| According to“The State Report of Nutrition and Chronic Diseases in China(2020)”,the overweight and obese population in China has reached 50.7%by 2020.The"Healthy China 2030"Plan states that the increase rate of overweight and obese population by 2030is to be slowed down significantly via strengthening the research of food nutrition as well as culturing the scientific dietary habits.Obesity is caused by an imbalance in energy metabolism.Increasing exercise and reducing energy intake are two conventional means of antagonising weight gain,however both of them lack of compliances.Therefore,developing the meal replacement powder with both satiaty and less energy intake is highlighted in food industry.Konjac glucomannan(KGM)is a high viscosity dietary fibre.Previous studies have shown that KGM is widely used as a meal replacement ingredient as it enhances satiety and resists high-fat diet-induced obesity in mice.Dihydromyricetin(DMY)is a dihydroflavonoid polyphenol derived from the new food resource,the ampelopsis grape leaves.DMY has the ability to reduce oxidative stress damage,however,the poor stability of DMY limits its use in food fortification.To date,there is no reports on the viscosity modulation of KGM by DMY.This project investigated the effect of DMY and KGM interaction on the viscosity of KGM and the stability of DMY,and the underlying mechanism.DMY was applied to stimulate the energy metabolism.KGM-DMY complex is applied to the high-fat-diet induced obese mice,lipid metabolism,oxidative stress damage and resistance,exercise capacity as well as energy procudtion were investigated.The accomplishement of the project would provide a theoretical and technical support for the development of multifunctional KGM-based meal replacements.The main research contents of this thesis are as follows:(1)Interaction study between konjac glucomannan and dihydromyricetinKGM was mixed with DMY in distilled water with one-step method,which increased the viscosity of KGM.Further in vitro simulated digestion was used to study the rheological properties of KGM during gastric digestion and the results showed that the viscosity of the mixture was increased with the addition of DMY;the microstructure of the KGM-DMY was examined with transmission electron microscopy;the chemical structure of the substance was determined with infrared spectroscopy,which revealed a decrease in the intensity of the hydroxyl absorption peak of the complex and presumably resulting from hydrogen bonding interactions;the heat of reaction was further measured with isothermal titration calorimetry,it was found out thatΔH<0 andΔS<0,indicating that the main hydrogen bonding force exsited in the forming complex;the crystallinity was measured by X-ray diffraction and it was found that the crystallinity of the complexes was lower than that of DMY,which may be beneficial to increase the solubility of DMY.At last,the effect of KGM on the thermal stability of DMY as well as the scavenging of ABTS~+and DPPH radicals was also investigated,it was found out that KGM reduced the thermal decomposition of DMY and improved scavenging rate of radicals.(2)The regulation of lipid metabolism of KGM-DMY in high-fat-diet induced obese miceMice were subjected to intervention studies follows:(1)NCD+distilled water,(2)NCD+KGM,(3)NCD+KGM-DMY,(4)NCD+DMY,(5)HFD+distilled water,(6)HFD+KGM,(7)HFD+KGM-DMY,(8)HFD+DMY.After 6 weeks of intervention,the results showed that the body fat,body fat rate and Lee’s value in KGM-DMY intervention under the high-fat diet were significantly lower than those in the HFD group(p<0.05);the DMY reduced the epididymis fat content and Lee’s value in HFD(p<0.05),while the KGM only reduced the Lee’s index in HFD(p<0.05).KGM-DMY and DMY significantly reduced blood TG,TC and LDL-C levels(p<0.05)and alleviated HDL-C content due to high-fat diets(p<0.05).The KGM-DMY group had with lower serum TG compared to the DMY group(p<0.05).Morphological observations of liver and adipose tissue showed that both DMY and KGM-DMY significantly alleviated liver damage,reduced adipocyte expansion and adipocyte expansion and lipid deposittion in HFD.(3)Study on the anti-fatigue effect of KGM-DMYThe results showed that the time of exhaustion swimming was significantly higher in KGM-DMY interventions than in the control group under normal dietary patterns(p<0.05),indicating that the exercise endurance of KGM-DMY group was higher than DMY group(p<0.05);Compared with KGM group,KGM-DMY decreased the contents of lactate,lactate dehydrogenase and urea nitrogen(p<0.05),reduced the accumulation of metabolites and enhanced the exercise endurance of the body;the antioxidant enzymes and oxidative damage indexes were measured,and it was found that compared with the KGM group,KGM-DMY increased the enzyme activity of SOD,GPX and CAT,decreased MDA and AST contents(p<0.05),while DMY only increased CAT enzyme activities and decreased AST contents(p<0.05),the results showed that KGM-DMY enhanced the body’s ability to scavenge free radicals and alleviated oxidative damage;measuring the content of liver glycogen,AMP and ATP,and it was found that the content of liver glycogen increased after KGM-DMY intervention(p<0.05),which might be due to the conversion of lactic acid produced by exercise into liver glycogen through gluconeogenesis,the ratio of AMP/ATP decreased(p<0.05),and the content of ATP increased(p<0.05),which might be due to the enhancement of mitochondrial function and the promotion of energy conversion.LD,MDA,AST and ALT of KGM-DMY groups in HFD were lower than those of HFD group(p<0.05);SOD,GPX and liver glycogen were higher than those in HFD group(p<0.05).However,there was no significant difference in exhaustive swimming time,which may be that high fat diet affected the behavior of mice and limited the activity ability. |
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