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F Homo-Delarche

Publications and source records attributed to F Homo-Delarche.

At least 19 recordsLinked to original sources

Oestradiol restores cell proliferation in dentate gyrus and subventricular zone of streptozotocin-diabetic mice.

Type 1 diabetes mellitus correlates with several brain disturbances, including hypersensitivity to stress, cognitive impairment, increased risk of stroke and dementia. Within the central nervous system, the hippocampus is considered a special target for alterations associated with diabetes. Neurogenesis is a plastic event restricted to few adult brain areas: the subgranular zone of the dentate gyrus and the subventricular zone (SVZ). First, we studied the ability for neurogenesis in the dentate gyrus and SVZ of chronic diabetic mice induced by streptozotocin (STZ). Using bromodeoxyuridine (BrdU) labelling of cells in the S-phase, we observed a strong reduction in cell proliferation rate in both brain regions of diabetic mice killed 20 days after STZ administration. Second, because oestrogens are active neuroprotective agents, we investigated whether 17beta-oestradiol (200 micro g pellet implant in cholesterol during 10 days) restored brain cell proliferation in the diabetic mouse brain. Our results demonstrated a complete reversibility of dentate gyrus cell proliferation in oestrogen-treated diabetic mice. This plasticity change was not exclusive to the hippocampus because oestrogen treatment restored BrdU incorporation into newborn cells of the SVZ region of diabetic animals. Oestrogen treatment did not alter the hyperglycemic status of STZ-diabetic mice. Moreover, oestrogen did not modify BrdU incorporation in control animals. These data show that oestrogen treatment strongly stimulates brain neurogenesis of diabetic mice and open up new venues for understanding the potential neuroprotective role of steroid hormones in diabetic encephalopathy.

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Abnormalities in dendritic cell and macrophage accumulation in the pancreas of nonobese diabetic (NOD) mice during the early neonatal period.

Dendritic cell (DC), macrophage (Mphi) and lymphocyte infiltrations have been observed in normal human perinatal pancreata, but have never been investigated so early in control mice. In type 1 diabetes-prone NOD mice, these cells are thought to infiltrate first the periphery of the islets of Langerhans around weaning before further islet infiltration and beta-cell destruction. We quantified, during the first month of life, the numbers of DC (characterized by CD11c positivity and dendritic morphology), histiocyte-like Mphi (characterized by ER-MP23 positivity) and Mphi with scavenging potential (characterized by BM8 positivity) in C57BL/6, DBA/2 and BALB/c control, and NOD and lymphocyte-deficient NODscid mouse pancreata. First, CD11c+ DC were present at low densities from birth onwards in control pancreata, while densities were higher in NOD and NODscid. Second, high numbers of BM8+ and ER-MP23+ Mphi were observed at birth in all strains investigated. After birth, particularly BM8+ cells disappeared progressively in control strains, but not in NOD and NODscid. Third, NOD mice also had more ER-MP23+ Mphi at birth compared to controls. Finally, DC and Mphi localizations were similar in all strains, i.e., mostly as dispersed cells in perivascular, periductular, peri-islet areas and interlobular septa. The most remarkable finding was that particularly BM8+ Mphi, were seen at sites of islet neogenesis and predominantly at the duct-islet interface. Our data showed that different types of APC were present in the pancreas during postnatal development in various control mouse strains and some differences were observed in NOD and NODscid mice from birth onwards.

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Pancreatic hormone and glutamic acid decarboxylase expression in the mouse thymus: a real-time PCR study.

We devised a real-time RT-PCR method for the quantification of preproinsulin 1 and 2, proglucagon, prosomatostatin, and GAD 65 and 67 mRNAs in the thymus, using specific primers and internal probes. Corresponding standard cRNA synthesis and normalization to 18S ribosomal RNA allowed direct quantification. Then, during the first month of life, the expression of each substance of interest was measured in the thymus of NOD mice (a spontaneous model of type 1 diabetes), C57BL/6, BALB/c and lymphocyte-deficient mice (NODscid, NODrag, BALB/cscid and C57BL/6rag). In all mouse thymuses, preproinsulin 1 and GAD 65 were undetectable, preproinsulin 2 and proglucagon showed low expression, whereas that of GAD 67 and somatostatin were high. In 7-day-old mice, GAD 67 and prosomatostatin thymic expressions were lower in NOD than in C57BL/6, and at the same age, the scid mutation but not the rag mutation induced higher expression of all investigated genes compared to control mice. In conclusion, our data allowed the quantification of the expression of pancreatic factors in the mouse thymus. Investigations are underway to quantify, at the cellular level, i.e., in thymic dendritic/macrophage cells, the RNA expression of potential autoantigens, such as preproinsulin 2 and GAD 67.

