In Ovo injection of betaine affects hepatic cholesterol metabolism through epigenetic gene regulation in newly hatched chicks

Early-life environmental effects on birds: epigenetics and microbiome as mechanisms underlying long-lasting phenotypic changes

Although the long-lasting effects of variation in early-life environment have been well documented across organisms, the underlying causal mechanisms are only recently starting to be unraveled. Yet understanding the underlying mechanisms of long-lasting effects can help us predict how organisms will respond to changing environments. Birds offer a great system in which to study developmental plasticity and its underlying mechanisms owing to the production of large external eggs and variation in developmental trajectories, combined with a long tradition of applied, physiological, ecological and evolutionary research. Epigenetic changes (such as DNA methylation) have been suggested to be a key mechanism mediating long-lasting effects of the early-life environment across taxa. More recently, changes in the early-life gut microbiome have been identified as another potential mediator of developmental plasticity. As a first step in understanding whether these mechanisms contribute to developmental plasticity in birds, this Review summarizes how changes in early-life environment (both prenatal and postnatal) influence epigenetic markers and the gut microbiome. The literature shows how both early-life biotic (such as resources and social environment) and abiotic (thermal environment and various anthropogenic stressors) factors modify epigenetic markers and the gut microbiome in birds, yet data concerning many other environmental factors are limited. The causal links of these modifications to lasting phenotypic changes are still scarce, but changes in the hypothalamic-pituitary-adrenal axis have been identified as one putative pathway. This Review identifies several knowledge gaps, including data on the long-term effects, stability of the molecular changes, and lack of diversity in the systems studied, and provides directions for future research.

How Does Nutrition Affect the Epigenetic Changes in Dairy Cows?

Dairy cows require a balanced diet that provides enough nutrients to support milk production, growth, and reproduction. Inadequate nutrition can lead to metabolic disorders, impaired fertility, and reduced milk yield. Recent studies have shown that nutrition can affect epigenetic modifications in dairy cows, which can impact gene expression and affect the cows' health and productivity. One of the most important epigenetic modifications in dairy cows is DNA methylation, which involves the addition of a methyl group to the DNA molecule. Studies have shown that the methylation status of certain genes in dairy cows can be influenced by dietary factors such as the level of methionine, lysine, choline, and folate in the diet. Other important epigenetic modifications in dairy cows are histone modification and microRNAs as regulators of gene expression. Overall, these findings suggest that nutrition can have a significant impact on the epigenetic regulation of gene expression in dairy cows. By optimizing the diet of dairy cows, it may be possible to improve their health and productivity by promoting beneficial epigenetic modifications. This paper reviews the main nutrients that can cause epigenetic changes in dairy cattle by analyzing the effect of diet on milk production and its composition.

Maternal dietary methionine restriction alters hepatic expression of one-carbon metabolism and epigenetic mechanism genes in the ducklings

BACKGROUND

Embryonic and fetal development is very susceptible to the availability of nutrients that can interfere with the setting of epigenomes, thus modifying the main metabolic pathways and impacting the health and phenotypes of the future individual. We have previously reported that a 38% reduction of the methyl donor methionine in the diet of 30 female ducks reduced the body weight of their 180 mule ducklings compared to that of 190 ducklings from 30 control females. The maternal methionine-restricted diet also altered plasmatic parameters in 30 of their ducklings when compared to that of 30 ducklings from the control group. Thus, their plasma glucose and triglyceride concentrations were higher while their free fatty acid level and alanine transaminase activity were decreased. Moreover, the hepatic transcript level of 16 genes involved in pathways related to energy metabolism was significantly different between the two groups of ducklings. In the present work, we continued studying the liver of these newly hatched ducklings to explore the impact of the maternal dietary methionine restriction on the hepatic transcript level of 70 genes mostly involved in one-carbon metabolism and epigenetic mechanisms.

RESULTS

Among the 12 genes (SHMT1, GART, ATIC, FTCD, MSRA, CBS, CTH, AHCYL1, HSBP1, DNMT3, HDAC9 and EZH2) identified as differentially expressed between the two maternal diet groups (p-value < 0.05), 3 of them were involved in epigenetic mechanisms. Ten other studied genes (MTR, GLRX, MTHFR, AHCY, ADK, PRDM2, EEF1A1, ESR1, PLAGL1, and WNT11) tended to be differently expressed (0.05 < p-value < 0.10). Moreover, the maternal dietary methionine restriction altered the number and nature of correlations between expression levels of differential genes for one-carbon metabolism and epigenetic mechanisms, expression levels of differential genes for energy metabolism, and phenotypic traits of ducklings.

CONCLUSION

This avian model showed that the maternal dietary methionine restriction impacted both the mRNA abundance of 22 genes involved in one-carbon metabolism or epigenetic mechanisms and the mRNA abundance of 16 genes involved in energy metabolism in the liver of the newly hatched offspring, in line with the previously observed changes in their phenotypic traits.

Betaine: A Potential Nutritional Metabolite in the Poultry Industry

Poultry industry has been recognized as a fast-developing sector aiming to produce low-cost and high-nutrient foods for human consumption. This review article aimed to focus on the significant roles of dietary betaine supplementation in the poultry industry. In this respect, different effects of betaine on performance and carcass traits, as well as its osmoregulatory, anticoccidial, immune-modulatory, and heat-stress alleviation activities, were discussed. Different concentrations of betaine supplementation can improve the feed conversion ratio, final body weight, breast muscle yield, egg production ratio, and reduce body fat contents in broiler chicken, turkey, duck, geese, and quail diets. Betaine supplemented with methyl groups can eliminate the need to have some methyl-group donors, including choline and methionine, therefore having positive effects on feed conversion ratio in poultry diets. The osmolytic character of betaine can alleviate heat stress and have a positive impact on tonic immobility, which consequently reduces stress in poultry. By inhibiting distinct developmental stages of Eimeria species, betaine reduces the damaging effects of coccidiosis on broiler chickens and improves intestinal structure and function. The immunological, cardiovascular, neurological, renal, and hepatic metabolic systems benefit from betaine's osmo-protective properties. Therefore, betaine has the potential to be considered as an alternative to feed additives and enhances the health status and productive performance of poultry.

