Molecular Characterization, Tissue Distribution Profile, and Nutritional Regulation of acsl Gene Family in Golden Pompano (Trachinotus ovatus)

Long chain acyl-coA synthase (acsl) family genes activate the conversion of long chain fatty acids into acyl-coA to regulate fatty acid metabolism. However, the evolutionary characteristics, tissue expression and nutritional regulation of the acsl gene family are poorly understood in fish. The present study investigated the molecular characterization, tissue expression and nutritional regulation of the acsl gene family in golden pompano (Trachinotus ovatus). The results showed that the coding regions of acsl1, acsl3, acsl4, acsl5 and acsl6 cDNA were 2091 bp, 2142 bp, 2136 bp, 1977 bp and 2007 bp, encoding 697, 714, 712, 659 and 669 amino acids, respectively. Five acsl isoforms divided into two branches, namely, acsl1, acsl5 and acsl6, as well as acsl3 and acsl4. The tissue expression distribution of acsl genes showed that acsl1 and acsl3 are widely expressed in the detected tissues, while acsl4, acsl5 and acsl6 are mainly expressed in the brain. Compared to the fish fed with lard oil diets, the fish fed with soybean oil exhibited high muscular C₁₈ PUFA contents and acsl1 and acsl3 mRNA levels, as well as low muscular SFA contents and acsl4 mRNA levels. High muscular n-3 LC-PUFA contents, and acsl3, acsl4 and acsl6 mRNA levels were observed in the fish fed with fish oil diets compared with those of fish fed with lard oil or soybean oil diets. High n-3 LC-PUFA levels and DHA contents, as well as the acsl3, acsl4 and acsl6 mRNA levels were exhibited in the muscle of fish fed diets with high dietary n-3 LC-PUFA levels. Additionally, the muscular acsl3, acsl4 and acsl6 mRNA expression levels, n-3 LC-PUFA and DHA levels were significantly up-regulated by the increase of dietary DHA proportions. Collectively, the positive relationship among dietary fatty acids, muscular fatty acids and acsl mRNA, indicated that T. ovatus Acsl1 and Acsl3 are beneficial for the C₁₈ PUFA enrichment, and Acsl3, Acsl4 and Acsl6 are for n-3 LC-PUFA and DHA enrichment. The acquisition of fish Acsl potential function in the present study will play the foundation for ameliorating the fatty acids nutrition in farmed fish products.

Triggers for the Nrf2/ARE Signaling Pathway and Its Nutritional Regulation: Potential Therapeutic Applications of Ulcerative Colitis

Ulcerative colitis (UC), which affects millions of people worldwide, is characterized by extensive colonic injury involving mucosal and submucosal layers of the colon. Nuclear factor E2-related factor 2 (Nrf2) plays a critical role in cellular protection against oxidant-induced stress. Antioxidant response element (ARE) is the binding site recognized by Nrf2 and leads to the expression of phase II detoxifying enzymes and antioxidant proteins. The Nrf2/ARE system is a key factor for preventing and resolving tissue injury and inflammation in disease conditions such as UC. Researchers have proposed that both Keap1-dependent and Keap1-independent cascades contribute positive effects on activation of the Nrf2/ARE pathway. In this review, we summarize the present knowledge on mechanisms controlling the activation process. We will further review nutritional compounds that can modulate activation of the Nrf2/ARE pathway and may be used as potential therapeutic application of UC. These comprehensive data will help us to better understand the Nrf2/ARE signaling pathway and promote its effective application in response to common diseases induced by oxidative stress and inflammation.

Nutritional regulation influencing colony dynamics and task allocations in social insect colonies

In this paper, we use an adaptive modeling framework to model and study how nutritional status (measured by the protein to carbohydrate ratio) may regulate population dynamics and foraging task allocation of social insect colonies. Mathematical analysis of our model shows that both investment to brood rearing and brood nutrition are important for colony survival and dynamics. When division of labour and/or nutrition are in an intermediate value range, the model undergoes a backward bifurcation and creates multiple attractors due to bistability. This bistability implies that there is a threshold population size required for colony survival. When the investment in brood is large enough or nutritional requirements are less strict, the colony tends to survive, otherwise the colony faces collapse. Our model suggests that the needs of colony survival are shaped by the brood survival probability, which requires good nutritional status. As a consequence, better nutritional status can lead to a better survival rate of larvae and thus a larger worker population.

