Corrigendum: Effects of Caragana korshinskii tannin on fermentation, methane emission, community of methanogens, and metabolome of rumen in sheep.

[This corrects the article DOI: 10.3389/fmicb.2024.1334045.].

Effects of Caragana korshinskii tannin on fermentation, methane emission, community of methanogens, and metabolome of rumen in sheep.

The purpose of this research was to investigate the impact of dietary supplementation of Caragana korshinskii tannin (CKT) on rumen fermentation, methane emission, methanogen community and metabolome in rumen of sheep. A total of 15 crossbred sheep of the Dumont breed with similar body conditions, were divided into three groups (n = 5), which were fed with CKT addition at 0, 2 and 4%/kg DM. The study spanned a total of 74 days, with a 14-day period dedicated to adaptation and a subsequent 60-day period for conducting treatments. The results indicated that the levels of ammonia nitrogen (NH3-N) and acetate were reduced (p < 0.05) in rumen sheep fed with 2 and 4% CKT; The crude protein (CP) digestibility of sheep in 2 and 4% CKT groups was decreased(p < 0.05); while the neutral detergent fiber (NDF) digestibility was increased (p < 0.05) in 4% CKT group. Furthermore, the supplementation of CKT resulted in a decrease (p < 0.05) in daily CH4 emissions from sheep by reducing the richness and diversity of ruminal methanogens community, meanwhile decreasing (p < 0.05) concentrations of tyramine that contribute to methane synthesis and increasing (p < 0.05) concentrations of N-methy-L-glutamic acid that do not contribute to CH4 synthesis. However, CH4 production of DMI, OMI, NDFI and metabolic weight did not differ significantly across the various treatments. To sum up, the addition of 4% CKT appeared to be a viable approach for reducing CH4 emissions from sheep without no negative effects. These findings suggest that CKT hold promise in mitigating methane emissions of ruminant. Further investigation is required to evaluate it effectiveness in practical feeding strategies for livestock.

Effects of L-arginine and arginine-arginine dipeptide on amino acids uptake and αS1-casein synthesis in bovine mammary epithelial cells.

Arginine (Arg), as an important functional amino acids (AA), is essential for milk protein synthesis in lactating ruminants. Arg shares transporters with cationic and neutral AA in mammary epithelial cells. Therefore, competitive inhibition might exist among these AA in uptake by mammary epithelial cells. In this study, cultured bovine mammary epithelial cells (BMEC) were used as the model to investigate whether the availability of L-Arg (0.7, 1.4, 2.8, 5.6, and 11.2 mM) affects the uptake of other AA and if this related to αS1-casein synthesis, and whether Arginine-Arginine (Arg-Arg) substituting part of free L-Arg can alleviate competitive inhibition among Arg and other AA, so as to promote αS1-casein synthesis. Our results showed that 2.8 mM L-Arg generated the greatest positive effects on αS1-casein synthesis and the activation of mammalian target of rapamycin (mTOR) signaling pathway (P < 0.01). With L-Arg supply increasing from 0.7 to 11.2 mM, the net-uptake of other AA (except Glu and Ala) decreased linearly and quadratically (Plinear < 0.01; Pquadratic < 0.01). Compared with 2.8 mM, the net-uptake of essential amino acids (EAA) and total amino acids (TAA) were lower at 11.2 mM L-Arg group, while greater at 1.4 mM L-Arg group (P < 0.01). Arg-Arg dipeptide replacing 10% free L-Arg increased αS1-casein synthesis (P < 0.05), net-uptake of EAA and TAA, as well as phosphorylation level of mTOR and p70 ribosomal protein S6 kinase (P70S6K) and mRNA expression of oligopeptide transporter 2 (PepT2; P < 0.01). These observations suggested that the increased αS1-casein synthesis by 10% Arg-Arg dipeptide might be related to the increase of AA availability and the activation of mTOR signaling pathway in BMEC.

