Identification of polymorphisms influencing feed intake and efficiency in beef cattle

Feed efficiency is an economically important trait in beef cattle. Net feed efficiency, measured as residual feed intake (RFI), is the difference between actual feed intake and the predicted feed intake required for maintenance and gain of the animal. SNPs that show associations with RFI may be useful quantitative trait nucleotides for marker-assisted selection. This study identified associations between SNPs underlying five RFI QTL on five bovine chromosomes (BTA2, 5, 10, 20 and 29) with measures of dry matter intake (DMI), RFI and feed conversion ratio (FCR) in beef cattle. Six SNPs were found to have effects on RFI (P < 0.05). The largest single SNP allele substitution effect for RFI was -0.25 kg/day located on BTA2. The combined effects of the SNPs found significant in this experiment explained 6.9% of the phenotypic variation of RFI. Not all the RFI SNPs showed associations with DMI and FCR even though these traits are highly correlated with RFI (r = 0.77 and r = 0.62 respectively). This shows that these SNPs may be affecting the underlying biological mechanisms of feed efficiency beyond feed intake control and weight gain efficiency. These SNPs can be used in marker-assisted selection but first it will be important to verify these effects in independent populations of cattle.     

Association of single nucleotide polymorphisms in the microRNA miR‐1596 locus with residual feed intake in chickens

MicroRNAs are an abundant class of small non‐coding RNAs that regulate gene expression. Genetic variations in microRNA sequences may be associated with phenotype differences by influencing the expression of microRNAs and/or their targets. This study identified two single nucleotide polymorphisms (SNPs) in the genomic region of the microRNA miR‐1596 locus of chicken. Of the two SNPs, one was 95 bp upstream of miR‐1596 (g.5678784A>T) and the other was in the middle of the sequence producing the mature microRNA gga‐miR‐1596‐3p (g.5678944A>G). Genotypic distribution of the two SNPs had large differences among 12 chicken breeds (lines), especially between the fast‐growing commercial lines and the slow‐growing Chinese indigenous breeds for the g.5678784A>T SNP. Only the g.5678784A>T SNP was significantly associated with residual feed intake (RFI) in the F₂ population derived from a fast‐growing and a slow‐growing broiler as well as in the pure Huiyang bearded chicken. The birds with the AA genotype of the g.5678784A>T SNP had lower RFI and higher expression of the mature gga‐miR‐1596‐3p microRNA of miR‐1596 than did those with the other genotypes of the same SNP. We also found that the expression of the mature gga‐miR‐1596‐3p microRNA of miR‐1596 was significantly associated with RFI. These findings suggest that miR‐1596 can become a candidate gene related to RFI, and its genetic variation may contribute to changes in RFI by altering expression levels of the mature gga‐miR‐1596‐3p microRNA in chicken.     

Mitochondrial abundance and function in muscle from beef steers with divergent residual feed intakes

The objective of this study was to evaluate the relationship between muscle mitochondrial function and residual feed intake (RFI) in growing beef cattle. A 56-day feeding trial was conducted with 81 Angus × Hereford steers (initial BW = 378 ± 43 kg) from the University of California Sierra Foothills Research Station (Browns Valley, CA, USA). All steers were individually fed the same finishing ration (metabolizable energy = 3.28 Mcal/kg DM). Average daily gain (ADG), DM intake (DMI) and RFI were 1.82 ± 0.27, 8.89 ± 1.06 and 0.00 ± 0.55 kg/day, respectively. After the feeding trial, the steers were categorized into high, medium and low RFI groups. Low RFI steers consumed 13.6% less DM (P < 0.05) and had a 14.1% higher G : F ratio (P < 0.05) than the high RFI group. No differences between RFI groups were found in age, ADG or BW (P > 0.10). The most extreme individuals from the low and high RFI groups were selected to assess mitochondrial function (n = 5 low RFI and n = 6 high RFI). Mitochondrial respiration was measured using an oxygraph (Hansatech Instruments Ltd., Norfolk, UK). State 3 and State 4 respiration rates were similar between both groups (P > 0.10). Respiratory control ratios (RCRs, i.e., State 3 : State 4 oxygen uptakes) declined with animal age and were greater in low RFI steers (4.90) as compared to high RFI steers (4.26) when adjusted for age by analysis of covariance (P = 0.003). Mitochondrial complex II activity levels per gram of muscle were 42% greater in low RFI steers than in high RFI steers (P = 0.004). These data suggest that skeletal muscle mitochondria have greater reserve respiratory capacity and show greater coupling between respiration and phosphorylation in low RFI than in high RFI steers.     

