Increased nitric oxide availability attenuates high fat diet metabolic alterations and gene expression associated with insulin resistance.

BACKGROUND: High fat diet impairs nitric oxide (NO) bioavailability, and induces insulin resistance. The link between NO availability and the metabolic adaptation to a high fat diet is not well characterized. The purpose of this study was to investigate the effect of high fat diet on metabolism in mice with decreased (eNOS-/-) and increased (DDAH overexpressed) NO bioavailability. METHODS: eNOS-/- (n = 16), DDAH (n = 24), and WT (n = 19) mice were fed a high fat diet (HFD) for 13 weeks. Body weight, biochemical parameters, adipokines and insulin were monitored. The matrigel in vivo model with CD31 immunostaining was used to assess angiogenesis. Gene expression in adipose tissues was analyzed by microarray and Real Time PCR. Comparisons of the mean values were made using the unpaired Student t test and p < 0.05 were considered statistically significant. RESULTS: eNOS-/- mice gained less weight than control WT and DDAH mice. In DDAH mice, a greater increase in serum adiponectin and a lesser increment in glucose level was observed. Fasting insulin and cholesterol levels remained unchanged. The angiogenic response was increased in DDAH mice. In adipose tissue of DDAH mice, genes characteristic of differentiated adipocytes were down-regulated, whereas in eNOS-/- mice, genes associated with adipogenesis, fatty acid and triglyceride synthesis were upregulated. CONCLUSIONS: Our results indicate that increased NO availability attenuates some HFD induced alterations in metabolism and gene expression associated with insulin resistance.

Angiogenesis in Balb/c mice under beta-carotene supplementation in diet.

Angiogenesis is a process of new blood vessel formation from pre-existing ones. The most important steps in angiogenesis include detachment, proliferation, migration, homing and differentiation of vascular wall cells, which are mainly endothelial cells and their progenitors. The study focused on the effect of beta-carotene (BC) supplementation (12,000 mg/kg) in the diet on angiogenesis in Balb/c mice. Female Balb/c mice were fed for 5 weeks with two different diets: with BC or without BC supplementation. After 4 weeks of feeding, Balb/c mice were injected subcutaneously with two matrigel plugs with or without basic fibroblast growth factor (bFGF). Six days later, the animals were killed, and the matrigel plugs were used for immunohistochemical staining with CD31 antibody and for gene expression analysis. Microarray and Real-Time PCR data showed down-regulation of genes involved in proliferation and up-regulation of genes encoding inhibitors of apoptosis, proteins regulating cell adhesion, matrix-degrading enzymes and proteins involved in the VEGF pathway. The results of this study demonstrated that BC proangiogenic activity (with or without bFGF) in vivo seemed to be more significantly associated with cells' protection from apoptosis and their stimulation of chemotaxis/homing than cell proliferation.

Modulatory effect of high saturated fat diet-induced metabolic disturbances on angiogenic response in hepatocyte RXRα knockout mice.

Metabolic syndrome and diabetes lead to pathological angiogenesis and angiopathy. Metabolic disturbances occur as an effect of genetic and environmental interaction. Hyperleptinemia accompanies obesity and leptin is a potent proangiogenic factor. The aim of the study was to investigate the effect of high fat diet-induced alterations in gene expression and angiogenic response in the hRXRα ko mice lacking of hyperglycemia. hRXRα ko and control mice were fed either standard or high saturated fat (HF) diet for 7 weeks. Body weight and biochemical parameters (glucose, triglycerides, cholesterol), insulin and adipokines (leptin, adiponectin) were monitored. At sixth week of feeding, mice were subcutaneously injected for 6 days with matrigel containing bFGF. Then, matrigel plugs were used for immunohistochemical staining of cells with CD31 antibody and gene expression assessment (by microarray confirmed for some genes with quantitative real time PCR). For description of angiogenesis CD31 positive structures were counted in the matrigel sections. HF diet feeding of the hRXRα ko mice resulted in increased serum cholesterol and leptin level and in tendency to decrease angiogenesis (number of vessels with lumen). The microarray studies revealed that HF diet down-regulated genes related to angiogenesis (Nos3, Kdr) and up-regulated genes connected with apoptosis (activators of caspase 3, proapoptotic genes Bcl2) and proinflammatory pathway (NfκB pathway, Tnfα). Summing up, HF diet feeding of hRXRα ko mice resulted in dyslipidemia and hyperleptinemia as well as impaired angiogenic response, and cell apoptosis. These results argue for independent participation of dyslipidemia and hyperleptinemia in pathology of angiogenic response associating metabolic syndrome.

Angiogenesis in the New Zealand obese mouse model fed with high fat diet.

BACKGROUND: Obesity and its complications lead to vascular injury, atherosclerosis, diabetes and pathological angiogenesis. One of the models to study the obesity and its entanglements is the New Zealand Obese mice model. Aim of this study was to check the effect of high fat diet on changes in biochemical parameters as well as on process of angiogenesis in NZO mice. METHODS: NZO mice were fed with standard (ST) or high fat (HF) diet for seven weeks. Body weight and serum biochemical parameters were monitored. The PECAM1 positive vessel-like structures immunostaining, as well as the gene expression of the matrigel penetrating cells by microarray (confirmed by real-time PCR method) were analyzed. RESULTS: Mice fed with HF diet developed obesity. Number of newly created vessels with lumen was correlated with hyperglycemia and animal weight gain. The number of PECAM1 positive cells in matrigel tended to increase during HF diet. Microarray results revealed changes in gene expression (activation of the oxidative stress and insulin resistance, inhibition of apoptosis and cell differentiation), however without markers of endothelial cell network maturation. CONCLUSION: Observed changes in the NZO mice on HF diet argue for the hyperglycemia related activation of angiogenesis, leading to the formation of pathological, immature network.

Hepatocyte RXR alpha deletion in mice leads to inhibition of angiogenesis.

To investigate the effect of RXRalpha deficiency in liver on angiogenesis, hepatocyte RXRalpha-deficient and control wild-type mice were fed either standard or high-fat diet (HF) for 7 weeks. In the 6th week of feeding, Matrigel model of in vivo angiogenesis was applied. Matrigel plug infiltrating cells were then used for visualization of vessels (CD31 staining) as well as for gene expression analysis. HF diet appeared to decrease angiogenesis in hRXRalpha-deficient mice. Genes related to angiogenesis (Nos3, Kdr) were down-regulated, whereas genes connected with adipogenesis (Cebpb, Srebf1), apoptosis (Gzmb, Bcl2) and proinflammatory pathway (NfkappaB, Tnfalpha) were up-regulated by HF diet in hRXRalpha-deficient mice in the microarray study. Our results suggest that impaired fatty acid metabolism in liver (hRXRalpha-deficient mice) leads to impaired angiogenesis due to lipotoxicity and promotion of adipogenesis.

Impaired leptin activity in New Zealand Obese mice: model of angiogenesis.

Leptin is prompt to drive angiogenesis, effecting proper vascularisation. Tissue remodeling (including adipose organ) is associated with the angiogenic response. The aim of this study was to investigate the effect of hyperleptinemia on angiogenesis in subcutaneous (s.c.) in vivo matrigel model in mice on a high fat (HF) diet. HF promoted adipose tissue accumulation and biochemical changes resembling metabolic syndrome. However, the impact of this dietary treatment on angiogenesis, measured in s.c. matrigel model was not significant. Changes in leptin concentration were not accompanied by significant angiogenic response. This lack of leptin activity and impaired signal transduction at the molecular level suggests malfunction of the leptin receptor in NZO mice.