Role of stearoyl-coenzyme A desaturase in regulating lipid metabolism

Nrf2 Mediates Metabolic Reprogramming in Non-Small Cell Lung Cancer

Nuclear factor erythroid-2–related factor-2 (NFE2L2/Nrf2) is a transcription factor that regulates the expression of antioxidant genes. Both Kelch-like ECH-associated protein 1 (Keap1) mutations and Nrf2 mutations contribute to the activation of Nrf2 in non-small cell lung cancer (NSCLC). Nrf2 activity is associated with poor prognosis in NSCLC. Metabolic reprogramming represents a cancer hallmark. Increasing studies reveal that Nrf2 activation promotes metabolic reprogramming in cancer. In this review, we discuss the underlying mechanisms of Nrf2-mediated metabolic reprogramming and elucidate its role in NSCLC. Inhibition of Nrf2 can alter metabolic processes, thus suppress tumor growth, prevent metastasis, and increase sensitivity to chemotherapy in NSCLC. In conclusion, Nrf2 may serve as a therapeutic target for the treatment of NSCLC.

Lipid metabolism in colon cancer: Role of Liver X Receptor (LXR) and Stearoyl-CoA Desaturase 1 (SCD1)

Colorectal cancer (CRC) is one of the most commonly occurring cancers worldwide. Although several genetic alterations have been associated with CRC onset and progression, nowadays the reprogramming of cellular metabolism has been recognized as a fundamental step of the carcinogenic process. Intestinal tumor cells frequently display an aberrant activation of lipid metabolism. Indeed, to satisfy the growing needs of a continuous proliferation, cancer cells can either increase the uptake of exogenous lipids or upregulate the endogenous lipogenesis and cholesterol synthesis. Therefore, strategies aimed at limiting lipid accumulation are now under development in order to counteract malignancies. Two major players of lipids metabolism have been so far identified for their contribution to CRC development: the nuclear receptor Liver X Receptor (LXRs) and the enzyme Stearoyl-CoA Desaturase 1 (SCD1). Whereas LXR is mainly recognized for its role as a cholesterol sensor, finally promoting the loss of cellular cholesterol and whole-body homeostasis, SCD1 acts as the major regulator of new fatty acids, finely tuning the monounsaturated fatty acids (MUFA) to saturated fatty acids (SFA) ratio. Intriguingly, SCD1 is directly regulated by LXRs. Despite LXRs agonists have elicited great interest as a promising therapeutic target for cancer, LXR's ability to induce SCD1 and new fatty acids synthesis represent a major obstacle in the development of new effective treatments. Thus, further investigations are required to fully dissect the concomitant modulation of both players, to develop specific therapies aimed at blocking intestinal cancer cells proliferation, eventually counteracting CRC progression.

The aryl hydrocarbon receptor as a mediator of host-microbiota interplay

Increasing evidence suggests a significant role for microbiota dependent metabolites and co-metabolites, acting as aryl hydrocarbon receptor (AHR) ligands, to facilitate bidirectional communication between the host and the microbiota and thus modulate physiology. Such communication is particularly evident within the gastrointestinal tract. Through binding to or activating the AHR, these metabolites play fundamental roles in various physiological processes and likely contribute to the maintenance of intestinal homeostasis. In recent years, tryptophan metabolites were screened to identify physiologically relevant AHR ligands or activators. The discovery of specific microbiota-derived indole-based metabolites as AHR ligands may provide insight concerning how these metabolites affect interactions between gut microbiota and host intestinal homeostasis and how this relates to chronic GI disease and overall health. A greater understanding of the mechanisms that modulate the production of such metabolites and associated AHR activity may be utilized to effectively treat inflammatory diseases and promote human health. Here, we review microbiota-derived AHR ligands generated from tryptophan that modulate host-gut microbiota interactions and discuss possible intervention strategies for potential therapies in the future.

Bovine Stearoyl-CoA Desaturase 1 Promotes Adipogenesis by Activating the PPARγ Receptor

Stearoyl-CoA desaturase 1 (SCD1) is a rate-limiting enzyme that mainly catalyzes the saturated fatty acids (SFAs) into the monounsaturated fatty acids (MUFAs). The expression level of SCD1 is positively correlated with the marbling score. However, the functional mechanism of SCD1 in adipogenesis is still unclear. In this study, we identified SCD1 as highly expressed in subcutaneous and visceral fat, peaking at 2 days after differentiation in bovine stromal vascular fraction (SVF) cells. When the SCD1 was overexpressed in bovine SVF cells, lipid droplets accumulation was increased from 142.46 ± 21.77 to 254.89 ± 11.75 μg/mg (P < 0.01). Further, the expression levels of FABP4, FASN, and ACCα were increased (P < 0.01), while the expression of PPARγ or C/EBPα was not changed at mRNA or protein level (P > 0.05). Dual-luciferase reporter assay showed that the activity of the PPARγ receptor was enhanced by 3.69 times (P < 0.01). Moreover, the contents of palmitoleate (C16:1) and oleate (C18:1) were significantly increased (P < 0.05). Furthermore, 100 μM exogenous oleate increased the lipid accumulation by 22.28 times (P < 0.01). These results suggest that oleate is probably a strong ligand of the PPARγ receptor to enhance adipogenesis.

Glued in lipids: Lipointoxication in cystic fibrosis

Cystic Fibrosis (CF) is an autosomal recessive disease caused by mutations in the CF transmembrane regulator (CFTR) gene, which encodes a chloride channel located at the apical surface of epithelial cells. Unsaturated Fatty Acid (UFA) deficiency has been a persistent observation in tissues from patients with CF. However, the impacts of such deficiencies on the etiology of the disease have been the object of intense debates. The aim of the present review is first to highlight the general consensus on fatty acid dysregulations that emerges from, sometimes apparently contradictory, studies. In a second step, a unifying mechanism for the potential impacts of these fatty acid dysregulations in CF cells, based on alterations of membrane biophysical properties (known as lipointoxication), is proposed. Finally, the contribution of lipointoxication to the progression of the CF disease and how it could affect the efficacy of current treatments is also discussed.

Metabolic engineering for increased lipid accumulation in Yarrowia lipolytica - A Review

Current energy security and climate change policies encourage the development and utilization of bioenergy. Oleaginous yeasts provide a particularly attractive platform for the sustainable production of biofuels and industrial chemicals due to their ability to accumulate high amounts of lipids. In particular, microbial lipids in the form of triacylglycerides (TAGs) produced from renewable feedstocks have attracted considerable attention because they can be directly used in the production of biodiesel and oleochemicals analogous to petrochemicals. As an oleaginous yeast that is generally regarded as safe, Yarrowia lipolytica has been extensively studied, with large amounts of data on its lipid metabolism, genetic tools, and genome sequencing and annotation. In this review, we highlight the newest strategies for increasing lipid accumulation using metabolic engineering and summarize the research advances on the overaccumulation of lipids in Y. lipolytica. Finally, perspectives for future engineering approaches are proposed.

Metabolomic Analysis of SCD during Goose Follicular Development: Implications for Lipid Metabolism

Stearoyl-CoA desaturase (SCD) is known to be an important rate-limiting enzyme in the production of monounsaturated fatty acids (MUFAs). However, the role of this enzyme in goose follicular development is poorly understood. To investigate the metabolic mechanism of SCD during goose follicular development, we observed its expression patterns in vivo and in vitro using quantitative reverse-transcription (qRT)-PCR. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine a cellular model of SCD function in granulosa cells (GCs) via SCD overexpression and knockdown. qRT-PCR analysis showed that SCD was abundantly expressed in the GC layer, and was upregulated in preovulatory follicles. Peak expression was found in F1 and prehierarchal follicles with diameters of 4–6 mm and 8–10 mm, respectively. We further found that mRNA expression and corresponding enzyme activity occur in a time-dependent oscillation pattern in vitro, beginning on the first day of GC culture. By LC-MS/MS, we identified numerous changes in metabolite activation and developed an overview of multiple metabolic pathways, 10 of which were associated with lipid metabolism and enriched in both the overexpressed and knockdown groups. Finally, we confirmed cholesterol and pantothenol or pantothenate as potential metabolite biomarkers to study SCD-related lipid metabolism in goose GCs.

Osteoporosis: A role for lipids

An inverse relationship between bone marrow (BM) adiposity and bone mass has been described in different physiological and pathological conditions, including osteoporosis (OP). In osteoporotic patients, lower bone mass density is indeed associated with higher BM fat content, suggesting a potential role for bone lipids in the OP pathogenesis. Nevertheless, some questions remain. Is that BM adiposity a cause or a consequence of the bone loss? What kinds of lipids are involved? Human data are somehow contradictories regarding bone lipid signature related to OP, and animal data are needed to support on one or another way the human observations. Bone lipid signature associated to OP needs to be clarified if we want to understand better their roles in OP. In that context, by using an ovariectomy-induced OP murine model and looking at lipids in two bone compartments: BM and mineralized tissue (MT), our first challenge was to identify local lipid changes in relation to OP, in view to explore later the mechanisms by which those compounds could alter bone quality, particularly during the mineralization process. As the most striking data, long-term OP resulted in an accumulation of triglycerides, reduced levels of arachidonic and docosahexaenoic acids, an increase of stearoyl-CoA desaturase indices and a reduction of sphingomyelin in the MT, and potential consequences on bone properties and cell activities are discussed. The reader will appreciate that we are at an early stage of understanding the roles of lipids in the OP development and more investigations will be necessary.

