京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18145号 / 医博第3865号 / 新制||医||1002(附属図書館) / 31003 / 京都大学大学院医学研究科医学専攻 / (主査)教授 萩原 正敏, 教授 柳田 素子, 教授 稲垣 暢也 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20621号 / 医博第4270号 / 新制||医||1023(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 山下 潤, 教授 木村 剛, 教授 渡邉 大 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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The number of people living with diabetes worldwide is continually increasing. The majority of these people will eventually die of cardiovascular disease, the major underlying cause of which is atherosclerosis. Despite the efforts of many researchers, gaps in our knowledge still exist regarding the molecular mechanism(s) linking the two conditions. Current data suggests that the hexosamine biosynthetic pathway (HBP) may have a role in the development of hyperglycemia-accelerated atherosclerosis. About 2-3% of glucose entering a cell is diverted into this pathway where it is modified through a series of reactions to yield the end product, UDP-N-acetylglucosamine (UDP-GlcNAc); a substrate for both N- and O-linked glycosylation of various molecules. N-linked glycosylation occurs in the endoplasmic reticulum (ER) and is an important process in the maintenance of ER homeostasis. We hypothesized that a dysregulation in the HBP can ultimately trigger ER stress – an event associated with the development of atherosclerosis. We have established a method that allows us to monitor levels of UDP-GlcNAc both in cultured cells and mouse tissues through high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS). Using this technique, we’ve shown that both glucosamine supplementation and overexpression of the rate limiting enzyme of the HBP, GFAT, in cultured cells results in elevated UDP-GlcNAc levels. Furthermore, glucosamine was shown to trigger ER stress. In contrast, three GFAT inhibitors that were previously identified in a high throughput screen were shown to decrease UDP-GlcNAc levels and one inhibitor, dehydroiso-β-lapachone, appears to prevent ER stress induction. Finally, we use complementary methods to show that the HBP is augmented in the livers of hyperglycemic mice. This process may play a role in the accelerated development of atherosclerosis. Together, these results provide further insight into the role of the HBP in diabetic atherosclerosis and the established methods provide a platform for the further investigation of this mechanism. / Thesis / Master of Science (MSc)

Prior studies of lipid and lipoprotein levels alterations associated with the administration of danazol, a testosterone derivative, in patients treated for endometriosis have been conflicting. We administered danazol to 7 normal menstruating women and measured plasma lipid and lipoprotein cholesterol levels prior to and 2 months after treatment. Small, non-significant decreases in total plasma cholesterol and triglyceride levels were seen, largely due to a dramatic decline in one woman with type IV hyperlipoproteinemia. No significant change in low density or very low density lipoprotein cholesterol levels was seen. However, a marked (40%) reduction of high density lipoprotein cholesterol level in the mean was found. These findings have implications for the atherogenic potential of danazol, the treatment of hyperlipidemia, and the relationship between gonadal hormones and lipoprotein levels.

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Atherosclerosis is a chronic inflammatory disorder of medium and large vessels. Immune signaling and dyslipidemia are two of several processes which influence lesion development in atherosclerosis. Cannabinoids, such as those found in marijuana, exert their effects through two cannabinoid receptors, CB1 and CB2. Recent studies using CB2 knockout mice and CB2-selective ligands have shed light on a protective role of CB2 in early stages of atherosclerosis. However, the role of CB2 in advanced stages of atherosclerosis remains unclear. To determine if CB2 plays a role in advanced atherosclerotic lesion composition and progression, we investigated the effects of systemic CB2 gene deletion on advanced atherogenesis in Ldlr-null mice fed an atherogenic high fat diet (HFD) for 20-24 weeks. CB2 deficiency did not significantly affect aortic root lesion area, however, CB2-/- mice had a significant increase (~1.9 fold) in the percentage of abdominal aorta surface occupied by lesion. CB2-/- mice also displayed increased lesional macrophage content (~2.3 fold) and an unstable phenotype characterized by significantly reduced smooth muscle cell/macrophage ratio and increased matrix metalloproteinase-9 activity and mineralization. These results suggest that although CB2 does not affect the size of atherosclerotic lesions, it does modulate the cellular and extracellular matrix composition and promotes a stable phenotype. CB2+/+ and CB2-/- mice were also subjected to treatments with either CB2-selective agonist, JWH-015, or antagonist, SR144528, over the last four weeks of a 24 week atherogenic diet to identify the effects of CB2 stimulation on calcification of advanced lesions. No change was observed in body weight or cholesterol in response to either treatment. SR144528 reduced triglycerides and mineralization of aortic root lesions in CB2+/+ mice only. Aortic Runx2 and osteopontin were increased in response to JWH-015 by a CB2-dependent mechanism. Administration of synthetic cannabinoids in an ex vivo organ culture of CB2+/+ aortas revealed increased vascular calcification in response to CB2 blockade and decreased vascular calcification in response to CB2 activation. All together, these results support a protective role for CB2 in late stages of atherosclerosis and suggests that drugs targeting CB2 may be beneficial in the treatment of advanced atherosclerosis by affecting osteogenic mechanisms implicated in the mineralization of lesions.