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Diabetes increases the expression of hypothalamic neuropeptides in a spontaneous model of type I diabetes, the nonobese diabetic (NOD) mouse.

1. Synthesis of oxytocin (OT) and arginine-vasopressin (AVP) is increased in induced models of Type I diabetes, such as the streptozotocin model. However, these parameters have not yet been evaluated in spontaneous models, such as the nonobese diabetic mouse (NOD). Therefore, we studied in the magnocellular cells of the paraventricular nucleus (PVN) of nondiabetic and diabetic 16-week-old female NOD mice and control C57B1/6 mice, the immunocytochemistry of OT and AVP peptides and their mRNA expression, using nonisotopic in situ hybridization (ISH). 2. In nondiabetic and diabetic NOD female mice, the number of OT- and AVP-immunoreactive cells were similar to those of the controls, whereas immunoreaction intensity was significantly higher for both peptides in diabetic NOD as compared with nondiabetic NOD and control C57B1/6 mice. 3. ISH analysis showed that the number of OT mRNA-containing cells was in the same range in the three groups, whereas higher number of AVP mRNA expressing cells was found in diabetic NOD mice. However, the intensity of hybridization signal was also higher for both OT and AVP mRNA in the diabetic group as compared with nondiabetic NOD and control mice. 4. Blood chemistry demonstrated that haematrocrit, total plasma proteins, urea, sodium, and potassium were within normal limits in diabetic mice. Thus, NOD mice were neither hypernatremic nor dehydrated. 5. We suggest that upregulation of OT and AVP reflects a high-stress condition in the NOD mice. Diabetes may affect neuropeptide-producing cells of the PVN, with the increased AVP and OT playing a deleterious role on the outcome of the disease.

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Sex steroids influence pancreatic islet hypertrophy and subsequent autoimmune infiltration in nonobese diabetic (NOD) and NODscid mice.

Female nonobese diabetic (NOD) mice more frequently develop autoimmune diabetes than NOD males. Orchidectomy of the latter aggravates insulitis and diabetes. Because clear differences in immune function have not been observed between prediabetic females and males, before or after castration, we hypothesized that sex-related differences in diabetes incidence are related to target organ-specific actions of sex steroids. Previously, we showed that prediabetic NOD females develop hyperinsulinemia and subsequently mega-islets. Infiltration of the first inflammatory leukocytes is predominantly associated with these mega-islets. Here, we determined the relationship between sex hormones, mega-islet formation, and infiltrating cells in NOD and nonobese diabetic/severe combined immune-deficient (NODscid) mice. Mega-islet formation was reduced in NOD males compared with NOD females, and orchidectomy increased it, indicating a relationship between androgen levels and mega-islet formation. Moreover, enhanced mega-islet formation in castrated NOD males was associated with increased numbers of infiltrating leukocytes. Castrated NODscid males also exhibited increased mega-islet formation and dendritic cell infiltration, indicating that lymphocytes are not required for castration-induced effects. In conclusion, we show that androgens influence pancreatic islets and autoimmune infiltration in NOD and NODscid mice. This suggests that the gender difference in diabetes incidence in NOD mice is related to target organ-specific androgen effects.

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Abnormal organogenesis in salivary gland development may initiate adult onset of autoimmune exocrinopathy.