Nutrient-Mediated Perception and Signalling in Human Metabolism: A Perspective of Nutrigenomics

The interaction between selective nutrients and linked genes involving a specific organ reveals the genetic make-up of an individual in response to a particular nutrient. The interaction of genes with food opens opportunities for the addition of bioactive compounds for specific populations comprising identical genotypes. The slight difference in the genetic blueprints of humans is advantageous in determining the effect of nutrients and their metabolism in the body. The basic knowledge of emerging nutrigenomics and nutrigenetics can be applied to optimize health, prevention, and treatment of diseases. In addition, nutrient-mediated pathways detecting the cellular concentration of nutrients such as sugars, amino acids, lipids, and metabolites are integrated and coordinated at the organismal level via hormone signals. This review deals with the interaction of nutrients with various aspects of nutrigenetics and nutrigenomics along with pathways involved in nutrient sensing and regulation, which can provide a detailed understanding of this new leading edge in nutrition research and its potential application to dietetic practice.

Distinct Patterns of GR Transcriptional Regulation in Liver and Muscle of LPS-Challenged Weaning Piglets

Glucocorticoid receptor (GR), which is ubiquitously expressed in nearly all cell types of various organs, mediates the tissue-specific metabolic and immune responses to maintain homeostasis and ensure survival under stressful conditions or pathological challenges. The neonatal period is metabolically demanding, and piglets are subjected to multiple stressors in modern intensive farms, especially around weaning. The liver is more responsive to LPS challenge compared to muscle, which is indicated by significantly increased TLR4 and p-p65, TNF-α, and IL-6 levels in association with GR down-regulation at both mRNA and protein levels. GR binding to the putative nGRE on TNF-α and IL-6 gene promoters decreased in the liver, but not muscle, upon LPS stimulation. The transcriptional regulation of GR also showed striking differences between liver and muscle. GR exon 1 mRNA variants 1–4, 1–5, and 1–6 were down-regulated in both liver and muscle, but a significant up-regulation of GR exon 1–9/10 mRNA variants abolished the change of total GR mRNA in the muscle in response to LPS stimulation. The significant down-regulation of GR in the liver corresponded with significantly decreased binding of p-GR and diminished histone acetylation in GR gene promoters. These results indicate that tissue-specific GR transcriptional regulation is involved in the differential inflammation responses between liver and muscle.

Betaine Promotes Fat Accumulation and Reduces Injury in Landes Goose Hepatocytes by Regulating Multiple Lipid Metabolism Pathways

Betaine is a well-established supplement used in livestock feeding. In our previous study, betaine was shown to result in the redistribution of body fat, a healthier steatosis phenotype, and an increased liver weight and triglyceride storage of the Landes goose liver, which is used for foie-gras production. However, these effects are not found in other species and strains, and the underlying mechanism is unclear. Here, we studied the underpinning molecular mechanisms by developing an in vitro fatty liver cell model using primary Landes goose hepatocytes and a high-glucose culture medium. Oil red-O staining, a mitochondrial membrane potential assay, and a qRT-PCR were used to quantify lipid droplet characteristics, mitochondrial β-oxidation, and fatty acid metabolism-related gene expression, respectively. Our in vitro model successfully simulated steatosis caused by overfeeding. Betaine supplementation resulted in small, well-distributed lipid droplets, consistent with previous experiments in vivo. In addition, mitochondrial membrane potential was restored, and gene expression of fatty acid synthesis genes (e.g., sterol regulatory-element binding protein, diacylglycerol acyltransferase 1 and 2) was lower after betaine supplementation. By contrast, the expression of lipid hydrolysis transfer genes (mitochondrial transfer protein and lipoprotein lipase) was higher. Overall, the results provide a scientific basis and theoretical support for the use of betaine in animal production.

Maternal dietary methionine restriction alters the expression of energy metabolism genes in the duckling liver

Background

In mammals, the nutritional status experienced during embryonic development shapes key metabolic pathways and influences the health and phenotype of the future individual, a phenomenon known as nutritional programming. In farmed birds as well, the quantity and quality of feed offered to the dam can impact the phenotype of the offspring. We have previously reported that a 38% reduction in the intake of the methyl donor methionine in the diet of 30 female ducks during the growing and laying periods - from 10 to 51 weeks of age - reduced the body weight of their 180 mule ducklings compared to that of 190 ducklings from 30 control females. The maternal dietary methionine restriction also altered the hepatic energy metabolism studied in 30 of their ducklings. Thus, their plasma glucose and triglyceride concentrations were higher while their plasma free fatty acid level was lower than those measured in the plasma of 30 ducklings from the control group. The objective of this new study was to better understand how maternal dietary methionine restriction affected the livers of their newly hatched male and female ducklings by investigating the hepatic expression levels of 100 genes primarily targeting energy metabolism, amino acid transport, oxidative stress, apoptotic activity and susceptibility to liver injury.

Results

Sixteen of the genes studied were differentially expressed between the ducklings from the two groups. Maternal dietary methionine restriction affected the mRNA levels of genes involved in different pathways related to energy metabolism such as glycolysis, lipogenesis or electron transport. Moreover, the mRNA levels of the nuclear receptors PPARGC1B, PPARG and RXRA were also affected.

