Microvascular dysfunction is believed to precede the development and contribute to the progression of obesity related diseases such as insulin resistance, hypertension, and coronary artery disease. Multiple studies have found impaired microvascular endothelium-dependent vasodilation occurs prior to the onset of disease in middle aged adults. In order to test the hypothesis that the cutaneous microvasculature of young obese (BMI>30kg/m²), but otherwise healthy, adults would exhibit impaired microvascular response, we recruited 12 obese and 12 lean (BMI<25 kg/m²) individuals. Each group was age-matched and consisted of 5 females and 7 males. Each participant was instrumented with two microdialysis probes inserted in the dermis of the non-dominant forearm for a wide dose range of infusions of either the endothelium-dependent vasodilator methacholine (MCh) or the endothelium-independent vasodilator sodium nitroprusside (SNP). Each microdialysis site was clamped at 33°C with a local heater and affixed with a laser Doppler flux (LDF) probe for determination of local red blood cell flux, an index of blood flow. LDF was recorded continuously while 7 doses of each drug (MCh: 10⁻³-10³mM; SNP: 5x10⁻⁵-50mM) were infused at a rate of 2 [mu]l/min for 8 minutes per dose. Both sites finished with heating to 43°C and infusion of 50mM SNP to confirm site specific maximal vasodilation. Blood pressure was recorded in the last minute of each stage and the corresponding LDF was used to calculate cutaneous vascular conductance (CVC). Dose response curves for CVC at each dose, as well as maximal CVC were analyzed. MCh dose response showed a trend toward endothelium–dependent impairment in obese (p=0.06) and maximal absolute CVC at the MCh site was attenuated in obese versus lean (2.70 ± 0.73 vs 3.30 ± 0.81 LDF/mmHg, p=0.027). Endothelium-independent vasodilation with SNP was impaired at the 4 highest doses of SNP (all P<0.006) and maximal CVC was attenuated in obese compared to lean (2.44 ± 0.74 vs 3.31 ± 0.65 LDF/mmHg, p=0.004). These results support the hypothesis that microvascular function is impaired in young, healthy obese, individuals; however they suggest the impairment is partially endothelium-independent. / text

In systemic sclerosis (SSc), interstitial lung disease (ILD) and engagement of the vascular system lead to increased morbidity and mortality. The aim of this thesis was to elucidate, in a consecutively included cohort of SSc (limited and diffuse) patients (n = 33), the T cell cytokine profile driving the disease in ILD and to explore the role of matrix metalloproteinase 9 (MMP-9) and its inhibitor: tissue inhibitor of metalloproteinase 1 (TIMP-1) in the extracellular matrix (ECM) degrading process leading to fibrous scarring and honey combing. Moreover, to characterize the role of nitric oxide (NO) in vascular engagement. Peripheral arterial changes cause Raynaud’s phenomenon and digital ulcers. Nitric oxide (NO) a main inducer of vasodilation is produced by endothelial nitric oxide synthase (eNOS) in response to changes in blood flow or by inflammatory cytokine inducible (i) NOS. In the vascular smooth muscle cell (VSMC) NO activates guanylate cyclase to produce cGMP, causing relaxation. We showed elevated plasma nitrate, a degradation product of NO, and increased urinary excretion of nitrate and cGMP. Plasma nitrate correlated with elevated levels of endothelial adhesion molecules: endothelial (E) selectin and vascular adhesion molecule 1, indicating that the activated endothelium is the site of NO synthesis by iNOS. Endothelial staining for E-selectin and the finding of iNOS and eNOS in SSc skin biopsies supported this notion. In SSc increased vascular stiffness may limit the NO vasodilatory effects. We found normal endothelium-dependent (i.e. flow mediated (FMD%)) and endothelium-independent (i.e. nitroglycerin-induced (NTG%)) vasodilation in the brachial artery. Radial arterial wall stiffness measured as maximum increase in pulse pressure (dP/dtmax) was increased. FMD% and especially NTG% correlated negatively and dP/dtmax positively to measures of endothelial inflammation: plasma- nitrate and adhesion molecule levels. Thus inflammatory vascular wall changes may interfere with dilation as may the presence of nitrate tolerance. We found elevated alveolar MMP-9 in both its pro- and active form in ILD. The levels correlated to decline in lung capacity, pointing at a causal relation. We suggest that neutrophils secrete MMP-9, which may degrade collagen IV, (the main constituent of basal membranes), collagen V, gelatins, proteoglycans and elastin. MMP-9 activity is partly regulated by the binding of pro- and active form to TIMP-1. Alveolar TIMP-1, which even stimulates fibroblast ECM synthesis, was increased independent of ILD. The inflammatory process in ILD is orchestrated by activated T helper (h) lymphocytes. We found a mixed Th1/Th2 reaction in SSc alveolar T cells expressing messenger for interferon gamma (Th1), IL-6 and IL-10 (both Th2). No particular cytokine mRNA profile distinguished alveolar T cells in ILD. Neutrophils invaded the bronchial epithelium, which seemed otherwise inert as levels of inflammatory cytokine sensitive transcription factors and their nuclear translocation tended to be low. The neutrophil recruitment pathway is uncertain as chemoattractants and endothelial adhesion molecules were normally expressed. In conclusion, MMP-9 probably causes degradation of lung tissue in ILD and may represent a future therapeutic target. Alveolar T cells show a mixed Th1/Th2 cytokine profile independent of ILD. Neutrophils invade the bronchial epithelium. Activated endothelium produces increased amounts of NO and adhesion molecules and the level of activation influences brachial arterial FMD% and NTG% and radial arterial compliance. Nitrate tolerance may be present.