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Clinical investigation of intestinal fatty acid-binding protein (I-FABP) as a biomarker of SARS-CoV-2 infection

Open AccessPublished:September 27, 2021DOI:https://doi.org/10.1016/j.ijid.2021.09.051

      ABSTRACT

      Objectives

      SARS-CoV-2 exhibits tropism for the gastrointestinal tract; however, lesions in enterocytes and their correlation with disease severity and patient prognosis are still unknown.

      Methods

      SARS-CoV-2 patients were enrolled in 5 medical centres in São Paulo, Brazil and their clinical characteristics and laboratory findings recorded. At admission, day 7 and day 14 of hospitalisation, plasma and urine samples were collected, and cytokine levels and intestinal fatty acid-binding protein (I-FABP) concentrations measured.

      Results

      COVID-19 patients displayed ≈48-, 74- and 125-fold increased urinary I-FABP levels at admission (n=283; P<0.001), day 7 (n=142; P<0.01) and day 14 (n=75; P<0.01) of hospitalisation. Critically ill patients and nonsurvivors showed higher I-FABP concentrations compared with patients with less severe illness. At admission, infected patients demonstrated enhanced production of plasma interferon (IFN)-γ and interleukin (IL)-6. The receiver operating characteristic curve suggested I-FABP as a biomarker for COVID-19 disease severity at admission (P<0.0001; Youden index=6.89; area under the curve=0.699). Patients with I-FABP ≥6.89 showed higher IL-6 and C-reactive protein levels (P<0.001) at admission and had a prolonged length of hospital stay.

      Conclusions

      Our findings revealed damage to enterocytes in SARS-CoV-2 infection, which is associated with illness severity, poor prognosis and exacerbated inflammatory response.

