Glycine supplementation can partially restore oxidative stress-associated glutathione deficiency in ageing cats.

Intracellular levels of glutathione, the major mammalian antioxidant, are reported to decline with age in several species. To understand whether ageing affects circulating glutathione levels in cats, blood was sampled from two age groups, < 3 years and > 9 years. Further, to determine whether dietary supplementation with glutathione precursor glycine (GLY) affects glutathione concentrations in senior cats (> 8 years), a series of free GLY inclusion level dry diets were fed. Subsequently, a 16-week GLY feeding study was conducted in senior cats (> 7 years), measuring glutathione, and markers of oxidative stress. Whole blood and erythrocyte total, oxidised and reduced glutathione levels were significantly decreased in senior cats, compared with their younger counterparts (P ≤ 0·02). The inclusion level study identified 1·5 % free GLY for the subsequent dry diet feeding study. Significant increases in erythrocyte total and reduced glutathione were observed between senior cats fed supplemented and control diets at 4 weeks (P ≤ 0·03; maximum difference of 1·23 µM). Oxidative stress markers were also significantly different between groups at 8 (P = 0·004; difference of 0·68 nG/ml in 8-hydroxy-2'-deoxyguanosine) and 12 weeks (P ≤ 0·049; maximum difference of 0·62 nG/mG Cr in F2-isoprostane PGF2α). Senior cats have lower circulating glutathione levels compared with younger cats. Feeding senior cats a complete and balanced dry diet supplemented with 1·5 % free GLY for 12 weeks elevated initial erythrocyte glutathione and altered markers of oxidative stress. Dietary supplementation with free GLY provides a potential opportunity to restore age-associated reduction in glutathione in cats.

Adaptations Supporting Plasma Methionine on a Limited-Methionine, High-Cystine Diet Alter the Canine Plasma Metabolome Consistent with Interventions that Extend Life Span in Other Species.

BACKGROUND: Using indicator amino acid oxidation methodology, the mean dietary requirement of adult dogs for methionine (Met) was estimated to be ∼66% of the current recommended allowance. Dogs fed a diet formulated to provide the estimated mean Met requirement for 32 wk maintained plasma Met, seemingly supported by betaine oxidation. OBJECTIVE: To gain a better understanding of the metabolic changes that were associated with supporting plasma Met when dogs were fed a limited Met diet over 32 wk, we analyzed plasma samples taken from that study using a data-driven metabolomics approach. METHODS: Labrador retrievers (20 females/13 males; mean age: 4.9 y; range: 2.0-7.9 y) were fed semi-purified, nutritionally complete diets. After 4 wk of feeding a control diet (DL-Met; 1.37 g/1000 kcal), 17 dogs remained on this diet and 16 were transitioned to a test diet formulated to the estimated mean Met requirement (0.55 g/1000 kcal), with dietary total sulfur amino acid maintained with additional l-cystine (Cys). Dogs were individually fed diets to maintain a stable body weight at an ideal body condition score for 32 wk. Plasma samples from fasted blood collected at baseline and 8 and 32 wk were analyzed using untargeted metabolic profiling. RESULTS: Analysis of metabolites (n = 593) confirmed our primary findings (increased Met, betaine, and dimethylglycine). Metabolite changes consistent with repartitioning choline to support Met cycling included reduced pools of lipids derived via phosphatidylethanolamine N-methyltransferase and enhanced fatty acid oxidation. Some changes were consistent with metabolomics studies reported in other species that used interventions known to extend life span (caloric- and Met-restricted diets or feeding strategy). CONCLUSIONS: Changes in the plasma metabolome were consistent with reported adaptations to support Met-dependent activities. We propose that feeding a limited-Met, high-Cys diet using the estimated mean Met requirement in adult Labrador retrievers alters regulation of the Met cycle, thereby altering metabolism, similar to interventions that extend life span.

Effects of solar radiation on endurance exercise capacity in a hot environment.

PURPOSE: The present study investigated the effects of variations in solar radiation on endurance exercise capacity and thermoregulatory responses in a hot environment. METHODS: Eight male volunteers performed four cycle exercise trials at 70 % maximum oxygen uptake until exhaustion in an environmental chamber maintained at 30 °C and 50 % relative humidity. Volunteers were tested under four solar radiation conditions: 800, 500, 250 and 0 W/m(2). RESULTS: Exercise time to exhaustion was less on the 800 W/m(2) trial (23 ± 4 min) than on all the other trials (500 W/m(2) 30 ± 7 min; P < 0.05, 250 W/m(2) 43 ± 10 min; P < 0.001, 0 W/m(2) 46 ± 10 min; P < 0.001), and on the 500 W/m(2) trial than the 250 W/m(2) (P < 0.05) and 0 W/m(2) (P < 0.01) trials. There were no differences in core (rectal) temperature, total sweat loss, heart rate, skin blood flow, cutaneous vascular conductance and percentage changes in plasma volume between trials (P > 0.05). Mean skin temperature was higher on the 800 W/m(2) trial than the 250 and 0 W/m(2) trials (P < 0.05), and on the 500 W/m(2) trial than the 0 W/m(2) trial (P < 0.05). The core-to-skin temperature gradient was narrower on the 800 W/m(2) trial than the 250 and 0 W/m(2) trials (P < 0.05). CONCLUSION: The present study demonstrates that endurance exercise capacity in a hot environment falls progressively as solar radiation increases.

