G-protein-coupled receptor (GPCR) agonists are well-known inducers of cardiac hypertrophy. We found that the shedding of heparin-binding epidermal growth factor (HB-EGF) resulting from metalloproteinase activation and subsequent transactivation of the epidermal growth factor receptor occurred when cardiomyocytes were stimulated by GPCR agonists, leading to cardiac hypertrophy. A new inhibitor of HB-EGF shedding, KB-R7785, blocked this signaling. We cloned a disintegrin and metalloprotease 12 (ADAM12) as a specific enzyme to shed HB-EGF in the heart and found that dominant-negative expression of ADAM12 abrogated this signaling. KB-R7785 bound directly to ADAM12, suggesting that inhibition of ADAM12 blocked the shedding of HB-EGF. In mice with cardiac hypertrophy, KB-R7785 inhibited the shedding of HB-EGF and attenuated hypertrophic changes. These data suggest that shedding of HB-EGF by ADAM12 plays an important role in cardiac hypertrophy, and that inhibition of HB-EGF shedding could be a potent therapeutic strategy for cardiac hypertrophy.

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Neuropilins (NP1 and NP2) are vascular endothelial growth factor (VEGF) receptors that mediate developmental and tumor angiogenesis. Transgenic mice, in which both NP1 and NP2 were targeted (NP1 ؊/؊ NP2 ؊/؊ ) died in utero at E8.5. Their yolk sacs were totally avascular. Mice deficient for NP2 but heterozygous for NP1 (NP1 ؉/؊ NP2 ؊/؊ ) or deficient for NP1 but heterozygous for NP2 (NP1 ؊/؊ NP2 ؉/؊ ) were also embryonic lethal and survived to E10 -E10.5. The E10 yolk sacs and embryos were easier to analyze for vascular phenotype than the fragile poorly formed 8.5 embryos. The vascular phenotypes of these E10 mice were very abnormal. The yolk sacs, although of normal size, lacked the larger collecting vessels and had less dense capillary networks. PECAM staining of yolk sac endothelial cells showed the absence of branching arteries and veins, the absence of a capillary bed, and the presence of large avascular spaces between the blood vessels. The embryos displayed blood vessels heterogeneous in size, large avascular regions in the head and trunk, and blood vessel sprouts that were unconnected. The embryos were about 50% the length of wild-type mice and had multiple hemorrhages. These double NP1͞NP2 knockout mice had a more severe abnormal vascular phenotype than either NP1 or NP2 single knockouts. Their abnormal vascular phenotype resembled those of VEGF and VEGFR-2 knockouts. These results suggest that NRPs are early genes in embryonic vessel development and that both NP1 and NP2 are required. vascular endothelial growth factor ͉ vascular endothelial growth factor receptors ͉ blood vessels ͉ endothelial cells ͉ semaphorins

Background-Some studies have shown that metformin activates AMP-activated protein kinase (AMPK) and has a potent cardioprotective effect against ischemia/reperfusion injury. Because AMPK also is activated in animal models of heart failure, we investigated whether metformin decreases cardiomyocyte apoptosis and attenuates the progression of heart failure in dogs. Methods and Results-Treatment with metformin (10 mol/L) protected cultured cardiomyocytes from cell death during exposure to H 2 O 2 (50 mol/L) via AMPK activation, as shown by the MTT assay, terminal deoxynucleotidyl transferasemediated dUTP nick-end labeling staining, and flow cytometry. Continuous rapid ventricular pacing (230 bpm for 4 weeks) caused typical heart failure in dogs. Both left ventricular fractional shortening and left ventricular end-diastolic pressure were significantly improved in dogs treated with oral metformin at 100 mg · kg Ϫ1 · d Ϫ1 (nϭ8) (18.6Ϯ1.8% and 11.8Ϯ1.1 mm Hg, respectively) compared with dogs receiving vehicle (nϭ8) (9.6Ϯ0.7% and 22Ϯ0.9 mm Hg, respectively). Metformin also promoted phosphorylation of both AMPK and endothelial nitric oxide synthase, increased plasma nitric oxide levels, and improved insulin resistance. As a result of these effects, metformin decreased apoptosis and improved cardiac function in failing canine hearts. Interestingly, another AMPK activator (AICAR) had effects equivalent to those of metformin, suggesting the primary role of AMPK activation in reducing apoptosis and preventing heart failure. Conclusions-Metformin attenuated oxidative stress-induced cardiomyocyte apoptosis and prevented the progression of heart failure in dogs, along with activation of AMPK. Therefore, metformin may be a potential new therapy for heart failure. (Circulation. 2009;119:2568-2577.)Key Words: AMP-activated protein kinase Ⅲ heart failure Ⅲ metformin Ⅲ nitric oxide M etformin is widely used as an antidiabetic drug with an insulin-sensitizing effect. A large-scale clinical trial (the UK Prospective Diabetes Study [UKPDS] 34) has shown that metformin therapy decreased the risk of cardiovascular death and the incidence of myocardial infarction associated with diabetes mellitus, 1 suggesting that this drug may be useful for patients who have both cardiovascular disease and diabetes mellitus. Eurich and colleagues 2 recently reported the results of a meta-analysis showing that metformin was the only antidiabetic agent to reduce all-cause mortality without causing any harm in patients who had heart failure and diabetes mellitus. These results suggest that a tight link exists between cardiovascular disease and diabetes mellitus and that metformin has a cardioprotective effect. Metformin is known to activate AMP-activated protein kinase (AMPK), [3][4][5] which is expressed in various tissues, including the myocardium, and plays a central role in the regulation of energy metabolism under stress conditions. 6 AMPK is activated by ischemia/reperfusion, 7-9 as well as in hearts with pressure overload hypertrophy 10 and subseque...