Coronary microvascular disease as an early culprit in the pathophysiology of diabetes and metabolic syndrome

Mitoprotection attenuates myocardial vascular impairment in porcine metabolic syndrome

Metabolic syndrome (MetS) leads to cardiac vascular injury, which may reflect in increased retention of endothelial progenitor cells (EPCs). Coronary endothelial cell (EC) mitochondria partly regulate vascular function and structure. We hypothesized that chronic mitoprotection would preserve EC mitochondria and attenuate coronary vascular injury and dysfunction in swine MetS. Pigs were studied after 16 wk of diet-induced MetS, MetS treated for the last 4 wk with the mitochondria-targeted peptide elamipretide (ELAM; 0.1 mg/kg sc once daily), and lean controls ( n = 6 each). Cardiac remodeling and function were assessed in vivo by multidetector-computed tomography (CT), and coronary artery and sinus blood samples were collected. EC mitochondrial density, apoptosis, oxidative stress, endothelial nitric oxide synthase immunoreactivity, myocardial microvascular density (three-dimensional microcomputed tomography), and coronary endothelial function (organ bath) were assessed ex vivo. The number and arteriovenous gradient of CD34⁺/KDR⁺ EPCs were calculated by FACS (a negative net gradient indicating EPC retention). MetS and MetS + ELAM pigs developed similar MetS (obesity, hyperlipidemia, insulin resistance, and hypertension). EC mitochondrial density decreased in MetS animals compared with lean animals but normalized in MetS + ELAM animals. ELAM also attenuated EC oxidative stress and apoptosis and improved subendocardial microvascular density. ELAM-induced vasculoprotection was reflected by decreased coronary retention of EPCs. ELAM also partly improved endothelial nitric oxide synthase immunoreactivity, coronary endothelial function, and vessel maturity, whereas myocardial perfusion was unaffected. Chronic mitoprotection improved coronary EC mitochondrial density and decreased vascular remodeling and dysfunction. However, additional mitochondria-independent mechanisms likely contribute to MetS-induced cardiac vascular injury. NEW & NOTEWORTHY The present study shows that chronic mitoprotection preserved coronary endothelial cell mitochondria and decreased vascular injury, subendocardial microvascular loss, coronary retention of endothelial progenitor cells, and release of markers of vascular injury. However, myocardial perfusion remained blunted, suggesting that additional mitochondria-independent mechanisms likely contribute to metabolic syndrome-induced cardiac vascular injury.

Coronary flow reserve is predictive of the risk of cardiovascular death regardless of chronic kidney disease stage

Microvascular rarefaction is found in experimental uremia, but data from patients with chronic kidney disease (CKD) are limited. We therefore quantified absolute myocardial blood flow and coronary flow reserve (the ratio of peak to resting flow) from myocardial perfusion positron emission tomography scans at a single institution. Individuals were classified into standard CKD categories based on the estimated glomerular filtration rate. Associations of coronary flow reserve with CKD stage and cardiovascular mortality were analyzed in models adjusted for cardiovascular risk factors. The coronary flow reserve was significantly associated with CKD stage, declining in early CKD, but it did not differ significantly among individuals with stage 4, 5, and dialysis-dependent CKD. Flow reserve with preserved kidney function was 2.01, 2.06 in stage 1 CKD, 1.91 in stage 2, 1.68 in stage 3, 1.54 in stage 4, 1.66 in stage 5, and 1.55 in dialysis-dependent CKD. Coronary flow reserve was significantly associated with cardiovascular mortality in adjusted models (hazard ratio 0.76, 95% confidence interval: 0.63-0.92 per tertile of coronary flow reserve) without evidence of effect modification by CKD. Thus, coronary flow reserve is strongly associated with cardiovascular risk regardless of CKD severity and is low in early stage CKD without further decrement in stage 5 or dialysis-dependent CKD. This suggests that CKD physiology rather than the effects of dialysis is the primary driver of microvascular disease. Our findings highlight the potential contribution of microvascular dysfunction to cardiovascular risk in CKD and the need to define mechanisms linking low coronary flow reserve to mortality.