Relação entre síndrome metabólica e doença periodontal em ratos : efeitos da suplementação com Ômega-3

Abstract

The Global Burden of Disease database indicates that approximately 800-million people have severe periodontitis worldwide. In addition, recent estimations point to 3.4-million deaths by complications concerning overweight or obesity, with an alarming 62% of obese individuals in developing countries. Relevantly, there is a clear relationship between periodontitis and metabolic disorders, although further studies are still needed to better understand the connection between these conditions, aiming to identify new therapeutic options. The present study investigated the effects of supplementation with fish oil-derived omega-3 in an experimental model combining periodontal disease (PD) and metabolic syndrome (MS) in rats. The experimental protocols were approved by the Ethics Committee on the Use of Animals of the Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS; CEUA 10154). A total number of 64 male Wistar rats, distributed into eight experimental groups (eight rats/group) was used. Initially, the animals were divided into two groups that received filtered water or 10-% fructose ad libitum, for MS induction. After 30 days, the animals were separated into four experimental groups, which received omega-3 supplementation (1 g/kg), administered orally, once a day. Control animals received a vehicle solution (0.9% NaCl, 1 ml/kg). Seven days after the onset of omega-3 treatment, the animals were divided again for PD induction. For this purpose, the animals were anesthetized by a combination of xylazine and ketamine (10 and 100 mg/kg, respectively, via i.p. route). A 4.0-silk ligature was inserted at the cervical region of the first mandibular molar, with the knot facing the vestibular aspect of the tooth (PD+). The ligature was kept at the position for 21 days to allow the development of PD. Control animals were anesthetized, but the ligature was not inserted (PD-). The total time of fructose consumption was 60 days, and omega-3 was dosed for 30 days. The experimental groups were: (i) water-saline-PD-; (ii) water-omega-3-PD-; (iii) water-saline-PD+; (iv) water-omega-3-PD+; (v) fructose-saline-PD-; (vi) fructose-omega-3-PD-; (vii) fructose-saline-PD+; (viii) fructose-omega-3-PD+. All over the experimental period, the animals were weighed, and the volume of water or fructose intake was recorded. At the end of the 60 days, the animals were euthanized for sample collection. A blood drop was used for glycemia assessment (mg/dl). Subsequently, the blood samples were centrifuged, and the serum was stored at –80 oC for measurement of total cholesterol, HDL, LDL, triglycerides, leptin, and adiponectin, using commercial kits. In addition, liver, inguinal subcutaneous white adipose tissue, aorta, and mandibles were collected. The tissues were weighed and fixed in 10-% formaldehyde for macroscopic and histological analyses. The following anthropometric parameters were analyzed: (i) final weight-initial weight (g); (ii) body mass index (BMI; weight g/length cm2); (iii) Lee index (cubic root of weight g/length cm); (iv) specific rate of body mass gain (final weight-initial weight/initial weight). The results were analyzed by two-way ANOVA (water or fructose vs. treatment with omega-3 and PD induction, as variables), followed by Šidák’s or Tukey’s posthoc tests. P values <0.05 were considered as indicative of significance. P values >0.05 and <0.1 were indicated in the description of the results. The results show that the consumption of liquids was higher in all animals that received fructose, as an indication of polydipsia, independent of treatment with omega-3 or PD induction. A slight increase in glycemic levels was observed in the fructose-saline-PD+ group, an effect that was prevented by omega-3 supplementation. BMI was significantly higher in the groups that received 10-% fructose and omega-3, with no effects for PD induction. A similar profile was observed for the Lee index. Only the animals in the fructose-omega-3-PD- group showed a significant increase in the specific rate of body mass gain, compared with the respective control group, without omega-3 treatment. All animals supplemented with 10-% fructose had a significant increase in liver weight, regardless of the other interventions. Interestingly, there was an increase in the wet weight of inguinal white adipose tissue in all groups that received fructose, except in the fructose-omega-3-PD- group. The measurement of the adipocyte areas revealed a significant difference between the 10-% fructose group versus water, in animals with PD that received omega-3. An analysis of the thickness or area of the aortas did not show any significant difference among the groups No significant differences were detected for total cholesterol, HDL, or LDL levels. However, triglyceride amounts were significantly higher in the combined SM + PD group, an effect that was partially prevented by omega-3 supplementation. There was a tendency for an increase in leptin levels in all groups with MS induction; however, these differences were not significant. The induction of MS caused a marked reduction in adiponectin levels, which was reversed by the administration of omega-3, only in the PD group. Finally, the levels of bone loss and periodontal inflammation were higher in the groups with PD, regardless of the induction of MS. Omega-3 supplementation was able to revert these parameters in the PD groups, with or without fructose. It was possible to observe a higher level of bone loss in animals with MS, in the absence of PD, although significant differences were not identified. The results of the present study provide new evidence on the relationship between MS and PD, indicating more relevant changes concerning glycemia and triglyceride levels. The effects of omega-3 supplementation were significant concerning the prevention of bone loss and recovery of adiponectin levels. Our data uncover the importance of developing experimental models for common comorbidities, opening new perspectives of scientific investigations on the relationship between MS and PD.