Tissue-specific, nutritional, and developmental regulation of rat fatty acid elongases

Genome-wide selection signatures address trait specific candidate genes in cattle indigenous to arid regions of India

The peculiarity of Indian cattle lies in milk quality, resistance to diseases and stressors as well as adaptability. The investigation addressed selection signatures in Gir and Tharparkar cattle, belonging to arid ecotypes of India. Double digest restriction-site associated DNA sequencing (ddRAD-seq) yielded nearly 26 million high-quality reads from unrelated seven Gir and seven Tharparkar cows. In all, 19,127 high-quality SNPs were processed for selection signature analysis. An approach involving within-population composite likelihood ratio (CLR) statistics and between-population FST statistics was used to capture selection signatures within and between the breeds, respectively. A total of 191 selection signatures were addressed using CLR and FST approaches. Selection signatures overlapping 86 and 73 genes were detected as Gir- and Tharparkar-specific, respectively. Notably, genes related to production (CACNA1D, GHRHR), reproduction (ESR1, RBMS3), immunity (NOSTRIN, IL12B) and adaptation (ADAM22, ASL) were annotated to selection signatures. Gene pathway analysis revealed genes in insulin/IGF pathway for milk production, gonadotropin releasing hormone pathway for reproduction, Wnt signalling pathway and chemokine and cytokine signalling pathway for adaptation. This is the first study where selection signatures are identified using ddRAD-seq in indicine cattle breeds. The study shall help in conservation and leveraging genetic improvements in Gir and Tharparkar cattle.

Silencing the fatty acid elongase gene elovl6 induces reprogramming of nutrient metabolism in male Oreochromis niloticus

Elongation of very long-chain fatty acids protein 6 (ELOVL6) plays a pivotal role in the synthesis of endogenous fatty acids, influencing energy balance and metabolic diseases. The primary objective of this study was to discover the molecular attributes and regulatory roles of ELOVL6 in male Nile tilapia, Oreochromis niloticus. The full-length cDNA of elovl6 was cloned from male Nile tilapia, and was determined to be 2255-bp long, including a 5'-untranslated region of 193 bp, a 3'-untranslated region of 1252 bp, and an open reading frame of 810 bp encoding 269 amino acids. The putative protein had typical features of ELOVL proteins. The transcript levels of elovl6 differed among various tissues and among fish fed with different dietary lipid sources. Knockdown of elovl6 in Nile tilapia using antisense RNA technology resulted in significant alterations in hepatic morphology, long-chain fatty acid synthesis, and fatty acid oxidation, and led to increased fat deposition in the liver and disrupted glucose/lipid metabolism. A comparative transcriptomic analysis (elovl6 knockdown vs. the negative control) identified 5877 differentially expressed genes with significant involvement in key signaling pathways including the peroxisome proliferator-activated receptor signaling pathway, fatty acid degradation, glycolysis/gluconeogenesis, and the insulin signaling pathway, all of which are crucial for lipid and glucose metabolism. qRT-PCR analyses verified the transcript levels of 13 differentially expressed genes within these pathways. Our findings indicate that elovl6 knockdown in male tilapia impedes oleic acid synthesis, culminating in aberrant nutrient metabolism.

iLipidome: enhancing statistical power and interpretability using hidden biosynthetic interdependencies in the lipidome

Numerous biological processes and diseases are influenced by lipid composition. Advances in lipidomics are elucidating their roles, but analyzing and interpreting lipidomics data at the systems level remain challenging. To address this, we present iLipidome, a method for analyzing lipidomics data in the context of the lipid biosynthetic network, thus accounting for the interdependence of measured lipids. iLipidome enhances statistical power, enables reliable clustering and lipid enrichment analysis, and links lipidomic changes to their genetic origins. We applied iLipidome to investigate mechanisms driving changes in cellular lipidomes following supplementation of docosahexaenoic acid (DHA) and successfully identified the genetic causes of alterations. We further demonstrated how iLipidome can disclose enzyme-substrate specificity and pinpoint prospective glioblastoma therapeutic targets. Finally, iLipidome enabled us to explore underlying mechanisms of cardiovascular disease and could guide the discovery of early lipid biomarkers. Thus, iLipidome can assist researchers studying the essence of lipidomic data and advance the field of lipid biology.

Dietary docosahexaenoic acid (DHA) downregulates liver DHA synthesis by inhibiting eicosapentaenoic acid elongation

DHA is abundant in the brain where it regulates cell survival, neurogenesis, and neuroinflammation. DHA can be obtained from the diet or synthesized from alpha-linolenic acid (ALA; 18:3n-3) via a series of desaturation and elongation reactions occurring in the liver. Tracer studies suggest that dietary DHA can downregulate its own synthesis, but the mechanism remains undetermined and is the primary objective of this manuscript. First, we show by tracing 13C content (δ13C) of DHA via compound-specific isotope analysis, that following low dietary DHA, the brain receives DHA synthesized from ALA. We then show that dietary DHA increases mouse liver and serum EPA, which is dependant on ALA. Furthermore, by compound-specific isotope analysis we demonstrate that the source of increased EPA is slowed EPA metabolism, not increased DHA retroconversion as previously assumed. DHA feeding alone or with ALA lowered liver elongation of very long chain (ELOVL2, EPA elongation) enzyme activity despite no change in protein content. To further evaluate the role of ELOVL2, a liver-specific Elovl2 KO was generated showing that DHA feeding in the presence or absence of a functional liver ELOVL2 yields similar results. An enzyme competition assay for EPA elongation suggests both uncompetitive and noncompetitive inhibition by DHA depending on DHA levels. To translate our findings, we show that DHA supplementation in men and women increases EPA levels in a manner dependent on a SNP (rs953413) in the ELOVL2 gene. In conclusion, we identify a novel feedback inhibition pathway where dietary DHA downregulates its liver synthesis by inhibiting EPA elongation.

A comprehensive review of the family of very-long-chain fatty acid elongases: structure, function, and implications in physiology and pathology

BACKGROUND

The very-long-chain fatty acid elongase (ELOVL) family plays essential roles in lipid metabolism and cellular functions. This comprehensive review explores the structural characteristics, functional properties, and physiological significance of individual ELOVL isoforms, providing insights into lipid biosynthesis, cell membrane dynamics, and signaling pathways.

AIM OF REVIEW

This review aims to highlight the significance of the ELOVL family in normal physiology and disease development. By synthesizing current knowledge, we underscore the relevance of ELOVLs as potential therapeutic targets.

KEY SCIENTIFIC CONCEPTS OF REVIEW

We emphasize the association between dysregulated ELOVL expression and diseases, including metabolic disorders, skin diseases, neurodegenerative conditions, and cancer. The intricate involvement of ELOVLs in cancer biology, from tumor initiation to metastasis, highlights their potential as targets for anticancer therapies. Additionally, we discuss the prospects of using isoform-specific inhibitors and activators for metabolic disorders and cancer treatment. The identification of ELOVL-based biomarkers may advance diagnostics and personalized medicine.

CONCLUSION

The ELOVL family's multifaceted roles in lipid metabolism and cellular physiology underscore its importance in health and disease. Understanding their functions offers potential therapeutic avenues and personalized treatments.

Allyl Isothiocyanate Maintains DHA-Containing Glycerophospholipids and Ameliorates the Cognitive Function Decline in OVX Mice

Low-temperature-induced fatty acid desaturation is highly conserved in animals, plants, and bacteria. Allyl isothiocyanate (AITC) is an agonist of the transient receptor potential ankyrin 1 (TRPA1), which is activated by various chemophysiological stimuli, including low temperature. However, whether AITC induces fatty acid desaturation remains unknown. We showed here that AITC increased levels of glycerophospholipids (GP) esterified with unsaturated fatty acids, especially docosahexaenoic acid (DHA) in TRPA1-expressing HEK cells. Additionally, GP-DHA including phosphatidylcholine (18:0/22:6) and phosphatidylethanolamine (18:0/22:6) was increased in the brain and liver of AITC-administered mice. Moreover, intragastrical injection of AITC in ovariectomized (OVX) female C57BL/6J mice dose-dependently shortened the Δlatency time determined by the Morris water maze test, indicating AITC ameliorated the cognitive function decline in these mice. Thus, the oral administration of AITC maintains GP-DHA in the liver and brain, proving to be a potential strategy for preventing cognitive decline.

The physiological and pathological properties of Mead acid, an endogenous multifunctional n-9 polyunsaturated fatty acid

Mead acid (MA, 5,8,11-eicosatrienoic acid) is an n-9 polyunsaturated fatty acid (PUFA) and a marker of essential fatty acid deficiency, but nonetheless generally draws little attention. MA is distributed in various normal tissues and can be converted to several specific lipid mediators by lipoxygenase and cyclooxygenase. Recent pathological and epidemiological studies on MA raise the possibility of its effects on inflammation, cancer, dermatitis and cystic fibrosis, suggesting it is an endogenous multifunctional PUFA. This review summarizes the biosynthesis, presence, metabolism and physiological roles of MA and its relation to various diseases, as well as the significance of MA in PUFA metabolism.

Time course of western diet (WD) induced nonalcoholic steatohepatitis (NASH) in female and male Ldlr-/- mice

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a global health problem. Identification of factors contributing to the onset and progression of NAFLD have the potential to direct novel strategies to combat NAFLD.