Conclusions

Our results show that the 38% reduction in methionine intake in the diet of female ducks during the growing and egg-laying periods impacted the liver transcriptome of their offspring, which may explain the previously observed differences in their liver energy metabolism. These changes in mRNA levels, together with the observed phenotypic data, suggest an early modulation in the establishment of metabolic pathways.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08634-1.

Early Phenotype Programming in Birds by Temperature and Nutrition: A Mini-Review

Early development is a critical period during which environmental influences can have a significant impact on the health, welfare, robustness and performance of livestock. In oviparous vertebrates, such as birds, embryonic development takes place entirely in the egg. This allows the effects of environmental cues to be studied directly on the developing embryo. Interestingly, beneficial effects have been identified in several studies, leading to innovative procedures to improve the phenotype of the animals in the long term. In this review, we discuss the effects of early temperature and dietary programming strategies that both show promising results, as well as their potential transgenerational effects. The timing, duration and intensity of these procedures are critical to ensure that they produce beneficial effects without affecting animal survival or final product quality. For example, cyclic increases in egg incubation temperature have been shown to improve temperature tolerance and promote muscular growth in chickens or fatty liver production in mule ducks. In ovo feeding has also been successfully used to enhance digestive tract maturation, optimize chick development and growth, and thus obtain higher quality chicks. In addition, changes in the nutritional availability of methyl donors, for example, was shown to influence offspring phenotype. The molecular mechanisms behind early phenotype programming are still under investigation and are probably epigenetic in nature as shown by recent work in chickens.

Pre-hatching and post-hatching environmental factors related to epigenetic mechanisms in poultry

Epigenetic modifications are phenotypic changes unrelated to the modification of the DNA sequence. These modifications are essential for regulating cellular differentiation and organism development. In this case, epigenetics controls how the animal's genetic potential is used. The main epigenetic mechanisms are microRNA activity, DNA methylation and histone modification. The literature has repeatedly shown that environmental modulation has a significant influence on the regulation of epigenetic mechanisms in poultry. The aim of this review is to give an overview of the current state of the knowledge in poultry epigenetics in terms of issues relevant to overall poultry production and the improvement of the health status in chickens and other poultry species. One of the main differences between birds and mammals is the stage of embryonic development. The bird's embryo develops outside its mother, so an optimal environment of egg incubation before hatching is crucial for development. It is also the moment when many factors influence the activation of epigenetic mechanisms, i.e., incubation temperature, humidity, light, as well as in ovo treatments. Epigenome of the adult birds, might be modulated by: nutrition, supplementation and treatment, as well as modification of the intestinal microbiota. In addition, the activation of epigenetic mechanisms is influenced by pathogens (i.e., pathogenic bacteria, toxins, viruses and fungi) as well as, the maintenance conditions. Farm animal epigenetics is still a big challenge for scientists. This is a research area with many open questions. Modern methods of epigenetic analysis can serve both in the analysis of biological mechanisms and in the research and applied to production system, poultry health and welfare.

How Does Protein Nutrition Affect the Epigenetic Changes in Pig? A Review

Simple Summary

Epigenetic mechanisms regulate gene expression and depend of nutrition. In farm animals, and concretely, in pigs, some papers on protein nutrition have been realized to improve several productive traits. Changes in protein diet influence on epigenetic mechanisms that could affect productive and reproductive traits in individuals and their offspring. The purpose of this review was to update the current knowledge about the effects of these nutritional changes on epigenetic mechanisms in pigs.

Abstract

Epigenetic changes regulate gene expression and depend of external factors, such as environment and nutrition. In pigs, several studies on protein nutrition have been performed to improve productive and reproductive traits. Indeed, these studies aimed not only to determine broad protein requirements but also pigs’ essential amino acids requirements. Moreover, recent studies tried to determine these nutritional requirements for each individual, which is known as protein precision nutrition. However, nutritional changes could affect different epigenetic mechanisms, modifying metabolic pathways both in a given individual and its offspring. Modifications in protein nutrition, such as change in the amino acid profile, increase or decrease in protein levels, or the addition of metabolites that condition protein requirements, could affect the regulation of some genes, such as myostatin, insulin growth factor, or genes controlling cholesterol and glucose metabolism pathways. This review summarizes the impact of most common protein nutritional strategies on epigenetic changes and describes their effects on regulation of gene expression in pigs. In a context where animal nutrition is shifting towards precision protein nutrition (PPN), further studies evaluating the effects of PPN on animal epigenetic are necessary.

Fatty Acid Composition and Regulatory Gene Expression in Late-Term Embryos of ACRB and COBB Broilers

Cobb broilers (COBB) have been heavily selected for their production performance in the past several decades, while the Athens Canadian Random Bred (ACRB) chickens, a meat-type breed, have been kept as a non-selected control strain. The purpose of this study was to compare these two lines of chickens at late embryonic development and identify the molecular markers and fatty acid profiles underlining their differences in growth performance due to selection. Fertilized eggs of the ACRB (n = 6) and COBB (n = 6) were used at 14 and 18 embryonic days. Genes involved in lipogenesis and myogenesis were measured using quantitative real-time reverse transcroption-polymerase chain reaction (RT-PCR), and fatty acid (FA) compositions of egg yolk, muscle, and liver were measured using gas chromatography. COBB had higher egg weight, embryo weight, and breast and fat ratio. The gene expression in the liver showed an interaction between age and breed on FASN expression, with the highest level in COBB at E18. ACRB had higher ApoB and MTTP expression, but lower SREBP-1 expression compared to COBB. No difference was found in myogenesis gene expression in the muscle between two breeds. For the FA composition, muscle was largely affected by both breed and age. Yolk and liver were affected mainly by breed and age, respectively. Constant interaction effects in docosahexaenoic acid (DHA), indicating the highest level in all the tested tissues of ACRB at E14 and the constant main effects with higher myristic, palmitic, and gondoic, but lower linolenic acid in the liver and yolk of COBB compared to the levels in those of ACRB. Finally, fat accumulation in the liver had no obvious difference between the breeds but was higher when embryo was older. In conclusion, broiler breed affects egg, embryo, and tissue weight, as well as FA composition in initial egg yolk and throughout the embryonic development. The highest docosahexaenoic percentage was observed in ACRB, indicating that genetic selection may result in fatty acid profile changes such as lower DHA content in chicken tissues and eggs.

