Effects of octacosanol extracted from rice bran on blood hormone levels and gene expressions of glucose transporter protein-4 and adenosine monophosphate protein kinase in weaning piglets

摘要

Abstract The object of this study was to explore the regulatory mechanism of octacosanol to the body of animals and the effects of octacosanol on blood hormone levels and gene expressions of glucose transporter protein (GLUT-4) and adenosine monophosphate protein kinase (AMPK) in liver and muscle tissue of weaning piglets. A total of 105 crossbred piglets ([Yorkshire?×?Landrace]?×?Duroc) with an initial BW of 5.70?±?1.41?kg (21?d of age) were used in a 6-wk trial to evaluate the effects of octacosanol and tiamulin supplementation on contents of triiodothyronine (T₃), thyroxine (T₄), growth hormone (GH), glucagon (GU) and adrenaline (AD) in blood and gene expressions of GLUT-4 and AMPK in liver and muscle. Piglets were randomly distributed into 3 dietary treatments on the basis of BW and sex. Each treatment had 7 replicate pens with 5 piglets per pen. Treatments were as followed: control group, tiamulin group and octacosanol group. The results showed that compared with control group and tiamulin group, octacosanol greatly promoted the secretion of T₃, GH, GU and AD ( P 3, T₄, GH, GU or AD ( P >?0.05). Results of the present study has confirmed that octacosanol affects energy metabolism of body by regulating secretion of blood hormones and related gene expression in tissue of weaning piglets, which can reduce stress response and has an impact on performance. Keywords Octacosanol ; Weaning piglets ; Hormone ; GLUT-4 ; AMPK prs.rt("abs_end"); 1. Introduction Octacosanol, which mainly exists in a natural wax product that naturally occurs in fruits, leaves and on the surface of plants ( Taylor et?al., 2003 ), is a kind of natural senior fatty alcohol with prominent physiological activity. Because only very few amounts can be ingested from diets, octacosanol must be supplied in extra to gain health benefits. Most studies that were evaluating the efficacy of octacosanol used either a wheat-germ oil extract (policosanol) or a natural mixture of primary alcohols isolated from sugar cane wax ( Saccharum officinarum L.), of which octacosanol is the main component ( Saint-John and McNaughton, 1986 and Kato et?al., 1995 ). Recent studies in humans and rodents have demonstrated that octacosanol is involved in the functions of antifatigue ( Kim et?al., 2003 ), regulating lipid metabolism ( Kato. et?al., 1995 ), reducing cholesterol ( Hernandez et?al., 1992 ), cytoprotective activity ( Carbajal et?al., 1996 ) and promoting the energy metabolism ( Oliaro-Bosso et?al., 2009 ) and so on. Now, octacosanol has been widely used in health food, medicine and other fields. With the gradual improvement of the concerns to food safety, the development and application of green feed additives become the research hot spots. Octacosanol with high safety ( Casta?o et?al., 1995 ) and effective functions can be regarded as a new feed additive, which will have great development and application value. Tiamulin is a kind of double terpene antibiotics, which can inhibit bacteria and promote the growth of animals by combining with the 50S subunit of bacterial ribosome. However, the safety problems of antibiotics and drug residues have been paid more and more attention in recent years. There are few studies on octacosanol in the domestic animals. The research in broilers showed that feed supplementation with 25?mg/kg octacosanol increased the body weight by 4% and improved the feed efficiency by 5.9% compared with the control diet ( Xu and Shen, 1997 ). In our previous study in weaning piglets, we found dietary octacosanol supplementation obviously increased the average daily gain (ADG) by 6.45% and significantly improved feed conversion ratio (FCR) by 6.35% compared with the control diet, and had no differences in growth performance compared with the tiamulin diet. Moreover, pigs fed octacosanol had lower diarrhea ratio and higher antioxidant ability ( Long et?al., 2015 ). The mechanism may be that octacosanol can regulate the glycogen in body and maintain the balance of energy metabolism ( Xiang et?al., 2012a ). At present, the studies on the energy metabolism of octacosanol in the domestic animal are few reported. In order to probe the active mechanism of octacosanol in animal body and amplify the application in livestock and poultry productions, this study therefore, discussed the variation of indexes on energy metabolism through determining triiodothyronine (T₃), thyroxine (T₄), growth hormone (GH), glucagon (GU) and adrenaline (AD) in blood of weaning piglets, and analyzing the gene expressions of glucose transporter protein (GLUT-4) and adenosine monophosphate protein kinase (AMPK) in the liver and muscle tissue. Meanwhile, by comparing with the effects of tiamulin, the different regulatory mechanism on animal body was illustrated between octacosanol and antibiotics, which provided a theoretical basis for the application of octacosanol in feed field. 2. Materials and me