Profiles

Distinguished Professor (with tenure) and Vice-Chairman for Basic and Translational Research, Department of Medicine
School of Medicine

Distinguished Professor (with tenure), Department of Physiology & Biophysics
School of Medicine


Research Abstract
The water-soluble vitamins [thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folate (B9) , ascorbate] are essential micro-nutrients for normal cellular functions, growth and development. They are involved in a variety of critical metabolic reactions, and thus, their deficiency/suboptimal levels leads to a variety of clinical abnormalities. Humans (other mammals) cannot synthesize these micro-nutrients endogenously, and thus, must obtain them from exogenous sources (diet and gut microbiota) via intestinal/colonic absorption. In addition, the human body has a limited capacity to store these micro-nutrients, and thus, rely heavily on their efficient absorption. Thus, the intestinal tract plays central role in maintaining and regulating normal body homeostasis of these vitamins. Because of that, and since variety of conditions affect intestinal absorption of these micro-nutrients (e.g., genetic defects in the transport systems involved, intestinal inflammation, chronic exposure to alcohol, certain entero-pathogens, certain medications, etc.), studies that aim at understanding the cellular/molecular aspects of vitamin transport are of significant physiological/patho-physiological/nutritional importance.

Studies in our laboratory over the past thirty five years have characterized many physiological/pathophysiological and cell biological aspects of vitamin transport in the small and large intestine and in other organs of the digestive system. Our studies have covered the whole spectrum of biological complexity from the whole (integrative) animal level, to intact tissues, isolated/cultured cells, sub-cellular organelle/components, to the molecular levels, and have utilized state-of-the-art cell/molecular/imaging approaches as well as appropriate transgenic animal models. Currently our focus is on characterizing transcriptional, post-transcriptional and epigenetic regulation of vitamin transport events, cell biology of the trasnport proteins involved (structure-function activity, involvement of accessary proteins, membrane targeting, intracellualr trafficking), effect of external, environmental factors (e.g. chronic alcohol use, chronic exposure to cigarette smoke, infection with certain entero-pathogenic bacteria), and chronic inflammation on the transport processes.