The tissue connection and support teeth in position are demolished by an infectious inflammatory illness known as periodontitis. By transitioning from a symbiotic to a dysbiotic condition, pathobionts also harm the tissue. ^{1 , 2} Immune responses are mostly controlled by genotypes, and dysbiotic flora also influences the response. The distribution and severity of diseases are influenced by genetic factors, which also have a substantial impact on the immune response to bacterial infections. ³ In response to an increase in the levels of lipids and low-density lipoprotein (LDL) in the blood, the immune system launches, propagates, and triggers atheroma throughout the circulatory system, resulting in atherosclerosis (AS), an inflammatory disease. Atherosclerosis is one sign of coronary heart disease (CHD). ^{4 , 5} An assembly of several proteins, known as the AIM2 inflammasome, occurs in response to microbiome or sterile allusions. During apoptosis, inflammatory mediators are released into cells as a result of the active form of caspase-1. Moreover, it is linked to osteoclast stimulation, atheroma formation, and progressive periodontal ligament injury. ^{6 – 8} Numerous studies have documented a correlation between genetic variation in the inflammasome constituent genomes and heightened tendency toward periodontal disease or CHD among diverse ethnic groups. ^{9 , 10} Genetic illnesses, such as autoimmune sickness, dermatitis, and periodontal disease, have also been reported to be associated with variants of the AIM2 genetic factor, known as DNA, which consists of two strands of sensors. ¹¹ To date, there is no evidence from any research linking a variant of the AIM2 gene to periodontal disease risk in people with or without CHD. This sheds insight into the current investigation, which aims to determine the relationship between AIM2 gene polymorphisms and periodontal disease propensity in both people with and without CHD, and to detect whether males or females are more susceptible to these diseases. We also evaluated the correlation between AIM2 single nucleotide polymorphisms and indicators of periodontal disease severity.

Case-control study design from November 2022 to May 2023, the inquiry occurred in numerous centers in Baghdad City. The study was conducted in accordance with the Declaration of Helsinki, and approved by the Ethics Committee of the University of Baghdad, College of Dentistry (Ref. 652, 13/09/2022, Project # 652622) that gave their stamp of approval to the study’s moral foundations. All the human research protocols complied with the ethical standards laid out in the Helsinki Statement and its later modifications. Each participant signed an informed written consent form after being provided detailed information about the study and its purposes. The present study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) in terms of design of the study and results reporting.

A total of 1370 people examined to participate in the current investigation, whereas 1230 individuals declined based on the grounds for exclusion, as illustrated in ( Figure 2). The average value was computed considering the demographic factors of the 140 individuals in the four groups (healthy (c), periodontal disease (P), coronary heart disease with intact periodontium (AS-C), and coronary heart disease with periodontal disease (AS-P)). The sex distribution of all groups was 80% males and 20% females. This study examined the body mass index (BMI) of individuals with a weight of 24 kg/m ². Variations in age, sex, and body mass index across the groups were not statistically significant (p ≤ 0.05) ( Table 1). Moreover, the present outcomes determined a significant increase in the average values of indicators of periodontal disease severity in the periodontitis patient groups. Sequencing of the AIM2 SNP using the Sanger method in the four study groups is shown in Figure 3. This SNP, rs 2793845, results from the replacement of guanine (G) with thymine (T) in the intron region of one chromosome.

A solitary “T” top point to the presence of a T homozygous for allele. A solitary “G” top point to the presence of a G homozygous for allele. The existence of the “G” and “T” points suggests the existence of the G/T heterozygous allele.

Furthermore, the present study was identified TT genotype of AIM2 G/T (rs 2793845) was a high odd/ratio (OR=14.9 (3.990 to 45.98), P-value=0.0) in P group, (OR=16.43 (0.5094 to 0.4878), P-value = 0.0013) in AS-C group and (OR=16.45 (0.05094 to 0.4878), P-value=0.0013) in AS-P group as compared to control healthy group, whereas genotype GT was a high odd/ratio (OR=22.44 (0.009776 to 0.7495), P-value=0.0227) in P group, (OR=9.12 (0.007127 to 0.6108), P-value=0.0056) in AS-C group and (OR=6.93 (0.004114 to 0.3088), P-value=0.0002) in AS-P group than control healthy group, (p-value<0.000), as described in Table 2. Data analysis of alleles frequencies in patients and controls groups are summarized in Table 3, the T allele of the AIM2 G/T (rs 2793845) gene showed greater frequenting in the P group was (0.85), AS-C group was (0.72), and AS-P group was (0.8) compared to the G allele, and it is slightly higher than the allele frequency in Asians was 0.65 and the global population was 0.86 from the Genome Aggregation Database (gnom AD). In addition, the frequencies of alleles and genotypes in the AIM2 gene polymorphism did not show any substantial variation relative to the Hardy-Weinberg equilibrium (HWE) in any group of participants. The correlation of AIM2 with indicators of periodontal disease severity in the patient groups is shown in Table 4. There was a significant correlation between AIM2 G/T (rs 2793845) and BOP (r=0.444, p=0.013; r=0.463, p=0.030), PPD (r=0.364, p=0.048; r=0.399, p=0.029), and CAL (r=0.504, p=0.005; r=0.536, p= 0.004) in the P group and AS-P group, respectively.

