Upregulation of low density lipoprotein receptor activity by tumor necrosis factor,a process independent of tumor necrosis factor-induced lipid synthesis and secretion

It has been shown that tumor necrosis factor (TNF) rapidly upregulates expression of the low density lipoprotein (LDL) receptors on Hep G2 cells and acutely stimulates hepatic lipid synthesis and secretionin vivo. It may thus be possible that TNF-induced expression of LDL receptors is secondary to a decrease in cellular cholesterol content caused by TNF-stimulated lipid secretion. In order to know whether TNF upregulates LDL receptors by depletion of the cellular cholesterol content, the present experiments were designed to study the temporal relationship between TNF-stimulated expression of LDL receptor activity and TNF-induced changes in lipid synthesis and secretion in anin vitro setting by using Hep G2 cells (a highly differentiated human hepatoma cell line) as a hepatocyte model. Hep G2 cells were incubated with TNF (usually 2.5 nmol/L) for certain periods, and LDL receptor activity was evaluated by measuring [¹²⁵I]LDL binding at 4°C; lipid synthesis and secretion were assayed by measuring [³H]glycerol incorporation into triglycerides and phospholipids as well as [¹⁴C]acetate incorporation into cholesterol. We found that a 30-h exposure of the cells to TNF was needed for the effect of TNF to be seen on lipid synthesis and secretion as measured by incorporation of [³H]glycerol into triglycerides and phospholipids, whereas TNF rapidly (in several hours) upregulated LDL receptor activity. TNF stimulated triglyceride synthesis, but did not stimulate phospholipid synthesis. On the other hand, TNF stimulated phospholipid secretion, but did not stimulate triglyceride secretion. Exposure of the cells to TNF for 16 or 24 h neither decreased cholesterol synthesis nor stimulated cholesterol secretion as measured by [¹⁴C]acetate incorporation into cholesterol. Upregulation of LDL receptor activity through inhibition of cellular cholesterol synthesis with compactin (a competitive inhibitor of the 3-hydroxyl-3-methylglutaryl-CoA reductase) was augmented by TNF, whereas downregulation of LDL receptor activity through stimulation of cellular cholesterol synthesis with mevalonolactone almost completely blocked the upregulatory effect of TNF. In conclusion, TNF-stimulated expression of LDL receptor activity is not secondary to a depletion of cellular cholesterol content through TNF-stimulated lipid secretion or inhibition of cholesterol synthesis.     

Epidermal growth factor modulates release of arachidonic acid from embryonic cells

The calcium ionophore A23187 stimulates release of free [³H]arachidonic acids from radiolabeled cultures of MEPM cells which are growing, but not from those which are confluent. However, when confluent MEPM cells are pretreated with EGF or PMA, release of [³H]arachidonic acids does occur in response to A23187. Since neither EGF nor PMA themselves stimulate release of [³H]arachidonic acids from these cells, but do activate protein kinase C, these data support the hypothesis that protein kinase C modulates the activities of phospholipid hydrolases in MEPM cells.     

Effect of phagocytosis and lonophores on release and metabolism of arachidonic acid from human neutrophils

Challenge of human neutrophils prelabeled with [³H]arachidonate and [¹⁴C] palmitate or [¹⁴C]-stearate with opsonized zymosan or the Ca²⁺ ionophores A23187 or Ionomycin caused the release of [³H], but not [¹⁴C], fatty acid. With the ionophores, but not zymosan, considerable conversion of the [³H] arachidonate to hydroxyeicosatetraenoates occurred. Although various isomers were recovered, the 5-hydroxyeicosatetraenoate appeared to be the major product. In these experiments, no [¹⁴C] products were detected such as lysophospholipid, diglyceride or monoglyceride. Although no definitive statement can be made about the mechanism of release of arachidonate, our data are most easily interpreted as the result of the action of a phospholipase A₂.     

Effect of platelet-activating factor on tumor necrosis factor-induced superoxide generation from human neutrophils. Possible involvement of G proteins

The effect of platelet-activating factor (PAF) and of two specific PAF antagonists on tumor necrosis factor (TNF) induced superoxide production by human polymorphonuclear neutrophils (PMN) was examined. PAF alone (0.1 pM to 0.1 nM) failed to evoke superoxide production; however, when PAF was added for 10 min to cells upon prior incubation with 10 ng/mL TNF for 50 min, superoxide production was significantly enhanced as compared to that induced by TNF alone. Maximum amplification (+30%) was obtained with 10 pM PAF; however, the effect was completely abolished by two structurally unrelated PAF antagonists, BN 52021 and BN 52111. The antagonists also decreased by 25% the superoxide production elicited solely by TNF, implicating the involvement of endogenous PAF in this process. Pretreatment of the PMN with either pertussis or cholera toxin attenuated the PAF amplified superoxide production in TNF stimulated cells, suggesting that G proteins sensitive to these toxins may be involved in the mechanisms controlling amplification. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May, 1989.     

