Overexpression of PER2 Promotes De Novo Fatty Acid Synthesis, Fatty Acid Desaturation, and Triglyceride Accumulation in Bovine Mammary Epithelial Cells

The core clock gene Period2 (PER2) is associated with mammary gland development and lipid synthesis in rodents and has recently been found to have a diurnal variation in the process of lactation, but has not yet been demonstrated in bovine mammary epithelial cells (BMECs). To explore the regulatory function of PER2 on milk fat synthesis in bovine mammary epithelial cells, we initially assessed the expression of clock genes and milk fat metabolism genes for 24 h using real-time quantitative PCR and fitted the data to a cosine function curve. Subsequently, we overexpressed the PER2 in BMECs using plasmid vector (pcDNA3.1-PER2), with empty vector pcDNA3.1-myc as the control. After transfecting BMECs for 48 h, we assessed the protein abundance related to milk fat synthesis by Western blot, the expression of genes coding for these proteins using real time-quantitative PCR, the production of triacylglycerol, and the fatty acid profile. The findings indicated that a total of nine clock genes (PER1/2, CRY1/2, REV-ERBα, BMAL1, NCOR1, NR2F2, FBXW11), seven fatty acid metabolism genes (CD36, ACSS2, ACACA, SCD, FADS1, DGAT1, ADFP), and six nuclear receptor-related genes (INSIG1, SCAP, SREBF1, C/EBP, PPARG, LXR) exhibited oscillation with a period close to 24 h in non-transfected BMECs (R2 ≥ 0.7). Compared to the control group (transfected with empty pcDNA3.1-myc), the triglyceride content significantly increased in the PER2 overexpression group (p < 0.05). The lipogenic genes for fatty acid transport and triglyceride synthesis (ACACA, SCD, LPIN1, DGAT1, and SREBF1) were upregulated after PER2 overexpression, along with the upregulation of related protein abundance (p < 0.05). The contents and ratios of palmitic acid (C16:0), oleic acid (C18:1n9c), and trans-oleic acid (C18:1n9t) were significantly increased in the overexpression group (p < 0.05). Overall, the data supported that PER2 participated in the process of milk fat metabolism and is potentially involved in the de novo synthesis and desaturation of fatty acid in bovine mammary epithelial cells.

INVITED REVIEW: Research on ruminal biohydrogenation: Achievements, gaps in knowledge, and future approaches from the perspective of dairy science

Scientific knowledge about ruminal biohydrogenation (BH) has improved greatly since this metabolic process was empirically confirmed in 1951. For years, BH had mostly been perceived as a process to be avoided to increase the post-ruminal flow of UFA from the diet. Two milestones changed this perception and stimulated great interest in BH intermediates themselves: In 1987, the in vitro anticarcinogenic properties of CLA were described, and in 2000, the inhibition of milk fat synthesis by trans-10 cis-12 CLA was confirmed. Since then, numerous BH metabolites have been described in small and large ruminants, and the major deviation from the common BH pathway (i.e., the trans-10 shift) has been reasonably well established. However, there are some less well-characterized alterations, and the comprehensive description of new BH intermediates (e.g., using isotopic tracers) has not been coupled with research on their biological effects. In this regard, the low quality of some published fatty acid profiles may also be limiting the advance of knowledge in BH. Furthermore, although BH seems to no longer be considered a metabolic niche inhabited by a few bacterial species with a highly specific metabolic capability, researchers have failed to elucidate which specific microbial groups are involved in the process and the basis for alterations in BH pathways (i.e., changes in microbial populations or their activity). Unraveling both issues may be beneficial for the description of new microbial enzymes involved in ruminal lipid metabolism that have industrial interest. From the perspective of diary science, other knowledge gaps that require additional research in the coming years are evaluation of the relationship between BH and feed efficiency and enteric methane emissions, as well as improving our understanding of how alterations in BH are involved in milk fat depression. Addressing these issues will have relevant practical implications in dairy science.

The Effects of trans-10, cis-12 Conjugated Linoleic Acid on the Production Performance of Dairy Cows and the Expression and Transcription Regulation of Lipid Metabolism-Related Genes in Bovine Mammary Epithelial Cells

Dietary fatty acids (FAs) determine the quality of dairy products. The trans-10, cis-12 conjugated linoleic acid (t10c12-CLA) is commonly considered an FA factor leading to milk fat depression syndrome (MFDs) in dairy cow. However, its effect on dairy cow performance and involvement in milk fat metabolism have been insufficiently explored. This study administered 136.17 g/day of rumen-protected CLA (RP-CLA) to dairy cows and found a diminution in milk fat percentage and a trend of increasing milk protein percentage on day 21 postpartum. Lactose content, milk yield, and net energy for lactation were unaffected. In the cell experiments, Oil Red O staining showed a notable increase in lipid droplets. Gene and protein expression analysis showed that 300 μM t10c12-CLA upregulated the expression of CD36, DGAT2, and ADRP, while downregulating the expression of ACACA, FASN, SREBP1, FABP3, FATP3, ACSL4, LPIN1, DGAT1, BTN1A1, XDH, SNAP23, and VAMP4. This provides a possible mechanistic pathway for the contradictory phenomenon of t10c12-CLA reducing milk fat while increasing lipid droplets. Overall, t10c12-CLA, as a long-chain fatty acid, can promote lipid droplet synthesis but may reduce milk fat by inhibiting lipid droplet fusion and secretion, FAs de novo synthesis, and triglyceride biosynthesis.

Liver Transcriptomic Profiles of Ruminant Species Fed Spent Hemp Biomass Containing Cannabinoids

The inclusion of spent hemp biomass (SHB), an extracted byproduct from industrial cannabidiol (CBD) production, in the diets of dairy cows and lambs appears to be safe with minor effects on the metabolism, including a decrease in circulating cholesterol and increase bilirubinemia, both associated with liver metabolism. Those effects could be consequence of the presence of cannabinoids, particularly Δ9-tetrahydrocannabinol (THC) and CBD in the SHB. This study aimed to study the transcriptional profile of the liver of dairy cows and lambs fed SHB. Dairy cows received SHB or alfalfa pellet for four weeks of intervention (IP) and four weeks of withdrawal periods (WP). Finishing lambs were fed a control diet (CON), 10% (LH2), or 20% (HH2) SHB for 2 months or 1 month followed by 1-month SHB withdrawal (LH1 and HH1, respectively). RNA sequencing was performed, and the mRNA was annotated using the latest reference genomes. The RNAseq data were filtered, normalized for library size and composition, and statistically analyzed by DESeq2. The bioinformatic analysis was performed by using DAVID, Gene Set Enrichment Analysis (GSEA), and the Dynamic Impact Approach. Using a 0.2 FDR cut-off, we identified only ≤24 differentially expressed genes (DEG) in the liver by feeding SHB in dairy cows and a larger number of DEGs in lambs (from 71 in HH1 vs. CON to 552 in LH1 vs. CON). The KEGG analysis demonstrated that feeding SHB in dairy cows and lambs had relatively minor to moderate metabolic alterations in dairy cows and lambs mainly associated with amino acids and lipid metabolism whereas cholesterol synthesis was overall activated in lambs. GSEA identified activation of the PPAR signaling pathway only in dairy cows. We found an opposite effect on activation of metabolism of drug and xenobiotics by cytochrome P450 enzymes in dairy cows and lambs receiving less SHB but an inhibition in HH2 lambs. Immune system-related pathways were inhibited by feeding SHB in lambs, but the impact was minor. Cumulatively, inclusion of SHB containing cannabinoids in dairy and lambs demonstrate very little effects on the alteration of transcriptomic profile of the liver.

Effect of Dietary Eicosapentaenoic and Docosahexaenoic Fatty Acid Supplementation during the Last Month of Gestation on Fatty Acid Metabolism and Oxidative Status in Charolais Cows and Calves

Fatty acids (FAs) are of utmost importance in the peripartal period for the development of the central nervous and immune systems of the newborn. The transport of polyunsaturated fatty acids (PUFAs) through the placenta is considered to be minimal in ruminants. Nevertheless, the cow's FAs are the main source of FAs for the calf during gestation. This research aimed to investigate the influence of low-dose eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplementation during late gestation on the FA metabolism of cows and their calves. A total of 20 Charolais cows during the last month of their gestation were included in the feeding trial and were divided into a control group (CON) and an experimental group (EPA + DHA). The latter received a supplement in the amount of 100 g/day (9.1 and 7.8 g/cow/day of EPA and DHA, respectively). Supplementation of low-dose EPA and DHA alters colostrum and milk fatty acid composition through the elevation of n-3 long-chain polyunsaturated fatty acids (LC-PUFAs) without affecting milk fat and protein concentrations and oxidative status. Plasma composition in cows was significantly altered, while the same effect was not detected in calf plasma. No significant change in mRNA expression was detected for the genes fatty acid synthase (FASN) and acetyl-CoA carboxylase alpha (ACACA).

Maternal Cannabis Use during Lactation and Potential Effects on Human Milk Composition and Production: A Narrative Review

Cannabis use has increased sharply in the last 20 y among adults, including reproductive-aged women. Its recent widespread legalization is associated with a decrease in risk perception of cannabis use during breastfeeding. However, the effect of cannabis use (if any) on milk production and milk composition is not known. This narrative review summarizes current knowledge related to maternal cannabis use during breastfeeding and provides an overview of possible pathways whereby cannabis might affect milk composition and production. Several studies have demonstrated that cannabinoids and their metabolites are detectable in human milk produced by mothers who use cannabis. Due to their physicochemical properties, cannabinoids are stored in adipose tissue, can easily reach the mammary gland, and can be secreted in milk. Moreover, cannabinoid receptors are present in adipocytes and mammary epithelial cells. The activation of these receptors directly modulates fatty acid metabolism, potentially causing changes in milk fatty acid profiles. Additionally, the endocannabinoid system is intimately connected to the endocrine system. As such, it is probable that interactions of exogenous cannabinoids with the endocannabinoid system might modify release of critical hormones (e.g., prolactin and dopamine) that regulate milk production and secretion. Nonetheless, few studies have investigated effects of cannabis use (including on milk production and composition) in lactating women. Additional research utilizing robust methodologies are needed to elucidate whether and how cannabis use affects human milk production and composition.

