Effects of different energy levels in low-protein diet on liver lipid metabolism in the late-phase laying hens through the gut-liver axis

Background The energy/protein imbalance in a low-protein diet induces lipid metabolism disorders in late-phase laying hens.Reducing energy levels in the low-protein diet to adjust the energy-to-protein ratio may improve fat deposition,but this also decreases the laying performance of hens.This study investigated the mechanism by which different energy levels in the low-protein diet influences liver lipid metabolism in late-phase laying hens through the enterohepatic axis to guide feed optimization and nutrition strategies.A total of 288 laying hens were randomly allocated to the normal-energy and normal-protein diet group(positive control:CK)or 1 of 3 groups:lowenergy and low-protein diet(LL),normal-energy and low-protein diet(NL),and high-energy and low-protein diet(HL)groups.The energy-to-protein ratios of the CK,LL,NL,and HL diets were 0.67,0.74,0.77,and 0.80,respectively.Results Compared with the CK group,egg quality deteriorated with increasing energy intake in late-phase laying hens fed low-protein diet.Hens fed LL,NL,and HL diets had significantly higher triglyceride,total cholesterol,acetylCo A carboxylase,and fatty acid synthase levels,but significantly lower hepatic lipase levels compared with the CK group.Liver transcriptome sequencing revealed that genes involved in fatty acid beta-oxidation(ACOX1,HADHA,EHHADH,and ACAA1)were downregulated,whereas genes related to fatty acid synthesis(SCD,FASN,and ACACA)were upregulated in LL group compared with the CK group.Comparison of the cecal microbiome showed that in hens fed an LL diet,Lactobacillus and Desulfovibrio were enriched,whereas riboflavin metabolism was suppressed.Cecal metabolites that were most significantly affected by the LL diet included several vitamins,such as riboflavin(vitamin B2),pantethine(vitamin B5 derivative),pyridoxine(vitamin B6),and 4-pyridoxic acid.Conclusion A lipid metabolism disorder due to deficiencies of vitamin B2 and pantethine originating from the metabolism of the cecal microbiome may be the underlying reason for fat accumulation in the liver of late-phase laying hens fed an LL diet.Based on the present study,we propose that targeting vitamin B2 and pantethine(vitamin B5 derivative)might be an effective strategy for improving lipid metabolism in late-phase laying hens fed a low-protein diet.

Low-protein diets supplemented with casein hydrolysate favor the microbiota and enhance the mucosal humoral immunity in the colon of pigs

Background:High-protein diets can increase the colonic health risks.A moderate reduction of dietary crude-protein(CP)level can improve the colonic bacterial community and mucosal immunity of pigs.However,greatly reducing the dietary CP level,even supplemented with all amino acids(AAs),detrimentally affects the colonic health,which may be due to the lack of protein-derived peptides.Therefore,this study evaluated the effects of supplementation of casein hydrolysate(peptide source)in low-protein(LP)diets,in comparison with AAs supplementation,on the colonic microbiota,microbial metabolites and mucosal immunity in pigs,aiming to determine whether a supplementation of casein hydrolysate can improve colonic health under very LP level.Twenty-one pigs(initial BW 19.90±1.00 kg,63±1 days of age)were assigned to three groups and fed with control diet(16%CP),LP diets(13%CP)supplemented with free AAs(LPA)or casein hydrolysate(LPC)for 4 weeks.Results:Compared with control diet,LPA and LPC diet decreased the relative abundance of Streptococcus and Escherichia coli,and LPC diet further decreased the relative abundance of Proteobacteria.LPC diet also increased the relative abundance of Lactobacillus reuteri.Both LP diets decreased concentrations of ammonia and cadaverine,and LPC diet also reduced concentrations of putrescine,phenol and indole.Moreover,LPC diet increased total short-chain fatty acid concentration.In comparison with control diet,both LP diets decreased protein expressions of Toll-like receptor-4,nuclear factor-κB,interleukin-1βand tumor necrosis factor-α,and LPC diet further decreased protein expressions of nucleotide-binding oligomerization domain protein-1 and interferon-γ.LPC diet also increased protein expressions of G-protein coupled receptor-43,interleukin-4,transforming growth factor-β,immunoglobulin A and mucin-4,which are indicators for mucosal defense activity.Conclusions:The results showed that supplementing casein hydrolysate showed beneficial effects on the colonic microbiota and mucosal immunity and barrier function in comparison with supplementing free AAs in LP diets.These findings may provide new framework for future nutritional interventions for colon health in pigs.

