Hypermetabolism and Nutritional Support in Sepsis

Octanoic acid-rich enteral nutrition attenuated hypercatabolism through the acylated ghrelin-POMC pathway in endotoxemic rats

OBJECTIVES

Metabolic disorders and no response to intravenous nutrition because of sepsis have been urgent problems for clinical nutrition support. Enteral nutrition (EN) has been an important clinical therapeutic measure in septic patients; however, simple EN has not demonstrated good performance. This study aimed to investigate the effects of different concentrations of octanoic acid (OA)-rich EN on hypercatabolism in endotoxemic rats and test whether OA-rich EN could attenuate hypercatabolism through the acylated ghrelin-proopiomelanocortin (POMC) pathway.

METHODS

Rats were randomly divided into six groups: sham, lipopolysaccharide (LPS), LPS + EN and LPS + EN + OA (0.25, 0.5, and 1 g/kg, respectively) groups to investigate the effects of different concentrations of OA-rich EN on hypercatabolism in endotoxemic rats. The rats were then randomly divided into four groups: sham, LPS, LPS + OA, and LPS + OA + Go-CoA-Tat, to test whether OA-rich EN attenuated hypercatabolism through the acylated ghrelin-POMC pathway. Rats received nutrition support via a gastric tube for 3 d (100 kcal/kg daily). Insulin resistance, muscle protein synthesis and atrophy, inflammatory cytokines, ghrelin in circulation and hypothalamus, ghrelin O-acyltransferase (GOAT), and the adenosine 5'-monophosphate-activated protein kinase (AMPK)-autophagy-POMC pathway were measured.

RESULTS

Compared with simple EN, OA-rich EN promoted the acylation of ghrelin in a dose-dependent manner and attenuated POMC-mediated hypercatabolism in endotoxemic rats. Inhibition of GOAT activity decreased the level of acylated ghrelin and aggravated POMC-mediated hypercatabolism conferred by OA-rich EN.

CONCLUSIONS

OA-rich EN could increase the level of acylated ghrelin and attenuate hypercatabolism through the acylated ghrelin-POMC pathway compared with simple EN in endotoxemic rats.

U-shaped association between serum triglyceride levels and mortality among septic patients: An analysis based on the MIMIC-IV database

BACKGROUND

Sepsis is characterized by upregulated lipolysis in adipose tissue and a high blood triglyceride (TG) level. It is still debated whether serum TG level is related to mortality in septic patients. The aim of this study is to investigate the association between serum TG level and mortality in septic patients admitted to the intensive care unit (ICU).

METHODS

Data from adult septic patients (≥18 years) admitted to the ICU for the first time were obtained from the Multiparameter Intelligent Monitoring in Intensive Care IV (MIMIC-IV) database. The patients' serum TG levels that were measured within the first week after ICU admission were extracted for statistical analysis. The endpoints were 28-day, ICU and in-hospital mortality.

RESULTS

A total of 2,782 septic patients were included. Univariate analysis indicated that the relationship between serum TG levels and the risk of mortality was significantly nonlinear. Both the Lowess smoothing technique and restricted cubic spline analyses revealed a U-shaped association between serum TG levels and mortality among septic patients. The lowest mortality rate was associated with a serum TG level of 300-500 mg/dL. Using 300∼500 mg/dL as the reference range, we found that both hypo-TG (<300 mg/dL) and hyper-TG (≥500 mg/dL) were associated with increased mortality. The result was further adjusted by Cox regression with and without the inclusion of some differential covariates.

CONCLUSIONS

There was a U-shaped association between serum TG and mortality in septic ICU patients. The optimal concentration of serum TG levels in septic ICU patients is 300-500 mg/dL.

