Soy yoghurts produced with efficient GABA (γ-aminobutyric acid)-producing Lactiplantibacillus plantarum ameliorate hyperglycaemia and re-establish gut microbiota in streptozotocin (STZ)-induced diabetic mice.

Soy yogurt has been gaining popularity as a vegan food produced simply by soymilk fermentation with proper microbial manipulation. It is well known that soy containing rich isoflavones is beneficial for ameliorating hyperglycaemic disorders. Soy fermentation can improve the bioavailability of these precious nutrients. Lactiplantibacillus plantarum is one of the most abundant and frequently isolated species in soymilk manufacturing. Soy yogurts produced with efficient GABA (γ-aminobutyric acid)-producing L. plantarum and the deglycosylating activity of L. plantarum were functionally assessed in a STZ-induced hyperglycaemic mouse model. Hyperglycaemic mice were assigned into groups and treated with daily gavage of either dH2O, soymilk, soy yoghurts produced with high GABA-producing L. plantarum GA30 (LPGA30), low GABA-producing L. plantarum PV30 (LPPV30) or the soy yoghurts fortified with additional 30 mg g-1 GABA counterparts (GA + GABA and PV + GABA groups). Except the dH2O group, all soy yoghurt groups retained body weight with improved glucose homeostasis, glucose tolerance test results and renal tissue integrity, while the soymilk group shows partial benefits. Plasma GABA concentrations in the daily soy yoghurt-supplemented groups (LPGA30 and LPPV30) plateaued at 5 times higher than the average 0.5 µM in dH2O and soymilk groups, and their GABA-fortified soy yoghurt counterparts (GA + GABA and PV + GABA) groups were accountable for the restored plasma insulin levels. Gut microbiome analysis revealed dysbiosis in STZ-induced hyperglycemic mice of the dH2O group with breached out facultative anaerobic Proteobacteria over the normal phyla Firmicutes and Bacteroidetes. Restored gut microbiota with transitionally populated Actinobacteria was demonstrated in the LPGA30 group but not in the LPPV30 group. Soy yoghurts produced with efficient GABA-producing L. plantarum GA30 showed exceptional benefits in modulating gut microbiota with dominant genera of Enterococcus, Lactobacillus and Bifidobacterium, and the presence of some minor beneficial microbial communities including Akkermansia muciniphila, Butyricicoccus pullicaecorum, Corynebacterium spp. and Adlercreutzia spp. Efficient GABA-producing L. plantarum GA30 fermented soymilk to produce soy yoghurts that exhibit profound synergistic protections over rich soy isoflavones to restore pancreatic ß-cell functions for insulin production in STZ-induced hyperglycaemic mice. Additionally, the probiotic role of GABA-producing L. plantarum in re-establishing healthy gut microbiota in hyperglycaemic mice implies a possible symbiotic relationship, awaiting further exploration.

Hepatoprotective effects of litchi (Litchi chinensis) procyanidin A2 on carbon tetrachloride-induced liver injury in ICR mice.

Drug tolerance, lacking liver regenerative activity and inconclusive inhibition of steatosis and cirrhosis by silymarin treatment during chronic liver injury have increased the demand for novel alternative or synergistic treatments for liver damage. Litchi fruit is abundant in polyphenolic compounds and is used in traditional Chinese medicine for treatments that include the strengthening of hepatic and pancreatic functions. Unique polyphenolic compounds obtained from litchi pericarp extract (LPE) were studied in vitro and in vivo for hepatoprotection. Epicatechin (EC) and procyanidin A2 (PA2) of LPE were obtained by fractionated-extraction from pulverized litchi pericarps. All fractions, including LPE, were screened against silymarin in carbon tetrachloride (CCl4)-treated murine embryonic liver cell line (BNL). The effects of daily gavage-feeding of LPE, silymarin (200 mg/kg body weight) or H2O in CCl4-intoxicated male ICR mice were evaluated by studying serum chemicals, liver pathology and glutathione antioxidative enzymes. The effects of EC and PA2 on liver cell regenerative activity were investigated using a scratch wound healing assay and flow cytometric cell cycle analysis; the results of which demonstrated that LPE protected BNL from CCl4-intoxication. Gavage-feeding of LPE decreased serum glutamic oxaloacetate transaminase and glutamic pyruvic transaminase levels, and exhibited superior retention of the hexagonal structure of hepatocytes and reduced necrotic cells following liver histopathological examinations in CCl4-intoxicated ICR mice. Glutathione peroxidise and glutathione reductase activities were preserved as the normal control level in LPE groups. EC and PA2 were principle components of LPE. PA2 demonstrated liver cell regenerative activity in scratch wound healing assays and alcohol-induced liver cell injury in vitro. The present findings suggest that litchi pericarp polyphenolic extracts, including EC and PA2, may be a synergistic alternative to silymarin in hepatoprotection and liver cell regeneration.

The phytogestrogenic stilbenes, arachidin-1 and resveratrol, modulate regulatory T cell functions responsible for successful aging in aged ICR mice.

CD4+CD25+ regulatory T cells (Tregs) are recognized as a distinctive T helper cell population which controls immunosuppression during the maintenance of immunological self-tolerance and immunohomeostasis. Sex steroids modulate fundamental immune functions, including immune cell development, differentiation and polarization, and facilitate specific immunophysiological microenvironments, such as pregnancy. The supplementation of exogenous phytoestrogens is beneficial to post-menopausal women. Stilbenes are a potent group of phytoestrogens, of which resveratrol (Res) is a well-known representative exhibiting a variety of immunomodulatory activities, including the attenuation of autoimmune diseases and boosting anti-tumor immunity. In the present study, arachidin-1 (Ara­1) and Res, primary stilbenes, enriched in peanut sprouts as phytoalexins, were investigated for their immunomodulatory properties for successful aging. We found that similar to 17-ß-estradiol (E2), Ara­1 or Res significantly inhibited concanavalin A (ConA)-activated lymphoblastogenesis of cell repertories from splenic or thymic origins. However, these inhibitory effects were partially reversed by the E2 receptor blocker, tamoxifen. While the ratios of the CD4+CD25+ cell population of ConA-activated T cell repertories were not significantly altered, treatment with E2, Ara­1 or Res led to an increase in the number of cytotoxic T-lymphocyte associated protein 4 (CTLA-4; also known as CD152)-positive cells and in the gene expression levels of CTLA-4, Forkhead box P3 (FoxP3), interleukin (IL)-10 and transforming growth factor-ß (TGF-ß). When low (L-S-PNT) and high (H-S-PNT) levels of stilbene-enriched peanut sprout-fortified diets were provided ad libitum to 12­week-old ICR mice for 48 weeks, their circulating Treg populations were assessed following magnetic bead enrichment. The gene expression levels of CTLA-4 and TGF-ß were significantly (P<0.05) elevated, as assessed by semi-quantitative RT-PCR. The findings of the present study support the beneficial roles of the phytoestrogenic stilbenes, Res and Ara­1, in facilitating a successful aging immune status which may attribute to longevity.