Sepsis causes neutrophil infiltration in muscle leading to muscle atrophy and weakness in mice

Respiratory muscle ultrasound echo characteristics and weaning outcomes in mechanically ventilated patients with sepsis: a prospective observational study

AIM

This study aimed to determine the relationship between changes in the ultrasound echo intensity of respiratory muscles and weaning outcomes in mechanically ventilated patients with sepsis.

METHODS

We prospectively observed patients with sepsis receiving mechanical ventilation admitted to the Department of Critical Care Medicine at our hospital, and categorized them into weaning success (n = 75) and weaning failure (n = 35) groups according to their weaning outcomes. The baseline respiratory muscle echo intensity of the patients was observed, and the relationship between the respiratory muscle ultrasonographic echo characteristics and weaning outcomes was evaluated.

RESULTS

Baseline respiratory muscle echo intensity was significantly higher in the weaning failure group than in the weaning success group. The incidence of respiratory muscle echoes during mechanical ventilation was significantly higher in the weaning failure group than in the weaning success group. The respiratory muscle echo characteristics changed after ICU admission. Increased respiratory muscle echo intensity was detected earlier and more readily in patients with weaning failure than in those with respiratory muscle atrophy, and enhanced respiratory muscle echo was associated with a decrease in the incidence of cumulative weaning success.

CONCLUSION

Mechanically ventilated patients with sepsis with failed weaning had higher respiratory muscle echo intensities than those in the weaning success group. Futhermore, there was an association between the respiratory muscle echo intensity and weaning outcomes.

Prognostic potential of neutrophil-to-lymphocyte ratio for appendicular skeletal muscle mass reduction in males aged 70 and older

Inflammation plays a pivotal role in the age-related decline of skeletal muscle mass, leading to sarcopenia in the elderly. The prevalence of sarcopenia notably increases among males aged ≥ 70. However, it remains unclear whether inflammatory indexes are associated with the reduction in skeletal muscle mass in the elderly population. Thirty-one males aged ≥ 70, without severe diseases or dementia, were enrolled in the study. They underwent muscle mass measurements, physical measurements, and hematological tests at the onset of the study and after a one-year follow-up. Twenty-eight participants were successfully followed for one year. Appendicular skeletal muscle mass index (ASMI) decreased by 3.30 ± 2.41% in 14 participants and increased by 2.66 ± 1.61% in the other 14 participants compared to baseline levels. The baseline neutrophil-to-lymphocyte ratio (NLR) was 2.14 ± 0.56 in the ASMI-decreased group and 1.66 ± 0.62 in the ASMI-increased group. A statistically significant negative correlation was found between baseline NLR and the change in ASMI in linear regression analyses. The area under the curve (AUC) of the baseline NLR for predicting ASMI decline was 0.724, with an optimal sensitivity of 64.3% and specificity of 78.6% at a cut-off value of 1.94. NLR emerged as a potential prognostic marker for ASMI reduction in elderly males. However, further studies are necessary to assess its clinical utility.

Post-sepsis chronic muscle weakness can be prevented by pharmacological protection of mitochondria

BACKGROUND

Sepsis, mainly caused by bacterial infections, is the leading cause of in-patient hospitalizations. After discharge, most sepsis survivors suffer from long-term medical complications, particularly chronic skeletal muscle weakness. To investigate this medical condition in detail, we previously developed a murine severe sepsis-survival model that exhibits long-term post-sepsis skeletal muscle weakness. While mitochondrial abnormalities were present in the skeletal muscle of the sepsis surviving mice, the relationship between abnormal mitochondria and muscle weakness remained unclear. Herein, we aimed to investigate whether mitochondrial abnormalities have a causal role in chronic post-sepsis muscle weakness and could thereby serve as a therapeutic target.

