Felix Leung, PhD

Professor of Medicine, UCLA, Department of Medicine

Currently, I am in pursuit of a new direction in laboratory research. I performed a number of studies to determine the role of capsaicin-sensitive intestinal mucosal afferent nerves in the regulation of gastrointestinal blood flow and adipose tissue blood flow. The inhibition of these changes was used to confirm functional ablation of the capsaicin-sensitive intestinal mucosal afferent nerves. An associated reduction of the proportion of total body fat in the visceral site and an increase of the proportion of total body fat in the subcutaneous site suggests functional blockade of the capsaicin-sensitive intestinal mucosal afferents plays a role in regulating the distribution of adipose tissue between visceral and subcutaneous sites. The hypothesis derived from these pilot studies is that orally administered TRPV1 antagonist(s) may play a role in regulating adipose tissue distribution, re-distributing visceral fat to subcutaneous sites. This is a novel hypothesis, not previously proposed by other investigators in the field, who focused on the direct effect of capsaicin on adipose tissue. The current commercial availability of TRPV1 antagonist(s) with fewer side effects will facilitate the execution of these proposed experiments. While awaiting a wider selection of commercially available antagonist(s), I took up a clinical focus of research closely related to modulation of afferent nerve function (i.e. sensing pain), namely, development of techniques to minimize insertion pain of colonoscopy.

My clinical research interest   is focused on developing less painful colonoscopy insertion methods which can also increase adenoma detection. Since 2002 I have done many colonoscopies in Veteran patients without using sedation medication. The failure rate of 20% due to pain prompted the search for a less painful insertion method. It was a simple conversion from using air insufflation to using water to distend the lumen with exclusion of all air. The less painful method (now called water exchange) emphasizes removal of infused water predominantly during insertion. Not only is it less painful, it has also led to a significant increase in adenoma detection rate (a quality marker) compared with traditional air insufflation colonoscopy. The impact on adenoma detection is likely related to salvage cleaning during insertion and minimized distraction from the search for polyps during withdrawal inspection. The result has been confirmed in retrospective studies in the United States and in  Europe, as well as in prospective randomized controlled trials performed in mainland China, Taiwan, Italy and the Czech Republic. We are currently funded by the Veterans Administration Merit Review Board to assess whether the addition of a cap to the tip of the colonoscope will further decrease insertion pain when water exchange is used. We are also supported by  the American Society of Gastrointestinal Endoscopy to assess whether the addition of a cap to the tip of the colonoscope will further increase adenoma detection when water exchange is used.

(818) 891-7711 x32520 (VA Sepulveda)

Felix Leung
BOX 951692, Sep VAMC (111G)
Los Angeles, CA 90095-1692