| Obesity is one of the most common and major health problems in the world.Obesity is associated with metabolic disorders,such as high blood pressure,type 2diabetes,etc.,which pose a huge physical and financial burden to patients.The traditional method of reducing weight has some disadvantages,such as insufficient curative effect,high cost,big side effect and so on.Therefore,the development of dietary supplements with weight loss function by using natural,green and safe plant extracts has become a hot research topic at present.Sweet orange essential oil(Sweet orange essential oil,SOEO)is a natural plant extract from citrus fruits of the family Rutaceae.It has physiological functions such as anti-oxidation,anti-inflammatory,anti-cancer,anti-obesity,protecting blood vessels and so on.However,SOEO is very sensitive to oxygen,light and humidity,and can be oxidized or degraded rapidly after long-term exposure to the outside world.After oral intake of SOEO,it can be absorbed rapidly by gastrointestinal tract and quickly excreted from the body.The residence time in the body is relatively short,which is not conducive to the full pla y of its physiological activity.At the same time,because gut microbiota can affect the metabolism of the whole body by affecting energy balance,intestinal permeability,gene expression,etc.,will dietary supplements with weight loss function affect gut microbiota of obese individuals?In addition,oxidative stress may be the initiator of obesity-related lipid metabolism disorder,so it is necessary to study the effects of dietary supplements on oxidative stress in obese individuals and to discuss the relationship between obesity and oxidative stress.In order to solve the above problems,sweet orange essential oil microcapsule(SOEO-MC)were prepared by SOEO and?-CD in this study,and the obese SD rats were selected as the research object.The effect and mechanism of SOEO-MC on weight loss were studied by oral administration of SOEO-MC,and the effects of SOEO-MC on gut microbiota and oxidative stress in obese SD rats were studied.The aim of this study was to provide scientific basis for the development of SOEO dietary supplement with weight loss effect.The main conclusions are as follows:(1)Preparation and characterization of SOEO-MC.?-CD was used to encapsulate SOEO to form microcapsules.The results of response surface experiment showed that the encapsulation efficiency of microcapsules with 5.66 g SOEO,at 53.7?for 3.24 h was the highest,and the maximum theoretical value was 50.32‰.The micromorphology and physicochemical properties of optimized SOEO-MC were observed by laser scattering particle size analyzer,scanning electron microscopy,fourier transform infrared spectroscopy(FT-IR)and differential scanning calorimetry(DSC).It turned out that:the particle size of SOEO-MC was smaller than that of blank microcapsules,which was 1.34±0.58?m,and the plane formed by SOEO-MC was relatively smooth under electron microscope;rhomboid,trapezoid and parallelogram could be found in the aggregated particles.The different micromorphology of SOEO-MC and blank microcapsule suggested that SOEO might have entered into?-CD molecular cavity,which affected the recrystallization of?-CD molecule.At the same time,the peaks in the FT-IR and DSC curves of SOEO-MC were different from those of SOEO and blank microcapsules,which was the result of non-covalent bonds the formated between?-CD and SOEO.It was further confirmed that SOEO was successfully encapsulated by?-CD and microencapsulated.In addition,the composition changes of SOEO before and after encapsulation were determined and the results showed that the relative content of _D-limonene in SOEO was 97.42%,and the retention of the main active components of SOEO was high.Finally,the release experiment of SOEO-MC in vitro showed that the microcapsule could protect SOEO well under high temperature and light conditions,and its retention rate was much higher than that of unencapsulated SOEO.The slow release of SOEO-MC in simulated intestinal fluid is beneficial for prolonging the retention time of SOEO in vivo.(2)The weight loss effect and mechanism of SOEO-MC on obese SD rats.In this study,the effects of SOEO-MC on body weight,food intake,blood lipid and liver tissue morphology of obese rats were studied.The results showed that SOEO-MC reduced the body weight gain of obese rats by 41.4%,and the fat rate of obese SD rats decreased to3.37%.But SOEO-MC did not significantly decrease the liver coefficient of obese rats.Dietary intervention with SOEO-MC reduced the serum total cholesterol and low density lipoprotein cholesterol levels by 17.2%and 14.1%in obese rats,respectively.However,the effect of SOEO-MC on serum triglyceride and high density lipoprotein cholesterol was not significant.SOEO-MC could also significantly reduce the fatty degeneration of the liver in obese SD rats,repair the pathological changes of liver cells,and decrease the size of adipocytes in white adipose tissue.We also measured the contents of