      Keywords

      Gastrointestinal (GI) symptoms, including vomiting, abdominal discomfort and diarrhoea, have been reported in COVID-19 infections at the onset of hospitalisation, affecting 10%–30% of patients (
      • Parasa S
      • Desai M
      • Thoguluva Chandrasekar V
      • Patel HK
      • Kennedy KF
      • Roesch T
      • et al.
      Prevalence of Gastrointestinal Symptoms and Fecal Viral Shedding in Patients With Coronavirus Disease 2019: A Systematic Review and Meta-analysis.
      ). SARS-CoV-2 RNA has been detected in faeces and stomach, duodenum and colon biopsies (
      • Lin L
      • Jiang X
      • Zhang Z
      • Huang S
      • Fang Z
      • Gu Z
      • et al.
      Gastrointestinal symptoms of 95 cases with SARS-CoV-2 infection.
      ;
      • Zhao F
      • Yang Y
      • Wang Z
      • Li L
      • Liu L
      • Liu Y.
      The Time Sequences of Respiratory and Rectal Viral Shedding in Patients With Coronavirus Disease 2019.
      ). COVID-19 patients with ongoing diarrhoea have displayed enhanced concentration of faecal calprotectin (a marker of gut inflammation), as well as systemic interleukin (IL)-6 production, regardless of viral load (
      • Effenberger M
      • Grabherr F
      • Mayr L
      • Schwaerzler J
      • Nairz M
      • Seifert M
      • et al.
      Faecal calprotectin indicates intestinal inflammation in COVID-19.
      ). Although SARS-CoV-2 exhibits tropism for the GI tract, it remains unknown whether lesions in the intestinal epithelium occur.
      Intestinal fatty acid-binding protein (I-FABP) is a cytosolic protein expressed in mature enterocytes of the small and large intestines (
      • Pelsers MM
      • Namiot Z
      • Kisielewski W
      • Namiot A
      • Januszkiewicz M
      • Hermens WT
      • et al.
      Intestinal-type and liver-type fatty acid-binding protein in the intestine. Tissue distribution and clinical utility.
      ). A basal level of urinary I-FABP represents the physiological turnover rate of the epithelium, whilst its increment may indicate enterocytes cell damage. In sepsis and inflammatory bowel disease (IBD), the increased urinary concentration of I-FABP has been confirmed as a reliable biomarker and predictor of disease reactivation, worse prognosis and clinical complications (
      • Ho SS
      • Wall C
      • Gearry RB
      • Keenan J
      • Day AS.
      A Pilot Study Evaluating Novel Urinary Biomarkers for Crohn’s Disease.
      ). Therefore, our study assessed the levels of I-FABP in hospitalised patients with SARS-CoV-2 infection and investigated its role as a predictor of disease severity and poor prognosis.
      This prospective cohort study enrolled 283 inpatients from 5 medical centres (Hospital das Clínicas, Hospital Santa Lydia, Hospital Unimed and Santa Casa de Misericórdia in Ribeirão Preto city and also Hospital e Maternidade Santa Isabel in Jaboticabal city), São Paulo State, Brazil (Supplementary methods). SARS-CoV-2 infection was confirmed through viral RNA detection in nasopharyngeal swabs by real-time reverse transcriptase-polymerase chain reaction, and positive cases were recruited from April 23rd to September 25th 2020. Comorbidities such as GI disorders (IBD, celiac disease and cancer), HIV, and alcohol and drugs addictions were exclusion criteria. At admission, day 7 and day 14 of hospitalisation (in infirmary or intensive care unit), venous blood and urine samples were collected in the morning (06:00–08:00), chilled and transferred to the research laboratory. Total blood and urine were centrifuged (1200 g, 15 min, 4 °C), the supernatants aliquoted and kept at -70 °C for further analysis. Healthy volunteers were seronegative for the presence of anti-SARS-CoV-2 immunoglobulin (Ig)M and IgG antibodies (Supplementary methods).
      I-FABP and cytokines [tumour necrosis factor (TNF)-α, interferon (IFN)-γ and IL-6] were quantified by enzyme-linked immunosorbent assay, according to the manufacturer's instructions (R&D Systems, Minneapolis, MN, USA). Urinary data were normalised to creatinine concentrations (LabTest, Lagoa Santa, MG, Brazil). Continuous variables were expressed as median (interquartile range [IQR]) or 10–90 percentile range and then compared using Mann-Whitney U-test or Kruskal-Wallis test (Supplementary results). Categorical variables were compared by Fisher's exact test or Pearson χ2 test. Statistical significance was considered different when P<0.05.
