Effects of Dietary Supplementation of Lauric Acid on Lactation Function, Mammary Gland Development, and Serum Lipid Metabolites in Lactating Mice

Human milk sphingomyelin: Function, metabolism, composition and mimicking

Human milk, which contains various nutrients, is the "gold standard" for infant nutrition. Healthy human milk meets all the nutritional needs of early infant development. Polar lipids mainly exist in the milk fat globule membrane, accounting for approximately 1-2% of human milk lipids; sphingomyelin (SM) accounts for approximately 21-24% of polar lipids. SM plays an important role in promoting the development of the brain and nervous system, regulating intestinal flora, and improving skin barriers. Though SM could be synthesized de novo, SM nutrition from dietary is also important for infants. The content and composition of SM in human milk has been reported, however, the molecular mechanisms of nutritional functions of SM for infants required further research. This review summarizes the functional mechanisms, metabolic pathways, and compositional, influencing factors, and mimicking of SM in human milk, and highlights the challenges of improving maternal and infant early/long-term nutrition.

Potential Role of Lauric Acid in Milk Fat Synthesis in Chinese Holstein Cows Based on Integrated Analysis of Ruminal Microbiome and Metabolome

The composition and metabolic profile of the ruminal microbiome have an impact on milk composition. To unravel the ruminal microbiome and metabolome affecting milk fat synthesis in dairy cows, 16S rRNA and internal transcribed spacer (ITS) gene sequencing, as well as ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS/MS) methods were used to investigate the significant differences in ruminal bacterial and fungal communities as well as metabolome among Chinese Holstein cows with contrasting milk fat contents under the same diet (H-MF 5.82 ± 0.41% vs. L-MF 3.60 ± 0.12%). Another objective was to culture bovine mammary epithelial cells (BMECs) to assess the effect of metabolites on lipid metabolism. Results showed that the acetate-to-propionate ratio and xylanase activity in ruminal fluid were both higher in H-MF. Microbiome sequencing identified 10 types of bacteria and four types of fungi differently abundant at the genus level. Metabolomics analysis indicated 11 different ruminal metabolites between the two groups, the majority of which were lipids and organic acids. Among these, lauric acid (LA) was enriched in fatty acid biosynthesis with its concentration in milk fat of H-MF cows being greater (217 vs. 156 mg per 100 g milk), thus, it was selected for an in vitro study with BMECs. Exogenous LA led to a marked increase in intracellular triglyceride (TG) content and lipid droplet formation, and it upregulated the mRNA abundance of fatty acid uptake and activation (CD36 and ACSL1), TG synthesis (DGAT1, DGAT2 and GPAM), and transcriptional regulation (SREBP1) genes. Taken together, the greater relative abundance of xylan-fermenting bacteria and fungi, and lower abundance of bacteria suppressing short-chain fatty acid-producing bacteria or participating in fatty acid hydrogenation altered lipids and organic acids in the rumen of dairy cows. In BMECs, LA altered the expression of genes involved in lipid metabolism in mammary cells, ultimately promoting milk fat synthesis. Thus, it appears that this fatty acid plays a key role in milk fat synthesis.

Lithium Chloride Promotes Milk Protein and Fat Synthesis in Bovine Mammary Epithelial Cells via HIF-1α and β-Catenin Signaling Pathways

