Low levels of small HDL particles predict but do not influence risk of sepsis

Association of healthy sleep patterns with incident sepsis: a large population-based prospective cohort study

BACKGROUND

The role that sleep patterns play in sepsis risk remains poorly understood.

OBJECTIVES

The objective was to evaluate the association between various sleep behaviours and the incidence of sepsis.

METHODS

In this prospective cohort study, we analysed data from the UK Biobank (UKB). A total of 409,570 participants who were free of sepsis at baseline were included. We used a composite sleep score that considered the following five sleep behaviours: sleep chronotype, sleep duration, insomnia, snoring, and daytime sleepiness. Cox proportional hazards regression analysis was used to estimate the associations between healthy sleep scores and incident sepsis.

RESULTS

During a mean follow-up of 13.54 years, 13,357 (3.26%) incident sepsis cases were recorded. Among the 409,570 participants with a mean age of 56.47 years, 184,124 (44.96%) were male; 9942 (2.43%) reported 0 to 1 of the five healthy sleep behaviours; 46,270 (11.30%) reported 2 behaviours; 115,272 (28.14%) reported 3 behaviours; 150,522 (36.75%) reported 4 behaviours; and 87,564 (21.38%) reported 5 behaviours at baseline. Each one-point increase in the sleep score was associated with a 5% lower risk of developing sepsis (hazard ratio (HR), 0.95; 95% confidence interval (CI), 0.93-0.97). Compared with a healthy sleep score of 0-1, for a sleep score of 5, the multivariate-adjusted HR (95% CI) for sepsis was 0.76 (0.69-0.83). In addition, we found that the negative correlation was stronger in participants who were aged < 60 years than in their older counterparts (p for interaction < 0.001). However, healthy sleep pattern was not associated with sepsis-related death and critical care admission.

CONCLUSIONS

Findings from this cohort study suggest that a healthy sleep pattern may reduce the risk of developing sepsis, particularly among younger individuals.

High-density lipoprotein cholesterol as a prognostic marker for 90-day transplant-free mortality in hepatitis B virus-related acute-on-chronic liver failure

Background

Hepatitis B virus-related acute-on-chronic liver failure (HBV-ACLF) is linked to dyslipidemia and inflammatory responses. This study aimed to investigate the correlation between high-density lipoprotein cholesterol (HDL-C) levels and 90-day transplant-free (TF) mortality in patients with HBV-ACLF.

Methods

A prospective cohort of 287 patients with HBV-ACLF from Beijing Ditan Hospital was enrolled between January 2016 and December 2019. The prognostic accuracy of lipid profile parameters was evaluated by the area under the receiver operating characteristic curve (AUC), and the association between HDL-C levels and mortality was assessed using a restricted cubic spline analysis. Correlations between lipid profile parameters and inflammatory factors were analyzed. Kaplan-Meier curves were used to assess 90-day TF mortality, and log-rank tests were used for comparison analysis. These results were internally validated between January 2020 and December 2023 (n=125).

Results

Patients with lower HDL-C levels exhibited higher mortality rates (adjusted hazard ratio for HDL-C < 0.13 mmol/L: 4.04, 95% confidence interval: 1.35-11.85) compared with those in the reference group (with HDL-C levels above 0.36 mmol/L). An "L-shaped" association was observed between HDL-C levels and TF mortality. The prognostic value of HDL-C (AUC at day 90: 0.732) was comparable to the model for end-stage liver disease score of 0.729. Additionally, HDL-C levels were inversely correlated with interleukin (IL)-4, IL-6, and tumor necrosis factor-α (all P<0.05). In the training cohort, the 90-day TF mortality rates were 8.3%, 15.2%, 24.0%, and 43.2% for the extremely low, low, medium, and high-risk subgroups, respectively, while in the validation cohort, they were 4.5%, 18.5%, 31.2%, and 44.7%, respectively.

Conclusions

HDL-C levels < 0.13 mmol/L were associated with increased 90-day transplant-free mortality in patients with HBV-ACLF. An inverse correlation was found between HDL-C levels and inflammatory markers.

