Anatomical site-specific carbohydrate availability impacts Streptococcus pneumoniae virulence and fitness during colonization and disease

Streptococcus pneumoniae ( Spn ) colonizes the nasopharynx asymptomatically but can also cause severe life-threatening disease. Importantly, stark differences in carbohydrate availability exist between the nasopharynx and invasive disease sites, such as the bloodstream, which most likely impact Spn ’s behavior. Herein, using chemically-defined media (CDM) supplemented with physiological levels of carbohydrates, we examined how anatomical-site specific carbohydrate availability impacted Spn physiology and virulence. Spn grown in CDM modeling the nasopharynx (CDM-N) had reduced metabolic activity, slower growth rate, demonstrated mixed acid fermentation with marked H 2 O 2 production, and were in a carbon-catabolite repression (CCR)-derepressed state versus Spn grown in CDM modeling blood (CDM-B). Using RNA-seq, we determined the transcriptome for Spn WT and its isogenic CCR deficient mutant in CDM-N and CDM-B. Genes with altered expression as a result of changes in carbohydrate availability or catabolite control protein deficiency, respectively, were primarily involved in carbohydrate metabolism, but also encoded for established virulence determinants such polysaccharide capsule and surface adhesins. We confirmed that anatomical site-specific carbohydrate availability directly influenced established Spn virulence traits. Spn grown in CDM-B formed shorter chains, produced more capsule, were less adhesive, and were more resistant to macrophage killing in an opsonophagocytosis assay. Moreover, growth of Spn in CDM-N or CDM-B prior to the challenge of mice impacted relative fitness in a colonization and invasive disease model, respectively. Thus, anatomical site-specific carbohydrate availability alters Spn physiology and virulence, in turn promoting anatomical-site specific fitness.

Hydration Is More Important Than Exogenous Carbohydrate Intake During Push-to-the-Finish Cycle Exercise in the Heat

Dehydration ≥2% loss of body mass is associated with reductions in performance capacity, and carbohydrate (CHO)-electrolyte solutions (CES) are often recommended to prevent dehydration and provide a source of exogenous carbohydrate during exercise. It is also well established that performance capacity in the heat is diminished compared to cooler conditions, a response attributable to greater cardiovascular strain caused by high skin and core temperatures. Because hydration status, environmental conditions, and carbohydrate availability interact to influence performance capacity, we sought to determine how these factors affect push-to-the-finish cycling performance. Ten young trained cyclists exercised at a moderate intensity (2.5 W·kg−1) in a hot-dry condition [40°C, 20% relative humidity (RH)] until dehydration of ~2% body mass. Subjects then consumed either no fluid (NF) or enough fluid (water, WAT; Gatorade®, GAT; or GoodSport™, GS) to replace 75% of lost body mass over 30 min. After a 30-min light-intensity warm-up (1.5 W·kg−1) in a 35°C, 20% RH environment, subjects then completed a 120-kJ time trial (TT). TT time-to-completion, absolute power, and relative power were significantly improved in WAT (535 ± 214 s, 259 ± 99 W, 3.3 ± 0.9 W·kg−1), GAT (539 ± 226 s, 260 ± 110 W, 3.3 ± 1.0 W·kg−1), and GS (534 ± 238 s, 262 ± 105 W, 3.4 ± 1.0 W·kg−1) compared to NF (631 ± 310 s, 229 ± 96 W, 3.0 ± 0.9 W·kg−1) all (p < 0.01) with no differences between WAT, GAT, and GS, suggesting that hydration is more important than carbohydrate availability during exercise in the heat. A subset of four subjects returned to the laboratory to repeat the WAT, GAT, and GS treatments to determine if between-beverage differences in time-trial performance were evident with a longer TT in thermoneutral conditions. Following dehydration, the ambient conditions in the environmental chamber were reduced to 21°C and 20% RH and subjects completed a 250-kJ TT. All four subjects improved TT performance in the GS trial (919 ± 353 s, 300 ± 100 W, 3.61 ± 0.86 W·kg−1) compared to WAT (960 ± 376 s, 283 ± 91 W, 3.43 ± 0.83 W·kg−1), while three subjects improved TT performance in the GAT trial (946 ± 365 s, 293 ± 103 W, 3.60 ± 0.97 W·kg−1) compared to WAT, highlighting the importance of carbohydrate availability in cooler conditions as the length of a push-to-the-finish cycling task increases.

