Mitochondrial-derived vesicles in skeletal muscle remodeling and adaptation.

Mitochondrial remodeling is crucial to meet the bioenergetic demand to support muscle contractile activity during daily tasks and muscle regeneration following injury. A set of mitochondrial quality control (MQC) processes, including mitochondrial biogenesis, dynamics, and mitophagy, are in place to maintain a well-functioning mitochondrial network and support muscle regeneration. Alterations in any of these pathways compromises mitochondrial quality and may potentially lead to impaired myogenesis, defective muscle regeneration, and ultimately loss of muscle function. Among MQC processes, mitophagy has gained special attention for its implication in the clearance of dysfunctional mitochondria via crosstalk with the endo-lysosomal system, a major cell degradative route. Along this pathway, additional opportunities for mitochondrial disposal have been identified that may also signal at the systemic level. This communication occurs via inclusion of mitochondrial components within membranous shuttles named mitochondrial-derived vesicles (MDVs). Here, we discuss MDV generation and release as a mitophagy-complementing route for the maintenance of mitochondrial homeostasis in skeletal myocytes. We also illustrate the possible role of muscle-derived MDVs in immune signaling during muscle remodeling and adaptation.

Transcriptomic and Proteomic of Gastrocnemius Muscle in Peripheral Artery Disease.

BACKGROUND: Few effective therapies exist to improve lower extremity muscle pathology and mobility loss due to peripheral artery disease (PAD), in part because mechanisms associated with functional impairment remain unclear. METHODS: To better understand mechanisms of muscle impairment in PAD, we performed in-depth transcriptomic and proteomic analyses on gastrocnemius muscle biopsies from 31 PAD participants (mean age, 69.9 years) and 29 age- and sex-matched non-PAD controls (mean age, 70.0 years) free of diabetes or limb-threatening ischemia. RESULTS: Transcriptomic and proteomic analyses suggested activation of hypoxia-compensatory mechanisms in PAD muscle, including inflammation, fibrosis, apoptosis, angiogenesis, unfolded protein response, and nerve and muscle repair. Stoichiometric proportions of mitochondrial respiratory proteins were aberrant in PAD compared to non-PAD, suggesting that respiratory proteins not in complete functional units are not removed by mitophagy, likely contributing to abnormal mitochondrial activity. Supporting this hypothesis, greater mitochondrial respiratory protein abundance was significantly associated with greater complex II and complex IV respiratory activity in non-PAD but not in PAD. Rate-limiting glycolytic enzymes, such as hexokinase and pyruvate kinase, were less abundant in muscle of people with PAD compared with non-PAD participants, suggesting diminished glucose metabolism. CONCLUSIONS: In PAD muscle, hypoxia induces accumulation of mitochondria respiratory proteins, reduced activity of rate-limiting glycolytic enzymes, and an enhanced integrated stress response that modulates protein translation. These mechanisms may serve as targets for disease modification.

Sirt3 mediates reduction of oxidative damage and prevention of age-related hearing loss under caloric restriction.

Caloric restriction (CR) extends the life span and health span of a variety of species and slows the progression of age-related hearing loss (AHL), a common age-related disorder associated with oxidative stress. Here, we report that CR reduces oxidative DNA damage in multiple tissues and prevents AHL in wild-type mice but fails to modify these phenotypes in mice lacking the mitochondrial deacetylase Sirt3, a member of the sirtuin family. In response to CR, Sirt3 directly deacetylates and activates mitochondrial isocitrate dehydrogenase 2 (Idh2), leading to increased NADPH levels and an increased ratio of reduced-to-oxidized glutathione in mitochondria. In cultured cells, overexpression of Sirt3 and/or Idh2 increases NADPH levels and protects from oxidative stress-induced cell death. Therefore, our findings identify Sirt3 as an essential player in enhancing the mitochondrial glutathione antioxidant defense system during CR and suggest that Sirt3-dependent mitochondrial adaptations may be a central mechanism of aging retardation in mammals.

The Lipid Intensive Drug Therapy for Sepsis Phase II Pilot Clinical Trial.

OBJECTIVES: Low cholesterol levels in early sepsis patients are associated with mortality. We sought to test if IV lipid emulsion administration to sepsis patients with low cholesterol levels would prevent a decline or increase total cholesterol levels at 48 hours. DESIGN: Phase II, adaptive, randomized pilot clinical trial powered for 48 patients. SETTING: Emergency department or ICU of an academic medical center. PATIENTS: Sepsis patients (first 24 hr) with Sequential Organ Failure Assessment greater than or equal to 4 or shock. INTERVENTIONS: Patients meeting study criteria, including screening total cholesterol levels less than or equal to 100 mg/dL or high-density lipoprotein cholesterol (HDL-C) + low-density lipoprotein cholesterol (LDL-C) less than or equal to 70 mg/dL, were randomized to receive one of three doses of lipid emulsion administered twice in 48 hours or no drug (controls). The primary endpoint was a change in serum total cholesterol (48 hr - enrollment) between groups. MEASUREMENTS AND MAIN RESULTS: Forty-nine patients were enrolled and randomized. Two patients randomized to lipid emulsion were withdrawn before drug administration. Data for 24 control patients and 23 lipid emulsion patients were analyzed. The mean change in total cholesterol from enrollment to 48 hours was not different between groups and was 5 mg/dL (sd 20) for lipid emulsion patients, and 2 mg/dL (sd 18) for control patients (p = 0.62). The mean changes in HDL-C and LDL-C were similar between groups. Mean change in triglycerides was elevated in lipid emulsion patients (61 mg/dL, sd 87) compared with controls (20 mg/dL, sd 70, p = 0.086). The 48-hour change in SOFA score was -2 (interquartile range [IQR] -4, -1) for control patients and -2 (IQR -3, 0) for lipid emulsion patients (p = 0.46). CONCLUSIONS: Administration of IV lipid emulsion to early sepsis patients with low cholesterol levels did not influence change in cholesterol levels from enrollment to 48 hours.

