Thermogenic flux induced by lignoceric acid in peroxisomes isolated from HepG2 cells and from X-adrenoleukodystrophy and control fibroblasts.

This work analyzes the thermogenic flux induced by the very long-chain fatty acid (VLCFA) lignoceric acid (C24:0) in isolated peroxisomes. Specific metabolic alterations of peroxisomes are related to a variety of disorders, the most frequent one being the neurodegenerative inherited disease X-linked adrenoleukodystrophy (X-ALD). A peroxisomal transport protein is mutated in this disorder. Due to reduced catabolism and enhanced fatty acid (FA) elongation, VLCFA accumulates in plasma and in all tissues, contributing to the clinical manifestations of this disorder. During peroxisomal metabolism, heat is produced but it is considered lost. Instead, it is a form of energy that could play a role in molecular mechanisms of this pathology and other neurodegenerative disorders. The thermogenic flux induced by lignoceric acid (C24:0) was estimated by isothermal titration calorimetry in peroxisomes isolated from HepG2 cells and from fibroblasts obtained from patients with X-ALD and healthy subjects. Heat flux induced by lignoceric acid in HepG2 peroxisomes was exothermic, indicating normal peroxisomal metabolism. In X-ALD peroxisomes the heat flux was endothermic, indicating the requirement of heat/energy, possibly for cellular metabolism. In fibroblasts from healthy subjects, the effect was less pronounced than in HepG2, a kind of cell known to have greater FA metabolism than fibroblasts. Our hypothesis is that heat is not lost but it could act as an activator, for example on the heat-sensitive pathway related to TRVP2 receptors. To investigate this hypothesis we focused on peroxisomal metabolism, considering that impaired heat generation could contribute to the development of peroxisomal neurodegenerative disorders.

Antimicrobial Effect of Picea abies Extracts on E. coli Growth.

This study aims to investigate the effect of essential oils extracted from wood residues of Picea abies on the growth of Escherichia coli. The essential oils were extracted by supercritical carbon dioxide, leading to a yield of 3.4 ± 0.5% (w/w) in 120 min. The antimicrobial effect was tested at 37 °C by isothermal calorimetry. The heat-flow (dq/dt vs. time) was integrated to give a fractional reaction curve (α vs. time). Such curves were fitted by a modified Gompertz function to give the lag-time (λ) and the maximum growth rate (µmax) parameters. The results showed that λ was linearly correlated with E. coli concentration (λ = 1.4 h/log (CFU/mL), R2 = 0.997), whereas µmax was invariant. Moreover, the overall heat was nearly constant to all the dilutions of E. coli. Instead, when the essential oil was added (with concentrations ranging from 1 to 5 mg/L) to a culture of E. coli (104 CFU/mL), the lag-time increased from 14.1 to 33.7 h, and the overall heat decreased from 2120 to 2.37 J. The results obtained by the plate count technique were linear with the lag-time (λ), where (λ = -7.3 × log (CFU/mL) + 38.3, R2 = 0.9878). This suggested a lower capacity of E. coli to metabolize the substrate in the presence of the essential oils. The results obtained in this study promote the use of essential oils from wood residues and their use as antimicrobial products.

Inhibition of lipid autoxidation by vegetable waxes.

This study aims to evaluate the effect of vegetable waxes on the kinetics of lipid oxidation of linseed oil. Apple and orange waxes were obtained using supercritical carbon dioxide. The capacity of waxes to inhibit or retard the oxidation of linseed oil was determined by isothermal calorimetry at 298 K. The results show that waxes were able to slow down linseed oil autoxidation, with apple waxes being more active than orange waxes. However, such activity was visible only at relatively high concentrations (>1% of waxes), greatly higher than the concentration used with radical chain breakers like BHT (0.2%). The inhibition activity was explained by considering three different mechanisms: (1) residual polyphenol content in the wax, (2) high termination rate of the radical chain process, and (3) physical hindrance of the oxidation process by change in viscosity. All these mechanisms were possible, although the latter seemed to be the most important. Finally, the importance of waxes in the inhibition of lipid autoxidation was determined by testing their inhibition activity in combination with primary antioxidants. A mixture of waxes with BHA, ethoxyquin and α-tocopherol showed a higher rate of inhibition than when present individually. This suggested a strong cooperative radical scavenging activity, whose beneficial effect might pave the way to the formulation of novel functional ingredients.

A microcalorimetry study on the oxidation of linoleic acid and the control of rancidity.

The oxidative deterioration of unsaturated lipids fatty acids is a great concern for the food industry as it is associated with the development of rancid off-odors and the reduction of food quality. This work describes the potential use of isothermal microcalorimetry to monitor the oxidation of linoleic acid, an important conjugated fatty acid responsible for the development of rancidity. The heat flow signal developed during the oxidation process reflects a multistep mechanism typical of radical chain reactions. From the analysis of the thermograms, it is possible to identify a period of the reaction that occurs with an order equal to 0.5. This period is correlated with the propagation period of the radical chain reaction. In addition, it allows detecting the early appearance of rancidity notes, as confirmed with the analysis of the samples headspace by Proton-Transfer-Reaction Mass Spectrometry (PTR-MS). The proposed approach was finally applied to compare the capacity of natural and synthetic antioxidants to inhibit the oxidation process of linoleic acid and the occurrence of rancidity. The results presented here show the advantages of microcalorimetry to study oxidation reactions and their control.

Low phytic acid 1 mutation in maize modifies density, starch properties, cations, and fiber contents in the seed.

Monogastric animals are unable to digest phytic acid, so it represents an antinutritional factor and also an environmental problem. One strategy to solve this problem is the utilization of low phytic acid (lpa) mutants that accumulate low levels of phytic P and high levels of free phosphate in the seeds; among the lpa maize mutants lpa1 exhibited the highest reduction of phytic acid in the seed. This study indicated that the low phytic acid mutations exerted pleiotropic effects not directly connected to the phytic acid pathway, such as on seed density, content of ions, and the antioxidant compounds present in the kernels. Furthermore some nutritional properties of the flour were altered by the lpa1 mutations, in particular lignin and protein content, while the starch does not seem to be modified as to the total amount and in the amylose/amylopectin ratio, but alterations were noticed in the structure and size of granules.