Single-base editing in IGF2 improves meat production and intramuscular fat deposition in Liang Guang Small Spotted pigs

Background Chinese indigenous pigs are popular with consumers for their juiciness,flavour and meat quality,but they have lower meat production.Insulin-like growth factor 2(IGF2) is a maternally imprinted growth factor that promotes skeletal muscle growth by regulating cell proliferation and differentiation.A single nucleotide polymorphism(SNP) within intron 3 of porcine IGF2 disrupts a binding site for the repressor,zinc finger BED-type containing 6(ZBED6),leading to up-regulation of IGF2 and causing major effects on muscle growth,heart size,and backfat thickness.This favorable mutation is common in Western commercial pig populations,but absent in most Chinese indigenous pig breeds.To improve meat production of Chinese indigenous pigs,we used cytosine base editor 3(CBE3)to introduce IGF2 intron3-C3071T mutation into porcine embryonic fibroblasts(PEFs) isolated from a male Liang Guang Small Spotted pig(LGSS),and single-cell clones harboring the desired mutation were selected for somatic cell nuclear transfer(SCNT) to generate the founder line of IGF2^(T/T) pigs.Results We found the heterozygous progeny IGF2^(C/T) pigs exhibited enhanced expression of IGF2,increased lean meat by 18%-36%,enlarged loin muscle area by 3%-17%,improved intramuscular fat(IMF) content by 18%-39%,marbling score by 0.75-1,meat color score by 0.53-1.25,and reduced backfat thickness by 5%-16%.The enhanced accumulation of intramuscular fat in IGF2^(C/T) pigs was identified to be regulated by the PI3K-AKT/AMPK pathway,which activated SREBP1 to promote adipogenesis.Conclusions We demonstrated the introduction of IGF2-intron3-C3071T in Chinese LGSS can improve both meat production and quality,and first identified the regulation of IMF deposition by IGF2 through SREBP1 via the PI3KAKT/AMPK signaling pathways.Our study provides a further understanding of the biological functions of IGF2and an example for improving porcine economic traits through precise base editing.

Developmental Changes of the FAS and HSL mRNA Expression and Their Effects on the Content of Intramuscular Fat in Kazak and Xinjiang Sheep

Twenty-four male Kazak sheep and 30 Xinjiang fine wool sheep at different ages were selected to investigate the development-dependent expression levels of fatty acid synthase （FAS） gene and hormone-sensitive lipase （HSL） gene in muscle and their effects on the contents of intramuscular fat （IMF）. Longissimus dorsal muscle was sampled to measure IMF and total RNA was extracted to determine FAS and HSL mRNA expression levels by real-time PCR. The results showed that： l） The IMF content increased continuously with growth and showed significant differences （P 〈 0.05） between different age groups in male Kazak sheep, but in Xinjiang fine wool sheep there was no such difference observed. Furthermore, the IMF contents in Kazak were much higher （P 〈 0.01） than that of the other breed from day 30 to 90. 2） FAS mRNA expression level was the highest （P 〈 0.05） on day 0 in Kazak sheep and then declined with growth, in the other breed the gene showed a d‘ecline-rise-decline-rise＇ expression manner as the animals grew. HSL mRNA expression level had a similar model in two breeds, in Kazak sheep it was the highest on day 0 （P 〈 0.05） and in Xinjiang fine wool sheep on day 30 （P 〈 0.01）, then both decreased after this term. 3） In male Kazak sheep, FAS and HSL mRNA expression level were both negatively related to IMF content （r= -0.485 （P = 0.02）, r= -0.423 （P = 0.05））, and the ratio of FAS/HSL expression exhibited significantly negatively related IMF contents. In male Xinjiang sheep, there were no obvious relationship between FAS and HSL expression and IMF content （P 〉 0.05）.