Effect of low-protein diet with supplementing different levels of DL-methionine on production performance of minks in growing-furring period

A study was conducted to evaluate production performance of minks in growing-furring period with supplementing DL-Methinnine （Met） in low protein diet. Seventy healthy male minks were randomly divided into five groups of 14 minks each. The minks were fed in five kinds of experiment diets （HP, LP, LP＋M1, LP＋M2 and LP＋M3）. The dietary protein levels, expressed as percentage of dry matter （DM）, were 32% （high protein, HP） and 24% （low protein, LP）. LP was supple- mented with Met 0.4% （M1）, 0.8% （M2） and 1.2% （M3） DM. From mid of September to December 10, apparent digestibility of CP （crude pro- tein）, N intake and urinary N excretion were decreased with declining dietary protein levels （p 〈 0.05） and N retained was the highest in treat- ment LP＋M2. No significant difference was found in total serum protein （TP） and serum urea nitrogen （SUN） among all treatment groups （p 〉 0.05）. Skin length of treatment HP and LP^M2 was higher than that of other groups （p 〈 0.05）. Body length, skin weight, length of guard hair and under hair were not affected by different dietary protein levels （p〉0.05）. The best performance could be observed in treatment LP＋M2. In diet, 24% （DM） protein level with 1.54% Met supplementing was enough for minks during growing-farring period. Dietary protein lowered from 32% to 24% with supplementing Met in diets would result in a37.9% decrease in urinary N excretion. Furthermore, addition of Met in diets for minks would be beneficial in terms of reducing feed expenses and lessening nitrogen emissions to the environment.

Effects of adding sodium dichloroacetate to low-protein diets on nitrogen balance and amino acid metabolism in the portaldrained viscera and liver of pigs

Background:Identifying regulatory measures to promote glucose oxidative metabolism while simultaneously reducing amino acid oxidative metabolism is one of the foremost challenges in formulating low-protein(LP)diets designed to reduce the excretion of nitrogen-containing substances known to be potential pollutants.In this study,we investigated the effects of adding sodium dichloroacetate(DCA)to a LP diet on nitrogen balance and amino acid metabolism in the portal-drained viscera(PDV)and liver of pigs.To measure nitrogen balance,18 barrows(40±1.0 kg)were fed one of three diets(n=6 per group):18%crude protein(CP,control),13.5%CP(LP),and 13.5%CP+100 mg DCA/kg dry matter(LP-DCA).To measure amino acid metabolism in the PDV and liver,15 barrows(40±1.0 kg)were randomly assigned to one of the three diets(n=5 per group).Four essential amino acids(Lys,Met,Thr,and Trp)were added to the LP diets such that these had amino acid levels comparable to those of the control diet.Results:The LP-DCA diet reduced nitrogen excretion in pigs relative to that of pigs fed the control diet(P<0.05),without any negative effects on nitrogen retention(P>0.05).There were no differences between the control and LP-DCA groups with respect to amino acid supply to the liver and extra-hepatic tissues in pigs(P>0.05).The net release of ammonia into the portal vein and production rate of urea in the liver of pigs fed the LP-DCA diet was reduced relative to that of pigs fed the control and LP diets(P<0.05).Conclusion:The results indicated that addition of DCA to a LP diet can efficiently reduce nitrogen excretion in pigs and maximize the supply of amino acids to the liver and extra-hepatic tissues.

Analysis of Overall Popularization of Low-Protein Diet

The shortage of protein feed resources and environmental pollution restrict the healthy and sustainable development of breeding industry,so it is imperative to promote low protein diet. Based on the current industry trends and national policies, this paper analyzes the background con-ditions, significance and specific measures of popularizing low-protein diets, in order to provide policy, theoretical and technical support for the im-plementation of low-protein diets throughout the year.

Lipid metabolism and m^(6)A RNA methylation are altered in lambs supplemented rumen-protected methionine and lysine in a low-protein diet

