Β-oxidation Pathway Research Articles

Significant enhancement by casamino acids of caproate production via chain elongation

In this study, the effects of casamino acids, as the main component in yeast extract, on the bioproduction of caproate were evaluated. A dosage of 5 g/L casamino acids addition significantly promoted caproate production and shortened the lag phase for caproate production by 7.6-folds compared with the control. Both the net carbon and electron conversion efficiencies were enhanced. The addition of casamino acids shaped a dissimilar microbial community from that of the control and that of the inoculum. The caproate-producing Clostridium and Caproiciproducens, the proteolytic Proteiniphilum and Brassicibacter, and the saccharide-utilizing Hydrogenoanaerobacteriu were enriched, and their abundance were distinguished between with and without the addition of casamino acids as fermentation progressed. Further metagenomics analysis recovered genome bins of Clostridium kluyveri, Clostridium cochlearium, Caprobacter fermentans and Proteiniphilum acetatigenes, representing the majority of the functional bacteria with casamino acids addition. The complete reverse β-oxidation and amino acids (serine/glycine) metabolic pathway for caproate production and butyrate formation, respectively, were fully recovered. Furthermore, all the genes involved were highly expressed and metabolically active in meta-transcriptomics analysis. The finding proved that casamino acids was able to enhance caproate formation by promoting ethanol utilization and butyrate formation. In general, yeast extract could not only support microbial growth but also contribute to the formation of medium chain fatty acids, therefore promoting the efficiency of chain elongation process.

GHB degradation via TCA cycle is the major metabolic route in Arabidopsis thaliana

Gamma-hydroxybutyric acid (GHB) is a product of the reduction reaction of chemically reactive succinic semi-aldehyde (SSA), which itself is produced from the degradation of GABA. It is regarded as a short-chain fatty acid. Despite our understanding of the synthesis of GHB, little is known about its fate. Exogenous application of 0.1 mM GHB to pop2 x ssadh, a double mutant incapable of catabolizing GABA, increased the endogenous GHB level by 13-fold compared to the wild type. The GHB dynamic studies by feeding and relieving from treatments showed that GHB is rapidly metabolized in wild-type plants compared to the pop2 x ssadh double mutant. Although regarded as a short-chain fatty acid, GHB level was not altered in mutants of the beta oxidation (β-oxidation) pathway following exogenous feeding. Therefore, the metabolism back to SSA, and then the TCA cycle appears to be the major route for GHB degradation. However, the presence of another catabolic route such as secondary modifications cannot be ruled out.

The metabolite alpha-ketobutyrate extends lifespan by promoting peroxisomal function in C. elegans

Metabolism is intimately linked to aging. There is a growing number of studies showing that endogenous metabolites may delay aging and improve healthspan. Through the analysis of existing transcriptome data, we discover a link between activation of the transsulfuration pathway and a transcriptional program involved in peroxisome function and biogenesis in long-lived glp-1(e2141ts) mutant Caenorhabditis elegans worms. Subsequently, we show that supplementation with α-ketobutyrate, an intermediate of the transsulfuration pathway, extends lifespan in wild-type worms. Alpha-ketobutyrate augments the production of NAD+ via the lactate dehydrogenase LDH-1, leading to SIR-2.1/SIRT1-mediated enhanced peroxisome function and biogenesis, along with a concomitant increase in the expression of acox-1.2/ACOX1 in the peroxisomal fatty acid β-oxidation pathway. ACOX-1.2/ACOX1 promotes H2O2 formation, thereby resulting in activation of SKN-1/NRF2. This transcription factor in turn extends the lifespan of worms by driving expression of autophagic and lysosomal genes. Finally, we show that α-ketobutyrate also delays the cellular senescence in fibroblast cells through the SIRT1-ACOX1-H2O2-NRF2 pathway. This finding uncovers a previously unknown role for α-ketobutyrate in organismal lifespan and healthspan by coordinating the NAD+-SIRT1 signaling and peroxisomal function.

Biosynthesis of aliphatic plastic monomers with amino residues in Yarrowia lipolytica.