Changes of Intramuscular Fat Composition,Lipid Oxidation and Lipase Activity in Biceps femoris and Semimembranosus of Xuanwei Ham During Controlled Salting Stages

Fatty acid composition of neutral lipids （NLs）, phospholipids （PLs） and free fatty acids （FFAs） from intramuscular fat （IMF）, lipid oxidation and lipase activity in muscle Semimembranosus （SM） and msucle Biceps femoris （BF） of dry-cured Xuanwei ham during the 90-d salting stages were analysed. The salt content increased from 0.34 to 3.52%in BF and from 0.10 to 5.42%in SM during the 90 d salting stage, respectively. PLs of IMF in both BF and SM decreased 54.70%（P〈0.001） and 34.64%（P〈0.05）, furthermore, the saturated fatty acids （SFA）, monounsaturated fatty acids （MUFA） and polyunsaturated fatty acids （PUFA） of PLs in both muscles were hydrolysed almost isochronously. FFAs were increased from 0.46 g 100 g-1 lipids to 2.92 g 100 g-1 lipids in BF at the end of salting, which was lower than SM （from 1.29 g 100 g-1 lipids to 9.70 g 100 g-1 lipids）. The activities of acid lipase, neutral lipase and acid phospholipase all remained active in the 90 d. The thiobarbituric acid reactive substances （TBARS） was slowly increased to 1.34 mg kg-1 muscle in BF and to 2.44 mg kg-1 muscle in SM during the salting stage. In conclusion, the controlled salting process prompted the hydrolysis of PLs of IMF notably and increased the lipid oxidation of muscles within some limits.

A Review of Factors Influencing Intramuscular Fat Content in Porcine Meat

Intramuscular fat （IMF）, an important flavor precursor of porcine meat, is closely related to pork quality traits such as pH, color, tenderness, water-holding capacity （WHC） and juiciness, and thus is one of the important factors affecting pork quality. Pork IMF content is not only associated with swine breed on heredity, but also influenced by the alteration of nutrients in diet. These may give a possibility for researchers to improve the IMF content and pork quality by their work on swine breed or heredity, and nutrition regulation in diet. Therefore, this article summarizes the effects of swine breed and nutrition regulation on IMF content briefly to provide some information for future researches.

A selected population study reveals the biochemical mechanism of intramuscular fat deposition in chicken meat

Background:Increasing intramuscular fat(IMF)is an important strategy to improve meat quality,but the regulation mechanism of IMF deposition needs to be systematically clarified.Results:A total of 520 chickens from a selected line with improved IMF content and a control line were used to investigate the biochemical mechanism of IMF deposition in chickens.The results showed that the increased IMF would improve the flavor and tenderness quality of chicken meat.IMF content was mainly determined both by measuring triglyceride(TG)and phospholipid(PLIP)in muscle tissue,but only TG content was found to be decisive for IMF deposition.Furthermore,the increase in major fatty acid(FA)components in IMF is mainly derived from TGs(including C16:0,C16:1,C18:1n9c,and C18:2n6c,etc.),and the inhibition of certain very-long-chain FAs would help to IMF/TG deposition.Conclusions:Our study elucidated the underlying biochemical mechanism of IMF deposition in chicken:Prevalent accumulation of long-chain FAs and inhibitions of medium-chain FAs and very long chain FA would jointly result in the increase of TGs with the FA biosynthesis and cellular uptake ways.Our findings will guide the production of high-quality chicken meat.

In vivo prediction of intramuscular fat in pigs using computed tomography

One hundred and four pure-bred Norwegian Duroc boars were CT (computed tomography) scanned to predict the in vivo intramuscular fat percentage in the loin. The animals were slaughtered and the loin was cut commercially. A muscle sample of the m. Longissimus dorsi was sampled and analyzed by the use of near-infrared spectroscopy. Data from CT images were collected using an in-house MATLAB script. Calibration models were made using PLS (partial least square) regression, containing independent data from CT images and dependent data from near-infrared spectroscopy. The data set used for calibration was a subset of 72 animals. The calibration models were validated using a subset of 32 animals. Scaling of independent data and filtering using median filtering were tested to improve predictions. The results showed that CT is not a feasible method for in vivo prediction of intramuscular content in swine.

