Torularhodin Alleviates Hepatic Dyslipidemia and Inflammations in High-Fat Diet-Induced Obese Mice via PPARα Signaling Pathway

Torularhodin is a β-carotene-like compound from Sporidiobolus pararoseus, and its protective effect against high-fat diet (HFD)-induced hepatic dyslipidemia and inflammation was investigated. Compared to mice of C57BL/6J fed on HFD, the addition of Torularhodin into the HFD (HFD-T) significantly reduced body weight, serum triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL), and the inflammatory mediators of TNF-α, IL-6, IL-1β, and lipopolysaccharide (LPS). A significant increase of high-density lipoprotein cholesterol (HDL-c), which is beneficial to cholesterol clearance, was also observed in HFD-T group. Proteomic analysis showed HDL-C-c is highly correlated with proteins (e.g., CPT1A and CYP7A1) involved in lipid β-oxidation and bile acid synthesis, whereas the other phenotypic parameters (TC, TG, LDL, and inflammatory cytokines) are highly associated with proteins (e.g., SLC27A4) involved in lipid-uptake. The up-regulated anti-inflammation proteins FAS, BAX, ICAM1, OCLN, GSTP1, FAF1, LRP1, APEX1, ROCK1, MANF, STAT3, and INSR and down-regulated pro-inflammatory proteins OPTN, PTK2B, FADD, MIF, CASP3, YAP1, DNM1L, and NAMPT not only demonstrate the occurrence of HFD-induced hepatic inflammation, but also prove the anti-inflammatory property of Torularhodin. KEGG signaling pathway analysis revealed that the PPARα signaling pathway is likely fundamental to the health function of Torularhodin through up-regulating genes related to fatty acid β-oxidation, cholesterol excretion, HDL-Cc formation, and anti-inflammation. Torularhodin, as a new food resource, may act as a therapeutic agent to prevent hepatic dyslipidemia and related inflammation for improved health.

Microbial torularhodin – a comprehensive review

The demand for food, feed, cosmeceutical, and nutraceutical supplements/additives from natural sources has been rapidly increasing, with expectations for a faster expansion than the growth of the global markets in the coming years. In this framework, a particular interest is given to carotenoids due to their outstanding antioxidant activities, particularly the xanthophylls class. Torularhodin is one of these carotenoids that stands out for its multifunctional role as: antioxidant, anticancer and antimicrobial, yet its commercial potential is still unexplored. Although most xanthophylls can be naturally found in: microbial, plant and animal sources, torularhodin is only produced by microbial species, especially red oleaginous yeast. The microbial production of xanthophylls has many advantages as compared to other natural sources, such as: the need for low production area, easier extraction, high yields (at optimum operating conditions), and low (or no) seasonal, climatic, and geographic variation dependency. Due to the importance of natural products and their relevance to the market, this review provides a comprehensive overview of the: properties, characteristics and potential health benefits of torularhodin. Moreover, the most promising developments in both upstream and downstream processing to obtain this colorant from microbial sources are considered. For this purpose, the main microorganisms used for torularhodin production are firstly reviewed, including biosynthesis pathway and torularhodin properties. Following, an overall analysis of the processing aspects related with its: extraction, separation and purification is provided. Lastly, current status and future trends of torularhodin-based processes and products such as therapeutic agents or biomaterials are discussed, indicating promising directions toward biorefinery and circular economy.

The impact of the physical form of torularhodin on its metabolic fate in the gastrointestinal tract

Torularhodin is a fungal carotenoid with multiple health benefits. However, the relationship between its physical form and metabolic fate in the gastrointestinal tract (GIT), which is essential to its bioavailability and health efficacy, has rarely been studied. Thus, physical forms of torularhodin including nanoemulsion powder (T-EP), capsules of the T-EP by alginate (T-EPA), and solution in MCT oil (T-oil) were used in the study. T-EP was produced through OSA-starch-mediated torularhodin emulsification and spray drying whereas the T-EPA was alginate-based capsules of the T-EP particles that were entrapped in the network structure of the alginate matrix as observed by scanning electron microscopy (SEM). The oil digestibility in the simulated small intestine was decreased from T-EP (100%), T-oil (60%) to T-EPA (40%), and the bioaccessibilities were 27%, 15% and 12%, respectively. The in vivo study using mice revealed that the content of torularhodin gradually decreased along with the digestion time in both the stomach and small intestine while a significantly higher colonic accumulation was observed in T-EPA compared to T-oil and T-EP. In vitro fecal fermentation showed that propionate (32 mM) was the predominant metabolite produced by torularhodin in the physical form of T-EPA. Thus, the physical form of torularhodin is a significant contributing factor to its GIT metabolic fate, and a health outcome-oriented design of the physical form of torularhodin or other nutraceuticals is beneficial for the development of functional foods with enhanced health benefits.

