Thia fatty acids, metabolism and metabolic effects

Preparation and Preliminary Evaluation of a Promising 99mTc-Labeled Isonitrile-Containing 6-Thia-Fatty Acid Derivative for Myocardial Metabolism Imaging

For over 40 years, none of the previous ^99mTc-labeled fatty acids for myocardial imaging has potential clinical use. ^99mTc-(C10-6-thia-CO₂H)(MIBI)₅ is the first ^99mTc-labeled fatty acid to exhibit good myocardial uptake (2.06 ± 0.06%ID/g) at 60 min post injection, high heart-to-liver ratio (6.43 ± 1.85 and 9.68 ± 0.76), high heart-to-lung ratio (9.48 ± 1.39 and 11.02 ± 0.89), and high heart-to-blood ratio (164.01 ± 43.51 and 197.36 ± 32.29) at 60 and 120 min in Sprague-Dawley (SD) rats, respectively. It also demonstrated excellent myocardial imaging quality. The above target-to-nontarget ratios exceeded those of [¹²³I]BMIPP and were higher than or close to those of ^99mTc-MIBI at 60 and 120 min. Most of ^99mTc-(C10-6-thia-CO₂H)(MIBI)₅ was partially β-oxidized to protein-bound metabolites in myocardium. Administration of trimetazidine dihydrochloride (TMZ, a fatty acid β-oxidation inhibitor) to rats caused 51% reduction in the myocardial uptake of ^99mTc-(C10-6-thia-CO₂H)(MIBI)₅ and 61% reduction in the distribution of ^99mTc-radioactivity in a residual tissue pellet at 60 min, indicating its considerable sensitivity to myocardial fatty acid β-oxidation.

Multiomics Approach Captures Hepatic Metabolic Network Altered by Chronic Ethanol Administration

Using a multiplatform and multiomics approach, we identified metabolites, lipids, proteins, and metabolic pathways that were altered in the liver after chronic ethanol administration. A functional enrichment analysis of the multiomics dataset revealed that rats treated with ethanol experienced an increase in hepatic fatty acyl content, which is consistent with an initial development of steatosis. The nuclear magnetic resonance spectroscopy (NMR) and liquid chromatography-mass spectrometry (LC-MS) metabolomics data revealed that the chronic ethanol exposure selectively modified toxic substances such as an increase in glucuronidation tyramine and benzoyl; and a depletion in cholesterol-conjugated glucuronides. Similarly, the lipidomics results revealed that ethanol decreased diacylglycerol, and increased triacylglycerol, sterol, and cholesterol biosynthesis. An integrated metabolomics and lipidomics pathway analysis showed that the accumulation of hepatic lipids occurred by ethanol modulation of the upstream lipid regulatory pathways, specifically glycolysis and glucuronides pathways. A proteomics analysis of lipid droplets isolated from control EtOH-fed rats and a subsequent functional enrichment analysis revealed that the proteomics data corroborated the metabolomic and lipidomic findings that chronic ethanol administration altered the glucuronidation pathway.

Endothelial Cell Metabolism in Vascular Functions

Simple Summary

Recent findings in the field of vascular biology are nourishing the idea that targeting the endothelial cell metabolism may be an alternative strategy to antiangiogenic therapy, as well as a novel therapeutic approach for cardiovascular disease. Deepening the molecular mechanisms regulating how ECs re-adapt their metabolic status in response to the changeable conditions of the tissue microenvironment may be beneficial to develop novel innovative treatments to counteract the aberrant growth of vasculature.

Abstract

The endothelium is the innermost layer of all blood and lymphatic vessels composed of a monolayer of specialized endothelial cells (ECs). It is regarded as a dynamic and multifunctional endocrine organ that takes part in essential processes, such as the control of blood fluidity, the modulation of vascular tone, the regulation of immune response and leukocyte trafficking into perivascular tissues, and angiogenesis. The inability of ECs to perform their normal biological functions, known as endothelial dysfunction, is multi-factorial; for instance, it implicates the failure of ECs to support the normal antithrombotic and anti-inflammatory status, resulting in the onset of unfavorable cardiovascular conditions such as atherosclerosis, coronary artery disease, hypertension, heart problems, and other vascular pathologies. Notably, it is emerging that the ability of ECs to adapt their metabolic status to persistent changes of the tissue microenvironment could be vital for the maintenance of vascular functions and to prevent adverse vascular events. The main purpose of the present article is to shed light on the unique metabolic plasticity of ECs as a prospective therapeutic target; this may lead to the development of novel strategies for cardiovascular diseases and cancer.

Increased expression of acyl-CoA oxidase 2 in the kidney with plasma phytanic acid and altered gut microbiota in spontaneously hypertensive rats

We performed a DNA microarray analysis of the renal medulla and cortex from spontaneously hypertensive rats (SHRs), stroke-prone SHRs (SHRSPs), and Wistar-Kyoto (WKY) rats to identify pivotal molecules in the kidney associated with the onset of hypertension and found increased expression of acyl-CoA oxidase 2 (Acox2) mRNA. Real-time polymerase chain reaction revealed that Acox2 mRNA expression in the renal medulla and cortex of SHRs and SHRSPs was increased in comparison to WKY rats. These findings indicate that increased renal ACOX2 (an enzyme that induces the β-oxidation of fatty acids) is associated with the onset of hypertension. Immunostaining of ACOX2 in the distal tubules from SHRs was stronger than that in the distal tubules from WKY rats. Western blot analysis showed increased expression of ACOX2 protein in renal medulla from SHRs. Regarding the overexpression of ACOX2, plasma levels of phytanic acid in SHRs were significantly higher than those in WKY rats. There were no differences in other short-chain fatty acids. Plasma phytanic acid was affected by the gut microbiota through the conversion from phytol by yeast in the intestinal tract. We compared the gut microbiota profile in three strains of 5-week-old rats by the terminal-restriction fragment length polymorphism method. The gut microbiota profile and ratio of Firmicutes/Bacteroides differed between SHRs and WKY rats. These findings suggest that the increased expression of ACOX2 in the kidney along with increases in plasma phytanic acid and the altered gut microbiota may be involved in the oxidation in the kidney and the pathogenesis of hypertension.

Regional similarities and differences in mature human milk fatty acids in Chinese population: A systematic review

Maternal factors such as the diet can impact human milk fatty acid profiles. We hypothesized that mature human milk fatty acid profiles differ among regions of China. To test our hypothesis, we conducted a systematic review to calculate regional average contents of fatty acids and the statistical significance of regional differences in fatty acids. We searched both Chinese and English literature databases and selected 21 articles, including 11 in Chinese and 10 in English. We categorized regions of China by 3 ways: 1) north vs. south; 2) inland vs. coastal; 3) socioeconomic development levels. The ratios of ΣSFAs:ΣMUFAs:ΣPUFAs were similar between regions and the average was 1:1:0.7. Contents of palmitic, oleic, and linoleic acids were also similar between regions and together they accounted for more than 70% of all fatty acids in mature human milk. Conversely, concentrations of ALA and DHA differed more than palmitic, oleic, and linoleic acids. We also found that it might be necessary to reduce maternal dietary contents of potentially harmful fatty acids such as erucic acid to minimize detrimental effects on infant health. To our knowledge, this study represents the first systematic review that quantitatively investigated the regional similarities and differences in mature human milk fatty acid contents and is therefore significant for academia and policy makers.

Radiation induced oxidation of [18F]fluorothia fatty acids under cGMP manufacturing conditions

OBJECTIVE

The objectives of the present work were to optimize and validate the synthesis and stability of 14(R,S)-[¹⁸F]fluoro-6-thia-heptadecanoic acid ([¹⁸F]FTHA) and 16-[¹⁸F]fluoro-4-thia-palmitic acid ([¹⁸F]FTP) under cGMP conditions for clinical applications.

METHODS

Benzyl-14-(R,S)-tosyloxy-6-thiaheptadecanoate and methyl 16-bromo-4-thia-palmitate were used as precursors for the synthesis of [¹⁸F]FTHA and [¹⁸F]FTP, respectively. For comparison, a fatty acid analog lacking a thia-substitution, 16-[¹⁸F]fluoro-palmitic acid ([¹⁸F]FP), was synthesized from the precursor methyl 16-bromo-palmitate. A standard nucleophilic reaction using cryptand (Kryptofix/K222, 8.1 mg), potassium carbonate (K₂CO₃, 4.0 mg) and ¹⁸F-fluoride were employed for the ¹⁸F-labeling and potassium hydroxide (0.8 M) was used for the post-labeling ester hydrolysis. The final products were purified via reverse phase semi-preparative HPLC and concentrated via trap and release on a C-18 plus solid phase extraction cartridge. The radiochemical purities of the [¹⁸F]fluorothia fatty acids and [¹⁸F]FP were examined over a period of 4 h post-synthesis using an analytical HPLC. All the syntheses were optimized in an automated TRACERlab FX-N Pro synthesizer. Liquid chromatography mass spectrometry (LCMS) and high resolution mass spectrometry (HRMS) was employed to study the identity and nature of side products formed during radiosynthesis and as a consequence of post-synthesis radiation induced oxidation.