Dietary calcium supplementation promotes the accumulation of intramuscular fat

Background:In the livestock industry,intramuscular fat content is a key factor affecting meat quality.Many studies have shown that dietary calcium supplementation is closely related to lipid metabolism.However,few studies have examined the relationship between dietary calcium supplementation and intramuscular fat accumulation.Methods:Here,we used C2C12 cells,C57BL/6 mice(n=8)and three-way cross-breeding pigs(Duroc×Landrace×Large white)(n=10)to study the effect of calcium addition on intramuscular fat accumulation.In vitro,we used calcium chloride to adjust the calcium levels in the medium(2 mmol/L or 3 mmol/L).Then we measured various indicators.In vivo,calcium carbonate was used to regulate calcium levels in feeds(Mice:0.5%calcium or 1.2%calcium)(Pigs:0.9%calcium or 1.5%calcium).Then we tested the mice gastrocnemius muscle triglyceride content,pig longissimus dorsi muscle meat quality and lipidomics.Results:In vitro,calcium addition(3 mmol/L)had no significant effect on cell proliferation,but promoted the differentiation of C2C12 cells into slow-twitch fibers.Calcium supplementation increased triglyceride accumulation in C2C12 cells.Calcium addition increased the number of mitochondria and also increased the calcium level in the mitochondria and reduced the of key enzymes activity involved inβ-oxidation such as acyl-coenzyme A dehydrogenase.Decreasing mitochondrial calcium level can alleviate lipid accumulation induced by calcium addition.In addition,calcium addition also reduced the glycolytic capacity and glycolytic conversion rate of C2C12 cells.In vivo,dietary calcium supplementation(1.2%)promoted the accumulation of triglycerides in the gastrocnemius muscle of mice.Dietary calcium supplementation(1.5%)had no effect on pig weight,but significantly improved the flesh color of the longissimus dorsi muscle,reduced the backfat thickness and increased intramuscular fat content in pigs.Besides,calcium addition had no effect on longissimus dorsi pH,electrical conductivity and shear force.Conclusions:These results suggest that calcium addition promotes intramuscular fat accumulation by inhibiting the oxidation of fatty acids.These findings provide a new tool for increasing intramuscular fat content and an economical strategy for improving meat quality.

Linoleic acid metabolic pathway allows for an efficient increase of intramuscular fat content in pigs

Background: Intramuscular fat(IMF) content is a relevant trait for high-quality meat products such as dry-cured ham,but increasing IMF has the undesirable correlated effect of decreasing lean growth.Thus,there is a need to find selection criteria for IMF independent from lean growth.In pigs,the proportion of linoleic(C18:2) and arachidonic(C20:4) acids decline with fat deposition and therefore they can be considered as indicators of fatness.The aim of this research was to estimate the genetic variation for C18:2 and C20:4 in IMF and their genetic correlations with IMF and lean growth traits,with the objective to assess their potential as specific biomarkers of IMF.The analysis was conducted using a full-pedigreed Duroc resource line with 91,448 records of body weight and backfat thickness(BT) at 180 days of age and 1371 records of fatty acid composition in the muscle gluteus medius.Results: The heritability estimates for C18:2 and C20:4 in IMF,whether expressed in absolute(mg/g of muscle) or in relative(mg/g of fatty acid) terms,as well as for their ratio(C20:4/C18:2),were high(> 0.40),revealing that the C18:2 to C20:4 pathway is subjected to substantial genetic influence.Litter effects were not negligible,with values ranging from8% to 15% of the phenotypic variance.The genetic correlations of C18:2 and C20:4 with IMF and BT were negative(-0.75 to-0.66,for IMF,and-0.64 to-0.36,for BT),if expressed in relative values,but almost null(-0.04 to 0.07),if expressed in absolute values,except for C18:2 with IMF,which was highly positive(0.88).The ratio of C20:4 to C18:2 also displayed a stronger genetic correlation with IMF(-0.59) than with BT(-0.10).Conclusions: The amount of C18:2 in muscle can be used as an IMF-specific biomarker.Selection for the absolute amount of C18:2 is expected to deliver a similar response outcome as selection for IMF at restrained BT.Further genetic analysis of the C18:2 metabolic pathway may provide new insights into differential fat deposition among adipose tissues and on candidate genes for molecular markers targeting specifically for one of them.

Activation of skeletal carbohydrate-response element binding protein(ChREBP)-mediated de novo lipogenesis increases intramuscular fat content in chickens

