Daily consumption of one teaspoon of trehalose can help maintain glucose homeostasis: a double-blind, randomized controlled trial conducted in healthy volunteers.

BACKGROUND: Trehalose is a natural disaccharide that is widely distributed. A previous study has shown that daily consumption of 10 g of trehalose improves glucose tolerance in individuals with signs of metabolic syndrome. In the present study, we determined whether a lower dose (3.3 g/day) of trehalose improves glucose tolerance in healthy Japanese volunteers. METHODS: This was a randomized, double-blind, placebo-controlled study of healthy Japanese participants (n = 50). Each consumed 3.3 g of trehalose (n = 25) or sucrose (n = 25) daily for 78 days. Their body compositions were assessed following 0, 4, 8, and 12 weeks; and serum biochemical parameters were assayed and oral 75-g glucose tolerance tests were performed at baseline and after 12 weeks. RESULTS: There were similar changes in body composition and serum biochemistry consistent with established seasonal variations in both groups, but there were no differences in any of these parameters between the two groups. However, whereas after 12 weeks of sucrose consumption, the plasma glucose concentration 2 h after a 75-g glucose load was significantly higher than the fasting concentration, after 12 weeks of trehalose consumption the fasting and 2-h plasma glucose concentrations were similar. Furthermore, an analysis of the participants with relatively high postprandial blood glucose showed that the plasma glucose concentration 2 h after a 75-g glucose load was significantly lower in the trehalose group than in the sucrose group. CONCLUSIONS: Our findings suggest that trehalose helps lower postprandial blood glucose in healthy humans with higher postprandial glucose levels within the normal range, and may therefore contribute to the prevention of pathologies that are predisposed to by postprandial hyperglycemia,, even if the daily intake of trehalose is only 3.3 g, an amount that is easily incorporated into a meal. TRIAL REGISTRATION: UMIN, UMIN000033536 . Registered 27 July 2018.

Trehalose itself plays a critical role on lipid metabolism: Trehalose increases jejunum cytoplasmic lipid droplets which negatively correlated with mesenteric adipocyte size in both HFD-fed trehalase KO and WT mice.

BACKGROUND: Trehalose is a functional disaccharide that has anti-metabolic activities such as suppression of adipocyte hypertrophy in mice and alleviation of impaired glucose tolerance in humans. Trehalase hydrolyzes trehalose in the small intestine into two glucose molecules. In this study, we investigated whether trehalose can suppress adipocyte hypertrophy in mice in the presence or absence of trehalase. METHODS: Trehalase knockout (KO) mice and wild-type (WT) mice were fed a high fat diet (HFD) and administered water with 0.3% (w/v) or without trehalose for 8 weeks. At the end of the experimental period, mesenteric adipose tissues and the small intestine were collected and the adipocyte size and proportion of cytoplasmic lipid droplets (CLDs, %) in jejunum epithelium were measured by image analysis. RESULTS: Trehalose treatment was associated with suppressed adipocyte hypertrophy in both trehalase KO and WT mice. The rate of CLDs in the jejunal epithelium was increased in both trehalase KO and WT mice given water containing trehalose relative to untreated control mice. There was a negative correlation between jejunal epithelial lipid droplet volume and mesenteric adipocyte size. Chylomicron-TG tended to be decreased in both trehalose-treated trehalase KO and WT mice. Addition of trehalose to differentiated Caco-2 cells in vitro increased intracytoplasmic lipid droplets and decreased secretion of the chylomicron marker ApoB-48. Moreover, the jejunal epithelium containing lipid droplets falled into the intestinal lumen, and triglyceride (TG) levels in feces tended to be higher in the KO/HFD/Tre group than in the KO/HFD/Water group. Since then, the accumulation of CLDs has been reported to suppress CM secretion, and along with our results, the effect of trehalose to increase jejunum CLDs may induce adipocyte hypertrophy. CONCLUSIONS: The suppression of adipocyte hypertrophy in the presence and absence of trehalase indicates that trehalose mediates effects prior to being hydrolyzed into glucose. In both trehalase KO and WT mice, trehalose treatment increased the rate of CLDs in jejunal epithelium, reduced chylomicron migration from the intestinal epithelium to the periphery, and suppressed adipocyte hypertrophy. Thus, trehalose ingestion could prevent metabolic syndrome by trapping fat droplets in the intestinal epithelium and suppressing rapid increases in chylomicrons.

