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R C McEvoy

Publications and source records attributed to R C McEvoy.

At least 19 recordsLinked to original sources
PubMed2000

Glucose-stimulated and self-limiting insulin production by glucose 6-phosphatase promoter driven insulin expression in hepatoma cells.

The liver is an attractive target organ for insulin gene expression in type 1 diabetes as it contains appropriate cellular mechanisms of regulated gene expression in response to blood glucose and insulin. We hypothesize that insulin production regulated by both glucose and insulin may be achieved using the promoter of the glucose 6-phosphatase gene (G6Pase), the expression of which in the liver is induced by glucose and suppressed by insulin. Recombinant adenoviral vectors expressing the reporter gene CAT or insulin under transcriptional direction of the G6Pase promoter were constructed. Glucose-stimulated as well as self-limiting insulin production was achieved in vector-transduced hepatoma cells in which expression of the insulin gene was controlled by the G6Pase promoter. While insulin strongly inhibited the G6Pase promoter activity under low glucose conditions, its inhibitory capacity was attenuated when glucose levels were elevated. At the physiologic glucose level of 5.5 mM glucose, vector-transduced hepatoma cells produced a self-limited level of insulin at approximately 0.2-0.3 ng/ml, which is within the range of fasting levels of insulin in normal animals. These results indicate that the G6Pase promoter possesses desirable features and may be developed for regulated hepatic insulin gene expression in type 1 diabetes.

Adenoviridae↗
PubMed1999

Human insulin B chain but not A chain decreases the rate of diabetes in BB rats.

The autoimmune response seen in insulin-dependent diabetes mellitus (IDDM) includes a humoral immune response against human insulin. Early insulin treatment has been used to prevent IDDM in the rodent models of IDDM, and a prevention trial is underway in humans. The metabolic effects of insulin may not be involved in this prevention since, in NOD mice, the use of metabolically inert human insulin B chain was effective. We wished to ascertain whether immunization of diabetes-prone BB/W rats with insulin B chain, A chain, or both could alter the incidence of diabetes. Immunizations began by 30 days of age and the rats were followed until 120 days of age. Only immunization with insulin B chain plus adjuvant was effective in reducing the rate of diabetes. All immunization frequencies were effective, but a significantly lower rate of diabetes was achieved with injections every week. All of the doses tested resulted in significantly lower rates of diabetes. These data confirm in the BB rat model that immunization with insulin B chain in the presence of adjuvant can reduce diabetes incidence. The absence of any metabolic effect of B chain and the requirement for adjuvant suggest that this effect is mediated via modulation of the autoimmune response.

Animals↗
PubMed1999

Targeted deletion of the Vgf gene indicates that the encoded secretory peptide precursor plays a novel role in the regulation of energy balance.

To determine the function of VGF, a secreted polypeptide that is synthesized by neurons, is abundant in the hypothalamus, and is regulated in the brain by electrical activity, injury, and the circadian clock, we generated knockout mice lacking Vgf. Homozygous mutants are small, hypermetabolic, hyperactive, and infertile, with markedly reduced leptin levels and fat stores and altered hypothalamic proopiomelanocortin (POMC), neuropeptide Y (NPY), and agouti-related peptide (AGRP) expression. Furthermore, VGF mRNA synthesis is induced in the hypothalamic arcuate nuclei of fasted normal mice. VGF therefore plays a critical role in the regulation of energy homeostasis, suggesting that the study of lean VGF mutant mice may provide insight into wasting disorders and, moreover, that pharmacological antagonism of VGF action(s) might constitute the basis for treatment of obesity.

Aggression↗
PubMed1999

Escape from self-tolerance leads to neonatal insulin-dependent diabetes mellitus.