Association of three single nucleotide polymorphisms in the LPIN1 gene with milk production traits in cows of the Yaroslavl breed

Lipin-1 is a member of the evolutionarily conserved family of proteins and is expressed predominantly in adipose tissue and skeletal muscle. On the one hand, lipin-1 is an enzyme that catalyzes the dephosphorylation of phosphatidic acid to diacylglycerol (DAG) and thus participates in the metabolic pathways of biosynthesis of storage lipids in the cell, membrane phospholipids, and intracellular signaling molecules. On the other hand, lipin-1 is able to be transported from the cytoplasm to the nucleus and is a coactivator of lipid metabolism gene transcription. It was shown, using the analysis of single nucleotide polymorphism (SNP) associations, that the lipin-1 coding gene (LPIN1) is a promising candidate gene for milk production traits in Holstein and Brown Swiss cows. However, it is unclear how much of its effect depends on the breed. The Yaroslavl dairy cattle breed was created in the 18-19 centuries in Russia by breeding northern Great Russian cattle, which were short and poor productive, but well adapted to local climatic conditions and bad food base. It was shown by whole genome genotyping and sequencing that the Yaroslavl breed has unique genetics compared to Russian and other cattle breeds. The aim of the study was to assess the frequency of alleles and genotypes of three SNPs in the LPIN1 gene and to study the association of these SNPs with milk production traits in Yaroslavl cows. Blood samples from 142 cows of the Yaroslavl breed were obtained from two farms in the Yaroslavl region. Genotyping of SNPs was carried out by polymerase chain reaction-restriction fragment length polymorphism method. Associations of SNPs with 305-day milk yield, fat yield, fat percentages, protein yield, and protein percentages were studied from the first to the fourth lactation. Statistical tests were carried out using a mixed linear model, taking into account the relationship between individuals. We identified three SNPs - rs110871255, rs207681322 and rs109039955 with a frequency of a rare allele of 0.042-0.261 in Yaroslavl cows. SNP rs110871255 was associated with fat yield during the third and fourth lactations. SNP rs207681322 was associated with milk yield for the second, third and fourth lactations, as well as protein yield for the third lactation. Thus, we identified significant associations of SNPs rs207681322 and rs110871255 in the LPIN1 gene with a number of milk production traits during several lactations in Yaroslavl cows.

Research Progress on the Mechanism of Milk Fat Synthesis in Cows and the Effect of Conjugated Linoleic Acid on Milk Fat Metabolism and Its Underlying Mechanism: A Review

Milk fat synthesis in cows mainly includes the synthesis of short- and medium-chain fatty acids, the uptake, transport, and activation of long-chain fatty acids (LCFAs), the synthesis of triglycerides, and the synthesis of the genes, transcription factors, and signaling pathways involved. Although the various stages of milk fat synthesis have been outlined in previous research, only partial processes have been revealed. CLA consists of an aggregation of positional and geometric isomers of linoleic fatty acid, and the accumulated evidence suggests that the two isomers of the active forms of CLA (cis-9, trans-11 conjugated linoleic acid and trans-10, cis-12 conjugated linoleic acid, abbreviated as c9, t11-CLA and t10, c12-CLA) can reduce the fat content in milk by regulating lipogenesis, fatty acid (FA) uptake, oxidation, and fat synthesis. However, the mechanism through which CLA inhibits milk fat synthesis is unique, with most studies focusing only on the effects of CLA on one of the genes, transcription factors, or signaling pathways involved. In this study, we summarized the structure and function of classic genes and pathways (mTOR, SREBP, AMPK, and PPARG) and new genes or pathways (THRSP, METTL3, ELOVL, and LPIN1) involved in each stage of milk fat synthesis and demonstrated the interactions between genes and pathways. We also examined the effects of other substances (melanin, nicotinic acid, SA, etc.). Furthermore, we evaluated the influence of β-sitosterol, sodium butyrate, Met arginine, and Camellia oleifera Abel on milk fat synthesis to improve the mechanism of milk fat synthesis in cows and provide a mechanistic reference for the use of CLA in inhibiting milk fat biosynthesis.

Milk fat globule size: Unraveling the intricate relationship between metabolism, homeostasis, and stress signaling

Fat is an important component of milk which delivers energy, nutrients, and bioactive molecules from the lactating mother to the suckling neonate. Milk fat consists of a complex mixture of different types of lipids; hundreds of fatty acids, triglycerides, phospholipids, sphingolipids, cholesterol and cholesteryl ester, and glycoconjugates, secreted by the mammary gland epithelial cells (MEC) in the form of a lipid-protein assembly termed the milk fat globule (MFG). The mammary gland in general, and specifically that of modern dairy cows, faces metabolic stress once lactation commences, which changes the lipogenic capacity of MECs directly by reducing available energy and reducing factors required for both lipid synthesis and secretion or indirectly by activating a proinflammatory response. Both processes have the capacity to change the morphometric features (e.g., number and size) of the secreted MFG and its precursor-the intracellular lipid droplet (LD). The MFG size is tightly associated with its lipidome and proteome and also affects the bioavailability of milk fat and protein. Thus, MFG size has the potential to regulate the bioactivity of milk and dairy products. MFG size also plays a central role in the functional properties of milk and dairy products such as texture and stability. To understand how stress affects the structure-function of the MFG, we cover: (i) The mechanism of production and secretion of the MFG and the implications of MFG size, (ii) How the response mechanisms to stress can change the morphometric features of MFGs, and (iii) The possible consequences of such modifications.

Chlorogenic acid enhances PPARγ-mediated lipogenesis through preventing Lipin 1 nuclear translocation in Staphylococcus aureus-exposed bovine mammary epithelial cells

Chlorogenic acid (CGA) as one of the most ubiquitously dietary polyphenolic compounds, has been reported to have various antimicrobial effects and exhibit strong anti-inflammatory ability. Staphylococcus aureus is a gram-positive bacterium that can induce mastitis. However, the mechanism through which S. aureus infection affects lipid synthesis and whether CGA have protective effect on S. aureus reduced lipid synthesis is not fully understood. In this study, the internalization of S. aureus reduced intracellular lipid droplet formation, decreased the levels of intracellular triacylglycerol, total cholesterol and 7 types of fatty acid and downregulated the expression of lipogenic genes FAS, ACC, and DGAT1 in bovine mammary epithelial cells (BMECs). In addition, we found that S. aureus intracellular infection attenuated mTORC1 activation resulting in Lipin 1 nuclear localization. Remarkablely, S. aureus infection-mediated repression of lipid synthesis related to the mTORC1 signaling and Lipin 1 nuclear localization can be alleviated by CGA. Thus, our findings provide a novel mechanism by which lipid synthesis is regulated under S. aureus infection and the protective effects of CGA on lipid synthesis in BMECs.

Docosahexaenoic Acid Alters Lipid Metabolism Processes via H3K9ac Epigenetic Modification in Dairy Goat

Goat milk is increasingly recognized by consumers due to its high nutritional value, richness in short- and medium-chain fatty acids, and richness in polyunsaturated fatty acids (PUFA). Exogenous supplementation of docosahexaenoic acid (DHA) is an important approach to increasing the content of PUFA in goat milk. Several studies have reported benefits of dietary DHA in terms of human health, including potential against chronic diseases and tumors. However, the mechanisms whereby an increased supply of DHA regulates mammary cell function is unknown. In this study, we investigated the effect of DHA on lipid metabolism processes in goat mammary epithelial cells (GMEC) and the function of H3K9ac epigenetic modifications in this process. Supplementation of DHA promoted lipid droplet accumulation increased the DHA content and altered fatty acid composition in GMEC. Lipid metabolism processes were altered by DHA supplementation through transcriptional programs in GMEC. ChIP-seq analysis revealed that DHA induced genome-wide H3K9ac epigenetic changes in GMEC. Multiomics analyses (H3K9ac genome-wide screening and RNA-seq) revealed that DHA-induced expression of lipid metabolism genes (FASN, SCD1, FADS1, FADS2, LPIN1, DGAT1, MBOAT2), which were closely related with changes in lipid metabolism processes and fatty acid profiles, were regulated by modification of H3K9ac. In particular, DHA increased the enrichment of H3K9ac in the promoter region of PDK4 and promoted its transcription, while PDK4 inhibited lipid synthesis and activated AMPK signaling in GMEC. The activation of the expression of fatty acid metabolism-related genes FASN, FADS2, and SCD1 and their upstream transcription factor SREBP1 by the AMPK inhibitor was attenuated in PDK4-overexpressing GMEC. In conclusion, DHA alters lipid metabolism processes via H3K9ac modifications and the PDK4-AMPK-SREBP1 signaling axis in goat mammary epithelial cells, providing new insights into the mechanism through which DHA affects mammary cell function and regulates milk fat metabolism.