Protective effects of AMP‐activated protein kinase in the cardiovascular system

Cardiovascular diseases remain the leading cause of mortality worldwide. Recent studies of AMP-activated protein kinase (AMPK), a highly conserved sensor of cellular energy status, suggest that there might be therapeutic value in targeting the AMPK signaling pathway. AMPK is found in most mammalian tissues, including those of the cardiovascular system. As cardiovascular diseases are typically associated with blood flow occlusion and blood occlusion may induce rapid energy deficit, AMPK activation may occur during the early phase upon nutrient deprivation in cardiovascular organs. Therefore, investigation of AMPK in cardiovascular organs may help us to understand the pathophysiology of defence mechanisms in these organs. Recent studies have provided proof of concept for the idea that AMPK is protective in heart as well as in vascular endothelial and smooth muscle cells. Moreover, dysfunction of the AMPK signalling pathway is involved in the genesis and development of various cardiovascular diseases, including atherosclerosis, hypertension and stroke. The roles of AMPK in the cardiovascular system, as they are currently understood, will be presented in this review. The interaction between AMPK and other cardiovascular signalling pathways such as nitric oxide signalling is also discussed.     

Changes in contraction‐induced phosphorylation of AMP‐activated protein kinase and mitogen‐activated protein kinases in skeletal muscle after ovariectomy

Recent evidence suggests that ovarian hormones contribute to altered function of skeletal muscle, however the signaling processes thought to regulate muscle function remain undefined in females. Thus, the purpose of this investigation is to determine if ovarian hormone status is critical for contraction‐induced activation of AMPK or MAPK in skeletal muscle. Female mice were divided into two groups, ovariectomy (OVX) and SHAM, which were then subjected to in situ isometric contractile protocols. AMPK, ERK 1/2, p38, and JNK phosphorylation were measured in the control and contracting limb. In the in situ protocol, OVX muscles were significantly more resistant to fatigue compared to the SHAM animals. In addition, the muscles from OVX mice demonstrated significantly lower levels of normalized AMPK phosphorylation at rest. AMPK phosphorylation was not increased in the muscles from SHAM mice after the in situ contractile protocol, while the OVX demonstrated significant increases in AMPK phosphorylation. After contraction, normalized ERK2 phosphorylation was significantly higher in the OVX group compared to the SHAM group. Both p38 and JNK phosphorylation increased in response to contraction; but no group differences were detected. A second set of SHAM and OVX animals were subjected to fatigue stimulated under in vitro conditions. Significant increases in AMPK and ERK2 phosphorylation were detected, but no differences were found between groups. In conclusion, removal of the ovaries results in different responses to contraction‐induced changes in phosphorylation of AMPK and ERK2 in female mice and suggests hormones secreted from the ovaries significantly impacts cellular signaling in skeletal muscle. J. Cell. Biochem. 107: 171–178, 2009. © 2009 Wiley‐Liss, Inc.     

Genetic markers on BTA14 predictive for residual feed intake in beef steers and their effects on carcass and meat quality traits

