Digoxin reduces senescence and restores dysfunctional endothelial-subcutaneous adipocyte cross-talk and dysregulated glucose homeostasis in patients with type 2 diabetes mellitus

Abstract

Abstract Background Normal subcutaneous adipose tissue (SAT) function is dependent on SAT microvascular expansion. Heart failure with reduced ejection fraction (HF) and type 2 diabetes mellitus (DM) have a synergistic deleterious relationship and, of relevance to this, metabolic dysregulation may drive HF progression in DM. Chronic hyperinsulinemia is associated with adipocyte senescence, however any contributing role of SAT microvascular endothelial cell (SATMVEC) senescence on adverse microvascular expansion in type 2 diabetes mellitus (DM) remains unknown. Digoxin has been shown to have senolytic activity in murine cancer models. However, the potential therapeutic role of digoxin on SAT metabolic function is unexplored. Purpose We establish the presence of SATMVEC senescence and its effects on adipocyte function in people with HF and DM (HFDM). Moreover, we establish a therapeutic role for digoxin in targeting SATMVEC senescence, modulating SATMVEC-adipocyte crosstalk and restoring metabolic homeostasis. Methods We took pectoral SAT biopsies from 59 patients undergoing pacemaker implantation of whom 25 (42%) had HF and DM (HFDM). SATMVEC were isolated from SAT and were treated with 1ng/mL digoxin vs control for 24 hours before characterisation (cell function, expression of senescence-associated ß-galactosidase (ß-gal) and senescence associated secretory phenotype, SASP). Crosstalk between SATMVEC and subcutaneous white adipocytes were examined using co-culture techniques (Fig 1A). Paired digoxin vs control treated SATMVEC were seeded co-cultured with adipocytes for 24 hours, before adipocyte health was quantified, through 2-NBD-glucose uptake and expression of key adipogenic genes and proteins. Results Compared to HF alone, isolated SATMVEC from patients with HFDM had a senescent phenotype with increased SASP and ß-gal expression (p<0.05), reduced metabolic activity, ATP production, proliferative capacity, and impaired angiogenesis (p<0.05). In co-culture, SATMVEC from patients with HFDM had deleterious effects on adipocyte function: increasing expression of IL-6 (Fig 1C) and reducing 2-NBD-glucose uptake (p<0.05). Treatment of SATMVEC with digoxin reduced the SATMVEC senescent phenotype (Fig 1B) and increased 2-NBD-glucose adipocyte uptake (Figure 1D) (p<0.001). Conclusions SATMVEC from patients with HFDM have a senescent phenotype, and when in co-culture induce a proinflammatory adipocyte phenotype, resistant to glucose uptake. Digoxin reduces SATMVEC senescence, restores healthy adipocyte glucose homeostasis, and thus has the potential to repair dysfunctional SAT in patients with HFDM.