Physiological Fitness of U.S. Army Aviators Compared to the U.S. General Population.

INTRODUCTION: U.S. Army aviators are required to maintain a level of physiological fitness as part of their qualifying process, which suggests that they are generally physically healthy. However, it has not been statistically proven that they are more "physiologically fit" than the general population.METHODS: This retrospective study compares physiological measurements of U.S. Army aviators from the Aeromedical Electronic Resource Office database to the U.S. general population using the Center for Disease Control's National Health and Nutrition Examination Survey data. To enable an accurate comparison of physiological metrics between U.S. Army aviators and the U.S. general population, aviators were categorized into the same age groups and biological genders used for segmentation of the national population data.RESULTS: On average, pulse rate was 4.85 bpm lower in male aviators and 6.84 bpm lower in female aviators. Fasting glucose levels were, on average, 10.6 mg · dL-1 lower in aviators compared to the general population. Key metrics like pulse rate and fasting glucose were lower in aviators, indicating cardiovascular and metabolic advantages. However, parameters like cholesterol showed less consistent differences.DISCUSSION: While aviation physical demands and administrative policies selecting for elite physiological metrics produce improvements on some dimensions, a nuanced view accounting for the multitude of factors influencing an aviator's physiological fitness is still warranted. Implementing targeted health monitoring and maintenance programs based on assessments conducted more frequently than the current annual flight physical may optimize aviator safety and performance over the course of a career.D'Alessandro M, Mackie R, Wolf S, McGhee JS, Curry I. Physiological fitness of U.S. Army aviators compared to the U.S. general population. Aerosp Med Hum Perform. 2024; 95(4):175-186.

Novel targets of ß-TrCP cooperatively accelerate carbohydrate and fatty acid consumption.

Cellular energy is primarily produced from glucose and fat through glycolysis and fatty acid oxidation (FAO) followed by the tricarboxylic acid cycle in mitochondria; energy homeostasis is carefully maintained via numerous feedback pathways. In this report, we uncovered a new master regulator of carbohydrate and lipid metabolism. When ubiquitin E3 ligase ß-TrCP2 was inducibly knocked out in ß-TrCP1 knockout adult mice, the resulting double knockout mice (DKO) lost fat mass rapidly. Biochemical analyses of the tissues and cells from ß-TrCP2 KO and DKO mice revealed that glycolysis, FAO, and lipolysis were dramatically upregulated. The absence of ß-TrCP2 increased the protein stability of metabolic rate-limiting enzymes including 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB3), adipose triglyceride lipase (ATGL), carnitine palmitoyltransferase 1A (CPT1A), and carnitine/acylcarnitine translocase (CACT). Our data suggest that ß-TrCP is a potential regulator for total energy homeostasis by simultaneously controlling glucose and fatty acid metabolism and that targeting ß-TrCP could be an effective strategy to treat obesity and other metabolic disorders.

Wake-sleep cycles are severely disrupted by diseases affecting cytoplasmic homeostasis.

The circadian clock is based on a transcriptional feedback loop with an essential time delay before feedback inhibition. Previous work has shown that PERIOD (PER) proteins generate circadian time cues through rhythmic nuclear accumulation of the inhibitor complex and subsequent interaction with the activator complex in the feedback loop. Although this temporal manifestation of the feedback inhibition is the direct consequence of PER's cytoplasmic trafficking before nuclear entry, how this spatial regulation of the pacemaker affects circadian timing has been largely unexplored. Here we show that circadian rhythms, including wake-sleep cycles, are lengthened and severely unstable if the cytoplasmic trafficking of PER is disrupted by any disease condition that leads to increased congestion in the cytoplasm. Furthermore, we found that the time delay and robustness in the circadian clock are seamlessly generated by delayed and collective phosphorylation of PER molecules, followed by synchronous nuclear entry. These results provide clear mechanistic insight into why circadian and sleep disorders arise in such clinical conditions as metabolic and neurodegenerative diseases and aging, in which the cytoplasm is congested.

