Identification of Key Excipients for the Solubilization and Structural Characterization of Lipoprotein Lipase, An Enzyme for Hydrolysis of Triglyceride

A comparison of Polysorbates and Alternative Surfactants for Interfacial Stress Protection and Mitigation of Fatty Acid Particle Formation in the Presence of an Esterase

The hydrolysis of polysorbate surfactants in large molecule drug product formulations caused by residual host cell proteins presents numerous stability concerns for pharmaceuticals. The fatty acids (FA) released by polysorbate hydrolysis can nucleate into particulates or challenge the conformational stability of the proteinaceous active pharmaceutical ingredient (API). The loss of intact polysorbate may also leave the Drug Product (DP) vulnerable to interfacial stresses. Polysorbate 20 and 80 are available in several different quality grades (Multi-compendial, Super Refined, Pure Lauric Acid (PLA)/Pure Oleic Acid (POA)). All variations of polysorbate as well as three alternative surfactants: Brij L23, Brij O20 and Poloxamer 188 were compared for their ability to protect against air-water interfacial stresses as well as their risk for developing particulates when in the presence of lipoprotein lipase (LPL) (Pseudomonas). Results show a meaningful difference in the timing and morphology of FA particle formation depending on the type of polysorbate used. All grades of polysorbate, while susceptible to hydrolysis, still offered sufficient protection to interfacial stresses, even when hydrolyzed to concentrations as low as 0.005 % (w/v). Alternative surfactants that lack an ester bond were resistant to lipase degradation and showed good protection against shaking stress.

A highly sensitive optical fiber sensor enables rapid triglycerides-specific detection and measurement at different temperatures using convolutional neural networks

For specific recognition and sensitive detection of triglycerides (TGs), an optical fiber sensor (OFS) based on an enhanced core diameter mismatch was proposed. The sensitivity of the sensor is significantly increased due to the repetitive excitation of the higher-order cladding modes. A technique for immobilizing lipase using covalent binding technology was presented and demonstrated by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy. The interference dip of the sensor was shifted due to TGs being hydrolyzed in the presence of lipase. The sensor shows an optimal response within 3 min and exhibits a high sensitivity of 0.9933 nm/(mg/ml) and a limit of detection of 0.0822 mg/ml in the concentration range 0-8 mg/ml at a temperature of 37 °C and a pH of 7.4. The response of the sensor to TGs concentration at different temperatures and pH was investigated. The reproducibility, reusability, and stability of the proposed sensor were tested and verified experimentally. The biosensor is highly specific for TGs and unaffected by many other interfering substances. Further, the measurement of TGs concentration at different temperatures was realized. This method provides a new way to detect TGs rapidly and reliably and has potential applications in medical research and clinical diagnosis.

Dual-fiber optic bioprobe system for triglyceride detection using surface plasmon resonance sensing and lipase-immobilized magnetic bead hydrolysis

The rapid and accurate detection of triglyceride (TG) plays a valuable role in the prevention and control of dyslipidemia. In this paper, a novel method for TG detection using a dual-fiber optic bioprobe system, which can accurately detect different levels of TG concentration in serum, is proposed. The system employs disposable microprobe-type fiber optic surface plasmon resonance (SPR) biosensors for signal acquisition, providing high stability and portability while avoiding cross-contamination caused by repeated use. The proposed biosensor with a high sensitivity of 1.25 nm/(mg/mL) for TG detection in serum and a tiny diameter of 125 μm, was fabricated using a novel multimode fiber-single-mode fiber-reflector (MSR) structure, which has been scarcely ever reported to the best of our knowledge. In the process of TG detection, lipase-immobilized magnetic beads were introduced to specifically hydrolyze TG, and the relationship between the TG content and the SPR differential signal was obtained from dual-fiber optic bioprobe measurements of the TG sample before and after hydrolysis. The proposed method achieved TG detection in the concentration range of 0-8 mg/mL (including healthy and unhealthy levels of TG concentration in the human body). Additionally, the miniaturized fiber optic biosensors used in this work have the advantages of low sample consumption, high sensitivity, simple operation, label-free measurement, high selectivity, and low cost. This method provides a new pathway for rapid and reliable TG detection and has potential applications in medical research and clinical diagnosis.

GPIHBP1 and ANGPTL4 Utilize Protein Disorder to Orchestrate Order in Plasma Triglyceride Metabolism and Regulate Compartmentalization of LPL Activity

Intravascular processing of triglyceride-rich lipoproteins (TRLs) is crucial for delivery of dietary lipids fueling energy metabolism in heart and skeletal muscle and for storage in white adipose tissue. During the last decade, mechanisms underlying focal lipolytic processing of TRLs along the luminal surface of capillaries have been clarified by fresh insights into the functions of lipoprotein lipase (LPL); LPL's dedicated transporter protein, glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1); and its endogenous inhibitors, angiopoietin-like (ANGPTL) proteins 3, 4, and 8. Key discoveries in LPL biology include solving the crystal structure of LPL, showing LPL is catalytically active as a monomer rather than as a homodimer, and that the borderline stability of LPL's hydrolase domain is crucial for the regulation of LPL activity. Another key discovery was understanding how ANGPTL4 regulates LPL activity. The binding of ANGPTL4 to LPL sequences adjacent to the catalytic cavity triggers cooperative and sequential unfolding of LPL's hydrolase domain resulting in irreversible collapse of the catalytic cavity and loss of LPL activity. Recent studies have highlighted the importance of the ANGPTL3-ANGPTL8 complex for endocrine regulation of LPL activity in oxidative organs (e.g., heart, skeletal muscle, brown adipose tissue), but the molecular mechanisms have not been fully defined. New insights have also been gained into LPL-GPIHBP1 interactions and how GPIHBP1 moves LPL to its site of action in the capillary lumen. GPIHBP1 is an atypical member of the LU (Ly6/uPAR) domain protein superfamily, containing an intrinsically disordered and highly acidic N-terminal extension and a disulfide bond-rich three-fingered LU domain. Both the disordered acidic domain and the folded LU domain are crucial for the stability and transport of LPL, and for modulating its susceptibility to ANGPTL4-mediated unfolding. This review focuses on recent advances in the biology and biochemistry of crucial proteins for intravascular lipolysis.