Fabio Sanna

Adiponectin as a Link Between Type 2 Diabetes and Vascular NADPH Oxidase Activity in the Human Arterial Wall: The Regulatory Role of Perivascular Adipose Tissue

Oxidative stress plays a critical role in the vascular complications of type 2 diabetes. We examined the effect of type 2 diabetes on NADPH oxidase in human vessels and explored the mechanisms of this interaction. Segments of internal mammary arteries (IMAs) with their perivascular adipose tissue (PVAT) and thoracic adipose tissue were obtained from 386 patients undergoing coronary bypass surgery (127 with type 2 diabetes). Type 2 diabetes was strongly correlated with hypoadiponectinemia and increased vascular NADPH oxidase–derived superoxide anions (O2˙−). The genetic variability of the ADIPOQ gene and circulating adiponectin (but not interleukin-6) were independent predictors of NADPH oxidase–derived O2˙−. However, adiponectin expression in PVAT was positively correlated with vascular NADPH oxidase–derived O2˙−. Recombinant adiponectin directly inhibited NADPH oxidase in human arteries ex vivo by preventing the activation/membrane translocation of Rac1 and downregulating p22phox through a phosphoinositide 3-kinase/Akt-mediated mechanism. In ex vivo coincubation models of IMA/PVAT, the activation of arterial NADPH oxidase triggered a peroxisome proliferator–activated receptor-γ–mediated upregulation of the adiponectin gene in the neighboring PVAT via the release of vascular oxidation products. We demonstrate for the first time in humans that reduced adiponectin levels in individuals with type 2 diabetes stimulates vascular NADPH oxidase, while PVAT “senses” the increased NADPH oxidase activity in the underlying vessel and responds by upregulating adiponectin gene expression. This PVAT-vessel interaction is identified as a novel therapeutic target for the prevention of vascular complications of type 2 diabetes.

Methionine sulfoxide reductase A down-regulation in human breast cancer cells results in a more aggressive phenotype

Breast cancer is one of the most frequent of human malignacies, and it is therefore fundamental to identify the underlying molecular mechanisms leading to cancer transformation. Among other causative agents in the development of breast cancers, an important role for reactive oxygen species (ROS) has emerged. However, most studies on the role of ROS in cancer have not reached specific conclusions, and many issues remain controversial. In the present study, we show that methionine sulfoxide reductase A (MsrA), which is known to protect proteins from oxidation and which acts as a ROS scavenger, is down-regulated in a number of breast cancers. Moreover, levels of MsrA correlate with advanced tumor grade. We therefore investigated the functional role of MsrA in breast cancer cells. Our data show that reduction of MsrA levels results in increased cell proliferation and extracellular matrix degradation, and consequently in a more aggressive cellular phenotype, both in vivo and in vitro. We also show that the underlying molecular mechanisms involve increased ROS levels, resulting in reduction of phosphatase and tensin homolog deleted on chromosome ten protein (PTEN), and activation of the phosphoinositide 3-kinase pathway. In addition, MsrA down-regulation results in up-regulation of VEGF, providing additional support for tumor growth in vivo.

Mutual Regulation of Epicardial Adipose Tissue and Myocardial Redox State by PPAR-γ/Adiponectin Signalling.

Supplemental Digital Content is available in the text.