Hepatic DNA Methylation in Response to Early Stimulation of Microbiota with Lactobacillus Synbiotics in Broiler Chickens

DNA methylation inhibits DNA transcription by the addition of methyl residues to cysteine within the CpG islands of gene promoters. The process of DNA methylation can be modulated by environmental factors such as intestinal microbiota. In poultry, the composition of the intestinal microbiota can be stimulated by in ovo delivery of synbiotics. The present study aims to determine the effect of Lactobacillus synbiotics delivered in ovo on the level of hepatic DNA methylation in broiler chickens. In ovo stimulation was performed on day 12 of egg incubation. Bioactive compounds delivered in ovo included (S1)—Lactobacillus salivarius with GOS and (S2)—Lactobacillus plantarum with RFO. Samples were collected from six individuals from each group on day 42 post-hatching. DNA methylation of five genes selected on the basis of the transcriptome data were analyzed using the qMSP method. Significant changes were observed in DNA methylation of genes in liver including ANGPTL4 and NR4A3, after S2 delivery. The obtained results confirm that the downregulation of metabolic gene expression in the liver mediated by in ovo stimulation had epigenetic characteristics.

Dietary Betaine Addition Promotes Hepatic Cholesterol Synthesis, Bile Acid Conversion, and Export in Rats

It is widely reported how betaine addition regulates lipid metabolism but how betaine affects cholesterol metabolism is still unknown. This study aimed to investigate the role of betaine in hepatic cholesterol metabolism of Sprague-Dawley rats. Rats were randomly allocated to four groups and fed with a basal diet or a high-fat diet with or without 1% betaine. The experiment lasted 28 days. The results showed that dietary betaine supplementation reduced the feed intake of rats with final weight unchanged. Serum low-density-lipoprotein cholesterol was increased with the high-fat diet. The high-fat diet promoted cholesterol synthesis and excretion by enhancing the HMG-CoA reductase and ABCG5/G8, respectively, which lead to a balance of hepatic cholesterol. Rats in betaine groups showed a higher level of hepatic total cholesterol. Dietary betaine addition enhanced cholesterol synthesis as well as conversion of bile acid from cholesterol by increasing the levels of HMGCR and CYP7A1. The high-fat diet decreased the level of bile salt export pump, while dietary betaine addition inhibited this decrease and promoted bile acid efflux and increased total bile acid levels in the intestine. In summary, dietary betaine addition promoted hepatic cholesterol metabolism, including cholesterol synthesis, conversion of bile acids, and bile acid export.

Maternal betaine supplementation decreases hepatic cholesterol deposition in chicken offspring with epigenetic modulation of SREBP2 and CYP7A1 genes

Maternal betaine was reported to regulate offspring hepatic cholesterol metabolism in mammals. However, it is unclear whether and how feeding betaine to laying hens affects hepatic cholesterol metabolism in offspring chickens. Rugao yellow-feathered laying hens (n = 120) were fed basal or 0.5% betaine-supplemented diet for 28 D before the eggs were collected for incubation. Maternal betaine significantly decreased the hepatic cholesterol content (P < 0.05) in offspring chickens. Accordingly, the cholesterol biosynthetic enzymes, sterol regulator element-binding protein 2 (SREBP2) and 3-hydroxy-3-methylglutaryl coenzyme A reductase, were decreased, while cholesterol-7alpha-hydroxylase (CYP7A1), which converts cholesterol to bile acids, was increased at both mRNA and protein levels in betaine-treated offspring chickens. Hepatic mRNA and protein expression of low-density lipoprotein receptor was significantly (P < 0.05) increased, while the mRNA abundance of cholesterol acyltransferase 1 (ACAT1) that mediates cholesterol esterification was significantly (P < 0.05) decreased in the betaine group. Meanwhile, hepatic protein contents of DNA methyltransferases 1 and betaine homocysteine methyltransferase were increased (P < 0.05), which was associated with modifications of CpG methylation on affected cholesterol metabolic genes. Furthermore, the level of CpG methylation on gene promoters was increased (P < 0.05) for sterol regulator element-binding protein 2 and abundance of cholesterol acyltransferase 1 yet decreased (P < 0.05) for cholesterol-7alpha-hydroxylase. These results indicate that maternal betaine supplementation significantly decreases hepatic cholesterol deposition through epigenetic regulation of cholesterol metabolic genes in offspring juvenile chickens.