The intracellular lipids in muscle cells of farm animals play a crucial role in determining the overall intramuscular fat(IMF)content,which has a positive impact on meat quality.However,the mechanisms underlying the deposition of lipids in muscle cells of farm animals are not yet fully understood.The purpose of this study was to determine the roles of carbohydrate-response element binding protein(ChREBP)and fructose in IMF deposition of chickens.For virus-mediated ChREBP overexpression in tibialis anterior(TA)muscle of chickens,seven 5-d-old male yellow-feather chickens were used.At 10 d after virus injection,the chickens were slaughtered to obtain TA muscles for analysis.For fructose administration trial,sixty 9-wk-old male yellow-feather chickens were randomly divided into 2 groups,with 6 replicates per group and 5 chickens per replicate.The chickens were fed either a basal diet or a basal diet supplemented with 10%fructose(purity≥99%).At 4 wk later,the chickens were slaughtered,and breast and thigh muscles were collected for analysis.The results showed that the skeletal ChREBP mRNA levels were positively associated with IMF content in multiple species,including the chickens,pigs,and mice(P<0.05).ChREBP overexpression increased lipid accumulation in both muscle cells in vitro and the TA muscles of mice and chickens in vivo(P<0.05),by activation of the de novo lipogenesis(DNL)pathway.Moreover,activation of ChREBP by dietary fructose administration also resulted in increased IMF content in mice and notably chickens(P<0.05).Furthermore,the lipidomics analysis revealed that ChREBP activation altered the lipid composition of chicken IMF and tented to improve the flavor profile of the meat.In conclusion,this study found that ChREBP plays a pivotal role in mediating the deposition of fat in chicken muscles in response to fructose-rich diets,which provides a novel strategy for improving meat quality in the livestock industry.

Lysine 2-hydroxyisobutyrylation levels determined adipogenesis and fat accumulation in adipose tissue in pigs

Background Excessive backfat deposition lowering carcass grade is a major concern in the pig industry,especially in most breeds of obese type pigs.The mechanisms involved in adipogenesis and fat accumulation in pigs remain unclear.Lysine 2-hydroxyisobutyrylation(Khib),is a novel protein post-translational modification(PTM),which play an important role in transcription,energy metabolism and metastasis of cancer cells,but its role in adipogenesis and fat accumulation has not been shown.Results In this study,we first analyzed the modification levels of acetylation(Kac),Khib,crotonylation(Kcr)and succinylation(Ksu)of fibro-adipogenic progenitors(FAPs),myogenic precursors(Myo)and mesenchymal stem cells(MSCs)with varied differentiation potential,and found that only Khib modification in FAPs was significantly higher than that in MSCs.Consistently,in parallel with its regulatory enzymes lysine acetyltransferase 5(KAT5)and histone deacetylase 2(HDAC2)protein levels,the Khib levels increased quadratically(P<0.01)during adipogenic differentiation of FAPs.KAT5 knockdown in FAPs inhibited adipogenic differentiation,while HDAC2 knockdown enhanced adipogenic differentiation.We also demonstrated that Khib modification favored to adipogenic differentiation and fat accumulation by comparing Khib levels in FAPs and backfat tissues both derived from obese-type pigs(Laiwu pigs)and lean-type pigs(Duroc pigs),respectively.Accordingly,the expression patterns of KAT5 and HDAC2 matched well to the degree of backfat accumulation in obese-and lean-type pigs.Conclusions From the perspective of protein translational modification,we are the first to reveal the role of Khib in adipogenesis and fat deposition in pigs,and provided new clues for the improvement of fat accumulation and distribution as expected via genetic selection and nutritional strategy in obese-type pigs.

Subcutaneous and intramuscular fat transcriptomes show large differences in network organization and associations with adipose traits in pigs

Subcutaneous fat(SCF)and intramuscular fat(IMF)deposition is relevant to health in humans,as well as meat production and quality in pigs.In this study,we generated RNA sequence data for 122 SCF,120 IMF,and 87 longissimus dorsi muscle(LDM)samples using 155 F6 pigs from a specially designed heterogeneous population generated by intercrossing four highly selected European commercial breeds and four indigenous Chinese pig breeds.The phenotypes including waist back fat thickness and intramuscular fat content were also measured in the 155 F6 pigs.We found that the genes in SCF and IMF differed largely in both expression levels and network connectivity,and highlighted network modules that exhibited strongest gain of connectivity in SCF and IMF,containing genes that were associated with the immune process and DNA double-strand repair,respectively.We identified 215 SCF genes related to kinase inhibitor activity,mitochondrial fission,and angiogenesis,and 90 IMF genes related to lipolysis and fat cell differentiation,displayed a tissue-specific association with back fat thickness and IMF content,respectively.We found that cis-expression QTL for trait-associated genes in the two adipose tissues tended to have tissuedependent predictability for the two adipose traits.Alternative splicing of genes was also found to be associated with SCF or IMF deposition,but the association was much less extensive than that based on expression levels.This study provides a better understanding of SCF and IMF gene transcription and network organization and identified critical genes and network modules that displayed tissue-specific associations with subcutaneous and intramuscular fat deposition.These features are helpful for designing breeding programs to genetically improve the two adipose traits in a balanced way.

