<p>Postmortem aging has been
extensively practiced as value-adding process due to the beneficial impacts on
meat palatability. Meat tenderization occurred through proteolytic
fragmentation of myofibrillar structural proteins via endogenous protease
systems, which is considered as the primary drive to enhance major palatability
attributes including tenderness, juiciness, and flavor. Recent theoretical
framework proposes apoptosis, or programmed cell death, as the preceding step
that initiates postmortem proteolysis. Whereas small heat shock proteins have
been consistently recognized as meat quality biomarkers, probably due to their
protective activities against proteolysis through anti-stress, anti-apoptotic,
and chaperoning functionalities. To shed light on detailed mechanisms
controlling postmortem proteolysis and consequential impacts on the development
of fresh meat quality characteristics, postmortem proteolytic changes of small
heat shock proteins, apoptotic factors, and myofibrillar structural proteins
were profiled in postmortem skeletal muscles under different metabolic
backgrounds and across species. </p>
<p>In beef, three muscles, <i>longissimus
lumborum</i> (LL), <i>semimembranosus</i> (SM), and <i>psoas major</i> (PM),
have been selected to represent glycolytic, intermediate, and oxidative muscle
types. Tenderness and water - holding capacity were determined, and
proteolysis, apoptotic features, and small heat shock proteins were measured in
8 beef carcasses at 1, 2, 9, 16, and 23 days of aging. PM exhibited limited
aging potential in quality developments shown by lower extents of shear force,
water-holding capacity, and proteolytic changes, including calpain 1 autolysis,
troponin T, and HSP27 compared to LL and SM. Conversely, LL had an increase in
tenderization and water-holding capacity, which was accompanied with more
extended calpain 1 autolysis, proteolysis and HSP27 degradation, compared with
other muscles. The results of this study suggest that postmortem proteolytic
changes of myofibrillar proteins, small HSPs and apoptotic factors occur in a
muscle-specific manner, which is likely attributed to different rate and extent
of meat quality developments of each muscle during aging. </p>
<p>Callipyge lambs are a unique
genetic background showing calpastatin over-expression, muscle hypertrophy in
loin and hindquarter area, substantially compromised meat tenderization
potential, and a shift of muscle fiber composition towards fast-glycolytic
directions. Proteome and metabolome changes in muscles from callipyge mutation
(+/C) and non-callipyge phenotype (+/+, C/+, and C/C) lambs were profiled to
provide insight into the biochemical changes affecting meat quality attributes.
M. longissimus thoracis from lambs with all four possible callipyge genotype (n
= 4, C/+, C/C, +/C, and +/+) were collected after 3d aging and analyzed using
mass-spectrometry based platforms. Among identified proteomes, cytochrome c (pro-apoptotic
protein) was detected with significantly lower abundances in +/C.
Anti-apoptotic HSP70, BAG3, and PARK7 were over-abundant in +/C, which could
result in delayed apoptosis and possibly attributed to tougher meat in
callipyge lambs. Eight glycolysis enzymes were overabundant in +/C lambs,
whereas 3 enzymes involved in TCA cycle were overabundant in non-callipyge ones
(C/C and/or C/+). Twenty-five metabolites were affected by genotypes (P <
0.05), including metabolic co-factors, polyphenols, and AA/short peptides.</p>
<p>Pig production is facing increased
public pressure regarding antibiotic usage restriction. Recently, dietary
L-glutamine at cost effective level (0.2%) was identified as an effective antibiotic
alternative in post-transport nursery pig diets. To evaluate carcass and meat
quality characteristics in market-ready pigs when 0.2% dietary L-glutamine was
applied as for early-life post-weaning and transport recovery, pigs (N=480)
were weaned and transported in two replication trials in SPRING (April of 2017)
vs. SUMMER (July of 2016), fed 3 different diets (Non: no antibiotic, Anti: 441
ppm chlortetracycline and + 38.6 ppm tiamulin, Gln: 0.20% L-glutamine) for 14
days after transport, and fed basal diet until reaching market weight. Pairs of
<i>longissimus dorsi</i> (LD) and <i>psoas major</i> (PM) muscles from each
carcass (n=10/diet/trial) were separated at 1 d and 7 d postmortem,
respectively. Carcass yield and meat physical and quality attributes were
evaluated. Overall impacts of Gln on physical attributes of carcasses and
porcine muscles were minimal. No dietary effects were found in carcass,
proximate composition, water-holding capacity, or shear force. Significant
difference between trials were found in terms of productivity and pork/carcass
qualities, where SPRING replicates showed increased body weight, faster pH
decline, paler surface color, higher intra-muscular fat deposition, and
improved tenderness and water-holding capacity as indicated by lower shear
force values, thaw-purge loss, and cooking loss (P < 0.05).</p>
<p>The pork and carcass quality
results give rise to a postulation that different metabolism and animal growth
might have been occured between the two production trials, consequentially
differentiated meat quality development. In this regard, myofibrillar
proteolysis, small heat shock proteins, and apoptotic factors were characterized
during 7 d postmortem aging in porcine LD and PM muscles from both seasonal
trials, combined with metabolomics profiles of 1d samples using the
GC-TOF-MS/MS platform. Compared to SUMMER counterparts, SPRING muscles showed
concurrence of more extended apoptosis, further calpain 1 autolysis, and
increased structural protein degradation (P<0.05). SPRING muscles showed
more ATP catabolism compounds and increase in carbohydrates, branched-chain
amino acids, and 16-18 carbon fatty acids, which could be chemistry
fingerprints of increased cellular oxidative stress, consequentially favoring
onset of apoptosis and proteolysis. Meanwhile, SUMMER pigs showed increased
stress-defending metabolites, such as ascorbic acid, antioxidant amino acids,
and decreased inhibitory neuro-transmitter GABA, which may indicate elevated
stress-defending activity in SUMMER pigs that possibly inhibited apoptosis and
proteolysis. </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/12196857 |
| Date | 28 April 2020 |
| Creators | Danyi Ma (8202711) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Unlocking_the_role_of_small_heat_shock_proteins_and_apoptosis_in_postmortem_proteolysis_and_meat_quality_characteristics_of_skeletal_muscles_under_different_conditions/12196857 |
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