Marsha L. Langhorst

Hypocholesterolemic Effects of Hydroxypropyl Methylcellulose Are Mediated by Altered Gene Expression in Hepatic Bile and Cholesterol Pathways of Male Hamsters

Hydroxypropyl methylcellulose (HPMC), a semisynthetic, nonfermentable soluble dietary fiber, is not absorbed by the body, but its presence in the intestinal lumen increases fecal fat, sterol, and bile acid excretions and decreases intestinal cholesterol absorption, all of which may indirectly affect hepatic lipid metabolism. We measured the expression of hepatic genes involved in cholesterol, bile acid, and fatty acid metabolism in hamsters fed diets containing 39% of energy as fat and 5% of weight as HPMC or microcrystalline cellulose (control) for 4 wk. HPMC-fed hamsters gained significantly less body weight than the control group but did not differ in food intake. They had significantly lower plasma triglyceride and total-, VLDL-, HDL-, and LDL-cholesterol concentrations and hepatic total lipid, total and free cholesterol and triglyceride concentrations than controls. Compared with controls, HPMC-fed hamsters had greater levels of mRNA for CYP7A1 (cytochrome P450 7A1; 8-fold of control; P < 0.05), CYP51 (lanosterol 14alpha-demethylase; 5.3-fold of control; P < 0.05), and HMG-CoAR (3-hydroxy-3-methylglutaryl CoA reductase; 1.8-fold of control; P < 0.05). The plasma total cholesterol concentrations from both the control and HPMC groups were inversely correlated with expression of hepatic CYP7A1 (r = -0.54; P < 0.05), CYP51 (r = -0.79; P < 0.005), and HMG-CoAR (r = -0.75; P < 0.005) genes. This suggests that HPMC supplementation affected both cholesterol and bile acid synthesis. Our data confirm that altered hepatic expression of lipid metabolism-related genes, possibly due to modulation of fecal bile acid excretion and intestinal cholesterol absorption, contributes to the lipid-lowering effects of HPMC.

Immunodepletion of high abundance proteins coupled on-line with reversed-phase liquid chromatography: A two-dimensional LC sample enrichment and fractionation technique for mammalian proteomics

Proteomic analysis can be hampered by the large concentration distribution of proteins. Immunoaffinity techniques have been applied to selectively remove high abundant proteins (HAPs) from samples prior to analysis. Although immunodepletion of HAPs has been shown to enable greater detection of low abundance proteins, the resulting fractions are often diluted 5-10-fold during the process. Various concentration techniques can be applied; however, many are incompatible with the high salt content of the fractions. To help overcome this limitation, a two-dimensional liquid chromatography (2D-LC) method was developed which couples an IgY immunodepletion column in the first dimension with a large pore C18 analytical column in the second. A protein trap cartridge serves as an injection loop between the columns to facilitate on-line concentration and desalting. Feasibility of this 2D-LC system was demonstrated for mammalian proteomics. Beyond depletion of interfering proteins, this instrumentation provides four advantages which make immunodepletion technology more convenient, including: (1) on-line desalting (2) automatic buffer exchange (3) facile concentration and (4) fractionation by polarity.

Effect of hydroxypropyl methylcellulose on obesity and glucose metabolism in a diet-induced obesity mouse model

Background:  To investigate the effect of hydroxypropyl methylcellulose (HPMC) on weight loss and metabolic disorders associated with obesity using a high‐fat diet‐induced obese mouse model under a high‐fat diet regimen.

Determination of F2-isoprostanes in urine by online solid phase extraction coupled to liquid chromatography with tandem mass spectrometry.

F(2)-isoprostanes are a unique class of prostaglandin-like compounds formed in vivo, which have been established as biomarkers of oxidative stress. Accurate analysis has been challenging due to lack of specificity for the isoforms of isoprostanes and lengthy sample preparation procedures to enable trace quantitative analysis. A quantitative analytical method was developed for the determination of F(2)-isoprostanes in rat and hamster urine by online solid phase extraction (SPE) coupled with liquid chromatography and tandem mass spectrometry (LC-MS/MS). The online SPE LC-MS/MS procedure has significant advantages over alternative methods with respect to specificity, sensitivity, simplicity, and speed. The assay enables the detection of iPF(2alpha)-III, iPF(2alpha)-IV, and iPF(2alpha)-VI over a linear dynamic range of 0.1-50 ng/mL in rat urine samples. This range covers the basal levels of these F(2)-isoprostanes. The limit of quantitation (LOQ) for the standard isoprostanes was about 0.3 ng/mL. The average recoveries ranged from 73 to 115% depending upon the individual F(2)-isoprostane isomers in rat urine. Additionally, the method was used to determine increases of endogenous urine iPF(2alpha)-VI and iPF(2alpha)-III in hamsters challenged with either low-fat or high-fat diets.

Dietary hydroxypropyl methylcellulose increases excretion of saturated and trans fats by hamsters fed fast food diets.