Genomics and lipidomics analysis of the biotechnologically important oleaginous red yeast Rhodotorula glutinis ZHK provides new insights into its lipid and carotenoid metabolism

Background

Rhodotorula glutinis is recognized as a biotechnologically important oleaginous red yeast, which synthesizes numerous meritorious compounds with wide industrial usages. One of the most notable properties of R. glutinis is the formation of intracellular lipid droplets full of carotenoids. However, the basic genomic features that underlie the biosynthesis of these valuable compounds in R. glutinis have not been fully documented. To reveal the biotechnological potential of R. glutinis, the genomics and lipidomics analysis was performed through the Next-Generation Sequencing and HPLC-MS-based metabolomics technologies.

Results

Here, we firstly assemble the genome of R. glutinis ZHK into 21.8 Mb, containing 30 scaffolds and 6774 predicted genes with a N50 length of 14, 66,672 bp and GC content of 67.8%. Genome completeness assessment (BUSCO alignment: 95.3%) indicated the genome assembly with a high-quality features. According to the functional annotation of the genome, we predicted several key genes involved in lipids and carotenoids metabolism as well as certain industrial enzymes biosynthesis. Comparative genomics results suggested that most of orthologous genes have underwent the strong purifying selection within the five Rhodotorula species, especially genes responsible for carotenoids biosynthesis. Furthermore, a total of 982 lipids were identified using the lipidomics approaches, mainly including triacylglycerols, diacylglyceryltrimethylhomo-ser and phosphatidylethanolamine.

Conclusion

Using whole genome shotgun sequencing, we comprehensively analyzed the genome of R. glutinis and predicted several key genes involved in lipids and carotenoids metabolism. By performing comparative genomic analysis, we show that most of the ortholog genes have undergone strong purifying selection within the five Rhodotorula species. Furthermore, we identified 982 lipid species using lipidomic approaches. These results provided valuable resources to further advance biotechnological applications of R .glutinis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-020-07244-z.

Torularhodin from Sporidiobolus pararoseus Attenuates d-galactose/AlCl3-Induced Cognitive Impairment, Oxidative Stress, and Neuroinflammation via the Nrf2/NF-κB Pathway

Oxidative stress and neuroinflammation are considered as crucial culprits in Alzheimer's disease (AD). Torularhodin, a carotenoid pigment, possesses powerful antioxidant activity. This study aimed to elucidate the protective effects of torularhodin in the AD-like mouse model and investigated the underlying mechanisms. Behavioral and histopathological results suggested that torularhodin relieved cognitive impairments, attenuated Aβ accumulation, and inhibited glial overactivation in d-gal/AlCl₃-induced ICR mice. Simultaneously, torularhodin also markedly increased antioxidant enzyme capacities, lowered the contents of RAGE, and reduced levels of inflammatory cytokines. Western blot results showed that torularhodin ameliorated neuronal oxidative damage via activation of Nrf2 translocation, upregulation of HO-1, and inactivation of NF-κB in vivo and in vitro. Thus, torularhodin effectively ameliorated cognitive impairment, oxidative stress, and neuroinflammation, possibly through the Nrf2/NF-κB signaling pathways, suggesting torularhodin might offer a promising prevention strategy for neurodegenerative diseases.

Analysis of carotenoid profile changes and carotenogenic genes transcript levels in Rhodosporidium toruloides mutants from an optimized Agrobacterium tumefaciens-mediated transformation method

Rhodosporidium toruloides has been reported as a potential biotechnological microorganism to produce carotenoids. The most commonly used molecular and genetic manipulation methods based on Agrobacterium-mediated transformation (ATMT). However, this method was of relatively lower transformation efficiency. In this study, we optimized the ATMT method for R. toruloides on account of the promoter on T-DNA, the ratio of A. tumefaciens to R. toruloides NP11, acetosyringone concentration, cocultivation temperature and time, and a transformation efficiency of 2,369 cells per 10⁵ recipient cells was obtained and was 24 times as that of the previous report. With this optimized method, four redder mutants and four yellower mutants were selected out with torularhodin and β-carotene production preference, respectively. The highest torularhodin production was 1,638.15 µg/g dry cell weight in A1-13. The yellower mutants were found to divert the metabolic flux from torularhodin and torulene to γ-carotene and β-carotene, and the proportion of γ-carotene and β-carotene were all over 92%. TAIL-PCR was carried out to found T-DNA insertion in these mutants, and insertion hotspot was found. RT-qPCR results showed that CTA1 genes in these mutants were closely related to the synthesis of total carotenoids, especially torularhodin, and was a potenial metabolic engineering site in the future.