The current investigation identified a correlation between genomic variations related to inflammation in individuals and increased vulnerability to developing periodontitis, both with and without coronary heart disease. This was achieved by analyzing certain genotypes that played a role in the progress of both conditions. Additionally, indicators of periodontal disease severity and the AIM2 gene showed a significant association. The results revealed that males were more susceptible to developing these diseases in all groups at a ratio of 80 males and 20 females. In the AIM2 (rs 2793845) gene, the P, AS-C, and AS-P groups had noticeably greater frequencies of T allele and distribution (GT, TT) genotypes in blood samples than the control group. An analysis of the AIM2 gene’s single nucleotide polymorphism linked the AIM2 gene’s downstream functional area to the occurrence of periodontitis and coronary heart disease through abnormal gene expression and activation of AIM2 proteins and host molecules. This results in the degradation of the periodontium, impaired functioning of endothelial cells, and production of plaques that contribute to the development of atherosclerosis. This SNP influences the process of inflammation through changes in the shift-regulating activity. Therefore, the presence of these abnormal genetic variations in AIM2 was linked to a higher likelihood of developing periodontitis, both with and without coronary heart disease. Marchesan et al. found that the frequency of a specific gene variant (allele) and the distribution of different genetic combinations (genotypes) of the AIM2 gene (specifically SNP rs 1057028) may have a substantial impact on the development of periodontal diseases. ²¹ In contrast, Figueira et al. observed that individuals with a specific genetic variation (SNP) in the AIM2 gene (rs 1103577) had a considerably reduced chance of developing pulmonary tuberculosis (PTB) compared to healthy individuals. ²² In polymorphisms of the AIM2 gene, the frequency of the T allele appears to be slightly higher than that in Asians and in the global population. In addition, the association of T alleles of the AIM2 SNP with the probability of periodontal diseases and/or coronary heart disease has been assessed, which suggests the validity of this SNP as a putative genetic risk factor for both diseases in the Iraqi population. The Hardy-Weinberg equilibrium of the AIM2 SNP did not deviate and determined the quality of frequencies of genotypes and alleles for each study group. The current study found that periodontal indicators were greater in the AS-P group than in other study groups. The microbiome of plaque secretes a wide range of microbial residues, which in turn accelerates the degradation of periodontium, leading to pocket formation, resorption of bone, and missing teeth by initiating an inflammatory response, which is in agreement with previous studies. ^{16 , 23 , 24} Research on the Iraqi population has consistently shown that periodontitis is more common in males than females. This may be attributed to variations in hygienic protocols. ^{25 , 26} Male individuals exhibit a higher incidence of atherosclerosis than females because of the protective benefits of estrogen hormones in females. Estrogen has numerous influences on fatty acids, oxygen consumption, blood flow, and oxidative characteristics. ^{27 , 28} Therefore, the males appear to be more susceptible to periodontitis and CHD in the patient groups. The Pearson’s correlation coefficient results of this study indicate that AIM2 genetic variation is meaningfully associated with indicators of periodontal disease severity in periodontal disease patient groups. One possible explanation for this association is the presence of genetic and inflammatory mechanisms that contribute to the progression of periodontal disease and plaque production in atherosclerosis in cardiovascular disease. The present study has several limitations. Popular risk variables for periodontitis and CHD, including cigarette use, high blood pressure, diabetes, and obesity, which might potentially influence or enhance the effects of certain genetic mutations, were deliberately eliminated from the present investigation to prevent bias. Nevertheless, in the presence of various polymorphisms, they may be vulnerable to periodontal and coronary heart diseases. This study is unique in its investigation of the genetic underpinnings of periodontal disease with and without CHD. It had an adequate number of participants, which could be comprehended based on the pilot study to support numerous test adjustments and helped avoid false-positive results commonly found in applicant genes looking at research. Additionally, the results of this case-control study can only be used to establish a link and potential genetic vulnerability in the Iraqi population. To determine whether the AIM2 SNP is applicable to other populations, further experiments are necessary. Considering the correlation between AIM2 genetic substitution and disease severity, our findings not only shed light on disease progression but also suggest a novel approach for treating periodontal disease and coronary heart disease.

The presence of the T allele and (GT, TT) genotypes of the AIM2 gene, which reveal a wide range of effects on several traits, corresponds to increased vulnerability to both periodontitis and CHD. This genetic variation plays a role in the development of both the diseases. The presence of the AIM2 genetic variation might potentially disrupt the control of epigenetic processes. This can lead to the production of abnormal AIM2 polypeptides and increase the release of inflammatory mediators in both periodontitis and atheroma formation. The AIM2 SNP was also found to be significantly correlated with indicators of periodontal disease severity. The association between these ailments can be attributed to the presence of shared inflammation and molecular mechanisms in their development. The results of the current study raise issues regarding the validity of this SNP as a putative inherited risk factor for these illnesses in Iraqi males.

Concept and design: Zina Ali Daily and Batool Hassan Al-Ghurabi data collection, processing, or interpreting: the authors; writing up the manuscript: Zina Ali Daily; revising the work critically for key ideas and analyses of statistics: Zina Ali Daily and Batool Hassan Al-Ghurabi; supervision: Batool Hassan Al-Ghurabi.

The research followed the tenets of the Declaration of Helsinki and its later amendments for human research. The Ethics Committee of college of Dentistry, University of Baghdad approved this study (Ref. 652, 13/09/2022, Project # 652622in 13/09/2022). All participants entered the study after they were received full information about the nature, aims and processes of the study before signing an informed written consent form.

All participant signed an informed written consent form which approved by the Ethics Committee following provision of detailed information about the study and its purpose in a consecutive series manner.