Distortions to the passage of time for annual events: Exploring why Christmas and Ramadan feel like they come around more quickly each year.

BACKGROUND: Commonly heard statements such as "Christmas comes around more quickly each year" suggest that the passage of time between annual events can become distorted, leading to the sensation of time passing more quickly than normal. At present however, it is unclear how prevalent such beliefs are and, what factors are predictive of it. AIM: To explore the prevalence of beliefs that annual events such as Christmas (Study 1 UK sample) and Ramadan (Study 2 Iraqi sample) feel like they come around more quickly each year. To establish the association between distortions to the passage of time between annual events and emotional wellbeing, event specific enjoyment, memory function and self-reported attention to time. METHODS: Participants completed an online questionnaire exploring their subjective experience of time in relation to Christmas and Ramadan. In addition, measures of attention to time, memory function, quality of life and event specific emotion were also taken. FINDINGS: There was widespread agreement that Christmas and Ramadan appeared to come around more quickly each year. In both countries, this belief was associated with greater prospective memory errors, greater attention to time and greater enjoyment of the event. Furthermore, in the UK greater belief that Christmas comes around more quickly was associated with lower social quality of life and in Iraq, greater belief that Ramadan comes around more quickly each year was associated with lower age and female gender. CONCLUSIONS: Distortions to the passage of time for annual events are widespread, occur across multiple cultures and are consistently predicted by prospective function, event enjoyment and attention to time. The absence of an association between older age (above 55 years) and a faster passage of time suggests that caution should be taken when concluding that time passes more quickly with increasing age.

The relationship between heart rate variability and glucose clearance in healthy men and women.

Heart rate variability (HRV) is a non-invasive indicator of the activity of the autonomic nervous system, which regulates many physiological functions including metabolism. The purpose of this study was to quantify the relationship between resting markers of HRV and oral glucose tolerance test (OGTT) response. Eighteen healthy individuals (10 males, 8 females, (23.8±2.9 years) underwent a 10-minute resting HRV recording. The final five minutes were evaluated via Kubios HRV Standard for: root mean square of successive differences (RMSSD), standard deviation of normal-to-normal sinus beats (SDNN), high frequency (HF), and low frequency (LF). A standard 2-hour OGTT was then administered. Glucose was measured via finger stick before, 30-minutes post, 1-hour post, and 2-hours post OGTT. Pearson correlations demonstrated that RMSSD, SDNN, HF and LF were strongly correlated to fasting blood glucose (FBG) for the group (p<0.05) but not for glucose area under the curve (AUC). When analyzed by sex, only males demonstrated significant correlations between AUC and RMSSD, SDNN, and LF (p<0.05). An independent samples t-test revealed no sex differences for FBG, AUC, RMSSD, SDNN, HF and LF. These findings provide new and interesting insights into the relationship of autonomic activity and glucose uptake, highlighting sex-based relationships.

Scoping review: Exploring the relationship between chrononutrition and glycemic responses in the adult population.

Chrononutrition, an emerging body of evidence on the relationship between biological rhythms and metabolism, has been established to be associated with glycemic responses. However, the available evidence is inconsistent, due to protocol variations. Therefore, this review aims to summarize the findings on chrononutrition characteristics and their association with glycemic responses among adults. Systematic searches were conducted across six databases (PubMed, EBSCO Host, ProQuest Central, MEDLINE & Ovid, Scopus and Web of Science) to identify all relevant studies published from January 2012. Two reviewers independently screened the abstracts and full-text articles based on the inclusion and exclusion criteria. Details about population characteristics, study methods and key findings were extracted following the PRISMA-ScR guideline. The quality of selected studies was evaluated using the mixed methods appraisal tool. The searchers identified 49 studies eligible for analysis. The results showed that meal timing, particularly night-time eating and snacking were associated with glycemic responses. Regarding meal regularity, skipping breakfast may affect glycemic responses, but no clear conclusion was drawn about its effect on insulin. The association between meal frequency and glycemic responses was inconclusive. Night fasting duration and restricted eating window are potentially associated with glycemic responses. The current review extensively investigates the association between chrononutrition factors and glycemic responses in adults. However, more prospective cohort and interventional studies are needed to better understand this causal-effect relationship.

NPY-mediated synaptic plasticity in the extended amygdala prioritizes feeding during starvation.

