Lipoprotein(a) (Lp[a]) is one of the strongest genetic risk factor for coronary artery disease (CAD). Although the variation in plasma Lp(a) levels has been shown to be strongly influenced by genetics, whether Lp(a) is associated with an altered cardiometabolic risk profile and whether lifestyle changes could improve Lp(a) levels in patients with CAD is unknown. The aim of the study was to determine if patients with high Lp(a) levels were characterized by a deteriorated cardiometabolic risk profile and whether a 1-year lifestyle modification program aiming at increasing physical activity levels and improve diet quality could decrease Lp(a) levels in post coronary artery bypass graft (CABG) patients.

Interleukin-6 (IL-6) has been long known for its immune function and is also considered as a key inflammatory mediator in several chronic diseases including atherosclerosis and obesity-linked type 2 diabetes. However, IL-6 is also produced by skeletal muscle and mediates some of the metabolic effects of physical exercise. However, therapeutic applications of muscle IL-6 remain unknown. We have recently identified a lipid mediator (protectin DX) derived from the metabolism of the long chain omega-3 polyunsaturated fatty acid DHA, that can reduce insulin resistance in lipid-infused and genetically diabetic (db/db) mice through its ability to act as a muscle IL-6 secretagogue. PDX increases the activity of the energy sensor AMPK in skeletal muscle, as does muscle contraction. In addition we have shown that PDX triggers a muscle/liver glucoregulatory axis whereby myocyte IL-6 activates hepatic STAT-3 signaling and improves insulin suppression of hepatic glucose production through down-regulation of gluconeogenic genes. Together these data present PDX as a novel muscle IL-6 secretagogue that carries exciting therapeutic potential for insulin resistance and type 2 diabetes. This concept is supported by other groups reporting that adipocyte IL-6 release can also trigger similar effect on hepatic glucose metabolism, whereas IL-6 can also improve pancreatic function through promoting GLP-1 release from intestinal L cells and pancreatic alpha cells.

We investigated the therapeutic effects of 2thio-UTP on the early phase of calcific aortic stenosis in vivo by using a new murine model (coined IGF-II) combining atherosclerosis (LDLr-/-xApoB48-/-) and type 2 diabetes (beta-cell IGF-II overexpression).

Obesity-linked type 2 diabetes is well recognized to be associated with a chronic inflammatory state. However the mechanisms that link inflammation with obesity and development of type 2 diabetes are still poorly understood. We have already established that iNOS expression in metabolic tissues plays a major role in promoting insulin resistance in the context of obesity and metabolic endotoxemia. One of the mechanisms by which iNOS can mediate insulin resistance is through tyrosine nitration of insulin signalling proteins through the formation of peroxynitrite (ONOO–) from nitric oxide (NO) and superoxide anion (O2 –). To clarify the mechanism underlying tyrosine nitration of insulin signalling proteins, we hypothesize that superoxide (O2–) generation is a major contributor to ONOO– production and tyrosine nitration in insulin target cells treated with cytokines. We found that NOX3, a critical component of NADPH oxidase, can be markedly induced by inflammatory cytokines in 3T3 L1 adipocytes and primary hepatocytes. We have confirmed that NOX3 induction leads to O2– production in 3T3L1 cells as measured by the nitrotetrazolium reduction assay (NBT assay), and in FAO cells as measured by electro paramagnetic resonance and that this can be blunted by treatment with diphenyliodonium (DPI), a NADPH oxidase inhibitor. NOX3 induction and O2–generation are tightly coupled with iNOS-linked NO production and tyrosine nitration upon cytokine activation. These initial studies show that O2– is generated by key insulin target cells upon treatment with cytokines, and that NOX3 may be a key NADPH oxidase system responsible for this O2– production in inflammatory settings.