RESULTS

Radiosyntheses of [¹⁸F]FTHA, [¹⁸F]FTP and [¹⁸F]FP were achieved in moderate (8-20% uncorrected) yields. However, it was observed that the HPLC-purified [¹⁸F]fluorothia fatty acids, [¹⁸F]FTHA and [¹⁸F]FTP at higher radioactivity concentrations (>1.11 GBq/mL, 30 mCi/mL) underwent formation of ¹⁸F-labeled side products over time but [¹⁸F]FP (lacking a sulfur heteroatom) remained stable up to 4 h post-synthesis. Various radiation protectors like ethanol and ascorbic acid were examined to minimize the formation of side products formed during [¹⁸F]FTHA and [¹⁸F]FTP synthesis but showed only limited to no effect. Analysis of the side products by LCMS showed formation of sulfoxides of both [¹⁸F]FTHA and [¹⁸F]FTP. The identity of the sulfoxide side product was further confirmed by synthesizing a non-radioactive reference standard of the sulfoxide analog of FTP and matching retention times on HPLC and molecular ion peaks on LC/HRMS. Radiation-induced oxidation of the sulfur heteroatom was mitigated by dilution of product with isotonic saline to reduce the radioactivity concentration to <0.518 GBq/mL (14 mCi/mL).

CONCLUSIONS

Successful automated synthesis of [¹⁸F]fluorothia fatty acids were carried out in cGMP facility for their routine production and clinical applications. Instability of [¹⁸F]fluorothia fatty acids were observed at radioactivity concentrations exceeding 1.11 GBq/mL (30 mCi/mL) but mitigated through dilution of the product to <0.518 GBq/mL (14 mCi/mL). The identities of the side products formed were established as the sulfoxides of the respective thia fatty acids caused by radiation-induced oxidation of the sulfur heteroatom.

Occurrence of Sulfur-Containing Fatty Acids in Allium sativum

The occurrence of saturated (14:0, 15:0, 16:0, and 18:0), and unsaturated (7–16:1, 7–18:1, 9–18:1, 9,12–18:2, 9,12,15–18:3) acids, together with novel cyclic sulfur-containing fatty acids in garlic ( Allium sativum) is reported. Organosulfur compounds, fatty acids, and sulfur-containing fatty acids were separated and characterized by GC–MS with serially coupled capillary columns with consecutive nonpolar and semipolar stationary phases.

Investigation of Efficacy Enhancing and Toxicity Reducing Mechanism of Combination of Aconiti Lateralis Radix Praeparata and Paeoniae Radix Alba in Adjuvant-Induced Arthritis Rats by Metabolomics

Combination of Aconiti Lateralis Radix Praeparata (FZ) and Paeoniae Radix Alba (BS) shows a significant effect in rheumatoid arthritis (RA). This study aimed to investigate the efficacy enhancing and toxicity reducing mechanism of combination of them in adjuvant-induced arthritis (AIA) rats by metabolomics. Rats were randomly divided into seven groups, including A (healthy control), B (model control), C1 (therapy group), C2 (efficacy enhancing group), D1 (toxicity group), and D2 (toxicity reducing group), and dexamethasone group was used as positive control. The plasma biochemical indexes showed that therapeutic dose of lipid-soluble alkaloids of FZ could significantly inhibit the concentrations of IL-1β, TNF-α, and IFN-γ in AIA rats, and combination with total glucosides of peony could further reduce the concentration of IL-1β. Then, UPLC-LTQ/Orbitrap MS with untargeted metabolomics was performed to identify the possible metabolites and pathways. Through multivariate data analysis of therapeutic dose groups (A vs. B vs. C1 vs. C2) and multivariate data analysis of toxic dose groups (A vs. B vs. D1 vs. D2), 10 and 7 biomarkers were identified based on biomarker analysis, respectively. After inducing AIA model, the plasma contents of spermidine, vanillylmandelic acid, catechol, and linoleate were increased significantly, and the contents of citric acid, L-tyrosine, L-phenylalanine, leucine, L-tryptophan, and uridine 5'-monophosphate (UMP) were decreased significantly. High dose of lipid-soluble alkaloids of FZ could increase the plasma contents of L-lysine, L-arginine, and deoxycholic acid, while the plasma contents of UMP, carnitine, N-formylanthranilic acid, and adenosine were decreased significantly. The pathway analysis indicated that therapeutic dose of lipid-soluble alkaloids of FZ could regulate energy and amino acid metabolic disorders in AIA rats. However, toxic dose could cause bile acid, fat, amino acid, and energy metabolic disorders. And combination with total glucosides of peony could enhance the therapeutic effects and attenuate the toxicity induced by lipid-soluble alkaloids of FZ.

Effects of tetradecylthioacetic acid (TTA) treatment on lipid metabolism in salmon hearts-in vitro and in vivo studies

In intensive farming of Atlantic salmon, a large proportion of observed mortality is related to cardiovascular diseases and circulatory failure, indicating insufficient robustness and inadequate cardiac performance. This paper reports on the use of tetradecylthioacetic acid (TTA) where the main objective was to enhance utilisation of fatty acids (FA), considered the main energy source of the heart. In this study, three experiments were conducted: (I) an in vivo study where salmon post-smolt were administrated dietary TTA in sea, (II) an in vitro study where isolated salmon heart cells were pre-stimulated with increasing doses of TTA and (III) an in vivo experiment where salmon post-smolt were subjected to injections with increasing doses of TTA. In study I, TTA-treated fish had a smaller decrease in heart weight relative to fish bodyweight (CSI) in a period after sea transfer compared to the control. This coincided with lowered condition factor and muscle fat in the TTA-treated fish, which may indicate a higher oxidation of lipids for energy. In study II, the isolated hearts treated with the highest dose of TTA had higher uptake of radiolabelled FA and formation of CO₂ and acid-soluble products. In study III, expression of genes regulating peroxisomal FA oxidation, cell growth, elongation and desaturation were upregulated in the heart of TTA injected salmon. In contrast, genes involved in FA transport into the mitochondria were not influenced. In conclusion, these experiments indicate that TTA enhances energy production in salmon hearts by stimulation of FA oxidation.

Associations between fatty acid oxidation, hepatic mitochondrial function, and plasma acylcarnitine levels in mice

Background

The 4-thia fatty acid tetradecylthiopropionic acid (TTP) is known to inhibit mitochondrial β-oxidation, and can be used as chemically induced hepatic steatosis-model in rodents, while 3-thia fatty acid tetradecylthioacetic acid (TTA) stimulates fatty acid oxidation through activation of peroxisome proliferator activated receptor alpha (PPARα). We wished to determine how these two compounds affected in vivo respiration and mitochondrial efficiency, with an additional goal to elucidate whether mitochondrial function is reflected in plasma acylcarnitine levels.

Methods

C57BL/6 mice were divided in 4 groups of 10 mice and fed a control low-fat diet, low-fat diets with 0.4% (w/w) TTP, 0.4% TTA or a combination of these two fatty acids for three weeks (n = 10). At sacrifice, β-oxidation and oxidative phosphorylation (OXPHOS) capacity was analysed in fresh liver samples. Hepatic mitochondria were studied using transmission electron microscopy. Lipid classes were measured in plasma, heart and liver, acylcarnitines were measured in plasma, and gene expression was measured in liver.

Results

The TTP diet resulted in hepatic lipid accumulation, plasma L-carnitine and acetylcarnitine depletion and elevated palmitoylcarnitine and non-esterified fatty acid levels. No significant lipid accumulation was observed in heart. The TTA supplement resulted in enhanced hepatic β-oxidation, accompanied by an increased level of acetylcarnitine and palmitoylcarnitine in plasma. Analysis of mitochondrial respiration showed that TTP reduced oxidative phosphorylation, while TTA increased the maximum respiratory capacity of the electron transport system. Combined treatment with TTP and TTA resulted in a profound stimulation of genes involved in the PPAR-response and L-carnitine metabolism, and partly prevented triacylglycerol accumulation in the liver concomitant with increased peroxisomal β-oxidation and depletion of plasma acetylcarnitines. Despite an increased number of mitochondria in the liver of TTA + TTP fed mice, the OXPHOS capacity was significantly reduced.

Conclusion

This study indicates that fatty acid β-oxidation directly affects mitochondrial respiratory capacity in liver. As plasma acylcarnitines reflected the reduced mitochondrial β-oxidation in TTP-fed mice, they could be useful tools to monitor mitochondrial function. As mitochondrial dysfunction is a major determinant of metabolic disease, this supports their use as plasma markers of cardiovascular risk in humans. Results however indicate that high PPAR activation obscures the interpretation of plasma acylcarnitine levels.

Electronic supplementary material

The online version of this article (10.1186/s12986-018-0241-7) contains supplementary material, which is available to authorized users.

Investigation of Liver Injury of Polygonum multiflorum Thunb. in Rats by Metabolomics and Traditional Approaches

Liver injury induced by Polygonum multiflorum Thunb. (PM) have been reported since 2006, which aroused widespread concern. However, the toxicity mechanism of PM liver injury remained unclear. In this study, the mechanism of liver injury induced by different doses of PM after long-term administration was investigated in rats by metabolomics and traditional approaches. Rats were randomly divided into control group and PM groups. PM groups were oral administered PM of low (10 g/kg), medium (20 g/kg), high (40 g/kg) dose, while control group was administered distilled water. After 28 days of continuous administration, the serum biochemical indexes in the control and three PM groups were measured and the liver histopathology were analyzed. Also, UPLC-Q-TOF-MS with untargeted metabolomics was performed to identify the possible metabolites and pathway of liver injury caused by PM. Compared with the control group, the serum levels of ALT, AST, ALP, TG, and TBA in middle and high dose PM groups were significantly increased. And the serum contents of T-Bil, D-Bil, TC, TP were significantly decreased. However, there was no significant difference between the low dose group of PM and the control group except serum AST, TG, T-Bil, and D-Bil. Nine biomarkers were identified based on biomarkers analysis. And the pathway analysis indicated that fat metabolism, amino acid metabolism and bile acid metabolism were involved in PM liver injury. Based on the biomarker pathway analysis, PM changed the lipid metabolism, amino acid metabolism and bile acid metabolism and excretion in a dose-dependent manner which was related to the mechanism of liver injury.