Dietary betaine improves egg-laying rate in hens through hypomethylation and glucocorticoid receptor-mediated activation of hepatic lipogenesis-related genes

In avian species, liver lipid metabolism plays an important role in egg laying performance. Previous studies indicate that betaine supplementation in laying hens improves egg production. However, it remains unclear if betaine improves laying performance by affecting hepatic lipid metabolism and what mechanisms are involved. We fed laying hens a 0.5% betaine-supplemented diet for 4 wks to investigate its effect on hepatic lipids metabolism in vivo and confirmed its mechanism via in vitro experiments using embryonic chicken hepatocytes. Results showed that betaine supplemented diet enhanced laying production by 4.3% compared with normal diet, accompanied with increased liver and plasma triacylglycerol concentrations (P < 0.05) in hens. Simultaneously, key genes involved in hepatic lipid synthesis, such as sterol regulatory element binding protein 1 (SREBP-1), fatty acid synthase, acetyl-CoA carboxylase, and stearoyl-CoA desaturase 1 (SCD1) were markedly upregulated at the mRNA level (P < 0.05). Western blot results showed that SREBP-1 and SCD1 protein levels were also increased (P < 0.05). Moreover, mRNA expression of main apolipoprotein components of yolk-targeted lipoproteins, apolipoprotein B (ApoB) and apolipoprotein-V1 (ApoV1), in addition to microsomal triglyceride transfer proteins, which is closely related to the synthesis and release of very-low density lipoprotein, were also markedly elevated (P < 0.05). Methylated DNA immunoprecipitation combined with PCR detects reduction of methylation levels in certain regions of the above gene promoters. Chromatin immunoprecipitation PCR assays showed increased binding of glucocorticoid receptor (GR) to SREBP1 and ApoB gene promoters. Similar results of ApoV1 gene expression were obtained from cultured hepatocytes treated with betaine. Additionally, betaine increased the expression of GR and some genes involved in methionine cycle in vitro. These results suggest that betaine supplementation could alter the expression of liver lipid synthesis and transport-related genes by modifying the methylation status and GR binding on their promoter and hence promote the synthesis and release of yolk precursor substances in the liver.

Fetal betaine exposure modulates hypothalamic expression of cholesterol metabolic genes in offspring cockerels with modification of promoter DNA methylation

In documents, maternal betaine modulates hypothalamic cholesterol metabolism in chicken posthatchings, but it remains unclear whether this effect can be passed on by generations. In present study, eggs were injected with saline or betaine at 2.5 mg/egg, and the hatchlings (F1) were raised under the same condition until sexual maturation. Both the control group and the betaine group used artificial insemination to collect sperm from their cockerels. Fertilized eggs were incubated, and the hatchlings of the following generation (F2) were raised up to 64 D of age. F2 cockerels in betaine group showed significantly (P < 0.05) lower body weight, which was associated with significantly decreased (P < 0.05) hypothalamic content of total cholesterol and cholesterol ester. Concordantly, hypothalamic expression of cholesterol biosynthetic genes, SREBP2 and HMGCR, were significantly downregulated (P < 0.05), together with cholesterol conversion-related and excretion-related genes, CYP46A1 and ABCA1. These changes coincided with a significant downregulation in mRNA expression of regulatory neuropeptides including brain-derived neurotrophic factor, neuropeptide Y, and corticotropin-releasing hormone. Moreover, genes involved in methyl transfer cycle were also modified. Betaine homocysteine methyltransferase (P < 0.05) was downregulated, yet DNA methyltransferase1 tended to be upregulated (P = 0.06). S-adenosyl methionine/S-adenosylhomocysteine ratio was higher in the hypothalamus of betaine-treated F2 cockerels, which was associated with significantly modified CpG methylation on the promoter of those affected genes. These results suggested that betaine might regulate central cholesterol metabolism and hypothalamic expression of genes related to brain function by altering promoter DNA methylation in F2 cockerels.

Chronic corticosterone exposure induces liver inflammation and fibrosis in association with m6A-linked post-transcriptional suppression of heat shock proteins in chicken

Our previous study had shown that chronic corticosterone (CORT) exposure causes excessive fat deposition in chicken liver, yet it remains unknown whether it is associated with inflammation and fibrosis. In general, heat shock proteins (HSPs) are activated in response to acute stress to play a cytoprotective role, and this activation is associated with m6A-mediated post-transcriptional regulation. However, changes of HSPs and the m6A methylation on their mRNAs in response to chronic CORT treatment in chicken liver have not been reported. In this study, chronic CORT exposure induced inflammation and fibrosis in chicken liver, associated with significantly modulated expression of HSPs that was significantly upregulated at mRNA level yet downregulated at protein level. Concurrently, m6A methyltransferases METTL3 content was upregulated together with the level of m6A methylation on HSPs transcripts. The m6A-seq analysis revealed 2-6 significantly (P < 0.05) hypermethylated m6A peaks in the mRNA of 4 different species of HSPs in CORT-treated chicken liver. HSP90B1 transcript had 6 differentially methylated m6A peaks among which peaks on exon 16 and exon 17 showed 3.14- and 4.72-fold of increase, respectively. Mutation of the 8 predicted m6A sites on exon 16 and exon 17 resulted in a significant (P < 0.05) increase in eGFP-fused content of HSP90B1 exon 16 and exon 17 fragment in 293 T cells, indicating a possible role of m6A in post-transcriptional regulation of HSPs. In conclusion, chronic CORT exposure induces inflammation and fibrosis in chicken liver along with an increase in the levels and m6A methylation of several HSPs mRNAs; HSPs levels were however reduced under the indicated conditions. Results presented suggest that the reduction in HSPs levels may be associated with m6A methylation in CORT-exposed chickens.

Maternal betaine suppresses adrenal expression of cholesterol trafficking genes and decreases plasma corticosterone concentration in offspring pullets

Background

Laying hens supplemented with betaine demonstrate activated adrenal steroidogenesis and deposit higher corticosterone (CORT) in the egg yolk. Here we further investigate the effect of maternal betaine on the plasma CORT concentration and adrenal expression of steroidogenic genes in offspring pullets.