Walking Exercise Therapy Effects on Lower Extremity Skeletal Muscle in Peripheral Artery Disease.

Walking exercise is the most effective noninvasive therapy that improves walking ability in peripheral artery disease (PAD). Biologic mechanisms by which exercise improves walking in PAD are unclear. This review summarizes evidence regarding effects of walking exercise on lower extremity skeletal muscle in PAD. In older people without PAD, aerobic exercise improves mitochondrial activity, muscle mass, capillary density, and insulin sensitivity in skeletal muscle. However, walking exercise increases lower extremity ischemia in people with PAD, and therefore, mechanisms by which this exercise improves walking may differ between people with and without PAD. Compared with people without PAD, gastrocnemius muscle in people with PAD has greater mitochondrial impairment, increased reactive oxygen species, and increased fibrosis. In multiple small trials, walking exercise therapy did not consistently improve mitochondrial activity in people with PAD. In one 12-week randomized trial of people with PAD randomized to supervised exercise or control, supervised treadmill exercise increased treadmill walking time from 9.3 to 15.1 minutes, but simultaneously increased the proportion of angular muscle fibers, consistent with muscle denervation (from 7.6% to 15.6%), while angular myofibers did not change in the control group (from 9.1% to 9.1%). These findings suggest an adaptive response to exercise in PAD that includes denervation and reinnervation, an adaptive process observed in skeletal muscle of people without PAD during aging. Small studies have not shown significant effects of exercise on increased capillary density in lower extremity skeletal muscle of participants with PAD, and there are no data showing that exercise improves microcirculatory delivery of oxygen and nutrients in patients with PAD. However, the effects of supervised exercise on increased plasma nitrite abundance after a treadmill walking test in people with PAD may be associated with improved lower extremity skeletal muscle perfusion and may contribute to improved walking performance in response to exercise in people with PAD. Randomized trials with serial, comprehensive measures of muscle biology, and physiology are needed to clarify mechanisms by which walking exercise interventions improve mobility in PAD.

Cigarette smoking and mitochondrial dysfunction in peripheral artery disease.

BACKGROUND: This study evaluated the association of smoking with mitochondrial function in gastrocnemius muscle of people with peripheral artery disease (PAD). METHODS: Participants were enrolled from Chicago, Illinois and consented to gastrocnemius biopsy. Mitochondrial oxidative capacity was measured in muscle with respirometry. Abundance of voltage-dependent anion channel (VDAC) (mitochondrial membrane abundance), peroxisome proliferator-activated receptor-γ coactivator (PGC-1α) (mitochondrial biogenesis), and electron transport chain complexes I-V were measured with Western blot. RESULTS: Fourteen of 31 people with PAD (age 72.1 years, ABI 0.64) smoked cigarettes currently. Overall, there were no significant differences in mitochondrial oxidative capacity between PAD participants who currently smoked and those not currently smoking (complex I+II-mediated oxidative phosphorylation: 86.6 vs 78.3 pmolO2/s/mg, respectively [p = 0.39]). Among participants with PAD, those who currently smoked had a higher abundance of PGC-1α (p < 0.01), VDAC (p = 0.022), complex I (p = 0.021), and complex III (p = 0.021) proteins compared to those not currently smoking. People with PAD who currently smoked had lower oxidative capacity per VDAC unit (complex I+II-mediated oxidative phosphorylation [137.4 vs 231.8 arbitrary units, p = 0.030]) compared to people with PAD not currently smoking. Among people without PAD, there were no significant differences in any mitochondrial measures between currently smoking (n = 5) and those not currently smoking (n = 63). CONCLUSIONS: Among people with PAD, cigarette smoking may stimulate mitochondrial biogenesis to compensate for reduced oxidative capacity per unit of mitochondrial membrane, resulting in no difference in overall mitochondrial oxidative capacity according to current smoking status among people with PAD. However, these results were cross-sectional and a longitudinal study is needed.

Frailty and risk of mortality in older cancer survivors and adults without a cancer history: Evidence from the National Health and Nutrition Examination Survey, 1999-2014.

