3.1. Establishment of T2DM model and the loss of alveolar bone
Following two weeks of adaptive feeding, SD rats were fed with Western food for 4–6 weeks, and thereafter, multiple intraperitoneal injections of low-dose STZ (25 mg/Kg) were administered, and fasting plasma glucose or random blood glucose was monitored. Model standard: FPG>7.8 mmol/L, or RBG≥17.8 mmol/L (Figure 2).
The distances from the cement-enamel junction (CEJ) to the alveolar bone crest of the tooth were measured at three points (mesial, medial, and distal aspects), both in the buccal and lingual sides. The measurements of each point were repeated three times, and the mean was computed. The mean crystal bone level of the tooth was calculated (Figure 3a, b).
3.2 Effect of adiponectin, hs-CRP on periodontitis with or without type 2 diabetes in rats
Disease progression documented a gradual reduction in the level of APN in groups B, C, and D. Serum adiponectin levels in group B decreased gradually with the progression of the disease, though the difference was statistically insignificant (p>0.05). Compared to the A group, the significantly higher (p<0.05) APN level in group C at T1, T2, may be related to acute inflammation in the early modeling of periodontitis. On the contrary, at T3, T4, T5, the level of APN was significantly lower in groups C and D (p<0.05) compared to group A(Table1,figure4a,b). The inflammatory factor hs-CRP in natural process was higher in groups B, C, and D, relative to group A. Serum hs-CRP gradually increased with the natural progression of the disease, but group B manifested no statistical difference (p>0.05) (Table2, figure5 a,b).
Table1 Serum APN values of each group during natural process(n=7, ±s,unit:ng/ml)
Group
|
T1
|
T2
|
T3
|
T4
|
T5
|
A
|
59.085±9.731
|
55.800±10.498
|
56.586±7.815
|
54.329±5.915
|
55.129±7.319
|
B
|
57.957±13.696
|
47.857±10.195
|
52.157±4.433
|
48.985±3.831
|
47.157±1.988
|
C
|
82.071±15.730
|
75.129±6.176*
|
37.800±4.699*
|
37.629±3.375*
|
33.271±6.205*
|
D
|
68.486±18.038
|
46.243±8.234
|
45.829±8.907
|
31.657±8.372*
|
31.143±5.482*
|
Note:A:normal control, B:DM,C:chronic periodontitis, D:DM +CP, compared to group A,*p<0.05.
Table2 Serum hs-CRP values of each group during natural process (n=7, ±s, unit: ng/ml)
Group
|
T1
|
T2
|
T3
|
T4
|
T5
|
A
|
381.372±33.495
|
403.996±25.396
|
371.362±68.992
|
359.266±66.649
|
381.622±63.395
|
B
|
476.051±28.914
|
426.301±32.647
|
468.340±17.227
|
450.58±70.09
|
423.347±62.691
|
C
|
544.541±139.025*
|
551.477±77.024*
|
573.838±97.880*
|
602.447±46.125*
|
679.076±103.723*
|
D
|
766.103±91.914*
|
800.349±97.084*
|
873.435±96.394*
|
920.534±176.731*
|
1141.06±270.507*
|
Note: compared to group A,*p<0.05.
3.3. The ratio of APN/hs-CRP in each group
The ratio of APN/hs-CRP signified the balance between anti-inflammation and pro-inflammation. The results revealed, at T1, significantly lower (p<0.05) ratio of APN/CRP in D group, but no significant difference (p>0.05) in group B, C group as compared to A group; at T2, compared to A group, the ratio was significantly lower (p<0.05) in both B and D group. However, C group demonstrated no difference (p>0.05); the ratio was significantly lower (p<0.05) in the B, C, D group at T3, T4, T5, compared to A group. Overall, with the disease progression, the ratio of the B group failed to reflect any significant downward trend, whereas, C, D group manifested a gradual downward trend(Table3,Figure6).
Table 3 The ratio of serum APN/CRP in each group(n=7, ±s)
|
A
|
B
|
C
|
D
|
T1
|
0.1562±0.0313
|
0.1221±0.0302
|
0.1613±0.0582
|
0.0909±0.0280*
|
T2
|
0.1385±0.0275
|
0.1125±0.0242*
|
0.1382±0.0205
|
0.0584±0.0115*
|
T3
|
0.1577±0.0412
|
0.1116±0.0117*
|
0.0683±0.0174*
|
0.0532±0.0128*
|
T4
|
0.1547±0.0257
|
0.1074±0.0084*
|
0.0628±0.0089*
|
0.0348±0.0096*
|
T5
|
0.1481±0.0316
|
0.1136±0.0175*
|
0.0488±0.0048*
|
0.0284±0.0070*
|
Note: compared to group A,*p<0.05.
3.4. The lipid of each group
Disorders of lipid metabolism can induce the development of atherosclerosis. Our results revealed that compared to the A group, TG of group B, TC, LDL, TG of group D were significantly increased (p<0.05). In the case of the C group, a significant decrease (p<0.05) was obtained for HDL as compared to the A group. However, the other lipid indicators showed no significant difference (p>0.05).(Table4, Figure7).
3.5. Effects of periodontitis and diabetes on carotid artery in rats.
A group: An intact intima, flattened endothelial cells, orderly arrangement of the elastic fibers and smooth muscle cells of the media, no thickening of the vessel wall were observed; B group: Variation was noted in the blood vessel walls thickness, part of the endothelial cells were missing, the elastic fibers of the media were disordered, partially dissolved and fractured, and the smooth muscle cells were vacuolated; C group: The intima was incomplete, and some endothelial cells were exfoliated, the elastic fibers of the media were disordered, some of them were broken, and some specimens manifested calcium salt deposition; D group: The intima was incomplete, and some endothelial cells were missing, local necrosis of the smooth muscle tissue of the media was prominent, with amorphous particles and deepened staining, the elastic fibers in the necrotic area were disordered and some of them were broken(Figure8). These results suggest that periodontitis accelerates the lesion of carotid artery in diabetic rats.