ACE and ACE2 polymorphism had been studied as a putative mediator of DN, especially ACE gene. In our results for demographic characteristics, clinical and laboratory data was found significant differences for some variables between the groups analyzed. Elevated creatinine rate and decreased GFR are characteristic of diabetic renal disease [17, 18], which is consistent with our findings. In addition, patients on dialysis have a marked decrease in GFR and high creatinine rate indicate that renal function is already compromised in about 50% of cases [18, 19]. We also found a decrease in the BMI of individuals in the DN group. This difference can be explained by the level of metabolic decompensation in patients who had diabetes for several years and were undergoing hemodialysis [18, 20].
It is also known that adult hemoglobin (HbA) is formed by the non-enzymatic binding of HbA with glucose in the blood and this glycation is irreversible . When glucose levels are high, the glycation process is intensified so that the HbA1C ratio also increases. Considering that the diabetic patient presents with chronic hyperglycemia, then high values of HbA were expected in patients with DN [22, 23]. Our results revealed a decrease in HbA1C in DN group when compared to DM without DN group. However, patients with DN with D/D genotype had higher HbA1C and fasting plasma glucose compared to other genotypic profiles for ACE polymorphism.
The fasting plasma glucose did not present a significant difference, remaining high in both DN and DM groups, respectively. This observation might have occurred because the patients had recently undergone the hemodialysis process. In addition, the glycation process may undergo some interference which reduces the functionality of the red blood cells. Among these interferences we can mention chronic kidney disease (CKD) and this causes a false reduction in HbA1c levels . And the fact that the duration of diabetes, together with the uncontrolled hyperglycemia is the most important factor associated with the development of diabetic vascular complications .
The relationship between blood pressure and the risk and progression of DN is well established [25, 26]. It is known that CKD is characterized by a marked decrease in renal autoregulation capacity, as already mentioned. This directly implies systemic blood pressure which, in turn, affects the glomeruli and consequently accelerates the progression of CKD. Thus, as expected, our results indicate an increase in diastolic pressure, which is in agreement with the literature [27–29].
By considering the time of development of DM, the patients from the DN group were diagnosed with DM earlier. This confirms studies carried out by Salgado et al. , which report that the peak incidence of DN is usually found between 10 to 20 years of disease. It was also observed that in the DN patients the number of smokers was lower than when compared to DM group (48,42%). In addition, these diabetics smokers present a risk for the development of DN.
According to Eliimas Júnior et al. , smoking is a risk factor for CKD. Thus, the abandonment of smoking is one of the leading medical recommendations for diabetic patients, especially those undergoing hemodialysis treatment. Diabetic patients naturally constitute a risk group for CKD. However, smoking is a risk factor that should be modified as a strategy to prevent the progression of CKD in these patients.
When we observed the distribution of genotypes for ACE, D allele is suggested as a risk factor for DN development. These findings confirm the reports made in the study by Rodrigues  that demonstrated that D/D genotype in ACE gene presented a greater decline in the GFR, the main characteristic of the patient with DN. It is noteworthy that our results indicate a significant difference for the increased risk (OR = 2.5, p = 0.01) of I/D genotype in the development of DN, due to the presence of D allele. This observation contradicts an initial study by Kunz et al.  which failed to confirm the association between I/D polymorphism in DN patients in the Caucasian population.
In addition, Tziastoudi et al.  findings showed the D allele of I/D polymorphism in ACE gene is an independent risk factor for both the onset and progression of DN. We suggest that D allele influences the circulating levels of angiotensin II and, as a consequence, response to pressure increases, the glomeruli will be affected, culminating in glomerular damage and, consequently, DN .
In the meta-analysis by Smyth et al. , the authors demonstrated a significant association between I/D polymorphism in ACE gene and the risk for DN development. Other studies with suggest that ACE polymorphism favors the progression of renal disease, microvascular disorders and cardiovascular mortality, particularly among patients with DM [8, 12, 37, 38].
In the genotypic analysis, it is also observed that in both groups, there are a higher number of heterozygotes, whereas there the number of individuals with mutant genotype for ACE is practically the same in both groups. This is partially consistent with studies by Aggarwal et al.  and Wyawahare et al. , where the population of heterozygotes was also larger than homozygotes and mutants. Moreover, our results are consistent with studies conducted in the population of Kutch origin . In this population, the genotypic distribution had the same profile as the population studied in central Brazil population: most individuals were heterozygous, but in the population of Kutch were reported a substantial number of individuals with mutant genotype for ACE in the DM group with DN.
It is important to highlight that the G8790A polymorphism in ACE2 gene in male, did not reveal any influence of the analyzed variables regardless of gender. The decreased in creatinine rate in female with AA genotype and declining trend this is same rate in female with GA genotype when compared to GG genotype, this may be justified by the smaller number of women with mutant genotype than with wild-type genotype. Some studies have considered males as a risk factor for DN occurrence [40, 41], but not at all [42–44]. We then analyzed the phenotypic frequency distribution according to gender and our results showed no difference between any of the genotypes, probably because they had a high number of wild-type individuals in both groups.
The Hardy-Weinberg Equilibrium Test indicated that the distribution of the D allele in ACE gene had maintained the distribution ratios in the two groups. The same not occurred in the distribution of A allele in ACE2 gene. This equilibrium profile for D allele distribution differs in the literature. Parchwani et al.  described a trend of significance for the disproportion of D allele distribution in the ACE gene in diabetic patients with and without DN. In these studies, patients with DN showed a trend towards a higher proportion of D alleles in the genotypes. At this point, it should be noted that certain non-Caucasian races are at higher risk of developing DN . However, this information is still controversial in the literature.
By combining ACE and ACE2 genotypes, we observed an evident risk tendency (OR: 2.51, p = 0.07) associated with the combination of the ACE (I/D or D/D) and wild type ACE (GG) polymorphisms, as well as for the combination of the same polymorphism and ACE2 heterozygous or mutant (GA or AA or A) (OR = 2.61, p = 0.08). This finding confirms from the observations of Wang et al. , where an association between the I/D polymorphism in the ACE gene and the risk for DN development in the Asian population was found. Ahluwalia et al.  and Yu et al.  who also showed that individuals with polymorphic ACE gene present greater DN susceptibility. In addition, our findings do not corroborate studies conducted with the Moroccan population, which did not reveal an association between the D/D genotype and diabetic patients with and without DN .
Currently, polymorphisms in RAAS components have been highlighted due to their relationship with the severity of COVID-19, caused by SARS-CoV-2. ACE2 is the cellular receptor for this coronavirus, and its expression may possibly regulate an individual's susceptibility to infection. In contrast, high ACE activity would increase the risk of lung disease. Thus, the balance between the activity of the two enzymes has been evaluated in the pathogenesis and severity of COVID-19 .
Finally, to our knowledge, this is the first study to describe the effects of polymorphisms in ACE and ACE2 genes on DN susceptibility, especially in the central Brazilian population. Considering all these findings, we observed that the association between ACE I/D and ACE2 G8790A polymorphisms and the susceptibility to DN are still not fully elucidated. In this way, our observations in the central Brazilian population favor the understanding of this association and emphasize the real need to investigate these polymorphisms more deeply, especially in the mentioned population.