Although the complex roles of macrophages in myocardial injury are widely appreciated, the function of neutrophils in nonischemic cardiac pathology has received relatively little attention.
To ...examine the regulation and function of neutrophils in pressure overload-induced cardiac hypertrophy, mice underwent treatment with Ly6G antibody to deplete neutrophils and then were subjected to transverse aortic constriction.
Neutrophil depletion diminished transverse aortic constriction-induced hypertrophy and inflammation and preserved cardiac function. Myeloid deficiency of Wnt5a, a noncanonical Wnt, suppressed neutrophil infiltration to the hearts of transverse aortic constriction-treated mice and produced a phenotype that was similar to the neutropenic conditions. Conversely, mice overexpressing Wnt5a in myeloid cells displayed greater hypertrophic growth, inflammation, and cardiac dysfunction. Neutrophil depletion reversed the Wnt5a overexpression-induced cardiac pathology and eliminated differences in cardiac parameters between wild-type and myeloid-specific Wnt5a transgenic mice.
These findings reveal that Wnt5a-regulated neutrophil infiltration has a critical role in pressure overload-induced heart failure.
It is established that the adipocyte-derived cytokine adiponectin protects against cardiovascular and metabolic diseases, but the effect of this adipokine on macrophage polarization, an important ...mediator of disease progression, has never been assessed. We hypothesized that adiponectin modulates macrophage polarization from that resembling a classically activated M1 phenotype to that resembling alternatively-activated M2 cells. Peritoneal macrophages and the stromal vascular fraction (SVF) cells of adipose tissue isolated from adiponectin knock-out mice displayed increased M1 markers, including tumor necrosis factor-α, interleukin-6, and monocyte chemoattractant protein-1 and decreased M2 markers, including arginase-1, macrophage galactose N-acetyl-galactosamine specific lectin-1, and interleukin-10. The systemic delivery of adenovirus expressing adiponectin significantly augmented arginase-1 expression in peritoneal macrophages and SVF cells in both wild-type and adiponectin knock-out mice. In culture, the treatment of macrophages with recombinant adiponectin protein led to an increase in the levels of M2 markers and a reduction of reactive oxygen species and reactive oxygen species-related gene expression. Adiponectin also stimulated the expression of M2 markers and attenuated the expression of M1 markers in human monocyte-derived macrophages and SVF cells isolated from human adipose tissue. These data show that adiponectin functions as a regulator of macrophage polarization, and they indicate that conditions of high adiponectin expression may deter metabolic and cardiovascular disease progression by favoring an anti-inflammatory phenotype in macrophages.
Adipose tissue dysfunction plays a pivotal role in the development of insulin resistance in obese individuals. Cell culture studies and gain-of-function mouse models suggest that canonical Wnt ...proteins modulate adipose tissue expansion. However, no genetic evidence supports a role for endogenous Wnt proteins in adipose tissue dysfunction, and the role of noncanonical Wnt signaling remains largely unexplored. Here we provide evidence from human, mouse, and cell culture studies showing that Wnt5a-mediated, noncanonical Wnt signaling contributes to obesity-associated metabolic dysfunction by increasing adipose tissue inflammation. Wnt5a expression is significantly upregulated in human visceral fat compared with subcutaneous fat in obese individuals. In obese mice, Wnt5a ablation ameliorates insulin resistance, in parallel with reductions in adipose tissue inflammation. Conversely, Wnt5a overexpression in myeloid cells augments adipose tissue inflammation and leads to greater impairments in glucose homeostasis. Wnt5a ablation or overexpression did not affect fat mass or adipocyte size. Mechanistically, Wnt5a promotes the expression of proinflammatory cytokines by macrophages in a Jun NH2-terminal kinase-dependent manner, leading to defective insulin signaling in adipocytes. Exogenous interleukin-6 administration restores insulin resistance in obese Wnt5a-deficient mice, suggesting a central role for this cytokine in Wnt5a-mediated metabolic dysfunction. Taken together, these results demonstrate that noncanonical Wnt signaling contributes to obesity-induced insulin resistance independent of adipose tissue expansion.
