| The redox homeostasis constitutes an important background of maintaining the normal growth of poultry. However, poultry were affected by numerous environmental-related factors. Reactive oxygen species (ROS) were induced and antioxidant defense system was destroyed, then the state of oxidative stress occurs. The occurrence of oxidative stress not only brought about the nutrition metabolism dysfunction and growth inhibition, but also led to various diseases, even to death. Special attentions were paid on antioxidants which could be used as agents for diminishing the oxidative stress induced by environmental-related factors and improving the antioxidant defense system.a-lipoic acid (LA) is a carboxylic acid which contains eight carbon found in vivo. The main function of LA is involed in maintaining mitochondrial function as a cofactor multi-enzyme comples during oxidative phosphorylation process. The supplementation of LA improve the antioxidant capacity and showed the protect effects of LA on the mitochondrial dysfunction induced by aging and the oxidative stress induced by lipopolysaccharide or ultraviolet radiation. The administration of diquat and rotenone triggered the occurrence of oxidative stress. So, in present study, diquat and rotenone were used to set up the acute oxidative stress model and chronic oxidative stress model respectively, in order to investigate whether the supplementation of LA has the protective effects on the intestinal and hepatic oxidative injury induced by diquat and rotenone respectively, further explore the protective mechanism.1. This study aimed to investigate dietary supplementation with a-lipoic acid (LA) on growth performance, antioxidant capacity and meat quality in broiler chickens. A total of 2401 d-old male Arbor Acres broilers were randomly allocated to 1 of 5 dietary treatments (0,250 mg/kg,500 mg/kg,750 mg/kg, and 1000 mg/kg dietary LA supplementation, respectively). Each treatment included 8 replicates; with 6 chickens each. The experiment lasted 42 days. The results shows that the supplementation of LA at the levels of 500 mg/kg and 750 mg/kg increased the average feed intake (AFI) and body weight gain (BWG) (P< 0.05), however the LA supplementation at the levels of 1000 mg/kg decreased AFI and BWG (P< 0.05), especially in the starter period (P< 0.01). There was no significant difference on feed conversion ratio (FCR) among treatments including the starter period, the grower period and the whole experiment period (P> 0.05). The supplementation of LA decreased abdominal fat yield (P< 0.05). The supplementation of LA increased the pH24h (P< 0.05), decreased the drip loss (P< 0.05) and cooking loss (P< 0.05), LA supplementation also decreased the share force value (P< 0.05) and hardness (P < 0.01). LA supplementation increased the cohesiveness in breast muscle (P< 0.05). The supplementation of LA improved antioxidant properties reflecting the increased total-antioxidant capacity (T-AOC) and the content of glutathione (GSH) in serum, liver and breast muscle (P< 0.05), decreased the content of malondialdehyde (MDA) (P< 0.05), but increased the activities of total superoxide dismutase (T-SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) (P< 0.05). LA supplementation decreased the activities of xanthine oxidase (XO) and monoamine oxidase (MAO) (P<0.05), but increased the activity of total nitric oxide synthase (T-NOS) (P< 0.05). The LA supplementation increased the activity of T-SOD (P< 0.05) and the content of GSH (P< 0.05) in breast muscle during cold storage. The activity of T-SOD and the contents of GSH increased in the first two days (P< 0.05) and then decreased in the followed five days (P< 0.05). The contents of MDA and protein carbonyl gradually decreased with higher levels of LA supplementation (P< 0.05), however decreased in the first two days (P< 0.05) and then increased in the followed five days (P< 0.05) during the progress of cold storage. The supplementation of LA decreased the myofibrillar protein solubility (P< 0.05) and increased the sarcoplasmic protein solubility (P< 0.05).2. The experiment was designed to investigate the effects of LA supplementation to basal diets at the level of 500mg/kg at different periods on growth performance, antioxidant capacity and meat quality in broiler chickens. A total of 256 Arbor Acre male chickens were randomly assigned into four treatment groups:group one was the control group without LA supplementation (control group), group two was the starter period group with LA supplementation (S+LA), group three was the grower period group with LA supplementation (G+LA), group four