The Protective Effects Of Phytosterols From Rice Bran On The Dopaminergic Neurons Of C.elegans

Rice bran oil is a kind of healthy oil and is rich in a variety of bioactive ingredients.In recent years,studies have found that rice bran oil has a health promoting effect in regulating lipid metabolism and inflammation level.Rice bran is an important by-product of rice processing and contains many natural active ingredients.However,the attention and utilization of rice bran still need to be improved.Phytosterols are a class of natural triterpenoids and the important components of rice bran and rice bran oil.Dopaminergic neuron(DA neuron)is a kind of neuron which is closely related to the physiological activities such as body movement and emotion.The damage of DA neuron will cause many adverse effects to the body.Studies have found that triterpenoids have potential health promoting effects on nervous system,but it is not clear whether phytosterols have the protective effects on DA neurons.Therefore,in order to understand whether phytosterols derived from rice bran(i.e.rice bran and rice bran oil)have protective effects on DA neurons and explore their potential mechanisms,the following studies were carried out:Firstly,the phytosterol compositions of different rice bran and rice bran oil were quantitatively analyzed by chromatography.The results showed that rice bran contained4.07% ～ 17.64% of the steryl glycosids and high proportion of 4,4-dimethylsteryl ferulates.Rice bran oil contained no sterol glycosides and could be divided into:(1)High steryl ferulate rice bran oil(steryl ferulate accounts for more than 80% of total sterols);(2)High free sterol rice bran oil(free sterol accounts for more than 70% of total sterols);(3)Equal proportion of steryl ferulate and free sterol rice bran oil(the ratio of steryl ferulate to free sterol is about50:50).Secondly,the dopaminergic neuroprotective effects of cycloartenyl ferulate(CYC-SF),24-methylene cycloartanyl ferulate(24-M-SF),sitosteryl 3β-D-glucopyranoside(SITO-SG)in rice bran,and sitosterol(SITO),campesteryl ferulate(CAM-SF)in rice bran oil were evaluated in the nematode model.The results showed that except for SITO-SG,free sterol SITO,4,4-dimethylsteryl ferulates CYC-SF,24-M-SF and 4-demethylsteryl ferulate CAM-SF had significant protective effects on DA neurons of the nematodes.Finally,the potential protective mechanisms of SITO,CAM-SF,CYC-SF and 24-M-SF on the DA neurons were studied.It was found that the mitochondrial protection effects,the antioxidant ability,and the inhibition of apoptotic proteins of the abolve phytosterols might play an important role in protecting the DA neurons of the nematodes.In the aspect of regulating the function of mitochondria: SITO,CAM-SF,CYC-SF and 24-M-SF could significantly improve the inhibition of the activity of mitochondrial respiratory chain(ETC)complex induced by rotenone(ROT);SITO and CAM-SF could also significantly increase the content of ATP and the mitochondrial membrane potential;in the aspect of the antioxidant activity: SITO,CAM-SF,CYC-SF and 24-M-SF could significantly reduce the content of reactive oxygen species(ROS),and increase the expression of gst-4(a II phase detoxification enzyme)and sod-3(an antioxidant enzyme).In addition,we also found that the antioxidant capacity of these phytosterols depended on the activation of DAF-16 pathway;in terms of inhibiting the overexpression of apoptotic proteins,we found that SITO,CAM-SF,CYC-SF and 24-M-SF could significantly reduce the overexpression of CED-3 induced by ROT.In addition,SITO,CAM-SF,CYC-SF and 24-M-SF did not regulate SKN-1 which was related to stress resistance,and pink-1 which was related to mitophagy in C.elegans.In conclusion,through the analysis of phytosterols from rice bran,it was found that SITO,CAM-SF,CYC-SF and 24-M-SF could regulate the function of mitochondria,regulate the expression of the apoptotic protein CED-3,and improve the oxidative stress resistance of the nematode by activating the DAF-16 pathway.This study revealed the potential dopaminergic neuroprotective mechanism of the phytosterols from rice bran and provided a theoretical basis for the processing and utilization of rice bran as well as the nutritional evaluation of rice bran oil.