With the high cost of feed for animal production, genetic selection for animals that metabolize feed more efficiently could result in substantial cost savings for cattle producers. The purpose of this study was to identify DNA markers predictive for differences among cattle for traits associated with feed efficiency. Crossbred steers were fed a high‐corn diet for 140 days and average daily feed intake (ADFI), average daily gain (ADG), and residual feed intake (RFI) phenotypes were obtained. A region on chromosome 14 was previously associated with RFI in this population of animals. To develop markers with the highest utility for predicting an animal's genetic potential for RFI, we genotyped additional markers within this chromosomal region. These polymorphisms were genotyped on the same animals (n = 1066) and tested for association with ADFI, ADG and RFI. Six markers within this region were associated with RFI (P ≤ 0.05). After conservative correction for multiple testing, one marker at 25.09 Mb remained significant (P = 0.02) and is responsible for 3.6% of the RFI phenotypic variation in this population of animals. Several of these markers were also significant for ADG, although none were significant after correction. Marker alleles with positive effects on ADG corresponded to lower RFI, suggesting an effect increasing growth without increasing feed intake. All markers were also assessed for their effects on meat quality and carcass traits. All of the markers associated with RFI were associated with adjusted fat thickness (AFT, P ≤ 0.009) and three were also associated with hot carcass weight (HCW, P ≤ 0.003). Marker alleles associated with lower RFI were also associated with reduced AFT, and if they were associated for HCW, the effect was an increase in weight. These markers may be useful as prediction tools for animals that utilize feed more efficiently; however, validation with additional populations of cattle is required.     

Berberine suppresses neuroinflammatory responses through AMP‐activated protein kinase activation in BV‐2 microglia

The AMPK cascade is a sensor of cellular energy change, which monitors the AMP/ATP ratio to regulate cellular metabolism by restoring ATP levels, but its regulation of neuroinflammation mechanism remains unclear. Berberine, one of the major constituents of Chinese herb Rhizoma coptidis, has been shown to improve several metabolic disorders, such as obesity and type II diabetes. However, the effect of berberine on neuroinflammatory responses in microglia are poorly understood. This study shows that berberine represses proinflammatory responses through AMP‐activated protein kinase (AMPK) activation in BV‐2 microglia. Our findings also demonstrate that berberine significantly down‐regulates LPS‐ or interferon (IFN)‐γ‐induced nitric oxide synthase (iNOS) and cyclo‐oxygenase‐2 (COX‐2) expression in BV‐2 microglia cells. Berberine also inhibited LPS‐ or IFN‐γ‐induced nitric oxide production. In addition, berberine effectively inhibited proinflammatory cytokines such as TNF‐α, IL‐1β, and IL‐6 expression. On the other hand, upon various inflammatory stimulus including LPS and IFN‐γ, berberine suppressed the phosphorylated of ERK but not p38 and JNK in BV‐2 microglia. AMPK activation is catalyzed by upstream kinases such as LKB1 and Ca2+/calmodulin‐dependent protein kinase kinase‐II (CaMKK II). Moreover, berberine induced LKB1 (Ser428), CaMKII (Thr286), and AMPK (Thr172) phosphorylation, but not AMPK (Ser485). Furthermore, the inhibitory effect of berberine on iNOS and COX‐2 expression was abolished by AMPK inhibition via Compound C, an AMPK inhibitor. Berberine‐suppressed ERK phosphorylation was also reversed by Compound C treatment. Our data demonstrate that berberine significantly induces AMPK signaling pathways activation, which is involved in anti‐neuroinflammation. J. Cell. Biochem. 110: 697–705, 2010. © 2010 Wiley‐Liss, Inc.     

The relationship between energy status and AMP‐activated protein kinase in human H460 lung cancer cells

In cultured cells, glucose and serum provide constant sources of energy and growth factors, both of which are important for cell survival and proliferation. AMP‐activated protein kinase (AMPK) plays a key role in sensing intracellular ATP levels and acts as a critical regulator of energy homeostasis. To investigate the relationship between energy status and AMPK activity in lung cancer, H460 cells were starved in either glucose‐free or serum‐free medium and then re‐stimulated with glucose and serum, respectively. The levels of ATP and lactate and the activities of AMPK and lactate dehydrogenase (LDH) were analyzed at different time intervals. During glucose treatment, the activity of AMPK was induced by glucose and showed biphasic reaction kinetics. The ATP level was gradually increased up to 2‐fold compared with that in serum treatment after 24 h and lactate level was decreased to approximately 60%. The LDH activity slightly increased and reached a peak after 6 h. During serum treatment, the activity of AMPK was suppressed and the ATP level showed a dramatic 30% increase after 1 h. In contrast, the lactate level was gradually increased and then reverted to the background level after 24 h. The activity of LDH was slightly decreased after 12 h and eventually returned to the background level. This study showed the alteration of energy status in lung cancer cells in response to altered levels of glucose and serum. We suggest that the activation of AMPK and inhibition of glycolysis might be exploited as therapeutic tactics in cancer treatment. Copyright © 2010 John Wiley & Sons, Ltd.     