BACKGROUND: Epidemiologic evidence reporting the role of frailty in survival among older adults with a prior cancer diagnosis is limited. METHODS: A total of 2050 older adults (≥60 years old) surviving for at least 1 year after a cancer diagnosis and 9474 older adults without a cancer history from the National Health and Nutrition Examination Survey (1999-2014) were included for analysis. The exposure variable, a 45-item frailty index (FI), was categorized on the basis of validated cutoffs (FI ≤ 0.10 [fit], 0.10 < FI ≤ 0.21 [prefrail], and FI > 0.21 [frail]). All-cause mortality was ascertained via the National Death Index. Multivariable Cox proportional hazards models were used to estimate adjusted hazard ratios (aHRs) and 95% confidence interval (CIs) for the FI, and this was followed by restricted cubic splines depicting dose-response curves. RESULTS: For older cancer survivors, the mean age at the baseline was 72.6 years (SD, 7.1 years); 5.9% were fit, 38.2% were prefrail, and 55.9% were frail. Older adults without a cancer history were slightly younger (mean age, 70.0 years) and less frail (47.9% were frail). At each level of the FI, cancer survivors (1.9 per 100 person-years for FI ≤ 0.10, 3.4 per 100 person-years for 0.10 < FI ≤ 0.21, and 7.5 per 100 person-years for FI > 0.21) had higher mortality than their cancer-free counterparts (1.4 per 100 person-years for FI ≤ 0.10, 2.4 per 100 person-years for 0.10 < FI ≤ 0.21, and 5.4 per 100 person-years for FI > 0.21). The multivariable model suggested a positive association between the FI and all-cause mortality for survivors (aHR for FI > 0.21 vs FI ≤ 0.10, 2.80; 95% CI, 1.73-4.53) and participants without a cancer history (aHR for FI > 0.21 vs FI ≤ 0.10, 2.75; 95% CI, 2.29-3.32). Restricted cubic splines indicated that all-cause mortality risk increased with the FI in a monotonic pattern. CONCLUSIONS: Frailty is associated with a higher risk of death in older cancer survivors and the elderly without a cancer history.

Transcriptomic responses from improved murine sepsis models can better mimic human surgical sepsis.

Historically, murine models of inflammation in biomedical research have been shown to minimally correlate with genomic expression patterns from blood leukocytes in humans. In 2019, our laboratory reported an improved surgical sepsis model of cecal ligation and puncture (CLP) that provides additional daily chronic stress (DCS), as well as adhering to the Minimum Quality Threshold in Pre-Clinical Sepsis Studies (MQTiPSS) guidelines. This model phenotypically recapitulates the persistent inflammation, immunosuppression, and catabolism syndrome observed in adult human surgical sepsis survivors. Whether these phenotypic similarities between septic humans and mice are replicated at the circulating blood leukocyte transcriptome has not been demonstrated. Our analysis, in contrast with previous findings, demonstrated that genome-wide expression in our new murine model more closely approximated human surgical sepsis patients, particularly in the more chronic phases of sepsis. Importantly, our new model of murine surgical sepsis with chronic stress did not reflect well gene expression patterns from humans with community-acquired sepsis. Our work indicates that improved preclinical murine sepsis modeling can better replicate both the phenotypic and transcriptomic responses to surgical sepsis, but cannot be extrapolated to other sepsis etiologies. Importantly, these improved models can be a useful adjunct to human-focused and artificial intelligence-based forms of research in order to improve septic patients' morbidity and mortality.

Cocoa to Improve Walking Performance in Older People With Peripheral Artery Disease: The COCOA-PAD Pilot Randomized Clinical Trial.

RATIONALE: Cocoa and its major flavanol component, epicatechin, have therapeutic properties that may improve limb perfusion and increase calf muscle mitochondrial activity in people with lower extremity peripheral artery disease (PAD). OBJECTIVE: In a phase II randomized clinical trial, to assess whether 6 months of cocoa improved walking performance in people with PAD, compared with placebo. METHODS AND RESULTS: Six-month double-blind, randomized clinical trial in which participants with PAD were randomized to either cocoa beverage versus placebo beverage. The cocoa beverage contained 15 g of cocoa and 75 mg of epicatechin daily. The identical appearing placebo contained neither cocoa nor epicatechin. The 2 primary outcomes were 6-month change in 6-minute walk distance measured 2.5 hours after a study beverage at 6-month follow-up and 24 hours after a study beverage at 6-month follow-up, respectively. A 1-sided P<0.10 was considered statistically significant. Of 44 PAD participants randomized (mean age, 72.3 years [±7.1]; mean ankle brachial index, 0.66 [±0.15]), 40 (91%) completed follow-up. Adjusting for smoking, race, and body mass index, cocoa improved 6-minute walk distance at 6-month follow-up by 42.6 m ([90% CI, +22.2 to +∞] P=0.005) at 2.5 hours after a final study beverage and by 18.0 m ([90% CI, -1.7 to +∞] P=0.12) at 24 hours after a study beverage, compared with placebo. In calf muscle biopsies, cocoa improved mitochondrial COX (cytochrome c oxidase) activity (P=0.013), increased capillary density (P=0.014), improved calf muscle perfusion (P=0.098), and reduced central nuclei (P=0.033), compared with placebo. CONCLUSIONS: These preliminary results suggest a therapeutic effect of cocoa on walking performance in people with PAD. Further study is needed to definitively determine whether cocoa significantly improves walking performance in people with PAD. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02876887. Visual Overview: An online visual overview is available for this article.