METHODS

We examined the time course of western diet (WD)-induced NAFLD and its progression to nonalcoholic steatohepatitis (NASH) in age-matched female and male Ldlr-/- mice, with time-points at 1, 4, 8, 20 and 40 weeks on the WD. Controls included Ldlr-/- mice maintained on a purified low-fat diet (LFD) for 1 and 40 weeks. The approach included quantitation of anthropometric, plasma and liver markers of disease, plus hepatic histology, lipids, oxylipins, gene expression and selected metabolites.

RESULTS

One week of feeding the WD caused a significant reduction in hepatic essential fatty acids (EFAs: 18:2, ω6, 18:3, ω3) which preceded the decline in many C20-22 ω3 and ω6 polyunsaturated fatty acids (PUFA) and PUFA-derived oxylipins after 4 weeks on the WD. In addition, expression of hepatic inflammation markers (CD40, CD44, Mcp1, Nlrp3, TLR2, TLR4, Trem2) increased significantly in both female & male mice after one week on the WD. These markers continued to increase over the 40-week WD feeding study. WD effects on hepatic EFA and inflammation preceded all significant WD-induced changes in body weight, insulin resistance (HOMA-IR), oxidative stress status (GSH/GSSG ratio) and histological and gene expression markers of macrosteatosis, extracellular matrix remodeling and fibrosis.

CONCLUSIONS

Our findings establish that feeding Ldlr-/- mice the WD rapidly lowered hepatic EFAs and induced key inflammatory markers linked to NASH. Since EFAs have an established role in inflammation and hepatic inflammation plays a major role in NASH, we suggest that early clinical assessment of EFA status and correcting EFA deficiencies may be useful in reducing NASH severity.

Different Dietary Ratios of Camelina Oil to Sandeel Oil Influence the Capacity to Synthesise and Deposit EPA and DHA in Zucker Fa/Fa Rats

Plant-based food provides more ALA (α-linolenic acid) and less EPA (eicosapentaenoic acid) and DHA (docosahexanoic acid) than marine food. Earlier studies indicate that cetoleic acid (22:1n-11) stimulates the n-3 pathway from ALA to EPA and DHA. The present study aimed to investigate the dietary effects of camelina oil (CA) high in ALA and sandeel oil (SA) high in cetoleic acid on the conversion of ALA to EPA and DHA. Male Zucker fa/fa rats were fed a diet of soybean oil (Ctrl) or diets of CA, SA, or a combination of CA and SA. Significantly higher levels of DPA (docosapentaenoic acid) and DHA in blood cells from the CA group compared to the Ctrl indicate an active conversion of ALA to DPA and DHA. Increasing the uptake and deposition of EPA and DHA meant that a trend towards a decrease in the liver gene expression of Elovl5, Fads1, and Fads2 along with an increase in the dietary content of SA was observed. However, 25% of the SA could be exchanged with CA without having a significant effect on EPA, DPA, or DHA in blood cells, indicating that bioactive components in SA, such as cetoleic acid, might counteract the inhibiting effect of the high dietary content of DHA on the n-3 biosynthetic pathway.

Profound Modification of Fatty Acid Profile and Endocannabinoid-Related Mediators in PPARα Agonist Fenofibrate-Treated Mice

Fenofibrate (FBR), an oral medication used to treat dyslipidemia, is a ligand of the peroxisome proliferator-activated receptor α (PPARα), a nuclear receptor that regulates the expression of metabolic genes able to control lipid metabolism and food intake. PPARα natural ligands include fatty acids (FA) and FA derivatives such as palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), known to have anti-inflammatory and anorexigenic activities, respectively. We investigated changes in the FA profile and FA derivatives by HPLC and LC-MS in male C57BL/6J mice fed a standard diet with or without 0.2% fenofibrate (0.2% FBR) for 21 days. Induction of PPARα by 0.2% FBR reduced weight gain, food intake, feed efficiency, and liver lipids and induced a profound change in FA metabolism mediated by parallel enhanced mitochondrial and peroxisomal β-oxidation. The former effects led to a steep reduction of essential FA, particularly 18:3n3, with a consequent decrease of the n3-highly unsaturated fatty acids (HUFA) score; the latter effect led to an increase of 16:1n7 and 18:1n9, suggesting enhanced hepatic de novo lipogenesis with increased levels of hepatic PEA and OEA, which may activate a positive feedback and further sustain reductions of body weight, hepatic lipids and feed efficiency.

The Association between Maternal Oral Inflammation and Neutrophil Phenotypes and Poly-Unsaturated Fatty Acids Composition in Human Milk: A Prospective Cohort Study

This prospective cohort study aimed to investigate the impact of maternal oral inflammation on human milk composition including neutrophil counts, activation state (based on cluster of differentiation (CD) markers expression), and fatty acid levels. Fifty mothers were recruited from St. Michael's hospital, Toronto, and followed up from 2-4 weeks until 4 months postpartum. Oral rinse and human milk samples were collected at both timepoints. Oral polymorphonuclear neutrophils (oPMNs) within the rinses were quantified using flow cytometry and the participants' oral health state was categorized into three groups (i.e., healthy, moderate, and severe) based on the oPMNs counts. Fatty acids were identified and quantified using a gas chromatography-flame ionization detector (GC-FID). Compared to mothers with a healthy oral health state, mothers with moderate to severe oral inflammation had a statistically significant decrease in the expression of CD64 biomarker, an increase in the expression of CD14 biomarker on human milk neutrophils and a decrease in the levels of eicosapentaenoic acid (C20:5n-3) in their human milk at follow-up compared to baseline. This study demonstrates for the first time that maternal oral inflammation can affect human milk composition. The mechanism by which these alterations can affect infant health outcomes in the long term critically needs to be considered.

Obesity promotes lipid accumulation in mouse cartilage-A potential role of acetyl-CoA carboxylase (ACC) mediated chondrocyte de novo lipogenesis

Obesity promotes the development of osteoarthritis (OA). It is also well-established that obesity leads to excessive lipid deposition in nonadipose tissues, which often induces lipotoxicity. The objective of this study was to investigate changes in the levels of various lipids in mouse cartilage in the context of obesity and determine if chondrocyte de novo lipogenesis is altered. We used Oil Red O to determine the accumulation of lipid droplets in cartilage from mice fed high-fat diet (HFD) or low-fat diet (LFD). We further used mass spectrometry-based lipidomic analyses to quantify levels of different lipid species. Expression of genes involving in fatty acid (FA) uptake, synthesis, elongation, and desaturation were examined using quantitative polymerase chain reaction. To further study the potential mechanisms, we cultured primary mouse chondrocytes under high-glucose and high-insulin conditions to mimic the local microenvironment associated with obesity and subsequently examined the abundance of cellular lipid droplets. The acetyl-CoA carboxylase (ACC) inhibitor, ND-630, was added to the culture medium to examine the effect of inhibiting de novo lipogenesis on lipid accumulation in chondrocytes. When compared to the mice receiving LFD, the HFD group displayed more chondrocytes with visible intracellular lipid droplets. Significantly higher amounts of total FAs were also detected in the HFD group. Five out of six significantly upregulated FAs were ω-6 FAs, while the two significantly downregulated FAs were ω-3 FAs. Consequently, the HFD group displayed a significantly higher ω-6/ω-3 FA ratio. Ether linked phosphatidylcholine was also found to be higher in the HFD group. Fatty acid desaturase (Fad1-3), fatty acid-binding protein 4 (Fabp4), and fatty acid synthase (Fasn) transcripts were not found to be different between the treatment groups and fatty acid elongase (Elovl1-7) transcripts were undetectable in cartilage. Ceramide synthase 2 (Cers-2), the only transcript found to be changed in these studies, was significantly upregulated in the HFD group. In vitro, chondrocytes upregulated de novo lipogenesis when cultured under high-glucose, high-insulin conditions, and this observation was associated with the activation of ACC, which was attenuated by the addition of ND-630. This study provides the first evidence that lipid deposition is increased in cartilage with obesity and that this is associated with the upregulation of ACC-mediated de novo lipogenesis. This was supported by our observation that ACC inhibition ameliorated lipid accumulation in chondrocytes, thereby suggesting that ACC could potentially be targeted to treat obesity-associated OA.

Composition of Fatty Acids and Localization of SREBP1 and ELOVL2 Genes in Cauda Epididymides of Hu Sheep with Different Fertility

The epididymis is an organ that transports, matures and stores sperm, and has functions such as secretion and absorption. Polyunsaturated fatty acid (PUFA) compositions in sperm membrane were changed during the process of epididymis maturation and influence the male fertility. This study aimed to investigate differences in crude fat and fatty acid content in cauda epididymis between high and low fertility of Hu sheep. One hundred and seventy-nine Hu ram lambs were fed from 56 days to 6 months under the same environment. After the feeding trial, all rams were slaughtered, and the body weight, testicular weight, epididymal weight and sperm density were measured. Pearson correlation analysis showed significantly moderate positive correlation between epididymal weight and sperm density and testicular weight. Eighteen rams were selected and divided into the high fertility group (H, n = 9) and low fertility group (L, n = 9) according to the epididymal weight, sperm density and histomorphology. The crude fat content, fatty acid profile and genes related to fatty acid metabolism were detected. The crude fat content, total fatty acid, total n-3 PUFA and docosahexaenoic acid (C22:6n-3, DHA) content of cauda epididymis in high fertility group was significantly higher than those in low fertility group (p < 0.05). However, the ratio of n-6/n-3 PUFA was significantly lower than that in group L (p < 0.05). Immunohistochemistry results showed that SREBP1 and ELOVL2 were expressed in pseudostratified columnar ciliated epithelium and smooth muscle cells. The mRNA expression of SREBP1 (p = 0.09) and ELOVL2 (p < 0.05) in the high fertility group were increased. In conclusion, the high expression of SREBP1 and ELOVL2 may contribute to high n-3 PUFA content in cauda epididymis of high-fertility Hu sheep.