Efficient control of feeding behavior requires the coordinated adjustment of complex motivational and affective neurocircuits. Neuropeptides from energy-sensing hypothalamic neurons are potent feeding modulators, but how these endogenous signals shape relevant circuits remains unclear. Here, we examine how the orexigenic neuropeptide Y (NPY) adapts GABAergic inputs to the bed nucleus of the stria terminalis (BNST). We find that fasting increases synaptic connectivity between agouti-related peptide (AgRP)-expressing 'hunger' and BNST neurons, a circuit that promotes feeding. In contrast, GABAergic input from the central amygdala (CeA), an extended amygdala circuit that decreases feeding, is reduced. Activating NPY-expressing AgRP neurons evokes these synaptic adaptations, which are absent in NPY-deficient mice. Moreover, fasting diminishes the ability of CeA projections in the BNST to suppress food intake, and NPY-deficient mice fail to decrease anxiety in order to promote feeding. Thus, AgRP neurons drive input-specific synaptic plasticity, enabling a selective shift in hunger and anxiety signaling during starvation through NPY.

Regulation of metabolism by circadian rhythms: Support from time-restricted eating, intestinal microbiota & omics analysis.

Circadian oscillatory system plays a key role in coordinating the metabolism of most organisms. Perturbation of genetic effects and misalignment of circadian rhythms result in circadian dysfunction and signs of metabolic disorders. The eating-fasting cycle can act on the peripheral circadian clocks, bypassing the photoperiod. Therefore, time-restricted eating (TRE) can improve metabolic health by adjusting eating rhythms, a process achieved through reprogramming of circadian genomes and metabolic programs at different tissue levels or remodeling of the intestinal microbiota, with omics technology allowing visualization of the regulatory processes. Here, we review recent advances in circadian regulation of metabolism, focus on the potential application of TRE for rescuing circadian dysfunction and metabolic disorders with the contribution of intestinal microbiota in between, and summarize the significance of omics technology.

Effects of fasting during Ramadan month on soccer-specific technical performance, cognitive function, and perceptions in soccer players.

We aimed to examine the effects of Ramadan fasting (RF) and high-intensity short-term maximal performance on elite soccer players' shooting accuracy, executive function (EF), and perceptions. Sixteen Muslim elite players fasting during Ramadan underwent assessments before (BR), during (DR), and after Ramadan (AR). Soccer-specific technical performance was evaluated using the Loughborough Soccer Shooting Test (LSST) before and after a 5-metre shuttle run test (5mSRT), conducted at the same time-of-day (17:00 h). Performance metrics recorded included higher distance (HD), total distance (TD), and fatigue index (FI). RPE after a 5-min warm-up and each repetition of the 5mSRT were obtained, and the mean RPE score was calculated. Trail Making Test (TMT Parts A and B) were used after the warm-up and the 5mSRT. Perceived difficulty (PD) was assessed following the LSST. HD, TD, and FI were not affected by RF (p > 0.05). DR, RPE and accuracy scores in the LSST were significantly lower after the 5mSRT compared to BR (1.29 vs. 1.24 AU; 1.29 vs. 1.24, respectively). In conclusion, RF had no adverse effects on physical performance. However, when combined with high-intensity running sessions, RF may impact accuracy and PD, and these adverse effects seem to have been translated into EF.

Effects of fasting and environmental factors on appetite regulators in pond loach Misgurnus anguillicaudatus.

The pond loach (Misgurnus anguillicaudatus) is an important aquaculture freshwater species, used as an ornamental fish, food source for humans and angling bait. Pond loaches are resistant to fasting and extreme environmental conditions, including temperature and low oxygen levels. Little is known about how these factors affect the feeding physiology and the endocrine regulation of feeding of loaches. In this study, we examined the effects of fasting, as well as increased temperature and decreased oxygen levels on food intake and transcript levels of appetite regulators. Fasted fish had lower blood glucose levels, and lower expression levels of intestine CCK and PYY, and brain CART1, but had higher levels of brain orexin and ghrelin than fed fish. Fish held at 30 °C had higher food intake, glucose levels, and mRNA levels of intestine CCK and PYY, and brain CART2, but lower brain orexin levels than fish at 20 °C. Fish held at low oxygen levels had a lower food intake, higher intestine CCKa and ghrelin, and brain orexin, CART2 and ghrelin mRNA expression levels than fish held at high O2 levels. Our results suggest that fasting and high temperatures increase the expression of orexigenic and anorexigenic factors respectively, whereas the increase in expression of both orexigenic and anorexigenic factors in low O2 environments might not be related to their role in feeding, but possibly to protection from tissue damage. The results of our study might shed new light on how pond loaches are able to cope with extreme environmental conditions such as low food availability, extreme temperatures and hypoxia.