Differences in fat accumulation between immature male and female Atlantic salmon Salmo salar after dietary administration of tetradecylthioacetic acid

This study provoked sex-specific differences in fat metabolism in Atlantic salmon Salmo salar, by dietary administration of tetradecylthioacetic acid (TTA) during their first spring and winter in the sea. The effects of TTA were evaluated in June of the first spring and May of the second spring in the sea, by analysing white muscle-fat content. Muscle fat in males and females differed significantly as a result of TTA in their diet and diet interacted with the sex of the fish. The fat content during the first spring after dietary TTA was lowered by a greater amount in females than in males, 3·1-4·3%, respectively (P < 0·05). In contrast, during the second spring, fat content was lowered by a greater amount in males than in females, 15·8-16·7%, respectively (P < 0·01). Condition factor followed a similar pattern to the muscle fat. The results indicate that the difference in male and female fat accumulation dynamics is related to sex-specific reproduction biology of S. salar. In addition, the findings show that it is important to consider the sex of the fish and the season of the year when studying fat dynamics and reproductive biology of S. salar.

Probing fatty acid metabolism in bacteria, cyanobacteria, green microalgae and diatoms with natural and unnatural fatty acids

In both eukaryotes and prokaryotes, fatty acid synthases are responsible for the biosynthesis of fatty acids in an iterative process, extending the fatty acid by two carbon units every cycle. Thus, odd numbered fatty acids are rarely found in nature. We tested whether representatives of diverse microbial phyla have the ability to incorporate odd-chain fatty acids as substrates for their fatty acid synthases and their downstream enzymes. We fed various odd and short chain fatty acids to the bacterium Escherichia coli, cyanobacterium Synechocystis sp. PCC 6803, green microalga Chlamydomonas reinhardtii and diatom Thalassiosira pseudonana. Major differences were observed, specifically in the ability among species to incorporate and elongate short chain fatty acids. We demonstrate that E. coli, C. reinhardtii, and T. pseudonana can produce longer fatty acid products from short chain precursors (C3 and C5), while Synechocystis sp. PCC 6803 lacks this ability. However, Synechocystis can incorporate and elongate longer chain fatty acids due to acyl-acyl carrier protein synthetase (AasS) activity, and knockout of this protein eliminates the ability to incorporate these fatty acids. In addition, expression of a characterized AasS from Vibrio harveyii confers a similar capability to E. coli. The ability to desaturate exogenously added fatty acids was only observed in Synechocystis and C. reinhardtii. We further probed fatty acid metabolism of these organisms by feeding desaturase inhibitors to test the specificity of long-chain fatty acid desaturases. In particular, supplementation with thia fatty acids can alter fatty acid profiles based on the location of the sulfur in the chain. We show that coupling sensitive gas chromatography mass spectrometry to supplementation of unnatural fatty acids can reveal major differences between fatty acid metabolism in various organisms. Often unnatural fatty acids have antibacterial or even therapeutic properties. Feeding of short precursors now gives us easy access to these extended molecules.

Tetradecylthiopropionic acid induces hepatic mitochondrial dysfunction and steatosis, accompanied by increased plasma homocysteine in mice

BACKGROUND

Hepatic mitochondrial dysfunction plays an important role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Methyl donor supplementation has been shown to alleviate NAFLD, connecting the condition to the one-carbon metabolism. Thus, the objective was to investigate regulation of homocysteine (Hcy) and metabolites along the choline oxidation pathway during induction of hepatic steatosis by the fatty acid analogue tetradecylthiopropionic acid (TTP), an inhibitor of mitochondrial fatty acid oxidation.

METHODS

Mice were fed a control diet, or diets containing 0.3 %, 0.6 %, or 0.9 % (w/w) TTP for 14 days. Blood and liver samples were collected, enzyme activities and gene expression were analyzed in liver, lipid and fatty acid composition in liver and plasma, one-carbon metabolites, B-vitamin status, carnitine and acylcarnitines were analyzed in plasma.

RESULTS

Liver mitochondrial fatty acid oxidation decreased by 40 % and steatosis was induced in a dose dependent manner; total lipids increased 1.6-fold in animals treated with 0.3 % TTP, 2-fold with 0.6 % TTP and 2.1 fold with 0.9 % TTP compared to control. The higher hepatic concentration of fatty acids was associated with shortening of carbon-length. Furthermore, the inhibited fatty acid oxidation led to a 30-fold decrease in plasma carnitine and 9.3-fold decrease in acetylcarnitine at the highest dose of TTP, whereas an accumulation of palmitoylcarnitine resulted. Compared to the control diet, TTP administration was associated with elevated plasma total Hcy (control: 7.2 ± 0.3 umol/L, 0.9 % TTP: 30.5 ± 5.9 umol/L) and 1.4-1.6 fold increase in the one-carbon metabolites betaine, dimethylglycine, sarcosine and glycine, accompanied by changes in gene expression of the different B-vitamin dependent pathways of Hcy and choline metabolism. A positive correlation between total Hcy and hepatic triacylglycerol resulted.

CONCLUSIONS

The TTP-induced inhibition of mitochondrial fatty acid oxidation was not associated with increased hepatic oxidative stress or inflammation. Our data suggest a link between mitochondrial dysfunction and the methylation processes within the one-carbon metabolism in mice.

Chemical genetics of acetyl-CoA carboxylases

Chemical genetic studies on acetyl-CoA carboxylases (ACCs), rate-limiting enzymes in long chain fatty acid biosynthesis, have greatly advanced the understanding of their biochemistry and molecular biology and promoted the use of ACCs as targets for herbicides in agriculture and for development of drugs for diabetes, obesity and cancers. In mammals, ACCs have both biotin carboxylase (BC) and carboxyltransferase (CT) activity, catalyzing carboxylation of acetyl-CoA to malonyl-CoA. Several classes of small chemicals modulate ACC activity, including cellular metabolites, natural compounds, and chemically synthesized products. This article reviews chemical genetic studies of ACCs and the use of ACCs for targeted therapy of cancers.

AMP-activated protein kinase and ATP-citrate lyase are two distinct molecular targets for ETC-1002, a novel small molecule regulator of lipid and carbohydrate metabolism

ETC-1002 (8-hydroxy-2,2,14,14-tetramethylpentadecanedioic acid) is a novel investigational drug being developed for the treatment of dyslipidemia and other cardio-metabolic risk factors. The hypolipidemic, anti-atherosclerotic, anti-obesity, and glucose-lowering properties of ETC-1002, characterized in preclinical disease models, are believed to be due to dual inhibition of sterol and fatty acid synthesis and enhanced mitochondrial long-chain fatty acid β-oxidation. However, the molecular mechanism(s) mediating these activities remained undefined. Studies described here show that ETC-1002 free acid activates AMP-activated protein kinase in a Ca(2+)/calmodulin-dependent kinase β-independent and liver kinase β 1-dependent manner, without detectable changes in adenylate energy charge. Furthermore, ETC-1002 is shown to rapidly form a CoA thioester in liver, which directly inhibits ATP-citrate lyase. These distinct molecular mechanisms are complementary in their beneficial effects on lipid and carbohydrate metabolism in vitro and in vivo. Consistent with these mechanisms, ETC-1002 treatment reduced circulating proatherogenic lipoproteins, hepatic lipids, and body weight in a hamster model of hyperlipidemia, and it reduced body weight and improved glycemic control in a mouse model of diet-induced obesity. ETC-1002 offers promise as a novel therapeutic approach to improve multiple risk factors associated with metabolic syndrome and benefit patients with cardiovascular disease.

Tetradecylthioacetic acid inhibits proliferation of human SW620 colon cancer cells--gene expression profiling implies endoplasmic reticulum stress

Background

Previous reports have shown an antiproliferative effect of the synthetic, 3-thia fatty acid tetradecylthioacetic acid (TTA) on different cancer cells in vitro and in vivo. The mechanisms behind the observed effects are poorly understood. We therefore wanted to explore the molecular mechanisms involved in TTA-induced growth inhibition of the human colon cancer cell line SW620 by gene expression profiling.

Methods

An antiproliferative effect of TTA on SW620 cells in vitro was displayed in real time using the xCELLigence System (Roche). Affymetrix gene expression profiling was performed to elucidate the molecular mechanisms behind the antiproliferative effect of TTA. Changes in gene expression were verified at protein level by western blotting.

Results

TTA reduced SW620 cell growth, measured as baseline cell index, by 35% and 55% after 48 h and 72 h, respectively. We show for the first time that TTA induces an endoplasmic reticulum (ER) stress response in cancer cells. Gene expression analysis revealed changes related to ER stress and unfolded protein response (UPR). This was verified at protein level by phosphorylation of eukaryote translation initiation factor 2 alpha (eIF2α) and downstream up-regulation of activating transcription factor 4 (ATF4). Transcripts for positive and negative cell cycle regulators were down- and up-regulated, respectively. This, together with a down-regulation of Cyclin D1 at protein level, indicates inhibition of cell cycle progression. TTA also affected transcripts involved in calcium homeostasis. Moreover, mRNA and protein level of the ER stress inducible C/EBP-homologous protein (CHOP), Tribbles homolog 3 (Drosophila) (TRIB3) and CCAAT/enhancer binding protein beta (C/EBPβ) were enhanced, and the C/EBPβ LIP/LAP ratio was significantly increased. These results indicate prolonged ER stress and a possible link to induction of cell death.

