Simplified method for the measurement of plasma alkylresorcinols: Biomarkers of whole-grain intake.

RATIONALE: Consumption of whole grains is negatively associated with cardiovascular disease (CVD) risk but quantification of whole-grain intake is challenging. Alkylresorcinols (ARs) are biomarkers of whole-grain intake. Current methods for AR quantification involve a time-consuming multi-step separation process that hampers applicability in large-scale studies. METHODS: We developed a streamlined method to quantify ARs in human plasma based on protein precipitation and direct injection into an ultra-high-performance liquid chromatograph coupled to a quadrupole time-of-flight mass spectrometer operating in atmospheric pressure chemical ionization negative ion mode. RESULTS: Separation of five major ARs was achieved, with linearity in the 5 to 550 nmol/L range and a lower limit of detection (LOD) of 0.5 nmol/L and quantification (LOQ) of 5 nmol/L. The within-run and between-run precision and accuracy were below 15%, and recoveries above 90%. Once validated, the method was applied to measure concentrations of plasma ARs in subjects who participated in a randomized, crossover trial evaluating the effect of carbohydrate type on CVD risk factors. The unrefined carbohydrate diet with the highest fiber content resulted in the highest plasma AR concentration (93 ± 78 nmol/L), and was significantly different (p <0.01) from lower fiber diets (18 ± 26 nmol/L and 19 ± 26 nmol/L, simple and unrefined carbohydrate, respectively). CONCLUSIONS: This method offers a simplified approach to measure concentrations of plasma ARs as an objective biomarker of whole-grain intake that can be applied to large-scale cohort studies.

Micro-scale environmental variation amplifies physiological variation among individual mussels.

The contributions of temporal and spatial environmental variation to physiological variation remain poorly resolved. Rocky intertidal zone populations are subjected to thermal variation over the tidal cycle, superimposed with micro-scale variation in individuals' body temperatures. Using the sea mussel (Mytilus californianus), we assessed the consequences of this micro-scale environmental variation for physiological variation among individuals, first by examining the latter in field-acclimatized animals, second by abolishing micro-scale environmental variation via common garden acclimation, and third by restoring this variation using a reciprocal outplant approach. Common garden acclimation reduced the magnitude of variation in tissue-level antioxidant capacities by approximately 30% among mussels from a wave-protected (warm) site, but it had no effect on antioxidant variation among mussels from a wave-exposed (cool) site. The field-acclimatized level of antioxidant variation was restored only when protected-site mussels were outplanted to a high, thermally stressful site. Variation in organismal oxygen consumption rates reflected antioxidant patterns, decreasing dramatically among protected-site mussels after common gardening. These results suggest a highly plastic relationship between individuals' genotypes and their physiological phenotypes that depends on recent environmental experience. Corresponding context-dependent changes in the physiological mean-variance relationships within populations complicate prediction of responses to shifts in environmental variability that are anticipated with global change.