was the whole periods group with LA supplementation (W+LA). Each group included 8 replicates of 8 chickens in each. The concentration of LA supplementation in this experiment was 500 mg/kg. The results showed that:The supplementation of LA increased the AFI and BWG, especially in the first period (P< 0.05), but no significant difference was observed among the treatment groups and control group (P> 0.05). The birds in G+LA and W+LA groups had a lower abdominal fat yield than that in the control and S+LA groups (P< 0.05). The supplementation of LA increased the T-AOC in serum, liver and breast muscle (P< 0.05), but there was no significant difference between groups with LA supplementation in the starter period and in the grower period (P> 0.05). The LA supplementation also increased the activity of antioxidase, at the same time LA decreased the level of MDA (P< 0.05), but no significant difference was observe between the LA supplementation in the starter period and grower period (P> 0.05). The supplementation of LA decreased the activities of XO and MAO (P< 0.05), but increased the activity of T-NOS (P< 0.05). The LA supplementation in the grower period decreased the activity of XO than that in starter period (P< 0.05), however showed no significant difference on the activity of MAO between groups in the grower and starter period in liver and breast muscle (P> 0.05). The supplementation of LA showed the same variation like the study of different concentrations, in present research the results further indicated that there was no significant difference on meat quality.3. Acute oxidative stress model was set up by using intraperitoneal injection of diquat in order to investigate the effect of LA supplementation and diquat administration to the body redox states. Jejunum and liver were sampled respectively to explore the protective mechanism of dietary with LA supplementation on intestinal inflammation and liver apoptosis. In this part,2×2 factorial arrangement was selected, such as detary treatment (basal diet or the basal diet supplemented with 500 mg/kg LA) and oxidative stress treatment (intraperitoneal injection with saline or diquat,20 mg/Kg·BW). A total of 400 one-day-old male Arbor Acres broilers were randomly allocated four treatments as follows:Group A was fed the basal diet followed by saline administration; Group B was fed the basal diet followed by diquat administration; Group C was fed the basal diet supplemented with LA at the level of 500 mg/kg followed by saline administration; Group D was fed the basal diet supplemented with LA at the level of 500 mg/kg followed by diquat administration. After 21-day growth,3 birds per replicate with near-mean body weight were randomly selected and followed saline or diquat administration according to experimental design. The content of diquat administration was 20 mg/kg per kilogram. The results showed that:(1)Diquat administration decreased BWG and immune organ index in broiler (P< 0.05).The LA supplementation ameliorated the decreased immune organ index showing on the bursa of fabricius index. The diquat administration disturbed jejunal redox balance by decreasing the level of GSH (P< 0.05), the activities of T-SOD, GSH-Px, and DAO (P< 0.05); increasing the level of MDA and the activity of XO (P< 0.05). The LA supplementation ameliorated the redox states induced by diquat through increasing the antioxidant capacity showing not only on the increased level of GSH (P< 0.05), the activities of T-SOD and GSH-Px (P< 0.05) but also on the decreased level of MDA and the activity of XO (P< 0.05), at the same time, LA elevated the activity of DAO in jejunal mucosa (P< 0.05). The diquat administration elevated the levels of pro-inflammatory cytokines IL-1β and TNF-α (P< 0.05), and also increased the levels of IgG and SIgA. Diquat also caused significant damage, reflected on the decreased villus height and villus height/crypt depth ratio (P< 0.05), the increased level of soluble intracellular cell adhesion molecule 1 (sICAM-1) and the expression of tight junction protein 1(TJP1). The LA supplementation showed the protective effect on the oxidative injury induced by diquat administration reflected in the increased villus height and decreased crypt depth, the deceased level of sICAM-1 and the increased expression of TJP-1. Diquat increased the expression of nuclear factor-KB (NF-κB), cyclooxygenase-2 (COX-2) and myeloid differentiation primary response gene 88 (MyD88) (P< 0.05), also increased the translocation of NF-κB-p65 from cytoplasm to nucleus (P< 0.05). LA supplementation not only decreased the expression of NF-κB, COX-2 and MyD88, but also inhibited the translocation of NF-κB-p65.