Age- and duration-dependent effects of whey protein on high-fat diet-induced changes in body weight, lipid metabolism, and gut microbiota in mice

Bovine whey protein has been demonstrated to exert a positive effect on energy balance, lipid metabolism, and nutrient absorption. Additionally, it affects gut microbiota configuration. Thus, whey protein is considered as good dietary candidate to prevent or ameliorate metabolic diseases, such as obesity. However, the relationship that links energy balance, metabolism, and intestinal microbial population mediated by whey protein intake remains poorly understood. In this study, we investigated the beneficial effects attributed to whey protein in the context of high-fat diet (HFD) in mice at two different ages, with short or longer durations of whey protein supplementation. Here, a 5-week dietary intervention with HFD in combination with either whey protein isolate (WPI) or the control nonwhey milk protein casein (CAS) was performed using 5-week or 10-week-old C57BL/6J mice. Notably, the younger mice had no prior history of ingestion of WPI, while older mice did. 5-week-old HFD-WPI-fed mice showed a decrease in weight gain and changes in the expression of genes within the epidydimal white adipose tissue including those encoding leptin, inflammatory marker CD68, fasting-induced adipose factor FIAF and enzymes involved in fatty acids catabolism, relative to HFD-CAS-fed mice. Differences in β-diversity and higher proportions of Lactobacillus murinus, and related functions, were evident within the gut microbiota of HFD-WPI mice. However, none of these changes were observed in mice that started the HFD dietary intervention at 10-weeks-old, with an extended period of WPI supplementation. These results suggest that the effect of whey protein on mouse body weight, adipose tissue, and intestinal parameters depends on diet duration and stage of life during which the diet is provided. In some instances, WPI influences gut microbiota composition and functional potential, which might orchestrate observed metabolic and physiological modifications.

Standardized rice bran extract improves hepatic steatosis in HepG2 cells and ovariectomized rats

BACKGROUD/OBJECTIVES

Hepatic steatosis is the most common liver disorder, particularly in postmenopausal women. This study investigated the protective effects of standardized rice bran extract (RBS) on ovariectomized (OVX)-induced hepatic steatosis in rats.

MATERIALS/METHODS

HepG2 cells were incubated with 200 µM oleic acid to induce lipid accumulation with or without RBS and γ-oryzanol. OVX rats were separated into three groups and fed a normal diet (ND) or the ND containing 17β-estradiol (E2; 10 µg/kg) and RBS (500 mg/kg) for 16 weeks.

RESULTS

RBS supplementation improved serum triglyceride and free fatty acid levels in OVX rats. Histological analysis showed that RBS significantly attenuated hepatic fat accumulation and decreased hepatic lipid, total cholesterol, and triglyceride levels. Additionally, RBS suppressed the estrogen deficiency-induced upregulation of lipogenic genes, such as sterol regulatory element-binding protein 1 (SREBP1), acetyl-CoA carboxylase 1, fatty acid synthase, glycerol-3-phosphate acyltransferase, and stearoyl-CoA desaturase 1.

CONCLUSIONS

RBS and γ-oryzanol effectively reduced lipid accumulation in a HepG2 cell hepatic steatosis model. RBS improves OVX-induced hepatic steatosis by regulating the SREBP1-mediated activation of lipogenic genes, suggesting the benefits of RBS in preventing fatty liver in postmenopausal women.

Mutations in SREBF1, Encoding Sterol Regulatory Element Binding Transcription Factor 1, Cause Autosomal-Dominant IFAP Syndrome

IFAP syndrome is a rare genetic disorder characterized by ichthyosis follicularis, atrichia, and photophobia. Previous research found that mutations in MBTPS2, encoding site-2-protease (S2P), underlie X-linked IFAP syndrome. The present report describes the identification via whole-exome sequencing of three heterozygous mutations in SREBF1 in 11 unrelated, ethnically diverse individuals with autosomal-dominant IFAP syndrome. SREBF1 encodes sterol regulatory element-binding protein 1 (SREBP1), which promotes the transcription of lipogenes involved in the biosynthesis of fatty acids and cholesterols. This process requires cleavage of SREBP1 by site-1-protease (S1P) and S2P and subsequent translocation into the nucleus where it binds to sterol regulatory elements (SRE). The three detected SREBF1 mutations caused substitution or deletion of residues 527, 528, and 530, which are crucial for S1P cleavage. In vitro investigation of SREBP1 variants demonstrated impaired S1P cleavage, which prohibited nuclear translocation of the transcriptionally active form of SREBP1. As a result, SREBP1 variants exhibited significantly lower transcriptional activity compared to the wild-type, as demonstrated via luciferase reporter assay. RNA sequencing of the scalp skin from IFAP-affected individuals revealed a dramatic reduction in transcript levels of low-density lipoprotein receptor (LDLR) and of keratin genes known to be expressed in the outer root sheath of hair follicles. An increased rate of in situ keratinocyte apoptosis, which might contribute to skin hyperkeratosis and hypotrichosis, was also detected in scalp samples from affected individuals. Together with previous research, the present findings suggest that SREBP signaling plays an essential role in epidermal differentiation, skin barrier formation, hair growth, and eye function.

Current and Future Treatments in the Fight Against Non-Alcoholic Fatty Liver Disease

Obesity is recognised as a risk factor for many types of cancers, in particular hepatocellular carcinoma (HCC). A critical factor in the development of HCC from non-alcoholic fatty liver disease (NAFLD) is the presence of non-alcoholic steatohepatitis (NASH). Therapies aimed at NASH to reduce the risk of HCC are sparse and largely unsuccessful. Lifestyle modifications such as diet and regular exercise have poor adherence. Moreover, current pharmacological treatments such as pioglitazone and vitamin E have limited effects on fibrosis, a key risk factor in HCC progression. As NAFLD is becoming more prevalent in developed countries due to rising rates of obesity, a need for directed treatment is imperative. Numerous novel therapies including PPAR agonists, anti-fibrotic therapies and agents targeting inflammation, oxidative stress and the gut-liver axis are currently in development, with the aim of targeting key processes in the progression of NASH and HCC. Here, we critically evaluate literature on the aetiology of NAFLD-related HCC, and explore the potential treatment options for NASH and HCC.

Dietary Fat and Cancer-Which Is Good, Which Is Bad, and the Body of Evidence

A high-fat diet (HFD) induces changes in gut microbiota leading to activation of pro-inflammatory pathways, and obesity, as a consequence of overnutrition, exacerbates inflammation, a known risk factor not only for cancer. However, experimental data showed that the composition of dietary fat has a greater impact on the pathogenesis of cancer than the total fat content in isocaloric diets. Similarly, human studies did not prove that a decrease in total fat intake is an effective strategy to combat cancer. Saturated fat has long been considered as harmful, but the current consensus is that moderate intake of saturated fatty acids (SFAs), including palmitic acid (PA), does not pose a health risk within a balanced diet. In regard to monounsaturated fat, plant sources are recommended. The consumption of plant monounsaturated fatty acids (MUFAs), particularly from olive oil, has been associated with lower cancer risk. Similarly, the replacement of animal MUFAs with plant MUFAs decreased cancer mortality. The impact of polyunsaturated fatty acids (PUFAs) on cancer risk depends on the ratio between ω-6 and ω-3 PUFAs. In vivo data showed stimulatory effects of ω-6 PUFAs on tumour growth while ω-3 PUFAs were protective, but the results of human studies were not as promising as indicated in preclinical reports. As for trans FAs (TFAs), experimental data mostly showed opposite effects of industrially produced and natural TFAs, with the latter being protective against cancer progression, but human data are mixed, and no clear conclusion can be made. Further studies are warranted to establish the role of FAs in the control of cell growth in order to find an effective strategy for cancer prevention/treatment.

Identification of Molecular Mechanisms Related to Pig Fatness at the Transcriptome and miRNAome Levels

Fat deposition and growth rate are closely related to pork quality and fattening efficiency. The next-generation sequencing (NGS) approach for transcriptome and miRNAome massive parallel sequencing of adipocyte tissue was applied to search for a molecular network related to fat deposition in pigs. Pigs were represented by three breeds (Large White, Pietrain, and Hampshire) that varied in fat content within each breed. The obtained results allowed for the detection of significant enrichment of Gene Ontology (GO) terms and pathways associated directly and indirectly with fat deposition via regulation of fatty acid metabolism, fat cell differentiation, inflammatory response, and extracellular matrix (ECM) organization and disassembly. Moreover, the results showed that adipocyte tissue content strongly affected the expression of leptin and other genes related to a response to excessive feed intake. The findings indicated that modification of genes and miRNAs involved in ECM rearrangements can be essential during fat tissue growth and development in pigs. The identified molecular network within genes and miRNAs that were deregulated depending on the subcutaneous fat level are proposed as candidate factors determining adipogenesis, fatness, and selected fattening characteristics in pigs.

