Significance of serum microRNAs in pre-diabetes and newly diagnosed type 2 diabetes: a clinical study

Abstract

To explore the clinical significance of seven diabetes-related serum microRNAs (miR-9, miR-29a, miR-30d, miR34a, miR-124a, miR146a and miR375) during the pathogenesis of type 2 diabetes (T2D), 56 subjects were recruited to this study: 18 cases of newly diagnosed T2D (n-T2D) patients, 19 cases of pre-diabetes individuals (impaired glucose tolerance [IGT] and/or impaired fasting glucose [IFG]) and 19 cases of T2D-susceptible individuals with normal glucose tolerance (s-NGT). Serum miRNAs were determined by real-time RT-PCR. Expression levels of single miRNAs and the expression signatures of miRNAs as a panel were analysed among the three groups. In n-T2D, all 7 miRNAs were significantly up-regulated compared with s-NGT and five were significantly up-regulated compared with pre-diabetes, while miRNA expression was not significantly different between s-NGT and pre-diabetes. By Canonical discriminant analysis, 70.6% of n-T2D subjects (12/17) were recognized by canonical discriminant function, while s-NGT and pre-diabetes subjects could not be discriminated from each other. Similar results were found in Hierarchical Clustering analysis based on the expression levels of all seven miRNAs. In different statistical analysis, miR-34a always showed the most significant differences. We conclude that the expression levels of seven diabetes-related miRNAs in serum were significantly elevated in n-T2D compared with pre-diabetes and/or s-NGT, and the latter two groups featured similar expression patterns of these miRNAs, suggesting that during the pathogenesis of T2D, the peripheral diabetes-related miRNAs have not changed significantly from s-NGT at pre-diabetic stage.

Circulating microRNAs and diabetes: potential applications in medical practice

“…The observation of the deregulation of miRNA profiles in different biological fluids of diabetic patients compared with healthy controls was the first evidence supporting the idea that miRNAs could be biomarkers of the diabetic disease (Table 1). Indeed, a differential miRNA profile between type 2 diabetic patients and healthy controls was found in whole blood [20,21], serum [22][23][24][25][26], plasma [27][28][29][30][31][32][33] and plasma exosomes [34]. Studies revealed a different miRNA pattern in serum of type 1 diabetic patients compared with healthy individuals [35], as well as in plasma [36,37] and urine [36].…”

“…Its altered expression in islets and/or pancreas has been observed in animal models with a predisposition to type 2 diabetes [52] and overt diabetes [7]. While miR-375 expression is not significantly augmented in human islets from glucose intolerant donors [53], increased levels have been observed in the pancreas [54] and blood of type 2 diabetic patients [22,33]. Given that miRNAs have been described as being responsive to cellular and extracellular stress and to be used by cells to adjust changes in their environment, it is conceivable that, under conditions of harsh stress, such as type 2 diabetes, miR-375 is increased, while under circumstances of mild stress, such as glucose intolerance, its expression remains in the normal range.…”

“…Only a few miRNAs appear to show a comparable change in levels in type 2 and type 1 diabetic patients compared with controls. For example, miR-29a is increased in the serum of both type 2 [22] and type 1 [35] diabetic patients. In contrast, several groups have reported a decrease in the plasma level of miR-126 in type 2 diabetes [27,30,31], but no difference or an increase in type 1 diabetes [36,37].…”

“…Urine measurements apply exogenous controls such as miR-39, Uni SP3 or endogenous controls such as RNA U6, while studies based on blood utilise exogenous controls such as miR-39 or endogenous controls such as RNU 6b, RNU 48, RNA U6, miR-16, miR-19b, miR-30c, miR-103, miR-106a, miR-191, miR-146a, miR-221, miR-223, miR-238, miR-423-3p, miR-425, miR-454, or miRNAs belonging to the let-7 family. Although these miRNAs have been selected for their relative stability, the levels of some may vary in diabetic populations such as miR-let-7a [21,34] and miR-let-7f [34], miR-let-7i [25], miR-191 [27,38], miR-223 [27] or miR-146a [22,29,41]. Given these shortcomings, a consensus for data normalisation is urgently needed based, for example, on the geometric mean of a common set of miRNAs.…”

“…Several studies have identified age-related modifications in circulating miRNA levels [77][78][79][80][81][82]. Notably, among these, miR-29b [27,28,70], miR-130b [31], miR-222 [31], miR-375 [22], miR-21 [26,27,36] and miR-126 [23,27,30,31] were found to be deregulated in diabetic patients. These results underline that age could induce a bias, which has to be dealt with.…”