The role of high-density lipoproteins in sepsis

High density lipoproteins (HDLs) are best known for their role in atherosclerotic cardiovascular diseases. However, efforts to reduce cardiovascular risk by increasing the concentration of cholesterol in HDL have failed, raising the question of whether HDL may have other, more central aspects to its role in health and disease. In epidemiological studies, low levels of HDL cholesterol are strongly associated with risk of infectious diseases and death from sepsis and, during sepsis, a larger decline in HDL cholesterol predicts a worse outcome. Many preclinical studies have examined strategies to augment HDL genetically or pharmacologically and have shown that this leads to protection from sepsis in animal models. Data in humans are more limited, but suggest a clinically relevant role of HDL in mediating the response to pathogen-associated lipids and preventing excessive inflammation. Collectively, these data raise the intriguing possibility that a clinically important biological function of HDL is as a component of the innate immune system and suggest that pharmacological manipulation of HDL may be a strategy to reduce the organ dysfunction and death that results from uncontrolled inflammation during sepsis. This review article discusses recent advances in our understanding of the role of HDL in sepsis.

Association of Small HDL Subclasses with Mortality Risk in Chronic Kidney Disease

High-density lipoproteins (HDL) exist in various subclasses, with smaller HDL particles possessing the highest anti-oxidative and anti-inflammatory properties. Understanding the role of these specific subclasses in chronic kidney disease (CKD) could provide valuable insights into disease progression and potential therapeutic targets. In the present study, we assessed HDL subclass composition in 463 patients with CKD stage 2-4 using nuclear magnetic resonance spectroscopy. Over a mean follow-up period of 5.0 years, 18.6% of patients died. Compared to survivors, deceased patients exhibited significantly lower levels of cholesterol, ApoA-I, and ApoA-II within the small and extra-small (XS) HDL subclasses. Multivariable Cox regression analysis, adjusted for traditional cardiovascular and renal risk factors, demonstrated that reduced levels of XS-HDL-cholesterol, XS-HDL-ApoA-I, and XS-HDL-ApoA-II were independently associated with an increased risk of mortality. Furthermore, receiver operating characteristic analysis identified XS-HDL-ApoA-II as the most potent prognostic marker for mortality. In conclusion, reduced small and XS-HDL subclasses, especially XS-HDL-ApoA-II, are strongly associated with increased all-cause mortality risk in CKD patients. Assessment of HDL subclass distribution could provide valuable clinical information and help identify patients at high risk.

Quantification of high-density lipoprotein particle number by proton nuclear magnetic resonance: don't believe the numbers

PURPOSE OF REVIEW

Proton nuclear magnetic resonance (NMR) can rapidly assess lipoprotein concentrations and sizes in biological samples. It may be especially useful for quantifying high-density lipoprotein (HDL), which exhibits diverse particle sizes and concentrations. We provide a critical review of the strengths and limitations of NMR for quantifying HDL subclasses.

RECENT FINDINGS

Recent studies using NMR have shed light on HDL's role in various disorders, ranging from residual cardiovascular risk to host susceptibility to infection. However, accurately quantifying HDL particle number, size, and concentration (HDL-P) remains a challenge. Discrepancies exist between NMR and other methods such as gel electrophoresis, ion mobility analysis and size-exclusion chromatography in estimating the abundance of HDL species and the ratio of apolipoprotein A-I (APOA1) to HDL particles.

SUMMARY

NMR is a low-cost method for quantifying HDL-P that is readily applicable to clinical and translational studies. However, inconsistencies between the results of NMR quantification of HDL-P and other independent methods hinder the interpretation of NMR results. Because proton NMR apparently fails to accurately quantify the sizes and concentrations of HDL, the relevance of such studies to HDL biology poses challenges. This limits our understanding of pathophysiological implications of HDL-P as determined by NMR, particularly in determining cardiovascular disease (CVD) risk.

ABCA1 and apoA-I dependent 12-hydroxyeicosatetraenoic acid efflux regulates macrophage inflammatory signaling

Aberrant high-density lipoprotein (HDL) function is implicated in inflammation-associated pathologies. While HDL ABCA1-mediated reverse cholesterol and phospholipid transport are well described, the movement of pro-/anti-inflammatory lipids has not been explored. HDL phospholipids are the largest reservoir of circulating arachidonic acid-derived oxylipins. Endotoxin-stimulation activates inflammatory cells leading to hydroxyeicosatetraenoic acid (HETE) production, oxylipins which are involved in inflammatory response coordination. Active signaling in the non-esterified (NE) pool is terminated by sequestration of HETEs as esterified (Es) forms and degradation. We speculate that an ABCA1-apoA-I-dependent efflux of HETEs from stimulated cells could regulate intracellular HETE availability. Here we test this hypothesis both in vitro and in vivo. In endotoxin-stimulated RAW-264.7 macrophages preloaded with d8-arachidonic acid we use compartmental tracer modeling to characterize the formation of HETEs, and their efflux into HDL. We found that in response to endotoxin: I) Cellular NE 12-HETE is positively associated with MCP-1 secretion (p<0.001); II) HETE transfer from NE to Es pools is ABCA1-depedent (p<0.001); III) Cellular Es HETEs are transported into media when both apoA-I and ABCA1 are present (p<0.001); IV) The stimulated efflux of HETEs >> arachidonate (p<0.001). Finally, in endotoxin challenged humans (n=17), we demonstrate that intravenous lipopolysaccharide (0.6 ng/kg body weight) resulted in accumulation of 12-HETE in HDL over a 168-hour follow-up. Therefore, HDL can suppress inflammatory responses in macrophages by regulating intracellular HETE content in an apoA-I/ABCA1 dependent manner. The described mechanism may apply to other oxylipins and explain anti-inflammatory properties of HDL. This newly defined HDL property opens new doors for the study of lipoprotein interactions in metabolic diseases.