Double transgenic (dTg) mice expressing the hemagglutinin (HA) of influenza virus under the insulin promoter and the TCR specific for the immunodominant CD4 T cell epitope of HA (HA110-120) develop insulin-dependent diabetes mellitus (IDDM). In order to gain information on the breaking down of neonatal self-tolerance we studied the occurrence of IDDM after birth. Our results showed that newborn mice develop fulminant IDDM characterized by occurrence of insulitis as early as 3 days after birth, followed by hyperglycemia by 7 days, and significant hypoinsulinemia by 28 days. The neonatal breakdown of self-tolerance of T cells positively selected in the thymus is supported by the facts that: (i) peripheral HA110-120 specific T cells from neonates are fully functional and proliferated upon stimulation with the nominal peptide, and (ii) peptide-specific T cells were accumulated in the pancreas of dTg mice as early as 3 days after birth. Our results demonstrate that diabetes occurring in young dTg mice is due to early activation of self-reactive T cells immediately after birth. Accumulation of specific T cells in the target organ leads to destruction of pancreatic beta-cells and IDDM. These mice may provide a useful model to evaluate new strategies for the prevention of diabetes.

Animals↗
PubMed1998

Metabolic control and quality-of-life self-assessment in adolescents with IDDM.

OBJECTIVE: To examine the relation between metabolic control and self-assessed quality of life in adolescents with IDDM. RESEARCH DESIGN AND METHODS: The Diabetes Quality of Life (DQOL) questionnaire for youths was given to 69 subjects with IDDM aged 10-20 years at the time of their outpatient visit. Subjects with IDDM of < 1 year's duration or with documented psychotic disorder or mental retardation were excluded. Metabolic control was assessed by the mean HbA1c during the preceding year (long-term), by a single HbA1c at the time of the visit (short-term), and by the number of acute events related to IDDM in the preceding year. RESULTS: The DQOL score correlated with mean HbA1c (beta = 6.13, R2 = 0.22, P = 0.0122) and single HbA1c (beta = 3.94, R2 = 0.18, P = 0.05). Self-health assessment was the best predictor of DQOL score (beta = -44.42, R2 = 0.45, P < 0.0001). The Worries subscale score on DQOL correlated with the occurrence of acute events (beta = 6.97, R2 = 0.2, P = 0.006), but did not correlate with either HbA1c level. Correlations of mean HbA1c with the predictors were stronger than the correlations of single HbA1c with the same predictors. CONCLUSIONS: Metabolic control and quality of life are two important outcomes of IDDM care. In our study, adolescents in better metabolic control report better quality of life. Both components need to be addressed in developing successful diabetes treatment strategies for adolescents with IDDM.

Adolescent↗
PubMed1996

Anti-islet autoantibodies detected by monoclonal antibody 1A2: further studies suggesting a role in the pathogenesis of IDDM.

Insulin-dependent diabetes mellitus (IDDM) is associated with autoantibodies to several pancreatic islet antigens. We have described an assay in which autoantibodies displace a radiolabelled monoclonal anti-islet antibody. Sera from 87% of 429 children at time of diagnosis of IDDM were positive, while sera from control groups had much lower prevalences (1.3-19%). Sera from 41.9% of diabetic subjects remained positive after 20 years duration of IDDM. Sera from 23.6% of parents and 37.9% of non-diabetic siblings were positive. Twenty relatives who subsequently developed IDDM had the same prevalence of the antibodies (85%) as did the patients at time of diagnosis. These findings confirm that the autoantibodies detected by monoclonal antibody (mAb) 1A2 are common at the onset of IDDM and their presence prior to the onset of hyperglycaemia suggests that this method may be useful in screening non-diabetic populations. The high prevalence of antibodies in relatives reduces the efficacy for diabetes prediction, but suggests either that generation of these antibodies is an autosomal dominant trait, or that the antigen detected by these antibodies is cross-reactive with a common environmental antigen. Differentiation between these hypotheses will await the identification of the specific islet-cell antigen detected by mAb 1A2.

Adolescent↗
PubMed1995

Insulin-like growth factor I receptor expression and function in fibroblasts from two patients with deletion of the distal long arm of chromosome 15.

