Risk Factors Associated With Altered Circulating Micro RNA -125b and Their Influences on Uremic Vascular Calcification Among Patients With End-Stage Renal Disease

Background

MicroRNA‐125b (miR‐125b) has been shown to regulate vascular calcification (VC), and serum miR‐125b levels are a potential biomarker for estimating the risk of uremic VC status. However, it is unknown whether clinical features, including chronic kidney disease–mineral bone disorder molecules, affect serum miR‐125b levels.

Methods and Results

Patients receiving chronic dialysis for ≥3 months were recruited from different institutes. Serum miR‐125b and chronic kidney disease–mineral bone disorder effectors, including intact parathyroid hormone, 25‐OH‐D, fibroblast growth factor‐23, osteoprotegerin, and fetuin‐A, were quantified. We used multivariate regression analyses to identify factors associated with low serum miR‐125b levels and an area under receiver operating characteristic curve curve to derive optimal cutoffs for factors exhibiting close associations. Further regression analyses evaluated the influence of miR‐125b on VC risk. Among 223 patients receiving chronic dialysis (mean age, 67.3 years; mean years of dialysis, 5.2), 54 (24.2%) had high serum miR‐125b levels. Osteoprotegerin (P=0.013), fibroblast growth factor‐23 (P=0.006), and fetuin‐A (P=0.036) were linearly associated with serum miR‐125b levels. High osteoprotegerin levels independently correlated with high serum miR‐125 levels. Adding serum miR‐125b levels and serum osteoprotegerin levels (≥400 pg/mL) into models estimating the risk of uremic VC increased the area under receiver operating characteristic curve values (for models without miR‐125b/osteoprotegerin, with miR‐125b, and both: 0.74, 0.79, and 0.81, respectively).

Conclusions

Serum osteoprotegerin levels ≥400 pg/mL and serum miR‐125b levels synergistically increased the accuracy of estimating VC risk among patients receiving chronic dialysis. Taking miR‐125b and osteoprotegerin levels into consideration when estimating VC risk may be recommended.

MicroRNA-125b induces tau hyperphosphorylation and cognitive deficits in Alzheimer's disease

Sporadic Alzheimer's disease (AD) is the most prevalent form of dementia, but no clear disease-initiating mechanism is known. Aβ deposits and neuronal tangles composed of hyperphosphorylated tau are characteristic for AD. Here, we analyze the contribution of microRNA-125b (miR-125b), which is elevated in AD. In primary neurons, overexpression of miR-125b causes tau hyperphosphorylation and an upregulation of p35, cdk5, and p44/42-MAPK signaling. In parallel, the phosphatases DUSP6 and PPP1CA and the anti-apoptotic factor Bcl-W are downregulated as direct targets of miR-125b. Knockdown of these phosphatases induces tau hyperphosphorylation, and overexpression of PPP1CA and Bcl-W prevents miR-125b-induced tau phosphorylation, suggesting that they mediate the effects of miR-125b on tau. Conversely, suppression of miR-125b in neurons by tough decoys reduces tau phosphorylation and kinase expression/activity. Injecting miR-125b into the hippocampus of mice impairs associative learning and is accompanied by downregulation of Bcl-W, DUSP6, and PPP1CA, resulting in increased tau phosphorylation in vivo. Importantly, DUSP6 and PPP1CA are also reduced in AD brains. These data implicate miR-125b in the pathogenesis of AD by promoting pathological tau phosphorylation.