Incorporation and metabolic conversion of saturated and unsaturated fatty acids in SK-Hep1 human hepatoma cells in culture

Marra, Carlos Alberto; Alaniz, María J. T. de

doi:10.1007/bf00230749

Cited by 35 publications

(31 citation statements)

References 49 publications

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“…Significant decreases were also found in the level of n-6 PUFA, in particular linoleic acid, 18:2 (n-6). Similar results have been previously reported (Marra & Alaniz 1992;Lane et al 2003). Low percentages of n-6 PUFA could be due to the inability of these cells to incorporate linoleic acid present in the medium.…”

Section: Resultssupporting

confidence: 90%

Influence of environmental medium on membrane fatty acid composition of Reuber H35 hepatoma cells

García-Pelayo

Garcia-Peregrin

Martínez-Cayuela

2013

Frontiers in Life Science

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Cell membrane proteins are sensitive to their fatty acid environment; however, the effects of those fatty acids are not completely understood. In this work, we have optimized a model for the study of membrane protein regulation, which allows the investigation of lipid metabolism in cultured tumor cells. The membrane fatty acid composition of Reuber H35 hepatoma cells was modified by enriching phospholipids in individual fatty acids of different length and degree of saturation. Lauric, myristic, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids were supplemented to the culture medium of cells growing in presence or absence of lipoproteins. The four fatty acids were incorporated into membrane phospholipids in a dosedependent manner. Lauric and myristic acids were actively metabolized, increasing percentages of longer and unsaturated chain fatty acids, but they did not modify the unsaturated index. As expected, EPA and DHA significantly decreased the unsaturated index. Incorporation of EPA and DHA was accompanied of a significant decrease of total monounsaturated fatty acids and an increase of total saturated fatty acids. Our results demonstrate that Reuber H35 hepatoma cells constitute a suitable model to manipulate the lipid composition of the cell membranes and perform functionality studies on the membrane proteins in response to their lipid environment.

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Section: Resultssupporting

confidence: 90%

Influence of environmental medium on membrane fatty acid composition of Reuber H35 hepatoma cells

García-Pelayo

Garcia-Peregrin

Martínez-Cayuela

2013

Frontiers in Life Science

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“…In this study, we measured the change in phospholipid composition after supplementation, a net effect of synthesis and incorporation, to evaluate the efficacy of various n-3 substrates in altering membrane fatty acid composition. Previous studies have demonstrated the synthesis of EPA, DPA, and DHA from radiolabeled ALA in HepG2 cells (17,18). In this study, the level of ALA in HepG2 cell phospholipids peaked at 6 h and equilibrated by 48 h, yet the accumulation of its metabolites, EPA and DPA, increased steadily.…”

Section: Discussionsupporting

confidence: 46%

Competition between 24:5n-3 and ALA for Δ6 desaturase may limit the accumulation of DHA in HepG2 cell membranes

Portolesi

Powell

Gibson

2007

Journal of Lipid Research

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The use of #6 desaturase (D6D) twice in the conversion of a-linolenic acid (ALA; 18:3n-3) to docosahexaenoic acid (DHA; suggests that this enzyme may play a key regulatory role in the synthesis and accumulation of DHA from ALA. We examined this using an in vitro model of fatty acid metabolism to measure the accumulation of the long-chain metabolites of ALA in HepG2 cell phospholipids. The accumulation of ALA, eicosapentaenoic acid (20:5n-3), docosapentaenoic acid (22:5n-3), and 24:5n-3 in cell phospholipids was linearly related to the concentration of supplemented ALA over the range tested (1.8-72 mM). The accumulation of the post-D6D products of 22:5n-3, 24:6n-3 and DHA, in cell phospholipids was saturated at concentrations of .18 mM ALA. Supplementation of HepG2 cells with preformed DHA revealed that, although the accumulation of DHA in cell phospholipids approached saturation, the level of DHA in cell phospholipids was significantly greater compared with the accumulation of DHA from ALA, indicating that the accumulation of DHA from ALA was not limited by incorporation. The parallel pattern of accumulation of 24:6n-3 and DHA in response to increasing concentrations of ALA suggests that the competition between 24:5n-3 and ALA for D6D may contribute to the limited accumulation of DHA in cell membranes. The synthesis of long-chain polyunsaturated fatty acids (LCPUFAs) from a-linolenic acid (ALA; 18:3n-3) and linoleic acid (LA; 18:2n-6) is well documented, yet regulation of the pathway, particularly the regulation of the conversion of ALA to docosahexaenoic acid (DHA; 22:6n-3), remains a focus of investigation. This is attributable to the observation that increased dietary intakes of ALA in animals and humans result in an increased level of eicosapentaenoic acid (EPA; 20:5n-3) but little or no change in the level of DHA in tissues or plasma (1-3). Direct measurement of fatty acid synthesis in humans using labeled ALA has demonstrated the conversion of ALA to EPA and docosapentaenoic acid (DPA; 22:5n-3) with limited conversion to DHA (1, 4-6). There are several plausible explanations for the disparity between the intake of ALA and its conversion to DHA in vivo. Ingested ALA has several metabolic fates, including b-oxidation, carbon recycling, conversion to LCPUFA, and direct incorporation into structural lipids (7). The balance between these metabolic fates influences the accumulation of DHA from ALA in tissues. Additionally, both n-3 and n-6 fatty acids use common enzymes in the synthesis of fatty acids; therefore, the competition between n-3 and n-6 fatty acid substrates for these enzymes is an important determinant of DHA synthesis. ALA and LA are both substrates for D6 desaturase (D6D). When both of these substrates are present, there is competition for active sites on D6D, with ALA being the preferred substrate (8). The affinity of D6D for ALA is approximately two to three times that of LA (9). The competition between substrates for D6D also extends to the 24 carbon fatty acids (24:5n-3 and 24:4n-6) a...

