Vascular Regenerative Cell Deficiencies in South Asian Adults

BACKGROUND

South Asian individuals shoulder a disproportionate burden of cardiometabolic diseases.

OBJECTIVES

The purpose of this study was to determine if vascular regenerative cell content varies significantly between South Asian and White European people.

METHODS

Between January 2022 and January 2023, 60 South Asian and 60 White European adults with either documented cardiovascular disease or established diabetes with ≥1 other cardiovascular risk factor were prospectively enrolled. Vascular regenerative cell content in venous blood was enumerated using a flow cytometry assay that is based on high aldehyde dehydrogenase (ALDHhi) activity and cell surface marker phenotyping. The primary outcome was the difference in frequency of circulating ALDHhi progenitor cells, monocytes, and granulocytes between the 2 groups.

RESULTS

Compared with White European participants, those of South Asian ethnicity were younger (69 ± 10 years vs 66 ± 9 years; P < 0.05), had lower weight (88 ± 19 kg vs 75 ± 13 kg; P < 0.001), and exhibited a greater prevalence of type 2 diabetes (62% vs 92%). South Asian individuals had markedly lower circulating frequencies of pro-angiogenic ALDHhiSSClowCD133+ progenitor cells (P < 0.001) and ALDHhiSSCmidCD14+CD163+ monocytes with vessel-reparative capacity (P < 0.001), as well as proportionally more ALDHhi progenitor cells with high reactive oxygen species content (P < 0.05). After correction for sex, age, body mass index, and glycated hemoglobin, South Asian ethnicity was independently associated with lower ALDHhiSSClowCD133+ cell count.

CONCLUSIONS

South Asian people with cardiometabolic disease had less vascular regenerative and reparative cells suggesting compromised vessel repair capabilities that may contribute to the excess vascular risk in this population. (The Role of South Asian vs European Origins on Circulating Regenerative Cell Exhaustion [ORIGINS-RCE]; NCT05253521).

Restoration of blood vessel regeneration in the era of combination SGLT2i and GLP-1RA therapy for diabetes and obesity

Ischaemic cardiovascular diseases, including peripheral and coronary artery disease, myocardial infarction, and stroke, remain major comorbidities for individuals with type 2 diabetes (T2D) and obesity. During cardiometabolic chronic disease (CMCD), hyperglycaemia and excess adiposity elevate oxidative stress and promote endothelial damage, alongside an imbalance in circulating pro-vascular progenitor cells that mediate vascular repair. Individuals with CMCD demonstrate pro-vascular 'regenerative cell exhaustion' (RCE) characterized by excess pro-inflammatory granulocyte precursor mobilization into the circulation, monocyte polarization towards pro-inflammatory vs. anti-inflammatory phenotype, and decreased pro-vascular progenitor cell content, impairing the capacity for vessel repair. Remarkably, targeted treatment with the sodium-glucose cotransporter-2 inhibitor (SGLT2i) empagliflozin in subjects with T2D and coronary artery disease, and gastric bypass surgery in subjects with severe obesity, has been shown to partially reverse these RCE phenotypes. SGLT2is and glucagon-like peptide-1 receptor agonists (GLP-1RAs) have reshaped the management of individuals with T2D and comorbid obesity. In addition to glucose-lowering action, both drug classes have been shown to induce weight loss and reduce mortality and adverse cardiovascular outcomes in landmark clinical trials. Furthermore, both drug families also act to reduce systemic oxidative stress through altered activity of overlapping oxidase and antioxidant pathways, providing a putative mechanism to augment circulating pro-vascular progenitor cell content. As SGLT2i and GLP-1RA combination therapies are emerging as a novel therapeutic opportunity for individuals with poorly controlled hyperglycaemia, potential additive effects in the reduction of oxidative stress may also enhance vascular repair and further reduce the ischaemic cardiovascular comorbidities associated with T2D and obesity.

