Pediatric Research 48:511-517 (2000)
© 2000 International Pediatric Research Foundation, Inc.
in Colostrum Enhance Myofibrillar Protein Synthesis in the Newborn Pig
MARTA L. FIOROTTO, TERESA A. DAVIS, PETER J. REEDS and
DOUGLAS G. BURRIN
USDA/ARS Childrens Nutrition Research Center, Department of Pediatrics,
Baylor College of Medicine, Houston, Texas 77030, U.S.A.
Department of Pediatrics, 1100 Bates St., Houston,
TX 77030, U.S.A.
Colostrum is a complex source of nutrients, immune factors, and bioactive
substances consumed by newborn mammals. In previous work, we observed
that protein synthesis in the skeletal muscle of newborn piglets is
enhanced when they are fed colostrum rather than a nutrient-matched
formula devoid of growth factors.
To elucidate the mechanisms responsible for this response, we contrasted
the fractional rates of sarcoplasmic and myofibrillar protein synthesis
of newborn piglets that received only water with those fed for 24 h
with colostrum, a nutrient-matched formula, or mature sows milk.
Compared with water, feeding resulted in a 2.5- to 3-fold increase
in total skeletal muscle protein synthesis, and this increase was 28%
greater in the colostrum-fed than either the formula- or mature milk-fed
piglets. Feeding also stimulated muscle ribosome and total polyadenylated
RNA accretion. Ribosomal translational efficiency, however, was similar
across all fed groups.
The greater stimulation of protein synthesis in colostrum-fed pigs
was restricted entirely to the myofibrillar protein compartment and
was associated with higher ribosome and myosin heavy chain mRNA abundance.
Taken together, these data suggest that nonnutritive factors in colostrum
enhance ribosomal accretion and muscle-specific gene transcription that,
in turn, stimulate specifically the synthesis of myofibrillar proteins
in the skeletal musculature of the newborn.
FSR, fractional synthesis rate
MHC, myosin heavy chain
GAPDH, glyceraldehyde phosphate dehydrogenase
polyA, polyadenylated RNA
rRNA, ribosomal RNA
Colostrum is a source of nutrients, immune factors, and bioactive substances
for the newborn mammal. Although the benefits of the consumption of
nutrients and immune factors are readily apparent, the functional significance
to the offspring of the numerous hormones and growth factors present
in colostrum is unclear. Studies that have compared the growth of newborns
have demonstrated an enhanced anabolic response, especially of the visceral
organs, associated with colostrum feeding (14).
This response is often attributed to the presence of trophic factors,
but this speculation remains to be proven. In addition, inadequate consideration
has been given to the fact that the consumption of colostrum also entails
the ingestion of a larger quantity of nutrients than that typically
provided by mature milk or many formulas.
Thus, to distinguish between the stimulatory effects of macronutrient
intake and the trophic effects of other growth-promoting substances
in colostrum, we compared the protein synthetic response of newborn
piglets to feeding with colostrum, mature sows milk, or a formula
with a macronutrient composition similar to that of colostrum but devoid
of potentially bioactive molecules (5, 6). We observed that protein
synthesis rates in skeletal and cardiac muscle, brain, and jejunum were
higher in colostrum-fed than formula-fed piglets; other organs did not
show this enhanced response.
The high rate of protein synthesis associated with colostrum consumption
could have resulted from an increase in the capacity for protein synthesis
due to a stimulation of ribosomal accretion and/or an increase in the
quantity of proteins synthesized per ribosome, i.e. an increase in ribosome
translational efficiency. Improvements in translational efficiency usually
occur when there is an enhancement in the initiation of translation
due to increases in the availability of active initiation factors.
An increase in the abundance of mRNA presented to the ribosome for
translation could also lead to an apparent increase in translational
efficiency, although this would indicate that mRNA availability rather
than ribosomal abundance is a primary limitation to protein synthesis.
Our overall objective was to identify the mechanism whereby the ingestion
of colostrum stimulates skeletal muscle protein synthesis rates in the
neonate. Specifically, we wished to determine whether the response was
due to an increase in translation efficiency and/or ribosomal abundance
and whether the increase in protein synthesis was specific for individual
We found that the synthesis rate of only the myofibrillar proteins
was stimulated by colostrum and, therefore, further examined whether
this effect could be explained by changes in the abundance muscle-specific
Experimental design and animals.
The experimental procedures have been described previously (6). Briefly,
three litters of conventional cross-bred pigs were removed from the
sow immediately after birth and not allowed to suckle. Piglets were
fitted with umbilical artery catheters under general isoflurane anesthesia.
