We investigated plasma microRNA (miRNA) profiles associated with variation of hyperglycemia, measured as hemoglobin A_1c (HbA_1c), in two panels of patients with type 1 diabetes (T1D). Using the HTG Molecular Diagnostics EdgeSeq platform, 2,083 miRNAs were measured in plasma from 71 patients included in a screening panel. Quantitative real-time polymerase chain reaction was used to measure the candidate miRNAs in plasma from 95 patients included in an independent replication panel. We found 10 miRNAs replicated in both panels and four with high statistical significance. The strongest positive correlations with HbA_1c were found with miR-125b-5p (r_s= 0.40, p=6.0x10^-5) and miR-365a-3p (r_s=0.35, p=5.9x10^-4). The strongest negative correlations were found with miR-5190 (r_s=-0.30, p=0.003) and miR-770-5p (r_s=-0.27, p=0.008). Pathway analysis revealed that 50 KEGG pathways were significantly enriched by genes targeted by these 4 miRNAs. The axon guidance signaling pathway was enriched (p<1x10^-7) by genes targeted by all 4 miRNAs. And three other pathways (the Rap1 signaling, focal adhesion and neurotrophin signaling) were also significantly enriched but with genes targeted by only by 3 of the identified miRNAs. In conclusion, our study identified 4 circulating miRNAs that were influenced by variation in hyperglycemia. Dis-regulation of these miRNAs, which are associated with hyperglycemia in patients with T1D, may contribute to the development of diabetic complications. However, there are multitudes of possible mechanisms/pathways through which dis-regulation of these miRNAs may impact risk of diabetic complications.

OBJECTIVE The role of fibrosis in early progressive renal decline in type 2 diabetes is unknown. Circulating WFDC2 (WAP four-disulfide core domain protein 2) and matrix metalloproteinase 7 (MMP-7; Matrilysin) are postulated to be biomarkers of renal fibrosis. This study examined an association of circulating levels of these proteins with early progressive renal decline. RESEARCH DESIGN AND METHODS Individuals with type 2 diabetes enrolled in the Joslin Kidney Study with an estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m² were monitored for 6–12 years to ascertain fast early progressive renal decline, defined as eGFR loss ≥5 mL/min/1.73 m²/year. RESULTS A total of 1,181 individuals were studied: 681 without and 500 with albuminuria. Median eGFR and albumin-to-creatinine ratio (ACR) at baseline were 97 mL/min/1.73 m² and 24 mg/g, respectively. During follow-up, 152 individuals experienced fast early progressive renal decline: 6.9% in those with normoalbuminuria and 21% with albuminuria. In both subgroups, the risk of renal decline increased with increasing baseline levels of WFDC2 (P < 0.0001) and MMP-7 (P < 0.0001). After adjustment for relevant clinical characteristics and known biomarkers, an increase by one quartile in the fibrosis index (combination of levels of WFDC2 and MMP-7) was associated with higher risk of renal decline (odds ratio 1.63; 95% CI 1.30–2.04). The association was similar and statistically significant among patients with and without albuminuria. CONCLUSIONS Elevation of circulating profibrotic proteins is associated with the development of early progressive renal decline in type 2 diabetes. This association is independent from albuminuria status and points to the importance of the fibrotic process in the development of early renal decline.

Circulating proteins associated with transforming growth factor–β (TGF-β) signaling are implicated in the development of diabetic kidney disease (DKD). It remains to be comprehensively examined which of these proteins are involved in the pathogenesis of DKD and its progression to end-stage kidney disease (ESKD) in humans. Using the SOMAscan proteomic platform, we measured concentrations of 25 TGF-β signaling family proteins in four different cohorts composed in total of 754 Caucasian or Pima Indian individuals with type 1 or type 2 diabetes. Of these 25 circulating proteins, we identified neuroblastoma suppressor of tumorigenicity 1 (NBL1, aliases DAN and DAND1), a small secreted protein known to inhibit members of the bone morphogenic protein family, to be most strongly and independently associated with progression to ESKD during 10-year follow-up in all cohorts. The extent of damage to podocytes and other glomerular structures measured morphometrically in 105 research kidney biopsies correlated strongly with circulating NBL1 concentrations. Also, in vitro exposure to NBL1 induced apoptosis in podocytes. In conclusion, circulating NBL1 may be involved in the disease process underlying progression to ESKD, and its concentration in circulation may identify subjects with diabetes at increased risk of progression to ESKD.

Significance Statement: Mechanisms underlying the progression of diabetic kidney disease to ESKD are not fully understood. Through profiling of circulating microRNAs (miRNAs) and proteins in individuals with type 1 and type 2 diabetes from four independent cohorts, the authors identified a signature of 17 miRNAs and six axon guidance pathway proteins that were robustly associated with severity of early structural lesions in kidney biopsy specimens and with an increased 10-year risk of ESKD. The study reveals novel mechanisms and proteins that govern progression to ESKD and point to the importance of systemic factors in the development of diabetic kidney disease. Some of the circulating miRNAs and axon guidance pathway proteins represent potential targets for new therapies to prevent and treat this condition. Background: Mechanisms underlying the pro gression of diabetic kidney disease to ESKD are not fully understood. Methods: We performed global microRNA (miRNA) analysis on plasma from two cohorts consisting of 375 individuals with type 1 and type 2 diabetes with late diabetic kidney disease, and targeted proteomics analysis on plasma from four cohorts consisting of 746 individuals with late and early diabetic kidney disease. We examined structural lesions in kidney biopsy specimens from the 105 individuals with early diabetic kidney disease. Human umbilical vein endothelial cells were used to assess the effects of miRNA mimics or inhibitors on regulation of candidate proteins. Results: In the late diabetic kidney disease cohorts, we identified 17 circulating miRNAs, represented by four exemplars (miR-1287-5p, miR-197-5p, miR-339-5p, and miR-328-3p), that were strongly associated with 10-year risk of ESKD. These miRNAs targeted proteins in the axon guidance pathway. Circulating levels of six of these proteins—most notably, EFNA4 and EPHA2—were strongly associated with 10-year risk of ESKD in all cohorts. Furthermore, circulating levels of these proteins correlated with severity of structural lesions in kidney biopsy specimens. In contrast, expression levels of genes encoding these proteins had no apparent effects on the lesions. In in vitro experiments, mimics of miR-1287-5p and miR-197-5p and inhibitors of miR-339-5p and miR-328-3p upregulated concentrations of EPHA2 in either cell lysate, supernatant, or both. Conclusions: This study reveals novel mechanisms involved in progression to ESKD and points to the importance of systemic factors in the development of diabetic kidney disease. Some circulating miRNAs and axon guidance pathway proteins represent potential targets for new therapies to prevent and treat this condition.

Global proteomics profiling identified FGF20, TNFSF12, and ANGPT1 as protective against progression of renal function decline in those with diabetes.