Effects of α lipoic acid on noise induced oxidative stress in rats

This study was conducted to identify how exposure to ambient noise that is over 75 dB affects the oxidant-antioxidant profile using hematological and biochemical indicators, and to investigate the effects of a strong and current antioxidant, $\alpha$ lipoic acid, on rats that were subjected to noise stress. For this purpose, five groups of eight rats were formed as follows: Control (K), Noise Exposure (GK), Lipoic Acid (LA), Noise Pollution + $\alpha$Lipoic Acid (GK + LA) and Oil (Y). The blood samples collected from rats were analyzed and MDA (malondialdehyde), GSH (glutathione), SOD (superoxide dismutase), CAT (catalase), NO (nitrit oxide), GPx (glutathione peroxidase), leukocytes, monocytes, lymphocytes, erythrocytes, hemoglobin, hematocrit, glucose, cholesterol, total protein, triglycerides, HDL (high density lipoprotein), LDL (low density lipoprotein), and urea-N levels were measured. The physical factory environment in a textile factory was preferred to simulate the noise exposure. Ambient noise was measured to be 75 dB. Exposure to physical ambient noise was sustained for 30 days. MDA level was measured at the lowest level in the LA and GKLA groups while it was statistically significantly higher in other groups than it was in the control group. It was observed that GSH reached its lowest level in the group that was exposed to noisy environment, the 100 mg/kg/day $\alpha$lipoic acid administered on the experimental model increased this level to that of the control group and this change was statistically significant (p < 0.05). Considering the urea levels, the increases in GK and GKLA groups and the decreases in LA and Y groups were observed to be statistically significant. When glucose levels were compared to the control group, they were found to be statistically significantly lower in all groups. As a result, it was observed that exposure to noise for 30 days was likely to lead to leukocyte-based immune deficiency and using $\alpha$ lipoic acid as an antioxidant might provide a significant protection against the noise stress.     

Role of α-CGRP in the regulation of neurotoxic responses induced by kainic acid in mice

Kainic acid (KA) is an excitatory and neurotoxic substance. The role of α-calcitonin gene-related peptide (α-CGRP) in the regulation of KA-induced hippocampal neuronal cell death was investigated in the present study. The intracerebroventricular (i.c.v.) administration with KA (0.07 μg) increased hippocampal α-CGRP mRNA level in ICR mice. The α-CGRP mRNA level began to increase at 1 h, reached at maximal level at 6 and 12 h, and returned to the control level by 24 h after i.c.v. administration with KA. In addition, KA-induced hippocampal CA3 neuronal death in C57BL6 (wild type) group was more pronounced compared to KA-induced hippocampal CA3 pyramidal cell death in α-CGRP knock-out (KO) group. Furthermore, sumatriptan, a CGRP releasing inhibitor, significantly protected the pyramidal cell death in CA3 hippocampal region induced by KA administered i.c.v. in ICR mice. Our results suggest that α-CGRP may play an important role in the regulation of KA-induced pyramidal cell death in CA3 region of the hippocampus.     

Isomers of conjugated linoleic acid induce insulin resistance through a mechanism involving activation of protein kinase Cε in liver cells

