- Email: [email protected]
Can Resistin be a New Indicator of Neonatal Sepsis?
Pediatrics and Neonatology (2014) 55, 53e57
Available online at www.sciencedirect.com
journal homepage: http://www.pediatr-neonatol.com
ORIGINAL ARTICLE
Can Resistin be a New Indicator of Neonatal Sepsis? ¨rsoy b, Osman C Didem Aliefendioglu a,*, Tu ¸aglayan a, gba Gu Alev Aktas‚ b, Fahri Ovalı b a b
Pediatrics and Biochemistry Department, Kırıkkale University Medical Faculty, Kırıkkale, Turkey Zeynep Kamil Maternity and Children’s Education and Training Hospital, NICU, Istanbul, Turkey
Received Jan 3, 2013; received in revised form Mar 16, 2013; accepted May 23, 2013
Key Words C-reactive protein; interleukin-6; premature; procalcitonin; resistin; sepsis
Background: Sepsis is an important cause of neonatal death and perinatal brain damage, particularly in preterm infants. It is thought that activation of the inflammatory cascade triggered by cytokine might play a role in the pathogenesis of sepsis. Recent evidence supports a role for resistin in inflammation. There are no data in the literature on resistin levels of premature newborns with sepsis, which can also cause inflammatory response. The objective of this study was to evaluate whether resistin can be used as an indicator in neonatal sepsis of preterm babies. Materials and methods: Forty-three premature newborns considered to have sepsis were included in the study. Forty-three gestational and postnatal age- and sex-matched premature newborns without premature prolonged rupture of membrane or sepsis served as controls. Results: The median resistin and interleukin-6 (IL-6) levels of the premature babies with sepsis were 85.9 ng/mL and 342.7 pg/mL, respectively, and were higher than those of the control group (29.9 ng/mL and 17.7 pg/mL, respectively). The sensitivity, specificity, positive, and negative predictive values for resistin were 73.7%, 45.8%, 68.3%, and 52.4%, respectively. Conclusion: Resistin levels were higher in premature newborns with sepsis and correlated with IL-6 levels, which is an indicator of neonatal sepsis. This suggests that resistin may also be used in the diagnosis of neonatal sepsis. However, it has limited value when compared with the other inflammatory markers including C-reactive protein, procalcitonin, and IL-6. Copyright ª 2013, Taiwan Pediatric Association. Published by Elsevier Taiwan LLC. All rights reserved.
* Corresponding author. Angora Sitesi, Altınbel Villaları 40/B, Mutlukent Mahallesi, Ankara, Turkey. E-mail address: [email protected] (D. Aliefendioglu). 1875-9572/$36 Copyright ª 2013, Taiwan Pediatric Association. Published by Elsevier Taiwan LLC. All rights reserved. http://dx.doi.org/10.1016/j.pedneo.2013.04.012
54
1. Introduction
D. Aliefendioglu et al need for oxygen or ventilatory support, lethargy/hypotonia, and hypotension. The components of the laboratory investigation are hematological counts and ratios such as total leukocyte count, absolute neutrophil count, thrombocyte count, immature-to-total neutrophil ratio, and serum or plasma concentrations of the acute-phase proteins such as CRP and PCT. Sepsis was suspected if the infant had any of the aforementioned clinical signs and two or more laboratory parameters had abnormal values. Subsequently, a blood culture was performed to confirm sepsis. A positive blood culture confirms the diagnosis of sepsis.
