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SJ Conroy, I Green, G Dixon, PM Byrne, J Nolan, YH Abdel-Wahab, N McClenaghan, PR Flatt and P Newsholme

We have previously reported that newly diagnosed Type-1 diabetic patient sera potently suppressed insulin secretion from a clonal rat pancreatic beta-cell line (BRIN BD11) but did not alter cell viability. Here, we report that apoptosis in BRIN BD11 cells incubated in various sera types (fetal calf serum (FCS), normal human serum and Type-1 diabetic patient) was virtually undetectable. Although low levels of necrosis were detected, these were not significantly different between cells incubated in sera from different sources. ATP levels were reduced by approximately 30% while nitrite production increased twofold from BRIN BD11 cells incubated for 24 h in the presence of Type-1 diabetic patient sera compared with normal human sera. Additionally, ATP levels were reduced by approximately 40% and DNA fragmentation increased by more than 20-fold in BRIN BD11 cells incubated in FCS in the presence of a pro-inflammatory cytokine cocktail (interleukin-1beta, tumour necrosis factor-alpha and interferon-gamma), compared with cells incubated in the absence of cytokines. Nitric oxide production from BRIN BD11 cells was markedly increased (up to 10-fold) irrespective of sera type when the cytokine cocktail was included in the incubation medium. Type-1 diabetic patient sera significantly (P<0.001) raised basal levels of intracellular free Ca(2+ )concentration ([Ca(2+)](i)) in BRIN BD11 cells after a 24-h incubation. The alteration in [Ca(2+)](i) concentration was complement dependent, as removal of the early complement components C1q and C3 resulted in a significant reduction (P<0.01) of sera-induced [Ca(2+)](i )changes. We propose that the mechanism of Type-1 diabetic patient sera-induced inhibition of insulin secretion from clonal beta-cells may involve complement-stimulated elevation of [Ca(2+)](i) which attenuates the nutrient-induced insulin secretory process possibly by desensitizing the cell to further changes in Ca(2+).

Free access

Rhonda D Prisby, Joshua M Swift, Susan A Bloomfield, Harry A Hogan and Michael D Delp

Osteopenia and an enhanced risk of fracture often accompany type 1 diabetes. However, the association between type 2 diabetes and bone mass has been ambiguous with reports of enhanced, reduced, or similar bone mineral densities (BMDs) when compared with healthy individuals. Recently, studies have also associated type 2 diabetes with increased fracture risk even in the presence of higher BMDs. To determine the temporal relationship between type 2 diabetes and bone remodeling structural and mechanical properties at various bone sites were analyzed during pre-diabetes (7 weeks), short-term (13 weeks), and long-term (20 weeks) type 2 diabetes. BMDs and bone strength were measured in the femora and tibiae of Zucker diabetic fatty rats, a model of human type 2 diabetes. Increased BMDs (9–10%) were observed in the distal femora, proximal tibiae, and tibial mid- shafts in the pre-diabetic condition that corresponded with higher plasma insulin levels. During short- and long-term type 2 diabetes, various parameters of bone strength and BMDs were lower (9–26%) in the femoral neck, distal femora, proximal tibiae, and femoral and tibial mid-shafts. Correspondingly, blood glucose levels increased by 125% and 153% during short- and long-term diabetes respectively. These data indicate that alterations in BMDs and bone mechanical properties are closely associated with the onset of hyperinsulinemia and hyperglycemia, which may have direct adverse effects on skeletal tissue. Consequently, disparities in the human literature regarding the effects of type 2 diabetes on skeletal properties may be associated with the bone sites studied and the severity or duration of the disease in the patient population studied.

Free access

Elisabet Estil.les, Noèlia Téllez, Joan Soler and Eduard Montanya

Interleukin-1β (IL1B) is an important contributor to the autoimmune destruction of β-cells in type 1 diabetes, and it has been recently related to the development of type 2 diabetes. IGF2 stimulates β-cell proliferation and survival. We have determined the effect of IL1B on β-cell replication, and the potential modulation by IGF2 and glucose. Control-uninfected and adenovirus encoding for IGF2 (Ad-IGF2)-infected rat islets were cultured at 5.5 or 22.2 mmol/l glucose with or without 1, 10, 30, and 50 U/ml of IL1B. β-Cell replication was markedly reduced by 10 U/ml of IL1B and was almost nullified with 30 or 50 U/ml of IL1B. Higher concentrations of IL1B were required to increase β-cell apoptosis. Although IGF2 overexpression had a strong mitogenic effect on β-cells, IGF2 could preserve β-cell proliferation only in islets cultured with 10 U/ml IL1B, and had no effect with 30 and 50 U/ml of IL1B. In contrast, IGF2 overexpression induced a clear protection against IL1B-induced apoptosis, and higher concentrations of the cytokine were needed to increase β-cell apoptosis in Ad-IGF2-infected islets. These results indicate that β-cell replication is highly sensitive to the deleterious effects of the IL1B as shown by the inhibition of replication by relatively low IL1B concentrations, and the almost complete suppression of β-cell replication with high IL1B concentrations. Likewise, the inhibitory effects of IL-β on β-cell replication were not modified by glucose, and were only modestly prevented by IGF2 overexpression, in contrast with the higher protection against IL1B-induced apoptosis afforded by glucose and by IGF2 overexpression.