Peripheral artery disease (PAD) generates tissue ischemia through arterial occlusions and insufficient collateral vessel formation. Vascular insufficiency in PAD occurs despite higher circulating ...levels of vascular endothelial growth factor A (VEGF-A), a key regulator of angiogenesis. Here we show that clinical PAD is associated with elevated levels of an antiangiogenic VEGF-A splice isoform (VEGF-A165b) and a corresponding reduction in levels of the proangiogenic VEGF-A165a splice isoform. In mice, VEGF-A165b expression was upregulated by conditions associated with impaired limb revascularization, including leptin deficiency, diet-induced obesity, genetic ablation of the secreted frizzled-related protein 5 (Sfrp5) adipokine and transgenic overexpression of Wnt5a in myeloid cells. In a mouse model of PAD, delivery of VEGF-A165b inhibited revascularization of ischemic hind limbs, whereas treatment with an isoform-specific neutralizing antibody reversed impaired revascularization caused by metabolic dysfunction or perturbations in the Wnt5a-Sfrp5 regulatory system. These results indicate that inflammation-driven expression of the antiangiogenic VEGF-A isoform can contribute to impaired collateralization in ischemic cardiovascular disease.
There is growing recognition that adipose tissue-derived proatherogenic mediators contribute to obesity-related cardiovascular disease. We sought to characterize regional differences in perivascular ...adipose tissue (PVAT) phenotype in relation to atherosclerosis susceptibility. Approach and Results: We examined thoracic PVAT samples in 34 subjects (body mass index 32±6 kg/m
, age 59±11 years) undergoing valvular, aortic, or coronary artery bypass graft surgeries and performed transcriptomic characterization using whole-genome expression profiling and quantitative polymerase chain reaction analyses. We identified a highly inflamed region of PVAT surrounding the human aortic root in close proximity to coronary takeoff and adjoining epicardial fat. In subjects undergoing coronary artery bypass graft, we found 300 genes significantly upregulated (false discovery rate
<0.1) in paired samples of PVAT surrounding the aortic root compared with nonatherosclerotic left internal mammary artery. Genes encoding proteins mechanistically implicated in atherogenesis were enriched in aortic PVAT consisting of signaling pathways linked to inflammation,
(wingless-related integration site) signaling, matrix remodeling, coagulation, and angiogenesis. Overexpression of several proatherogenic transcripts, including
,
(
), and
, were confirmed by quantitative polymerase chain reaction and significantly bolstered in coronary artery disease subjects. Angiographic coronary artery disease burden quantified by the Gensini score positively correlated with the expression of inflammatory genes in PVAT. Moreover, periaortic adipose inflammation was markedly higher in obese subjects with striking upregulation (≈8-fold) of
expression compared to nonobese individuals.
Proatherogenic mediators that originate from dysfunctional PVAT may contribute to vascular disease mechanisms in human vessels. Moreover, PVAT may adopt detrimental properties under obese conditions that play a key role in the pathophysiology of ischemic heart disease. Graphic Abstract: A graphic abstract is available for this article.
Visceral adiposity is much more strongly associated with cardiometabolic disease in humans than subcutaneous adiposity. Browning, the appearance of brown-like adipocytes in the white adipose tissue ...(WAT), has been shown to protect mice against metabolic dysfunction, suggesting the possibility of new therapeutic approaches to treat obesity and type 2 diabetes. In mice, subcutaneous WAT depots express higher levels of browning genes when compared with visceral WAT, further suggesting that differences in WAT browning could contribute to the differences in the pathogenicity of the two depots. However, the expression of browning genes in different WAT depots of human has not been characterized. Here, it is shown that the expression of browning genes is higher in visceral than in subcutaneous WAT in humans, a pattern that is opposite to what is observed in mice. These results suggest that caution should be applied in extrapolating the results of murine browning gene expression studies to human pathophysiology.
We previously reported that adenosine monophosphate-activated protein kinase (AMPK) activity is lower in adipose tissue of morbidly obese individuals who are insulin resistant than in comparably ...obese people who are insulin sensitive. However, the number of patients and parameters studied were small. Here, we compared abdominal subcutaneous, epiploic, and omental fat from 16 morbidly obese individuals classified as insulin sensitive or insulin resistant based on the homeostatic model assessment of insulin resistance. We confirmed that AMPK activity is diminished in the insulin resistant group. A custom PCR array revealed increases in mRNA levels of a wide variety of genes associated with inflammation and decreases in PGC-1α and Nampt in omental fat of the insulin resistant group. In contrast, subcutaneous abdominal fat of the same patients showed increases in PTP-1b, VEGFa, IFNγ, PAI-1, and NOS-2 not observed in omental fat. Only angiotensinogen and CD4+ mRNA levels were increased in both depots. Surprisingly, TNFα was only increased in epiploic fat, which otherwise showed very few changes. Protein carbonyl levels, a measure of oxidative stress, were increased in all depots. Thus, adipose tissues of markedly obese insulin resistant individuals uniformly show decreased AMPK activity and increased oxidative stress compared with insulin sensitive patients. However, most changes in gene expression appear to be depot-specific.