Mitochondrial Calcium Uniporter Regulator 1 (MCUR1) Relieves Mitochondrial Damage Induced by Lipopolysaccharide by Mediating Mitochondrial Ca2+ Homeostasis in Bovine Mammary Epithelial Cells

The metabolic stress triggered by negative energy balance after calving induces mitochondrial damage of bovine mammary epithelial cells. Mitochondrial calcium uniporter regulator 1 (MCUR1) is a key protein-coding gene that mediates mitochondrial calcium ion (Ca²⁺) uptake and plays an important role in mediating homeostasis of mitochondria. The aim of the present study was to elucidate the effects of MCUR1-mediated Ca²⁺ homeostasis on mitochondria of bovine mammary epithelial cells in response to an inflammatory challenge with lipopolysaccharide (LPS). Exogenous LPS resulted in upregulation of the MCUR1 mRNA and protein abundance, mitochondrial Ca²⁺ content, and mitochondrial reactive oxygen species (Mito-ROS) content while decreasing mitochondrial membrane potential, causing mitochondrial damage, and increasing the rate of apoptosis. Ryanodine pretreatment attenuated the upregulation of the mitochondrial Ca²⁺ content and Mito-ROS content induced by LPS. Overexpression of MCUR1 increased the mitochondrial Ca²⁺ content and Mito-ROS content, while it decreased mitochondrial membrane potential, damaged mitochondria, and induced cell apoptosis. In addition, knockdown of MCUR1 by small interfering RNA attenuated LPS-induced mitochondrial dysfunction by inhibiting mitochondrial Ca²⁺ uptake. Our results revealed that exogenous LPS induces MCUR1-mediated mitochondrial Ca²⁺ overload in bovine mammary epithelial cells, which leads to mitochondrial injury. Thus, MCUR1-mediated Ca²⁺ homeostasis may be a potential therapeutic target against mitochondrial damage induced by metabolic challenges in bovine mammary epithelial cells.

Effects of high-grain diet feeding on fatty acid profiles in milk, blood, muscle, and adipose tissue, and transcriptional expression of lipid-related genes in muscle and adipose tissue of dairy cows

BACKGROUND

High-grain (HG) diets affect lipid metabolism in the liver and mammary tissue of dairy cows, but its effects on muscle and adipose tissue have not been wide evaluated. Thus, the aim of this study is to clarify this issue.

METHODS

Twelve Holstein cows were randomly divided into two groups: conventional diet group (CON, n = 6) and the HG diet group (n = 6). On day 7 of week 4, rumen fluid was sampled to measure pH, milk was sampled to measure components, and blood was sampled to measure biochemical parameters and fatty acid composition. After the experiment, cows were slaughtered to collect muscle and adipose tissue for fatty acid composition and transcriptome analysis.

RESULTS

HG feeding decreased the ruminal pH, milk's fat content and long-chain fatty acid proportion (P < 0.05) and increased the proportion of short- and medium-chain fatty acids in the milk (P < 0.05) as compared with CON diets. The concentrations of blood cholesterol, low-density lipoprotein, and polyunsaturated fatty acids in the HG cows were lower than those in CON cows (P < 0.05). In muscle tissue, HG feeding tended to increase the triacylglycerol (TG) concentration (P < 0.10). Transcriptome analysis revealed changes in the biosynthesis of the unsaturated fatty acids pathway, the regulation of lipolysis in the adipocytes pathway, and the PPAR signalling pathway. In adipose tissue, HG feeding increased the concentration of TG and decreased the concentration of C18:1 cis9 (P < 0.05). At the transcriptome level, the fatty acid biosynthesis pathway, linoleic acid metabolism pathway, and PPAR signalling pathway were activated.

CONCLUSION

HG feeding leads to subacute rumen acidosis and a decreased milk fat content. The fatty acid profiles in the milk and plasma of dairy cows were changed by HG feeding. In muscle and adipose tissue, HG feeding increased TG concentration and up-regulated the expression of genes related to adipogenesis, while down-regulated the expression of genes related to lipid transport. These results complement our knowledge of the fatty acid composition of muscle and adipose tissue in dairy cows and expand our understanding of the mechanisms by which HG diets affect lipid metabolism in muscle and adipose tissue.

Transcriptome Profile in Dairy Cows Resistant or Sensitive to Milk Fat Depression

Feeding linseed to dairy cows results in milk fat depression (MFD), but there is a wide range of sensitivity among cows. The objectives of this study were to identify target genes containing SNP that may play a key role in the regulation of milk fat synthesis in cows resistant or sensitive to MFD. Four cows were selected from a dairy farm after a switch from a control diet to a linseed-rich diet; two were resistant to MFD with a high milk fat content in the control (4.06%) and linseed-rich (3.90%) diets; and two were sensitive to MFD with the milk fat content decreasing after the change from the control (3.87%) to linseed-rich (2.52%) diets. Transcriptome and SNP discovery analyses were performed using RNA-sequencing technology. There was a large number of differentially expressed genes in the control (n = 1316) and linseed-rich (n = 1888) diets. Of these, 15 genes were detected as key gene regulators and harboring SNP in the linseed-rich diet. The selected genes MTOR, PDPK1, EREG, NOTCH1, ZNF217 and TGFB3 may form a network with a principal axis PI3K/Akt/MTOR/SREBP1 involved in milk fat synthesis and in the response to diets that induced MFD. These 15 genes are novel candidate genes to be involved in the resistance or sensitivity of dairy cows to milk fat depression.

C/EBPα promotes triacylglycerol synthesis via regulating PPARG promoter activity in goat mammary epithelial cells

CCAAT/enhancer binding protein α (C/EBPα) is the key transcription factor involved in lipid metabolism, however, the role of C/EBPα in milk fat synthesis of dairy goats remains unknown. The objective of the present research was to clarify the function of C/EBPα in goat mammary epithelial cells (GMECs) and its impact on peroxisome proliferator-activated receptor gamma (PPARG) promoter activity. In this study, C/EBPα overexpression increased its mRNA and protein levels by 42-fold and 6-fold, respectively. In contrast, transfecting siRNA targeting C/EBPα decreased its mRNA level to 20% and protein abundance to 80% of the basal level. The contents of lipid droplets, triacylglycerol (TAG), and cholesterol were increased (P < 0.05) in C/EBPα-overexpressing GMECs, and knockdown of C/EBPα led to the opposite results. Overexpression of C/EBPα significantly increased the expression levels of genes involved in TAG synthesis (AGPAT6, DGAT2, P < 0.01), lipid droplet formation (PLIN2, P < 0.01), and fatty acid synthesis (FADS2, P < 0.05; ELOVL6, P < 0.01). Knockdown of C/EBPα decreased (P < 0.05) the expression levels of AGPAT6, DGAT1, DGAT2, PLIN2, FADS2, and ELOVL6. C/EBPα upregulated the expression level of PPARG (P < 0.05), and four C/EBPα binding regions were identified in the PPARG promoter at -1,112 to -1,102 bp, -734 to -724 bp, -248 to -238 bp, and -119 to -109 bp. Knockdown of C/EBPα reduced (P < 0.05) the PPARG promoter activity when the C/EBPα binding regions were mutated at -1,112 to -1,102 bp, -734 to -724 bp, and -248 to -238 bp locations of the promoter. However, the promoter activity did not change when the mutation was located at -119 bp. In conclusion, our results suggest that C/EBPα can promote TAG synthesis in GMECs through its effects on mRNA abundance of genes related to lipid metabolism and regulation of the PPARG promoter activity via C/EBPα binding regions.

Effects of PUFA-Rich Dietary Strategies on Ruminants' Mammary Gland Gene Network: A Nutrigenomics Review

Although the inclusion of polyunsaturated fatty acids (PUFAs) in ruminants' diets appears to be a well-documented strategy to enrich milk with PUFAs, several gene networks that regulate milk synthesis and mammary gland homeostasis could be impaired. The objective of this literature review is to assess the effects of nutritional strategies focused on enriching milk with PUFAs on gene networks regulating mammary gland function and lipogenesis, as well as the impact of feed additives and bioactive compounds with prominent antioxidant potential on immune-oxidative transcriptional profiling, as a part of mammary gland homeostasis and health. The findings support the conclusion that PUFAs' inclusion in ruminants' diets more strongly downregulate the stearoyl-CoA desaturase (SCD) gene compared to other key genes involved in de novo fatty acid synthesis in the mammary gland. Additionally, it was revealed that seed oils rich in linoleic and linolenic acids have no such strong impact on networks that regulate lipogenic homeostasis compared to marine oils rich in eicosapentaenoic and docosahexaenoic acids. Furthermore, ample evidence supports that cows and sheep are more prone to the suppression of lipogenesis pathways compared to goats under the impact of dietary marine PUFAs. On the other hand, the inclusion of feed additives and bioactive compounds with prominent antioxidant potential in ruminants' diets can strengthen mammary gland immune-oxidative status. Considering that PUFA's high propensity to oxidation can induce a cascade of pro-oxidant incidences, the simultaneous supplementation of antioxidant compounds and especially polyphenols may alleviate any side effects caused by PUFA overload in the mammary gland. In conclusion, future studies should deeply investigate the effects of PUFAs on mammary gland gene networks in an effort to holistically understand their impact on both milk fat depression syndrome and homeostatic disturbance.

The effect of dietary pioglitazone supplementation on milk yield, insulin sensitivity and GH-IGF-I axis in Holstein dairy cows during the transition period

BACKGROUND

High-yielding dairy cows develop insulin resistance during late gestation associated with disruption of the growth hormone (GH)-insulin-like growth factor (IGF)-I axis and cause metabolic and reproductive disorders.

OBJECTIVE

This study aimed to determine the effects of dietary pioglitazone (PIO) supplementation as an insulin sensitizer agent on milk yield, plasma metabolite status and GH-IGF-I axis in transition Holstein dairy cows.

