The Effect Of Omega-3 Fatty Acids On Oxidative Stress And Inflammation In Diabetic Rats Exposed To PM_2.5

ObjectivesTo explore the effect of ambient particulate matter(PM_2.5)on inflammation and oxidative stress in type 2 diabetes mellitus?T2DM?,and the protective effect of n-3 polyunsaturated fatty acids?PUFA?on PM_2.5 exposed T2DM rats.Methods1.Animal grouping and processing:The T2DM rat model was established by intraperitoneal injection of streptozotocin?STZ?combined with high-fat and high-sugar feeding.The T2DM model was defined as random blood glucose?16.7mmol/L.Seventy male SD rats aged four weeks were randomly divided into two groups based on body weight:8 in the control group?NC?and 62 in the T2DM model group?MD?,and fed with the lab chow and high-fat and high-sugar diet respectively for six weeks.Then the rats in the MD group were accepted one-shot intraperitoneal injection with STZ?30 mg/kg?.After one week,the rats successfully modeled as T2DM?54 rats?were randomly divided into T2DM control group,PM_2.5 trachea infusion control group,corn oil?CO?control group,and low,medium,and high dose of fish oil?FO?groups?named as FOL,FOM,FOH?,nine rats per group.The rats in NC and T2DM control groups were instilled with the equal volume of normal saline,while the rats in other 5 groups were instilled with PM_2.5 suspension,5 mg/mL(5 mg PM_2.5/kg·bw·d-1)through the trachea under anesthesiafor one week.Then the following four weeks,the rats in FOL,FOM,FOH groups were administered with FO?diluted in corn oil?at the doses of 75,150 and 300 mg n-3 PUFA/kg·bw·d-1 respectively through gavage,and the rats in CO group were administered with equal volume of CO once a day.After the intervention,the blood was collected from the abdominal aorta of the rats under anesthesia.The serum and dissected liver,kidney,pancreas,and adipose tissues were stored at-80? until use.2.Measurements of oxidative stress and inflammation indicators:WST-1 method was used to detect superoxide dismutase?SOD?activities in serum and liver.The malondialdehyde?MDA?content was measured by the thiobarbituric acid?TBA?method.The serum uric acid?SUA?level was quantified through the urase method.Immunoturbidimetric method was used to measure C-reactive protein?CRP?in serum.The enzyme-linked immunosorbent assay?ELISA?was used for detecting the levels of interleukin-6?IL-6?,interleukin-10?IL-10?and nuclear transcription factor-kappa B?NF-?B?,tumor necrosis factor ??TNF-??.The total protein concentration in rat liver was measured by BCA protein concentration assay kit.3.Histology observation of visceral tissues in rats:Hematoxylin-eosin staining?HE?was performed on liver,kidney,pancreas,and adipose tissues in the rats for checking the morphologic changes.Results1.Oxidative stress:In comparison to the NC group,serum SOD activity was decreased,but the SUA level was increased in the T2DM control group rats.Compared with the T2DM control group,both the hepatic MDA and SUA levels were increased in PM_2.5 infusion group rats.The SUA levels of three n-3 PUFA intervention groups were all decreased than that of the PM_2.5 control and CO groups.All of these differences were significant?P<0.05?.2.Inflammation:Compared with the NC group,the serum CRP,IL-6,and hepatic NF-?B levels were increased in the T2DM group rats.Compared with the T2DM group,both the serum IL-6 and hepatic NF-?B levels were increased in the PM_2.5 group rats.Compared with the PM_2.5 control group,both the serum IL-6 and hepatic NF-?B levels were decreased in all n-3 PUFA intervention groups.In comparison to the CO group,the serum IL-6 level was decreased in all n-3 PUFA intervention groups,but the hepatic NF-?B levels were increased in FOM and FOH groups.The serum level of NF-?B was decreased both in the CO and FOL groups than that in FOH group.All of these differences had statistical significance?P<0.05?.3.Histopathological changes:Compared with NC group,the pathological changes of liver,kidney,pancreas and adipose tissue were noted at varied degrees in T2DM and PM_2.5 groups,such as inflammatory cell infiltration,cell morphology and structural changes,etc.Compared with CO group,the pathological conditions of the rats in the FOL,FOM,and FOH groups were improved.Conclusions1.PM_2.5 tracheal infusion exacerbated oxidative stress,lipid peroxidation and increased inflammation in T2DM rats,which could be improved by intervention with n-3 PUFA.2.The n-3 PUFA intervention reduced the increase of SUA levels in T2DM rats induced by PM_2.5 exposure,which may have certain preventive or ameliorative effects on T2DM complications in the context of PM_2.5 exposure.