Caveolae are 50-100 nm invaginations in the plasma membrane. Caveolae and the protein caveolin-1 (Cav1) have been shown to be important in many signaling pathways in different cell types; however, in some cell types caveolae and Cav1 do not seem to affect the investigated signaling pathways. In my thesis, I have investigated the role of caveolin-1 (Cav1) in metabolism and b3-adrenergic, LPA-, EGF- and PDGF-receptor signaling in brown adipocytes. Brown adipose tissue is responsible for nonshivering thermogenesis. Recent studies have shown that not only infants but also adult man can have brown adipose tissue and that the presence is negatively correlated with both obesity and age. By understanding how signaling for proliferation and differentiation in brown adipocytes is regulated, it could be possible in the future to activate brown adipose tissue to combat obesity and the metabolic syndrome. In brown adipocytes, both epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) were able to induce proliferation, which was dependent on Erk1/2 activation. However, EGF and PDGF utilized different pathways to activate Erk1/2, with EGF signaling partially occurring via a Src-pathway (not involving PI3K/PKC) and PDGF via a PI3K/PKC/Src-pathway. Furthermore, LPA receptors were able to activate Erk1/2 via two pathways, one Gi/PKC/Src-pathway and one PI3K-pathway. For these receptors, Cav1-ablation did not affect the agonist-induced Erk1/2 activation. Cav1 was, however, required for proper b3-adrenergic receptor (b3-AR) signaling to cAMP and for adenylyl cyclase activity. In Cav1-ablated mice, the adrenergic receptors are desensitized. However, this desensitization could be overcome physiologically, and the Cav1-ablated mice were therefore able to survive in prolonged cold by nonshivering thermogenesis. In conclusion, ablation of Cav1 affected certain signaling pathways in brown adipocytes, while other pathways were not affected or could be physiologically rescued. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.

This thesis is focused on the role of mitochondria in pancreatic β-cells and brown adipose tissue (BAT). Two main aspects of mitochondria were explored; mitochondrial functional efficiency and the interrelationship between mitochondrial shape and function. Mitochondria in β-cells were found to exhibit heterogeneity in mitochondrial membrane potential. This functional diversity decreased when cells were challenged with glucose stimuli, suggesting that at higher fuel levels low-activity mitochondria are recruited into a pool of high-activity mitochondria. Glucolipotoxic conditions increased the functional diversity suggesting that this may be of importance for diabetes pathophysiology. To examine mitochondrial efficiency in intact islets a high throughput islet respirometry method was developed. Due to increased uncoupling, islets from a diabetic animal model exhibit lower respiratory efficiency. Glucose, free fatty acids and amino acids all decreased respiratory efficiency. A large portion of the respiratory efficiency was mediated by reactive oxygen species and the adenine nucleotide translocase. In β-cells mitochondria were found to undergo cycles of fusion and fission. During glucolipotoxicity mitochondria fragmented and lost their fusion ability. Knock down of the fission protein Fis1 rescued the β-cells from glucolipotoxic induced cell death. BAT mitochondria also showed fusion and fission. The mitochondrial dynamics proteins Mfn2 and Drp1 were shown to strongly affect BAT mitochondrial morphology. In response to a combination of adrenergic and free fatty acid stimuli mitochondria drastically changed from long filamentous structures to fragmented spheres. Inhibiting fission by the negative form of Drp1 decreased BAT response to adrenergic stimuli by half. In conclusion, mitochondrial efficiency may be of importance for normal as well as compromised β-cell and islet function. Mitochondrial morphology appears critical for mitochondrial function in β-cells and BAT. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Adipose tissue volume and distribution is related to metabolic diseases such as diabetes and atherosclerosis. This relationship is in focus for much research, much due to a worldwide increase in obesity. It is in many cases of interest to calculate the amount of adipose tissue in different compartments within the body. Commonly used methods are however prone to introduce errors due to partial volume effects. Previous studies have successfully segmented three adipose tissue compartments from abdominal two-point Dixon fat-water MRI volumes using Morphon registration and atlas segmentation. This thesis extends upon the previous work by enabling segmentation of whole-body MRI volumes and by improving the registration with the use of both fat and water data. Possible methods for bone marrow segmentation are also tested and evaluated. The methods presented seem to be sufficient for creating whole-body volumes from a set of smaller volumes. The adipose tissue segmentation was adequate for subjects with relatively small volumes of adipose tissue, whereas segmentation of subjects with large amounts of adipose tissue require further improvement. Of the evaluated methods for bone marrow segmentation one seemed to perform adequately on all the tested datasets. Due to the few datasets available for testing it was not possible to draw any general conclusions as to how well the presented methods perform.

