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G Ailhaud

Publications and source records attributed to G Ailhaud.

At least 163 records · Page 9Linked to original sources
PubMed1981

Differentiation of ob 17 preadipocytes to adipocytes. Effects of prostaglandin F2alpha and relationship to prostaglandin synthesis.

The adipose conversion of ob 17 preadipose cells can be irreversibly blocked when prostaglandin F2alpha is included post-confluence for a minimum of 24 h in insulin-containing media. Prostaglandins E1 and E2 are inactive. The lack of adipose conversion is accompanied by the maintenance of a fusiform cell shape, by a slow increase in cell number and by a potent rise in de novo prostaglandin synthesis; it is paralleled by the absence of the characteristic phenotypes of adipose conversion. The multiple effects of prostaglandin F2alpha are dose-dependent, with half-maximal concentrations ranging from 10 to 40 nM. The absence of differentiation and the high rate of prostaglandin synthesis in the presence of prostaglandin F2alpha are likely a consequence of a sustained growth, as also observed with other growth-promoting agents (bovine retinal extract and cat serum). Indomethacin, while suppressing endogenous prostaglandin synthesis, is unable to reverse the long-term and multiple effects of prostaglandin F2alpha. Although adipose conversion normally follows a decrease in prostaglandin production (R. Négrel and G. Ailhaud, Biochem. Biophys. Res. Commun. (1981) 98, 768-777), these results indicate that both events can be dissociated.

Adipose Tissue↗
PubMed1981

Lipoprotein lipase and monoacylglycerol lipase activities during maturation of ob17 preadipocytes.

Lipoprotein lipase and monoacylglycerol lipase activities of developing ob17 preadipocytes were assayed through the selective inhibition of the former activity by 0.4% Triton X-100. After confluence both enzymes rose tao a peak activity around 13--15 days which was enhanced in insulin-treated cells. Inclusion of differentiation-blocking agents (bromodeoxyuridine, prostaglandin F2 alpha and bovine retinal extract) in the culture medium led in both enzymes to levels similar to those obtained in exponentially growing cells, in contrast to unspecific monoester hydrolase. Marked changes in the relative proportion of released to intracellular lipoprotein lipase activities were observed during adipose conversion. Our studies indicate that lipoprotein lipase and monoacylglycerol lipase are integral part of the program of differentiation of adipose cells.

Adipose Tissue↗
PubMed1981

Differentiation of ob 17 preadipocytes to adipocytes. Triggering effects of clofenapate and indomethacin.

Conversion of ob 17 preadipocytes to mature adipose cells is accelerated by addition of clofenapate or of indomethacin, in either the absence or presence of insulin. General stimulation of triacylglycerol-pathway enzymes is observed, as well as dramatic increase in endogenous fatty-acid synthesis. This increase is a function of drug concentration and exposure time. In contrast to indomethacin, the continuous presence of clofenapate after the cells reached confluence was required to observe the effects on adipose conversion. Growth of ob 17 fibroblasts in the presence of 5-bromo-2'-deoxyuridine normally prevents their differentiation to adipose cells. Addition of either clofenapate or indomethacin to these cells at confluence overrides this block. The effects of hypolipidemic drugs such as clofenapate observed on a long-term basis in vitro are consistent with the results of studies on adipose tissue in vivo.

Adipose Tissue↗
PubMed1981

Triiodothyronine and adipose conversion of OB17 preadipocytes : binding to high affinity sites and effects on fatty acid synthetizing and esterifying enzymes.

Cells of a preadipocyte clonal line (ob 17) isolated from epididymal fat pad of ob/ob mouse possess high-affinity binding sites for triiodothyronine. A single class of sites was found on growing and early confluent cells (KD 0.14 +/- 0.025 nM ; 5,000 +/- 600 sites per cell). A two-fold increase in the number if T3 binding sites occurs during adipose conversion, with no significant change in KD values. The order of potency of structural analogs to compete with 125I-T3 is in favor of nuclear binding sites. A correlation was obtained 3 between this order of potency and the ability of the analogs, included on a long-term basis to confluent cells, to increase 14 C-acetate incorporation into lipids, suggesting an enhancement of de novo fatty acid synthesis, This hypothesis was supported by increased activity levels of fatty acid synthetase after chronic exposure to 1.5 nM triiodothyronine. Under these conditions activity levels of acid:CoA ligase and glycerol-3-phosphate dehydrogenase were also increased significantly. Inclusion of bromodeoxyuridine as a differentiation-blocking agent in the culture medium of growing cells decreases drastically the T3 effects, favoring the role of the latter hormone as amplifier of specific phenotypes expressed during adipose conversion. These results show that ob17 cell line should be an useful tool to study the role of thyroid hormones in the regulation of fatty acid synthesis and esterification in adipose cells.