Lithium is one of the trace elements with many physiological properties, such as being anti-cancer, anti-viral, and anti-inflammatory. However, little is known about its effect on milk synthesis during lactation. Therefore, we selected different concentrations (5 mM, 10 mM, and 20 mM) of lithium chloride (LiCl) and assessed the effect of LiCl on bovine mammary epithelial (MAC-T) cells that underwent 4 days of differentiation induction. Moreover, we analyzed the effect of LiCl on the expression of genes related to milk fat and milk protein synthesis. Herein, LiCl (5-20 mM) significantly increased the expression of β-casein, promoted mRNA expression and phosphorylated protein expression of the signal transduction molecule and activator of transcription 5β (STAT5-β), and inhibited mRNA and protein expression of suppressor of cytokine signaling 2 (SOCS2). In contrast, 5 and 10 mM LiCl significantly inhibited expression of SOCS3. LiCl at concentration of 5-20 mM enhanced phosphorylation level of mTOR protein; at 10 mM and 20 mM, LiCl significantly promoted expression and phosphorylation of downstream ribosomal protein S6 kinase beta-1 (S6K1) protein. Considering milk fat synthesis, mRNA expression of acetyl CoA carboxylase (ACC) and lipoprotein lipase (LPL) genes was considerably increased in the presence of LiCl (5-20 mM). Additionally, increased protein expression levels of stearoyl-CoA desaturase (SCD), peroxisome proliferator-activated receptor-γ (PPARγ), and sterol regulatory element-binding protein 1 (SREBP1) were observed at all LiCl concentrations tested. Subsequently, LiCl (5-20 mM) significantly promoted protein expression and phosphorylation of β-catenin, while 10 mM and 20 mM of LiCl significantly promoted protein expression of hypoxia-inducible factor-1α (HIF-1α). Collectively, it has been shown that 10 mM LiCl can effectively activate HIF-1α, β-catenin, and β-catenin downstream signaling pathways. Conversely, at 10 mM, LiCl inhibited SOCS2 and SOCS3 protein expression through JAK2/STAT5, mTOR, and SREBP1 signaling pathways, improving synthesis of milk protein and fat. Therefore, LiCl can be used as a potential nutrient to regulate milk synthesis in dairy cows.

Lipid metabolism and endometrial receptivity

BACKGROUND

Obesity has now been recognized as a high-risk factor for reproductive health. Although remarkable advancements have been made in ART, a considerable number of infertile obese women still suffer from serial implantation failure, despite the high quality of embryos transferred. Although obesity has long been known to exert various deleterious effects on female fertility, the underlying mechanisms, especially the roles of lipid metabolism in endometrial receptivity, remain largely elusive.

OBJECTIVE AND RATIONALE

This review summarizes current evidence on the impacts of several major lipids and lipid-derived mediators on the embryonic implantation process. Emerging methods for evaluating endometrial receptivity, for example transcriptomic and lipidomic analysis, are also discussed.

SEARCH METHODS

The PubMed and Embase databases were searched using the following keywords: (lipid or fatty acid or prostaglandin or phospholipid or sphingolipid or endocannabinoid or lysophosphatidic acid or cholesterol or progesterone or estrogen or transcriptomic or lipidomic or obesity or dyslipidemia or polycystic ovary syndrome) AND (endometrial receptivity or uterine receptivity or embryo implantation or assisted reproductive technology or in vitro fertilization or embryo transfer). A comprehensive literature search was performed on the roles of lipid-related metabolic pathways in embryo implantation published between January 1970 and March 2022. Only studies with original data and reviews published in English were included in this review. Additional information was obtained from references cited in the articles resulting from the literature search.

OUTCOMES

Recent studies have shown that a fatty acids-related pro-inflammatory response in the embryo-endometrium boundary facilitates pregnancy via mediation of prostaglandin signaling. Phospholipid-derived mediators, for example endocannabinoids, lysophosphatidic acid and sphingosine-1-phosphate, are associated with endometrial receptivity, embryo spacing and decidualization based on evidence from both animal and human studies. Progesterone and estrogen are two cholesterol-derived steroid hormones that synergistically mediate the structural and functional alterations in the uterus ready for blastocyst implantation. Variations in serum cholesterol profiles throughout the menstrual cycle imply a demand for steroidogenesis at the time of window of implantation (WOI). Since 2002, endometrial transcriptomic analysis has been serving as a diagnostic tool for WOI dating. Numerous genes that govern lipid homeostasis have been identified and, based on specific alterations of lipidomic signatures differentially expressed in WOI, lipidomic analysis of endometrial fluid provides a possibility for non-invasive diagnosis of lipids alterations during the WOI.

WIDER IMPLICATIONS

Given that lipid metabolic dysregulation potentially plays a role in infertility, a better understanding of lipid metabolism could have significant clinical implications for the diagnosis and treatment of female reproductive disorders.

