Enhanced polyamine catabolism alters homeostatic control of white adipose tissue mass, energy expenditure, and glucose metabolism.

Peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1 alpha) is an attractive candidate gene for type 2 diabetes, as genes of the oxidative phosphorylation (OXPHOS) pathway are coordinatively downregulated by reduced expression of PGC-1 alpha in skeletal muscle and adipose tissue of patients with type 2 diabetes. Here we demonstrate that transgenic mice with activated polyamine catabolism due to overexpression of spermidine/spermine N(1)-acetyltransferase (SSAT) had reduced white adipose tissue (WAT) mass, high basal metabolic rate, improved glucose tolerance, high insulin sensitivity, and enhanced expression of the OXPHOS genes, coordinated by increased levels of PGC-1 alpha and 5'-AMP-activated protein kinase (AMPK) in WAT. As accelerated polyamine flux caused by SSAT overexpression depleted the ATP pool in adipocytes of SSAT mice and N(1),N(11)-diethylnorspermine-treated wild-type fetal fibroblasts, we propose that low ATP levels lead to the induction of AMPK, which in turn activates PGC-1 alpha in WAT of SSAT mice. Our hypothesis is supported by the finding that the phenotype of SSAT mice was reversed when the accelerated polyamine flux was reduced by the inhibition of polyamine biosynthesis in WAT. The involvement of polyamine catabolism in the regulation of energy and glucose metabolism may offer a novel target for drug development for obesity and type 2 diabetes.

Adenovirus-mediated gene transfer of human vascular endothelial growth factor-d induces transient angiogenic effects in mouse hind limb muscle.

We evaluated the therapeutic potential of adenovirus (Ad)-mediated human vascular endothelial growth factor-D (hVEGF-D) gene delivery in mice. Hind limbs of hypercholesterolemic mice ( n = 120) were injected with AdhVEGF-D, AdhVEGF-A, control AdLacZ (all at 1x10(11)viral particles) or saline. Animals were killed at 4, 7, 14, 28, and 42 days. Newly formed vessels were characterized for their quantity, sprouting, angiogenic versus lymphangiogenic phenotype, and arterial versus venous phenotype by endothelial enzymes markers, pericyte coverage, and electron microscopy. Perfusion was measured by power Doppler ultrasound and edema by magnetic resonance imaging (MRI). AdhVEGF-D induced significant formation of new blood vessels, which featured lumenal enlargement, branching, and sprouting. Branching originated mainly from arterioles. The highest vessel density was present on days 4-7 and the effect lasted up to 28 days. Endothelial marker enzyme activity indicated the predominance of arterial capillaries and arterioles. Forty percent of the neovessels were positive for desmin, indicating that VEGF-D increased pericyte coverage. However, branching vessels were highly positive for smooth muscle actin pericyte marker but negative for desmin. Maximal perfusion was measured during the first week after AdhVEGF-D gene transfer. Ultrastructural analysis showed endothelial cells enriched with vesiculo-vacuolar organelles and cytoplasmic protrusions. Modest lymphangiogenic activity was also detected, which could contribute to the relatively low level of edema detected by MRI. In conclusions, AdhVEGF-D has a strong angiogenic effect and a modest lymphangiogenic effect in mouse skeletal muscle. VEGF-D also increases the presence of pericytes/smooth muscle cells in neovessels. AdhVEGF-D is a potential new agent for the induction of therapeutic vascular growth in skeletal muscle.

Short and long-term effects of hVEGF-A(165) in Cre-activated transgenic mice.

We have generated a transgenic mouse where hVEGF-A(165) expression has been silenced with loxP-STOP fragment, and we used this model to study the effects of hVEGF-A(165) over-expression in mice after systemic adenovirus mediated Cre-gene transfer. Unlike previous conventional transgenic models, this model leads to the expression of hVEGF-A(165) in only a low number of cells in the target tissues in adult mice. Levels of hVEGF-A(165) expression were moderate and morphological changes were found mainly in the liver, showing typical signs of active angiogenesis. Most mice were healthy without any major consequences up to 18 months after the activation of hVEGF-A(165) expression. However, one mouse with a high plasma hVEGF-A(165) level died spontaneously because of bleeding into abdominal cavity and having liver hemangioma, haemorrhagic paratubarian cystic lesions and spleen peliosis. Also, two mice developed malignant tumors (hepatocellular carcinoma and lung adenocarcinoma), which were not seen in control mice. We conclude that long-term uncontrolled hVEGF-A(165) expression in only a limited number of target cells in adult mice can be associated with pathological changes, including possible formation of malignant tumors and uncontrolled bleeding in target tissues. These findings have implications for the design of long-term clinical trials using hVEGF-A(165) gene and protein.

Gene transfers of vascular endothelial growth factor-A, vascular endothelial growth factor-B, vascular endothelial growth factor-C, and vascular endothelial growth factor-D have no effects on atherosclerosis in hypercholesterolemic low-density lipoprotein-receptor/apolipoprotein B48-deficient mice.

BACKGROUND: The role of vascular endothelial growth factors (VEGFs) in large arteries has been proposed to be either vasculoprotective or proatherogenic. Because VEGF family members are used for human therapy, it is important to know whether they could enhance atherogenesis. We tested the effects of the members of the VEGF gene family on atherogenesis in LDL-receptor/apolipoprotein (apo) B48 double-knockout (LDLR/apoB48) mice using systemic adenoviral gene transfer. METHODS AND RESULTS: Six groups of LDLR/apoB48-deficient mice (n=110) were kept 3 months on a Western-type diet. After 6 weeks of diet, mice were injected via tail vein with recombinant adenoviruses expressing VEGF-A, -B, -C, or -D or LacZ (1 x 10(9) PFU) or rhVEGF-A protein (2 microg/kg) and euthanized 6 weeks later. Also, older mice (n=36) were injected after 4 months on the diet and euthanized 6 weeks later (total time on the diet, 22 weeks) to evaluate the effects of gene transfers on the development of more mature lesions. Aortas were analyzed for the presence of macroscopic lesions, cross-sectional lesion areas, neovascularization, and cellular composition of the lesions. All groups had equivalent plasma cholesterol and triglyceride levels. Gene transfers with recombinant adenoviruses or administration of rhVEGF-A protein had no statistically significant effects on en face atherosclerotic lesions in the aorta, cross-sectional lesion area, neovascularization, or cellular composition of the lesions. CONCLUSIONS: This study shows no proatherogenic effects of adenovirus-mediated gene transfers of VEGF-A, -B, -C, or -D in the LDLR/apoB48-deficient hypercholesterolemic mice, in which lipoprotein profile and atherosclerosis closely resemble those in human disease.