Conclusion

We find that TTA-induced growth inhibition of SW620 cells seems to be mediated through induction of ER stress and activation of the UPR pathway.

Anti-inflammatory effects of tetradecylthioacetic acid (TTA) in macrophage-like cells from Atlantic salmon (Salmo salar L.)

Background

Commercial Atlantic salmon is fed diets with high fat levels to promote fast and cost-effective growth. To avoid negative impact of obesity, food additives that stimulate fat metabolism and immune function are of high interest. TTA, tetradecylthioacetic acid, is a synthetic fatty acid that stimulates mitochondrial β-oxidation most likely by activation of peroxysome proliferator-activated receptors (PPARs). PPARs are important transcription factors regulating multiple functions including fat metabolism and immune responses. Atlantic salmon experiments have shown that TTA supplemented diets significantly reduce mortality during natural outbreaks of viral diseases, suggesting a modulatory role of the immune system.

Results

To gain new insights into TTA effects on the Atlantic salmon immune system, a factorial, high-throughput microarray experiment was conducted using a 44K oligo nucleotide salmon microarray SIQ2.0 and the Atlantic salmon macrophage-like cell line ASK. The experiment was used to determine the transcriptional effects of TTA, the effects of TTA in poly(I:C) elicited cells and the effects of pretreating the cells with TTA. The expression patterns revealed that a large proportion of genes regulated by TTA were related to lipid metabolism and increased mitochondrial β-oxidation. In addition we found that for a subset of genes TTA antagonized the transcriptional effects of poly(I:C). This, together with the results from qRT-PCR showing an increased transcription of anti-inflammatory IL10 by TTA, indicates anti-inflammatory effects.

Conclusions

We demonstrate that TTA has significant effects on macrophage-like salmon cells that are challenged by the artificial dsRNA poly(I:C). The immune stimulatory effect of TTA in macrophages involves increased lipid metabolism and suppressed inflammatory status. Thus, suggesting that TTA directs the macrophage-like cells towards alternative, anti-inflammatory, activation. This has positive implications for TTA as a feed additive.

Synthesis and preliminary evaluation of 18-(18)F-fluoro-4-thia-oleate as a PET probe of fatty acid oxidation

Fatty acid oxidation (FAO) is a major energy-providing process with important implications in cardiovascular, oncologic, neurologic, and metabolic diseases. A novel 4-thia oleate analog, 18-(18)F-fluoro-4-thia-oleate ((18)F-FTO), was evaluated in relationship to the previously developed palmitate analog 16-(18)F-fluoro-4-thia-palmitate ((18)F-FTP) as an FAO probe.

METHODS

(18)F-FTO was synthesized from a corresponding bromoester. Biodistribution and metabolite analysis studies were performed in rats. Preliminary small-animal PET studies were performed with (18)F-FTO and (18)F-FTP in rats.

RESULTS

A practical synthesis of (18)F-FTO was developed, providing a radiotracer of high radiochemical purity (>99%). In fasted rats, myocardial uptake of (18)F-FTO (0.70 +/- 0.30% dose kg [body mass]/g [tissue mass]) was similar to that of (18)F-FTP at 30 min after injection. At 2 h, myocardial uptake of (18)F-FTO was maintained, whereas (18)F-FTP uptake in the heart was 82% reduced. Similar to (18)F-FTP, (18)F-FTO uptake by the heart was approximately 80% reduced at 30 min by pretreatment of rats with the CPT-I inhibitor etomoxir. Folch-type extraction analyses showed 70-90% protein-bound fractions in the heart, liver, and skeletal muscle, consistent with efficient trafficking of (18)F-FTO to the mitochondrion with subsequent metabolism to protein-bound species. Preliminary small-animal PET studies showed rapid blood clearance and avid extraction of (18)F-FTO and of (18)F-FTP into the heart and liver. Images of (18)F-FTO accumulation in the rat myocardium were clearly superior to those of (18)F-FTP.

CONCLUSION

(18)F-FTO is shown to be a promising metabolically trapped FAO probe that warrants further evaluation.

Dietary supplementation of tetradecylthioacetic acid increases feed intake but reduces body weight gain and adipose depot sizes in rats fed on high-fat diets

AIM

The pan-peroxisome proliferator-activated receptor (PPAR) ligand and fatty acid analogue tetradecylthioacetic acid (TTA) may reduce plasma lipids and enhance hepatic lipid metabolism, as well as reduce adipose tissue sizes in rats fed on high-fat diets. This study further explores the effects of TTA on weight gain, feed intake and adipose tissue functions in rats that are fed a high-fat diet for 7 weeks.

METHODS

The effects on feed intake and body weight during 7 weeks' dietary supplement with TTA ( approximately 200 mg/kg bw) were studied in male Wistar rats fed on a lard-based diet containing approximately 40% energy from fat. Adipose tissue mass, body composition and expression of relevant genes in fat depots and liver were measured at the end of the feeding.

RESULTS

Despite higher feed intake during the final 2 weeks of the study, rats fed on TTA gained less body weight than lard-fed rats and had markedly decreased subcutaneous, epididymal, perirenal and mesenteric adipose depots. The effects of TTA feeding with reduced body weight gain and energy efficiency (weight gain/feed intake) started between day 10 and 13. Body contents of fat, protein and water were reduced after feeding lard plus TTA, with a stronger decrease in fat relative to protein. Plasma lipids, including Non-Esterified Fatty Acids (NEFA), were significantly reduced, whereas fatty acid beta-oxidation in liver and heart was enhanced in lard plus TTA-fed rats. Hepatic UCP3 was expressed ectopically both at protein and mRNA level (>1900-fold), whereas Ucp1 mRNA was increased approximately 30-fold in epididymal and approximately 90-fold in mesenteric fat after lard plus TTA feeding.

CONCLUSION

Our data support the hypothesis that TTA feeding may increase hepatic fatty acid beta-oxidation, and thereby reduce the size of adipose tissues. The functional importance of ectopic hepatic UCP3 is unknown, but might be associated with enhanced energy expenditure and thus the reduced feed efficiency.

Stearoyl-CoA desaturase inhibitors: update on patented compounds

BACKGROUND

Stearoyl-CoA desaturase 1 (SCD1) has been implicated as a novel therapeutic target for the treatment of a variety of disease states, including hepatic steatosis, metabolic diseases, skin and eye disorders, and certain cancers.

OBJECTIVE/METHOD

This review focuses on the novel composition of matter patents in the area of small molecule SCD1 inhibitors, along with their pharmacological effects in relevant disease models. The prospect of targeting SCD1 inhibition as a novel therapeutic approach is discussed.

CONCLUSION

The rapid development of SCD1 inhibitors is evidenced by the increasing number of patent applications published and the number of promising preclinical compounds that have emerged in the past 5 years. Between January 2005 and February 2009, there were approximately 70 SCD1 inhibitor patent applications published.

miRNA in the regulation of skeletal muscle adaptation to acute endurance exercise in C57Bl/6J male mice

MicroRNAs (miRNAs) are evolutionarily conserved small non-coding RNA species involved in post-transcriptional gene regulation. In vitro studies have identified a small number of skeletal muscle-specific miRNAs which play a crucial role in myoblast proliferation and differentiation. In skeletal muscle, an acute bout of endurance exercise results in the up-regulation of transcriptional networks that regulate mitochondrial biogenesis, glucose and fatty acid metabolism, and skeletal muscle remodelling. The purpose of this study was to assess the expressional profile of targeted miRNA species following an acute bout of endurance exercise and to determine relationships with previously established endurance exercise responsive transcriptional networks. C57Bl/6J wild-type male mice (N = 7/group) were randomly assigned to either sedentary or forced-endurance exercise (treadmill run @ 15 m/min for 90 min) group. The endurance exercise group was sacrificed three hours following a single bout of exercise. The expression of miR- 181, 1, 133, 23, and 107, all of which have been predicted to regulate transcription factors and co-activators involved in the adaptive response to exercise, was measured in quadriceps femoris muscle. Endurance exercise significantly increased the expression of miR-181, miR-1, and miR-107 by 37%, 40%, and 56%, respectively, and reduced miR-23 expression by 84% (P≤0.05 for all), with no change in miR-133. Importantly, decreased expression of miRNA-23, a putative negative regulator of PGC-1α was consistent with increased expression of PGC-1α mRNA and protein along with several downstream targets of PGC-1α including ALAS, CS, and cytochrome c mRNA. PDK4 protein content remains unaltered despite an increase in its putative negative regulator, miR-107, and PDK4 mRNA expression. mRNA expression of miRNA processing machinery (Drosha, Dicer, and DGCR8) remained unchanged. We conclude that miRNA-mediated post-transcriptional regulation is potentially involved in the complex regulatory networks that govern skeletal muscle adaptation to endurance exercise in C57Bl/6J male mice.

