PRKAA2 variation and the clinical characteristics of patients newly diagnosed with type 2 diabetes mellitus in Yogyakarta, Indonesia

We included 166 patients newly diagnosed with T2DM in the present study. We had excluded 20 participants who had FPG <126 mg/dL or HbA1c <6.5% from the initial 190 patients. We had also excluded 4 participants because of lysis of their blood sample. Genotypes of all participants were analyzed successfully. The baseline characteristics of the participants are presented in Table 2. The mean age of the patients in our sample was 54.0 ± 9.7 years, and 70.5% were female. Mean blood pressure in our participants was categorized as prehypertension with systolic ≥120 mmHg and diastolic ≥80 mmHg. The mean BMI and waist circumference indicated that our population tended to be overweight. In our present study the patients newly diagnosed with T2DM tended to have elevated blood pressure, but normal renal function as determined by eGFR. The mean of HbA1c was high for patients newly diagnosed with T2DM.

Genotype frequencies of the PRKAA2 genetic variations are described in Figure 1. The genotype frequencies of PRKAA2 rs2796498, rs9803799, and rs2746342 genetic variations were in Hardy–Weinberg equilibrium (P = 0.35; P = 0.08; and P = 0.36, respectively). Only 4.2% wild type of rs2796498 and 1.2% wild type of rs980799 were found in the genotyping results of this study.

Figure 1

The mean differences of clinical characteristics and genotype frequencies are listed in Table 3. Patients with a mutant genotype (TT) of rs2746342 tended to have a higher BMI than those with the wild type. Waist circumference was greater in patients with GT of rs9803799 than in those with TT or GG. Systolic blood pressure in rs2796498 was higher in patients with the wild type (AA), while in those with rs9803799 it was higher than in those with the mutant (TT) type. HbA1c was lower in patients with the wild-type genotype both for rs2796498 and rs9803799. Serum creatinine was higher in patients with the mutant genotype of rs2796498 and rs9803799, but it was higher in heterozygotes for rs2746342. The means of patients’ age, sex, blood pressure, BMI, waist circumference, and FPG, HbA1c, and serum creatinine concentrations, and eGFR were not significantly different between groups with rs2796498, rs9803799, and rs2746342.

We also analyzed the association between PRKKA2 genetic variations and clinical characteristics. As shown in Table 4, when the GG, TT, and GG in rs2796498, rs9803799, and rs2746342, respectively, were used as a reference, there was no significant association between PRKKA2 genetic variation and clinical characteristics (P > 0.05). We did not find any significant association in dominant, recessive, or allele models (P > 0.05). However, we found that AG, dominant model, and A allele in rs2796498 tended to increase the risk of higher FPG, higher CrSr, and eGFR <60 mL/min/m² (P > 0.05). By contrast, GT, dominant model, and G allele in rs9803799 reduced the risk of higher HbA1c and higher blood pressure, but increased the risk of eGFR <60 mL/min/m². Meanwhile, only the recessive model in rs2746342 indicated any reduction of the risk for higher FPG, higher HbA1c, higher CrSr concentration, and eGFR <60 mL/min/m², but was not significantly associated (P > 0.05).

Even after adjusting for age and sex (Table 5), our study did not find any association of PRKAA2 genetic variations in rs2796498, rs9803799, or rs2746342 with clinical characteristics in the Indonesian population, specifically in Yogyakarta, in patients newly diagnosed with T2DM (P > 0.05). Remarkably, the highest association was found in rs2746342 with renal function, both serum creatinine concentration and eGFR, but the association was not significant.

Our third model is presented in Table 6. The present study failed to discover any significant association of PRKAA2 genetic variation with clinical characteristics. It is notable that the recessive model of rs27476342 had a lower OR in association with FPG, HbA1c, eGFR, and obesity status compared with the genotype or dominant models.

Several studies have revealed the physiological functions of AMPK. AMPK comprises 3 groups, which are AMPKα, β, and γ, and has been studied as a target for T2DM therapy [19]. The role of AMPK in reducing T2DM risk has been discovered. AMPK has a role in glucose uptake in skeletal muscle, suppressing lipogenesis, protein synthesis, lipolysis, stimulating anti-inflammatory effects, and inhibition of gluconeo-genesis [15, 34, 35]. Therefore, a mutation in AMPK might induce susceptibility of T2DM. PRKKA2 encodes AMPKα2 as one of the active forms of AMPK related to hyperglycemia and insulin resistance [18, 36].