Multi-omics analysis reveals gut microbiota-induced intramuscular fatdeposition via regulating expression of lipogenesis-associated genes

The gut microbiome has great effects on the digestion, absorption, and metabolism of lipids. However,the microbiota composition that can alter the fat deposition and the meat quality of pigs remains unclear.Here, we used Laiwu (LW) pigs (a native Chinese breed with higher intramuscular fat) compared withcommercial crossbreed Duroc×(Landrace×Yorkshire) (DLY) pigs to investigate the effects of microbiotaon meat quality, especially in intramuscular fat content. A total of 32 DLY piglets were randomly allottedto 4 groups and transplanted with fecal microbiota from healthy LW pigs. The results indicated that thehigh dose of fecal microbiota transplantation (HFMT) selectively enhanced fat deposition in longissimusdorsi (P < 0.05) but decreased backfat thickness (P < 0.05) compared with control group. HFMT significantlyaltered meat color and increased feed conversation ratio (P < 0.05). Furthermore, the multi-omicsanalysis revealed that Bacteroides uniformis, Sphaerochaeta globosa, Hydrogenoanaerobacterium saccharovorans,and Pyramidobacter piscolens are the core species which can regulate lipid deposition. A total of140 male SPF C57BL/6j mice were randomly allotted into 7 groups and administrated with these 4 microbesalone or consortium to validate the relationships between microbiota and lipid deposition.Inoculating the bacterial consortium into mice increased intramuscular fat content (P < 0.05) comparedwith control mice. Increased expressions of lipogenesis-associated genes including cluster of differentiation36 (Cd36), diacylglycerol O-acyltransferase 2 (Dgat2), and fatty acid synthase (FASN) wereobserved in skeletal muscle in the mice with mixed bacteria compared with control mice. Together, ourresults suggest that the gut microbiota may play an important role in regulating the lipid deposition in the muscle of pigs and mice.

Follicle-stimulating hormone increases the intramuscular fat content and expression of lipid biosynthesis genes in chicken breast muscle

Intramuscular fat （IMF） is a crucial factor in the quality of chicken meat. The genetic basis underlying it is complex. Follicle-stimulating hormone （FSH）, well-known as an effector in reproductive tissues, was recently discovered to stimulate abdominal fat accumulation in chicken. The effect of FSH on IMF accumulation and the underlying molecular regulatory mechanisms controlling both IMF and abdominal fat deposition in vivo are largely unknown. In this study, two groups of chickens were treated with chicken FSH or a placebo. The lipid content of breast muscle, abdominal fat volume, and serum concentrations of FSH were examined. Related genes implicated in breast muscle and abdominal fat accumulation were also investigated. Compared to the control group, the triglyceride （TG） content of breast muscle and the percentage of abdominal fat in FSH-treated chickens were significantly increased by 64.9% and 56.5% （P〈0.01）, respectively. The FSH content in the serum of FSH-treated chickens was 2.1 times than that of control chickens （P〈0.01）. Results from quantitative real-time polymerase chain reaction （qRT-PCR） assays showed that relative expression levels of fatty acid synthase （FAS）, lipoprotein lipase （LPL）, diacylglycerol acyltransferase 2 （DGAT2）, adipocyte fatty acid binding protein （A-FABP）, and peroxisome proliferator-activated receptor ~ （PPARy） were significantly upregulated in breast muscle following FSH treatment （P〈0.01）. Treatment with FSH also signifi- cantly increased relative expression levels of FAS, LPL, DGA T2, A-FABP, and PPARy in abdominal fat tissue （P〈0.05） The results of principal component analysis （PCA） for gene expression （breast muscle and abdominal fat） showed that the control and FSH treatment groups were well separated, which indicated the reliability of the data. This study demonstrates that FSH plays an important role in IMF accumulation in female chickens, which likely involves the regulation of biosynthesis genes related to lipid metabolism.

