Danielle Evé Levitt

The purpose of this study was to determine whether the trajectory and magnitude of physiological adaptation to controlled work rate heat acclimation (HEAT) differ between male and female highly trained endurance runners, while comparing adaptations with work rate matched temperate exercise training (TEMP). Eighteen highly trained endurance runners (8 males, 10 females) completed two seven-session interventions consisting of HEAT (40°C, 35% relative humidity [RH]) and TEMP (22°C, 35% RH) in a randomized, counterbalanced crossover design. Each session consisted of 60 min of running at 50% of velocity at maximal oxygen uptake. Physiological adaptation was quantified as the change (Δ) relative to session 1 for core temperature (T _c ), skin temperature, heart rate (HR), whole-body sweat rate (WBSR), and plasma volume (PV). No intervention × sex × session interactions were observed for T _c , HR, or WBSR (p > 0.05), indicating that the trajectory of adaptation did not differ between sexes or interventions. Likewise, no sex differences in the overall magnitude of adaptation were observed for any HEAT outcome. Significant main effects of intervention demonstrated greater reductions in mean and peak T _c ; baseline, mean, and peak HR; as well as greater increases in WBSR during HEAT compared with TEMP (p < 0.05). PV did not change following either intervention. Male and female highly trained endurance runners exhibited comparable thermoregulatory and cardiovascular adaptation to controlled work rate heat acclimation. Although work rate matched temperate exercise induced partial physiological adaptation, environmental heat stress enhanced the overall adaptation magnitude without altering the adaptation trajectory between sexes.

Surface-enhanced Raman scattering (SERS) nanotags provide highly sensitive platforms for molecular analysis but often require extensive customization to generate target-specific optical signatures. Biomineralization, in which biomolecules mediate inorganic material synthesis, offers a versatile yet underexplored strategy for generating functional SERS nanotags. Here, we demonstrate that biomolecule-directed biomineralization of gold nanoparticles (AuNPs) using amino acids and exosomes generates distinct nano–bio interfacial architectures that encode biomolecular identity into machine learning-resolvable SERS fingerprints through modulation of plasmonic coupling and Raman reporter organization. As a proof-of-concept system, amino acid-biomineralized AuNPs were synthesized using biomolecules with diverse physicochemical properties, including differences in size, polarity, and charge. The resulting nanotags were characterized using UV–vis spectroscopy, SERS spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). Random forest and support vector machine (SVM) models successfully differentiated amino acid-dependent SERS signatures with near-perfect classification performance. Extending this approach to a biologically complex preclinical cancer model, exosome-biomineralized AuNP nanotags were generated using exosomes derived from clinically relevant pediatric patient-derived osteosarcoma and neuroblastoma tumors. Distinct exosome-dependent spectral fingerprints enabled 85.9% classification accuracy through a regularized logistic regression model, while Shapley Additive exPlanations (SHAP) and t-distributed stochastic neighbor embedding (t-SNE) analyses identified diagnostically relevant spectral regions and visualized clustering between tumor classes. Collectively, this work establishes biomineralization as a strategy for encoding biomolecular identity into computationally resolvable optical fingerprints through engineered nano–bio interfaces, providing a versatile framework for machine learning-enabled classification of complex biological samples.

Introduction: Glycemic dysregulation is a hallmark of type 2 diabetes (T2D) and contributes to skeletal muscle (SKM) loss and frailty risk, especially in older adults. Glycemic control and physical function are supported by SKM capillarization and mitochondrial function, and their impairment contributes to T2D development. While high-intensity interval training (HIIT) is a promising intervention, adherence and effectiveness remain concerns for prescribing HIIT among older adults at risk for T2D. Local heat therapy (LHT) may be a more practical initial strategy to improve SKM architectural factors and precondition SKM, enhancing physiological adaptations to exercise in this population. Methods and analysis: Heat and Exercise in Aging as Therapy (HEAT) is a two-phase, randomized, sham-controlled clinical trial investigating the efficacy of LHT to improve glycemic control and decrease frailty risk via improved SKM architecture among older adults with prediabetes. LHT is tested as a standalone intervention and as a means to precondition SKM for subsequent HIIT, improving exercise adaptations. In Phase 1, LHT and sham (CON) groups apply heat pads for 90 minutes/day, 6 days/week, for 12 weeks. A separate HIIT group completes 4x4-minute cycling intervals at 90–95% VO₂peak, 3 days/week. In Phase 2, LHT and CON groups begin HIIT. Participants (≥50 years) have impaired fasting glucose (100–125 mg/dL) and/or HbA1c (5.7–6.4%). Biospecimen collection and clinical assessments occur at baseline (T1), after Phase 1 (T2), and Phase 2 (T3). To our knowledge, this is the first study to determine the use of local heat pad on pre-diabetic older population. If successful, LHT may be a practical, scalable, non-invasive intervention to improve glycemic control and reduce frailty risk in older adults with prediabetes, preventing progression to T2D.

