Progress 01/01/14 to 12/31/18
Outputs
Target Audience:The target audience for the report are scientists and graduate students. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project supported PI and graduate student travel for presentation of results at the annual ASAS meeting in 2014, 2015 and 2017. How have the results been disseminated to communities of interest?The results were presented as peer-reviewed publications, invited talks and abstracts. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Economic and environmental concerns are forcing beef producers to reevaluate their management schemes in an effort to remain financially viable while generating a consumer-friendly product. An attractive management system involves weaning calves at a young age (90 days) and metabolic imprinting (MI) wherein the animal is fed a high concentrate diet for 90 days followed by traditional back grounding and feedlot programs. MI steers managed offer better carcasses at slaughter that includes a meat product with improved consumer appeal. The objectives of the grant were to fine-tune the MI process in Brangus calves and to define the mechanisms in muscle that allow for the improved performance measures. Our hypothesis was that MI alters the activities of satellite cells (SC), the requisite progenitor cell for optimal muscle growth. The bioactivity of these cells is controlled through local and blood-born growth factors that increase their activation, proliferation and fusion into the growing muscle fiber. Specific Aim 1: Define the impact of niche factors on muscle growth and gene expression. The objective was to identify changes in gene expression that correlate with growth factor initiated alterations in myogenesis. A major transcriptional mediator that participates in chromatin remodeling and metabolism is PGC1α. Due to its importance as an energy-sensing transcription factor, PGC1α may play a pivotal role during muscle growth. The hypothesis was tested using calves fed a normal or calorie restricted (CR) diet. 1) Major activities completed / experiments conducted To mimic growth experienced by MI calves, Holstein calves were fed an accelerated growth (CON) diet or a conventional diet that met basal energy needs (CR) for 8 wks. Measures of whole body and muscle growth were recorded and correlated with changes in protein turnover and PGC1α content. 2) Data collected Daily diet intake and weekly body weights were measured. At wk 8, LM subsamples were collected for histology, RNA isolation and protein lysates. Immunohistology was performed to measure fiber size and SC number. Protein lysates were analyzed by SDS-PAGE and Western blot for mediators of protein turnover and hypertrophy. Total RNA was isolated for reverse-transcription quantitative PCR. 3) Summary statistics and discussion of results Calves maintained on CR gained less (P<0.05) body weight than CON (220 g/d vs. 771 g/d, respectively). LM fibers from CR calves were smaller (P<0.05) and contained less (P<0.05) PGC1α mRNA and PGC1α4 protein than CON. IGF-I expression was 40% lower (P<0.05)in CR and PI3K activation was blunted (P<0.05). No differences in phosphorylation of the downstream effectors of PI3K (ERK1/2, 4EBP1, S6K) were noted between the two groups. CR muscle lysates contained a greater (P<0.05) amount of bioactive CAPN1 and less (P<0.05) CAPSTNmRNA by comparison to CON. 4) Key outcomes New knowledge from the experiments defines reduced amounts of PGC1α4 and its downstream target gene, IGF-I, as a mechanism underlying suboptimal muscle growth. Specific Aim 2: Provide baseline information on satellite cell numbers and activities with age. A rapid decline in SC numbers occurs postnatal with numbers reaching adult levels within the first 120 days of life in cattle. Because SC are requisite for efficient muscle hypertrophy, identification of critical windows to modify their behavior is necessary. 1) Major activities completed / experiments conducted Activation and proliferative capacity was examined in young calves during a period of rapid muscle hypertrophy and in response to plane of nutrition. Two experiments were conducted with calves fed normal (CON) or calorie restricted (CR) diets for 8 wks. The impact of diet on SC biology was examined. 2) Data collected Animal performance measures (ADG, G:F, BW) were collected each wk for both experiments. Animals (CON and CR) were euthanized at 2-wk intervals in Experiment 1 (Expt 1) and after 8-wks in Expt 2. Expt 1 measures included body composition, organ weights, LM morphometrics and SC isolation. SC proliferation in vitro was measured by EdU incorporation and calculation of a mitotic index. Measures in Expt 2 were muscle morphometrics and LM gene expression. 