Genome-wide association analysis reveals genetic loci and candidate genes associated with intramuscular fat in Duroc pigs

Intramuscular fat(IMF) is a major meat-quality trait in pigs. The content of IMF is directly associated with the taste and flavor of pork. As a complex trait, there could be multiple genes affecting IMF content in pork. Genomewide association study is a powerful tool to detect genomic regions associated with phenotypic variations. The objectives of the present study were to identify or refine the positions of genomic regions affecting IMF, and to characterize candidate genes and pathways that may influence this trait. Of note, we identified a significant region in longissium dorsi muscle in a Duroc pig population for IMF content with Porcine SNP60 v2 Bead Chip. This region spans 1.24 Mb on chromosome 8 and had been identified as a quantitative trait locus for IMF in Pietrain, Large White, Landrace, and Leicoma pigs. In this region, eight SNPs were significantly associated with IMF content. Three genes proximal to these significant SNPs were considered candidate genes, including ZDHHC16, LOC102162218 and PCDH7. Our results confirm several previous findings and highlight several genes that may contribute to IMF variation in Duroc pigs.

The relationship between body mass index, thickness of subcutaneous fat, and the gluteus muscle as the intramuscular injection site

An intramuscular injection (IMI) is an injection given directly into the central area of a specific muscle. Certain medicines need to be administered by the gluteal route for these to be effective. The aim of this study was to determine the influence of body mass index (BMI), subcutaneous fat, and muscular thickness of the dorsogluteal IMI site among healthy Japanese women. There were 39 healthy female subjects who volunteered and met the criteria. Their ages ranged from 40s to 60s (50.82 ± 6.04). With the data collected using the B-mode ultrasound images of the dorsogluteal site, it was found that the distance from the epidermis to the under-fascia (DEUF) of the gluteus maximus was dissimilar between the subject’s right and left buttocks. It was found that the distance from the epidermis to the iliac bone (DEI) was significantly more on the right than on the left buttocks. In the case of an adult Japanese woman with a BMI of 21 or more, the DEUF of the gluteus medius was found to be about 30 mm, and the DEI was approximately 50 mm or more. Based on these findings, it is recommended that a needle length of 38 mm (1.5 inches) can be safely used to administer IMIs to the gluteus medius muscle to effectively and efficiently deliver medications through the IMI route.

调控肉牛肌内脂肪沉积的分子机制研究进展

肉牛肌内脂肪(intramuscular fat,IMF)是指存在于肌纤维内的脂肪组织,含量与牛肉的多汁性、嫩度和适口性呈正相关关系,是决定牛肉质量等级的重要因素之一。明确肉牛IMF沉积的产生和调控机制是提高牛肉IMF含量的有效途径。文章对肉牛IMF沉积过程及调控IMF沉积的候选基因、转录因子和非编码RNA(non-coding RNA,ncRNA)进行综述,旨在为进一步解析肉牛IMF沉积的分子机制和推动肉牛肉质性状选育进程提供参考。

Exploring the associations between skeletal muscle echogenicity and physical function in aging adults:A systematic review with meta-analyses

Background:Assessment and quantification of skeletal muscle within the aging population is vital for diagnosis,treatment,and injury/disease prevention.The clinical availability of assessing muscle quality through diagnostic ultrasound presents an opportunity to be utilized as a screening tool for function-limiting diseases.However,relationships between muscle echogenicity and clinical functional assessments require authoritative analysis.Thus,we aimed to(a) synthesize the literature to assess the relationships between skeletal muscle echogenicity and physical function in older adults(≥60 years),(b) perform pooled analyses of relationships between skeletal muscle echogenicity and physical function,and(c) perform sub-analyses to determine between-muscle relationships.Methods:CINAHL,Embase,MEDLINE,PubMed,and Web of Science databases were systematically searched to identify articles relating skeletal muscle echogenicity to physical function in older adults.Risk-of-bias assessments were conducted along with funnel plot examination.Meta-analyses with and without sub-analyses for individual muscles were performed utilizing Fisher's Z transformation for the most common measures of physical function.Fisher's Z was back-transformed to Pearson's r for interpretation.Results:Fifty-one articles(n=5095,female=~2759,male=~2301,72.5± 5.8 years,mean±SD(1 study did not provide sex descriptors))were extracted for review,with previously unpublished data obtained from the authors of 13 studies.The rectus femoris(n=34) and isometric knee extension strength(n=22) were the most accessed muscle and physical qualities,respectively.The relationship between quadriceps echogenicity and knee extensor strength was moderate(n=2924,r=-0.36(95% confidence interval:-0.38 to-0.32),p <0.001),with all other meta-analyses(grip strength,walking speed,sit-to-stand,timed up-and-go) resulting in slightly weaker correlations(r:-0.34 to-0.23,all p <0.001).Sub-analyses determined minimal differences in predictive ability between muscle groups,although combining muscles(e.g.,rectus femoris+vastus lateralis) often re sulted in stronger correlations with maximal strength.Conclusion:While correlations are modest,the affordable,portable,and noninvasive ultrasonic assessment of muscle quality is a consistent predictor of physical function in older adults.Minimal between-muscle differences suggest that echogenicity estimates of muscle quality are systemic.Therefore,practitioners may be able to scan a single muscle to estimate full-body skeletal muscle quality/composition,while researchers should consider combining multiple muscles to strengthen the model.