Effects of n−3 and n−6 fatty acids on tumor necrosis factor cytotoxicity in WEHI fibrosarcoma cells

Modulation by fatty acids of the cytotoxic effect of recombinant tumor necrosis factor alpha (TNF) toward WEHI 164 mouse fibrosarcoma cells has been examined. Preincubating the highly TNF-sensitive WEHI clone 13 cells for 44 hr with 50 μmol/L of 20∶5n−3, 22∶6n−3, 18∶3n−6, 20∶3n−6 or 20∶4n−6 reduced cell survival 22 hr after challenge with TNF (40 ng/L) by 65%, 72%, 60%, 98% and 85%, respectively. In comparison, 18∶3n−3, 18∶2n−6 and 18∶1n−9 had only negligible effects on TNF-induced toxicity. Different extent of fatty acid incorporation into cell total phospholipids or triglycerides could not explain the observed effects on TNF cytotoxicity, and the enhanced cytotoxicity could therefore not be explained merely by an increased unsaturation of the cell membranes. In addition to the fatty acid supplied, preincubation with 18∶2n−6, 18∶3n−6 or 18∶3n−3 also enriched the cells with 20∶2n−6, 20∶3n−6 and 20∶3n−3, respectively, most likely due to chain elongation. The results suggest that the WEHI cells have a low Δ6 desaturase activity, and that n−6 and n−3 acids must have at least 3 or 4 double bonds, respectively, to enhance TNF cytotoxicity in WEHI cells. Dexamethasone partly inhibited TNF-induced cytotoxicity, while cyclooxygenase, thromboxane synthetase or lipoxygenase inhibitors had no or negligible effects. The antioxidant butylated hydroxyanisole (BHA) completely inhibited TNF-induced cytotoxicity, while the structurally and functionally similar antioxidant butylated hydroxy-toluene had no such effect, indicating that BHA does not block TNF cytotoxicity through its antioxidant effect. The results suggest that TNF cytotoxicity involves, directly or indirectly, metabolism of long-chain polyun-saturated fatty acids, and we speculate that fatty acid metabolites are involved.     

In vitro cytotoxicity and ion release of multi-ion doped hydroxyapatite

Multi-ion doped hydroxyapatite (HA) is gaining more attention due to its potential in enhancing multifunctional biological, structural, and mechanical properties for orthopedic and dental applications. In this study, HA doped with multiple cations (Sr⁺², Zn⁺², Ag⁺) and anion (F⁻) was prepared by high-energy ball milling. Sintered HA samples were evaluated for their in vitro cytocompatibility, ion release, and bioactivity. The composition of multi-ion doped HA was optimized using Design of experiments (DOE). Our analysis showed that the contribution of each dopant on cell proliferation changes with culture duration. During first 3 days, F⁻ exhibited strongest influence and during 7-day proliferation Sr⁺² and Ag⁺ had maximum influence. Binary ion doping found to have strong interaction on cell proliferation, while the ternary and quaternary ion doping did not show any interactions. In general, up to twofold increase in the cell viability was achieved with ternary and quaternary ion doping consisting of Sr⁺², Zn⁺², Ag⁺ and F⁻. Although large number of compositions has been identified to exhibit better in vitro cell viability than pure HA, for enhanced long-term cytocompatibility the compositions of multi-ion doped HA would be 2.5Sr-2.5Zn-2.5Ag, 2.5Sr-5Zn-2.5Ag, and 5Sr-2.5Zn-2.5Ag with up to 5 wt% F.     

