Dipeptidyl peptidase IV (DPP-IV) inhibitors occupy a growing place in the drugs used for the management of type 2 diabetes. Recently, food components, including food-derived bioactive peptides, have been suggested as sources of DPP-IV inhibitors without side effects. Chinese black tea is a traditional health beverage, and it was used for finding DPP-IV inhibitory peptides in this study. The ultra-filtrated fractions isolated from the aqueous extracts of black tea revealed DPP-IV inhibitory activity in vitro. Four peptides under 1 kDa were identified by SDS-PAGE and LC-MS/MS (Liquid Chromatography-Mass Spectrometry-Mass Spectrometry) from the ultra-filtrate. The peptide II (sequence: AGFAGDDAPR), with a molecular mass of 976 Da, showed the greatest DPP-IV inhibitory activity (in vitro) among the four peptides. After administration of peptide II (400 mg/day) for 57 days to streptozotocin (STZ)-induced hyperglycemic mice, the concentration of glucagon-like peptide-1 (GLP-1) in the blood increased from 9.85 ± 1.96 pmol/L to 19.22 ± 6.79 pmol/L, and the insulin level was increased 4.3-fold compared to that in STZ control mice. Immunohistochemistry revealed the improved function of pancreatic beta-cells and suppressed proliferation of pancreatic alpha-cells. This study provides new insight into the use of black tea as a potential resource of food-derived DPP-IV inhibitory peptides for the management of type 2 diabetes.

Light-harvesting chlorophyll a/b-binding (LHCB) protein complexes of photosystem II are integral to the formation of thylakoid structure and the photosynthetic process. They play an important role in photoprotection, a crucial process in leaf development under low-temperature stress. Nonetheless, potential key genes directly related to low-temperature response and albino phenotype have not been precisely identified in tea plant. Moreover, there are no studies simultaneously investigating multiple albino tea cultivars with different temperature sensitivity. The study aimed to clarify the basic characteristics of CsLHCB gene family members, and identify critical CsLHCB genes potentially influential in leaf color phenotypic variation and low-temperature stress response by contrasting green and albino tea cultivars. Concurrently, exploring the differential expression of the CsLHCB gene family across diverse temperature-sensitive albino tea cultivars. We identified 20 putative CsLHCB genes according to phylogenetic analysis. Evolutionary relationships, gene duplication, chromosomal localization, and structures were analyzed by TBtools; the physiological and biochemical characteristics were analyzed by protein analysis websites; the differences in coding sequences and protein accumulation in green and albino tea cultivars, gene expression with maturity were tested by molecular biology technology; and protein interaction was analyzed in the STRING database. All genes were categorized into seven groups, mapping onto 7 chromosomes, including three tandem and one segmental duplications. They all own a conserved chlorophyll A/B binding protein domain. The expression of CsLHCB genes was tissue-specific, predominantly in leaves. CsLHCB5 may play a key role in the process of leaf maturation and senescence. In contrast to CsLHCB5, CsLHCB1.1, CsLHCB2, and CsLHCB3.2 were highly conserved in amino acid sequence between green and albino tea cultivars. In albino tea cultivars, unlike in green cultivars, the expression of CsLHCB1.1, CsLHCB1.2, and CsLHCB2 was down-regulated under low-temperature stress. The accumulation of CsLHCB1 and CsLHCB5 proteins was lower in albino tea cultivars. Greater accumulation of CsLHCB2 protein was detected in RX1 and RX2 compared to other albino cultivars. CsLHCB1.1, CsLHCB1.2, and CsLHCB2 played a role in the response to low-temperature stress. The amino acid sequence site mutation of CsLHCB5 would distinguish the green and albino tea cultivars. The less accumulation of CsLHCB1 and CsLHCB5 had a C_hl influence on albino leaves. Albino cultivars more sensitive to temperature exhibited lower CsLHCB gene expression. CsLHCB2 may serve as an indicator of temperature sensitivity differences in albino tea cultivars. This study could provide a reference for further studies of the functions of the CsLHCB family and contribute to research on the mechanism of the albino in tea plant.

