Let’s shear a moment, then take it inside

Glycemic control after aortic valve replacement: A retrospective study

Background

Aortic stenosis (AS) is treated through transcatheter aortic valve implantation (TAVI) or surgical aortic valve replacement (SAVR), with diabetes being prevalent among these patients. Inflammation participates in the pathogenesis of AS, and emerging evidence suggests that TAVI may exert anti-inflammatory effects. Given the established link between diabetes and inflammation, we sought to evaluate the impact of aortic valve replacement (AVR) on glycemic control.

Methods

Data from 10,129 consecutive patients undergoing either TAVI or SAVR between January 2010 and January 2022 were analyzed. Of these, 3,783 with diabetes had available pre- and post-procedural glycated hemoglobin (HbA1c) measurements. Analysis of 1,284 individuals with HbA1c ≥ 7 % was conducted. Propensity-score matching produced two well-matched cohorts of 266 TAVI and SAVR patients, enabling comparison of periprocedural HbA1c.

Results

In the total cohort (n = 1,284), HbA1c decreased from 8.15 ± 1.12 to 7.88 ± 1.38 (p < 0.001). After matching, the TAVI group showed a significant reduction from 8.31 ± 1.31 to 7.86 ± 1.56 (p < 0.001), while a modest decrease from 8.33 ± 1.33 to 8.15 ± 1.61 (p = 0.046) was observed in SAVR group. The TAVI group showed a trend toward a greater percentage change in HbA1c (p = 0.051). Clinically meaningful improvement in HbA1c (≥ 0.3 %) was similar between TAVI (53.1 %) and SAVR (45.6 %) patients (OR = 1.34, 95 % CI 0.93-1.95).

Conclusions

Management of AS through either intervention improved post-procedural glycemia in patients with uncontrolled diabetes. The extent of glycemic improvement was more pronounced with TAVI. Further investigations through controlled and prospective studies could provide more conclusive insights into this matter.

Transcatheter Aortic Valve Implantation Represents an Anti-Inflammatory Therapy Via Reduction of Shear Stress-Induced, Piezo-1-Mediated Monocyte Activation

BACKGROUND

Aortic valve stenosis is an increasingly prevalent degenerative and inflammatory disease. Transcatheter aortic valve implantation (TAVI) has revolutionized its treatment, thereby avoiding its life-threatening/disabling consequences. Whether aortic valve stenosis is accelerated by inflammation and whether it is itself a cause of inflammation are unclear. We hypothesized that the large shear forces exerted on circulating cells, particularly on the largest circulating cells, monocytes, while passing through stenotic aortic valves result in proinflammatory effects that are resolved with TAVI.

METHODS

TAVI provides a unique opportunity to compare the activation status of monocytes under high shear stress (before TAVI) and under low shear stress (after TAVI). The activation status of monocytes was determined with a single-chain antibody, MAN-1, which is specific for the activated β₂-integrin Mac-1. Monocyte function was further characterized by the adhesion of myocytes to stimulated endothelial cells, phagocytic activity, uptake of oxidized low-density lipoprotein, and cytokine expression. In addition, we designed a microfluidic system to recapitulate the shear rate conditions before and after TAVI. We used this tool in combination with functional assays, Ca²⁺ imaging, siRNA gene silencing, and pharmacological agonists and antagonists to identify the key mechanoreceptor mediating the shear stress sensitivity of monocytes. Last, we stained for monocytes in explanted stenotic aortic human valves.

RESULTS

The resolution of high shear stress through TAVI reduces Mac-1 activation, cellular adhesion, phagocytosis, oxidized low-density lipoprotein uptake, and expression of inflammatory markers in monocytes and plasma. Using microfluidics and pharmacological and genetic studies, we could recapitulate high shear stress effects on isolated human monocytes under highly controlled conditions, showing that shear stress-dependent calcium influx and monocyte adhesion are mediated by the mechanosensitive ion channel Piezo-1. We also demonstrate that the expression of this receptor is shear stress dependent and downregulated in patients receiving TAVI. Last, we show monocyte accumulation at the aortic side of leaflets of explanted aortic valves.

CONCLUSIONS

We demonstrate that high shear stress, as present in patients with aortic valve stenosis, activates multiple monocyte functions, and we identify Piezo-1 as the mainly responsible mechanoreceptor, representing a potentially druggable target. We demonstrate an anti-inflammatory effect and therefore a novel therapeutic benefit of TAVI.

Clinical update on hypomethylating agents

Hypomethylating agents (HMAs), azacitidine and decitabine, are standards of care in higher-risk myelodysplastic syndromes and in acute myeloid leukemia patients ineligible for intensive therapy. Over the last 10 years, research efforts have sought to better understand their mechanism of action, both at the molecular and cellular level. These efforts have yet to robustly identify biomarkers for these agents. The clinical activity of HMAs in myeloid neoplasms has been firmly established now but still remains of limited magnitude. Besides optimized use at different stages of the disease, most of the expected clinical progress with HMAs will come from the development of second-generation compounds orally available and/or with improved pharmacokinetics, and from the search, so far mostly empirical, of HMA-based synergistic drug combinations.