The use of accelerometers to improve estimation of the thermic effect of food in whole room calorimetry studies.

We tested whether spontaneous physical activity (SPA) from accelerometers could be used in a whole room calorimeter to estimate thermic effect of food (TEF). Eleven healthy participants (n = 7 females; age: 27 ± 4 yr; body mass index: 22.8 ± 2.6 kg/m2) completed two 23-h visits in randomized order: one "fed" with meals provided and one "fasted" with no food. SPA was measured by ActivPAL and Actigraph accelerometers. Criterion TEF was calculated as the difference in total daily energy expenditure (TDEE) between fed and fasted visits and compared with three methods of estimating TEF: 1) SPA-adjusted TEF (adjTEF)-difference in TDEE without SPA between visits, 2) Wakeful TEF-difference in energy expenditure obtained from linear regression and basal metabolic rate during waking hours, 3) 24-h TEF-increase in TDEE above SPA and sleeping metabolic rate. Criterion TEF was 9.4 ± 4.5% of TDEE. AdjTEF (difference in estimated vs. criterion TEF: activPAL: -0.3 ± 3.3%; Actigraph: -1.8 ± 8.0%) and wakeful TEF (activPAL: -0.9 ± 6.1%; Actigraph: -2.8 ± 7.6%) derived from both accelerometers did not differ from criterion TEF (all P > 0.05). ActivPAL-derived 24-h TEF overestimated TEF (6.8 ± 5.4%, P = 0.002), whereas Actigraph-derived 24-h TEF was not significantly different (4.3 ± 9.4%, P = 0.156). TEF estimations using activPAL tended to show better individual-level agreement (i.e., smaller coefficients of variation). Both accelerometers can be used to estimate TEF in a whole room calorimeter; wakeful TEF using activPAL is the most viable option given strong group-level accuracy and reasonable individual agreement.NEW & NOTEWORTHY Two research-grade accelerometers can effectively estimate spontaneous physical activity and improve the estimation of thermic effect of food (TEF) in whole room calorimeters. The activPAL demonstrates strong group-level accuracy and reasonable individual-level agreement in estimating wakeful TEF, whereas a hip-worn Actigraph is an acceptable approach for estimating 24-h TEF. These results highlight the promising potential of accelerometers in advancing energy balance research by improving the assessment of TEF within whole room calorimeters.

Self-initiated lifestyle changes during a fasting-mimicking diet programme in patients with type 2 diabetes: a mixed-methods study.

BACKGROUND: Lifestyle changes, especially regarding diet quality and physical activity, are important in the management of type 2 diabetes (T2D). This mixed-methods study explores self-initiated lifestyle changes in patients with T2D who followed a periodic fasting-mimicking diet (FMD). METHODS: Quantitative data were obtained from the Fasting In diabetes Treatment trial (November 2018 to August 2021) in which 100 participants with T2D, using metformin only or no medication, were randomised to receive a monthly 5-day FMD for twelve months next to usual care, or usual care only. Diet quality and physical activity questionnaires were completed at baseline, six and twelve months. Changes over time were analysed using linear mixed models. Focus groups were organized with FMD participants to explore experiences regarding self-initiated lifestyle changes. The qualitative data was analysed using the Theoretical Domains Framework. RESULTS: Questionnaires were available from 49 FMD participants and 43 controls. No differences in diet quality were found. Total physical activity in the FMD participants changed from 34.6 to 38.5 h per week (h/wk) from baseline to twelve months, while in controls it changed from 34.9 to 29.0 h/wk (between group difference, p = 0.03). In six focus groups with FMD participants (n = 20), individual participants perceived the FMD as an encouragement for (minor) lifestyle changes. There were no barriers to behaviour change related to the FMD. Important facilitators of healthy behaviour were an increase in awareness of the impact of lifestyle on health (knowledge), better physical fitness (physical) and health improvement (reinforcement). Facilitators unrelated to the FMD included family support (social influences) and opportunities in the neighbourhood (environmental context and resources), while barriers unrelated to the FMD were experiencing health problems (physical) and social events (social influences). CONCLUSIONS: Using an FMD for five consecutive days per month did not affect diet quality in between FMD periods in quantitative analysis, but increased the number of hours per week spent on physical activity. Qualitative analysis revealed self-initiated improvements in both diet quality and physical activity in individual participants using an FMD. Healthcare professionals could use an FMD programme as a 'teachable moment' to stimulate additional lifestyle changes. TRIAL REGISTRATION: ClinicalTrials.gov; NCT03811587. Registered 22 January 2019.

