Yu-Lei Chen

Dipeptidyl peptidase 4 (DPP4) is a membrane-anchored protein ubiquitously expressed across various cell types, primarily responsible for cleaving N-terminal X-Pro or X-Ala dipeptides from polypeptides. It plays a crucial role in glucose metabolism by degrading incretin hormones, thereby regulating blood glucose homeostasis and establishing itself as a key therapeutic target for type 2 diabetes mellitus. In addition, DPP4 has emerged as a potential biomarker and intervention target in pathologies such as fibrosis, inflammation, and cancer. In terms of therapeutic strategies, in addition to conventional small-molecule inhibitors, DPP4-inhibitory peptides have shown significant efficacy in vitro, underscoring their potential for the control of high blood glucose. Advancements in the development of DPP4-specific antibodies are creating new opportunities for diagnosing and treating DPP4-related diseases. This review systematically delineates the established enzymatic functions and blood glucose-rising mechanisms of DPP4, its novel pathological roles in fibrotic, inflammatory, and oncological processes, and discusses recent progress in diverse intervention strategies, including small molecules, inhibitory peptides, and antibodies. It helps deepen the overall understanding of the multifaceted biological functions of DPP4 and its associations with disease, and provides a theoretical basis for optimizing DPP4-targeted therapeutic strategies and developing novel treatment approaches.

The rapid post-mortem softening of abalone muscle is primarily attributed to collagen degradation mediated by matrix metalloproteinases (MMPs), although the synergistic mechanisms of different MMPs remain inadequately understood. In this study, we heterologously expressed MMP-3 and MMP-16 to investigate their combined effects on in vitro degradation of type I collagen and collagen fibers and then analyzed degradation products via mass spectrometry to elucidate the mechanism. Our findings showed that both enzymes degraded collagen individually, but their combined action accelerated collagen fiber degradation, causing more comprehensive breakdown. Mass spectrometry analysis revealed that MMP-3 initiated degradation by cleaving collagen telopeptides and disrupting the triple helix, facilitating MMP-16 infiltration into relaxed fibers to promote extensive proteolysis. This study elucidates a synergistic loosening-then-degradation mechanism of MMP-mediated collagen degradation, which underlies post-mortem muscle softening of abalone and thus provides a theoretical basis for seafood preservation strategies.

Sharks produce a unique antibody type, whose variable domain (VNAR) is the smallest known antibody fragment. VNARs possess high affinity, stability, and tissue penetration, making them attractive for biomedical applications. In this study, a synthetic VNAR library with extensive CDR3 sequence diversity was constructed through a three‐step PCR amplification process of VNAR gene fragments, which were subsequently cloned into the pR2 phagemid vector. The resulting library achieved a size of 1.17 × 10 ¹⁰ colony‐forming units (CFU). Using green fluorescent protein (GFP) and hemoglobin as coating proteins, six GFP‐specific VNARs and two hemoglobin‐specific VNARs were screened from the constructed synthetic library using phage display technology. The binding affinities and physicochemical stability of these VNARs were evaluated through ELISA and BLI assays, revealing that the GFP‐specific VNARs (14A‐4C, 15A‐5C, 14‐3H, and 14‐1A) and the hemoglobin‐specific VNAR (13F‐1A) exhibited nanomolar‐level affinities, comparable to those derived from immune libraries. Hence, the synthetic VNAR library developed in this study holds great potential for biological research and applications, providing a versatile platform for screening VNARs specific to various antigens.

Sodium-proton antiporter NhaA of Escherichia coli is a paradigm to investigate the mechanistic basis of the fundamental Na⁺/H⁺ exchange in cells. However, all existing crystal structures of NhaA are inward-facing (IF), and the putative outward-facing (OF) structures are still unsolved by experiment, limiting a complete understanding of the transport cycle in which Lys300 plays a key role in both structural stability and transport function. Here, we report a set of atomistic molecular dynamics (MD) simulations that start from the structure predicted by an artificial intelligence model that generates function-relevant alternative conformations. It is found that NhaA rapidly relaxes into either the IF or the OF conformation. Furthermore, the neutralization of Lys300 allows the binding of two sodium ions, a configuration that is associated with enhanced conformational sampling. Based on these observations, we propose a sodium-coupled mechanism of Na⁺/H⁺ antiporting.

The fat covered by fat globule membrane is scattered in a water phase rich in lactose and milky protein, forming the original emulsion structure of milk. In order to develop low-fat milk products with good performance or dairy products with nutritional reinforcement, the original emulsion structure of milk can be restructured. According to the type of lipid and emulsion structure in milk, the remolded emulsion structure can be divided into three types: restructured single emulsion structure, mixed emulsion structure, and double emulsion structure. The restructured single emulsion structure refers to the introduction of another kind of lipid to skim milk, and the mixed emulsion structure refers to adding another type of oil or oil-in-water (O/W) emulsion to milk containing certain levels of milk fat, whose final emulsion structure is still O/W emulsion. In contrast, the double emulsion structure of milk is a more complicated structural remodeling method, which is usually performed by introducing W/O emulsion into skim milk (W₂) to obtain milk containing (water-in-oil-in-water) W₁/O/W₂ emulsion structure in order to encapsulate more diverse nutrients. Causal statistical analysis was used in this review, based on previous studies on remodeling the emulsion structures in milk and its gelling products. In addition, some common processing technologies (including heat treatment, high-pressure treatment, homogenization, ultrasonic treatment, micro-fluidization, freezing and membrane emulsification) may also have a certain impact on the microstructure and properties of milk and its gelling products with four different emulsion structures. These processing technologies can change the size of the dispersed phase of milk, the composition and structure of the interfacial layer, and the composition and morphology of the aqueous phase substance, so as to regulate the shelf-life, stability, and sensory properties of the final milk products. This research on the restructuring of the emulsion structure of milk is not only a cutting-edge topic in the field of food science, but also a powerful driving force in promoting the transformation and upgrading of the dairy industry to achieve high-quality and multi-functional dairy products, in order to meet the diversified needs of consumers for health and taste.

Matrix metalloproteinases (MMPs) play critical roles in the degradation of collagens, while their mechanism remains unclear. In the present study, the involvement of matrix metalloproteinases (MMPs) in collagen degradation of sea bass muscle during cold storage was explored. Immunohistochemical staining results showed significant degradation of type I collagen in the connective tissue of muscle endomysium during cold storage, thus affecting the muscle structural integrity and quality. Western blot analysis revealed an increment in the α1 chain and a decrease in the β and γ chains of type I collagen. Immunofluorescence staining showed that MMP-2, MMP-9, and MMP-13 were distributed in the endomysium surrounding the muscle fibers. Additionally, the catalytic domains of MMP-2, MMP-9, and MMP-13 with biological activities were successfully expressed. The degradation trend of type I collagen by MMPs under 4 °C was similar to that of muscle collagen during cold storage, suggesting that the degradation of type I collagen was attributed to the cooperative action of the MMPs. In conclusion, our study elucidated that the MMPs-engaged degradation of type I collagen is quite possibly the leading cause of sea bass muscle softening during cold storage.