Conjugated linoleic acid (CLA) constitutes a group of isomers derived from linoleic acid. Diverse studies have suggested that these unsaturated fatty acids have beneficial effects on human health. However, it has also been reported that their consumption can generate alterations in hepatic tissue. Thus, in the present study, we evaluated the effect of two of the major isomers of CLA, cis-9, trans-11-CLA and trans-10, cis-12-CLA, in the regulation of insulin signaling in a hepatic cell model, clone 9 (C9). We found that the two isomers decrease insulin-stimulated phosphorylation of the main proteins involved in insulin signaling, such as Akt at Ser⁴⁷³ and Thr³⁰⁸, the insulin receptor at Tyr¹¹⁵⁸, IRS-1 at Tyr⁶³², and GSK-3 at Ser^9/21. Protein expression, however, was unaffected. Interestingly, both isomers of CLA promoted phosphorylation and activation of PKCε. Inhibition of PKCε activity by a dominant-negative form or knockdown of endogenous PKCε prevented the adverse effects of CLA isomers on insulin-induced Akt phosphorylation. Additionally, we also found that both isomers of CLA increase phosphorylation of IRS-1 at Ser⁶¹², a mechanism that probably underlies the inhibition of IRS-1 signaling by PKCε. Using confocal microscopy, we found that both isomers of CLA induced lipid accumulation in C9 cells with the presence of spherical cytosolic vesicles, suggesting their identity as neutral lipid droplets. These findings indicate that cis-9, trans-11-CLA and trans-10, cis-12-CLA isomers could have a significant role in the development of insulin resistance in hepatic C9 cells through IRS-1 serine phosphorylation, PKCε activation, and hepatic lipid accumulation.     

Activation of the AMP-activated protein kinase–p38 MAP kinase pathway mediates apoptosis induced by conjugated linoleic acid in p53-mutant mouse mammary tumor cells

Conjugated linoleic acid (CLA) inhibits tumorigenesis and tumor growth in most model systems, an effect mediated in part by its pro-apoptotic activity. We previously showed that trans-10,cis-12 CLA induced apoptosis of p53-mutant TM4t mouse mammary tumor cells through both mitochondrial and endoplasmic reticulum stress pathways. In the current study, we investigated the role of AMP-activated protein kinase (AMPK), a key player in fatty acid metabolism, in CLA-induced apoptosis in TM4t cells. We found that t10,c12-CLA increased phosphorylation of AMPK, and that CLA-induced apoptosis was enhanced by the AMPK agonist 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) and inhibited by the AMPK inhibitor compound C. The increased AMPK activity was not due to nutrient/energy depletion since ATP levels did not change in CLA-treated cells, and knockdown of the upstream kinase LKB1 did not affect its activity. Furthermore, our data do not demonstrate a role for the AMPK-modulated mTOR pathway in CLA-induced apoptosis. Although CLA decreased mTOR levels, activity was only modestly decreased. Moreover, rapamycin, which completely blocked the activity of mTORC1 and mTORC2, did not induce apoptosis, and attenuated rather than enhanced CLA-induced apoptosis. Instead, the data suggest that CLA-induced apoptosis is mediated by the AMPK–p38 MAPK–Bim pathway: CLA-induced phosphorylation of AMPK and p38 MAPK, and increased expression of Bim, occurred with a similar time course as apoptosis; phosphorylation of p38 MAPK was blocked by compound C; the increased Bim expression was blocked by p38 MAPK siRNA; CLA-induced apoptosis was attenuated by the p38 inhibitor SB-203580 and by siRNAs directed against p38 MAPK or Bim.     

Effect of theβ-adrenoceptor agonist BRL 26830 on fatty acid synthesis and on the activities of pyruvate dehydrogenase and acetyl-CoA carboxylase in adipose tissues of the rat

BRL 26830 is a thermogenic-adrenoceptor agonist which stimulates lipolysis and fatty acid oxidationin vivo. It also stimulates insulin secretion, and hence promotes glucose utilisationin vivo. The effect of this agent on white and brown adipose tissue of the rat was investigated. BRL 26830 increased the rate of fatty acid synthesisin vivo in white adipose tissue by 135% but reduced the rate of fatty acid synthesisin vivo in brown adipose tissue by 78%. The increase was abolished in white adipose tissue of streptozotocin-diabetic rats, indicating that the effect involved a rise in circulating insulin levels. The reduction in fatty acid synthesis in brown adipose tissues was associated with a reduction in the activity of acetyl-CoA carboxylase in the tissue consistent with a direct-adrenoceptor-mediated effect. BRL 26830 also increased the proportion of pyruvate dehydrogenase in its active formin vivo in brown adipose tissue and this increase was abolished in streptozotocin-diabetic rats. These findings illustrate different sensitivities of white and brown adipose tissues to combined-adrenergic and insulin stimulation.     