METHODS

Twenty multiparous cows were randomly assigned into two experimental groups (n = 10 animals per group) and either fed with a basal diet (control) or the basal diet supplemented with 6 mg PIO/kg body weight (BW) from day 14 before parturition to day 21 postpartum. The BW and body condition score (BCS), non-esterified fatty acids, beta-hydroxybutyrate (BHBA), insulin, glucose, GH and IGF-I concentrations, milk production and composition were measured weekly.

RESULTS

BW and BCS losses were lower in PIO than in control cows (p < 0.05). The percentage and amount of milk fat were decreased, and the amount of protein increased only in the first post-calving week in the PIO-treated cows compared to the control (p < 0.05). Dietary PIO supplementation increased glucose concentration at calving, but insulin concentration was increased at calving and in the first post-calving week (p < 0.05). Plasma concentrations of IGF-I and the ratio of IGF to GH were increased in the PIO group (p < 0.05). The mean revised quantitative insulin sensitivity check index with BHBA, as an insulin sensitivity index, was greater in PIO-supplemented cows (p < 0.05).

CONCLUSIONS

Our results showed beneficial effects of PIO supplementation on improving insulin sensitivity and the GH-IGF-I axis that may cause lower negative energy balance and better metabolic and health status in transition dairy cows.

Integrative methylome and transcriptome analysis of porcine abdominal fat indicates changes in fat metabolism and immune responses during different development

Fat is involved in synthesizing fatty acids (FAs), FA circulation, and lipid metabolism. Various genetic studies have been conducted on porcine fat but understanding the growth and specific adipose tissue is insufficient. The purpose of this study is to investigate the epigenetic difference in abdominal fat according to the growth of porcine. The samples were collected from the porcine abdominal fat of different developmental stages (10 and 26 weeks of age). Then, the samples were sequenced using MBD-seq and RNA-seq for profiling DNA methylation and RNA expression. In 26 weeks of age pigs, differentially methylated genes (DMGs) and differentially expressed genes (DEGs) were identified as 2,251 and 5,768, compared with 10 weeks of age pigs, respectively. Gene functional analysis was performed using GO and KEGG databases. In functional analysis results of DMGs and DEGs, immune responses such as chemokine signaling pathways, B cell receptor signaling pathways, and lipid metabolism terms such as PPAR signaling pathways and fatty acid degradation were identified. It is thought that there is an influence between DNA methylation and gene expression through changes in genes with similar functions. The effects of DNA methylation on gene expression were investigated using cis-regulation and trans-regulation analysis to integrate and interpret different molecular layers. In the cis-regulation analysis using 629 overlapping genes between DEGs and DMGs, immune response functions were identified, while in trans-regulation analysis through the TF-target gene network, the co-expression network of lipid metabolism-related functions was distinguished. Our research provides an understanding of the underlying mechanisms for epigenetic regulation in porcine abdominal fat with aging.

The LXRB-SREBP1 network regulates lipogenic homeostasis by controlling the synthesis of polyunsaturated fatty acids in goat mammary epithelial cells

Background

In rodents, research has revealed a role of liver X receptors (LXR) in controlling lipid homeostasis and regulating the synthesis of polyunsaturated fatty acids (PUFA). Recent data suggest that LXRB is the predominant LXR subtype in ruminant mammary cells, but its role in lipid metabolism is unknown. It was hypothesized that LXRB plays a role in lipid homeostasis via altering the synthesis of PUFA in the ruminant mammary gland. We used overexpression and knockdown of LXRB in goat primary mammary epithelial cells (GMEC) to evaluate abundance of lipogenic enzymes, fatty acid profiles, content of lipid stores and activity of the stearoyl-CoA desaturase (SCD1) promoter.

Results

Overexpression of LXRB markedly upregulated the protein abundance of LXRB while incubation with siRNA targeting LXRB markedly decreased abundance of LXRB protein. Overexpression of LXRB plus T0901317 (T09, a ligand for LXR) dramatically upregulated SCD1 and elongation of very long chain fatty acid-like fatty acid elongases 5–7 (ELOVL 5–7), which are related to PUFA synthesis. Compared with the control, cells overexpressing LXRB and stimulated with T09 had greater concentrations of C16:0, 16:1, 18:1n7,18:1n9 and C18:2 as well as desaturation and elongation indices of C16:0. Furthermore, LXRB-overexpressing cells incubated with T09 had greater levels of triacylglycerol and cholesterol. Knockdown of LXRB in cells incubated with T09 led to downregulation of genes encoding elongases and desaturases. Knockdown of LXRB attenuated the increase in triacylglycerol and cholesterol that was induced by T09. In cells treated with dimethylsulfoxide, knockdown of LXRB increased the concentration of C16:0 at the expense of C18:0, while a significant decrease in C18:2 was observed in cells incubated with both siLXRB and T09. The abundance of sterol regulatory element binding transcription factor 1 precursor (pSREBP1) and its mature fragment (nSREBP1) was upregulated by T09, but not LXRB overexpression. In the cells cultured with T09, knockdown of LXRB downregulated the abundance for pSREBP1 and nSREBP1. Luciferase reporter assays revealed that the activities of wild type SCD1 promoter or fragment with SREBP1 response element (SRE) mutation were decreased markedly when LXRB was knocked down. Activity of the SCD1 promoter that was induced by T09 was blocked when the SRE mutation was introduced.

Conclusion

The current study provides evidence of a physiological link between the LXRB and SREBP1 in the ruminant mammary cell. An important role was revealed for the LXRB-SREBP1 network in the synthesis of PUFA via the regulation of genes encoding elongases and desaturases. Thus, targeting this network might elicit broad effects on lipid homeostasis in ruminant mammary gland.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00774-4.

Feeding of palm oil fatty acids or rapeseed oil throughout lactation: Effects on mammary gene expression and milk production in Norwegian dairy goats

Lipid added as rapeseed or palm oil to the diet of dairy goats over 8 mo of one lactation alters fat secretion and milk fatty acid (FA) and protein composition. In this study, we examined the contribution of mammary gene expression to these changes and included 30 multiparous goats of Norwegian dairy goat breed for a 230-d experimental period, with indoor feeding from 1 to 120 d in milk (DIM), mountain grazing from 120 to 200 DIM, and indoor feeding from 200 to 230 DIM. After an initial period (1-60 DIM) when the control diet was given to all goats, the animals were subdivided into 3 groups of 10 goats. Treatments (60-230 DIM) were basal concentrate (control) alone or supplemented with either 8% (by weight) hydrogenated palm oil enriched with palmitic acid (POFA) or 8% (by weight) rapeseed oil (RSO). Milk was sampled individually from all animals throughout lactation, at 60, 120, 190, and 230 DIM for milk yield and composition. On d 60, 120, 190, and 230, mammary tissue was collected by biopsy to measure mRNA abundance of 19 key genes. None of the 19 genes involved in milk protein, apoptosis, lipid metabolism, transcription factors, and protein of the milk fat globule membrane, as measured by mRNA abundance, were affected by the lipid supplements, although POFA increased milk fat content, and POFA and RSO affected milk FA composition. Over the experimental period (120-230 DIM), the mRNA abundance of 13 of the 19 studied genes was affected by lactation stage. For some genes, expression either gradually increased from 120 to 230 DIM (CSN2,CASP8,CD36,GLUT4) or increased from 120 to 200 and then remained stable (XDH), or decreased (CSN3,G6PD,SREBF1,PPARG1) or increased only at 230 DIM (SCD1,SCD5,ELF3). For a second group of genes (CSN1, LALBA, FABP3, FASN, LPL, MFGE8), expression was stable over the lactation period. Our results suggest that factors other than gene expression, such as substrate availability or posttranscriptional regulation of these genes, could play an important role in the milk fat and FA responses to dietary fat composition in the goat. In conclusion, mammary gene expression in goats was more regulated by stage of lactation than by the dietary treatments applied.

Effect of arginine supplementation on the production of milk fat in dairy cows

Arginine, one of the conditionally essential AA, has been reported to affect fat synthesis and metabolism in nonruminant animals by influencing adenosine monophosphate activated protein kinase (AMPK) in some organs. In dairy cows, the effect of Arg on milk fat production is not clear, and any potential mechanism that underlies the effect is unknown. We tested the hypothesis that Arg infusion would improve the production of milk fat, and explored possible mechanism that might underlie any effect. We used 6 healthy lactating cows at 20 ± 2 d in milk, in fourth parity, with a body weight of 508 ± 14 kg, body condition score of 3.0 ± 0, and a milk yield of 30.6 ± 1.8 kg/d (mean ± standard deviation). The cows were blocked by days in milk and milk yield and each cow received 3 treatments in a replicated 3 × 3 Latin square design, with each of the experimental periods lasting 7 d with a 14-d washout between each period. The treatments, delivered in random order, were (1) infusion of saline (control); (2) infusion of 0.216 mol/d of l-Arg in saline (Arg); (3) infusion of 0.868 mol/d of l-Ala in saline (the Arg and Ala treatments were iso-nitrogenous) through a jugular vein. On the last day of each experimental period, blood was sampled to measure insulin, nitric oxide, glucose, and nonesterified fatty acid, and the liver and mammary gland were biopsied to measure the expression of genes. Milk yield was recorded, and milk fat percentage was measured daily during each of the experimental periods. The yield and composition of fatty acid (FA) in milk was measured daily on the last 3 d during each of the experimental periods. The data were analyzed using a mixed model with treatment as a fixed factor, and cow, period, and block as random factors. The daily milk yield and milk fat yield when the cows were infused with Arg were 2.2 kg and 76 g, respectively, higher than that in control, and 1.8 kg and 111 g, respectively, higher than that in Ala. When the cows were infused with Arg they had higher concentration and yield of de novo synthesized FA, than when they received the control or Ala infusions, although milk fat percentage, daily feed intake, and the digestibility of nutrients were not affected by treatment. The serum concentration of nitric oxide and insulin were higher during Arg than during control or Ala, with no difference between control and Ala. In the liver, the expression of the genes coding for AMPK (PRKAA1, PRKAB1, and PRKAG1) and genes related to the oxidation of FA were higher during Arg than during control or Ala, whereas in the mammary gland the expression PRKAB1 was lowest, and the expression of genes involved in the synthesis of milk fat were highest, during Arg infusion. The results suggest the intravenous infusion of Arg enhanced the production of milk fat by promoting the de novo synthesis of FA and increasing milk yield.

