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Increased plasma concentrations of acylcarnitines (ACs) are suggested as a marker of metabolism disorders. The aim of the present study was to clarify which tissues are responsible for changes in the AC pool in plasma. The concentrations of medium- and long-chain ACs were changing during the fed-fast cycle in rat heart, muscles and liver. After 60 min running exercise, AC content was increased in fasted mice muscles, but not in plasma or heart. After glucose bolus administration in fasted rats, the AC concentrations in plasma decreased after 30 min but then began to increase, while in the muscles and liver, the contents of medium- and long-chain ACs were unchanged or even increased. Only the heart showed a decrease in medium- and long-chain AC contents that was similar to that observed in plasma. In isolated rat heart, but not isolated-contracting mice muscles, the significant efflux of medium- and long-chain ACs was observed. The efflux was reduced by 40% after the addition of glucose and insulin to the perfusion solution. Overall, these results indicate that during fed-fast cycle shifting the heart determines the medium- and long-chain AC profile in plasma, due to a rapid response to the availability of circulating energy substrates.

Since milk whey is an abundant dairy by-product and a significant threat to the environment, its utilization is of great interest. The study compares valorization of lactose and lactates—the main carbon sources of whey—by fermentation—an environmentally friendly process. Antimicrobials released during fermentation by food-grade bacteria can help increase the microbiological safety of food. Propionic acid—a strong antimicrobial—is obtained mainly by the petrochemical route, yet there is increasing interest in its synthesis in biotechnological pathway. Five strains of propionic acid bacteria (Acidipropionibacterium acidipropionici, Propionibacterium cyclohexanicum, Propionibacterium freudenreichii, Acidipropionibacterium jensenii and Acidipropionibacterium thoenii) were investigated for their ability to produce organic acids and biomass using Na lactate or lactose as carbon sources. Selected fermentates were investigated for their antimicrobial efficacy during in vitro studies with foodborne pathogens: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. Results confirm that the production of acids and biomass is considerably influenced by the added carbon source. The tested fermentates have strong and specific antimicrobial activity against Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. In addition, inhibition of Staphylococcus aureus and Klebsiella pneumonia depends on the activity of produced bacteriocins. The article also discusses the possibility of increasing the antimicrobial activity of fermentates by acidification.

In the heart, a nutritional state (fed or fasted) is characterized by a unique energy metabolism pattern determined by the availability of substrates. Increased availability of acylcarnitines has been associated with decreased glucose utilization; however, the effects of long-chain acylcarnitines on glucose metabolism have not been previously studied. We tested how changes in long-chain acylcarnitine content regulate the metabolism of glucose and long-chain fatty acids in cardiac mitochondria in fed and fasted states. We examined the concentrations of metabolic intermediates in plasma and cardiac tissues under fed and fasted states. The effects of substrate availability and their competition for energy production at the mitochondrial level were studied in isolated rat cardiac mitochondria. The availability of long-chain acylcarnitines in plasma reflected their content in cardiac tissue in the fed and fasted states, and acylcarnitine content in the heart was fivefold higher in fasted state compared to the fed state. In substrate competition experiments, pyruvate and fatty acid metabolites effectively competed for the energy production pathway; however, only the physiological content of acylcarnitine significantly reduced pyruvate and lactate oxidation in mitochondria. The increased availability of long-chain acylcarnitine significantly reduced glucose utilization in isolated rat heart model and in vivo. Our results demonstrate that changes in long-chain acylcarnitine contents could orchestrate the interplay between the metabolism of pyruvate–lactate and long-chain fatty acids, and thus determine the pattern of energy metabolism in cardiac mitochondria.