Effect of Telmisartan on Walking Performance in Patients With Lower Extremity Peripheral Artery Disease: The TELEX Randomized Clinical Trial.

Importance: Patients with lower extremity peripheral artery disease (PAD) have reduced lower extremity perfusion, impaired lower extremity skeletal muscle function, and poor walking performance. Telmisartan (an angiotensin receptor blocker) has properties that reverse these abnormalities. Objective: To determine whether telmisartan improves 6-minute walk distance, compared with placebo, in patients with lower extremity PAD at 6-month follow-up. Design, Setting, and Participants: Double-blind, randomized clinical trial conducted at 2 US sites and involving 114 participants. Enrollment occurred between December 28, 2015, and November 9, 2021. Final follow-up occurred on May 6, 2022. Interventions: The trial randomized patients using a 2 × 2 factorial design to compare the effects of telmisartan plus supervised exercise vs telmisartan alone and supervised exercise alone and to compare telmisartan alone vs placebo. Participants with PAD were randomized to 1 of 4 groups: telmisartan plus exercise (n = 30), telmisartan plus attention control (n = 29), placebo plus exercise (n = 28), or placebo plus attention control (n = 27) for 6 months. The originally planned sample size was 240 participants. Due to slower than anticipated enrollment, the primary comparison was changed to the 2 combined telmisartan groups vs the 2 combined placebo groups and the target sample size was changed to 112 participants. Main Outcomes and Measures: The primary outcome was the 6-month change in 6-minute walk distance (minimum clinically important difference, 8-20 m). The secondary outcomes were maximal treadmill walking distance; Walking Impairment Questionnaire scores for distance, speed, and stair climbing; and the 36-Item Short-Form Health Survey physical functioning score. The results were adjusted for study site, baseline 6-minute walk distance, randomization to exercise vs attention control, sex, and history of heart failure at baseline. Results: Of the 114 randomized patients (mean age, 67.3 [SD, 9.9] years; 46 were women [40.4%]; and 81 were Black individuals [71.1%]), 105 (92%) completed 6-month follow-up. At 6-month follow-up, telmisartan did not significantly improve 6-minute walk distance (from a mean of 341.6 m to 343.0 m; within-group change: 1.32 m) compared with placebo (from a mean of 352.3 m to 364.8 m; within-group change: 12.5 m) and the adjusted between-group difference was -16.8 m (95% CI, -35.9 m to 2.2 m; P = .08). Compared with placebo, telmisartan did not significantly improve any of the 5 secondary outcomes. The most common serious adverse event was hospitalization for PAD (ie, lower extremity revascularization, amputation, or gangrene). Three participants (5.1%) in the telmisartan group and 2 participants (3.6%) in the placebo group were hospitalized for PAD. Conclusions and Relevance: Among patients with PAD, telmisartan did not improve 6-minute walk distance at 6-month follow-up compared with placebo. These results do not support telmisartan for improving walking performance in patients with PAD. Trial Registration: ClinicalTrials.gov Identifier: NCT02593110.

Clinical characteristics and response to supervised exercise therapy of people with lower extremity peripheral artery disease.

BACKGROUND: Among people with lower extremity peripheral artery disease (PAD), little is known about variation in response to supervised exercise therapy (SET). Clinical characteristics associated with greater responsiveness to SET have not been identified. METHODS: Data from participants with PAD in two randomized clinical trials comparing SET vs nonexercising control were combined. The exercise intervention consisted of three times weekly supervised treadmill exercise. The control groups received lectures on health-related topics. RESULTS: Of 309 unique participants randomized (mean age, 67.9 years [standard deviation, 9.3 years]; 132 [42.7%] women; 185 [59.9%] black), 285 (92%) completed 6-month follow-up. Compared with control, those randomized to SET improved 6-minute walk distance by 35.6 meters (95% confidence interval, 21.4-49.8; P < .001). In the 95 (62.1%) participants who attended at least 70% of SET sessions, change in 6-minute walk distance varied from -149.4 to +356.0 meters. Thirty-four (35.8%) had no 6-minute walk distance improvement. Among all participants, age, sex, race, body mass index, prior lower extremity revascularization, and other clinical characteristics did not affect the degree of improvement in 6-minute walk distance after SET relative to the control group. Participants with 6-minute walk distance less than the median of 334 meters at baseline had greater percentage improvement in 6-minute walk distance compared with those with baseline 6-minute walk distance above the median (+20.5% vs +5.3%; P for interaction = .0107). CONCLUSIONS: Among people with PAD, substantial variability exists in walking improvement after SET. Shorter 6-minute walk distance at baseline was associated with greater improvement after SET, but other clinical characteristics, including age, sex, prior lower extremity revascularization, and disease severity, did not affect responsiveness to exercise therapy.

