Inhibition of ∆9-desaturase activity with sterculic acid: Effect on the endogenous synthesis of cis-9 18:1 and cis-9, trans-11 18:2 in dairy sheep

• Published in: Journal of dairy science 2012-09, Vol.95 (9), p.5242-5252
• Main Authors: Bichi, E., Toral, P.G., Hervás, G., Frutos, P., Gómez-Cortés, P., Juárez, M., de la Fuente, M.A.
• Format: Article
• Language: English
• Subjects: alpha-linolenic acid; Animals; bioactive properties; Cyclopropanes - pharmacology; cyclopropene fatty acid; dairy sheep; desaturase system; ewe milk; ewes; Fatty Acids - analysis; Fatty Acids - biosynthesis; Fatty Acids, Monounsaturated - pharmacology; Female; intravenous injection; lactation; Lactation - drug effects; Lactation - physiology; Linoleic Acids, Conjugated - analysis; Linoleic Acids, Conjugated - biosynthesis; lipogenesis; milk; Milk - chemistry; milk fat; oleic acid; pastures; rumenic acid; Sheep; Stearoyl-CoA Desaturase - antagonists & inhibitors; sterculic acid
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2012-5349

This study was conducted in lactating ewes to examine the involvement of ∆9-desaturase in mammary lipogenesis, especially in the endogenous synthesis of cis-9, trans-11 18:2 and cis-9 18:1, because no information on this matter was available for dairy sheep. With this aim, 6 Assaf ewes were monitored in a 15-d experiment, which included a 5-d pretreatment period, a 5-d treatment period, and a 5-d posttreatment period. During the treatment period, ewes received 0.5g/d of sterculic acid (a cyclopropene fatty acid that inhibits ∆9-desaturase), delivered intravenously in 4 equal doses at 6-h intervals. Animals were fed pasture to supply mainly α-linolenic acid and minimize the amount of milk cis-9, trans-11 18:2 of ruminal origin. Sterculic acid administration was calculated to inhibit ∆9-desaturase by 70% based on the milk content of cis-9 14:1. This inhibition resulted in decreases in the milk content of the enzyme products (e.g., cis-9 10:1, cis-9 14:1, cis-9 16:1, cis-9 18:1, and cis-9, trans-11 18:2) and increases in its substrates (e.g., 14:0, 18:0, and trans-11 18:1), as well as in reductions in the desaturase indexes. Some other milk fatty acids, further to previously reported products or substrates of ∆9-desaturase (e.g., cis-15 18:1 and cis-9, cis-15 18:2, or trans-11, trans-15 18:2, and cis-9, trans-11, trans-15 18:3), were also affected by sterculic acid administration. Endogenous synthesis was the major source of cis-9 18:1 and cis-9, trans-11 18:2, accounting for 63 and 74% of its content in milk fat, respectively. To our knowledge, the present study provides the first estimates of endogenous synthesis of these 2 bioactive fatty acids in ovine milk fat.