Protective Effect Of Sitagliptin On Bone In Diabetic Rats And Its Relationship With The Expression Of TLR4/NF-κB

Objective：1.To investigate the changes of BMD and bone turnover markers in high sucrose-fat dietswith STZ-induced diabetic rats by sitagliptin.2. Analysis the relationship between the protective effect on bone by sitagliptin and theexpression of the TLR4/NF-κB in diabetic rats.Methods:1. Diabetes rat model:60male sprague-dawlry(SD) rats were randomly divided intonormal control group(NC group,n=15) and model group(n=45). Normal control groupwas fed with standard chow, while model group was fed with high sucrose-fat diets(HSFDs) for8weeks, the fast blood glucose(FBG) was assayed and the subjects in modelgroup were injected intraperitoneally with streptozotocin(STZ,30mg/kg) while the onesin group NC were injected intraperitoneally with the similar dose of normal saline.Subjects with FBG higher than16.7mmol/L in three consecutive days were successfullymodeled.2. Pharmaceutical intervention:31modeled rats were grouped into Type2diabetesmellitus group(T2DM group,n=16) and sitagliptin treated group(SitA group,100mg/kg·d,n=15). After2weeks, sitagliptin was solubled in physiological saline and subjects weregavaged at9:00AM daily.Group NC and group T2DM were gavaged equal physiologicalsaline. Group NC were fed with the standard chow, while the remaining two groups werefed with HSFDs.3. The observation of relevant indicators:Body weight and FBG were measured20weeksrespectively, Intraperitoneal glucose tolerance test(IPGTT) was conducted before andafter sitagliptin treated for20weeks, and calculate the area under the curve(AUC).Radioimmunoassay detecte the serum insulin. 4. The detection of BMD and bone turnover markers: DEXA was used to measure lowerlimbs, upper limbs, trunk, spine and whole body bone mineral density(BMD); The serumOCN and TRAP5b activity were detected by ELISA; AMP-buffer tested serum ALP level5. The detection of gene and protein: RT-PCR and western blot detected the mRNA andprotein expression of BMP-2,TLR4, NF-κB of the femur respectively.Results:1. Diabetic rats induced by HSFDs with STZ showed hyperglycemia, mean FPG was18.83±2.05; Compared with group NC, the area under the curve(AUC) of IPGTT ingroup model increased obviously(P<0.05).2. After sitagliptin treatment for20weeks, compaired with group NC, FBG and AUC ofIPGTT increased significantly(P<0.05), while FINS and body weight in group sitAdecreased obviously in group T2DM(P<0.05). FBG and AUC increased in group sitA(P>0.05), while FINS decreased(P>0.05) and body weight has no significantdifference(P>0.05). Compaired with group T2DM, FBG and AUC of IPGTT in groupsitA decreased significantly(P<0.05), while FINS and body weight increased obviously(P<0.05).3. Compaired with group NC, BMD of lower limbs, upper limbs, trunk, spine and wholebody in group T2DM decreased, especially in lower limbs, upper limbs and whole bodyBMD(P<0.05), while BMD of lower limbs, upper limbs, spine and whole body in groupsitA decreased(P>0.05), while trunk increased(P>0.05). Compaired with group T2DM,BMD of all parts in group sitA increased, especially in lower limbs, upper limbs andwhole body BMD(P<0.05).4. Compaired with group NC, the expression of serum ALP decreased(P<0.05), OCNdecreased(P>0.05), TRAP5b increased in group T2DM(P<0.05), while ALP decreased(P<0.05), OCN increased(P<0.05), TRAP5b increased in group SitA(P>0.05). Compairedwith group T2DM, The expression of ALP increased (P<0.05), OCN increased obviously(P<0.05), TRAP5b decreased(P<0.05) in group SitA.5. Compaired with group NC, the expression of TLR4、 NF-κB mRNA and proteinincreased in group T2DM and group sitA, especially in group T2DM (P<0.05),conversely, the expression of BMP-2decreased in group T2DM and group sitA,especially in group T2DM (P<0.05). Compaired with group T2DM, the expression of TLR4, NF-κB mRNA and protein decreased while BMP-2increased significantly ingroup sita(P<0.05).Conclusions:1. Sitagliptin can effectively decrease FBG, increase plasma insulin and recover bodyweight in HSFDs with STZ-induced diabetic rats.2. Sitagliptin could promote bone formation, inhibit bone resorption and increase BMD indiabetic rats.3. Sitagliptin may play a protective effect on bone by reducing the expression of TLR4/NF-κB in diabetic rats.