Incorporation of arachidonic acid and eicosapentaenoic acid into phospholipids by polymorphonuclear leukocytes in vitro

The present study demonstrated that the patterns of the incorporation of [1-¹⁴C] arachidonic acid and [1-¹⁴C] eicosapentaenoic acid into individual phospholipids by polymorphonuclear leukocytes were similar. However, human leukocytes exhibited higher activity than guinea pig periotoneal leukocytes in the formation of arachidonoyl- and eicosapentaenoyl-phosphatidic acid. Cells from both origins showed a decrease of label in phosphatidylcholine accompanied by an increase of label in phosphatidylethanolamine after a longer period (30–120 min) of incubation, suggesting that part of the arachidonoyl or eicosapentaenoyl moiety in phosphatidylethanolamine may be derived from that of phosphatidylcholine. The observed difference between human cells and elicited cells in the time-course of the incorporation of both fatty acids into phosphatidylcholine and phosphatidylethanolamine appears to be due to different contents of the diacyl and ether-linked class compositions of these phospholipids in cells from different origins. Both labeled fatty acids were incorporated more rapidly into the diacyl-linked class, but were retained to a greater extent in alkylacyl-phosphatidyl-choline and alkenylacyl-phosphatidylethanolamine. The data suggest that, in addition to alkylacyl-phosphatidylcholine and phosphatidylinositol, alkenylacyl-phosphatidylethanolamine may be an important endogenous source of arachidonic acid and eicosapentaenoic acid in stimulated human leukocytes.     

Alteration in membrane permeability by diacylglycerol and phosphatidylcholine containing arachidonic acid

The phospholipid metabolites, stearoylarachidonylglycerol and diarachidonylglycerol, stimulate transepithelial sodium transport in frog skin epithelium. The increase in Na transport is due to an increase in the unidirectional influx of sodium, is amiloride sensitive and is prevented with pretreatment with indomethacin, mefanamic acid and phospholipase inhibitor, mepacrine. The data suggest a possible role of phospholipid metabolism and prostaglandin biosynthesis in the regulation of transepithelial ion transport.     

Saponin-loaded SBA-15: release properties and cytotoxicity to Panc-I cancer cells

In this study, first time a nanoformulation, saponin-loaded SBA-15 has been developed for an improved and continuous release. The SBA-15 nanopowder was synthesized by a hydrothermal process. Saponin was introduced into the mesoporous channels of SBA-15 and its concentration in SBA-15 was measured by UV–visible spectrophotometry. The pristine SBA-15 and saponin-loaded SBA-15 were characterized by small-angle XRD, FESEM, HRTEM, TGA, FTIR. N₂ adsorption–desorption isotherms were used to measure the specific surface area and pore channel structure parameters of pristine and loaded SBA-15. Saponin release was studied in phosphate buffered saline (pH 7.4), which revealed that the release rate could be effectively controlled. The controlled drug release is highly desired for cancer treatment. The cytotoxicity of pristine and loaded SBA-15 was analyzed on Panc-I cancer cells. Both the pristine SBA-15 and saponin-loaded SBA-15 nanoparticles showed specific toxicity on the cancer cells. The preliminary results showed that saponin-loaded SBA-15 could be an effective therapeutic agent for Panc-I cancer cells.     

The in vivo incorporation of labeled linoleic acid, α-linolenic acid and arachidonic acid into rat liver lipids

The incorporation of 1-¹⁴C-linoleic acid, 1-¹⁴C-α-linolenic acid and 1-¹⁴C-arachidonic acid into rat liver lipids was measured and the per cent distribution of radioactivity into the different lipid fractions determined. Normal rats were injected into the portal vein with the labeled solutions during a one minute period. Livers were quickly frozen, pulverized, and the lipids extracted and fractioned by thin layer chromatography. No significant differences were observed in the amounts of labeled fatty acids incorporated per gram of rat liver. While 1-¹⁴C-linoleic acid and 1-¹⁴C-α-linolenic acid were found in appreciable amounts in the 1,2 diacylglycerol fraction, about one fifth as much 1-¹⁴C-arachidonic acid was esterified in this fraction. 1-¹⁴C-arachidonic acid was the leading acid esterified in the phospholipid fractions.     

