Insulin Regulates Nitric Oxide Production in the Kidney Collecting Duct Cells

Abstract

The kidney is an important organ for arterial blood pressure (BP) maintenance. Reduced NO generation in the kidney is associated with hypertension in insulin resistance. NO is a critical regulator of vascular tone; however, whether insulin regulates NO production in the renal inner medullary collecting duct (IMCD), the segment with the greatest enzymatic activity for NO production in kidney, is not clear. Using an NO-sensitive 4-amino-5-methylamino-2',7'-difluorofluorescein (DAF-FM) fluorescent dye, we found that insulin increased NO production in mouse IMCD cells (mIMCD) in a time- and dose-dependent manner. A concomitant dose-dependent increase in the NO metabolite (NOx) was also observed in the medium from insulin-stimulated cells. NO production peaked in mIMCD cells at a dose of 100 nm insulin with simultaneously increased NOx levels in the medium. At this dose, insulin significantly increased p-eNOS(Ser1177) levels in mIMCD cells. Pretreatment of cells with a PI 3-kinase inhibitor or insulin receptor silencing with RNA interference abolished these effects of insulin, whereas insulin-like growth factor-1 receptor (IGF-1R) silencing had no effect. We also showed that chronic insulin infusion to normal C57BL/6J mice resulted in increased endothelial NOS (eNOS) protein levels and NO production in the inner medulla. However, insulin-infused IRKO mice, with targeted deletion of insulin receptor from tubule epithelial cells of the kidney, had ∼50% reduced eNOS protein levels in their inner medulla along with a significant rise in BP relative to WT littermates. We have previously reported increased baseline BP and reduced urine NOx in IRKO mice. Thus, reduced insulin receptor signaling in IMCD could contribute to hypertension in the insulin-resistant state.

Enhanced Glucose Tolerance and Pancreatic Beta Cell Function by Low Dose Aspirin in Hyperglycemic Insulin-Resistant Type 2 Diabetic Goto-Kakizaki (GK) Rats

“…Low levels of H 2 O 2 have also been shown to induce NO production. There are reports that NO synthesis is reduced in T2D and hypertension and that insulin regulates NO production [29,30]. We observed that NO level was low in GK rats and ASA treatment increased NO production, which may have stimulated glucose tolerance and increased insulin response.…”

“…We observed that NO level was low in GK rats and ASA treatment increased NO production, which may have stimulated glucose tolerance and increased insulin response. There are reports that ASA increases NO production in cells and tissues [28] and that NO plays an important role in increasing insulin sensitivity [28,29,30]. …”

Role of insulin during the development of oligofructose (OF)-induced equine laminitis

“…At the same time, hyperinsulinaemia might accelerate the secretion of NO and ET-1 (8,21). In the present study, the results demonstrated that the NO and ET-1 increased significantly from 8 th h of the experiment and reached a peak at 28-32 h (Figs 1 and 2).…”

Insulin Resistance in Kidney Disease: Is There a Distinct Role Separate from That of Diabetes or Obesity

“…These effects occur in parallel to a reduction in glucose uptake and utilization. In the context of renal glomerular hemodynamics, this impairment in insulin metabolic signaling and reduction in PI3K/Akt due to insulin resistance promotes reduced NO production and associated impairment of tubuloglomerular feedback, hyperfiltration, and sodium retention [25,26,27,28,29,30]. Tubuloglomerular feedback is the mechanism by which the kidney autoregulates renal blood flow and glomerular filtration.…”