OBJECTIVES: Salivary gland organogenesis was evaluated in NOD mice, an animal model for autoimmune exocrinopathy, to determine when disease onset is first present in the target tissues. METHODS: Submandibular glands were removed for histological, immunohistochemical and biochemical evaluation from neonatal NOD and congenic strains as well as healthy control C57BL/6 mice. RESULTS: Histomorphological analyses of neonatal submandibular glands, the primary target for autoimmune exocrinopathy at 1 day postpartum, revealed delayed morphological differentiation during organogenesis in autoimmune-susceptible NOD mice when compared to nonsusceptible C57BL/6 mice. Acinar cell proliferation was reduced, while expression of Fas, FasL and bcl-2 were increased. Acinar cell proliferation was reduced, while expression, of Fas, FasL and bcl-2 were increased. Throughout the preweaning period (21 days) submandibular glands from NOD and NOD congenic strains aberrantly expressed an increased matrix metalloproteinase (MMP)-2 and MMP-9 activity. Substitution of two susceptibility alleles (Idd3 and Idd5) in NOD mice resulted in an hierarchical and additive reversal of delayed organogenesis, elevated MMP-9 activity, and aberrant expression of parotid secretory protein. DISCUSSION: NOD-derived mice whose submandibular glands showed normal organogenesis did not progress to develop autoimmune exocrinopathy. Altered organogenesis of target tissue may therefore provide a cellular microenvironment capable of activating autoimmunity.

Aging↗

Is pancreas development abnormal in the non-obese diabetic mouse, a spontaneous model of type I diabetes?

Despite extensive genetic and immunological research, the complex etiology and pathogenesis of type I diabetes remains unresolved. During the last few years, our attention has been focused on factors such as abnormalities of islet function and/or microenvironment, that could interact with immune partners in the spontaneous model of the disease, the non-obese diabetic (NOD) mouse. Intriguingly, the first anomalies that we noted in NOD mice, compared to control strains, are already present at birth and consist of 1) higher numbers of paradoxically hyperactive beta cells, assessed by in situ preproinsulin II expression; 2) high percentages of immature islets, representing islet neogenesis related to neonatal beta-cell hyperactivity and suggestive of in utero beta-cell stimulation; 3) elevated levels of some types of antigen-presenting cells and FasL+ cells, and 4) abnormalities of extracellular matrix (ECM) protein expression. However, the colocalization in all control mouse strains studied of fibroblast-like cells (anti-TR-7 labeling), some ECM proteins (particularly, fibronectin and collagen I), antigen-presenting cells and a few FasL+ cells at the periphery of islets undergoing neogenesis suggests that remodeling phenomena that normally take place during postnatal pancreas development could be disturbed in NOD mice. These data show that from birth onwards there is an intricate relationship between endocrine and immune events in the NOD mouse. They also suggest that tissue-specific autoimmune reactions could arise from developmental phenomena taking place during fetal life in which ECM-immune cell interaction(s) may play a key role.

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Islet endocrine-cell behavior from birth onward in mice with the nonobese diabetic genetic background.

BACKGROUND: Glucagon-producing alpha cells play a crucial role during the perinatal period. Because of their peri-islet localization near the early dendritic and macrophage cell infiltration, we thought it pertinent to investigate alpha cells in greater depth in nonobese diabetic (NOD) mice, a well-recognized spontaneous model for human type I diabetes. MATERIALS AND METHODS: We determined alpha-cell distribution (glucagon immunohistochemistry and image analysis) and activity (real-time reverse transcriptase polymerase chain reaction [RT-PCR] and glucagon radioimmunoassay [RIA]), in relationship to glycemia in NOD and lymphocyte-deficient NODscid mice as compared to control mice (C57BL/6) from birth onward. RESULTS: NOD and NODscid mice, particularly at 1 day of age, had twice as many very small islets (<2,000 pixels) as C57BL/6 mice. During the postnatal period, the percentages of glucagon-positive areas in islets less than 2000 pixels were higher in NOD mice than C57BL/6; only a trend was found in NODscid. Pancreatic mRNA expression and glucagon content decreased in all strains at weaning. However, before weaning, pancreatic and blood glucagon levels were significantly lower in NOD and NODscid compared to C57BL/6 mice. Low basal nonfasting glycemia was observed in all strains before weaning with some strain differences: glycemia was significantly lower in NOD than C57BL/6, and higher in NODscid than NOD and C57BL/6. CONCLUSION: These data suggest that, before weaning, NOD and, to some extent NODscid pancreata contain more immature islets (as reflected by their small size and high percentages of glucagon-positive areas, concomitant with lower glucagon storage and basal secretion) than C57BL/6 pancreata.

