Renal impact of systemic inhibition of miRNA‐451 in a mouse model of insulin resistance

Abstract

MicroRNAs (miRNA) affect transcription of a number of genes involved in the development and progression of diabetic nephropathy (DN), and have become attractive therapeutic targets and biomarkers. Elevated renal gluconeogenesis, fibrosis, and albuminuria are early markers of incipient DN. Recent studies report that renal miRNA‐451 may protect against DN and reduce renal gluconeogenesis in rodent models. It is hypothetically thought to act by targeting select factors resulting from disrupted insulin and growth factor signaling and the mechanistic‐target of rapamycin (mTOR) in early DN. To further elucidate the role of miRNA‐451 in DN, we placed male insulin‐resistant, TALLYHO/Jng mice on a high‐fat diet (60% kCal). The mice were divided into two treatment groups and received 8 consecutive weekly intraperitoneal injections of locked nucleic acid (LNA) miR‐451‐inhibitor or LNA‐scrambled compound (2 mg/kg·bw; n = 8/treatment). Mice were euthanized after 12 weeks (4 weeks sans injections). Renal expression of miRNA‐451 was drastically reduced in inhibitor treated mice (~6‐fold) in comparison to scramble‐treated mice. Western blotting of cortex homogenates for indicators of fibrosis and targets of miRNA‐451 revealed a significant reduction in collagen IV (marker of epithelial integrity) in inhibitor treated mice. In addition, metalloproteinase type 9 (MMP9, a known type IV collagenase), YWHAZ (a scaffolding protein and known target of miR‐451), mTOR, and fructose bisphosphatase (FBP1, a rate‐limiting gene in gluconeogenesis) were significantly increased in this group in comparison to scramble‐treated mice. However, no differences were found in protein levels for glucose‐6‐phosphatase (G‐6‐Pase) or phosphoenolpyruvate (PEPCK), 2 additional gluconeogenic rate‐limiting genes. MiRNA‐451 antagonist did not significantly affect final body weight or blood glucose; however, mean blood sodium concentrations were slightly, but significantly higher (2%) in the LNA‐inhibitor treated group (when compared to the scramble‐treated group). No differences in blood potassium or chloride were found. Anion gap was 90% higher in the LNA‐inhibitor treated group when compared to scramble‐treated mice. No differences in urinary albumin to creatinine ratio were found between the two treatment groups. However, Masson's Trichrome scoring revealed a 59% increase in fibrosis in inhibitortreated mice. Overall, these studies support a potentially protective role of miRNA‐451 in attenuating signaling via mTOR that may alter both renal gluconeogenic potential (contributing to the diabetic phenotype) and activation and progression of renal fibrosis. Therapies to enhance miRNA‐451 signaling may be beneficial to reduce renal pathology associated with DN.Support or Funding InformationResearch reported in this abstract was supported by the National Center For Advancing Translational Sciences of the National Institutes of Health under Award Number TL1TR001431 and the Georgetown University Department of Medicine. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of HealthThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.