Glucocorticoid and mineralocorticoid hormones depress liver delta 5 desaturase activity through different mechanisms

Milk lipid composition is modified by perinatal exposure to bisphenol A

To evaluate whether bisphenol A (BPA) modifies the synthesis, composition and/or profile of fatty acids (FAs) in the mammary glands of perinatally exposed animals, pregnant rats were orally exposed to 0, 0.6 or 52 µg BPA/kg/day from gestation day (GD) 9 until weaning. F1 females were bred, and on GD21, lactation day 2 (LD2) and LD10, mammary glands were obtained. On LD10, milk samples were collected, and FA profiles and lipid compositions were established. On GD21 and LD2, BPA exposure delayed mammary alveolar maturation and modified the synthesis of milk fat globules. On LD10, mammary gland histo-architecture was restored; however, the milk of BPA-exposed F1 dams had a FA profile and lipid concentration different from those of the control milk. Furthermore, the body weight gain of BPA52 F2 pups was increased compared with control animals. Thus, perinatal exposure to BPA modifies milk quality, compromising the normal growth of offspring.

Enteral nutrition with eicosapentaenoic acid, γ-linolenic acid and antioxidants in the early treatment of sepsis: results from a multicenter, prospective, randomized, double-blinded, controlled study: the INTERSEPT study

Introduction

Enteral nutrition (EN) with eicosapentaenoic acid (EPA)/γ-linolenic acid (GLA) is recommended for mechanically ventilated patients with severe lung injury. EPA/GLA has anti-inflammatory benefits, as evidenced by its association with reduction in pulmonary inflammation, improvement in oxygenation and improved clinical outcomes in patients with severe forms of acute lung injury. This study was a prospective, multicenter, randomized, double-blinded, controlled trial designed to investigate whether EPA/GLA could have an effective role in the treatment of patients with early sepsis (systemic inflammatory response syndrome with confirmed or presumed infection and without any organ dysfunction) by reducing the progression of the disease to severe sepsis (sepsis associated with at least one organ failure) or septic shock (sepsis associated with hypotension despite adequate fluid resuscitation). Secondary outcomes included the development of individual organ failure, increased ICU and hospital length of stay, need for mechanical ventilation and 28-day all-cause mortality.

Methods

Randomization was concealed, and patients were allocated to receive, for seven days, either an EPA/GLA diet or an isocaloric, isonitrogenous control diet not enhanced with lipids. Patients were continuously tube-fed at a minimum of 75% of basal energy expenditure × 1.3. To evaluate the progression to severe sepsis and/or septic shock, daily screening for individual organ failure was performed. All clinical outcomes were recorded during a 28-day follow-up period.

Results

A total of 115 patients in the early stages of sepsis requiring EN were included, among whom 106 were considered evaluable. Intention-to-treat (ITT) analysis demonstrated that patients fed the EPA/GLA diet developed less severe sepsis and/or septic shock than patients fed the control diet (26.3% versus 50%, respectively; P = 0.0259), with similar results observed for the evaluable patients (26.4% versus 50.9% respectively; P = 0.0217). The ITT analysis demonstrated that patients in the study group developed cardiovascular failure (36.2% versus 21%, respectively; P = 0.0381) and respiratory failure (39.6% versus 24.6%, respectively; P = 0.0362) less often than the control group. Similarly, when considering only the evaluable patients, fewer patientsdeveloped cardiovascular failure (20.7% versus 37.7%, respectively; P = 0.03) and respiratory failure (26.4% versus 39.6%, respectively; P = 0.04). The percentage of patients fed the EPA/GLA diet requiring invasive mechanical ventilation was reduced compared with controls (ITT patients: 18.9% versus 33.9%, respectively; P = 0.394; evaluable patients: 17.5% versus 34.5%, respectively; P = 0.295). Patients nourished with the EPA/GLA diet remained in the ICU fewer days than the control population (ITT patients: 21.1 ICU-free days versus 14.7 ICU-free days, respectively; P < 0.0001; evaluable patients: 20.8 ICU-free days versus 14.3 ICU-free days, respectively; P < 0.0001) and fewer days at the hospital (ITT patients: 19.5 hospital-free days versus 10.3 hospital-free days, respectively; P < 0.0001; evaluable patients: 19.1 hospital-free days versus 10.2 hospital-free days, respectively; P < 0.001) (all numbers expressed as means). No significant differences in 28-day all-cause mortality were observed (ITT patients: 26.2% EPA/GLA diet versus 27.6% control diet, respectively; P = 0.72; evaluable: 26.4 EPA/GLA diet versus 30.18 control diet, respectively; P = 0.79).