Torularhodin Ameliorates Oxidative Activity in Vitro and d-Galactose-Induced Liver Injury via the Nrf2/HO-1 Signaling Pathway in Vivo

Torularhodin is a natural product extracted from Sporidiobolus pararoseus and has a similar chemical structure to β-carotene. The antioxidative effects of torularhodin were investigated using DPPH, ABTS, a cell oxidative damage model in vitro, and a d-galactose-induced liver-injured mouse model in vivo. Cell experiments demonstrated that torularhodin had a powerful effect on oxidative damage caused by H₂O₂ to AML12 cells. Torularhodin significantly reduced inflammatory cytokines and increased the activity of antioxidant enzymes both in mouse serum and the liver. The inhibition of d-galactose-induced oxidative damage in the liver was correlated with the torularhodin-mediated effects on improving the activity of Nrf2/HO-1, reducing the expression of Bax and NF-κB p65 by western blot analysis. RT-PCR results demonstrated torularhodin upregulated the antioxidative mRNA expression of Nrf2, NQO1, and HO-1 in the liver. In summary, torularhodin significantly scavenged free radicals and prevented oxidative damage in vitro and reduced d-galactose-induced liver oxidation via promotion of the Nrf2/HO-1 pathways in vivo.

Ameliorating effects of Sporidiobolus pararoseus extract on dyslipidemia in mice with high fat diet induced obesity

The study investigated how an extract of Sporidiobolus pararoseus (S.p.) affects lipid metabolism in Kunming mice that were obese as a result of being fed a high-fat diet; the control group were administered Max EPA fish oil. Ten mice were randomly selected from a pool of 60 mice for the control group and the remaining 50 mice were fed with a high-fat diet to establish a dyslipidemia model. After 4 weeks, these 50 mice were randomly distributed among 5 groups: high-fat model group; Max EPA group; and 3 groups of mice fed different doses of S.p. extract (low dose, medium dose, and high dose). After 8 weeks, the mice were sacrificed and the relevant parameters were measured. Compared with the high-fat model group, the group administered the high dose of S.p. extract showed significantly decreased body mass and serum levels of total cholesterol, triglycerides, and low-density lipoprotein cholesterol, and increased levels of high-density lipoprotein cholesterol. The results from RT-PCR showed that the mRNA expression of sterol regulatory element-binding protein 1c, fatty acid synthesis enzyme, and acetyl-CoA carboxylase was lower in the groups supplemented with S.p. extract than in the high-fat model group, whereas the expression of carnitine palmitoyltransferase 1 was higher in the group supplemented with S.p. extract than in the high-fat model group. Our results suggest that taking S.p. extract could benefit patients with dyslipidemia. Therefore, S.p. extract should be developed as a dietary supplement to improve lipid metabolism in obese people.

Torulene and torularhodin: "new" fungal carotenoids for industry?

Torulene and torularhodin represent the group of carotenoids and are synthesized by yeasts and fungi. The most important producers of these two compounds include yeasts of Rhodotorula and Sporobolomyces genera. The first reports confirming the presence of torulene and torularhodin in the cells of microorganisms date to the 1930s and 1940s; however, only in the past few years, the number of works describing the properties of these compounds increased. These compounds have strong anti-oxidative and anti-microbial properties, and thus may be successfully used as food, feedstock, and cosmetics additives. In addition, tests performed on rats and mice showed that both torulene and torularhodin have anti-cancerous properties. In order to commercialize the production of these two carotenoids, it is necessary to obtain highly efficient yeast strains, for example, via mutagenization and optimization of cultivation conditions. Further studies on the activity of torulene and torularhodin on the human body are also needed.

Torulene and torularhodin, protects human prostate stromal cells from hydrogen peroxide-induced oxidative stress damage through the regulation of Bcl-2/Bax mediated apoptosis

The current study was designed to elucidate the cytoprotective effects and possible mechanisms of torulene and torularhodin on hydrogen peroxide (H₂O₂)-induced oxidative stress damage in human prostate stromal cells (WPMY-1). After treated with H₂O₂, a notable decrease was appeared in cell viability, yet the decrease was attenuated when cells were pretreated with torulene and torularhodin (0.5-10 μM) as evaluated by WST-1 assay. Pretreatment with these two carotenoids significantly attenuated H₂O₂-induced apoptosis in WPMY-1 cells through the inhibition of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) overproduction, as well as the activation of the activities in catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px). Finally, pretreatment of cells with carotenoids resulted in the regulation of the mRNA and protein expression of Bcl-2 and Bax in H₂O₂-exposed prostate stromal cells. The present results indicate that both torulene and torularhodin can protect human prostate stromal cells from oxidative stress damage via Bcl-2/Bax mediated apoptosis.