| Royal jelly(RJ)is a yellowish-white and acidic secretion of hypopharyngeal and mandibular glands of nurse bees used to feed young worker larvae during the first three days and the entire life of queen bees.It plays an important role in nutrition and health care for human.10-Hydroxy-2-Decenoic acid(10-HDA)is the main fatty acid in royal jelly and the main index to evaluate the quality of royal jelly,which is secreted by the mandibular gland of worker bees.Previous studies have shown that the food(pollen and honey)collected by bees from the outside has an important impact on the quality of royal jelly.However,it has not been reported whether oleic acid supplementation in the diet affects the 10-HDA secretion of worker bee.Royal jelly and 10-HDA had hypoglycemic effect,but the effect is not clear.In our study,firstly,we aimed to explore the effects of oleic acid supplementation in diet on 10-HDA synthesis in mandibular gland of worker bees;then,through establishment of type 2 diabetes mouse model,we aimed to explore the effect of 10-HDA intervention on the hypoglycemic effect,and molecular and metabolic mechanism.The main research findings are summarized as follows:1.Study on changes of lipid composition in mandibular gland of worker bees with ageThe purpose of this study was to investigate the changes of lipid composition in the mandibular gland of worker bees with the increase of age.Five colonies with similar population and no disease were selected to collect the mandibular glands of newly emerged bees,3,6,9,12,15,18 and 21-day old worker bees for lipid composition analysis.The results showed that1)from1d worker bee(15.12 ± 0.84 ?g/ MG)to 15 d worker bee(54.39 ± 1.96 ?g/ MG),the content of 10-HDA in the mandibular gland increased gradually,and the content of 10-HDA in mandibular gland of worker bees was basically unchanged from 15 to 21 days.2)The genes expression of A4,FAS,ETF-??CYP6AS8,CPTI and ACOX1 basically increased with the increase of age.3)Through analyzing the non-targeted lipidomics of mandibular gland of 1 d,6 d and 15 d worker bees,PC and TAG were the main lipids of mandibular gland,and the unsaturation of carbon chain in PC and TAG increased in 6 d and 15 d worker bees.The abundance of TAG(18:0-18:0-18:1)and TAG(18:0-18:1-18:1)decreased significantly in 6 d and 15 d worker bees compared with 1 d worker bees(P < 0.05).In conclusion,PC and TAG are the main lipid subclasses in worker bee mandibular gland.The carbon chain unsaturation of TAG,PC and PE increased with age.In different TAG species,the abundances of TAG(18:0-18:0-18:1)and TAG(18:0-18:1-18:1)decreased significantly with the increase of age.2.Effects of oleic acid supplementation on 10-HDA synthesis in mandibular gland of worker beesThis study was carried out to assess the effect of oleic acid(OA)addition on the biosynthesis of 10-HDA.In the experiment of worker bees reared in cage,1200 1-day-old newly emerged worker bees were randomly divided into 5 groups(4 replicates/group,60 worker bees/replicate).The control group was fed with the basal diet,and the experimental group was added with 2%,4%,6% and 8% oleic acid in the basal diet.The mandibular glands of worker bees were collected when fed to 9 days.Based on the above research results,2400 1-day-old newly emerged worker bees were randomly divided into two groups(12replicates/group,100 worker bees/replicate).The control group was fed with the basal diet,the experimental group was added with 8% oleic acid in the basal diet,and the mandibular glands of worker bees were collected when fed to 9 days.In the free-flying colonies experiment,10 healthy bee colonies were randomly divided into two groups(5 replicates/group).The control group was fed with the basal diet,and the experimental group was added with 8% oleic acid in the basal diet for 75 days.After 21 days of the formal experiment,royal jelly and mandibular glands were collected.The samples were analyzed for 10-HDA content,lipidomics and transcriptomics.The results showed that 1)in worker bees reared in cage,the content of 10-HDA of the worker bee in the 8% oleic acid group was significantly higher than that in the control group(P < 0.05).The genes expression of A4,FAS,ACOX1,ACOX3,CPTI,CYP6AS8,ETF-? and KAT in mandibular gland of worker bees in 8% oleic acid group were significantly higher than those in the control group(P < 0.05).2)In worker bees reared in cage,154 kinds of TAGs were detected by lipodomics analysis of mandibular glands,and TAG(18:1-18:1-18:1)was the most abundant.The addition of 8% oleic acid to the diet significantly increased the abundance of 10 TAGs species(P < 0.05),among which TAG(18:1-18:1-18:1)and TAG(18:0-18:1-18:1)accounted for the highest proportion.3)In worker bees reared in cage,transcriptome analysis of the mandibular glands showed that the addition of 8% oleic acid to the diet significantly increased the transcriptional levels of GPAT and GK(P < 0.05).4)In free-flying colonies,the addition of 8% oleic acid to the diet significantly increased the content of 10-HDA in royal jelly(P < 0.05).In conclusion,the addition of 8% oleic acid in diet promotes the biosynthesis of 10-HDA in worker bee mandibular gland,in part by increasing the abundances of TAG(18:1-18:1-18:1)and TAG(18:0-18:1-18:1).3.Hypoglycemic mechanism of 10-HDA on diabetic mice induced by HFD/STZHere,we used high fat diet(HFD)combined with streptozotocin(STZ)injection to establish a diabetes model,with the aim of exploring the hypoglycemic effects of 10-hydroxy-2-decenoic acid(10-HDA),and underlying molecular mechanisms.A total of 60 male C57BL/6J mice were fed a 60% HFD for 6 weeks,and intraperitoneally injected with STZ(100mg/kg body weight)to establish a type 2 diabetes mellitus(T2DM)model.Mice were randomly divided into four groups(8 mice per group): control group,10-HDA group,T2 DM group,and T2DM+10-HDA group.The 10-HDA and T2DM+10-HDA groups were administered intragastric 10-HDA(100 mg/kg body weight),while the control and T2 DM group were administered vehicle,daily for 4 weeks.There was no significant difference in body weight between T2DM+10-HDA and control group mice(P > 0.05).Treatment with 10-HDA reduced fasting blood glucose and increased insulin levels in diabetic mice(P < 0.05),as well as increasing the area of pancreatic islets(P < 0.05),and alleviating vacuolar degeneration in the liver.Further,10-HDA intervention increased superoxide dismutase,catalase,and glutathione peroxidase activities in diabetic mouse liver,decreased MDA content,inhibited liver P-NF-?B protein level,decreased IL-6 and TNF-? content,and increased P-PI3 K,P-AKT,and P-GSK3?protein levels(all P < 0.05).Fifteen potential biomarkers were screened by analysis of liver metabolomics data,of which hexadecanamide,stearamide,pentadecanoic acid,and fatty acid esters of hydroxy fatty acids(16:0/18:1)were highly abundant.In conclusion,10-HDA has clear hypoglycemic effects on diabetic mice,through the PI3K/AKT/GSK3? signaling pathway.In conclusion,oleic acid supplementation in diet significantly promotes the synthesis and secretion of 10-HDA in mandibular gland.10-HDA has obvious hypoglycemic effect on diabetic mice,through PI3K/AKT/GSK3? signal pathway. |
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