Acetates↗
PubMed1980

Sugar transport in chick embryo cardiac cells in culture: analysis by countertransport, relationship to phosphorylation and effect of glucose starvation.

Embryonic chick heart cells in culture transport 2-deoxy-D-glucose and 3-O-methyl-D-glucose very rapidly. By direct measurements of uptake, it was not possible to estimate accurately transport rates, nor, with 2-deoxyglucose, to discriminate clearly between its transport and phosphorylation. In contrast, the technique of countertransport made it possible to determine precisely initial transport velocity and to make the following observations: (1) phosphorylation, and not transport, is rate-limiting in 2-deoxyglucose uptake; (2) hexose transport is stimulated 5-fold by removal of glucose from culture medium; and (3) this stimulation is followed by an increase in phosphorylation, but the effect is much less pronounced (2-fold stimulation only). In conclusion, the adaptative regulation of glucose transport described in many fibroblast cell lines exists also in cardiac cells.

Animals↗
PubMed1980

Amino acid and glucose transport in sarcolemmal vesicles from chick embryo heart.

Purified plasma membranes from chick embryo heart are shown to retain several functional properties of intact cardiac cells. (1) Muscarinic cholinergic receptors copurify with previously used cell-surface markers, i.e., (K+-dependent) p-nitrophenylphosphatase and insulin receptors (Paris, S., Fosset, M., Samuel, D. and Ailhaud, G. (1977) J. Mol. Cell. Cardiol. 9, 161-174). (2) Neutral amino acids (L-alanine and alpha-aminoisobutyric acid) are actively transported into these osmotically active vesicles when an Na+ electrochemical gradient is imposed. The affinity and specificity for amino acids are similar to those described for intact cardiac cells. (3) D-Glucose is taken up more rapidly than L-glucose. The sterospecific transport system is saturable and Na+-independent. The Km value is close to that observed in intact cells with glucose analogues.

Alanine↗
PubMed1979

Differentiation of ob 17 preadipocytes to adipocytes. Effect of insulin on the levels of insulin receptors and on the transport of alpha-aminoisobutyrate.

Cells of a clonal cell line (ob 17) isolated from the epididymal fat pad of ob/ob mouse possess insulin receptors. Their number was increased 1.5-fold after growth arrest, with no significant change in the Kd values of the "high affinity" sites determined by extrapolation of the high affinity portion of the curvilinear Scatchard plots. With chronic insulin exposure for 3 to 11 days after confluence, ob 17 cells showed a decrease in insulin receptor concentrations from 8,000 to 1,600 high affinity sites/cell (Kd from 0.45 to 1.10(-9) M) while similar levels of "low affinity" sites were found (80,000 to 100,000 sites/cell; Kd from 10(-8) to 3 x 10(-8) M). The loss of the high affinity binding sites is accompanied by the disappearance of the stimulatory effect by insulin of alpha-aminoisobutyrate uptake. Therefore, in contrast to 3T3-L1 fibroblasts, the ob 17 cells present, in culture, a self-modulation of insulin receptors and a loss of insulin sensitivity after chronic exposure to insulin.

Adipose Tissue↗
PubMed1979

Uptake of fatty acids by cultured cardiac cells from chick embryo: evidence for a facilitation process without energy dependence.

Cultured heart cells from chick embryo accumulate fatty acids up to 50 fold at a steady-state level under defined conditions [ref.1]. Studies of fatty acid uptake as a function of different cellular parameters (intracellular ATP and pH, membrane potential and electrochemical gradients for monovalent and divalent cations) show the lack of effect of these factors. The rate of uptake is temperature-dependent. The maximum velocity V is affected with no change in the Km value of the saturable component; the activation energies were found to be 35.5 kJ.mol-1 for palmitate and 42 kJ.mol-1 for oleate. The results are in favour of a facilitation process which leads to an accumulation of fatty acids without energy dependence. The accumulation of fatty acids could be due to their association to intracellular membraneous and/or cytosolic components.

Acetates↗
PubMed1978

The role of serum albumin in the uptake of fatty acids by cultured cardiac cells from chick embryo.