The Role of Interferon-Induced Proteins with Tetratricopeptide Repeats 1 and 2 in Sepsis-Induced Acute Liver Injury

Background

Sepsis refers to a life-threatening organ dysfunction which can be resulted from the infection-induced dysregulated host response. A large number of inflammatory cytokines are released to act on the liver, making the liver one of the common target organs for the development of multiple organ dysfunction syndrome (MODS) in patients with sepsis. Sepsis-induced acute liver injury (SALI) can aggravate systemic disease. As a result, it is of great clinical significance to comprehend the molecular biological mechanism of SALI and to identify the markers for evaluating SALI. Interferon-induced proteins with tetratricopeptide repeats 1 and 2 (IFIT1, IFIT2) have been recognized as the anti-inflammatory factors that are widely expressed in various organs. The present study was aimed at clarifying the roles of IFIT1 and IFIT2 in the development of SALI.

Methods

A two-sample Mendelian randomization (MR) analysis was employed. Summary statistics datas were obtained from GWAS for inflammatory factors [tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6)], IFIT2, and sepsis as well as liver injury. Independent SNPs were selected as instrumental variables (IVs). Inverse variance weighted (IVW) in the MR analysis was adopted as the primary method for estimating the causal associations of inflammatory factors and IFIT2 with two diseases, and the associations of inflammatory factors with IFIT2. Additionally, weighted median method, MR-Egger and sensitivity analyses were applied in assessing the robustness of the results and ensure the result reliability. Subsequently, 119 healthy volunteers, 116 patients with sepsis and 116 SALI patients were recruited. The ELISA method was employed to quantify the expression levels of TNF-α, IL-1β, and IL-6. Additionally, qRT-PCR was conducted to measure the expression of IFIT1 and IFIT2. Furthermore, the correlations of IFIT1 and IFIT2 with inflammatory factors, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were explored.

Results

As shown by the MR analysis, the genetically predisposed sepsis was significantly associated with the risk of IL-1β, with an odds ratio (OR) of 1.069 (95% confidence interval (CI), 1.015-1.127, p = 0.0119), and negatively associated with the risk of IL-6, with an OR of 0.880 (95% CI: 0.792-0.979, p= 0.0184). Meanwhile, there were positive causal effects of IL-6 (OR = 1.269, 95% CI: 1.032-1.561, p= 0.0238), IL-1β (OR = 1.106, 95% CI: 1.010-1.211, p = 0.0299) and IFIT2 (OR = 1.191, 95% CI: 1.045-1.359, p = 0.0090) on liver injury. Additionally, there was a positive causal effect of IFIT2 (OR = 1.164, 95% CI: 1.035-1.309, p= 0.0110) on IL-1β. Upon sensitivity analyses, there was weak evidence of such effects, indicating that the findings of this study were robust and reliable. Our results revealed the elevated levels of TNF-α, IL-1β, and IL-6 in the blood samples of sepsis and SALI patients (p < 0.0001). Conversely, IFIT1 and IFIT2 demonstrated the significantly decreased levels in peripheral blood mononuclear cells (PBMCs) of SALI patients (p < 0.0001). Furthermore, the expression levels of IFIT1 and IFIT2 were both negatively correlated with ALT activity (r = -0.3426, p = 0.0002; r = -0.3069, p = 0.0008) and AST activity (r = -0.2483, p = 0.0072; r = -0.3261, p = 0.0004), respectively. Moreover, the expression of IFIT1 and IFIT2 was both negatively related to the levels of TNF-α (r = -0.5027, p < 0.0001; r = -0.4218, p < 0.0001), IL-1β (r = -0.3349, p = 0.0002; r = -0.4070, p < 0.0001) and IL-6 (r = -0.2734, p = 0.0030; r = -0.3536, p < 0.0001), respectively.