Sepsis is one of the most important diseases in preterm babies and is responsible for 45% of late deaths in the neonatal intensive care units (NICUs).1 Early diagnosis and treatment of the newborn infant with suspected sepsis are essential to prevent severe and life-threatening complications. Compared with the clear and valuable therapeutic options, the diagnosis of suspected neonatal sepsis is challenging. In preterm infants, the diagnosis of sepsis is more difficult, because of the nonspecific clinical presentation and the lack of reliable diagnostic tests.2 Blood culture is the gold standard for the diagnosis of sepsis in newborns. However, technical problems such as insufficient blood sample or maternal antibiotic usage can be a barrier in isolating the responsible pathogens. In recent years there has been great interest in the potential diagnostic value of a range of hematological and immunological surrogate indicators of infection, and the studies in adults and children have demonstrated the important role of interleukin-6 (IL-6), IL-8, C-reactive protein (CRP), and procalcitonin (PCT) in the diagnosis of sepsis.2,3 Resistin is a newly discovered metabolic hormone and it has been implicated in adipogenesis and in the development of insulin resistance.4 In mice, resistin is mainly secreted by adipocyte, whereas in humans, it is expressed and/or secreted by mononuclear cells, macrophages, and neutrophils.5 The initial studies showed the relationship between resistin levels and anthropometric parameters in neonates, and resistin was suggested to be involved in the maintenance of neonatal metabolic homeostasis.6 However, recent studies showed the role of resistin in inflammation and there is emerging evidence that resistin may also function as a proinflammatory agent.7 Studies in adult patients with sepsis demonstrated that resistin expression and secretion by macrophages and neutrophils are elevated in the presence of acute bacterial infection.8e10 In addition, it has been emphasized that resistin is an indicator of the severity of disease and possibly a mediator of the prolonged inflammatory state seen in critically ill patients with infection.9 Limited data are available on resistin levels in neonatal sepsis, which can also cause an inflammatory response.11 The objective of this study was to evaluate whether resistin can be used as an indicator in neonatal sepsis of preterm babies.
Data were expressed as mean standard deviation for normally distributed continuous variables or median (minemax values) for skewed continuous variables and as proportions for categorical variables. A p value <0.05 was considered statistically significant. Differences were analyzed between the groups by Student t test when data were normally distributed; otherwise, ManneWhitney U test was used. Correlations were analyzed by Spearman correlation test. The receiver operating characteristics (ROC) curve analysis was performed to identify the optimal cutoff value for resistin to distinguish between the cases with sepsis and the healthy cases.
2. Materials and Methods
3. Results
2.1. Patients
Mean gestational age, mean birth weight, and male-tofemale ratio of the babies included in the study are shown in Table 1. Forty-three premature newborns with sepsis were included in the study and a pathogen could be isolated in 75% of them. The isolated microorganisms were as follows: methicillin-resistant Staphylococcus aureus in nine cases, methicillin-resistant Staphylococcus epidermidis in three cases, Streptococcus agalactiae in one case, S. aureus in three cases, Enterococcus faecalis in two cases, Klebsiella species in four cases, Escherichia coli in six cases, Pseudomonas aeruginosa in one case, Enterobacter aerogenes in one case, and Candida species in two cases.
The study was approved by the local ethics committee. Informed consents were obtained from the families of the infants included in the study. Forty-three premature newborns (19 male and 24 female) considered to have sepsis were included in the study; 43 gestational and postnatal age- and gender-matched newborns without premature prolonged rupture of membrane (PPROM) or sepsis served as controls. Sepsis was diagnosed based on clinical and laboratory findings, and positive culture results. the clinical findings of sepsis included apnea, gastrointestinal problems, increased
2.2. Blood samples Venous blood samples were drawn to measure whole blood count, resistin, IL-6, CRP, and PCT level on the 1st day of sepsis. Levels of resistin and IL-6 were further determined on the 3rd and 7th days of sepsis. The CRP levels were quantitatively evaluated by the nephelometric method using a CardioPhase hsCRP kit (Dade Behring, Marburg, Germany) on a nephelometer (BN II Nephelometer; Siemens, Dade Behring, Marburg, Germany). The PCT levels were analyzed by the luminescence method using a PCT kit (B.R.A.H.M.S. Diagnostica, Berlin, Germany) on a liaison analyzer (DiaSorin S.p.A., Saluggia, Vercelli, Italy). The IL-6 concentrations (BioSource International, Camarillo, CA, USA) and resistin levels (LINCO Research, St. Charles, MO, USA) were determined using enzyme-linked immunosorbent assay kit.