Fatty acids enter the cultured cardiac cells from chicken embryo through two mechanisms, one involving a saturable process, the other resembling passive diffusion. Studies of the saturable component, at fixed concentrations of palmitate or of oleate and at increasing concentrations of albumin, show that this protein increases the rate of palmitate uptake with a maximum at palmitate/albumin molar ratios between 7 and 10 while it decreases the rate of oleate uptake under all conditions. Albumin cannot be replaced by other serum proteins; its effect is specific to saturated fatty acids, can be mimicked by the detergent Tween 40 and involves the binding of the fatty acid to the protein, prior to its delivery to the cell. Both with labelled saturated and unsaturated fatty acids the presence of albumin lowers the proportion of unesterified fatty acids and enhances the proportion of esterified fatty acids recovered in the cardiac cell after uptake. A similar effect of albumin was also found with hepatocytes and permanent cell lines. A specific role for serum albumin is presented, which assumes a 'dispersing' effect of this protein towards dimers (or higher aggregates) of saturated fatty acids and the entry of fatty acids into the cell as monomers.

Animals↗
PubMed1978

Establishment of preadipocyte clonal line from epididymal fat pad of ob/ob mouse that responds to insulin and to lipolytic hormones.

A clonal cell line that responds to insulin and to lipolytic hormones has been established from the epididymal fat pad of the C57BL/6J ob/ob mouse. This line, designated ob 17, has a doubling time of 12.5 or 19 hr in 10% or 1% fetal calf serum, respectively. It presents a heterogeneous chromosome number with 40% of the cells containing 35-44 chromosomes and expresses the characteristic H2-LA antigen. After cessation of growth, ob 17 cells accumulate droplets of triglycerides; this accumulation occurs to a significant extent even in the absence of insulin normally added after confluence. Lipoprotein lipase activity is negligible in exponentially growing cells but appears at its maximal level just after confluence with or without insulin. Acid:CoA ligase and acylCoA:diglyceride acyltransferase develop later than lipoprotein lipase. The appearance of lipolytic and lipogenic enzymes, but not of triglycerides, seems to be independent of the presence of lipoproteins or of unesterified fatty acids in the culture medium. Therefore, the differentiation program becomes operative when growth is arrested, and differentiation occurs, providing a source of exogenous lipids. Differentiated ob 17 cells in which endogenous triglycerides have been prelabeled on the fatty acid moiety do respond to epinephrine and corticotropin by release of radioactive fatty acid. This lipolytic response is counteracted by prior addition of insulin. The ob 17 cell line appears to be a useful model for study of growth and differentiation of adipose cells as compared to preadipocyte cell lines from the nongenetically obese mouse.

Acyl Coenzyme A↗
PubMed1977

Incorporation of a fatty acid containing a photosensitive group into lipids of cultured cardiac cells from chick embryo.

Radioactive 12-(4-azido-2-nitrophenoxy)-stearic acid (NAP-stearate) was synthetized; it behaves as a competitive inhibitor of long-chain fatty acids for the entry into cultured cardiac cells from chick embryo. After uptake, [3H] NAP-stearate was incorporated by an energy-dependent process into neutral and polar lipids. Photoactivation as a function of time leads to a covalent labelling of the cells: up to 31 per cent of the radioactivity was recovered in the 105 000 g cell pellet, mainly in proteins. These experiments show that fatty acids containing photosensitive groups would potentially allow to localize the proteins involved in the binding and/or in the transport of fatty acids.

Animals↗
PubMed1977

Lipolytic activities against trioctanoin and monoolein in rat intestinal mucosa.

The hydrolysis of trioctanoin and of monoolein by rat intestinal homogenates, catalyzed by the previously described "trioctanoin hydrolase" and "monoglyceride lipase" [Ref. 6 and 11], was shown to be entirely due to the action of the intestinal glycerol-ester hydrolase [Ref. 1 and 2] and to contaminating pancreatic lipase firmly bound to the intestinal cells. These conclusions are supported by experiments based on the chromatographic behaviour of the different lipolytic activities, the use of an immunoserum directed against rat pancreatic juice and the relief of bile salt inhibitions by pancreatic colipase. The results are in favour of the existence of a single lipolytic enzyme in the rat intestinal mucosa, i.e. glycerol-ester hydrolase, active against short- and medium chain mono-, di- and triglycerides and against long chain monoglycerides.

Animals↗