Lipid metabolism and m6A RNA methylation are altered in lambs supplemented rumen-protected methionine and lysine in a low-protein diet

Rumen-protected methionine and lysine supplementation to the low protein diet improves animal growth through modulating colonic microbiome in lambs

BACKGROUND

Dietary protein level and amino acid (AA) balance are crucial determinants of animal health and productivity. Supplementing rumen-protected AAs in low-protein diets was considered as an efficient strategy to improve the growth performance of ruminants. The colon serves as a crucial conduit for nutrient metabolism during rumen-protected methionine (RPMet) and rumen-protected lysine (RPLys) supplementation, however, it has been challenging to clarify which specific microbiota and their metabolites play a pivotal role in this process. Here, we applied metagenomic and metabolomic approaches to compare the characteristic microbiome and metabolic strategies in the colon of lambs fed a control diet (CON), a low-protein diet (LP) or a LP diet supplemented with RPMet and RPLys (LR).

RESULTS

The LP treatment decreased the average daily weight gain (ADG) in lambs, while the LR treatment tended to elicit a remission in ADG. The butyrate molar concentration was greater (P < 0.05), while acetate molar concentration (P < 0.05) was lower for lambs fed the LP and LR diets compared to those fed the CON diet. Moreover, the LP treatment remarkably decreased total AA concentration (P < 0.05), while LR treatment showed an improvement in the concentrations of methionine, lysine, leucine, glutamate, and tryptophan. Metagenomic insights proved that the microbial metabolic potentials referring to biosynthesis of volatile fatty acids (VFAs) and AAs in the colon were remarkably altered by three dietary treatments. Metagenomic binning identified distinct microbial markers for the CON group (Alistipes spp., Phocaeicola spp., and Ruminococcus spp.), LP group (Fibrobacter spp., Prevotella spp., Ruminococcus spp., and Escherichia coli), and LR group (Akkermansia muciniphila and RUG099 spp.).

CONCLUSIONS

Our findings suggest that RPMet and RPLys supplementation to the low-protein diet could enhance the microbial biosynthesis of butyrate and amino acids, enriche the beneficial bacteria in the colon, and thereby improve the growth performance of lambs.

Different lysine-to-methionine ratios in a low-protein diet affect the microbiome and metabolome, influencing the jejunal barrier function in Tibetan sheep

Introduction

The objective of this study was to evaluate the effects of the dietary lysine (Lys)/ methionine (Met) ratio in a low-protein diet on short-chain fatty acid (SCFA) profiles, villus morphology, antioxidant capacity, and immune status of the jejunum in Tibetan sheep.

Methods

A total of 90 weaned Tibetan sheep, each 2 months old with an initial weight of 15.37 ± 0.92 kg, were randomly divided into three treatment groups. These groups were supplemented with different Lys/Met ratios of 3 [low protein-high methionine (LP-H)], 2 [low protein-medium methionine (LP-M)], and 1 [low protein-low methionine (LP-L)] in the basal diet (10% crude protein). The feeding trial lasted 100 days, including a 10-day acclimation period and a 90-day experimental period.