Meaningful change in 6-minute walk in people with peripheral artery disease.

OBJECTIVE: The 6-minute walk test is a common outcome measure in clinical trials of people with lower extremity peripheral artery disease (PAD). However, what constitutes a meaningful change in the 6-minute walk distance has not been well defined for people with PAD. The present study related the change in the 6-minute walk distance to the degree of participant-reported improvement or decline in the 6-minute walk distance to define a meaningful change in the 6-minute walk distance for those with PAD. METHODS: Participants with PAD from three observational longitudinal studies completed the walking impairment questionnaire (WIQ) distance score and 6-minute walk at baseline and 1 year later. The WIQ distance score measures participants' perceived difficulty walking seven different distances without stopping (ranging from walking around the home to walking 5 blocks) on a 0 to 4 Likert scale, with 0 representing an inability to walk the distance and 4 representing no difficulty. The mean changes in the 6-minute walk distance corresponding to the participants' report of no change, 1-unit change, or 2-unit change, respectively, in the Likert scale score between the baseline and 1-year follow-up measures were calculated for each WIQ distance. RESULTS: A total of 777 participants with PAD (mean age, 71.2 ± 8.8 years; mean baseline 6-minute walk distance, 350.1 ± 118.1 meters) completed 5439 questions about their difficulty walking each WIQ distance at baseline and follow-up. Participants with PAD who reported no change in their difficulty in walking each WIQ distance between baseline and follow-up had a decline of 7.2 meters (95% confidence interval [CI], -11.6 to -2.8 meters) in the 6-minute walk test. Relative to those reporting no change in difficulty walking, the participants reporting 1- and 2-point improvements in walking ability showed 6-minute walk distance improvements of 7.8 meters (95% CI, -0.3 to 15.9 meters) and 20.1 meters (95% CI, 1.1-39.2 meters), respectively. Relative to those reporting no change in walking difficulty, those reporting 1- and 2-point declines in perceived walking difficulty showed declines of -11.2 meters (95% CI, -19.0 to -3.4 meters) and -23.8 meters (95% CI, -37.4 to -10.3 meters) in the 6-minute walk distance. CONCLUSIONS: Among people with PAD, ∼8- and ∼20-meter improvements in the 6-minute walk distance represent small and large improvements in walking ability, respectively. People with PAD who reported no change in their ability to walk distances over 1 year simultaneously declined by a mean of 7 meters in the 6-minute walk test. These findings will be useful for interpreting the results from randomized trials of interventions to improve the walking performance of people with PAD.

Skeletal Muscle Pathology in Peripheral Artery Disease: A Brief Review.

This brief review summarizes current evidence regarding lower extremity peripheral artery disease (PAD) and lower extremity skeletal muscle pathology. Lower extremity ischemia is associated with reduced calf skeletal muscle area and increased calf muscle fat infiltration and fibrosis on computed tomography or magnetic resonance imaging. Even within the same individual, the leg with more severe ischemia has more adverse calf muscle characteristics than the leg with less severe ischemia. More adverse computed tomography-measured calf muscle characteristics, such as reduced calf muscle density, are associated with higher rates of mobility loss in people with PAD. Calf muscle in people with PAD may also have reduced mitochondrial activity compared with those without PAD, although evidence is inconsistent. Muscle biopsy document increased oxidative stress in PAD. Reduced calf muscle perfusion, impaired mitochondrial activity, and smaller myofibers are associated with greater walking impairment in PAD. Preliminary evidence suggests that calf muscle pathology in PAD may be reversible. In a small uncontrolled trial, revascularization improved both the ankle-brachial index and mitochondrial activity, measured by calf muscle phosphocreatine recovery time. A pilot clinical trial showed that cocoa flavanols increased measures of myofiber health, mitochondrial activity, and capillary density while simultaneously improving 6-minute walk distance in PAD. Calf muscle pathological changes are associated with impaired walking performance in people with PAD, and interventions that both increase calf perfusion and improve calf muscle health are promising therapies to improve walking performance in PAD.

Sustained physical activity in peripheral artery disease: Associations with disease severity, functional performance, health-related quality of life, and subsequent serious adverse events in the LITE randomized clinical trial.