Author Correction: Efficient increase of ɣ-aminobutyric acid (GABA) content in tomato fruits by targeted mutagenesis.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Continuous intake of Trehalose induces white adipose tissue Browning and Enhances energy metabolism.

BACKGROUND: Trehalose is well known as a functional disaccharide with anti-metabolic activities such as suppression of adipocyte hypertrophy in mice and alleviation of impaired glucose tolerance in humans. Recently, a new type of adipocyte beige cells, involved in so-called white adipocyte tissue (WAT) browning, has received much attention as a target for adaptive thermogenesis. To clarify the relationship between adipocyte hypertrophy suppression and beige cells involved in thermogenesis, we examined the effect of trehalose on the changes in beige adipocytes in mice under normal dietary conditions. METHODS: Mice fed a normal diet were administered water containing 0.3% (W/V) trehalose for 16 weeks, 0.3% (W/V) maltose, or water without saccharide (controls). Body temperature and non-fasting blood glucose levels were measured every 3 weeks. After 16 weeks of these treatments, mesenteric and inguinal adipose tissues were collected for measuring adipocyte size, counting the number of UCP1 positive cells by image analysis, and preparing mRNA to analyze beige adipocyte-related gene expression. RESULTS: Mice administered a continuous intake of trehalose exhibited a thermogenic ability as represented by an increase in rectal temperature, which was maintained at a relatively high level from 3 to 9 weeks and was significantly higher at 15 weeks in comparison with that of the maltose group. In addition to the reduced hypertrophy of mesenteric and inguinal adipose tissues, the trehalose group showed a significant increase in the rates of beige adipocytes in each WAT in comparison with those of the maltose and the water groups. Interestingly, a negative correlation was found between the mean cell sizes of adipocytes and the rates of beige adipocytes in the WAT. Furthermore, real-time PCR showed that the expression of Cidea and Ucp1 mRNAs, which are markers for beige adipocytes in the inguinal adipose tissue, increased in the trehalose group. CONCLUSIONS: Continuous administration of trehalose to mice fed a normal diet induced WAT browning accompanied by suppression of white adipocyte hypertrophy, elevated body temperature and decreased blood glucose levels, which resulted in enhancement of energy metabolism. Therefore, we propose trehalose as a new type of thermogenic dietary component to prevent obesity by promoting WAT browning.

Efficient increase of ɣ-aminobutyric acid (GABA) content in tomato fruits by targeted mutagenesis.

γ-Aminobutyric acid (GABA) is a non-proteinogenic amino acid that has hypotensive effects. Tomato (Solanum lycopersicum L.) is among the most widely cultivated and consumed vegetables in the world and contains higher levels of GABA than other major crops. Increasing these levels can further enhance the blood pressure-lowering function of tomato fruit. Glutamate decarboxylase (GAD) is a key enzyme in GABA biosynthesis; it has a C-terminal autoinhibitory domain that regulates enzymatic function, and deleting this domain increases GAD activity. The tomato genome has five GAD genes (SlGAD1-5), of which two (SlGAD2 and SlGAD3) are expressed during tomato fruit development. To increase GABA content in tomato, we deleted the autoinhibitory domain of SlGAD2 and SlGAD3 using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas)9 technology. Introducing a stop codon immediately before the autoinhibitory domain increased GABA accumulation by 7 to 15 fold while having variable effects on plant and fruit size and yield. This is the first study describing the application of the CRISPR/Cas9 system to increase GABA content in tomato fruits. Our findings provide a basis for the improvement of other types of crop by CRISPR/Cas9-based genetic modification.

Trehalose prevents adipocyte hypertrophy and mitigates insulin resistance in mice with established obesity.