Introduciton: The α,ω-diamines (NH2-(CH2)n-NH2) and ω -amino fatty acids (NH2-(CH2)n-COOH) have been widely used as building blocks in polymerindustries. Medium- to long-chain (C8 to C18) fatty acid monomers with amino residues are almost exclusively produced via chemical processes that generate hazardous waste and induce severe environmental problems, such as global warming and pollution. Here, we present the construction platformstrains of Yarrowia lipolytica a cheese-ripening yeast, for direct biotransformation of hydrocarbons into medium- to long-chain α,ω-diamines and ωamino fatty acids using metabolic engineering of endogenous fatty acid ω- and β-oxidation pathways and introducing heterologous ω-transaminase in Y. lipolytica. Methods: We deleted six genes encoding the acyl-CoA oxidase (ACO1-6) and four fatty aldehyde dehydrogenase genes (FALDH1-4), which catalyze fatty acid β-oxidation and downstream oxidation of fatty aldehydes in Y. lipolytica, respectively. The ω-transaminase from Chromobacterium violaceum DSM30191 was introduced into the genome of the ΔPOX ΔFALDH strain under the control of Y. lipolytica-derived EXP1 promoters. Results and Discussion: The ΔPOX ΔFALDH strains with ω-CvTA successfully accumulated the corresponding C12 αω-diamines into a shaking culture medium with dodecane or dodecanol. In addition, these strains accumulated C12 ω-amino fatty acids from dodecanoic acid. With the commercially available α,ω-diacid bioprocess, this yeast biosynthesis producing medium- and longchain α,ω-diamines and ω-amino fatty acids could complete the yeast platform technology generating all medium- and long-chain aliphatic polyamide monomers, α,ω-biofunctionalized with one or both carboxylic acid and amino residues.

De novo biosynthesis of carminic acid in Saccharomyces cerevisiae

Carminic acid is a natural red dye extracted from the insect Dactylopius coccus. Due to its ideal dying effect and high safety, it is widely used in food and cosmetics industries. Previous study showed that introduction of polyketide synthase (OKS) from Aloe arborescens, cyclase (ZhuI) and aromatase (ZhuJ) from Streptomyces sp. R1128, and C-glucosyltransferase (UGT2) from D. coccus into Aspergillus nidulans could achieve trace amounts of de novo production. These four genes were introduced into Saccharomyces cerevisiae, but carminic acid was not detected. Analysis of the genome of A. nidulans revealed that 4′-phosphopantetheinyl transferase (NpgA) and monooxygenase (AptC) are essential for de novo biosynthesis of carminic acid in S. cerevisiae. Additionally, endogenous hydroxylase (Cat5) from S. cerevisiae was found to be responsible for hydroxylation of flavokermesic acid to kermesic acid. Therefore, all enzymes and their functions in the biosynthesis of carminic acid were explored and reconstructed in S. cerevisiae. Through systematic pathway engineering, including regulating enzyme expression, enhancing precursor supply, and modifying the β-oxidation pathway, the carminic acid titer in a 5 L bioreactor reached 7580.9 μg/L, the highest yet reported for a microorganism. Heterologous reconstruction of the carminic acid biosynthetic pathway in S. cerevisiae has great potential for de novo biosynthesis of anthraquinone dye.

Impacts of organic loading rate and hydraulic retention time on organics degradation, interspecies interactions and functional traits in thermophilic anaerobic co-digestion of food waste and sewage sludge

This study provided novel insights into the effects of organic loading rate (OLR) and hydraulic retention time (HRT) on thermophilic anaerobic co-digestion of food waste and sewage sludge. The obtained maximum methane (CH4) yield of 328 ± 4 mL CH4/g CODfed at HRT of 15 days (OLR = 5.8 g VS/L/d) was partly attributable to the enhanced acidogenesis, acetogenesis, and methanogenesis phases. The increased key enzyme activities, particularly acetate kinase (improved by 5.2-fold), providing substantial methanogenic substrates for efficient CH4 production. The functional syntrophs that were related to syntrophic decarboxylation, novel acetate oxidation & reductive acetyl-CoA, and β-oxidation pathways could drive trophic interactions with methanogens. This markedly stimulated hydrogenotrophic Methanoculleus thermophilus metabolism and concomitantly enriched mixotrophic Methanosarcina thermophila. The distinctive cross-feeding interspecies interactions significantly affected the assembly and dynamics of thermophilic consortia. These findings shed light on the physicochemical and microbial mechanisms of HRT- and OLR-dependent enhancement of methanogenesis.