ELOVL gene family plays a virtual role in response to breeding selection and lipid deposition in different tissues in chicken (Gallus gallus)

Background

Elongases of very long chain fatty acids (ELOVLs), a family of first rate-limiting enzymes in the synthesis of long-chain fatty acids, play an essential role in the biosynthesis of complex lipids. Disrupting any of ELOVLs affects normal growth and development in mammals. Genetic variations in ELOVLs are associated with backfat or intramuscular fatty acid composition in livestock. However, the effects of ELOVL gene family on breeding selection and lipid deposition in different tissues are still unknown in chickens.

Results

Genetic variation patterns and genetic associations analysis showed that the genetic variations of ELOVL genes were contributed to breeding selection of commercial varieties in chicken, and 14 SNPs in ELOVL2-6 were associated with body weight, carcass or fat deposition traits. Especially, one SNP rs17631638T > C in the promoter of ELOVL3 was associated with intramuscular fat content (IMF), and its allele frequency was significantly higher in native and layer breeds compared to that in commercial broiler breeds. Quantitative real-time PCR (qRT-PCR) determined that the ELOVL3 expressions in pectoralis were affected by the genotypes of rs17631638T > C. In addition, the transcription levels of ELOVL genes except ELOVL5 were regulated by estrogen in chicken liver and hypothalamus with different regulatory pathways. The expression levels of ELOVL1-6 in hypothalamus, liver, abdominal fat and pectoralis were correlated with abdominal fat weight, abdominal fat percentage, liver lipid content and IMF. Noteworthily, expression of ELOVL3 in pectoralis was highly positively correlated with IMF and glycerophospholipid molecules, including phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl glycerol and phospholipids inositol, rich in ω-3 and ω-6 long-chain unsaturated fatty acids, suggesting ELOVL3 could contribute to intramuscular fat deposition by increasing the proportion of long-chain unsaturated glycerophospholipid molecules in pectoralis.

Conclusions

In summary, we demonstrated the genetic contribution of ELOVL gene family to breeding selection for specialized varieties, and revealed the expression regulation of ELOVL genes and their potential roles in regulating lipid deposition in different tissues. This study provides new insights into understanding the functions of ELOVL family on avian growth and lipid deposition in different tissues and the genetic variation in ELOVL3 may aid the marker-assisted selection of meat quality in chicken.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08932-8.

Influence of the nutritional status and oxidative stress in the desaturation and elongation of n-3 and n-6 polyunsaturated fatty acids: Impact on non-alcoholic fatty liver disease

Polyunsaturated fatty acids (PUFA) play essential roles in cell membrane structure and physiological processes including signal transduction, cellular metabolism and tissue homeostasis to combat diseases. PUFA are either consumed from food or synthesized by enzymatic desaturation, elongation and peroxisomal β-oxidation. The nutritionally essential precursors α-linolenic acid (C18:3n-3; ALA) and linoleic acid (C18:2n-6; LA) are subjected to desaturation by Δ6D/Δ5D desaturases and elongation by elongases 2/5, enzymes that are induced by insulin and repressed by PUFA. Maintaining an optimally low n-6/n-3 PUFA ratio is linked to prevention of the development of several diseases, including nonalcoholic fatty liver disease (NAFLD) that is characterized by depletion of PUFA promoting hepatic steatosis and inflammation. In this context, supplementation with n-3 PUFA revealed significant lowering of hepatic steatosis in obese patients, whereas prevention of fatty liver by high-fat diet in mice is observed in n-3 PUFA and hydroxytyrosol co-administration. The aim of this work is to review the role of nutritional status and nutrient availability on markers of PUFA biosynthesis. In addition, the impact of oxidative stress developed as a result of NAFLD, a redox imbalance that may alter the expression and activity of the enzymes involved, and diminished n-3 PUFA levels by free-radical dependent peroxidation processes will be discussed.

Hyperandrogenism diminishes maternal-fetal fatty acid transport by increasing FABP 4-mediated placental lipid accumulation

Long-chain polyunsaturated fatty acids (LCPUFAs) are critical for fetal brain development. Infants born to preeclamptic mothers or those born growth restricted due to placental insufficiency have reduced LCPUFA, and are at higher risk for developing neurodevelopmental disorders. Since plasma levels of testosterone (T) and fatty acid-binding protein 4 (FABP4) are elevated in preeclampsia, we hypothesized that elevated T induces the expression of FABP4 in the placenta leading to compromised transplacental transport of LCPUFAs. Increased maternal T in pregnant rats significantly decreased n-3 and n-6 LCPUFA levels in maternal and fetal circulation, but increased their placental accumulation. Dietary LCPUFAs supplementation in T dams increased LCPUFA levels in the maternal circulation and further augmented placental storage, while failing to increase fetal levels. The placenta in T dams exhibited increased FABP4 mRNA and protein levels. In vitro, T dose-dependently upregulated FABP4 transcription in trophoblasts. T stimulated androgen receptor (AR) recruitment to the androgen response element and trans-activated FABP4 promoter activity, both of which were abolished by AR antagonist. T in pregnant rats and cultured trophoblasts significantly reduced transplacental transport of C14-docosahexaenoic acid (DHA) and increased C14-DHA accumulation in the placenta. Importantly, FABP4-overexpression by itself in pregnant rats and trophoblasts increased transplacental transport of C14-DHA with no significant placental accumulation. T exposure, in contrast, inhibited this FABP4-mediated effect by promoting C14-DHA placental accumulation. In summary, our studies show that maternal hyperandrogenism increases placental FABP4 expression via transcriptional upregulation and preferentially routes LCPUFAs toward cellular storage in the placenta leading to offspring lipid deficiency.

Starvation causes changes in the intestinal transcriptome and microbiome that are reversed upon refeeding

BACKGROUND

The ability of animals and their microbiomes to adapt to starvation and then restore homeostasis after refeeding is fundamental to their continued survival and symbiosis. The intestine is the primary site of nutrient absorption and microbiome interaction, however our understanding of intestinal adaptations to starvation and refeeding remains limited. Here we used RNA sequencing and 16S rRNA gene sequencing to uncover changes in the intestinal transcriptome and microbiome of zebrafish subjected to long-term starvation and refeeding compared to continuously fed controls.

RESULTS

Starvation over 21 days led to increased diversity and altered composition in the intestinal microbiome compared to fed controls, including relative increases in Vibrio and reductions in Plesiomonas bacteria. Starvation also led to significant alterations in host gene expression in the intestine, with distinct pathways affected at early and late stages of starvation. This included increases in the expression of ribosome biogenesis genes early in starvation, followed by decreased expression of genes involved in antiviral immunity and lipid transport at later stages. These effects of starvation on the host transcriptome and microbiome were almost completely restored within 3 days after refeeding. Comparison with published datasets identified host genes responsive to starvation as well as high-fat feeding or microbiome colonization, and predicted host transcription factors that may be involved in starvation response.

CONCLUSIONS

Long-term starvation induces progressive changes in microbiome composition and host gene expression in the zebrafish intestine, and these changes are rapidly reversed after refeeding. Our identification of bacterial taxa, host genes and host pathways involved in this response provides a framework for future investigation of the physiological and ecological mechanisms underlying intestinal adaptations to food restriction.

Camelina (Camelina sativa (L.) Crantz) as Feedstuffs in Meat Type Poultry Diet: A Source of Protein and n-3 Fatty Acids

Simple Summary

One of the main problems in poultry production is to find more sustainable feed protein sources, other than the most widely used soya bean meal. An alternative protein source could be the underexploited oilseed crop camelina (Camelina sativa (L.) Crantz), which is mostly grown for biodiesel production, but is also characterized by disease and pest resistance, tolerance to cold weather, drought and low fertility soil. This review presents the nutritive value of camelina seeds, oil and cake (a by-product of biodiesel production), and their effect on the growth performance and fatty acid profile of muscles and liver in meat type poultry. The research results indicated that supplementation of poultry diets with camelina feedstuffs beneficially modified the fatty acid composition of meat and liver. The ratio of n-6/n-3 polyunsaturated fatty acids (PUFA) decreased, whereas the content of α-linolenic and long-chain n-3 PUFA increased in poultry tissues.