Results

Maternal betaine significantly reduced (P < 0.05) plasma CORT concentration and the adrenal expression of vimentin that is involved in trafficking cholesterol to the mitochondria for utilization in offspring pullets. Concurrently, voltage-dependent anion channel 1 and steroidogenic acute regulatory protein, the two mitochondrial proteins involved in cholesterol influx, were both down-regulated at mRNA and protein levels. However, enzymes responsible for steroid syntheses, such as cytochrome P450 family 11 subfamily A member 1 and cytochrome P450 family 21 subfamily A member 2, were significantly (P < 0.05) up-regulated at mRNA or protein levels in the adrenal gland of pullets derived from betaine-supplemented hens. Furthermore, expression of transcription factors, such as steroidogenic factor-1, sterol regulatory element-binding protein 1 and cAMP response element-binding protein, was significantly (P < 0.05) enhanced, together with their downstream target genes, such as 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, LDL receptor and sterol regulatory element-binding protein cleavage-activating protein. The promoter regions of most steroidogenic genes were significantly (P < 0.05) hypomethylated, although methyl transfer enzymes, such as AHCYL, GNMT1 and BHMT were up-regulated.

Conclusions

These results indicate that the reduced plasma CORT in betaine-supplemented offspring pullets is linked to suppressed cholesterol trafficking into the mitochondria, despite the activation of cholesterol and corticosteroid synthetic genes associated with promoter hypomethylation.

Effect of Supplementation with Trimethylglycine (Betaine) and/or Vitamins on Semen Quality, Fertility, Antioxidant Status, DNA Repair and Welfare of Roosters Exposed to Chronic Heat Stress

In this study, we investigated the influence of betaine (Bet, 1000 mg/kg), with or without vitamin C (VC, 200 mg/kg ascorbic acid) and/or vitamin E (VE, 150 mg/kg α-tocopherol acetate) on semen quality, seminal and blood plasma constituents, antioxidants' status, DNA repair, and the welfare of chronic heat stress (CHS)-exposed roosters. A total of 54 roosters were divided into six groups of nine replicates. One group was kept under thermoneutral conditions, whereas the other five were kept under CHS. One of the five groups served as an unsupplemented CHS group, and was fed with a basal diet. The other four CHS groups were supplemented with Bet, Bet + VC, Bet + VE, and Bet + VC + VE, respectively. Our data indicate that supplementation with Bet, Bet + VC, Bet + VE, and Bet + VC + VE, resulted in complete recovery of the CHS effect on sperm concentration and livability, semen pH, and fertility compared to the thermoneutral group. Seminal plasma total antioxidant capacity (TAC) was significantly (p < 0.05) increased with Bet, with or without vitamins, compared to the thermoneutral and CHS groups. Urea and blood plasma malondialdehyde (MDA) were totally recovered with Bet, with or without vitamin treatments. Both the jejunum and ileum DNA were partially recovered following Bet, with or without vitamin supplementation. In conclusion, Bet, at 1000 mg/kg feed, may be a useful agent for increasing semen quality, fertility, welfare, and to improve the breeding strategy of breeder males in hot climates.

Enhanced hepatic cholesterol accumulation induced by maternal betaine exposure is associated with hypermethylation of CYP7A1 gene promoter

PURPOSE

Betaine contains three methyl groups and plays a critical role in regulating glucose and lipid metabolism via epigenetic modifications. However, it is unclear whether prenatal betaine intake could affect cholesterol metabolism of progeny through DNA methylation.

METHODS

Hence, pregnant rats were randomly divided into control and betaine groups fed standard diet or 1% betaine supplementation diet, respectively, throughout gestation and lactation.

RESULTS

Maternal betaine exposure significantly (P < 0.05) increased serum and hepatic cholesterol contents but not triglyceride levels in offspring rats. Accordantly, maternal intake of betaine markedly downregulated (P < 0.05) hepatic cholesterol 7 alpha-hydroxylase (CYP7A1) expression at both the mRNA and protein level, while the protein content of low-density lipoprotein receptor (LDLR) was upregulated in the liver of betaine-exposed rats. In addition, prenatal betaine supplementation extremely increased (P < 0.05) hepatic betaine-homocysteine methyltransferase (BHMT) expression at the mRNA and protein level but not affected the expression of other key enzymes involved in methionine metabolism. Furthermore, hepatic hypermethylation of CYP7A1 gene promoter was observed in progeny rats derived from betaine-supplemented dams.

CONCLUSIONS

Our results provide evidence that maternal betaine supplementation significantly enhances hepatic cholesterol contents accompanied with alterations of cholesterol metabolic genes and hypermethylation in offspring rats at weaning.

The role of dietary fibre in pig production, with a particular emphasis on reproduction

Fibres from a variety of sources are a common constituent of pig feeds. They provide a means to utilise locally-produced plant materials which are often a by-product of the food or drink industry. The value of a high fibre diet in terms of producing satiety has long been recognised. However the addition of fibre can reduce feed intake, which is clearly detrimental during stages of the production cycle when nutrient needs are high, for example in growing piglets and during lactation. More recently, fibre has been found to promote novel benefits to pig production systems, particularly given the reduction in antimicrobial use world-wide, concern for the welfare of animals fed a restricted diet and the need to ensure that such systems are more environmentally friendly. For example, inclusion of dietary fibre can alter the gut microbiota in ways that could reduce the need for antibiotics, while controlled addition of certain fibre types may reduce nitrogen losses into the environment and so reduce the environmental cost of pig production. Of particular potential value is the opportunity to use crude fibre concentrates as ‘functional’ feed additives to improve young pig growth and welfare. Perhaps the greatest opportunity for the use of high fibre diets is to improve the reproductive efficiency of pigs. Increased dietary fibre before mating improves oocyte maturation, prenatal survival and litter size; providing a consumer-acceptable means of increasing the amount of saleable meat produced per sow. The mechanisms responsible for these beneficial effects remain to be elucidated. However, changes in plasma and follicular fluid concentrations of key hormones and metabolites, as well as effects of the hypothalamic satiety centre on gonadotrophin secretion and epigenetic effects are strong candidates.

