The Role Of Diabetes And Glucose Transporter Glut1 In Osteoarthritis And Joint Morphological Changes

Background and Objective:Osteoarthritis(OA)is the most widely spread joint disease in the world.To date,the most effective treatment for end-stage OA is total joint replacement,however,the outcomes are far from perfect,some study indicated that the unsatisfactory rate was as high as 20%.The reason for that might be the unclearness of the inner mechanism of OA.Recently,metabolic diseases are considered to play important roles in aging and OA,but the specific mechanism between glucose metabolism and OA,and OA induced knee morphology changes still remain unclear.Thus,our study aims to:1)verify whether diabetes could accelerate the OA progression by using Akita mice,and further investigate the glucose transporter Glut1 expression in articular cartilage of diabetes mice.We construct Ai9;Prg4-Cre ERT2 to confirm the Prg4marked cell layers in articular cartilage in different time point and construct Glut1^f/f;Prg4-Cre ERT2 to knock out Glut1 in superficial layer of articular cartilage,thus investigate the necessity of Glut1 in joint cartilage.2)construct Glut1-TRE;R26-rt TA(IRES-EGFP);Aggrecan Cre ERT2 mice to investigate the sufficiency of protection effect of overexpression Glut1 on articular cartilage.3)use 3D Geometric Morphometric analysis and HFD mice to study the knee morphology changes in the process of aging and diabetes-induced OA progression.Materials and Methods:(1)Establish the Akita mice diabetes model to confirm the phenotype of diabetes-induced OA,measure the Glut1 expression and glucose consumption in both wildtype mice and diabetes mice by using DMM surgery to investigate the correlation between glucose transporter Glut1 and diabetes induced/post-traumatic osteoarthritis.(2)According to the glucose consumption and lactate production,we construct Ai9;Prg4-Cre ERT2 mice to observe the Prg4 marked chondrocyte layers in articular cartilage in different time point and construct Glut1^f/f;Prg4-Cre ERT2 to knock out Glut1 in superficial layer of articular cartilage,thus observe the cartilage matrix alteration,cartilage destruction and change of synovium.(3)Construct Glut1-TRE;R26-rt TA(IRES-EGFP);Aggrecan Cre ERT2 mice and perform DMM surgery to investigate overexpression of Glut1 and its protection effect on articular cartilage.(4)By using HFD mice and DMM surgery,we observe the diabetes-induced OA and its subsequent knee morphologic changes.Collect the dicom of CT scan and 3D reconstruction of patients of different age,sex and diabetes condition in our hospital,import the data in to Amira software(Amira 4.1.1(?)software(Mercury Computer System,Inc.,Chelmsford,MA,USA)and use 3D Geometric Morphometric analysis and principal component analysis to investigate the relationship among aging,diabetes,osteoarthritis and OA induced joint deformities.Results:(1)The wildtype mice present with osteoarthritis 4 weeks,8 weeks and 12 weeks after DMM surgery.By using the immunofluorescence technique,we found a gradual decrease of Glut1 expression in OA group compare to control group 4 weeks,8 weeks and 12 weeks after DMM surgery.The non-hypertrophic layer of cartilage showed almost no Glut1expression at 12 weeks after surgery.(2)Compared with the control group,Akita diabetes mice showed accelerated OA phenotype after DMM surgery.We further found that joint cartilage of Akita mice showed less glucose consumption and lactate production in comparison with the control group.At the same time,Glut1was significantly decreased at 6 month old and 12 month old Akita mice compared with the control group.(3)Double heterozygous Ai9;Prg4Cre ERT2 mice was constructed and we found that the Prg4 marked cells kept in 3-5 cartilage layers of non-hypertrophic chondrocyte.(4)Glut1^f/f;Prg4-Cre ERT2 was constructed,Glut1^f/fas control group.After tamoxifen induction,no Glut1 expression was found in non-hypertrophic cartilage of Glut1^f/f;Prg4-Cre ERT2 mice,indicating good knock out efficiency.Moreover,compared with control group,Glut1^f/f;Prg4-Cre ERT2 mice showed accelerated OA progression phenotype.(5)By using 3D Geometric Morphometric analysis and principal component analysis,we found that distal femur morphology alters among age groups,different sex,different ethnic and different status of diabetes patients.HFD diabetes mice showed more severe knee deformities compared to control group.ConclusionThe results of this study indicate that diabetes could accelerate the progression of osteoarthritis.Possible mechanism:the hyperglycemia that diabetes caused would lead to decrease of glucose transporter Glut1 of the joint cartilage,which is a key factor for the survival of articular cartilage,and thus caused the acceleration of OA progression.From clinical perspectives,the knee morphology of patients with aging and diabetes alters compared to control group,indicating that the joint deformities that OA caused should not be ignored and prostheses design should take those into account.Starting from clinical problems,this study uses knockout and overexpression mouse model to investigate the relationship between glucose metabolism and OA progression.Moreover,results were verified by clinical samples.We believe this study provides us with new insight into future metabolic therapy on treating and preventing OA progression.