Conclusions

These data suggest that EPA/GLA may play a beneficial role in the treatment of enterally fed patients in the early stages of sepsis without associated organ dysfunction by contributing to slowing the progression of sepsis-related organ dysfunction, especially with regard to cardiovascular and respiratory dysfunction.

Trial Registration

ClinicalTrials.gov: NCT00981877

Effect of cyclosporine and sirolimus on fatty acid desaturase activities in cultured HEPG2 cells

The aim of the present work was to evaluate the influence of cyclosporine (CsA) and sirolimus (SRL) on fatty acid (FA) desaturase activities. These enzymes (named Delta9, Delta6, and Delta5 desaturases) catalyze reactions leading to the biosynthesis of n-9, n-6, and n-3 FA families. n-3 FA family, derived from alpha-linolenic acid, is involved in the prevention of vascular events, which appear after successful kidney transplantation. Five groups of HepG(2) cells in culture were treated with either CsA (1 microg/microL and 2 microg/microL) or SRL (10 ng/mL and 20 ng/mL) for 3 days, including a control group without immunosuppressive treatment. We studied the incorporation and metabolic conversion of radioactive [1-(14)C]palmitic, linoleic, and eicosatrienoic acids. We also analyzed fatty acid composition. The distribution of radioactive metabolic products after incubation of these cells with [1-(14)C]palmitic acid revealed a decrease in Delta9 desaturase activity in the presence of each immunosuppressive drug: CsA = 0.61 +/- 0.01; SRL = 0.59 +/- 0.04 versus control = 0.79 +/- 0.05 (P < .01). We observed a significant increase in Delta6 and Delta5 desaturase activities under the influence of the immunosuppressive drugs: radiolabeled linoleic acid (CsA: 0.93 +/- 0.04; SRL: 1.02 +/- 0.03 vs control 0.60 +/- 0.03; P < .01) and eicosatrienoic acid (CsA: 1.12 +/- 0.02; SRL: 1.07 +/- 0.01 vs control 0.75 +/- 0.01; P < .01). In conclusion, CsA and SRL modulated the biosynthesis of polyunsaturated FAs, decreasing Delta9 desaturase and increasing Delta6 and Delta5 desaturase activities.

Relationship between Plasma Phospholipid Polyunsaturated Fatty Acid Composition and Bone Disease in Renal Transplantation

To investigate the relationship between polyunsaturated fatty acid (PUFA) and bone metabolism in renal transplant patients, plasma phospholipid (PP) PUFA levels, biochemical markers of bone turnover and bone mineral density (BMD) were determined in 22 recipients of a first renal allograft at baseline and after a mean 24.4 month follow-up. A significant increase in PP n-3 PUFA content, in the [n-3 PUFA/ arachidonic acid] ratio and in BMD values was observed, as well as a close correlation between the increase in PP n-3 PUFA content and femoral neck BMD. Multivariate regression analysis showed that BMD improvement was positively related to PP n-3 PUFA variation and baseline PP eicosapentaenoic acid levels, and negatively to PP arachidonic acid modification. Tacrolimus- versus cyclosporine-treated patients demonstrated a significant increase in femoral neck BMD and PP n-3 PUFA content. This is the first longitudinal study showing a link between PP-PUFA composition and bone disease in renal transplantation.

Increased response of liver microsomal delta 6-desaturase activity to dietary methionine in rats

The effects of dietary casein level (5-40%) on the liver microsomal phospholipid profile, delta 6-desaturase activity and related variables were investigated in rats to examine whether the dietary protein level affected the delta 6-desaturase activity through an alteration of the liver microsomal phospholipid profile. The effects of supplementing a 10% casein diet with certain amino acids were also investigated. The concentration of hepatic S-adenosylmethionine (SAM), the ratio of phosphatidylcholine (PC) to phosphatidylethanolamine (PE) and the delta 6-desaturase activity in liver microsomes, and the ratio of arachidonate to linoleate of microsomal PC increased with increasing dietary casein level. There were significant correlations between the dietary methionine content and hepatic SAM concentration, hepatic SAM concentration and microsomal PE concentration, and microsomal PE concentration and delta 6-desaturase activity. Supplementation of the 10% casein diet with methionine significantly increased the hepatic SAM concentration, PC/PE ratio, delta 6-desaturase activity, and arachidonate/linoleate ratio, whereas cystine supplementation had no or little effect on these variables. These increases induced by methionine were significantly suppressed by additional glycine. The results obtained here, together with those in our previous report, suggest that quantity and type of dietary protein might affect the delta 6-desaturase activity through an alteration of the liver microsomal profile of phospholipids, especially PE, and that the alteration of phospholipid profile might be mediated by a hepatic SAM concentration that reflects the dietary methionine level.