A feasibility study on preoperative carbohydrate loading in older patients undergoing hip fracture surgery.

BACKGROUND: Preoperative carbohydrate loading in Enhanced Recovery After Surgery is an independent predictor of postoperative outcomes. By reducing the impact of surgical stress response, fasting-induced insulin resistance is modulated. As a clear fluid, consuming carbohydrate drink is safe up to 2 h preoperatively. Widely practiced in abdominal surgeries, its implementation in hip fracture surgeries is yet to be recognized. This study aimed to identify the feasibility of preoperative carbohydrate loading in hip fracture surgery and assess its clinical effects. METHODS: This was a randomized controlled, open labelled trial. Patients ≥ 65 years old without diabetes mellitus, has hip fracture were recruited in a tertiary hospital between November 2020 and May 2021. The intervention was carbohydrate loading versus standard preoperative fasting. RESULTS: Thirty-four ASA I-III patients (carbohydrate loading and control, n = 17 each), mean age 78 years (SEM ± 1.5), mean body mass index 23.7 (SEM ± 0.6 kg/m2) were recruited. Analysis for feasibility of carbohydrate loading (n = 17) demonstrated attrition rate of 29% (n = 5). Otherwise, all recruited patients were compliant (100% compliance) with no adverse events reported. There was no significant difference among groups in the postoperative nausea and vomiting, pain score, fatigue level, muscle strength, postoperative infection and length of hospital stay assessed at 24-48 h postoperatively. CONCLUSION: The implementation of preoperative carbohydrate loading was found to be feasible preoperatively in hip fracture surgeries but requires careful coordination among multidisciplinary teams. An adequately powered randomized controlled study is needed to examine the full benefits of preoperative carbohydrate loading in this group of patients. TRIAL REGISTRATION: This study was registered in ClinicalTrial.gov (ClinicalTrials.gov identifier: NCT04614181, date of registration: 03/11/2020).

Fasting duration impacts ribosome protein 6 phosphorylation in zebrafish brain: New insights in aquatic organisms' welfare.

BACKGROUND: Short- or mid-term fasting, full or partial, triggers metabolic response known to have in turn health effects in an organism. At central level, the metabolic stimulus triggered by fasting is known to be perceived firstly by hypothalamic neurons. In the field of neuroscience, ribosomal protein S6 (S6) phosphorylation is commonly used as a readout of the mammalian target of rapamycin complex 1 signalling activation or as a marker for neuronal activity. The aim of this study is addressed to evaluate whether the phosphorylation of S6 occurs in the central neurons of zebrafish exposed to four (short-term) and seven (mid-term) days of complete fasting. METHODS: Group-housed adult zebrafish were exposed to four and seven days of complete food withdrawal. At the end of the experimental period, Western blotting analyses were carried out to measure the expression levels of the phosphorylated S6 (pS6) by comparing the two experimental conditions versus the control group. The same antibody was then used to identify the distribution pattern of pS6 immunoreactive neurons in the whole brain and in the taste buds. RESULTS: We did not observe increased pS6 levels expression in the brain of animals exposed to short-term fasting compared to the control, whereas the expression increased in brain homogenates of animals exposed to mid-term fasting. pS6 immunoreactivity was reported in some hypothalamic neurons, as well as in the dorsal area of telencephalon and preoptic area, a neurosecretory region homolog to the mammalian paraventricular nucleus. Remarkably, we observed pS6 immunostaining in the sensory cells of taste buds lining the oral epithelium. CONCLUSIONS: Taken together, our data show that in zebrafish, differently from other fish species, seven days of fasting triggers neuronal activity. Furthermore, the immunostaining on sensory cells of taste buds suggests that metabolic changes may modulate also peripheral sensory cells. This event may have valuable implications when using zebrafish to design metabolic studies involving fasting as well as practical consequences on the animal welfare, in particularly stressful conditions, such as transportation.