Most patients with deletion of the distal long arm of chromosome 15 have intrauterine growth retardation and postnatal growth deficiency in addition to developmental abnormalities. It has been proposed that the absence of one copy of the insulin-like growth factor I (IGF-I) receptor gene may play a role in the growth deficiency seen in this syndrome. To address this question we examined IGF-I receptor expression and function in fibroblasts from two patients with deletion of the distal long arm of chromosome 15 (15q26.1-->qter). Quantitative Southern blot analysis of the IGF-I receptor gene was performed on HindIII digests of fibroblast DNA. Radioactivity in the 1.7-kilobase receptor fragment in the two patients was 55% and 51% of the values in controls, consistent with the absence of one copy of the IGF-I receptor gene. IGF-I receptor messenger ribonucleic acid levels were quantitated by a solution hybridization/nuclease protection assay. Receptor messenger ribonucleic acid levels in the two patients were 45% and 52% of the values in controls. Northern blotting demonstrated normal size IGF-I receptor transcripts and affinity crosslinking of [125I]IGF-I to Triton X-100-solubilized fibroblasts demonstrated a normal size receptor in the patients. Analysis of placental membranes prepared from one patient revealed no difference in [125I]IGF-I binding. In the patients' fibroblasts, however, binding of [125I]long [R3]-IGF-I to the IGF-I receptor was significantly reduced, as assessed by the amount of radioactivity competed by the monoclonal antibody alpha IR-3 or insulin and Scatchard analysis of binding data. To assess IGF-I receptor function, stimulation of [alpha-1-14C]-methylaminoisobutyric acid transport and stimulation of [methyl-3H]thymidine incorporation into DNA by a full range of IGF-I concentrations was examined in patient and control fibroblasts. There was a significant decrease in the maximal response to IGF-I in both assays for one of the two patients when data were expressed as fold response over the basal value. However, there was no evidence for impairment of response to IGF-I in either patient's fibroblasts when data were expressed as net stimulation (maximal response minus basal). In conclusion, although IGF-I receptor expression was decreased in fibroblasts from two patients with deletion of the distal long arm of chromosome 15, we were unable to provide conclusive evidence for impairment of the biological response to IGF-I.

Child↗
PubMed1991

Gestational diabetes mellitus: evidence for autoimmunity against the pancreatic beta cells.

Diabetes mellitus is a frequent transient or rare permanent complication of pregnancy. The role of autoimmune phenomena in this gestational form of diabetes is incompletely understood. We have examined sera from 312 pregnant women who had abnormal glucose tolerance (based on a screening examination during the second trimester) for the presence of islet cell surface antibodies or insulin autoantibodies. Fifty-eight of these women were lost to follow-up. Of the remaining subjects, 144 (57.1%) had gestational diabetes diagnosed by formal glucose tolerance testing and the others (42.9%) were normal. Sixty percent of the women with gestational diabetes eventually required insulin to control their blood glucose during pregnancy. One serum from the non-diabetic women was positive for insulin antibodies (0.9%); 8 of the sera from the patients with gestational diabetes were positive (5.6%). Subsequent analysis revealed that all nine of the women whose sera were positive for insulin autoantibodies had been treated with insulin previously. Islet cell surface antibodies were strongly correlated with gestational diabetes. Forty-five of 144 gestational diabetic sera were positive (31.3%) whereas only 9 of 108 suspect control sera (8.3%) and 7 of 60 unknown sera (11.7%) were positive. These data suggest that a high percentage of pregnant women who screen positive for glucose intolerance have serological evidence of an autoimmune response against the pancreatic islets, in spite of the state of relative immune tolerance during pregnancy. These data suggest that autoimmune phenomena may play a role in gestational diabetes and that the presence of islet cell antibodies can predict insulin-requiring gestational diabetes.

Autoantibodies↗
PubMed1990

Strong association between diabetes and displacement of mouse anti-rat insulinoma cell monoclonal antibody by human serum in vitro.

