Abstract

Background: Normal subcutaneous adipose tissue (SAT) function is dependent on healthy endothelial function and microvascular expansion. In type 2 diabetes mellitus (DM) and heart failure (HF) this becomes synergistically dysregulated, resulting in inflamed, fibrotic and metabolically dysfunctional SAT and may drive HF progression in DM. Hyperinsulinemia is associated with adipocyte senescence, however the role of endothelial senescence in SAT and its therapeutic potential is unknown. Aims: We examine the presence and sequelae of SAT microvascular endothelial cell (SATMVEC) senescence and its effects on adipocyte function in people with DM. Next, we examine the therapeutic role of digoxin at targeting SATMVEC senescence, modulating SATMVEC-adipocyte crosstalk and restoring metabolic homeostasis. Methods: We took pectoral SAT biopsies from 59 patients with HF undergoing pacemaker implant of whom 25 (42%) had DM (HFDM). SATMVEC were isolated from SAT, treated with 1ng/mL digoxin vs control for 24 hours and then characterised for functional senescence. Crosstalk between SATMVEC and subcutaneous white adipocytes from a single healthy donor were examined using co-culture (Fig 1A). Paired digoxin vs control treated SATMVEC were co-cultured with adipocytes for 24 hours. Adipocyte health was assessed using 2-NBD-glucose uptake, RNA and protein expression. Results: Isolated SATMVEC from patients with HFDM had a senescent phenotype with increased senescence associated secretory phenotype (SASP) and senescence associated ß-gal expression (p<0.05), reduced ATP production, proliferative capacity, and impaired angiogenesis (p<0.05). Adipocytes co-cultured with SATMVEC from patients with HFDM had increased expression of IL-6 (Fig 1B) and reduced 2-NBD-glucose uptake (p<0.05). Treatment of SATMVEC with digoxin reduced SATMVEC senescence (Fig 1C), increased adipocyte 2-NBD-glucose uptake (Figure 1D) and reduced IL-6 expression (p<0.01). Conclusions: SATMVEC from patients with HFDM are senescent and when co-cultured with adipocytes, results in a proinflammatory adipocyte phenotype resistant to glucose uptake. Digoxin reduces SATMVEC senescence, restores adipocyte glucose homeostasis and may repair dysfunctional SAT in patients with HFDM.