Imprinted Genes Impact Upon Beta Cell Function in the Current (and Potentially Next) Generation

Beta cell failure lies at the centre of the aetiology and pathogenesis of type 2 diabetes and the epigenetic control of the expression of critical beta cell genes appears to play a major role in this decline. One such group of epigenetically-controlled genes, termed 'imprinted' genes, are characterised by transgenerational monoallelic expression due to differential allelic DNA methylation and play key functional roles within beta cells. Here, we review the evidence for this functional importance of imprinted genes in beta cells as well as their nutritional regulation by the diet and their altered methylation and/or expression in rodent models of diabetes and in type 2 diabetic islets. We also discuss imprinted genes in the context of the next generation, where dietary overnutrition in the parents can lead to their deregulation in the offspring, alongside beta cell dysfunction and defective glucose handling. Both the modulation of imprinted gene expression and the likelihood of developing type 2 diabetes in adulthood are susceptible to the impact of nutritional status in early life. Imprinted loci, therefore, represent an excellent opportunity with which to assess epigenomic changes in beta cells due to the diet in both the current and next generation.

Molecular Cloning, Characterization, and Nutritional Regulation of Elovl6 in Large Yellow Croaker (Larimichthys crocea)

Elongation of very long chain fatty acids protein 6 (Elovl6) is a key enzyme in fatty acid synthesis, which participates in converting palmitate (C16:0) to stearate (C18:0). Although studies of Elovl6 have been carried out in mammals, the nutritional regulation of elovl6 in fish remains poorly understood. In the present study, the cloning and nutritional regulation of elovl6 were determined in large yellow croaker. Sequence and phylogenetic analysis revealed that the full-length cDNA of elovl6 was 1360 bp, including an open reading frame of 810 bp encoding a putative protein of 269 amino acid that possesses the characteristic features of Elovl proteins. The transcript level of elovl6 was significantly increased in the liver of croaker fed the diets with soybean oil (enriched with 18: 2n-6, LA) or linseed oil (enriched with 18: 3n-3, ALA) than that in croaker fed the diet with fish oil (enriched with 20: 5n-3 and 22: 6n-3). Correspondingly, the elovl6 expression in croaker’s hepatocytes treated with ALA or LA was remarkably increased compared to the controls. Furthermore, the transcription factors including hepatocyte nuclear factor 1α (HNF1α), CCAAT-enhancer-binding protein β (CEBPβ), retinoid X receptor α (RXRα), and cAMP response element-binding protein 1 (CREB1) greatly enhanced promoter activity of elovl6 in large yellow croaker, and the expression of transcription factors is consistent with the changes of elovl6 expression in response to fatty acids in vivo and in vitro. In conclusion, this study revealed that elovl6 expression in large yellow croaker could be upregulated by dietary ALA or LA via the increased transcriptional expression of transcription factors including hnf1α, cebpβ, rxrα, and creb1.

Regulation of Botulinum Neurotoxin Synthesis and Toxin Complex Formation by Arginine and Glucose in Clostridium botulinum ATCC 3502