Reactivation of PPARα alleviates myocardial lipid accumulation and cardiac dysfunction by improving fatty acid β-oxidation in Dsg2-deficient arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM), a fatal heart disease characterized by fibroadipocytic replacement of cardiac myocytes, accounts for 20% of sudden cardiac death and lacks effective treatment. It is often caused by mutations in desmosome proteins, with Desmoglein-2 (DSG2) mutations as a common etiology. However, the mechanism underlying the accumulation of fibrofatty in ACM remains unknown, which impedes the development of curative treatment. Here we investigated the fat accumulation and the underlying mechanism in a mouse model of ACM induced by cardiac-specific knockout of Dsg2 (CS-Dsg2 -/-). Heart failure and cardiac lipid accumulation were observed in CS-Dsg2 -/- mice. We demonstrated that these phenotypes were caused by decline of fatty acid (FA) β-oxidation resulted from impaired mammalian target of rapamycin (mTOR) signaling. Rapamycin worsened while overexpression of mTOR and 4EBP1 rescued the FA β-oxidation pathway in CS-Dsg2 -/- mice. Reactivation of PPARα by fenofibrate or AAV9-Pparα significantly alleviated the lipid accumulation and restored cardiac function. Our results suggest that impaired mTOR-4EBP1-PPARα-dependent FA β-oxidation contributes to myocardial lipid accumulation in ACM and PPARα may be a potential target for curative treatment of ACM.

The origin and evolution of salicylic acid signaling and biosynthesis in plants

Salicylic acid (SA) plays a pivotal role in plant response to biotic and abiotic stress. Several core SA signaling regulators and key proteins in SA biosynthesis have been well characterized. However, much remains unknown about the origin, evolution, and early diversification of core elements in plant SA signaling and biosynthesis. In this study, we identified 10 core protein families in SA signaling and biosynthesis across green plant lineages. We found that the key SA signaling receptors, the nonexpresser of pathogenesis-related (NPR) proteins, originated in the most recent common ancestor (MRCA) of land plants and formed divergent groups in the ancestor of seed plants. However, key transcription factors for SA signaling, TGACG motif-binding proteins (TGAs), originated in the MRCA of streptophytes, arguing for the stepwise evolution of core SA signaling in plants. Different from the assembly of the core SA signaling pathway in the ancestor of seed plants, SA exists extensively in green plants, including chlorophytes and streptophyte algae. However, the full isochorismate synthase (ICS)-based SA synthesis pathway was first assembled in the MRCA of land plants. We further revealed that the ancient abnormal inflorescence meristem 1 (AIM1)-based β-oxidation pathway is crucial for the biosynthesis of SA in chlorophyte algae, and this biosynthesis pathway may have facilitated the adaptation of early-diverging green algae to the high-light-intensity environment on land. Taken together, our findings provide significant insights into the early evolution and diversification of plant SA signaling and biosynthesis pathways, highlighting a crucial role of SA in stress tolerance during plant terrestrialization.

Hybrid electron donors of ethanol and lactate stimulation chain elongation in microbial electrosynthesis with different inoculants

Microbial electrosynthesis (MES) is a new technology that uses electrically driven biocatalysts to convert CO2 into valuable chemicals. However, C2 as the primary product limits the development of MES. To address this issue, ethanol and lactate as additional electron donor (ED) were introduced into MES systems with different inoculants (anaerobic sludge and sediment) for chain elongation. The hybrid EDs in MES with sediment can produce the highest concentrations of butyrate (6.30 g/L) and caproate (1.60 g/L), and the corresponding total electron recovery efficiency reached the maximum value (94.51 ± 1.04%). Hybrid EDs not only provided sufficient reducing force, but also enhanced the gas mass transfer rate by releasing CO2 from lactate in situ. Metagenomic analysis showed that reverse β-oxidation pathway and fatty acid biosynthesis pathway were the main pathways. This study demonstrated that the addition of ethanol and lactate is promising method for improving the performance of MES.