      Table 1 lists the demographic, clinical characteristics, and laboratory findings of SARS-CoV-2 patients (survivors and nonsurvivors) and healthy volunteers. Nonsurvivors showed higher number of underlying comorbidities (cardiovascular and pulmonary diseases, diabetes, degenerative and malignancies), as well as deviations of the laboratory parameters (anaemia, leucocytosis, lymphocytopenia, D-dimers, C-reactive protein (CRP), lactate dehydrogenase, serum creatinine and urea), requirement of mechanic ventilation and intensive care at admission. At day 7 and day 14 of hospitalisation, aging, pre-existing diseases, leucocytosis, and the need for mechanical ventilation were relevant factors in nonsurvivor patients.
      Table 1Demographic, clinical characteristics and laboratory parameters of healthy volunteers and SARS-CoV-2 infected patients (Survivors and Nonsurvivors)
      ParametersHealthy Volunteers (n=37)SARS-CoV-2 infected patients
      Admission (n=283)Day 7 (n=142)Day 14 (n=75)
      Survivors(n=181)Nonsurvivors(n=102)Survivors(n=76)Nonsurvivors(n=66)Survivors(n=42)Nonsurvivors(n=33)
      Gender M/F (%)33/67 γ60/4052/4857/4351/4967/3348/52
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      Age, years
      Values expressed as median [interquartile range]
      55 [49-60]
      P<0.05
      61 [50-71]69 [62-77] c62 [54-70]68 [58-77]
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      61 [53-70]68 [58-77]
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      Ethnicity (C/AA/H) (%)87/8/5
      P<0.01 and γ P<0.001 vs SARS-CoV-2 patients (survivors and nonsurvivors) at the admission
      70/15/1580/16/4
      P<0.05
      75/18/786/2/12 c74/12/1485/1/14
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      BMI, kg/m2
      Values expressed as median [interquartile range]
      27.5 [24.5-30.3]
      P<0.05
      30.5 [26.7-34.2]28.7 [26.0-35.3]31.5 [27.5-35.2]29.0 [25.9-35.8]29.8 [26.8-34.4]28.9 [25.5-37.6]
      MAP, mmHg
      Values expressed as median [interquartile range]
      90.0 [80.0-96.7]93.3 [80.5-99.1]88.0 [76.3-96.0]91.0 [78.3-98.3]87.0 [75.3-96.7]91.0 [78.3-98.3]88.5 [77.9-104.2]
      HR, beats/min
      Values expressed as median [interquartile range]
      75 [69-79] γ85 [73-92]86 [77-98]85 [76-96]90 [79-98]85 [76-96]91 [83-104]
      P<0.05
      Underlying Comorbidities, no. (%)
      Smoker/ex-smoker0 (0) γ29 (16.0)31 (30.4)
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      15 (19.7)16 (24.2)8 (19.0)8 (24.2)
      Arterial hypertension10 (27.0) γ99 (54.7)74 (72.5)
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      51 (67.1)50 (75.6)28 (66.7)30 (90.9)
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      Cardiovascular diseases1 (2.7) γ32 (17.7)31 (30.4)
      P<0.05
      18 (23.7)22 (33.3)11 (26.2)10 (30.3)
      Diabetes2 (5.4) γ61 (33.7)50 (49.0)
      P<0.05
      33 (43.4)29 (43.9)19 (45.2)18 (54.5)
      Pulmonary diseases0 (0)
      P<0.01 and γ P<0.001 vs SARS-CoV-2 patients (survivors and nonsurvivors) at the admission
      9 (5.0)15 (14.7)
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      2 (2.6)7 (10.6)2 (4.8)4 (12.1)
      Chronic kidney diseases0 (0)7 (3.9)9 (8.8)2 (2.6)5 (7.6)0 (0)4 (12.1)
      P<0.05
      Thyroid disease1 (2.7)11 (6.1)12 (11.8)9 (11.8)9 (13.6)4 (9.5)4 (12.1)
      Dyslipidaemia2 (5.4)23 (12.7)16 (15.7)15 (19.7)11 (16.7)9 (21.4)4 (12.1)
      Degenerative disorders0 (0) γ1 (0.5)9 (8.8) c0 (0)4 (6.1)
      P<0.05
      0 (0)0 (0)
      Neurological diseases1 (2.7)12 (6.6)6 (5.9)8 (10.5)7 (10.6)5 (11.9)4 (12.1)
      Malignancies0 (0) γ2 (1.1)15 (14.7) c1 (1.3)9 (13.6)
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      1 (2.4)6 (18.2)
      P<0.05
      Other diseases3 (8.1)
      P<0.05
      8 (3.9)13 (12.7)
      P<0.05
      5 (6.6)8 (12.1)3 (7.1)5 (15.2)
      Haematological Indexes
      Values expressed as median [interquartile range]