Empagliflozin improves circulating vascular regenerative cell content in people without diabetes with risk factors for adverse cardiac remodeling

Sodium glucose-cotransporter 2 (SGLT2) inhibitors have been reported to reduce cardiovascular events and heart failure in people with and without diabetes. These medications have been shown to counter regenerative cell exhaustion in the context of prevalent diabetes. This study sought to determine if empagliflozin attenuates regenerative cell exhaustion in people without diabetes. Peripheral blood mononuclear cells were collected at the baseline and 6-mo visits from individuals randomized to receive empagliflozin (10 mg/day) or placebo who were participating in the EMPA-HEART 2 CardioLink-7 trial. Precursor cell phenotypes were characterized by flow cytometry for cell-surface markers combined with high aldehyde dehydrogenase activity to identify precursor cell subsets with progenitor (ALDHhi) versus mature effector (ALDHlow) cell attributes. Samples from individuals assigned to empagliflozin (n = 25) and placebo (n = 21) were analyzed. At baseline, overall frequencies of primitive progenitor cells (ALDHhiSSClow), monocyte (ALDHhiSSCmid), and granulocyte (ALDHhiSSChi) precursor cells in both groups were similar. At 6 mo, participants randomized to empagliflozin demonstrated increased ALDHhiSSClowCD133+CD34+ proangiogenic cells (P = 0.048), elevated ALDHhiSSCmidCD163+ regenerative monocyte precursors (P = 0.012), and decreased ALDHhiSSCmidCD86 + CD163- proinflammatory monocyte (P = 0.011) polarization compared with placebo. Empagliflozin promoted the recovery of multiple circulating provascular cell subsets in people without diabetes suggesting that the cardiovascular benefits of SGLT2 inhibitors may be attributed in part to the attenuation of vascular regenerative cell exhaustion that is independent of diabetes status.NEW & NOTEWORTHY Using an aldehyde dehydrogenase (ALDH) activity-based flow cytometry assay, we found that empagliflozin treatment for 6 mo was associated with parallel increases in circulating vascular regenerative ALDHhi-CD34/CD133-coexpressing progenitors and decreased proinflammatory ALDHhi-CD14/CD86-coexpressing monocyte precursors in individuals without diabetes but with cardiovascular risk factors. The rejuvenation of the vascular regenerative cell reservoir may represent a mechanism via which sodium glucose-cotransporter 2 (SGLT2) inhibitors limit maladaptive repair and delay the development and progression of cardiovascular diseases.

Lessons from bariatric surgery: Can increased GLP-1 enhance vascular repair during cardiometabolic-based chronic disease?

Type 2 diabetes (T2D) and obesity represent entangled pandemics that accelerate the development of cardiovascular disease (CVD). Given the immense burden of CVD in society, non-invasive prevention and treatment strategies to promote cardiovascular health are desperately needed. During T2D and obesity, chronic dysglycemia and abnormal adiposity result in systemic oxidative stress and inflammation that deplete the vascular regenerative cell reservoir in the bone marrow that impairs blood vessel repair and exacerbates the penetrance of CVD co-morbidities. This novel translational paradigm, termed 'regenerative cell exhaustion' (RCE), can be detected as the depletion and dysfunction of hematopoietic and endothelial progenitor cell lineages in the peripheral blood of individuals with established T2D and/or obesity. The reversal of vascular RCE has been observed after administration of the sodium-glucose cotransporter-2 inhibitor (SGLT2i), empagliflozin, or after bariatric surgery for severe obesity. In this review, we explore emerging evidence that links improved dysglycemia to a reduction in systemic oxidative stress and recovery of circulating pro-vascular progenitor cell content required for blood vessel repair. Given that bariatric surgery consistently increases systemic glucagon-like-peptide 1 (GLP-1) release, we also focus on evidence that the use of GLP-1 receptor agonists (GLP-1RA) during obesity may act to inhibit the progression of systemic dysglycemia and adiposity, and indirectly reduce inflammation and oxidative stress, thereby limiting the impact of RCE. Therefore, therapeutic intervention with currently-available GLP-1RA may provide a less-invasive modality to reverse RCE, bolster vascular repair mechanisms, and improve cardiometabolic risk in individuals living with T2D and obesity.

