Circulating leptin, soluble leptin receptor and free leptin index in critically ill patients with sepsis: a prospective observational study

Utilize proteomic analysis to identify potential therapeutic targets for combating sepsis and sepsis-related death

Background

Sepsis is an inflammatory disease that leads to severe mortality, highlighting the urgent need to identify new therapeutic strategies for sepsis. Proteomic research serves as a primary source for drug target identification. We employed proteome-wide Mendelian randomization (MR), genetic correlation analysis, and colocalization analysis to identify potential targets for sepsis and sepsis-related death.

Methods

Genetic data for plasma proteomics were obtained from 35,559 Icelandic individuals and an initial MR analysis was conducted using 13,531 sepsis cases from the FinnGen R10 cohort to identify associations between plasma proteins and sepsis. Subsequently, significant proteins underwent genetic correlation analysis, followed by replication in 54,306 participants from the UK Biobank Pharma Proteomics Project and validation in 11,643 sepsis cases from the UK Biobank. The identified proteins were then subjected to colocalization analysis, enrichment analysis, and protein-protein interaction network analysis. Additionally, we also investigated a MR analysis using plasma proteins on 1,896 sepsis cases with 28-day mortality from the UK Biobank.

Results

After FDR correction, MR analysis results showed a significant causal relationship between 113 plasma proteins and sepsis. Genetic correlation analysis revealed that only 8 proteins had genetic correlations with sepsis. In the UKB-PPP replication analysis, only 4 proteins were found to be closely associated with sepsis, while validation in the UK Biobank sepsis cases found overlaps for 21 proteins. In total, 30 proteins were identified in the aforementioned analyses, and colocalization analysis revealed that only 2 of these proteins were closely associated with sepsis. Additionally, in the 28-day mortality MR analysis of sepsis, we also found that only 2 proteins were significant.

Conclusions

The identified plasma proteins and their associated metabolic pathways have enhanced our understanding of the complex relationship between proteins and sepsis. This provides new avenues for the development of drug targets and paves the way for further research in this field.

25-hydroxyvitamin D and parathyroid hormone in new onset sepsis: A prospective study in critically ill patients

Hypovitaminosis D is highly prevalent in critically ill patients, and it has been suggested to be a risk factor for infections, sepsis and higher mortality. We sought to investigate whether serum 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone (PTH) in critically ill patients with new onset sepsis are associated with severity and outcome. We prospectively included 50 consecutive critically ill adult cases with new onset sepsis and 50 healthy controls matched for age and sex. PTH and 25(OH)D were determined in serum via electrochemiluminescence immunoassays at inclusion in the study in all cases and controls, and one week after sepsis onset in cases. Patients had reduced 25(OH)D compared to controls at sepsis onset (7.9 ± 3 vs 24.6 ± 6.7 ng/mL, p < 0.001), whilst PTH was similar (median (range): 34.5 (5.7-218.5) vs 44.2 (14.2-98.1) pg/mL, p = 0.35). In patients, 25(OH)D upon enrollment and one week after did not differ significantly (7.9 ± 3 vs 7 ± 4.3 ng/mL, p = 0.19). All patients presented with hypovitaminosis D (25(OH)D < 20 ng/mL), while 40 patients (80 %) had vitamin D deficiency (25(OH)D < 12 ng/mL) at sepsis onset, including all ten (20 %) nonsurvivors, who died within 28 days from sepsis onset. Patients with sepsis (N = 28) and septic shock (N = 22) as well as survivors (N = 40) and nonsurvivors (N = 10) had similar 25(OH)D at enrollment (p > 0.05). 25(OH)D was positively correlated with ionized calcium (r = 0.46, p < 0.001) and negatively with PTH (p < 0.05), while inflammatory biomarkers or the severity scores exhibited no correlation with 25(OH)D. Patients with septic shock and nonsurvivors had lower PTH than patients with sepsis and survivors respectively (42.2 ± 42.9 vs 73.4 ± 61.9 pg/mL, p = 0.04, and 18.3 ± 10.7 vs 69.9 ± 58.8 pg/mL, p = 0.001, respectively). C-reactive protein was negatively associated with PTH (r = -0.44, p = 0.001). In conclusion, vitamin D deficiency was present in 80 % of critically ill patients at sepsis onset, while nonsurvivors exhibited lower PTH than survivors. Additional, larger and multicenter studies are warranted to elucidate the contribution of vitamin D and PTH to the pathogenesis of sepsis and its outcomes.