Influence of α-tocopherol supplementation on trans-18:1 and conjugated linoleic acid profiles in beef from steers fed a barley-based diet

The current study was conducted to determine the effect of different α-tocopherol (vitamin E) inclusion levels on trans(t)-18:1 and conjugated linoleic acid (CLA) profiles in subcutaneous and intramuscular fat of steers fed a barley-based diet. Fifty-six feedlot steers were offered a barley-based finisher diet (73% steam rolled barley, 22% barley silage and 5% supplement as-fed basis) with four levels of supplementary dl-α-tocopheryl acetate (340, 690, 1040 or 1740 IU/steer per day) for 120 days. Adding vitamin E to the diet had little effect on the overall fatty acid composition of intramuscular fat. The proportion of individual and total t,t- and cis(c),t-CLA, n-3 fatty acids, total polyunsaturated fatty acids (PUFA), mono-unsaturated fatty acids and saturated fatty acids to PUFA ratio in subcutaneous fat were not influenced (P > 0.05) by dietary vitamin E supplementation. Increasing levels of vitamin E led to linear reductions in t6-/t7-/t8-18:1 and t10-18:1 (P < 0.05), and linear increase in t11-/t10-18:1 ratio (P < 0.05) in subcutaneous fat. The content of 20:3n-6 and total n-6 in subcutaneous fat decreased (P < 0.05) linearly with increasing amounts of vitamin E. The subcutaneous fat n-6:n-3 ratio showed a quadratic (P < 0.05) response to vitamin E. In conclusion, although vitamin E supplementation has some potential to reduce t10-18:1 formation and increase t11-/t10-18:1 ratio in subcutaneous fat of cattle fed barley-based diets, the changes in the present study were limited and may not have been sufficient to impact on human health.     

Role of ω-3 fatty acid desaturases in the regulation of the level of trienoic fatty acids during leaf cell maturation

Trienoic fatty acids, namely -linolenic acid and hexadecatrienoic acid, present in leaf lipids are produced by -3 fatty acid desaturases located in the endoplasmic reticulum and plastid membranes. The changes in the level of trienoic fatty acids during leaf maturation were investigated in wild-type plants of Arabidopsis thaliana (L.) Heynh. and in the fad7 mutant deficient in the activity of a plastid -3 desaturase. The levels of trienoic fatty acids increased in 26 °C- and 15 °C-grown wild-type plants with maturation of leaves. The increase in trienoic fatty acids was mainly due to galactolipids enriched in plastid membranes. In addition, the relative levels of trienoic fatty acids in major glycerolipids, including phospholipids enriched in the endoplasmic reticulum membranes, also increased with leaf maturation. By contrast, when the fad7 mutant was grown at 26 °C, the relative levels of trienoic fatty acids in individual lipids decreased with leaf maturation. The decreases in the levels of trienoic fatty acids, however, were alleviated when the fad7 mutant was grown at 15 °C. These results suggest that the plastid -3 desaturase plays a major role in increasing the levels of trienoic fatty acids with leaf maturation.Abbreviations 163 hexadecatrienoic acid - 183 -linolenic acid - DGD digalactosyldiacylglycerol - MGD monogalactosyldiacylglycerol - PC phosphatidylcholine - PE phosphatidylethanolamine - TA trienoic fatty acid - WT wild type - -3 refers to the position of the double bond from the methyl end of a fatty acid This research was supported in part by Grants-in-Aid for Scientific research (#07251214 and #06804050 to K.I.) from the Ministry of Education, Science and Culture, Japan, and by the research grant from Shorai Foundation.     