Expression of polyalanine stretches induces mitochondrial dysfunction

In recent years, several novel types of disorders have been characterized, including what have been termed polyalanine diseases, in which patients have expanded triplet repeats in specific genes, resulting in the translation of aberrantly elongated polyalanine stretches. In this study, we showed that yellow fluorescent protein (YFP)-fused elongated polyalanine stretches localized exclusively to the cytoplasm and formed aggregates. Additionally, the polyalanine stretches themselves were toxic. We sought to identify proteins that bound directly to the polyalanine stretches, as factors that might be involved in triggering cell death. Many mitochondrial proteins were identified as polyalanine-binding proteins. We showed that one of the identified proteins, succinate dehydrogenase subunit A, was decreased in the mitochondria of cells expressing polyalanine stretches; as a result, succinate oxidative activity was decreased. Furthermore, the polyalanine stretches also associated directly with mitochondria. This suggests that polya-lanine stretches might directly induce cell death. Additionally, the mitochondrial membrane potential was reduced in cells expressing polyalanine stretches. We propose a novel mechanism by which polyalanine stretches may cause cytotoxicity through mitochondrial dysfunction. This may be a common mechanism underlying the pathogenesis of all polyalanine diseases.

Regulation of obesity and lipid disorders by herbal extracts from Morus alba, Melissa officinalis, and Artemisia capillaris in high-fat diet-induced obese mice

Melissa officinalis L. (Labiatae), Morus alba L. (Moraceae), and Artemisia capillaris Thunb. (Compositae) are suggested to be involved in the regulation of hyperlipidemia. We hypothesized that Ob-X, a mixture of three herbs, Morus alba, Melissa officinalis and Artemisia capillaris [corrected] improves lipid metabolism, body weight gain and adiposity and that peroxisome proliferator-activated receptor alpha (PPARalpha) is associated with these events. Mice fed a high-fat diet for 12 weeks exhibited increases in body weight gain and adipose tissue mass compared with mice fed a low fat diet. However, feeding a high-fat diet supplemented with Ob-X significantly reduced these effects. Ob-X treatment also decreased the circulating levels of triglycerides and total cholesterol, and inhibited hepatic lipid accumulation. Ob-X supplementation was found to increase the hepatic mRNA levels of PPARalpha target enzymes responsible for fatty acid beta-oxidation. Moreover, Ob-X elevated the endogenous expression of a luciferase reporter gene containing three copies of a PPAR response element (PPRE) in NMu2Li liver cells. These data demonstrate that Ob-X regulates body weight gain, adipose tissue mass, and lipid metabolism in part through changes in the expression of hepatic PPARalpha target genes.

Thia fatty acids with the sulfur atom in even or odd positions have opposite effects on fatty acid catabolism

As tools for mechanistic studies on lipid metabolism, with the long-term goal of developing a drug for the treatment of lipid disorders, thia FA with the sulfur atom inserted at positions 3-9 from the carboxyl group were fed to male Wistar rats for 1 wk to determine their impact on key parameters in lipid metabolism and hepatic levels of thia FA metabolites. Thia FA with the sulfur atom in even positions decreased hepatic and cardiac mitochondrial beta-oxidation and profoundly increased hepatic and cardiac TAG levels. The plasma TAG level was unchanged and the hepatic acyl-CoA oxidase activity increased. In contrast, thia FA with the sulfur atom in odd positions, especially 3-thia FA, tended to increase hepatic and cardiac FA oxidation and acyl-CoA oxidase and carnitine palmitoyltransferase-II activities, and decreased the plasma TAG levels. The effects seem to be related to differences in the catabolic rate of the thia FA. Differences between the two groups of acids were also observed with respect to the regulation of genes involved in FA transport and catabolism. Feeding experiments with 3- and 4-thia FA in combination indicated that the 4-thia FA partly attenuated the effects of the 3-thia FA on mitochondrial FA oxidation and the hepatic TAG level. In summary, the position of the sulfur atom in the alkyl chain, especially whether it is placed in the even or odd position, is crucial for the biological effect of the thia FA.

Energizing miRNA research: a review of the role of miRNAs in lipid metabolism, with a prediction that miR-103/107 regulates human metabolic pathways

MicroRNAs (miRNAs) are powerful regulators of gene expression. Although first discovered in worm larvae, miRNAs play fundamental biological roles-including in humans-well beyond development. MiRNAs participate in the regulation of metabolism (including lipid metabolism) for all animal species studied. A review of the fascinating and fast-growing literature on miRNA regulation of metabolism can be parsed into three main categories: (1) adipocyte biochemistry and cell fate determination; (2) regulation of metabolic biochemistry in invertebrates; and (3) regulation of metabolic biochemistry in mammals. Most research into the 'function' of a given miRNA in metabolic pathways has concentrated on a given miRNA acting upon a particular 'target' mRNA. Whereas in some biological contexts the effects of a given miRNA:mRNA pair may predominate, this might not be the case generally. In order to provide an example of how a single miRNA could regulate multiple 'target' mRNAs or even entire human metabolic pathways, we include a discussion of metabolic pathways that are predicted to be regulated by the miRNA paralogs, miR-103 and miR-107. These miRNAs, which exist in vertebrate genomes within introns of the pantothenate kinase (PANK) genes, are predicted by bioinformatics to affect multiple mRNA targets in pathways that involve cellular Acetyl-CoA and lipid levels. Significantly, PANK enzymes also affect these pathways, so the miRNA and 'host' gene may act synergistically. These predictions require experimental verification. In conclusion, a review of the literature on miRNA regulation of metabolism leads us believe that the future will provide researchers with many additional energizing revelations.

Synthesis and antifungal properties of alpha-methoxy and alpha-hydroxyl substituted 4-thiatetradecanoic acids

4-thiatetradecanoic acid exhibited weak antifungal activities against Candida albicans (ATCC 60193), Cryptococcus neoformans (ATCC 66031), and Aspergillus niger (ATCC 16404) (MIC=4.8-12.7 mM). It has been demonstrated that alpha-methoxylation efficiently blocks beta-oxidation and significantly improve the antifungal activities of fatty acids. We examined whether antifungal activity of 4-thiatetradecanoic acid can be improved by alpha-substitution. The unprecedented (+/-)-2-hydroxy-4-thiatetradecanoic acid was synthesized in four steps (20% overall yield), while the (+/-)-2-methoxy-4-thiatetradecanoic acid was synthesized in five steps (14% overall yield) starting from 1-decanethiol. The key step in the synthesis was the hydrolysis of a trimethylsilyloxynitrile. In general, the novel (+/-)-2-methoxy-4-thiatetradecanoic acid displayed significantly higher antifungal activities against C. albicans (ATCC 60193), C. neoformans (ATCC 66031), and A. niger (ATCC 16404) (MIC=0.8-1.2 mM), when compared with 4-thiatetradecanoic acid. In the case of C. neoformans the (+/-)-2-hydroxy-4-thiatetradecanoic acid was more fungitoxic (MIC=0.17 mM) than the alpha-methoxylated analog, but not as effective against A. niger (MIC=5.5 mM). The enhanced fungitoxicity of the (+/-)-2-methoxy-4-thiatetradecanoic acid, as compared to decylthiopropionic acid, might be the result of a longer half-life in the cells due to a blocked beta-oxidation pathway which results in more time to exert its toxic effects. Thus, these novel fatty acids may have applications as probes to study fatty acid metabolic routes in human cells.

Synthesis of a novel series of 2-methylsulfanyl fatty acids and their toxicity on the human K-562 and U-937 leukemia cell lines

The hitherto unknown 2-methylsulfanyldecanoic acid and 2-methylsulfanyldodecanoic acid were synthesized from methyl decanoate and methyl dodecanoate, respectively, through the reaction of lithium diisopropylamide and dimethyldisulfide in THF followed by saponification with potassium hydroxide in ethanol. Both alpha-methylsulfanylated FA were cytotoxic to the human chronic myelogenous leukemia K-562 and the human histiocytic lymphoma U-937 cell lines with EC50 values in the 200-300 microM range, which makes them more cytotoxic to these cell lines than decanoic and/or dodecanoic acid. The cytotoxicity of the studied FA toward K-562 followed the order 2-SCH3-12:0 > 2-SCH3-10:0 > 10:0 > 12:0 > 2-OCH3-12:0, whereas toward U-937 the cytotoxicity was 2-SCH3-10:0 > 2-SCH3-12:0 > 12:0 > 10:0 > 2-OCH3-12:0. These results indicate that the alpha-methylsulfanyl substitution increases the cytotoxicity of the C10 and C12 FA toward the studied leukemia cell lines.

Antiinflammatory Effects of Tetradecylthioacetic Acid Involve Both Peroxisome Proliferator–Activated Receptor α–Dependent and –Independent Pathways

OBJECTIVE

Tetradecylthioacetic acid (TTA) is a hypolipidemic antioxidant with immunomodulating properties involving activation of peroxisome proliferator-activated receptors (PPARs). Human endothelial cells express PPARs. We hypothesized that TTA could modulate endothelial cell activation at least partly through PPAR-related mechanisms.

METHODS AND RESULTS

We explored this hypothesis by different experimental approaches involving both in vitro studies in human endothelial cells (HUVECs) and in vivo studies in humans and PPAR-alpha-/- mice. Our main findings were as follows: (1) TTA suppressed the tumor necrosis factor alpha-induced expression of vascular cell adhesion molecule 1 (VCAM-1) and interleukin 8 (IL-8) in HUVECs. (2) No TTA-mediated attenuation of VCAM-1 and chemokine expression was seen in the liver of PPAR-alpha-/- mice. (3) Whereas TTA markedly enhanced PPAR-alpha-target genes in the liver of wild-type, but not of PPAR-alpha-/-, mice, no such effect on PPAR-alpha-target genes was seen in HUVECs. (4) The relevance of our findings to human disease was suggested by a TTA-mediated downregulation of serum levels of soluble VCAM-1 and IL-8 in psoriasis patients.

