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

Investigation of the Neuroprotective Action of Japanese Sake Yeast on Dementia Type of Alzheimer Disease in Rats: Behavioral and Neurobiochemical Assessment

Dementia involves several factors, and it is required to administer an agent with several efficiencies for its treatment. Sake is known to have antioxidant and anti-inflammatory properties and improves the serum concentration of BDNF. This study aimed to evaluate the neuroprotective action of Japanese sake yeast on dementia of the Alzheimer disease type in rats by behavioral evaluation and neurobiochemical assessment. The rats were grouped as non-Alzheimer rats (control rats) and Alzheimer rats administrated with 0 (AD), 10 (10-AD), 20 (20-AD), 30 (30-AD), and 40 mg/kg (40-AD) of sake. Anxiety-like and depression-like behaviors, the concentrations of brain-derived neurotrophic factor (BDNF), malondialdehyde (MDA), and ferric reducing ability of plasma (FRAP) were evaluated. The expressions of IL-1β, TNF-α, and IL-6 were assessed. The results showed that Alzheimer disease caused anxiety-like and depression-like behaviors (p = 0.000), decreased the concentrations of BDNF (p = 0.000) and FRAP (p = 0.000), increased the concentration of MDA (p = 0.000), and increased the expressions of IL-1β (p = 0.000), TNF-α (p = 0.000), and IL-6 (p = 0.000). The results showed that oral gavage of sake in higher doses decreased anxiety-like and depression-like behaviors (p = 0.000), increased the concentrations of BDNF (p = 0.000) and FRAP (p = 0.000), and reduced the concentration of MDA (p = 0.000) and the expressions of IL-1β (p = 0.000), TNF-α (p = 0.000), and IL-6 (p = 0.000). In sum, Japanese sake yeast can have roles in treating dementia of the Alzheimer disease type, but its mechanisms must be assessed in future studies.

Protective Mechanism of Rice-Derived Lipids and Glucosylceramide in an In Vitro Intestinal Tract Model

We previously reported that the ethanol extract from polished rice suppresses inflammation and the formation of aberrant crypt foci in the mouse colon and particularly focused on the plant sphingolipid glucosylceramide (GlcCer). Here, we investigated the effects of rice lipid fractions and GlcCer on differentiated Caco-2 cells treated with lipopolysaccharide (LPS), in particular, we evaluated the mechanism of action of GlcCer using related substances and metabolic enzyme inhibitors. Rice-derived polar lipids suppressed the LPS-induced reduction in the number of cells. The polar lipids with higher GlcCer content exerted a better effect than the other fractions. GlcCer-related substances reversed the LPS-induced reduction in the number of cells, and GlcCer-metabolic inhibitors, including a sphingosine kinase inhibitor, suppressed the beneficial effects of GlcCer-related substances. These results suggest that GlcCer is a rice component with intestinal protection. Secondly, GlcCer is metabolized during inflammation and protects intestinal cells by maintaining the sphingolipid levels in cells and producing sphingoid base-1-phosphate.

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.