This study investigated cross-sectional associations of peripheral artery disease (PAD) severity (defined by the ankle-brachial index (ABI)) and amounts of daily sustained physical activity (PA) (defined as > 100 activity counts per minute lasting 5 consecutive minutes or more). This study also investigated associations of amounts of daily sustained PA with 6-minute walk (6MW) distance and the Short Form-36 physical functioning domain (SF-36 PF) score in cross-sectional analyses and with serious adverse events (SAEs) in longitudinal analyses of people with PAD. PA was measured continuously for 10 days using a tri-axial accelerometer at baseline in 277 participants with PAD randomized to the LITE clinical trial. In regression analyses, each 0.15 lower ABI value was associated with a 5.67% decrease in the number of daily bouts of sustained PA (95% CI: 3.85-6.54; p < 0.001). Every additional bout of sustained PA per day was associated with a 4.56-meter greater 6MW distance (95% CI: 2.67-6.46; p < 0.0001), and a 0.81-point improvement in SF-36 PF score (95% CI: 0.34-1.28; p < 0.001). Participants with values of daily bouts of sustained PA below the median had higher rates of SAEs during follow-up, compared to participants above the median (41% vs 24%; p = 0.002). In conclusion, among participants with PAD, lower ABI values were associated with fewer bouts of daily sustained PA. A greater number of bouts of daily sustained PA were associated with better 6MW performance and SF-36 PF score, and, in longitudinal analyses, lower rates of SAEs. Clinicaltrials.gov ID: NCT02538900.

A hypolipoprotein sepsis phenotype indicates reduced lipoprotein antioxidant capacity, increased endothelial dysfunction and organ failure, and worse clinical outcomes.

OBJECTIVE: Approximately one-third of sepsis patients experience poor outcomes including chronic critical illness (CCI, intensive care unit (ICU) stay > 14 days) or early death (in-hospital death within 14 days). We sought to characterize lipoprotein predictive ability for poor outcomes and contribution to sepsis heterogeneity. DESIGN: Prospective cohort study with independent replication cohort. SETTING: Emergency department and surgical ICU at two hospitals. PATIENTS: Sepsis patients presenting within 24 h. METHODS: Measures included cholesterol levels (total cholesterol, high density lipoprotein cholesterol [HDL-C], low density lipoprotein cholesterol [LDL-C]), triglycerides, paraoxonase-1 (PON-1), and apolipoprotein A-I (Apo A-I) in the first 24 h. Inflammatory and endothelial markers, and sequential organ failure assessment (SOFA) scores were also measured. LASSO selection assessed predictive ability for outcomes. Unsupervised clustering was used to investigate the contribution of lipid variation to sepsis heterogeneity. MEASUREMENTS AND MAIN RESULTS: 172 patients were enrolled. Most (~ 67%, 114/172) rapidly recovered, while ~ 23% (41/172) developed CCI, and ~ 10% (17/172) had early death. ApoA-I, LDL-C, mechanical ventilation, vasopressor use, and Charlson Comorbidity Score were significant predictors of CCI/early death in LASSO models. Unsupervised clustering yielded two discernible phenotypes. The Hypolipoprotein phenotype was characterized by lower lipoprotein levels, increased endothelial dysfunction (ICAM-1), higher SOFA scores, and worse clinical outcomes (45% rapid recovery, 40% CCI, 16% early death; 28-day mortality, 21%). The Normolipoprotein cluster patients had higher cholesterol levels, less endothelial dysfunction, lower SOFA scores and better outcomes (79% rapid recovery, 15% CCI, 6% early death; 28-day mortality, 15%). Phenotypes were validated in an independent replication cohort (N = 86) with greater sepsis severity, which similarly demonstrated lower HDL-C, ApoA-I, and higher ICAM-1 in the Hypolipoprotein cluster and worse outcomes (46% rapid recovery, 23% CCI, 31% early death; 28-day mortality, 42%). Normolipoprotein patients in the replication cohort had better outcomes (55% rapid recovery, 32% CCI, 13% early death; 28-day mortality, 28%) Top features for cluster discrimination were HDL-C, ApoA-I, total SOFA score, total cholesterol level, and ICAM-1. CONCLUSIONS: Lipoproteins predicted poor sepsis outcomes. A Hypolipoprotein sepsis phenotype was identified and characterized by lower lipoprotein levels, increased endothelial dysfunction (ICAM-1) and organ failure, and worse clinical outcomes.

Effect of Low-Intensity vs High-Intensity Home-Based Walking Exercise on Walk Distance in Patients With Peripheral Artery Disease: The LITE Randomized Clinical Trial.

