Objective—: Serum uric acid (UA) has been associated with increased risk of cardiovascular and metabolic diseases. However, the causal mechanisms linking elevated UA levels to cardio-metabolic diseases are still unsettled. One potential explanation for how UA might contribute to cardio-metabolic disease might be its ability to induce systemic inflammation. Approach and Results—: Herein, we report a positive relationship between serum UA and acute-phase reactants, such as high-sensitivity C-reactive protein, fibrinogen, ferritin, complement C3, and erythrocyte sedimentation rate, in a cohort of 2731 nondiabetic adults. The relationship remains significant after adjustment for several confounders, including age, sex, adiposity, anti-hypertensive treatments or diuretics use. To confirm the existence of a causal relationship, we examined the effect of UA on the expression of inflammatory biomarkers in human hepatoma HepG2 cells and characterized the signaling pathway by which UA acts. We show that UA stimulates the expression of C-reactive protein, fibrinogen, ferritin, and complement C3 in a dose-dependent fashion. The proinflammatory effects of UA were abrogated by benzbromarone, a specific inhibitor of UA transporters. Exposure of cells to UA resulted in activation of the IκB kinase/IκBα/NF-κB signaling pathway that was attenuated by benzbromarone. The effect of UA was completely blocked by the antioxidant N -acetylcysteine. Conclusions—: These in vivo and in vitro data suggest that hyperuricemia might induce the expression of hepatic inflammatory molecules by activating the proinflammatory NF-κB signaling cascade. Because inflammation has an important pathogenetic role in metabolic and cardiovascular disease, our study may help understanding the mechanism by which hyperuricemia may contribute to organ damage.

Diabetic status is characterized by chronic low-grade inflammation and an increased burden of senescent cells. Recently, the senescence-associated secretory phenotype (SASP) has been suggested as a possible source of inflammatory factors in obesity-induced type 2 diabetes. However, while senescence is a known consequence of hyperglycaemia, evidences of SASP as a result of the glycaemic insult are missing. In addition, few data are available regarding which cell types are the main SASP-spreading cells in vivo. Adopting a four-pronged approach we demonstrated that: i) an archetypal SASP response that was at least partly attributable to endothelial cells and macrophages is induced in mouse kidney after in vivo exposure to sustained hyperglycaemia; ii) reproducing a similar condition in vitro in endothelial cells and macrophages, hyperglycaemic stimulus largely phenocopies the SASP acquired during replicative senescence; iii) in endothelial cells, hyperglycaemia-induced senescence and SASP could be prevented by SOD-1 overexpression; and iiii) ex vivo circulating angiogenic cells derived from peripheral blood mononuclear cells from diabetic patients displayed features consistent with the SASP. Overall, the present findings document a direct link between hyperglycaemia and the SASP in endothelial cells and macrophages, making the SASP a highly likely contributor to the fuelling of low-grade inflammation in diabetes.

Innovative biomarkers are needed to improve the management of patients with type 2 diabetes mellitus (T2DM). Blood circulating miRNAs have been proposed as a potential tool to detect T2DM complications, but the lack of tissue specificity, among other reasons, has hampered their translation to clinical settings. Extracellular vesicle (EV)-shuttled miRNAs have been proposed as an alternative approach. Here, we adapted an immunomagnetic bead–based method to isolate plasma CD31⁺ EVs to harvest vesicles deriving from tissues relevant for T2DM complications. Surface marker characterization showed that CD31⁺ EVs were also positive for a range of markers typical of both platelets and activated endothelial cells. After characterization, we quantified 11 candidate miRNAs associated with vascular performance and shuttled by CD31⁺ EVs in a large (n = 218) cross-sectional cohort of patients categorized as having T2DM without complications, having T2DM with complications, and control subjects. We found that 10 of the tested miRNAs are affected by T2DM, while the signature composed by miR-146a, -320a, -422a, and -451a efficiently identified T2DM patients with complications. Furthermore, another CD31⁺ EV-shuttled miRNA signature, i.e., miR-155, -320a, -342-3p, -376, and -422a, detected T2DM patients with a previous major adverse cardiovascular event. Many of these miRNAs significantly correlate with clinical variables held to play a key role in the development of complications. In addition, we show that CD31⁺ EVs from patients with T2DM are able to promote the expression of selected inflammatory mRNAs, i.e., CCL2, IL-1α, and TNFα, when administered to endothelial cells in vitro. Overall, these data suggest that the miRNA cargo of plasma CD31⁺ EVs is largely affected by T2DM and related complications, encouraging further research to explore the diagnostic potential and the functional role of these alterations.