Stability of Wake-Sleep Cycles Requires Robust Degradation of the PERIOD Protein.

Robustness in biology is the stability of phenotype under diverse genetic and/or environmental perturbations. The circadian clock has remarkable stability of period and phase that-unlike other biological oscillators-is maintained over a wide range of conditions. Here, we show that the high fidelity of the circadian system stems from robust degradation of the clock protein PERIOD. We show that PERIOD degradation is regulated by a balance between ubiquitination and deubiquitination, and that disruption of this balance can destabilize the clock. In mice with a loss-of-function mutation of the E3 ligase gene ß-Trcp2, the balance of PERIOD degradation is perturbed and the clock becomes dramatically unstable, presenting a unique behavioral phenotype unlike other circadian mutant animal models. We believe that our data provide a molecular explanation for how circadian phases, such as wake-sleep onset times, can become unstable in humans, and we present a unique mouse model to study human circadian disorders with unstable circadian rhythm phases.

Regulation of Energy Homeostasis After Gastric Bypass Surgery.

The obesity epidemic continues to escalate each year in the United States more than anywhere else in the world. The existing pharmaceutical and other nonsurgical treatments for morbid obesity produce suboptimal physiologic outcomes compared with those of Roux-en-Y gastric bypass (RYGB) surgery. RYGB has been the gold standard of bariatric surgery because the beneficial long-term outcomes, which include sustainable weight loss and type 2 diabetes mellitus (T2DM) resolution, are far superior to those obtained with other bariatric surgeries. However, the current understanding of RYGB's mechanisms of actions remains limited and incomplete. There is an urgent need to understand these mechanisms as gaining this knowledge may lead to the development of innovative and less invasive procedures and/or medical devices, which can mirror the favorable outcomes of RYGB surgery. In this review, we highlight current observations of the metabolic and physiologic events following RYGB, with a particular focus on the role of the anatomical reconfiguration of the gastrointestinal tract after RYGB.

Multi-omic network-based interrogation of rat liver metabolism following gastric bypass surgery featuring SWATH proteomics.

Morbidly obese patients often elect for Roux-en-Y gastric bypass (RYGB), a form of bariatric surgery that triggers a remarkable 30% reduction in excess body weight and reversal of insulin resistance for those who are type II diabetic. A more complete understanding of the underlying molecular mechanisms that drive the complex metabolic reprogramming post-RYGB could lead to innovative non-invasive therapeutics that mimic the beneficial effects of the surgery, namely weight loss, achievement of glycemic control, or reversal of non-alcoholic steatohepatitis (NASH). To facilitate these discoveries, we hereby demonstrate the first multi-omic interrogation of a rodent RYGB model to reveal tissue-specific pathway modules implicated in the control of body weight regulation and energy homeostasis. In this study, we focus on and evaluate liver metabolism three months following RYGB in rats using both SWATH proteomics, a burgeoning label free approach using high resolution mass spectrometry to quantify protein levels in biological samples, as well as MRM metabolomics. The SWATH analysis enabled the quantification of 1378 proteins in liver tissue extracts, of which we report the significant down-regulation of Thrsp and Acot13 in RYGB as putative targets of lipid metabolism for weight loss. Furthermore, we develop a computational graph-based metabolic network module detection algorithm for the discovery of non-canonical pathways, or sub-networks, enriched with significantly elevated or depleted metabolites and proteins in RYGB-treated rat livers. The analysis revealed a network connection between the depleted protein Baat and the depleted metabolite taurine, corroborating the clinical observation that taurine-conjugated bile acid levels are perturbed post-RYGB.

Morphine-Modified Hepatobiliary Scanning Protocol for the Diagnosis of Acute Cholecystitis.

