Recent evidence suggests that glucagon-like peptide-1 (GLP-1) enhances recovery of left ventricular (LV) function after transient coronary artery occlusion. However, it is uncertain whether GLP-1 has direct effects on normal or ischemic myocardium and whether the mechanism involves increased myocardial glucose uptake. LV function and myocardial glucose uptake and lactate production were measured under basal conditions and after 30 min of low-flow ischemia and 30 min of reperfusion in the presence and absence of GLP-1-(7-36) amide. The response was compared with standard buffer alone or buffer containing insulin (100 U/ml). GLP-1 decreased the left ventricular developed pressure (baseline: 100 Ϯ 2 mm Hg; GLP-1: 75 Ϯ 3 mm Hg, p Ͻ 0.05) and LV dP/dt (baseline: 4876 Ϯ 65 mm Hg/s; GLP-1: 4353 Ϯ 76 mm Hg/s, p Ͻ 0.05) in normal hearts. GLP-1 increased myocardial glucose uptake (baseline: 33 Ϯ 3 mol/min/g; GLP-1: 81 Ϯ 7 mol/min/g, p Ͻ 0.05) by increasing nitric oxide production and glucose transporter (GLUT)-1 translocation. GLP-1 enhanced recovery after 30 min of low-flow ischemia with significant improvements in LV end-diastolic pressure (control: 13 Ϯ 4 mm Hg; GLP-1: 3 Ϯ 2 mm Hg, p Ͻ 0.05) and LV developed pressure (control: 66 Ϯ 6 mm Hg; GLP-1: 98 Ϯ 5 mm Hg, p Ͻ 0.05). GLP-1 increased LV function, myocardial glucose uptake, and GLUT-1 and GLUT-4 translocation during reperfusion to an extent similar to that with insulin. GLP-1 has direct effects on the normal heart, reducing contractility, but increasing myocardial glucose uptake through a non-Akt-1-dependent mechanism, distinct from the actions of insulin. However, GLP-1 increased myocardial glucose uptake and enhanced recovery of cardiac function after low-flow ischemia in a fashion similar to that of insulin.

Background-The mechanism of delayed preconditioning induced by activation of adenosine A 1 receptors (A 1 ARs) is not fully understood. We determined the role of inducible nitric oxide synthase (iNOS) in mediating adenosine-induced late cardioprotection using pharmacological inhibitors and iNOS gene-knockout mice. Methods and Results-Adult male mice were treated with saline or an A 1 AR agonist, 2-chloro-N 6 -cyclopentyladenosine (CCPA). Twenty-four hours later, the hearts were perfused in Langendorff mode and subjected to 30 minutes of global ischemia followed by 30 minutes of reperfusion. 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX; 0.1 mg/kg IP) and S-methylisothiourea (SMT; 3 mg/kg IP) were used to block A 1 ARs and iNOS, respectively. Infarct size (IS) was measured by triphenyltetrazolium chloride staining, and iNOS expression was measured by Western blots. Myocardial IS was reduced from 24.0Ϯ3.2% in the saline group to 12.2Ϯ2.5% in CCPA-treated mice (PϽ0.05). The infarct-reducing effect of CCPA was abrogated by DPCPX (29.3Ϯ3.4%) and SMT (32.3Ϯ2.6%) and was absent in mice with targeted ablation of iNOS (23.9Ϯ1.6%). CCPA produced improvement in postischemic end-diastolic pressure, developed pressure, and rate-pressure product, which was also blocked by DPCPX and SMT. Increased iNOS protein expression observed in CCPA-treated hearts was diminished by DPCPX. Conclusions-Selective

Regulatory mechanisms of chondrocyte differentiation in the growth plate are incompletely understood. Here, we find that histone deacetylase 4 (HDAC4) is located in the nucleus of chondrocytes in the proliferation zone and relocates to the cytoplasm of chondrocytes in the prehypertrophic zone in vivo. This suggests that the relocation of HDAC4 from the nucleus to the cytoplasm may play a role during chondrocyte differentiation. Expression of active CaMKIV in chondrocytes promotes HDAC4 relocation into cytoplasm in primary chondrocytes. Conversely, HDAC4 relocation is blocked by a Ca(2+)/calmodulin-dependent kinase IV (CaMKIV) inhibitor. This indicates that CaMKIV signaling plays an important role in regulating HDAC4 relocation. In addition, CaMKIV is required for HDAC4 phosphorylation, which is required for HDAC4 association with the cytoplasmic protein 14-3-3. Active CaMKIV also stimulates runt-related transcription factor-2 (RunX2) and type X collagen (Col X) promoter activities and overcomes repression of these promoter activities by HDAC4. Furthermore, CaMKIV increases gene expression of the chondrocyte differentiation markers Ihh and Col X. Our results demonstrate that CaMKIV induces chondrocyte differentiation through regulation of HDAC4 subcellular relocation, from the nucleus to the cytoplasm, which results in increased activity of RunX2 and transition of chondrocytes from the proliferative to the prehypertrophic stage. Thus, CaMKIV plays an important regulatory role during chondrocyte differentiation.