Developmental Changes of the LPL mRNA Expression and Its Effect on IMF Content in Sheep Muscle

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This study investigates the developmental changes of the lipoprotein lipase ( LPL) mRNA level in sheep muscle and its effect on intramuscular fat (IMF) accumulation. Male Kazak and Xinjiang Merino sheep at 2–120 days old were selected. Six animals of each breed were slaughtered at 2, 30, 60, 90, and 120 days (only the Xinjiang Merino sheep at 120-day old were available) to collect samples from longissimus dorsi muscle for the purpose of determining the IMF content and extracting total RNA that was used to investigate the developmental changes of the LPL mRNA expression by real-time PCR. The results showed that in male Kazak sheep, the IMF content increased with the progress of development and there were significant differences ( P<0.05) between the age groups. However, there was no difference ( P>0.05) between age groups in Xinjiang Merino sheep. Furthermore, the IMF content of the male Kazak sheep was significantly higher ( P< 0.01) than that of the Xinjiang Merino sheep aged from 30 to 90 days. The highest LPL mRNA expression appeared at day 2 and it was significantly higher than that of all other age groups ( P<0.01), while animals at 60-day old had the lowest LPL mRNA expression in the male Kazak sheep. In Xinjiang Merino sheep, the highest one occurred at 30-day old ( P<0.01), followed by a continuous decrease to the lowest level at 90-day old, and then it started to increase slightly. At 2 to 60-day old, the LPL mRNA expression was negatively correlated to the IMF content ( r = -0.625, P<0.05) in male Kazak sheep, but no such relationship was detected in the male Xinjiang Merino sheep.