Recently Completed Studies
Plasma Dipeptidyl-peptidase IV and Body Composition
We found that people with a lot of lean tissue had higher DPP-IV activity, while people with higher fat mass had lower DPP-IV activity. We have a follow-up study planned to see if having very high or very low DPP-IV activity affects blood flow.
The relationship between body composition and salivary DPP-IV activity and neuropeptide Y
We have collected data on over 100 participants. So far, we have found that salivary DPP-IV activity does not have any relationship with body composition. However, DPP-IV activity does decline with age. We are putting the finishing touches on this study now.
Our Current Studies
The role of hormones in vocal function
We are involved in a very exciting collaboration with the Department of Communication Disorders, College of Liberal Arts, with Professors Plexico and Sandage, which started in Fall 2014. Over the next three years we will collect blood and vocal testing from women with a normal reproductive cycle and women post-menopause. The purpose of this study is to better understand the development of vocal disorders in women. We will measure estrogen, testosterone, progesterone, neuropeptide Y and DPP-IV activity over the course of several months. This study is funded by NIH.
The role of DPP-IV in signaling carbohydrate content of foods
We are currently recruiting participants for the second part of “Factors influencing DPP-IV activity”. For this part of the study, we are interested in the role of sugar and diet sugars on DPP-IV activity in the mouth and the translation of that signal to the body. Participants will drink or swish and spit out a regular soda and a diet soda. We will take saliva and blood samples before and after.
Physiological impact of having very high or very low DPP-IV activity
We will be screening people for DPP-IV activity in the plasma and accepting people that have higher than average and lower than average DPP-IV activity. We plan to use a classic method of increasing sympathetic nervous system activity called the “cold pressor test.” Basically, you put your hand in a bucket of ice-water.
We expect blood pressure to go up and blood flow in the arms to go down during the cold-pressor test. This test should release one of the natural targets of DPP-IV, neuropeptide Y. Neuropeptide Y is one of the neurotransmitters that causes blood pressure to increase and blood flow to decrease. Having high DPP-IV activity should result in a shorter half-life of neuropeptide Y. This results in less increase in blood pressure and less decrease in blood flow, compared to the low DPP-IV people.