2.3. Statistics
Resistin in neonatal sepsis Table 1
55
Demographic characteristics of the premature newborns with sepsis and controls.
Gestational age (wk) Birth weight (g) Gender (M/F)
Control group (n Z 43)
Study group (n Z 43)
p
30 3 (23.5e35) 1448 428 (700e2800) 22/21
30 4 (24e36.3) 1394 592 (545e2800) 19/24
0.58 0.63 0.52
Data are presented as mean standard deviation (minemax values).
Table 2 shows CRP, PCT, IL-6, and resistin levels in both the study and the control groups. Both resistin and IL-6 levels substantially decreased on the 3rd and 7th days of sepsis and positive correlations were observed between them (Figure 1). A positive correlation was observed between IL-6 and PCT levels on the 1st day of sepsis (r Z 0.49, p Z 0.006). However, IL-6 was positively correlated with CRP only on the 3rd day of sepsis (r Z 0.7, p Z 0.000). The cutoff value for resistin that can be used to distinguish the babies with sepsis from healthy ones was found to be 50 ng/mL. The area under the curve value for resistin was 0.74 (95% confidence interval Z 0.63e0.85; p < 0.001). However, the area under the curve for the remaining parameters, such as CRP, PCT, and IL-6 were 0.94, 0.86, and 0.83, respectively. The sensitivity, specificity, positive, and negative predictive values for this cutoff value were 74%, 46%, 68%, and 52%, respectively.
4. Discussion In this study, we showed that median resistin levels of the babies with sepsis were significantly higher than those without sepsis, and there were significant correlations between IL-6 and resistin levels in babies with sepsis. It has been thought that activation of the inflammatory cascade triggered by cytokine may play a role in the pathogenesis of sepsis.12,13 The first step of the inflammatory response is largely characterized by an influx of neutrophils.14 The switch in leukocyte recruitment involves IL-6 transsignaling.15 IL-6 is a well-known biomarker of inflammatory response that alters the expression of other inflammatory proteins.6 Besides its direct proinflammatory effects, IL-6 also increases resistin messenger RNA expression in human peripheral blood mononuclear cells.16 As previously mentioned, resistin, originally described as an adipokine, has emerged as a potent proinflammatory protein associated with inflammation, and its role in both
acute and chronic inflammation has been shown.17e19 Recently, we showed that resistin levels were higher in neonates with PPROM than those without PPROM.20 In addition, we observed that the babies of mothers who had received antenatal steroids had significantly lower resistin levels than those who had not. Therefore, we thought that elevated resistin levels in babies with PPROM and suppressed levels in babies whose mothers received antenatal steroids might have been due to fetal inflammation on resistin levels. The findings of our study reported herein support the role of resistin in the regulation of inflammatory responses in premature newborns. However, no research showing its relationship with inflammation in neonates has been carried out. Similarly, there are limited data in the literature on resistin levels of premature newborns with sepsis. Recently, Cekmez et al11 investigated the predictive value of resistin in near-term and term babies with sepsis and they showed that resistin could be used in the diagnosis of neonatal sepsis with a similar efficacy as other markers such as CRP, PCT, and IL-6. In adult patients with sepsis, resistin has been proposed as a powerful indicator of sepsis severity, as well as a predictor of survival of critically ill patients. Johansson et al9 investigated the resistin levels in adult patients with severe sepsis and septic shock, and they showed that resistin is a marker of severity of disease and possibly a mediator of the prolonged inflammatory state seen in infected critically ill patients. Similarly, in the study by Koch and co-workers,21 serum resistin levels were investigated in critically ill adult patients, and the authors highlighted that resistin has a role as an acute-phase protein in critical-care circumstances. In the same study, they also observed a strong correlation between resistin levels and CRP, IL-6, and tumor necrosis factor-a. However, we could not find any association between resistin and these parameters except for IL-6. It is believed that PCT is produced by the liver and peripheral blood mononuclear
Table 2 C-reactive protein, procalcitonin, interleukin-6, and plasma resistin levels in babies with sepsis (on the 1st day) compared with control.
