BackgroundRecent changes in nutrition and lifestyle have provoked an unprecedented increase in the prevalence of obesity and metabolic disorders. Recognition of the adverse effects on health has prompted intense efforts to understand the molecular determinants of insulin sensitivity and dysglycemia. In many respects, actions of insulin-like growth factors (IGFs) mirror those of insulin in metabolic regulation. Unlike insulin, however, the bioactivity of IGFs is regulated by a family of seven high-affinity binding proteins (IGFBPs) which confer temporospatial modulation with implications for metabolic homeostasis. In addition, evidence is accumulating that IGF-independent actions of certain of the IGFBPs can directly modulate insulin sensitivity.Scope of reviewIn this review, we discuss the experimental data indicating a critical role for IGF/IGFBP axis in metabolic regulation. We highlight key discoveries through which IGFBPs have emerged as biomarkers or putative therapeutic targets in obesity and diabetes.Major conclusionsGrowing evidence suggests that several components of the IGF-IGFBP system could be explored for therapeutic potential in metabolic disorders. Both IGFBP-1 and IGFBP-2 have been favorably linked with insulin sensitivity in humans and preclinical data implicate direct involvement in the molecular regulation of insulin signaling and adiposity respectively. Further studies are warranted to evaluate clinical translation of these findings.

We have discovered that two mutations at the actin binding domain (ABD) of α-actinin-2 (ACTN2), which cause hypertrophic cardiomyopathy (HCM), have minor effects on its structure and ability to bind actin and integrate into Z-discs, providing a potential disease mechanism.

We have introduced a 6.5 Mb human mini-chromosome with a complex centromere structure into DT40 cells and have used sequence targeting and telomere-directed chromosome breakage to dissect the sequence requirements for centromere function. These experiments proved that a vertebrate centromere with two blocks of functional alphoid DNA separated by 2.5 Mb can exist as a stable structure in some but not all vertebrate cells. Further experiments indicated that recovery of chromosomes with less than approximately 100 kb of alphoid DNA is very inefficient, suggesting that a functional centromere requires a minimum of approximately 100 kb of alphoid DNA. Mini-chromosomes with minimal centromeres segregate accurately in some but not all vertebrate cells and should be useful for the detection of sequence-specific factors required for vertebrate centromere maintenance.

Rationale: In the endothelium, insulin stimulates endothelial nitric oxide synthase (eNOS) to generate the anti-atherosclerotic signalling radical NO. Insulin resistant type 2 diabetes is associated with reduced NO availability and accelerated atherosclerosis. The effect of enhancing endothelial insulin sensitivity on NO availability is unclear. Objective: To answer this question we generated a mouse with endothelial cell (EC)-specific over-expression of the human insulin receptor (hIRECO) using the Tie2 promoter-enhancer. Methods and Results: hIRECO demonstrated significant endothelial dysfunction measured by blunted endothelium-dependent vasorelaxation to acetylcholine which was normalized by a specific Nox2 NADPH oxidase inhibitor. Insulin-stimulated phosphorylation of Akt was increased in hIRECO EC as was Nox2 NADPH oxidase-dependent generation of superoxide, whereas insulin and shear stress-stimulated eNOS activation were blunted. Phosphorylation at the inhibitory residue Y657 of eNOS and expression of PYK2 which phosphorylates this residue were significantly higher in hIRECO EC. Inhibition of PYK2 improved insulin and shear-induced eNOS activation in hIRECO EC. Conclusions: Enhancing insulin sensitivity specifically in EC leads to a paradoxical decline in endothelial function, mediated by increased tyrosine phosphorylation of eNOS and excess Nox2 derived superoxide. Increased EC insulin sensitivity leads to a pro-atherosclerotic imbalance between NO and superoxide. Inhibition of PYK2 restores insulin-and shearinduced NO production. This study demonstrates for the first time that increased endothelial insulin sensitivity leads to a pro-atherosclerotic imbalance between NO and superoxide.Key Words: Insulin; Insulin Resistance; Endothelial Dysfunction; PYK2; Reactive oxygen Species; Superoxide Non-standard Abbreviations and Acronyms: NO-nitric oxide, hIR-human Insulin Receptor; hIRECO-endothelial cell (EC)-specific over-expression of the human insulin receptor; EC-endothelial cells; PEC-pulmonary endothelial cells; PYK2-proline-rich tyrosine kinase 2; Akt-protein kinase B; ACh-acetylcholine; PE-phenylephrine; SNP-sodium nitroprusside; eNOS-endothelial nitric oxide synthase.3