Abstract

Camelina seed or seed processing derivatives, i.e., cake, are cheap alternative protein feed ingredients for meat type poultry. Camelina is an oilseed crop containing 36.8% oil in seeds, while in the cake the oil content accounts for 6.4–22.7%. If compared with other Brassicaceae family plants, camelina is distinguished by a unique fatty acid composition, because the content of α-linolenic fatty acid (C18:3n-3; ALA) varies from 25.9 to 36.7% of total fatty acids. The total tocopherol content in camelina oil and cake are, respectively, 751–900 and 687 mg/kg. Addition of camelina to poultry nutrition increases the amount of n-3 polyunsaturated fatty acids (PUFA) in poultry meat and liver. The content of ALA in chicken muscles increases by 1.3–4.4, 2.4–2.9 and 2.3–7.2 times after supplementing chicken diets with, respectively, camelina cake (8–24%), seed (10%), and oil (2.5–6.9%) in comparison with the control group. Camelina cake (5–25%), seed (10%) and oil (2.5–4%) inclusion in chicken diets results in 1.5–3.9 times higher total n-3 PUFA content in muscles and liver. Meanwhile, supplementation of chicken diets with camelina oil (4–6.9%), seed (5–10%) and cake (5–25%) results in, respectively, a 1.8–8.4, 1.6–1.9 and 1.3–2.9 times lower n-6/n-3 PUFA ratio in muscles, and 3.29 times lower n-6/n-3 PUFA ratio in the liver. After inclusion of different amounts of camelina cake in chicken diets, a healthy for human nutrition n-6/n-3 PUFA ratio from 1.6 to 2.9 was found in chicken muscles.

Independent of Calorie Intake, Short-term Alternate-day Fasting Alleviates NASH, With Modulation of Markers of Lipogenesis, Autophagy, Apoptosis, and Inflammation in Rats

Non-alcoholic steatohepatitis (NASH) is a worldwide health problem. Alternate-day fasting (ADF), although thought to be aggressive, has proven safety and efficacy. We aimed to evaluate the effect of short-term ADF against already established high-fat-fructose (HFF)-induced NASH, independent of the amount of calorie intake, and to study the effect of ADF on lipogenesis, apoptosis, and hepatic inflammation. Male Sprague Dawley rats were divided into two groups: (1) negative control and (2) NASH group fed on HFF for 9 weeks, and then randomized into two subgroups of either HFF alone or with ADF protocol for 3 weeks. The ADF could improve HFF-related elevation in serum lactate dehydrogenase and could decrease the mRNA expression of lipogenesis genes; acetyl CoA carboxylase, peroxisome proliferator-activated receptor γ, and peroxisome proliferator-activated receptor α; apoptotic genes caspase-3, p53, and inflammatory cyclo-oxygenase 2; and immunohistochemical staining for their proteins in liver with upregulation of LC3 and downregulation of P62 immunoexpression. Moreover, ADF ameliorated HFF-induced steatosis, inflammation, ballooning, and fibrosis through hematoxylin and eosin, Oil Red O, and Sirius Red staining, confirmed by morphometric analysis, without significant weight loss. Significant correlation of morphometric parameters with levels of gene expression was found. These findings suggest ADF to be a safe effective therapeutic agent in the management of NASH.

Fatty Acid Synthesis in Glial Cells of the CNS

Fatty acids (FAs) are of crucial importance for brain homeostasis and neural function. Glia cells support the high demand of FAs that the central nervous system (CNS) needs for its proper functioning. Additionally, FAs can modulate inflammation and direct CNS repair, thereby contributing to brain pathologies such Alzheimer’s disease or multiple sclerosis. Intervention strategies targeting FA synthesis in glia represents a potential therapeutic opportunity for several CNS diseases.

Long-Term Fluoxetine Administration Causes Substantial Lipidome Alteration of the Juvenile Macaque Brain

Fluoxetine is an antidepressant commonly prescribed not only to adults but also to children for the treatment of depression, obsessive-compulsive disorder, and neurodevelopmental disorders. The adverse effects of the long-term treatment reported in some patients, especially in younger individuals, call for a detailed investigation of molecular alterations induced by fluoxetine treatment. Two-year fluoxetine administration to juvenile macaques revealed effects on impulsivity, sleep, social interaction, and peripheral metabolites. Here, we built upon this work by assessing residual effects of fluoxetine administration on the expression of genes and abundance of lipids and polar metabolites in the prelimbic cortex of 10 treated and 11 control macaques representing two monoamine oxidase A (MAOA) genotypes. Analysis of 8871 mRNA transcripts, 3608 lipids, and 1829 polar metabolites revealed substantial alterations of the brain lipid content, including significant abundance changes of 106 lipid features, accompanied by subtle changes in gene expression. Lipid alterations in the drug-treated animals were most evident for polyunsaturated fatty acids (PUFAs). A decrease in PUFAs levels was observed in all quantified lipid classes excluding sphingolipids, which do not usually contain PUFAs, suggesting systemic changes in fatty acid metabolism. Furthermore, the residual effect of the drug on lipid abundances was more pronounced in macaques carrying the MAOA-L genotype, mirroring reported behavioral effects of the treatment. We speculate that a decrease in PUFAs may be associated with adverse effects in depressive patients and could potentially account for the variation in individual response to fluoxetine in young people.

Impact of High-Sucrose Diet on the mRNA Levels for Elongases and Desaturases and Estimated Protein Activity in Rat Adipose Tissue

Fatty acids (FAs) present in the adipose tissue (AT) can be modified by elongases and desaturases. These enzymes are regulated by different factors including nutrients. The aim of the study was to evaluate the impact of high-sucrose diet (HSD; 68% sucrose) on the levels of mRNAs for elongases (Elovl2, Elovl5, Elovl6) and desaturases (Fads1, Fads2, Scd) and on the activity of the corresponding proteins in the rat AT. Male Wistar rats were randomized into two study groups: fed with an HSD and with a standard diet (ST). The mRNA levels were determined by a semi-quantitative reverse transcription-PCR. FA composition was analyzed by gas chromatography, and FA ratios were used to estimate the activity of the enzymes. In the HSD rats, the levels of Elovl5, Elovl6, Fads1, and Scd mRNAs were higher, while the level of Fads2 mRNA was lower than in the ST group. Higher levels of Elovl5 and Elovl6 mRNAs corresponded to higher relative activities of these enzymes, while downregulation of the Fads2 mRNA was associated with the lower activity of this desaturase. In contrast, an increase in the level of Scd mRNA was accompanied by a decrease in the enzyme activity. Less monounsaturated FAs were detected in the AT of HSD rats than in the ST group. The composition of individual FAs differed between the groups. This study supports the notion that the regulation of mRNA levels and activity of both elongases and desaturases play an important role in managing the AT lipid composition in response to changes in the dietary status.

ELOVL6 promoter binding sites directly targeted by sterol regulatory element binding protein 1 in fatty acid synthesis of goat mammary epithelial cells

The elongation of long-chain fatty acid family member 6 (ELOVL6) gene plays an important role in the synthesis of long-chain saturated and monounsaturated fatty acids. Although some studies have revealed that ELOVL6 is the target of sterol regulatory element binding protein 1 (SREBP1; gene name SREBF1) in rodents, the mechanism underlying ELOVL6 regulation during lactation in dairy goats remains unknown. The present study aimed to investigate the transcriptional regulation mechanism of ELOVL6 in goat mammary epithelial cells (GMEC). We used PCR to clone and sequenced a 2,370 bp fragment of the ELOVL6 5' flanking region from goat genomic DNA. Deletion analysis revealed a core promoter region located -105 to -40 bp upstream of the transcriptional start site. Mutant sterol regulatory elements (SRE) 1 and 3 significantly reduced the ELOVL6 promoter activities in GMEC. Both SRE1 and SRE3 binding sites were required for the basal transcriptional activity of ELOVL6. Luciferase reporter assays showed that SREBF1 knockdown decreased ELOVL6 promoter activities in GMEC. Furthermore, SRE1 and SRE3 sites were simultaneously mutated completely abolished the stimulatory effect of SREBF1 and the repressive effect of linoleic acid on ELOVL6 gene promoter activities. Furthermore, chromatin immunoprecipitation assays confirmed that SREBP1 directly bound to SRE sites in the ELOVL6 promoter. In conclusion, these results indicate that SREBP1 regulates ELOVL6 transcription via the SRE elements located in the ELOVL6 promoter in goat mammary gland.

Different Dietary N-3 Polyunsaturated Fatty Acid Formulations Distinctively Modify Tissue Fatty Acid and N-Acylethanolamine Profiles

We investigated the influence of different dietary formulation of n-3 polyunsaturated fatty acids (PUFA) on rat tissue fatty acid (FA) incorporation and consequent modulation of their bioactive metabolite N-acylethanolamines (NAE). For 10 weeks, rats were fed diets with 12% of fat from milk + 4% soybean oil and 4% of oils with different n-3 PUFA species: soybean oil as control, linseed oil rich in α-linolenic (ALA), Buglossoides arvensis oil rich in ALA and stearidonic acid (SDA), fish oil rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), Nannochloropsis microalga oil rich in EPA or Schizochytrium microalga oil rich in DHA. FA and NAE profiles were determined in plasma, liver, brain and adipose tissues. Different dietary n-3 PUFA distinctively influenced tissue FA profiles and consequently NAE tissue concentrations. Interestingly, in visceral adipose tissue the levels of N-arachidonoylethanolamide (AEA) and N-docosahexaenoylethanolamide (DHEA), NAE derived from arachidonic acid (AA) and DHA, respectively, significantly correlated with NAE in plasma, and circulating DHEA levels were also correlated with those in liver and brain. Circulating NAE derived from stearic acid, stearoylethanolamide (SEA), palmitic acid and palmitoylethanolamide (PEA) correlated with their liver concentrations. Our data indicate that dietary n-3 PUFA are not all the same in terms of altering tissue FA and NAE concentrations. In addition, correlation analyses suggest that NAE levels in plasma may reflect their concentration in specific tissues. Given the receptor-mediated tissue specific metabolic role of each NAE, a personalized formulation of dietary n-3 PUFA might potentially produce tailored metabolic effects in different pathophysiological conditions.