Effects of overfeeding on liver lipid metabolism in mule ducks based on transcriptomics and metabolomics

ABSTRACT 1. In this study, transcriptomics and metabolomics were used to analyse changes in gene expression and metabolites in the liver of 70-d-old mule ducks after 10 and 20 d of continuous overfeeding. 2. In the free-feeding group, 995 differentially expressed genes and 51 metabolites (VIP >1, P < 0.05) were detected in the early stage, and 3,448 differentially expressed genes and 55 metabolites (VIP >1, P < 0.05) were detected in the later stage. There were 775 differentially expressed genes and 47 metabolites (VIP >1, P < 0.05) detected in the early stage of the overfeeding group, and 6,719 differentially expressed genes and 57 metabolites (VIP >1, P < 0.05) detected in the later stage. 3. There were no significant differences between the early stage in the overfeeding and free-feeding groups at the transcriptional and metabolic levels. Oleic acid and palmitic acid synthesis increased in the early stage of the overfeeding and free-feeding groups, however, these were inhibited in the late stage. Fatty acid oxidation and β-oxidation pathways were inhibited and insulin resistance was enhanced significantly in the late overfeeding stage. 4. In the early stage, the digestion and absorption of fat in the overfeeding and free-feeding groups were enhanced. In the later stage, the ability to store triglyceride in the overfeeding group was greater than in the free-feeding group. 5. The expression of nuclear factor κB (NFκB), a key inflammatory factor, was inhibited in the late stage of overfeeding, while arachidonic acid (AA), a metabolite with anti-inflammatory properties, increased in the late stage of overfeeding to inhibit the inflammatory effects caused by excessive lipid accumulation. These results add to the understanding of the mechanism of production of fatty liver in mule ducks and facilitate the development of treatments for non-alcoholic fatty liver disease.

Biosynthesis of cannabinoid precursor olivetolic acid in genetically engineered Yarrowia lipolytica

Engineering microbes to produce plant-derived natural products provides an alternate solution to obtain bioactive products. Here we report a systematic approach to sequentially identify the rate-limiting steps and improve the biosynthesis of the cannabinoid precursor olivetolic acid (OLA) in Yarrowia lipolytica. We find that Pseudomonas sp LvaE encoding a short-chain acyl-CoA synthetase can efficiently convert hexanoic acid to hexanoyl-CoA. The co-expression of the acetyl-CoA carboxylase, the pyruvate dehydrogenase bypass, the NADPH-generating malic enzyme, as well as the activation of peroxisomal β-oxidation pathway and ATP export pathway are effective strategies to redirect carbon flux toward OLA synthesis. Implementation of these strategies led to an 83-fold increase in OLA titer, reaching 9.18 mg/L of OLA in shake flask culture. This work may serve as a baseline for engineering cannabinoids biosynthesis in oleaginous yeast species.

Management of Waste Cooking Oil and its Potential for Value-added Materials: A Mini Review

Improper management of waste cooking oil in food industries like restaurants, hotels, and the use of retort technology in food processing is causing a devastating impact towards the environment. This is observed through odor problems and oil film formation on the surface of water bodies that increases the biological oxygen demand. Additionally, different types of cooking oil represent different physicochemical properties. This allows for the potential use of waste cooking oil as a carbon source for fungal growth thus contributing to the production of value-added products at a low cost and eco-friendly process. Biodegradation may take place by the enzymatic reaction which involves the hydrolysis of triglycerides and metabolized through the β-oxidation pathway to acetyl-CoA. Many fungal and bacterial strains capable of degrading vegetable cooking oils have been reported with most from the genus Aspergillus, Pseudomonas, Enterobacter, and others. From the industrial perspective, with the correct technology and proper recycling technique, waste cooking oil can be readily utilized as chemical building blocks in lubricant, candle, and fuel productions.

Proteomics unveil a central role for peroxisomes in butyrate assimilation of the heterotrophic Chlorophyte alga Polytomella sp.