Peroxisome Proliferator-Activated Receptor Activation in Precision-Cut Bovine Liver Slices Reveals Novel Putative PPAR Targets in Periparturient Dairy Cows

Metabolic challenges experienced by dairy cows during the transition between pregnancy and lactation (also known as peripartum), are of considerable interest from a nutrigenomic perspective. The mobilization of large amounts of non-esterified fatty acids (NEFA) leads to an increase in NEFA uptake in the liver, the excess of which can cause hepatic accumulation of lipids and ultimately fatty liver. Interestingly, peripartum NEFA activate the Peroxisome Proliferator-activated Receptor (PPAR), a transcriptional regulator with known nutrigenomic properties. The study of PPAR activation in the liver of periparturient dairy cows is thus crucial; however, current in vitro models of the bovine liver are inadequate, and the isolation of primary hepatocytes is time consuming, resource intensive, and prone to errors, with the resulting cells losing characteristic phenotypical traits within hours. The objective of the current study was to evaluate the use of precision-cut liver slices (PCLS) from liver biopsies as a model for PPAR activation in periparturient dairy cows. Three primiparous Jersey cows were enrolled in the experiment, and PCLS from each were prepared prepartum (−8.0 ± 3.6 DIM) and postpartum (+7.7± 1.2 DIM) and treated independently with a variety of PPAR agonists and antagonists: the PPARα agonist WY-14643 and antagonist GW-6471; the PPARδ agonist GW-50156 and antagonist GSK-3787; and the PPARγ agonist rosiglitazone and antagonist GW-9662. Gene expression was assayed through RT-qPCR and RNAseq, and intracellular triacylglycerol (TAG) concentration was measured. PCLS obtained from postpartum cows and treated with a PPARγ agonist displayed upregulation of ACADVL and LIPC while those treated with PPARδ agonist had increased expression of LIPC, PPARD, and PDK4. In PCLS from prepartum cows, transcription of LIPC was increased by all PPAR agonists and NEFA. TAG concentration tended to be larger in tissue slices treated with PPARδ agonist compared to CTR. Use of PPAR isotype-specific antagonists in PCLS cultivated in autologous blood serum failed to decrease expression of PPAR targets, except for PDK4, which was confirmed to be a PPARδ target. Transcriptome sequencing revealed considerable differences in response to PPAR agonists at a false discovery rate-adjusted p-value of 0.2, with the most notable effects exerted by the PPARδ and PPARγ agonists. Differentially expressed genes were mainly related to pathways involved with lipid metabolism and the immune response. Among differentially expressed genes, a subset of 91 genes were identified as novel putative PPAR targets in the bovine liver, by cross-referencing our results with a publicly available dataset of predicted PPAR target genes, and supplementing our findings with prior literature. Our results provide important insights on the use of PCLS as a model for assaying PPAR activation in the periparturient dairy cow.

Effect of Diet Enriched With Hemp Seeds on Goat Milk Fatty Acids, Transcriptome, and miRNAs

In dairy ruminants, a diet supplemented with feed rich in unsaturated fatty acids can be an effective medium to increase the health-promoting properties of milk, although their effect on the pathways/genes involved in these processes has not been properly and completely defined to date. To improve our knowledge of the cell’s activity in specific conditions, next-generation RNA-sequencing technology was used to allow whole transcriptome characterization under given conditions. In addition to this, microRNAs (miRNAs) have recently been known as post-transcriptional regulators in fatty acid and cholesterol metabolism by targeting lipid metabolism genes. In this study, to analyze the transcriptome and miRNAs in goat milk after a supplemental diet enriched with linoleic acid (hemp seeds), next-generation RNA-sequencing was used in order to point out the general biological mechanisms underlying the effects related to milk fat metabolism. Ten pluriparous Alpine goats were fed with the same pretreatment diet for 40 days; then, they were arranged to two dietary treatments consisting of control (C) and hemp seed (H)-supplemented diets. Milk samples were collected at 40 (time point = T0) and 140 days of lactation (time point = T1). Milk fatty acid (FA) profiles revealed a significant effect of hemp seeds that determined a strong increment in the preformed FA, causing a reduction in the concentration of de-novo FA. Monounsaturated and polyunsaturated n−3 FAs were increased by hemp treatment, determining a reduction in the n−6/n−3 ratio. After removing milk fats and proteins, RNA was extracted from the milk cells and transcriptomic analysis was conducted using Illumina RNA-sequencing. A total of 3,835 genes were highly differentially expressed (p-value &lt; 0.05, fold change &gt; 1.5, and FDR &lt; 0.05) in the H group. Functional analyses evidenced changes in metabolism, immune, and inflammatory responses. Furthermore, modifications in feeding strategies affected also key transcription factors regulating the expression of several genes involved in milk fat metabolism, such as peroxisome proliferator-activated receptors (PPARs). Moreover, 38 (15 known and 23 novel) differentially expressed miRNAs were uncovered in the H group and their potential functions were also predicted. This study gives the possibility to improve our knowledge of the molecular changes occurring after a hemp seed supplementation in the goat diet and increase our understanding of the relationship between nutrient variation and phenotypic effects.

Enrichment of Ewe’s Milk with Dietary n-3 Fatty Acids from Palm, Linseed and Algae Oils in Isoenergetic Rations

Increasing the levels of n-3 fatty acids (FA) in dairy products is an important goal in terms of enhancing the nutritional value of these foods for the consumer. The purpose of this research was to evaluate the effects of linseed and algae oil supplements in ovine isoenergetic diets on healthy milk fatty acid composition, mainly n-3. Seventy-two Churra dairy ewes were divided and randomly assigned to four experimental treatments for 6 weeks. The treatments consisted of a TMR (40:60 forage:concentrate ratio) that varied according to the inclusion of different types of fat (23 g/100 g TMR): hydrogenated palm oil (control), linseed oil (LO), calcium soap of linseed oil (CaS-LO) and marine algae oil (AO). The most effective lipid supplement to increase n-3 FA in milk was AO. 22:6 n-3 and total n-3 PUFA content increased from 0.02 and 0.60% (control) to 2.63 and 3.53% (AO), respectively. All diets supplemented with n-3 FA diminished the content of saturated FA in milk and its atherogenic index, while the levels of trans-11 18:1 and cis-9 trans-11 18:2 significantly increased. Overall, the enhancement of n-3 FA in ewe’s milk would be advantageous for the manufacture of nutritionally improved cheeses.

The Knockout of the ASIP Gene Altered the Lipid Composition in Bovine Mammary Epithelial Cells via the Expression of Genes in the Lipid Metabolism Pathway

Agouti signalling protein (ASIP) is a coat colour-related protein and also is a protein-related to lipid metabolism, which had first been found in agoutis. According to our previous study, ASIP is a candidate gene that affects the lipid metabolism in bovine adipocytes. However, its effect on milk lipid has not been reported yet. This study focused on the effect of the ASIP gene on the lipid metabolism of mammary epithelial cells in cattle. The ASIP gene was knocked out in bMECs by using CRISPR/Cas9 technology. The result of transcriptome sequencing showed that the differentially expressed genes associated with lipid metabolism were mainly enriched in the fatty acids metabolism pathways. Furthermore, the contents of intracellular triglycerides were significantly increased (p < 0.05), and cholesterol tended to rise (p > 0.05) in bMECs with the knockout of the ASIP gene. Fatty acid assays showed a significant alteration in medium and long-chain fatty acid content. Saturated and polyunsaturated fatty acids were significantly up-regulated (p < 0.05), and monounsaturated fatty acids were significantly decreased in the ASIP knockout bMECs (p < 0.05). The Q-PCR analysis showed that knockout of ASIP resulted in a significant reduction of gene expressions like PPARγ, FASN, SCD, and a significant up-regulation of genes like FABP4, ELOVL6, ACSL1, HACD4 prompted increased mid-to long-chain fatty acid synthesis. Overall, ASIP plays a pivotal role in regulating lipid metabolism in bMECs, which could further influence the component of lipid in milk.

Inhibiting nuclear factor erythroid 2 related factor 2-mediated autophagy in bovine mammary epithelial cells induces oxidative stress in response to exogenous fatty acids

Background

In early lactation, bovine mammary epithelial cells undergo serious metabolic challenges and oxidative stress both of which could be alleviated by activation of autophagy. Nuclear factor erythroid 2 related factor 2 (NFE2L2), a master regulator of cellular redox homeostasis, plays an important role in the regulation of autophagy and oxidative stress. Thus, the objective of this study was to investigate the role of NFE2L2-mediated autophagy on oxidative stress of bovine mammary epithelial cells in response to exogenous free fatty acids (FFA).