CONCLUSIONS

We show that TTA has the ability to attenuate tumor necrosis factor alpha-mediated endothelial cell activation, further supporting antiinflammatory effects of this fatty acid, possibly involving both PPAR-alpha-dependent and -independent pathways.

Effects of 3-thia fatty acids on feed intake, growth, tissue fatty acid composition, beta-oxidation and Na+,K+-ATPase activity in Atlantic salmon

Atlantic salmon (Salmo salar) with an initial mass of 86 g were reared in 12 degrees C seawater for 8 weeks to a final average mass of 250 g. The fish were fed fish meal and fish oil-based diet supplemented with either 0%, 0.3% or 0.6% of tetradecylthioacetic acid (TTA), a 3-thia fatty acid. The specific growth rate (SGR) decreased with increasing dietary dose of TTA. The SGR of the group fed 0% of TTA (Control) was 1.8; that of the group fed 0.3% of TTA (TTA-L) was 1.7, and that of the group fed 0.6% of TTA (TTA-H) was 1.5. The mortality increased with increased dietary dose of TTA. The mitochondrial beta-oxidation capacity in the liver of fish fed the TTA diets was 1.5 to 2 times higher than that of the Control fish. TTA supplementation caused substantial changes in the fatty acid compositions of the phospholipids (PL), triacylglycerols (TAG) and free fatty acids (FFA) of gills, heart and liver. The percentages of n-3 fatty acids, particularly 22:6 n-3, increased in fish fed diets containing TTA, while the percentage of the saturated FAs 14:0 and 16:0 in the PL fractions of the gills and heart decreased. The sum of monounsaturated FAs in the PL and TAG fractions from liver was significantly higher in fish fed diets containing TTA. TTA itself was primarily incorporated into PL. Two catabolic products of TTA (sulphoxides of TTA) were identified, and these products were particularly abundant in the kidney. TTA supplementation had no significant effect on the activity of the membrane-bound enzyme Na(+),K(+)-ATPase.

Effects of structural changes of fatty acids on lipid accumulation in adipocytes and primary hepatocytes

Conjugated linoleic acids (CLAs), tetradecylthioacetic acid (TTA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are all shown to differently affect lipid homeostasis. Additionally, previous studies have shown that introducing a methyl group in the molecule potentiates the hypolipidemic effect of EPA. The objective of this study was to determine how cis9,trans11 CLA, trans10,cis12 CLA, TTA, EPA and DHA affect lipid accumulation in 3T3-L1 adipocytes and in cultured primary rat hepatocytes, and to what extent changes in cis/trans configuration or introducing a methyl group in the molecules influence their way of affecting lipid accumulation in these cells. Our results show that trans10,cis12 CLA is highly specific in preventing lipid accumulation in adipocytes, and that small structural changes in the molecule (changing to trans/trans or introducing an alpha-methyl group) totally abolish this effect and up-regulate the expression levels of adipogenic marker genes towards control levels. Furthermore, all the fatty acids increased hepatic lipid accumulation, whereas the lipid content was normalized after adding an alpha-methyl group into the molecules. Taken together, our data demonstrate that the various fatty acids are highly specialized molecules, and that small structural changes markedly alter their way of affecting lipid accumulation in adipocytes and hepatocytes.

Genomic filtering: an approach to discovering novel antiparasitics

Genomic filtering is a rapid approach to identifying and prioritizing molecular targets for drug discovery. For infectious disease applications, comparative genomics filters allow the selection of pathogen-specific gene products, whereas functional genomics filters, such as RNA interference (RNAi), allow the selection of gene products essential for pathogen survival. The approach is especially applicable to antiparasitic drug discovery where the phylogenetic distance between parasite and host make the likelihood of drug cross-toxicity due to conservation of molecular targets greater than for more distantly related pathogens such as prokaryotes. This article discusses some of the inherent challenges of applying genomics to the early steps of drug discovery and describes one successful comparative and functional genomics filtering strategy that has been implemented to prioritize molecular targets and identify chemical leads for nematode control.

Effects of a novel dual lipid synthesis inhibitor and its potential utility in treating dyslipidemia and metabolic syndrome

We have identified a novel omega-hydroxy-alkanedicarboxylic acid, ESP 55016, that favorably alters serum lipid variables in obese female Zucker (fa/fa) rats. ESP 55016 reduced serum non-HDL-cholesterol (non-HDL-C), triglyceride, and nonesterified fatty acid levels while increasing serum HDL-C and beta-hydroxybutyrate levels in a dose-dependent manner. ESP 55016 reduced fasting serum insulin and glucose levels while also suppressing weight gain. In primary rat hepatocytes, ESP 55016 increased the oxidation of [(14)C]palmitate in a dose- and carnitine palmitoyl transferase-I (CPT-I)-dependent manner. Furthermore, in primary rat hepatocytes and in vivo, ESP 55016 inhibited fatty acid and sterol synthesis. The "dual inhibitor" activity of ESP 55016 was unlikely attributable to the activation of the AMP-activated protein kinase (AMPK) pathway because AMPK and acetyl-CoA carboxylase (ACC) phosphorylation states as well as ACC activity were not altered by ESP 55016. Further studies indicated the conversion of ESP 55016 to a CoA derivative in vivo. ESP 55016-CoA markedly inhibited the activity of partially purified ACC. The activity of partially purified HMG-CoA reductase was not altered by the xenobiotic-CoA. These data suggest that ESP 55016-CoA favorably alters lipid metabolism in a model of diabetic dyslipidemia in part by initially inhibiting fatty acid and sterol synthesis plus enhancing the oxidation of fatty acids through the ACC/malonyl-CoA/CPT-I regulatory axis.

Changed energy state and increased mitochondrial beta-oxidation rate in liver of rats associated with lowered proton electrochemical potential and stimulated uncoupling protein 2 (UCP-2) expression: evidence for peroxisome proliferator-activated receptor-alpha independent induction of UCP-2 expression

Lowering of plasma triglyceride levels by hypolipidemic agents is caused by a shift in the liver cellular metabolism, which become poised toward peroxisome proliferator-activated receptor (PPAR) alpha-regulated fatty acid catabolism in mitochondria. After dietary treatment of rats with the hypolipidemic, modified fatty acid, tetradecylthioacetic acid (TTA), the energy state parameters of the liver were altered at the tissue, cell, and mitochondrial levels. Thus, the hepatic phosphate potential, energy charge, and respiratory control coefficients were lowered, whereas rates of oxygen uptake, oxidation of pyridine nucleotide redox pairs, beta-oxidation, and ketogenesis were elevated. Moderate uncoupling of mitochondria from TTA-treated rats was confirmed, as the proton electrochemical potential (Delta(p)) was 15% lower than controls. The change affected the Delta(Psi) component only, leaving the (Delta)pH component unaltered, suggesting that TTA causes induction of electrogenic ion transport rather than electrophoretic fatty acid activity. TTA treatment induced expression of hepatic uncoupling protein 2 (UCP-2) in rats as well as in wild type and PPARalpha-deficient mice, accompanied by a decreased double bond index of the mitochondrial membrane lipids. However, changes of mitochondrial fatty acid composition did not seem to be related to the effects on mitochondrial energy conductance. As TTA activates PPARdelta, we discuss how this subtype might compensate for deficiency of PPARalpha. The overall changes recorded were moderate, making it likely that liver metabolism can maintain its function within the confines of its physiological regulatory framework where challenged by a hypolipemic agent such as TTA, as well as others.

Effects of sterculic acid on stearoyl-CoA desaturase in differentiating 3T3-L1 adipocytes

The effects of sterculic acid on cell size, adiposity, and fatty acid composition of differentiating 3T3-L1 adipocytes are correlated with stearoyl-CoA desaturase (SCD) expression (mRNA and protein levels) and enzyme activity. Fluorescence-activated cell scanning (FACS) analysis showed that adipocytes differentiated with methylisobutylxanthine, dexamethasone, and insulin (MDI) plus 100 microM sterculic acid comprised a population of predominantly large cells with reduced adiposity compared to MDI-treated cells. Although both groups had similar amounts of total fat, their fatty acid profiles were strikingly different: MDI-treated cells had high levels of the unsaturated palmitoleic (Delta(9)-16:1) and oleic (Delta(9)-18:1) acids, whereas the cells cultured with MDI plus sterculic acid accumulated palmitic (16:0) and stearic (18:0) acids together with a marked reduction in Delta(9)-16:1. Although the cells treated with MDI plus sterculic acid had similar levels of scd1 and scd2 mRNAs and antibody-detectable SCD protein as the MDI-treated cells, the SCD enzyme activity was inhibited more than 90%. The accumulation of 16:0 and 18:0, together with normal levels of fatty acid synthase (FAS) and aP2 mRNAs, shows that de novo synthesis and elongation of fatty acids, as well as cell differentiation, were not affected by sterculic acid. Because of the increase in cell size in the sterculic acid-treated cells, the insulin-stimulated 2-deoxyglucose (2-DOG) uptake was determined. Compared to MDI-treated cells, the 2-DOG uptake in the cells treated with sterculic acid was not affected. These results indicate that sterculic acid directly inhibits SCD activity, possibly by a turnover-dependent reaction, without affecting the processes required for adipocyte differentiation, scd gene expression or SCD protein translation.

