Characteristics of BRIN-BG5 and BRIN-BG7, two novel glucose-responsive insulin-secreting cell lines produced by electrofusion

Morphological and biochemical changes in the pancreas associated with acute systemic hypoxia

This study aimed to investigate the changes associated with acute systemic hypoxia in the endocrine system, particularly in pancreatic tissues. The investigation was based on macroscopic, pathohistological, biochemical, and molecular biological findings in cell lines and human cadavers. The results showed that cases of death due to asphyxia more frequently showed severe subcapsular/interstitial hemorrhage versus the other causes of death. Histological examination showed that asphyxia cases were associated with severe morphological changes. Although measured insulin levels in the asphyxia were higher compared to other causes of death, no differences were noted for the glucagon and amylase levels with regard to the cause of death. Increased blood insulin levels were not associated with macro- and micromorphological changes, and did not show any association with glucose or cortisol levels. The experiment conducted under hypoxic conditions in cultured cells demonstrated that insulin mRNA expression and insulin protein levels peaked at 10 min after hypoxia exposure. However, there were no changes in either the amylase mRNA or protein levels. Corticosterone level peaked at 120 min after exposure to hypoxic conditions. Overall, acute systemic hypoxic conditions can directly affect the mechanisms involved in pancreatic insulin secretion.

Starch synthase IIIa and starch branching enzyme IIb-deficient mutant rice line ameliorates pancreatic insulin secretion in rats: screening and evaluating mutant rice lines with antidiabetic functionalities

Diabetes mellitus is a metabolic disease spreading worldwide that has been reported to worsen the development and progression of other diseases (cancer, vascular diseases and dementia). To establish functional rice lines with anti-postprandial hyperglycaemic effects, we developed mutant rice lines, which lack one or two gene(s) related to starch synthesis, and evaluated their effects. Powder of mutant rice lines or other grains was loaded to rats fasted overnight (oral grain powder loading test). Incremental area under time-concentration curves (iAUC) were calculated with monitored blood glucose levels. Rice lines with anti-postprandial hyperglycaemic effects were separated by cluster analysis with calculated iAUC. A double mutant rice #4019 (starch synthase IIIa (ss3a)/branching enzyme IIb (be2b)), one of the screened mutant rice lines, was fed to Goto-Kakizaki (GK) rats, an animal model for type 2 diabetes, for 5 weeks. Plasma levels of C-peptide, a marker of pancreatic insulin secretion, were measured with ELISA. Forin vitrostudy, a rat pancreatic cell line was cultured with a medium containing rat serum which was sampled from rats fed #4019 diet for 2 d. After 24-h of incubation, an insulin secretion test was performed. Through the oral rice powder loading test, seven rice lines were identified as antidiabetic rice lines. The intake of #4019 diet increased plasma C-peptide levels of GK rats. This result was also observedin vitro.In rat serum added to cell medium, ornithine was significantly increased by the intake of #4019. In conclusion, the mutant rice #4019 promoted pancreatic insulin secretion via elevation of serum ornithine levels.

Cellular models for beta-cell function and diabetes gene therapy

Diabetes is characterized by the destruction and/or relative dysfunction of insulin-secreting beta-cells in the pancreatic islets of Langerhans. Consequently, considerable effort has been made to understand the physiological processes governing insulin production and secretion in these cells and to elucidate the mechanisms involved in their deterioration in the pathogenesis of diabetes. To date, considerable research has exploited clonal beta-cell lines derived from rodent insulinomas. Such cell lines have proven to be a great asset in diabetes research, in vitro drug testing, and studies of beta-cell physiology and provide a sustainable, and in many cases, more practical alternative to the use of animals or primary tissue. However, selection of the most appropriate rodent beta cell line is often challenging and no single cell line entirely recapitulates the properties of human beta-cells. The generation of stable human beta-cell lines would provide a much more suitable model for studies of human beta-cell physiology and pathology and could potentially be used as a readily available source of implantable insulin-releasing tissue for cell-based therapies of diabetes. In this review, we discuss the history, development, functional characteristics and use of available clonal rodent beta-cell lines, as well as reflecting on recent advances in the generation of human-derived beta-cell lines, their use in research studies and their potential for cell therapy of diabetes.