Recent advances in molecular cloning of fatty acid desaturase genes and the regulation of their expression by dietary vitamin A and retinoic acid

Vitamin A, as an essential micronutrient, is involved in higher animals in embryonic development and postnatal growth, reproduction and maintenance of normal skin, immunity and vision. Recently, studies in vivo and in cell lines have shown that vitamin A and its active metabolite, retinoic acid, regulate the expression of fatty acid desaturases including stearoyl-CoA desaturase and delta-5 desaturase. Whereas the former desaturase catalyzes the formation of monounsaturated from saturated fatty acids, the latter enzyme is involved in the desaturation pathway of dietary essential fatty acids for production of polyunsaturated fatty acids. The reaction products of these desaturases serve as critical regulators in a wide range of physiological processes which include fetal growth and development, reproduction, cell differentiation, immune and inflammatory responses.

Changes in the fatty acid composition of phospholipids in tissues of farmed sea bass (Dicentrarchus labrax) during an annual cycle. Roles of environmental temperature and salinity

We quantified seasonal effects on fatty acid composition of tissue phospholipids in farmed sea bass. Major changes in percent phosphatidylethanolamine and phosphatidylcholine were observed in all tissues between February and March, and the phosphatidylcholine/phosphatidylethanolamine ratio was drastically reduced at this time. Different changes in the fatty acid composition of total phospholipids were observed in all tissues examined. Fish fed all year on the same commercial diet showed a significant correlation between water salinity and percentage of 22:6n-3 in muscle, liver and gill phospholipids, but no correlation was found between percent 22:6n-3 of phospholipids and water temperature. In each tissue, we observed annual variation in the 20:5n-3/20:4n-6 ratio in phospholipids, but maximum and minimum values occurred at different times in each organ. From these results, we conclude that salinity can play a significant role in modulating the activities of enzymes acting on lipid metabolism during their natural circannual cycles.

Effect of dexamethasone on the fatty acid composition of total liver microsomal lipids and phosphatidylcholine molecular species

Dexamethasone depresses delta6 and delta5 and increases delta9 desaturase and synthase activities. Therefore, we investigated the effect on the fatty acid composition of microsomal liver lipids and phosphatidylcholine (PtdCho) molecular species. After 15 d of treatment we found a notable decrease in arachidonic acid, a small decrease in stearic acid, and increases of linoleic, oleic, palmitoleic, and palmitic acids in liver microsomal total lipids and PtdCho. The study of the distribution of the PtdCho molecular species indicated that 18:0/20:4n-6, 16:0/20:4n-6, and 16:0/18:2n-6 predominated in the control animals. Dexamethasone, as expected because of its depressing effect on arachidonic acid synthesis and activation of oleic and palmitic acid synthesis, evoked a very significant decrease in 18:0/20:4n-6 PtdCho (P<0.001) and an important increase in 16:0/18:2n-6. The invariability of 16:0/20:4n-6 PtdCho could be related to the antagonistic effect of arachidonic and palmitic acid synthesis. PtdCho species containing oleic acid were not significant. The bulk fluidity and dynamic properties of the microsomal lipid bilayer measured by fluorometry using the probes 1,6-diphenyl-1,3,5-hexatriene and 4-trimethylammonium-phenyl-6-phenyl-1,3,5-hexatriene showed no significant modification, probably owing to a compensatory effect of the different molecular species, but changes of particular domains not detected by this technique are possible. However, the extremely sensitive Laurdan detected increased lipid packing in the less-fluid domains of the polar-nonpolar interphase of the bilayer, possibly evoked by the change of molecular species and cholesterol/phospholipid ratio. The most important effect found is the decrease of arachidonic acid pools in liver phospholipids as one of the corresponding causes of dexamethasone-dependent pharmacological effects.

