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Inflammation plays a central role in stroke-induced brain injury. The alpha7 nicotinic acetylcholine receptor (α7nAChR) can modulate immune responses in both the periphery and the brain. The aims of the present study were to investigate α7nAChR expression in different brain regions and evaluate the potential effect of the selective α7nAChR agonist AR-R17779 on ischemia–reperfusion brain injury in mice. Droplet digital PCR (ddPCR) was used to evaluate the absolute expression of the gene encoding α7nAChR (Chrna7) in hippocampus, striatum, thalamus and cortex in adult, naïve mice. Mice subjected to transient middle cerebral artery occlusion (tMCAO) or sham surgery were treated with α7nAChR agonist AR-R17779 (12 mg/kg) or saline once daily for 5 days. Infarct size and microglial activation 7 days after tMCAO were analyzed using immunohistochemistry. Chrna7 expression was found in all analyzed brain regions in naïve mice with the highest expression in cortex and hippocampus. At sacrifice, white blood cell count was significantly decreased in AR-R17779 treated mice compared with saline controls in the sham groups, although, no effect was seen in the tMCAO groups. Brain injury and microglial activation were evident 7 days after tMCAO. However, no difference was found between mice treated with saline or AR-R17779. In conclusion, α7nAChR expression varies in different brain regions and, despite a decrease in white blood cells in sham mice receiving AR-R17779, this compound does not affect stroke-induced brain injury.

Significance The only known homeostatic regulator of fat mass is the leptin system. We hypothesized that there is a second homeostat regulating body weight with an impact on fat mass. In this study we have added and removed weight loads from experimental animals and measured the effects on the biological body weight. The results demonstrate that there is a body weight homeostat that regulates fat mass independently of leptin. As the body weight-reducing effect of increased loading was dependent on osteocytes, we propose that there is a sensor for body weight in the long bones of the lower extremities acting as “body scales.” This is part of a body weight homeostat, “gravitostat,” that keeps body weight and body fat mass constant., Subjects spending much time sitting have increased risk of obesity but the mechanism for the antiobesity effect of standing is unknown. We hypothesized that there is a homeostatic regulation of body weight. We demonstrate that increased loading of rodents, achieved using capsules with different weights implanted in the abdomen or s.c. on the back, reversibly decreases the biological body weight via reduced food intake. Importantly, loading relieves diet-induced obesity and improves glucose tolerance. The identified homeostat for body weight regulates body fat mass independently of fat-derived leptin, revealing two independent negative feedback systems for fat mass regulation. It is known that osteocytes can sense changes in bone strain. In this study, the body weight-reducing effect of increased loading was lost in mice depleted of osteocytes. We propose that increased body weight activates a sensor dependent on osteocytes of the weight-bearing bones. This induces an afferent signal, which reduces body weight. These findings demonstrate a leptin-independent body weight homeostat (“gravitostat”) that regulates fat mass.

Dietary polyunsaturated fatty acids (PUFA) are suggested to modulate immune function, but the effects of dietary fatty acids composition on gene expression patterns in immune organs have not been fully characterized. In the current study we investigated how dietary fatty acids composition affects the total transcriptome profile, and especially, immune related genes in two immune organs, spleen (SPL) and bone marrow cells (BMC). Four tissues with metabolic function, skeletal muscle (SKM), white adipose tissue (WAT), brown adipose tissue (BAT), and liver (LIV), were investigated as a comparison. Following 8 weeks on low fat diet (LFD), high fat diet (HFD) rich in saturated fatty acids (HFD-S), or HFD rich in PUFA (HFD-P), tissue transcriptomics were analyzed by microarray and metabolic health assessed by fasting blood glucose level, HOMA-IR index, oral glucose tolerance test as well as quantification of crown-like structures in WAT. HFD-P corrected the metabolic phenotype induced by HFD-S. Interestingly, SKM and BMC were relatively inert to the diets, whereas the two adipose tissues (WAT and BAT) were mainly affected by HFD per se (both HFD-S and HFD-P). In particular, WAT gene expression was driven closer to that of the immune organs SPL and BMC by HFDs. The LIV exhibited different responses to both of the HFDs. Surprisingly, the spleen showed a major response to HFD-P (82 genes differed from LFD, mostly immune genes), while it was not affected at all by HFD-S (0 genes differed from LFD). In conclusion, the quantity and composition of dietary fatty acids affected the transcriptome in distinct manners in different organs. Remarkably, dietary PUFA, but not saturated fat, prompted a specific regulation of immune related genes in the spleen, opening the possibility that PUFA can regulate immune function by influencing gene expression in this organ.

Angiotensin II (Ang II) is of importance for a number of physiological processes but also plays an important pathophysiological role in cardiovascular disease. The aim of this thesis was to evaluate the role of Ang II in hypertension-related atherosclerosis and vascular disease and to investigate possible anti-atherosclerotic effects of the angiotensin II, type 2 (AT2) receptor. Interactions with salt intake and with insulin were also investigated. The studies in the current thesis have been performed in rats and genetically modified, atherosclerosis prone mice. The animals have been treated with Ang II, exogenously administered as well as endogenously activated. Animals have also been treated with insulin and/or different dietary manipulations. Interventions in the renin angiotensin system have been performed using antagonists of the angiotensin type 1 (AT1) and AT2 receptors, respectively. We found that both exogenous and endogenous Ang II increased atherosclerosis, however, no evidence for the AT2 receptor to have the suggested anti-atherosclerotic effect. This was true despite an up-regulated AT2 receptor on both mRNA and protein levels and that the major expression site for the AT2 receptor is in the atherosclerotic lesions. The accelerating effect of Ang II on atherosclerosis after endogenous activation is most likely due to its increased blood pressure. High salt diet per se is only mildly atherogenic, however, the combination of Ang II and high salt acts synergistically and increases atherosclerosis to a greater extent compared to Ang II treatment alone. This synergistic effect could be due to an increase in oxidative stress. In the last paper we investigated the in vivo interactions between the renin angiotensin system and insulin in a hyperinsulinemic rat model. This revealed that insulin infusion does not cause hypertension but sensitizes the rats blood pressure to the renin angiotensin system. We found no evidence of sympathoexcitation from insulin and no evidence that hyperinsulinemic rats are hyper-reactive to stressful stimulus. The major conclusions from this thesis are that hyperinsulinemia makes blood pressure control Ang II sensitive. This sensitization may be of importance for vascular damage in diabetes. Ang II accelerates atherosclerosis but the AT2 receptor does not have any anti-atherosclerotic effects. High salt diet does not accelerate atherosclerosis as long as you are able to modulate your renin angiotensin system. However, if the regulation of the renin angiotensin system is defect, for example due to genetics or during stress, high salt diet accelerates atherosclerosis.