Germinated barley downregulates hepatic stearoyl-CoA desaturase-1 enzyme gene expression in a hepatic steatohepatitis rat model

Steatohepatitis, fibrosis, and cirrhosis are common pathological features in the progression of hepatic steatosis. In the current work, we investigated the effect of germinated barely on the structure and function of the liver and its regulatory mechanism on SDC1 gene expression in a steatohepatitis rat model. Forty-eight adult male white Wistar rats were randomly divided into four groups: Group I, control; Group II, rats fed a germinated barley diet; Group III, rats fed a high-fat diet (HFD); and Group IV, rats fed both germinated barley (GB) and a high-fat diet for 14 weeks. Biochemical, histopathological, immunohistochemical, and morphometric studies, as well as qRT-PCR, were used to analyze the effect of germinated barley on steatohepatitis. The rats in Group IV had a lower liver index percentage and improved altered lipid profile and liver function tests compared to those in Group III. Supplementation of GB with a HFD ameliorated the histopathological features in the livers of rats fed a HFD, decreased the percentage of CD68-positive macrophages, and lowered the upregulated expression of SDC1. Supplementation of a HFD with GB prohibited the deterioration of liver function, lipid profile, and alteration of liver structure; it also decreased the associated hepatic inflammation and downregulated SDC1 in liver tissue.

Stearoyl-CoA Desaturase is Essential for Porcine Adipocyte Differentiation

Fat deposition, which influences pork production, meat quality and growth efficiency, is an economically important trait in pigs. Numerous studies have demonstrated that stearoyl-CoA desaturase (SCD), a key enzyme that catalyzes the conversion of saturated fatty acids into monounsaturated fatty acids, is associated with fatty acid composition in pigs. As SCD was observed to be significantly induced in 3T3-L1 preadipocytes differentiation, we hypothesized that it plays a role in porcine adipocyte differentiation and fat deposition. In this study, we revealed that SCD is highly expressed in adipose tissues from seven-day-old piglets, compared to its expression in tissues from four-month-old adult pigs. Moreover, we found that SCD and lipogenesis-related genes were induced significantly in differentiated porcine adipocytes. Using CRISPR/Cas9 technology, we generated SCD^-/- porcine embryonic fibroblasts (PEFs) and found that the loss of SCD led to dramatically decreased transdifferentiation efficiency, as evidenced by the decreased expression of known lipid synthesis-related genes, lower levels of oil red O staining and significantly lower levels of triglyceride content. Our study demonstrates the critical role of SCD expression in porcine adipocyte differentiation and paves the way for identifying it as the promising candidate gene for less fat deposition in pigs.

Reversal of obesity and liver steatosis in mice via inhibition of aryl hydrocarbon receptor and altered gene expression of CYP1B1, PPARα, SCD1, and osteopontin

BACKGROUND/OBJECTIVES

Obesity is a global epidemic and the underlying basis for numerous comorbidities. We report that the aryl hydrocarbon receptor (AHR) plays a key role in the metabolism of obesity. The AHR is a promiscuous, ligand-activated nuclear receptor primarily known for regulating genes involved in xenobiotic metabolism and T cell polarization. The aims of the work reported here were to understand the underlying mechanism of AHR-based obesity and to determine whether inhibition of AHR activity would reverse obesity.

METHODS

Mice were fed control (low fat) and Western (high fat) diets with and without the AHR antagonist alpha-naphthoflavone (aNF). Gene expression of identified AHR-regulated genes from liver and adipose tissue was characterized. To determine the role of the AHR in obesity reversal, selected mice in control and Western diet regimens were switched at midpoint to the respective control and Western diets containing aNF, and the identified AHR-regulated genes characterized.

RESULTS

AHR inhibition prevented obesity in mice on a 40-week diet regimen. The likely AHR-regulated and cross-regulated downstream effectors of AHR-based obesity were shown to be CYP1B1, PPARα-target genes, SCD1, and SPP1 (osteopontin). Western diet caused an increase of mRNA and protein expression of the Cyp1b1, Scd1, and Spp1, and PPARα-target genes in the liver, and inhibition of the AHR maintained expression of these genes near control levels. The body weight of obese mice on Western diet switched to Western diet containing aNF decreased to that of mice on control diet concurrently with a reduction in the expression of liver CYP1B1, PPARα-target genes, SCD1, and SPP1. AHR inhibition prevented hypertrophy and hyperplasia in visceral adipose tissue and limited expression levels of CYP1B1 and SPP1 to that of mice on control diet.

CONCLUSIONS

AHR inhibition prevents and reverses obesity by likely reducing liver expression of the Cyp1b1, Scd1, Spp1, and PPARα-target genes; and the AHR is a potentially potent therapeutic target for the treatment and prevention of obesity and linked diseases.

Insulin activates hepatic Wnt/β-catenin signaling through stearoyl-CoA desaturase 1 and Porcupine

The Wnt/β-catenin pathway plays a pivotal role in liver structural and metabolic homeostasis. Wnt activity is tightly regulated by the acyltransferase Porcupine through the addition of palmitoleate. Interestingly palmitoleate can be endogenously produced by the stearoyl-CoA desaturase 1 (SCD1), a lipogenic enzyme transcriptionally regulated by insulin. This study aimed to determine whether nutritional conditions, and insulin, regulate Wnt pathway activity in liver. An adenoviral TRE-Luciferase reporter was used as a readout of Wnt/β-catenin pathway activity, in vivo in mouse liver and in vitro in primary hepatocytes. Refeeding enhanced TRE-Luciferase activity and expression of Wnt target genes in mice liver, revealing a nutritional regulation of the Wnt/β-catenin pathway. This effect was inhibited in liver specific insulin receptor KO (iLIRKO) mice and upon wortmannin or rapamycin treatment. Overexpression or inhibition of SCD1 expression regulated Wnt/β-catenin activity in primary hepatocytes. Similarly, palmitoleate added exogenously or produced by SCD1-mediated desaturation of palmitate, induced Wnt signaling activity. Interestingly, this effect was abolished in the absence of Porcupine, suggesting that both SCD1 and Porcupine are key mediators of insulin-induced Wnt/β-catenin activity in hepatocytes. Altogether, our findings suggest that insulin and lipogenesis act as potential novel physiological inducers of hepatic Wnt/β-catenin pathway.

Long Term Ovariectomy-Induced Osteoporosis is Associated with High Stearoyl-CoA Desaturase Indexes in Rat Femur

Osteoporosis is characterized by a bone loss associated to an increased bone marrow adiposity; however, it is still unclear what kind of lipids are involved. Therefore, the main purpose of this study was to see if there is any local bone lipid changes related to osteoporosis, by using the ovariectomy-induced osteoporosis (OVX) rat model. Female SD rats (operated at 6 months of age for skeletal maturity) were divided in control SHAM and OVX groups (n = 6/group) and maintained for 9 month post-surgery. Lipids were analyzed in two compartments of femoral diaphyses: bone marrow (BM) and mineralized tissue (MT), by chromatographic methods. As expected, osteoporotic femurs had a larger BM mass associated with a two-fold increase of lipid content. The MT had a similar lipid enrichment, indicating that adiposity affected the mineral part as well. The main lipids concerned were triglycerides, sphingomyelin, phosphatidylcholine and phosphatidylserine in BM, and triglycerides and cholesterol esters in MT. The increase of both energy-storage and membrane-associated lipids in BM suggested that cell number and/or size was enhanced to allow more triglyceride storage. Interestingly, in MT of osteoporotic femurs, sphingomyelin was decreased, suggesting that its catabolism could be linked to osteoporosis. In both femoral compartments, fatty acid profiles were enriched in 14:0 and 16:1, lowered in 18:0 and 20:4 n-6, and two-fold higher stearoyl-CoA desaturase indexes (16:1/16:0 and 18:1/18:0 ratios), suggesting an increased de novo lipogenesis in osteoporotic femurs. Thus, the present study is first to report local changes of individual lipids in rat osteoporotic femurs and suggests that osteoporosis is a pathologic condition associated with an enhanced de novo lipogenesis. Further studies will be needed to better understand the consequences of these lipid changes in osteoporotic bones.

