Effects And Mechanism Of Betaine On Growth And Intestinal Functions Of Piglets

Betaine,also known as trimethylglycine,is first extracted from sugar beets.Betaine acts as an efficient methyl donor because of its three liable methyl groups.In husbandry,betaine is used as a substitution for other methyl group donors,such as choline and methionine,to save feed costs.Betaine is also used as a carcass modifier by reducing the carcass fat content to increase lean rate for playing an important role in lipid metabolism through transmethylation reactions.However,betaine is also an excellent osmoprotectant due to its zwitterionic property.The contents in intestinal lumen vary dramatically,especially during the process of digestion and absorption of nutrients,the intestinal epithelial cells have to undergo fluctuating osmolarity.The intestinal epithelial cells control the exchange of water,inorganic ions,nutrients and macromolecules between plasma and the intestinal lumen.As such,it is of profound significance both in physiology and in practice for betaine to play the role of osmoregulation in intestine.This study was carried out firstly to investigate the effects of betaine on growth performance,digestive enzyme activities,intestinal morphology,gut barrier,intestinal osmotic pressure and nutrients digestibility of piglets;and secondly to explore the mechanisms of betaine on the structural and functional protection of digestive enzymes via enzyme activities and enzymatic dynamics in vitro;and then to dig the mechanisms of the osmoprotection role of betaine in the hyperosmolarity stressed intestinal epithelial IPEC-J2 cells;and finally to further evaluate the effects of betaine on the intestinal functions of model animal,SD rats,under hyperosmotic stress induced by high-salt diet.The main results are described as follows:Experiment 1.Effects of betaine on growth performance and intestinal functions of piglets.A total of 150 crossbred weaned piglets(Duroc × Landrace ×Yorkshire),with an average initial body weight of 8.52 ± 0.26 kg and age of 39 d(weaned on d 25),were randomly divided into three dietary treatments,each of which was replicated five times with ten pigs per replicate.The dietary treatments were basal diet supplemented with 0,1 250,and 2 500 mg/kg betaine,respectively.The trial lasted 30 days.The results showed that betaine could increase the activities of digestive enzymes,ameliorate intestinal morphology,maintain the integrity of the gut,alleviate intestinal stress,enhance the digestion and absorption of nutrients,decrease the diarrhea rate,and improve the growth performance of pigletsExperiment 2.Effects of betaine on digestive enzymes activities and enzymatic dynamics in vitro.Enzyme-catalyzed reaction of trypsin and a-amylase were proceeded in vitro to simulate the somatic isoosmolarity(Tris-HCl buffer solution)and hyperosmolarity(buffer solution with 0.3 mol/L,0.6 mol/L and 1 mol/L NaCl,respectively),an identical concentration of betaine was added to both the buffer solution and the NaCl solution.The results showed that betaine could also increase the enz:yme activities in vitro.Enzymatic dynamics analysis made it clear that betaine enhanced the catalytic efficiency mainly via boosting the affinity of enzyme and substrate.In the hyperosmotic environment,betaine could counteract the inhibition effects of NaCl on enzymes to some extentExperiment 3.Osmoprotection role of betaine in the hyperosmolarity stressed intestinal epithelial IPEC-J2 cells.IPEC-J2 cells were cultured in isoosmolarity medium(300 mOsm),isoosmolarity medium(300 mOsm)supplemented with betaine(10 mmol/L),hyperosmolarity medium(600 mOsm),and hyperosmolarity medium(600 mOsm)supplemented with betaine(10 mmol/L),respectively.The results showed that betaine could improve the liability of IPEC-J2 cells,retrench the energy expenditure of NKA,and increase the gene expression of p53 to repair damaged cells to survive the adverse osmotic environmentsExperiment 4.Effects of betaine on intestinal functions of hyperosmolarity stressed SD rats.Thirty two four-week-old male Sprague-Dawley rats weighing 128.0± 5.06 g were randomly allotted to four groups.The control group was fed with standard chow diet(0.4%NaCl),while the treatment groups were fed a high-salt diet(4.0%NaCl)supplemented with betaine at 0.0%,0.5%,and 1.0%,respectively.The experiment lasted 28 days.The results showed that betaine could enhance digestive enzymes,ameliorate intestinal morphology,decrease the release of ADH and COR,counteract the osmotic stress induced by high-salt diet.Furthermore,betaine could maintain the equilibrium of microbiota in the gut of SD rats under hyperosmotic stress induced by high-salt diet.In summary,betaine could increase the activities of digestive enzymes,ameliorate intestinal morphology,maintain the integrity of the gut,alleviate intestinal stress,promote the digestion and absorption of nutrients,decrease the diarrhea rate,and improve the growth performance of piglets.In vitro enzymatic dynamics study showed that betaine could boost the affinity of enzyme and substrate to augment enzymatic activity and catalytic efficiency.Cell culture study revealed that betaine could retrench the energy expenditure of NKA,improve the liability of intestinal epithelial cells,and enhance the repair ment of damaged cells to survive the hyperosmotic environment.Besides,model animal study in SD rats demonstrated that betaine could counteract the osmotic stress induced by high-salt diet and maintain the equilibrium of microbiota in intestine under osmotic stress.