Soluble Neuropilin-1 Response to Hypoglycemia in Type 2 Diabetes: Increased Risk or Protection in SARS-CoV-2 Infection?

Abstract

Introduction: Neuropilin-1(NRP1) is a cofactor that enhances SARS-CoV-2 coronavirus cell infectivity when co-expressed with angiotensin-converting enzyme 2(ACE2). The Renin-Angiotensin System (RAS) is activated in type 2 diabetes (T2D); therefore, the aim of this study was to determine if hypoglycaemia-induced stress in T2D would potentiate serum NRP1(sNRP1) levels, reflecting an increased risk for SARS-CoV-2 infection.

Methods: A case-control study of aged-matched T2D (n = 23) and control (n = 23) subjects who underwent a hyperinsulinemic clamp over 1-hour to hypoglycemia(<40mg/dl) with subsequent timecourse of 4-hours and 24-hours. Slow Off-rate Modified Aptamer (SOMA)-scan plasma protein measurement determined RAS-related proteins: renin (REN), angiotensinogen (AGT), ACE2, soluble NRP1(sNRP1), NRP1 ligands (Vascular endothelial growth factor, VEGF and Class 3 Semaphorins, SEM3A) and NRP1 proteolytic enzyme (A Disintegrin and Metalloproteinase 9, ADAM9).

Results: Baseline RAS overactivity was present with REN elevated and AGT decreased in T2D (p<0.05); ACE2 was unchanged. Baseline sNRP1, VEGF and ADAM9 did not differ between T2D and controls and remained unchanged in response to hypoglycaemia. However, 4-hours post-hypoglycemia, sNRP1, VEGF and ADAM9 were elevated in T2D(p<0.05). SEMA3A was not different at baseline; at hypoglycemia, SEMA3A decreased in controls only. Post-hypoglycemia, SEMA3A levels were higher in T2D versus controls. sNRP1 did not correlate with ACE2, REN or AGT. T2D subjects stratified according to ACE inhibitor (ACEi) therapies showed no difference in sNRP1 levels at either glucose normalization or hypoglycaemia.

Conclusion: Hypoglycemia potentiated both plasma sNRP1 level elevation and its ligands VEGF and SEMA3A, likely through an ADAM9-mediated mechanism that was not associated with RAS overactivity or ACEi therapy; however, whether this is protective or promotes increased risk for SARS-CoV-2 infection in T2D is unclear.

Clinical trial registration: https://ichgcp.net/clinical-trials-registry/NCT03102801" title="See in ClinicalTrials.gov">NCT03102801.

Keywords: ACE inhibitors; ADAM9; COVID-19; Neuropilin-1; SARS-CoV-2; type 2 diabetes.

Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Copyright © 2021 Moin, Al-Qaissi, Sathyapalan, Atkin and Butler.

Figures

Figure 1

Schematic diagram of the insulin clamp study, showing the intervention and blood sampling time points.

Figure 2

Circulatory levels of Neuropilin-1 (soluble neuropilin-1, sNRP1) in plasma before, during and after iatrogenic induction of hypoglycemia. Blood sampling was performed at baseline (BL), euglycemia (30 min before hypoglycemia in type 2 diabetes (T2D) only), at hypoglycemia (0 min) and post-hypoglycemia (30 minutes, 1-hour, 2-hours, 4-hours and 24-hours). At baseline (BL), blood glucose (BG) was 7.6 ± 0.4 mmol/L (for T2D) and 5.0 ± 0.1 mmol/L (for control, C). At glucose normalization, BG was 4.5 ± 0.07 mmol/L (for T2D). At the point of hypoglycemia, BG was 2.0 ± 0.03 mmol/L (for T2D) and 1.8 ± 0.05 mmol/L (for control). (A) Effect of glucose normalization on plasma sNRP1 levels in T2D (black squares) and control (open squares) subjects. (B), Changes in sNRP1 levels in response to hypoglycaemia and post-hypoglycemic timepoints in control (white circles) and in T2D (black squares) subjects. (C), Effect of glucose normalization and hypoglycaemia on plasma levels of sNRP1 in T2D patients who were treated with ACE inhibitors (ACEi) (black squares) and those without ACEi therapy (white squares). *p < 0.05, T2D vs control; Hypo, hypoglycaemia; RFU, relative fluorescent units; ns, not significant.

Figure 3

Correlation of plasma levels of soluble NRP1 (sNRP1) with basal levels of renin angiotensinogen system (RAS) proteins. Correlation of soluble NRP1 (sNRP1) with Renin (A), angiotensinogen (ANG) (B) and angiotensin-converting enzyme 2 (ACE2) (C). No correlation of sNRP1 with these RAS proteins was found in either T2D or control subjects. Control subjects, open black circles; T2D subjects, solid blue squares; ns, not significant.

Figure 4

Plasma levels of A Disintegrin and Metalloproteinase 9 (ADAM9), class 3 semaphorins (SEMA3A) and vascular endothelial growth factor (VEGF) before, during and after iatrogenic induction of hypoglycemia. Changes in plasma ADAM9 (A), VEGF (B) and SEMA3A (C) levels in response to hypoglycaemia and post-hypoglycemic timepoints in control (white circles) and T2D (black squares) subjects. *p < 0.05, **p < 0.01, control vs T2D; ^p < 0.05, control hypoglycaemia vs control post-hypoglycemia timepoints; &p < 0.05, &&p < 0.01, T2D hypoglycaemia vs T2D post-hypoglycemia timepoints; ##p < 0.01, T2D 2-h post-hypoglycemia vs T2D 4-h post-hypoglycemia. Hypo, hypoglycemia; RFU, relative fluorescent units.