Adiponectin and visfatin are newly discovered adipokines that are strongly expressed in human visceral adipose tissue. To identify new regulatory mechanisms in fat, the effect of TNF-alpha (TNF) on adiponectin, on its two receptors, and on visfatin was investigated by incubating human visceral adipose tissue from patients without diabetes mellitus with TNF for 24, 48 and 72 hours. The mRNA expression of visfatin, adiponectin, and its two receptors, as well as the protein expression of adiponectin were determined. A decrease of adiponectin mRNA expression of 97% after incubation with TNF (5.75 nmol/l) for 24 hours, a decrease of 91% after 48 hours, and a decrease of 96% after 72 hours were measured. The reduction of protein expression was measured to be 42% after 24 hours, 28% after 48 hours, and 39% after 72 hours of incubation with TNF (5.75 nmol/l). The mRNA level of adiponectin receptor 1 (AdipoR1) was elevated about 72% after 48 hours of incubation and 67% after 72 hours of incubation, whereas the mRNA expression of adiponectin receptor 2 (AdipoR2) was not altered significantly. The visfatin mRNA level was found to be highly increased by 255% after 24 hours and 335% after 48 hours and 341% after 72 hours of incubation with TNF (5.75 nmol/l). Our results support the concept of visceral adipose tissue as an endocrine organ. We demonstrate that TNF has regulatory functions on adiponectin, AdipoR1 and on visfatin in human visceral adipose tissue. TNF levels are elevated in states of obesity and insulin resistance. Due to this fact TNF could be the reason that there is a decrease in the level of adiponectin, whereas there is an increase in the level of visfatin in states of obesity and insulin resistance.

Vascular alterations are the most common causes of morbidity and mortality in diabetic patients. Despite the impact of endothelial dysfunction on microcirculatory properties, little is known about the endothelial cell alteration during the development of diabetes and its correlation to the metabolic situation. For that reason we continuously monitored in vivo functional and morphological alterations of the microvasculature in hyperglycemic and hyperinsulinemic transgenic UCP1/DTA mice with brown fat deficiency, using a dorsal skin-fold chamber preparation and fluorescence microscopy. UCP1/DTA mice showed a dramatic decrease in vascular density due to a remarkable reduction of small vessels. Vascular permeability and leukocyte endothelial interactions (LEIs) significantly increased. The extent of vascular alteration correlated with the extent of metabolic dysfunction. Decreased tissue perfusion observed in UCP1/DTA mice might play a role in impaired wound healing observed in diabetes. The increased permeability in subcutaneous tissue may serve as predictor of vascular changes in early stages of diabetes. The increased LEI and serum tumor necrosis factor-␣ levels, which mirror the inflammatory process, support the growing evidence of the inflammatory component of diabetic disease. The results suggest that anti-inflammatory strategies might be able to prevent vascular deterioration in early stages of diabetes. Further investigations are required to evaluate the benefit of such therapeutic strategies. Diabetes 52:542-549, 2003 V ascular alterations are the most common causes of morbidity and mortality in diabetic patients. The microcirculation not only governs the efficacy of substrate delivery but also mediates adaptations to changing local requirements and metabolic conditions. Functional alterations of the microcirculation precede morphological changes and determine the resultant vascular morphology (1). Microvascular disease has been shown to have a high prevalence in diabetes (2,3). Several studies described endothelial dysfunction and functional alterations in the microcirculation of diabetic patients. Animal models of diabetes show increased vascular permeability (4), alterations in erythrocyte velocity (5), sequestration of leukocytes in the microcirculation (5-7), and morphological alterations such as altered vascular density (5). These alterations are mainly described as the result of hyperglycemia and advanced glycation end products (8,9) and develop sequentially. Functional alterations, such as increased microvascular permeability and increased entrapment of leukocytes, have been described as an early event in diabetes and in animal models and could be partially observed after only a few hours of hyperglycemia (4,7). Morphological alterations, such as altered microvascular density and diameter, appear later (5,10). However, mechanisms that lead to microangiopathies in diabetic patients remain only partially understood.Monitoring of microcirculatory alterations in patients is limited by the invasive chara...