Sirtuin 1 (SIRT1), an NAD⁺-dependent deacetylase, is a crucial regulator that produces multiple physiological benefits, such as the prevention of cancer and age-related diseases. SIRT1 is activated by sirtuin-activating compounds (STACs). Here, we report that quercetin 3,5,7,3′,4′-pentamethyl ether (KPMF-8), a natural STAC from Thai black gingerKaempferia parviflora, interacts with SIRT1 directly and stimulates SIRT1 activity by enhancing the binding affinity of SIRT1 with Ac-p53 peptide, a native substrate peptide without a fluorogenic moiety. The binding affinity between SIRT1 and Ac-p53 peptide was enhanced 8.2-fold by KPMF-8 but only 1.4-fold by resveratrol. The specific binding sites of KPMF-8 to SIRT1 were mainly localized to the helix2–turn–helix3 motif in the N-terminal domain of SIRT1. Intracellular deacetylase activity in MCF-7 cells was promoted 1.7-fold by KPMF-8 supplemented in the cell medium but only 1.2-fold by resveratrol. This work reveals that KPMF-8 activates SIRT1 more effectively than resveratrol does.

Gut microbiota regulate physiological functions in various hosts, such as energy metabolism and immunity. Lactic acid bacteria, including Lactobacillus plantarum, have a specific polyunsaturated fatty acid saturation metabolism that generates multiple fatty acid species, such as hydroxy fatty acids, oxo fatty acids, conjugated fatty acids, and trans-fatty acids. How these bacterial metabolites impact host physiology is not fully understood. Here, we investigated the ligand activity of lactic acid bacteria–produced fatty acids in relation to nuclear hormone receptors expressed in the small intestine. Our reporter assays revealed two bacterial metabolites of γ-linolenic acid (GLA), 13-hydroxy-cis-6,cis-9-octadecadienoic acid (γHYD), and 13-oxo-cis-6,cis-9-octadecadienoic acid (γKetoD) activated peroxisome proliferator-activated receptor delta (PPARδ) more potently than GLA. We demonstrate that both γHYD and γKetoD bound directly to the ligand-binding domain of human PPARδ. A docking simulation indicated that four polar residues (T289, H323, H449, and Y473) of PPARδ donate hydrogen bonds to these fatty acids. Interestingly, T289 does not donate a hydrogen bond to GLA, suggesting that bacterial modification of GLA introducing hydroxy and oxo group determines ligand selectivity. In human intestinal organoids, we determined γHYD and γKetoD increased the expression of PPARδ target genes, enhanced fatty acid β-oxidation, and reduced intracellular triglyceride accumulation. These findings suggest that γHYD and γKetoD, which gut lactic acid bacteria could generate, are naturally occurring PPARδ ligands in the intestinal tract and may improve lipid metabolism in the human intestine.

• Analysis using NMR and HPLC can be used to identify countries of origin but not producing years of bee pollens. • Flavanoids in bee pollens from different countries were characterized using HPLC. • Bee pollens from Spain and Australia were high in sucrose and adenosine. • Bee pollens from China were high in trigonelline, uridine, and cytidine. • Only the bee pollens from China contained acetic acid.

Background: New strategies are needed to combat multidrug-resistant bacteria. The restriction of iron uptake by bacteria is a promising way to inhibit their growth. We aimed to suppress the growth of Vibrio bacterial species by inhibiting their ferric ion-binding protein (FbpA) using food components. Methods: Twenty spices were selected for the screening of FbpA inhibitors. The candidate was applied to antibacterial tests, and the mechanism was further studied. Results: An active compound, rosmarinic acid (RA), was screened out. RA binds competitively and more tightly than Fe³⁺ to VmFbpA, the FbpA from V. metschnikovii, with apparent K_D values of 8 μM vs. 17 μM. Moreover, RA can inhibit the growth of V. metschnikovii to one-third of the control at 1000 μM. Interestingly, sodium citrate (SC) enhances the growth inhibition effect of RA, although SC only does not inhibit the growth. The combination of RA/SC completely inhibits the growth of not only V. metschnikovii at 100/100 μM but also the vibriosis-causative pathogens V. vulnificus and V. parahaemolyticus, at 100/100 and 1000/100 μM, respectively. However, RA/SC does not affect the growth of Escherichia coli. Conclusions: RA/SC is a potential bacteriostatic agent against Vibrio species while causing little damage to indigenous gastrointestinal bacteria.