The piglets were randomly assigned to one of three dietary groups and
fed for 24 h with mature sows milk (n = 5), formula (n = 5), or
sow colostrum (n = 5); a fourth group (n = 4) was studied at approximately
5 h of age, having received only water. Blood samples were collected
for analysis of glucose, amino acids, insulin, and IGF-I concentrations
before and during the feeding period. After 24 h, protein synthesis
was measured in vivo, and the longissimus dorsi muscle was collected
for determination of total myofibrillar and sarcoplasmic protein FSR,
total protein and total RNA concentrations, polyA RNA, 18S rRNA, and
MHC mRNA abundance. The animal protocol was conducted in accordance
with the National Research Councils Guide for the Care and Use
of Laboratory Animals and was approved by the Baylor College of Medicine
Animal Care and Use Committee.
The piglets were weighed at the start of the feeding protocol and then
bottle-fed hourly one of the three feeds at a rate of 20 mL/kg body
weight. The exact weight consumed was determined by weighing the bottle
before and after the feed. The colostrum and mature milk were collected
from conventional sows within 24 h of parturition and during the third
week postpartum, respectively.
A single batch of each feed was used throughout the experiment. The
colostrum was analyzed for fat (7), lactose (YSI automatic analyzer,
model 127, Yellow Springs, OH, U.S.A.), total protein (Kjeldahl method
after trichloroacetic acid precipitation of protein and assuming a conversion
factor of 6.38 for nitrogen to protein; Kjeltec Auto Analyzer 1030,
Tecator, Hoganas, Sweden), and total energy content (adiabatic bomb
calorimetry; Parr Instruments, Moline, IL, U.S.A.).
The formula then was constructed from semipurified ingredients to match
the macronutrient composition of the colostrum. The composition of the
formula per liter was (in grams) 51.4 casein, 53.9 lactalbumin, 23.1
albumin, 35.0 lactose, 35.0 corn oil, 35.0 coconut oil, 5.0 vitamin
mix (containing per gram of mix 900 IU retinyl acetate, 106 IU vitamin
D2, 22 mg DL--tocopherol acetate, 45 mg ascorbic acid, 5 mg inositol,
75 mg choline chloride, 2.25 mg menadione, 5 mg p-aminobenzoic acid,
4.25 mg niacin, 1 mg riboflavin, 1 mg pyridoxine hydrochloride, 1 mg
thiamine hydrochloride, 3 mg Ca pantothenate, 20 µg biotin, 90
µg folic acid, 1.4 µg cyanocobalamin; ICN Pharmaceuticals,
Cleveland, OH, U.S.A.), and 20.0 mineral mix (containing per gram of
mix 300 mg monocalcium phosphate, 80 mg calcium carbonate, 158 mg potassium
chloride, 138 mg sodium bicarbonate, 24 mg magnesium sulfate, 3 mg zinc
sulfate, 1.1 mg ferrous sulfate, 1 mg cobalt carbonate, 0.9 mg manganese
sulfate, 0.6 mg cuprous sulfate, 16.5 µg potassium iodide; ICN
Pharmaceuticals, Cleveland, OH, U.S.A.).
In vivo protein synthesis determinations.
Each piglet was administered via the umbilical artery catheter a single
dose (10 mL/kg body weight) of a sterile solution of L-phenylalanine
(150 mM) containing L-[4-3H]phenylalanine (3.7 Mbq/mL; Amersham, Arlington
Heights, IL, U.S.A.). Blood samples were collected 5, 15, and 30 min
after the injection. After the last blood sample was taken, the piglets
were anesthetized, exsanguinated, and a sample of one longissimus dorsi
muscle was removed rapidly and frozen in liquid nitrogen.
Muscle protein fractionation.
The frozen muscle from each piglet was powdered in liquid nitrogen and
homogenized in a low-ionic-strength buffer. A sample of homogenate was
retained for total protein (8) and RNA concentration (9) measurements.
The sarcoplasmic and myofibrillar components were isolated using a modification
(10) of the method of Solaro et al. (11). Proteins soluble in low-ionic-strength
buffer after high-speed centrifugation (15,000 x g at 2oC for 45 min)
were defined as the sarcoplasmic proteins.
Determination of [4-3H]phenylalanine specificradioactivity.
The acid-insoluble protein precipitates of the various muscle protein
fractions and blood samples were hydrolyzed to free amino acids in 6
M HCl. Phenylalanine in the neutralized homogenate and blood supernatants
and the hydrolysates of the total, sarcoplasmic, and myofibrillar proteins
was isolated by anion exchange HPLC as described previously (10). Amino
acids were postcolumn derivatized with orthophthalaldehyde reagent and
detected fluorimetrically. The phenylalanine concentration was determined
by comparison to a known standard. The eluted fraction containing the
phenylalanine peak was collected, and the associated radioactivity was
Isolation and quantification of mRNA and rRNA.
Total RNA was extracted from the powdered muscle with Ultraspec (12)
(Biotecx Laboratories, Houston, TX, U.S.A.). The extracted RNA was dissolved
in diethylpyrocarbonate-treated water, and the concentration was determined
spectrophotometrically at 260 nm. Ten-microgram aliquots of RNA were
fractionated on a 1% agarose/0.66 M formaldehyde gel.