3) Summary statistics and discussion of results Expt 1: Calves maintained on CR for 2, 4 and 8 wks had lower body weights, shorter hip heights and reduced ADG (P<0.05) by comparison to CON. CON calves contained a greater (P<0.05) percentage of body fat at 8 wks than CR. Liver, thymus and spleen weights were less (P<0.05) in CR than CON. Longissimus muscle fibers were smaller (P<0.05) in CR than CON at 4 and 8 wks. No differences in the number of SC/fiber were noted between the groups at any age. SC proliferative activity was measured by EdU incorporation during log-phase growth. Results demonstrate an age-dependent decline in mitotic index for CON SC with approximately 50% proliferative in 2-wk isolates compared to 20% at 4 and 8 wKs. By contrast, CR SC exhibit an approximate 40% mitotic index at all time points. Expt 2: Muscle gene expression and morphometry was examined after 8-wks of diet treatment in LM, infraspinatus (INF) and semitendinosus (ST) muscle to determine if all muscles are affected equivalently by caloric restriction. Cross-sectional area of LM and ST was larger (P<0.05) in CON than CR; no differences were noted in the INF. Coincident with a larger fiber, greater (P<0.05) amounts of Pax7, myogenin, BTG2 and E2F6 transcripts were measured in the CON LM by comparison to CR LM. The smaller muscle fibers in CR contained greater (P<0.05) expression of HDAC1, HDAC3 and KDM2A suggesting modification of the epigenome. 4) Key outcomes Poor diet may have long lasting impacts on muscle precursor cell activity. Specific Aim 3: Create an epigenomic fingerprint for metabolically imprinted steers. Enzymes and transcription factors that affect chromatin structure, and that are differentially expressed in mitotically active and quiescent SC, were evaluated as markers of muscle hypertrophy in Brangus steers maintained on different nutritional planes. 1) Major activities completed / experiments conducted A 2-year experiment was conducted using Brangus steers metabolically imprinted with a calorie-dense diet at 90-days of age. 2) Data collected Brangus steers were weaned at 90 days of age and placed on an energy dense diet for 90 days (EW-MI), grazed on rye-grass pastures (EW) or maintained on the cows until normal weaning (NW). The EW groups were comingled after 90-d and reared on warm season grasses for 90 d, at which time the suckled calves were weaned. Muscle biopsies were collected from the LM at experimental days 0, 90 and 180 for all groups. Total RNA was isolated for quantitative PCR measurement of gene expression. Live animal performance measures (ADG, G:F) were collected at 2-wk intervals. 3) Summary statistics and discussion of results Expression of KDMA2, NCoA7 and HDAC1 was greater (P<0.05) at 90-d and 180-d for the steers indicating that these chromatin modifiers likely participate in muscle growth.Myogenin expression was greater (P<0.05) in EW and EW-MI than NW at d90; no differences was noted between EW and EW-MI. Return to forage resulted in a decrease (P<0.05)in myogenin expression in the EW-MI steers by comparison to EW suggesting the transciptional imprint is not maintained. Metabolic imprinting caused a reduction (P<0.05) in PGC1a expression at d90 which was maintained after 90-days on a forage diet. EW steers experienced a similar reduction (P<0.05) in PGC1a expression at d90 but the expression increased (P<0.05) to initial values (d0) following a 90-d forage diet. 4) Key outcomes Epigenome modifiers are differentially expressed with animal age. Metabolic imprinting has a longterm effect on PGC1a expression which may affect muscle composition.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Lu, Y., J.S. Bradley, S.R. McCoski, J.M. Gonzalez, A.D. Ealy and S.E. Johnson. 2017. Reduced skeletal muscle fiber size following caloric restriction is associated with calpain-mediated proteolysis and attenuation of IGF-1 signaling. Am. J. Physiol. 312:R806-R815.
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
MacGhee, M.E., J.S. Bradley, S.R. McCoski, A.M. Reeg, A.D. Ealy and S.E. Johnson. 2016. Plane of nutrition affects growth rate, organ size and skeletal muscle satellite cell activity in newborn calves. J. Anim. Physiol. Anim. Nutr. 101:475-483.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
MacGhee, M.E., S.R. McCoski, C.H.K. Hughes, S.E. Johnson and A.D. Ealy. 2015. Plane of nutrition affects Holstein bull calf growth, bone mineral density and organ size. ADSA/ASAS Joint Annual Meeting, July 12-16, Orlando, FL.