Results

The hematoxylin-eosin (H&E) sections showed that the LP-L group had a significantly increased villus height compared to the LP-M and LP-H groups (p < 0.05). In addition, the LP-L group showed higher levels of Superoxide dismutase (SOD) activity and Total Antioxidant Capacity (T-AOC) concentrations (p < 0.05). A lower concentration of Interleukin-1 beta (IL-1β) was observed in the LP-H group (p < 0.05). The activities of α-amylase, chymotrypsin, and lipase were higher in the LP-L group compared to the LP-H group (p < 0.05). Bacterial sequencing showed that both Chao1 and ACE richness were significantly increased in the LP-L group (p < 0.05), suggesting that the species richness in the jejunum is connected to the ratio of dietary Lys/Met. Furthermore, lowering the dietary Lys/ Met ratio significantly increased the abundance of Romboutsia, the Ruminococcus gauvreauii group, the Lachnospiraceae NK3A20 group, Ruminococcus 2, and the Christensenellaceae R-7 group (p < 0.05) while decreasing the abundance of Methanobrevibacter (p < 0.05). Several differential metabolites, including beta-alanine, pantothenate, pantothenic acid, phosphoenolpyruvate, cysteine, adenosine 5'-diphosphate, isodeoxycholic acid, glutamate conjugated cholic acid, and 3-dehydrocholic acid, were significantly increased in the LP-L group (p < 0.05). The functional analysis based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations indicated that these metabolites were mainly involved in pantothenate and CoA biosynthesis, ferroptosis, and the tricarboxylic acid cycle. Several genes related to barrier function, such as Occludin and Muc- 2, were upregulated in the LP-L group (p < 0.05), while IL-6 and TNF-α were downregulated (p < 0.05).

Discussion

Collectively, our results suggest that the dietary Met/ Lys ratio could affect the jejunal SCFA concentration by modulating the microbial community and regulating metabolism, thereby contributing to jejunal barrier function. Our findings provide a theoretical basis for the application of Lys/Met diet supplementation in the nutritional management of Tibetan sheep, particularly when reducing the dietary crude protein (CP) level.

Integrated Transcriptomic Analyses of Liver and Mammary Gland Tissues Reveals the Regulatory Mechanism Underlying Dairy Goats at Late Lactation When Feeding Rumen-Protected Lysine

Although low-protein diets can improve the nitrogen utilization efficiency and alleviate economic pressures in ruminants, they may also negatively impact dairy performance. Rumen-protected lysine (RPL) supplementation can improve the health status and growth performance of ruminants without compromising nitrogen utilization efficiency and feed intake. In this study, a total of thirty-three multiparous dairy goats in the late-lactation period were randomly divided into three groups that were separately fed the control diet (namely the protein-adequacy group), the low-protein diet (namely the protein-deficient group), and the RPL-supplemented protein-deficient diet (namely RPL-supplementation group) for five weeks. Here, we investigated the molecular mechanisms regarding how low-protein diets with RPL supplementation compromise lactation phenotypes in dairy goats through cross-tissue transcriptomic analyses. Dietary protein deficiency caused an imbalance in amino acid (AA) intake, disrupted hepatic function, and impaired milk synthesis. Transcriptomic analyses further showed that RPL supplementation exhibited some beneficial effects, like mitigating abnormal lipid and energy metabolism in the liver, elevating hepatic resistance to oxidative stress, improving the mammary absorption of AAs, as well as activating mammary lipid and protein anabolism primarily through peroxisome proliferator-activated receptor (PPAR) and janus kinase-signal transducer (JAK)-signal transducer and activator of transcription (STAT) signaling, respectively. RPL supplementation of a low-protein diet contributes to maintaining late lactation in dairy goats primarily through mitigating hepatic energy disturbances and activating both lipid and protein metabolism in the mammary glands. Since RPL supplementation initiated a series of comprised events on mammary protein and lipid metabolism as well as the hepatic function and energy generation in dairy goats under protein deficiency during late lactation, these findings thus provide some insights into how RPL supplementation helps maintain milk production and health in dairy mammals especially at late lactation.

