Samuel Stephens, PhD

Contact Information

Office: 3334 PBDB
Phone: 319-335-4843
Faculty Profile


Brief description of current research:

The regulated release of the pancreatic islet hormones glucagon and insulin coordinate changes in nutrient availability during fasting/feeding to maintain whole animal nutrient status. Chronic dysregulation of islet hormone release and loss of islet cell mass result in persistent hyperglycemia and the development of diabetes. My laboratory is interested in understanding mechanisms of islet hormone release and identifying novel islet cell survival strategies. We and others have shown that peptides derived from the islet prohormone VGF have direct action on the islet beta-cell as novel secretagogues. In addition, pro-VGF also functions intracellularly to facilitate secretory granule formation and transport. Our current studies focus on understanding the role of endogenous VGF in regulating islet cell function. The second major interest of the lab is to understand mechanisms of islet cell adaptation, such as autophagy, that may be used to mitigate stress and promote survival. Insight into these pathways may identify therapeutic targets useful in preventing islet cell demise and restoring islet cell function during diabetes progression. My laboratory uses a diverse set of experimental approaches including physiological, cellular, biochemical, and ultrastructural models to explore these questions in islet cell biology.

3 most influential diabetes/obesity/metabolism publications:

  •  Stephens SB, Schisler JC, Hohmeier HE, An J, Sun AY, Pitt GS, and Newgard CB. A VGF-derived peptide attenuates development of type 2 diabetes via enhancement of islet β-cell survival and function. Cell Metabolism. 2012; 16(1):33-43
  • Tessem JS, Moss LG, Chao LC, Arlotto M, Lu D, Jensen MV, Stephens SB, Tontonoz P, Hohmeier HE, Newgard CB. Nkx6.1 regulates islet β-cell proliferation via Nr4a1 and Nr4a3 nuclear receptors. Proceedings of the National Academy of Sciences of the United States of America. 2014; 111(14):5242-7
  • Hayes HL, Zhang L, Becker TC, Haldeman J, Stephens SB, Arlotto M, Moss LG, Newgard CB, Hohmeier HE. A Pdx-1-regulated soluble factor activates rat and human islet cell proliferation. Mol Cell Biol. 2016; pii: MCB.00103-16

 

Quote:

“Over and over again, scientific discoveries have provided answers to problems that had no apparent connection with the phenomena that gave rise to the discovery.” -Isaac Asimov