The integrity of the RNA was established from the presence of intact
28S and 18S rRNA bands in a ratio of approximately 2:1 after ethidium
bromide staining. The RNA was transferred to a nylon membrane by capillary
action and UV cross-linked to the membrane for subsequent Northern analyses.
For each muscle, 0.25- and 0.50-µg (each in duplicate) RNA aliquots
also were applied to nylon membranes for slot blot analysis. On each
membrane, a set of polyA RNA (1 to 4 ng; Midland Certified Reagent Company,
Midland, TX, U.S.A.) and 18S rRNA (5 to 25 ng) standards and a skeletal
muscle RNA control from 7-d-old piglets were applied. The 18S rRNA standard
was generated by in vitro transcription of a 616-base cDNA to rat 18S
rRNA (13) subcloned into the pBluescript SK vector (Stratagene, La Jolla,
CA, U.S.A.); all ribonucleotides were added in equimolar amounts and
were nonradioactive but for a trace quantity of 3H-UTP for accurate
quantification. Full-length transcripts were obtained by gel purification.
A factor of 3.04 was used to calculate the absolute mass of 18S rRNA,
based on the mass equivalence of a mole of standard and a mole of the
full-length 18S rRNA transcript.
The Northern membranes were probed simultaneously for GAPDH and MHC
mRNA, and the slot blots were probed sequentially for MHC mRNA, polyA
RNA, and 18S rRNA. DNA probes were generated by random prime labeling
(14) using the following templates: pTRI-GAPDH-rat (Ambion, Austin,
TX, U.S.A.); a 407-bp fragment of human perinatal MHC from a highly
conserved segment in the rod and that cross-hybridizes with all sarcomeric
MHC (15) (kindly provided by Dr. Leslie Leinwand, University of Colorado,
Boulder, CO, U.S.A.); and the same rat 18S rRNA template described above.
A 32P-labeled poly(dT) probe was generated by reverse transcription
of the polyA template (14). Membranes were prehybridized and hybridized
for Northern and polyA analyses (14).
Posthybridization washing conditions were optimized for each probe;
Northern blots of the control RNA were processed with each slot blot
membrane to verify that slot blots were appropriately washed. The 32P
signal intensity associated with each band was quantified using a PhosphoImager
and associated software (Molecular Dynamics, Sunnyvale, CA, U.S.A.).
Protein FSR (percent of protein mass synthesized per day) was calculated
where SB is the specific radioactivity of the protein-bound phenylalanine,
SFP is the mean specific radioactivity of the muscle-free phenylalanine
for the labeling period (6), and t is the time of labeling in minutes.
We have demonstrated that the specific radioactivity of the muscle-free
phenylalanine, after it is administered as a flooding dose, is in equilibrium
with the amino-acyl transfer RNA-specific radioactivity and, therefore,
provides an equally valid measure of FSR (16). Ribosome translational
efficiency was calculated as grams of protein synthesized per day per
microgram of 18S rRNA.
Dose-response curves were generated from the polyA RNA and 18S rRNA
standards and used to interpret the intensity of the signals from the
muscle RNA samples; MHC data were expressed in terms of pixels. Blot-to-blot
variations were corrected on the basis of the values derived for the
control RNA samples. Values were expressed per microgram of total RNA
loaded and per milligram of muscle protein using the value for the ratio
of total RNA to protein derived from the same muscle.
Values are expressed as mean ± 1 SEM. The effect of feeding group
on the various parameters assessed was analyzed by ANOVA using a general
linear model (MINITAB, version 12.21, State College, PA, U.S.A.) with
protein compartment, i.e. sarcoplasmic or myofibrillar protein, as a
repeated measure. Interactions were evaluated, and differences between
groups were tested post hoc by F test with a Fisher least significant
difference adjustment for multiple comparisons.
We evaluated statistically the extent to which variations in muscle
rRNA and mRNA (total and MHC) abundance and plasma insulin, IGF-I, and
amino acids (total, essential, or branched chain) contributed to the
differences in FSR among groups by determining whether a feeding group
effect would account for any of the residual variance after controlling
for the variance attributable to RNA, hormones, and substrates. Regression
analysis was performed against total, sarcoplasmic, and myofibrillar
protein FSR in fed piglets.
Protein and energy intakes over 24 h of colostrum- and formula-fed piglets
were similar and significantly higher than those of the mature milk-fed
animals (Table 1). These differences were reflected in the higher plasma
insulin and essential amino acid concentrations (Table 1). However,
the increases in plasma nonessential amino acids (not shown), glucose
(not shown), and IGF-I were similar among fed groups. Plasma insulin
concentrations correlated more highly with plasma total amino acid concentration
(r = 0.73; p < 0.001) than with glucose (r = 0.33; p < 0.05).