OBJECTIVE: We report a morphine-modified hepatoiminodiacetic acid (HIDA) scanning protocol that uses 2 mg of morphine IV push at the bedside as a pretreatment. We compared this protocol with the original HIDA scanning protocol, which included delayed imaging for up to 4 hours without the use of morphine. Moreover, we contrast our results with the results of studies in the literature. MATERIALS AND METHODS: We retrospectively reviewed the charts of inpatients who underwent HIDA scanning for the diagnosis of acute cholecystitis between 2003 and 2013. The study group consisted of 374 HIDA studies of 365 patients who received 2 mg of morphine IV push at bedside and then underwent dynamic imaging for 1 hour using 222 MBq of 99mTc-mebrofenin. No delayed images were obtained. The control group consisted of 232 studies of 227 patients who underwent conventional HIDA scanning using our standard protocol with delayed imaging and without morphine. Either strict pathologic criteria or the results of a percutaneous gallbladder drainage procedure were used for the confirmation of acute cholecystitis. RESULTS: The true-negative rate in the study group was 77% and in the control group, 72%. The positive predictive value in the study group was 81% and in the control group, 45%. The negative predictive value in the study group was 98% and in the control group, 99%. The accuracy in the study group was 95% and in the control group, 84%. The sensitivity in the study group was 93% and in the control group, 93%. The specificity in the study group was 95% and in the control group, 83%. The differences in the true-negative rate, accuracy, specificity, and positive predictive value of the morphine-modified protocol used for the study group and the original protocol used for the control group were statistically significant (p < 0.0005). CONCLUSION: Pretreatment using 2 mg of IV morphine at bedside before radionuclide imaging is superior to routine HIDA scanning with only delayed images for the diagnosis of acute cholecystitis. The results of our pretreatment morphine-modified protocol are comparable to those reported in the literature for posttreatment morphine-augmented protocols.

A tunable artificial circadian clock in clock-defective mice.

Self-sustaining oscillations are essential for diverse physiological functions such as the cell cycle, insulin secretion and circadian rhythms. Synthetic oscillators using biochemical feedback circuits have been generated in cell culture. These synthetic systems provide important insight into design principles for biological oscillators, but have limited similarity to physiological pathways. Here we report the generation of an artificial, mammalian circadian clock in vivo, capable of generating robust, tunable circadian rhythms. In mice deficient in Per1 and Per2 genes (thus lacking circadian rhythms), we artificially generate PER2 rhythms and restore circadian sleep/wake cycles with an inducible Per2 transgene. Our artificial clock is tunable as the period and phase of the rhythms can be modulated predictably. This feature, and other design principles of our work, might enhance the study and treatment of circadian dysfunction and broader aspects of physiology involving biological oscillators.

miRNAs are required for generating a time delay critical for the circadian oscillator.

BACKGROUND: Circadian clocks coordinate an organism's activities and regulate metabolic homeostasis in relation to daily environmental changes, most notably light/dark cycles. As in other organisms, the timekeeping mechanism in mammals depends on a self-sustaining transcriptional negative feedback loop with a built-in time delay in feedback inhibition. Although the time delay is essential for generating a slow, self-sustaining negative feedback loop with a period close to 24 hr, the exact mechanisms underlying the time delay are not known. RESULTS: Here, we show that RNAi mediated by microRNAs (miRNAs) is an essential mechanism in generating the time delay. In Dicer-deficient (and thus miRNA-deficient) cells and mice, circadian rhythms were dramatically shortened (by ∼2 hr), although the rhythms remained robust. The period shortening was caused by faster PER1 and PER2 translation in the Dicer-deficient cells. We also identified three specific miRNAs that regulate Per expression and showed that knockdown of these miRNAs in wild-type cells also shortened the circadian period. CONCLUSIONS: Consistent with the canonical function of miRNAs as translational modulators of target genes and their widespread roles in cell physiology, circadian rhythms are also modulated by miRNA-mediated RNAi acting on posttranscriptional regulation of key clock genes. Our present study definitively shows that RNAi is an important modulator of circadian rhythms by controlling the pace of PER synthesis and presents a novel layer of regulation for the clock.