Background:Methionine or lysine has been reported to influence DNA methylation and fat metabolism,but their combined effects in N6-methyl-adenosine(m^(6)A)RNA methylation remain unclarified.The combined effects of rumen-protected methionine and lysine(RML)in a low-protein(LP)diet on lipid metabolism,m^(6)A RNA methylation,and fatty acid(FA)profiles in the liver and muscle of lambs were investigated.Sixty-three male lambs were divided into three treatment groups,three pens per group and seven lambs per pen.The lambs were fed a 14.5%crude protein(CP)diet(adequate protein[NP]),12.5%CP diet(LP),and a LP diet plus RML(LP+RML)for 60 d.Results:The results showed that the addition of RML in a LP diet tended to lower the concentrations of plasma leptin(P=0.07),triglyceride(P=0.05),and non-esterified FA(P=0.08).Feeding a LP diet increased the enzyme activity or m RNA expression of lipogenic enzymes and decreased lipolytic enzymes compared with the NP diet.This effect was reversed by supplementation of RML with a LP diet.The inclusion of RML in a LP diet affected the polyunsaturated fatty acids(PUFA),n-3 PUFA,and n-6 PUFA in the liver but not in the muscle,which might be linked with altered expression of FA desaturase-1(FADS1)and acetyl-Co A carboxylase(ACC).A LP diet supplemented with RML increased(P<0.05)total m^(6)A levels in the liver and muscle and were accompanied by decreased expression of fat mass and obesity-associated protein(FTO)and alk B homologue 5(ALKBH5).The m RNA expressions of methyltransferase-like 3(METTL3)and methyltransferase-like 14(METTL14)in the LP+RML diet group were lower than those in the other two groups.Supplementation of RML with a LP diet affected only liver YTH domain family(YTHDF2)proteins(P<0.05)and muscle YTHDF3(P=0.09),which can be explained by limited m^(6)Abinding proteins that were mediated in m RNA fate.Conclusions:Our findings showed that the inclusion of RML in a LP diet could alter fat deposition through modulations of lipogenesis and lipolysis in the liver and muscle.These changes in fat metabolism may be associated with the modification of m^(6)A RNA methylation.

Effects of Abrus cantoniensis Hance Extract on Blood Lipid of Laying Hen Feed with High Energy and Low Protein Diet

[Objectives]To explore the effects of Abrus cantoniensis Hance(ACH)extract on blood lipid indicators of laying hen fed with high energy and low protein diet.[Methods]Sixty 90-day-old laying hens were randomly divided into five groups:the blank control group(basic diet),the model group(high-energy and low-protein diet,HELPD),the low-dose group(HELPD+0.5 g ACH extract per hen,LACH),and the medium-dose group(HELPD+1 g ACH extract per hen,MACH),high dose group(HELPD+2 g ACH extract per hen,HACH).The ACH extract was administrated by drinking water for 48 d.[Results]Different doses of ACH could improve the pathological changes induced by high energy and low protein.ACH extract had no significant effect on blood routine indicators of laying hens(P>0.05).The contents of total cholesterol(TC),triglyceride(TG)and low density lipoprotein cholesterol(LDL-C)in the model group were significant-ly higher than those in the control group(P<0.05),while the content of high density lipoprotein cholesterol(HDL-C)was significantly lower than that in the control group(P<0.05).There was no significant difference in blood lipid between LACH group and model group(P>0.05).In MACH and HACH groups,the contents of TC,TG and LDL-C were significantly lower than those in the model group(P<0.05),and the content of HDL-C was significantly higher than that in the model group(P<0.05).[Conclusions]The ACH extract can regulate theHELPD-induced dyslipidemia in laying hens.

低蛋白饲粮中添加益生素对蛋雏鸡生长性能及营养物质利用率的影响

研究旨在探讨在低蛋白饲粮中添加益生素对蛋雏鸡早期生长和营养物质利用率的影响。选取1日龄健康麻黄鸡36只,采用单因素随机试验设计,试验设2个处理,每个处理3个重复。对照组饲喂基础饲粮,试验组饲喂低蛋白饲粮(比对照组低1.48%)并添加0.2%益生素,试验期为28 d。结果表明:整个试验期间,与对照组相比,试验组粗脂肪的表观利用率提高了7.34%(P=0.04),具有提高蛋雏鸡营养物质表观利用率,降低日采食量和料肉比及N、Ca、P排泄量的趋势(P>0.05)。

Leucine Supplementation in a Chronically Protein-Restricted Diet Enhances Muscle Weight and Postprandial Protein Synthesis of Skeletal Muscle by Promoting the mTOR Pathway in Adult Rats