Volatile fatty acids found in effluents of the dark fermentation of biowastes can be used for mixotrophic growth of microalgae, improving productivity and reducing the cost of the feedstock. Microalgae can use the acetate in the effluents very well, but butyrate is poorly assimilated and can inhibit growth above 1 gC.L-1. The non-photosynthetic chlorophyte alga Polytomella sp. SAG 198.80 was found to be able to assimilate butyrate fast. To decipher the metabolic pathways implicated in butyrate assimilation, quantitative proteomics study was developed comparing Polytomella sp. cells grown on acetate and butyrate at 1 gC.L-1. After statistical analysis, a total of 1772 proteins were retained, of which 119 proteins were found to be overaccumulated on butyrate vs. only 46 on acetate, indicating that butyrate assimilation necessitates additional metabolic steps. The data show that butyrate assimilation occurs in the peroxisome via the β-oxidation pathway to produce acetyl-CoA and further tri/dicarboxylic acids in the glyoxylate cycle. Concomitantly, reactive oxygen species defense enzymes as well as the branched amino acid degradation pathway were strongly induced. Although no clear dedicated butyrate transport mechanism could be inferred, several membrane transporters induced on butyrate are identified as potential condidates. Metabolic responses correspond globally to the increased needs for central cofactors NAD, ATP and CoA, especially in the peroxisome and the cytosol.

Transcriptome analysis of malate-induced Schizochytrium sp. FJU-512 reveals a novel pathway for biosynthesis of docosahexaenoic acid with enhanced expression of genes responsible for acetyl-CoA and NADPH accumulation.

Schizochytrium is one of the few oleaginous microalgae that produce docosahexaenoic acid (DHA)-rich lipids. In this study, global changes in gene expression levels of Schizochytrium sp. FJU-512 cultured with malate in a 15 l-bioreactor was analyzed using comparative transcriptomics. The changes were found mainly in the genes involved in oxidative phosphorylation, β-oxidation, and pentose phosphate pathways. Consequently, the global changes in genes associated with the pathways could lead to an increase in the influx throughputs of pyruvate, branched-chain amino acids, fatty acids, and vitamin B6. Our transcriptome analysis indicated pyruvate dehydrogenase E2 component and acetolactate synthase I/II/III large subunit as major contributors to acetyl-CoA biosynthesis, whereas glucose-6-phosphate dehydrogenase was indicated as the major contributor to the biosynthesis of NADPH. An increase in DHA titer of up to 22% was achieved with the addition of malate to the fed-batch culture of Schizochytrium sp. FJU-512. This study provides an alternate method to enhance DHA production in Schizochytrium sp. FJU-512 through malate induced upregulation of genes responsible for acetyl-CoA and NADPH biosynthesis.

Intestinal metabolomics of juvenile lenok (Brachymystax lenok) in response to heat stress.

Changes in the metabolic profile within the intestine of lenok (Brachymystax lenok) when challenged to acute and lethal heat stress (HS) are studied using no-target HPLC-MS/MS metabonomic analysis. A total of 51 differentially expressed metabolites (VIP > 1, P < 0.05) were identified in response to HS, and 34 occurred in the positive ion mode and 17 in negative ion mode, respectively. After heat stress, changes in metabolites related to glycolysis (i.e., alpha-D-glucose, stachyose, and L-lactate) were identified. The metabolites (acetyl carnitine, palmitoylcarnitine, carnitine, and erucic acid) related to fatty acid β-oxidation accumulated significantly, and many amino acids (L-tryptophan, D-proline, L-leucine, L-phenylalanine, L-aspartate, L-tyrosine, L-methionine, L-histidine, and L-glutamine) were significantly decreased in HS-treated lenok. The mitochondrial β-oxidation pathway might be inhibited, while severe heat stress might activate the anaerobic glycolysis and catabolism of amino acid for energy expenditure. Oxidative damage in HS-treated lenok was indicated by the decreased glycerophospholipid metabolites (i.e., glycerophosphocholine, 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphoethanolamine, 1-palmitoyl-sn-glycero-3-phosphocholine, 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine, and 1, 2-dioleoyl-sn-glycero-3-phosphatidylcholine) and the increased oxylipin production (12-HETE and 9R, 10S-EpOME). The minor oxidative pathways (omega-oxidation and peroxisomal beta-oxidation) were likely to be induced in HS-treated lenok.