Skeletal muscle protein FSR.
Feeding resulted in a 2.5- to 3-fold increase in total protein FSR (Fig.
1), which was 28% greater when colostrum was fed rather than formula
or mature milk (p < 0.001). There was no difference between the formula-
and mature milk-fed piglets despite their widely disparate nutrient
intakes. The greater stimulation in the colostrum-fed pigs was attributable
entirely to the increase in myofibrillar FSR (+39%), as the FSR of the
sarcoplasmic compartment was similar among all fed groups. Hence, the
ratio of myofibrillar to sarcoplasmic proteins synthesized was higher
in the colostrum-fed piglets (1.15 ± 0.05) than in either formula-
or milk-fed (0.90 ± 0.01) or unfed piglets (0.80 ± 0.02)
(p < 0.001).
rRNA abundance and translational efficiency.
Feeding increased 18S rRNA abundance, and the increase was greatest
in the colostrum-fed piglets (Table 2). In all groups, this rise in
ribosome abundance was accompanied by an increase in their translational
efficiency, although the efficiency attained was similar regardless
of diet composition. Thus, the increase in ribosome abundance in the
colostrum-fed piglets was crucial to the overall increase in skeletal
muscle FSR. Again, differences between formula- and mature milk-fed
piglets in rRNA abundance were not significant despite their disparate
intakes. Because rRNA is the predominant component of total RNA, similar
results were obtained when total RNA concentrations rather than 18S
rRNA were used to estimate translational efficiency.
PolyA concentration (ng/mg muscle protein) provides a measure of the
total translatable cytoplasmic mRNA. Feeding resulted in an average
3-fold increase in the concentration of polyA. Relative to protein content,
the increase was greatest for the formula-fed piglets, intermediate
for colostrum-fed piglets, and least for the mature milk-fed group (Table
3). Indeed, among the fed groups, there was a strong correlation between
plasma branched-chain amino acid and muscle polyA concentrations (r
= 0.62; p < 0.02).
In a previous study, we showed that the FSR of myofibrillar proteins
in immature skeletal muscle quantitatively reflects that of the MHC
component (10). Thus, we measured the relative abundance of MHC mRNA
to determine whether it could account for the observed differences in
the composition of muscle proteins synthesized. The cDNA used is homologous
to the C-terminal coding region of human perinatal MHC, a sequence that
is highly conserved across all sarcomeric MHC (15), so that the estimates
of MHC mRNA abundance reflect the sum of all immature and fast isoforms
The abundance of MHC mRNA relative to both the total polyA content
and to a nonmuscle-specific mRNA (GAPDH) was greatest in the colostrum-fed
and unfed piglets. The relative proportion of MHC mRNA did not change
with feeding colostrum, even though there was an approximately 3-fold
increase in polyA concentration. However, when either mature milk or
formula was fed, there was a reduction in the relative abundance of
MHC mRNA despite the increase in total polyA, suggesting that, in these
groups, the stimulation of mRNA accretion apparently selected against
No significant correlations between plasma hormone or substrate concentrations
and tissue mRNA concentration or protein synthesis rates could be identified.
Differences in total protein FSR among feeding groups were attributable
only to the variation in ribosomal abundance (mg rRNA/g total protein)
(r2 = 0.40; p < 0.005). We could identify no variable that would
explain the variance in sarcoplasmic protein FSR, whereas both ribosomal
abundance and MHC mRNA [pixels mRNA/µg polyA] contributed to the
variance in myofibrillar protein FSR (r2 = 0.64; p < 0.001) and did
so independently of each other.
In previous work, we found that the enhanced stimulation of skeletal
muscle protein synthesis in newborn piglets fed colostrum as opposed
to other feeds is not due solely to the provision of nutrients (5, 6).
The primary objective of the present study was to identify which components
of the protein synthetic pathway respond specifically to colostrum feeding.
The results suggest that there are two components to the anabolic
effect of feeding colostrum: a quantitative one and a qualitative one.
First, there was the general stimulation of protein synthesis by feeding
regardless of diet that resulted from an increase in the abundance and
translational efficiency of muscle ribosomes.
This incurred a proportional stimulation in the synthesis of both sarcoplasmic
and myofibrillar proteins. However, colostrum augmented the effect of
feeding by promoting a more marked accretion of ribosomes. Second, in
the colostrum-fed piglets, the enhanced synthesis rate was specifically
restricted to the myofibrillar proteins and reflected a disproportionate
increase in the abundance of myofibrillar mRNA, as exemplified by MHC
Ribosomal abundance and translational efficiency.