Variation of the by-product spectrum during α-ketoglutaric acid production from raw glycerol by overexpression of fumarase and pyruvate carboxylase genes in Yarrowia lipolytica

The yeast Yarrowia lipolytica secretes high amounts of various organic acids, like citric, isocitric, pyruvic (PA), and α-ketoglutaric (KGA) acids, triggered by growth limitation and excess of carbon source. This is leading to an increased interest in this non-conventional yeast for biotechnological applications. To improve the KGA production by Y. lipolytica for an industrial application, it is necessary to reduce the amounts of by-products, e.g., fumarate (FU) and PA, because production of by-products is a main disadvantage of the KGA production by this yeast. We have examined whether the concentration of secreted organic acids (main product KGA and PA as major by-product and FU, malate (MA), and succinate (SU) as minor by-products) can be influenced by a gene-dose-dependent overexpression of fumarase (FUM) or pyruvate carboxylase (PYC) genes under KGA production conditions. Recombinant Y. lipolytica strains were constructed, which harbor multiple copies of the respective FUM1, PYC1 or FUM1, and PYC1 genes. Overexpression of the genes FUM1 and PYC1 resulted in strongly increased specific enzyme activities during cultivation of these strains on raw glycerol as carbon source in bioreactors. The recombinant Y. lipolytica strains showed different product selectivity of the secreted organic acids KGA, PA, FU, MA, and SU. Concentrations of the by-products FU, MA, SU, and PA decreased significantly at overproduction of FUM and increased at overproduction of PYC and also of FUM and PYC simultaneously. In contrast, the production of KGA with the multicopy strains H355A(FUM1) and H355A(FUM1-PYC1) was comparable with the wild-type strain H355 or slightly lower in case of H355(PYC1). KGA productivity was not changed significantly compared with strain H355 whereas product selectivity of the main product KGA was increased in H355A(FUM1).     

Development and endocrine regulation of mitochondrial cytochrome biosynthesis in the insect fat body: δ-[14C]aminolevulinic acid incorporation

The rate of incorporation of [¹⁴C]aminolevulinic acid (ALA) into cytochrome hemes was used to measure mitochondrial cytochrome synthesis in the fat body of adult male Blaberus discoidalis cockroaches. The hemes of cytochromes aa₃+b and c+c₁, were chemically separated to observe differential rates in their synthesis and regulation. [¹⁴C]ALA was linearly incorporated into cytochrome hemes for at least 8 h. No significant pool of endogenous ALA was detected relative to the amount of administered [¹⁴C]ALA. Peak cytochrome synthesis occurred 4 to 6 days after adult emergence. Endocrine disruption by corpora cardiaca-corpora allata extirpation or cervical ligation eliminated the 4-day developmentally related increase in the rate of cytochrome aa₃+b synthesis but had no effect on the production of cytochromes c+c₁. Injections of corpora cardiaca extracts into cervically ligated animals stimulated the rate of production of cytochromes aa₃+b by 2.5 times but did not affect cytochromes c+c₁. By comparison, juvenile hormone injections did not affect the rate of synthesis of either cytochrome fraction. These findings indicate that a neurohormone regulates the rate of synthesis of cytochromes a+b in insect fat body mitochondria.     

Abomasal infusion of arginine stimulates SCD and C/EBPß gene expression,and decreases CPT1ß gene expression in bovine adipose tissue independent of conjugated linoleic acid