To evaluate if plasma kisspeptin concentrations are associated with insulin secretion, as suggested by recent in vitro studies, independently of confounders. 261 nondiabetic subjects were stratified into tertiles according to kisspeptin values. Insulin secretion was assessed using indexes derived from oral glucose tolerance test (OGTT). After adjusting for age, gender, and BMI, subjects in the highest (tertile 3) kisspeptin group exhibited significantly lower values of insulinogenic index, corrected insulin response (CIR₃₀), and Stumvoll indexes for first-phase and second-phase insulin release as compared with low (tertile 1) or intermediate (tertile 2) kisspeptin groups. Univariate correlations between kisspeptin concentration and metabolic variables showed that kisspeptin concentration was significantly and positively correlated with age, blood pressure, and 2-h post-load glucose, and inversely correlated with BMI, and waist circumference. There was an inverse relationship between kisspeptin levels and OGTT-derived indexes of glucose-stimulated insulin secretion. A multivariable regression analysis in a model including all the variables significantly correlated with kisspeptin concentration showed thar age (β = -0.338, P<0.0001), BMI (β = 0.272, P<0.0001), 2-h post-load glucose (β = -0.229, P<0.0001), and kisspeptin (β = -0.105, P = 0.03) remained associated with insulinogenic index. These factors explained 34.6% of the variance of the insulinogenic index. In conclusion, kisspeptin concentrations are associated with insulin secretion independently of important determinants of glucose homeostasis such as gender, age, adiposity, 2-h post-load glucose, and insulin sensitivity.

We hypothesized that a disproportionate activation of the glucosamine (GlcN) pathway, caused by a prolonged exposure to hyperglycaemia, could impair endothelial integrity promoting endoplasmic reticulum (ER) stress. We also tested the possibility that SRT1720 may be able to counteract GlcN-induced ER stress. Human umbilical vein endothelial cells (HUVECs), human cardiac microvascular endothelial cells, and human retinal endothelial cells were treated with GlcN in the presence or absence of the chemical chaperone phenyl butyric acid (PBA) or SRT1720. Expression of ER stress markers, activation of apoptosis, and pro-inflammatory/pro-thrombotic pathways were evaluated by western blot, real-time RT-PCR, and ELISA assays. GlcN treatment resulted in a significantly increased expression of the major ER stress mediators. ER stress activation was paralleled by increased levels of apoptotic markers and by pro-inflammatory/pro-coagulant pathway activation. In HUVECs, ER stress inhibition by PBA alleviated a GlcN-induced pro-apoptotic and pro-inflammatory/pro-thrombotic state, suggesting a crucial role of ER stress in endothelial dysfunction caused by GlcN. Furthermore, SRT1720 treatment abolished GlcN-induced ER stress and reversed its effects on apoptosis and pro-inflammatory/pro-coagulant pathways. This SRT1720 action was mediated by its ability to modulate Raptor acetylation, thus inhibiting mammalian target of Rapamycin complex 1 (mTORC1)-dependent protein synthesis and alleviating ER overload. Our data show that GlcN promotes a pro-apoptotic and pro-inflammatory/pro-thrombotic phenotype in endothelial cells by activating ER stress. The observation that SRT1720, inhibiting ER stress, was able to counteract GlcN effects lays the basis for future studies aimed to exploit this drug and cognate compounds in the treatment of endothelial dysfunction and atherosclerosis.