(2) The diquat administration caused the liver redox imbalance; diquat decreased the antioxidant capacity in liver, showing both on the decreased level of GSH, the decreased activity of GSH-Px, and the increased level of MDA and protein carbonyl (P< 0.05). The diquat administration also elevated the activities of some oxidase (P< 0.05). LA supplementation ameliorated the redox imbalance induced by diquat administration, showing not only on the increased level of GSH, the increased activities of T-SOD and GSH-Px, but also on the decreased level of MDA and protein carbonyl (P< 0.05). LA supplementation also inhibited the activities of some oxidase (P< 0.05). The diquat administration caused the mitochondrial dysfunction, showing on the impaired mitochondrial structure (mitochondrial swelling, the ridge disappears), diquat also reduced the mitochondrial membrane potential and activity of caspase-3, decreased activity of 20S proteasome and increased apoptotic index (P< 0.05). LA supplementation maintain the normal mitochondrial function showed LA elevated the decreased mitochondrial membrane potential, reduced the injured the mitochondrial morphology, decreased the activity of MAO (P< 0.05). LA also improved the decreased 20S proteasome activity and suppressed the increased activity of caspase-3, decreased the apoptotic index (P< 0.05). The diquat administration increased the expression of Nrf2 gene, UCP gene and BAX gene (P< 0.05), LA increased the expression of Nrf2 gene, NQO1 gene and UCP gene, decreased the expression of BAX gene (P< 0.05). Diquat administration increased the translocation of Nrf2 protein fron cytoplasm to nucleus (P< 0.05). The LA supplementation further increased the translocation of Nrf2 protein.4. Chronic oxidative stress model was set up by using intraperitoneal injection of rotenone in order to investigate the effect of LA supplementation and rotenone administration to the body redox states. Jejunum and liver were sampled respectively to explore the protective mechanism of dietary with LA supplementation on intestinal inflammation and liver apoptosis. In this part,2×2 factorial arrangement was selected, such as detary treatment (basal diet or the basal diet supplemented with 500 mg/kg LA) and oxidative stress treatment (intraperitoneal injection with sunflower oil administration or rotenone,8 mg/Kg·BW/day for seven days). A total of 400 one-day-old male healthy Arbor Acres broilers were randomly allocated to 4 treatment groups, each treatment comprising 10 replicates; with 10 chickens each replicate. The experiments design was as follows:Group A was fed the basal diet followed by sunflower oil administration; Group B was fed the basal diet followed by rotenone administration; Group C was fed the basal diet supplemented with LA at the level of 500 mg/kg followed by sunflower oil administration; Group D was fed the basal diet supplemented with LA at the level of 500 mg/kg followed by rotenone administration. At day 21,3 broilers per replicate were selected and received sunflower oil or rotenone administration according to experimental design. The content of rotenone administration was 8 mg per kilogram per day for 7 days by using intraperitoneal injection, whereas the other selected broilers received same volume of sunflower oil using the same mode of administration. The results showed that:(1)The rotenone administration decreased the ADG, LA supplementation ameliorated the negative effect induced by rotenone (P< 0.05). The rotenone decreased immune organ index of thymus and bursa of fabricius (P< 0.05), The LA supplementation showed the protective effect on the decreased immune organ index showing on the thymus index (P< 0.05). The rotenone decreased the antioxidant capacity in jejunal mucosa showing on the decreased level of GSH, the decreased activities of T-SOD and GSH-Px, increased the level of MDA and the activity of XO (P< 0.05). The supplementation of LA ameliorated the decreased antioxidant capacity showing on the increased level of GSH, the increased activities of T-SOD and GSH-Px, the decreased level of MDA and the activity of XO (P< 0.05). The production of pro-inflammatory cytokines like IL-1β and TNF-a was induced by rotenone (P< 0.05), the level of IgG and SIgA was also increased (P< 0.05). The LA supplementation attenuated the production of IL-1(3 and TNF-a (P< 0.05), but further increased the level of IgG and SIgA (P< 0.05). Rotenone administration increased the expression of NF-κB gene, COX-2 gene and the level of sICAM-1, decreased the expression of TJP-1 gene and the activity of DAO (P< 0.05). The LA supplementation inhibited the expression of NF-κB gene and COX-2 gene, decreased the activity of DAO, increased the expression of TJP-1 gene and the level of sICAM-1 (P< 0.05). Rotenone administration increased the translocation of NF-κB-p65 from cytoplasm to nucleus (P< 0.05), LA supplementation attenuated the translocation of NF-κB-p65 (P> 0.05).