      Haemoglobin, g/dL14.8 [14.0-15.2] γ12.6 [11.3-14.0]11.6 [10.0-13.3]
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      11.7 [10.2-12.9]10.0 [8.5-12.3] c9.7 [8.7-11.3]9.2 [8.2-11]
      Erythrocytes, 106/µL4.5 [4.42-4.90]
      P<0.05
      4.3 [3.9-4.7]4.2 [3.6-4.6]4.0 [3.6-4.4]3.67 [3.0-4.3]
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      3.3 [2.9-3.8]3.12 [2.74-3.69]
      Leukocytes, 103/µL5.38 [4.35-5.71] γ8.2 [6.1-11.08]11.4 [7.78-15.2] c11.45 [8.23-16.03]14.5 [10.2-23.2]
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      10.2 [8.2-12.8]12.6 [9.34-19.83]
      P<0.05
      Neutrophils, 103/µL2.65 [1.97-3.08] γ6.01 [4.2-8.7]8.89 [6.01-12.9] c9.00 [6.0-12.4]11.8 [7.45-19.85] c7.8 [4.3-9.8]10.75 [6.31-17.05]
      P<0.05
      Monocytes, 103/µL0.34 [0.27-0.38]0.36 [0.22-0.54]0.4 [0.27-0.68]0.5 [0.3-0.7]0.5 [0.31-0.8]0.5 [0.3-0.8]0.5 [0.3-0.8]
      Lymphocytes, 103/µL1.94 [1.47-2.17]
      P<0.01 and γ P<0.001 vs SARS-CoV-2 patients (survivors and nonsurvivors) at the admission
      1.1 [0.7-1.44]0.89 [0.6-1.34]
      P<0.05
      1.23 [0.71-1.79]1.0 [0.6-1.59]1.51 [1.0-2.1]1.27 [0.93-1.82]
      Platelets, 103/µL209 [181-247]230 [173-304]230 [181-287]271 [224-358]250 [172-322]
      P<0.05
      232 [165-304]235 [143-327]
      D-dimer, µg/mL
      Healthy volunteers with standardized reference values
      < 0.5 γ1.4 [0.59-3.25]3.17 [1.84-6.84] c2.31 [1.32-3.32]2.61 [1.93-3.58]2.51 [1.74-4.37]3.4 [2.55-10.11]
      P<0.05
      Biochemical Indexes
      Values expressed as median [interquartile range]
      Glycaemia, mg/dL78 [75-87] γ155 [119-229]168 [138-230]170 [116-234]176 [127-232]142 [117-198]133 [114-208]
      CRP, mg/L0.3 [0.2-0.4] γ41.7 [16.7-109.3]76.8 [20.1-163.3]
      P<0.05
      21.3 [7.0-54.0]33.6 [9.1-109.7]67.0 [21.1-143.5]53.5 [12.1-180.0]
      ALT, U/L20.4 [13.8-28.6] γ45.5 [27.3-66.3]39.5 [22.5-67.2]61.0 [43.0-95.7]58 [31.0-110.7]66.0 [43.1-106.5]57.1 [45.3-101.7]
      AST, U/L21.0 [19.0-27.0] γ42.0 [30.0-65.9]50.0 [29.0-71.2]42.3 [31.0-55.3]47.1 [33.0-86.0]42.5 [29.0-69.5]39.2 [34.9-111.5]
      LDH, U/L183.0 [172-189] γ340.0 [263-466.4]437.1 [293.6-675]
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      345.0 [279-470]408.3 [327.9-607]
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      326.0 [259-401]392.2 [285-571.9]
      Serum creatinine, mg/dL0.8 [0.7-0.9]
      P<0.05
      1.0 [0.8-1.3]1.43 [0.97-2.63] c1.0 [0.8-1.5]1.56 [1.01-2.87] c1.1 [0.8-1.5]1.66 [0.87-2.12]
      P<0.05
      Serum urea, mg/dL31.0 [28.0-38.0]
      P<0.05
      45.0 [31.2-62.0]74.9 [46.6-119.1] c62.0 [40.0-99.9]111.9 [56.2-167.8] c62.0 [41.0-108.2]102.6 [46.3-155.3]
      P<0.05
      Respiratory Indexes
      Values expressed as median [interquartile range]
      pH
      Healthy volunteers with standardized reference values
      7.4 [7.35-7.45]7.4 [7.32-7.44]7.32 [7.23-7.40] c7.4 [7.34-7.43]7.34 [7.25-7.4]7.4 [7.35-7.44]7.33 [7.28-7.4]
      PaO2, mmHg
      Healthy volunteers with standardized reference values
      90.0 [80-100]83.9 [71.0-95.2]78.4 [67.7-91.5]72.5 [67.0-82.2]75.4 [68.9-83.3]73.4 [64.6-80.7]73.0 [67.4-80.4]
      PaCO2, mmHg
      Healthy volunteers with standardized reference values
      40.0 [35.0-45.0]34.8 [27.8-45.0]42.2 [34.0-48.6]
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      44.1 [38.9-51.9]45.4 [35.0-51.8]38.4 [33.4-46.1]42.5 [32.6-49.2]
      SaO2, %
      Healthy volunteers with standardized reference values
      96.5 [95.0-98.0]96.4 [93.8-97.1]95.6 [92.3-97.1]
      P<0.05
      96.4 [94.1-97.2]95.7 [94.1-97.2]96.0 [94.8-97.0]95.5 [93.0-97.0]
      Lactate, mmol/L
      Healthy volunteers with standardized reference values
      1.25 [0.5-2.0]2.0 [1.45-2.6]2.0 [1.42-2.75]1.89 [1.37-2.6]1.77 [1.28-2.6]1.80 [1.4-2.4]1.51 [0.76-2.71]
      Treatments, no. (%)
      Antibiotic therapy-132 (72.9)102 (100.0) c59 (77.6)51 (77.3)40 (95.2)33 (100.0)
      Antiviral therapy-25 (13.8)12 (11.8)2 (2.6)1 (1.5)0 (0)0 (0)
      Corticosteroids-123 (68.0)81 (79.4)
      P<0.05
      58 (76.3)51 (77.3)21 (50.0)24 (72.7)
      Anticoagulants-112 (61.9)93 (91.2) c75 (98.7)55 (83.3) c41 (97.6)33 (100.0)
      Hydroxychloroquine-12 (6.6)4 (3.9)3 (3.9)3 (4.5)0 (0)0 (0)
