Effects of a Single Dose of BURN-XT™ on Resting Metabolic Rate, Substrate Oxidation, and Various Indices of Affect

Introduction: Many consumers use dietary supplements in the hopes of increasing energy and burning more calories, which if sustained over time may help accelerate weight loss. The purpose of this clinical trial was to investigate the effects of an over-the-counter thermogenic supplement called Burn-XT™ (BXT) on metabolic rate, substrate oxidation, and various psychometric indices of affect that impact weight management. Methods: Using a double-blind, placebo-controlled, cross-over design, 16 women and 10 men (29.3 ± 7.3 yr, 169.4 ± 8.6 cm, 75.5 ± 14.3 kg) underwent two testing sessions: placebo (PL) and BXT. Seated metabolic rate and substrate oxidation, vital signs, and anchored visual analogue scale (VAS) assessments of energy, mood, motivation, focus, fatigue, concentration, and appetite were made before supplementation and hourly for three hours post-ingestion. Two-factor (2x4) factorial ANOVAs and paired sample t-tests (corrected for multiple comparisons) were used for analyses. Results: Significant increases in metabolic rate (oxygen consumption) were noted at 60 minutes in BXT (+11.9 mL O2/min) vs. PL (-2.5 mL O2/min), p = 0.004, d = -0.74. Only BXT increased metabolic rate compared to baseline at 60 minutes (+11.9 mL O2/min, p = 0.021, d = -0.53) and 120 minutes (+12.1 mL O2/min, p = 0.019, d = -0.54). The AUC for resting energy expenditure increased more in BXT vs. PL (p = 0.007, d = -0.57). VAS detected significant improvements in energy, mood, focus, and concentration for BXT vs. PL at 120 and 180 minutes (all p < 0.05, d = -0.58 to -0.68). In all cases, within-group changes from baseline for these VAS parameters were significant (all p < 0.05, d = -0.76 to -1.38) in BXT but not in PL. No within or between group differences in appetite, substrate oxidation, or heart rate were noted. Small (~3-4 mm Hg), but statistically significant (p < 0.05, d = -0.51 to -0.69) increases in diastolic blood pressure were noted in BXT at 60, 120, and 180 min vs. PL; and in systolic blood pressure at 60 min vs. PL. In all cases, values remained within normal clinical hemodynamic ranges. Conclusions: A single dose of BXT safely increased metabolic rate, energy, mood, focus, and concentration. Given that these factors are known to favorably impact weight management, future studies should determine whether daily supplementation with BXT reduces body weight and improves body composition.

Mimicking Elementary Reactions of Manganese Lipoxygenase Using Mn-hydroxo and Mn-alkylperoxo Complexes

Manganese lipoxygenase (MnLOX) is an enzyme that converts polyunsaturated fatty acids to alkyl hydroperoxides. In proposed mechanisms for this enzyme, the transfer of a hydrogen atom from a substrate C-H bond to an active-site MnIII-hydroxo center initiates substrate oxidation. In some proposed mechanisms, the active-site MnIII-hydroxo complex is regenerated by the reaction of a MnIII-alkylperoxo intermediate with water by a ligand substitution reaction. In a recent study, we described a pair of MnIII-hydroxo and MnIII-alkylperoxo complexes supported by the same amide-containing pentadentate ligand (6Medpaq). In this present work, we describe the reaction of the MnIII-hydroxo unit in C-H and O-H bond oxidation processes, thus mimicking one of the elementary reactions of the MnLOX enzyme. An analysis of kinetic data shows that the MnIII-hydroxo complex [MnIII(OH)(6Medpaq)]+ oxidizes TEMPOH (2,2′-6,6′-tetramethylpiperidine-1-ol) faster than the majority of previously reported MnIII-hydroxo complexes. Using a combination of cyclic voltammetry and electronic structure computations, we demonstrate that the weak MnIII-N(pyridine) bonds lead to a higher MnIII/II reduction potential, increasing the driving force for substrate oxidation reactions and accounting for the faster reaction rate. In addition, we demonstrate that the MnIII-alkylperoxo complex [MnIII(OOtBu)(6Medpaq)]+ reacts with water to obtain the corresponding MnIII-hydroxo species, thus mimicking the ligand substitution step proposed for MnLOX.

