In polytocous species such as the pig there is intralitter variation in birth weight and skeletal muscle fiber number. It is commonly recognized that low birth weight in piglets correlates with decreased survival and lower postnatal growth rates. In the majority of low birth weight piglets low numbers of muscle fibers differentiate during prenatal myogenesis, for genetic or maternal reasons, and those low birth weight piglets with reduced fiber numbers are unable to exhibit postnatal catch-up growth. Pigs of low birth weight show the lowest growth performance and the lowest lean percentage at slaughter. In addition, they tend to develop extremely large muscle fibers (giant fibers) and poor meat quality, which results in part from the inverse correlation between fiber number and fiber size. Prenatal growth and myogenesis are under the control of various genetic and environmental factors, which can be targeted for growth manipulation. Genetic selection is considered a suitable tool to improve fetal growth and myogenesis. Prenatal development is mainly dependent on a close interrelation between nutritional supply/use and regulation by hormones and growth factors. In particular, the maternal somatotropic axis plays a significant role in the control of myogenesis. Thus, treatment of sows with GH until mid-gestation was able to increase birth weight and the number of muscle fibers in the small littermates of the progeny that are disadvantaged by insufficient nutrient supply. Growth hormone treatment was associated with increased nutrient availability to the embryos and changes in regulatory proteins of the GH-IGF axis. Interactions between maternal nutrition and the somatotropic axis in determining prenatal growth and myogenesis are worthy of further investigation.
Isoflavones, rich in soybean, are currently receiving much attention because of their potential role in preventing and treating cancer and other human chronic diseases. The present review provides an overview of the recent results in this research field. Data from epidemiological reports and laboratories have shown that isoflavones have multi-biological and pharmacological effects in animals and humans. These include estrogenic and antiestrogenic effects, cell signalling conduction, as well as cell growth and death. Based on these properties, soy protein and isoflavones have been associated with reduced incidences of breast and prostate cancers, cardiovascular diseases or osteoporosis, and exhibit some other favorable effects. The mechanism through which isoflavones may exert the above-mentioned functions are not only based on the estrogenic properties of isoflavones, but also on their role as protein tyrosine kinase inhibitors, as regulators of gene transcription, modulators of transcription factors, antioxidants, as well as by altering some enzyme activities. However, to draw a clear conclusion regarding the clinical use of isoflavones further investigation would be required, although only a few effects of short- or long-term use of soy proteins are known in humans.
The present study was undertaken to determine the tissue-specific expression of estrogen receptor beta (ER ), and the effects of a daidzein supplement to the diet of pregnant sows on the expression of ER , and type 1 insulin-like growth factor receptor (IGF-1R) genes in newborn piglets by using semi-quantitative RT-PCR. Eight sows received a dietary supplement of daidzein at a dosage of 8 mg per kg feed from day 85 of gestation, and six sows were used as controls. After parturition, 2 male neonatal piglets were selected from each litter for sampling. ER mRNA was detected in intestine, lung, thymus, kidney, pituitary and hypothalamus tissues, but not in heart, adrenal, skeletal muscle, liver or placental tissues. Daidzein treatment significantly increased the birth weight of male piglets and markedly reduced the level of ER mRNA in the hypothalamus, but not in the pituitary. An up-regulation of IGF-1R gene transcription was observed in skeletal muscles of newborn piglets. In addition, the IGF-1R mRNA was found to be most abundant in pituitary and hypothalamus, followed by skeletal muscle, thymus, and liver tissues in decreasing order. Our results demonstrate that (1) ER is expressed in a tissue-specific manner in newborn piglets, (2) daidzein down-regulates ER gene expression in the hypothalamus, possibly indicating central effects of daidzein, and (3) daidzein influences fetal growth associated with higher IGF-IR gene expression in skeletal muscle.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.