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Background: The processes of osteogenesis, bone remodelling, fracture repair and metastasis to bone are determined by complex sequential interactions involving cellular and microcirculatory parameters. Consequently studies targeting the analysis of microcirculatory parameters on such processes should mostly respect these complex conditions. However these conditions could not yet be achieved in vitro and therefore techniques that allow a long-term observation of functional and structural parameters of microcirculation in bone in vivo at a high spatial resolution are needed to monitor dynamic events, such as fracture healing, bone remodelling and tumor metastasis.Methods: We developed a bone chamber implant (femur window) for long-term intravital microscopy of pre-existing bone and its microcirculation at an orthotopic site in mice preserving the mechanical properties of bone. After bone chamber implantation vascular density, vessel diameter, vessel perfusion, vascular permeability and leukocyte-endothelial interactions (LEIS) in femoral bone tissue of c57-black mice ( n = 11) were measured quantitatively over 12 days using intravital fluorescence microscopy. Furthermore a model for bone defect healing and bone metastasis in the femur window was tested.Results: Microvascular permeability and LEIS showed initially high values after chamber implantation followed by a significant decrease to a steady state at day 6 and 12, whereas structural parameters remained unaltered. Bone defect healing and tumor growth was observed over 12 and 90 days respectively. Conclusion:The new femur window design allows a long-term analysis of structural and functional properties of bone and its microcirculation quantitatively at a high spatial resolution. Altered functional parameters of microcirculation after surgical procedures and their time dependent return to a steady state underline the necessity of long-term observations to achieve unaltered microcirculatory parameters. Dissection of the complex interactions between bone and microcirculation enables us to evaluate physiological and pathological processes of bone and may give new insights especially in dynamic events e.g. fracture healing, bone remodeling and tumor metastasis.

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Functional and morphological properties of tumor microcirculation play a pivotal role in tumor progression, metastasis and inefficiency of tumor therapies. Despite enormous insights into tumor angiogenesis in solid tumors, little is known about the time-course-dependent properties of tumor vascularization in hematologic malignancies. The aim of this study was to establish a model of myeloid leukemia, which allows long-term monitoring of tumor progression and associated microcirculation. Red fluorescent protein-transduced human leukemic cell lines (M-07e) were implanted into cranial windows of severe combined immunodeficient mice. Intravital microscopy was performed over 55 days to measure functional (microvascular permeability, tissue perfusion rate and leukocyte-endothelium interactions) and morphological vascular parameters (vessel density, distribution and diameter). Tumor progression was associated with elevated microvascular permeability and an initial angiogenic wave followed by decreased vessel density combined with reduced tissue perfusion due to loss in small vessels and development of heterogenous tumor vascularization. Following altered geometric resistance of microcirculation, leukocyte-endothelium interactions were more frequent without increased leukocyte extravasation. It was concluded that time-dependent alterations of leukemic tumor vascularization exhibit strong similarities to those found in solid tumors. The potential contribution to the development of barriers to drug delivery in leukemic tumors is discussed.

These results highlight the complex mechanisms involved during disc degeneration and the need to distinguish between acute and chronic processes as well as different anatomical regions, namely the AF and NP. They also highlight potential problems in disc nucleus replacement therapies because the results suggest a biochemical link between AF and NP cytokine expression.

Mechanisms regulating angiogenesis are crucial in adjusting tissue perfusion on metabolic demands. We demonstrate that overexpression of nerve growth factor (NGF) in brown adipose tissue (BAT) of NGF-transgenic mice elevates both mRNA and protein levels of vascular endothelial growth factor (VEGF) and VEGF-receptors. Increased vascular permeability, leukocyte-endothelial interactions (LEI), and tissue perfusion were measured using intravital microscopy. NGF-stimulation of adipocytes and endothelial cells elevates mRNA expression of VEGF and its receptors, an effect blocked by NGF neutralizing antibodies. These data suggest an activation of angiogenesis as a result of both: stimulation of adipozytes and direct mitogenic effects on endothelial cells. The increased nerve density associated with vessels strengthened our hypothesis that tissue perfusion is regulated by neural control of vessels and that the interaction between the NGF and VEGF systems is the critical driver for the activated angiogenic process. The interaction of VEGF- and NGF-systems gives new insights into neural control of organ vascularization and perfusion.