Conjugated linoleic acid alleviates glycolipid metabolic disorders by modulating intestinal microbiota and short-chain fatty acids in obese rats.

Although conjugated linoleic acid (CLA) has been shown to have anti-obesity properties, the effect and mechanism of CLA in alleviating glycolipid metabolism disorders remains unclear. In this work, it was observed that rats fed a high-fat diet (HFD) had lower body weight and body fat levels after 9 weeks of low-dose and high-dose CLA interventions. The results of blood biochemical indices showed that CLA significantly reduced the levels of total cholesterol, triglycerides, fasting blood glucose and insulin. Additionally, high-dose CLA could restore the intestinal microbiota composition, including increasing the relative abundances of short-chain fatty acid (SCFA)-producing microbiota, such as Dubosiella, Faecalibaculum and Bifidobacterium; decreasing the relative abundances of Enterococcus and Ruminococcus_2; and increasing the content of SCFAs in feces and serum. Further analysis showed that high-dose CLA could increase the expression levels of Insr, Irs-2, Akt and Glut4 in the liver tissue of HFD-induced obese rats. Consistently, high dose of CLA could reversibly improve the downregulation of INSR, AKT, PI3K and GLUT4 protein expression caused by HFD and reverse the decline in AKT phosphorylation levels. Correlation clustering analysis with a heatmap showed that the changes in specific microbiota induced by high-dose CLA were correlated with changes in obesity-related indices and gene expression. The molecular docking analysis showed that the molecular docking of SCFAs with the IRS-2, AKT and GLUT4 proteins had high linking activity. The results supported that CLA can alleviate glycolipid metabolic imbalances associated with obesity by altering the intestinal microbiota to induce the production of SCFAs and thereby activate the INSR/IRS-2/AKT/GLUT4 pathway. This study supports CLA may be preferentially used by the intestinal microbiota of the host to promote its health.

Hydroxyapatite surface-functionalized monolithic column for selective in-tube solid phase microextraction of zoleronic acid and risedronic acid.

To date, hydroxyapatite (HAP) based monoliths were mainly fabricated by directly doping of HAP, which suffered from less effective coverage of HAP. Herein, a HAP surface-functionalized monolithic column (HAP@PDA@UF) has been prepared by in-situ biomineralization and applied as sorbent for selective in-tube solid phase microextraction of zoleronic acid and risedronic acid. A polydopamine coating was first generated on the surface of the parent urea-formaldehyde resin monolith; and then HAP microcrystals were further grew on the polydopamine coating to achieve this preparation. SEM, EDAX, FTIR, XPS and mercury intrusion method were utilized for the characterization of the HAP@PDA@UF monolith, and provided evidences of this successful preparation. The selective extraction mechanism of the HAP@PDA@UF monolith was investigated by the optimization of methanol percentage in the sampling solution, phosphate concentration in the eluent. Other crucial factors, including sampling and elution flow rate, and collection time span, were also optimized for the desired SPME performance. Under the optimal conditions, the proposed method showed low LODs of 0.1 µg/mL, satisfactory recoveries of 79.6%-92.5% with RSDs less than 2.7%, and good reproducibility with RSD less than 6.9%, which demonstrated the excellent application of the HAP@PDA@UF monolith, and its potential as a promising selective sorbent for bisphosphonates.

Hydroxyapatite-embedded monolithic column for selective on-line solid-phase extraction of adenosine triphosphate and its phosphorylated metabolites.

A novel hydroxyapatite-embedded monolithic column has been facilely prepared in a stainless-steel column with inner diameter of 2.1 mm by the strong adhesion of urea-formaldehyde (UF) resin and exploited as a sorbent for selective on-line solid-phase extraction (on-line SPE) of adenosine triphosphate and its phosphorylated metabolites. The composition for this preparation, including the amount of hydroxyapatite nanopowders and the porogen were investigated to obtain a suitable monolith with large surface area and satisfactory permeability. Owing to anion exchange interaction of hydroxyapatite and hydrophilic interaction of UF monolithic matrix, the prepared monolith showed good extraction efficiency and selectivity towards these phosphorylated analytes. Several parameters for on-line SPE, including ACN percentage in the sampling solution, collection time span, salt concentration of the eluent, sampling and elution flow rate, were optimized with respect to the extraction efficiencies of the target compounds. Under the optimized conditions, the LODs of the analytes were in the range of 0.01-0.04 µg/g, the recoveries in the spiked samples ranged from 78.3%-92.5% with RSDs <4.7%. Due to the excellent extraction ability towards phosphorylated compounds in practical samples, a simple on-line SPE-HPLC method using hydroxyapatite-embedded monolith as sorbent has been proposed for monitoring freshness of grass carp.

Poly (Octadecyl Methacrylate-Co-Trimethylolpropane Trimethacrylate) Monolithic Column for Hydrophobic in-Tube Solid-Phase Microextraction of Chlorophenoxy Acid Herbicides.

