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Robert Sorenson, Ph.D

Professor

Mailing Address:
University of Minnesota
Department of Genetics, Cell Biology, and Development
6-160 Jackson
321 Church St. SE
Minneapolis, MN 55455
USA
Education:
Ph.D., University of Minnesota, Twin Cities, 1967
Office:
4-128 BSBE
P: 612-624-6414

Email:
soren001@umn.edu

 Lab:
4-290 BSBE
P: 612-624-9115

Areas of Research Strength:

Hormone regulation of islet structure and function
Adaptation of islets to pregnancy

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Research Techniques:

Islet cytochemistry
Insulin secretion
Confocal microscopy
Intracellular communication

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Research Interests:

Sorenson's research focuses on the long term modulating effects of
pregnancy on pancreatic islets of Langerhans. Although rapid regulation
of insulin secretion by nutrients and hormones has been the focus of
considerable research, the examination of long-term modulation of
islets has received much less attention. Pregnancy is a normally
occurring physiological condition where there is a long term need
for increased insulin secretion at normal serum glucose levels. This
demand is met by many major alterations in islet structure and
function. Among these changes the most important are: (a) an
increase in glucose-stimulated insulin secretion (4-10 fold at
normal serum glucose concentrations); (b) a lowering of the
glucose-stimulation threshold; and (c) increased ß-cell proliferation.
Using species specific lactogenic hormones (placental lactogen and
prolactin which share a common receptor) Sorenson and his lab have
demonstrated that these hormones induce all of the known changes
in islets that occur during pregnancy.

Using islets from pregnancy and islets treated with lactogenic hormones
in vitro the lab is investigating: (1) The signal transduction pathways
used by prolactin receptors in islets. (2) How the lactogen induced changes
in gene expression lead to enhanced insulin secretion. (3) How the lactogen
induced changes in metabolism lead to enhanced insulin secretion. (4) How
lactogens stimulate ß-cell proliferation. (5) The role of lactogens in the
development and growth of islets. (6) The glucose dependence of the lactogen
induced changes in vivo and how these changes compare with those induced by
in vivo glucose infusion. Although mechanisms of lactogen regulation of islets will
likely share some features with other prolactin sensitive cells, they will also be
very unique as they must include features for affecting the islet specific metabolic
sensing system. The Sorenson lab's long term goal is to delineate the mechanisms
responsible for the increased islet function observed during pregnancy.

These studies will provide important information on the long term regulation
of islet function and ß-cell mass. Understanding the regulation of ß-cell glucose
sensitivity has important implications for understanding the progression of events
that lead to gestational and type II diabetes. In addition, the studies on regulation
of islet ß-cell growth will provide essential information on development of ß-cells
and the growth potential of differentiated islet ß-cells.

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Selected Publications:

A.J. Weinhaus, L.E. Stout, N.V. Bhagroo, T. Clark Brelje, R.L. Sorenson, (2007) Regulation of Islet Glucokinase in Pancreatic Islets by Prolactin: A Mechanism for Increasing Glucose-Stimulated Insulin Secretion during Pregnancy.  Journal of Endocrinology (in press)

R.L. Sorenson, L.E. Stout, T.C. Brelje, T.L. Jetton and F.M. Matschinsky (2007)  Immunohistochemical Evidence for the Presence of Glucokinase in the Gonadotropes and Thyrotropes of the Anterior Pituitary Gland of Rat and Monkey. Journal Histochemistry and Cytochemistry (in press)

R.L. Sorenson, D.G. Garry and T.C. Brelje,  (2006) Structural and Functional Considerations of GABA in Islets of Langerhans:  β-cells and Nerves  A Retrospective. In Perspectives in Diabetes, Vol I, ed. R. Paul Robertson.

Sorenson RL, Weinhaus AJ, and Brelje TC (2004) Regulation of Gluckinase as Islet Adapt to Pregnancy in Clucose and Glycemic Diseases: from Basics to Novel Therapeutics (F Matschinsky and M Magnuson eds.) S Karger AG Basel

Brelje TC, Stout LE, Bhagroo NV, and Sorenson RL (2004) Distinctive Roles for Prolactin and Growth hormone in the Acivation of STAT5 in Pancreatic Islets of Langerhans. Endocrinology 145:4162-4175.

Brelje, TC, Svensson AM, Stout LE, Bhagroo NV and Sorenson RL 2002 An Immunohistochemical approach to monitor the prolactin-induced activation of the JAK/Stat5 pathway in pancreatic islets of Langerhans. Journal Histochemistry and Cytochemistry 50:365-383.

Sorenson, R.L., and Brelje, T.C. 2001 Differences in the regulation of pancreatic islets by prolactin, growth hormone and placental lactogen. In Prolactin (ed. Nelson Horseman) Kluwer, Boston. 297-316.

Brelje, TC, Svensson AM, Stout LE, Bhagroo NV and Sorenson RL 2001 An Immunohistochemical approach to monitor the prolactin-induced activation of the JAK/Stat5 pathway in pancreatic islets of Langerhans. Journal Histochemistry and Cytochemistry

Weinhaus, A.J., Bhagroo, N.V., Brelje, T.C. and Sorenson, R.L. 2000 Dexamethasone counteracts the effect of prolactin on islet function: Implications for islet regulation in late pregnancy. Endocrinology 141:4:1384-1393

Weinhaus, A.J, Bhagroo, N.V., Brelje, T.C. and Sorenson, R.L. 1998 Role of cAMP in Up-Regulation of Insulin Secretion during the Adaptation of Islets of Langerhans to Pregnancy. Diabetes 47:9:1426-1435

Stout, L.E., A.M. Svensson, and R.L. Sorenson 1997 Prolactin regulation of islet-derived INS-1 Cells: Characteristics and immunocytochemical analysis of STAT5 translocation. Endocrinology 138:1592-1603.

Sorenson RL, and Brelje T.C. 1997 Adaptation of islets of Langerhans to pregnancy: -cell growth, enhanced insulin secretion and the role of lactogenic hormones. Horm. and Metab. Res. 29:5:1-7.

Brelje, TC, and Sorenson RL 1997 The physiological roles of prolactin, growth hormone, and placental lactogen in the regulation of islet b-cell proliferation. In Pancreas Regeneration (ed. Nora Sarvetnick) Landes Company Biomedical Publishers. pg. 1-23

Weinhaus, A.J., L.E. Stout and R.L. Sorenson 1996 Glucokinase, hexokinase, glucose transporter 2 and glucose metabolism in islets during pregnancy and prolactin treated islets in vitro: Mechanisms for long term up-regulation of islets. Endocrinology 137:1640-1649



To view these and other publications visit http://www.ncbi.nlm.nih.gov/PubMed
search menu should say PubMed
type Sorenson RL in the avaliable line

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