Based on previous research with bovine peadipocytes, we hypothesized that infusion of arginine into the abomasum of Angus steers stimulates stearoyl-CoA desaturase (SCD) gene expression in bovine subcutaneous (s.c.) adipose tissue, and that this would be attenuated by conjugated linoleic acid (CLA). Growing Angus steers were infused abomasally with l-arginine 50 g/day; n = 13; provided as l-arginine HCl) or l-alanine (isonitrogenous control, 100 g/day; n = 11) for 14 days. For the subsequent 14 days, half of the steers in each amino acid group were infused with CLA (100 g/day). Body weight gain and average daily gain were unaffected (P > 0.15) by infusion of arginine or CLA into the abomasum. The plasma concentrations of cis-9, trans-11 and trans-10, cis-12 CLA were increased CLA infusion (P = 0.001) and infusion of arginine increased plasma arginine (P = 0.01). Compared with day 0, fatty acid synthase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase enzyme activities in s.c. adipose tissue increased by day 14 in steers infused with either alanine or arginine (all P < 0.01). NADP-MDH activity was higher (P = 0.01) in steers infused with arginine than in steers infused with arginine plus CLA by day 28, but lipid synthesis in vitro from glucose and acetate was unaffected by infusion of either arginine or CLA (P > 0.40). By day 28, C/EBPβ and SCD gene expression was higher, and CPT1β gene expression was lower, in s.c. adipose tissue of steers infused with arginine than in steers infused with alanine (±CLA) (P = 0.05). CLA decreased adipose tissue oleic acid (18:1n-9) in alanine- or arginine-infused steers (P = 0.05), although CLA had no effect on SCD gene expression. The data indicate that supplemental arginine promotes adipogenic gene expression and may promote lipid accumulation in bovine adipose tissue. l-Arginine may beneficially improve beef quality for human consumption.     

Protective effects of dipeptidyl peptidase-4 (DPP-4) inhibitor against increased β cell apoptosis induced by dietary sucrose and linoleic acid in mice with diabetes

Chronic exposure to high glucose and fatty acid levels caused by dietary sugar and fat intake induces β cell apoptosis, leading to the exacerbation of type 2 diabetes. Oleic acid and linoleic acid are two major dietary fatty acids, but their effects in diabetes are unclear. We challenged β cell-specific glucokinase haploinsufficient (Gck(+/-)) mice with a diet containing sucrose and oleic acid (SO) or sucrose and linoleic acid (SL) and analyzed β cell apoptosis. In Gck(+/-) but not wild-type mice, SL significantly decreased the β cell mass and β cell proportion in islet cells arising from increased apoptosis to a greater degree than did SO. The mRNA expression of SREBP-1c was significantly higher, and that of E-cadherin was significantly lower in the islets of Gck(+/-) mice fed SL compared with mice fed SO. We next evaluated monotherapy with desfluorositagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, in these mouse groups. DPP-4 inhibitor protected against β cell apoptosis, restored the β cell mass, and normalized islet morphology in Gck(+/-) mice fed SL. DPP-4 inhibition normalized the changes in the islet expression of SREBP-1c and E-cadherin mRNA induced by the SL diet. Furthermore, linoleic acid induced β cell apoptosis to a greater degree in the presence of high glucose levels than in the presence of low glucose levels in vitro in islets and MIN6 cells, whereas a GLP-1 receptor agonist prevented apoptosis. In conclusion, SL exacerbated β cell apoptosis in diabetic Gck(+/-) mice but not in euglycemic wild-type mice, and DPP-4 inhibition protected against these effects.     

Effect of dietary cation–anion difference on ruminal metabolism,total apparent digestibility,blood and renal acid–base regulation in lactating dairy cows

The present study aimed to evaluate the effect of dietary cation–anion difference (DCAD) on ruminal fermentation, total apparent digestibility, blood and renal metabolism of lactating dairy cows. Sixteen Holstein cows were distributed in four contemporary 4×4 Latin Square designs, which consisted of four periods of 21 days and four treatments according to DCAD: +290; +192; +98 and −71 milliequivalent (mEq)/kg dry matter (DM). Ruminal pH and concentrations of acetic and butyric acid increased linearly according to the increase of DCAD. Similarly, NDF total apparent digestibility linearly increased by 6.38% when DCAD increased from −71 to 290 mEq/kg DM [Y=65.90 (SE=2.37)+0.0167 (SE=0.0068)×DCAD (mEq/kg DM)]. Blood pH was also increased according to DCAD, which resulted in reduction of serum concentrations of Na, K and ionic calcium (iCa). To maintain the blood acid–base homeostasis, renal metabolism played an important role in controlling serum concentrations of Na and K, since the Na and K urinary excretion increased linearly by 89.69% and 46.06%, respectively, from −71 to 290 mEq/kg DM. Changes in acid–base balance of biological fluids may directly affect the mineral composition of milk, as milk concentrations of Na, K, iCa and chlorides were reduced according to blood pH increased. Thus, it can be concluded that the increase of DCAD raises the pH of ruminal fluid, NDF total apparent digestibility, and blood pH, and decreases the milk concentration of cationic minerals, as well as the efficiency of Na utilization to milk production.     