Antiproliferative effects of a non-beta-oxidizable fatty acid, tetradecylthioacetic acid, in native human acute myelogenous leukemia blast cultures

The lipid metabolism is important in the regulation of cell proliferation. We have examined effects of a fatty acid analogue, tetradecylthioacetic acid (TTA), on the functional phenotype of native, human AML cells. TTA inhibited AML blast proliferation in the presence of single cytokines (GM-CSF and SCF: P > 0.05, 35 patients with detectable proliferation) and a combination of cytokines (P < 0.005, n = 21). This antiproliferative effect was generally stronger than for the normal fatty acid palmitic acid (PA). Both TTA and PA increased the secretion of tumor necrosis factor alpha (TNFalpha) (P < 0.05, 27 patients with detectable cytokine release), but only PA increased interleukein 1beta (IL-1beta) release (P < 0.005, n = 34). AML blast populations varied significantly in their levels and activities of metabolites and enzymes characterizing oxidative status and fatty acid metabolism, and there was no significant correlation between the intrinsic oxidative status and the effects of PA and TTA on blast proliferation. Although TTA reduced the proliferation of mitogen-stimulated normal T cells derived from healthy individuals (P < 0.05, n = 8), no adverse effects were seen on peripheral blood cell counts (reticulocytes, platelets, total white blood cells, differential leukocyte counts) for healthy volunteers receiving TTA (oral administration of 1000 mg/day for 7 consecutive days). Our results suggest that TTA can inhibit AML blast proliferation through pathways that are unrelated to autocrine cytokine secretion and intrinsic oxidative status.

Nuclear import of factors involved in signaling is inhibited in C3H/10T1/2 cells treated with tetradecylthioacetic acid

The non-beta-oxidisable tetradecylthioacetic acid (TTA) is incorporated into cellular membranes when C3H/10T1/2 cells are cultured in TTA-containing medium. We here demonstrate that this alteration in cellular membranes affect the nuclear translocation of proteins involved in signal transduction. Analysis of cellular fatty acid composition shows that TTA and TTA:1n-8 constitute approximately 40 mol% of total fatty acids in cellular/nuclear membranes. Activation of c-fos expression is significantly inhibited in TTA-treated cells but the enzymatic activation of mitogen activated protein kinase (ERK) is not affected. Immunofluorescence and confocal microscopy studies demonstrate that in mitogene-stimulated TTA-treated cells, the translocation of phosphorylated ERK1/2, protein kinase C alpha (PKC alpha), and PKC beta(1) from the cytoplasm into the nucleus is considerably decreased and delayed. Concomitant with a decreased nuclear import, ERK1/2 dephosphorylation is decreased in TTA-treated cells. There is no TTA-induced inhibition of nuclear import of proteins with a classical nuclear localization signal (NLS), as seen by in vitro nuclear import experiments of BSA fused to the NLS from SV40 large T, or in vivo studies of hnRNP A1 nuclear import. The expression levels of Importin alpha, Importin beta, Importin 7, and NTF2 are not altered in the TTA-treated cells. Taken together, our data indicate that TTA treatment causes changes in cellular fatty acid composition that negatively affect NLS-independent mechanisms of protein translocation through the nuclear pore complex.

Origin of membrane dipole potential: contribution of the phospholipid fatty acid chains

The large intrinsic membrane dipole potential, phi(d), is important for protein insertion and functioning as well as for ion transport across natural and model membranes. However, the origin of phi(d) is controversial. From experiments carried out with lipid monolayers, a significant dependence on the fatty acid chain length is suggested, whereas in experiments with lipid bilayers, the contribution of additional -CH(2)-groups seems negligibly small compared with that of the phospholipid carbonyl groups and lipid-bound water molecules. To compare the impact of the -CH(2)-groups of dipalmitoylphosphatidylcholine (DPPC) near and far from the glycerol backbone, we have varied the structure of DPPC by incorporation of sulfur atoms in place of methylene groups in different positions of the fatty acid chain. The phi(d) of symmetric lipid bilayers containing one heteroatom was obtained from the charge relaxation of oppositely charged hydrophobic ions. We have found that the substitution for a S-atom of a -CH(2)-group decreases phi(d). The effect (deltaphi(d) = -22.6 mV) is most pronounced for S-atoms near the lipid head group while a S-atom substitution in the C(13)- or C(14)-position of the hydrocarbon chain does not effect the bilayer dipole potential. Most probably deltaphi(d) does not originate from an altered dipole potential of the acyl chain containing an heteroatom but is mediated by the disruption of chain packing, leading to a decreased density of lipid dipoles in the membrane.

Metabolic effects of thia fatty acids

Thia substituted fatty acids are saturated fatty acids which are modified by insertion of a sulfur atom at specific positions in the carbon backbone. During the last few years pleiotropic effects of the 3-thia fatty acid tetradecylthioacetic acid have been revealed. The biological responses to tetradecylthioacetic acid include mitochondrial proliferation, increased catabolism of fatty acids, antiadiposity, improvement in insulin sensitivity, antioxidant properties, reduced proliferation and induction of apoptosis in rapidly proliferating cells, cell differentiation and antiinflammatory action. These biological responses indicate that tetradecylthioacetic acid changes the plasma profile from atherogenic to cardioprotective. As a pan-peroxisome proliferator-activated receptor ligand, tetradecylthioacetic acid regulates the adipose tissue mass and the expression of lipid metabolizing enzymes, particularly those involved in catabolic pathways. In contrast, circumstantial evidences suggest that peroxisome proliferator-activated receptor-independent metabolic pathways may be of importance for the antioxidant, antiproliferative and antiinflammatory action of tetradecylthioacetic acid.

Identification of novel sulfur-containing bacterial polyesters: biosynthesis of poly(3-hydroxy-S-propyl-omega-thioalkanoates) containing thioether linkages in the side chains

This study describes the biosynthesis of novel sulfur-containing polyhydroxyalkanoates (PHAs), which consist exclusively of hydroxypropylthioalkanoic acid containing thioether groups in the side chains. In addition, the utilization of alkylthioalkanoic acids (=thia fatty acids) by various bacteria was investigated. Based on feedings with propylthiooctanoic acid (PTO) or propylthiohexanoic acid, the metabolically engineered PHA-negative mutant PHB(-)4 of Ralstonia eutropha, which harbours plasmid pBBR1::phaC1 expressing the PHA synthase of Pseudomonas mendocina, synthesized two novel poly(3-hydroxy-S-propyl-omega-thioalkanoic) acids [poly(3HPTA)s]. A terpolyester consisting of 3-hydroxypropylthiobutyric acid (3HPTB), 3-hydroxypropylthiohexanoic acid (3HPTHx) and 3-hydroxypropyl- thiooctanoic acid (3HPTO) was synthesized from PTO, whereas a co-polyester of 3HPTB and 3HPTHx was synthesized from propylthiohexanoic acid. Fed-batch fermentation of R. eutropha PHB(-)4(pBBR1::phaC1) on PTO was done on a 26-litre scale, providing a cell density of 7.3 g l(-1), from which 45 g of the novel poly(3HPTB-co-3HPTHx-co-3HPTO) were isolated. The chemical structures of the poly(3HPTA)s were identified by gas chromatography/mass spectrometry, elemental sulfur analysis, partial pyrolysis and detailed mass spectrometric analysis, exhibiting 3HPTB, 3HPTHx and 3HPTO as constituents. These novel, hitherto undescribed, constituents of PHAs were randomly distributed in the co-polyesters.

The biochemistry of hypo- and hyperlipidemic fatty acid derivatives: metabolism and metabolic effects

A selection of amphipatic hyper- and hypolipidemic fatty acid derivatives (fibrates, thia- and branched chain fatty acids) are reviewed. They are probably all ligands for the peroxisome proliferation activation receptor (PPARalpha) which has a low selectivity for its ligands. These compounds give hyper- or hypolipidemic responses depending on their ability to inhibit or stimulate mitochondrial fatty acid oxidation in the liver. The hypolipidemic response is explained by the following metabolic effects: Lipoprotein lipase is induced in liver where it is normally not expressed. Apolipoprotein CIII is downregulated. These two effects in liver lead to a facilitated (re)uptake of chylomicrons and VLDL, thus creating a direct transport of fatty acids from the gut to the liver. Fatty acid metabolizing enzymes in the liver (CPT-I and II, peroxisomal and mitochondrial beta-oxidation enzymes, enzymes of ketogenesis, and omega-oxidation enzymes) are induced and create an increased capacity for fatty acid oxidation. The increased oxidation of fatty acids "drains" fatty acids from the body, reduces VLDL formation, and ultimately explains the antiadiposity and improved insulin sensitivity observed after administration of peroxisome proliferators.

