Sake (Rice Wine) Brewing Hydrolyzes Highly Polar Sphingolipids to Ceramides and Increases Free Sphingoid Bases

In plants and fungi, sphingolipids, characterized by the presence of a sphingoid base (SB), comprise neutral classes, including ceramide (Cer) and glucosylceramide (GlcCer), and acidic classes, including glycosyl inositol phosphoryl ceramide (GIPC). The major class of plant and fungal sphingolipids is GIPC; however, owing to their complicated extraction and analysis, there is still little information regarding the food characteristics of GIPC compounds. In the present study, we evaluated the content and SB composition of highly polar sphingolipids (HPS) in materials that had been obtained from our previous food processing study for GlcCer and Cer. This assessment was based on the changes that occur in HPS containing GIPC in sake rice (saka-mai) during the rice polishing and sake (rice wine) brewing process. In addition, we report a new investigation into the composition of sphingolipids in koji rice and sake yeast. HPS levels were the highest among the sphingolipid classes in brown rice cultivars and highly polished rice. Sake and sake lees (sake-kasu) were produced using three different starter cultures. In sake lees, Cer levels were the highest among the classes, while HPS was greatly reduced based on the amount of highly polished rice and koji rice, and these HPS were mainly composed of sphinganine (d18:0), which is a minor SB in highly polished rice, koji rice, and sake yeast. In addition, considerable levels of free SBs, mainly comprising d18:0, were detected in sake lees. The levels of HPS and free SBs in sake lees were dependent on the starter culture. These results suggest that HPS was hydrolyzed to Cer and that sake yeast also affected the levels of Cer and free SBs during brewing. One interesting question raised by these results is whether changes in the class and base compositions of sphingolipids during brewing contribute to taste of the final product and other food functions.

Dietary Sphingolipids Contribute to Health via Intestinal Maintenance

As sphingolipids are constituents of the cell and vacuole membranes of eukaryotic cells, they are a critical component acquired from our daily diets. In the present review, we highlight the knowledge regarding how dietary sphingolipids affect our health, particularly our intestinal health. Animal- and plant-derived foods contain, respectively, sphingomyelin (SM) and glucosylceramide (GlcCer) as their representative sphingolipids, and the sphingoid base as a specific structure of sphingolipids also differs depending upon the source and class. For example, sphingosine is predominant among animal sphingolipids, and tri-hydroxy bases are present in free ceramide (Cer) from plants and fungi. Dietary sphingolipids exhibit low absorption ratios; however, they possess various functions. GlcCer facilitates improvements in intestinal impairments, lipid metabolisms, and skin disorders, and SM can exert both similar and different effects compared to those elicited by GlcCer. We discuss the digestion, absorption, metabolism, and function of sphingolipids while focused on the structure. Additionally, we also review old and new classes in the context of current advancements in analytical instruments.

Sphingolipid Properties in Sake Rice Cultivars and Changes During Polishing and Brewing

Sphingolipids, including ceramide (Cer) and glucosylceramide (GlcCer), have the characteristic structural units called sphingoid bases, and are constituents of cell and vacuole membranes. Plant sphingolipids bear highly diverse base structures and the base composition differs depending on the plant species. It is thought that the composition of sphingolipid classes and sphingoid bases is related to membrane fractions. However, there is little information about differences in sphingolipids among plant cultivars and the changes occurring in sphingolipids during food processing. This study investigated sphingolipids in sake rice (saka-mai) cultivars grown for sake (rice wine), and the changes in sphingolipids during polishing and brewing. In six brown rice samples, there were no large differences of the base composition among Cer or GlcCer of cultivars, whereas there were differences in their sphingolipid contents. When compared to brown rice, highly polished rice contained lower levels of sphingolipids, especially Cer. For three rice brans from different polishing steps, the Cer content was higher in the outer bran than in the inner bran. Sake and sake lees (sake-kasu) were produced by three different starter cultures (shubo preparations: the mixture of koji rice as an enzyme cocktail containing amylases, sake yeast, and adding rice as a carbohydrate source). The Cer/GlcCer ratio in sake and sake lees depended on the starter culture; Cer and GlcCer in sake lees possessed a fungi-specific base, 9-methyl-trans-4,trans-8- sphingadienine. In addition, sake lees had a higher Cer/GlcCer ratio when compared to highly polished rice as a sake source. These results suggest that the sphingolipid content of brown rice differs depending on the rice cultivar; further, the sphingolipids and the sphingolipid composition in sake and sake lees are affected by fungal sphingolipids and self-digestion during brewing.