Originally identified in macrophages, iNOS is also expressed in insulin target tissues such as liver, adipose tissues and skeletal muscles under acute or chronic inflammatory conditions. We and others have previously shown that obesity (diet-induced or genetic) and LPS-induced endotoxemia cause iNOS induction and insulin resistance in association with disrupted insulin signaling to PI3K/Akt. Although the mechanisms by which LPS increases iNOS expression has been intensively studied, the pathways leading to iNOS induction in obesity remain poorly understood. The present study was thus undertaken to test the role of iNOS in mediating the effects of acutely infused TNF-alpha and lipids, two factors known to be increased in obesity. Wild-type (WT) and iNOS-/- mice were infused for 6 hrs with TNF-α mix with Intralipid (TIL)emulsion or intralipid alone (LIP) and insulin sensitivity was assessed during a hyperinsulinemiceuglycemic clamp. Another group of mice was infused with LPS to compare the metabolic effects of TIL and LIP infusion to that of an acute systemic endotoxemia (LPS). Infusion of either LPS, TIL and LIP significantly diminished the glucose infusion rate (GIR: insulin sensitivity index) of WT mice compared to the saline-infused group (p<0.05). However, iNOS-/-mice were protected from the insulin-resistant effects of either LPS, TIL and LIP treatment. WT but not iNOS-/- mice had an elevated basal hepatic glucose output (Ra) in LPS, TIL and LIP conditions compared to saline-infused controls. During the clamp, the inhibitory effect of insulin on liver glucose output (EndoRa) was significantly blunted (p<0.05) in WT mice treated with either LPS, TIL or LIP compared to saline, while the lipid and inflammatory insults failed to impair hepatic insulin action in iNOS-/- mice. iNOS-/- mice also displayed an overall greater whole body glucose disposal rate during the clamp procedure when compared to WT mice (p=0.003). Western blot analyses of liver extracts further revealed that iNOS gene disruption blunted the activation of the NF-kB pathway upon LPS or TIL infusion. In contrast to WT mice, insulin-induced IRS-1/2 tyrosine phosphorylation was preserved while its serine phosphorylation was blunted in liver of iNOS-/- mice challenged with lipid and inflammatory mediators. In the present study, we saw that deletion of iNOS maintained FoxO1 phosphorylation following LPS and TIL treatments, suggesting a sustained inhibition of key gluconeogenic enzymes despite known insulin resistant inducers. Confirming the aforementioned observation, PEPCK protein expression in iNOS-/- mice subjected to either LPS or TIL treatment was maintain to levels comparable to saline treated mice. Taken together, the present data show that iNOS gene disruption prevents in vivo hepatic insulin resistance in models of acute inflammation and lipid infusion.

In this study we evaluated the role of the neuronal nitric oxide synthase (nNOS) in lipopolysaccharide (LPS)-induced diaphragmatic contractile dysfunction and sarcolemmal injury. Wild-type (WT) mice or mice deficient in the nNOS gene (nNOS(-/-)) were injected with either saline (control) or Escherichia coli LPS (LPS groups) and sacrificed 12 h later. The diaphragm was then examined for NOS expression, NOS activity, and in-vitro contractility. We also assessed sarcolemmal injury in isolated muscle strips under resting condition and after 3 min of artificial stimulations. In WT mice, LPS injection reduced maximum force to about 75% of that of control animals and raised total NOS activity significantly due to the induction of the iNOS isoform. Although muscle fiber injury was minimal under resting condition, the percentage of injured fibers in control and LPS-injected mice approached 27% and 40% of total fibers, respectively, in response to artificial stimulation. By comparison, LPS injection in nNOS(-/-) mice elicited a worsening of muscle contractility (maximum force < 60% of control animals) but elicited degrees of sarcolemmal injury similar to those observed in the WT animals. In addition, muscle NOS activity and iNOS protein level in nNOS(-/-) mice injected with LPS reached about 10% and 60% of that of WT animals, respectively (p < 0.05 compared with WT animals). Protein level of endothelial NOS isoform in the diaphragm was not altered by LPS injection in either WT or nNOS(-/-) animals. We conclude that nNOS plays a protective role in attenuating the negative influence of sepsis on diaphragmatic contractility but is not involved in the pathogenesis of sepsis-induced sarcolemmal injury.

We investigated the long-term effect of metformin treatment on blood pressure, insulin sensitivity, and vascular responses to insulin in conscious spontaneously hypertensive rats (SHR). The rats were instrumented with intravascular catheters and pulsed Doppler flow probes to measure blood pressure, heart rate, and blood flow. Insulin sensitivity was assessed by the euglycemic hyperinsulinemic clamp technique. Two groups of SHR received metformin (100 or 300 mg x kg(-1) x day(-1)) for 3 wk while another group of SHR and a group of Wistar Kyoto (WKY) rats were left untreated. We found that vasodilation of skeletal muscle and renal vasculatures by insulin is impaired in SHR. Moreover, a reduced insulin sensitivity was detected in vivo and in vitro in isolated soleus and extensor digitorum longus muscles from SHR compared with WKY rats. Three weeks of treatment with metformin improves the whole-body insulin-mediated glucose disposal in SHR but has no blood pressure-lowering effect and no influence on vascular responses to insulin (4 mU x kg(-1) x min(-1)). An improvement in insulin-mediated glucose transport activity was detected in isolated muscles from metformin-treated SHR, but in the absence of insulin no changes in basal glucose transport activity were observed. It is suggested that part of the beneficial effect of metformin on insulin resistance results from a potentiation of the hormone-stimulating effect on glucose transport in peripheral tissues (mainly skeletal muscle). The results argue against a significant antihypertensive or vascular effect of metformin in SHR.