Aging↗

Islet abnormalities associated with an early influx of dendritic cells and macrophages in NOD and NODscid mice.

In the nonobese diabetic (NOD) mouse model for type 1 diabetes, the inflammatory infiltration of islets starts with an influx of dendritic cells (DC) and macrophages (Mphi) at approximately 4 weeks of age. Around this time, NOD mice show endocrine abnormalities, indicated by a transient hyperinsulinemia that lasts until 8 weeks of age. Subsequently, they develop abnormally large islets of Langerhans, here designated as "mega-islets." NODscid mice, which lack functional lymphocytes, also exhibit transient hyperinsulinemia, but to a lesser extent. First, to determine the role of lymphocytes in the morphological islet abnormalities, we compared 6-week-old (prediabetic) NOD and NODscid females regarding mega-islet development and accumulation of antigen-presenting cells (APC), particularly CD11c+ DC and ERMP23+ Mphi. In NODscid mice, early APC infiltration and mega-islets were present, but less marked compared with NOD mice, thus suggesting a role of lymphocytes in mega-islet formation. In both NOD and NODscid mice, the APC infiltration was predominantly found around the mega-islets, suggesting a relationship between both parameters. Second, to analyze the role of beta-cell hyperactivity in mega-islet formation, we studied the effect of short-term prophylactic insulin treatment on these parameters. Prophylactic insulin treatment decreased the percentages of mega-islets in both NOD and NODscid mice, indicating that beta-cell hyperactivity is also involved in mega-islet formation. In conclusion, mega-islet formation in mice with the NOD genetic background takes place under the influence of both beta-cell hyperactivity and leukocytes.

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Increased sensitivity of prediabetic nonobese diabetic mouse to the behavioral effects of IL-1.

The nonobese diabetic (NOD) mouse is a model of spontaneous insulin-dependent diabetes mellitus (IDDM) or type I diabetes. In humans, and in animal models of IDDM, the progression of the disease is modulated by various environmental factors, particularly infectious agents. Interleukin-1 (IL-1) plays a pivotal role in the development of IDDM, and modulation of its synthesis may be a mechanism by which environmental modulation of disease progression occurs. Since various alterations at the level of the gene, number, and sensitivity of IL-1 receptors have been described in different animal models of autoimmune disease, we investigated, in the prediabetic NOD mouse, the presence of IL-1 receptors and their functional behavioral characteristics. Here we present evidence that prediabetic NOD mice exhibit a normal distribution and density of functional brain IL-1 receptors, but are more sensitive to the behavioral effects of IL-1 than the control ICR strain.

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Glucose homeostasis in the nonobese diabetic mouse at the prediabetic stage.

Because few data were available on glucose homeostasis at the early prediabetic stage in the nonobese diabetic (NOD) mouse, we investigated glycemia, insulinemia, and pancreatic insulin content under basal conditions in both sexes of 4-, 6-, and 8-week-old fed NOD mice, compared with sex- and age-matched fed C57BL/6 mice. We also investigated glucose tolerance in both sexes of fasting 8-week-old NOD and C57BL/6 mice. The main results obtained under basal fed conditions, when comparing both strains, were lower glycemia and higher insulinemia in NOD females at all ages investigated and in NOD males (particularly at 6 weeks of age). Glucose tolerance tests showed that: 1) the blood glucose response to 1 g/kg i.p. glucose was less sustained in both sexes of 8-week-old NOD mice than in their control counterparts; 2) the blood insulin response to glucose (1 g/kg i.p.) appeared earlier in both sexes of NOD mice than in sex-matched C57BL/6 mice; 3) an unusual sexual dimorphism existed in NOD mice, compared with controls, with females secreting, in response to glucose, twice as much insulin as males; 4) dose-response studies (1-6 g/kg glucose) confirmed the lower increase in blood glucose levels in both sexes of NOD mice and their unusual sexual dimorphism in insulin secretion; and 5) glucose tolerance tests in 4- to 8-week-old NOD mice showed that although the sexual dimorphism in insulin secretion was not observed in 4-week-old mice, it was particularly striking at 6 weeks of age. Taken together, these results suggest that beta-cell hyperactivity exists in the NOD mouse at the early prediabetic stage, especially in NOD females.