Influence of fibre and betaine on development of the gastrointestinal tract of broilers between hatch and 14 d of age

An experiment was designed to determine the influence of fibre and betaine on the development of the intestine, liver and pancreas of broilers from hatch to 14 d of age. A total of 250-day-old Cobb 500 male broilers were allocated to 16 cages with 15 broilers each. Treatments were arranged in a 2 × 4 factorial design, consisting of 2 feed formulations (low and high fibre diets) and 4 levels of betaine (0, 1, 3 or 5 kg/t). At hatch, 10 birds in total were euthanised, and samples of the liver, pancreas, yolk sac and intestine were collected for reference of the analysed parameters before the start of the trial. On d 4, 9 and 14, 5 birds per cage (10 birds per treatment) were selected, euthanised and treated as the same as the birds at hatch. Villus height and width and crypt depth were determined on the duodenum samples, and absorptive area was calculated. The number of enterocytes in mitosis at the villus was determined by a positive reaction to antibody for Ki67 protein, and fused villus was evaluated visually. The relative weight of the yolk sac reduced (P < 0.05) as birds aged while the intestine and liver reached a maximum (P < 0.05) at around d 4 and the pancreas at d 9. Birds fed the high fibre diet had greater feed intake, lower relative weight of the pancreas and higher villus (P < 0.05) than birds fed the low fibre diet. Villus width increased (P < 0.05) at 4 d of age, and this was associated with fused villus. Betaine inclusion reduced (P < 0.05) villus width, increased (P < 0.05) villus size and absorptive area, and reduced (P < 0.05) the number of enterocytes with positive reaction for the antibody Ki-67. Betaine inclusion reduced the width and increased the absorptive area and the villus height of the duodenum of birds up to 14 d of age. The higher fibre diet increased feed intake and villus height, yet reduced pancreas relative weight, while not affecting body weight gain. This response was possibly due to a dilution effect of the fibre, reducing nutrient absorption and consequently stimulating villus growth to improve absorption rates.

Corticosterone-Induced Lipogenesis Activation and Lipophagy Inhibition in Chicken Liver Are Alleviated by Maternal Betaine Supplementation

Background

We have shown previously that in ovo betaine injection can prevent nonalcoholic fatty liver induced by glucocorticoid exposure in chickens; yet it remains unknown whether feeding betaine to laying hens may exert similar effects in their progeny.

Objective

In this study, we fed laying hens a betaine-supplemented diet, and the progeny were later exposed chronically to corticosterone (CORT) to test hepatoprotective effects and further elucidate underlying mechanisms.

Methods

Rugao yellow-feathered laying hens (n = 120) were fed a basal (control, C) diet or a 0.5% betaine-supplemented (B) diet for 28 d before their eggs were collected for incubation. At 49 d of age, male chickens selected from each group were daily injected subcutaneously with solvent (15% ethanol; vehicle, VEH) or CORT (4.0 mg/kg body mass) for 7 d to establish a fatty liver model. Chickens in the 4 groups (C-VEH, C-CORT, B-VEH, and B-CORT) were killed at day 57. Plasma and hepatic triglyceride (TG) concentrations, as well as the hepatic expression of genes involved in lipogenesis and lipophagy, were determined.

Results

CORT induced a 1.6-fold increase in the plasma TG concentration (P < 0.05) and a 1.8-fold increment in the hepatic TG concentration (P < 0.05), associated with activation of lipogenic genes (70-780%). In contrast, lipophagy and mitochondrial β-oxidation genes were inhibited by 30-60% (P < 0.05) in CORT-treated chickens. These CORT-induced changes were completely normalized by maternal betaine supplementation or were partially normalized to intermediate values that were significantly different from those in the C-VEH and C-CORT groups. These effects were accompanied by modifications in CpG methylation and glucocorticoid receptor binding to the promoters of major lipogenic and lipophagic genes (P < 0.05).

Conclusions

These results indicate that maternal betaine supplementation protects male juvenile chickens from CORT-induced TG accumulation in the liver via epigenetic modulation of lipogenic and lipophagic genes.

Activation of epithelial proliferation induced by Eimeria acervulina infection in the duodenum may be associated with cholesterol metabolism

Cell proliferation in the intestine is commonly occurred during infection and inflammation to replace damaged enterocytes, and cholesterol as an essential constituent of cell membrane, is required for cell proliferation and growth. Here we found that coccidium-challenged (CC) chickens showed severe damages in intestinal structure, a significant increase of cell proliferation, and an activation of genes expression involved in the innate immune response. Compared to control (CON), CC chickens showed a marked decrease of cholesterol (Tch) level in the circulating system, but a significant increase in local duodenum epithelium. Increase of LDLR protein combined with a significant decrease of CYP27A1 protein expression in duodenum epithelium may contribute to intestinal cholesterol accumulation in CC chickens. Moreover, we found miRNAs targeting to CYP27A1 gene participating in post-transcriptional regulation. Hence, these results provide a new insight for the intervention of epithelial proliferation and cholesterol metabolism in the gastrointestinal tracts.

