The International Complex Trait Consortium
Initial Steps in Development of Rat Genetic Models for the Response to Exercise Training
S.L. Britton, M.L. Troxell, L.G. Koch
Medical College of Ohio, Toledo, OH
ABSTRACT
Evidence suggests that two types of genetic substrates influence
aerobic capacity. First, there is a complement of genes that determine
intrinsic capacity in the untrained state. On top of intrinsic capacity
is apparently another set of genes that dictate the response to
exercise. We recently developed rat genetic models of intrinsic aerobic
capacity by artificial selection. Our next goal is to create rat
genetic models for the response to training.
PURPOSE: As initial
steps, we tested: 1) If wide variation exists for the response to
training in a genetically heterogeneous population of rats (N:NIH
stock), and 2) If intrinsic aerobic capacity and the response to
training are correlated phenotypes.
METHODS: Forty rats were first
tested for intrinsic aerobic capacity by measuring distance run to
exhaustion on a treadmill using a ramped protocol. Each rat was then
trained for treadmill running 3-days per week for eight weeks. An
absolute training protocol was used so that the same environment was
applied to all rats. The training protocol started at a speed of 10
m/min for 20 min at a 15¡ grade and was gradually increased daily in
speed and duration to reach 16 m/min for 30 min. A post-test for
maximal treadmill running capacity was performed at week 9. The
response to training was taken as the difference in distance run to
exhaustion before and after training.
RESULTS: Differences in pre- and
post tests for treadmill running to exhaustion (delta meters run) were
highly variant and ranged from -72 meters to +430 meters. The
distribution of these data was not different from normal (P > 0.169).
Data demonstrated no correlation between pre-trained intrinsic aerobic
capacity (meters) and the response to treadmill training (delta meters)
(r = 0.242, P< 0.132).
CONCLUSIONS: These data demonstrate a
sufficiently wide selection differential for the adaptational response
to training to support the initiation of divergent selective breeding
from a large founder population. In addition, these data are consistent
with the idea that intrinsic aerobic capacity and the adaptational
response to training are determined by separate genetic substrates
(i.e., not correlated).
[Supported by the National Institutes of Health (HL64270)]