Repeatable inter‐individual variation in the thermal sensitivity of metabolic rate

Abstract

Assessing whether trait variations among individuals are consistent over time and among environmental conditions is crucial to understand evolutionary responses to new selective pressures such as climate change. According to the universal thermal dependence hypothesis, thermal sensitivity of metabolic rate should not vary strongly and consistently among organisms, implying limited evolutionary response for metabolic traits under climate change. However, this hypothesis has been rarely tested at an individual level, leaving a gap in our understanding of climate change impacts on metabolic responses and their potential evolution. Using the amphipod Gammarus fossarum, we investigated the variability and repeatability of individual metabolic thermal reaction norms over time. We found large variations in both the thermal sensitivity (i.e. slope) and expression level (i.e. intercept) of individual metabolic reaction norms. Moreover, differences among individuals were consistent over time, and therefore repeatable. Inter‐individual variations in body mass resulted in a high repeatability of metabolic expression level but had no significant effect on the repeatability of thermal sensitivity. Overall, our results highlight that inter‐individual variability and repeatability of thermal reaction norms can be substantial. We conclude that these consistent differences among individuals should not be overlooked when apprehending the ecological and evolutionary effects of climate change.

Alternative Sweeteners Modify the Urinary Excretion of Flavanones Metabolites Ingested through a New Maqui-Berry Beverage

“…The beverages developed using the latter sweeteners showed a 9.9% lesser amount of excretion than sucralose, on average. However, despite the trend observed, the large variation between volunteers did not allow for providing significant differences [21].…”

“…Interestingly, neither H, nor its phase II derivative, were detected, although H was the main flavanone in the maqui-citrus based beverages, accounting for 73.3% of the total flavanones, on average. Since the metabolism of the precursors of flavanone metabolites is closely dependent on the metabolic traits of the volunteers and the inter-individual variation [21], a range of metabolites (E, E-disulfate, HE, HE-diglucuronide, and HE-glucuronide-sulfate) was found in urine of a reduced number of volunteers. These compounds were present in quantifiable amount but the limited number of volunteers excreting these molecules indicates that these were not representative.…”

Beverages Based on Second Quality Citrus Fruits and Maqui Berry, a Source of Bioactive (Poly)phenols: Sorting Out Urine Metabolites upon a Longitudinal Study

“…Indeed, these compounds were found in quantifiable concentrations in the urine of a limited number of volunteers that turns them into no representative. This fact may be due to interindividual variations regarding metabolic traits, also responsible, in the frame of the assessments described in the present work, for the dispersion featuring the concentrations of the metabolites identified in vivo [ 21 ]. On the other hand, caffeic acid (CA) and its metabolites (CA glucuronide, CA sulfate, and CA glucuronide-sulfate), 3,4-di-hydroxyphenylacetic acid (DHPAA) and its metabolites (DHPAA glucuronide, DHPAA di-glucuronide, DHPAA glucuronide-sulfate, and DHPAA di-sulfate), eriodictyol (E) and its metabolites (E glucuronide and E sulfate), homoeriodictyol (HE) glucuronide, hippuric acid (HA), and HA sulfate, naringenin (N) and its metabolites (N glucuronide, N di-glucuronide, and N sulfate), trans-ferulic acid (TFA) metabolites (TFA glucuronide, TFA sulfate, and TFA di-sulfate), trans-isoferulic acid (TIFA) sulfate, and vanillic acid (VA) and its metabolites (VA di-glucuronide, VA glucuronide-sulfate, and VA di-sulfate) were identified and quantified in the urine of all volunteers.…”

Anthocyanin Metabolites in Human Urine after the Intake of New Functional Beverages

“…In addition, although the Dp class of anthocyanins was the most-commonly found in the drinks, representing up to 81.0% of the total anthocyanins, on average, for all beverages, its direct metabolite (GA), a fragmentation product of delphinidin glycosides, was not detected [26,27]. This could be the result of the degradation of GA, the most relevant DP metabolite in the human body, to form different molecules such as 4-O-methylgallic acid, pyrogallol, 2-O-methylpyrogallol, and resorcinol [28].…”