Conclusion

IFIT1 and IFIT2 can serve as the diagnostic markers for sepsis-related liver injury, and IFIT1 and IFIT2 may participate in the pathological process of sepsis-related liver injury by regulating inflammation and liver function.

The high-density lipoprotein cholesterol (HDL-C)-concentration-dependent association between anti-inflammatory capacity and sepsis: A single-center cross-sectional study

INTRODUCTION

Known to have pleiotropic functions, high-density lipoprotein (HDL) helps to regulate systemic inflammation during sepsis. As preserving HDL-C level is a promising therapeutic strategy for sepsis, the interaction between HDL and sepsis worth further investigation. This study aimed to determine the impact of sepsis on HDL's anti-inflammatory capacity and explore its correlations with disease severity and laboratory parameters.

METHODS AND MATERIALS

We enrolled 80 septic subjects admitted to the intensive care unit and 50 controls admitted for scheduled coronary angiography in this cross-sectional study. We used apolipoprotein-B depleted (apoB-depleted) plasma to measure the anti-inflammatory capacity of HDL-C. ApoB-depleted plasma's anti-inflammatory capacity is defined as its ability to suppress tumor necrosis factor-α-induced vascular cell adhesion molecule-1 (VCAM-1) expression in human umbilical-vein endothelial cells. A subgroup analysis was conducted to investigate in septic subjects according to disease severity.

RESULTS

ApoB-depleted plasma's anti-inflammatory capacity was reduced in septic subjects relative to controls (VCAM-1 mRNA fold change: 50.1% vs. 35.5%; p < 0.0001). The impairment was more pronounced in septic subjects with than in those without septic shock (55.8% vs. 45.3%, p = 0.0022). Both associations were rendered non-significant with the adjustment for the HDL-C level. In sepsis patients, VCAM-1 mRNA fold change correlated with the SOFA score (Spearman's r = 0.231, p = 0.039), lactate level (r = 0.297, p = 0.0074), HDL-C level (r = -0.370, p = 0.0007), and inflammatory markers (C-reactive protein level: r = 0.441, p <0.0001; white blood cell: r = 0.353, p = 0.0013).

CONCLUSION

ApoB-depleted plasma's anti-inflammatory capacity is reduced in sepsis patients and this association depends of HDL-C concentration. In sepsis patients, this capacity correlates with disease severity and inflammatory markers. These findings explain the prognostic role of the HDL-C level in sepsis and indirectly support the rationale for targeting HDL-C as sepsis treatment.

Low circulatory levels of total cholesterol, HDL-C and LDL-C are associated with death of patients with sepsis and critical illness: systematic review, meta-analysis, and perspective of observational studies

BACKGROUND

Mechanistic studies have established a biological role of sterol metabolism in infection and immunity with clinical data linking deranged cholesterol metabolism during sepsis with poorer outcomes. In this systematic review we assess the relationship between biomarkers of cholesterol homeostasis and mortality in critical illness.

METHODS

We identified articles by searching a total of seven electronic databases from inception to October 2023. Prospective observational cohort studies included those subjects who had systemic cholesterol (Total Cholesterol (TC), HDL-C or LDL-C) levels assessed on the first day of ICU admission and short-term mortality recorded. Meta-analysis and meta-regression were used to evaluate overall mean differences in serum cholesterol levels between survivors and non-survivors. Study quality was assessed using the Newcastle-Ottawa Scale.

FINDINGS

From 6469 studies identified by searches, 24 studies with 2542 participants were included in meta-analysis. Non-survivors had distinctly lower HDL-C at ICU admission -7.06 mg/dL (95% CI -9.21 to -4.91, p < 0.0001) in comparison with survivors. Corresponding differences were also seen less robustly for TC -21.86 mg/dL (95% CI -31.23 to -12.49, p < 0.0001) and LDL-C -8.79 mg/dL (95% CI, -13.74 to -3.83, p = 0.0005).

INTERPRETATION

Systemic cholesterol levels (TC, HDL-C and LDL-C) on admission to critical care are inversely related to mortality. This finding is consistent with the notion that inflammatory and metabolic setpoints are coupled, such that the maladaptive-setpoint changes of cholesterol in critical illness are related to underlying inflammatory processes. We highlight the potential of HDL-biomarkers as early predictors of severity of illness and emphasise that future research should consider the metabolic and functional heterogeneity of HDLs.

FUNDING

EU-ERDF-Welsh Government Ser Cymru programme, BBSRC, and EU-FP7 ClouDx-i project (PG).