Beta-Sitosterol Promotes Milk Protein and Fat Syntheses-Related Genes in Bovine Mammary Epithelial Cells

Abstract

β-sitosterol, a phytosterol with multiple biological activities, has been used in the pharmaceutical industry. However, there are only a few reports on the use of β-sitosterol in improving milk synthesis in dairy cows. This study aimed to investigate the effects of β-sitosterol on milk fat and protein syntheses in bovine mammary epithelial cells (MAC-T) and its regulatory mechanism. MAC-T cells were treated with different concentrations (0.01, 0.1, 1, 5, 10, 20, 30, or 40 μM) of β-sitosterol, and the expression levels of milk protein and fat synthesis-related genes and proteins were analyzed. β-sitosterol at 0.1, 1, and 10 μM concentrations promoted the mRNA and protein expression of β-casein. β-sitosterol (0.1, 1, 10 μM) increased the mRNA and protein expression levels of signal transducer activator of transcription 5 (STAT5), mammalian target of rapamycin (mTOR), and ribosomal protein S6 kinase beta-1 (S6K1) of the JAK2/STAT5 and mTOR signaling pathways. It also stimulated the milk fat synthesis-related factors, including sterol regulatory element-binding protein 1 (SREBP1), peroxisome proliferator-activated receptor-gamma (PPARγ), acetyl-CoA carboxylase (ACC), lipoprotein lipase (LPL), and stearyl CoA desaturase (SCD). β-sitosterol (0.1, 1, 10 μM) also significantly increased the expression of growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis and hypoxia-inducible factor-1α (HIF-1α)-related genes. Notably, the compound inhibited the expression of the negative regulator, the suppressor of cytokine signaling 2 (SOCS2) at the two lower concentrations (0.1, 1 μM), but significantly promoted the expression at the highest concentration (30 μM). These results highlight the role of β-sitosterol at concentrations ranging from 0.1 to 10 μM in improving milk protein and fat syntheses, regulating milk quality. Therefore, β-sitosterol can be used as a potential feed additive to improve milk quality in dairy cows.

Dietary β‐sitosterol supplementation enhanced intestinal immune function of large yellow croaker ( Larimichthys crocea ) infected with Aeromonas hydrophila

“…Interestingly, dietary β‐sitosterol supplementation did not affect IgM content in the PI (rather than the latter two intestinal segments), which is possibly connected with protein and threonine. Liu et al (2021) found that β‐sitosterol could promote milk protein synthesis in the mammary epithelial cells of bovine. It had been reported that elevating dietary protein level enhanced muscle threonine content in grass carp (Xu et al, 2018).…”

“…β-sitosterol supplementation enhanced LZ and ACP activities, C3, C4 and IgM (not in PI) contents and up-regulated LEAP-2C and hepcidin mRNA expressions in all intestinal segments of large yellow croaker, indicating that dietary β-sitosterol supplementation enhanced intestinal immunity of fish.Interestingly, dietary β-sitosterol supplementation did not affect IgM content in the PI (rather than the latter two intestinal segments), which is possibly connected with protein and threonine Liu et al (2021). found that β-sitosterol could promote milk protein synthesis in the mammary epithelial cells of bovine.…”

“…A study on young grass carp demonstrated that dietary cholesterol supplementation could enhance LZ activities and antimicrobial peptide mRNA levels in the immune organs (Wang et al, 2018). Liu et al (2021) reported that β‐sitosterol promoted lipid syntheses in bovine mammary epithelial cells. Appropriate lipids level in diet could increase immunoglobulin M contents in the immune organs of grass carp (Ni et al, 2016).…”

Functional sterol improves breast milk quality by modulating the gut microbiota: A proposed opinion for breastfeeding mothers

“…B-sitosterol improves the expression of the JAK2/STAT5 signaling pathway by activating the GH axis and inhibiting SOCS2, further promoting the synthesis of β-casein. It promotes mTOR expression by activating IGF-1 and HIF-1α/EPO and increasing the downstream factor of mTOR S6K1, thereby influencing the synthesis of β-casein and aiding in infant growth ( 38 ). In addition, β-sitosterol increases the diversity of Staphylococcus and Streptococcus , which are found in colostrum and are very nutritious for babies ( 33 ).…”

KRAS Affects the Lipid Composition by Regulating Mitochondrial Functions and MAPK Activation in Bovine Mammary Epithelial Cells

“…MAC-T, the immortalized bovine mammary epithelial cell line, is a cell model for researching mammary developmental biology, mammary pathology, mammary bioreactors, and lactation engineering [ 28 , 29 , 30 ]. It can also be used to explore the effects of functional genes [ 31 , 32 ] and compounds [ 33 ] on the development of mammary components and milk fat synthesis.…”