Results

Exogenous FFA induced linear and quadratic decreases in activities of glutathione peroxidase (GSH-Px), catalase (CAT), and superoxide dismutase (SOD), and increases in the contents of reactive oxygen species (ROS) and malondialdehyde (MDA). Protein abundance of LC3-phosphatidylethanolamine conjugate (LC3-II) and the number of autophagosomes and autolysosomes decreased in a dose-dependent manner, while protein abundance of p62 increased in cells challenged with FFA. Activation of autophagy via pre-treatment with Rap attenuated the FFA-induced ROS accumulation. Importantly, FFA inhibited protein abundance of NFE2L2 and the translocation of NFE2L2 into the nucleus. Knockdown of NFE2L2 by siRNA decreased protein abundance of LC3-II, while it increased protein abundance of p62. Furthermore, sulforaphane (SFN) pre-treatment attenuated the FFA-induced oxidative stress by activating NFE2L2-mediated autophagy.

Conclusions

The data suggested that NFE2L2-mediated autophagy is an important antioxidant mechanism in bovine mammary epithelial cells experiencing increased FFA loads.

An evaluation of maternal serum dynamic thiol-disulfide homeostasis and ischemia modified albumin changes in pregnant women with COVID-19

Objective:

It is thought that oxidative stress, free radicals, reactive oxygen species and reactive nitrogen species affect the pathophysiology of coronavirus disease-2019 (COVID-19). This study aimed to evaluate the oxidative status in pregnant patients with COVID-19 infection according to the changes seen in the levels of maternal serum thiol-disulfide and ischemia-modified albumin (IMA).

Materials and Methods:

A study group was formed of 40 pregnant women with confirmed COVID-19 infection (study group) and a control group of 40 healthy pregnant women with no risk factors determined. In this prospective, case-controlled study, analyses were made of the maternal serum native thiol, total thiol, disulfide, IMA, and disulfide/native thiol concentrations.

Results:

The maternal serum native thiol and total thiol concentrations in the study group were determined to be statistically significantly lower (p=0.007 and p=0.006, respectively), and the disulfide/native thiol ratio was higher but not to a level of statistical significance (p=0.473). There was no difference between the two groups regarding IMA levels (p=0.731).

Conclusion:

The thiol-disulfide balance was seen to shift in the oxidant direction in pregnancies with COVID-19, which might support the view that ischemic processes play a role in the etiopathogenesis of this novel disease.

Evolutionary and Association Analysis of Buffalo FABP Family Genes Reveal Their Potential Role in Milk Performance

The fatty acid-binding protein (FABP) family gene encode a group of proteins that affect long-chain fatty acid (LCFAs) trafficking and play a crucial function in the regulation of milk fat synthesis. Nevertheless, little is known regarding the identification of members, theevolutionary background, and functional characteristics of FABP genes in buffalo. In this study, in silico analysis was performed to identify the members of FABPs in buffalo. The results revealed that a total of 17 FABP genes were identified. Based on their phylogenetic relationships, these sequences clustered into five groups with similar motif patterns and gene structures. According to positive selection analyses, all duplicated gene pairs containing FABPs in buffalo had Ka/Ks (nonsynonymous/synonymous) ratios that were less than 1, suggesting that they were under purifying selection. Association analysis showed that one SNP in LOC102401361 was found significantly associated with buffalo milk yield. The expression levels of several FABPs in buffalo mammary epithelial cells were regulated by palmitic and stearic acid treatment. The findings of this study provide valuable information for further research on the role of FABPs in regulating buffalo milk synthesis.

CircEZH2 Regulates Milk Fat Metabolism through miR-378b Sponge Activity

Simple Summary

Heat stress has seriously threatened the performance and health of dairy cows and has become one of the most important factors restricting the development of the dairy industry. In our previous study, we found that heat stress markedly altered the expression patterns of circRNAs in dairy cow’s mammary gland tissue, and heat-induced circRNAs participated in the regulation of milk fat metabolism through competing endogenous RNA (ceRNA) networks. Therefore, we evaluated the roles of heat-induced circEZH2 in the regulation of milk fat metabolism in this study. In more detail, we found that circEZH2 affects the proliferation, apoptosis, and lipid metabolism of mammary gland epithelial cells, and successfully verified the targeting relationship of circEZH2-bta-miR378b-LPL and circEZH2-bta-miR378b-CD36. This experiment expands the basic data on the role of circRNA in milk fat regulation, and provides a theoretical basis for alleviating heat stress in dairy cows.

Abstract

In this study, we evaluated the roles of heat-induced circEZH2 in the regulation of milk fat metabolism. CircEZH2 overexpression increased HC11 cell proliferation and decreased apoptosis. These changes were accompanied by increased expression of proliferation marker proteins (PCNA, Cyclin D, and Cyclin E) and the anti-apoptotic protein Bcl2, while expression of the pro-apoptotic proteins Bax and cleaved-caspase was reduced. SiRNA-mediated silencing of EZH2 in HC11 cells had the opposite effects. CircEZH2 overexpression promoted the uptake of a fluorescent fatty acid (Bodipy) as well as expression of the fatty acid transport-related protein CD36, lipolysis-related protein LPL, and unsaturated fatty acid metabolism-related proteins FADS1 and SCD1. Dual luciferase reporter assays verified the targeting relationship of the two ceRNA networks, circEZH2-miR378b-LPL and circEZH2-miR378b-CD36. This information provides further clarification of the role of circRNAs in milk fat regulation in addition to a theoretical basis for alleviating the effects of heat stress on milk production by dairy cows.

Progress on the Regulation of Ruminant Milk Fat by Noncoding RNAs and ceRNAs

Milk fat is not only a key factor affecting the quality of fresh milk but also a major target trait forbreeding. The regulation of milk fat involves multiple genes, network regulation and signal transduction. To explore recent discoveries of pathway regulation, we reviewed the published literature with a focus on functional noncoding RNAs and epigenetic regulation in ruminants. Results indicate that miRNAs play key roles in the regulation of milk fat synthesis and catabolism in ruminants. Although few data are available, merging evidence indicates that lncRNAs and circRNAs act on milk fat related genes through indirect action with microRNAs or RNAs in the ceRNA network to elicit positive effects on transcription. Although precise regulatory mechanisms remain unclear, most studies have focused on the regulation of the function of target genes through functional noncoding RNAs. Data to help identify factors that can regulate their own expression and function or to determine whether self-regulation involves positive and/or negative feedback are needed. Despite the growing body of research on the role of functional noncoding RNA in the control of ruminant milk fat, most data are still not translatable for field applications. Overall, the understanding of mechanisms whereby miRNA, lncRNA, circRNA, and ceRNA regulate ruminant milk fat remains an exciting area of research.

Lycium barbarum polysaccharides alleviate LPS-induced inflammatory responses through PPARγ/MAPK/NF-κB pathway in bovine mammary epithelial cells

As the main component of the gram-negative bacterial cell wall, lipopolysaccharide (LPS) is well-documented as an inducer of inflammation in bovine mammary cells. Lycium barbarum (goji) polysaccharides (LBP) have been used in non-ruminants as prebiotics to improve growth performance, immune ability and antioxidant capacity. We aimed to investigate the underlying effects of LBPs on pro-inflammatory responses in LPS-stimulated primary bovine mammary epithelial cells (bMECs). Cells were isolated from mammary tissue of 3 lactating Holstein cows without clinical disease (30.26 ± 3.1 kg/d of milk yield; 175 ± 6 DIM). For the pre-experimental treatment, bMECs were precultured with serum-free medium for 12 h. Treatments were as follows: pretreatment with culture medium devoid of LPS or LBP for 30 h (CON); CON for 24 h followed by challenge with 2 μg/mL LPS for 6 h (LPS); pretreatment with 100 μg/mL or 300 μg/mL LBP for 24 h followed by LPS challenge (2 μg/mL) for 6 h (LBP(100)+LPS; LBP(300)+LPS). To further determine if the effect of LBP on immune-regulation is PPARγ activation-dependent, an inhibitor of PPARγ, GW9662, at a concentration of 1 μM was used. Cells treated with LBP at 100, 300 and 500 μg/mL had upregulated protein abundance of PPARγ, while PGC1α had a higher expression only at 300 μg/mL of LBP treatment. Compared with CON, cells pretreated with LBP at 100 and 300 μg/mL had greater protein abundance of SCD1 and SREBP1. EdU staining and cell wound healing assays showed that the negative effect of LPS alone on cell proliferation was reversed by pretreatment with LBP at both 100 and 300 μg/mL. Upregulation of gene and protein abundance of proinflammatory factors and cytokines (COX-2, NLRP3, TNF-α, IL-1β and IL-6) induced by LPS stimulation were alleviated by LBP pretreatment at 300 μg/mL (more than 2-fold decrease). Compared with LPS challenge alone, phosphorylation of proteins involved in NF-κB (IκBα and p65) and MAPK (p38, JNK and ERK) pathways was downregulated following LBP treatment. Additionally, inhibition of PPARγ by GW9662 weakened the protective effect of LBP on LPS-induced protein abundance of phosphorylated p65, COX-2, IL-1β and TNF-α. These results indicated that the protective effect of LBP on LPS-induced bMECs inflammatory responses is PPARγ activation-dependent. As such, this knowledge might help design strategies for intervening against the detrimental effects of bovine mastitis.

Multi-Omics Analysis of Mammary Metabolic Changes in Dairy Cows Exposed to Hypoxia

Hypoxia exposure can cause a series of physiological and biochemical reactions in the organism and cells. Our previous studies found the milk fat rate increased significantly in hypoxic dairy cows, however, its specific metabolic mechanism is unclear. In this experiment, we explored and verified the mechanism of hypoxia adaptation based on the apparent and omics results of animal experiments and in vitro cell model. The results revealed that hypoxia exposure was associated with the elevation of AGPAT2-mediated glycerophospholipid metabolism. These intracellular metabolic disorders consequently led to the lipid disorders associated with apoptosis. Our findings update the existing understanding of increased adaptability of dairy cows exposure to hypoxia at the metabolic level.

