Lipid metabolism inTrichuris globulosa(Nematoda)

Abstract

Adult males and females ofTrichuris globulosa, an intestinal nematode parasite of goats, were studied for their lipid composition, capability of incorporation of (Na)-1-14C-acetate into different lipid classes and the activity of certain key enzymes of lipid metabolism. The parasite possesses a large variety of lipids including certain complex lipids. These are phosphatidylcholine (PC), diphosphatidylglycerol (cardiolipin), lysophosphatidylcholine (LPC), lysophosphatidylethanolamine (LPE), phosphatidylserine (PS), phosphatidylinositol (PI), plasmalogens (choline+ethanolamine), mono-, di- and triacylglycerols, free and esterified cholesterol, non-esterified fatty acids (NEFA), gangliosides, cerebrosides (glycosyl ceramide) and sulphuric acid esters of cerebrosides (sulphatides). The females contain more lipids than males, particularly the acylglycerols and phospholipids, possibly to meet the energy requirement and structural entities for the daily production of large numbers of eggs. Incorporation studies of labelled substrate, sodium-1-14C acetate demonstrate that the adult female has extremely active mechanisms for biosynthesizing these lipids. Most of the labels are found in PC, PE, SM, acylglycerols, NEFA, gangliosides, cerebrosides and sulphatides. Cholesterol, although a minor component of the parasitic lipids, incorporates large amount of label and also undergoes fast turnover. Kinetic analysis of the incorporation by measuring the rate constant (k) and half life (t½) reveals that gangliosides are the fastest biosynthesizing and turning over lipids, although they constitute only 0·1% of the total lipids. The presence of important enzymes of lipid biosynthesis, glucose-6-phosphate dehydrogenase, malate dehydrogenase and hydroxymethyl glutaryl-CoA reductase and an enzyme of lipid ester hydrolysis, triacylglycerol lipase, is also established inT. globulosa. Michaelis-Menten kinetic characteristics of the parasitic enzymes (Km, Vmax, v and the first order rate constant, k) are comparable with those of rat liver homogenates.

Gene expression analysis distinguishes tissue-specific and gender-related functions among adult Ascaris suum tissues

“…Thus, specific functions were identified that may differ between intestinal tissues of the sexes. From whole worm studies, female worm associated lipid transport functions were also reported in Trichuris globulosa (Sarwal et al 1989). …”

Variation in lipid and fatty acid uptake among nematode and cestode parasites and their host, domestic fowl: host–parasite interaction

“…These variations might occur due to the availability of food materials, which is influenced by the food habit of the host, in the different microhabitat of the parasites. Key enzymes of lipid biosynthesis have been observed in Haemonchus contortus (Kapur and Sood 1987), Trichuris globulosa (Sarwal et al 1989) and A. galli (Aggarwal et al 1989). A. galli, being capable of synthesizing lipids into other forms, absorbs less TL than cestode.…”

Understanding chronic nematode infections: Evolutionary considerations, current hypotheses and the way forward

“…Consequently it would not be surprising to discover that some parasitic nematode lineages have evolved the pathways necessary to produce host-metabolism regulating molecules from steroids and/or other precursors. Lipid metabolism has been documented in Trichurisglobulosa (see Sarwal, Sanyal& Khera, 1989) and 0. gibsoni (see Maloney & Semprevivo,199 Korant & Knight, 1986). It is conceivable (although we concede highly speculative at this stage) that nematode parasites have evolved similar molecules through which they might downregulate host immunity.…”