We hypothesized that slip point of subcutaneous (s.c.) adipose tissue lipids would predict beef carcass quality. To address our hypothesis, 79 M. longissimus dorsi (LD) steaks from cattle of unknown background were used to provide information on slip points, percentage intramuscular lipid, fatty acid composition, and MUFA:SFA ratios. Overlying s.c. adipose tissue was separated from the muscle lean, which contained intramuscular (i.m.) adipose tissue. Lipids were extracted from s.c. adipose tissue and muscle lean by a modified chloroform:methanol procedure and subjected to various analyses. The hypothesis was tested by developing regression equations to determine which fatty acid variables were most useful in predicting carcass composition. There was a high correlation between s.c. MUFA:SFA ratio and s.c. slip points (P < 0.001) with an R2 of 0.557. Also, the MUFA:SFA fatty acid ratios of s.c. and i.m. adipose tissue were significantly correlated and an R2 of 0.440 was observed (P < 0.001) when regressed against each other. The current data set observed s.c. MUFA:SFA ratios (0.73) lower than previous studies, which suggests a population of young or unfinished cattle. This study demonstrated that it is possible to predict the intramuscular lipid (IML) MUFA:SFA ratio by measuring s.c. slip point (R2 of 0.097; P < 0.01). However, our hypothesis of predicting amount of marbling, hence quality grade, from the melting temperature of s.c. adipose tissue lipids proved incorrect (R2 = 0.001). Nonetheless, these data indicate that LD fatty acid composition can be estimated by measuring s.c. adipose tissue slip point.

No description available.

ABSTRACT Background: Developmental exposure to endocrine disrupting chemical (EDC), such as Bisphenol A (BPA) has been shown to affect the health during early stages in life. Aim: To assess whether developmental low-dose exposure to BPA alters adipocyte distribution and blood lipid levels in Fischer 344 (F344) rats. Method: Pregnant F344 rats were exposed to BPA via their drinking water from gestational day 3.5 throughout lactation. Doses given were one below the current European Food Safety Authority´s preliminary tolerable daily intake (TDI) of 4 µg BPA/kg bw/day, 0.5 [lower dose, Ld] and one equal to the previous TDI; 50 [higher dose, Hd] µg BPA/kg bw/day. Half the offspring was sacrificed at 5, and half at 52 weeks of age. Body weight was registered, and plasma lipid levels were analyzed. Inguinal white adipose tissue (iWAT) was weighed, Oil red O-stained and analyzed histologically. Results: Five-week-old Ld males and females Hd exhibited significantly higher triglyceride levels (31%, p&lt;0.01; 41%,p&lt;0.05, respectively) compared to control. Total cholesterol was borderline significantly increased (9%, p=0.0554) in 5-week-old Ld males, compared with control. Adipocyte cell density in the 5-week-old offspring was significantly increased; Ld female rats had increased cell density compared to control and Hd (22% and 23%,p&lt;0.05, respectively), whereas the cell density of Hd males increased compared to Ld (29%, p&lt;0.05). In the 52-week-old offspring blood lipid levels and iWAT cell density were not significantly affected. Conclusions: Results of the present study supports that developmental low-dose BPA exposure contributes to elevated triglyceride levels in 5-week-old animals.

Temperature dependent optical properties of lipid tissue verify critical information of tissue dynamics which can be applied to tissue treatment and diagnosis of various pathological features. Current methods of treating lipid rich tissues via heating are associated with post operation complications. Recent studies shows potential of lipid rich tissue removal by cooling. For monitoring cooling procedure and physical and chemical changes in lipid tissue, temperature dependent optical properties in subzero cooling need to be verified. This study designed heat transfer system estimating heat flux by cooling and programmed codes for image and data processing to obtain refractive indices of rodent subcutaneous lipid tissue. Phase transition of lipid tissue was observed and finally verified temperature dependent refractive index coefficient of lipid tissue from 24°C to -10°C. / text

No description available.

It would be a great advantage in reconstructive surgery to have an off-the-shelf biomaterial to promote regeneration and volume augmentation following soft tissue damage. With this long-term objective, human adipose tissue (fat) is an abundant and accessible source of extracellular matrix (ECM) for bioscaffold fabrication. The main goal of the current research project was to optimize the established 5-day detergent-free decellularization protocol developed by the Flynn group, by shortening it to a maximum of 3 days, while achieving comparable results in terms of cell and lipid extraction with preservation of the ECM. The effectiveness of the optimized protocol was assessed by examination of the decellularized adipose tissue (DAT) and its characteristic biological properties, including in vitro bioactivity assays with human adipose-derived stem cells (ASCs) to measure adipogenic potential, as well as in vivo testing of scaffold biocompatibility. In the optimized approach, the addition of mechanical processing steps including repeated pressing and centrifugation were shown to enhance cell extraction. Fibrous ultrastructure was observed under scanning electron microscopy (SEM) for the original and optimized protocols. The preservation of collagen fibres was assessed with picro-sirius red staining and confirmed by high hydroxyproline content. Enhanced preservation of glycosaminoglycans (GAGs) was determined for the optimized protocol. Residual DNA content was higher in the DAT scaffolds processed with the optimized protocol, including larger DNA fragments that were not typically observed in the samples treated with the original protocol, which incorporated additional enzymatic treatment stages with DNase, RNase and lipase. However, no residual nuclei were visualized through DAPI staining for both protocols. Enhanced removal of DNA was achieved with electron beam (e-beam) sterilization. E-beam sterilization caused some changes in the fine fibrous structure of the ECM, but did not negatively affect the adipo-conductive potential in vitro. In comparison to the original protocol, DAT produced via the optimized protocol exhibited similar adipo-conductive properties in vitro. The in vivo biocompatibility study over a 16 week period using an immunocompetent Wistar rat model showed promising results. DAT implants produced with the original and optimized protocols promoted adipogenesis and angiogenesis, gradually being remodelled to resemble mature adipose tissue. / Thesis (Master, Chemical Engineering) -- Queen's University, 2014-01-30 12:25:22.044

No description available.