Metabolic adaptation characterizes short-term resistance to weight loss induced by a low-calorie diet in overweight/obese individuals.

BACKGROUND: Low-calorie diet (LCD)-induced weight loss demonstrates response heterogeneity. Physiologically, a decrease in energy expenditure lower than what is predicted based on body composition (metabolic adaptation) and/or an impaired capacity to increase fat oxidation may hinder weight loss. Understanding the metabolic components that characterize weight loss success is important for optimizing weight loss strategies. OBJECTIVES: We tested the hypothesis that overweight/obese individuals who had lower than expected weight loss in response to a 28-d LCD would be characterized by 1) impaired fat oxidation and 2) whole-body metabolic adaptation. We also characterized the molecular mechanisms associated with weight loss success/failure. METHODS: This was a retrospective comparison of participants who met their predicted weight loss targets [overweight/obese diet sensitive (ODS), n = 23, females = 21, males = 2] and those that did not [overweight/obese diet resistant (ODR), n = 14, females = 12, males = 2] after a 28-d LCD (900-1000 kcal/d). We used whole-body (energy expenditure and fat oxidation) and tissue-specific measurements (metabolic proteins in skeletal muscle, gene expression in adipose tissue, and metabolites in serum) to detect metabolic properties and biomarkers associated with weight loss success. RESULTS: The ODR group had greater mean ± SD metabolic adaptation (-175 ± 149 kcal/d; +119%) than the ODS group (-80 ± 108 kcal/d) after the LCD (P = 0.030). Mean ± SD fat oxidation increased similarly for both groups from baseline (0.0701 ± 0.0206 g/min) to day 28 (0.0869 ± 0.0269 g/min; P < 0.001). A principal component analysis factor comprised of serum 3-hydroxybutyric acid, citrate, leucine/isoleucine, acetyl-carnitine, and 3-hydroxylbutyrlcarnitine was associated with weight loss success at day 28 (std. ß = 0.674, R2 = 0.479, P < 0.001). CONCLUSIONS: Individuals who achieved predicted weight loss targets after a 28-d LCD were characterized by reduced metabolic adaptation. Accumulation of metabolites associated with acetyl-CoA excess and enhanced ketogenesis was identified in the ODS group.This trial was registered at clinicaltrials.gov as NCT01616082.

Sub-2 microm HPLC coupled with sub-ppm mass accuracy for analysis of pharmaceutical compound libraries.

Recent advances in accurate mass analysis are poised to allow the high-throughput production of accurate mass data on many more compounds than was previously available. It is shown that sub-ppm mass accuracy (producing elemental compositions) can be obtained on a simple TOF mass spectrometer operating in the manufacturer's standard mode. Concomitantly, there have been important technological advances in LC with respect to speed of analysis using sub-2 microm particle columns. Much of the sub-2 microm work in the literature has been under the label ultra performance LC (UPLC), however, we show that very high-speed results can be obtained using other manufacturer's pumps by using elevated column temperatures. Using elevated temperatures, HPLC peak widths on the order of 1 s can be obtained. We report the coupling of these two technologies (sub-ppm mass accuracy MS with high-speed HPLC) for the rapid analysis of compounds entering pharmaceutical libraries.

Automated sub-ppm mass accuracy on an ESI-TOF for use with drug discovery compound libraries.

An automated, routine method to obtain sub-ppm accurate mass data on a benchtop electrospray ionization time-of-flight (ESI-TOF) mass spectrometer is described. Standards in the mass range 114 to 734 Da were analyzed over a 5-day period to demonstrate intra- and interday precision and mean mass accuracy less than 1 ppm. One hundred drug discovery pharmaceutical compounds were used to demonstrate an absolute average mass accuracy of 0.47 +/- 0.31 ppm. This is in contrast to previous reports of accurate mass analysis using time-of-flight mass spectrometry (TOFMS) technology that operates within 3 to 5 ppm. The same 100 samples were also analyzed using Fourier transform mass spectrometry (FTMS) technology and yielded comparable results to the TOFMS analysis.