Vascular repair and regeneration in cardiometabolic diseases

Chronic cardiometabolic assaults during type 2 diabetes (T2D) and obesity induce a progenitor cell imbalance in the circulation characterized by overproduction and release of pro-inflammatory monocytes and granulocytes from the bone marrow alongside aberrant differentiation and mobilization of pro-vascular progenitor cells that generate downstream progeny for the coordination of blood vessel repair. This imbalance can be detected in the peripheral blood of individuals with established T2D and severe obesity using multiparametric flow cytometry analyses to discern pro-inflammatory vs. pro-angiogenic progenitor cell subsets identified by high aldehyde dehydrogenase activity, a conserved progenitor cell protective function, combined with lineage-restricted cell surface marker analyses. Recent evidence suggests that progenitor cell imbalance can be reversed by treatment with pharmacological agents or surgical interventions that reduce hyperglycaemia or excess adiposity. In this state-of-the-art review, we present current strategies to assess the progression of pro-vascular regenerative cell depletion in peripheral blood samples of individuals with T2D and obesity and we summarize novel clinical data that intervention using sodium-glucose co-transporter 2 inhibition or gastric bypass surgery can efficiently restore cell-mediated vascular repair mechanisms associated with profound cardiovascular benefits in recent outcome trials. Collectively, this thesis generates a compelling argument for early intervention using current pharmacological agents to prevent or restore imbalanced circulating progenitor content and maintain vascular regenerative cell trafficking to sites of ischaemic damage. This conceptual advancement may lead to the design of novel therapeutic approaches to prevent or reverse the devastating cardiovascular comorbidities currently associated with T2D and obesity.

Isolation and characterization of circulating pro-vascular progenitor cell subsets from human whole blood samples

The examination of circulating pro-vascular progenitor cell frequency and function is integral in understanding aberrant blood vessel homeostasis in individuals with cardiometabolic disease. Here, we outline the characterization of progenitor cell subsets from peripheral blood using high aldehyde dehydrogenase (ALDH) activity, an intracellular detoxification enzyme previously associated with pro-vascular progenitor cell status. Using this protocol, cells can be examined by flow cytometry for ALDH activity and lineage restricted cell surface markers simultaneously.

For complete details on the use and execution of this protocol, please refer to Terenzi et al. (2019) and Hess et al. (2019, 2020).

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Aldehyde dehydrogenase is superior in the isolation of progenitor cells

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Flow cytometry is an effective method to characterize pro-vascular cells

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Aggressive gating strategies allows for in-depth progenitor cell characterization

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The use of fresh blood samples will yield most accurate cell prevalence

Vascular Risk Reduction in Obesity through Reduced Granulocyte Burden and Improved Angiogenic Monocyte Content following Bariatric Surgery

Bariatric surgery, in addition to the benefit of sustained weight loss, can also reduce cardiometabolic risk and mortality. Lifelong vessel maintenance is integral to the prevention of cardiovascular disease. Using aldehyde dehydrogenase activity, an intracellular detoxifying enzyme present at high levels within pro-vascular progenitor cells, we observed an association between chronic obesity and “regenerative cell exhaustion” (RCE), a pathology whereby chronic assault on circulating regenerative cell types can result in adverse inflammation and diminished vessel repair. We also describe that, at 3 months following bariatric surgery, systemic inflammatory burden was reduced and pro-angiogenic macrophage precursor content was improved in subjects with severe obesity, suggesting the restoration of a microenvironment to support vessel homeostasis. These data suggest that bariatric surgery may reverse deleterious events that predispose patients with morbid obesity to cardiovascular risk.

Obesity features a low frequency of ALDH and CD133 co-expressing cells

Bariatric surgery results in lower granulocyte precursors expressing ALDH

Macrophage balance favors M2 polarization following bariatric surgery

Cellular changes after bariatric surgery give insight into reducing CV risk

SGLT-2 Inhibitors and Regenerative Cell Exhaustion

In response to the Letter by Fadini, Hess et al. discuss the interpretation of their data and the details of the multiparametric analyses employed to measure the changes in circulating provascular cell content in patients with type 2 diabetes receiving empagliflozin compared to placebo treatment.

P317A novel role of SGLT2 inhibitors to increase circulating proangiogenic progenitor cells in patients with type 2 diabetes and cardiovascular disease: A sub-study of the EMPA-HEART CardioLink-6 Trial

Background

SGLT2 inhibitors (SGLT2i) have been demonstrated to reduce major adverse cardiovascular events and mortality in patients with type 2 diabetes (T2D) who are at high risk for cardiovascular disease (CVD). However, the mechanism(s) of the underlying benefit remain unclear. Since regenerative cell exhaustion resulting in impaired vascular homeostasis has been proposed as a key driver of CV events in T2D, we hypothesised that modulation of circulating vascular regenerative cell content by SGLT2i may be a novel basis of cardioprotection.