A comprehensive serum lipidome profiling of amyotrophic lateral sclerosis

Objective: To perform a comprehensive lipid profiling to evaluate potential lipid metabolic differences between patients with amyotrophic lateral sclerosis (ALS) and controls, and to provide a more profound understanding of the metabolic abnormalities in ALS. Methods: Twenty patients with ALS and 20 healthy controls were enrolled in a cross-sectional study. Untargeted lipidomics profiling in fasting serum samples were performed by optimized UPLC-MS platforms for broad lipidome coverage. Datasets were analyzed by univariate and a variety of multivariate procedures. Results: We provide the most comprehensive blood lipid profiling of ALS to date, with a total of 416 lipids measured. Univariate analysis showed that 28 individual lipid features and two lipid classes, triacylglycerides and oxidized fatty acids (FAs), were altered in patients with ALS, although none of these changes remained significant after multiple comparison adjustment. Most of these changes remained constant after removing from the analysis individuals treated with lipid-lowering drugs. The non-supervised principal component analysis did not identify any lipid clustering of patients with ALS and controls. Despite this, we performed a variety of linear and non-linear supervised multivariate models to select the most reliable features that discriminate the lipid profile of patients with ALS from controls. These were the monounsaturated FAs C24:1n-9 and C14:1, the triglyceride TG(51:4) and the sphingomyelin SM(36:2). Conclusions: Peripheral alterations of lipid metabolism are poorly defined in ALS, triacylglycerides and certain types of FAs could contribute to the different lipid profile of patients with ALS. These findings should be validated in an independent cohort.

Cyp1b1 directs Srebp-mediated cholesterol and retinoid synthesis in perinatal liver; Association with retinoic acid activity during fetal development

Background

Cytochrome P450 1b1 (Cyp1b1) deletion and dietary retinol deficiency during pregnancy (GVAD) affect perinatal liver functions regulated by Srebp. Cyp1b1 is not expressed in perinatal liver but appears in the E9.5 embryo, close to sites of retinoic acid (RA) signaling.

Hypothesis

Parallel effects of Cyp1b1 and retinol on postnatal Srebp derive from effects in the developing liver or systemic signaling.

Approach

Cluster postnatal increases in hepatic genes in relation to effects of GVAD or Cyp1b1 deletion. Sort expression changes in relation to genes regulated by Srebp1 and Srebp2.Test these treatments on embryos at E9.5, examining changes at the site of liver initiation. Use in situ hybridization to resolve effects on mRNA distributions of Aldh1a2 and Cyp26a1 (RA homeostasis); Hoxb1 and Pax6 (RA targets). Assess mice lacking Lrat and Rbp4 (DKO mice) that severely limits retinol supply to embryos.

Results

At birth, GVAD and Cyp1b1 deletion stimulate gene markers of hepatic stellate cell (HSC) activation but also suppress Hamp. These treatments then selectively prevent the postnatal onset of genes that synthesize cholesterol (Hmgcr, Sqle) and fatty acids (Fasn, Scd1), but also direct cholesterol transport (Ldlr, Pcsk9, Stard4) and retinoid synthesis (Aldh1a1, Rdh11). Extensive support by Cyp1b1 is implicated, but with distinct GVAD interventions for Srebp1 and Srebp2. At E9.5, Cyp1b1 is expressed in the septum transversum mesenchyme (STM) with β-carotene oxygenase (Bco1) that generates retinaldehyde. STM provides progenitors for the HSC and supports liver expansion. GVAD and Cyp1b1-/- do not affect RA-dependent Hoxb1 and Pax6. In DKO embryos, RA-dependent Cyp26a1 is lost but Hoxb1 is sustained with Cyp1b1 at multiple sites.

Conclusion

Cyp1b1-/- suppresses genes supported by Srebp. GVAD effects distinguish Srebp1 and Srebp2 mediation. Srebp regulation overlaps appreciably in cholesterol and retinoid homeostasis. Bco1/Cyp1b1 partnership in the STM may contribute to this later liver regulation.

Associations of the SCD1 gene SNP with fatty acids composition of Holstein cows

The research presents the findings of DNA testing of allelic polymorphism by the PCR-RFLP method of the SCD1 gene and the relationship of genotypes with the milk fatty acid composition of Holstein cows of Tatarstan population. The research was conducted among 172 Holstein cows at the Integrated Agricultural Production Centre “Stud farm named after Lenin” in Atninsky district of the Republic of Tatarstan in 2017–2018. All genotypes of the SCD1 gene were identified through the research. The milk yield test showed that the maximum content of the mass fraction of fat was in animals with the TT genotype. The significant difference between the content of the mass fraction of fat in milk in individuals by the locus of the SCD1-Fsp4H I gene was: TT to CC – 0.32 % (p < 0.05) and TT to TC – 0.40 % (p < 0.01). The results of chromatography indicate the balance of the milk fatty acid composition of cows with the TT genotype and, as a consequence, its positive effect on the human body. Cows with a homozygous TT genotype are characterized by the optimum ratio of fatty acids in milk fat. The maximum value of the oxygen desaturation index is also observed in animals with the TT genotype by the SCD1 gene.

AMPKα pathway involved in hepatic triglyceride metabolism disorder in diet-induced obesity mice following Escherichia coli Infection

To investigate the different effects of acute pulmonary infection induced by Escherichia coli (E. coli) on lipid metabolism between diet-induced obesity (DIO, fed with high-fat diet) mice and lean mice. A total of 180 ICR mice were selected to be challenged intranasally with phosphate-buffered saline or 10⁹ CFUs/mL of E. coli, and the body character indexes, biochemical indexes and expressions of genes and proteins involved in lipid metabolism were examined pre- and post-infection. Results revealed that, before infection, DIO mice had significantly higher body weight, adipose and liver indexes, free fatty acid and triglyceride contents than lean mice. After infection, increased free fatty acid and triglyceride contents, increased expressions of resistin, SREBP-1c, ACC1, FAS and SCD-1, and declined PPARα, CPT-1α expressions and AMPKα phosphorylation were detected in the infected group, while the change rates were more serious in the lean mice than the DIO mice. The above-mentioned findings verified that, after being infected with E. coli, hepatic lipid metabolism disorder was aggravated by activating SREBP-1c related lipid synthesis pathway and inhibiting PPARα related fatty acid oxidation pathway. However, infection-induced lipid metabolic disorders was slighter in the DIO mice than the lean mice through AMPKα pathway.

The Effect of Dietary Camelina sativa Oil or Cake in the Diets of Broiler Chickens on Growth Performance, Fatty Acid Profile, and Sensory Quality of Meat

The aim of the present study was to determine the effect of supplementing the diets of broiler chickens with Camelina sativa oil or cake as a source of polyunsaturated fatty acids (PUFAs) on their growth performance, fatty acid profile, and sensory quality of meat. The 456 Ross 308 broilers aged 21-42 days were divided into 3 groups with 4 replicates of 38 birds in each. Chickens in the control group I (CTR) were fed a standard grower-finisher feed mixture containing 60 g/kg rapeseed oil. The experimental components, C. sativa oil-CSO (group II) or cake-CSC (group III), were included in a diet based on wheat and soybean at 40 and 100 g/kg, respectively. The use of Camelina oil and cake as feed components did not have a significant effect on the growth performance of the chickens. Analysis of the fatty acid profile in the lipids of the breast muscles showed that Camelina oil and cake reduced the content of monounsaturated fatty acids (p < 0.05) but increased the content of n-3 polyunsaturated fatty acids, especially α-linolenic acid (C18:3) (p < 0.01). Furthermore, both components reduced the ratio of n-6/n-3 PUFAs in the breast muscles (p < 0.01). Sensory analysis revealed that Camelina oil had a beneficial effect on meat juiciness, whereas Camelina cake slightly worsened the flavor and tastiness of the meat. In conclusion, supplementing the diet of broiler chickens with Camelina oil or cake can be an efficient method for modifying the fatty acid profile of the meat lipids in a beneficial way, without any negative impact on the growth performance of the chickens. According to the dietetic recommendations for humans, broiler chicken meat with a higher level of PUFA n-3 can be a good alternative source of these fatty acids in the human diet. Furthermore, Camelina oil improved the juiciness of breast meat.

Role of Oleic Acid in the Gut-Liver Axis: From Diet to the Regulation of Its Synthesis via Stearoyl-CoA Desaturase 1 (SCD1)

The consumption of an olive oil rich diet has been associated with the diminished incidence of cardiovascular disease and cancer. Several studies have attributed these beneficial effects to oleic acid (C18 n-9), the predominant fatty acid principal component of olive oil. Oleic acid is not an essential fatty acid since it can be endogenously synthesized in humans. Stearoyl-CoA desaturase 1 (SCD1) is the enzyme responsible for oleic acid production and, more generally, for the synthesis of monounsaturated fatty acids (MUFA). The saturated to monounsaturated fatty acid ratio affects the regulation of cell growth and differentiation, and alteration in this ratio has been implicated in a variety of diseases, such as liver dysfunction and intestinal inflammation. In this review, we discuss our current understanding of the impact of gene-nutrient interactions in liver and gut diseases, by taking advantage of the role of SCD1 and its product oleic acid in the modulation of different hepatic and intestinal metabolic pathways.