      Hospitalisation Characteristics
      Length of hospital stay (days)-11 [4-22]13 [8-21]
      P<0.05
      ----
      ICU length of stay (days)-0 [0-12]11 [6-19] c----
      Severe/critical care type, no. (%)
      Severe/critical care type was defined as respiratory failure requiring mechanical ventilation and ICU admission
      -73 (40.3)88 (86.3) c54 (71.1)63 (95.5) c35 (83.3)33 (100.0)
      P<0.05
      Mechanic ventilation, no. (%)-60 (33.1)73 (71.6) c52 (68.4)59 (89.4)
      P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      28 (66.7)33 (100.0) c
      Legend: ALT (alanine aminotransferase); AST (aspartate aminotransferase); BMI (body mass index); CRP (C-reactive protein); Ethnicity (C = Caucasian, AA = Afro American, H = Hispanic); HR (heart rate); ICU (intensive care unit); LDH (lactate dehydrogenase); MAP (mean arterial pressure); PaCO2 (partial pressure of carbon dioxide in arterial blood); PaO2 (partial pressure of oxygen in arterial blood); SaO2 (arterial oxygen saturation).
      & Values expressed as median [interquartile range]
      Healthy volunteers with standardized reference values
      # Severe/critical care type was defined as respiratory failure requiring mechanical ventilation and ICU admission
      α P<0.05
      β P<0.01 and γ P<0.001 vs SARS-CoV-2 patients (survivors and nonsurvivors) at the admission
      a P<0.05
      b P<0.01 and c P<0.001 vs survivors SARS-CoV-2 patients at the respective period of hospitalisation
      Noteworthy, COVID-19 patients displayed ≈48-, 74- and 125-fold increased urinary I-FABP levels at admission, day 7 and day 14 of hospitalisation, respectively (Figure 1A; P<0.001). Critically ill patients showed higher I-FABP concentrations compared with those in the infirmary within the same hospital stay periods (Figure 1B). Likewise, nonsurvivor patients were distinguished by increased I-FABP levels in contrast to survivors (Figure 1C). At admission, the inflammatory response was characterised by augmented plasma IFN-γ and IL-6 levels in SARS-CoV-2 patients (Figure 1D). Interestingly, urinary IL-6 concentrations were elevated in infected patients and nonsurvivors (Figure 1E). The receiver operating characteristic (ROC) curve analysis indicated I-FABP as a good biomarker for disease severity and predictor for poor prognosis of COVID-19 at admission (Figure 1F; Youden index=6.89; p<0.0001) and prolonged hospital stay (Figure 1G). Patients with I-FABP ≥6.89 ng/mg showed higher plasma and urine IL-6 and serum CRP concentrations, suggesting an interaction between inflammation and damage to enterocytes (Figure 1G).
      Figure 1
      Figure 1Urinary intestinal fatty acid-binding protein (I-FABP) as a prognostic biomarker of SARS-CoV-2 disease severity. (A) Urinary I-FABP concentration determined by enzyme-linked immunosorbent assay (ELISA) in healthy volunteers and SARS-CoV-2 infected patients at admission, day 7 and day 14 of hospitalisation (Kruskal-Wallis test and Dunn's multiple comparison post-test). (B) Urinary I-FABP concentration in SARS-CoV-2 patients in non-critical and critical clinical conditions at admission, day 7 and day 14 of hospitalisation (Mann-Whitney test). (C) Urinary I-FABP concentration in SARS-CoV-2 survivor and nonsurvivor patients at admission, day 7 and day 14 of hospitalisation (Mann-Whitney test). (D) Plasma cytokines levels of tumour necrosis factor (TNF)-α, interferon (IFN)-γ and interleukin (IL)-6 determined by ELISA at admission (Mann-Whitney test). (E) Urinary IL-6 concentration at admission in healthy volunteers, SARS-CoV-2 infected patients, survivors and nonsurvivors (Mann-Whitney test). (F) Comparison of receiver operating characteristics (ROC) curve analysis of urinary I-FABP (area under the curve (AUC)=0.699, 95% CI=0.636–0.762, P<0.0001), urinary IL-6 (AUC=0.573, 95% CI=0.476–0.671, P=0.14), plasma IL-6 (AUC=0.509, 95% CI=0.436–0.582, p=0.82), plasma IFN-γ (AUC=0.523, 95% CI=0.445–0.602, P=0.54) and serum CRP (AUC=0.591, 95% CI=0.519–0.662, P=0.01) for SARS-CoV-2 survivor and non-survivor patients. Cr: creatinine. (G) Plasma and urinary IL-6 concentrations, serum C-reactive protein levels at admission and length of hospital stay in SARS-CoV-2 infected patients divided according to the Youden index=6.89 ng/mg creatinine (low I-FABP <6.89 and high I-FABP ≥6.89 ng/mg) obtained from the ROC curve in (F) (Mann-Whitney test). Results shown as bars and violin plots are expressed as median and 10–90 interquartile range. n represents the number of patients per group. P values indicate the statistical significance between groups.
