Heterogeneous nuclear ribonucleoproteins F and K mediate insulin inhibition of renal angiotensinogen gene expression and prevention of hypertension and kidney injury in diabetic mice

Abstract

Aims/hypothesis We investigated whether heterogeneous nuclear ribonucleoproteins F and K (hnRNP F, hnRNP K) mediate insulin inhibition of renal Agt expression and prevention of hypertension and kidney injury in an Akita mouse model of type 1 diabetes. Methods Adult male Akita mice (12 weeks old) were treated with insulin implants and killed at week 16. Untreated nonAkita littermates served as controls. The effects of insulin on blood glucose, systolic BP (SBP), renal proximal tubular cell (RPTC) gene expression and interstitial fibrosis were studied. We also examined immortalised rat RPTCs stably transfected with control plasmid or with plasmid containing rat Agt promoter in vitro.Results Insulin treatment normalised blood glucose levels and SBP, inhibited renal AGT expression but enhanced hnRNP F, hnRNP K and angiotensin-converting enzyme-2 expression, attenuated renal hypertrophy and glomerular hyperfiltration and decreased urinary albumin/creatinine ratio, as well as AGT and angiotensin II levels, in Akita mice. In vitro, insulin inhibited Agt but stimulated Hnrnpf and Hnrnpk expression in high-glucose media via p44/42 mitogen-activated protein kinase signalling in RPTCs. Transfection with Hnrnpf or Hnrnpk small interfering RNAs prevented insulin inhibition of Agt expression in RPTCs. Conclusions/interpretation These data indicate that insulin prevents hypertension and attenuates kidney injury, at least in part, through suppressing renal Agt transcription via upregulation of hnRNP F and hnRNP K expression in diabetic Akita mice. HnRNP F and hnRNP K may be potential targets in the treatment of hypertension and kidney injury in diabetes.

Angiotensin-(1–7) prevents systemic hypertension, attenuates oxidative stress and tubulointerstitial fibrosis, and normalizes renal angiotensin-converting enzyme 2 and Mas receptor expression in diabetic mice

“…SBP was monitored in the morning with a BP-2000 tail-cuff pressure monitor (Visitech Systems) at least two or three times each week per animal, for 10 weeks [14][15][16][17][18][22][23][24][25][26]. The mice were habituated to the procedure for at least 15-20 min per day for 5-7 days before the first SBP measurements.…”

“…The GFR (glomerular filtration rate) was estimated as described by Qi et al [27], as recommended by the Animal Models of Diabetic Complications Consortium (http://www.diacomp.org/) with slight modifications [18,22,28].…”

“…Mouse urinary AngII and Ang-(1-7) levels were quantified by specific ELISAs after extraction in accordance with the manufacturer's protocol (Bachem Americas) and were normalized by urinary creatinine levels [17,18,22,25,26].…”

Renal Angiotensinogen and Sodium-Glucose Cotransporter-2 Inhibition: Insights from Experimental Diabetic Kidney Disease

“…RAS activation in turn promotes increased intraglomerular pressure, hypertension, and activation of proinflammatory and profibrotic mediators of kidney injury. Of particular importance for the current study by Woods et al [1] is the previous observation by Chan and colleagues [2] that hyperglycemia increases intrarenal angiotensinogen production at the proximal tubule via nuclear proteins such heterogeneous nuclear ribonucleoprotein (hnRNP) F and hnRNP K [2]. As a consequence of ambient hyperglycemia, intrarenal RAS activation is observed in animals and humans, even though systemic, circulating levels of RAS hormones can be markedly suppressed.…”

“…This phenomenon has been called the "paradox of the low renin state in diabetes," whereby intrarenal RAS activation is characteristic of diabetes in the setting of suppressed circulating levels. In animals, targeted inhibition of hnRNP F and hnRNP K, or overexpression of catalase to attenuate ROS production, blocks hyperglycemia-mediated RAS activation and angiotensinogen production [2]. As a consequence of the deleterious effect of RAS activation on cardiorenal disease, in clinical practice, angiotensin-converting enzyme (ACE) inhibitors and angiotensin II type 1 receptor (ARB) blockers are the standard of care to reduce blood pressure and slow DKD progression in patients with type 1 diabetes (T1D) and type 2 diabetes (T2D).…”