CRP (mg/L) PCT (ng/mL) IL-6 (pg/mL) Resistin (ng/mL)
Control group (n Z 43)
Study group (n Z 43)
p
0.1 0.1 17.7 29.9
2.32 1.80 342.7 85.9
0.000 0.000 0.001 0.001
(0.1e5.7) (0.1e3.18) (2e2500) (7.2e176.7)
Data are presented as median (minemax values). CRP Z C-reactive protein; IL-6 Z interleukin-6; PCT Z procalcitonin.
(0.1e23.1) (0.1e90) (2e3184) (17.5e229.9)
56
D. Aliefendioglu et al cells, modulated by lipopolysaccharides and sepsis-related cytokines.22 Cytokines such as IL-6 and IL-8 are also induced by lipopolysaccharides or other bacterial compounds and are potentially valuable parameters in the early diagnosis of bacterial sepsis as their levels are increased even before infants develop any clinical symptoms and routine laboratory tests become positive.23 The CRP, which is widely used as a parameter in the diagnosis of sepsis is also synthesized by the liver, mainly in response to IL-6. IL-6 drives the acute-phase response based on IL-6-response elements within the promoter region of CRP and thus the increase in CRP follows that of IL-6. Interestingly, in our study, the correlation between IL-6 and CRP was observed on the 3rd day of sepsis, while the correlation with PCT was observed on the 1st day of sepsis. However, although both are diagnostic markers of infection, PCT increased and returned to the normal range quicker than CRP, suggesting that PCT may be an early marker of a favorable outcome.24 It has been reported that PCT is a better diagnostic marker of sepsis than CRP in a study comparing area under the ROC curve, optimum predictive values, and optimum diagnostic cutoff values for PCT and CRP.25 The diagnosis of sepsis is difficult in neonates who are admitted to the NICU due to nonspecific clinical signs. Therefore, reliable indicators of sepsis would be helpful in an accurate diagnosis, resulting in a decrease in the unnecessary use of antibiotics. In this study, we investigated the practical use of resistin in the diagnosis of neonatal sepsis and compared it with the other markers. The cutoff value for resistin that can be used to discriminate the babies with sepsis from healthy babies was found to be 50 ng/ mL. The sensitivity, specificity, positive, and negative predictive values for this cutoff value were found to be 74%, 46%, 68%, and 52%, respectively. The area under the curve was 0.74 for resistin; however, the values for the remaining parameters, such as CRP, PCT, and IL-6 were 0.94, 0.86, and 0.83, respectively. As can be seen here, these markers, which are frequently used in the diagnosis of neonatal sepsis, have more priority for the diagnosis. In conclusion, plasma resistin levels were significantly increased in premature babies with sepsis. Increased levels of resistin and also correlations found with the IL-6 levels (which is a frequently used marker of neonatal sepsis) suggest that resistin may be used as an indicator of sepsis in preterm babies. However, it has a limited value compared with other inflammatory markers, including CRP, PCT, and IL-6.
Conflicts of Interest The authors declare that they have no financial or nonfinancial conflicts of interest related to the subject matter or materials discussed in the manuscript.
Figure 1 Correlations between plasma resistin and interleukin-6 (IL-6) levels in the patients with sepsis (A) on the 1st day of sepsis (r Z 0.46, p Z 0.003); (B) on the 3rd day (r Z 0.55, p Z 0.002); and (C) on the 7th day (r Z 0.52, p Z 0.01).
Acknowledgments This study was supported by the Mother and Child Health Foundation, Istanbul, Turkey.