Chlorophenoxy acid herbicides (CAHs), which are widely used on cereal crops, have become an important pollution source in grains. In this work, a highly hydrophobic poly (octadecyl methacrylate-co-trimethylolpropane trimethacrylate) [poly (OMA-co-TRIM)] monolithic column has been specially prepared for hydrophobic in-tube solid-phase microextraction (SPME) of CAHs in rice grains. Due to the hydrophobicity of CAHs in acid conditions, trace CAHs could be efficiently extracted by the prepared monolith with strong hydrophobic interaction. Several factors for online hydrophobic in-tube SPME, including the length of the monolithic column, ACN and trifluoroacetic acid percentage in the sampling solution, elution volume, and elution flow rate, were investigated with respect to the extraction efficiencies of CAHs. Under the optimized conditions, the limits of detection of the four CAHs fell in the range of 0.9-2.1 µg/kg. The calibration curves provided a wide linear range of 5-600 µg/kg and showed good linearity. The recoveries of this method ranged from 87.3% to 111.6%, with relative standard deviations less than 7.3%. Using this novel, highly hydrophobic poly (OMA-co-TRIM) monolith as sorbent, a simple and sensitive online in-tube SPME-HPLC method was proposed for analysis of CAHs residue in practical samples of rice grains.

Silver nanoparticles-coated monolithic column for in-tube solid-phase microextraction of monounsaturated fatty acid methyl esters.

Based on our developed sodium hyaluronate-functionalized urea-formaldehyde (HA-UF) monolith, a silver nanoparticles-coated monolithic column has been fabricated via the interaction between silver nanoparticles (Ag NPs) and HA. The successful coating of Ag NPs on the parent monolith was proven by SEM, EDAX, UV-vis spectrum and XPS. Nitrogen adsorption desorption isotherms and Barret-Joyner-Halenda (BJH) pore size distributions of the parent and resultant monolith were also performed. Due to the Ag+-like affinity interaction caused by the contact of unsaturated compounds and Ag NPs, the Ag NPs-coated monolith showed satisfactory extraction efficiency towards these compounds, and was applied for in-tube solid-phase microextraction (SPME) of monounsaturated fatty acid methyl esters (MUFAMEs). Several factors for in-tube SPME, such as ACN percentage in the sampling solution, elution volume, sampling and elution flow rate, were investigated with respect to the extraction efficiency of model MUFAMEs. Under the optimized SPME conditions, a simple in tube SPME-Ag+-HPLC method for detection of model MUFAMEs has been proposed, the limits of detection (LODs) were less than 5.2 µg/kg, and the recoveries of spiked French fry samples were ranged from 86.6% to 96.1% with relative standard deviations (RSDs) less than 5.2%. This study provided an Ag NPs-coated monolith with good reproducibility and repeatable extraction performance, and developed an efficient method for in-tube SPME of MUFAMEs in practical food samples.

Sodium hyaluronate-functionalized urea-formaldehyde monolithic column for hydrophilic in-tube solid-phase microextraction of melamine.

A novel sodium hyaluronate-functionalized urea-formaldehyde (UF) monolithic column has been developed by in-situ polycondensation of urea, formaldehyde and sodium hyaluronate (HA). HA plays both the roles of crosslinking and hydrophilic functionalization. The preparation factors including different molecular weights of HA and different amounts of HA were optimized, and then a uniform monolith with satisfactory permeability and hydrophilic binding capacity was obtained. Due to the excellent hydrophilicity of HA, HA-functionalized UF monolith showed higher hydrophilic extraction efficiency than UF monolith, and was applied for hydrophilic in-tube solid-phase microextraction (SPME) of melamine (MEL). Several factors for hydrophilic in-tube SPME, such as ACN percentage in the sampling solution, salt concentration and pH value of the sampling solution, elution volume, sampling and elution flow rate, were investigated with respect to the extraction efficiency of MEL. Under the optimized SPME conditions, the limit of detection (LOD) of MEL was found to be 0.2ng/mL in the milk formula samples, the recoveries of MEL spiked in milk formula samples ranged from 87.3% to 96.7% with relative standard deviations (RSDs) less than 5.1%. Owing to the excellent hydrophilic extraction ability, the novel HA-functionalized UF monolith could provide a promising tool for the sensitive analysis of polar analytes in complicated samples.

Urea-formaldehyde monolithic column for hydrophilic in-tube solid-phase microextraction of aminoglycosides.

A novel urea-formaldehyde (UF) monolithic column has been developed and exploited as a sorbent for hydrophilic in-tube solid-phase microextraction (in-tube SPME) of aminoglycosides (AGs). Because of the innate hydrophilicity, UF monolith showed high extraction efficiency towards these hydrophilic analytes. The adsorption capacities for target compounds dissolved in water/ACN (1:1, v/v) were in the range of 5.18-7.36µg/cm. Due to the lack of a chromophore, evaporative light scattering detector (ELSD) was selected as the detector for AGs, and coupled with the online in-tube SPME-HPLC system. Several factors of the online system, such as trifluoroacetic acid (TFA) and ACN percentage in the sampling solution, ionic strength in the sample solution, elution volume, sampling and elution flow rate, were optimized with respect to the extraction efficiencies. Under the optimized conditions, the limits of detection (LODs) of streptomycin, tobramycin and neomycin were discovered in the range of 3.0-5.2µg/kg. The recoveries were ranged from 82.1 to 96.7% with relative standard deviations (RSDs) of 2.3-5.1% (n=4) at spiking levels of 50, 200 and 500µg/kg, respectively. The excellent applicability of the UF monolithic column was examined by the determination of streptomycin in practical tilapia samples, which showed the potential advantages for the analysis of polar analytes in complicated samples.