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Microassay for glucose-induced preproinsulin mRNA expression to assess islet functional potency for islet transplantation.

ABSTRACT: BACKGROUND:The capacity for insulin synthesis in islets is important for islet transplantation to succeed. We developed a microassay that evaluates the potency of human islets by measuring changes in glucose-induced human insulin gene (INS) expression using a single islet in octuplicate samples. METHODS:Poly (A) messenger RNA (mRNA) was purified from a set of single handpicked human islets. Glucose-induced mature (postspliced) and premature (prespliced) insulin mRNA were quantified by reverse-transcriptase polymerase chain reaction using several insulin mRNA primers designed at different locations including, intron, exon, and an exon-intron junction. RESULTS:The synthesis of premature INS mRNA was significantly increased in islets exposed to high glucose for 16 vs. 4 hr (P<0.01), whereas mature INS mRNA showed no difference. Glucose-induced premature INS mRNA synthesis was attenuated in heat-damaged islets. Stimulation index (SI) calculated by normalizing premature by mature INS mRNA (SI_INS mRNA) positively correlated with SI of insulin release (SI_16h insulin) from the same set of islets during 16-hr incubation in high or low glucose media, and SI of glucose-mediated insulin release obtained from the same islet lot in a perifusion system (n=12). Furthermore, linear multiple regression analysis using SI_INS mRNA and SI_16h insulin predicted islet transplantation outcome in nonobese diabetic (NOD) scid mice (n=8). CONCLUSION:The measurement of glucose-induced premature INS mRNA normalized by mature INS mRNA can be used to assess the functional quality of human islets and may predict islet function after transplantation in type 1 diabetic patients.

SUBMITTER: Omori K

PROVIDER: S-EPMC2852640 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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Microassay for glucose-induced preproinsulin mRNA expression to assess islet functional potency for islet transplantation.

Omori Keiko K Mitsuhashi Masato M Todorov Ivan I Rawson Jeffrey J Shiang Keh-Dong KD Kandeel Fouad F Mullen Yoko Y

Transplantation 20100101 2

<h4>Background</h4>The capacity for insulin synthesis in islets is important for islet transplantation to succeed. We developed a microassay that evaluates the potency of human islets by measuring changes in glucose-induced human insulin gene (INS) expression using a single islet in octuplicate samples.<h4>Methods</h4>Poly (A) messenger RNA (mRNA) was purified from a set of single handpicked human islets. Glucose-induced mature (postspliced) and premature (prespliced) insulin mRNA were quantifie ...[more]

PMID: 20098276

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Project description:ObjectivePancreatic ?-cell failure is central to the development and progression of type 2 diabetes (T2D). The aggregation of human islet amyloid polypeptide (hIAPP) has been associated with pancreatic islet inflammation and dysfunction in T2D. Alpha1-antitrypsin (AAT) is a circulating protease inhibitor with anti-inflammatory properties. Here, we sought to investigate the potential therapeutic effect of AAT treatment in a mouse model characterized by hIAPP overexpression in pancreatic ?-cells.MethodsMice overexpressing hIAPP (hIAPP-Tg) in pancreatic ?-cells were used as a model of amyloid-induced ?-cell dysfunction. Glucose homeostasis was evaluated by glucose tolerance tests and insulin secretion assays. Apoptosis and amyloid formation was assessed in hIAPP-Tg mouse islets cultured at high glucose levels. Dissociated islet cells were cocultured with macrophages obtained from the peritoneal cavity.ResultsNontreated hIAPP-Tg mice were glucose intolerant and exhibited impaired insulin secretion. Interestingly, AAT treatment improved glucose tolerance and restored the insulin secretory response to glucose in hIAPP-Tg mice. Moreover, AAT administration normalized the expression of the essential ?-cell genes MafA and Pdx1, which were downregulated in pancreatic islets from hIAPP-Tg mice. AAT prevented the formation of amyloid deposits and apoptosis in hIAPP-Tg islets cultured at high glucose concentrations. Since islet macrophages mediate hIAPP-induced ?-cell dysfunction, we investigated the effect of AAT in cocultures of macrophages and islet cells. AAT prevented hIAPP-induced ?-cell apoptosis in these cocultures without reducing the hIAPP-induced secretion of IL-1? by macrophages. Remarkably, AAT protected ?-cells against the cytotoxic effects of conditioned medium from hIAPP-treated macrophages. Similarly, AAT also abrogated the cytotoxic effects of exogenous proinflammatory cytokines on pancreatic ?-cells.ConclusionsThese results demonstrate that treatment with AAT improves glucose homeostasis in mice overexpressing hIAPP and protects pancreatic ?-cells from the cytotoxic actions of hIAPP mediated by macrophages. These results support the use of AAT-based therapies to recover pancreatic ?-cell function for the treatment of T2D.

Dataset Information

Microassay for glucose-induced preproinsulin mRNA expression to assess islet functional potency for islet transplantation.

Publications

Microassay for glucose-induced preproinsulin mRNA expression to assess islet functional potency for islet transplantation.

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