Circulating Chemerin and Its Kinetics May Be a Useful Diagnostic and Prognostic Biomarker in Critically Ill Patients with Sepsis: A Prospective Study

Chemerin, a novel adipokine, is a potent chemoattractant molecule with antimicrobial properties, implicated in immune responses. Our aim was to investigate circulating chemerin and its kinetics, early in sepsis in critically ill patients and its association with severity and prognosis. Serum chemerin was determined in a cohort of 102 critically ill patients with sepsis during the first 48 h from sepsis onset and one week later, and in 102 age- and gender-matched healthy controls. Patients were followed for 28 days and their outcomes were recorded. Circulating chemerin was significantly higher in septic patients at onset compared to controls (342.3 ± 108.1 vs. 200.8 ± 40.1 μg/L, p < 0.001). Chemerin decreased significantly from sepsis onset to one week later (342.3 ± 108.1 vs. 308.2 ± 108.5 μg/L, p < 0.001), but remained higher than in controls. Chemerin was higher in patients presenting with septic shock than those with sepsis (sepsis onset: 403.2 ± 89.9 vs. 299.7 ± 99.5 μg/L, p < 0.001; one week after: 374.9 ± 95.3 vs. 261.6 ± 91.9 μg/L, p < 0.001), and in nonsurvivors than survivors (sepsis onset: 427.2 ± 96.7 vs. 306.9 ± 92.1 μg/L, p < 0.001; one week after: 414.1 ± 94.5 vs. 264.2 ± 79.9 μg/L, p < 0.001). Moreover, patients with septic shock and nonsurvivors, presented a significantly lower absolute and relative decrease in chemerin one week after sepsis onset compared to baseline (p < 0.001). Based on ROC curve analyses, the diagnostic performance of chemerin (AUC 0.78, 95% CI 0.69–0.87) was similar to C-reactive protein (CRP) (AUC 0.78, 95% CI 0.68–0.87) in discriminating sepsis severity. However, increased chemerin at sepsis onset and one week later was an independent predictor of 28-day mortality (sepsis onset: HR 3.58, 95% CI 1.48–8.65, p = 0.005; one week after: HR 10.01, 95% CI 4.32–23.20, p < 0.001). Finally, serum chemerin exhibited significant correlations with the severity scores, white blood cells, lactate, CRP and procalcitonin, as well as with biomarkers of glucose homeostasis, but not with cytokines and soluble urokinase-type plasminogen activator receptor (suPAR). Circulating chemerin is increased early in sepsis and its kinetics may have diagnostic and prognostic value in critically ill patients. Further studies are needed to shed light on the role of chemerin in sepsis.

SARS-CoV-2 adipose tissue infection and hyperglycemia: A further step towards the understanding of severe COVID-19

Numerous studies have highlighted the prognostic significance of hyperglycemia in the outcomes of SARS-CoV-2 infection. A number of mechanisms have been proposed as potential drivers of this association, which were, however, up until recently based rather on speculation than on investigational evidence. It has been recently come to light that the development of insulin resistance in the frame of COVID-19 is likely the driving force behind the development of overt hyperglycemia. This results through the infectious insult of the adipose tissue, and is observed in conjunction with aberrant adipokine secretion by host adipocytes, such as decreased adiponectin, as well as a switch towards an antiviral immune secretory profile. These data could have a considerable relevance not only for the management of hyperglycemia in the course of the infection but also for the overall understanding of the pathogenesis of severe COVID-19.

Leptin in the Respiratory Tract: Is There a Role in SARS-CoV-2 Infection?

Leptin is a pleiotropic adipocytokine involved in several physiologic functions, with a known role in innate and adaptive immunity as well as in tissue homeostasis. Long- and short-isoforms of leptin receptors are widely expressed in many peripheral tissues and organs, such as the respiratory tract. Similar to leptin, microbiota affects the immune system and may interfere with lung health through the bidirectional crosstalk called the “gut-lung axis.” Obesity leads to impaired protective immunity and altered susceptibility to pulmonary infections, as those by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although it is known that leptin and microbiota link metabolism and lung health, their role within the SARS-CoV2 coronavirus disease 2019 (COVID-19) deserves further investigations. This review aimed to summarize the available evidence about: (i) the role of leptin in immune modulation; (ii) the role of gut microbiota within the gut-lung axis in modulating leptin sensitivity; and (iii) the role of leptin in the pathophysiology of COVID-19.