Dietary Lipid Modulation of Intestinal Serotonin in Ballan Wrasse (Labrus bergylta)-In Vitro Analyses

Serotonin (5-HT) is pivotal in the complex regulation of gut motility and consequent digestion of nutrients via multiple receptors. We investigated the serotonergic system in an agastric fish species, the ballan wrasse (Labrus bergylta) as it represents a unique model for intestinal function. Here we present evidence of the presence of enterochromaffin cells (EC cells) in the gut of ballan wrasse comprising transcriptomic data on EC markers like adra2a, trpa1, adgrg4, lmxa1, spack1, serpina10, as well as the localization of 5-HT and mRNA of the rate limiting enzyme; tryptophan hydroxylase (tph1) in the gut epithelium. Second, we examined the effects of dietary marine lipids on the enteric serotonergic system in this stomach-less teleost by administrating a hydrolyzed lipid bolus in ex vivo guts in an organ bath system. Modulation of the mRNA expression from the tryptophan hydroxylase tph1 (EC cells isoform), tph2 (neural isoform), and other genes involved in the serotonergic machinery were tracked. Our results showed no evidence to confirm that the dietary lipid meal did boost the production of 5-HT within the EC cells as mRNA tph1 was weakly regulated postprandially. However, dietary lipid seemed to upregulate the post-prandial expression of tph2 found in the serotonergic neurons. 5-HT in the intestinal tissue increased 3 hours after "exposure" of lipids, as was observed in the mRNA expression of tph2. This suggest that serotonergic neurons and not EC cells are responsible for the substantial increment of 5-HT after a lipid-reach "meal" in ballan wrasse. Cells expressing tph1 were identified in the gut epithelium, characteristic for EC cells. However, Tph1 positive cells were also present in the lamina propria. Characterization of these cells together with their implications in the serotonergic system will contribute to broad the scarce knowledge of the serotonergic system across teleosts.

Cerebellar and hepatic alterations in ACBD5-deficient mice are associated with unexpected, distinct alterations in cellular lipid homeostasis

ACBD5 deficiency is a novel peroxisome disorder with a largely uncharacterized pathology. ACBD5 was recently identified in a tethering complex mediating membrane contacts between peroxisomes and the endoplasmic reticulum (ER). An ACBD5-deficient mouse was analyzed to correlate ACBD5 tethering functions with the disease phenotype. ACBD5-deficient mice exhibit elevated very long-chain fatty acid levels and a progressive cerebellar pathology. Liver did not exhibit pathologic changes but increased peroxisome abundance and drastically reduced peroxisome-ER contacts. Lipidomics of liver and cerebellum revealed tissue-specific alterations in distinct lipid classes and subspecies. In line with the neurological pathology, unusual ultra-long chain fatty acids (C > 32) were elevated in phosphocholines from cerebelli but not liver indicating an organ-specific imbalance in fatty acid degradation and elongation pathways. By contrast, ether lipid formation was perturbed in liver towards an accumulation of alkyldiacylglycerols. The alterations in several lipid classes suggest that ACBD5, in addition to its acyl-CoA binding function, might maintain peroxisome-ER contacts in order to contribute to the regulation of anabolic and catabolic cellular lipid pathways.

Darwisch, von Spangenberg et al. show that ACBD5‐deficient mice exhibit elevated levels of very long‐chain fatty acids and a progressive cerebellar pathology. A complex metabolic phenotype suggests that ACBD5 with its acyl‐CoA binding and peroxisome‐ER tethering functions might contribute to the regulation of anabolic and catabolic cellular lipid pathways.

Diet Regulation of Long-Chain PUFA Synthesis: Role of Macronutrients, Micronutrients, and Polyphenols on Δ-5/Δ-6 Desaturases and Elongases 2/5

Deficiencies in the n-3 (ω-3) long-chain PUFAs (LC-PUFAs) EPA and DHA are associated with increased risk for the development of numerous diseases. Although n-3 LC-PUFAs can be obtained by consuming marine products, they are also synthesized endogenously through a biochemical pathway regulated by the Δ-5/Δ-6 desaturase and elongase 2/5 enzymes. This narrative review collates evidence from the past 40 y demonstrating that mRNA expression and activity of desaturase and elongase enzymes are influenced by numerous dietary components, including macronutrients, micronutrients, and polyphenols. Specifically, we highlight that both the quantity and the composition of dietary fats, carbohydrates, and proteins can differentially regulate desaturase pathway activity. Furthermore, desaturase and elongase mRNA levels and enzyme activities are also influenced by micronutrients (folate, vitamin B-12, vitamin A), trace minerals (iron, zinc), and polyphenols (resveratrol, isoflavones). Understanding how these various dietary components influence LC-PUFA synthesis will help further advance our understanding of how dietary patterns, ranging from caloric excesses to micronutrient deficiencies, influence disease risks.

Dietary L-carnitine affects the expression of genes involved in apoptosis and fatty acid metabolism in rooster testes

Thirty-six 12-week-old breeder roosters (Ross 308) were randomly allocated into three groups to receive L-carnitine (LC): LC-0, LC-250 or LC-500 mg/kg of diet to evaluate the effects of dietary LC on the expression of apoptotic-related genes and desaturases and elongase mRNA transcript levels, in the cockerel testicles. Alteration of Bak (Bcl2 antagonist/killer), Bcl2, Cas3, Cas8, Cas9, Elovl2, Elovl4, Elovl5, Fads1, Fads2 and Scd expression at 24 and 34 weeks of age was compared by real-time quantitative PCR. The expression of Bcl2 and Elovl5 was significantly up-regulated (p < .05), while Cas8 expression (p < .05) and Bak/Bcl2 ratio were reduced (p < .02) in the cockerel testicles at 24 weeks of age. Although Bak mRNA abundance decreased by dietary LC, Bak/Bcl2 ratio was not affected by the treatments at 34 weeks of age. The expression of Cas3 was down-regulated, while Fads2 was up-regulated in the cockerel testicles by dietary LC at 34 weeks of age (p < .05). The results demonstrate the beneficial effects of LC supplementation in suppression of the Bak/Bcl2 ratio by altering Bak and Bcl2 mRNA abundance and, ultimately, prevention of apoptosis. Furthermore, LC increased the expression of Elovl5 and Fads2 genes which are involved in the metabolism of long chain fatty acids.

Genes controlling polyunsaturated fatty acid synthesis are developmentally regulated in broiler chicks

1. The objective of this study was to characterise the regulation of the pathways that synthesise long-chain polyunsaturated fatty acids (PUFA) on developing adipose deposits in broiler embryos and chicks. Subcutaneous adipose depots were harvested from embryos and embryonic d E13, E15 and E17. Subcutaneous, abdominal and crop (neck) adipose, as well as liver, were collected at 7 and 14 d post-hatch. 2. Targeted RNA sequencing was used to quantify expression of 6 elongation of very long-chain fatty acid (ELOVL) genes, two isoforms of stearoyl-CoA desaturase (SCD and SCD5), and three fatty acid desaturases (FADS1, FADS2, and FADS6) in each depot and in the liver. Expression levels of marker genes for fatty acid oxidation and adipogenesis (peroxisome proliferator-activated receptor gamma (PPARG)) were quantified. Fatty acid composition of subcutaneous adipose was analysed using gas chromatograph-mass spectrometry (GC/MS). 3. Genes in the PUFA synthetic pathway were differentially expressed across developmental ages and between depots. These include elongase and desaturase genes, that have not previously been characterised in chicken. Correlation analyses identified subsets of co-regulated genes and fatty acids and highlighted relationships that may influence adipose metabolism and development. 4. It was concluded that PUFA synthesis is an active and dynamically regulated pathway in developing adipose deposits in the broiler chick. These data highlighted potential novel roles for specific elongase and desaturase genes in adipose deposition and metabolism.

Maternal ω3 docosapentaenoic acid inhibits infant allergic dermatitis through TRAIL-expressing plasmacytoid dendritic cells in mice

Background

Maternal dietary exposures are considered to influence the development of infant allergies through changes in the composition of breast milk. Cohort studies have shown that ω3 polyunsaturated fatty acids (PUFAs) in breast milk may have a beneficial effect on the preventing of allergies in infants; however, the underlying mechanisms remain to be investigated. We investigated how the maternal intake of dietary ω3 PUFAs affects fatty acid profiles in the breast milk and their pups and reduced the incidence of allergic diseases in the pups.

Methods

Contact hypersensitivity (CHS) induced by 2,4‐dinitrofluorobenzene (DNFB) and fluorescein isothiocyanate was applied to the skin in pups reared by mother maintained with diets mainly containing ω3 or ω6 PUFAs. Skin inflammation, immune cell populations, and expression levels of immunomodulatory molecules in pups and/or human cell line were investigated by using flow cytometric, immunohistologic, and quantitative RT‐PCR analyses. ω3 PUFA metabolites in breast milk and infant's serum were evaluated by lipidomics analysis using LC‐MS/MS.