Age Factors↗

Pancreatic hormone expression in the murine thymus: localization in dendritic cells and macrophages.

The expression of preproinsulin (ppIns), proglucagon, prosomatostatin, and propancreatic polypeptide was investigated in thymic extracts, thymic cells, and thymic cell lines from C57BL/6 mice by RT-PCR. The expression of pancreatic hormones was similar in thymic extracts taken from neonatal and 2-, 4-, and 8-week-old animals, but was decreased in 20-week-old animals. Pancreatic hormone expression was not observed in mouse liver, salivary gland, or spleen. Analysis of thymic cell populations revealed a 10- to 20-fold enrichment in expression of all hormones in low buoyant density cells. No expression was detected in high buoyant density cells (predominantly thymocytes) or in thymic epithelial cell lines, primary cultures of epithelial cells, or peripheral macrophages. In addition, immunoreactive insulin, measured by specific RIA, was detectable in the low buoyant density population, but not in high buoyant density cells. The enriched cell population was depleted of contaminating lymphocytes and sorted based on reactivity to the cell surface markers F4/80 (macrophage) or N418 (dendritic cells). Cells gated for N418 demonstrated expression for ppIns, but not the other pancreatic hormones. Conversely, expression for proglucagon, prosomatostatin, and propancreatic polypeptide, but not ppIns, was detected in F4/80-gated cells. Our data indicate that pancreatic endocrine hormones are differentially expressed by dendritic cells and macrophages in a normal mice.

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Basal concentrations of various steroids in the nonobese diabetic (NOD) mouse and effect of immobilization stress.

The progression of type I diabetes in the NOD mouse is modulated by, among other things, stressful events and steroids. We measured in 2-month-old prediabetic NOD mice various circulating steroids (progesterone, corticosterone, dehydroepiandrosterone, delta4-androstenedione, testosterone, estrone and estradiol) under basal and stressful conditions (1.5h immobilization). Basal progesterone concentrations were low but measurable in randomized cycling NOD females and under the detection limit in NOD males. Immobilization increased progesterone concentrations in both sexes. Serum corticosterone concentrations also increased after immobilization but with the sexual dimorphism normally observed in rodents. Dehydroepiandrosterone concentrations were similar in both sexes and remained unaffected by stress. Testosterone and delta4-androstenedione were drastically reduced after immobilization in NOD males. Serum estrone and estradiol were not found to be statistically different in NOD females and males, but slightly higher to that described in the literature, and immobilization increased estrone concentrations in NOD males. In conclusion, while nonspecific to the NOD mouse, the modulation of circulating corticosteroids, estrogens and androgens induced by environmental factors may be part of the mechanism(s) by which these factors modulate the progression of type I diabetes. The hormonal changes may act in a complex manner at different levels: the immune system, the islet of Langerhans and the other structures involved in glucose homeostasis.

Adrenalectomy↗

Beta-cell behavior during the prediabetic stage. Part I. Beta-cell pathophysiology.

beta-Cell function in non-insulin dependent diabetes mellitus (NIDDM) or type II diabetes, in particular during the prediabetic stage, has been more extensively investigated than in insulin-dependent diabetes mellitus (IDDM) or type I diabetes. Recently, however, the existence of a beta-cell dysfunction, early during the prediabetic stage of IDDM, and its possible contribution to the amplification of the autoimmune reaction have been underlined. Here, in a first of two parts, an attempt is made to review the various ways normal beta cells cope with increased demands on their resources in different models of hyperglycaemia in order to better delineate and compare the mechanisms implicating beta cells in the pathogenesis of both types of diabetes.

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Beta-cell behaviour during the prediabetic stage. Part II. Non-insulin-dependent and insulin-dependent diabetes mellitus.

