| Aging refers to an organism that develops and matures under normal conditions.With the increase of age and the decrease of environmental stability and stress ability in the body,the structure and function of the body will gradually degenerate and eventually die as a complex and irreversible natural phenomenon.Advanced glycation end products(AGEs)is the binding products of excess reducing sugar and protein,which can not only accumulate with age in human and animal serum or tissue,but also initiate multiple signal pathways after binding to its receptor(receptor for advanced glycation end products,RAGE)protein,mediate oxidative stress and pro-inflammatory response,destroy the internal environmental balance of tissue cells,and affect the normal structure and function of cells.It causes functional senescence and degeneration of tissues and organs of the body.Therefore,AGEs is regarded as a biomarker to evaluate the aging process.With the decline of the global fertility rate and the extension of life expectancy,the world begins to enter the aging society,how to achieve the healthy aging of the elderly is a great challenge for human beings.Therefore,the inhibition of AGEs accumulation and RAGE expression through food nutrition intervention has important scientific significance to maintain the homeostasis of the internal environment,delay the aging process and achieve healthy aging.L-theanine is a safe non-protein amino acid in tea.In liver,brain and kidney tissues or in vitro cell tests,L-theanine shows good effects in resisting endogenous or exogenous damage,such as anti-oxidation,anti-inflammation,reducing mitochondrial damage,repairing DNA damage,inhibiting amyloid folding,improving body immunity and so on.However,whether L-theanine can inhibit the accumulation of AGEs in vivo to achieve anti-aging effect and mechanism remains to be further explored.In this study,combined with the characteristics that AGEs mainly metabolizes in the liver,induces ?-amyloid protein(A?)accumulation in brain tissue and is cleared in vitro by kidney,on the basis of aging induced by daily subcutaneous injection of D-galactose(200mg/kg/d)in 5-6-week-old SPF male healthy SD rats,different doses of L-theanine(100,200,400mg/kg/d)intervention were used to induce 56 days.The histopathological sections were sampled and made,and the effects and mechanisms of L-theanine on inhibition of AGEs accumulation and anti-aging induced by D-galactose in rats were studied and analyzed from the level of AGEs-RAGE pathway by means of enzyme-linked immunosorbent assay(Elisa),q RT-PCR and Western blot,so as to provide scientific basis for delaying aging,promoting the diversified development of food nutrition intervention and deep utilization of L-theanine.The main results and conclusions are as follows:(1)The results of detection and analysis showed that compared with the normal group,the content of AGEs in serum,liver,brain and kidney of D-galactose-induced model rats increased significantly(P < 0.05),which indicated that D-galactose induced AGEs rats successfully.(2)Regulatory effect of L-theanine on physiological function induced by D-galactose in rats.Compared with the normal group,L-theanine decreased the content of AGEs in serum(P < 0.05),increased the organ index of spleen and thymus in immune tissue(P < 0.05),and increased the activities of SOD,CAT,GSH-Px and T-AOC in serum and the contents of anti-inflammatory factors IL-4 and IL-10(P < 0.05).The activity of NOS and the content of MDA in serum were decreased(P < 0.05),and the contents of pro-inflammatory factors TNF-?,IL-1 ? and IL-6 in rats were also decreased(P < 0.05).(3)Regulatory effect of L-theanine on AGEs metabolism induced by D-galactose in rat liver and its mechanism.Compared with the normal group,the pathological sections of liver tissue stained by HE showed that L-theanine could effectively prevent the degeneration symptoms of hepatocyte edema,vacuole and cytoplasmic porosity induced by D-galactose(P < 0.05),and keep the liver tissue healthy.L-theanine could reduce the content of AGEs in liver induced by D-galactose(P < 0.05),down-regulate the m RNA and protein expression of receptor protein RAGE(P < 0.05),and the expression of m RNA and phosphorylated protein of transcription factor NF-kappa B(p65)(P < 0.05).At the same time,down-regulate the m RNA expression and protein expression of inflammatory mediators(TNF-?,TNFR1,IL-1?,IL-1R,IL-6,i NOS,ICAM-1 and VCAM-1)(P < 0.05).It could up-regulate the m RNA expression of SOD2,SOD3,CAT and transcription factor Fox O1(P < 0.05),inhibit the expression of FOXO1 phosphorylated protein(P < 0.05),and up-regulate the protein expression of SOD2 and CAT in rat liver(P < 0.05).It can up-regulate the m RNA and protein expression of Bcl-2(P < 0.05),down-regulate the m RNA and protein expression of Bax and cleaved-caspase-3(P < 0.05),inhibit the apoptosis of liver tissue induced by D-galactose,maintain the normal liver function index(ALT and AST)and blood lipid constant(TC and TG)(P < 0.05).It is suggested that L-theanine can improve the homeostasis imbalance of liver tissue induced by D-galactose,prevent the deterioration of liver function and promote AGEs metabolism.(4)The effect and mechanism of L-theanine on D-galactose-induced brain injury in rats by inhibiting AGEs accumulation.Compared with the normal group,HE staining sections of brain tissue showed that L-theanine could improve the disorder,atrophy or apoptosis of hippocampal neurons induced by D-galactose,decrease the content of AGEs and down-regulate the m RNA and protein expression of RAGE in brain tissue of rats induced by D-galactose(P < 0.05).It can up-regulate the protein expression of SOD2 and CAT in the induced brain tissue(P < 0.05),alleviate the oxidative stress injury of the brain tissue,inhibit the expression level of p-NF-kappa B(p65)protein(P < 0.05),down-regulate the contents of inflammatory factors TNF-?,IL-1 ?,IL-6 and n NOS(P < 0.05),and maintain the inflammatory balance in the induced brain tissue.It can up-regulate the expression of m RNA and protein of PGC-1a in rat brain and promote mitochondrial biosynthesis(P < 0.05).It could increase the content of neurotransmitter ACh(P < 0.05),up-regulate the expression of m RNA and protein of BDNF(P < 0.05),up-regulate the expression of Bcl-2 protein and down-regulate the expression of Bax and cleaved-caspase-3 protein and inhibit the apoptosis of hippocampal neurons(P < 0.05).It is suggested that L-theanine can maintain the homeostasis of brain tissue induced by D-galactose and prevent the degeneration of cerebral nerve aging.(5)The effect and mechanism of L-theanine on D-galactose-induced renal injury in rats by inhibiting AGEs accumulation.Compared with the normal group,L-theanine could decrease the contents of AGEs and MDA in renal tissue(P < 0.05),increase the activities of GSH-Px and T-AOC of D-galactose(P < 0.05),down-regulate the expression levels of RAGE,NF-kappa B(p65),Bax and cleaved-caspase-3 protein(P < 0.05),and the contents of inflammatory factors TNF-?,IL-1 ?,IL-6 and i NOS(P < 0.05),and up-regulate the expression level of Bcl-2 protein in renal tissue of rats induced by L-theanine(P < 0.05).It is suggested that L-theanine can improve the degree of induced renal amyloidosis,maintain the homeostasis of renal tissue and alleviate the damage of renal tissue function.In summary,L-theanine can reduce the content of AGEs in serum,liver,brain and kidney induced by D-galactose,down-regulate the expression of RAGE protein in liver,brain and kidney,inhibit redox imbalance,pro-inflammatory response and apoptosis,maintain homeostasis,and thus play a role in anti-aging induced by D-galactose. |
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