Insulin Sensitivity and Metabolism in Bovine Muscle Treated with β-Adrenergic Agonists
Abstract
A limited number of ß-adrenergic agonists (ß-AA) are currently used for
redirecting dietary energy from adipose tissue accretion towards muscle growth. At the
end of typical feedlot finishing, cattle have depressed insulin sensitivity, similar to type
II diabetes in humans. The objective of this study was to compare the effects of a known
βv3-AA (BRL 37344) to a novel ß-AA (Experior) on muscle metabolism in vitro. We
hypothesized that Experior would attenuate insulin insensitivity by promoting glucose
metabolism in muscle. The M. longissimus lumborum (LL) was removed from the 9th to
11th rib from four steers. From the LL samples, muscle strips were dissected parallel to
muscle fiber orientation. The conversion of glucose to glycogen, COv2, and lactate was
tested in muscle strips incubated for 90 min with 50 μM Experior, 50 μM BRL 37344,
or no β-AA (Control), and different insulin concentrations. Incubation time was
established by a preliminary experiment that determined the effect of different
incubation times (30 min, 60 min, 90 min) on glycogen, COv2, and lactate production.
There were no (P > 0.05) insulin concentration x treatment effects, insulin concentration
effects, and no significant effect of treatment on lactate production. There was a
significant treatment effect of conversion of glucose to glycogen (P < 0.001) and COv2 (P
= 0.018). BRL 37344 caused 62% lower glycogen production compared to Control
samples, and 50% lower glycogen production compared to Experior samples. Control
samples produced 4.3 nmol/100 mg·90 min, Experior samples produced 3.1 nmol/100
mg·90 min glycogen, while BRL 37344 samples produced 1.6 nmol/100 mg·90 min.
BRL 37344 elicited 23% more COv2 than Experior, and 41% more COv2 than Control
samples. Control samples produced 171.3 nmol/100 mg·90 min COv2, Experior samples
produced 222.9 nmol/100 mg·90 min COv2, while BRL 37344 samples produced 292.6
nmol/100 mg·90 min COv2. Experior did not have a consistent effect on glycogen or COv2
production. We discovered the presence of ßv3- AR in muscle, since there was a distinct
response of the muscle strips to BRL 37344. The relative insensitivity of bovine muscle
to insulin is consistent with insulin resistance observed in feedlot cattle.
Citation
Jobe, Jillian Taylor (2018). Insulin Sensitivity and Metabolism in Bovine Muscle Treated with β-Adrenergic Agonists. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /188941.