Conjugated linoleic acid (CLA) affects in different ways acetyl-CoA carboxylase alpha (ACC-α) transcripts from different promoters in mammary and adipose tissue from lactating ewes

Abstract Text: Feeding trans-10, cis-12 CLA to lactating ewes reduces milk fat by down-regulating gene expression of enzymes involved in lipid synthesis in mammary gland. An example is acetyl-CoA carboxylase alpha (ACC-α), a key enzyme in the de novo fatty acid synthesis pathway. ACC-α is encoded by mRNAs transcribed from three promoters, PI, PII and PIII, characterized as tissue-specific in the ovine genome. This study evaluated the effects of a rumen-unprotected trans-10, cis-12 CLA supplement fed to crossbred Lacaune/Texel lactating ewes, on gene expression of different mRNA transcripts of ACC-α. Twelve ewes arranged in a completely randomized design received for 15 days one of the following treatments: Control (forage + 1 kg of concentrate) and CLA [forage + 1 kg of concentrate + 28 g/d of CLA (29.9% trans-10, cis-12)]. The CLA supplement (an oil mixture) was orally dosed. Mammary gland and adipose tissue biopsies were taken on day 15. Subsequently RNA was extracted, cDNA synthesized and quantitative real-time reverse transcriptase PCR analysis conducted. Data were analyzed by MIXED procedure using ribosomal protein S18 housekeeping gene as a covariate in the model. Compared to Control, in the mammary gland CLA reduced by 29.1% (P = 0.037) transcript from PIII with no changes on transcripts from PI and PII (P > 0.05). In the adipose tissue, transcript from PI was increased by 379.8% (P = 0.028) in the CLA treated group when compared to Control. There was no treatment effect on transcripts from promoters II and III in the adipose tissue. Overall, our results suggest that trans-10, cis-12 CLA down-regulates ACC-α gene expression by decreasing expression from promoter III in mammary tissue and increases ACC-α gene expression by increasing expression promoter I in adipose tissue.

Keywords: adipose tissue,  gene expression, mammary gland