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“…This low enzymatic activity may be partially attributed to the fact that these cell lines are from humans in which the A5 desaturase activity is low compared with other species (El Bustani et al, 1986). However, substantial A5-desaturase activity was detected in ZR-75-1 cells ( Figure 5) and in other human hepatoma cells (Marra and Alaniz, 1992). The metabolic pathways for n-6 fatty acids were also demonstrated in a human lung mucoepidermoid carcinoma grown in immunodeficient mice (de Antueno et al, 1988).…”

Section: Discussionmentioning

confidence: 90%

In vivo and in vitro biotransformation of the lithium salt of gamma-linolenic acid by three human carcinomas

Antueno¹,

Elliot²,

Ells³

et al. 1997

Br J Cancer

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Summary Lipid metabolism has been considered recently as a novel target for cancer therapy. In this field, lithium gamma-linolenate (LiGLA) is a promising experimental compound for use in the treatment of human tumours. In. vivo and in vitro studies allowed us to assess the metabolism of radiolabelled LiGLA by tumour tissue and different organs of the host. In vitro studies demonstrated that human pancreatic (AsPC-1), prostatic (PC-3) and mammary carcinoma (ZR-75-1) cells were capable of elongating GLA from LiGLA to dihomo-gamma-linolenic acid (DGLA) and further desaturating it to arachidonic acid (AA). AsPC-1 cells showed the lowest A5-desaturase activity on DGLA. In the in vivo studies, nude mice bearing the human carcinomas were given Li[1-14C]GLA (2.5 mg kg-') by intravenous injection for 30 min. Mice were either sacrificed after infusion or left for up to 96 h recovery before sacrifice. In general, the organs showed a maximum uptake of radioactivity 30 min after the infusion started (t = 0). Thereafter, in major organs the percentage of injected radioactivity per g of tissue declined below 1% 96 h after infusion. In kidney, brain, testes/ovaries and all three tumour tissues, labelling remained constant throughout the experiment. The ratio of radioactivity in liver to tumour tissues ranged between 16-and 24-fold at t = 0 and between 3.1-and 3.7-fold at 96 h. All tissues showed a progressive increase in the proportion of radioactivity associated with AA with a concomitant decrease in radiolabelled GLA as the time after infusion increased. DGLA declined rapidly in liver and plasma, but at a much slower rate in brain and malignant tissue. Seventy-two hours after the infusion, GLA was only detected in plasma and tumour tissue. The sum of GLA + DGLA varied among tumour tissues, but it remained 2-4 times higher than in liver and plasma. In brain, DGLA is the major contributor to the sum of these fatty acids. Data showed that cytotoxic GLA and DGLA, the latter provided either by the host or by endogenous synthesis, remained in human tumours for at least 4 days.

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Incorporation and metabolic conversion of saturated and unsaturated fatty acids in SK-Hep1 human hepatoma cells in culture

Cited by 35 publications

References 49 publications

Influence of environmental medium on membrane fatty acid composition of Reuber H35 hepatoma cells

Influence of environmental medium on membrane fatty acid composition of Reuber H35 hepatoma cells

Competition between 24:5n-3 and ALA for Δ6 desaturase may limit the accumulation of DHA in HepG2 cell membranes

In vivo and in vitro biotransformation of the lithium salt of gamma-linolenic acid by three human carcinomas

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