Preferential intracellular pH regulation represents a general pattern of pH homeostasis during acid–base disturbances in the armoured catfish,Pterygoplichthys pardalis

Preferential intracellular pH (pH_i) regulation, where pH_i is tightly regulated in the face of a blood acidosis, has been observed in a few species of fish, but only during elevated blood PCO₂. To determine whether preferential pH_i regulation may represent a general pattern for acid–base regulation during other pH disturbances we challenged the armoured catfish, Pterygoplichthys pardalis, with anoxia and exhaustive exercise, to induce a metabolic acidosis, and bicarbonate injections to induce a metabolic alkalosis. Fish were terminally sampled 2–3 h following the respective treatments and extracellular blood pH, pH_i of red blood cells (RBC), brain, heart, liver and white muscle, and plasma lactate and total CO₂ were measured. All treatments resulted in significant changes in extracellular pH and RBC pH_i that likely cover a large portion of the pH tolerance limits of this species (pH 7.15–7.86). In all tissues other than RBC, pH_i remained tightly regulated and did not differ significantly from control values, with the exception of a decrease in white muscle pH_i after anoxia and an increase in liver pH_i following a metabolic alkalosis. Thus preferential pH_i regulation appears to be a general pattern for acid–base homeostasis in the armoured catfish and may be a common response in Amazonian fishes.     

Compensatory regulation of acid–base balance during salinity transfer in rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>)

In seawater-acclimated rainbow trout (Oncorhynchus mykiss), base secretion into the intestine is a key component of the intestinal water absorption that offsets osmotic water loss to the marine environment. Acid–base balance is maintained by the matched excretion of acid equivalents via other routes, presumably the gill and/or kidney. The goal of the present study was to examine acid–base balance in rainbow trout upon transfer to more dilute environments, conditions under which base excretion into the intestine is predicted to fall, requiring compensatory adjustments of acid excretion at the gill and/or kidney if acid–base balance is to be maintained. Net acid excretion via the gill/kidney and rectal fluid, and blood acid–base status were monitored in seawater-acclimated rainbow trout maintained in seawater or transferred to iso-osmotic conditions. As predicted, transfer to iso-osmotic conditions significantly reduced base excretion into the rectal fluid (by ~48%). Transfer to iso-osmotic conditions also significantly reduced the excretion of titratable acidity via extra-intestinal routes from 183.4 ± 71.3 to −217.5 ± 42.7 μmol kg⁻¹ h⁻¹ (N = 7). At the same time, however, ammonia excretion increased significantly during iso-osmotic transfer (by ~72%) so that the apparent overall reduction in net acid excretion (from 419.7 ± 92.9 to 189.2 ± 76.5 μmol kg⁻¹ h⁻¹; N = 7) was not significant. Trout maintained blood acid–base status during iso-osmotic transfer, although arterial pH was significantly higher in transferred fish than in those maintained in seawater. To explore the mechanisms underlying these adjustments of acid–base regulation, the relative mRNA expression and where possible, activity of a suite of proteins involved in acid–base balance were examined in intestine, gill and kidney. At the kidney, reduced mRNA expression of carbonic anhydrase (CA; cytosolic and membrane-associated CA IV), V-type H⁺-ATPase, and Na⁺/HCO₃ ⁻ co-transporter were consistent with a reduced role in net acid excretion following iso-osmotic transfer. Changes in relative mRNA expression and/or activity at the intestine and gill were consistent with the roles of these organs in osmotic rather than acid–base regulation. Overall, the data emphasize the coordination of acid–base, osmoregulatory and ionoregulatory processes that occur with salinity transfer in a euryhaline fish.