Free access

L Monetini, F Barone, L Stefanini, A Petrone, T Walk, G Jung, R Thorpe, P Pozzilli and MG Cavallo

Enhanced cellular immune response to bovine beta-casein has been reported in patients with type 1 diabetes. In this study we aimed to establish beta-casein-specific T cell lines from newly diagnosed type 1 diabetic patients and to characterise these cell lines in terms of phenotype and epitope specificity. Furthermore, since sequence homologies exist between beta-casein and putative beta-cell autoantigens, reactivity to the latter was also investigated. T cell lines were generated from the peripheral blood of nine recent onset type 1 diabetic patients with different HLA-DQ and -DR genotypes, after stimulation with antigen pulsed autologous irradiated antigen presenting cells (APCs) and recombinant human interleukin-2 (rhIL-2). T cell line reactivity was evaluated in response to bovine beta-casein, to 18 overlapping peptides encompassing the whole sequence of beta-casein and to beta-cell antigens, including the human insulinoma cell line, CM, and a peptide from the beta-cell glucose transporter, GLUT-2. T cell lines specific to beta-casein could not be isolated from HLA-matched and -unmatched control subjects. beta-Casein T cell lines reacted to different sequences of the protein, however a higher frequency of T cell reactivity was observed towards the C-terminal portion (peptides B05-14, and B05-17 in 5/9 and 4/9 T cell lines respectively). Furthermore, we found that 1 out of 9 beta-casein-specific T cell lines reacted also to the homologous peptide from GLUT-2, and that 3 out of 4 of tested cell lines reacted also to extracts of the human insulinoma cell line, CM. We conclude that T cell lines specific to bovine beta-casein can be isolated from the peripheral blood of patients with type 1 diabetes; these cell lines react with multiple and different sequences of the protein particularly towards the C-terminal portion. In addition, reactivity of beta-casein T cell lines to human insulinoma extracts and GLUT-2 peptide was detected, suggesting that the potential cross-reactivity with beta-cell antigens deserves further investigation.

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P. F. Terranova, J. Th. J. Uilenbroek, L. Saville, D. Horst and Y. Nakamura

ABSTRACT

Preovulatory follicles from adult hamsters on the morning of pro-oestrus were used in this study. Serotonin stimulated oestradiol production by preovulatory follicles during a 5-h incubation in 1 ml Krebs–Ringer bicarbonate glucose medium containing isobutylmethylxanthine (0.1 mmol/l; IBMX) and androstenedione (1 μmol/l). The enhanced oestradiol production by serotonin was dependent on the dose of IBMX and androstenedione. Mianserin, a serotonin type-1 and serotonin type-2 receptor antagonists, prevented the serotonin-enhanced oestradiol production in a dose-dependent manner. Ketanserin, a specific serotonin type-2 receptor antagonist, was ineffective in blocking the action of serotonin, indicating that the effect of serotonin was mediated by the serotonin type-1 receptor. In the presence of androstenedione (1 μmol/l), serotonin was unable to enhance oestradiol production in isolated granulosa cells. It was also unable to enhance oestradiol production in early atretic follicles; atresia was induced experimentally by an injection of phenobarbital in order to prevent ovulation.

The data indicate that serotonin stimulates oestradiol production by hamster preovulatory follicles in vitro. The mechanism of action of serotonin involves an intact healthy follicle, a serotonin type-1 receptor and possibly cyclic AMP. The increased oestradiol secretion might be related to increased androgen production by the follicle and increased permeability (leakiness) of the follicle to androstenedione which serves as substrate for aromatization to oestradiol by the granulosa cell.

Journal of Endocrinology (1990) 125, 433–438

Free access

Sachiko Kitanaka, Utako Sato and Takashi Igarashi

Mutations in hepatocyte nuclear factor-1β (HNF-1β) lead to type 5 maturity-onset diabetes of the young (MODY5). Moreover, mutations in the HNF-1β gene might cause multiorgan abnormalities including renal diseases, genital malformations, and abnormal liver function. The objective of this study was to investigate the molecular mechanism of diabetes mellitus, intrauterine growth retardation, and cholestasis observed in MODY5 patients. We analyzed the transactivity of wild-type and three mutant HNF-1β on native human insulin, IGF-I, and multidrug resistance protein 2 (MRP2) promoters in combination with HNF-1α, using a reporter-assay system in transiently transfected mammalian cells. In the human insulin gene promoter, we found that the cooperation of HNF-1α and HNF-1β is prominent. Absence of this cooperation was observed in all of the HNF-1β mutants. In the human IGF-I and MRP2 promoters, we found that the HNF-1β His153Asn (H153N) mutant had a mutant-specific repressive effect on both HNF-1α and wild-type HNF-1β transactivity. Absence of the cooperation of HNF-1β mutants with HNF-1α in the human insulin gene promoter might be one cause of defective insulin secretion. The H153N mutant-specific repression of HNF-1α and HNF-1β transactivity in human IGF-I and MRP2 promoters might explain the case-specific clinical features of growth retardation and cholestasis observed only in early infancy. We found differential property of HNF-1α/HNF-1β activity and the effect of HNF-1β mutants by the promoters. We consider that analyses of HNF-1β mutants on the intended human native promoters in combination with HNF-1α may be useful in investigating the molecular mechanisms of the various features in MODY5.