key hormones that maintain energy balance in rats and the gene expression related to fat decomposition and synthesis.The results showed that SOEO-MC could significantly reduce the serum insulin and leptin levels in obese rats(P<0.05).These results suggested that SOEO-MC could improve the resistance of insulin and leptin to some extent in obese rats.However,the effect o f SOEO-MC on the level of neuropeptide Y in serum of obese rats was not obvious,and the content of neuropeptide Y in each group was relatively stable.We also found that SOEO-MC could up-regulate the hormone-sensitive lipase and carnitine palmitoyltransferase 1 genes by 6.2 times and 1.7 times,respectively,and down-regulate acetyl CoA carboxylase and peroxisome proliferator activated receptor-?genes,which suggested that SOEO-MC promoted fat decomposition and oxidation,inhibited fatty acid biosynthesis and adipocyte differentiation in obese rats.In addition,SOEO-MC could significantly up-regulate the expression of uncoupling protein 2 gene(P<0.05)and relieve the coupling between electron transport and phosphorylation in some normal respiratory cha ins,which increased the body's heat production.(3)The effects of SOEO-MC on gut microbiota in rats and the study of gut microbiota species distribution in SD rats with different phenotypes.In this experiment,the V4 region of the 16SrDNA in rat gut microbiota was sequenced.The rat included different phenotypes and group,such as normal control rats(LFD),obese control rats(HFD),SOEO-MC diet intervention rats(HFD-MC),easy to fat rats(EF)and high-fat tolerance rats(HT).On the basis of?-diversity analysis,there was a significant difference in species diversity between low-fat diet-fed rat samples(LFD,EF)and high-fat diet-fed rats samples(HFD,HFD-MC,HT),without considering abundance.This conclusion suggested that different diets might result in different gut microbiota composition.Under the condition of considering species composition and abundance,the differences of species diversity between normal(LFD),high fat tolerance(HT)rats and obese rats(HFD)were small.The result indicated that the composition and abundance of most of the gut microbiota between lean and obese individuals were relatively stable,while individual non-dominant flora might play a key role in phenotypes.Further analysis of species composition and abundance at p hylum level showed that Firmicutes and Bacteroidetes were dominant in gut microbiota of each group,and the relative abundance of Firmicutes and Bacteroidetes were not significantly different in LFD and HFD groups,which indicated that different phenotypes in LFD and HFD might be caused by non-dominant flora.The Gram-negative bacteria(Bacteroidetes and Proteobacteria)in the EF group were higher,accounting for 78%of the total,which might lead to the easy fat phenotype of the rats with low-fat diet.In HT group,rats developed lean phenotype on a high-fat diet,which was the result of a combination of Firmicutes(low abundance)and Bacteroidetes(high abundance)in their gut microbiota.Studies on species composition and abundance in genus level showed that,SOEO-MC increased the abundance of Bifidobacterium and Lactobacillus in gut microbiota of obese rats,which was conducive to reducing intestinal endotoxin level,protecting intestinal barrier and reducing the absorption of TC.The endotoxin level in HFD-MC group was significantly lower than that in HFD group,which confirmed the obove conclusion.(4)Effect of SOEO-MC on oxidative stress in obese SD rats.In this experiment,we found that SOEO-MC treatment could significantly decrease the content of malondialdehyde(MDA)in serum and the content of carbonyl protein in liver of obese rats by 17.8%.The results showed that SOEO-MC alleviated lipid peroxidation in serum and protein carbonylation(PC)in liver and alleviated oxidative stress level in obese rats.At the same time,SOEO-MC treatment increased serum glutathione(GSH)content by 21.3%,catalase(CAT)activity in adipose tissue by 67.3%,and superoxide dismutase(SOD)activity in serum,liver and adipose tissue by 10.3%,15.2%and17.7%,respectively.These results confirmed that SOEO-MC could significantly improve the level of antioxidant enzymes and antioxidant capacity in obese rats.Nrf2gene can regulate the expression of a variety of antioxidant factors.It was found that the expression of Nrf2 gene in adipose tissue of HFD-MC group was significantly higher than that of HFD group,which was consistent with the increased activity or content of SOD,CAT and GSH in adipose tissue.However,there was no significant difference in the expression of Nrf2 gene in liver.In addition,the correlation analysis showed that there was a strong positive correlation between the content of serum MDA and fat rate(R~2=0.7648,P<0.05),and there was a significant negative correlation between SOD activity in adipose tissue and fat rate(R~2=0.6303,P<0.05),which was also consistent with the results of the previous study. |
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