Enteral nutrition alleviated lipopolysaccharides-induced hypercatabolism through ghrelin/GHS-R1α-POMC

Sustained hypercatabolism induced by sepsis contributed to serious complications and mortality in the intensive care unit. Enteral nutrition (EN) was required to maintain the energy balance during sepsis. Ghrelin, which was stimulated secretion by EN, had been shown to regulate energy homeostasis. Therefore, we tested whether EN alleviated hypercatabolism through ghrelin/GH secretagogue receptor 1α (GHS-R1α)-proopiomelanocortin (POMC) in endotoxemic rats. Rats in the Sham and lipopolysaccharide (LPS) groups were free access to rodent chow diet and water. Rats in the EN, EN + Lys and EN + 3-MA groups were intracerebroventricularly injected with saline, D-Lys3-GHRP-6 or 3-MA and then received EN for three days. Hypercatabolism was measured by the change of body weight, insulin resistance, leptin, corticosterone, muscle protein synthesis and atrophy. Serum and hypothalamic total ghrelin, acylated ghrelin, GHS-R1α and AMP-activated protein kinase (AMPK)-autophagy-POMC pathway were also detected. The results showed that EN increased serum and hypothalamic total ghrelin, acylated ghrelin and GHS-R1α, effectively activated the hypothalamic AMPK-autophagy-POMC pathway and alleviated hypercatabolism in endotoxemic rats. The improving effects of EN on hypercatabolism and hypothalamic AMPK-autophagy-POMC pathway were abolished with the central administration of D-Lys3-GHRP-6 to inhibited hypothalamic GHS-R1α. And with the central administration of 3-MA to inhibited hypothalamic autophagy, the improving effect of EN on hypercatabolism was also abolished in endotoxemic rats. In conclusions, EN could significantly alleviate hypercatabolism through ghrelin/GHS-R1α-POMC in endotoxemic rats.

Necrotizing Fasciitis in a Patient on Long-Term Intramuscular Interferon-Beta for Multiple Sclerosis: A Case Report

CASE

Immunomodulatory injections are becoming common long-term treatments for neuromuscular diseases such as multiple sclerosis (MS), although they carry a risk of local site infection. We describe a case of a 57-year-old man who developed necrotizing fasciitis of the anterior thigh secondary to intramuscular (IM) injections of interferon-beta-1A for MS, ultimately developing septic shock and requiring serial debridements for source control.

CONCLUSIONS

This is the first reported case of necrotizing fasciitis from chronic IM injections for MS and deserves particular attention because of the immunosuppressive nature of the injections. In patients with underlying predisposing factors for infection, such as decubitus ulcers, it may be prudent to reconsider the administration route. Patients in hypermetabolic states should be closely monitored for impaired response to infections.

Single-cell deconstruction of post-sepsis skeletal muscle and adipose tissue microenvironments

BACKGROUND

Persistent loss of skeletal muscle mass and function as well as altered fat metabolism are frequently observed in severe sepsis survivors. Studies examining sepsis-associated tissue dysfunction from the perspective of the tissue microenvironment are scarce. In this study, we comprehensively assessed transcriptional changes in muscle and fat at single-cell resolution following experimental sepsis induction.

METHODS

Skeletal muscle and visceral white adipose tissue from control mice or mice 1 day or 1 month following faecal slurry-induced sepsis were used. Single cells were mechanically and enzymatically prepared from whole tissue, and viable cells were further isolated by fluorescence activated cell sorting. Droplet-based single-cell RNA-sequencing (scRNA-seq; 10× Genomics) was used to generate single-cell gene expression profiles of thousands of muscle and fat-resident cells. Bioinformatics analyses were performed to identify and compare individual cell populations in both tissues.

RESULTS

In skeletal muscle, scRNA-seq analysis classified 1438 single cells into myocytes, endothelial cells, fibroblasts, mesenchymal stem cells, macrophages, neutrophils, T-cells, B-cells, and dendritic cells. In adipose tissue, scRNA-seq analysis classified 2281 single cells into adipose stem cells, preadipocytes, endothelial cells, fibroblasts, macrophages, dendritic cells, B-cells, T-cells, NK cells, and gamma delta T-cells. One day post-sepsis, the proportion of most non-immune cell populations was decreased, while immune cell populations, particularly neutrophils and macrophages, were highly enriched. Proportional changes of endothelial cells, neutrophils, and macrophages were validated using faecal slurry and cecal ligation and puncture models. At 1 month post-sepsis, we observed persistent enrichment/depletion of cell populations and further uncovered a cell-type and tissue-specific ability to return to a baseline transcriptomic state. Differential gene expression analyses revealed key genes and pathways altered in post-sepsis muscle and fat and highlighted the engagement of infection/inflammation and tissue damage signalling. Finally, regulator analysis identified gonadotropin-releasing hormone and Bay 11-7082 as targets/compounds that we show can reduce sepsis-associated loss of lean or fat mass.