影响肉牛肌内脂肪沉积的主要通路

决定大理石花纹水平的肌内脂肪含量被认为是影响牛肉嫩度、多汁性、风味和颜色等感官质量的重要因素之一。脂肪细胞的成熟须经历细胞增殖和细胞分化两个阶段。在此过程中,一些促进因子(包括PPARγ、IGF-l等)以及抑制因子(包括糖蛋白、转化生长因子β等)协同作用,通过不同通路影响肌内脂肪沉积。本文分析了脂肪生成的转录调控,阐述了信号通路在脂肪生成中的作用,以期为相关研究人员提高牛肉大理石花纹水平提供参考。

动物肌内脂肪沉积的影响因素及其分子机制

肌内脂肪(IMF)指在肌肉内、肌纤维间所沉积的脂肪,其含量与肌肉的多汁度、剪切力、嫩度以及肉质显著正相关,因此合理的IMF含量将有助于改善肉品的质量和提高其风味。IMF生成的过程涉及复杂且高度协调的基因表达调控程序,受多种因素影响。因此,本文综述了影响动物IMF沉积的转录因子、关键代谢酶、信号通路以及非编码RNA。研究显示,转录因子在调节脂肪细胞分化和脂肪合成的过程中起着重要作用;酶催化反应则介导了脂肪生成和降解的关键步骤;此外,通过调控特定信号通路和非编码RNA的表达,也能够对IMF沉积进行调控。深入了解和运用这些分子机制对于肉制品质量的提升和生产优质肉制品具有重要意义。本综述为进一步研究和运用这些分子机制提供了参考依据,以期改善肉制品的质量,满足消费者对优质肉制品的需求。

去势对武定鸡胸肌组织脂质组成的影响

为揭示去势对鸡胸肌组织脂质组成的影响,试验采用索氏提取法和UHPLC/Q-TOF-MS检测技术对去势组和假手术组武定鸡肌肉组织进行肌内脂肪(IMF)含量测定和非靶向脂质组学研究。结果显示:去势组武定鸡胸肌组织IMF含量显著高于假手术组(P<0.05);脂质组学检测到21种脂质亚类和553个脂质分子,其中去势组胸肌组织单糖基神经酰胺(CerG1)、脂肪酸(FA)、溶血磷脂酰甘油(LPG)、溶血磷脂乙醇胺(LPE)、溶血磷脂酰丝氨酸(LPS)、辅酶(Co)、磷脂酰甘油(PG)、神经酰胺(Cer)、磷脂酰乙醇胺(PE)、鞘氨醇(So)、甘油二酯(DG)、心磷脂(CL)、磷脂酰胆碱(PC)、甘油三酯(TG)、酰基肉碱(AcCa)、磷脂酰肌醇(PI)和磷脂酰丝氨酸(PS)丰度上调,溶血磷脂酰胆碱(LPC)、鞘磷脂(SM)、溶血磷脂酰肌醇(LPI)、单半乳糖基二酰甘油酯(MGDG)丰度下调;筛选出16种差异脂质分子,其中去势组胸肌组织PE(18∶1p/20∶4)、PE(18∶0/18∶1)、PE(38∶2p)、PE(18∶0e/22∶6)、PC(38∶6)、PC(34∶1e)、PS(41∶4)、PS(18∶0/22∶4)、LPC(22∶5)、LPI(20∶4)、PI(16∶0/20∶4)、Cer(d18∶1/24∶1)、Cer(d18∶1/24∶1)、TG(16∶0/8∶0/16∶0)丰度上调,PC(39∶5)和PI(16∶0/20∶3)丰度下调(VIP>1,P<0.05)。结果表明,去势促进武定鸡胸肌组织IMF沉积,影响脂质组成,改善肉质特性。