Purpose

To evaluate the effects of the SGLT2i, empagliflozin (EMPA), vs placebo on circulating vascular regenerative and pro-inflammatory cells in patients with T2D and CVD.

Methods

This was a biomarker sub-study of the EMPA-HEART Cardiolink-6 randomised trial of EMPA (10mg QD) vs placebo in patients with T2D and a history of coronary artery disease (prior myocardial infarction and/or coronary revascularisation). Blood samples (baseline N=48; study end N=26) underwent multiparametric progenitor cell analyses by flow cytometry. Circulating cells were assessed for aldehyde dehydrogenase (ALDH) activity, a self-protective enzyme highly expressed in several proangiogenic progenitor cell lineages, as well as cell surface co-expression of the primitive progenitor (CD34, CD133) or M1/M2 macrophage (CD80, CD163) markers.

Results

Individuals with increased inflammatory burden (ALDHhi granulocytes above the baseline median) were older (61±2 vs 67±2 years), more likely to be current or past smokers (21% vs 42%) and had reduced LV function, assessed by echocardiography. The placebo- and EMPA-assigned groups were equivalent at baseline with respect to the frequency and distribution of proangiogenic progenitor cells (ALDHhiSSClo), monocyte/macrophage (ALDHhiSSCmid) and inflammatory granulocyte (ALDHhiSSChi) precursors. Following 6-months of treatment with EMPA, there was a marked increase in the number of circulating primitive ALDHhiSSClo cells with CD133 (Placebo: −2.8±3.8%, EMPA: +8.6±2.5%, P<0.02) or CD133/CD34 (Placebo: 0.4±4.5%, EMPA: +13.3±3.8%, P<0.05) co-expression. Furthermore, EMPA treatment was associated with an increase in the frequency of circulating anti-inflammatory cells with M2 macrophage polarisation marked by CD163 (Placebo: −0.7±0.8%, EMPA = +3.9±1.3%, P<0.01) expression. Non-significant increases in circulating proangiogenic monocytes, and decreases in the frequency of circulating inflammatory granulocytes were also observed after EMPA treatment (vs placebo).

Conclusion

We provide the first evidence showing that SGLT2i treatment with EMPA alters the balance of key circulating vascular progenitor and inflammatory cells in patients with T2D and CVD. We suggest that SGLT2i may afford cardioprotection through a novel and previously unrecognised capacity to limit regenerative cell exhaustion in T2D.

Acknowledgement/Funding

This trial was supported by an unrestricted investigator-initiated study grant from Boehringer Ingelheim.

SGLT2 Inhibition with Empagliflozin Increases Circulating Provascular Progenitor Cells in People with Type 2 Diabetes Mellitus

Hess et al. quantified circulating aldehyde dehydrogenase-expressing (ALDH^hi) cell subsets in people with T2DM given either empagliflozin (EMPA) or placebo. EMPA treatment increased circulating pro-angiogenic CD133⁺ progenitor cells, decreased pro-inflammatory ALDH^hi granulocyte precursors, and increased ALDH^hi monocytes with M2 polarization. EMPA treatment improved T2DM-associated "regenerative cell depletion" contributing to enhanced vascular health.

Vascular Regenerative Cell Exhaustion in Diabetes: Translational Opportunities to Mitigate Cardiometabolic Risk

Ischemic cardiovascular complications remain a major cause of mortality in people with type 2 diabetes (T2D). Individuals with T2D may have a reduced ability to revascularize ischemic tissues due to abnormal production of circulating provascular progenitor cells. This 'regenerative cell exhaustion' process is intensified by increasing oxidative stress and inflammation and during T2D progression. Chronic exhaustion may be mediated by changes in the bone marrow microenvironment that dysregulate the wingless related integration site network, a central pathway maintaining the progenitor cell pool. Restoration of vascular regenerative cell production by reducing glucotoxicity with contemporary antihyperglycemic agents, by reducing systemic inflammation postbariatric surgery, or by modulating progenitor cell provascular functions using exosomal manipulation, may provide unique approaches for mitigating ischemic disease.