Replicating human characteristics: A promising animal model of central fatigue.

Central fatigue is a common pathological state characterized by psychological loss of drive, lack of appetite, drowsiness, and decreased psychic alertness. The mechanism underlying central fatigue is still unclear, and there is no widely accepted successful animal model that fully represents human characteristics. We aimed to construct a more clinically relevant and comprehensive animal model of central fatigue. In this study, we utilized the Modified Multiple Platform Method (MMPM) combined with alternate-day fasting (ADF) to create the animal model. The model group rats are placed on a stationary water environment platform for sleep deprivation at a fixed time each day, and they were subjected to ADF treatment. On non-fasting days, the rats were allowed unrestricted access to food. This process was sustained over a period of 21 days. We evaluated the model using behavioral assessments such as open field test, elevated plus maze test, tail suspension test, Morris water maze test, grip strength test, and forced swimming test, as well as serum biochemical laboratory indices. Additionally, we conducted pathological observations of the hippocampus and quadriceps muscle tissues, transmission electron microscope observation of mitochondrial ultrastructure, and assessment of mitochondrial energy metabolism and oxidative stress-related markers. The results revealed that the model rats displayed emotional anomalies resembling symptoms of depression and anxiety, decreased exploratory behavior, decline in learning and memory function, and signs of skeletal muscle fatigue, successfully replicating human features of negative emotions, cognitive decline, and physical fatigue. Pathological damage and mitochondrial ultrastructural alterations were observed in the hippocampus and quadriceps muscle tissues, accompanied by abnormal mitochondrial energy metabolism and oxidative stress in the form of decreased ATP and increased ROS levels. In conclusion, our ADF+MMPM model comprehensively replicated the features of human central fatigue and is a promising platform for preclinical research. Furthermore, the pivotal role of mitochondrial energy metabolism and oxidative stress damage in the occurrence of central fatigue in the hippocampus and skeletal muscle tissues was corroborated.

Impact of Ramadan fasting on vision and headache-related quality of life in women with idiopathic intracranial hypertension: A prospective observational study.

BACKGROUND: Ramadan fasting is an obligatory religious practice for Muslims. However, research data on the effect of Ramadan on idiopathic intracranial hypertension (IIH) symptoms are lacking. This study aimed to study the effect of Ramadan fasting on the severity of headache and visual symptoms and related quality-of-life activities. METHODS: This prospective cohort study targeted females diagnosed with IIH (n = 102) who were eligible to fast for Ramadan in 2023. The patients were recruited from the Neurology Clinic in Beni-Suef University Hospital, Egypt. Body mass index (BMI), monthly headache days and intensity of headache attacks, six-item Headache Impact Test (HIT-6), and the 25-item National Eye Institute Visual Function Questionnaire (NEI-VFQ-25) scores during Ramadan were compared to those during the (non-fasting) month of Shaaban, the preceding month to Ramadan. RESULTS: There was a significant increase in the BMI of patients with IIH in Ramadan compared to the (non-fasting) month of Shaaban, at a median (interquartile range [IQR]) of 30.5 (26.6-35.8) kg/m2 and 30.1 (26.6-35.2) kg/m2, respectively (p = 0.002). The median (IQR) value of monthly headache days was significantly increased during Ramadan in comparison to the (non-fasting) month of Shaaban, at 20 (11.5-30) vs. 15 (10-25) (p < 0.001). There was a statistically significant worsening in the visual analog scale (VAS) scores (median [IQR] 7 [5-8] vs. 6.5 [5-8]), HIT-6 scores (median [IQR] 61 [58-67] vs. 59 [53-61.5]), and NEI-VFQ-25 total scores (median [IQR] 1312.5 [1238.8-1435] vs 1290 [1165-1417.5]) during Ramadan in comparison to the (non-fasting) month of Shaaban (p < 0.001 for all comparisons). The change in BMI in Ramadan was positively correlated with the change in monthly headache days (r = 0.24, p = 0.014), VAS (r = 0.20, p = 0.043), HIT-6 (r = 0.25, p = 0.010) and NEI-VFQ-25 scores (r = 0.24, p = 0.016). CONCLUSION: Ramadan fasting had an aggravating effect on headache, visual symptoms, and related quality-of-life activities, which might be attributed to weight gain during this month. Whether proper nutritional management to prevent weight gain during Ramadan may help mitigate this worsening effect is a mission of future studies.