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Brandt, A.M., J. Kania, B. Reinholt and S.E. Johnson. 2018. Human IL6 but not bovine IL6 stimulates proliferation of bovine satellite cells. Domest. Anim. Endocrinol. 62:32-38
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Bradley, J.S., M.E. MacGhee, S.R. McCoski, A.M. Reeg, A.D. Ealy and S.E. Johnson. 2015. Plane of nutrition affects muscle fiber hypertrophy and satellite cell activity in neonatal bull calves. ADSA/ASAS Joint Annual Meeting, July 12-16, Orlando, FL.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Lu, Y., J.S. Bradley, S.R. McCoski, J.M. Gonzalez, A.J. Geiger, R.M. Akers, A.D. Ealy and S.E. Johnson. 2015. Caloric restriction reduces protein accretion in skeletal muscle by attenuating IGF-I signaling in young calves. ADSA/ASAS Joint Annual Meeting, July 12-16, Orlando, FL.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Lu, Y., J.S. Bradley, S.R. McCoski, A.J. Geiger, R.M. Akers, A.D. Ealy and S.E. Johnson. 2015. Muscle fiber hypertrophy is associated with increased expression of key transcriptional and epigenome regulatory genes. ADSA/ASAS Joint Annual Meeting, July 12-16, Orlando, FL.
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Progress 01/01/17 to 12/31/17
Outputs
Target Audience:The target audience for this report is animal scientists and graduate students. Data was presented at regional and national meetings. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The postdoc gained extensive experience with bioinformatics which improved his CV. How have the results been disseminated to communities of interest?The data will be presented at 2018 ASAS annual meeting in an invited talk and with abstracts. What do you plan to do during the next reporting period to accomplish the goals?The data analysis is complete for chromatin modification enzyme gene expression. The final report will include qPCR of additional genes.
Impacts
What was accomplished under these goals?
During 2017, the transcriptome of metabolic imprinted steers was examined. A two year study was completed with muscle samples taken at weaning (90-d of age; t=0), 90-d of treatment and 180-d of treatment. The treatments included a conventional rearing system (NW) wherein the suckled calf was sampled, an early weaned steer (EW) and EW steers receiving a metabolic imprint (EW-MI). Data was analyzed as repeated measures with management system and time as the main effects. Genes selected for qPCR were identified from a previous study examining diet as an imprinting insult. Chromatin modifer genes (HDAC1, NCoA7, KDM2A), myogenic transcription factors (MGN, PAX7), transcriptional suppressors (E2F6, PGC1A, BTG2) and growth factors (IGF1, MSTN) were measured at each time point. Differences in growth between year 1 and year 2. Independent of the year effect and management system, HDAC1, MGN and PGC1a changed (P < 0.05) over time indicating that these genes are regulated developmentally. Transcription of IGF-1 tended (P < 0.1) to behave in a similar manner. Both MGN and PGC1a transcription were affected (P < 0.05) by management system with greater amounts of PGC1a and less MGN found in EW and EW-MI by comparison to NW. Thus, early weaning alone can alter muscle gene expression. During Year 2, the ADG (0.8 kg/d) did not differ (P > 0.05) between EW and EW-MI indicating that the imprint did not affect performance during the 180-d experimental time frame; steers in both management systems exhibited lower (P > 0.05) ADG than suckled steers. Pax7 mRNAin EW and EW-MI steers did not differ from one another at 90-d post-weaning but both groups containedgreater (P < 0.05) amounts thanNW calves. A decline in MSTN mRNA occured over time in early weaned steers with the least amount of transcriptapparent at d180. These results indicate that muscle stem cell activity is increasing coincident with a loss of the inhibitor, MSTN, to support muscle growth in the initial 90-d after weaning. Although EW-MI calves performed better (P <0.05) than EW during the imprinting period (1.0 vs. 0.8 kg/d) , gene expression was not different indicating muscle hypertropy is not correlated solely with altered satellite cell and myostatin activities.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Brandt AM, Kania JM, Reinholt BM, Johnson SE. 2018. Human IL6 stimulates bovine satellite cell proliferation through a Signal transducer and activator of transcription 3 (STAT3)-dependent mechanism. Domest Anim Endocrinol. 62:32-38.
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Progress 01/01/16 to 12/31/16
Outputs
Target Audience:The target audience for this report is animal scientists and graduate students. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The results were presented by the PI at two seminars to scientists at Virginia Tech and Kansas State. How have the results been disseminated to communities of interest?The results are published (SA 2) or in preparation to peer-reviewed journals. What do you plan to do during the next reporting period to accomplish the goals?Analyze the RNA isolates from the MI, EW and NW steers for target gene expression. Analyze the feedlot data from the 2-yr experiment described in Specific Aim 3.
Impacts
What was accomplished under these goals?
