Effects of short- and long-chain fatty acids on the expression of stearoyl-CoA desaturase and other lipogenic genes in bovine mammary epithelial cells

Abstract

Stearoyl-CoA desaturase (SCD) in the bovine mammary gland introduces a cis-double bond at the D9 position in a wide range of fatty acids (FA). Several long-chain polyunsaturated fatty acids (PUFA) inhibit expression of SCD, but information on the effect of short-chain fatty acids on mammary SCD expression is scarce. We used a bovine mammary cell line (MAC-T) to assess the effect of acetic acid (Ac) and b-hydroxybutyric acid (BHBA) in comparison with the effect of various long-chain fatty acids on the mRNA expression of the lipogenic enzymes SCD, acetyl-CoA carboxylase (ACACA), fatty acid synthase (FASN) and their associated gene regulatory proteins sterol regulatory element binding transcription factor 1 (SREBF1), insulin-induced gene 1 protein (INSIG1) and peroxisome proliferator-activated receptor alpha (PPARA)and peroxisome proliferator-activated receptor delta (PPARD) by quantitative real-time PCR. MAC-T cells were treated for 12 h without FA additions (CON) or with either 5 mM Ac, 5 mM BHBA, a combination of 5 mM Ac 1 5 mM BHBA, 100 mM C16:0, 100 mM C18:0, 100 mM C18:1 cis-9, 100 mM C18:1 trans-11, 100 mM C18:2 cis-9,12 or 100 mM C18:3 cis-9,12,15. Compared with control, mRNA expression of SCD1 was increased by Ac (161%) and reduced by C18:1 cis-9 (261%), C18:2 cis-9,12 (284%) and C18:3 cis-9,12,15 (288%). In contrast to native bovine mammary gland tissue, MAC-T cells did not express SCD5. Expression of ACACA was increased by Ac (144%) and reduced by C18:2 cis-9,12 (248%) and C18:3 cis-9,12,15 (249%). Compared with control, FASN expression was not significantly affected by the treatments. The mRNA level of SREBF1 was not affected by Ac or BHBA, but was reduced by C18:1 cis-9 (244%), C18:1 trans-11 (242%), C18:2 cis-9,12 (262%) and C18:3 cis-9,12,15 (268%) compared with control. Expression of INSIG1 was downregulated by C18:0 (237%), C18:1 cis-9 (263%), C18:1 trans-11 (253%), C18:2 cis-9,12 (281%) and C18:3 cis-9,12,15 (291%). Both PPARA and PPARD expression were not significantly affected by the treatments. Our results show that Ac upregulated mRNA expression of SCD1 and ACACA in MAC-T cells. The opposite effect of the PUFA C18:2 cis-9,12 and C18:3 cis-9,12,15 on the these genes and the failure of Ac to mimic the PUFA-inhibited SREBF1 and INSIG1 mRNA expression, suggest that Ac can stimulate mammary lipogenesis via a transcriptional regulatory mechanism different from PUFA.

Biosynthesis of milk fat, protein, and lactose: roles of transcriptional and posttranscriptional regulation

“…The authors observed a positive effect of acetate on the expression of SCD1 and ACACA and a negative effect of oleic, linoleic, and linolenic acid on expression of SCD1, SREBF1, and INSIG1, with a downregulation of INSIG1 by the treatment with stearate. Contrary to previous observations by Kadegowda and collaborators (108), Jacobs and collaborators (103) did not observed an increase in the expression of any of the lipogenic genes by palmitate and the stearate in MAC-T cells. The two experiments differed in that, for Kadegowda and collaborators (108), the LCFA were not coupled with bovine serum albumin (BSA), and in Jacobs and collaborators, a calculated ratio of ϳ6:1 of LCFA/BSA was used.…”

“…The positive response to LCFA treatment of bovine mammary epithelial cells was not observed in a recent study by Jacobs and collaborators (103), where MAC-T cells were treated with 0.1 mM of several LCFA, 5 mM of acetate, 5 mM of BHBA, or a mixture of the two (5 mM acetate ϩ 5 mM BHBA). The authors observed a positive effect of acetate on the expression of SCD1 and ACACA and a negative effect of oleic, linoleic, and linolenic acid on expression of SCD1, SREBF1, and INSIG1, with a downregulation of INSIG1 by the treatment with stearate.…”

Effect of the ratios of acetate and β-hydroxybutyrate on the expression of milk fat- and protein-related genes in bovine mammary epithelial cells

“…Acetate and β-hydroxybutyric acid (BHBA) are the main short-chain fatty acids produced by microbial fermentation in the rumen and hindgut that are taken up into the blood. Circulating acetate can be taken up by the mammary gland and incorporated into milk FAs (Chilliard et al 2000;Bernard et al 2008;Jacobs et al 2013). Almost 50% of the FAs in ruminant milk are synthesized in the mammary gland from acetate and BHBA (Mensink et al 2003;Gebauer et al 2007).…”

“…Almost 50% of the FAs in ruminant milk are synthesized in the mammary gland from acetate and BHBA (Mensink et al 2003;Gebauer et al 2007). It was reported that acetate affects milk fat synthesis and lipogenic gene expression (Purdie et al 2008;Maxin et al 2011;Jacobs et al 2013) as well as milk protein synthesis (Purdie et al 2008). The limited information available indicated that BHBA stimulated the accumulation of triglycerides (TAG) in the BMECs, but it was not involved in forming lipid droplets (Yonezawa et al 2004).…”

“…Data in the same experiment also indicated that BHBA inhibited leptin expression and lipid synthesis in the BMECs (Yonezawa et al 2004). Jacobs et al (2013) found that BHBA upregulated the expression of stearoyl-CoA desaturase 1 (SCD1, 44%), acetyl-coenzyme A carboxylase α (ACACA, 28%), and fatty acid synthase (FASN,29%). BMECs treated with different concentrations of BHBA (0-1.25mM) significantly increased TAG accumulation and upregulated the expression of FASN and ACACA mRNAs.…”