AMP-Activated Protein Kinase and Adipogenesis in Sheep Fetal Skeletal Muscle and 3T3-L1 Cells

¹ Department of Animal Science and Interdepartmental Molecular and Cellular Life Sciences Program, University of Wyoming, Laramie, WY 82071

^* To whom correspondence should be addressed. E-mail: mindu{at}uwyo.edu.

	Abstract

Marbling, or i.m. fat, is an important factor determining beef quality. Both adipogenesis and hypertrophy of existing adipocytes contribute to enhanced marbling. We hypothesized that the fetal stage is important for the formation of i.m. adipocytes and that AMP-activated protein kinase (AMPK) has a key role in adipogenesis during this stage. The objective of this study was to assess the role of AMPK in adipogenesis in fetal sheep muscle and 3T3-L1 cells. Non pregnant ewes were randomly assigned to a control (Con, 100% of NRC recommendations, n = 7) or over-fed (OF, 150% of NRC, n = 7) diet from 60 d before to 75 d after conception when ewes were euthanized. The fetal LM muscle was collected at necropsy for biochemical analyses. The activity of AMPK was less in the fetal muscle of OF sheep. The expression of peroxisome proliferator-activated receptor (PPAR) , a marker of adipogenesis, was greater in OF fetal muscle compared with Con fetal muscle. To further show the role of AMPK in adipogenesis, we used 3T3-L1 cells. The 3T3-L1 cells were incubated in a standard adipogenic medium for 24 h and 10 d. Activation of AMPK by 5-aminoimidazole-4-carboxamide 1-beta-d-ribonucleoside dramatically inhibited the expression of PPAR and reduced the presence of adipocytes after 10 d of differentiation. Inhibition of AMPK by Compound C, enhanced the expression of PPAR. In conclusion, these data show that AMPK activity is inversely related to adipogenesis in fetal sheep muscle and 3T3-L1 cells.

Key Words: 3T3-L1 cells, adipogenesis, AMP-activated protein kinase, fetus, sheep, skeletal muscle