Cyclic Change of Fatty Acid Composition in Meibum During the Menstrual Cycle

Purpose

To evaluate the fatty acid (FA) composition in the meibum of pre- and postmenopausal women and age-matched men.

Methods

This prospective study involved 24 healthy subjects; six premenopausal women in their 30s with a regular menstrual cycle (young-female [yF] group), six postmenopausal women in their 60s (elderly-female [eF] group), and 12 age-matched men (i.e., young-male [yM] and elderly-male [eM] groups, respectively). The menstrual cycle was divided into six phases (phase I–VI). Meibum was obtained from the meibomian gland orifices via a Daviel spoon, and its FA composition was then analyzed via gas chromatography mass spectrometry (GC-MS). Principal component analysis (PCA) was performed on the GC-MS results.

Results

The mean FA composition of all subjects was 40% saturated FAs (SFA) and 60% unsaturated FAs (UFAs). The PCA results of all groups indicated two categories (PC1 [77.5%] and PC2 [12.4%]); one consisting of yF-group samples of mainly phase II and III and the other consisting of the yF-group samples of the rest of the cycle, as well as from eF-group, yM-group, and eM-group samples. Each group had a distinctive nature. The FAs that most contributed to PC1 were C_14:0, C_16:0, and C_18:0 in a positive correlation, and C_18:1n9 in a negative correlation.

Conclusions

FA composition noticeably changes during the menstrual cycle and is somewhat affected by sex and age. The ratio of SFAs (C_16:0, C_18:0) to mono-UFAs (C_18:1n9) in the FA composition might have an impact on the lipid quality of meibum, thus suggesting alteration of its melting temperature and viscosity.

Stearoyl-CoA Desaturase 1 as a Therapeutic Target for the Treatment of Cancer

A distinctive feature of cancer cells of various origins involves alterations of the composition of lipids, with significant enrichment in monounsaturated fatty acids. These molecules, in addition to being structural components of newly formed cell membranes of intensely proliferating cancer cells, support tumorigenic signaling. An increase in the expression of stearoyl-CoA desaturase 1 (SCD1), the enzyme that converts saturated fatty acids to ∆9-monounsaturated fatty acids, has been observed in a wide range of cancer cells, and this increase is correlated with cancer aggressiveness and poor outcomes for patients. Studies have demonstrated the involvement of SCD1 in the promotion of cancer cell proliferation, migration, metastasis, and tumor growth. Many studies have reported a role for this lipogenic factor in maintaining the characteristics of cancer stem cells (i.e., the population of cells that contributes to cancer progression and resistance to chemotherapy). Importantly, both the products of SCD1 activity and its direct impact on tumorigenic pathways have been demonstrated. Based on these findings, SCD1 appears to be a significant player in the development of malignant disease and may be a promising target for anticancer therapy. Numerous chemical compounds that exert inhibitory effects on SCD1 have been developed and preclinically tested. The present review summarizes our current knowledge of the ways in which SCD1 contributes to the progression of cancer and discusses opportunities and challenges of using SCD1 inhibitors for the treatment of cancer.

Stearoyl-CoA Desaturase 1 Protects Ovarian Cancer Cells from Ferroptotic Cell Death

Activation of ferroptosis, a recently described mechanism of regulated cell death, dramatically inhibits growth of ovarian cancer cells. Given the importance of lipid metabolism in ferroptosis and the key role of lipids in ovarian cancer, we examined the contribution to ferroptosis of stearoyl-CoA desaturase (SCD1, SCD), an enzyme that catalyzes the rate-limiting step in monounsaturated fatty acid synthesis in ovarian cancer cells. SCD1 was highly expressed in ovarian cancer tissue, cell lines, and a genetic model of ovarian cancer stem cells. Inhibition of SCD1 induced lipid oxidation and cell death. Conversely, overexpression of SCD or exogenous administration of its C16:1 and C18:1 products, palmitoleic acid or oleate, protected cells from death. Inhibition of SCD1 induced both ferroptosis and apoptosis. Inhibition of SCD1 decreased CoQ₁₀, an endogenous membrane antioxidant whose depletion has been linked to ferroptosis, while concomitantly decreasing unsaturated fatty acyl chains in membrane phospholipids and increasing long-chain saturated ceramides, changes previously linked to apoptosis. Simultaneous triggering of two death pathways suggests SCD1 inhibition may be an effective component of antitumor therapy, because overcoming this dual mechanism of cell death may present a significant barrier to the emergence of drug resistance. Supporting this concept, we observed that inhibition of SCD1 significantly potentiated the antitumor effect of ferroptosis inducers in both ovarian cancer cell lines and a mouse orthotopic xenograft model. Our results suggest that the use of combined treatment with SCD1 inhibitors and ferroptosis inducers may provide a new therapeutic strategy for patients with ovarian cancer. SIGNIFICANCE: The combination of SCD1 inhibitors and ferroptosis inducers may provide a new therapeutic strategy for the treatment of ovarian cancer patients.See related commentary by Carbone and Melino, p. 5149.

Comparison of the Effects of Long-chain Monounsaturated Fatty Acid Positional Isomers on Lipid Metabolism in 3T3-L1 Cells

Long chain monounsaturated fatty acids (LC-MUFAs) have shown beneficial health effects in previous studies. They occur as mixtures of positional isomers (PIs) in food. The functionalities of LC-MUFA PIs have not been studied extensively. Common LC-MUFA PIs, namely cis-octadecenoic acid (c-18:1), cis-eicosenoic acid (c-20:1), and cis-docosenoic acid (c-22:1), were screened based on their effects on lipid accumulation. We selected nine fatty acids (FAs) to assess their effects on cellular lipid metabolism using 3T3-L1 preadipocytes. Lipid accumulation was found to be higher in cells treated with LC-MUFAs than in the non-treated cells. When comparing the influence of chain length of LC-MUFAs, TG levels tended to be higher in cells treated with c-22:1 group than that of the c18:1 and c-20:1 groups. Among the c-22:1 group, c9-22:1 treatment showed higher lipid accumulation, and was accompanied with elevated expression of transcription factors related to adipogenesis and lipogenesis, such as PPARγ and C/EBPα, and SREBP-1, respectively. In contrast, the effects of c-20:1 FAs were less pronounced than those of c-18:1 and c-22:1. Levels of accumulated lipid in cells treated with c15-20:1 were the same as in non-treated control. PPARγ, C/EBPα, and SREBP-1 were expressed at lower levels with c15-20:1 FA. Furthermore, mRNA levels of SCD-1 and FAS were lowered more by c15- and c11-20:1 than by other MUFAs. These results revealed that differences in the effects of LC-MUFAs on lipid metabolism depend on their chain lengths and on the position of the double bond.

Effects of dietary crude protein levels and cysteamine supplementation on meat quality and related indices of finishing pigs

The aim of this study was to investigate the effects of dietary crude protein levels and cysteamine (CS) supplementation on meat quality and related indices in longissimus dorsi muscle of finishing pigs. One hundred and twenty barrows were randomly allocated to a 2 × 2 factorial arrangement with five replicates of six pigs each. The primary variations were crude protein levels (14% or 10%) and CS supplemental levels (0 or 140 mg kg−1). After 41 d, 10 pigs per treatment were slaughtered. The results showed that low-protein level diets (LPDs) decreased Warner–Bratzler shear force (P < 0.01) and increased the content of intramuscular fat (P < 0.01). The mRNA expressions of lipogenic genes were up-regulated (P < 0.01), and the mRNA expressions of lipolytic genes were down-regulated (P < 0.01) in pigs fed LPD. LPDs increased the mRNA expressions of μ-calpain, and decreased the mRNA expression of calpastatin (P < 0.01). In addition, CS supplementation increased the mRNA expression of μ-calpain (P < 0.01). In conclusion, LPD improved the meat quality probably through regulating the lipogenesis, lipolysis, and the proteolysis process in muscle. The CS supplementation did not affect the meat quality of finishing pigs. Moreover, no significant interaction between dietary protein levels and CS supplementation for the meat quality of finishing pigs was observed.

Dietary fatty acid intake in hemodialysis patients and associations with circulating fatty acid profiles: A cross-sectional study

OBJECTIVES

The aims of this study were threefold: first, to assess the dietary fatty acid (FA) intake and blood FA status in Malaysian patients on hemodialysis (HD); second, to examine the association between dietary FA intakes and blood FA profiles in patients on HD; and third, to determine whether blood FAs could serve as a biomarker of dietary fat intake quality in these patients.

METHODS

Using 3 d of dietary records, FA intakes of 333 recruited patients were calculated using a food database built from laboratory analyses of commonly consumed Malaysian foods. Plasma triacylglycerol (TG) and erythrocyte FAs were determined by gas chromatography.