Integrating Serum Metabolome and Gut Microbiome to Evaluate the Benefits of Lauric Acid on Lipopolysaccharide- Challenged Broilers

Lauric acid (LA) is a crucial medium-chain fatty acid (MCFA) that has many beneficial effects on humans and animals. This study aimed to investigate the effects of LA on the intestinal barrier, immune functions, serum metabolism, and gut microbiota of broilers under lipopolysaccharide (LPS) challenge. A total of 384 one-day-old broilers were randomly divided into four groups, and fed with a basal diet, or a basal diet supplemented with 75 mg/kg antibiotic (ANT), or a basal diet supplemented with 1000 mg/kg LA. After 42 days of feeding, three groups were intraperitoneally injected with 0.5 mg/kg Escherichia coli- derived LPS (LPS, ANT+LPS and LA+LPS groups) for three consecutive days, and the control (CON) group was injected with the same volume of saline. Then, the birds were sacrificed. Results showed that LA pretreatment significantly alleviated the weight loss and intestinal mucosal injuries caused by LPS challenge. LA enhanced immune functions and inhibited inflammatory responses by upregulating the concentrations of immunoglobulins (IgA, IgM, and IgY), decreasing IL-6 and increasing IL-4 and IL-10. Metabolomics analysis revealed a significant difference of serum metabolites by LA pretreatment. Twenty-seven serum metabolic biomarkers were identified and mostly belong to lipids. LA also markedly modulated the pathway for sphingolipid metabolism, suggesting its ability to regulate lipid metabolism. Moreover,16S rRNA analysis showed that LA inhibited LPS-induced gut dysbiosis by altering cecal microbial composition (reducing Escherichia-Shigella, Barnesiella and Alistipes, and increasing Lactobacillus and Bacteroides), and modulating the production of volatile fatty acids (VFAs). Pearson’s correlation assays showed that alterations in serum metabolism and gut microbiota were strongly correlated to the immune factors; there were also strong correlations between serum metabolites and microbiota composition. The results highlight the potential of LA as a dietary supplement to combat bacterial LPS challenge in animal production and to promote food safety.

Phytochemicals as PI3K/ Akt/ mTOR Inhibitors and Their Role in Breast Cancer Treatment

BACKGROUND

Breast cancer is the predominant form of cancer in women; various cellular pathways are involved in the initiation and progression of breast cancer. Among the various types of breast cancer that differ in their growth factor receptor status, PI3K/Akt signaling is a common pathway where all these converge. Thus, the PI3K signaling is of great interest as a target for breast cancer prevention; however, it is less explored.

OBJECTIVE

The present review is aimed to provide a concise outline of the role of PI3K/Akt/mTOR pathway in breast carcinogenesis and its progression events, including metastasis, drug resistance and stemness. The review emphasizes the role of natural and synthetic inhibitors of PI3K/Akt/m- TOR pathway in breast cancer prevention.

METHODS

The data were obtained from PubMed/Medline databases, Scopus and Google patent literature.

RESULTS

PI3K/Akt/mTOR signaling plays an important role in human breast carcinogenesis; it acts on the initiation and progression events associated with it. Numerous molecules have been isolated and identified as promising drug candidates by targeting the signaling pathway. Results from clinical studies confirm their application in the treatment of human breast cancer alone and in combination with classical chemotherapeutics as well as monoclonal antibodies.

CONCLUSION

PI3K/mTOR signaling blockers have evolved as promising anticancer agents by interfering breast cancer development and progression at various stages. Natural products and bioactive components are emerging as novel inhibitors of PI3K signaling and more research in this area may yield numerous drug candidates.