Detecting human coronary inflammation by imaging perivascular fat

Adipocyte size and lipid content in perivascular adipose tissue are inversely associated with coronary inflammation and atherosclerotic plaque burden in human patients. Picturing plaques and imaging inflammation To determine risk of future coronary artery disease, calcium content in vascular plaques is typically evaluated by coronary calcium scoring, which uses computerized tomography (CT) imaging. To detect inflammation and subclinical coronary artery disease (soft, noncalcified plaques), Antonopoulos et al. developed an alternative metric called the perivascular CT fat attenuation index (FAI). The perivascular FAI uses CT imaging of adipose tissue surrounding the coronary arteries to assess adipocyte size and lipid content. Larger, more mature adipocytes exhibit greater lipid accumulation, which is inversely associated with the FAI. Inflammation reduces lipid accumulation and slows preadipocyte differentiation. Imaging pericoronary fat in human patients after myocardial infarction revealed that unstable plaques had larger perivascular FAIs than stable plaques and that the FAI was greatest directly adjacent to the inflamed coronary artery. The perivascular FAI may be a useful, noninvasive method for monitoring vascular inflammation and the development of coronary artery disease. Early detection of vascular inflammation would allow deployment of targeted strategies for the prevention or treatment of multiple disease states. Because vascular inflammation is not detectable with commonly used imaging modalities, we hypothesized that phenotypic changes in perivascular adipose tissue (PVAT) induced by vascular inflammation could be quantified using a new computerized tomography (CT) angiography methodology. We show that inflamed human vessels release cytokines that prevent lipid accumulation in PVAT-derived preadipocytes in vitro, ex vivo, and in vivo. We developed a three-dimensional PVAT analysis method and studied CT images of human adipose tissue explants from 453 patients undergoing cardiac surgery, relating the ex vivo images with in vivo CT scan information on the biology of the explants. We developed an imaging metric, the CT fat attenuation index (FAI), that describes adipocyte lipid content and size. The FAI has excellent sensitivity and specificity for detecting tissue inflammation as assessed by tissue uptake of 18F-fluorodeoxyglucose in positron emission tomography. In a validation cohort of 273 subjects, the FAI gradient around human coronary arteries identified early subclinical coronary artery disease in vivo, as well as detected dynamic changes of PVAT in response to variations of vascular inflammation, and inflamed, vulnerable atherosclerotic plaques during acute coronary syndromes. Our study revealed that human vessels exert paracrine effects on the surrounding PVAT, affecting local intracellular lipid accumulation in preadipocytes, which can be monitored using a CT imaging approach. This methodology can be implemented in clinical practice to noninvasively detect plaque instability in the human coronary vasculature.

Predictive value of telomere length on outcome following acute myocardial infarction: evidence for contrasting effects of vascular vs. blood oxidative stress

Abstract Aims Experimental evidence suggests that telomere length (TL) is shortened by oxidative DNA damage, reflecting biological aging. We explore the value of blood (BTL) and vascular TL (VTL) as biomarkers of systemic/vascular oxidative stress in humans and test the clinical predictive value of BTL in acute myocardial infarction (AMI). Methods and results In a prospective cohort of 290 patients surviving recent AMI, BTL measured on admission was a strong predictor of all-cause [hazard ratio (HR) [95% confidence interval (CI)]: 3.21 [1.46–7.06], P = 0.004] and cardiovascular mortality (HR [95% CI]: 3.96 [1.65–9.53], P = 0.002) 1 year after AMI (for comparisons of short vs. long BTL, as defined by a T/S ratio cut-off of 0.916, calculated using receiver operating characteristic analysis; P adjusted for age and other predictors). To explore the biological meaning of these findings, BTL was quantified in 727 consecutive patients undergoing coronary artery bypass grafting (CABG), and superoxide (O2.-) was measured in peripheral blood mononuclear cells (PBMNC). VTL/vascular O2.- were quantified in saphenous vein (SV) and mammary artery (IMA) segments. Patients were genotyped for functional genetic polymorphisms in P22ph°x (activating NADPH-oxidases) and vascular smooth muscle cells (VSMC) selected by genotype were cultured from vascular tissue. Short BTL was associated with high O2.- in PBMNC (P = 0.04) but not in vessels, whereas VTL was related to O2.- in IMA (ρ = −0.49, P = 0.004) and SV (ρ = −0.52, P = 0.01). Angiotensin II (AngII) incubation of VSMC (30 days), as a means of stimulating NADPH-oxidases, increased O2.- and reduced TL in carriers of the high-responsiveness P22ph°x alleles (P = 0.007). Conclusion BTL predicts cardiovascular outcomes post-AMI, independently of age, whereas VTL is a tissue-specific (rather than a global) biomarker of vascular oxidative stress. The lack of a strong association between BTL and VTL reveals the importance of systemic vs. vascular factors in determining clinical outcomes after AMI.

Perivascular adipose tissue as an endocrine organ: the role of statins.

Adipose tissue (AT), aside from being an energy storage site, functions as a source of cytokines, adipokines and other vasoactive molecules. Dysfunctional AT contributes to the development of cardiovascular disease by shifting to a pro-oxidant, pro-inflammatory phenotype. Perivascular AT (PVAT) is of particular importance to the development of vascular disease, due to its close proximity to the vascular wall. Molecules released from PVAT can exert both pro- and anti-contractile effects, the balance of which plays a role in controlling vascular tone. Recent evidence supports the existence of reciprocal, two-way interactions between PVAT and the vascular wall. Statins, with their pivotal role in cardiovascular disease prevention, have been shown to exert lipid-lowering independent, pleiotropic effects on the vascular wall, some of which may be mediated by modulatory effects on PVAT inflammation and secretome. These effects of statins provide a paradigm for the development of new therapeutic agents aimed at modulating PVAT function, as a novel treatment strategy against cardiovascular disease.