Stearic acid does not overcome conjugated linoleic acid trans-10, cis-12-induced milk fat depression in lactating ewes

The objective of this study was to test the hypothesis that stearic acid (SA) supplementation increases milk fat content and overcomes the antilipogenic effects of trans-10, cis-12 conjugated linoleic acid (CLA) in lactating ewes. Twenty-eight Lacaune ewes (36 (sd 2) days in lactation; 70·5 (sd) 9·6 kg of body weight), producing 1·8 (sd 0·4) kg of milk/d, were used in a completely randomised design (seven ewes/treatment) for 21 d. The treatments were: (1) Control; (2) CLA (6·4 g/d of trans-10, cis-12 CLA); (3) SA (28 g/d of SA) and (4) SA in association with trans-10, cis-12 CLA (CLASA; 6·4 g/d of trans-10, cis-12 CLA plus 28 g/d of SA). All data were analysed using a mixed model that included the fixed effect of treatment and the random effect of ewe. SA did not alter milk fat content and yield relative to Control (91·9 v. 91·2 (sd 4·1) g/d). CLASA was not able to overcome the reduction in fat content and fat yield induced by CLA (75 v. 82 (sd 0·14) g/d). SA increased the relative abundance of CD36, fatty acid-binding protein 4 (FABP4) and PPAR-γ mRNA by 140, 112 and 68 % compared with CLASA. SA also reduced the relative abundance of acetyl-CoA carboxylase α promoter II and stearoyl-CoA desaturase (SCD) when compared with Control (45 and 39 %). Compared with CLA, CLASA treatment had no effect on the mRNA abundance of fatty acid synthase, lipoprotein lipase, CD36, SCD, FABP4, acylglycerolphosphate acyltransferase 6, sterol regulatory element-binding protein 1 and PPAR-γ. In conclusion, SA supplementation did not increase milk fat synthesis and did not overcome the CLA-induced milk fat depression when associated with trans-10, cis-12 CLA.

Liver X receptor α promotes milk fat synthesis in buffalo mammary epithelial cells by regulating the expression of FASN

Liver X receptor α (LXRα; NR1H3) is an important transcription factor that can facilitate milk fat synthesis by regulating the transcription of FASN in mice and goats. Nevertheless, the lipid synthesis related to LXRα and its regulation on FASN in the buffalo mammary gland remain elusive. Here, we demonstrated that the mRNA and protein expression of LXRα in buffalo mammary tissue increased in lactation compared with that in the dry-off period. Overexpression of NR1H3 enhanced the lipid droplet formation and triacylglycerol concentration in buffalo mammary epithelial cells (BuMEC), whereas the knockdown of NR1H3 resulted in a decrease in the number of lipid droplets. At the same time, NR1H3 also affected the expression of regulatory factors (INSIG1, INSIG2, SREBF1, and PPARG) related to milk fat synthesis and that of genes involved in de novo synthesis (FASN, ACACA, and SCD), and uptake and transport (LPL, CD36, and FABP3) of fatty acids as well as triacylglycerol synthesis (GPAM, APGAT6, and DGAT1). Luciferase reporter assays indicated that overexpression of NR1H3 resulted in an increase in the activity of FASN promoter, whereas the knockdown of NR1H3 had an opposite effect. When NR1H3 was overexpressed, mutations in LXRE or SRE could decrease the promoter activity of FASN. Furthermore, mutagenesis of both LXRE and SRE within the FASN promoter completely eliminated the induced activity of LXRα. Our results reveal that buffalo LXRα promotes milk fat synthesis through regulating the expression of FASN by directly interacting with FASN promoter and affecting the SREBF1 expression. This study underscores a crucial role of LXRα in regulating lipid synthesis of the buffalo mammary gland.

Peroxisome proliferator-activated receptor gamma regulates genes involved in milk fat synthesis in mammary epithelial cells of water buffalo

Peroxisome proliferator-activated receptor gamma (PPARγ) is a critical transcription factor regulating lipid and glucose metabolism. However, the regulatory effect of PPARγ on milk fat synthesis in buffalo mammary gland is not clear. In order to explore the role of buffalo PPARG gene in milk fat synthesis, lentivirus-mediated interference was used to knock it down and then the recombinant fusion expression vector was transfected into buffalo mammary epithelial cell (BMEC) to overexpress it. PPARG gene knockdown significantly decreased the expression of CD36, FABP3, FABP4, ACSS2, ELOVL6, DGAT2, BTN1A1, AGPAT6, LPIN1, ABCG2, PPARGC1A, INSIG1, FASN, and SREBF2 genes and significantly upregulated the expression of INSIG2 gene but had no significant effect on the expression of ACSL1, GPAM, and SREBF1 genes. PPARG overexpression significantly increased the relative mRNA abundance of CD36, FABP3, FABP4, ACSS2, ELOVL6, DGAT2, BTN1A1, AGPAT6, LPIN1, PPARGC1A, INSIG1, and SREBF2 genes and significantly downregulated the expression of INSIG2 gene but had no significant effect on the expression of ACSL1, GPAM, ABCG2, FASN, and SREBF1 genes. In addition, knockdown/overexpression of PPARG gene significantly decreased/increased triacylglycerol (TAG) content in BMECs. This study revealed that buffalo PPARG gene is a key gene regulating buffalo milk fat synthesis.

When Two plus Two Is More than Four: Evidence for a Synergistic Effect of Fatty Acids on Peroxisome Proliferator-Activated Receptor Activity in a Bovine Hepatic Model

The inclusion of fat in livestock diets represents a valuable and cost-effective way to increase the animal’s caloric intake. Beyond their caloric value, fatty acids can be understood in terms of their bioactivity, via the modulation of the ligand-dependent nuclear peroxisome proliferator-activated receptors (PPAR). Isotypes of PPAR regulate important metabolic processes in both monogastric and ruminant animals, including the metabolism of fatty acids (FA), the production of milk fat, and the immune response; however, information on the modulation of bovine PPAR by fatty acids is limited. The objective of this study was to expand our understanding on modulation of bovine PPAR by FA, both when used individually and in combination, in an immortalized cell culture model of bovine liver. Of the 10 FA included in the study, the greatest activation of the PPAR reporter was detected with saturated FA C12:0, C16:0, and C18:0, as well as phytanic acid, and the unsaturated FA C16:1 and C18:1. When supplemented in mixtures of 2 FA, the most effective combination was C12:0 + C16:0, while in mixtures of 3 FA, the greatest activation was caused by combinations of C12:0 with C16:0 and either C18:0, C16:1, or C18:1. Some mixtures display a synergistic effect that leads to PPAR activation greater than the sum of their parts, which may be explained by structural dynamics within the PPAR ligand-binding pocket. Our results provide fundamental information for the development of tailored dietary plans that focus on the use of FA mixtures for nutrigenomic purposes.

Effect of concentrate enriched with palmitic acid versus rapeseed oil on dairy performance, milk fatty acid composition, and mammary lipogenic gene expression in mid-lactation Holstein cows

This study was performed to characterize the effect of a concentrate supplemented with free palmitic acid (4% on a DM basis; PA) or rapeseed oil (4% on a DM basis; RO) compared with a no-added-lipid control concentrate (CT) on the performance of dairy cows fed a corn silage-based diet over a 9-wk period. After a 3-wk pre-experimental period, 54 Holstein cows were randomly allocated to 3 experimental treatments to receive forage ad libitum with a fixed amount of CT, RO, or PA (8 kg/d for 2-yr-old primiparous; 10 kg/d for older cows). During the experiment, dry matter intake, milk yield and composition, fatty acid (FA) yields and FA profile, and feed efficiency were determined. At wk 9 of the experimental period, the mRNA levels of 10 genes involved in lipid metabolism in mammary tissue biopsy samples were measured. Compared with CT, RO and PA increased forage intake. Compared with CT, RO increased concentrate intake, the value being intermediate for PA. Compared with CT, RO increased milk yield (+2.0 kg/d) and decreased milk fat and protein content (-3.8 and -1.2 g/kg, respectively), whereas PA increased milk fat content (+4.1 g/kg). Compared with CT and RO treatments, PA increased milk fat yield (+179 g/d) and 3.5% fat-corrected milk and energy-corrected milk output (+2.8 and +2.3 kg/d, respectively), and thus improved feed efficiency (+7.3%). Compared with CT treatment, RO increased milk contents of the sum of >C16 FA, monounsaturated FA, polyunsaturated FA, trans FA, and n-3 FA, whereas PA decreased these FA contents (except n-3 FA) and also decreased n-6 FA. The variations in milk fat yield and content and FA secretion at wk 9 were not associated with modifications in mammary expression of 10 genes involved in major lipid pathways, except for the transcription factor PPARG1, which tended to be higher in PA versus RO treatment. This study demonstrated that PA improved milk fat yield and feed efficiency compared with RO and suggests that factors other than gene expression, such as substrate availability for mammary metabolism or other levels of regulation (transcriptional, posttranscriptional, translational or posttranslational), could play a key role in milk fat and FA responses to changes in diet composition in cows.

