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Leukemia cells in the bone marrow (BM) must meet the biochemical demands of increased cell proliferation and also survive by continually adapting to fluctuations in nutrient and oxygen availability. Thus, targeting metabolic abnormalities in leukemia cells located in the BM is a novel therapeutic approach. In the present study, we investigated the metabolic role of BM adipocytes in supporting the growth of leukemic blasts. Prevention of nutrient starvation-induced apoptosis of leukemic cells by BM adipocytes, as well as the metabolic and molecular mechanisms involved in this process, were investigated using various analytical techniques. In acute monocytic leukemia (AMoL) cells, the prevention of spontaneous apoptosis by BM adipocytes was associated with an increase in fatty acid β-oxidation (FAO) along with the upregulation of PPARγ, FABP4, CD36, and BCL2 genes. In AMoL cells, BM adipocyte co-culture increased adiponectin receptor gene expression and its downstream target stress response kinase AMPK, p38 MAPK with autophagy activation, and upregulated antiapoptotic chaperone heat shock proteins. Inhibition of FAO disrupted metabolic homeostasis, increased reactive oxygen species production, induced the integrated stress response mediator ATF4, and apoptosis in AMoL cells co-cultured with BM adipocytes. Our results suggest that BM adipocytes support AMoL cell survival by regulating their metabolic energy balance, and that the disruption of FAO in BM adipocytes may be an alternative, novel therapeutic strategy for AMoL therapy.

Both receptor-mediated and diffusional processes have been proposed as mechanisms for the efflux of cellular cholesterol to plasma. The depletion of a minor high-density lipoprotein subfraction (pre beta-1-HDL) from plasma by incubation was associated with a proportional reduction in up to 58% of cholesterol and lecithin efflux from cultured fibroblasts. Pre beta-HDL-dependent efflux was blocked by protease pretreatment of the cells, while residual ("nonspecific") efflux was protease-insensitive. The whole of cholesterol efflux from blood erythrocytes was both pre beta-1-HDL-and protease-independent. These data suggest that two distinct pathways contribute to total efflux from fibroblast monolayers; one of these is directly proportional to plasma pre beta-1-HDL concentration and may involve a cell-surface protein.

A minor fraction of plasma high-density lipoprotein (pre beta-1 HDL) has been shown to promote cholesterol efflux from peripheral cell membranes [Castro, G. R., & Fielding, C. J. (1988) Biochemistry 27, 25-29]. When isolated native plasma is incubated at 37 degrees C, this fraction is specifically decreased. On the other hand, the level of plasma pre beta-1 HDL is fully protected in the presence of even very low levels of fibroblasts, vascular smooth muscle cells, or macrophages. Blood cells were completely inactive in maintaining plasma pre beta-1 HDL levels in the absence of peripheral cells, even at the relatively high levels present in whole blood. The loss of pre beta-1 observed in isolated plasma was dependent upon lecithin-cholesterol acyltransferase (LCAT) activity. These data suggest that reverse cholesterol transport catalyzed by pre beta-1 HDL, and subsequent LCAT-mediated cholesterol esterification, is directly dependent upon the interaction between this HDL species and competent peripheral cells.