CONCLUSIONS

These data demonstrate persistent post-sepsis muscle and adipose tissue disruption at the single-cell level and highlight opportunities to combat long-term post-sepsis tissue wasting using bioinformatics-guided therapeutic interventions.

Diagnostic accuracy of 18F-FDG-PET in abdominal sepsis in rats

Purpose

The objective of this study was to investigate the accuracy of 18F-FDG-PET in the diagnosis of multibacterial abdominal sepsis by cecum ligation and puncture (CLP) in rats.

Methods

Adult Wistar rats ( Rattus norvegicus ), weighing 227±35g, were allocated into a sepsis group by CLP (n=10) and sham group (n=10). 18F-FDG-PET using microPET was performed on all rats after 24 hours.

Results

All animals survived for postoperative 24h. The abdomen/liver ratio of the standardized uptake value (SUV) percentage was significantly higher in the sepsis group than in the sham (p=0.004). The ROC curve showed an accuracy of 18F-FDG-PET to detect abdominal sepsis of 88.9% (p=0.001), sensitivity of 90% and specificity of 88.9%. When a cut-off point of 79% of the ratio between the SUV on the abdominal region and liver was established, the sensitivity was 90%, specificity of 88.9%; positive and negative predictive values of 90.0% and 88.9%, respectively.

Conclusions

The diagnostic accuracy of 18F-FDG-PET in rats with abdominal sepsis was significantly high. It was also demonstrated the predictive ability of the abdomen/liver SUV ratio to diagnose abdominal sepsis. These findings may have implications for the clinical setting, locating septic foci with PETscan.

Why a d-β-hydroxybutyrate monoester?

Much of the world's prominent and burdensome chronic diseases, such as diabetes, Alzheimer's, and heart disease, are caused by impaired metabolism. By acting as both an efficient fuel and a powerful signalling molecule, the natural ketone body, d-β-hydroxybutyrate (βHB), may help circumvent the metabolic malfunctions that aggravate some diseases. Historically, dietary interventions that elevate βHB production by the liver, such as high-fat diets and partial starvation, have been used to treat chronic disease with varying degrees of success, owing to the potential downsides of such diets. The recent development of an ingestible βHB monoester provides a new tool to quickly and accurately raise blood ketone concentration, opening a myriad of potential health applications. The βHB monoester is a salt-free βHB precursor that yields only the biologically active d-isoform of the metabolite, the pharmacokinetics of which have been studied, as has safety for human consumption in athletes and healthy volunteers. This review describes fundamental concepts of endogenous and exogenous ketone body metabolism, the differences between the βHB monoester and other exogenous ketones and summarises the disease-specific biochemical and physiological rationales behind its clinical use in diabetes, neurodegenerative diseases, heart failure, sepsis related muscle atrophy, migraine, and epilepsy. We also address the limitations of using the βHB monoester as an adjunctive nutritional therapy and areas of uncertainty that could guide future research.

Ionic Modulation of Bacterial Virulence and Its Role in Surgical Infection

Background: Bacterial virulence is a dynamic property of pathogens that is expressed in a context-dependent manner. For a bacterial pathogen, the expression of virulence is a tradeoff, as there is an energy cost that can disturb other functions. As a result, virulence is activated only when bacteria sense the need for it. Methods: Recent work from our laboratory has identified many of the local cues in the environmental context that activate bacterial virulence during surgical injury, resulting in bacterial invasion, tissue inflammation, and, in some cases, lethal sepsis. Results: After surgical injury, cytokines, opioids, and end-products of ischemia can activate bacterial virulence circuits, such as the quorum-sensing signaling system, directly. However, when key ions are present, such as phosphate and iron, certain pathogenic bacteria become insensitive to these incoming host cues. Conclusion: In this review, we provide molecular insight into the process by which certain surgical infections may be prevented by ionic modulation of the local microenvironment.