Defining new approaches for the prevention and treatment of atherosclerosis is an important priority. Recently, measurement of endothelial function in patients has emerged as a useful tool for ...atherosclerosis research. Risk factors are associated with impaired endothelial function, and clinical syndromes relate, in part, to a loss of endothelial control of vascular homeostasis. Recent studies have shown that the severity of endothelial dysfunction relates to cardiovascular risk. A growing number of interventions known to reduce cardiovascular risk have been shown to improve endothelial function. This work suggests that studies of endothelial function could be used in the care of patients and as a surrogate marker for the evaluation of new therapeutic strategies. This article will review this growing literature in an effort to evaluate the current clinical utility of endothelial dysfunction.
Endothelial dysfunction is linked to insulin resistance, inflammatory activation, and increased cardiovascular risk in diabetes mellitus; however, the mechanisms remain incompletely understood. ...Recent studies have identified proinflammatory signaling of wingless-type family member (Wnt) 5a through c-jun N-terminal kinase (JNK) as a regulator of metabolic dysfunction with potential relevance to vascular function. We sought to gain evidence that increased activation of Wnt5a-JNK signaling contributes to impaired endothelial function in patients with diabetes mellitus.
We measured flow-mediated dilation of the brachial artery and characterized freshly isolated endothelial cells by protein expression, eNOS activation, and nitric oxide production in 85 subjects with type 2 diabetes mellitus (n=42) and age- and sex-matched nondiabetic controls (n=43) and in human aortic endothelial cells treated with Wnt5a. Endothelial cells from patients with diabetes mellitus displayed 1.3-fold higher Wnt5a levels (P=0.01) along with 1.4-fold higher JNK activation (P<0.01) without a difference in total JNK levels. Higher JNK activation was associated with lower flow-mediated dilation, consistent with endothelial dysfunction (r=0.53, P=0.02). Inhibition of Wnt5a and JNK signaling restored insulin and A23187-mediated eNOS activation and improved nitric oxide production in endothelial cells from patients with diabetes mellitus. In endothelial cells from nondiabetic controls, rWnt5a treatment inhibited eNOS activation replicating the diabetic endothelial phenotype. In human aortic endothelial cells, Wnt5a-induced impairment of eNOS activation and nitric oxide production was reversed by Wnt5a and JNK inhibition.
Our findings demonstrate that noncanonical Wnt5a signaling and JNK activity contribute to vascular insulin resistance and endothelial dysfunction and may represent a novel therapeutic opportunity to protect the vasculature in patients with diabetes mellitus.
High fat diet and its induced changes in glucose homeostasis, inflammation and obesity continue to be an epidemic in developed countries. The A2b adenosine receptor (A2bAR) is known to regulate ...inflammation. We used a diet-induced obesity murine knockout model to investigate the role of this receptor in mediating metabolic homeostasis, and correlated our findings in obese patient samples.
Administration of high fat, high cholesterol diet (HFD) for sixteen weeks vastly upregulated the expression of the A2bAR in control mice, while A2bAR knockout (KO) mice under this diet developed greater obesity and hallmarks of type 2 diabetes (T2D), assessed by delayed glucose clearance and augmented insulin levels compared to matching control mice. We identified a novel link between the expression of A2bAR, insulin receptor substrate 2 (IRS-2), and insulin signaling, determined by Western blotting for IRS-2 and tissue Akt phosphorylation. The latter is impaired in tissues of A2bAR KO mice, along with a greater inflammatory state. Additional mechanisms involved include A2bAR regulation of SREBP-1 expression, a repressor of IRS-2. Importantly, pharmacological activation of the A2bAR by injection of the A2bAR ligand BAY 60-6583 for four weeks post HFD restores IRS-2 levels, and ameliorates T2D. Finally, in obese human subjects A2bAR expression correlates strongly with IRS-2 expression.
Our study identified the A2bAR as a significant regulator of HFD-induced hallmarks of T2D, thereby pointing to its therapeutic potential.
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