(2) The rotenone administration decreased the antioxidant capacity in liver, showing both on the decreased level of GSH, the decreased activities of T-SOD and GSH-Px, the increased level of MDA and protein carbonyl (P< 0.05).. Rotenone also increased oxidant capacity in liver (P< 0.05). The LA supplementation ameliorated the redox imbalance in liver, showing on the increased level of GSH, the increased activity of T-SOD, the decreased level of MDA and protein carbonyl (P< 0.05). LA supplementation also inhibited the activities of NOX, XO, MAO and MPO (P< 0.05). Rotenone administration cause liver mitochondrial dysfunction, manifested in mitochondrial morphology structural damage and mitochondrial membrane potential loss (P< 0.05). At the same time, rotenone decreased the activities of 20S proteasome and mitochondrial complex I, increased the activity of caspase-3 and the expression of BAX gene, elevated apoptotic index (P< 0.05). The LA supplementation maintains the normal function of the mitochondria showing on the amelioration of mitochondrial morphology and the improvement of mitochondrial membrane potential (P< 0.05). LA also increased the activities of 20S proteasome and mitochondrial complex I, decreased the activity of caspase-3 and the expression of BAX gene, inhibited apoptotic index (P< 0.05). Rotenone administration increased the expression of Nrf2 gene and NQO1 gene, decreased the expression of UCP gene (P< 0.05). Rotenone increased the translocation of Nrf2 protein from cytoplasm to nucleus, LA supplementation further increased the translocation of Nrf2 protein to nucleus (P< 0.05).As stated above, the conclusions are as follows:(1) The supplementation of LA at the levels of 500 mg/kg and 750 mg/kg improve the growth performance, however, LA supplementation at the levels of 1000 mg/kg showed the growth inhibition. The supplementation of LA elevated the carcass characteristics and improved the antioxidant capacity, so as to ameliorate the meat quality, at the same time increase the oxidative capacity during chill storage.(2) The supplementation of LA can improve the growth performance, especially in the first period. LA supplementation in the grower period elevated the carcass characteristics through decreasing the abdominal fat yield. The supplementation of LA in two different periods ameliorated meat quality through improving the antioxidant capacity which obtained part of effects of the whole periods with LA supplementation.(3) Effects of LA supplementation on acute oxidative stress induced by using intraperitoneal injection of diquat:The supplementation of LA improved the antioxidant capacity in jejunal mucosa and ameliorated the jejunal morphology and injured function. The protective effect of LA was partly mediated through the reduction of pro-inflammatory cytokines, and attenuation of the NF-κB signalling pathway activation. LA also showed the protect effect on the liver oxidant stress and hepatocytes apoptosis through increasing the antioxidant capacity and attenuating oxidant capacity, maintaining the normal mitochondrial function, increasing the activity of 20S proteasome to accelerate the degradation of oxidative proteins, decreasing the activity of caspases-3 and the expression of BAX gene to inhibit the apoptosis, increasing the translocation of Nrf2 protein to maintain the redox balance.(4) Effects of LA supplementation on chronic oxidative stress induced by using intraperitoneal injection of rotenone:The supplementation of LA improved the antioxidant capacity and attenuated the intestinal oxidative damage induced by rotenone partly mediated via the improvement of its anti-oxidant property, decreased production of pro-inflammatory cytokines which also involved the attenuation of NF-κB signaling pathway. LA also showed the protective effect on the oxidative stress through the improvement of antioxidant capacity and the attenuation of oxidant capacity in liver. LA also maintains the normal mitochondrial function, increases the activity of 20S proteasome, the expression of UCP gene, and the translocation of Nrf2 protein to nucleus, then reduced the activity of caspase-3 and the expression of BAX gene, then decreased apoptotic index induced by rotenone. |
PDF Full Text Request