PITPNC1 promotes the thermogenesis of brown adipose tissue under acute cold exposure

Brown adipose tissue (BAT) plays an essential role in non-shivering thermogenesis. The phosphatidylinositol transfer protein, cytoplasmic 1 (PITPNC1) is identified as a lipid transporter that reciprocally transfers phospholipids between intracellular membrane structures. However, the physiological significance of PITPNC1 and its regulatory mechanism remain unclear. Here, we demonstrate that PITPNC1 is a key player in thermogenesis of BAT. While Pitpnc1−/− mice do not differ with wildtype mice in body weight and insulin sensitivity on either chow or high-fat diet, they develop hypothermia when subjected to acute cold exposure at 4°C. The Pitpnc1−/− brown adipocytes exhibit defective β-oxidation and abnormal thermogenesis-related metabolism pathways in mitochondria. The deficiency of lipid mobilization in Pitpnc1−/− brown adipocytes might be the result of excessive accumulation of phosphatidylcholine and a reduction of phosphatidic acid. Our findings have uncovered significant roles of PITPNC1 in mitochondrial phospholipid homeostasis and BAT thermogenesis.

Nutrient sensing pathways regulating adult reproductive diapause in C. elegans.

Genetic and environmental manipulations, such as dietary restriction, can improve both health span and lifespan in a wide range of organisms, including humans. Changes in nutrient intake trigger often overlapping metabolic pathways that can generate distinct or even opposite outputs depending on several factors, such as when dietary restriction occurs in the lifecycle of the organism or the nature of the changes in nutrients. Due to the complexity of metabolic pathways and the diversity in outputs, the underlying mechanisms regulating diet-associated pro-longevity are not yet well understood. Adult reproductive diapause (ARD) in the model organism Caenorhabditis elegans is a dietary restriction model that is associated with lengthened lifespan and reproductive potential. To explore the metabolic pathways regulating ARD in greater depth, we performed a candidate-based genetic screen analyzing select nutrient-sensing pathways to determine their contribution to the regulation of ARD. Focusing on the three phases of ARD (initiation, maintenance, and recovery), we found that ARD initiation is regulated by fatty acid metabolism, sirtuins, AMPK, and the O-linked N-acetyl glucosamine (O-GlcNAc) pathway. Although ARD maintenance was not significantly influenced by the nutrient sensors in our screen, we found that ARD recovery was modulated by energy sensing, stress response, insulin-like signaling, and the TOR pathway. Further investigation of downstream targets of NHR-49 suggest the transcription factor influences ARD initiation through the fatty acid β-oxidation pathway. Consistent with these findings, our analysis revealed a change in levels of neutral lipids associated with ARD entry defects. Our findings identify conserved genetic pathways required for ARD entry and recovery and uncover genetic interactions that provide insight into the role of OGT and OGA.

Salinomycin biosynthesis reversely regulates the β-oxidation pathway in Streptomyces albus by carrying a 3-hydroxyacyl-CoA dehydrogenase gene in its biosynthetic gene cluster.

Streptomyces is well known for synthesis of many biologically active secondary metabolites, such as polyketides and non-ribosomal peptides. Understanding the coupling mechanisms of primary and secondary metabolism can help develop strategies to improve secondary metabolite production in Streptomyces. In this work, Streptomyces albus ZD11, an oil-preferring industrial Streptomyces strain, was proved to have a remarkable capability to generate abundant acyl-CoA precursors for salinomycin biosynthesis with the aid of its enhanced β-oxidation pathway. It was found that the salinomycin biosynthetic gene cluster contains a predicted 3-hydroxyacyl-CoA dehydrogenase (FadB3), which is the third enzyme of β-oxidation cycle. Deletion of fadB3 significantly reduced the production of salinomycin. A variety of experimental evidences showed that FadB3 was mainly involved in the β-oxidation pathway rather than ethylmalonyl-CoA biosynthesis and played a very important role in regulating the rate of β-oxidation in S. albus ZD11. Our findings elucidate an interesting coupling mechanism by which a PKS biosynthetic gene cluster could regulate the β-oxidation pathway by carrying β-oxidation genes, enabling Streptomyces to efficiently synthesize target polyketides and economically utilize environmental nutrients.