Resistin in neonatal sepsis
References 1. Meadow W, Frain L, Ren Y, Lee G, Soneji S, Lantos J. Serial assessment of mortality in the neonatal intensive care unit by algorithm and intuition: certainty, uncertainty, and informed consent. Pediatrics 2002;109:878e86. 2. Edgar JD, Gabriel V, Gallimore JR, McMillan SA, Grant J. A prospective study of the sensitivity, specificity and diagnostic performance of soluble intercellular adhesion molecule 1, highly sensitive C-reactive protein, soluble E-selectin and serum amyloid A in the diagnosis of neonatal infection. BMC Pediatr 2010;10:22. 3. Kocabas‚ E, Sarikc ¸ioglu A, Aksaray N, Seydaoglu G, Seyhun Y, Yaman A. Role of procalcitonin, C-reactive protein, interleukin-6, interleukin-8 and tumor necrosis factor-alpha in the diagnosis of neonatal sepsis. Turk J Pediatr 2007;49:7e20. 4. Steppan CM, Bailey ST, Bhat S, Brown EJ, Banerjee RR, Wright CM, et al. The hormone resistin links obesity to diabetes. Nature 2001;409:307e12. 5. Tilg H, Moschen AR. Adipocytokines: mediators linking adipose tissue, inflammation and immunity. Nat Rev Immunol 2006;6: 772e83. 6. Ng PC, Lee CH, Lam CW, Chan IH, Wong E, Fok TF. Resistin in preterm and term newborns: relation to anthropometry, leptin, and insulin. Pediatr Res 2005;58:725e30. 7. Singer G, Granger DN. Inflammatory responses underlying the microvascular dysfunction associated with obesity and insulin resistance. Microcirculation 2007;14:375e87. 8. Mazaki-Tovi S, Vaisbuch E, Romero R, Kusanovic JP, Chaiworapongsa T, Kim SK, et al. Hyperresistinemiada novel feature in systemic infection during human pregnancy. Am J Reprod Immunol 2010;63:358e69. 9. Johansson L, Linne ´r A, Sunde ´n-Cullberg J, Haggar A, Herwald H, Lore ´ K, et al. Neutrophil-derived hyperresistinemia in severe acute streptococcal infections. J Immunol 2009;183: 4047e54. 10. Sunde ´n-Cullberg J, Nystro ¨m T, Lee ML, Mullins GE, Tokics L, Andersson J, et al. Pronounced elevation of resistin correlates with severity of disease in severe sepsis and septic shock. Crit Care Med 2007;35:1536e42. 11. Cekmez F, Canpolat FE, Cetinkaya M, Aydino ¨z S, Aydemir G, Karademir F, et al. Diagnostic value of resistin and visfatin, in comparison with C-reactive protein, procalcitonin and interleukin-6 in neonatal sepsis. Eur Cytokine Netw 2011;22: 113e7.
57 12. Bone RC. The pathogenesis of sepsis. Ann Intern Med 1991; 115:457e69. 13. Jacobi J. Pathophysiology of sepsis. Am J Health Syst Pharm 2002;59:S3e8. 14. DeLeo FR. Attractive shedding. Blood 2007;110:1711e2. 15. Hurst SM, Wilkinson TS, McLoughlin RM, Jones S, Horiuchi S, Yamamoto N, et al. IL-6 and its soluble receptor orchestrate a temporal switch in the pattern of leukocyte recruitment seen during acute inflammation. Immunity 2001;14:705e14. 16. Kaser S, Kaser A, Sandhofer A, Ebenbichler CF, Tilg H, Patsch JR. Resistin messenger-RNA expression is increased by proinflammatory cytokines in vitro. Biochem Biophys Res Commun 2003;309:286e90. 17. Pang SS, Le YY. Role of resistin in inflammation and inflammationrelated diseases. Cell Mol Immunol 2006;3:29e34. 18. Bokarewa M, Nagaev I, Dahlberg L, Smith U, Tarkowski A. Resistin, an adipokine with potent proinflammatory properties. J Immunol 2005;174:5789e95. 19. Silswal N, Singh AK, Aruna B, Mukhopadhyay S, Ghosh S, Ehtesham NZ. Human resistin stimulates the pro-inflammatory cytokines TNF-alpha and IL-12 in macrophages by NF-kappaBdependent pathway. Biochem Biophys Res Commun 2005; 334:1092e101. 