Studies On The Developmental Expression Of The Genes Involved In Intramuscular Adipocyte Differentiation And Of Key Enzymes Involved In Intramuscular Fat Metabolism In Sunit Lambs

16 castrated Sunit lambs with about 10kg BW were selected and yard-fed. The dietary nutrient levels for the lambs were arranged according to the recommendations of NY/T 816-2004 (Feeding standard of meat-producing sheep and goats). Four animals were slaughtered at 10kg, 20kg, 30kg and 40kg live weight respectively, and Longissimus Dorsi was sampled for further analysis. Intramuscular fat content and shear value were determined to study the developmental pattern of intramuscular fat and the relationship between intramuscular fat and meat quality. PPARγand ADD1 have been implicated as key regulators of adipocyte differentiation while Pref-1 is the marker of preadipocyte. It is well-known that ACC, FAS, LPL and HSL are key enzymes in lipid metabolism. The mRNA levels of these genes were determined to study the developmental expression of the genes involved in intramuscular adipocyte differentiation and of key enzymes involved in intramuscular fat metabolism in Sunit lambs by means of quantitative real-time RT-PCR.The results showed that:1. Intramuscular fat content and water-holding percentage increased as lambs grew while water content and shear value decreased. There was very significant negative correlation between shear value and intramuscular fat content of mutton (r=-0.983, p<0.01).2. There was a decreasing tendency of the developmental expression of PPARγ, ADD1 and Pref-1 genes from 10- to 40 kg BW. The mRNA levels of PPARγ, ADD1 and Pref-1 in 10- and 20kg lambs were significantly higher than that in 30- and 40kg lambs (p<0.05). There was significant negative correlation between Pref-1 mRNA abundance and IMF content (r=-0.659, p<0.05).3. As lambs grew, the mRNA levels of ACC and LPL genes increased. Their mRNA levels of 30kg lambs were higher than that of 10kg sheep while lower than that of 40kg lambs (p<0.05). There was very significant or significant positive correlation between ACC or LPL mRNA abundance and IMF content (r=0.775, p<0.01; r=0.758, p<0.05).4. The developmental expression of FAS and HSL genes decreased as lambs grew. Their mRNA levels in 10- and 20kg BW lambs were significantly higher than that in 30- and 40kg lambs.The results suggested that:Intramuscular adipocyte differentiation and IMF degradation in Sunit lambs decreased while IMF synthesis enhanced as lambs grew. In older animals IMF deposition was effected mainly by lipid accumulation in differentiated adipocytes rather than by adipocyte differentiation.