Biomedical subjects

Adrian J Bone

Publications and source records attributed to Adrian J Bone.

4 recordsLinked to original sources

PubMed2006

Monitoring exercise-induced changes in glycemic control in type 2 diabetes.

PURPOSE: The present study determined the efficacy of the Continuous Glucose Monitoring System (CGMS) during moderate exercise and monitored the changes in whole-day glucose profiles using the CGMS in individuals with and without type 2 diabetes. METHODS: Six, obese, diet-treated individuals with and four age-matched individuals without type 2 diabetes were monitored using the CGMS for 3 d. Subjects cycled at 90% of a predetermined lactate threshold for 1 h at approximately 09:00 h on day 2, during which venous blood was sampled at 10-min intervals and immediately analyzed for glucose concentrations. RESULTS: Venous blood glucose and CGMS values declined during exercise in the diabetes (P < 0.001) but not the control group (P = 0.085). The CGMS overestimated blood glucose in the control (P = 0.003) and the diabetes (P = 0.045) groups during exercise. The number of data points outside of the 95% confidence intervals was <5% in both groups, showing that there is a statistically acceptable level of agreement between venous blood glucose and CGMS values during exercise. Moderate exercise improved whole-day average glucose concentrations (P = 0.007) and whole-day area under the glucose curve (P = 0.016) values (AUCglu), and the time spent within +/-10% of fasting venous glucose (FVG) increased in the diabetes group (P = 0.021). No such effects were seen in the control group. CONCLUSION: Using continuous glucose monitoring we were able to demonstrate that a period of moderate exercise improved whole-day glycemic control in obese individuals with type 2 diabetes. The CGMS should only be used as an adjunct and not as an alternative to frequent blood glucose sampling when examining the changes in glucose values during exercise in individuals with and without type 2 diabetes.

Analysis of Variance↗

PubMed2004

Cell-to-cell contact influences proliferative marker expression and apoptosis in MIN6 cells grown in islet-like structures.

Cell-to-cell interactions play an important role in the development and maintenance of the beta-cell phenotype. Here, we have investigated whether E-cadherin plays a role in regulating the growth of insulin-secreting MIN6 cells configured as three-dimensional islet-like clusters (pseudoislets). Pseudoislets form by cell aggregation rather than by proliferation from individual cells and attain the size of primary mouse islets after approximately 7 days of maintenance in culture. E-cadherin is known to mediate homotypic cell adhesion between beta-cells and has also been implicated in a number of cellular processes, including proliferation, apoptosis, and differentiation. E-cadherin and its associated intracellular elements, alpha- and beta-catenin, were upregulated in MIN6 pseudoislets. Pseudoislet formation was associated with an increased expression of cyclin-dependent kinase inhibitors and a concomitant downregulation of Ki67, suggesting an overall reduction in cellular proliferation. However, measurements of 5-bromo-2'-deoxyuridine incorporation revealed that there were no differences in the rate of MIN6 cell proliferation whether they were configured as monolayers or as pseudoislets, which is likely to be a result of their being a transformed cell line. Cells within pseudoislets were not necrotic, but apoptosis appeared to be upregulated in the islet-like structures. However, no differential expression of Fas and FasL was detected in monolayers and pseudoislets. These results suggest that cell-to-cell interactions within islet-like structures may initiate antiproliferative and proapoptotic signals.

Animals↗

PubMed2004

Antioxidant enzyme activity and mRNA expression in the islets of Langerhans from the BB/S rat model of type 1 diabetes and an insulin-producing cell line.

It has been proposed that low activities of antioxidant enzymes in pancreatic beta cells may increase their susceptibility to autoimmune attack. We have therefore used the spontaneously diabetic BB/S rat model of type 1 diabetes to compare islet catalase and superoxide dismutase activities in diabetes-prone and diabetes-resistant animals. In parallel studies, we employed the RINm5F beta cell line as a model system (previously validated) to investigate whether regulation of antioxidant enzyme activity by inflammatory mediators (cytokines, nitric oxide) occurs at the gene or protein expression level. Diabetes-prone rat islets had high insulin content at the age used (58-65 days) but showed increased amounts of DNA damage when subjected to cytokine or hydrogen peroxide treatments. There was clear evidence of oxidative damage in freshly isolated rat islets from diabetes-prone animals and significantly lower catalase and superoxide dismutase activities than in islets from age-matched diabetes-resistant BB/S and control Wistar rats. The mRNA expression of antioxidant enzymes in islets from diabetes-prone and diabetes-resistant BB/S rats and in RINm5F cells, treated with a combination of cytokines or a nitric oxide donor, DETA-NO, was analysed semi-quantitatively by real time PCR. The mRNA expression of catalase was lower, whereas MnSOD expression was higher, in diabetes-prone compared to diabetes-resistant BB/S rat islets, suggesting regulation at the level of gene expression as well as of the activities of these enzymes in diabetes. The protein expression of catalase, CuZnSOD and MnSOD was assessed by Western blotting and found to be unchanged in DETA-NO treated cells. Protein expression of MnSOD was increased by cytokines in RINm5F cells whereas the expression of CuZnSOD was slightly decreased and the level of catalase protein was unchanged. We conclude that there are some changes, mostly upregulation, in protein expression but no decreases in the mRNA expression of catalase, CuZnSOD or MnSOD enzymes in beta cells treated with either cytokines or DETA-NO. The lower antioxidant enzyme activities observed in islets from diabetes-prone BB/S rats could be a factor in the development of disease and in susceptibility to DNA damage in vitro and could reflect islet alterations prior to immune attack or inherent differences in the islets of diabetes-prone animals, but are not likely to result from cytokine or nitric oxide exposure in vivo at that stage.

Animals↗

PubMed2004

Repair of cytokine-induced DNA damage in cultured rat islets of Langerhans.

Treatment of cultured rat pancreatic islets of Langerhans with the combined cytokines interleukin-1beta (IL-1beta), interferon gamma (IFN gamma) and tumour necrosis factor alpha (TNF alpha) leads to DNA damage including strand breakage. We have investigated the nature of this damage and its repairability. When islets are further incubated for 4 h in fresh medium, the level of cytokine-induced strand breakage remains constant. If the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine (NMMA) is present during cytokine treatment, then strand breakage is prevented. If NMMA is added following, rather than during,the cytokine treatment and islets are incubated for 4 h, further nitric oxide synthesis is prevented and most cytokine-induced strand breaks are no longer seen. To investigate DNA repair following cytokine treatment, cells were transferred to fresh medium and incubated for 4 h in the presence of hydroxyurea (HU) and 1-beta-D-arabinosyl cytosine (AraC), as inhibitors of strand rejoining. In the presence of these inhibitors there was an accumulation of strand breaks that would otherwise have been repaired. However, when further nitric oxide synthesis was inhibited by NMMA, significantly less additional strand breakage was seen in the presence of HU and AraC. We interpret this, as indicating that excision repair of previously induced base damage did not contribute significantly to strand breakage. Levels of oxidised purines, as indicated by formamidopyrimidine glycosylase (Fpg) sensitive sites, were not increased in cytokine-treated islets. We conclude that in these primary insulin-secreting cells: (a) the DNA damage induced by an 18h cytokine treatment is prevented by an inhibitor of nitric oxide synthase, (b) much of the damage is in the form of apparent strand breaks rather than altered bases such as oxidised purines, (c) substantial repair is ongoing during the cytokine treatment and this repair is not inhibited in the presence of nitric oxide.

Animals↗