Safety Toxicological Evaluation Of COST And Effect Of COSTG On Lipid Metabolism In Obese Rats

Obesity is defined as abnormal or excessive fat accumulation in the body that may impair health.With the improvement of living standards and lifestyle changes,obesity has become a worldwide public health problem.Studies have shown that obesity is not only a metabolic abnormality,but also an important risk factor for many diseases such as type 2 diabetes,nonalcoholic fatty liver disease,cardiovascular disease and cancer.Most of the existing drugs for the treatment of obesity have shortcomings,such as toxic and side effects and easy rebound.Therefore,finding a safe and effective weight loss active substance is the direction of scientific research workers.The previous research of the research group found that chitosan has good weight loss and lipid-lowering activity,but its development and utilization is greatly limited due to its poor water solubility and difficulty in absorption.As a hydrolysate of chitosan,chitosan oligosaccharides(referred to as COS)has a wide range of sources,low cost,high water solubility,high bioavailability and various biological activities,and thus widely used in the field of biomedicine and health food.This study with average molecular weight of less than or equal to 1000 Da COS(referred to as COST)as the research object.Firstly,the safety toxicological evaluation of COST is carried out,and the safe and non-toxic COST is prepared into granules(referred to as COSTG).Subsequently,a diet-induced obesity rat model was used to evaluate the weight loss activity of COSTG and its effect on lipid metabolism in obese rats.Finally,liver tissue was taken as the research object,and its mechanism of action was preliminarily discussed,which provided a scientific basis for the further development and utilization of COSTG.In order to evaluate the safety of COST,a systematic safety toxicology study was conducted.The results of acute toxicity test showed that the maximum tolerated dose of COST to male and female mice exceeded 54 g/kg·bw,which was classified as non-toxic according to the classification of acute poison.The Ames test,mouse bone marrow micronucleus test and mouse sperm abnormality test were used to evaluate the mutagenic effect of COST.The results of the above three genotoxicity tests were all negative,indicating that COST had no genotoxic effect in the test dose range.The results of the 30-day feeding test showed that the maximum unobserved adverse effect of COST on rats was 5.00 g/kg·bw or more,which was 100 times more than the recommended dose of 0.05 g/kg·bw.The above results indicate that COST is a non-toxic substance with high safety.According to the optimal prescription: 5% povidone as an adhesive,0.6% aspartame as a flavoring agent,and anhydrous ethanol as a wetting agent,COSTG was prepared by manual wet granulation.COSTG is a pale yellow-brown solid granule with uniform color,no deliquescence,softening and agglomeration.The taste is slightly sweet,the forming rate is 94.63%,the moisture content is 6.28%,the drying weight loss is 1.32%,and the granule examined for solubility are dissolved without turbidity.All indicators are in line with the requirements of the Chinese Pharmacopoeia(2015).Methodological studies have shown that the method for determining the COST content in COSTG by phenol sulfuric acid method has good accuracy,precision and stability.The average content of COST in COSTG was 92.13%,and the RSD was 0.74%,which met the set requirements.A nutritional obese rat model was established by high-fat diet,and the effect of COSTG on weight loss and its effect on lipid metabolism in obese rats was evaluated.The study found that COSTG significantly reduced the body weight gain of obese rats without affecting the food intake,effectively inhibited the adipose tissue hypertrophy and hyperplasia of obese rats,significantly reduced the fat/body ratio of obese rats.The above results indicate that COSTG exhibits good weight loss activity and exhibits a dose-dependent manner.In addition,in terms of lipid metabolism,COSTG can improve dyslipidemia in obese rats,mainly to significantly reduce serum TC and TG levels.COSTG can significantly reduce liver weight and liver weight index in obese rats,inhibit lipid accumulation in the liver,prevent liver steatosis,mainly to reduce TG content in the liver.High dose COSTG can significantly increase the excretion of TC and TG in feces.To further explore the molecular mechanism of COSTG in improving lipid metabolism in obese rats,the mechanism of action was examined from endoplasmic reticulum stress and lipid synthesis and catabolism.The results showed that COSTG can down-regulate the transcription of SREBP-1c,FAS and PPARγ in the liver,thereby inhibiting lipid synthesis;on the other hand,it can up-regulate the transcription of PPARα in the liver,thereby promoting the β-oxidative catabolism of fatty acids.In addition,COSTG can down-regulate the transcription of related factors in the endoplasmic reticulum stress response pathway,indicating that endoplasmic reticulum stress is improved.COSTG improves lipid metabolism disorders in obese rats by the above three pathways.In summary,COST is a non-toxic substance,and COSTG is prepared based on it.COSTG can significantly reduce weight gain in obese rats,correct dyslipidemia,improve lipid metabolism,and have significant activity in reducing weight and preventing fatty liver.The regulation of COSTG on hepatic lipid metabolism may be related to inhibition of lipid synthesis,promotion of lipid oxidative catabolism and reduction of endoplasmic reticulum stress.The results of the study will provide important theoretical support for the development and utilization of COSTG in health care products that treat obesity and prevent fatty liver.