In an attempt to identify novel pancreatic beta-cell surface antigens, mouse monoclonal antibodies (MoAbs) were raised against rat insulinoma (RIN5F) cells with standard techniques. Several clones were identified whose antibodies bound specifically to RIN5F cells but not to other rat, mouse, and human target cells. Each of these MoAbs was radiolabeled, and the specificity of binding of each MoAb was determined by the ability of excess cold homologous MoAb to displace the labeled MoAb. Six RIN5F cell-specific MoAbs of different epitopic specificities were identified. The relevance of these beta-cell epitopes to human insulin-dependent diabetes (IDDM) was demonstrated by the differential ability of human serums from control and diabetic children to displace the radiolabeled MoAbs from the RIN5F cells. Serums from 333 children without diabetes or a family history of diabetes and from 156 newly diagnosed IDDM patients were tested. Only one IgM MoAb was specifically displaced by the IDDM serums, i.e., 146 of 156, compared to serums from control children, i.e., 10 of 333. With immunofluorescence, the serum component responsible for the displacement of the mouse MoAb was identified as IgG. Most of the positive control serums were from children with active autoimmune thyroiditis. Serums from children with other forms of glucose intolerance did not displace MoAb 1A2. There was no correlation between age and the degree of displacement of 1A2. Thus, the displacement of 1A2 is a specific and sensitive marker of diabetes susceptibility easily applicable to mass screening.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Multiple low-dose streptozotocin-induced diabetes in the mouse: further evidence for involvement of an anti-B cell cytotoxic cellular auto-immune response.

Anti-B cell auto-immunity may play a role in the pathogenesis of diabetes in mice resulting from multiple subdiabetogenic doses of the pancreatic B cell toxin, streptozotocin. In the present study we have investigated the cytotoxic anti-B cell response in these mice. A major role for B lymphocytes, macrophages, or their products in the cytotoxic response originally detected in vitro was eliminated by passing splenocytes from the mice treated with multiple subdiabetogenic doses of streptozotocin over a nylon wool column. The removal of the adherent cells enhanced the cytotoxicity against a rat insulinoma cell line in vitro by that expected due to enrichment of T-lymphocytes by approximately two-fold. The induction of diabetes after multiple subdiabetogenic doses of streptozotocin is strain dependent. Mice of five strains were immunized with rat insulinoma cells, but only splenocytes from the two strains susceptible to multiple subdiabetogenic doses of streptozotocin demonstrated a significant cytotoxic response against the rat insulinoma cells in vitro. Mice pre-immunized with either the rat insulinoma cells or with syngeneic islets labelled in vitro with the hapten trinitrophenol developed hyperglycaemia more rapidly than control mice after multiple subdiabetogenic doses of streptozotocin. In the latter experiment the control mice immunized with complete Freund's adjuvant alone also became hyperglycaemic after a modified multiple subdiabetogenic dose of streptozotocin that did not cause diabetes in non-immunized mice. In mice pre-treated with either adjuvant or cyclophosphamide and then given a modified multiple subdiabetogenic dose of streptozotocin (35 mg/kg X 5 rather than 40 mg/kg) the degree of hyperglycaemia was reduced and there was no protective effect of cyclophosphamide.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Relationship of stressful housing conditions to the onset of diabetes mellitus induced by multiple, sub-diabetogenic doses of streptozotocin in mice.

The effect of the stress of crowded housing conditions (10 mice/cage) on the onset of diabetes after multiple, sub-diabetogenic doses of streptozotocin (MSZ) in male C57BL/KsJ mice was investigated. Prior to MSZ treatment, the group-housed and individually-housed animals had similar plasma glucose levels, while the former group's plasma corticosterone (CS) levels were elevated (54 +/- 8 ng/ml, p less than 0.03; 166% of the latter group). The group-housed animals became hyperglycemic (253 +/- 23 mg/dl) 2 days after the MSZ (day 7), with maximum hyperglycemia (506 +/- 23 mg/dl) developing by day 10. The individually housed animals did not become hyperglycemic until day 10 (303 +/- 24 mg/dl, p less than 0.001), and did not reach maximal hyperglycemia until between days 31 and 46, when plasma glucose levels were no longer different from the group-housed mice (507 +/- 37 mg/dl). There was a significant and progressive rise in CS levels of the stressed animals, reaching 218 +/- 25 ng/ml at day 46. The rise in CS of the unstressed animals was not significant until day 46, when the mean value reached 96 +/- 19 ng/ml (p less than 0.001 vs. basal). However, even at the conclusion of the experiment, the mean CS in the stressed animals was still 227% of that in the unstressed group (p less than 0.001). These studies demonstrate that the effects of stress (biochemically documented as an increase in CS levels) act synergistically with streptozotocin to promote an earlier onset of diabetes mellitus in males of this murine strain.

