Showing papers by "John K. G. Kramer published in 2006"

Systematic analysis of trans and conjugated linoleic acids in the milk and meat of ruminants.

Abstract: Conjugated fatty acids are defined as fatty acids (FA) in which any two double bonds in the molecule are separated by a single carbon-carbon bond (C=C–C=C). The number of possible conjugated fatty acids is considerable since the FA can differ in chain length, position of the conjugated system within the molecule, up to four possible geometric configurations for each positional isomer, and number of additional double bonds in the molecule. In addition to conjugated dienes, some plant oils have conjugated trienes or tetraenes in which there are three and four double bonds each separated by a single carbon-carbon bond (1). In this chapter we will restrict our discussion to the analysis of conjugated dienes derived mainly from ruminant animals. We will use the term conjugated linoleic acid (CLA) even though this term is somewhat restrictive and incorrect (2). For example, 9c11t15c-18:3 is a conjugated fatty acid but is not derived from linoleic acid. All CLA isomers give rise to unique ultraviolet and infrared absorptions, and their chemical properties and chromatographic behaviors are very different from the more common methylene interrupted unsaturated FA. These characteristic properties have been successfully used for their identification and quantification (2). However, it has not been these chemical and chromatographic differences that have distinguished CLA in the past 20 years with the challenges of handling, identification, and completeness of separation, but their unique biological effects. Systematic Analysis of trans and Conjugated Linoleic Acids in the Milk and Meat of Ruminants

The Conversion Efficiency of trans-11 and trans-12 18:1 by Δ9-Desaturation Differs in Rats

Abstract: The present study evaluated and compared the efficiency of the conversion of t11 18:1 and t12 18:1 to their corresponding dienoic acids (c9,tn 18:2) and assessed whether differences due to gender existed in several tissues of rats. Three groups of 4-wk-old male and female rats were fed for 3 wk a diet supplemented with 0, 0.5, or 1% of a trans-octadecenoic acid isomer mixture (tOIM) containing t11 18:1 and t12 18:1 in equal proportion. t11 18:1 and t12 18:1 were incorporated in a tissue-specific manner, and the accrual was significant with increased dietary intake of these trans fatty acid (tFA) isomers. The t12 18:1 isomer was more readily incorporated into the rat tissues than the t11 18:1 isomer. From t11 and t12 18:1, the respective desaturase products, c9,t11 18:2 and c9,t12 18:2, were formed. The calculated conversion rates varied greatly among the tissues of the rats but they were consistently lower for t12 18:1 than for t11 18:1, suggesting that t12 18:1 is a poorer substrate than t11 18:1 for Delta9-desaturase. For both fatty acids investigated, the calculated conversion rates in decreasing order of conversion efficiency were: testes = kidneys > adipose tissue > ovaries > muscle > liver > heart. Overall, there were distinct differences in the conversion of t11 18:1 and t12 18:1, indicating that these 2 fatty acids are metabolized differently despite their structural similarities. Such metabolic differences in tFA accumulation and metabolism may have potential implication in assessing the safety of these tFA isomers because there is a positive correlation between the intake of tFA and the incidence of various diseases.

Lipid Analysis and Lipidomics: NewTechniques and Applications

Abstract: New methods for the analysis of edible oils, fats, and cellular lipids have recently been developed, presented at scientific meetings, and published in peer-reviewed journals. These methods apply to biological and food matrices, edible oils and fats, as well as cellular fats of pathogenic bacteria and spores, and will cover many research applications in lipidomics, food analysis, food safety, food security, and counter-terrorism. This text offers the lipid analyst essential analytical tools in the fields of chromatography, mass spectrometry, spectroscopy, magnetic resonance, and chemometrics. It also serves as a reference for recent developments in the rapidly evolving field of lipid methodologies.