The role of RNA methylation in tumor immunity and its potential in immunotherapy

RNA methylation, a prevalent post-transcriptional modification, has garnered considerable attention in research circles. It exerts regulatory control over diverse biological functions by modulating RNA splicing, translation, transport, and stability. Notably, studies have illuminated the substantial impact of RNA methylation on tumor immunity. The primary types of RNA methylation encompass N6-methyladenosine (m6A), 5-methylcytosine (m5C), N1-methyladenosine (m1A), and N7-methylguanosine (m7G), and 3-methylcytidine (m3C). Compelling evidence underscores the involvement of RNA methylation in regulating the tumor microenvironment (TME). By affecting RNA translation and stability through the "writers", "erasers" and "readers", RNA methylation exerts influence over the dysregulation of immune cells and immune factors. Consequently, RNA methylation plays a pivotal role in modulating tumor immunity and mediating various biological behaviors, encompassing proliferation, invasion, metastasis, etc. In this review, we discussed the mechanisms and functions of several RNA methylations, providing a comprehensive overview of their biological roles and underlying mechanisms within the tumor microenvironment and among immunocytes. By exploring how these RNA modifications mediate tumor immune evasion, we also examine their potential applications in immunotherapy. This review aims to provide novel insights and strategies for identifying novel targets in RNA methylation and advancing cancer immunotherapy efficacy.

Effect of supplementing lysins and methionine to low-protein diets on growth performance, hepatic antioxidant capacity, immune status, and glycolytic activity of tibetan sheep

Reducing the levels of dietary protein is an effective nutritional approach in lowering feed cost and nitrogen emissions in ruminants. The purpose of this study was to evaluate the effects of dietary Lys/Met ratio in a low protein diet (10%, dry matter basis) on the growth performance and hepatic function (antioxidant capacity, immune status, and glycolytic activity) in Tibetan lambs. Ninety two-month-old rams with an average weight of 15.37 ± 0.92 kg were randomly assigned to LP-L (dietary Lys/Met = 1:1), LP-M (dietary Lys/Met = 2:1) and LP-H (dietary Lys/Met = 3:1) treatments. The trial was conducted over 100 d, including 10 d of adaption to the diets. Hepatic phenotypes, antioxidant capacity, immune status, glycolytic activity and gene expression profiling was detected after the conclusion of the feeding trials. The results showed that the body weight was higher in the LP-L group when compared to those on the LP-M group (P < 0.05). In addition, the activities of the catalase (CAT) and glutathione peroxidase (GSH-Px) in the LP-L group were significantly increased compared with the LP-M group (P < 0.05), while the malondialdehyde (MDA) levels in LP-H group were significantly decreased (P < 0.05). Compared with LP-H group, both hepatic glycogen (P < 0.01) and lactate dehydrogenase (LDH) (P < 0.05) were significantly elevated in LP-L group. For the LP-L group, the hepatocytes were arranged radially with the central vein in the center, and hepatic plates exhibited tight arrangement. Transcriptome analysis identified 29, 179, and 129 differentially expressed genes (DEGs) between the LP-M vs. LP-L, LP-H vs. LP-M, and LP-H vs. LP-L groups, respectively (Q-values < 0.05 and |log2Fold Change| > 1). Gene Ontology (GO) and correlation analyses showed that in the LP-L group, core genes (C1QA and JUNB) enriched in oxidoreductase activity were positively correlated with antioxidant indicators, while the MYO9A core gene enriched in the immune response was positively associated with immune indicators, and core genes enriched in molecular function (PDK3 and PDP2) were positively correlated with glycolysis indicators. In summary, low-protein diet with a low Lys/Met ratio (1:1) could reduce the hepatic oxidative stress and improve the glycolytic activity by regulating the expression of related genes of Tibetan sheep.

Circular RNAs, Noncoding RNAs, and N6-methyladenosine Involved in the Development of MAFLD