A new mutation in the coding region of the bovine leptin gene associated with feed intake

An experimental cattle population was screened for polymorphisms in the leptin gene and five SNPs were found in the regions containing the coding sequences. The association of these polymorphisms with feed intake and fat-related traits was evaluated. The results suggest an association between a polymorphism in exon 2, described here for the first time, and feed intake. Individuals with genotype A/T at this position had 19% greater mean feed intake than individuals with genotype A/A. There was also evidence for a link between leptin haplotypes and some fat-related traits.     

Single nucleotide polymorphisms in the corticotrophin-releasing hormone and pro-opiomelancortin genes are associated with growth and carcass yield in beef cattle

A single nucleotide polymorphism (SNP) in the corticotrophin-releasing hormone gene (CRH C22G) alters the fourth amino acid in the signal sequence from proline to arginine. Two other SNPs (CRH A145G and C240G) occur in the propeptide region at residue positions 45 and 77, respectively, that result in serine/asparagine and histidine/aspartic acid substitutions respectively. These SNPs, as well as SNPs in pro-opiomelancortin (POMC), leptin (LEP) and melanocortin-4 receptor (MC4R), were evaluated for associations with average daily gain, end-of-test rib-eye area, shipping weight and hot carcass weight in a group of 256 steers using a general linear model. The CRH C22G SNP was associated with end-of-test rib-eye area (P < 0.034) and hot carcass weight (P < 0.0015). The SNP in POMC was associated with shipping weight (P < 0.0078) and hot carcass weight (P = 0.006) while it approached significance for average daily gain (P < 0.07). The SNP in MC4R approached significance for hot carcass weight (P < 0.085) while no significance was observed between the leptin SNP and the above listed traits. Because both CRH and POMC regulate appetite, potential interaction effects between these two genes were assessed. The absence of an interaction effect between CRH and POMC with hot carcass weight suggests that these genes act independently to increase carcass yield. These gene effects used singularly or together could result in an economic benefit to the beef industry.     

Cold effect analysis and screening of SNPs associated with cold‐tolerance in the olive flounder Paralichthys olivaceus

Olive flounder Paralichthys olivaceus is an important mariculture fish and cold stress limits to its growth and survival during winter. In the present study, the cold‐tolerant (CT) and cold‐sensitive (CS) flounder were defined after cold treatment (0.7 ± 0.05°C). Cold effects on histological and physiological and gene expression levels were analyzed. The correlation analyses between single nucleotide polymorphism locus (SNP) in hsp70, yb‐1 and hmgb1 and the trait of cold tolerance were performed. The results showed that flounder gill was obviously damaged after treatment and more serious lesions in some of the epithelial cell layers were observed in the CS group. ATP concentration and pyruvate kinase activity in the CT group were significantly higher than those in the CS group (p < 0.05). Expression levels of hsp70 and yb‐1 were both up‐regulated markedly after cold treatment (p < 0.05). Nine, twenty‐one and ten SNPs were screened from hsp70, yb‐1 and hmgb1 partial sequences, respectively. Among them, 3 SNPs in hsp70 and 2 SNPs in hmgb1 showed significant difference in the two groups. Allele G of the SNP 8 (locus 1797) in hsp70 was only observed in the CT group. In the SNP 7 (locus 725) of hmgb1, genotype TT and allele T, and genotype CC and allele C were associated with cold tolerance and cold sensitive, respectively. Furthermore, one haplotype (TTG) generated from SNPs of hsp70 gene among CT and CS individuals showed significant relationship with cold tolerance (p = 0.031). Two haplotypes (ATG) and (TCT) generated from SNPs of hmgb1 were significantly associated with resistance (p = 0.001) and sensitive (p = 0.002) in cold treatment, respectively. These SNPs, genotype, alleles and haplotypes of hsp70 and hmgb1 may be related to the cold resistance of flounder, and could be candidate markers potentially for further selective breeding.