Genetic fusion of P450 BM3 and formate dehydrogenase towards self-sufficient biocatalysts with enhanced activity

Fusion of multiple enzymes to multifunctional constructs has been recognized as a viable strategy to improve enzymatic properties at various levels such as stability, activity and handling. In this study, the genes coding for cytochrome P450 BM3 from B. megaterium and formate dehydrogenase from Pseudomonas sp. were fused to enable both substrate oxidation catalyzed by P450 BM3 and continuous cofactor regeneration by formate dehydrogenase within one construct. The order of the genes in the fusion as well as the linkers that bridge the enzymes were varied. The resulting constructs were compared to individual enzymes regarding substrate conversion, stability and kinetic parameters to examine whether fusion led to any substantial improvements of enzymatic properties. Most noticeably, an activity increase of up to threefold was observed for the fusion constructs with various substrates which were partly attributed to the increased diflavin reductase activity of the P450 BM3. We suggest that P450 BM3 undergoes conformational changes upon fusion which resulted in altered properties, however, no NADPH channeling was detected for the fusion constructs.

Comparison of the Effect of Hot and Thermo-Neutral Environments on Fat Oxidation during Post-Exercise Recovery in Exercise-Trained Obese Women: A Preliminary Report

Exercise training is recommended to promote energy expenditure. Fat utilization occurs during exercise and continues for an extended period of time after the exercise session. The environmental temperatures can influence whole body substrate oxidation. The present study aimed to address the impacts of environmental temperature on fat oxidation during post-exercise recovery in exercise-trained obese women. Eleven sedentary obese women (age: 18 - 50 y, BMI: 27.5 - 40 kg/m2) with regular menstruation participated in the study. All subjects underwent a 4-week moderate-intensity aerobic exercise program. After training, each subject completed 2 occasions of post-exercise recovery testing in hot (31 - 32 °C) and thermo-neutral (22 - 23 °C) conditions in a randomized crossover fashion with 3 - 4 days of washout period. Two exercise bouts preceding each recovery condition were identically performed for 60 min at 60 % of heart rate reserve (HRreserve) in the thermo-neutral condition. Both experiments were conducted during the follicular phase of menstrual cycle. Substrate oxidations were determined during 1 h of post-exercise recovery using indirect calorimetry. The results showed that the fat oxidation during recovery in thermo-neutral environment (52.8 ± 26.5 mg.kg-1.h-1) was significantly greater than recovery in hot environment (32.3 ± 27.9 mg.kg-1.h-1, p = 0.0002). Total energy from substrate oxidation was not different between hot and thermo-neutral environments. Thus, in obese women with 4-week exercise training, recovery in the thermo-neutral condition has a higher fat oxidation than in the hot condition. This result may be implicated in weight management for temperature of choice to recover after routine exercise training sessions. HIGHLIGHTS Fat oxidation was greater during recovery in thermo-neutral environment after moderate-intensity exercise in trained obese women Recovery carbohydrate oxidation was greater in hot environment than in thermo-neutral environment after moderate-intensity exercise Energy expenditure from substrate oxidations during recovery in both thermo-neutral and hot environments were similar GRAPHICAL ABSTRACT

Mitochondrial capacity and reactive oxygen species production during hypoxia and reoxygenation in the ocean quahog, Arctica islandica

Oxygen fluctuations are common in marine waters, and hypoxia/reoxygenation (H/R) stress can negatively affect mitochondrial metabolism. The long-lived ocean quahog, Arctica islandica, is known for its hypoxia tolerance associated with metabolic rate depression, yet the mechanisms that sustain mitochondrial function during oxygen fluctuations are not well understood. We used top-down metabolic control analysis (MCA) to determine aerobic capacity and control over oxygen flux in the mitochondria of quahogs exposed to short-term hypoxia (24 h &lt;0.01% O­2) and subsequent reoxygenation (1.5 h 21% O­2) compared to normoxic control animals (21% O­2). We demonstrated that flux capacities of the substrate oxidation and proton leak subsystems were not affected by hypoxia, while the capacity of the phosphorylation subsystem was enhanced during hypoxia associated with a depolarization of the mitochondrial membrane. Reoxygenation decreased oxygen flux capacities of all three mitochondrial subsystems. Control over oxidative phosphorylation (OXPHOS) respiration was mostly exerted by substrate oxidation regardless of H/R stress, whereas the control of the proton leak subsystem over LEAK respiration increased during hypoxia and returned to normoxic level during reoxygenation. During hypoxia, reactive oxygen species (ROS) efflux was elevated in the LEAK state, while suppressed in the OXPHOS state. Mitochondrial ROS efflux returned to normoxic control levels during reoxygenation. Thus, mitochondria of A. islandica appear robust to hypoxia by maintaining stable substrate oxidation and upregulating phosphorylation capacity, but remain sensitive to reoxygenation. This mitochondrial phenotype might reflect adaptation of A. islandica to environments with unpredictable oxygen fluctuations and its behavioural preference for low oxygen levels.