The inhibitory effect of trans-10,cis-12 conjugated linoleic acid on sterol regulatory element binding protein-1 activation in bovine mammary epithelial cells involved reduced proteasomal degradation of insulin-induced gene-1

Trans 10,cis-12 conjugated linoleic acid (t10,c12 CLA) is well recognized as a key CLA isomer responsible for the reduction in milk fat synthesis that leads to milk fat depression in dairy cows. Sterol regulatory element binding protein-1 (SREBP1) is a key transcription factor in bovine mammary gland coordinating transcription of the genes for fatty acid synthesis. SREBP1 activation requires the removal of insulin-induced gene-1 (Insig1) that serves as a repressor of SREBP1 in the endoplasmic reticulum (ER). We hypothesized that t10,c12 CLA reduced SREBP1 activation by delaying Insig1 degradation. In the present study, we used undifferentiated bovine mammary epithelial cells (MAC-T cells) and treated them with t10,c12 CLA for 6 h. We found that SREBP1 protein expression declined over 56% when cells were treated with 60 µM or greater concentration of t10,c12 CLA. Such inhibitory effects were also observed in the mRNA expression of SREBP1-regulated genes including SREBP1, fatty acid synthetase, stearoyl-CoA desaturase, and Insig1. Compared with no CLA group, 60 µM or higher concentration of t10,c12 CLA increased Insig1 protein expression over 2-fold in cells transfected with FLAG-tagged Insig1. This stimulatory effect was not specific to t10,c12 CLA but also other polyunsaturated fatty acids including cis-9,trans-11 CLA and linoleic acid. Oleic acid had no effect on Insig1 protein expression, whereas palmitic acid decreased Insig1 protein expression. Further investigation revealed that increased abundance of FLAG-Insig1 with t10,c12 CLA was due to the inhibition of the proteasomal degradation of Insig1. The t10,c12 CLA delayed the Insig1 decay when protein synthesis was blocked. Immunoprecipitation also confirmed that the interaction between ubiquitin-like domain-containing protein 8 and Insig1, the key step of removing Insig1 from ER and freeing SREBP1 for proteolytic processing, was inhibited by t10,c12 CLA, but not palmitic acid. These findings suggested that t10,c12 CLA played a role in regulating SREBP1 activation by reducing proteasomal degradation of Insig1. We concluded that stabilized Insig1 retained SREBP1 in the ER from activation, thus reducing lipogenic gene transcription.

Muscle metabolome and adipose tissue mRNA expression of lipid metabolism-related genes in over-conditioned dairy cows differing in serum-metabotype

Over-conditioned dairy cows, classified by body condition score (BCS) and backfat thickness (BFT) are less able to metabolically adapt to the rapidly increasing milk yield after parturition. Based on serum metabolome and cluster analyses, high BCS cows (HBCS) could be classified into metabotypes that are more similar to normal (NBCS) cows, i.e., HBCS predicted normal (HBCS-PN) than the HBCS predicted high (HBCS-PH) cows—similar to the concept of obese but metabolically healthy humans. Our objective was to compare muscle metabolome and mRNA abundance of genes related to lipogenesis and lipolysis in adipose tissue between HBCS-PH (n = 13), HBCS-PN (n = 6), and NBCS-PN (n = 15). Tail-head subcutaneous fat was biopsied on d −49, 3, 21, and 84 relative to parturition. Potential differences in the oxidative capacity of skeletal muscle were assessed by targeted metabolomics in M. semitendinosus from d 21. Besides characteristic changes with time, differences in the mRNA abundance were limited to lipogenesis-related genes on d −49 (HBCS-PH > HBCS-PN). The HBCS-PH had more than two-fold higher muscle concentrations of short (C2, C4-OH, C6-OH) and long-chain acylcarnitines (C16, C18, and C18:1) than HBCS-PN, indicating a greater oxidative capacity for fatty acids (and utilization of ketones) in muscle of HBCS-PN than HBCS-PH cows.

ADIPOR1 regulates genes involved in milk fat metabolism in goat mammary epithelial cells

BACKGROUND

Fat metabolism is a complex process regulated by a number of factors. Adiponectin receptor 1 (ADIPOR1) gene takes active part in lipid metabolism. Although, there have been some researches indicating that ADIPOR1 could influence the milk fat metabolism through targeting some factors, little is known about the effect of ADIPOR1 on goat milk fat metabolism. To investigate the regulatory role of ADIPOR1 on milk fat metabolism in GMECs, we analysed overexpression in the presence and absence of AdipoRon (50 μM) and examined knockdown using siRNA. Using RT-qPCR, we assessed ADIPOR1 mRNA expressions among different lactation stages in goat mammary gland and the expression of six genes that regulate milk fat metabolism in GMECs.

RESULTS

ADIPOR1 mRNA expression level was higher during the various lactation stages, except dry-off period. Knockdown and overexpression results revealed a significant decrease and increase in mRNA expression of ADIPOR1 and genes considered: SREBF1, ACACA, FASN, SCD, ATGL, and HSL, respectively. Treatment of GMECs with AdipoRon 50 μM resulted in a significant (p < 0.05) increase in the mRNA expression of all measured genes, except SREBF1.

CONCLUSION

Overall, ADIPOR1 plays a central role in regulating the transcription of several genes involved in milk fat metabolism.

Neonatal hyperoxia inhibits proliferation and survival of atrial cardiomyocytes by suppressing fatty acid synthesis

Preterm birth increases the risk for pulmonary hypertension and heart failure in adulthood. Oxygen therapy can damage the immature cardiopulmonary system and may be partially responsible for the cardiovascular disease in adults born preterm. We previously showed that exposing newborn mice to hyperoxia causes pulmonary hypertension by 1 year of age that is preceded by a poorly understood loss of pulmonary vein cardiomyocyte proliferation. We now show that hyperoxia also reduces cardiomyocyte proliferation and survival in the left atrium and causes diastolic heart failure by disrupting its filling of the left ventricle. Transcriptomic profiling showed that neonatal hyperoxia permanently suppressed fatty acid synthase (Fasn), stearoyl-CoA desaturase 1 (Scd1), and other fatty acid synthesis genes in the atria of mice, the HL-1 line of mouse atrial cardiomyocytes, and left atrial tissue explanted from human infants. Suppressing Fasn or Scd1 reduced HL-1 cell proliferation and increased cell death, while overexpressing these genes maintained their expansion in hyperoxia, suggesting that oxygen directly inhibits atrial cardiomyocyte proliferation and survival by repressing Fasn and Scd1. Pharmacologic interventions that restore Fasn, Scd1, and other fatty acid synthesis genes in atrial cardiomyocytes may, thus, provide a way of ameliorating the adverse effects of supplemental oxygen on preterm infants.

Metabolic Transition of Milk Triacylglycerol Synthesis in Response to Varying Levels of Three 18-Carbon Fatty Acids in Porcine Mammary Epithelial Cells

This study aimed to examine the effects of increasing levels of three 18-carbon fatty acids (stearate, oleate and linoleate) on mammary lipogenesis, and to evaluate their effects on the milk lipogenic pathway in porcine mammary epithelial cells (pMECs). We found that increasing the three of 18-carbon fatty acids enhanced the cellular lipid synthesis in a dose-dependent manner, as reflected by the increased (triacylglycerol) TAG content and cytosolic lipid droplets in pMECs. The increased lipid synthesis by the three 18-carbon fatty acids was probably caused by the up-regulated expression of major genes associated with milk fat biosynthesis, including CD36 (long chain fatty acid uptake); GPAM, AGPAT6, DGAT1 (TAG synthesis); PLIN2 (lipid droplet formation); and PPARγ (regulation of transcription). Western blot analysis of CD36, DGAT1 and PPARγ proteins confirmed this increase with the increasing incubation of 18-carbon fatty acids. Interestingly, the mRNA expressions of ACSL3 and FABP3 (fatty acids intracellular activation and transport) were differentially affected by the three 18-carbon fatty acids. The cellular mRNA expressions of ACSL3 and FABP3 were increased by stearate, but were decreased by oleate or linoleate. However, the genes involved in fatty acid de novo synthesis (ACACA and FASN) and the regulation of transcription (SREBP1) were decreased by incubation with increasing concentrations of 18-carbon fatty acids. In conclusion, our findings provided evidence that 18-carbon fatty acids (stearate, oleate and linoleate) significantly increased cytosolic TAG accumulation in a dose-dependent manner, probably by promoting lipogenic genes and proteins that regulate the channeling of fatty acids towards milk TAG synthesis in pMECs.

Effect of acetate, β-hydroxybutyrate and their interaction on lipogenic gene expression, triglyceride contents and lipid droplet formation in dairy cow mammary epithelial cells

The purpose of this study was to assess the effects of acetate and β-hydroxybutyrate alone or in combination on lipogenic genes and their associated regulatory proteins in dairy cow mammary epithelial cells (DCMEC) using quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blotting, lipid droplet staining and a triglyceride content detection kit, to determine whether SCFA are related to milk fat synthesis regulation in DCMEC. Our experiment shows that addition of different concentrations of acetate, β-hydroxybutyrate and their combinations to DCMEC increase in relative mRNA abundance of lipogenic genes and key transcription factors suggest an increase in lipogenic capacity, which is supported by an increased in cytosolic triglyceride content. Similarly, the protein expression level of acetyl-coenzyme A carboxylase (ACACA), fatty acid synthase (FASN) and sterol-coenzyme desaturase-1 (SCD1) genes and the transcription factor sterol regulatory element-binding protein-1 (SREBP1) were found to be increased by addition of acetate, β-hydroxybutyrate and their combinations. The expression pattern of fat-related genes and proteins showed similar trends in almost all treatments, suggesting that common transcription factor are regulating these genes. These results show that acetate and β-hydroxybutyrate regulate fat synthesis, further confirming that SCFAs work by targeting genes to activate the SREBP1 and insulin-induced gene 1 protein (INSIG1) signalling pathways in DCMEC.