Animals↗
PubMed1987

Effect of aspirin on experimental diabetic nephropathy.

The decline in glomerular filtration rate (GFR) in long-term diabetes in humans and animals in preceded by a period of hyperfiltration that may be responsible for it. The mediators of the increase in glomerular filtration are unknown, but recent studies suggest a prominent role for prostaglandins. To test the hypothesis that prostaglandins mediate early hyperfiltration and contribute to the progression of diabetic nephropathy, we examined the effects of long-term aspirin (ASA) treatment on whole kidney GFR and renal prostaglandin E2 (PGE2) synthesis in control and diabetic rats 8 days and 16 weeks after streptozocin administration. The rats were divided into four groups, control, control with ASA (C/ASA), diabetic, and diabetic with ASA (D/ASA). We found that 8 days after streptozocin treatment, PGE2 synthesis and GFR were increased in diabetic rats. ASA treatment inhibited renal prostaglandin synthesis and prevented the GFR increase. ASA given to control rats reduced PGE2 synthesis without changing GFR. In the 16-week study diabetic rats had lower GFR and increased renal PGE2 synthesis. Diabetic rats also had thickened glomerular basement membrane compared with control rats. By contrast GFR did not fall and thickening of the glomerular basement membrane did not occur in diabetic rats receiving ASA. ASA had no effect on GFR or glomerular basement membrane in normal rats but decreased renal PGE2 synthesis. The data demonstrate that aspirin prevents early hyperfiltration and prevents the fall in GFR and glomerular basement membrane thickening that occurs over time in diabetic rats. Inhibition of PGE2 synthesis by aspirin, or some other effect of aspirin, may be responsible for the protection observed.

Animals↗
PubMed1986

Anti-insulin antibodies in children with type I diabetes mellitus. Genetic regulation of production and presence at diagnosis before insulin replacement.

We evaluated the production of antibodies against insulin in a genetically well-defined population. In the first study, 124 young patients with type I diabetes for longer than 6 mo were included. Anti-insulin antibodies were detected by polyethyleneglycol (PEG) precipitation after incubation of acidified, charcoal-stripped sera with 125I-labeled pork insulin and were expressed as microunits insulin bound per milliliter whole serum. For comparison, the patients were divided into six groups based on HLA DR antigens: 3/3, 3/-, 4/4, 4/-, 3/4, and -/-(-is non-DR3 or -DR4). The mean age of the patients was 14.7 +/- 0.5 yr; the duration of diabetes was 5.8 +/- 0.4 yr; and the glucose control, as measured by hemoglobin A1c was average (7.6 +/- 0.2%). There were no significant differences in any of these parameters among the patients in any of the HLA DR groups. Patients expressing DR3/3 had significantly lower insulin binding than the rest of the groups (2.5 +/- 0.4 vs. 13.6 +/- 1.4 microU/ml, P less than 0.0001). Patients with DR3/ - did not differ in insulin-binding capacity from the other groups. The type of insulin used for replacement was not correlated with the serum insulin-binding capacity. In a second study, sera from 48 children, newly diagnosed with type I diabetes, were examined for the presence of insulin binding before treatment with exogenous insulin and compared with sera from 80 children without diabetes or a family history of diabetes and from 103 unaffected HLA-identical or haploidentical siblings of a child with type I diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Biological differences in a rat insulinoma cell line obtained from different laboratories do not affect binding of human anti-islet immunoglobulins.