20. Gursoy T, Aliefendioglu D, Caglayan O, Aktas A, Ovali F. Resistin levels in preterms: are they influenced by fetal inflammatory course? J Perinatol 2011;31:171e5. 21. Koch A, Gressner OA, Sanson E, Tacke F, Trautwein C. Serum resistin levels in critically ill patients are associated with inflammation, organ dysfunction and metabolism and may predict survival of non-septic patients. Crit Care 2009;13:R95. 22. Oberhoffer M, Stonans I, Russwurm S, Stonane E, Vogelsang H, Junker U, et al. Procalcitonin expression in human peripheral blood mononuclear cells and its modulation by lipopolysaccharides and sepsis-related cytokines in vitro. J Lab Clin Med 1999;134:49e55. 23. Volante E, Moretti S, Pisani F, Bevilacqua G. Early diagnosis of bacterial infection in the neonate. J Matern Fetal Neonatal Med 2004;16:13e6. 24. Monneret G, Labaune JM, Isaac C, Bienvenu F, Putet G, Bienvenu J. Procalcitonin and C-reactive protein levels in neonatal infections. Acta Paediatr 1997;86:209e12. 25. Enguix A, Rey C, Concha A, Medina A, Coto D, Die ´guez MA. Comparison of procalcitonin with C-reactive protein and serum amyloid for the early diagnosis of bacterial sepsis in critically ill neonates and children. Intensive Care Med 2001;27:211e5.
Available online at www.sciencedirect.com
journal homepage: http://www.pediatr-neonatol.com
ORIGINAL ARTICLE
Can Resistin be a New Indicator of Neonatal Sepsis? ¨rsoy b, Osman C Didem Aliefendioglu a,*, Tu ¸aglayan a, gba Gu Alev Aktas‚ b, Fahri Ovalı b a b
Pediatrics and Biochemistry Department, Kırıkkale University Medical Faculty, Kırıkkale, Turkey Zeynep Kamil Maternity and Children’s Education and Training Hospital, NICU, Istanbul, Turkey
Received Jan 3, 2013; received in revised form Mar 16, 2013; accepted May 23, 2013
Key Words C-reactive protein; interleukin-6; premature; procalcitonin; resistin; sepsis
Background: Sepsis is an important cause of neonatal death and perinatal brain damage, particularly in preterm infants. It is thought that activation of the inflammatory cascade triggered by cytokine might play a role in the pathogenesis of sepsis. Recent evidence supports a role for resistin in inflammation. There are no data in the literature on resistin levels of premature newborns with sepsis, which can also cause inflammatory response. The objective of this study was to evaluate whether resistin can be used as an indicator in neonatal sepsis of preterm babies. Materials and methods: Forty-three premature newborns considered to have sepsis were included in the study. Forty-three gestational and postnatal age- and sex-matched premature newborns without premature prolonged rupture of membrane or sepsis served as controls. Results: The median resistin and interleukin-6 (IL-6) levels of the premature babies with sepsis were 85.9 ng/mL and 342.7 pg/mL, respectively, and were higher than those of the control group (29.9 ng/mL and 17.7 pg/mL, respectively). The sensitivity, specificity, positive, and negative predictive values for resistin were 73.7%, 45.8%, 68.3%, and 52.4%, respectively. Conclusion: Resistin levels were higher in premature newborns with sepsis and correlated with IL-6 levels, which is an indicator of neonatal sepsis. This suggests that resistin may also be used in the diagnosis of neonatal sepsis. However, it has limited value when compared with the other inflammatory markers including C-reactive protein, procalcitonin, and IL-6. Copyright ª 2013, Taiwan Pediatric Association. Published by Elsevier Taiwan LLC. All rights reserved.