Fatty acid delta(5)-desaturase mRNA is regulated by dietary vitamin A and exogenous retinoic acid in liver of adult rats

Delta(5)-Desaturase (D5D) catalyzes the Delta(5,6) desaturation of dietary essential fatty acids of the n-6 and n-3 series. By subtraction hybridization of vitamin A (VA)-deficient and control rat liver cDNA libraries, we isolated a 106-bp cDNA fragment that proved to be homologous to human liver D5D cDNA and used it as a probe to analyze rat D5D mRNA and clone the rat full-length cDNA. Delta(5)-Desaturase mRNA was threefold more abundant in liver from VA-deficient rats than in liver from VA-sufficient rats and was expressed dose dependently when dietary VA was varied (VA marginal > control > VA supplemented). Treatment of VA-deficient rats with all-trans-retinoic acid lowered the level of expression of D5D mRNA toward that of VA-sufficient rats. The 3413-bp full-length D5D cDNA cloned from rat liver contains an open reading frame of 447 amino acid residues sharing 92% similarity with its human counterpart. Expression of this cDNA in HEK293T cells incubated with dihomo-gamma-linolenic acid (20:3, n-6) resulted in a significantly increased ratio of the product, arachidonic acid (20:4, n-6), to substrate in cell lipid extracts. Delta(5)-Desaturase mRNA is expressed in relatively high abundance in rat adrenal gland and mammary tissue and moderately in liver, kidney, lung, spleen, thymus, brain, and eye. The regulation of D5D by VA could be important for growth and development, and reproduction, as well as in the control of inflammation.

Calcium deficiency modifies polyunsaturated fatty acid metabolism in growing rats

Fatty acid desaturase activities were determined in liver microsomes from calcium-deficient rats and compared to calcium-sufficient ones. The calcium-deprived diet (0.5 g/kg) administered for 60 d caused a 30% inhibition in the delta5 desaturase activity and a 45-55% decrease in delta6 and delta9, respectively, facts that cannot be attributed to a reduction in food intake. In vitro addition of calcium, ethyleneglycol-bis(Beta-aminoethyl ether)N,N-tetraacetic acid, and/or cytosol fractions from control or calcium-deficient rats to microsomes from both groups of animals indicates that the reduced desaturase capacities would be the consequence of an indirect effect of calcium deprivation. The present work shows that the reduced unsaturated fatty acid biosynthesis might be the result of modifications in the physicochemical properties of microsomal membranes. Such changes could also be derived from the inhibition of phospholipase A2 activity induced by calcium deficiency.

Aldosterone alters the phospholipid composition of rat colonocytes

Previous studies have shown that aldosterone treatment of amphibian epithelial cells results not only in stimulation of Na(+) absorption but also in changes in phospholipid composition which are necessary for the mineralocorticoid action of aldosterone. The present study was designed to investigate the effect of aldosterone on phospholipids of mammalian epithelia. Phospholipid and fatty acid composition was examined in colonic epithelium (mineralocorticoid target tissue) and thymus (non-mineralocorticoid but glucocorticoid target tissue) of rats which had received aldosterone or vehicle by a miniosmotic pump for 7 days. Aldosterone increased the mass of colonic phospholipids relative to cellular proteins with concomitant changes in the percentage distribution of fatty acids, whereas the relative distribution of membrane phospholipds was not changed. Phosphatidylcholine increased the content of polyunsaturated and decreased that of monounsaturated fatty acids, which predominantly reflected the accretion of arachidonic and a decrease in oleic and palmitoleic acids. Within the phosphatidylethanolamine subclass, pretreatment of rats with aldosterone decreased the content of monounsaturated fatty acids (predominantly oleic and palmitoleic acid) and of n-3 fatty acids, and increased the content of saturated fatty acids (palmitic acid). The saturated-to-nonsaturated fatty acid ratio also significantly increased after aldosterone treatment. No changes in thymic phospholipids were seen. The results are consistent with the contention that aldosterone specifically modulates phospholipid concentration and metabolism in mineralocorticoid target tissue. The changes in phospholipid content and its fatty acid composition during the fully developed effect of aldosterone may reflect a physiologically important phenomenon with long-term consequences for membrane structure and function.