Importance: Supervised high-intensity walking exercise that induces ischemic leg symptoms is the first-line therapy for people with lower-extremity peripheral artery disease (PAD), but adherence is poor. Objective: To determine whether low-intensity home-based walking exercise at a comfortable pace significantly improves walking ability in people with PAD vs high-intensity home-based walking exercise that induces ischemic leg symptoms and vs a nonexercise control. Design, Setting, and Participants: Multicenter randomized clinical trial conducted at 4 US centers and including 305 participants. Enrollment occurred between September 25, 2015, and December 11, 2019; final follow-up was October 7, 2020. Interventions: Participants with PAD were randomized to low-intensity walking exercise (n = 116), high-intensity walking exercise (n = 124), or nonexercise control (n = 65) for 12 months. Both exercise groups were asked to walk for exercise in an unsupervised setting 5 times per week for up to 50 minutes per session wearing an accelerometer to document exercise intensity and time. The low-intensity group walked at a pace without ischemic leg symptoms. The high-intensity group walked at a pace eliciting moderate to severe ischemic leg symptoms. Accelerometer data were viewable to a coach who telephoned participants weekly for 12 months and helped them adhere to their prescribed exercise. The nonexercise control group received weekly educational telephone calls for 12 months. Main Outcomes and Measures: The primary outcome was mean change in 6-minute walk distance at 12 months (minimum clinically important difference, 8-20 m). Results: Among 305 randomized patients (mean age, 69.3 [SD, 9.5] years, 146 [47.9%] women, 181 [59.3%] Black patients), 250 (82%) completed 12-month follow-up. The 6-minute walk distance changed from 332.1 m at baseline to 327.5 m at 12-month follow-up in the low-intensity exercise group (within-group mean change, -6.4 m [95% CI, -21.5 to 8.8 m]; P = .34) and from 338.1 m to 371.2 m in the high-intensity exercise group (within-group mean change, 34.5 m [95% CI, 20.1 to 48.9 m]; P < .001) and the mean change for the between-group comparison was -40.9 m (97.5% CI, -61.7 to -20.0 m; P < .001). The 6-minute walk distance changed from 328.1 m at baseline to 317.5 m at 12-month follow-up in the nonexercise control group (within-group mean change, -15.1 m [95% CI, -35.8 to 5.7 m]; P = .10), which was not significantly different from the change in the low-intensity exercise group (between-group mean change, 8.7 m [97.5% CI, -17.0 to 34.4 m]; P = .44). Of 184 serious adverse events, the event rate per participant was 0.64 in the low-intensity group, 0.65 in the high-intensity group, and 0.46 in the nonexercise control group. One serious adverse event in each exercise group was related to study participation. Conclusions and Relevance: Among patients with PAD, low-intensity home-based exercise was significantly less effective than high-intensity home-based exercise and was not significantly different from the nonexercise control for improving 6-minute walk distance. These results do not support the use of low-intensity home-based walking exercise for improving objectively measured walking performance in patients with PAD. Trial Registration: ClinicalTrials.gov Identifier: NCT02538900.

The Age-Sensitive Efficacy of Calorie Restriction on Mitochondrial Biogenesis and mtDNA Damage in Rat Liver.

Calorie restriction (CR) is the most efficacious treatment to delay the onset of age-related changes such as mitochondrial dysfunction. However, the sensitivity of mitochondrial markers to CR and the age-related boundaries of CR efficacy are not fully elucidated. We used liver samples from ad libitum-fed (AL) rats divided in: 18-month-old (AL-18), 28-month-old (AL-28), and 32-month-old (AL-32) groups, and from CR-treated (CR) 28-month-old (CR-28) and 32-month-old (CR-32) counterparts to assay the effect of CR on several mitochondrial markers. The age-related decreases in citrate synthase activity, in TFAM, MFN2, and DRP1 protein amounts and in the mtDNA content in the AL-28 group were prevented in CR-28 counterparts. Accordingly, CR reduced oxidative mtDNA damage assessed through the incidence of oxidized purines at specific mtDNA regions in CR-28 animals. These findings support the anti-aging effect of CR up to 28 months. Conversely, the protein amounts of LonP1, Cyt c, OGG1, and APE1 and the 4.8 Kb mtDNA deletion content were not affected in CR-28 rats. The absence of significant differences between the AL-32 values and the CR-32 counterparts suggests an age-related boundary of CR efficacy at this age. However, this only partially curtails the CR benefits in counteracting the generalized aging decline and the related mitochondrial involvement.

Comparing 6-minute walk versus treadmill walking distance as outcomes in randomized trials of peripheral artery disease.

BACKGROUND: Randomized trials of people with peripheral artery disease (PAD) and intermittent claudication have traditionally used maximal treadmill walking distance as the primary outcome, but the 6-minute walk test is increasingly used as a primary outcome in randomized trials of PAD. This study compared relative changes in maximal treadmill walking distance versus 6-minute walk distance in response to a therapeutic intervention or control in randomized trials of participants with PAD. METHODS: Data from four randomized trials of therapeutic interventions in participants with PAD that measured both 6-minute walk and treadmill walking performance at baseline and the 6-month follow-up were combined. Two trials studied supervised treadmill exercise, one studied home-based walking exercise, and one studied resveratrol. RESULTS: Of 467 participants (mean age, 69.8; standard deviation, 9.7), the mean ankle-brachial index was 0.66 (standard deviation, 0.17). At the 6-month follow-up, participants with PAD randomized to control or placebo significantly declined in 6-minute walk distance (-10.2 m; 95% confidence interval, -18.2 to -2.2; P = .013), but improved maximal treadmill walking distance (+25.7 m; 95% CI, +6.0 to +45.3 m; P = .010; difference between change in 6-minute walk versus maximal treadmill walking distance: -37.3 m; 95% CI, -56.4 to -18.2; P < .001). Home-based exercise improved the 6-minute walk distance by 43.2 m (95% CI, +28.4 to +57.9), and supervised treadmill exercise improved the 6-minute walk distance by 25.0 m (95% CI, +14.7 to +35.2; mean difference, +18.2 m favoring home-based exercise [95% CI, +0.2 to +36.2 m; P = .048]). Among all participants, the presence (vs absence) of treadmill exercise training was associated with a 141.3-m greater improvement in maximal treadmill walking distance compared to 6-minute walk distance (95% CI, 88.2-194.4; P < .001), suggesting a benefit from treadmill training on the treadmill outcome. CONCLUSIONS: Maximal treadmill walking distance and the 6-minute walk distance are not interchangeable outcomes in participants with PAD. Participants with PAD randomized to control groups improved treadmill walking distance but simultaneously meaningfully declined in 6-minute walk distance. Supervised treadmill exercise training amplified improvement in treadmill walking distance because of a training to the outcome measure phenomenon.