ObjectiveTo determine physicians’ knowledge, awareness and preferences regarding the care of familial hypercholesterolaemia (FH) in the Asia-Pacific region.SettingA formal questionnaire was anonymously completed by physicians from different countries/regions in the Asia-Pacific. The survey sought responses relating to general familiarity, awareness of management guidelines, identification (clinical characteristics and lipid profile), prevalence and inheritance, extent of elevation in risk of cardiovascular disease (CVD) and practice on screening and treatment.ParticipantsPractising community physicians from Australia, Japan, Malaysia, South Korea, Philippines, Hong Kong, China, Vietnam and Taiwan were recruited to complete the questionnaire, with the UK as the international benchmark.Primary outcomeAn assessment and comparison of the knowledge, awareness and preferences of FH among physicians in 10 different countries/regions.Results1078 physicians completed the questionnaire from the Asia-Pacific region; only 34% considered themselves to be familiar with FH. 72% correctly described FH and 65% identified the typical lipid profile, with a higher proportion of physicians from Japan and China selecting the correct FH definition and lipid profile compared with those from Vietnam and Philippines. However, less than half of the physician were aware of national or international management guidelines; this was significantly worse than physicians from the UK (35% vs 61%, p<0.001). Knowledge of prevalence (24%), inheritability (41%) and CVD risk (9%) of FH were also suboptimal. The majority of the physicians considered laboratory interpretative commenting as being useful (81%) and statin therapy as an appropriate cholesterol-lowering therapy (89%) for FH management.ConclusionsThe study identified important gaps, which are readily addressable, in the awareness and knowledge of FH among physicians in the region. Implementation of country-specific guidelines and extensive work in FH education and awareness programmes are imperative to improve the care of FH in the region.

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Abstract-Since the molecular identification of the low density lipoprotein receptor (LDLR), an ever increasing number of related proteins have been discovered. These receptors belonging to the LDLR family are thought to play key roles in lipoprotein metabolism in a variety of tissues, including the arterial wall. We have discovered that the expression of a 250-kDa mosaic LDLR-related protein, which we termed LR11 for the presence of 11 LDLR ligand-binding repeats, is markedly induced in smooth muscle cells in the hyperplastic intima of animal models used for the study of atherosclerosis. Here, we demonstrate that the human LR11, when overexpressed in hamster cells, binds and internalizes 39-kDa receptor-associated protein (RAP), an in vitro ligand for all receptors belonging to the LDLR family. Furthermore, LR11 binds the apolipoprotein E (apoE)-rich lipoproteins, ␤-very low density lipoproteins (VLDLs), with a high affinity similar to that of other members, such as the LDLR and VLDL receptor. RAP and ␤-VLDL compete with each other; however, other serum lipoproteins are not able to inhibit their binding. LR11 shows specific binding of apoE-enriched HDL prepared from human cerebrospinal fluid as well as of ␤-VLDL, suggesting that the apoE content of lipoproteins is most likely important for mediating the high-affinity binding to the receptor. LR11-overexpressing cells are able to internalize and degrade the bound ␤-VLDL; these cells also show increased accumulation of cholesteryl esters when incubated with ␤-VLDL. Incubation for 48 hours with ␤-VLDL of LR11-overexpressing cells, but not of control cells, promotes the appearance of numerous intracellular lipid droplets. Taken together, LR11, a mosaic LDLR family member whose expression in smooth muscle cells is markedly induced in atheroma, has all the properties of a receptor for the endocytosis of lipoproteins, particularly for the incorporation of apoE-rich lipoproteins. Key Words: LDL receptors Ⅲ atherosclerosis Ⅲ smooth muscle cells Ⅲ ␤-VLDL R eceptors belonging to the LDL receptor (LDLR) family are thought to play key roles in lipoprotein metabolism in a variety of tissues, including the arterial wall. [1][2][3][4] Recent extensive histochemical studies have shown that receptors belonging to the LDLR family, as well as scavenger receptors mediating the incorporation of modified lipoproteins such as oxidized LDL, show marked induction of their expression during the formation of atherosclerotic lesions. [5][6][7][8][9] For instance, 1 LDLR family member, the so-called VLDL receptor (VLDLR/LR8), has been shown to be highly expressed in smooth muscle cells (SMCs), macrophages, and endothelial cells in rabbit atherosclerotic lesions. 7-9 Furthermore, VLDLR/LR8 has been shown not to be downregulated during ␤-VLDL-induced foam cell formation in vitro, and overexpression of the receptor in fibroblasts causes excessive lipid droplet accumulation in the transformed cells. 10 We and others have discovered and molecularly characterized a novel, unusually complex, and hi...