Diabetes is a common chronic metabolic disease. Mounting evidence has elaborated that the major causes of morbidity and mortality in the diabetic population are retinopathy, nephropathy, cardiomyopathy, neuropathy, and atherosclerosis. These observations suggested that the macro- and microvascular affections are key features of such complications [15]. Growing evidence has illustrated that low-grade inflammatory changes associated with increased production of inflammatory mediators may be a key mechanism in the pathogenesis of chronic diabetic complications [16].
In the present study, we observed that out of sixty Egyptian patients with T2DM, twenty-two patients had DN with microalbuminuria (n=15) and seven patients had macroalbuminuria. Thus, about 36.7 % of patients with T2 diabetes mellitus had DN.
Similar to our result, a study conducted by Zelmanovitz et al. observed that about 30% of patients with T2DM develop clinically overt nephropathy [17]. DN is a multifactorial disorder that results from the interaction between environmental and genetic factors. Hyperglycemia, hypertension, and proteinuria are the main insults that cause structural abnormalities in a DN [18].
According to Elnajjar et al. study, about 78% of all the patients studied had DN. This study was conducted on both patients with T1DM and T2DM. Thus, the high prevalence of DN among their studied groups could be due to the inclusion of patients with T1DM [19]. However, in our study, we enrolled results in patients with T2DM only. In most type 2 diabetics, the prevalence of DN ranges from 30 to 50% [20].
Our study revealed clear evidence that in patients with macroalbuminuria, there was a statistically significant long duration of diabetes as well as higher values of BMI, waist/hip ratio, diastolic blood pressure, TG, and UACR compared to patients with normoalbuminuria and microalbuminuria.
Similar to our results, a study conducted by Elnajjar et al. revealed that there were statistically significant long duration of diabetes, higher systemic blood pressures, an evident decrease in eGFR, poor glycemic control, and obesity in patients with DN compared to patients without DN [21]. In agreement with our results, Kathryn et al. observed that there were significant correlations between the increasing duration of diabetes and the development of microproteinuria [22].
Regarding glycemic control, it was notable that in our observation patients with microalbuminuria had higher HbA1c values compared to patients with normoalbuminuria levels. Similar results were described in the ADVANCE Collaborative Group [22]. Nevertheless, the Veteran’s Affairs Diabetes Trial (VADT) observed that intensive therapy did not lead to a reduction in retinopathy or major nephropathy outcomes compared with standard therapy, but this study was for a short duration [23]. Mounting evidence has elaborated that BMI values were higher in patients with DN [18, 24, 25].
Despite the limited knowledge on the molecular mechanisms underlying the pathophysiology of microvascular complications of T2DM in particular CKD, emerging scientific evidence has indicated that the dysregulated epigenetic is associated with risk and progression of diabetic microvascular complications and could be used as predictors and diagnostic genetic markers of T2DM and CKD.
Emerging evidence demonstrated that about 30% of patients with T2DM develop clinically overt nephropathy. Consequently, early detection of DN is very useful for preventing progression to renal failure. Due to the high stability of ncRNAs in body fluids, they could be used as a noninvasive diagnostic biomarker for DN. Thus, the current study aimed to investigate the expression profile levels of circANKRD36 and ANKRD36 in Egyptian patients with T2DM and DN and to explore their associations with the risk and the progression of DN.
The results presented herein are innovative as this study performs a robust estimation of the expression levels of circANKRD36 and ANKRD36 in patients with T2DM in particular patients with DN. Expression of circANKRD36 and ANKRD36 were significantly higher in patients with T2DM compared to healthy control. Intriguingly, patients with macroalbuminuria had statistically significantly higher values of the relative expression level of circANKRD36 and ANKRD36 compared to patients with microalbuminuria and patients with normoalbuminuria levels.
In agreement with the present study, Fang et al. confirmed that the expression level of circANKRD36 is upregulated in patients with T2DM. Moreover, the level of ANKRD36 which is the host gene of circANKRD36 was upregulated in the T2DM group compared to the general population [26]. Previously, it was shown that ANKRD36 is the host gene of circANKRD36 and the level was increased in the T2DM group as the circ-RNAs can positively regulate their parent genes at the transcriptional level and post-transcriptional level [27,28,29].
The current study revealed that the relative expression of circANKRD36 and mRNA expression levels of ANKRD36 were positively correlated with duration of diabetes, diastolic blood pressure, TG, LDL, FPG, HbA1c, creatinine, and UACR and were significantly negatively correlated with eGFR. Currently, several pieces of evidence exist, demonstrating that miRNAs are involved in the regulation of vascular inflammation [30]. Furthermore, it has been also proposed that circRNAs influence the cardiometabolic risk factors which have a deleterious effect on blood vessels and can lead to the development of endothelial dysfunction and hence diabetic vascular complications [31].
Until the time of writing this article, only one experimental study was conducted to illuminate the roles of circRNA in CKD progression. In this study, circRNA_15698 upregulates TGFB1 expression and promotes ECM protein production. Thus, the inhibition of circRNA_15698 could delay the progression of CKD [32].
The current study aims to assess the correlations between circANKRD36 and ANKRD36 relative expression in patients with DN. We observed that, there were significant positive correlations between the levels of both genes and duration of diabetes, diastolic blood pressure, TG, LDL, FPG, HbA1c, creatinine, and UACR. However, there were significant negative correlations between both epigenetics and eGFR. A linear regression test was done to investigate the main independent parameters associated with the relative expression of circANKRD36 and the mRNA expression level of ANKRD36, and we observed that eGFR as well as UACR were independently correlated with both epigenetic biomarkers. Similar results were observed in a significant positive correlation between circANKRD36 and blood glucose as well as Hba1c [26].
ROC analysis was used to clarify the diagnostic power of circANKRD36 and the mRNA expression level of ANKRD36 for discriminating patients with T2DM from the control group. Our results revealed that the sensitivities and the specificities were 90% and 93% for circANKRD36 besides 88.3% and 87.5% for the mRNA expression level of ANKRD36. As regards, the differentiation of patients with microalbuminuria from patients with normoalbuminuria, the sensitivities and the specificities were 81.8% and 69.4% for circANKRD36 as well as 85.7% and 87.7% for the mRNA expression level of ANKRD36, respectively. We attempted to discriminate patients with macroalbuminuria from patients with microalbuminuria, the sensitivities, and the specificities were 80.1% and 80.7% for circANKRD36 in addition 85.7% and 87.7% for the mRNA expression level of ANKRD36, respectively.