Comparison Of Protein Composition From Different Sources And Its Impacts On Physiological Response Of Growing Rats

Meat is rich in many nutrients and plays an important role in human evolution.Along with the improvement of living standard,consumers have increasingly been aware of the relationship between diet and health.To reduce the risk of cardiovascular diseases has been our common goal in the new century.In the past few years,scientists have paid more attention to know the effects of the type and quantity of lipid on metabolic diseases.However,meat proteins and their nutrition have been less concerned.The objective of this study was to investigate effect of 90-day ingestion of different proteins isolated from fish,chicken,pork,beef,casein and soybean on growth performance,metabolic parameters and relative telomere length in liver tissue of rats.1.Comparison of protein composition from different sourcesProteins were extracted from casein,soybean,fish,chicken,pork and beef by a traditional method.The composition of test protein powder was determined according to national standard methods or internationally recognized methods,including crude protein,crude fat,mineral elements and amino acids.The results showed that,four meat protein powders had higher levels of threonine,alanine,and lysine but lower levels of serine,proline,and glutamate than casein and soy protein(P<0.05).2.Effect of protein type on growth performance and hormone level of ratsSix semisynthetic diets containing proteins isolated from casein,soybean,pork,beef,chicken and fish were individually prepared according to the AIN-93G formula.Sixty 4-week-old male Sprague-Dawley rats(100g)were categorized into six groups with ten repetitions and subjected to one of the following diets for 90d:the basal rat diets containing 20%casein,soy protein,fish protein,chicken protein,pork protein and beef protein.Food intake and body weight were recorded once a week.Rats were weighed and withdrawn with food for 4h before being sacrificed by decapitation.Blood was directly collected.Liver,heart,spleen,kidney,and epididymal and perinal adipose tissues were obtained.The results showed that,when compared to fish protein group,the rats fed soy and beef proteins showed a significant reduction in food intake and growth rate(P<0.05).The rats fed beef protein had the greater heart index and kidney index than the other groups(P<0.05),but rats fed beef protein had the smaller liver index,epididymal fat index and perirenal fat index than those fed casein(P<0.05).Chicken protein group had higher level of thyroid hormone(P<0.05).3.Effect of protein type on serum biochemistry and relative telomere lengthBlood samples and liver samples were analyzed to evaluate effect of protein type on serum biochemistry and relative telomere length.The results showed that,the rats fed chicken and pork proteins had higher(P<0.05)concentrations of alanine aminotransferase and aspartate transaminase in serum than did the rats fed casein.In addition,concentrations of total cholesterol and low density lipoprotein were slightly greater for the rats fed chicken protein than those fed casein.However,the rats fed beef protein showed a significant decrease(P<0.05)in serum glucose than control.The rats fed soybean,fish and beef proteins had longer(P<0.05)telomere length in liver cell compared with those fed casein.In addition,telomere length of fish protein group was significantly longer(P<0.05)than the other five groups.Thus,long-term consumption of meat proteins has different effects on body metabolism depending on the protein source and variation in digestion and absorption.The ingestion of chicken protein may increase the burden on the liver,and beef protein may lower hepatic metabolism,but fish protein may be beneficial for longevity and cardiovascular disease.