Pregnant sow nutrition has potential effects on the muscle fiber development of progeny in utero. A total of 199 Landrace x Large White sows from parities 0 to 6 and their offspring were used to evaluate the effects of increasing the feeding amount during midpregnancy on the muscle tissue, growth performance, and meat quality of the progeny. The experiment was divided into 2 study replicates, and in each replicate, sows were assigned to 1 of the 2 treatments: 1) sows in the control group (C sows) were fed 2.5 to 3.0 kg/d (feed: 12.1 MJ of ME/kg and 0.62% lysine) throughout gestation; and 2) sows in the high group (H sows) received an extra feed allowance of 1.5 kg/d for gilts and 2.0 kg/d for multiparous sows above the C amount from d 45 to 85 of gestation (period of secondary muscle fiber formation). Sow backfat was recorded on d 40 and 85 of gestation. Sow performance (litter size and piglet BW) at farrowing and on d 18 of lactation was measured. At weaning, pigs were divided into 5 BW groups/treatment, and progeny growth performance was measured during the nursery (n = 958) and the growing-finishing (n = 636) periods. At slaughter, carcass and meat quality traits (lean content, main cut weight, pH, Minolta color, and drip loss) were recorded from the second lightest group at weaning (BW group 4; n = 90), and samples from the longissimus thoracis muscle were taken to study muscle fiber characteristics (n = 70). The extra nutrition from d 45 to 85 of gestation did not lead to differences in litter size or piglet BW at farrowing and on d 18 of lactation. Pigs born to H mothers had fewer muscle fibers and fewer estimated primary and secondary fibers than did pigs born to C mothers (P < 0.05). However, postnatal growth performance was not consistently affected by the maternal treatment. The smaller number of muscle fibers found in the H group of pigs was associated with fewer type IIB fibers (P < 0.05) with greater cross-sectional areas (P < 0.10), which might be related to the significantly greater meat pH at 24 h postmortem and the smaller L* (lightness) values recorded in the H group of pigs. Results from the present study confirm the existence of effects of maternal nutrition on fetal development, at least in terms of muscle tissue development and meat quality, although with no beneficial effects were found for the postnatal growth performance of the progeny.

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Increased sow nutrition during midgestation affects muscle fiber.

Around the world and across taxa, subterranean mammals show remarkable convergent evolution in morphology (e.g., reduced external ears, small eyes, shortened limbs and tails). This is true of sensory systems as well (e.g., loss of object vision and high frequency hearing). The naked mole-rat (Heterocephalus glaber) displays these typical subterranean features, but also has unusual characteristics even among subterranean mammals. Naked mole-rats are cold-blooded, completely furless, very long-lived (> 30 years), and eusocial (like termites). They also live in large colonies, which is very unusual for subterraneans. Their cortical organization has reduced area for visual processing, utilizing 30% more cortex for tactile processing. They are extremely tolerant to oxygen deprivation, and can recover from 18 min of anoxia. Their pain pathway is reduced and they feel no pain from acidosis. They are the only rodent tested to date whose pheromone-detecting vomeronasal organ shows no postnatal growth. These features may be a result of this species' "extreme subterranean lifestyle" that combines living underground and living in large colonies. Many respiring animals cramped together in unventilated burrows elevates CO2 levels, high enough to cause acidosis pain, and depletes O2 concentrations low enough to kill other mammals. The naked mole-rat may be an extreme model of adaptation to subterranean life and provides insights into the complex interplay of evolutionary adaptations to the constraints of subterranean living. Anat Rec, 2018. © 2018 American Association for Anatomy.

Naked Mole-Rats: Blind, Naked, and Feeling No Pain.

