| Objective: There are some relations between lipid metabolism disorder and diabetes mellitus (DM). lipid metabolism disorder is associated with the occurrence of DM and development of diabetic chronic complication.The peroxisomal fatty acid β-oxidation system is involved in the oxidation of very-long-chain fatty acids(VLCFAs), pristanic acid and di- and trihydroxycholestanoic acid, so that shorter-chain fatty acids formed enter the mitochondrion and are further degraded.Recently, the D-bifunctional protein(D-BP),D-3-hydroxyacyl-CoA dehydratase/D-3-hydroxyacyl-CoA dehydrogenase bifunctional protein, has been recognized by us, which play a major role in the peroxisomal oxidation of the D-isomers of VLCFAs and polyunsaturated fatty acids, and the peroxisomal oxidation of intermediates in the formation of the primary bile acids.Peroxisomal fatty acid β-oxidation is activated in dabetic animals.And the higher levels of free fatty acids ( FFA) and triglyceride(TG) has been established in both type 1 and type 2 DM patients. Our previous studies demonstrated that the serum increased free fatty acids in DMwere mainly some VLCFAs , including C22:0 and C24:0 , and arachidonic acid.However, it is not yet know whether the Peroxisomalβ-oxidation is responsible for the increased VLCFAs in DM. So it is important to investigate the role of peroxisomal fatty acid β-oxidation in lipid metabolism of DM.For the purpose, the model of diabetic rats was induced by intraperitoneal injection of streptozotocin. Peroxisome proliferation in diabetic rat liver were assessed by observation under electronic microscope. We measured not only peroxisomalβ-oxidation activity, but also the activities of D-Bp and some other enzymes involved in peroxisomalβ-oxidation in diabetic rat liver.Methods: 1.Diabetic rat model was induced by injecting streptozotocin : Six-week-old SD rats were divided into weight-matched control and streptozotocin(STZ)-treated group. After overnight fasting, the latter group was injected intraperitoneally with 65 mg/kg of streptozotocin. Diabetes was confirmed 72 hours after the injection of streptozotocin by presence of high fasting blood gluclose concentration (≥15 mmol/L ).Two weeks following induction of diabetes, rats were intubated in carotid artery under 2% pentobarbital anesthesia(50 mg/kg), and the blood was used for all assays of fasting blood glucose(FBG), serum triglyceride(TＧ), serum cholestrol(TC) and serum high-density lipoproteir cholesterol(HDL-c). The livers were removed, rinsed with Saline. Control rats were sacrificed on the same day and weretreated similarly as the diabetic rats.2. Serum glucose concentrations were determined by glucose oxidase assay method. Serum triglyceride, and cholestrol were measured by the enzymatic assay. Serum high-density lipoprotein cholesterol were determined by immune turbidimetry method. 3.Electron microscopy sample preparation:The liver tissue was cut into 1×1 mm3 slices and the slices were fixed with 2% glutaraldehyde. The number of peroxisome and the change of morphology were observed by Electron microscopy. 4.Preparation of rat liver homogenates: One gram of rat liver was homogenized on ice with 4 ml homogenate buffer, then the homogenates were centrifuged for 10 min at 3000rpm.The resulting supernatants were used for all enzyme assays including catalase, peroxisomal fatty acid β-oxidation, acyl-CoA oxidase, L-3-hydroxyacyl-CoA dehydrogenase and D-BP. 5.Enzyme Assay:⑴The catalase activity was assayed at 37℃ by the decrease in absorbance at 240 nm in the presence of 0.03% H2O2 by spectrophotometric analysis. One enzyme unit was defined as the amount of catalase converting 1μmol H2O2 per min under the assay conditions. ⑵Peroxisomal fatty acid β-oxidation was assayed at 340 nm by Palmitoyl-CoA oxidation to elicit the reduction of NAD. One enzyme unit was defined as the amount of the enzyme reducing 1μmolNAD per min under the assay conditions. ⑶The D-BP and L-3-hydroxyacyl-CoA dehydrogenase activity...
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