Polar Lipid Fraction from Golden Oyster Mushrooms (Pleurotus citrinopileatus) Suppresses Colon Injuries from Inflammatory Stresses in vivo and in vitro

The rising incidence of inflammatory bowel disease (IBD) in East Asian countries has necessitated the implementation of preventive methods in the form of dietary supplementation and changes in dietary habits. We have previously reported that dietary golden oyster mushroom (Pleurotus citrinopileatus) ethanol extract (GOMEE) suppresses intestinal inflammation in mouse models of IBD induced by dextran sulfate sodium salt (DSS). Here, we investigated the components of GOMEE that exert suppressive effects on colon inflammation in vivo and in vitro. The total lipid fraction was extracted from GOMEE, and the polar and neutral lipid fractions were subsequently separated via solvent fractionation. Mice were assigned to dietary groups-control, 1% total lipid, 1% polar lipid, or 1% neutral lipid diet-and fed the respective diets for one week; mice were administered 1.5% DSS in drinking water ad libitum for 20 days. Dietary supplementation with the total or polar lipid fraction alleviated DSS-induced chorionic crypt injury as determined by morphological observation, while dietary supplementation with the neutral lipid fraction did not produce such effects. In the in vitro study, using differentiated Caco-2 cells as the colon model, treatment with the total or polar lipid fraction suppressed cell decrease by lipopolysaccharide (LPS)-induced apoptosis whereas treatment with the neutral lipid fraction did not. Moreover, accumulation of glucosylceramide (GlcCer), a fungal sphingolipid, was observed in the intestinal cells after treatment with polar lipid fraction. These results suggest that the active components of GOMEE that suppress colon inflammation are polar lipids, especially GlcCer. The structure of mushroom GlcCer differs from that of the plant counterpart and is therefore expected to exert different food functions.

Effects of Dietary Ethanol Extracts from Sake Rice and Sake Lees on Intestinal Impairment in Mice

Glucosylceramide (GlcCer), a major sphingolipid in plants and fungi, is known to have food functions, such as preventing intestinal impairment and enhancing the moisture content of skin. This study investigated the influence of fermentation on the composition and function of lipophilic components containing GlcCer in plant-based foods; we compared the effects of ethanol extracts from sake rice (SR) and sake lees (SL) on colon impairment in mice. GlcCer and ceramide (Cer) levels in SL were much higher than those in SR, and GlcCer in SL contained 9-methyl-trans-4,trans-8-sphingadienine as a fungi-specific sphingoid base. 1,2-dimethylhydrazine (DMH) treatment markedly increased the formation of aberrant crypt foci (ACF) and the levels of TNF-α and lipid oxidation in mice colons. However, dietary SR or SL significantly suppressed these DMH-induced changes, and SR demonstrated stronger effects than SL. In addition, dietary SR or SL suppressed the expression of apoptotic and anti-apoptotic proteins induced by DMH treatment. This study suggests that SR or SL intake could reduce colon ACF formation via the suppression of inflammation and oxidation-induced cell cycle disturbances. When compared to SR, the weaked effects of SL rich in GlcCer may be the result of the changes in sphingolipid composition (sphingoid base and Cer) and differences in the concentration of other bioactive compounds produced or digested during fermentation.

Effects of Sphingolipid Fractions from Golden Oyster Mushroom (Pleurotus citrinopileatus) on Apoptosis Induced by Inflammatory Stress in an Intestinal Tract in vitro Model

Previously, we reported that the polar lipid fraction from the golden oyster mushroom, Pleurotus citrinopileatus, suppresses colon injuries which result from apoptosis induced by inflammatory stresses in vivo and in vitro (Yamashita et al., J. Oleo Sci., 69, 751-757 (2020)). Here, we investigated the use of lipid classes in mushroom polar lipid fraction in alleviating colon injury using differentiated Caco-2 cells as an intestinal tract model. The mushroom polar lipid fraction was separated into four fractions using silica thin layer chromatography. Each mushroom polar lipid fraction suppressed lipopolysaccharide (LPS)-induced decreases in the viability of intestinal cells, and the effects of sphingolipid fractions were significantly stronger than those of fraction that did not contain sphingolipids. Addition of sphingolipid fractions suppressed the expression of apoptosis-related proteins (e.g., death receptors and caspases) in the LPS-treated cells. Mushroom polar lipids, especially sphingolipids suppress intestinal apoptosis induced by inflammatory stress, and highly polar sphingolipids may exert stronger suppressive effects.

Glycosylceramide modifies the flavor and metabolic characteristics of sake yeast

In the manufacture of sake, Japanese traditional rice wine, sake yeast is fermented with koji, which is steamed rice fermented with the non-pathogenic fungus Aspergillus oryzae. During fermentation, sake yeast requires lipids, such as unsaturated fatty acids and sterols, in addition to substances provided by koji enzymes for fermentation. However, the role of sphingolipids on the brewing characteristics of sake yeast has not been studied. In this study, we revealed that glycosylceramide, one of the sphingolipids abundant in koji, affects yeast fermentation. The addition of soy, A. oryzae, and Grifola frondosa glycosylceramide conferred a similar effect on the flavor profiles of sake yeast. In particular, the addition of A. oryzae and G. frondosa glycosylceramide were very similar in terms of the decreases in ethyl caprylate and ethyl 9-decenoate. The addition of soy glycosylceramide induced metabolic changes to sake yeast such as a decrease in glucose, increases in ethanol and glycerol and changes in several amino acids and organic acids concentrations. Tricarboxylic acid (TCA) cycle, pyruvate metabolism, starch and sucrose metabolism, and glycerolipid metabolism were overrepresented in the cultures incubated with sake yeast and soy glycosylceramide. This is the first study of the effect of glycosylceramide on the flavor and metabolic profile of sake yeast.