Hydration amongst nurses and doctors on-call (the HANDS on prospective cohort study).

BACKGROUND & AIMS: Dehydration of as little 2% of total body weight may impair physical and cognitive performance. The aim of this study was to investigate the prevalence of dehydration at the start and end of shifts in nurses and doctors on-call. The secondary aims were to assess the relation between hydration status and cognitive function. METHODS: This prospective cohort study was conducted on nurses and doctors working on medical and surgical admissions wards at a university teaching hospital. Participants arrived on the ward approximately 20 min before their shift and were asked to provide a urine sample. Height and weight were then measured. A 10 mL blood sample was analysed for full blood count, serum urea and electrolytes, and blood glucose. Cognitive function was assessed using a series of computer-based tests including the Stroop Colour Naming Interference Test and Sternberg Memory Paradigm. Participants then worked normally but were asked to keep a fluid diary for the duration of their shift and fluid balance was estimated. Tests were repeated at the end of the shift. Dehydration was defined as urine osmolality >800 mOsmol/kg and oliguria was defined as urine output <0.5 ml/kg/hour. RESULTS: We recruited 92 nurses and doctors, of whom 88 completed the study, amounting to 130 shifts. 52% participated for one shift, and 48% for two shifts. Thirty-six percent of participants were dehydrated at the start of the shift and 45% were dehydrated at the end of their shift. Mean (SD) urinary osmolality was significantly greater at the end of the shift when compared with the start [720 (282) vs. 622 (297) mOsm/kg, P = 0.031). Moreover, 41% were oliguric at the end of the shift. Single number and five-letter Sternberg short-term memory tests were significantly impaired in dehydrated participants (P < 0.05). CONCLUSIONS: This study highlights that a significant proportion of nurses and doctors were dehydrated at the start and end of medical and surgical shifts. Dehydration was associated with some impairment of cognitive function.

Implications of active lifestyles and environmental factors for water needs and consequences of failure to meet those needs.

Heat stress and exercise increase water loss from the body, primarily in the form of sweat. For some occupational groups, including miners, construction workers in hot climates, soldiers, and some athletes, daily water losses can reach 10-12 L. These losses must be replaced on a daily basis to maintain functional capacity. Both hyperhydration and hypohydration will, if sufficiently severe, impair all aspects of physiological function. Tests of strength and power are largely unaffected by dehydration of up to about 2%-4% of body mass. However, decrements in the performance of endurance tests may occur at these levels, especially in warm environments. Body water deficits, if sufficiently severe, also have adverse effects on measures of mood and on some elements of cognitive function and result in an increased subjective rating of the perception of effort. Beverages consumed during exercise can provide carbohydrates and electrolytes that may be beneficial in some situations; however, drinking in volumes required to match sweat loss may cause gastrointestinal discomfort that will generally impair performance.

Acute dopamine/noradrenaline reuptake inhibition enhances human exercise performance in warm, but not temperate conditions.

Nine healthy endurance-trained males were recruited to examine the effect of a dual dopamine/noradrenaline reuptake inhibitor on performance, thermoregulation and the hormonal responses to exercise. Subjects performed four trials, ingesting either a placebo (pla) or 2 x 300 mg bupropion (bup), prior to exercise in temperate (18 degrees C) or warm (30 degrees C) conditions. Trials consisted of 60 min cycle exercise at 55% W(max) immediately followed by a time trial (TT). TT performance in the heat was significantly improved by bupropion (pla: 39.8 +/- 3.9 min, bup: 36.4 +/- 5.7 min; P = 0.046), but no difference between treatments was apparent in temperate conditions (pla: 30.6 +/- 2.2 min, bup: 30.6 +/- 1.9 min; P = 0.954). While TT power output was consistently lower in the heat when compared to temperate conditions, this decrement was attenuated by bupropion. At the end of the TT in the heat, both core temperature (pla 39.7 +/- 0.3 degrees C, bup 40.0 +/- 0.3 degrees C; P = 0.017) and HR (pla 178 +/- 7 beats min(-1), bup 183 +/- 12 beats min(-1); P = 0.039), were higher in the bupropion trial than in the placebo. Circulating pituitary and adrenal hormone concentrations increased throughout exercise in all trials. Circulating serum prolactin was elevated above temperate levels during exercise in a warm environment (P < 0.001). These data indicate that performance in warm conditions is enhanced by acute administration of a dual dopamine/noradrenaline reuptake inhibitor. No such effect was apparent under temperate conditions. It appears that bupropion enabled subjects to maintain a greater TT power output in the heat with the same perception of effort and thermal stress reported during the placebo trial, despite the attainment of a higher core temperature.