It has long been established that b-cells within whole islets secrete more insulin than do isolated b-cells. This functional enhancement may arise from gap junctional coupling between cells in the intact islet. Until now, the behavior of b-cells within islets has been largely inferred from in vitro studies of dispersed cells and biochemical analysis of whole islets. Dr. Piston has begun to study the function of individual b- cells within intact islets by optimizing recent advances in quantitative optical imaging for this purpose. This has led to novel experiments which show marked differences between isolated b-cells and whole islets in NAD(P)H autofluoresence (an endogenous reporter of intracellular metabolism) and glucokinase (GK) expression. These results demonstrate a new level of biological complexity that can be investigated only by detailed studies of intact islets. Dr. Piston hypothesizes that insulin secretion is directly coupled to glucose metabolism, and that while both responses are rate-limited by GK activity under normal physiological conditions, this rate-limiting role may be lost by only a slightly over-expression of GK. The applicant also hypothesizes that gap junctional coupling between b- cells in the islet accounts for increased insulin secretion from b- cells in the intact islet over isolated b- cells. The validity and limits of these hypotheses will be addressed through three specific aims: 1) To determine the temporal relationship between the magnitude of glucose-stimulated NAD(P)H response and amount of insulin secretion; 2) To determine the range of expression levels over which GK maintains its rate-limiting role in islet metabolism and secretion; 3) To determine the ability of intercellular coupling to enhance insulin secretion. The proposed experiments take advantage of the applicant's demonstrated expertise in two-photon excitation and confocal microscopic techniques, combined with several available transgenic mouse models. The applicant concludes that these investigations will advance our understanding of the in vivo interplay of biochemical mechanisms known to be involved in glucose-stimulated insulin secretion from pancreatic islets.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
1R01DK053434-01
Application #
2453866
Study Section
Metabolism Study Section (MET)
Program Officer
Laughlin, Maren R
Project Start
1998-01-01
Project End
2001-12-31
Budget Start
1998-01-01
Budget End
1998-12-31
Support Year
1
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Vanderbilt University Medical Center
Department
Physiology
Type
Schools of Medicine
DUNS #
004413456
City
Nashville
State
TN
Country
United States
Zip Code
37212
Elliott, Amicia D; Ustione, Alessandro; Piston, David W (2015) Somatostatin and insulin mediate glucose-inhibited glucagon secretion in the pancreatic ?-cell by lowering cAMP. Am J Physiol Endocrinol Metab 308:E130-43
Short, Kurt W; Head, W Steve; Piston, David W (2014) Connexin 36 mediates blood cell flow in mouse pancreatic islets. Am J Physiol Endocrinol Metab 306:E324-31
Benninger, Richard K P; Hutchens, Troy; Head, W Steven et al. (2014) Intrinsic islet heterogeneity and gap junction coupling determine spatiotemporal Ca²? wave dynamics. Biophys J 107:2723-33
Hang, Yan; Yamamoto, Tsunehiko; Benninger, Richard K P et al. (2014) The MafA transcription factor becomes essential to islet ?-cells soon after birth. Diabetes 63:1994-2005
Benninger, Richard K P; Piston, David W (2014) Cellular communication and heterogeneity in pancreatic islet insulin secretion dynamics. Trends Endocrinol Metab 25:399-406
Kumar, Ankur N; Short, Kurt W; Piston, David W (2013) A motion correction framework for time series sequences in microscopy images. Microsc Microanal 19:433-50
Schwetz, Tara A; Ustione, Alessandro; Piston, David W (2013) Neuropeptide Y and somatostatin inhibit insulin secretion through different mechanisms. Am J Physiol Endocrinol Metab 304:E211-21
Elliott, Amicia D; Gao, Liang; Ustione, Alessandro et al. (2012) Real-time hyperspectral fluorescence imaging of pancreatic ?-cell dynamics with the image mapping spectrometer. J Cell Sci 125:4833-40
Le Marchand, Sylvain J; Piston, David W (2012) Glucose decouples intracellular Ca2+ activity from glucagon secretion in mouse pancreatic islet alpha-cells. PLoS One 7:e47084
Head, W Steven; Orseth, Meredith L; Nunemaker, Craig S et al. (2012) Connexin-36 gap junctions regulate in vivo first- and second-phase insulin secretion dynamics and glucose tolerance in the conscious mouse. Diabetes 61:1700-7

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