Non-alcoholic fatty liver disease (NAFLD) is a serious metabolic condition affecting millions of people worldwide. A “Western-style diet” has been shown to induce pediatric NAFLD with the potential disruption of skeletal muscle composition and metabolism. To determine the in vivo effect of a “Western-style diet” on pediatric skeletal muscle fiber type and fuel utilization, 28 juvenile Iberian pigs were fed either a control diet (CON) or a high-fructose, high-fat diet (HFF), with or without probiotic supplementation, for 10 weeks. The HFF diets increased the total triacylglycerol content of muscle tissue but decreased intramyocellular lipid (IMCL) content and the number of type I (slow oxidative) muscle fibers. HFF diets induced autophagy as assessed by LC3I and LC3II, and inflammation, as assessed by IL-1α. No differences in body composition were observed, and there was no change in insulin sensitivity, but HFF diets increased several plasma acylcarnitines and decreased expression of lipid oxidation regulators PGC1α and CPT1, suggesting disruption of skeletal muscle metabolism. Our results show that an HFF diet fed to juvenile Iberian pigs produces a less oxidative skeletal muscle phenotype, similar to a detraining effect, and reduces the capacity to use lipid as fuel, even in the absence of insulin resistance and obesity.

High-Fructose, High-Fat Diet Alters Muscle Composition and Fuel Utilization in a Juvenile Iberian Pig Model of Non-Alcoholic Fatty Liver Disease

To explore the effects of heterozygous myostatin-knockout (MSNT+/−) on muscle characteristics, specifically fiber-type distribution and expression of myosin heavy chain isoforms in pigs. The fiber cross-sectional area of the semitendinosus and semimembranosus muscles were much larger in MSTN+/− pigs at birth than in wild-type (WT) pigs. MSTN+/− pigs had a higher proportion of fast-type fibers and lower succinate dehydrogenase activity in muscles than WT pigs. The myosin heavy chain IIB mRNA level in both two muscles was ~ threefold higher in MSTN+/− pigs compared with WT pigs. MSTN+/− pigs exhibit a disproportionate increase in muscle mass and can have a higher body weight due to fiber hypertrophy, a change in the fiber-type distribution, and alteration of myosin heavy chain isoforms levels, leading to more fast glycolytic fibers.

Fiber-type distribution and expression of myosin heavy chain isoforms in newborn heterozygous myostatin-knockout pigs

The cationic amino acid transporter (CAT) protein family transports lysine and arginine in cellular amino acid pools. We hypothesized that CAT expression changes in pig skeletal muscles during rapid pig postnatal development. We aimed to investigate the tissue distribution and changes in the ontogenic expression of CATs in pig skeletal muscles during postnatal development. Six piglets at 1, 12, 26, 45, and 75 days old were selected from six litters, and their longissimus dorsi (LD), biceps femoris (BF), and rhomboideus (RH) muscles, and their stomach, duodenum, jejunum, ileum, colon, liver, kidney, heart, and cerebrum were collected. CAT-1 was expressed in all the 12 tissues investigated. CAT-2 (CAT-2A isoform) expression was highest in the skeletal muscle and liver and lowest in the jejunum, ileum, kidney, and heart. CAT-3 was expressed mainly in the colon and detected in the jejunum, ileum, and cerebrum. The CAT-1 expression was higher in the skeletal muscle of day 1 pigs than in that of older pigs (P   0.05); however, there was a change in CAT-2 expression. The CAT-2 expression was highest in the LD of 12-, 26-, 45-, and 75-day-old pigs, followed by the BF and RH (P < 0.05). These results suggest that CAT-1 and CAT-2 play different roles in pig skeletal muscles during postnatal development.

Expression of cationic amino acid transporters in pig skeletal muscles during postnatal development.

The purpose of this study is to elucidate developmental changes in muscle fiber type in the pig during pre- and postnatal development. For this purpose, we performed a histochemical analysis for myosin adenosine triphosphatase activity to assess muscle fiber type and determined abundances of messenger RNA (mRNA) of myosin heavy chain (MHC) isoforms. Samples of Longissimus dorsi (LD) muscle were taken from fetuses on day 90 of the fetal stage. Further, samples of LD, Rhomboideus and Biceps femoris (B. femoris) muscles were taken from pigs when they were 1, 12, 26, 45 or 75 days old. Expression of MHC 2b mRNA in the LD and the B. femoris muscles rapidly and considerably increased from the late fetal stage to the early postnatal stage and this increase was associated with the development of type 2b fibers at least in the LD muscle. As shown by the rapid and considerable changes in expression of MHC 2b mRNA, it seems that a certain plasticity of muscle fiber type still remains in this developmental stage.

Tomomi Yamaguchi

Papers

Changes in muscle fiber type and expression of mRNA of myosin heavy chain isoforms in porcine muscle during pre- and postnatal development.