The primary anabolic effect of colostrum feeding was an increase in
muscle ribosomal abundance. Other circumstances in which significant
changes in ribosomal abundance have been related to alterations in skeletal
muscle protein accretion and synthesis include the following:
1) the maturation from myotube to myofiber during normal development
when there is a reduction in ribosome concentration (10), a change that
is likely due to a fall in the rate of rRNA synthesis (17);
2) the changes after stretch-induced muscle hypertrophy when a rapid
increase in rDNA transcription initiates the muscle hypertrophic response
(18); and 3) the response to increases in circulating hormones such
as thyroid and GH (19, 20).
Although the magnitude of the ribosomal accretion response to feeding
was influenced by the composition of the diet, the increase in ribosomal
translational efficiency was not. We have shown previously that the
FSR of mixed muscle proteins in the neonate is highly sensitive to food
intake and is mediated in large part by insulin (21, 22). On the basis
of the relationship between plasma insulin concentration and FSR in
the immature muscle (23), maximal translation rates would be anticipated
even at the lower insulin concentration attained by the mature milk-fed
piglets. These findings suggest that there is a maximal rate of translation
that ribosomes can achieve and that this rate was achieved by all fed
piglets regardless of any metabolic differences incurred by the three
feeding regimens. Thus, it was the increase in ribosome abundance rather
than their translational efficiency that enabled the colostrum-fed piglets
to enhance their synthesis rate further than that achieved by those
fed mature milk or formula.
Total polyA abundance.
Feeding also resulted in the rapid increase in the steady state abundance
of polyA mRNA (150 to 250%), an increase that was greatest in the formula-fed
and least in the mature milk-fed piglets. The increase in polyA abundance
was correlated positively with plasma essential amino acid concentrations,
underscoring the capacity of amino acids to regulate gene expression
as has been demonstrated in the liver (24). However, the difference
in protein synthesis between the formula- and colostrum-fed groups showed
that the differences in the total abundance of polyA did not necessarily
alter protein synthesis rates.
Indeed, the efficiency with which total mRNA was translated, expressed
as milligram of total muscle protein synthesized per microgram of polyA,
was significantly lower in the formula-fed group in which polyA abundance
was the highest. This observation highlights the fact that once skeletal
muscle differentiation approaches completion, ribosome abundance rather
than total mRNA abundance primarily determines the maximal capacity
for protein synthesis.
Myofibrillar protein synthesis rates.
The second effect of feeding colostrum was a specific stimulation in
myofibrillar protein synthesis. There are other instances in which there
is a discoordinated response of myofibrillar and sarcoplasmic proteins.
These include both the period of myofiber maturation as well as the
aging process, during both of which there is a disproportionate down-regulation
in myofibrillar protein FSR (10, 25).
In addition, in adult rodents, myofibrillar protein synthesis rates
are more sensitive than sarcoplasmic proteins to variations in food
intake (26, 27), although our observations in this and a previous report
(10) indicate that this may not necessarily be true in very young animals.
Reports on the separate responses of myofibrillar and sarcoplasmic
protein synthesis and accretion to a variety of hormones such as plasma
insulin (our unpublished observations), glucocorticoids (28), androgens
(29), IGF-I (30), and ß-adrenergic agonists (31) have described
proportional responses of the two compartments. The effect of muscle
work on sarcoplasmic and myofibrillar proteins varies with age and fiber
type. In young rats, there is a proportional decrease in sarcoplasmic
and myofibrillar protein synthesis rates upon muscle unloading (32),
whereas overloading fast-twitch muscles results in a proportional increase
in their synthesis rates (33). Thus, our results are unique in that
they implicate the presence of a factor in colostrum that can acutely
induce an increase in the translational capacity and alter the composition
of proteins synthesized by the muscle.
MHC mRNA abundance.
One possible explanation for the increase in myofibrillar protein synthesis
is that a maternally derived factor(s) transmitted via the mammary gland
results in the increased transcription and/or stabilization of messages
that encode specifically the myofibrillar proteins such as MHC mRNA.
Thus, the abundance of muscle-specific mRNA relative to other mRNA in
the muscle increases, which then enhances their likelihood of being
translated relative to nonmuscle-specific mRNA. The lower MHC mRNA abundance
in the mature milk-fed piglets suggests that the production of this
factor decreases after parturition and presumably was absent in the
Neuromuscular development in the pig at birth is fairly advanced, and,
thus, the observed responses must involve cellular pathways that are
active in the differentiated muscle. However, as we noted above, most
stimuli or inhibitors of growth in mature muscle do not affect the synthesis
of myofibrillar proteins exclusively. It seems likely, therefore, that
any factor involved is most active in the differentiated muscle but
at a time before the muscle has attained its stable mature composition.
Possible candidates are the bHLH/myoD family of transcription factors,
myoD and myogenin specifically (34), and those proteins that can modulate
their activity (3538). It is of interest that in addition to skeletal
muscle, the principal tissues in which MEF2 and serum response factor
are expressed are those same tissues in which the stimulation of protein
synthesis was enhanced by feeding colostrum, i.e. the heart, neural
tissues including the brain, and tissues containing smooth muscle (such
as in the serosal layer of the intestine).