Intermittent Fasting-Improved Glucose Homeostasis Is Not Entirely Dependent on Caloric Restriction in db/db Male Mice.

Intermittent fasting (IF), which involves prolonged fasting intervals accompanied by caloric restriction (CR), is an effective dietary treatment for obesity and diabetes. Although IF offers many benefits, it is difficult to determine whether these benefits are the consequences of CR. Every-other-day feeding (EODF) is a commonly used IF research model. This study was designed to identify factors, in addition to CR, responsible for the effects of EODF and the possible underlying mechanisms. Diabetic db/db mice were divided into three groups: ad libitum (AL), meal feeding (MF), and EODF. The MF model was used to attain a level of CR comparable to that of EODF, with food distribution evenly divided between 10:00 a.m. and 6:00 p.m., thereby minimizing the fasting interval. EODF yielded greater improvements in glucose homeostasis than MF in db/db mice by reducing fasting glucose levels and enhancing glucose tolerance. However, these effects on glucose metabolism were less pronounced in lean mice. Furthermore, ubiquitination of the liver-specific glucocorticoid (GC) receptor (GR) facilitated its degradation and downregulation of Kruppel-like factor 9 (KLF9), which ultimately suppressed liver gluconeogenesis in diabetic EODF mice. Although GR and KLF9 might mediate the metabolic benefits of EODF, the potential benefits of EODF might be limited by elevated serum GC levels in diabetic EODF mice. Overall, this study suggests that the metabolic benefits of EODF in improving glucose homeostasis are independent of CR, possibly because of the downstream effects of liver-specific GR degradation.

Intermittent fasting and longevity: From animal models to implication for humans.

In recent years, intermittent fasting (IF) and its numerous modifications have been increasingly suggested as a promising therapy for age-related problems and a non-pharmacological strategy to extend lifespan. Despite the great variability in feeding schedules that we describe in the current work, underlying physiological processes are the same and include a periodic switch from glucose metabolism (generated by glycogenolysis) to fatty acids and fatty acid-derived ketones. Many of the beneficial effects of IF appear to be mediated by optimization of energy utilization. Findings to date from both human and animal experiments indicate that fasting improves physiological function, enhances performance, and slows aging and disease processes. In this review, we discuss some of the remarkable discoveries about the beneficial effects of IF on metabolism, endocrine and cardiovascular systems, cancer prevention, brain health, neurodegeneration and aging. Experimental studies on rodent models and human investigations are summarized to compare the outcomes and underlying mechanisms of IF. Metabolic and cellular responses triggered by IF could help to achieve the aim of preventing disease, and maximizing healthspan and longevity with minimal side effects.

Effects of hyperventilation on repeated breath-holding while in a fasting state: do risks outweigh the benefits?

Breath-holding preceded by either an overnight fast or hyperventilation has been shown to potentiate the risk of a hypoxic blackout. However, no study has explored the combined effects of fasting and hyperventilation on apneic performance and associated physiological responses. Nine nondivers (8 males) attended the laboratory on two separate occasions (≥48 h apart), both after a 12-h overnight fast. During each visit, a hyperoxic rebreathing trial was performed followed by three repeated maximal static apneas preceded by either normal breathing (NORM) or a 30-s hyperventilation (HYPER). Splenic volume, hematology, cardiovascular, and respiratory variables were monitored. There were no interprotocol differences at rest or during hyperoxic rebreathing for any variable (P ≥ 0.09). On nine occasions (8 in HYPER), the subjects reached our safety threshold (oxygen saturation 65%) and were asked to abort their apneas, with the preponderance of these incidents (6 of 9) occurring during the third repetition. Across the sequential attempts, longer apneas were recorded in HYPER [median(range), 220(123-324) s vs. 185(78-296) s, P ≤ 0.001], with involuntary breathing movements occurring later [134(65-234) s vs. 97(42-200) s, P ≤ 0.001] and end-apneic partial end-tidal pressures of oxygen (PETO2) being lower (P ≤ 0.02). During the final repetition, partial end-tidal pressure of carbon dioxide [(PETCO2), 6.53 ± 0.46 kPa vs. 6.01 ± 0.45 kPa, P = 0.005] was lower in HYPER. Over the serial attempts, preapneic tidal volume was gradually elevated [from apnea 1 to 3, by 0.26 ± 0.24 L (HYPER) and 0.28 ± 0.30 L (NORM), P ≤ 0.025], with a correlation noted with preapneic PETCO2 (r = -0.57, P < 0.001) and PETO2 (r = 0.76, P < 0.001), respectively. In a fasted state, preapnea hyperventilation compared with normal breathing leads to longer apneas but may increase the susceptibility to a hypoxic blackout.NEW & NOTEWORTHY This study shows that breath-holds (apneas) preceded by a 12-h overnight fast coupled with a 30-s hyperventilation as opposed to normal breathing may increase the likelihood of a hypoxic blackout through delaying the excitation of hypercapnic ventilatory sensory chemoreflexes. Evidently, this risk is exacerbated over a series of repeated maximal attempts, possibly due to a shift in preapneic gas tensions facilitated by an unintentional increase in tidal volume breathing.