Our group recently demonstrated that simultaneous administration of trehalose with a high-fat diet (HFD) suppresses adipocyte hypertrophy and mitigates insulin resistance in mice. For the present study, we hypothesized that similar effects of trehalose would be observed in mice with previously-established obesity. Obese mice were fed a HFD and drinking water containing 0.3 or 2.5% (weight/volume) trehalose or distilled water (DW) ad libitum for 8 wk. After 7 wk intake of a HFD and trehalose, fasting serum insulin levels and homeostasis model assessment-insulin resistance (HOMA-IR) in the 0.3% Tre/HFD group were significantly lower than those in the DW/HFD group (p<0.05). After 8 wk of treatment, mesenteric adipocytes in the 0.3% Tre/HFD group showed significantly less hypertrophy than those in the DW/HFD group. Mechanistic analysis indicated that levels of high molecular weight (HMW) adiponectin in the serum of the 0.3% Tre/HFD group were significantly higher than those in the DW/HFD group. The expression levels of insulin receptor substrate-1 (IRS-1) and insulin receptor substrate-2 (IRS-2) messenger RNA (mRNA) in muscle were also significantly increased by trehalose intake. Our data therefore suggest that administration of trehalose to obese mice mitigates insulin resistance by suppressing adipocyte hypertrophy and increasing serum HMW adiponectin, resulting in upregulation of IRS-1, and IRS-2 expression in muscle. These results further suggest that trehalose is a functional saccharide that may be used to prevent the progression of insulin resistance.

Trehalose prevents adipocyte hypertrophy and mitigates insulin resistance.

Trehalose has been shown to evoke lower insulin secretion than glucose in oral saccharide tolerance tests in humans. Given this hypoinsulinemic effect of trehalose, we hypothesized that trehalose suppresses adipocyte hypertrophy by reducing storage of triglyceride and mitigates insulin resistance in mice fed a high-fat diet (HFD). Mice were fed an HFD and given drinking water containing 2.5% saccharide (glucose [Glc], trehalose [Tre], maltose [Mal], high-fructose corn syrup, or fructose [Fru]) ad libitum. After 7 weeks of HFD and saccharide intake, fasting serum insulin levels in the Tre/HFD group were significantly lower than in the Mal/HFD and Glc/HFD groups (P < .05). Furthermore, the Tre/HFD group showed a significantly suppressed elevation of homeostasis model assessment-insulin resistance compared with the Mal/HFD group (P < .05) and showed a trend toward lower homeostasis model assessment-insulin resistance than the Glc/HFD group. After 8 weeks of feeding, mesenteric adipocyte size in the Tre/HFD group showed significantly less hypertrophy than the Glc/HFD, Mal/HFD, high-fructose corn syrup/HFD, or Fru/HFD group. Analysis of gene expression in mesenteric adipocytes showed that no statistically significant difference in the expression of monocyte chemoattractant protein-1 (MCP-1) messenger RNA (mRNA) was observed between the Tre/HFD group and the distilled water/standard diet group, whereas a significant increase in the MCP-1 mRNA expression was observed in the Glc/HFD, Mal/HFD, Fru/HFD, and distilled water/HFD groups. Thus, our data indicate that trehalose prevents adipocyte hypertrophy and mitigates insulin resistance in HFD-fed mice by reducing insulin secretion and down-regulating mRNA expression of MCP-1. These findings further suggest that trehalose is a functional saccharide that mitigates insulin resistance.

The effect of AgK114 on wound healing.

AgK114 is a newly isolated membrane-associated protein which is expressed on keratinocytes. Its expression is restricted to dermal sheath cells near sebaceous glands in normal skin. However, it is transiently induced by UV exposure or injury stimulation (Tatefuji T. et al., Biol. Pharm. Bull., 27, 1742-1749, 2004). Thus, the expression pattern of AgK114 suggested its potential role in wound healing response. We report here that expression of AgK114 is induced in the initial 24 h at the edge keratinocytes during keratinocyte migration, followed by disappearance once epithelialization is completed in the murine excisional wound model. We also demonstrate that exogenous recombinant mouse AgK114FL promoted wound healing process. Mouse AgK114FL up-regulated pro-matrix-metalloproteinase-9, vascular endothelial growth factor, transforming growth factor-beta, IL-6, and IL-1beta production in the early stage of wound tissue. Moreover, mouse AgK114FL induced the matrix-metalloproteinase-9 activity of wound fibroblasts prepared from impaired skin in the presence of proinflammatory cytokines. These results suggest that the AgK114 participates in the wound response during the healing process, and promotes wound repair.

Effect of AgK114 on picryl chloride-induced chronic contact hypersensitivity responses.