This study examined how 24-h fluid restriction affects mitochondrial stress and inflammatory responses in peripheral blood mononuclear cells (PBMCs) after high-volume resistance exercise in young men. Dehydration increased markers of mitophagy (PINK1 and p-DRP1 ^S616 ), autophagosome formation (LC3-II and p62), and oxidative stress (H ₂ O ₂ ), while systemic IL-6 and CRP were elevated compared with euhydration. Findings suggest dehydration amplifies mitochondrial stress and proinflammatory signaling, highlighting the importance of proper hydration during exercise and its implications on cellular homeostasis.

(1) Lifestyle changes to modify unhealthy dietary patterns with the goal of preventing MASLD have proven challenging. Here, dietary proteins and their modification with ammonium hydroxide enhancement (AHE) provide molecular evidence that this novel approach may attenuate the development of MASLD without undue dietary adjustments, potentially bypassing non-compliance. (2) High-fat diets containing dietary beef (HFB) or casein (HFC) + AHE (HFBN and HFCN, respectively) were fed to 256 C3H/HeJ female and male mice long term. At 6, 12, or 18 months, hepatic samples were analyzed with targeted metabolomics (glucose, lactate, alanine, glutamine, carnitine) and Western analysis (β-catenin, glutamine synthetase, CYP3A4). RNA sequencing was performed on samples collected at 18 months (n = 3; male HFC n = 2). (3) Metabolomics results showed that at 18 months, hepatic glutamine was greater in HFBN versus HFCN in females, whereas in males, hepatic glutamine, glucose and lactate were lower in HFBN versus HFCN. Additionally, diets with AHE decreased β-catenin and CYP3A4 protein expression in males. Ingenuity pathway analysis (IPA) of RNA-seq data predicted that HFBN activates PPARα signaling in the liver in both sexes compared to HFCN. Inflammatory activity showed predicted activation for females in the HFBN:HFCN comparison. In males, the inflammatory pathway molecular mechanisms of cancer was predicted as deactivated in HFBN:HFCN. (4) Dietary protein source impacts outcomes, and these outcomes improved with AHE. The HFBN diet improves signaling associated with lipid utilization for females and males, and improved inflammatory signaling for males compared with HFCN. Further exploration of AHE as a dietary intervention in high-fat diets is warranted.

Obesity remains a significant public health concern with substantial implications for military readiness. Rising rates of overweight and obesity among service members challenge recruitment, retention and deployability. Although the military continues to screen and manage obesity, current body composition tools and policies often fail to capture true health risk or operational capability. This narrative review evaluates the prevalence and impact of obesity in the US military, critiques existing assessment methods and discusses recent policy updates across service branches. Particular attention is given to limitations of traditional metrics such as body mass index and circumference-based measures, as well as the potential of modern approaches to improve accuracy and effectiveness. Despite policy revisions, obesity remains the leading medical disqualifier for service and a major contributor to lost workdays, injuries and medical costs. Aligning body composition standards with scientific evidence and operational demands is essential for supporting readiness across modern defence forces.

Background: Acute and chronic hyperglycemia in patients with type 2 diabetes mellitus (T2DM) causes endothelial dysfunction and arterial stiffness, contributing to early mortality from cardiovascular disease (CVD). Although L-citrulline (CIT) supplementation improves endothelial function in older women and decreases fasting glucose in those with T2DM, whether it improves vascular function and blood glucose during acute hyperglycemic states in T2DM is unknown. Methods: We randomized 16 patients with T2DM (age 62 ± 6 years) to consume either CIT (6 g/day) or placebo for 4 weeks. Brachial artery flow-mediated dilation (FMD), brachial and aortic blood pressure, aortic and leg arterial stiffness (pulse wave velocity, PWV), and blood glucose concentration were assessed in the fasted state and 60 min following glucose ingestion (during acute hyperglycemia). Results: Four weeks of L-citrulline supplementation improved FMD, femoral-ankle PWV, aortic systolic blood pressure, and blood glucose concentration in the fasted state compared to placebo (all p < 0.05). During acute hyperglycemia, CIT supplementation increased FMD and reduced femoral-ankle PWV, aortic systolic BP, and glucose levels compared to placebo (all p < 0.05). Conclusions: CIT supplementation is beneficial to improve vascular function and glucose levels during chronic and acute hyperglycemia in middle-aged and older adults with T2DM.