Synthesis of arachidonic acid metabolites by syrian hamster platelets and peritoneal cells

In this study, the metabolism of arachidonic acid by hamster platelets and peritoneal macrophages was assessed. Peritoneal macrophages stimulatedin vitro with the calcium ionophore A23187 or stimulatedin vivo by intraperitoneal injections of opsonized zymosan produced prostaglandin E₂, thromboxane B₂ (TxB₂) and 6-keto-prostaglandin F_1α, as determined by radioimmuno assays. Leukotriene B₄ (LTB₄), and 11- and 15-hydroxyeicosatetraenoic acids (HETE), which were identified by reverse-phase highperformance liquid chromatography coupled with diode array detection, were produced by peritoneal cells stimulatedin vitro with A23187 but were not found in the peritoneal exudate followingin vivo stimulation with opsonized zymosan. Synthesis of 11- and 15-HETE, but not LTB₄, was inhibited by 1 μM indomethacin but not by 10 μM nordihydroguaiaretic acid, which did inhibit LTB₄ synthesis. Washed hamster platelets were prepared and shown to synthesize TxB₂, 12-HETE and 12-hydroxyheptadecatrienoic acid following stimulation with thrombin. This paper is the first to report on eicosanoid metabolism in tissues related to atherosclerosis, thrombosis and inflammation in hamsters.     

Effect of tumor necrosis factor-α on triglyceride and phospholipid content and fatty acid composition of liver and carcass in rats

We have previously shown that a continuous infusion of tumor necrosis factor-α (TNF-α) in rats results in an increase in plasma triglyceride (TG), liver protein and DNA, and at the same time a reduction in muscle protein. However, there is no information on the associated effects of TNF-α on liver and muscle lipids. The present study, therefore, determined the effect of TNF-α on the TG and phospholipid (PL) content and their fatty acid composition, in the liver and carcass of rats and correlated with the plasma levels of insulin, corticosterone, and catecholamaines. Total parenteral nutrition that met the daily nutrient requirements was continuously infused for 10 d through a central vein catheter in two groups of rats, one receiving infused TNF-α (100 μg/kg/d) and a control group. Hepatic TG and PL, expressed either as mg/g dry weight or total organ content, were significantly increased in the TNF-α-infused group compared with controls. Livers of TNF-α infused rats contained significantly less saturated and monounsaturated fatty acids and significantly more polyunsaturated fatty acids (PUFA) of the ω3 and ω6 series than controls. The carcass, on the other hand, contained significantly more monounsaturated and significantly less polyunsaturated fatty acids of the ω6 series than controls. There were no changes in corticosterone level. Although plasma glucose levels were comparable between control and TNF-α infused rats, the latter had a marked increase in insulin levels, demonstrating insulin resistance. In addition TNF-α infused rats had raised norepinephrine levels. The fall in carcass and rise in liver TG and PL are consistent with the presence of insulin resistance and raised norepinephrine levels. However, the increase in PUFA content of the liver, especially the increase in 20∶4ω6 levels in liver PL and TG, is likely to be the effect of TNF-α and suggests increased activity of Δ5-desaturase.     

Modulation of arachidonic acid distribution by conjugated linoleic acid isomers and linoleic acid in MCF-7 and SW480 cancer cells

The relationship between growth and alterations in arachidonic acid (AA) metabolism in human breast (MCF-7) and colon (SW480) cancer cells was studied. Four different fatty acid preparations were evaluated: a mixture of conjugated linoleic acid (CLA) isomers (c9,t11, t10,c12, c11,t13, and minor amounts of other isomers), the pure c9,t11-CLA isomer, the pure t10,c12-CLA isomer, and linoleic acid (LA) (all at a lipid concentration of 16 microg/mL). 14C-AA uptake into the monoglyceride fraction of MCF-7 cells was significantly increased following 24 h incubation with the CLA mixture (P < 0.05) and c9,t11-CLA (P < 0.02). In contrast to the MCF-7 cells, 14C-AA uptake into the triglyceride fraction of the SW480 cells was increased while uptake into the phospholipids was reduced following treatment with the CLA mixture (P < 0.02) and c9,t11-CLA (P < 0.05). Distribution of 14C-AA among phospholipid classes was altered by CLA treatments in both cell lines. The c9,t11-CLA isomer decreased (P < 0.05) uptake of 14C-AA into phosphatidylcholine while increasing (P < 0.05) uptake into phosphatidylethanolamine in both cell lines. Both the CLA mixture and the t10,c12-CLA isomer increased (P < 0.01) uptake of 14C-AA into phosphatidylserine in the SW480 cells but had no effect on this phospholipid in the MCF-7 cells. Release of 14C-AA derivatives was not altered by CLA treatments but was increased (P < 0.05) by LA in the SW480 cell line. The CLA mixture of isomers and c9,t11-CLA isomer inhibited 14C-AA conversion to 14C-prostaglandin E2 (PGE2) by 20-30% (P < 0.05) while increasing 14C-PGF2alpha by 17-44% relative to controls in both cell lines. LA significantly (P < 0.05) increased 14C-PGD2 by 13-19% in both cell lines and increased 14C-PGE2 by 20% in the SW480 cell line only. LA significantly (P < 0.05) increased 5-hydroperoxyeicosatetraenoate by 27% in the MCF-7 cell line. Lipid peroxidation, as determined by increased levels of 8-epi-prostaglandin F2alpha (8-epi-PGF2alpha), was observed following treatment with c9,t11-CLA isomer in both cell lines (P < 0.02) and with t10,c12-CLA isomer in the MCF-7 cell line only (P < 0.05). These data indicate that the growth-promoting effects of LA in the SW480 cell line may be associated with enhanced conversion of AA to PGE2 but that the growth-suppressing effects of CLA isomers in both cell lines may be due to changes in AA distribution among cellular lipids and an altered prostaglandin profile.     