* Corresponding author. Angora Sitesi, Altınbel Villaları 40/B, Mutlukent Mahallesi, Ankara, Turkey. E-mail address: [email protected] (D. Aliefendioglu). 1875-9572/$36 Copyright ª 2013, Taiwan Pediatric Association. Published by Elsevier Taiwan LLC. All rights reserved. http://dx.doi.org/10.1016/j.pedneo.2013.04.012
54
1. Introduction
D. Aliefendioglu et al need for oxygen or ventilatory support, lethargy/hypotonia, and hypotension. The components of the laboratory investigation are hematological counts and ratios such as total leukocyte count, absolute neutrophil count, thrombocyte count, immature-to-total neutrophil ratio, and serum or plasma concentrations of the acute-phase proteins such as CRP and PCT. Sepsis was suspected if the infant had any of the aforementioned clinical signs and two or more laboratory parameters had abnormal values. Subsequently, a blood culture was performed to confirm sepsis. A positive blood culture confirms the diagnosis of sepsis.
Sepsis is one of the most important diseases in preterm babies and is responsible for 45% of late deaths in the neonatal intensive care units (NICUs).1 Early diagnosis and treatment of the newborn infant with suspected sepsis are essential to prevent severe and life-threatening complications. Compared with the clear and valuable therapeutic options, the diagnosis of suspected neonatal sepsis is challenging. In preterm infants, the diagnosis of sepsis is more difficult, because of the nonspecific clinical presentation and the lack of reliable diagnostic tests.2 Blood culture is the gold standard for the diagnosis of sepsis in newborns. However, technical problems such as insufficient blood sample or maternal antibiotic usage can be a barrier in isolating the responsible pathogens. In recent years there has been great interest in the potential diagnostic value of a range of hematological and immunological surrogate indicators of infection, and the studies in adults and children have demonstrated the important role of interleukin-6 (IL-6), IL-8, C-reactive protein (CRP), and procalcitonin (PCT) in the diagnosis of sepsis.2,3 Resistin is a newly discovered metabolic hormone and it has been implicated in adipogenesis and in the development of insulin resistance.4 In mice, resistin is mainly secreted by adipocyte, whereas in humans, it is expressed and/or secreted by mononuclear cells, macrophages, and neutrophils.5 The initial studies showed the relationship between resistin levels and anthropometric parameters in neonates, and resistin was suggested to be involved in the maintenance of neonatal metabolic homeostasis.6 However, recent studies showed the role of resistin in inflammation and there is emerging evidence that resistin may also function as a proinflammatory agent.7 Studies in adult patients with sepsis demonstrated that resistin expression and secretion by macrophages and neutrophils are elevated in the presence of acute bacterial infection.8e10 In addition, it has been emphasized that resistin is an indicator of the severity of disease and possibly a mediator of the prolonged inflammatory state seen in critically ill patients with infection.9 Limited data are available on resistin levels in neonatal sepsis, which can also cause an inflammatory response.11 The objective of this study was to evaluate whether resistin can be used as an indicator in neonatal sepsis of preterm babies.
Data were expressed as mean standard deviation for normally distributed continuous variables or median (minemax values) for skewed continuous variables and as proportions for categorical variables. A p value <0.05 was considered statistically significant. Differences were analyzed between the groups by Student t test when data were normally distributed; otherwise, ManneWhitney U test was used. Correlations were analyzed by Spearman correlation test. The receiver operating characteristics (ROC) curve analysis was performed to identify the optimal cutoff value for resistin to distinguish between the cases with sepsis and the healthy cases.
2. Materials and Methods
3. Results
2.1. Patients
Mean gestational age, mean birth weight, and male-tofemale ratio of the babies included in the study are shown in Table 1. Forty-three premature newborns with sepsis were included in the study and a pathogen could be isolated in 75% of them. The isolated microorganisms were as follows: methicillin-resistant Staphylococcus aureus in nine cases, methicillin-resistant Staphylococcus epidermidis in three cases, Streptococcus agalactiae in one case, S. aureus in three cases, Enterococcus faecalis in two cases, Klebsiella species in four cases, Escherichia coli in six cases, Pseudomonas aeruginosa in one case, Enterobacter aerogenes in one case, and Candida species in two cases.