Low protein intake causes a decrease in protein deposition in most animal tissues. The purpose of this study was to investigate whether leucine supplementation would increase the synthesis rate of protein and muscle weight in adult rats, which chronically consume only 58.8% of their protein requirements. Thirty-six male Sprague-Dawley rats were assigned to one of three dietary treatments including a 20% casein diet （CON）, a 10% casein ＋ 0.44% alanine diet （R）, and a 10% casein ＋ 0.87% leucine diet （RL）. After a 10 d dietary treatment, plasma amino acid levels were measured after feeding, the gastrocnemius muscles and soleus muscles were harvested and weighed, and the fractional synthesis rate （FSR） and mammalian target of rapamycin （mTOR） signaling proteins in skeletal muscle were measured. Regarding the plasma amino acid level, the RL group had the highest concentration of leucine （P 〈 0.05） and the lowest concentration of isoleucine （P 〈 0.05） among the three groups, and the CON group had a lower concentration of valine （P 〈 0.05） than the R and RL groups. Compared with the R and RE groups, the CON group diet significantly increased （P 〈 0.05） feed intake, protein synthesis rate, and the phosphorylation of eukaryutic initiation factor 4E binding protein 1 （4E-BP1）, and decreased the weight of abdominal adipose. Compared with the R group, the RL group significantly increased in gastrocnemius muscle weight, protein synthesis rate, and phosphorylation of both ribosomal protein $6 kinase 1 （56K1） and 4E-BP1. In conclusion, when protein is chronically restricted in adult rat diets, leucine supplementation moderately improves body weight gain and increases muscle protein synthesis through mTOR activation,

Different dietary starch patterns in lowprotein diets:effect on nitrogen efficiency,nutrient metabolism,and intestinal flora in growing pigs

Background:Protein releases amino acids faster than starch releases glucose in digestive tract of pigs fed lowprotein(LP)diets.Poor synchronization of dietary glucose and amino acids supply leads to compromised nitrogen efficiency.Dietary starch patterns modulation may improve this situation.Methods:Growing barrows(29.7±2.0 kg)were randomly allotted into 5 dietary treatments with LP diets consisting of different purified starches.Treatments included:waxy corn starch(W LP),corn starch+waxy corn starch(C+W LP),corn starch(C LP),pea starch+waxy corn starch(P+W LP)and pea starch(P LP).In the experiment,growth performance,protein deposition,nutrient metabolism,and fecal microbial community of pigs were investigated.In vitro starch digestion was used for predicting the in vivo glucose response.Results:Dietary starch in vitro glucose release profile was determined by starch source and the ratio of amylopectin and amylose.C+W LP treatment showed decreased total nitrogen excretion and plasma citrulline concentration and improved plasma leptin concentration among treatments(P<0.05).Besides,the highest nitrogen apparent biological value,whole-body protein deposition and growth performance and lowest urinary nitrogen excretion were also observed in C+W LP treatment.Compared with the other groups,C+W LP and C LP showed increased plasma pyruvate,IGF-1,and lipase concentrations(P<0.05).The W LP group presented dramatically increased plasma alanine and urea nitrogen concentration and decreased aldolase and leptin concentrations(P<0.05).Dietary starch patterns did not make an impact on bacterial richness and diversity,but changed the taxonomic and functional structures of the microbial communities.Microbial protein fermentation product(isobutyrate and isovalerate)presented increased in P LP treatments compared with the other treatments(P<0.05).Conclusions:Dietary starch patterns modulation can regulate dietary glucose release profile,nutrient metabolism,protein turnover,and fecal microbial fermentation in pigs.The optimal dietary glucose release profile effectively strengthened whole-body protein deposition and improve nitrogen efficiency and growth performance in growing pigs fed LP diets.

Serine-to-glycine ratios in low-protein diets regulate intramuscular fat by affecting lipid metabolism and myofiber type transition in the skeletal muscle of growing-finishing pigs

Serine and glycine are 2 of the first-affected nonessential amino acids in low crude protein(CP)diets for pigs.Therefore,we explored the effects of different dietary serine-to-glycine ratios on growth perfor-mance and lipid metabolism in growing-finishing pigs.A total of 160 crossbred healthy barrows,with a similar body weight of around 59.50 kg,were randomly allotted into 1 of 5 treatments(8 pens per treatment and 4 pigs per pen).The serine-to-glycine ratios of the 5 dietary treatments were as follows:diet A(NORMAL group),1.18∶1(16%CP);diet B(LOW group),1.2∶1(12%CP);diet C(S2G1 group),2∶1(12%CP);diet D(S1G2 group),1∶2(12%CP);and diet E(S1G1 group),1∶1(12%CP).We found that the pigs fed a low CP diet(12%CP),when maintaining serine-to-glycine ratio at 1∶2 and a total amount of 1.44%,had the same average daily gain as the pigs fed a normal CP diet(16%CP)(P>0.05),but they had increased intramuscular fat(P<0.05).Furthermore,they exhibited higher expression of genes involved in lipid oxidation(P<0.05),which was regulated by modulating methylation levels in the promoters of acyl-CoA oxidase 1(ACOX1)and acyl-CoA dehydrogenase medium chain(ACADM).When compared with the pigs fed a normal CP diet,these pigs had more oxidative myofibers(P<0.05),which were regulated by AMPK-PGC-1αand Calcineurin-MEF2/NFAT pathways in a coordinated manner.Our findings suggested that a dietary serine-to-glycine ratio of 1:2 is beneficial for improving meat quality in pigs fed a low CP diet.