Noncoding RNAs (ncRNAs), including circular RNAs (circRNAs) and N6-methyladenosine (m6A), have been shown to play a critical role in the development of various diseases including obesity and metabolic disorder-associated fatty liver disease (MAFLD). Obesity is a chronic disease caused by excessive fat accumulation in the body, which has recently become more prevalent and is the foremost risk factor for MAFLD. Causes of obesity may involve the interaction of genetic, behavioral, and social factors. m6A RNA methylation might add a novel inspiration for understanding the development of obesity and MAFLD with post-transcriptional regulation of gene expression. In particular, circRNAs, microRNAs (miRNAs), and m6A might be implicated in the progression of MAFLD. Interestingly, m6A modification can modulate the translation, degradation, and other functions of ncRNAs. miRNAs/circRNAs can also modulate m6A modifications by affecting writers, erasers, and readers. In turn, ncRNAs could modulate the expression of m6A regulators in different ways. However, there is limited evidence on how these ncRNAs and m6A interact to affect the promotion of liver diseases. It seems that m6A can occur in DNA, RNA, and proteins that may be associated with several biological properties. This study provides a mechanistic understanding of the association of m6A modification and ncRNAs with liver diseases, especially for MAFLD. Comprehension of the association between m6A modification and ncRNAs may contribute to the development of treatment tactics for MAFLD.

N6-methyladenosine RNA modification in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide, influencing numerous regulatory axes and extrahepatic vital organs. The molecular mechanisms that lead to the progression of NAFLD remain unclear and knowledge on the pathways causing hepatocellular damage followed by lipid accumulation is limited. Recently, a number of studies have shown that mRNA N6-methyladenosine (m6A) modification contributes to the progression of NAFLD. In this review, we summarize current knowledge on m6A modification in the metabolic processes associated with NAFLD and discuss the challenges of and prospects for therapeutic avenues based on m6A regulation for the treatment of liver disease.

RNA N6-methyladenosine of DHAPAT and PAP involves in regulation of diapause of Bombyx mori via the lipid metabolism pathway

Environment-induced epigenetics are involved in diapause regulation, but the molecular mechanism that epigenetically couples nutrient metabolism to diapause regulation remains unclear. In this study, we paid special attention to the significant differences in the level of N6-adenosine methylation (m6A) of dihydroxyacetone phosphate acyltransferase (DHAPAT) and phosphatidate phosphatase (PAP) genes in the lipid metabolism pathway of the bivoltine silkworm (Bombyx mori) strain Qiufeng developed from eggs incubated at a normal temperature (QFHT, diapause egg producer) compared to those from eggs incubated at a low temperature (QFLT, non-diapause egg producer). We knocked down DHAPAT in the pupal stage of the QFLT group, resulting in the non-diapause destined eggs becoming diapausing eggs. In the PAP knockdown group, the colour of the non-diapause destined eggs changed from light yellow to pink 3 days after oviposition, but they hatched as normal. Moreover, we validated that YTHDF3 binds to m6A-modified DHAPAT and PAP mRNAs to promote their stability and translation. These results suggest that RNA m6A methylation participates in the diapause regulation of silkworm by changing the expression levels of DHAPAT and PAP and reveal that m6A epigenetic modification can be combined with a lipid metabolism signal pathway to participate in the regulation of insect diapause traits, which provides a clearer image for exploring the physiological basis of insect diapause.

Non-genetic factors affecting the meat quality and flavor of Inner Mongolian lambs: A review

The Inner Mongolia Autonomous Region ranks first among the five major pastoral areas in terms of lamb breeding of China. The Inner Mongolia Autonomous Region has a vast territory, with many famous grasslands and thousands of forage plants and multiple local high-quality lamb breeds. After hundreds of years of artificial breeding and improvement, Mongolian sheep have developed many varieties. Different diets, feeding and treatment methods have effects on the production performance, lipid deposition and flavor composition of mutton sheep. Therefore, understanding the relationship among Inner Mongolian lamb, meat quality, and flavor will improve the production of high-quality mutton. The regulation of meat quality and flavor will have a profound impact on the deep processing and income-generating capabilities of mutton. Non-genetic factors affect the quality and flavor of mutton, which are more intuitive than genetic factors. In this review, we cover the contributions made by scientists to explore and improve the quality and flavor of Inner Mongolia lambs through non-genetic means, compare the differences between grazing and drylot-feeding in detail, and summarize some feed additives. We hope that based on our review, we can provide some inspiration to improve the meat quality of Mongolian sheep.