Results

We show that maternal intake of linseed oil, containing abundant ω3 α‐linolenic acid, resulted in the increased levels of ω3 docosapentaenoic acid (DPA) and its 14‐lipoxygenation products in the breast milk of mouse dams; these metabolites increased the expression of TNF‐related apoptosis‐inducing ligand (TRAIL) on plasmacytoid dendritic cells (pDCs) in their pups and thus inhibited infant CHS. Indeed, the administration of DPA‐derived 14‐lipoxygenation products to mouse pups ameliorated their DNFB CHS.

Conclusion

These findings suggest that an inhibitory mechanism in infant skin allergy is induced through maternal metabolism of dietary ω3 PUFAs in mice.

Towards understanding the cell surface phenotype, metabolic properties and immune functions of resident macrophages of the peritoneal cavity and splenic red pulp using high resolution quantitative proteomics

Background:Resident macrophages (Mϕs) are distributed throughout the body and are important for maintaining tissue homeostasis and for defence against infections. Tissue Mϕs are highly adapted to their microenvironment and thought to mediate tissue-specific functions involving metabolism and immune defence that are not fully elucidated. Methods:We have used high resolution quantitative proteomics to gain insights into the functions of two types of resident tissue Mϕs: peritoneal cavity Mϕs and splenic red pulp Mϕs.  The cellular expression levels of many proteins were validated by flow cytometry and were consistently in agreement with the proteomics data.Results:Peritoneal and splenic red pulp macrophages displayed major differences in cell surface phenotype reflecting their adaptation to different tissue microenvironments and tissue-specific functions. Peritoneal Mϕs were shown to be enriched in a number of key enzymes and metabolic pathways normally associated with the liver, such as metabolism of fructose, detoxification, nitrogen homeostasis and the urea cycle. Supporting these observations, we show that peritoneal Mϕs are able to utilise glutamine and glutamate which are rich in peritoneum for urea generation.  In comparison, splenic red pulp Mϕs were enriched in proteins important for adaptive immunity such as antigen presenting MHC molecules, in addition to proteins required for erythrocyte homeostasis and iron turnover. We also show that these tissue Mϕs may utilise carbon and nitrogen substrates for different metabolic fates to support distinct tissue-specific roles.Conclusions:This study provides new insights into the functions of tissue Mϕs in immunity and homeostasis.  The comprehensive proteomics data sets are a valuable resource for biologists and immunologists.

Biochemical and therapeutic effects of Omega-3 fatty acids in sickle cell disease

Sickle cell disease (SCD) is a hematologic disorder with complex pathophysiology that includes chronic hemolysis, vaso-occlusion and inflammation. Increased leukocyte-erythrocyte-endothelial interactions, due to upregulated expression of adhesion molecules and activated endothelium, are thought to play a primary role in initiation and progression of SCD vaso-occlusive crisis and end-organ damage. Several new pathophysiology-based therapeutic options for SCD are being developed, chiefly targeting the inflammatory pathways. Omega-3 fatty acids are polyunsaturated fatty acids that are known to have effects on diverse physiological processes. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are the principal biologically active omega-3 fatty acids. The therapeutic effects of DHA and EPA on chronic inflammatory disorders and cardiovascular diseases are well recognized. The therapeutic effects of omega-3 fatty acids are attributed to their anti-inflammatory and anti-thrombotic eicosanoids, and the novel class of EPA and DHA derived lipid mediators: resolvins, protectins and maresins. Blood cell membranes of patients with SCD have abnormal fatty acids composition characterized by high ratio of pro-inflammatory arachidonic acid (AA) to anti-inflammatory DHA and EPA (high omega-6/omega-3 ratio). In addition, experimental and clinical studies provide evidence that treatment with DHA does confer improvement in rheological properties of sickle RBC, inflammation and hemolysis. The clinical studies have shown improvements in VOC rate, markers of inflammation, adhesion, and hemolysis. In toto, the results of studies on the therapeutic effects of omega-3 fatty acids in SCD provide good body of evidence that omega-3 fatty acids could be a safe and effective treatment for SCD.

The impact of PUFA on cell responses: Caution should be exercised when selecting PUFA concentrations in cell culture

Polyunsaturated fatty acids (PUFA) are important components of cellular membranes, serving both structural and signaling functions. Investigation of the functional responses of cells to various PUFA often involves cell culture experiments, which can then inform or guide subsequent in vivo and clinical investigations. In this study, human carcinoma and leukemia cell lines (MCF-7, HepG2, THP-1, Jurkat) were incubated for 3 days in the presence of up to 150 μM of exogenous arachidonic or eicosapentaenoic acids. At concentrations up to 20 μM these PUFA were enriched in cellular phospholipids, but at concentrations of 20 μM or higher cells accumulated large quantities of these PUFA and their elongation products into triglycerides. This coincided with decreased cell proliferation and enhanced apoptosis. Inhibition of DGAT1 but not DGAT2 enhanced the cytotoxic effect of exogenous PUFA suggesting a protective role of PUFA sequestration into TGs. Lower (10 μM) and higher (50 μM) exogenous PUFA concentrations also had different impacts on the expression of PUFA metabolizing enzymes. Overall, these results indicate that caution must be exercised when planning in vitro experiments since elevated concentrations of PUFA can lead to dysfunctional cellular responses that are not predictive of in vivo responses to dietary PUFA.

ChREBP-Mediated Regulation of Lipid Metabolism: Involvement of the Gut Microbiota, Liver, and Adipose Tissue

Carbohydrate response element-binding protein (ChREBP) plays an important role in the development of type 2 diabetes, dyslipidemia, and non-alcoholic fatty liver disease, as well as tumorigenesis. ChREBP is highly expressed in lipogenic organs, such as liver, intestine, and adipose tissue, in which it regulates the production of acetyl CoA from glucose by inducing Pklr and Acyl expression. It has recently been demonstrated that ChREBP plays a role in the conversion of gut microbiota-derived acetate to acetyl CoA by activating its target gene, Acss2, in the liver. ChREBP regulates fatty acid synthesis, elongation, and desaturation by inducing Acc1 and Fasn, elongation of long-chain fatty acids family member 6 (encoded by Elovl6), and Scd1 expression, respectively. ChREBP also regulates the formation of very low-density lipoprotein by inducing the expression of Mtp. Furthermore, it plays a crucial role in peripheral lipid metabolism by inducing Fgf21 expression, as well as that of Angptl3 and Angptl8, which are known to reduce peripheral lipoprotein lipase activity. In addition, ChREBP is involved in the production of palmitic-acid-5-hydroxystearic-acid, which increases insulin sensitivity in adipose tissue. Curiously, ChREBP is indirectly involved in fatty acid β-oxidation and subsequent ketogenesis. Thus, ChREBP regulates whole-body lipid metabolism by controlling the transcription of lipogenic enzymes and liver-derived cytokines.

DPA shows comparable chemotherapy sensitizing effects as EPA upon cellular incorporation in tumor cells

Dietary supplementation with ω-3 polyunsaturated fatty acids (PUFAs) has been reported to enhance the sensitivity of tumor cells towards chemotherapy. Most enhancing effects are described for ω-3 PUFAs EPA and DHA; less evidence is available with the intermediate DPA. We studied the chemotherapy enhancing effects of EPA, DPA and DHA in murine colon C26 adenocarcinoma cells and showed that DPA displayed similar chemosensitizing effects as EPA. Moreover, EPA supplementation increased cellular DPA content. In a C26 tumor-bearing mouse model, we studied the incorporation of ω-3 PUFA in tumor and skeletal muscle after a diet with different ω-3 PUFA sources. Although little DPA was present in the fatty acid food sources, in those that contained considerable EPA concentrations, DPA levels were higher in tumor and muscle tissue. From these studies, we conclude that EPA and DPA show chemosensitizing effects and that intake of EPA or EPA-containing nutrition leads to increased cellular DPA content by elongation. These findings support the use of ω-3 PUFA containing nutritional supplementations in cancer patients during chemotherapy treatment.

Omega-3-rich Isochrysis sp. biomass enhances brain docosahexaenoic acid levels and improves serum lipid profile and antioxidant status in Wistar rats

BACKGROUND

Isochrysis sp. is a marine microalga, rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The potential use of its biomass as an alternative source of polyunsaturated fatty acids (PUFAs) has not been studied in animal models. Male albino Wistar rats were divided into three groups and treated for 28 days. The rats were fed with (1) standard chow (control group), (2) microalgal biomass rich in EPA and DHA along with standard chow (microalga group), and (3) fish oil that contains equivalent amounts of EPA and DHA along with standard chow (fish oil group). After intervention, biochemical indices, histopathological indices, relative mRNA expression of PUFA genes, antioxidant genes, inflammatory markers, and the fatty acid profile of major tissues were studied.

RESULTS

Animals treated with microalgal biomass showed significantly increased serum HDL levels (P < 0.05) and reduced oxidative stress markers with a concomitant decrease in urea and creatinine levels. Oral supplementation of microalgal biomass did not show any toxicity or damage in any major organs. The mRNA expression of PUFA genes was significantly downregulated (P < 0.05) and antioxidant genes were upregulated. Furthermore, the mRNA expression of pro-inflammatory markers was significantly downregulated (P < 0.05) and anti-inflammatory markers were upregulated. Oral supplementation of microalgal biomass improved DHA status in brain and liver.