RESULTS

High dietary saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA) consumption trends were observed. Patients on HD also reported low dietary ω-3 and ω-6 polyunsaturated fatty acid (PUFA) consumptions and low levels of TG and erythrocyte FAs. TG and dietary FAs were significantly associated respective to total PUFA, total ω-6 PUFA, 18:2 ω-6, total ω-3 PUFA, 18:3 ω-3, 22:6 ω-3, and trans 18:2 isomers (P < 0.05). Contrarily, only dietary total ω-3 PUFA and 22:6 ω-3 were significantly associated with erythrocyte FAs (P < 0.01). The highest tertile of fish and shellfish consumption reflected a significantly higher proportion of TG 22:6 ω-3. Dietary SFAs were directly associated with TG and erythrocyte MUFA, whereas dietary PUFAs were not.

CONCLUSION

TG and erythrocyte FAs serve as biomarkers of dietary PUFA intake in patients on HD. Elevation of circulating MUFA may be attributed to inadequate intake of PUFAs.

Preweaning nutrient supply alters mammary gland transcriptome expression relating to morphology, lipid accumulation, DNA synthesis, and RNA expression in Holstein heifer calves

The objective of this study was to analyze the mammary gland transcriptome to determine how preweaning nutrient supply alters the molecular mechanisms that regulate preweaning mammary development. Holstein heifers were fed via milk replacer (MR) either an elevated level of nutrient intake (ELE; on average, 5.9 ± 0.2 Mcal of ME in 8.4 L of MR/d, n = 6) or a restricted amount of nutrients (RES; 2.8 ± 0.2 Mcal of ME in 4 L of MR/d, n = 5) for 54 d after birth, at which point they were slaughtered and samples of mammary parenchyma tissue were obtained. Parenchymal mRNA was analyzed, and the fold change (FC) of 18,111 genes (ELE relative to RES) was uploaded to Ingenuity Pathway Analysis (IPA) software (Qiagen Bioinformatics, Redwood City, CA) for transcriptomic analysis. Using a threshold of P < 0.05, IPA identified that the FC of 1,931 of 18,811 differentially expressed genes (DEG) could be used for the analysis. A total of 18 molecular and cellular functions were relevant to DEG arising from the treatments; the 5 functions most associated with DEG were cell death and survival, cellular movement, cellular development, cellular growth and proliferation, and lipid metabolism. Based on the directional FC of DEG, the mammary gland of ELE heifers was predicted to have increased epithelial-mesenchymal transition (Z = 2.685) and accumulation of lipid (Z = 2.322), whereas the synthesis of DNA (Z = -2.137), transactivation of RNA (Z = -2.254), expression of RNA (Z = -2.405), transcription (Z = -2.482), and transactivation (Z = -2.611) were all predicted to be decreased. Additionally, IPA predicted the activation status of 13 upstream regulators with direct influence on DEG as affected by ELE feeding that were ligand-dependent nuclear receptors (n = 2), enzymes (n = 1), or transcription regulators (n = 10). Of these, 6 were activated (Z > 2) and 7 were inhibited (Z < -2). In summary, feeding ELE preweaning altered the mammary transcriptome of Holstein heifers, affecting cell functions involved in the morphological and physiological development of the mammary gland.

Identification of Candidate Genes and Regulatory Factors Underlying Intramuscular Fat Content Through Longissimus Dorsi Transcriptome Analyses in Heavy Iberian Pigs

One of the most important determinants of meat quality is the intramuscular fat (IMF) content. The development of high-throughput techniques as RNA-seq allows identifying gene pathways and networks with a differential expression (DE) between groups of animals divergent for a particular trait. The Iberian pig is characterized by having an excellent meat quality and a high content of intramuscular fat. The objectives of the present study were to analyze the longissimus dorsi transcriptome of purebred Iberian pigs divergent for their IMF breeding value to identify differential expressed genes and regulatory factors affecting gene expression. RNA-seq allowed identifying ∼10,000 of the 25,878 annotated genes in the analyzed samples. In addition to this, 42.46% of the identified transcripts corresponded to newly predicted isoforms. Differential expression analyses revealed a total of 221 DE annotated genes and 116 DE new isoforms. Functional analyses identified an enrichment of overexpressed genes involved in lipid metabolism (FASN, SCD, ELOVL6, DGAT2, PLIN1, CIDEC, and ADIPOQ) in animals with a higher content of IMF and an enrichment of overexpressed genes related with myogenesis and adipogenesis (EGR1, EGR2, EGR3, JUNB, FOSB, and SEMA4D) in the animals with a lower content of IMF. In addition to this, potential regulatory elements of these DE genes were identified. Co-expression networks analyses revealed six long non-coding RNAs (lncRNAs) (ALDBSSCG0000002079, ALDBSSCG0000002093, ALDBSSCG0000003455, ALDBSSCG0000004244, ALDBSSCG0000005525, and ALDBSSCG0000006849) co-expressed with SEMA4D and FOSB genes and one (ALDBSSCG0000004790) with SCD, ELOVL6, DGAT2, PLIN1, and CIDEC. Analyses of the regulatory impact factors (RIFs) revealed 301 transcriptionally regulatory factors involved in expression differences, with five of them involved in adipogenesis (ARID5B, CREB1, VDR, ATF6, and SP1) and other three taking part of myogenesis and development of skeletal muscle (ATF3, KLF11, and MYF6). The results obtained provide relevant insights about the genetic mechanisms underlying IMF content in purebred Iberian pigs and a set of candidate genes and regulatory factors for further identification of polymorphisms susceptible of being incorporated in a selection program.

Maternal long chain polyunsaturated fatty acid status and pregnancy complications

Maternal nutrition plays a crucial role in influencing fetal growth and birth outcome. Any nutritional insult starting several weeks before pregnancy and during critical periods of gestation is known to influence fetal development and increase the risk for diseases during later life. Literature suggests that chronic adult diseases may have their origin during early life - a concept referred to as Developmental Origins of Health and Disease (DOHaD) which states that adverse exposures early in life "program" risks for later chronic disorders. Long chain polyunsaturated fatty acids (LCPUFA), mainly omega-6 and omega-3 fatty acids are known to have an effect on fetal programming. The placental supply of optimal levels of LCPUFA to the fetus during early life is extremely important for the normal growth and development of both placenta and fetus. Any alteration in placental development will result in adverse pregnancy outcome such as gestational diabetes mellitus (GDM), preeclampsia, and intrauterine growth restriction (IUGR). A disturbed materno-fetal LCPUFA supply is known to be linked with each of these pathologies. Further, a disturbed LCPUFA metabolism is reported to be associated with a number of metabolic disorders. It is likely that LCPUFA supplementation during early pregnancy may be beneficial in improving the health of the mother, improving birth outcome and thereby reducing the risk of diseases in later life.

Triacylglycerol-Lowering Effect of Docosahexaenoic Acid Is Not Influenced by Single-Nucleotide Polymorphisms Involved in Lipid Metabolism in Humans

The triacylglycerol (TAG)-lowering effects of long-chain n-3 fatty acids, and in particular docosahexaenoic acid (DHA), are well documented, although these effects manifest large interindividual variability. The objective of this secondary analysis is to investigate whether common single-nucleotide polymorphisms (SNP) in genes involved in DHA synthesis and TAG metabolism are associated with the responsiveness of blood lipids, lipoprotein, and apolipoprotein concentration to dietary treatment by DHA supplied in high-oleic canola oil (HOCO). In a randomized, crossover-controlled feeding trial, 129 subjects with metabolic syndrome received high-oleic canola oil (HOCO) and high-oleic canola oil supplemented with DHA (HOCO-DHA), each for 4 weeks. During the HOCO-DHA phase, the intake of DHA ranged from 1 to 2.5 g/day. The subjects were genotyped for apolipoprotein E (APOE) isoforms, and SNP including FADS1-rs174561, FADS2-rs174583, ELOVL2-rs953413, ELOVL5-rs2397142, CETP-rs5882, SCD1-rs2234970, PPARA-rs6008259, and LIPF-rs814628 were selected as important genes controlling fatty acid metabolism. Overall, consumption of HOCO-DHA oil reduced blood concentrations of TAG by 24% compared to HOCO oil. The reduction in TAG was independent of genetic variations in the studied genes. Similarly, no treatment-by-gene interactions were evident in the response to other lipids, lipoproteins, or apolipoproteins to DHA supplementation. Nevertheless, a lower interindividual variation in the TAG response to DHA supplementation compared to other studies was observed in this analysis. The TAG-lowering effect of a supplemental body-weight-based dose of DHA was not influenced by genetic variations in APOE, FADS1, FADS2, ELOVL2, ELOVL5, CETP, SCD1, PPARA, and LIPF.

Holistic Approaches in Lipid Production by Yarrowia lipolytica

Concerns about climate change have driven research on the production of lipid-derived biofuels as an alternative and renewable liquid fuel source. Using oleaginous yeasts for lipid synthesis creates the potential for cost-effective industrial-scale operations due to their ability to reach high lipid titer, yield, and productivity resulting from their unique metabolism. Yarrowia lipolytica is the model oleaginous yeast, with the best-studied lipid metabolism, the greatest number of genetic tools, and a fully sequenced genome. In this review we highlight multiomics studies that elucidate the mechanisms allowing this yeast to achieve lipid overaccumulation and then present several major metabolic engineering efforts that enhanced the production metrics in Y. lipolytica. Recent achievements that applied novel engineering strategies are emphasized.