Increased carbohydrate availability effects energy and nutrient periodisation of professional male athletes from the Australian Football League

This research aims to explore the effect of increased carbohydrate availability intervention on energy intake and distribution in professional Australian Football athletes. Six 24-h energy and macronutrient intakes were quantified (n= 19 males; age 24 ±4 y, stature 187 ±8 cm, mass 87 ±9 kg) using photographic food diaries and Foodworks analyses. Energy expenditure was estimated for the same period using GeneActiv accelerometers. During three control days, athletes had ad libitum access to food, while the three intervention days increased carbohydrate availability, through greater prompting and access to carbohydrate foods. Daily energy intake was higher during intervention (185 ±40 kJ/kg/d) compared with control (172 ±31 kJ/kg/d; p<0.05) but remained below estimated expenditure, and carbohydrate intake was also greater with intervention (5.0 ±0.2 g/kg/d) than control (4.0 ±0.2 g/kg/d; p<0.05). Expenditure was highest during the morning which coincided with lowest intake on all days, while the intervention was associated with greater carbohydrate intake in the morning (0.6 g/kg, p< 0.05) compared with control. Increasing availability of carbohydrate during high-load training generated a modest increase in carbohydrate and energy intake, and the intervention was most effective in improving carbohydrate intake during mornings. Novelty Bullets • Increased access and provision of carbohydrate foods increased carbohydrate consumption and energy intake on high training load days. • Daily distribution of energy intake can be modified through actively promoting carbohydrate consumption.

Native and non-native sources of carbohydrate correlate with abundance of an invasive ant

Invasive species threaten many ecological communities and predicting which communities and sites are invasible remains a key goal of invasion ecology. Although invasive ants often reach high abundances in association with plant-based carbohydrate resources, the source and provenance of these resources are rarely investigated. We characterized carbohydrate resources across ten sites with a range of yellow crazy ant abundance in Arnhem Land, Australia and New Caledonia to determine whether yellow crazy ant (Anoplolepis gracilipes) abundance and trophic position correlate with carbohydrate availability, as well as the relative importance of native and non-native sources of carbohydrates to ant diet. In both locations, measures of yellow crazy ant abundance strongly positively correlated with carbohydrate availability, particularly honeydew production, the number of tended hemipterans, and the number of plants with tended hemipterans. In Arnhem Land, 99.6% of honeydew came from native species, whereas in New Caledonia, only 0.2% of honeydew was produced by a native hemipteran. More honeydew was available in Australia due to three common large-bodied species of Auchenorrhyncha honeydew producers (treehoppers and leafhoppers). Yellow crazy ant trophic position declined with increasing yellow crazy ant abundance indicating that in greater densities the ants are obtaining more of their diet from plant-derived resources, including honeydew and extrafloral nectar. The relationships between yellow crazy ant abundance and carbohydrate availability could not be explained by any of the key environmental variables we measured at our study sites. Our results demonstrate that the positive correlation between yellow crazy ant abundance and honeydew production is not contingent upon the provenance of the hemipterans. Native sources of carbohydrate may play an underappreciated role in greatly increasing community invasibility by ants.

Carbohydrate mouth rinse improves resistance exercise capacity in the glycogen-lowered state

The effect of carbohydrate mouth rinse (CHO MR) on resistance exercise performance is equivocal, and may be moderated by carbohydrate availability. This study determined the effect of CHO MR on low-load resistance exercise capacity completed in a fed but glycogen-lowered state. Twelve resistance-trained men (age: 22±4 years; height: 1.79±0.05m; weight: 78.7±7.8kg; bench press 1-RM: 87±21kg; squat 1-RM: 123±19kg) completed two fed-state resistance exercise bouts consisting of 6 sets of bench press and 6 sets of squat to failure at 40% 1-RM. Each bout was preceded by glycogen-depleting cycling the evening before, with feeding controlled to create acute energy deficit and maintain low muscle glycogen. During resistance exercise, participants rinsed with either a 6% CHO MR solution or a taste-matched placebo (PLA) between sets. Total volume workload was greater with CHO MR (9354±2051kg vs. 8525±1911kg, p=0.010). Total number of repetitions of squat were greater with CHO MR (107±26 vs. 92±16, p=0.017); the number of repetitions of bench press were not significantly different (CHO MR: 120±24 vs. PLA: 115±22, p=0.146). This was independent of differences in feeling or arousal. CHO MR may be an effective ergogenic aid for athletes completing resistance exercise when in energy deficit and with low carbohydrate availability. Novelty • CHO MR can increase low-load resistance exercise capacity undertaken in a glycogen-lowered but fed state. • This effect was driven by a greater number of repetitions-to-failure in the squat – using muscles lowered in glycogen content with exhaustive cycling on the evening prior to resistance exercise – but not bench press.