Periodontitis and type 2 diabetes among women with previous gestational diabetes: epidemiological and immunological aspects in a follow-up of three years

Abstract Periodontitis can contribute to the development of insulin resistance. Gestational diabetes is a risk factor for type 2 diabetes. Therefore, periodontitis, when associated with gestational diabetes, could increase the risk for the development of type 2 diabetes after pregnancy. Objective The aim of this study was to verify the incidence on the development of type 2 diabetes in women with previous gestational diabetes with and without periodontitis after a three-year time interval. Material and Methods Initial sample of this follow-up study consisted of 90 women diagnosed with gestational diabetes who underwent periodontal examination. After three years, 49 women were subjected to new periodontal examination and biological, behavioral, and social data of interest were collected. Additionally, the quantification of the C-reactive protein in blood samples was performed. Fasting glucose and glycated hemoglobin levels were requested. Saliva samples were collected for quantification of interleukin 6 and 10, tumor necrosis factor α, matrix metalloproteinase 2 and 9. Results The incidence of type 2 diabetes mellitus was 18.4% and of periodontitis was 10.2%. There was no significant difference in the incidence of type 2 diabetes mellitus among women with and without periodontitis. It was observed impact of C-reactive protein in the development of type 2 diabetes mellitus. However, it was not observed impact of periodontitis on the development of type 2 diabetes mellitus among women with previous gestational diabetes. Conclusions It was not observed impact of periodontitis on the development of type 2 diabetes among women with previous gestational diabetes. The impact of C-reactive protein in the development of type 2 diabetes mellitus highlights the importance of an inflammatory process in the diabetes pathogenesis.

Based on the possibility that periodontitis can contribute to the development of insulin resistance, periodontitis, when present in women with GDM, could also increase the risk for the development of DM-2 after the gestational period. To our knowledge, only one study evaluated the impact of periodontitis on the incidence of DM-2 among women with previous GDM, pointing out that women with a history of GDM and periodontitis have impaired glucose metabolism 29 .
Therefore, additional studies are necessary to better address this potential association.
The aim of the present follow-up study was to verify the incidence on the development of type 2 diabetes in women with previous gestational diabetes with and without periodontitis after a three-year time interval, and to quantify CRP in the blood as well as TNF-, IL-6, interleukin 10 (IL-10), matrix metalloproteinase 2 (MMP-2), and matrix metalloproteinase 9  in the saliva.

Sampling strategy
The sample of the present follow-up study initially comprised a cohort of 90 women previously diagnosed with GDM from a previous case-control study that investigated the association between periodontitis and GDM 13  Participants were informed about the study and signed an informed consent form.

Sociodemographic characteristics
Social and demographic data were collected for each participant through structured questionnaires.
We collected data regarding age, marital status, educational level, gestational period and delivery date, smokers, former smokers, and non-smokers 25 .

Medical data
Weight and height of participants were recorded and body mass index (BMI) was calculated. According Periodontitis and type 2 diabetes among women with previous gestational diabetes: epidemiological and immunological aspects in a follow-up of three years weight, overweight, or obese 27 .
Fasting glucose test and glycated hemoglobin levels were collected for each participant. When exams showed altered glycemic levels, they were performed than 125 mg/dl for fasting glucose and 6.4% for glycated hemoglobin were considered positive for the diagnosis of DM-2. Pre-diabetes was diagnosed as the presence of values higher than 99 mg/dl for fasting glucose and 5.6% for glycated hemoglobin, according to the American Diabetes Association 2 (2014). Sample was divided in two groups according to glycemic levels: a) normal fasting glucose group (NFG); b) altered fasting glucose group (AFG). Subsequently, they were subdivided in three groups according to glycemic diagnosis: normal, pre-diabetes, and DM-2.
Additionally, we requested a blood test for assessing the CRP levels. The CRP level less than 5 mg/l was considered normal. Values greater than or equal to 5 mg/l were considered abnormal 20 .

Periodontal clinical examination
Participants underwent a periodontal examination during gestation in a previous study 13  All collected data were recorded and evaluated The following exclusion criteria were also adopted during periodontal examination: third molars, teeth whose cementum-enamel junction was impossible to determine, teeth with gingival morphology alterations, teeth with extensive caries lesions, teeth with iatrogenic restorative procedures, excessive calculus presence. 15 . Periodontitis the number of affected sites: 30% of sites (localized), and >30% of sites (generalized). Periodontitis was amount of attachment loss: 1-2 mm (slight form), 3-4 3 .         In the present study, increased age showed no impact on the development of DM-2 among women with GDM. Increased age has been considered a risk factor for GDM 13 . In addition, it was also demonstrated that the prevalence of DM-2 increased with age 2 . The