BACKGROUND: Mouse AgK114 (a glycosylphosphatidylinositol (GPI) anchored membrane-associated protein) expression is found in somatotrophs of the pituitary gland in correlation with the expression of growth hormone. In this study, the effects of AgK114 on the systemic immune response were examined in contact hypersensitivity (CHS) model mice. MATERIALS AND METHODS: AgK114 was intraperitoneally injected into BALB/c mice that were sensitized and challenged with picryl chloride (PiCl). Serum IgE levels and the antigen-specific cytokine production by lymph node (LN) cells were examined. RESULTS: The serum IgE levels in the CHS mice treated with 10 microg/head of AgK114 during the repeated challenge with PiCl were significantly decreased compared with those of the control mice. Moreover, IL-4 production by LN cells in response to 2,4,6-trinitrobenzene-sulfonic acid sodium salt-treated splenocytes was decreased in the AgK114-treated CHS mice compared with that of the control mice. CONCLUSION: Our results suggest that systemic administration of AgK114 exerted immunoregulatory functions on the allergic responses, resulting in the inhibition of IgE production.

mAgK114 suppresses lymphocyte infiltration into epidermis in the picryl chloride-induced atopic dermatitis-like skin lesions of NC/Nga mice.

BACKGROUND: We have previously shown that when mouse AgK114 (mAgK114, a glycosylphosphatidylinositol anchored membrane-associated protein) is applied to the wound area, the inflammatory responses in the early recovery phase of damaged tissue are enhanced and wound closure is accelerated. This suggests that mAgK114 has an important effect on skin wound repairing. MATERIALS AND METHODS: Whether mAgK114 supresses the development, in NC/Nga mice, of atopic dermatitis (AD)-like skin lesions induced by repeated application of 2,4,6-trinitrochlorobenzene (picryl chloride, PiCl) was examined under specific pathogen-free conditions. RESULTS: Histopathologically, the application of mAgK114-ointment to the PiCl-treated NC/Nga mice remarkably suppressed severe lymphocytic infiltration into the epidermis, although total skin severity scores, histological changes in hypertrophy, erosion and infiltration of inflammatory cells into the corium and subcutaneous tissues were comparable between the mAgK114-treated group of mice and the control group. CONCLUSION: Our results suggest that mAgK114 would be beneficial for the treatment of atopic dermatitis by suppressing severe lymphocytic infiltration into the epidermis.

Identification of the novel membrane-associated protein AgK114 on hamster keratinocytes recognized by a monoclonal antibody K114.

We have established a monoclonal antibody K114 (mAbK114) against hamster keratinocytes. The mAbK114 recognizes a 50-95 kDa cell-surface protein that is expressed restrictedly in the dermal sheath cells near the bulge area of the hair follicle and in the differentiated sebocytes of the normal adult hamster skin. Upon being cultured in vitro, however, the keratinocytes strongly and transiently expressed this novel K114 antigen (AgK114) in spite of low expression level of AgK114 by the freshly prepared keratinocytes. The cDNA of AgK114 was isolated by expression cloning using mAbK114. Sequence analysis revealed that it had 242 amino acid residues with a signal peptide at the N terminus, potential six N-glycosylation sites, a characteristic repetitive threonine rich domain, and a possible glycosylphosphatidylinositol (GPI) anchoring site near the C terminus. We examined various conditions in which expression of AgK114 was enhanced in vivo. Interestingly, AgK114 molecule was expressed accompanying tissue damages of the skin. It was transiently induced in basal epidermal keratinocytes after UV exposure. In addition, AgK114 was also induced in elongating edge epidermal keratinocytes during tissue regeneration after an excised wounding. These results suggest that AgK114 is involved in the recovering process from injury.

Trehalose augments osteoprotegerin production in the FHs74Int human intestinal epithelial cell line.

The disaccharide trehalose has been shown to inhibit both bone loss in ovariectomized mice and excessive osteoclastogenesis in lipopolysaccharide-injected mice. However, the mechanism of osteoclastogenesis inhibition by oral administration of trehalose is still unclear. We report here for the first time that a human intestinal epithelial cell line, FHs74Int, also produces osteoprotegerin (OPG) and that trehalose augments OPG production by this cell line. Thus, these results suggest that trehalose promotes the production of OPG by intestinal epithelial cells, which then acts on bone marrow cells, resulting in the suppression of osteoclastogenesis.