The regulation of the expression of these factors by externally initiated
signals has not been clearly defined. However, in two instances of enhanced
muscle growth, weight-induced muscle hypertrophy and muscle regeneration,
an increase in the activity of these factors appears to be an essential
component of the anabolic response (3941).
The abundance of myogenic factors also responds to many of those same
variables that regulate ribosomal abundance, and, thus, their increase
may have been effected by the same stimulus.
Although at this time the nature of the colostral factor is unknown,
the present observations enable us to define some of its characteristics.
It should be more concentrated in colostrum than in mature milk and
retain its bioactivity as it passes through the digestive tract. It
is probably absorbable, although we cannot exclude the possibility that
an interaction between colostrum and the intestine generates a humoral
signal that is responsible for eliciting the observed effects.
The substance(s) also must act specifically on skeletal muscle and
potentially on cardiac muscle, brain, and the jejunum, or it could elicit
the production of endogenous factors that target those same tissues.
Finally, the effect on skeletal muscle must be to increase ribosomal
abundance and enhance muscle-specific gene expression. Although these
properties narrow down the potential field of candidates, it is probably
fair to say that, at this point, we can only exclude a number of potential
Notwithstanding the high concentrations of insulin and IGF-I in colostrum
and their decrease in concentration as lactation proceeds, it is unlikely
that they induced the observed responses.
Neither hormone apparently is absorbed in significant amounts in the
pig (5, 42, 43), and the observed muscle responses were not related
to the differences in plasma concentrations of the hormones among feeding
groups. Moreover, we (our unpublished observations) and Adams and McCue
(30) also have observed that although insulin and IGF can stimulate
muscle protein synthesis in the neonate, the increase is equivalent
for myofibrillar and sarcoplasmic proteins. Although thyroid hormones
are present in colostrum (44) and could elicit the observed responses,
differences in thyroid hormone are unlikely to have produced the observed
differences among groups.
Within the first 24 h of life, there is a postnatal surge in all thyroid
hormones that occurs regardless of whether colostrum or a semisynthetic
formula is fed to piglets (44). Additionally, the piglet demonstrates
a rapid postprandial surge in both thyroxine and triiodothyronine, but
the magnitude is dependent on the level of energy intake and this was,
by design, similar for colostrum- and formula-fed piglets (45).
An androgenic or GH effect also can be excluded because neither their
absence nor presence alters muscle protein synthesis in newborn pigs
(46, 47). Studies of the separate responses of myofibrillar and sarcoplasmic
protein synthesis to a variety of hormones, as noted previously, have
recorded proportional responses of the two compartments. There are a
variety of additional factors that are present in significantly higher
levels in swine colostrum than in mature milk, including epidermal growth
factor, estrogens, and prolactin (48, 49). However, the tissue specificity
of these factors in the neonate and their effect on the regulation of
ribosomal and muscle-specific gene expression are not well characterized.
These data show that feeding colostrum not only has quantitative consequences
for the anabolic processes in the skeletal musculature of the newborn
infant but also qualitative ones, with potential implications for the
development of muscle function. Improvement of skeletal muscle function
is advantageous insofar as it is critical for the development of the
newborns ability to survive independently from its mother. The
effects observed are likely attributable to nonnutritive factors present
in colostrum and possibly in mature milk, albeit at lower concentrations.
The identification of the mechanisms underlying this phenomenon, particularly
the relative importance of increased RNA synthesis and stability, will
be critical not only for advancing our understanding of the biologic
role of early mammary secretions in the regulation of neonatal growth
but also in establishing how diet contributes to the regulation of skeletal
muscle growth in early postnatal life.
Supported by the U.S. Department of Agriculture, Agricultural
Research Service under Cooperative Agreement number 586250-6001.
The authors thank Karen Clare and Monica Puppi for technical
assistance. We also thank Dr. E. OBrian Smith for his assistance
with statistical analyses and Leslie Loddeke for editorial assistance.
We wish to take the opportunity to pay tribute to the
late Dr. Elsie M. Widdowson CH, CBE, FRS, whose pioneering work on the
properties of colostrum was the driving force behind this research.
The contents of this publication do not necessarily reflect the views
or policies of the U.S. Department of Agriculture, nor does mention
of trade names, commercial products, or organization imply endorsement
by the U.S. Government.