Kinetics of photoperoxidation of arachidonic acid: Molecular mechanisms and effects of antioxidants

The kinetics of photoperoxidation of [1⁻¹⁴C]arachidonic acid (20∶4n−6) at 1.32 mM was studied either with the unsaturated fatty acid alone or in the presence of 10μM of antioxidants and/or inhibitors of eicosanoid metabolism. The photosensitizer used wasmeso-tetraphenylporphine. The time-course of the reactions was followed by ultraviolet spectral analysis, thiobarbituric acid reactivity and high-performance liquid chromatographic analysis of aliquots sampled every 15 min during the 4 h of irradiation. The kinetics of photoperoxidation of 20∶4n−6 can be divided into three main successive steps: (i) monohydroperoxidation, characterized by the appearance of conjugated diene patterns and monohydroperoxidized 20∶4n−6; (ii) secondary oxidation characterized by polyoxygenated products such as dihydroperoxidized 20∶4n−6 possessing conjugated triene patterns; and (iii) the disappearance of conjugated patterns and the oxidative cleavage of the products of the two first steps into aldehydic molecules reacting with thiobarbituric acid. During the first 90 min of irradiation, the mechanism of monohydroperoxidation (step one) is purely or predominantly type II photoperoxidation involving only singlet oxygen. This step was inhibited by β-carotene and by BW755C (3-amino-1-[3-trifluoromethylphenyl]2-pyrazoline). In contrast, the reactions involved in the second and third steps were predominantly type I photoperoxidation involving radical mechanisms. These latter steps were inhibited by β-carotene, BW755C, vitamin E and probucol. Indomethacin and 5,8,11,14-eicosatetraynoic acid did not alter 20∶4n−6 photoperoxidation. Thisin vitro model of lipid photoperoxidation allows the screening of antioxidants in accordance with their singlet oxygen quenching and/or free radical scavenging properties.     

Eicosapentaenoic and arachidonic acid: Comparison of metabolism and activity in murine epidermal cells

The biological activity, including metabolism and modulation of ornithine decarboxylase activity and DNA synthesis, of arachidonic acid (AA) and eicosapentaenoic acid (EPA) were compared in epidermal cells from SENCAR mice. Radiolabelled AA and EPA were found to be similarly incorporated into and released from membrane phospholipids of unstimulated cultures. However, when cells were stimulated with the tumor promoter 12-0-tetradecanoylphorbol-13-acetate (TPA), the release of AA was significantly higher than the release of EPA. The extent of metabolism of AA and EPA to prostaglandins was determined in both freeze-thawed cell preparations and in viable cultured cells. In the freeze-thawed preparations, use of AA as a substrate resulted in significantly more PGF than when EPA was used as the substrate. However, more PGE₃ was formed than PGE₂. PGD levels were the same for either fatty acid precursor. Prostaglandin production was also determined in viable cultured cells since other influences such as phospholipase A₂ activity can modify prostaglandin production. Control cultures prelabelled with either AA or EPA produced similar amounts of the respective PGF, PGE, and PGD. However, TPA-stimulated cultures produced significantly higher amounts of each prostaglandin in cultures prelabelled with AA compared to cells prelabelled with EPA. HETE or HEPE production was the same both for cultured cells prelabelled with AA or EPA and for homogenates from uncultured cells incubated directly with the radiolabelled fatty acids. TPA-induced ornithine decarboxylase (ODC) was significantly higher in AA-treated cultures compared to EPA-treated cultures. AA supports DNA synthesis to a greater extent than EPA, either alone or in the presence of TPA. These findings suggest that AA and EPA do not have equivalent biological activity in mouse epidermal cells.     