METHODS

Experimental polymicrobial abdominal sepsis was induced in 16-18 months old male and female mice using cecal slurry injection with subsequent antibiotic and fluid resuscitation. To evaluate the pathological roles of mitochondrial abnormalities in post-sepsis skeletal muscle weakness, we utilized a transgenic mouse strain overexpressing the mitochondria-specific antioxidant enzyme manganese superoxide dismutase (MnSOD). Following sepsis development in C57BL/6 mice, we evaluated the effect of the mitochondria-targeting synthetic tetrapeptide SS-31 in protecting mitochondria from sepsis-induced damage and preventing skeletal muscle weakness development. In vivo and in vitro techniques were leveraged to assess muscle function at multiple timepoints throughout sepsis development and resolution. Histological and biochemical analyses including bulk mRNA sequencing were used to detect molecular changes in the muscle during and after sepsis RESULTS: Our time course study revealed that post sepsis skeletal muscle weakness develops progressively after the resolution of acute sepsis and in parallel with the accumulation of mitochondrial abnormalities and changes in the mitochondria-related gene expression profile. Transgenic mice overexpressing MnSOD were protected from mitochondrial abnormalities and muscle weakness following sepsis. Further, pharmacological protection of mitochondria utilizing SS-31 during sepsis effectively prevented the later development of muscle weakness.

CONCLUSIONS

Our study revealed that the accumulation of mitochondrial abnormalities is the major cause of post-sepsis skeletal muscle weakness. Pharmacological protection of mitochondria during acute sepsis is a potential clinical treatment strategy to prevent post-sepsis muscle weakness.

Association between changes in disease severity and physical function after surviving a critical illness: A multicentre retrospective observational study

BACKGROUND

Whilst disease severity can significantly impact functional outcomes, the ability to predict the scale of this impact has not been consistent.

AIM

We aimed to investigate whether changes in disease severity within the first 48 h of ICU admission are more strongly associated with physical dysfunction than a single-time assessment of disease severity at ICU admission.

METHODS

A multicentre retrospective study in seven tertiary ICUs in Japan, including all consecutive adult ICU patients (>48 h ICU stay) between September 2019 and February 2020. The primary outcome was physical function defined as the Barthel Index, which is an ordinal scale (0-100: larger indicates better function) to measure physical independence and performance. The association between Barthel Index score at hospital discharge and the Sequential Organ Failure Assessment (SOFA) scores, measured at ICU admission, the highest recorded score within 48 h of ICU admission, and the level of change between these two timepoints were investigated in multivariable analysis.

RESULTS

A total of 199 patients were included. Median SOFA score at ICU admission and the highest recorded score within the first 48 h were 6 (interquartile range: 5-10) and 8 (interquartile range: 6-11), respectively. A quarter of patients had a Barthel Index score of 60 or less at hospital discharge. The highest SOFA score within 48 h of ICU admission and the level of change in SOFA scores between ICU admission and the highest recorded score within 48 h were significantly associated with lower Barthel Index scores at hospital discharge. No significant association was identified with regard to Barthel Index scores and SOFA score at ICU admission. An increase in SOFA score of 1 or more within the first 48 h of ICU admission was the threshold to predict a Barthel Index score of 60 or less at hospital discharge. Larger changes in SOFA scores over the first 48 h of ICU admission were also significantly associated with smaller changes in Barthel Index scores from ICU discharge to hospital discharge.

CONCLUSIONS

The level of change in SOFA score between ICU admission and the highest recorded score within the first 48 h of ICU stay can more accurately predict the presence of physical dysfunction at hospital discharge than a single-time assessment of disease severity at ICU admission. The larger worsening in SOFA potentially indicates lower recovery after a critical illness.

A scoping review of preclinical intensive care unit-acquired weakness models

Background

Animal models focusing on neuromuscular outcomes are crucial for understanding the mechanisms of intensive care unit-acquired weakness (ICU-AW) and exploring potential innovative prevention and treatment strategies.

Aim

To analyse and evaluate preclinical ICU-AW models.

Methods

We manually searched five English and four Chinese databases from 1 January 2002, to 1 February 2024, and reviewed related study references. Full-text publications describing animal models of muscle weakness and atrophy in critical illness were included. Detailed information about model types, animal species, sex, age, induction methods, outcome measures, drawbacks and strengths was extracted from each included study.

Results

A total of 3,451 citations were initially retrieved, with 84 studies included in the final analysis. The most frequently studied animal model included rodents (86.9%), 64.3% of which were male animals. ICU-AW animal models were mostly induced by comprehensive intensive care unit (ICU) interventions (38.1%) and sepsis (51.2%). Most studies focused on limb muscles (66.7%), diaphragm muscles (21.4%) or both (9.5%). Reported outcomes primarily included muscular pathological changes (83.3%), electrophysiological examinations of muscles (57.1%) and animal grip strength (16.6%). However, details such as animal age, mortality data, experimental design, randomisation, blinding, sample size and interventions for the experimental group and/or control group were inadequately reported.