Economic and environmental concerns are forcing beef producers to reevaluate their management schemes in an effort to remain financially viable while generating a consumer-friendly product. An attractive management system involves weaning calves at a young age (90 days) thus, preserving cow body condition and promoting her return to estrus. Importantly, the EW calf calf represents an excellent candidate for metabolic imprinting (MI) wherein the animal is fed a high concentrate diet for 90 days followed by traditional backgrounding and feedlot programs. Steers managed in this fashion offer better carcass characteristics at slaughter that includes a meat product with improved consumer appeal. Outcomes to the producer include calves that finish better allowing for increased profitablity and a reduction in cow costs through increased reproductive performance. Specific Aim 1: Examine the impact of niche factors. Impact Statement Cattle muscle cells respond to human IL6 but not to the endogenous bovine form of the ligand. The change in knowledge provides evidence for specie-specific niche factor responses. Major activities completed Bovine satellite cells were treated with human and bovine IL6 and examined for intracellular signal transduction and myogenic responses. Data collected Western blot was performed to measure STAT3, pSTAT3, ERK1/2, pERK1/2, AKT1 and pAKT1 amounts. Proliferation was measured by EdU incorporation and differentiation was measured by relative fluorescent intensity of myosin heavy chain expression. Summary stats and discussion Bovine SC do not generate a pSTAT3 signal and fail to elicit an effect on myogenesis. Bovine SC treated with 50 or 100 ng/mL human IL6 initiate STAT3 signals that culminate in increased (P<0.05) EdU incorporation. Neither hIL6 nor bIL6 altered fusion or myosin expression in SC. MDBK, a bovine epithelial cell line, treated with bIL6 invokes a STAT3 response indicating the ligand is bioactive. Key Outcomes Bovine SC do not respond to bIL6 even though the receptor (IL6R) and signaling system (STAT3) are present and functional. Specific Aim 2: Establish baseline information on satellite cell numbers and myogenic capacity. Impact Statement Young calves on a high plane of nutrition incorporate greater numbers of muscle stem cells into the growing muscle fiber, a fundamental change in knowledge. Major Activities Completed Activation and proliferative capacity was examined in young calves during a period of rapid muscle hypertrophy and in response to plane of nturition. Two experiments were conducted with calved fed normal (CON) or caloric restricted (CR) diets for 8 wks. The impact of diet on satellite cell biology was examined. Data Collected Animal performance measures (ADG, G:F, BW) were collected each week for both experiments. Animals were euthanized at 2-wk intervals in Expt. 1 and after 8-wks in Expt. 2. Expt 1 measures included body composition, organ weights, LM morphometrics and SC isolation. SC proliferation in vitro was measured by EdU incorporation and calculation of a mtitotic index. Measures in Expt 2 were muscle morphometrics and LM gene expression Summary stats and discussion of results Expt 1: Calvees maintained on CR for 2, 4, and 8 wks had lower body wweights, shorter hip heights and reduced ADG (P <0.05) by comparision to CON. CON calves contained a greater (P<0.05) percentage of body fat at 8 wks than CR. Liver, thymus and spleen weights were less (P<0.05) in CR than CON at 4 and 8 wks. No difference in the number of SC/fiber were noted between the groups at any age. SC proliferative activity was measured by EdU incorporation during log-phase growth. Results demonstrate an age-dpeendent decline in mittotic index for CON SC with approximately 50% proliferative in 2-wk isolated compared to 20% at 4 and 8 wks. By contrast, CR SC exhibit an approximate 40% mittoic index at all time points. Expt 2: Muscle gene epxression and morphometry was examined after 8-wks of diet treatment in LM, INF and ST msucle to determine if all muscle are affected equivalently CR. Cross-sectiona are of LM and ST are larger (P< 0.05) in CON than CR; no differences were noted in the iNF. Coincident with a larger fiber, greater (P<0.05) amounts of Pax7, myogenin, BTG2 and E2F6 transcripts were measured in the CON LM by comparison to CR LM. The smaller muscle fibers in CR contained greater (P<0.05) expression of HDAC1, HDAC3 and KDM2A suggesting modification of the epigenome. Key Outcomes: Our efforts provide new knowledge that not all muscles respond to diet equivalently and that poor diet may have long lasting impacts on muscle precursor cell activity. Specific Aim 3: create an epigenomic fingerprint for MI steers Major activities completed A 2-year expt was conducted using Brangus steers metabolically imprinted with a calorie dense diet at 90 days of age. Data Collected Brangus steers were weaned at 90 days of age and placed on an energy dense diet for 90 days (EW-MI), grazed on rye grass pastures (EW) or maintained on the cows until normal weaning (NW). The EW groups were comingled after 90-d and reared on warm season grasses for 90 d, at which time the NW calves were weaned. Muscle biopsies were collected from the M at experimental days 0, 90 and 180 for all groups. Total RNA was isolated for qPCR measurement of gene expression. Live animal performance measures (ADG, G:F) were collected at 2-wk intervals. Summary statistics and discussion RNA isolates from all samples are completed and quantitative PCR is on-going. Analyzed results from the study are expected by September 2017.
