James Fleet

Dr. Fleet is the Margaret McKean Love Endowed Professor in Nutrition, Cellular, and Molecular Sciences at the University of Texas at Austin.  He holds a BS and Ph.D. from Cornell University and has previously held faculty appointments at Tufts University, University of North Carolina at Greensboro, and Purdue University.  Dr. Fleet's research is focused on the molecular and physiological functions of vitamin D as they pertain to the control of calcium metabolism and the prevention of cancer. His research employs the tools of molecular biology, genomics, and genetics to address questions relevant to human health and disease prevention. He has published 158 primary journal articles, book chapters, and reviews and he has been an invited to speak on his work across the globe.  He has a strong commitment to graduate education and in that capacity he contributed to the establishment of the Tufts University School of Nutrition Science and Policy and served as the Graduate Program Director at UNC-Greensboro (2 years) and Purdue University (14 years). His research has received over $16 million in direct funding from the NIH, the USDA, and the American Institute for Cancer Research (AICR).  He served as a contributing editor to Nutrition Reviews, has been on the editorial boards of The Journal of Nutrition and Endocrinology, and is an associate editor for the Journal of Steroid Biochemistry and Molecular Biology. He has been a standing member on several NIH study sections.  He has organized FASEB Summer Conferences and a summer workshop on “Big Data analysis for Biomedical Researchers” and has served on the Program Committee for the Vitamin D Workshop (currently the CEO), the American Society for Nutrition (ASN), the AICR, and the American Society for Bone and Mineral Research. In 2001, he was the recipient of the Mead Johnson Award from the ASN (2004), he was honored as a "University Faculty Scholar" (2004-9) and a “distinguished professor” at Purdue, and he is a fellow of the American Society for Bone and Mineral Research (2019).

I am a nutritional scientist who takes a mechanistic approach to study the molecular and physiological functions of vitamin D in two major areas: (a) calcium and bone and (b) colon cancer prevention.  His research uses cell and animal models, and employs the tools of molecular biology, genomics, and genetics, to address questions relevant to human health and disease prevention. 

My research program has focused on the physiologic functions and molecular actions of the vitamin D hormone, 1,25 dihydroxyvitamin D, in two major areas: (a) the control of whole-body calcium and homeostasis and (b) as a modulator of colitis and in the prevention of colon cancer.  

In the area of calcium and bone homeostasis, my work has linked calcium absorption to building bone mass during growth and protecting adult bone mass.   Over the last decade I extended this interest to the use of mouse genetics to identify the natural genetic variation that regulates calcium and bone metabolism where we have examined the interaction between genetics and the dietary environment.  This work has demonstrated that the genetics controlling physiologic adaptation of calcium/bone metabolism to low dietary calcium intake is distinct from the genetics controlling basal calcium/bone metabolism.  

In the area of colitis and cancer, my research has evaluated the role of vitamin D as a regulator of innate immunity by shifting macrophage polarization away from proinflammatory M1 macrophages to wound-resolving M2 macrophages and by blunting of myeloid derived suppressor cell (MDSC) T cell suppressive function.  We have also developed and utilized unique animal models that have allowed us to test the role of vitamin D status in the development of colitis and cancer.  Within these areas, my research group has extensively used genomic tools (i.e. RNA-seq, ATAC-seq, ChIP-seq, single cell RNA-seq) to better understand the mechanisms by which 1,25 dihydroxyvitamin D regulates gene expression in target tissues.