Dietary arachidonic acid and hepatic desaturation of fatty acids in obese zucker rats

The effect of low levels of dietary arachidonic acid (20:4n-6) on Δ6 desaturation of linoleic acid (18:2n-6) and α-linolenic acid (18:3n-3), and on Δ5 desaturation of dihomo-γ-linolenic acid (20:3n-6) were studied in liver microsomes of obese Zucker rats, in comparison with their lean littermates. Fatty acid composition of serum total lipids and of phospholipids from liver microsomes and from total heart and kidney was determined to see whether modifications of desaturation rate, if any, were reflected in the tissue fatty acid profiles. Animals fed for 12 wk on a balanced diet, containing 20:4n-6 and 18:2n-6, were compared to those fed 18:2n-6 only. The low amount of dietary 20:4n-6 greatly inhibited Δ6 desaturation of 18:2n-6 and Δ5 desaturation of 20:3n-6, whereas Δ6 desaturation of 18:3n-3 was slightly increased in obese rats. Inhibition of the biosynthesis of long-chain n-6 fatty acids by dietary arachidonic acid was only slightly reflected in the 20:4n-6 content of liver microsome phospholipids. On the contrary, the enrichment of serum total lipids and heart and kidney phospholipids in this fatty acid was pronounced, more in obese than in lean animals. Our results show that, although the desaturation rate of the n-6 fatty acids in liver microsomes was greatly decreased by the presence of arachidonic acid in the diet, the tissue phospholipid content in arachidonic acid was not depressed. The potentiality of synthesis of eicosanoids of the 2 family from this fatty acid is consequently not lower, especially in obese rats, in which certain tissues are deficient in arachidonic acid, in comparison with their lean littermates.     

Fluorescent product formation and changes in structure of DNA reacted with peroxidizing arachidonic acid

Calf thymus DNA was reacted with peroxidizing arachidonic acid at 37 C for 76 hr. Fluorescent DNA products increased with reaction time. These products had characteristic fluorescence spectra with maximum excitation at 315 nm and maximum fluorescence at 420 nm. Structural changes occurred in the DNA reacted with peroxidizing arachidonic acid, as observed by decreased melting point, decreased hyperchromicity, partial resistance to hydrolysis by deoxyribonuclease and by decreased template activity for rat liver RNA polymerase.     

Genipin cross-linked chitosan hydrogel for the controlled release of tetracycline with controlled release property,lower cytotoxicity,and long-term bioactivity

To realize the controlled release property, lower cytotoxicity, and long-term bioactivity of tetracycline, the chitosan hydrogel had been prepared using genipin as the cross-linker and the tetracycline was in situ encapsulated. The formation process and strength of hydrogel were studied by rheological analysis, and the microtopography was observed by scanning electron microscope. It was found that the amount of genipin could modulate the physical property of the hydrogel. For in vitro release and antibacterial assays, the hydrogel could controllably release tetracycline and keep its bioactivity for a long time. The tetracycline-loaded chitosan hydrogel showed good antibacterial effect even under alkaline environment, which displayed better stability compared with free tetracycline. Moreover, the tetracycline-loaded chitosan hydrogel exhibited lower cytotoxicity than did tetracycline alone, suggesting that this tetracycline-loaded chitosan hydrogel could be a more useful dosage form than separate doses of tetracycline. The novel aspects of this study include the cytotoxicity study and the in vitro and in vivo assays, which might be useful for other researchers in this field.

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Graphical abstract To realize the controlled release property, lower cytotoxicity, and long-term bioactivity of tetracycline, genipin cross-linked chitosan hydrogel was used as the carrier of tetracycline. The hydrogel could controllably release tetracycline with bioactivity. The hydrogel showed good antibacterial effect even under alkaline environment. The hydrogel exhibited lower cytotoxicity than did tetracycline alone.

