P-210 Poster of distinction

Impaired glucagon secretion in islets isolated from donors with type 2 diabetes suggests these donors are unsuitable for clinical use

J.N Walker, R. Ramracheya, S.J. Hughes, K.E. Jones, M. Shigeto, M. Braun, A. Clark, P. Rorsman, P.R. Johnson
University of Oxford, Oxford, U.K.

Objective: Pancreases from donors in the early stages of non-insulin dependent type-2 diabetes (T2DM) have been proposed as a potential source of islets for clinical transplantation. The aim of this study was to determine the hormone content, secretory response to glucose and the alpha-cell exocytosis in response to depolarisation of human islets isolated from donors with T2DM, and compare these with islets isolated from non-diabetic similar aged controls,

Methods: With appropriate consent/ ethical approval, human islets were isolated using standard procedures. Batches of 15 islets (150µ diameter) from donors with T2DM n=6; donor age median 54.5y{range:34-67y}; all treated with diet or oral agents; median duration of diabetes 4.1y) and non-diabetic aged-matched controls (n=6; median age 51y{range:36-60y}) were incubated for 1hr in 1mmol/l glucose then for a further 1hr in Krebs-Ringer-Buffer supplemented with 1 or 20mml/l glucose. Hormone content/secretion was determined by radioimmunoassay. Membrane capacitance was recorded using the patch-clamp technique.

Results: The insulin content/islet was similar in both the control and T2DM groups (29.68±6.2 vs 23.29±3.88ng/islet). The mean fold increase in glucose stimulated insulin secretion was reduced in the T2DM group but this was not significant. The glucagon content was highly variable in the T2DM group; 2 of the donors contained over 250% more glucagon than the highest in the controls. In 5/6 T2DM donors there was no inhibition of glucagon secretion with 20mM glucose and in some cases a paradoxical rise was seen. The mean inhibition of glucagon secretion in the control group was 31.4±6.6%. No significant difference was seen in alpha-cell exocytosis in response to voltage-clamp depolarisation between the groups.

Conclusion: Although the insulin secretion was not significantly impaired in the T2DM islets, the glucagon secretion was markedly abnormal. This inappropriate alpha-cell response could severely impair a transplanted graft comprising T2DM islets by stimulating uncontrolled post transplant hyperglycaemia.

P-210 Poster of distinction

Impaired glucagon secretion in islets isolated from donors with type 2 diabetes suggests these donors are unsuitable for clinical use

J.N Walker, R. Ramracheya, S.J. Hughes, K.E. Jones, M. Shigeto, M. Braun, A. Clark, P. Rorsman, P.R. Johnson
University of Oxford, Oxford, U.K.

Objective: Pancreases from donors in the early stages of non-insulin dependent type-2 diabetes (T2DM) have been proposed as a potential source of islets for clinical transplantation. The aim of this study was to determine the hormone content, secretory response to glucose and the alpha-cell exocytosis in response to depolarisation of human islets isolated from donors with T2DM, and compare these with islets isolated from non-diabetic similar aged controls,

Methods: With appropriate consent/ ethical approval, human islets were isolated using standard procedures. Batches of 15 islets (150µ diameter) from donors with T2DM n=6; donor age median 54.5y{range:34-67y}; all treated with diet or oral agents; median duration of diabetes 4.1y) and non-diabetic aged-matched controls (n=6; median age 51y{range:36-60y}) were incubated for 1hr in 1mmol/l glucose then for a further 1hr in Krebs-Ringer-Buffer supplemented with 1 or 20mml/l glucose. Hormone content/secretion was determined by radioimmunoassay. Membrane capacitance was recorded using the patch-clamp technique.

Results: The insulin content/islet was similar in both the control and T2DM groups (29.68±6.2 vs 23.29±3.88ng/islet). The mean fold increase in glucose stimulated insulin secretion was reduced in the T2DM group but this was not significant. The glucagon content was highly variable in the T2DM group; 2 of the donors contained over 250% more glucagon than the highest in the controls. In 5/6 T2DM donors there was no inhibition of glucagon secretion with 20mM glucose and in some cases a paradoxical rise was seen. The mean inhibition of glucagon secretion in the control group was 31.4±6.6%. No significant difference was seen in alpha-cell exocytosis in response to voltage-clamp depolarisation between the groups.

Conclusion: Although the insulin secretion was not significantly impaired in the T2DM islets, the glucagon secretion was markedly abnormal. This inappropriate alpha-cell response could severely impair a transplanted graft comprising T2DM islets by stimulating uncontrolled post transplant hyperglycaemia.