CONCLUSION

The present study demonstrated that Isochrysis sp. can be used as a safe, alternative food supplement for ω-3 fatty acids. © 2019 Society of Chemical Industry.

N-3 Polyunsaturated Fatty Acids and the Resolution of Neuroinflammation

In the past few decades, as a result of their anti-inflammatory properties, n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFAs), have gained greater importance in the regulation of inflammation, especially in the central nervous system (in this case known as neuroinflammation). If sustained, neuroinflammation is a common denominator of neurological disorders, including Alzheimer’s disease and major depression, and of aging. Hence, limiting neuroinflammation is a real strategy for neuroinflammatory disease therapy and treatment. Recent data show that n-3 LC-PUFAs exert anti-inflammatory properties in part through the synthesis of specialized pro-resolving mediators (SPMs) such as resolvins, maresins and protectins. These SPMs are crucially involved in the resolution of inflammation. They could be good candidates to resolve brain inflammation and to contribute to neuroprotective functions and could lead to novel therapeutics for brain inflammatory diseases. This review presents an overview 1) of brain n-3 LC-PUFAs as precursors of SPMs with an emphasis on the effect of n-3 PUFAs on neuroinflammation, 2) of the formation and action of SPMs in the brain and their biological roles, and the possible regulation of their synthesis by environmental factors such as inflammation and nutrition and, in particular, PUFA consumption.

Molecular characterization and expression of SiFad1 in the sea urchin (Strongylocentrotus intermedius)

Fatty acid desaturases (Fads) are a key enzyme in the process of biosynthesis of highly unsaturated fatty acids (HUFAs). In this study, we cloned the full-length sequence of the SiFad1 gene (SiFad1) and analyzed its expression profiles during different developmental stages and in different tissues of Strongylocentrotus intermedius. The full-length cDNA of SiFad1 is composed of 1086 bp, with a putative open reading frame of 885 bp encoding a polypeptide of 294 amino acid (AA) residues. The predicted molecular mass of SiFad1 is 34.67 kDa and its theoretical pI is 8.41. The presence of conserved motifs including three histidine boxes (HXXXH, HXXHH, XXXHH), a FA_desaturases domain and three transmembrane domains suggests that SiFad1 belongs to the microsomal fatty acid desaturases family. Its tissue distribution showed that the highest expression of SiFad1 is in the intestine and the weakest expression is in Aristotle's lantern of S. intermedius. Time-course expression measurements in different developmental stages showed the highest expression of SiFad1 occurs in the gastrula and the weakest expression in the juvenile sea urchin. Knock-down of SiFad1 by specific siRNA revealed that the significantly depressed expression of Elovl5 had decreased in the coelomocytes, intestines and gonads at 24 h post transfection, indicating that the downstream target gene of SiFad1 is Elovl5 and SiFad1 and Elovl5 have positive regulatory effects. When we examined the changes in fatty acids in the gonads before and after interference, the results showed that after 24 h of interference, the content of C20:4n-6 produced by SiFad1 had decreased. Taken together, these results will enable us to understand the role of SiFad1 in fatty acid anabolism, which will help us to understand the fatty acid synthesis pathways and regulatory mechanisms of Strongylocentrotus intermedius and provide a theoretical experimental basis for improving the ability of sea urchins to synthesize fatty acids and cultivating sea urchins of higher quality and nutritional value.

Deficiency or activation of peroxisome proliferator-activated receptor α reduces the tissue concentrations of endogenously synthesized docosahexaenoic acid in C57BL/6J mice

BACKGROUND/OBJECTIVES

Docosahexaenoic acid (DHA), an n-3 long chain polyunsaturated fatty acid (LCPUFA), is acquired by dietary intake or the in vivo conversion of α-linolenic acid. Many enzymes participating in LCPUFA synthesis are regulated by peroxisome proliferator-activated receptor alpha (PPARα). Therefore, it was hypothesized that the tissue accretion of endogenously synthesized DHA could be modified by PPARα.

MATERIALS/METHODS

The tissue DHA concentrations and mRNA levels of genes participating in DHA biosynthesis were compared among PPARα homozygous (KO), heterozygous (HZ), and wild type (WT) mice (Exp I), and between WT mice treated with clofibrate (PPARα agonist) or those not treated (Exp II). In ExpII, the expression levels of the proteins associated with DHA function in the brain cortex and retina were also measured. An n3-PUFA depleted/replenished regimen was applied to mitigate the confounding effects of maternal DHA.

RESULTS

PPARα ablation reduced the hepatic Acox, Fads1, and Fads2 mRNA levels, as well as the DHA concentration in the liver, but not in the brain cortex. In contrast, PPARα activation increased hepatic Acox, Fads1, Fads2 and Elovl5 mRNA levels, but reduced the DHA concentrations in the liver, retina, and phospholipid of brain cortex, and decreased mRNA and protein levels of the brain-derived neurotrophic factor in brain cortex.

CONCLUSIONS

LCPUFA enzyme expression was altered by PPARα. Either PPARα deficiency or activation-decreased tissue DHA concentration is a stimulus for further studies to determine the functional significance.

Co-expression of fat1 and fat2 in transgenic pigs promotes synthesis of polyunsaturated fatty acids

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) are essential for the development and health of mammals, such as humans and livestock. n-3 PUFAs must be supplied by diet due to the absence of a key gene, namely, delta-15 desaturase (fat1), which is responsible for synthesizing n-3 PUFAs from a major type of n-6 PUFAs, linoleic acid (LA). To increase the dietary intake of n-3 PUFAs for humans, fat1-expressing transgenic (TG) livestock have been produced to provide n-3 PUFA-rich meats for humans. However, these TG livestock synthesized n-3 PUFAs from diet-derived, instead of endogenously produced, n-6 PUFAs because they still lack the delta-12 desaturase (fat2) gene for catalyzing conversion of internal oleic acid (OA) to LA. To fill the gap in the de novo n-3 PUFA biosynthesis pathway and to increase n-3 PUFA content in livestock, TG pigs co-expressing fat1-fat2 were generated in the present work. The OA content decreased in fat1-fat2 TG pigs, suggesting that OA was converted to LA by fat2 transgene-encoded delta-12 desaturase. The n-3 PUFA level was elevated, and the n-6/n-3 PUFA ratio dropped in fat1-fat2 TG pigs, revealing that fat1 transgene promoted the synthesis of n-3 PUFAs from n-6 analogs. The expression levels of fatty acid elongase-5 (ELOVL5) and fatty acid elongase-2 (ELOVL2), which are two key enzyme genes for PUFA synthesis, as well as their transcription factor peroxisome proliferator-activated receptor α, increased in fat1-fat2 TG pigs. Thus, the fat1 transgene enhanced n-3 PUFA synthesis by upregulating the expression of enzyme genes involved in the PUFA synthesis pathways. Overall, this study provided a new strategy to produce n-3 PUFA-rich meat for human consumption. The generated fat1-fat2 TG pigs can also serve as a large animal model for studying the roles of n-3 PUFAs in human development and health.

DHA Cycling Halves the DHA Supplementation Needed to Maintain Blood and Tissue Concentrations via Higher Synthesis from ALA in Long-Evans Rats

BACKGROUND

Eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) recommendations are frequently stated at 500 mg/d; however, adherence to these recommendations would result in a large global commercial EPA/DHA production deficit. Previously, our laboratory demonstrated that acute DHA intake in rats can increase the capacity for synthesis-secretion of n-3 (ω-3) polyunsaturated fatty acids (PUFAs).

OBJECTIVE

We aimed to investigate the utility of a dietary DHA cycling strategy that employs 2 wk of repeated DHA feeding for a total of 3 cycles over 12 wk.

METHODS

Male Long-Evans rats were fed a 10% fat diet by weight comprised of either 1) a 2-wk, 2% α-linolenic acid (ALA, DHA-ALA group 18:3n-3) diet followed by a 2-wk, 2% DHA + 2% ALA diet over 3 consecutive 4-wk periods ("DHA cycling," DHA-ALA group); 2) a 2% DHA + 2% ALA diet (DHA group) for 12 wk; or 3) a 2% ALA-only diet (ALA group) for 12 wk. At 15 wk old, blood and tissue fatty acid concentrations and liver mRNA expression and 13C-DHA natural abundances were determined.

RESULTS

DHA concentrations in plasma, erythrocytes, and whole blood between the DHA-ALA group and the DHA groups were not different (P ≥ 0.05), but were 72-110% higher (P < 0.05) than in the ALA group. Similarly, DHA concentrations in liver, heart, adipose, and brain were not different (P ≥ 0.05) between the DHA-fed groups, but were at least 62%, 72%, 320%, and 68% higher (P < 0.05) than in the ALA group in liver, heart, adipose, and skeletal muscle, respectively. Compound-specific isotope analysis indicated that 310% more liver DHA in the DHA-ALA group compared with the DHA group is derived from dietary ALA, and this was accompanied by a 123% and 93% higher expression of elongation of very long-chain (Elovl)2 and Elovl5, respectively, in the DHA-ALA group compared with the ALA group.