Background: Patients with type 2 diabetes (T2D) develop vascular complications due to arginine deficiency-induced microvascular endothelial dysfunction, which is related to the loss of muscle strength (MS) associated with aging. Thus, increased nitric oxide (NO)-mediated vasodilation may improve MS. We investigated the impact of the NO precursor citrulline on microvascular function (endothelial and muscle reactivity) and MS in T2D patients. Methods: Sixteen participants with T2D (53–72 years, nine females) were randomized to citrulline supplementation (CITS, 6 g/day) or placebo for 4 weeks prior to an 8-week washout period, followed by the opposite supplement for 4 weeks in a crossover trial. Endothelial function (log-transformed reactive hyperemia index, LnRHI), forearm muscle reactivity (near-infrared spectroscopy-derived tissue oxygen index (TOI) reperfusion indices), plasma arginine levels (ARG), and handgrip strength (HGS_rel) and calf MS (CMS_rel) adjusted for body weight were measured at baseline and 4 weeks for each condition. Results: CITS increased the LnRHI (∆0.11 ± 0.16 vs. ∆−0.08 ± 0.24, p < 0.05), TOI range (∆2.6 ± 3.3 vs. ∆−1.5 ± 4.8%, p < 0.01), TOI hyperemic response (∆1.2 ± 1.4 vs. ∆−0.6 ± 2.8%, p < 0.05), TOI 2 min area under the curve (∆154 ± 187 vs. ∆−41 ± 194%/s, p < 0.01), ARG (∆43 ± 28 vs. ∆1 ± 16μM/L, p < 0.001), CMS (∆1.5 ± 2.8 vs. ∆−0.3 ± 1.2 kg, p < 0.05), and CMS_rel (∆0.02 ± 0.03 vs. ∆−0.01 ± 0.02 kg/kg, p < 0.01) compared to placebo. The improvements in LnRHI and CMS_rel were correlated (r = 0.37, p < 0.05). Conclusions: This study showed that CITS improves microvascular endothelial function, muscle microvascular reactivity, and calf muscle strength in middle-aged and older patients with T2D.

Dehydration is prevalent and adversely affects exercise performance; however, its influence on cellular responses to exercise remains unclear. Thus, this study examined the intramuscular responses to resistance‐exercise (RE) in RE‐trained men under dehydrated and euhydrated states. Eleven men (21 ± 1 years, 175.9 ± 6.2 cm, 79.2 ± 12.3 kg, 18.4% ± 6.7% fat) completed two identical lower‐body RE sessions, either with (DEHY) or without (EUHY) fluid‐restriction from 24 h before to 3 h after RE. At pre‐RE (PRE), 1 h, and 3 h post‐RE, muscle samples were collected and analysed for protein content of AKT/mTOR/p70S6K/rpS6 and their corresponding phosphorylation sites, REDD1 and selected autophagy markers, cathepsin L, H ₂ O ₂ concentration, fibre cross‐sectional area (CSA), and muscle water content. Significant time × condition interaction effects revealed that p‐rpS6 ^S240/244 was greater in DEHY than EUHY at PRE and increased from PRE to 1 h and 3 h in both conditions. In DEHY, REDD1 increased from PRE to 1 h and 3 h, active‐cathepsin L decreased from 1 h to 3 h and was greater than EUHY at 1 h, and muscle water content increased from 1 h to 3 h. Significant condition main effects revealed that p‐S6K ^T389 and H ₂ O ₂ were greater, and CSA was smaller, in DEHY versus EUHY. Significant time main effects revealed that p‐AKT ^S473 and p‐mTOR ^S2448 increased from PRE to 1 h and 3 h, LC3‐I decreased from PRE and 1 h to 3 h, LC3‐II decreased from PRE to 1 h and 3 h, and LC3‐II/LC3‐I decreased from PRE to 1 h and increased from 1 h to 3 h. These results suggest that performing RE in a dehydrated state imposes additional stress on the muscle, leading to greater cellular stress and growth signalling. image Key points: Dehydration can negatively impact exercise performance, overall health, and cognitive function in humans. Water makes up about 70% of muscle mass, and dehydration has been shown to decrease muscle size in humans. However, the mechanisms by which dehydration affects muscle response on anabolic and catabolic signalling have only been observed in in vitro studies, leaving the processes in humans still not fully understood. Following 24 h of dehydration, there was an increase in the activation of rpS6 at rest. Additionally, young men exhibited greater activation of S6K during resistance exercise (RE) while dehydrated compared to when they were adequately hydrated. Concurrently, stress (H ₂ O ₂ and REDD1) and proteolytic (active‐cathepsin L) responses were elevated after RE in a dehydrated state compared to an adequately hydrated state. Our research offers new insights into the importance of hydration in muscle responses to exercise, particularly for individuals who are frequently dehydrated.