The effect of insulin on delta5 desaturation in hepG2 human hepatoma cells and L6 rat muscle myoblasts

In humans there is a correlation between the ratio of arachidonic acid (20:4n-6) to cis 8,11,14 eicosatrienoic acid (20:3n-6) in skeletal muscle phospholipids and insulin sensitivity. This has been interpreted as indicating a link between the activity of the delta5 desaturase enzyme and muscle insulin sensitivity. The present study addressed the possibility that insulin regulates delta5 desaturase activity using L6 rat myoblasts and hepG2 human hepatoma cells. Both cell lines responded to insulin by increasing the amount of D-[U-14C] glucose incorporated into glycogen. In L6 cells, insulin stimulated cis 8,11,14 eicosatrienoic acid uptake and arachidonic acid production but had no effect on the percentage conversion of cis 8,11,14 eicosatrienoic acid to arachidonic acid. In hepG2 cells, insulin had no effect on cis 8,11,14 eicosatrienoic acid uptake or arachidonic acid production. These results suggest that insulin has no direct effect on delta5 desaturase activity in the liver but can alter arachidonic acid production in muscle by altering substrate availability.

Metabolism of dietary alpha-linolenic acid vs. eicosapentaenoic acid in rat immune cell phospholipids during endotoxemia

Short-term (i.e., 3 d) continuous enteral feeding of diets containing eicosapentaenoic (EPA) and gamma-linolenic (GLA) polyunsaturated fatty acids (PUFA) to endotoxemic rats reduces the levels of arachidonic acid (AA) and linoleic acid (LA) in alveolar macrophage (AM) and liver Kupffer and endothelial (K&E) cell phospholipids with attendant decreases in prostaglandin formation by these cells in vitro. Diets that contain alpha-linolenic acid (LNA) as a substrate for endogenous formation of EPA may not be as effective in facilitating these immune cell modifications given the limited activity of delta6 desaturase. In the present study we compared the effectiveness of an LNA-enriched diet vs. an (EPA + GLA)-enriched diet to displace phospholipid AA from AM and liver K&E cells in vivo in endotoxemic rats fed enterally for 3 or 6 d. We determined the fatty acid composition of AM and K&E cell phospholipids by gas chromatography. We found that AM and K&E cells from rats that had received the EPA + GLA diet for 3 d had significantly (P < 0.001) higher mole percentage of EPA and the GLA metabolite, dihomoGLA, than corresponding cells from rats given the LNA diet or a control diet enriched with LA. Rats given the LNA diet had relatively low levels of stearidonic acid, EPA and other n-3 PUFA, while rats given the LA diet had low levels of GLA and dihomoGLA. We conclude that diets enriched with LNA or LA may not be as effective as those enriched with EPA + GLA for purposes of fostering incorporation of EPA or dihomoGLA into and displacement of AA from macrophage phospholipids under pathophysiologic conditions commonly found in acutely septic patients.

Regulatory effect of various steroid hormones on the incorporation and metabolism of [14C]stearate in rat hepatoma cells in culture

We have examined the incorporation and metabolism of [14C] stearic acid within the total lipids of HTC rat-hepatoma cells in suspension culture in presence and in absence of steroidal hormone stimulation. Both, glucocorticoids (dexamethasone, cortisol and corticosterone) and mineralocorticoids (deoxycorticosterone and aldosterone) as well as the estrogen beta-estradiol and the androgen testosterone enhanced the extent of delta 9 desaturation to oleic acid of the saturated precursors, whereas only the two mineralocorticoids affected the incorporation rate of the exogenous acid into total cellular lipids, thus promoting a little stimulation. Furthermore, all the hormones tested increased the radiolabelling of the total cellular phospholipids except deoxycorticosterone and testosterone, the former having no effect and the latter exerting a moderate inhibition. On the other hand, the incorporation of 14C into neutral lipids was stimulated by testosterone, in contrast to the inhibition of this parameter observed exclusively with either the mineralocorticoids or the estrogen. Within the phospholipid subclasses, the radiolabelling of phosphatidylcholine was augmented by means of all the steroids tested save deoxycorticosterone and testosterone, whereas phosphatidylethanolamine exhibited a decrease only in the presence of testosterone. In a similar fashion, within the neutral lipids, the predominating triglyceride fraction was preferentially labelled--at the expense of other subclasses of lesser abundance--upon treatment with the steroids except aldosterone, which exerted no effect. The results obtained were correlated with those changes observed in the mass distribution of the different lipid subclasses either with or without prior hormonal stimulation.