Comparative Impact of Various Fasting Periods on the Welfare of Sprague-Dawley Rats With or Without Supplementation.

In nonclinical toxicology studies, lab animals are fasted typically overnight, to reduce variability in some clinical pathology parameters. However, fasting adds undue stress, and this is particularly concerning in rodents given their fast metabolic rates. Furthermore, as rodents are nocturnal animals, an overnight fasting may cause a protracted negative metabolic state even when the fasting has technically ended, given their minimal activity and food consumption during the day. Therefore, to evaluate the impacts of different fasting durations (±DietGel supplementation) on rats' welfare, we assessed the traditional and ancillary clinical pathology parameters in Sprague-Dawley rats, along with body weight, organ weight, and histopathology. Although most endpoints were comparable between the different fasting durations (±DietGel supplementation), the long fasting times (≥8 hr) without DietGel supplementation caused significant decreases in body weight, liver weight, liver glycogen content, serum glucose, triglyceride, and creatinine concentrations-all findings suggestive of a negative energy balance that could impact animal welfare and consequently, data quality; while the short fasting time (4 hr) and DietGel supplementation were associated with higher triglycerides variability. Hence, we propose that short fasting time should be adequate for most toxicology studies in rats, and long fasting times should only be accommodated with scientific justification.

Anorexia of ageing is associated with elevated fasted and lower post-prandial ghrelin, independent of ghrelin O-acyltransferase.

The role of ghrelin metabolism in anorexia of ageing is unclear. The aim of this study was to determine acyl-ghrelin, total ghrelin, and ghrelin O-acyltransferase concentrations when fasted and in responses to feeding in older adults exhibiting anorexia of ageing. Twenty-five older adults (OA; 15f, 74 ± 7 years, 24.5 kg·m-2) and twelve younger adults (YA; 6f, 21 ± 2 years, 24.4 kg·m-2) provided a fasted measure of subjective appetite and fasted blood sample (0 min) before consuming a standardised porridge breakfast meal (450 kcal). Appetite was measured every 30 min for 240 min and blood was sampled at 30, 60, 90, 120, 180 and 240 min while participants rested. At 240 min, an ad libitum pasta-based lunch meal was consumed. Older adults were identified as those with healthy appetite (HA-OA) or low appetite (LA-OA), based on habitual energy intake, self-report appetite, BMI, and ad libitum lunch intake. YA ate more at lunch (1108 ± 235 kcal) than HA-OA (653 ± 133 kcal, p = 0.007) and LA-OA (369 ± 168 kcal; p < 0.001). LA-OA, but not HA-OA, had higher fasted concentrations of acyl- and total ghrelin than YA (acyl-ghrelin: 621 ± 307 pg·mL-1 vs. 353 ± 166 pg·mL-1, p = 0.047; total ghrelin: 1333 ± 702 pg·mL-1 vs. 636 ± 251 pg·mL-1, p = 0.006). Acyl-ghrelin (60 min and 90 min) and total ghrelin (90 min) were suppressed to a greater extent for LA-OA than for YA (p < 0.05). No differences were observed in subjective appetite, acyl-to-total ghrelin ratio, or plasma GOAT content (p > 0.1). Higher fasting ghrelin and an augmented ghrelin response to feeding in LA-OA, but not HA-OA, suggests that alterations to ghrelin metabolism are not functions of ageing per se and may be independent causal mechanisms of anorexia of ageing.