Conclusion

Many preclinical models are used to study ICU-AW, but the reporting of methodological details is often incomplete. Although current ICU animal models can mimic the characteristics of human ICU-AW, there is no standard model. Future preclinical studies should develop a standard ICU-AW animal model to enhance reproducibility and improve scientific rigor in exploring the mechanisms and potential treatment of ICU-AW.

The immunology of sickness metabolism

Everyone knows that an infection can make you feel sick. Although we perceive infection-induced changes in metabolism as a pathology, they are a part of a carefully regulated process that depends on tissue-specific interactions between the immune system and organs involved in the regulation of systemic homeostasis. Immune-mediated changes in homeostatic parameters lead to altered production and uptake of nutrients in circulation, which modifies the metabolic rate of key organs. This is what we experience as being sick. The purpose of sickness metabolism is to generate a metabolic environment in which the body is optimally able to fight infection while denying vital nutrients for the replication of pathogens. Sickness metabolism depends on tissue-specific immune cells, which mediate responses tailored to the nature and magnitude of the threat. As an infection increases in severity, so do the number and type of immune cells involved and the level to which organs are affected, which dictates the degree to which we feel sick. Interestingly, many alterations associated with metabolic disease appear to overlap with immune-mediated changes observed following infection. Targeting processes involving tissue-specific interactions between activated immune cells and metabolic organs therefore holds great potential for treating both people with severe infection and those with metabolic disease. In this review, we will discuss how the immune system communicates in situ with organs involved in the regulation of homeostasis and how this communication is impacted by infection.

Post-intensive care syndrome: Recent advances and future directions

Post-intensive care syndrome comprises physical, cognitive, and mental impairments in patients treated in an intensive care unit (ICU). It occurs either during the ICU stay or following ICU discharge and is related to the patients' long-term prognosis. The same concept also applies to pediatric patients, and it can greatly affect the mental status of family members. In the 10 years since post-intensive care syndrome was first proposed, research has greatly expanded. Here, we summarize the recent evidence on post-intensive care syndrome regarding its pathophysiology, epidemiology, assessment, risk factors, prevention, and treatments. We highlight new topics, future directions, and strategies to overcome post-intensive care syndrome among people treated in an ICU. Clinical and basic research are still needed to elucidate the mechanistic insights and to discover therapeutic targets and new interventions for post-intensive care syndrome.

Therapeutic effect of adipose-derived mesenchymal stem cells in a porcine model of abdominal sepsis

BACKGROUND

The term sepsis refers to a complex and heterogeneous syndrome. Although great progress has been made in improving the diagnosis and treatment of this condition, it continues to have a huge impact on morbidity and mortality worldwide. Mesenchymal stem cells are a population of multipotent cells that have immunomodulatory properties, anti-apoptotic effects, and antimicrobial activity. We studied these capacities in a porcine model of peritoneal sepsis.

METHODS

We infused human adipose-derived mesenchymal stem cells (ADSCs) into a porcine model of peritoneal sepsis. Twenty piglets were treated with antibiotics alone (control group) or antibiotics plus peritoneal infusion of ADSCs at a concentration of 2 × 106 cells/kg or 4 × 106 cells/kg (low- and high-dose experimental groups, respectively). The animals were evaluated at different time points to determine their clinical status, biochemical and hematologic parameters, presence of inflammatory cytokines and chemokines in blood and peritoneal fluid, and finally by histologic analysis of the organs of the peritoneal cavity.

RESULTS

One day after sepsis induction, all animals presented peritonitis with bacterial infection as well as elevated C-reactive protein, haptoglobin, IL-1Ra, IL-6, and IL-1b. Xenogeneic ADSC infusion did not elicit an immune response, and peritoneal administration of the treatment was safe and feasible. One day after infusion, the two experimental groups showed a superior physical condition (e.g., mobility, feeding) and a significant increase of IL-10 and TGF-β in blood and a decrease of IL-1Ra, IL-1b, and IL-6. After 7 days, all animals treated with ADSCs had better results concerning blood biomarkers, and histopathological analysis revealed a lower degree of inflammatory cell infiltration of the organs of the peritoneal cavity.

CONCLUSIONS

Intraperitoneal administration of ADSCs as an adjuvant therapy for sepsis improves the outcome and diminishes the effects of peritonitis and associated organ damage by regulating the immune system and reducing intra-abdominal adhesions in a clinically relevant porcine model of abdominal sepsis.