     

Blood lipid docosahexaenoic and arachidonic acid in term gestation infants fed formulas with high docosahexaenoic acid,low eicosapentaenoic acid fish oil

The effect of fish oil high in docosahexaenoic acid (22∶6n−3) and low in eicosapentaenoic acid (20∶5n−3) in formula on blood lipids and growth of full-term infants was studied. Infants were fed formula with about 15% oleic acid (18∶1), 32% linoleic acid (18∶2n−6), 4.9% linolenic acid (18∶3n−3) and 0, 0.10 or 0.22% 22∶6n−3, or 35% 18∶1, 20% 18∶2n−6, 2.1% 18∶3n−3 and 0, 0.11 or 0.24% 22∶6n−3 from 3 d to 16 wk of age (n=16, 18, 17, 21, 17, 16, respectively). The formulae had <0.1% 20∶5n−3 and no arachidonic acid (20∶4n−6). Breast-fed infants (n=26) were also studied. Plasma phospholipid and red blood cell (RBC) phosphatidylcholine (PC) and phosphatidylethanolamine (PE) fatty acids were determined at 3 d and 4, 8, and 16 wk of age. These longitudinal analyses showed differences in blood lipid 22∶6n−3 between breast-fed and formula-fed infants depending on the feeding duration. At 16 wk, infants fed formula with 0.10, 0.11% 22∶6n−3, or 0.22% 22∶6n−3 had similar 22∶6n−3 levels in the plasma phospholipid and RBC PC and PE compared with breast-fed infants and higher 22∶6n−3 than infants fed formula without 22∶6n−3. Formula with 0.24% 22∶6n−3, however, resulted in higher plasma phospholipid 22∶6n−3 than in breast-fed infants at 16, but not 4 or 8 wk of age. Plasma and RBC phospholipid 20∶4n−6 was lower in formula-fed than breast-fed infants, but no differences in growth were found. Higher blood lipid C₂₀ and C₂₂ n−6 and n−3 fatty acids in infants fed formula with 20% 18∶2n−6 and 2.4% 18∶3n−3 compared with 32% 18∶2n−6 and 4.9% 18∶3n−3 show the increase in blood lipid 22∶6n−3 in response to dietary 22∶6n−3 depending on other fatty acids in the formula.     

Diets rich in lean beef increase arachidonic acid and long-chain ω3 polyunsaturated fatty acid levels in plasma phospholipids

Diets rich in meat are claimed to contribute to the high tissue arachidonic acid (20∶4ω6) content in people in Westernized societies, but there are very few direct data to substantiate this assertion. Because meat contains a variety of long-chain polyunsaturated fatty acids (PUFA) that are susceptible to oxidation, we initially examined the effect of cooking on the long-chain PUFA content of beef, and then determined the effect of ingestion of lean beef on the concentration of long-chain PUFA in plasma phospholipids (PL). First, we examined the effect of grilling (5–15 min) and frying (10 min) different cuts of fat-trimmed lean beef on the long-chain PUFA content. Second, we investigated the effect of including 500 g lean beef daily (raw weight) for 4 wk on the fatty acid content and composition of plasma PL in 33 healthy volunteers. This study was part of a larger trial investigating the effect of lean beef on plasma cholesterol levels. In the first two weeks, the subjects ate a very low-fat diet (10% energy) followed by an increase in the dietary fat by 10% each week for the next 2 wk. The added fat consisted of beef fat, or olive oil (as the oil or a margarine) or safflower oil (as the oil or a margarine). This quantity of beef provided 60, 230, 125, 140 and 20 mg/d, respectively, of eicosatrienoic acid (20∶3ω6), 20∶4ω6, eicosapentaenoic acid (20∶5ω3), docosapentaenoic acid (22∶5ω3) and docosahexaenoic acid (22∶6ω3). Grilling for 10–15 min, but not frying, of the fat-trimmed lean beef resulted in 20–30% losses of the 20 and 22 carbon PUFA. The consumption of the lean beef during the first two-week period, when there was a very low level of dietary fat, was associated with significant increases in the proportion and concentration of 20∶3ω6, 20∶4ω6, 20∶5ω3 and 22∶5ω3 in the plasma PL and a significant decrease in the proportion and content of 18∶2ω6. The addition of beef fat or olive oil to the diets containing lean beef did not alter the plasma PL fatty acid profile compared with the very low-fat diet, whereas the addition of safflower oil maintained the significant increases in 20∶4ω6 and 22∶5ω3 but led to decreases in 18∶3ω3 and 20∶5ω3 compared with the very lowfat diet. The results showed that diets rich in lean beef increased the 20∶3ω6, 20∶4ω6 and the long-chain ω3 PUFA levels in the plasma PL. A high level of linoleic acid in diets rich in lean beef prevented the rise in the plasma level of 20∶3ω6 and 20∶5ω3, two fatty acids known to antagonize the effects of 20∶4ω6 on platelet aggregation.