Publications
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2016
Citation:
MacGhee, M.E., J.S. Bradley, S.R. McCoski, A.M. Reeg, A.D. Ealy and S.E. Johnson. 2016. Plane of nutrition affects growth rate, organ size and skeletal muscle satellite cell activity in newborn calves. J. Anim. Physiol. Anim. Nutr. In press. doi: 10.1111/jpn.12568
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2016
Citation:
Lu, Y., J.S. Bradley, S.R. McCoski, J.M. Gonzalez, A.D. Ealy and S.E. Johnson. 2016. Reduced skeletal muscle fiber size following caloric restriction is associated with calpain-mediated proteolysis and attenuation of IGF-1 signaling. Am. J. Physiol. In press. doi: 10.1152/ajpregu.00400.2016.
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Progress 01/01/15 to 12/31/15
Outputs
Target Audience:The target audience for this report is animal scientists and graduate students. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The results of our work were presented as posters by 1 graduate student, 1 postdoctoral fellow and 1 staff scientistat the Joint Annual Meeting held in Orlando, FL (July 9-12, 2015). The PI attended the PD Meeting in July 2015 and presented the results of the experiments. How have the results been disseminated to communities of interest?Yes. Presentation at the Animal Society of Animal Science annual (2015) meeting. What do you plan to do during the next reporting period to accomplish the goals?Manuscript preparation is underway for the 3-abstracts presented at JAM 2015. Our plans are to continue thework on chromatin modification gene expression profiles and their regulation by growth factors in satellite cells. In addition, a second round of metabolic imprinting with Brangus steers is planned.
Impacts
What was accomplished under these goals?
1) Measure the impact of niche localized IL6, IGF-1 and HGF on expression of corechromatin modification genes. Baseline expression of the core genes was measured in rapidly growing young calves andcalorierestricted (CR) young calves. Results demonstrate that growing calves have increased mRNA and protein expression of PGC1a4 in skeletal muscle,which drives expression of IGF-1 gene expression. This signaling axis is down-regulated in calves experiencing minimal growth. Because IGF-1 is a major driver of muscle fiber hypertrophy, reduced expression of PGC1a4/IGF-1may provide the mechanistic basis for zero net protein accretion in the muscle of CR animals.Other chromatin modification genes expressed in skeletal muscle that are attenuatedby a low plane of nutrition include NCoA7, KDM2A andHDAC1. Theirrelationship to lower expression of the transcriptional mediators, Pax7, BTG2, TGIF and myogenin, in CR animals is the focus of on-going experiments. A second component of the aim is to examine the impact of IL6 on bovine satellite cells (BSC). Treatment of cultures of BSC with recombinant bovine IL6 does not affect proliferation or differentiation rates. Examination of the IL6 signaling axis reveals that the receptor is expressed in the cells but is non-responsive to the ligand. Treatment of BSC with IL6 does not initiate either canonical STAT3 or non-canonicalERK1/2 phosphorylation and activity. The inability to initiate a signal argues that IL6 does not participate in the regulation of BSC myogenesis. 2) Establish baseline information on satellite cell numbers and myogenic capacity as a function of age. Nothing to report. 3) Create an epigenomic fingerprint for metabolically imprinted steers. Beef steers (90 d of age) were fed a high concentrate diet (HC), high forage diet (HF)or maintained as suckled calves (S) for 90 days. Steers subsequently were intermingled and maintained for an additional 90 days on pasture. Skeletal muscle and liver biopsies were retrieved at d0, d90 and d180 of the experiment. Total RNA was extracted and analyzed by quantitative PCR for expression of the core chromatin modification genes associated with growth (see Aim 1). No significant differences were observed for the main effects of time and diet with regard to expression of Pax7, MyoD, myogenin, PGC1a or IGF-1. On-going experiments are correlating average daily gain with expression of additional genes to determine if a genetic fingerprint for muscle growth is possible.