To our knowledge, this is the first study to investigate the association of PRKAA2 genetic variations (rs2796498, rs9803799, and rs2746342) with clinical characteristics of patients newly diagnosed with T2DM in an Indonesian population. Notably, our results indicated that those participants actually need dual therapy as initial therapy because the mean HbA1c was >9% (ADA). It is common to detect hypertensive problems in patients newly diagnosed with T2DM. However, hypertensive participants among patients newly diagnosed with T2DM tend to have lower risk of albuminemia and left ventricular hypertrophy than T2DM detection among patients newly diagnosed with hypertension [37]. Previous studies found obesity is common among patients newly diagnosed with T2DM [38]. While our participants were mostly women, BMI is a better tool to indicate the association between obesity and T2DM [39].

Genotype frequencies of rs2796498, rs9803799, and rs2746342 in our findings were in Hardy–Weinberg equilibrium. Therefore, those genetic variations remain relatively constant in our participant population [40], although there were low frequencies in wild-type rs2796498 and rs980799.

Of note, our study failed to discover any significant associations of FPG, HbA1c, serum creatinine, eGFR, blood pressure, or obesity status with genetic variations in rs2796498, rs9803799, or rs2746342. Several studies have investigated an association between PRKAA2 genetic variations and susceptibility to T2DM, but limited studies have observed their association with clinical characteristics. Shen et al. observed an association between PRKAA2 genetic variations (rs2746342 and rs2143754) and susceptibility to T2DM. Only rs2746342 was reported to have an association with T2DM risk in a Han Chinese population [24].

Similarly, Li et al. proposed that rs2746342 is associated with T2DM risk in a haplotype model, especially with increasing nephropathy. In addition, they studied rs2796498 and suggested it was significantly associated with susceptibility to T2DM [25]. Previously, rs9803799 was found to be correlated with metformin effectiveness [27]. However, only Shen et al. reported the PRKAA2 genetic variations were associated with clinical characteristics. There was a mean difference of FPG between the dominant and recessive models [24].

Even though AMPKα2 is correlated with hyperglycemia, our study could not ascertain the association of this genetic variation with FPG and HbA1c as glycemic indicators. Therefore, our findings suggest that we still could not combine glycemic indicators and genetic variation analysis as a diagnostic tool for T2DM in our population. Most notably, we found that our study's major allele is a risk factor of T2DM as shown in our previous study. Therefore, our results confirmed previous findings related to the association of PRKAA2 genetic variations with the susceptibility of T2DM because all of our participants were patients with T2DM.

We could not detect any association of these genetic variations with declining renal function (eGFR <60 mL/min/1.73 m²) nor elevated blood pressure as a common comorbidity in patients with T2DM. The absence of apparent association might be caused by our study's recruitment of patients newly diagnosed T2DM. Progressive declining renal function and elevated blood pressure among patients with T2DM depend on T2DM duration [41, 42]. It is possible that for patients newly diagnosed with T2DM, as in our patient population, renal function has not yet changed, and blood pressure remains controlled. AMPK has a unique role in diabetic nephropathy by influencing metabolic memory, podocytes, proximal tubule cells, and fibrosis [43]. The findings that rs2746342 had the highest OR for renal function after adjusting for sex and age warrants further investigation. AMPK has been well-studied in causing arterial dilatation by SERCA and BK_CA channels in vascular smooth muscle [44].

Our study did not find any significant association of PRKAA2 genetic variations and obesity status based on BMI. Because it is well-known that AMPK has a significant role in lipid regulation [34], it should be associated with obesity. Similarly, results were found in studies of Japanese and populations with European and Scandinavian ancestry that showed there was an absence of association of PRKAA2 genetic variations and BMI [21, 36].

We suggest that the lack of association between PRKAA2 variations and clinical characteristics in patients with T2DM as shown in our present study is because of their various ancestries. To our knowledge, this study is the first of its kind examining Indonesians, whereas the other studies observed Han Chinese and other populations. In addition, clinical characteristics are not solely the result of gene variation. They could also be influenced by gene–environment interaction [45]. Diet, physical activities, and access to health care facilities might be additional important factors affecting this apparent discrepancy [12, 46]. It could not be denied that access to health care facilities affects uncontrolled blood glucose level and development of T2DM complications. Indonesia is an archipelago, where the access to health care services varies from one area to another [47, 48]. In our study, we included patient participants from 10 different PHC, which have different patient accessibility.

The present study is limited, first, by our relatively small sample size, and the findings should be confirmed using a larger sample. Second, we did not examine other factors that could influence clinical characteristics, such as diet, physical activities, and medication adherence. Third, we recognize that there is genetic heterogeneity in the Indonesian population. Accordingly, to reduce this heterogeneity, we conducted the study only in Yogyakarta where the majority of the people are Javanese. Therefore, in light of our study's limitations, readers should be cautious when generalizing our findings.

PRKAA2 genetic variations (rs2796498, rs9803799, and rs2746) are unlikely to be associated with clinical characteristics of patients newly diagnosed with T2DM in our mainly Javanese patient population. Further studies with a larger sample of Indonesians with other specific ethnicities are required to discover the association of these SNPs with clinical characteristics.