Stearoyl-CoA desaturase activity in bovine cumulus cells protects the oocyte against saturated fatty acid stress

Metabolic rich and poor conditions are both characterized by elevated free fatty acid levels and have been associated with impaired female fertility. In particular, saturated free fatty acids have a dose-dependent negative impact on oocyte developmental competence, while monounsaturated free fatty acids appear less harmful. Cumulus cells seem to protect the oocyte against free fatty acids, and the aim of this study was to determine the mechanism behind this protection In particular, the role of the enzyme stearoyl-CoA desaturase (SCD) that converts saturated into monounsaturated fatty acids was investigated. SCD gene and protein were abundantly expressed in cumulus cells, but expression was low in oocytes. The level of SCD protein expression in cumulus cells did not change when COCs were exposed to saturated stearic acid during maturation. SCD inhibition in the presence of stearic acid significantly reduced the developmental competence of oocytes and increased the incidence of apoptosis in cumulus cells. The esterified oleic/stearic acid ratio of the neutral lipid fraction in cumulus cells decreased in the presence of SCD inhibitors when COCs were exposed to saturated free fatty acids during maturation, indicating the SCD-specific conversion of saturated fatty acids under noninhibiting conditions. The observation that cumulus cells can desaturate the potentially toxic stearic acid into oleic acid via SCD activity provides a mechanistic insight into how the cumulus cells protect the oocyte against toxicity by saturated fatty acid.

Developing cellulolytic Yarrowia lipolytica as a platform for the production of valuable products in consolidated bioprocessing of cellulose

BACKGROUND

Both industrial biotechnology and the use of cellulosic biomass as feedstock for the manufacture of various commercial goods are prominent features of the bioeconomy. In previous work, with the aim of developing a consolidated bioprocess for cellulose bioconversion, we conferred cellulolytic activity of Yarrowia lipolytica, one of the most widely studied "nonconventional" oleaginous yeast species. However, further engineering this strain often leads to the loss of previously introduced heterologous genes due to the presence of multiple LoxP sites when using Cre-recombinase to remove previously employed selection markers.

RESULTS

In the present study, we first optimized the strategy of expression of multiple cellulases and rescued selection makers to obtain an auxotrophic cellulolytic Y. lipolytica strain. Then we pursued the quest, exemplifying how this cellulolytic Y. lipolytica strain can be used as a CBP platform for the production of target products. Our results reveal that overexpression of SCD1 gene, encoding stearoyl-CoA desaturase, and DGA1, encoding acyl-CoA:diacylglycerol acyltransferase, confers the obese phenotype to the cellulolytic Y. lipolytica. When grown in batch conditions and minimal medium, the resulting strain consumed 12 g/L cellulose and accumulated 14% (dry cell weight) lipids. Further enhancement of lipid production was achieved either by the addition of glucose or by enhancing cellulose consumption using a commercial cellulase cocktail. Regarding the latter option, although the addition of external cellulases is contrary to the concept of CBP, the amount of commercial cocktail used remained 50% lower than that used in a conventional process (i.e., without internalized production of cellulases). The introduction of the LIP2 gene into cellulolytic Y. lipolytica led to the production of a strain capable of producing lipase 2 while growing on cellulose. Remarkably, when the strain was grown on glucose, the expression of six cellulases did not alter the level of lipase production. When grown in batch conditions on cellulose, the engineered strain consumed 16 g/L cellulose and produced 9.0 U/mL lipase over a 96-h period. The lipase yield was 562 U lipase/g cellulose, which represents 60% of that obtained on glucose. Finally, expression of the hydroxylase from Claviceps purpurea (CpFAH12) in cellulolytic Y. lipolytica procured a strain that can produce ricinoleic acid (RA). Using this strain in batch cultures revealed that the consumption of 11 g/L cellulose sustained the production of 2.2 g/L RA in the decane phase, 69% of what was obtained on glucose.

CONCLUSIONS

In summary, this study has further demonstrated the potential of cellulolytic Y. lipolytica as a microbial platform for the bioconversion of cellulose into target products. Its ability to be used in consolidated process designs has been exemplified and clues revealing how cellulose consumption can be further enhanced using commercial cellulolytic cocktails are provided.

Efficient delivery of nucleic acid molecules into skin by combined use of microneedle roller and flexible interdigitated electroporation array

Rationale: Delivery of nucleic acid molecules into skin remains a main obstacle for various types of gene therapy or vaccine applications. Here we propose a novel electroporation approach via combined use of a microneedle roller and a flexible interdigitated electroporation array (FIEA) for efficient delivery of DNA and siRNA into mouse skin. Methods: Using micromachining technology, closely spaced gold electrodes were made on a pliable parylene substrate to form a patch-like electroporation array, which enabled close surface contact between the skin and electrodes. Pre-penetration of the skin with a microneedle roller resulted in the formation of microchannels in the skin, which played a role as liquid electrodes in the skin and provided a uniform and deep electric field in the tissue when pulse stimulation was applied by FIEA. Results: Using this proposed method, gene (RFP) expression and siRNA transfection were successfully achieved in normal mice skin. Anti-SCD1 siRNA electroporated via this method mediated significant gene silencing in the skin. Moreover, electroporation assisted by the microneedle roller showed significant advantages over treatment with FIEA alone. This allowed nucleic acid transportation at low voltage, with ideal safety outcomes. Principal conclusions: Hence, the proposed electroporation approach in this study constitutes a novel way for delivering siRNA and DNA, and even other nucleic acid molecules, to mouse skin in vivo, potentially supporting clinical application in the treatment of skin diseases or intradermal/subcutaneous vaccination.

Liver-directed gene therapy for murine glycogen storage disease type Ib

Glycogen storage disease type-Ib (GSD-Ib), deficient in the glucose-6-phosphate transporter (G6PT), is characterized by impaired glucose homeostasis, myeloid dysfunction, and long-term risk of hepatocellular adenoma (HCA). We examined the efficacy of G6PT gene therapy in G6pt-/- mice using recombinant adeno-associated virus (rAAV) vectors, directed by either the G6PC or the G6PT promoter/enhancer. Both vectors corrected hepatic G6PT deficiency in murine GSD-Ib but the G6PC promoter/enhancer was more efficacious. Over a 78-week study, using dose titration of the rAAV vectors, we showed that G6pt-/- mice expressing 3-62% of normal hepatic G6PT activity exhibited a normalized liver phenotype. Two of the 12 mice expressing < 6% of normal hepatic G6PT activity developed HCA. All treated mice were leaner and more sensitive to insulin than wild-type mice. Mice expressing 3-22% of normal hepatic G6PT activity exhibited higher insulin sensitivity than mice expressing 44-62%. The levels of insulin sensitivity correlated with the magnitudes of hepatic carbohydrate response element binding protein signaling activation. In summary, we established the threshold of hepatic G6PT activity required to prevent tumor formation and showed that mice expressing 3-62% of normal hepatic G6PT activity maintained glucose homeostasis and were protected against age-related obesity and insulin resistance.

Ablation of prolactin receptor increases hepatic triglyceride accumulation

Increasing prevalence of non-alcoholic fatty liver disease (NAFLD) worldwide has necessitated a more thorough understanding of it and expanded the scope of research in this field. Women are more resistant to NAFLD than men despite equal exposure to major risk factors, such as obesity or hyperlipidemia. Female resistance is hormone-dependent, as evidenced by the sharp increase in NAFLD incidence in post-menopausal women who do not take hormone replacement therapy. Here, we found that the estrogen-responsive pituitary hormone prolactin (PRL), through specific PRL receptor (PRLR), down-regulates hepatic triglyceride (TG) accumulation. PRL was demonstrated to significantly down-regulate hepatic TG accumulation in female mice and protect male mice from liver steatosis induced by high-fat diet. Interestingly, Ad-shPRLR injected mice, whose hepatic PRLR abundance was effectively decreased at the protein levels, exhibited significantly aggravated liver steatosis. PRL could decrease the expression of stearoyl-coenzyme A desaturase 1 (SCD1), the rate-limiting enzyme in the biosynthesis of monounsaturated fatty acids, in animal models and multiple hepatic cell lines. Following knockdown of PRLR, the changes to PRL-triggered SCD1 expression disappeared. Thus, PRL acted as a previously unrecognized master regulator of liver TG metabolism, indicating that modification of PRL via PRLR might serve as a potential therapeutic target for NAFLD.

