.

Downregulation occurs normally in cultured Epstein-Barr virus-transformed lymphocytes from patients with extreme insulin resistance. Discrepancy between downregulation in vivo and in vitro.

Levels of fasting plasma insulin are generally inversely correlated with 125I-insulin binding to circulating blood cells. In disease states associated with hyperinsulinemia (e.g., obesity and non-insulin-dependent diabetes mellitus), 125I-insulin binding is usually low. In contrast, 125I-insulin binding to circulating cells may be normal in patients with certain forms of extreme insulin resistance despite marked hyperinsulinemia. To explain this paradox, it has been proposed that postbinding defects in insulin action may give rise to defects in downregulation. We have employed cultured Epstein-Barr virus (EBV)-transformed lymphocytes from eight patients with extreme insulin resistance to address the question of whether there is a defect in the downregulation process in vitro. In this cell type, insulin leads to a decrease in the number of insulin receptors on the cell surface by accelerating the rate of degradation of insulin receptors. We could not detect any abnormality in in vitro down-regulation with cultured EBV-transformed lymphocytes from insulin-resistant patients. The apparent discrepancy between the in vivo and in vitro studies raises the possibility that some factor in the patient's internal milieu may prevent insulin-induced downregulation. An alternative possible explanation might be that the mechanism of downregulation in vitro differs from the mechanism whereby receptor number is regulated in vivo in insulin's target cells.

The relevance of 25-hydroxycalciferol measurements in sera of patients with renal failure.

Iliac crest biopsies and serum specimens were obtained from 36 non-dialyzed uraemic patients. The mean serum 25-hydroxycalciferol concentration of the patients was lower than that of normal subjects and a significant correlation was found between 25-hydroxycalciferol values and the severity of osteomalacia. Parathyroid osteopathy was significantly correlated with serum immunoreactive parathyroid hormone but not with serum 25-hydroxycalciferol values. While normal serum 25-hydroxycalciferol concentrations in uraemic patients do not exclude the presence of osteomalacia, a low concentration is virtually diagnostic of this disorder.

Metastatic medullary carcinoma of the thyroid complicated by Cushing's syndrome.

A patient with metastatic medullary carcinoma of the thyroid, Cushing's syndrome, and severe diarrhoea is presented. The manifestations of Cushing's syndrome were controlled with a combination of aminogluthethimide and metyrapone. The cause of the diarrhoea has not been found, and it remains resistant to treatment.