Old Mice Demonstrate Organ Dysfunction as well as Prolonged Inflammation, Immunosuppression, and Weight Loss in a Modified Surgical Sepsis Model.

OBJECTIVES: Our goal was to "reverse translate" the human response to surgical sepsis into the mouse by modifying a widely adopted murine intra-abdominal sepsis model to engender a phenotype that conforms to current sepsis definitions and follows the most recent expert recommendations for animal preclinical sepsis research. Furthermore, we aimed to create a model that allows the study of aging on the long-term host response to sepsis. DESIGN: Experimental study. SETTING: Research laboratory. SUBJECTS: Young (3-5 mo) and old (18-22 mo) C57BL/6j mice. INTERVENTIONS: Mice received no intervention or were subjected to polymicrobial sepsis with cecal ligation and puncture followed by fluid resuscitation, analgesia, and antibiotics. Subsets of mice received daily chronic stress after cecal ligation and puncture for 14 days. Additionally, modifications were made to ensure that "Minimum Quality Threshold in Pre-Clinical Sepsis Studies" recommendations were followed. MEASUREMENTS AND MAIN RESULTS: Old mice exhibited increased mortality following both cecal ligation and puncture and cecal ligation and puncture + daily chronic stress when compared with young mice. Old mice developed marked hepatic and/or renal dysfunction, supported by elevations in plasma aspartate aminotransferase, blood urea nitrogen, and creatinine, 8 and 24 hours following cecal ligation and puncture. Similar to human sepsis, old mice demonstrated low-grade systemic inflammation 14 days after cecal ligation and puncture + daily chronic stress and evidence of immunosuppression, as determined by increased serum concentrations of multiple pro- and anti-inflammatory cytokines and chemokines when compared with young septic mice. In addition, old mice demonstrated expansion of myeloid-derived suppressor cell populations and sustained weight loss following cecal ligation and puncture + daily chronic stress, again similar to the human condition. CONCLUSIONS: The results indicate that this murine cecal ligation and puncture + daily chronic stress model of surgical sepsis in old mice adhered to current Minimum Quality Threshold in Pre-Clinical Sepsis Studies guidelines and met Sepsis-3 criteria. In addition, it effectively created a state of persistent inflammation, immunosuppression, and weight loss, thought to be a key aspect of chronic sepsis pathobiology and increasingly more prevalent after human sepsis.

Prognostic value of NT-proBNP levels in the acute phase of sepsis on lower long-term physical function and muscle strength in sepsis survivors.

BACKGROUND: Sepsis survivors often develop chronic critical illness (CCI) and demonstrate the persistent inflammation, immunosuppression, and catabolism syndrome predisposing them to long-term functional limitations and higher mortality. There is a need to identify biomarkers that can predict long-term worsening of physical function to be able to act early and prevent mobility loss. N-terminal pro-brain natriuretic peptide (NT-proBNP) is a well-accepted biomarker of cardiac overload, but it has also been shown to be associated with long-term physical function decline. We explored whether NT-proBNP blood levels in the acute phase of sepsis are associated with physical function and muscle strength impairment at 6 and 12 months after sepsis onset. METHODS: This is a retrospective analysis conducted in 196 sepsis patients (aged 18-86 years old) as part of the University of Florida (UF) Sepsis and Critical Illness Research Center (SCIRC) who consented to participate in the 12-month follow-up study. NT-proBNP was measured at 24 h after sepsis onset. Patients were followed to determine physical function by short physical performance battery (SPPB) test score (scale 0 to12-higher score corresponds with better physical function) and upper limb muscle strength by hand grip strength test (kilograms) at 6 and 12 months. We used a multivariate linear regression model to test an association between NT-proBNP levels, SPPB, and hand grip strength scores. Missing follow-up data or absence due to death was accounted for by using inverse probability weighting based on concurrent health performance status scores. Statistical significance was set at p ≤ 0.05. RESULTS: After adjusting for covariates (age, gender, race, Charlson comorbidity index, APACHE II score, and presence of CCI condition), higher levels of NT-proBNP at 24 h after sepsis onset were associated with lower SPPB scores at 12 months (p < 0.05) and lower hand grip strength at 6-month (p < 0.001) and 12-month follow-up (p < 0.05). CONCLUSIONS: NT-proBNP levels during the acute phase of sepsis may be a useful indicator of higher risk of long-term impairments in physical function and muscle strength in sepsis survivors.