Arginine (Arg) availability has been demonstrated to affect milk protein synthesis in dairy cows. Competitive inhibition exists among amino acids (AA) in uptake by mammary epithelial cells. This study aims to explore whether the availability of L-Arg affects the uptake of other AA by bovine mammary epithelial cells (BMEC) and if this is related to αS1-casein synthesis, and whether Arginine-Arginine (Arg-Arg) dipeptide substituting part of free L-Arg can alleviate competitive inhibition among Arg and other AA, so as to promote αS1-casein synthesis in BMEC. Our results showed that 2.8 mM L-Arg is the appropriate concentration for αS1-casein synthesis. With L-Arg supply increasing from 0.7 to 11.2 mM, the net-uptake of most AA decreased linearly and quadratically. Arg-Arg dipeptide substituting 10% of free L-Arg increased αS1-casein synthesis and the net-uptake of AA as well as expression of proteins related to mammalian target of rapamycin (mTOR) signaling pathway and mRNA expression of oligopeptide transporter 2 (PepT2). The positive effects of 10% Arg-Arg dipeptide on αS1-casein synthesis may be related to the increase of AA availability and the activation of mTOR signaling pathway.

Effects of glucose availability on αS1-casein synthesis in bovine mammary epithelial cells.

Glucose has been demonstrated to affect milk protein synthesis in dairy cows. However, its potential mechanisms has not been thoroughly studied. The objective of this study was to investigate the effects of glucose availability on αS1-casein synthesis, glucose uptake, metabolism, and the expression of proteins involved in AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling pathway in bovine mammary epithelial cells (BMEC). BMEC were treated for 24 h with different concentrations of glucose (0, 7, 10.5, 14, 17.5, and 21 mM). The results showed that 10.5 and 14 mM glucose supply increased the expression of αS1-casein, glucose uptake, cellular ATP content, and the phosphorylation of mTOR and P70S6K, but repressed AMPK phosphorylation in BMEC. Compared with 10.5 and 14 mM glucose supply, 17.5 and 21 mM glucose decreased the expression of αS1-casein, P70S6K phosphorylation as well as the activity of hexokinase (HK) and pyruvate kinase (PK), but increased the activity of glucose-6-phosphate dehydrogenase (G6PD). These results indicate that 10.5 to 14 mM glucose supply is the proper range for αS1-casein synthesis, and the promotion effects may be related to the increase of glucose uptake, ATP content and the changes of key proteins' phosphorylation in AMPK/mTOR signaling pathway. However, the inhibition of the expression of αS1-casein by 17.5 and 21 mM glucose may be associated with the changes of key enzymes' activity involved in glucose metabolism.

Glucose play an important role in milk protein synthesis in dairy cows. But the effects of glucose availability on casein synthesis and its underlying mechanisms has not been thoroughly studied. To elucidate the underlying mechanisms of glucose availability affecting casein synthesis, the effects of glucose availability on αS1-casein synthesis, glucose uptake, metabolism, and the expression of proteins involved in AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling pathway in bovine mammary epithelial cells were measured. We found that the expression of αS1-casein increased with 10.5 and 14 mM glucose supplementation, which may be associated with the increase of glucose uptake, ATP content and the changes of key proteins' phosphorylation in AMPK/mTOR signaling pathway. The inhibition of αS1-casein expression with 17.5 and 21 mM glucose supplementation may be related to the changes of key enzymes' activity involved in glucose metabolism. This study provided an insight into the potential mechanisms of glucose availability affecting milk protein synthesis.

Differential expression of Oct3/4 in human breast cancer and normal tissues.

Oct3/4, a transcription factor specifically expressed in mammalian totipotent embryonic stem and germ cells, has a critical role in the regulation and maintenance of pluripotency and self-renewal. However, reactivation of Oct3/4 expression is observed in several human breast cancer cell lines, but not in non­malignant cells. To examine Oct3/4 expression in human primary breast carcinomas and normal breast tissues, we obtained breast tumor tissues from 28 patients and normal breast tissues from 9 women. According to quantitative polymerase chain reaction, all of the tumor tissues, irrespective of tumor type or clinicopathological status, expressed Oct3/4 mRNA at 10- to 100- fold higher levels than that in the normal breast tissues. Expression of the Oct3/4 protein in tumors was confirmed by western blot analysis and immunofluorescent staining. Additionally, rapid amplification of cDNA ends and DNA sequencing revealed expression of multiple Oct4 gene transcripts from chromosome 6 (POU5F1) in normal breast tissues and the non­malignant breast epithelial cell line MCF­10A; by contrast, the breast tumors and malignant breast cancer cell line MCF­7 predominantly expressed transcripts of an Oct4-like gene (POU5F1B) from chromosome 8, which was termed Oct3 in the current study. The deduced amino acid sequences of full-length Oct3 and Oct4 are 96% identical. The findings of the current study indicated that Oct3, rather than Oct4, may serve as a novel clinical marker and a potential target for gene-specific therapy of breast cancer.