| Giardia lamblia: incorporation of free and conjugated fatty acids into glycerol-based phospholipids. | |
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MedLine Citation:
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PMID: 10329359 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Giardia lamblia trophozoites are flagellated protozoa that inhabit the human small intestine, where they are exposed to various dietary lipids and fatty acids. It is believed that G. lamblia, which colonizes a lipid-rich environment of the human small intestine, is unable to synthesize phospholipids, long-chain fatty acids, and sterols de novo. Therefore, it is possible that this protozoan has developed a special process for acquiring lipids from its host. We have previously shown that G. lamblia can take up saturated fatty acids and incorporate them into phosphatidylglycerol (PG) and other glycerol-based phospholipids (Stevens et al., Experimental Parasitology, 86, 133-143, 1997). In the present study, an attempt has been made to investigate the underlying mechanisms of transesterification and interesterification reactions of giardial phospholipids by free and conjugated fatty acids. Results show that exogenously supplied, unsaturated, fatty acids were taken up by Giardia and incorporated into various phosphoglycerides, including PG. To test whether this intestinal pathogen can utilize conjugated fatty acids, live trophozoites were exposed to either [3]H;cbphosphatidylcholine (PC), where the fatty acid was 3H-labeled at its sn2 position, or to [14C]lyso-PC (fatty acid was 14C-labeled at the sn1 position) for 90 min, followed by phospholipid analysis using thin-layer chromatography. The results suggest that conjugated fatty acids, like free fatty acids, were incorporated into PG. It was also observed that aristolochic acid, an inhibitor of Ca2+-ionophore-stimulated phospholipase A2, decreased the transfer of fatty acids from [3H]PC to PG, indicating that giardial phospholipases were involved in these esterification reactions. Additional experiments, which include culturing trophozoites in serum-supplemented and serum-deprived medium, along with numerous biochemical analyses suggest that (i) PG is a major transesterified and interesterified product, (ii) it is likely that giardial phospholipases are involved in esterification reactions, (iii) in G. lamblia, PG is localized in perinuclear membranes, as well as intracellularly, but not in the plasma membrane, and (iv) various synthetic analogs of PG inhibit the growth of the parasite in vitro. These studies suggest that PG is an important phospholipid of Giardia and a potential target for lipid-based chemotherapy against giardiasis. |
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Authors:
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G R Gibson; D Ramirez; J Maier; C Castillo; S Das |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: Experimental parasitology Volume: 92 ISSN: 0014-4894 ISO Abbreviation: Exp. Parasitol. Publication Date: 1999 May |
Date Detail:
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Created Date: 1999-05-28 Completed Date: 1999-05-28 Revised Date: 2007-11-14 |
Medline Journal Info:
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Nlm Unique ID: 0370713 Medline TA: Exp Parasitol Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 1-11 Citation Subset: IM |
Copyright Information:
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Copyright 1999 Academic Press. |
Affiliation:
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Department of Biological Sciences, University of Texas, El Paso, Texas 79968-0519, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Chromatography, High Pressure Liquid Chromatography, Thin Layer Esterification Fatty Acids / metabolism* Fatty Acids, Nonesterified / metabolism Giardia lamblia / drug effects, growth & development, metabolism* Microscopy, Confocal Microscopy, Fluorescence Phosphatidylglycerols / metabolism, pharmacology Phospholipids / metabolism* |
| Grant Support | |
ID/Acronym/Agency:
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AI 136597/AI/NIAID NIH HHS; GM 08012/GM/NIGMS NIH HHS; RR 08124/RR/NCRR NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Fatty Acids; 0/Fatty Acids, Nonesterified; 0/Phosphatidylglycerols; 0/Phospholipids |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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