Publications
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Progress 01/01/14 to 12/31/14
Outputs
Target Audience: The target audience for the reporting period is animal scientists and graduate students. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? Completion of the experiments associated with the grant objectives provided training in molecular and cellular biology to 1 graduate student,1 postdoctoral fellow and 1 research specialist. The individuals will present their efforts as abstracts at the ADSA/ASAS Joint Annual Meeting in 2015. How have the results been disseminated to communities of interest? Results will be presented atthe ADSA/ASAS Joint Annual Meeting in 2015. What do you plan to do during the next reporting period to accomplish the goals? Manuscripts are in preparation describing the effect of diet and age on satellite cell kinetics and muscle hypertrophy. These papers will be reported in the next cycle. Our plans for the upcoming year include analysis of muscle biopsies from metabolically imprinted steers and completion of the growth factor studies examining epigenomic gene expression as a function of muscle progenitor cell proliferation and differentiation.
Impacts
What was accomplished under these goals?
1) Measure the effect of IGF-I, HGF and IL6 on chromatin modification gene expression in bovine satellite cells. No progress was made on the aim. 2) Establish baseline information on satellite cell numbers as a function of age. With age, the numbers of satellite cells per unit of muscle weight declines. The greatest loss of satellite cells occurs during the first month of life in calves with many of these believed to be incorporated into the muscle fiber. Our work demonstrates that muscle fiber hypertrophy begins after the first month of life as indicated by an increase in cross-sectional area between 4 and 8 weeks. The numbers of satellite cells per fiber, however, remains unchanged at 2, 4 and 8 weeks of age indicating both a robust rate of self-renewal and rapid incorporation of muscle progenitors into the growing fiber. Calves growing at a reduced rate during the first 8 weeks of life and experience no fiber hypertrophy show no changes in the numbers of satellite cells per fiber across the period. Indeed, the numbers of satellite cells per fiber is equivalent between the growth-restricted and normal animals. The dynamics of the satellite cell population are altered by diet in the young calf. Satellite cells isolated from 2 week old, growing calves proliferate faster than those isolated from growth-restricted animals. By 4 weeks of age, the proliferative activity of satellite cells has rapidly declined in the growing animals such that cells isolated from growth-restricted individuals contain a greater proportion of actively dividing cells. These results indicate that the neonatal calf contains satellite cells that are highly proliferative and fuse into the adjacent fiber without an increase in fiber diameter. The addition of the myonuclei provides the framework for hypertrophy that occurs after 4 weeks of age. Satellite cell proliferation rates between 4 and 8 weeks are equivalent but lower than those at 2 weeks suggesting a change in subpopulations or genetic profiles. Growth restriction that reduces fiber hypertrophy disrupts satellite cell dynamics such that proliferative capacity remains elevated for at least 8 weeks. Importantly, these results indicate that fiber size drives satellite cell proliferative dynamics and further suggest that satellite cell quiescence is delayed until the onset of hypertrophy. 3) Create an epigenomic fingerprint for metabolically imprinted cattle. The first set of Brangus calves were biopsied in January 2015. The metabolic imprinting of the steers in on-going.
Publications
- Type:
Other
Status:
Accepted
Year Published:
2015
Citation:
Yue Lu, Jennifer S. Bradley, Sarah R. McCoski, John M. Gonzalez, Adam J. Geiger, R. Michael Akers, Alan D. Ealy and Sally E. Johnson. 2015. Caloric restriction reduces protein accretion in skeletal muscle by attenuating IGF-I signaling in young calves. ADSA-ASAS Joint Annual Meeting, July 12-16, 2015.
- Type:
Other
Status:
Accepted
Year Published:
2015
Citation:
Yue Lu, Jennifer S. Bradley, Sarah R. McCoski, Adam J. Geiger, R. Michael Akers, Alan D. Ealy, Sally E. Johnson. 2015. Muscle fiber hypertrophy is associated with increased expression of key transcriptional and epigenome regulatory genes. ADSA-ASAS Joint Annual Meeting, July 12-16, 2015.
- Type:
Other
Status:
Accepted
Year Published:
2015
Citation:
Jennifer S. Bradley, Meghan E. MacGhee, Sarah R. McCoski, Amanda Reeg, Alan D. Ealy and Sally E. Johnson. 2015. Plane of nutrition affects muscle fiber hypertrophy and satellite cell activity in neonatal bull calves. ADSA-ASAS Joint Annual Meeting, July 12-16, 2015.
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