      Figure 1
      Figure 1Urinary intestinal fatty acid-binding protein (I-FABP) as a prognostic biomarker of SARS-CoV-2 disease severity. (A) Urinary I-FABP concentration determined by enzyme-linked immunosorbent assay (ELISA) in healthy volunteers and SARS-CoV-2 infected patients at admission, day 7 and day 14 of hospitalisation (Kruskal-Wallis test and Dunn's multiple comparison post-test). (B) Urinary I-FABP concentration in SARS-CoV-2 patients in non-critical and critical clinical conditions at admission, day 7 and day 14 of hospitalisation (Mann-Whitney test). (C) Urinary I-FABP concentration in SARS-CoV-2 survivor and nonsurvivor patients at admission, day 7 and day 14 of hospitalisation (Mann-Whitney test). (D) Plasma cytokines levels of tumour necrosis factor (TNF)-α, interferon (IFN)-γ and interleukin (IL)-6 determined by ELISA at admission (Mann-Whitney test). (E) Urinary IL-6 concentration at admission in healthy volunteers, SARS-CoV-2 infected patients, survivors and nonsurvivors (Mann-Whitney test). (F) Comparison of receiver operating characteristics (ROC) curve analysis of urinary I-FABP (area under the curve (AUC)=0.699, 95% CI=0.636–0.762, P<0.0001), urinary IL-6 (AUC=0.573, 95% CI=0.476–0.671, P=0.14), plasma IL-6 (AUC=0.509, 95% CI=0.436–0.582, p=0.82), plasma IFN-γ (AUC=0.523, 95% CI=0.445–0.602, P=0.54) and serum CRP (AUC=0.591, 95% CI=0.519–0.662, P=0.01) for SARS-CoV-2 survivor and non-survivor patients. Cr: creatinine. (G) Plasma and urinary IL-6 concentrations, serum C-reactive protein levels at admission and length of hospital stay in SARS-CoV-2 infected patients divided according to the Youden index=6.89 ng/mg creatinine (low I-FABP <6.89 and high I-FABP ≥6.89 ng/mg) obtained from the ROC curve in (F) (Mann-Whitney test). Results shown as bars and violin plots are expressed as median and 10–90 interquartile range. n represents the number of patients per group. P values indicate the statistical significance between groups.
      Epithelial cells from ileum and colon express angiotensin-converting enzyme-2, the host cell entry receptor of coronaviruses, invading them for replication (
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      ) and shedding virions for several weeks after the onset of illness (
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      • Liu L
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      ). Enteric symptoms reflect a break in the gut mucosa homeostasis, triggering the immune response and cytokine release syndrome (
      • Effenberger M
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      • Mayr L
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      • et al.
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      • Hasselgren PO.
      Intestinal permeability is reduced and IL-10 levels are increased in septic IL-6 knockout mice.
      ). Indeed, our findings confirmed the detrimental contribution of SARS-CoV-2 to the loss of enterocyte membrane integrity, which is correlated with increased I-FABP levels (up to day 14 after hospitalisation) and patient clinical condition. Moreover, patients with I-FABP ≥6.89 ng/mg also showed exacerbated IL-6 production, a predictive cytokine of disease progression and acute respiratory distress syndrome complication (
      • Santa Cruz A
      • Mendes-Frias A
      • Oliveira AI
      • Dias L
      • Matos AR
      • Carvalho A
      • et al.
      Interleukin-6 Is a Biomarker for the Development of Fatal Severe Acute Respiratory Syndrome Coronavirus 2 Pneumonia.
      ). Our results revealed that increased I-FABP levels at admission may predict poor prognosis and SARS-CoV-2 illness severity, such as need for intensive care, mechanic ventilation and prolonged hospital stay.

