Effects of the circadian rhythm on milk composition in dairy cows: Does day milk differ from night milk?

Metabolism in most organisms can show variations between the day and night. These variations may also affect the composition of products derived from livestock. The aim of the present study was to investigate the difference in composition between the day milk and night milk of dairy cows. Ten multiparous Holstein cows (milk yield = 25.2 ± 5.00 kg/d) were randomly selected during mid lactation. Milk samples were collected at 0500 h ("night milk") and 1500 h ("day milk") and analyzed to determine their composition. Mid-infrared spectroscopy was used to analyze macronutrient content of milk. Metabolomics and lipidomics were used to detect and analyze small molecules and fatty acids, respectively. An automatic biochemical analyzer and ELISA kits were used to determine biochemical indicators, as well as antioxidant and immune parameters in the milk. Though milk fat, protein, lactose, and total milk solids were not different between day milk and night milk, small molecules, metabolites and lipids, and hormones and cytokines differed between day milk and night milk. Regarding biochemical and immune-related indicators, the concentrations of malondialdehyde, HSP70, and HSP90 in night milk were lower than that in day milk. However, interferon-γ levels were higher in night milk. Additionally, night milk was naturally rich in melatonin. Lipidomics analyses showed that the levels of some lipids in night milk were higher than those in day milk. Metabolomics analyses identified 36 different metabolites between day milk and night milk. Higher concentrations of N-acetyl-d-glucosamine, cis-aconitate, and d-sorbitol were observed in day milk. However, the other 33 metabolites analyzed, including carbohydrates, lipids, AA, and aromatic compounds, showed lower concentrations in day milk than in night milk. The present findings show that the composition of night milk differs considerably from that of day milk. Notable changes in the circadian rhythm also altered milk composition. These results provide evidence to support the strategic use and classification of day milk and night milk.

Regulatory effect of miRNA on multi-directional differentiation ability of mesenchymal stem cell in treatment of osteoporosis.

This study was designed to evaluate the effect of miRNA acting in regulating multi-directional differentiation ability of mesenchymal stem cell in treatment of osteoporosis (OP), with the aim of finding a new idea and approach for clinical treatment of OP. Estrogen deficiency-induced OP mice model was established by means of ovariectomy (OVX). Additionally, a sham group was set up for control. Bone Marrow Mesenchymal Stem Cells (BMMSCs) of OVX group (O/BMMSCs) and BMMSCs of sham group (S/BMMSCs) were separately cultured. Then surface markers of BMMSCs were detected. Multi-directional differentiation ability was identified in the two groups by giving cells targeted induced stimulation. It was found that the bone trabecula, bone density and bone volume fraction of distal femoral metaphysis in the OVX group were much lower than those of the sham group. Moreover, trabecular bone space in the OVX group became larger; O/BMMSCs and S/BMMSCs both had normal expression of surface markers as well as potentials of osteogenic and adipogenic differentiation; O/BMMSCs had a weaker osteogenic capability but a stronger adipogenic capability than S/BMMSCs. All the findings suggest that the regulatory effect of miRNA on multi-directional differentiation ability plays a vital role in the treatment of OP, and there is a close correlation between them; deficiency or functional defect of BMMSCs can result in the occurrence of OP.