Compensatory increases in tear volume and mucin levels associated with meibomian gland dysfunction caused by stearoyl-CoA desaturase-1 deficiency

The stearoyl-CoA desaturase (SCD) family of enzymes catalyzes monounsaturated fatty acid synthesis by inserting a cis double bond at the Δ9 position of saturated fatty acids. Disruption of these enzymes has been reported to induce a severe dry skin phenotype. Since lipid abnormalities in the meibomian glands have been associated with dry eye, we analyzed selected eye tissues contributing to tear volume and composition in genetically SCD-1-deficient mice (SCD-1 KO), including the lacrimal glands and conjunctiva. Previous histopathological analysis had revealed atrophy and loss of meibomian glands; taken together with the increased goblet cell and MUC5AC expression in the conjunctiva reported here, these findings suggest that the tear volume and mucin levels secreted are enhanced in the absence of lipid secretion as a compensatory mechanism. The expression of lipid metabolism genes in lacrimal glands was decreased in SCD1 KO mice. Thus, these results provide new pathophysiological mechanisms to pursue with regard to meibomian gland dysfunction. In addition, lack of SCD-1 causes a compensatory increase in the tear volume and mucin levels associated with changes in expression of lipid metabolism genes. These results may be useful as a new concept for dry eye treatment strategies.

Implantation of Neural Probes in the Brain Elicits Oxidative Stress

Clinical implantation of intracortical microelectrodes has been hindered, at least in part, by the perpetual inflammatory response occurring after device implantation. The neuroinflammatory response observed after device implantation has been correlated to oxidative stress that occurs due to neurological injury and disease. However, there has yet to be a definitive link of oxidative stress to intracortical microelectrode implantation. Thus, the objective of this study is to give direct evidence of oxidative stress following intracortical microelectrode implantation. This study also aims to identify potential molecular targets to attenuate oxidative stress observed postimplantation. Here, we implanted adult rats with silicon non-functional microelectrode probes for 4 weeks and compared the oxidative stress response to no surgery controls through postmortem gene expression analysis and qualitative histological observation of oxidative stress markers. Gene expression analysis results at 4 weeks postimplantation indicated that EH domain-containing 2, prion protein gene (Prnp), and Stearoyl-Coenzyme A desaturase 1 (Scd1) were all significantly higher for animals implanted with intracortical microelectrode probes compared to no surgery control animals. To the contrary, NADPH oxidase activator 1 (Noxa1) relative gene expression was significantly lower for implanted animals compared to no surgery control animals. Histological observation of oxidative stress showed an increased expression of oxidized proteins, lipids, and nucleic acids concentrated around the implant site. Collectively, our results reveal there is a presence of oxidative stress following intracortical microelectrode implantation compared to no surgery controls. Further investigation targeting these specific oxidative stress linked genes could be beneficial to understanding potential mechanisms and downstream therapeutics that can be utilized to reduce oxidative stress-mediated damage following microelectrode implantation.

Plasma stearoyl-CoA desaturase activity indices and bile acid concentrations after a low-fat meal: association with a genetic variant in the FTO gene

PURPOSE

Dietary macronutrient composition, stearoyl-CoA desaturase (SCD) activity indices, and primary bile acid (BA) concentrations are among the factors that have been associated with lipid metabolism and contributed to obesity. We investigated the association between the polymorphic expression of the fat mass and obesity-associated (FTO) gene and its relationship with SCD activity indices and primary BA concentrations after a low-fat meal.

SUBJECTS AND METHODS

Blood plasma samples were collected from 56 young (20-36 years) healthy subjects with different rs9939609 FTO genotypes. Fasting and post-meal (2 hours after a low-fat breakfast) blood samples were collected on the subsequent morning for the analysis of DNA methylation, SCD activity indices (product-to-precursor fatty acid ratios; 16:1n-7/16:0 and 18:1n-9/18:0), and chenodeoxycholic acid (CDCA) and cholic acid (CA) concentrations. Expression of lipogenic genes was investigated post-meal to assess the relationship between the CDCA and CA concentrations and mRNA levels of lipogenic genes.

RESULTS

The FTO AA (obesity risk) genotype group (n=18) had higher (P<0.05) post-meal SCD-16 activity index than the FTO TT (wild type) genotype group (n=26). In both the FTO TT (n=16) and AA (n=8) genotype groups, the post-meal concentrations of CDCA and CA were lower (P<0.05) compared with the fasted state. No difference in BA concentrations between the FTO TT and AA genotype groups in both meal states was observed. After adjusting for the body mass index, the highest 50% post-meal concentrations of CA were inversely (P=0.010) correlated with the level of mRNA SCD expression.

CONCLUSION

FTO AA carriers may be at a higher risk for obesity through higher SCD activity in a low-fat diet environment. This effect may be partly pronounced by very low CA concentrations.

Enzyme Replacement Therapy Ameliorates Multiple Symptoms of Murine Homocystinuria

Classical homocystinuria (HCU) is the most common inherited disorder of sulfur amino acid metabolism caused by deficiency in cystathionine beta-synthase (CBS) activity and characterized by severe elevation of homocysteine in blood and tissues. Treatment with dietary methionine restriction is not optimal, and poor compliance leads to serious complications. We developed an enzyme replacement therapy (ERT) and studied its efficacy in a severe form of HCU in mouse (the I278T model). Treatment was initiated before or after the onset of clinical symptoms in an effort to prevent or reverse the phenotype. ERT substantially reduced and sustained plasma homocysteine concentration at around 100 μM and normalized plasma cysteine for up to 9 months of treatment. Biochemical balance was also restored in the liver, kidney, and brain. Furthermore, ERT corrected liver glucose and lipid metabolism. The treatment prevented or reversed facial alopecia, fragile and lean phenotype, and low bone mass. In addition, structurally defective ciliary zonules in the eyes of I278T mice contained low density and/or broken fibers, while administration of ERT from birth partially rescued the ocular phenotype. In conclusion, ERT maintained an improved metabolic pattern and ameliorated many of the clinical complications in the I278T mouse model of HCU.

miR-192-5p regulates lipid synthesis in non-alcoholic fatty liver disease through SCD-1

AIM

To evaluate the levels of miR-192-5p in non-alcoholic fatty liver disease (NAFLD) models and demonstrate the role of miR-192-5p in lipid accumulation.

METHODS

Thirty Sprague Dawley rats were randomly divided into three groups, which were given a standard diet, a high-fat diet (HFD), and an HFD with injection of liraglutide. At the end of 16 weeks, hepatic miR-192-5p and stearoyl-CoA desaturase 1 (SCD-1) levels were measured. MiR-192-5p mimic and inhibitor and SCD-1 siRNA were transfected into Huh7 cells exposed to palmitic acid (PA). Lipid accumulation was evaluated by oil red O staining and triglyceride assays. Direct interaction was validated by dual-luciferase reporter gene assays.

RESULTS

The HFD rats showed a 0.46-fold decrease and a 3.5-fold increase in hepatic miR-192-5p and SCD-1 protein levels compared with controls, respectively, which could be reversed after disease remission by liraglutide injection (P < 0.01). The Huh7 cells exposed to PA also showed down-regulation and up-regulation of miR-192-5p and SCD-1 protein levels, respectively (P < 0.01). Transfection with miR-192-5p mimic and inhibitor in Huh7 cells induced dramatic repression and promotion of SCD-1 protein levels, respectively (P < 0.01). Luciferase activity was suppressed and enhanced by miR-192-5p mimic and inhibitor, respectively, in wild-type SCD-1 (P < 0.01) but not in mutant SCD-1. MiR-192-5p overexpression reduced lipid accumulation significantly in PA-treated Huh7 cells, and SCD-1 siRNA transfection abrogated the lipid deposition aggravated by miR-192-5p inhibitor (P < 0.01).

CONCLUSION

This study demonstrates that miR-192-5p has a negative regulatory role in lipid synthesis, which is mediated through its direct regulation of SCD-1.

Cyp1b1 deletion and retinol deficiency coordinately suppress mouse liver lipogenic genes and hepcidin expression during post-natal development

Cyp1b1 deletion and gestational vitamin A deficiency (GVAD) redirect adult liver gene expression. A matched sufficient pre- and post-natal diet, which has high carbohydrate and normal iron content (LF12), increased inflammatory gene expression markers in adult livers that were suppressed by GVAD and Cyp1b1 deletion. At birth on the LF12 diet, Cyp1b1 deletion and GVAD each suppress liver expression of the iron suppressor, hepcidin (Hepc), while increasing stellate cell activation markers and suppressing post-natal increases in lipogenesis. Hepc was less suppressed in Cyp1b1-/- pups with a standard breeder diet, but was restored by iron supplementation of the LF12 diet.

CONCLUSIONS

The LF12 diet delivered low post-natal iron and attenuated Hepc. Hepc decreases in Cyp1b1-/- and GVAD mice resulted in stellate activation and lipogenesis suppression. Endothelial BMP6, a Hepc stimulant, is a potential coordinator and Cyp1b1 target. These neonatal changes in Cyp1b1-/- mice link to diminished adult obesity and liver inflammation.