Widdowson EM, Crabb DE 1976 Changes in the organs of pigs in response
to feeding for the first 24 h after birth. I. The internal organs and
muscles. Biol Neonate 28: 261271
Widdowson EM, Colombo VE, Artavanis CA 1976 Changes in the organs of
pigs in response to feeding for the first 24 h after birth. II. The
digestive tract. Biol Neonate 28: 272281
Heird WC, Schwarz SM, Hansen IH 1984 Colostrum-induced enteric mucosal
growth in beagle puppies. Pediatr Res 18: 512515[Abstract]
Berseth CL, Lichtenberger LM, Morris FH 1983 Comparison of growth-promoting
effects of rat colostrum and mature milk in newborn rats in vivo. Am
J Clin Nutr 37: 5260[Abstract]
Burrin DG, Davis TA, Ebner S, Schoknecht PA, Fiorotto ML, Reeds PJ,
McAvoy S 1995 Nutrient-independent and nutrient-dependent factors stimulate
protein synthesis in colostrum-fed newborn pigs. Pediatr Res 37: 593599[Abstract]
Burrin DG, Davis TA, Ebner S, Schoknecht PA, Fiorotto ML, Reeds PJ 1997
Colostrum enhances the nutritional stimulation of vital organ protein
synthesis in neonatal pigs. J Nutr 127: 12841289[Abstract/Full
Jeejeebhoy KN, Ahmad S, Kozak G 1970 Determination of fecal fats containing
both medium and long chain fatty acids. Clin Biochem 3: 157163[Medline]
Lowry OH, Rosebrough NJ, Farr AL, Randall RJ 1951 Protein measurement
with the Folin phenol reagent. J Biol Chem 193: 265275
Munro HN, Fleck A 1966 Recent developments in the measurement of nucleic
acids in biological materials. Analyst 91: 7888[Medline]
Fiorotto ML, Davis TA, Reeds PJ 2000 Regulation of myofibrillar protein
turnover during maturation in normal and undernourished rat pups. Am
J Physiol 278: R845R854
Solaro RJ, Pang DC, Briggs FN 1971 The purification of cardiac myofibrils
with Triton-X100. Biochim Biophys Acta 245: 259262[Medline]
Chomczynski P, Sacchi N 1987 Single-step method of RNA isolation by
acid guanidinium thiocyanate-phenol-chloroform extraction. Anal Biochem
Rothblum LI, Parker DL, Cassidy B 1982 Isolation and characterization
of rat ribosomal DNA clones. Gene 17: 7477
Farrell RE 1993 RNA Methodologies: A Laboratory Guide for Isolation
and Characterization. Academic Press, San Diego, pp 47202
Feghali R, Leinwand LA 1987 Molecular genetic characterization of a
developmentally regulated human perinatal myosin heavy chain. J Cell
Biol 108: 17911797
Davis TA, Fiorotto ML, Nguyen HV, Burrin DG 1999 Aminoacyl t-RNA and
tissue free amino acid pools are equilibrated after a flooding dose
of phenylalanine. Am J Physiol 277: E103E109[Medline]
Jacobs FA, Bird RC, Sells BH 1985 Differentiation of rat myoblasts.
Regulation of turnover of ribosomal proteins and their mRNAs. Eur J
Biochem 150: 255263[Abstract]
Goldspink DF, Cox VM, Smith SK, Eaves LA, Obsaldeston NJ, Lee DN, Mantle
D 1995 Muscle growth in response to mechanical stimuli. Am J Physiol
Flaim KE, Li JB, Jefferson LS 1978 Effects of thyroxine on protein turnover
in rat skeletal muscle. Am J Physiol 235: E231E236[Medline]
Pell JM, Bates PC 1987 Collagen and non-collagen protein turnover in
skeletal muscle of growth hormone-treated lambs. J Endocrinol 115: R1R4[Medline]
Davis TA, Burrin DG, Fiorotto ML, Nguyen HV 1996 Protein synthesis in
skeletal muscle and jejunum is more responsive to feeding in 7- than
26-day-old pigs. Am J Physiol 270: E802E809[Medline]
Wray-Cahen D, Nguyen HV, Burrin DG, Beckett PR, Fiorotto ML, Reeds PJ,
Wester TJ, Davis TA 1998 Response of skeletal muscle protein synthesis
to insulin in suckling pigs decreases with development. Am J Physiol
Davis TA, Burrin DG, Fiorotto ML, Reeds PJ, Jahoor F 1998 Roles of insulin
and amino acids in the regulation of protein synthesis in the neonate.
J Nutr 128: 347S350S[Medline]
Marten NM, Burke EJ, Hayden JM, Straus DS 1994 Effect of amino acid
limitation on the expression of 19 genes in rat hepatoma cells. FASEB
J 8: 538544[Abstract]
Balagopal P, Rooyackers OE, Adey DB, Ades PA, Nair KS 1997 Effects of
aging on in vivo synthesis of skeletal muscle myosin heavy-chain and
sarcoplasmic protein in humans. Am J Physiol 273: E790E800[Medline]
Preedy VR, Sugden PH 1989 The effects of fasting or hypoxia on rates
of protein synthesis in vivo in subcellular fractions of rat heart and
gastrocnemius muscle. Biochem J 257: 519527[Medline]
Svanberg E, Zachrisson H, Ohlsson C, Iresjö BM, Lundholm KG 1996
Role of insulin and IGF-I in activation of muscle protein synthesis
after oral feeding. Am J Physiol 270: E614E620[Medline]
Hickson RC, Czerwinski SM, Wegrzyn LE 1995 Glutamine prevents downregulation
of myosin heavy chain synthesis and muscle atrophy from glucocorticoids.
