Combined Effects Of EGCG And Caffeine On Lipid Metabolism In Caenorhabditis Elegans

Abnormal lipid metabolism is mainly manifested as high cholesterol,triglyceride,and increased low-density lipoprotein cholesterol levels.And it is related to the occurrence of some chronic diseases,such as the certain cardiovascular diseases,cancers and other metabolic diseases.Current methods for the prevention and treatment of the abnormal lipid metabolism are encountered with unacceptable side effects,or in significant long term effects,or expensive spending.Therefore,it is urgent to find natural and non-toxic products to reduce fat.Some studies have shown that green tea could increase energy consumption,regulate lipids metabolism,but other studies have not observed these effects.the inconsistency of the results may be related to the different active ingredients and concentration in different teas.It was reported that catechins(especially epigallocatechin-3-gallate,EGCG)and caffeine contained in green tea could reduce body weight,lower the weight of viscera,subcutaneous fat,and cholesterol level in plasma.There are many researches about the fat-reducing effects of EGCG or caffeine alone,but few studies about the combined effect.What is more,the basis of the dosage seting were quite different,which would affect the judgment of the combined effect of EGCG and caffeine.Caenorhabditis elegans(C.elegans)has short life cycle,transparent body,and is easy to be maintained and operated in researches.In addition,the signaling pathways which are essential for the control of lipid metabolism in humans are conserved in C.elegans,so it can be used as a model organism for the study of EGCG and caffeine on lipid metabolism.Objective:Exploring the effects of EGCG and caffeine,either alone or in combination,on lipid metabolism in C.elegans under normal physiological conditions and high glucose stress conditions,provides a basis for the application of EGCG and caffeine in the control of lipid metabolism disorders.Methods:Acute toxicity experiments were conducted to obtain the appropriate concentrations for studying the fat-reducing effects of EGCG and caffeine.A 2×3factorial design was used to divide C.elegans into 9 groups,and the fat-reducing effects of EGCG and caffeine were explored under physiological conditions and high-glucose stress conditions.At 20°C,the synchronized L4 C.elegans were exposed to various doses of EGCG and caffeine alone or in combination for 24 hours.Then C.elegans was stained with Nile Red and fluorescence intensity was measured by a microplate reader.In addition,triglycerides and cholesterol levels in C.elegans were detected by triglyceride and cholesterol kits.The positive control group was 145?g/m L orlistat treated C.elegans.Results:1.Acute toxicity test resultsThe 24 h LC₅₀(50%lethal concentration)values were 1.58 m M for EGCG and69.31 m M for caffeine.Compared with the control group(0 m M EGCG+0 m M caffeine),the combined groups(EGCG+caffeine:0.78 m M+48 m M,1.58 m M+48m M)had statistically significantly higher mortality rates of C.elegans.The factorial analysis showed that the combination of EGCG and caffeine present a synergistic effect on mortality in C.elegans.2.The effect of EGCG and caffeine alone or in combination on the lipid metabolism(1)The lipid fluorescence intensities,triglyceride content and cholesterol level were significantly reduced in the 0.1,0.2 m M EGCG treated C.elegans and 10,20,and30 m M caffeine treated C.elegans when respectively compared with the control ones(0m M EGCG or 0 m M caffeine treated C.elegans)(all p<0.05).(2)Compared with the control group(0 m M EGCG+0 m M caffeine),the combined treatment with EGCG and caffeine(0.1 m M EGCG+0.5 m M caffeine,0.1m M EGCG+20 m M caffeine,0.2 m M EGCG+0.5 m M caffeine and 0.2 m M EGCG+20 m M caffeine)significantly decreased the lipid fluorescence intensities,triglyceride content and cholesterol level in C.elegans(all p<0.05).Factorial analysis suggested that the combined administration of EGCG and caffeine had a synergistic effect on lipid production,triglyceride reduction in C.elegans,but there was no interaction effect on cholesterol levels in C.elegans.(3)High concentration of glucose(100 m M)induced fat stores in C.elegans.Both EGCG(0.1,0.2 m M)and caffeine(20 m M)could antagonize the ability of glucose to induce the increase in lipid fluorescence intensity and triglyceride content in C.elegans,but did not significantly change the cholesterol level.The combination of EGCG and caffeine can reduce the lipid fluorescence intensities,triglyceride contents and cholesterol levels in glucose-treated C.elegans.Factorial analysis found a synergistic effect of EGCG and caffeine on reduction of lipid fluorescence intensity and triglyceride content in C.elegans under high glucose stress conditions,but there was no interaction effect was found on reduction of cholesterol levels.Conclusions:1.EGCG and caffeine used alone or in combination can reduce lipid production,triglyceride content and cholesterol levels in C.elegans under physiological conditions.The combination of EGCG and caffeine presented synergistic effects on lipid production and triglyceride content.2.Both EGCG and caffeine can antagonize glucose-induced increase in lipid production and triglyceride content in C.elegans under high-glucose stress conditions.And the combination of EGCG and caffeine presented synergistic effects on lipid production and triglyceride content.