Stearoyl-CoA desaturase (SCD) is an important enzyme in the bovine mammary gland, where it inserts a cis-double bond at the Δ9 position in a wide range of fatty acids. Investigating SCD expression in the bovine mammary gland generally requires invasive biopsy to obtain mammary tissue. The aim of this study was to evaluate the use of milk somatic cells as a non-invasive alternative to biopsy for measuring mammary SCD expression in dairy cows. Both milk somatic cells and mammary tissue were collected from 14 Holstein-Friesian cows and used for analysis of SCD expression by real-time PCR. The SCD5 mRNA levels in mammary tissue compared with SCD1 were low, and for several milk somatic cell samples, SCD5 expression was even below the limit of detection. A significant relationship was found between SCD1 expression in milk somatic cells and in mammary tissue. In addition, SCD1 expression in milk somatic cells was significantly related to Δ9-desaturase indices in milk, which are commonly used as an indicator of SCD1 activity within the mammary gland. Our study showed that milk somatic cells can be used as a source of mRNA to study SCD1 expression in dairy cows, offering a non-invasive alternative to mammary tissue samples obtained by biopsy.
"The aim of this study was to assess the effects of grazing season (from April to August), particularly referred to C18:2n-6 and C18:3n-3 levels in the pasture, on milk fatty acid composition, on milk delta-9 desaturation ratios commonly used as indicators of SCD activity and on mammary SCD gene expression of an autochthonous goat population called 'Cilentana', extensively bred in Cilento (Salerno province, southern Italy). Gene expression was studied using milk somatic cells as previously reported in goats (Boutinaud et al., 2002; Modesto et al., 2013), beef cows (Murrieta et al., 2006) and dairy cows (Feng et al., 2007; Boutinaud et al., 2008; Jacobs et al., 2013). "
[Show abstract][Hide abstract] ABSTRACT: The effect of pasture fatty acid profile along the year on the Stearoyl-CoA desaturase (SCD) expression was evaluated over 5 months using 30 pluriparous goats, delivered in February. The animals had free access to pasture constituted by 60% Leguminosae and 40% Gramineae, and received 500 g/head/day of concentrate. From the second half of April, goats were milked twice a day for 5 months. Daily milk yield was recorded and, monthly, representative individual milk and pasture samples were analysed for chemical composition and fatty acid profile. The SCD expression was studied by extraction of mRNA from milk somatic cells and analyzed by RT-PCR. Average milk yield, fat and protein were 1420 (g/d), 4.45 (%) and 3.62 (%), respectively. Milk yield decreased along the lactation (P < 0.01) while milk fat was higher in August. Milk total CLA showed the highest levels (P < 0.01) in June and August (mg/100 g fat: 0.98 and 1.21, respectively) as consequence of the highest levels of pasture C18:2 and C18:3 in June (% of total FA: 34.1 and 42.7, respectively) and August (% of total FA: 42.7 and 46.3, respectively). The grazing season as well as lactation stage affected the SCD mRNA abundance determined from milk somatic cells with values (arbitrary units) that progressively decreased from April (1.95) until June (1.40), increased in July (1.70) and decreased again in August (0.83).
Small Ruminant Research 07/2014; 122(1-3). DOI:10.1016/j.smallrumres.2014.07.016 · 1.13 Impact Factor
"It has been suggested that SCD is a primary candidate gene for altering the proportion of SFA versus MUFA in milk (Conte et al., 2010). Consistent with its function as a desaturase, strong associations between SCD activity and MUFA in bovine milk have been reported (Kgwatalala et al., 2009; Mele et al., 2009; Jacobs et al., 2013). Furthermore , a link between SCD and the concentration of MUFA was also reported in goats (Shi et al., 2012) and sheep (Reh et al., 2004). "
[Show abstract][Hide abstract] ABSTRACT: In rodents, peroxisome proliferator-activated receptor-γ (PPARG) plays a crucial role in fatty acid (FA) metabolism through regulation of gene expression, including stearoyl-coenzyme A desaturase (SCD), which is the rate-limiting enzyme for the biosynthesis of monounsaturated FA. However, whether or how PPARG regulates the activity of mammary SCD in ruminants is unknown. This study explored the potential role of PPARG isoforms in regulating SCD mRNA expression in lactating goat mammary epithelial cells (GMEC). Using quantitative real-time PCR, we observed a positive correlation between PPARG and SCD expression in the goat mammary gland at peak lactation. Overexpression of both PPARG1 and PPARG2 in GMEC increased markedly the expression of SCD, the concentration of 16:1 and 18:1, and the desaturation indices of 16:1 and 18:1. The PPARG ligand rosiglitazone further increased SCD expression and desaturation indices in GMEC, overexpressing PPARG1 and PPARG2. Incubation with rosiglitazone alone increased the expression of SCD, but did not alter the concentration of 16- to 18-carbon FA or their desaturation indices. The results provide evidence that PPARG regulates the expression and activity of SCD in GMEC. As such, PPARG may contribute to regulation of SCD and monounsaturated FA synthesis during lactation.
[Show abstract][Hide abstract] ABSTRACT: Stearoyl-CoA desaturase (SCD) in the bovine mammary gland introduces a cis-double bond at the Δ9 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 β-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 + 5 mM BHBA, 100 μM C16:0, 100 μM C18:0, 100 μM C18:1 cis-9, 100 μM C18:1 trans-11, 100 μM C18:2 cis-9,12 or 100 μM C18:3 cis-9,12,15. Compared with control, mRNA expression of SCD1 was increased by Ac (+61%) and reduced by C18:1 cis-9 (-61%), C18:2 cis-9,12 (-84%) and C18:3 cis-9,12,15 (-88%). In contrast to native bovine mammary gland tissue, MAC-T cells did not express SCD5. Expression of ACACA was increased by Ac (+44%) and reduced by C18:2 cis-9,12 (-48%) and C18:3 cis-9,12,15 (-49%). 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 (-44%), C18:1 trans-11 (-42%), C18:2 cis-9,12 (-62%) and C18:3 cis-9,12,15 (-68%) compared with control. Expression of INSIG1 was downregulated by C18:0 (-37%), C18:1 cis-9 (-63%), C18:1 trans-11 (-53%), C18:2 cis-9,12 (-81%) and C18:3 cis-9,12,15 (-91%). 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.
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