David M Thomson, Physiology and Developmental Biology
Evaluation of academic objectives and project findings
The purpose of this mentoring environment grant was to determine the effect of aging on skeletal muscle AMPK intracellular localization and activation by muscle contraction. Funding for the project is now completed. The primary research objectives and findings are listed below:
- Determine AMPK activity in aged rat skeletal muscle after contractions. Interestingly, activity of the AMPKα1 isoform was elevated while activity of the α2 isoform was decreased in aged skeletal muscle after contractions. This was very interesting because the α1 isoform is thought to inhibit protein synthesis while the α2 promotes beneficial adaptations to exercise. This could partially explain much of the dysfunction that occurs with aging in skeletal muscle.
- Determine high-energy phosphate concentrations in aged rat muscle after contractions. AMP concentration in aged muscle was significantly higher in aged muscle than young. The decrease in ATP and the increase in IMP after contractions was greater in aged muscle after contraction than in young muscle. The other nucleotides were not affected by age.
- AMPK localization in young and old muscles. Determining the localization of AMPK by immunofluorescence proved problematic as our antibodies did not seem to work well enough to do this. Nuclear isolation did not provide any interesting differences between young and old muscle. Indices related to glucose metabolism. No differences between young and old were noted here.
- Indices related to fat oxidation and mitochondrial content. ACC phosphorylation was not affected by age. We were unable to do the malonyl CoA assay.
- Indices related to protein metabolism. Interestingly, mTOR phosphorylation and S6k phosphorylation was elevated in the aged muscle. Also, eEF2 phosphorylation was elevated with age and did not decrease with stimulation as it did in young muscle. This may suggest that the activation of AMPK α1 in the aged muscle led to decreased protein synthesis after contraction. The raptor and FOXO blots did not work.
Overall, this was a successful project that resulted in valuable data, and good training for a number of students as described below. We were also able to partially fund work on an aging mouse study in which we partially activated AMPK.
Participating students and academic deliverables
The students who participated in the work associated with this grant were: Shalene Hardman (graduate student), Derrick Hall, Alyssa Cabrera, Kyler Black, Richard Compton, Matt Jacobs, Todd Sorenson, Brock Nelson and Zac Olesky. Each of them gained proficiency in several laboratory skills. Shalene and Derrick presented findings from this project at the Experimental Biology Meeting in San Diego in 2012. For Shalene, this was an invited oral presentation. They both did fantastic work and represented BYU well. Matt Jacobs also presented his findings at the Integrative Biology of Exercise conference in Denver, CO in October 2012. We recently submitted the work to the Journal of Physiology, and are currently waiting for the reviewers comments to come back on that. We plan on publishing the aging mouse data, that was partially funded by this grant, next year. We may also follow up on some of the findings that were not included in the manuscript, and flesh out a second paper from this work over the course of the next year or so.
Evaluation of mentoring environment
I currently have 17 undergraduate students working in the laboratory with me. I have found that direct interaction and training from me is crucial in helping them become independent and trustworthy in the laboratory. I try to dedicate 3 full mornings per week to laboratory research work with the students, oftentimes one-on-one, though I have recently not been able to achieve this goal as often as I would like. I’m focusing on improving in this area. I have 3 graduate students who are very knowledgeable and help greatly in guiding the undergraduate students. We have weekly lab meetings together, and I also meet regularly with the individual students to go over their data and discuss their progress. I’m satisfied with the learning and performance of the students in my lab. They continue to produce good data, and represent the university well at professional conferences. Furthermore, I think their work in the lab is helping them gain admittance to medical and dental school programs or other professional schools.