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D. R. NAIK and C. J. DOMINIC

Seven morphologically and tinctorially distinct types of cell (types 1–) have been distinguished in the pars anterior of the pituitary gland of the musk shrew (Suncus murinus L.). On the basis of their responses to various experimental stimuli, these cell types were correlated with the secretion of various trophic hormones. Type 1 cells exhibited conspicuous changes after thyroidectomy or inactivation of the thyroid gland and hence appeared to be the source of TSH. Types 2 and 3 cells responded to gonadectomy and administration of androgens, which suggests that they were associated with gonadotrophin secretion. The granules of the type 2, but not the type 3 cells could be extracted with 10% trichloroacetic acid, which may indicate that type 2 and 3 cells secrete FSH and LH respectively. After the administration of either reserpine or oestrogen, the type 4 cells underwent hypertrophy and hyperplasia, which suggests that they were the likely source of prolactin. Type 6 cells, which are distinguishable from type 4 cells by their thinly dispersed erythrosinophilic granulation, showed conspicuous changes after unilateral adrenalectomy, administration of metyrapone or exposure to stress and may therefore be responsible for secretion of ACTH. Type 5 cells tinctorially resembled the somatotrophic cells of other mammalian species and did not respond to any of the experimental treatments used in the present study. It is therefore possible that these cells have a somatotrophic function. The possible significance of type 7 cells has been discussed previously.

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C. L. FOSTER, E. CAMERON and B. A. YOUNG

SUMMARY

The ultrastructure of the adenohypophysis of the rabbit, after treatment with propylthiouracil, is described. All cells in the zona tuberalis and pars distalis proper, with the exception of the prolactin producing (type 1) and stellate cells (type 5), were affected. However, the only ones which presented some evidence of sequential changes were the type 4 cells. These became markedly degranulated and sometimes showed vesiculation of the cisternae of the granular endoplasmic reticulum, similar to that observed in the 'thyroidectomy' cells in some other species. Although changes occurred in the somatotrophs (type 2) and in the gonadotrophs (type 3) the evidence suggests that it is the type 4 cells which have a thyrotrophic function.

Free access

Richard W Nelson and Claudia E Reusch

Diabetes mellitus is a common disease in dogs and cats. The most common form of diabetes in dogs resembles type 1 diabetes in humans. Studies suggest that genetics, an immune-mediated component, and environmental factors are involved in the development of diabetes in dogs. A variant of gestational diabetes also occurs in dogs. The most common form of diabetes in cats resembles type 2 diabetes in humans. A major risk factor in cats is obesity. Obese cats have altered expression of several insulin signaling genes and glucose transporters and are leptin resistant. Cats also form amyloid deposits within the islets of the pancreas and develop glucotoxicity when exposed to prolonged hyperglycemia. This review will briefly summarize our current knowledge about the etiology of diabetes in dogs and cats and illustrate the similarities among dogs, cats, and humans.

Free access

Alison J Forhead, Juanita K Jellyman, Katherine Gillham, Janelle W Ward, Dominique Blache and Abigail L Fowden

The actions of angiotensin II on type 1 (AT1) and type 2 (AT2) receptor subtypes are important for normal kidney development before birth. This study investigated the effect of AT1 receptor antagonism on renal growth and growth regulators in fetal sheep during late gestation. From 125 days of gestation (term 145±2 days), chronically catheterised sheep fetuses were infused intravenously for 5 days with either an AT1-specific receptor antagonist (GR138950, 2–4 mg/kg per day, n=5) or saline (0.9% NaCl, n=5). Blockade of the AT1 receptor decreased arterial blood oxygenation and pH and increased blood pCO2, haemoglobin and lactate, and plasma cortisol and IGF-II. Blood glucose and plasma thyroid hormones and IGF-I were unchanged between the treatment groups. On the 5th day of infusion, the kidneys of the GR-treated fetuses were lighter than those of the control fetuses, both in absolute and relative terms, and were smaller in transverse cross-sectional width and cortical thickness. In the GR-infused fetuses, renal AT2 receptor protein concentration and glomerular density were significantly greater than in the saline-infused fetuses. Blockade of the AT1 receptor had no effect on relative cortical thickness, fractional or mean glomerular volumes, or renal protein levels of the AT1 receptor, IGF type 1 receptor, insulin receptor or protein kinase C ζ. Therefore, in the ovine fetus, AT1 receptor antagonism causes increased renal protein expression of the AT2 receptor subtype, which, combined with inhibition of AT1 receptor activity, may be partly responsible for growth retardation of the developing kidney.