| Lipids play an important role in the human diet,proving energy essential nutrients and bioactive components.However,it also have been associated with incidences of obesity and elevated risks of chronic noncommunicable diseases such as coronary heart disease and diabetes.Oat ?-glucan is a kind of water-soluble dietary fiber,a large number of experiments in vivo prove that it has significant physiological functions such as lowing blood glucose,lowing blood lipids,improving immunity and maintaining intestinal microecology.However,when oat P-glucan and lipids were ingested together,the impact of oat ?-glucan on lipids digestion,absorption,and the correlation mechanism is inconclusive.In this paper,based on a simulated gastrointestinal tract(GIT)model and Caco-2 cells monolayer model,we studied the impact of oat ?-glucan(supplemented at 0.0%,0.05%,0.1%,0.2%respectively)on soybean oil digestion and absorption characteristics in the single(protein-free matrix)and complex(with protein matrix)digestion system.The main research contents and results are as follws:(1)In the single digestion system(protein free matrix),when the addition amount of oat ?-glucan was increased from 0.0%to 0.2%,the percent of free fatty acids released in digestion products of four groups were 30.92%,28.69%,21.00%,and 18.60%respectively.In the complex digestion system(with protein matrix),the percent of free fatty acids released from digestion products of four groups were 89.41%,45.64%,31.10%,and 23.23%respectively.The percent of free fatty acids released in soybean oil digestion product decreased significantly(P<0.05)with the increasing of oat ?-glucan concentration in two kinds of digestive system(without/with protein matrix),but the released rate was no significant difference(P>0.05).The digestion extent of soybean oil in complex digestive system is higher than in single digestive system.These results suggest that oat ?-glucan can inhibit the digestion of soybean oil.The inhibition degree to soybean oil digestion of oat ?-glucan is lower in the complex digestive system.(2)In the single or complex lipid digestion system,when the addition amount of oat P-glucan was increased from 0.0%to 0.2%,at the same time of digestion(0min,15min,30min,60min,90min,120min),the average particle size of the stomach,intestinal digestion products,lipid droplets aggregation degree increased significantly(P<0.05),the zeta potential showed the increasing trend,and the particle size distribution peak of digestion product moved to the right.In the stomach digestion phase,particle size distribution peak changes of soybean oil digestion product was not obvious,but higher significantly than intestinal digestion product particle size volume.Compared with the single digestion system,the z-average diameter of soybean oil digestion product and the degree of lipid droplets were smaller in the complex digestion system with the same amount of oat ?-glucan.The results of this study showed that adding oat P-glucan to the lipid digestion system can change the interfacial properties of the lipid droplets in digestive system,promote the aggregation of lipid droplets,inhibit absorption of bile and lipase,and the protein in the digestion system decreased the lipid droplets accumulation degree.(3)In the single or complex lipid digestion system,when the addition amount of oat P-glucan was increased from 0.0%to 0.2%,at the same time of digestion,lipase activity in the intestinal digestion system(without/with protein matrix)showed a downward trend.At the end point(120min)of digestion,the lipase activity of digestion product in single digestion system of four groups were 1391±61 U/L,1389±89 U/L,1383±93 U/L,and 1380±56 U/L respectively.the lipase activity of digestion product in complex digestion system of four groups were 1281±61 U/L,1279±89 U/L,1288±103 U/L,1196±56 U/L.These results showed that oat ?-glucan has a inhibitory effect on lipase activity to a certain extent,but there were no significant different(P>0.05)among four experimental groups.(4)When the addition amount of oat ?-glucan was increased from 0.0%to 0.2%,the proportion of unsaturated fatty acids of soybean oil digestion product in single and complex lipid digestion system increased.When the adding amount of oat P-glucan was 0.2%,the proportion of unsaturated fatty acids of the digestion product in single and complex lipid digestion system were increased by 160%and 37.7%respectively.Compared with the single digestion system,the unsaturated fatty acids of soybean oil digestion product in digestion system with protein matrix were less increased.These results show that the influence of oat P-glucan on lipid droplets aggregation not only changed the digestion degree of soybean oil,but also affected the ratio of different fatty acids types(saturated or unsaturated fatty acids)in the digestion products.(5)Regard the soybean oil digestion product in digestion system without adding oat ?-glucan group as control,the soybean oil digestion product in digestion system with adding oat ?-glucan group as treatment group,whether oat P-glucan affect the fatty acids transport on intestinal epithelial cells through influencing the quantity and type of different fatty acids in soybean oil digestion product were studying.Compared with the control group,the secretion and synthesis of TG in treatment group were reduced by 48.8%,and the secretion of ApoB48 was reduced by 40.3%.The number of CMs in treatment group with TEM observing were more and lager.Compared with the control,the expression of FATP4,DGAT1,MTP and L-FABP mRNA in the in experimental group was reduced significantly(P<0.05).The above results reveal that oat ?-glucan can down-regulating the expression of fatty acid absorption and transport related proteins by affecting the release amount and type of fatty acids in the digestion products of soybean oil and regulate the absorption of fatty acids and the synthesis of TG,thereby inhibiting the assembly and secretion of CM and reducing lipid absorption and transport rate on cells.The results of this study showed that oat ?-glucan could promote lipase accumulation in soybean oil digestion system by altering the interfacial properties of lipid droplets in the single or complex lipid in vitro digestion system to a certain extent,while inhibiting lipase activity.That not only changed the degree of digestion of soybean oil,but also affected the release of fatty acids and the proportion of different types of(saturated,unsaturated)fatty acids in the digestion products of soybean oil.These effects caused fatty acid absorption in the Caco-2 cell monolayer and transport-related protein expression were significantly reduced,thereby changing the absorption process of fatty acids,inhibition of TG re-synthesis and CM assembly and secretion,reducing cell lipid absorption and transport rate. |
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