Nutritional Regulation of Mammary Gland Development and Milk Synthesis in Animal Models and Dairy Species

In mammals, milk is essential for the growth, development, and health. Milk quantity and quality are dependent on mammary development, strongly influenced by nutrition. This review provides an overview of the data on nutritional regulations of mammary development and gene expression involved in milk component synthesis. Mammary development is described related to rodents, rabbits, and pigs, common models in mammary biology. Molecular mechanisms of the nutritional regulation of milk synthesis are reported in ruminants regarding the importance of ruminant milk in human health. The effects of dietary quantitative and qualitative alterations are described considering the dietary composition and in regard to the periods of nutritional susceptibly. During lactation, the effects of lipid supplementation and feed restriction or deprivation are discussed regarding gene expression involved in milk biosynthesis, in ruminants. Moreover, nutrigenomic studies underline the role of the mammary structure and the potential influence of microRNAs. Knowledge from three lactating and three dairy livestock species contribute to understanding the variety of phenotypes reported in this review and highlight (1) the importance of critical physiological stages, such as puberty gestation and early lactation and (2) the relative importance of the various nutrients besides the total energetic value and their interaction.

Lauric Acid versus Palmitic Acid: Effects on Adipose Tissue Inflammation, Insulin Resistance, and Non-Alcoholic Fatty Liver Disease in Obesity

Simple Summary

The aim of this study was to compare the effect of palmitic acid (PA), a long-chain fatty acid, and lauric acid (LA), a medium-chain fatty acid, on obesity-related metabolic disorders. We used a mouse model of diet-induced obesity and fed them a modified high fat diet supplemented with 3% PA or LA for 12 wk. An LA diet led to an increase in visceral fat mass with a reduction in inflammation compared to the PA diet. We also noted that PA significantly increased systemic insulin resistance whereas LA showed only a trend towards an increase compared to lean control mice. The expression of a protein involved in muscle glucose uptake was higher in LA-treated mice compared to the PA-treated group, indicating improved muscle glucose uptake in LA-fed mice. Analysis of liver samples showed that hepatic steatosis was higher in both PA and LA-fed mice compared to lean controls. Markers of liver inflammation were not altered significantly in mice receiving PA or LA. Our data suggest that compared to PA, LA exerts less adverse effects on metabolic disorders and this could be due to the differential effects of these fatty acids in fat and muscle.

Abstract

Coconut oil, rich in medium-chain saturated fatty acids (MCSFA), in particular, lauric acid (LA), is known to exert beneficial metabolic effects. Although LA is the most abundant saturated fatty acid in coconut oil, the specific role of LA in altering obesity-related metabolic disorders remains unknown. Here, we examined the effects of supplementing a high fat (HF) diet with purified LA on obesity-associated metabolic derangements in comparison with palmitic acid (PA), a long-chain saturated fatty acid. Male C57BL/6 mice were fed a control chow diet (CD) or an HF diet supplemented with 3% LA (HF + LA) or PA (HF + PA) for 12 wk. Markers of adipose tissue (AT) inflammation, systemic insulin resistance (IR), and hepatic steatosis, were assessed. The body weight and total fat mass were significantly higher in both HF + LA and HF + PA diet-fed groups compared to CD controls. However, the visceral adipose tissue (VAT) mass was significantly higher (p < 0.001) in HF + LA-fed mice compared to both CD as well as HF + PA-fed mice. Interestingly, markers of AT inflammation were promoted to a lesser extent in HF + LA-fed mice compared to HF + PA-fed mice. Thus, immunohistochemical analysis of VAT showed an increase in MCP-1 and IL-6 staining in HF + PA-fed mice but not in HF + LA-fed mice compared to CD controls. Further, the mRNA levels of macrophage and inflammatory markers were significantly higher in HF + PA-fed mice (p < 0.001) whereas these markers were increased to a lesser extent in HF + LA-fed group. Of note, the insulin tolerance test revealed that IR was significantly increased only in HF + PA-fed mice but not in HF + LA-fed group compared to CD controls. While liver triglycerides were increased significantly in both HF + PA and HF + LA-fed mice, liver weight and plasma markers of liver injury such as alanine aminotransferase and aspartate aminotransferase were increased significantly only in HF + PA-fed mice but not in HF + LA-fed mice. Taken together, our data suggest that although both LA and PA increased AT inflammation, systemic IR, and liver injury, the extent of metabolic derangements caused by LA was less compared to PA in the setting of high fat feeding.