Am J Physiol 268: E730E734[Medline]
Brodsky IG, Balagopal P, Nair KS 1996 Effects of testosterone replacement
on muscle mass and muscle protein synthesis in hypogonadal mena
research center study. J Clin Endocrinol Metab 81: 34693475[Abstract]
Adams GR, McCue SA 1998 Localized infusion of IGF-I results in skeletal
muscle hypertrophy. J Appl Physiol 84: 17161722[Full Text]
Hesketh JE, Campbell GP, Lobley GE, Maltin CA, Acamovic F, Palmer RM
1992 Stimulation of actin and myosin synthesis in rat gastrocnemius
muscle by clenbuterol; evidence for translational control. Comp Biochem
Physiol 1 C 102: 2327
Munoz KA, Satarug S, Tischler ME 1993 Time course of the response of
myofibrillar and sarcoplasmic protein metabolism to unweighting of the
soleus muscle. Metabolism 42: 10061012[Medline]
Gregory P, Gagnon J, Essig DA, Reid SK, Prior G, Zak R 1990 Differential
regulation of actin and myosin isoenzyme synthesis in functionally overloaded
skeletal muscle. Biochem J 265: 525532[Medline]
Schwarz JJ, Martin JM, Olson EN 1993 Transcription factors controlling
muscle-specific gene expression. In: Karin M (ed) Gene Expression: General
and Cell-type Specific. Birkhauser, Boston, pp 93115
Molkentin JD, Olson EN 1996 Combinatorial control of muscle development
by basic helix-loop-helix and MADS-box transcription factors. Proc Natl
Acad Sci USA 93: 93669373[Abstract]
Kong Y, Flick MJ, Kudla AJ, Konieczny SF 1997 Muscle LIM protein promotes
myogenesis by enhancing the activity of MyoD. Mol Cell Biol 17: 47504760[Abstract]
Carnac G, Primig M, Kitzmann M, Chafey P, Tuil D, Lamb N, Fernandez
A 1998 RhoA GTPase and serum response factor control selectively the
expression of MyoD without affecting Myf5 mouse myoblasts. Mol Biol
Cell 9: 18911902[Abstract/Full Text]
Benezra R, Davis RL, Lockshon D, Davis DL, Weintraub H 1990 The protein
Id: a negative regulator of helix-loop-helix DNA binding proteins. Cell
Marsh DR, Carson JA, Stewart LN, Booth FW 1998 Activation of the skeletal
alpha-actin promoter during muscle regeneration. J Muscle Res Cell Motil
Carson JA, Schwartz RJ, Booth FW 1996 SRF and TEF-1 control of chicken
skeletal alpha-actin gene during slow-muscle hypertrophy. Am J Physiol
Carson JA, Booth FW 1998 Myogenin mRNA is elevated during rapid, slow,
and maintenance phases of stretch-induced hypertrophy in chicken slow-tonic
muscle. Pflugers Arch 435: 850858[Medline]
Burrin DG, Davis TA, Fiorotto ML, Reeds PJ 1997 Role of milk-borne vs
endogenous insulin-like growth factor I in neonatal growth. J Anim Sci
Shulman RJ 1990 Oral insulin increases small intestinal mass and disaccharidase
activity in the newborn miniature pig. Pediatr Res 28: 171175[Abstract]
lebodziski AB, Cogiel F 1983 Serum thyroid hormone levels in colostrum
deprived piglets and calves. Endocrinol Exp 17: 263270[Medline]
Dauncey MJ, Morovat A 1993 Investigation of mechanisms mediating the
increase in plasma concentrations of thyroid hormones after a meal in
young growing pigs. J Endocrinol 139: 131141[Medline]
Skjaerlund DM, Mulvaney DR, Bergen WG, Merkel RA 1994 Skeletal muscle
growth and protein turnover in neonatal boars and barrows. J Anim Sci
Wester TJ, Davis TA, Fiorotto ML, Burrin DG 1998 Exogenous growth hormone
stimulates somatotropic axis function and growth in neonatal pigs. Am
J Physiol 274: E29E37[Medline]
Jaeger LA, Lamar CH, Bottoms GD, Cline TR 1987 Growth-stimulating substances
in porcine milk. Am J Vet Res 48: 15311533[Medline]
Farmer C, Houtz SK, Hagen DR 1987 Estrone concentration in sow milk
during and after parturition. J Anim Sci 64: 10861089[Medline]
Received for publication January 26, 2000. Accepted for publication
May 12, 2000.
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