Effects of Asterias amurensis-derived Sphingoid Bases on the de novo Ceramide Synthesis in Cultured Normal Human Epidermal Keratinocytes

Asterias amurensis starfish provide several bioactive species in addition to being fishery waste. Glucosyl ceramides (GlcCers) were extracted from the viscera of these starfish and were isolated by silica gel column chromatography. Degraded GlcCers generated A. amurensis sphingoid bases (ASBs) that mainly consisted of the triene-type bases d18:3 and 9-methyl-d18:3. The effect of these bases on ceramide synthesis and content were analyzed using normal human epidermal keratinocytes (NHEKs). The bases significantly enhanced the de novo ceramide synthesis and gene expression in NHEKs for proteins, such as serine-palmitoyltransferase and ceramide synthase. Total ceramide, GlcCer, and sphingomyelin contents increased dramatically upon ASB treatment. In particular, GlcCer bearing very-long-chain fatty acids (≥C28) exhibited a significant content increase. These ASB-induced enhancements on de novo ceramide synthesis were only observed in undifferentiated NHEKs. This stimulation of the de novo sphingolipid synthesis may improve skin barrier functions.

4,8-Sphingadienine and 4-hydroxy-8-sphingenine activate ceramide production in the skin

Background

Ingestion of glucosylceramide improves transepidermal water loss (TEWL) from the skin, but the underlying mechanism by which a small amount of dietary glucosylceramide can vastly improve skin conditions remains unclear. In a previous report, glucosylceramides were shown to be digested to sphingoids, which were shown to be absorbed through the intestinal epithelium. Based on these observations, we hypothesized that sphingoids are the key molecules facilitating endogenous ceramide production. In this study, we assessed the effect of 4,8-sphingadienine (d18:2) and 4-hydroxy-8-sphingenine (t18:1), derived from konjac glucosylceramide, on stimulating ceramide production.

Methods

Konjac glucosylceramide acidolysis was performed using hydrochloric acid; the resulting d18:2 and t18:1 were fractionated by column chromatography. Real-time quantitative RT-PCR was performed to assess the effect of d18:2 and t18:1 on gene expression in normal human epidermal keratinocytes, while their effect on the nuclear receptor, peroxisome proliferator-activated receptor (PPAR)γ, was measured using a receptor-cofactor assay system. The effect of d18:2 and t18:1 on stimulating ceramide production was evaluated using HPTLC analysis in a 3-dimensional human skin model.

Results

We noted the upregulation of genes related to de novo ceramide synthesis as well as of those encoding the elongases of very long-chain fatty acids by d18:2 and t18:1, but not by glucosylceramide and 4-sphingenine. Both these sphingoids also facilitated the expression of PPARβ/δ and PPARγ; moreover, they also demonstrated ligand activity for PPARγ. These results indicated that d18:2 and t18:1 promote the differentiation of keratinocytes. Analysis of the lipids within the 3-dimensional human skin model indicated that treatment with d18:2 and t18:1 not only upregulated gene expression but also increased ceramide production.

Conclusions

The sphingoids d18:2 and t18:1 activated genes related to de novo ceramide synthesis and increased ceramide production, whereas glucosylceramide and 4-sphingenine could not. These results suggest that the effect of dietary glucosylceramides on the skin is mediated by d18:2 and t18:1.

Analysis and comparison of glucocerebroside species from three edible sea cucumbers using liquid chromatography-ion trap-time-of-flight mass spectrometry

Sphingolipids constitute a highly diverse and complex class of molecules and exhibit important physiological functions. Glucocerebrosides are anticipated to play a positive role in human nutrition. In this study, complicated glucocerebrosides from three specimens of edible sea cucumbers, specifically, Acaudina molpadioides, Cucumaria frondosa, and Apostichopus japonicus, were rapidly identified using liquid chromatography-ion trap-time-of-flight mass spectrometry (LCMS-IT-TOF), which is a powerful analysis tool. [M + H](+), [M + Na](+), and [M + H - H(2)O](+) in positive electrospray ionization (ESI) mode were used for MS/MS analysis to obtain product ion spectra. Various long-chain bases of glucocerebrosides were found in these sea cucumbers. Two of the most common long-chain bases were 2-amino-1,3-dihydroxy-4-heptadecene (d17:1) and 4,8-sphingadienine (d18:2), which were acylated to form saturated and monounsaturated nonhydroxy and monohydroxy fatty acids with 18-25 carbon atoms. The glucocerebroside molecular species were the most complicated in the sea cucumber C. frondosa and were the simplest in the sea cucumber A. molpadioides.