In animal studies, hydroxypropyl methylcellulose (HPMC) intake results in increased fecal fat excretion; however, the effects on dietary saturated fatty acids (SATs) and trans-fatty acids (TRANS) remain unknown. This study investigated the effect of HPMC on digestion and absorption of lipids in male Golden Syrian hamsters fed either freeze-dried ground pizza (PZ), pound cake (PC), or hamburger and fries (BF) supplemented with dietary fiber from either HPMC or microcrystalline cellulose (MCC) for 3 weeks. We observed greater excretion of SATs and TRANS by both diets supplemented with HPMC or MCC as compared to the feed. SAT, TRANS, and unsaturated fatty acids (UNSAT) contents of feces of the PZ diet supplemented with HPMC were 5-8 times higher than diets supplemented with MCC and tended to be higher in the PC- and BF-HPMC supplemented diets as well. We also observed significant increases in fecal excretion of bile acids (2.6-3-fold; P < 0.05), sterols (1.1-1.5-fold; P < 0.05), and unsaturated fatty acids (UNSAT, 1.7-4.5-fold; P < 0.05). The animal body weight gain was inversely correlated with the excretion of fecal lipid concentrations of bile acids (r = -0.56; P < 0.005), sterols (r = -0.48; P < 0.005), SAT (r = -0.69; P < 0.005), UNSAT (r = -0.67; P < 0.005), and TRANS (r = -0.62; P < 0.005). Therefore, HPMC may be facilitating fat excretion in a biased manner with preferential fecal excretion of both TRANS and SAT in hamsters fed fast food diets.

Effects of cationic hydroxyethyl cellulose on glucose metabolism and obesity in a diet-induced obesity mouse model.

Background:  To investigate the effect of a new soluble fiber, namely cationic hydroxyethyl cellulose (cHEC), on weight loss and metabolic disorders associated with obesity using a high‐fat diet‐induced obese mouse model.

Solid adsorbent collection and gas chromatographic determination of the propylene glycol butyl ether esters of 2,4,5-T in air

A method has been developed and validated for the collection of the propylene glycol butyl ether esters of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) in air and their determination by gas chromatography with electron capture detection. The samples are collected on XAD-2 resin, desorbed in diethyl ether prior to analysis. The procedure is designed for industrial hygiene monitoring to provide an accurate 4 hour time-weighted average of the exposure level. Recoveries were found to be 97 +/- 8% (2 sigma) for the propylene glycol butyl ether esters of 2,4, 5-T in the concentration range of 0.70 ppb (v/v) to 5.00 ppm (v/v). Breakthrough concentrations, storage effects and humidity effects were also investigated.

A Hollow Fiber Device for Separating Water Vapor from Organic Vapors

A hollow fiber device (HF device) has been designed, constructed and developed which utilizes the water transport property of Nafion®Registered trademark of E.I. du Pont de Nemours and Company for its perfluorinated membranes. perfluorinated membrane to separate water vapor from organic vapors. The device was designed for industrial hygiene applications to reduce or change humidity in an airstream prior to collection of organics on an adsorbent tube. Moisture affects collection of organics by causing early breakthrough of compounds collected on hygroscopic adsorbents and by reacting with hydrolyzable compounds during collection. This device has the potential for eliminating some of these problems. The device is capable of reducing humidity in an air sample from 94% to <20% RH (at 74°F) for a period of at least 9 hours. Many organic vapors (including aliphatic, aromatic and chlorinated hydrocarbons) and inorganic vapors do not permeate Nafion and can be recovered on an adsorbent tube after passing through ...

Glycol ethers - validation procedures for tube/pump and dosimeter monitoring methods

Methods were developed and validated for personal monitoring of exposures to airborne glycol ethers, both short-term and long-term time-weighted-averages. Either a 600 mg charcoal tube or a 780 mg silica gel tube is recommended for monitoring nine glycol ethers, depending upon the humidity and other organic compounds to be monitored. The charcoal tube allows maximum sensitivity and is unaffected by high humidity conditions. Two-phase solvent desorption with CS2 and water allows aqueous phase recoveries of DOWANOL EM, PM, EE, DM, DPM, and TM glycol ethers. DOWANOL EB, DB and TPM glycol ethers are partitioned between the two layers, necessitating chromatographic analysis of both layers. The silica gel tube method can be used to monitor all nine glycol ethers tested, but is affected by high humidity conditions, resulting in significant breakthrough of the more volatile glycol ethers. The 3M organic vapor monitor can accurately and conveniently determine exposure concentrations for DOWANOL EM, EE, and PM glycol ethers, but sensitivities may be inadequate for sampling periods less than one hour. These methods were validated at levels down to 0.1 times the Dow internal exposure guidelines for those substances with Dow exposure guidelines and well above the current ACGIH and OSHA guidelines. This paper also illustrates validation procedures for tube/pump and dosimeter methods, allowing good definition of method accuracy and precision. Some screening experiments are described for diffusional dosimeters to check the most important parameters in a minimum of time. This methodology will allow assessment of human airborne exposures relative to the new toxicology data available on animals.

Comparative laboratory evaluation of six chlorine monitoring devices

The performances of six chlorine monitoring methods/devices have been compared to expedite the development of several novel personal monitoring devices. The devices evaluated included a diffusional colorimetric dosimeter badge from Moleculon Research Corporation, three diffusional electrochemical sensors (the Dow membrane sensor, the Dow glass frit sensor, and the Compur MonitoxTrademark of Compur Electronic Gmbh, Munich, West Germany sensor), the sulfamic acid bubbler/ion specific electrode method, and the InterScan voltammetric instrument. To be useful for personal monitoring, the electrochemical sensors must be coupled with a digital readout or microprocessor-based unit to display, store, or average chlorine concentrations detected by the sensor. A Dow built microprocessor unit and the Compur Mini-Dosimeter were evaluated. The major evaluation parameters included: applicable concentration range, linear range, accuracy, precision, effects of humidity, temperature and air velocity, and interferences from...