An insulin-producing clone of rat insulinoma cells (RINm5F) has been used by several investigators as target cells for studies of both humoral and cell-mediated anti-islet immunity in diabetic animals and humans. We noted that the rate of proliferation of RINm5F cells obtained from different laboratories varied considerably, and, in the present study, we have compared the proliferation rates of RINm5F cells obtained from 3 laboratories (Uppsala, Sweden [UPP], Chicago [CHI] and New York [NY]). The cells were plated at 0.5 and 2.0 X 10(4)/cm2 and changes in cell number were measured over 5 days. Basal insulin release was also determined daily. In addition, binding of IgG from sera of human diabetics by each of the cell lines was also examined by a solid-phase, quantitative assay. Plating efficiency was significantly greater in the NY and CHI cells than UPP cells at both plating densities (p less than 0.025). When plated at 2 X 10(4)/cm2, the growth rate of the NY cells was faster than the others (NY: 100.1 +/- 7.8%/day, CHI: 72.2 +/- 8.1%/day, UPP: 78.3 +/- 14.0%/day, p less than 0.025). All growth rates were lower when cells were plated at 5 X 10(4)/cm2, and the differences in growth between the NY and the other cells was greater (NY: 94.1 +/- 12.2%/day, CHI: 61.8 +/- 5.8%/day, UPP: 58.1 +/- 5.6%/day). Insulin release also differed among the cells. More insulin was released by the NY cells than by the other cells on all days, and the CHI cells released more insulin than the UPP cells (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma, Islet Cell↗
PubMed1986

Maintenance of fetal human pancreatic beta cells in tissue culture.

Large quantities of viable human islet tissue (beta cells) are required for transplant and for investigations of the autoimmune basis of Type I diabetes. Fetal pancreas offers a potential advantage over other possible sources of beta cells in that it retains some capacity for growth in vitro. We have cultured a total of 45 human pancreata from fetuses of gestational ages from 18 to 23 weeks. Each pancreas was obtained within minutes after delivery and usually cultured within 30 minutes. Pancreata were dispersed and cultured for up to 32 days. Maintenance and growth of the beta cells was assessed by the content of insulin in extracts of cultured tissue. As has been reported by others, fetal human beta cells survived in vitro for over 4 weeks. In three experiments in which a direct comparison was made, collagenase digestion of the fetal pancreas resulted in a significantly greater loss of insulin content compared to minced tissue cultured without digestion. Storage of three pancreata in medium overnight at 4 degrees C significantly reduced the insulin content of the pancreas compared to pancreata cultured immediately. During culture, the majority of the beta cells (based on insulin content) were found in small, macroscopic clumps attached to the surface of the culture dish, and surrounded by a nearly confluent monolayer of fibroblastoid cells. There was a marked decrease in the insulin content of the tissue during culture, most of it (to less than 25% of the original) occurring over the first 4-6 days of culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Aggregation↗
PubMed1985

Ablation of serotonergic nerves in the rat pancreas. Lack of effects on hormone secretion and intrinsic blood flow.

The aim of the present study was to evaluate the physiological role of intrapancreatic serotonergic nerves for endocrine pancreatic function. The specific uptake of [3H]5-hydroxytryptamine (5-HT) into pancreatic slices from the rat was completely abolished after an intrapancreatic injection of 5,7-dihydroxytryptamine (5,7-DHT). Since also high-affinity uptake of [3H]5-HT was absent it was concluded that intrapancreatic serotonergic nerves were destroyed. The effects of this selective denervation on glucose-stimulated insulin and somatostatin secretion were investigated with the aid of perfused rat pancreatic glands removed 3, 7 or 14 days after the injection of 5,7-DHT. Neither the basal release of these hormones nor their response to a glucose challenge was significantly altered by the ablation of the intrapancreatic serotonergic nerves. The microsphere technique was used to investigate the blood flow through the pancreatic islets in rats injected intrapencreatically with 5,7-DHT 4 days previously. No significant changes in either the whole pancreatic blood flow or the islet blood flow could be demonstrated. These result show that in normal physiological conditions the intrapancreatic serotonergic nerves do not affect the hormonal release from or the blood flow through the endocrine pancreas.

5,7-Dihydroxytryptamine↗