The pathogenesis of autoimmune insulin-dependent (Type 1) diabetes mellitus (IDDM) is far from being resolved, despite extensive genetic and immunological research. However, recent experimental data from immune and endocrine studies using spontaneous or transgenic models of the disease have emphasized the role of the islet of Langerhans, and particularly beta cells, in IDDM pathogenesis. Part I of this review (Diabetes Metab, 1997, 23, 181-194) considered the various ways normal beta cells cope with increased demands on their resources in different models of hyperglycaemia in order to provide a better delineation and comparison of the mechanisms implicating these cells in the pathogenesis of IDDM and non-insulin-dependent (Type 2) diabetes mellitus (NIDDM). Part II attempts to improve our understanding of the various mechanisms through which beta cells, and perhaps the entire islet of Langerhans, may influence the immune system from the perinatal period to adulthood. Genetics and beta-cell behaviour are considered during prediabetes in human and experimental models of IDDM and NIDDM. Attention is focused on the spontaneous model of the disease, the non-obese diabetic (NOD) mouse, which in addition to providing genetic data, appears to be useful for sequential study of the early developmental, immune and endocrine events that occur in IDDM pathophysiology.

Aging↗

Effect of prophylactic insulin treatment on the number of ER-MP23+ macrophages in the pancreas of NOD mice. Is the prevention of diabetes based on beta-cell rest?

Prophylactic insulin treatment has been shown to have beneficial effects in type 1 diabetes, both in humans and in various animal models of the disease. In experimental models, the protective effect of prophylactic insulin treatment was observed in two parameters: (1) progression of insulitis and (2) diabetes incidence. The mechanism of protection still remains to be investigated. We therefore analysed by immunohistochemistry the effect of prophylactic insulin treatment vs placebo treatment (from 4 to 13 weeks of age) on ER-MP23+ macrophage infiltration in and around pancreatic islets in the non-obese diabetic (NOD) mouse, a spontaneous model for type 1 diabetes. BALB/c mice were used as diabetes-free controls. Using conventional haematoxylin-eosin staining, we detected a protective effect of prophylactic insulin treatment in NOD females on the lymphocytic insulitis, significant at 13 weeks, but not at 9 weeks of age. However, when assessed by immunostaining for early infiltration of ER-MP23+ macrophages around islets, the reduction in severity of insulitis could already be detected as early as 9 weeks of age. With regard to the early accumulation of ER-MP23+ cells, we observed that their numbers per mm2 surface area of the exocrine pancreas and per micron at the circumference of the islet were higher in placebo-treated NODs (197 +/- 13.8 and 14 +/- 0.9, respectively) as compared to age-matched BALB/c mice (123.1 +/- 7.1 and 3.5 +/- 0.9, respectively). Prophylactic insulin treatment of NODs lowered the attraction of ER-MP23+ macrophages to the exocrine pancreas and to the circumference of the islets (156.3 +/- 8.5 and 7.9 +/- 1, respectively). Interestingly also, the islet size was found to be larger in placebo-treated NODs (51% was larger than 10 microns2) than in age-matched BALB/c mice (9% larger than 10 microns2). Prophylactic insulin treatment of NODs reduced their islet size to sizes found in the control BALB/c strain. In conclusion, the decrease in islet size by early insulin administration, and the lower attraction of ER-MP23+ macrophages to the islets are morphological indications that prevention of diabetes development by prophylactic insulin treatment results from a down-regulation of islet metabolism and growth, with a concomitant decline in the release of islet factors attracting macrophages.

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Localization of gamma-aminobutyric acid and glutamic acid decarboxylase in the pancreas of the nonobese diabetic mouse.

Glutamic acid decarboxylase (GAD), among other potential autoantigens, is thought to play a crucial role in type I diabetes, particularly in a spontaneous model of the disease, the nonobese diabetic (NOD) mouse. In the pancreas, the presence of GAD and gamma-aminobutyric acid (GABA), the decarboxylation product of GAD and a putative neurotransmitter in the islets of Langerhans, is well documented in the beta-cells. This is particularly true in rats, in which another GABAergic structure exists near the islets, the neuronal bodies. In this study, first the GABA content was measured in isolated islets from NOD and C57BL/6 mice (controls), and a decrease was found in NOD females as their insulitis progressed. Second, for the first time in mice, confocal analysis of immunofluorescent-labeled pancreatic sections revealed near the islets neuronal structures in which GAD and neuropeptide Y were colocalized, as they are in the brain. These structures were always observed in the pancreata of both sexes of C57BL/6 mice at the various ages investigated. In NOD mice, however, these neuronal structures were only detected in young females ( < 10 weeks old) and in males until an intermediate age. Moreover, patches of T cells surrounding GAD-containing fibers were seen in the vicinity of the islets with incipient periinsulitis.

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