Thiafatty acids as tracers to investigate biosynthetic pathways of lepidopteran sex pheromones

In order to investigate the potential utility of thiafatty acids as tracers for biosynthetic studies of moth sex pheromones, a series of thiatetradecanoic acids, namely 8-, 9-, 10-, 11-, 12- and 13-thiatetradecanoic, were prepared and their metabolism was investigated in pheromone glands of Spodoptera littoralis. Analysis by gas chromatography coupled to mass spectrometry of extracts from pheromone glands treated with the above acids showed that only 8-thiatetradecanoic acid and 13-thiatetradecanoic acid were metabolized by desaturation and were incorporated into the sex pheromone biosynthetic pathway. 13-Thiatetradecanoic acid was converted into (E)- and (Z)-13-thiatetradec-11-enoic acids, (Z,E)-13-thiatetradeca-9,11-dienoic acid, 11-thiadodecanoic acid, (E)- and (Z)-11-thiadodec-9-enoic acids and 15-thiahexadecanoic acid. 8-Thiatetradecanoic acid gave rise to two monoenoic thiafatty acids and two dienoic thiafatty acids, which were assigned to (Z)- and (E)-8-thiatetradec-11-enoic acids, (Z,E)-8-thiatetradeca-9,11-dienoic acid and (E,E)-8-thiatetradeca-10,12-dienoic acid. The other thiafatty acids tested, 9-, 10-, 11- and 12-thiatetradecanoic acids, were not metabolized by desaturation, although the corresponding products of beta-oxidation and chain elongation were detected. The occurrence of sulfoxides was not detected in this case, in disagreement with results on the metabolism of some thiaacids previously reported by other authors in yeast, Saccharomyces cerevisiae.

Growth reduction in glioma cells after treatment with tetradecylthioacetic acid: changes in fatty acid metabolism and oxidative status

During aerobic metabolism, a small amount of partially reduced oxygen is produced, yielding reactive oxygen species (ROS). Peroxisomes and mitochondria are major contributors to cellular ROS production, which is normally balanced by consumption by antioxidants. The fatty acid analogue tetradecylthioacetic acid (TTA) promotes mitochondrial and peroxisomal proliferation, and may induce oxidative stress and change the growth potential of cancer cells. In the present study, we found that TTA reduced [(3)H]thymidine incorporation in the glioma cell lines BT4Cn (rat), D54Mg (human), and GaMg (human) in a dose- and time-dependent manner. The 50% inhibitory TTA doses were approximately 125 microM for BT4Cn and D54Mg cells and 40 microM for GaMg cells after 4 days. alpha-Tochopherol counteracted this inhibition in GaMg cells. TTA enhanced the oxidation of [1-(14)C]palmitic acid, which could be explained by stimulation of enzymes involved in peroxisomal (fatty acyl-CoA oxidase) and/or mitochondrial (carnitine palmitoyltransferase) fatty acid oxidation. The glutathione content and the activities of glutathione peroxidase, glutathione reductase, and glutathione S-transferase were differentially affected. Increased malondialdehyde (MDA) production was seen in TTA-treated GaMg and D54Mg cells, but not in BT4Cn cells, in vitro. In BT4Cn tumor tissue from TTA-treated rats, MDA was increased while the alpha-tocopherol content tended to decrease. TTA increased the level of cytosolic cytochrome c in BT4Cn cells, which suggests induction of apoptotic cascades. Although several mechanisms are likely to be involved in the TTA-mediated effects on growth, we propose that modulation of cellular redox conditions caused by changes in fatty acid metabolism may be of vital importance.

Optimization of methods and treatment conditions for studying effects of fatty acids on cell growth

Antiproliferative properties of molecular regulators of lipid metabolism have been increasingly studied during recent years. Discussion is ongoing concerning optimal treatment conditions and assays used for monitoring proliferation and cytotoxicity. The objective of the present work was to optimize methods and treatment conditions used for studying antiproliferative effects of fatty acids and analogs, represented by palmitic acid (PA) and the beta-oxidation-restricted fatty acid analog tetradecylthioacetic acid (TTA), in rat (BT4Cn) and human (D54Mg and GaMg) glioma cell lines. Changes in [3H]thymidine incorporation preceded changes in cell number in TTA-treated glioma cell cultures, and the growth inhibition was more significantly expressed by [3H]thymidine incorporation than cell number. Addition of bovine serum albumin decreased cellular fatty acid uptake and reduced the effects of TTA and PA on [3H]thymidine incorporation. Determination of the antiproliferative effect of TTA in BT4Cn cells by MTT conversion and [3H]thymidine incorporation yielded concordant results. TTA-mediated reduction in cell number corresponded to reduction in cellular protein and total DNA content in BT4Cn cells. Reduced growth potential in TTA-treated multicellular D54Mg and GaMg spheroids supported the findings from monolayer cultures. In conclusion, cell density, treatment period, fatty acid administration, and methods for growth determination may profoundly influence the outcome of cell growth experiments. Thus, experimental conditions should be carefully controlled when performing cell growth experiments, and effects on cell growth should preferably be confirmed by different methods.

Long-term retention of a novel antioxidant sulphur-substituted fatty acid analogue after local delivery in porcine coronary arteries

OBJECTIVE

Antioxidants have been suggested to reduce restenosis after balloon angioplasty. A novel sulphur-containing fatty acid, tetradecylthioacetic acid (TTA), with antioxidant properties, is efficiently incorporated into cellular phospholipids. We have determined the uptake and retention of TTA after local coronary artery delivery in 20 pigs.

DESIGN

Radiolabelled TTA was delivered to 40 main coronary arteries via a multiporous coronary angioplasty balloon catheter inflated before, after, or without overstretch vessel injury. The animals were killed at intervals of up to 6 weeks post-procedure. The radioactivity of the tissue sections was determined as nmol TTA/g tissue.

RESULTS

Concentrations of TTA in the coronary arteries were 1.84 +/- 0.45 nmol/g up to 24 h, 1.50 +/- 0.96 nmol/g at 2 weeks, 0.22 +/- 0.11 nmol/g at 4 weeks and a trace was present at 6 weeks (p-value for trend <0.01). The arterial wall uptake at the delivery site was higher than distal to delivery (1.84 +/- 0.37 vs 0.55 +/- 0.13 nmol/g, p = 0.006) and perivascular fat (p < 0.01) but not higher than in the myocardium. Infusion before, after or without vessel injury was not important for tissue concentration.

CONCLUSIONS

After local coronary artery delivery, the antioxidant TTA is taken up by the arterial wall in which it is retained for at least 4 weeks.

Oxidation of oxa and thia fatty acids and related compounds catalysed by 5- and 15-lipoxygenase

The modified fatty acids, (Z,Z,Z)-(octadeca-6,9,12-trienyloxy)acetic acid, (Z,Z,Z)-(octadeca-9,12,15-trienyloxy)acetic acid, (all-Z)-(eicosa-5,8,11,14-tetraenyloxy)acetic acid, (all-Z)-(eicosa-5,8,11,14-tetraenylthio)acetic acid, 3-[(all-Z)-(eicosa-5,8,11,14-tetraenylthio)]propionic acid, (all-Z)-(eicosa-5,8,11,14-tetraenylthio)succinic acid, N-[(all-Z)-(eicosa-5,8,11,14-tetraenoyl)]glycine and N-[(all-Z)-(eicosa-5,8,11,14-tetraenoyl)]aspartic acid, all react with soybean 15-lipoxygenase. The products were treated with triphenylphosphine to give alcohols, which were isolated using HPLC. Analysis of the alcohols using negative ion tandem electrospray mass spectrometry, and by comparison with compounds obtained by autoxidation of arachidonic acid, shows that each enzyme-catalysed oxidation occurs at the omega-6 position of the substrate. In a similar fashion, it has been found that (Z,Z,Z)-(octadeca-6,9,12-trienyloxy)acetic acid, (Z,Z,Z)-(octadeca-9,12,15-trienyloxy)acetic acid, (all-Z)-(eicosa-5,8,11,14-tetraenylthio)acetic acid and 3-[(all-Z)-(eicosa-5,8,11,14-tetraenylthio)]propionic acid each undergoes regioselective oxidation at the carboxyl end of the polyene moiety on treatment with potato 5-lipoxygenase. Neither (all-Z)-(eicosa-5,8,11,14-tetraenylthio)succinic acid nor N-[(all-Z)-(eicosa-5,8,11,14-tetraenoyl)]aspartic acid reacts in the presence of this enzyme, while N-[(all-Z)-(eicosa-5,8,11,14-tetraenoyl)]glycine affords the C11' oxidation product. The alcohol derived from (Z,Z,Z)-(octadeca-6,9,12-trienyloxy)acetic acid using the 15-lipoxygenase reacts at the C6' position with the 5-lipoxygenase.

Long-chain fatty acids promote opening of the reconstituted mitochondrial permeability transition pore

Adenine nucleotide translocase-porin-hexokinase complex isolated from rat brain, when reconstituted into phospholipid-cholesterol vesicles, exhibits all properties of the mitochondrial permeability transition pore [Beutner, G., Rück, A., Riede, B., Welte, W. and Brdiczka, D. (1996) FEBS Lett. 396, 189-195]. In the present work, the effect of long-chain fatty acids on such reconstituted pore was examined. Opening of the pore was measured by leakage of either malate or fluorescein sulphonate entrapped inside the vesicles. It was found that myristate and oleate in the presence of 50 or 100 microM Ca(2+) produced a partial release of the probes in a dose-dependent way. A dicarboxylic fatty acid analogue, that appeared inactive as protonophore in intact mitochondria, exerted no effect on pore opening in the reconstituted system. 100 microM Ca(2+) alone was without effect. Pore opening by fatty acids in the reconstituted system was partly prevented by cyclosporin A. The pore opening also occurred when the vesicles were incubated in the presence of pancreatic phospholipase A(2). In this case, the opening was decreased by cyclosporin A or serum albumin. These results indicate that long-chain fatty acids elicit opening of the permeability transition pore reconstituted in phospholipid vesicles in a similar way as in intact mitochondria [Wi&ecedil;ckowski, M.R. and Wojtczak, L. (1998) FEBS Lett. 423, 339-342].