The Occurrence Of Autophagy Induced By Early Weaning Stress In Piglets

With the improvement of feeding and nutrition level, Early weaning technology is widely used in modern animal production.Weaning age has been steadily decreased However, during the weaning the piglets are susceptible to the alteration of environment and nutrition which results in a series of early weaned stress syndrome. Autophagy is kind of lysosomal degradation pathway which generally existed in eukaryotic cells. It plays a very important role in the growth and development of cells. Previous research in our lab have confirmed that1-2days after weaning, autophagy can be activated immediately. But with the prolong of weaning time, the change of autophagy remains to be further studied. Besides, the weaning piglet is facing nutrients and energy intake limit, so with the extension of weaning time, the regulation of nutrition and energy pathway in vivo remains to be further study.This project composed of five parts:1.With the extension of the weaning time, the change of routine physiological and biochemical indicators in serum;2. The changes of hormonal in serum;3. The structure change of intestinal tract in weaned piglets;4.AMPK is the energy sensor, while energy intake is limited at weaning, whether AMPK also show some change;5.mTOR can regulate protein synthesis and response the concentration of amino acids in vivo, while nutrient intake is limited at weaning, whether mTOR show some change.6. Based on previous research in our lab, autophagy can be activated in1-2days after weaning. But with the extension of weaning time, whether there will be some variation of autophagy.The study results are as follows:(1) Through the determination of routine physiological and biochemical indexes in serum, we found that compared with the control group, WBC are tend to decrease in the piglets from1day to7days; RBC, HGB decline firstly and then increase. And the trend was not significant; MCHC first decreased and then increased, and only in the fourth day showed significantly decreased (P<0.05);RDW is a sign of anemia, it increased apparently in the second day of weaning indicating that the most serious anemia occurred at the second day, after that it showed a downward trend. Absolute lymphocyte percentage of lymphocytes to some extent also reflects the immune status of the body, and to some extent also reflects the level of the body’s immune have been affected.(2)Through the determination of the related hormones in serum,compared with the control, In the first day after weaning, interleukin-6in blood decreased by32.13%(P<0.05), in the second day after weaning, decreased by17.87%(P>0.05), however, the 4th day after weaning, increased by53.02%(P>0.05),7days after the weaning, increased by52.97%(P<0.05); Cortisol in blood increased by52.64%(P<0.05) in the first day after weaning, and in the second day to the seventh day after weaning, Cortisol increased by31.74%,8.41%,26.09%(P>0.05) respectively; In the first day to the seventh day after weaning, growth hormone respectively increased by7.21%,40.48%,0.5%,61.37%(P>0.05);the first day,second day,the fouth day and seventh day after weaning, insulin respectively reduced47.99%,7.57%,37.03%,22.52%(P>0.05); Glucagon showed a decrease by62.21%(P<0.01) in the first day after weaning, however in the second day, fouth day and seventh day after weaning,glucagon were respectively increased by22.73%,39.47%,39.41%(P>0.05). These results demonstrated that weaning at14days of age have a certain impact on the immunity, the level of energy intake and hormone, however, with the prolong of weaning time, the negative affection will be alleviated.(3) After analysis piglet intestinal villus length and crypt depth, we found that in weaning group villus length and crypt depth ratio is less than control.but the difference is not significant.(4) Using Western-blot to detection the expression level of AMPK, compared with the control group, After weaning1-2days, AMPK is significant activated (P<0.05), however, the4～7days after weaning,the AMPK activity decreased and the difference was not significant (P>0.05). Using periodic acid-Schiff staining (PAS) to dye the piglets liver tissue, we found that compared with the control group, the first day after weaning, the glycogen in the liver was significantly less than the control group. However,2days after weaning, though glycogen has decreased, but compared with the first day, there’s still an difference in glycogen.4day and day7after weaning, compared with the control group, there’s little difference. Analyzed the concentration of glucose in the blood, we found that compared with control group,1day to7day after weaning, the concentration of glucose were respectively decreased by5%,6.67%,30.15%,9.76%(P>0.05), the difference was not significant.(5) Using Western-blot to detection the expression of mTOR, we found that in1to2days after weaning, the activity of mTOR showed a significant reduction. But to the4day after weaning, the activity of mTOR has been raised, though the difference is not significant.(6) Detected the level of autophagy by Western-blot and transmission electron microscopy, results showed that weaned at14-days-old, after weaning1～2days, activity of autophagy was significantly enhanced firstly and then declined, and ultimately maintain a certain level.In summary, a conclusion came up that the early weaning stress in piglets will affect immune function and absorption of nutrients, however, after weaning4-7days,this influence will be declined; the early weaning stress will induced autophagy to occur, but in4-7days after weaning, autophagy activity decreased, and ultimately remained at baseline levels; the expression level of AMPK tend to increased firstly and then decreased along with the prolong of weaning time; mTOR activity showing the trend which first increased and then decreased with the prolong of the weaning time.