Very low-protein diet to postpone renal failure: Pathophysiology and clinical applications in chronic kidney disease

The uremic syndrome is a metabolic disorder characterized by the impairment of renal handling of several solutes, the resulting accumulation of toxic products and the activation of some adaptive but detrimental mechanisms which all together contribute to the progression of renal damage. In moderate to advanced renal failure, the dietary manipulation of nutrients improves metabolic abnormalities and may contribute to delay the time of dialysis initiation. This commentary focuses on the physiopathological rationale and the clinical application of the very low-protein diet supplemented with ketoanalogs for the management of chronic kidney disease.

Low-protein diet accelerates wound healing in mice post-acute injury

Background:Wound healing processes are influenced by macronutrient intake(protein,carbohydrate and fat).The most favourable diet for cutaneous wound healing is not known,although highprotein diets are currently favoured clinically.This experimental study investigates the optimal macronutrient balance for cutaneous wound healing using a mouse model and the Geometric Framework,a nutrient modelling method,capable of analyzing the individual and interactive effects of a wide spectrum of macronutrient intake.Methods:Two adjacent and identical full-thickness skin excisions(1 cm^(2))were surgically created on the dorsal area of male C57BL/6 mice.Mice were then allocated to one of 12 high-energy diets that varied in protein,carbohydrate and fat content.In select diets,wound healing processes,cytokine expression,energy expenditure,body composition,muscle and fat reserves were assessed.Results:Using the Geometric Framework,we show that a low-protein intake,coupled with a balanced intake of carbohydrate and fat is optimal for wound healing.Mice fed a low-protein diet progressed quickly through wound healing stages with favourable wound inflammatory cytokine expression and significantly accelerated collagen production.These local processes were associated with an increased early systemic inflammatory response and a higher overall energy expenditure,related to metabolic changes occurring in key macronutrient reserves in lean body mass and fat depots.Conclusions:The results suggest that a low-protein diet may have a greater potential to accelerate wound healing than the current clinically used high-protein diets.

Dietary crude protein and protein solubility manipulation enhances intestinal nitrogen absorption and mitigates reactive nitrogen emissions through gut microbiota and metabolome reprogramming in sheep

Dietary nutrient manipulation(e.g.protein fractions)could lower the environmental footprints of ruminants,especially reactive nitrogen(N).This study investigated the impacts of dietary soluble protein(SP)levels with decreased crude protein(CP)on intestinal N absorption,hindgut N metabolism,fecal microbiota and metabolites,and their linkage with N metabolism phenotype.Thirty-two male Hu sheep,with an age of six months and an initial BW of 40.37±1.18 kg,were randomly assigned to four dietary groups.The control diet(CON),aligning with NRC standards,maintained a CP content of 16.7%on a dry matter basis.Conversely,the experimental diets(LPA,LPB,and LPC)featured a 10%reduction in CP compared with CON,accompanied by SP adjustments to 21.2%,25.9%,and 29.4%of CP,respectively.Our results showed that low-protein diets led to significant reductions in the concentrations of plasma creatinine,ammonia,urea N,and fecal total short-chain fatty acids(SCFA)(P<0.05).Notably,LPB and LPC exhibited increased total SCFA and propionate concentrations compared with LPA(P<0.05).The enrichment of the Prevotella genus in fecal microbiota associated with energy metabolism and amino acid(AA)biosynthesis pathways was evident with SP levels in low-protein diets of approximately 25%to 30%.Moreover,LPB and LPC diets demonstrated a decrease in fecal NH_(4)^(+) eN and NO_(2) eN contents as well as urease activity,compared with CON(P<0.05).Concomitantly,reductions in fecal glutamic acid dehydrogenase gene(gdh),nitrite reductase gene(nirS),and nitric oxide reductase gene(norB)abundances were observed(P<0.05),pointing towards a potential reduction in reactive N production at the source.Of significance,the up-regulation of mRNA abundance of AA and peptide transporters in the small intestine(duodenum,jejunum,and ileum)and the elevated concentration of plasma AA(e.g.arginine,methionine,aspartate,glutamate,etc.)underscored the enhancement of N absorption and N efficiency.In summary,a 10%reduction in CP,coupled with an SP level of approximately 25%to 30%,demonstrated the potential to curtail reactive N emissions through fecal Prevotella enrichment and improve intestinal energy and N utilization efficiency.