Bis(monoacylglycero)phosphate (BMP), a Novel Macrophage Associated Phospholipid

Abstract

Bis(monoacylglycero)phosphate, BMP, is a negatively charged glycerol-phospholipid with an unusual sn-1;sn-1’ structural configuration. BMP is primarily enriched in endosomal/lysosomal membranes. BMP is thought to play a role in glycosphingolipid degradation and cholesterol transport. It constitutes only about 1-2% of the total phospholipids in most mammalian cells, but is abundant in lung alveolar macrophages where it can comprise up to 16% of the total phospholipids. BMP also accumulates in tissues of humans and animals with lysosomal storage disorders. However, little information is available on BMP levels in gangliosidosis brain tissue. In this work, I found that total BMP content was significantly greater in cells of macrophage/microglial origin than in cells of macroglial origin (astrocyte, oligodendrocyte progenitor), whether normal or tumorigenic. I also observed that BMP in brain was significantly greater in humans and in animals (mice, cats, American black bears) with either GM1 or GM2 ganglioside storage diseases, than in brains of normal subjects. Since BMP is associated with macrophages, I also analyzed the BMP levels in relation to disease-associated inflammation in gangliosidoses. I found that BMP levels were increased due to accumulation of primary storage material gangliosides, rather than an outcome of disease-associated inflammation. In addition, in this thesis I also explored the effect of new ketogenic diet formula from Solace Nutrition (KetoGen) on the growth and metastatic spread of the VM-M3 tumor. Most current drug therapies for cancer are toxic and only marginally effective in providing long-term management. Respiratory insufficiency with compensatory aerobic fermentation (Warburg effect) is the hallmark biochemical phenotype of nearly all neoplastic cells within tumors. Calorie restriction, which lowers blood glucose and elevates ketone bodies, is known to reduce tumor growth to a certain extent, however it does not reduce systemic metastasis. Tumor bearing VM mice were fed either a standard lab chow diet in unrestricted amounts (SD-UR), a standard lab chow restricted to obtain an 18% reduction in body weight (SD-R), or the KetoGen diet restricted (KG-R) to match the body weights of the SD-R group. Tumor size was significantly smaller and organ metastasis was significantly less in the KG-R group than in the SD-UR or SD-R groups. Even though blood glucose was reduced similarly in both the SD-R and KG-R groups, blood ketones were 3-fold higher in the KG-R group than in the SD-R group. These results show that VM-M3 tumor growth and systemic metastasis were managed better with the restricted KetoGen KD than with calorie restriction of a high carbohydrate standard diet. As all human and mouse tumors cells suffer from respiratory insufficiency, my findings suggest that the restricted KetoGen diet should be an effective non-toxic therapy against tumor growth and systemic metastatic cancer.