      Abbreviations list

      AUC: area under curve; CRP: C-reactive protein; ELISA: enzyme-linked immunosorbent assay; GI: gastrointestinal; IBD: inflammatory bowel diseases; IFN-γ: interferon-γ; Ig: immunoglobulin; IL: interleukin; ROC curve: receiver operating characteristic curve; RT-PCR: reverse transcriptase-polymerase chain reaction; TNF-α: tumour necrosis factor-α.

      Funding

      This study was supported by The Brazilian National Council for Scientific and Technological Development (CNPq, Grant #401337/2020-0), Ministry of Health and Ministry of Science, Technology and Innovation; The São Paulo Research Foundation (FAPESP, Grant #2020/10097-5); Foundation for Support to Education, Research and Assistance (FAEPA, Grant #416/2020 and #827/2021). The manuscript content is solely the responsibility of the authors and does not necessarily represent the official view of the Research Foundations.

      Ethics approval

      The study protocol was approved by the Research Ethics Committee of Clinics Hospital of Ribeirão Preto Medical School, University of São Paulo (protocol CAAE 30794820.7.0000.5440) and all patients or family members gave their informed consent to participate in this research.

      Patient and public involvement

      Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

      Acknowledgments

      We are grateful to the excellent support of the medical teams (doctors, nurses, physiotherapists and psychologists) in the hospitals involved in this study: 1) Santa Lydia Hospital: Dr. Marcelo César Carboneri, Dr. Walther de O. Campos Filho, Bárbara R. Bauduíno Brandão, Eliane Bernardes de Queiróz, Luís F. de Melo Bougleux, Paula C. Trugillo Silva Neves, Renata C. Braulio da Silva, Silmara Miamoto, Sílvio Tolomeotti; 2) Unimed Ribeirão Preto Hospital: Dr. Gustavo Ribeiro de Oliveira, Dr. Plínio José E. de Camargo, Adriana de Fátima S. dos Santos, Bruna Maritan da Costa, Giovana A. Faggion Nomellini, Larissa Mil-Homens Albergaria; 3) Santa Casa de Misericórdia de Ribeirão Preto: Dr. Luiz C. Fontes Mega, Mariana C. Corrêa Marcolla, Rafael Cruz da Silva; and 4) Hospital e Maternidade Santa Isabel: Dr. Pedro Miguel Verardino, Edson Alves Julião, Nayara A. Poltronieri Correa.

      Contributors

      Study concept and design: RSS, HG, FLS, ABF. Involved in patient care: FLS, MAM, KMLM, AMD, MRC. Patient recruitment: RSS, HG, FLS, KJBP, MAM, AMD, MRC. Laboratory Analyses: RSS, HG. Data collection: RSS, HG, FLS, KJBP. Statistical analysis: RSS, ABF. Drafting the manuscript: RSS. All the authors edited the manuscript and have approved the final version.

      Preprint Server

      The present results have not been published as a preprint version.

      Appendix. Supplementary materials

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