Improved liver lipid catabolism and utilization in growth hormone transgenic common carp (Cyprinus carpio L.) through enhanced lipolytic and fatty acid β-oxidation pathways.

Growth hormone (GH) transgenic common carp (Cyprinus carpio L.) show desirable aquaculture traits. Their specific growth rate (SGR) and feed efficiency (FE) are approximately 12% and 17% higher than the wild-type (WT) common carp, respectively. However, the mechanisms of lipid catabolism (lipolysis and fatty acid β-oxidation) and utilization in GH transgenic common carp are still unclear. In this study, we firstly compared the lipid metabolism of GH transgenic (initial weight 3.72 ± 0.32 g) and WT (initial weight 3.30 ± 0.28 g) common carp fed with a normal fat level diet (6% lipid, 33% protein) for two months, then compared the growth performance of GH transgenic (initial weight 3.65 ± 0.33 g) and WT (initial weight 3.27 ± 0.26 g) common carp fed with different fat levels diets (6% lipid and 12% lipid, 33% protein) for two months. We found that the lipid content in serum, liver and whole body was significantly reduced in GH transgenic common carp, the hepatic activities of the lipolytic enzymes hormone-sensitive lipase and adipose triglyceride lipase were enhanced, and the hepatic expression level of hormone-sensitive lipase was upregulated. In addition, the mitochondrion numbers were increased, and the expression level of carnitine palmitoyltransferase-1a and carnitine palmitoyltransferase-1b was upregulated in the liver of GH transgenic common carp. GH transgenic common carp showed higher weight gain and SGR than that in WT carp when fed with a normal-fat diet as they did when fed with a high-fat diet, and GH transgenic common carp showed higher FE than that in WT carp when fed with a high-fat diet. These results suggested that the lipid catabolism and utilization was improved in the GH transgenic common carp liver through enhanced lipolytic and fatty acid β-oxidation pathways. Our study provides new insights into improving lipid utilization in some aquaculture fish species.

SCP2 variant is associated with alterations in lipid metabolism, brainstem neurodegeneration, and testicular defects

BackgroundThe detoxification of very long-chain and branched-chain fatty acids and the metabolism of cholesterol to form bile acids occur largely through a process called peroxisomal β-oxidation. Mutations in several peroxisomal proteins involved in β-oxidation have been reported, resulting in diseases characterized by neurological defects. The final step of the peroxisomal β-oxidation pathway is catalyzed by sterol carrier protein-x (SCPx), which is encoded by the SCP2 gene. Previously, there have been two reports of SCPx deficiency, which resulted from a homozygous or compound heterozygous SCP2 mutation. We report herein the first patient with a heterozygous SCP2 mutation leading to SCPx deficiency.ResultsClinical presentations of the patient included progressive brainstem neurodegeneration, cardiac dysrhythmia, muscle wasting, and azoospermia. Plasma fatty acid analysis revealed abnormal values of medium-, long-, and very long-chain fatty acids. Protein expression of SCPx and other enzymes involved in β-oxidation were altered between patient and normal fibroblasts. RNA sequencing and lipidomic analyses identified metabolic pathways that were altered between patient and normal fibroblasts including PPAR signaling, serotonergic signaling, steroid biosynthesis, and fatty acid degradation. Treatment with fenofibrate or 4-hydroxytamoxifen increased SCPx levels, and certain fatty acid levels in patient fibroblasts.ConclusionsThese findings suggest that the patient’s SCP2 mutation resulted in decreased protein levels of SCPx, which may be associated with many metabolic pathways. Increasing SCPx levels through pharmacological interventions may reverse some effects of SCPx deficiency. Collectively, this work provides insight into many of the clinical consequences of SCPx deficiency and provides evidence for potential treatment strategies.