Physiological regulation of the pancreatic β-cell: functional insights for understanding and therapy of diabetes

Knowledge about the sites and actions of the numerous physiological and pharmacological factors affecting insulin secretion and pancreatic beta-cell function has been derived from the use of bioengineered insulin-producing cell lines. Application of an innovative electrofusion approach has generated novel glucose-responsive insulin-secreting cells for pharmaceutical and experimental research, including popular BRIN-BD11 beta-cells. This review gives an overview of the establishment and core characteristics of clonal electrofusion-derived BRIN-BD11 beta-cells. As discussed, BRIN-BD11 cells have facilitated studies aimed at dissecting important pathways by which nutrients and other bioactive molecules regulate the complex mechanisms regulating insulin secretion, and highlight the future potential of novel and diverse bioengineering approaches to provide a cell-based insulin-replacement therapy for diabetes. Clonal BRIN-BD11 beta-cells have been instrumental in: (a) characterization of K(ATP) channel-dependent and -independent actions of nutrients and established and emerging insulinotropic antidiabetic drugs, and the understanding of drug-induced beta-cell desensitization; (b) tracing novel metabolic and beta-cell secretory pathways, including use of state-of-the-art NMR approaches to provide new insights into the relationships between glucose and amino acid handling and insulin secretion; and (c) determination of the chronic detrimental actions of nutrients and the diabetic environment on pancreatic beta-cells, including the recent discovery that homocysteine, a risk factor for metabolic syndrome, may play a role in the progressive demise of insulin secretion and pancreatic beta-cell function in diabetes. Collectively, the studies discussed in this review highlight the importance of innovative experimental beta-cell physiology in the discovery and characterization of new and improved drugs and therapeutic strategies to help tackle the emerging diabetes epidemic.

Comparison of the secretory properties of four insulin-secreting cell lines

The insulin-secretory responsiveness of four popular and widely used insulin-secreting cells lines (RINm5F, HIT-T15, INS-1 and BRIN-BD11 cells) to a range of stimuli including glucose, amino acids, neurotransmitters, peptide hormones and sulphonylureas was studied. Differences were seen in the pattern of responsiveness of the cell lines to the various modulators of insulin release. While these studies revealed that INS-1 cells had the highest insulin content, only BRIN-BD11 cells exhibited a significant step-wise insulin secretory response to increasing glucose concentrations. BRIN-BD11 cells also showed pronounced insulin responses to leucine, KIC, L-arginine, L-alanine and palmitic acid. All the cell lines tested gave significant responses to the neurotransmitters carbachol and glibenclamide with increased insulin release. A comparison was made between the functional characteristics of the various cell lines with those of freshly isolated rat islets. This illustrated the general value of each cell line as a model for studies of insulin secretion. Electrofusion-derived BRIN-BD11 cells appeared to closely mimic the glucose sensitivity and overall secretory performance of normal rat islets.

Molecular characterization of the glucose-sensing mechanism in the clonal insulin-secreting BRIN-BD11 cell line

BRIN-BD11 cells represent a novel insulin-secreting cell line generated by electrofusion. Molecular characterization of these cells demonstrated the presence of mRNA and protein for the two key elements of the beta cell glucose-sensing system, GLUT2 and glucokinase. While levels of GLUT2 expression and 3-O-methyl-D-glucose equilibration were similar for both the BRIN-BD11 cell line and the parental control RINm5F cells, glucokinase expression was substantially higher in BRIN-BD11 cells. Expression of the two-component KATP channel complex, KIR6.2 and SUR1, was similar in both cells. However, while control RINm5F cells were completely unresponsive to glucose, BRIN-BD11 cells responded to physiological millimolar concentrations of this hexose sugar. These studies strongly suggest that the glucose-sensing ability of insulin-secreting cells is largely dictated by the level of glucokinase, as opposed to GLUT2, expression. Thus, BRIN-BD11 cells expressing the key attributes of the normal beta cell provide an interesting model for elucidation of regulatory principles of beta cell function.