Botulinum neurotoxin (BoNT), produced by neurotoxigenic clostridia, is the most potent biological toxin known and the causative agent of the paralytic disease botulism. The nutritional, environmental, and genetic regulation of BoNT synthesis, activation, stability, and toxin complex (TC) formation is not well studied. Previous studies indicated that growth and BoNT formation were affected by arginine and glucose in Clostridium botulinum types A and B. In the present study, C. botulinum ATCC 3502 was grown in toxin production medium (TPM) with different levels of arginine and glucose and of three products of arginine metabolism, citrulline, proline, and ornithine. Cultures were analyzed for growth (optical density at 600 nm [OD₆₀₀]), spore formation, and BoNT and TC formation by Western blotting and immunoprecipitation and for BoNT activity by mouse bioassay. A high level of arginine (20 g/liter) repressed BoNT production approximately 1,000-fold, enhanced growth, slowed lysis, and reduced endospore production by greater than 1,000-fold. Similar effects on toxin production were seen with equivalent levels of citrulline but not ornithine or proline. In TPM lacking glucose, levels of formation of BoNT/A1 and TC were significantly decreased, and extracellular BoNT and TC proteins were partially inactivated after the first day of culture. An understanding of the regulation of C. botulinum growth and BoNT and TC formation should be valuable in defining requirements for BoNT formation in foods and clinical samples, improving the quality of BoNT for pharmaceutical preparations, and elucidating the biological functions of BoNTs for the bacterium.IMPORTANCE Botulinum neurotoxin (BoNT) is a major food safety and bioterrorism concern and is also an important pharmaceutical, and yet the regulation of its synthesis, activation, and stability in culture media, foods, and clinical samples is not well understood. This paper provides insights into the effects of critical nutrients on growth, lysis, spore formation, BoNT and TC production, and stability of BoNTs of C. botulinum We show that for C. botulinum ATCC 3502 cultured in a complex medium, a high level of arginine repressed BoNT expression by ca. 1,000-fold and also strongly reduced sporulation. Arginine stimulated growth and compensated for a lack of glucose. BoNT and toxin complex proteins were partially inactivated in a complex medium lacking glucose. This work should aid in optimizing BoNT production for pharmaceutical uses, and furthermore, an understanding of the nutritional regulation of growth and BoNT formation may provide insights into growth and BoNT formation in foods and clinical samples and into the enigmatic function of BoNTs in nature.

Nutritional and Hormonal Regulation of Citrate and Carnitine/Acylcarnitine Transporters: Two Mitochondrial Carriers Involved in Fatty Acid Metabolism

The transport of solutes across the inner mitochondrial membrane is catalyzed by a family of nuclear-encoded membrane-embedded proteins called mitochondrial carriers (MCs). The citrate carrier (CiC) and the carnitine/acylcarnitine transporter (CACT) are two members of the MCs family involved in fatty acid metabolism. By conveying acetyl-coenzyme A, in the form of citrate, from the mitochondria to the cytosol, CiC contributes to fatty acid and cholesterol synthesis; CACT allows fatty acid oxidation, transporting cytosolic fatty acids, in the form of acylcarnitines, into the mitochondrial matrix. Fatty acid synthesis and oxidation are inversely regulated so that when fatty acid synthesis is activated, the catabolism of fatty acids is turned-off. Malonyl-CoA, produced by acetyl-coenzyme A carboxylase, a key enzyme of cytosolic fatty acid synthesis, represents a regulator of both metabolic pathways. CiC and CACT activity and expression are regulated by different nutritional and hormonal conditions. Defects in the corresponding genes have been directly linked to various human diseases. This review will assess the current understanding of CiC and CACT regulation; underlining their roles in physio-pathological conditions. Emphasis will be placed on the molecular basis of the regulation of CiC and CACT associated with fatty acid metabolism.

Jian: Gene characterization, mRNA expression, and nutritional regulation]

Elovl5 elongase is a critical enzyme involved in the highly unsaturated fatty acid (HUFA) biosynthesis. There is very little information on the evolution and functional characterization of Elovl5-a and Elovl5-b genes in common carp (Cyprinus carpio var. Jian). In the present study, the genomic sequences and structures of two putative Elovl5-like elongase genes in the common carp genome were obtained. The mRNA expression patterns of Elovl5-a and Elovl5-b in tissues, hatching carp embryos, and juveniles under nutritional regulation were investigated. The results show that the two Elovl5 elongase genes have similar organization, coding 8 exons of high identity and introns of distinct size and sequence composition. They are not allelic variants of a single gene. Both Elovl5 elongase genes are highly expressed in liver, intestine (pyloric caeca) and brain. Elovl5-a and Elovl5-b mRNAs showed increased expression from newly hatched to 20 days after hatching. The regulation of Elovl5-a and Elovl5-b in response to dietary fatty acid composition was determined in liver, brain and intestine (pyloric caeca) of common carp fed with diets: (i) fish oil (FO) rich in n-3 HUFA, (ii) corn oil (CO, 18:2n-6) or (iii) linseed oil (LO, 18:3n-3). Also the differential expression of Elovl5-a and Elovl5-b genes in liver, brain and intestine in common carps fed with different oil sources was studied. Further work aimed at the determination of the mechanisms of differential expression of the Elovl5-a and Elovl5-b in different tissues and the roles of transcription factors in regulating HUFA synthesis is in progress.