CONCLUSIONS

DHA cycling requires half the dietary DHA while achieving equal blood and tissue DHA concentrations in rats. Implementation of such dietary strategies in humans could reduce the gap between global dietary n-3 PUFA recommendations and commercial production.

Genome-wide characterization and expression of the elongation of very long chain fatty acid (Elovl) genes and fatty acid profiles in the alga (Tetraselmis suecica) fed marine rotifer Brachionus koreanus

To understand the lipid metabolism in invertebrate species, identification of the fatty acid (FA) synthesis gene families in invertebrate species is important, since some FA are unable to be synthesized in the organisms by themselves. In the study, to identify the elongation of very long chain fatty acid (Elovl) genes in the marine rotifer Brachionus koreanus, the genome-wide identification and phylogenetic analysis of Elovl genes have been conducted with the expression profile of Elovl genes on the alga Tetraslemis suecica-fed B. koreanus. A total 10 Elovl genes have been identified from the genome of B. koreanus, with conserved HXXHH motif. Synteny analysis showed that tandem duplication event has occurred (Elovl3/6a and b, Elovl9a and b, and Elovl9c and d) in the ancestor. Phylogenetic analysis have clearly revealed that Brachionus spp. has only 2/5 and 3/6 subfamilies, and two novel Elovl classes have been revealed, namely Elovl9 and 10. Transcriptional data showed that the 10 Elovl genes were differently expressed and their expression could be regulated by feeding the alga T. suecica. From fatty acid (FA) profile data of the alga Tetraslemis suecica-fed B. koreanus, we revealed that the marine rotifer B. koreanus may synthesize very long chain fatty acid (VLCFA; >22 carbons) by themselves, as VLCFA was hardly detected in the alga T. suecica. The study provides a better understanding of FA metabolism of the marine rotifer B. koreanus after feeding the T. suecica.

Omega-3 fatty acids and nonalcoholic fatty liver disease in adults and children: where do we stand?

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic fatty liver disease worldwide. The incidence of NAFLD parallels the prevalence of obesity. Moreover, NAFLD can progress to nonalcoholic steatohepatitis (NASH), cirrhosis and primary hepatocellular cancer (HCC). As such, NAFLD has become a major public health concern. We discuss recent clinical trials and meta-analyses evaluating the efficacy of C20-22 ω3 polyunsaturated fatty acids (PUFA) to attenuate preexisting NAFLD in adults and children.

RECENT FINDINGS

Humans with NAFLD and NASH; and preclinical mouse models of NASH, have a high abundance of hepatic saturated (SFA) and monounsaturated (MUFA) fat, but a low abundance of hepatic C20-22 ω3 PUFA. This change in hepatic fat type and abundance is associated with hepatic lipotoxicity, inflammation, oxidative stress and fibrosis. Recent meta-analyses and clinical trials evaluated the capacity of C20-22 ω3 PUFA dietary supplementation to improve health outcomes in adults and children with preexisting NAFLD. Diets supplemented with docosahexaenoic acid (DHA, 22 : 6,ω3) alone or with eicosapentaenoic acid (EPA, 20 : 5,ω3) are tolerated and effective at lowering liver fat in NAFLD patients. However, outcomes are mixed with respect to C20-22 ω3 PUFA attenuation of more severe NAFLD markers, such as hepatic injury, inflammation and fibrosis.

SUMMARY

These studies suggest that dietary supplementation with C20-22 ω3 PUFA should be considered as a viable and effective option to lower liver fat in obese adults and children with NAFLD.

The mechanism through which dietary supplementation with heated linseed grain increases n-3 long-chain polyunsaturated fatty acid concentration in subcutaneous adipose tissue of cashmere kids

The aim of this study was to investigate the effects of dietary supplementation with heated linseed on the fatty acid (FA) composition of the plasma, liver, and subcutaneous adipose tissue (SADT) of Albas white cashmere kids, particularly the effect on n-3 long-chain polyunsaturated FA profiles and the mRNA expression of genes related to lipid metabolism in SADT. Sixty 4-month-old castrated male kids (average BW 18.6 ± 0.1 kg) were selected and randomly allocated into three groups in a randomized block design. Three dietary treatments were used: (1) basal diet without supplementation (Control), (2) basal diet supplemented with linseed oil (LSO), and (3) basal diet supplemented with heated linseed grain (HLS). The diets were fed for 104 d, consisting of 14 d for adaptation followed by 90 d of measurement. Different FA profiles were found in SADT between LSO and HLS. Kids fed HLS had more C18:3n3 (P < 0.0001), C22:6n3 (P = 0.007), and n-3 PUFA (P < 0.0001) and a less (P < 0.0001) n-6/n-3 ratio than LSO kids. These FA differences between LSO and HLS kids were due to the increased expression of elongation of very long chain FA protein 5 (P < 0.0001), delta-6 desaturase (P < 0.0001), and peroxisome proliferator-activated receptor α (P = 0.003) in SADT of HLS kids and was also associated with liver fat metabolism. Together, these results suggest that the consumption of HLS leads to more C22:6n3 than LSO in SADT by increasing liver C22:6n3 content and by increasing SADT mRNA expression of ELOVL5 and FADS2 through promoting PPARα expression.

The elongation of very long-chain fatty acid 6 gene product catalyses elongation of n-13 : 0 and n-15 : 0 odd-chain SFA in human cells

Normal odd-chain SFA (OCSFA), particularly tridecanoic acid (n-13 : 0), pentadecanoic acid (n-15 : 0) and heptadecanoic acid (n-17 : 0), are normal components of dairy products, beef and seafood. The ratio of n-15 : 0:n-17 : 0 in ruminant foods (dairy products and beef) is 2:1, while in seafood and human tissues it is 1:2, and their appearance in plasma is often used as a marker for ruminant fat intake. Human elongases encoded by elongation of very long-chain fatty acid (ELOVL)1, ELOVL3, ELOVL6 and ELOVL7 catalyse biosynthesis of the dominant even-chain SFA; however, there are no reports of elongase function on OCSFA. ELOVL transfected MCF7 cells were treated with n-13 : 0, n-15 : 0 or n-17 : 0 (80 µm) and products analysed. ELOVL6 catalysed elongation of n-13 : 0→n-15 : 0 and n-15 : 0→n-17 : 0; and ELOVL7 had modest activity toward n-15 : 0 (n-15 : 0→n-17 : 0). No elongation activity was detected for n-17 : 0→n-19 : 0. Our data expand ELOVL specificity to OCSFA, providing the first molecular evidence demonstrating ELOVL6 as the major elongase acting on OCSFA n-13 : 0 and n-15 : 0 fatty acids. Studies of food intake relying on OCSFA as a biomarker should consider endogenous human metabolism when relying on OCSFA ratios to indicate specific food intake.

The Transcriptional Factor PPARαb Positively Regulates Elovl5 Elongase in Golden Pompano Trachinotus ovatus (Linnaeus 1758)

The nuclear peroxisome proliferator-activated receptors (PPARs) regulate the transcription of elongases of very long-chain fatty acids (Elovl), which are involved in polyunsaturated fatty acid (PUFA) biosynthesis in mammals. In the present study, we first characterized the function of Elovl5 elongase in Trachinotus ovatus. The functional study showed that ToElovl5 displayed high elongation activity toward C18 and C20 PUFA. To investigate whether PPARαb was a regulator of Elovl5, we also reported the sequence of T. ovatus PPARαb (ToPPARαb). The open reading frame (ORF) sequence encoded 469 amino acids possessing four typical characteristic domains, including an N-terminal hypervariable region, a DNA-binding domain (DBD), a flexible hinge domain and a ligand-binding domain (LBD). Thirdly, promoter activity experiments showed that the region from PGL3-basic-Elovl5-5 (-146 bp to +459 bp) was defined as the core promoter by progressive deletion mutation of Elovl5. Moreover, PPARαb overexpression led to a clear time-dependent enhancement of ToElovl5 promoter expression in HEK 293T cells. Fourth, the agonist of PPARαb prominently increased PPARαb and Elovl5 expression, while PPARαb depletion by RNAi or an inhibitor was correlated with a significant reduction of Elovl5 transcription in T. ovatus caudal fin cells (TOCF). In conclusion, the present study provides the first evidence of the positive regulation of Elovl5 transcription by PPARαb and contributes to a better understanding of the transcriptional mechanism of PPARαb in fish.

The gut microbiota promotes hepatic fatty acid desaturation and elongation in mice

Interactions between the gut microbial ecosystem and host lipid homeostasis are highly relevant to host physiology and metabolic diseases. We present a comprehensive multi-omics view of the effect of intestinal microbial colonization on hepatic lipid metabolism, integrating transcriptomic, proteomic, phosphoproteomic, and lipidomic analyses of liver and plasma samples from germfree and specific pathogen-free mice. Microbes induce monounsaturated fatty acid generation by stearoyl-CoA desaturase 1 and polyunsaturated fatty acid elongation by fatty acid elongase 5, leading to significant alterations in glycerophospholipid acyl-chain profiles. A composite classification score calculated from the observed alterations in fatty acid profiles in germfree mice clearly differentiates antibiotic-treated mice from untreated controls with high sensitivity. Mechanistic investigations reveal that acetate originating from gut microbial degradation of dietary fiber serves as precursor for hepatic synthesis of C16 and C18 fatty acids and their related glycerophospholipid species that are also released into the circulation.