Prenatal betaine exposure alleviates corticosterone-induced inhibition of CYP27A1 expression in the liver of juvenile chickens associated with its promoter DNA methylation

Sterol 27-hydroxylase (CYP27A1) plays an important role in cholesterol homeostasis by degrading cholesterol to bile acids. Betaine can alleviate high-fat diet-induced hepatic cholesterol accumulation and maternal betaine treatment programs the hepatic expression of CYP27A1 in offspring. Excessive corticosterone (CORT) exposure causes hepatic cholesterol deposition in chickens, yet it remains unknown whether prenatal betaine modulates CORT-induced cholesterol accumulation in chicken liver later in life and whether it involves epigenetic gene regulation of CYP27A1. In this study, fertilized eggs were injected with saline or betaine at 2.5mg/egg before incubation, and the hatchlings were raised under the same condition till 56days of age followed by 7days of subcutaneous CORT injection. Plasma concentrations of total cholesterol (Tch), HDL- and LDL-cholesterol were significantly increased (P<0.05), after CORT challenge, in both control and betaine groups. However, prenatal betaine exposure prevented CORT-induced increase (P<0.05) in hepatic Tch content. Hepatic expression of cholesterol biosynthesis genes and ACAT1 protein that esterifies cholesterol for storage, were activated in both control and betaine groups upon CORT challenge. However, betaine-treated chickens were protected from CORT-induced repression (P<0.05) in LXR and CYP27A1 expression in the liver. CORT-induced down-regulation of LXR and CYP27A1 coincided with significantly increased (P<0.05) CpG methylation on their promoters, which was significantly ameliorated in betaine-treated chickens. These results suggest that in ovo betaine injection alleviates CORT-induced hepatic cholesterol deposition most probably through epigenetic regulation of CYP27A1 and LXR genes in juvenile chickens.

In ovo injection of betaine alleviates corticosterone-induced fatty liver in chickens through epigenetic modifications

Betaine alleviates high-fat diet-induced fatty liver and prenatal betaine programs offspring hepatic lipid metabolism. Excessive corticosterone (CORT) exposure causes fatty liver in chickens, yet it remains unknown whether and how prenatal betaine modulates the susceptibility of CORT-induced fatty liver later in life. In this study, fertilized eggs were injected with saline or betaine before incubation, and the hatchlings were raised at 8 weeks of age followed by 7 days of subcutaneous CORT injection. CORT-induced fatty liver was less severe in betaine-treated chickens, with significantly reduced oil-red staining and hepatic triglyceride content (P < 0.05). The protective effect of prenatal betaine was associated with significantly up-regulated expression of PPARα and CPT1α, as well as mitochondrial DNA (mtDNA)-encoded genes (P < 0.05). Moreover, betaine rescued CORT-induced alterations in methionine cycle genes, which coincided with modifications of CpG methylation on CPT1α gene promoter and mtDNA D-loop regions. Furthermore, the elevation of hepatic GR protein content after CORT treatment was significantly reduced (P < 0.05), while the reduction of GR binding to the control region of affected genes was significantly increased (P < 0.05), in betaine-treated chickens. These results indicate that in ovo betaine injection protects the juvenile chickens from CORT-induced fatty liver.

Nutritional Influence on Epigenetic Marks and Effect on Livestock Production

Nutrition represents one of the greatest environmental determinants of an individual’s health. While nutrient quantity and quality impart direct effects, the interaction of nutrition with genetic and epigenetic modifications is often overlooked despite being shown to influence biological variation in mammals. Dissecting complex traits, such as those that are diet or nutrition related, to determine the genetic and epigenetic contributions toward a phenotype can be a formidable process. Epigenetic modifications add another layer of complexity as they do not change the DNA sequence itself but can affect transcription and are important mediators of gene expression and ensuing phenotypic variation. Altered carbohydrate metabolism and rates of fat and protein deposition resulting from diet-induced hypo- or hyper-methylation highlight the capability of nutritional epigenetics to influence livestock commodity quality and quantity. This interaction can yield either products tailored to consumer preference, such as marbling in meat cuts, or potentially increasing productivity and yield both in terms of carcass yield and/or offspring performance. Understanding how these and other desirable phenotypes result from epigenetic mechanisms will facilitate their inducible potential in livestock systems. Here, we discuss the establishment of the epigenome, examples of nutritional mediated alterations of epigenetics and epigenetic effects on livestock production.

Maternal Betaine Supplementation throughout Gestation and Lactation Modifies Hepatic Cholesterol Metabolic Genes in Weaning Piglets via AMPK/LXR-Mediated Pathway and Histone Modification

Betaine serves as an animal and human nutrient which has been heavily investigated in glucose and lipid metabolic regulation, yet the underlying mechanisms are still elusive. In this study, feeding sows with betaine-supplemented diets during pregnancy and lactation increased cholesterol content and low-density lipoprotein receptor (LDLR) and scavenger receptor class B type I (SR-BI) gene expression, but decreasing bile acids content and cholesterol-7a-hydroxylase (CYP7a1) expression in the liver of weaning piglets. This was associated with the significantly elevated serum betaine and methionine levels and hepatic S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) content. Concurrently, the hepatic nuclear transcription factor liver X receptor LXR was downregulated along with activated signal protein AMP-activated protein kinase (AMPK). Moreover, a chromatin immunoprecipitation assay showed lower LXR binding on CYP7a1 gene promoter and more enriched activation histone marker H3K4me3 on LDLR and SR-BI promoters. These results suggest that gestational and lactational betaine supplementation modulates hepatic gene expression involved in cholesterol metabolism via an AMPK/LXR pathway and histone modification in the weaning offspring.