The study was approved by the local ethics committee. Informed consents were obtained from the families of the infants included in the study. Forty-three premature newborns (19 male and 24 female) considered to have sepsis were included in the study; 43 gestational and postnatal age- and gender-matched newborns without premature prolonged rupture of membrane (PPROM) or sepsis served as controls. Sepsis was diagnosed based on clinical and laboratory findings, and positive culture results. the clinical findings of sepsis included apnea, gastrointestinal problems, increased
2.2. Blood samples Venous blood samples were drawn to measure whole blood count, resistin, IL-6, CRP, and PCT level on the 1st day of sepsis. Levels of resistin and IL-6 were further determined on the 3rd and 7th days of sepsis. The CRP levels were quantitatively evaluated by the nephelometric method using a CardioPhase hsCRP kit (Dade Behring, Marburg, Germany) on a nephelometer (BN II Nephelometer; Siemens, Dade Behring, Marburg, Germany). The PCT levels were analyzed by the luminescence method using a PCT kit (B.R.A.H.M.S. Diagnostica, Berlin, Germany) on a liaison analyzer (DiaSorin S.p.A., Saluggia, Vercelli, Italy). The IL-6 concentrations (BioSource International, Camarillo, CA, USA) and resistin levels (LINCO Research, St. Charles, MO, USA) were determined using enzyme-linked immunosorbent assay kit.
2.3. Statistics
Resistin in neonatal sepsis Table 1
55
Demographic characteristics of the premature newborns with sepsis and controls.
Gestational age (wk) Birth weight (g) Gender (M/F)
Control group (n Z 43)
Study group (n Z 43)
p
30 3 (23.5e35) 1448 428 (700e2800) 22/21
30 4 (24e36.3) 1394 592 (545e2800) 19/24
0.58 0.63 0.52
Data are presented as mean standard deviation (minemax values).
Table 2 shows CRP, PCT, IL-6, and resistin levels in both the study and the control groups. Both resistin and IL-6 levels substantially decreased on the 3rd and 7th days of sepsis and positive correlations were observed between them (Figure 1). A positive correlation was observed between IL-6 and PCT levels on the 1st day of sepsis (r Z 0.49, p Z 0.006). However, IL-6 was positively correlated with CRP only on the 3rd day of sepsis (r Z 0.7, p Z 0.000). The cutoff value for resistin that can be used to distinguish the babies with sepsis from healthy ones was found to be 50 ng/mL. The area under the curve value for resistin was 0.74 (95% confidence interval Z 0.63e0.85; p < 0.001). However, the area under the curve for the remaining parameters, such as CRP, PCT, and IL-6 were 0.94, 0.86, and 0.83, respectively. The sensitivity, specificity, positive, and negative predictive values for this cutoff value were 74%, 46%, 68%, and 52%, respectively.
4. Discussion In this study, we showed that median resistin levels of the babies with sepsis were significantly higher than those without sepsis, and there were significant correlations between IL-6 and resistin levels in babies with sepsis. It has been thought that activation of the inflammatory cascade triggered by cytokine may play a role in the pathogenesis of sepsis.12,13 The first step of the inflammatory response is largely characterized by an influx of neutrophils.14 The switch in leukocyte recruitment involves IL-6 transsignaling.15 IL-6 is a well-known biomarker of inflammatory response that alters the expression of other inflammatory proteins.6 Besides its direct proinflammatory effects, IL-6 also increases resistin messenger RNA expression in human peripheral blood mononuclear cells.16 As previously mentioned, resistin, originally described as an adipokine, has emerged as a potent proinflammatory protein associated with inflammation, and its role in both
acute and chronic inflammation has been shown.17e19 Recently, we showed that resistin levels were higher in neonates with PPROM than those without PPROM.20 In addition, we observed that the babies of mothers who had received antenatal steroids had significantly lower resistin levels than those who had not. Therefore, we thought that elevated resistin levels in babies with PPROM and suppressed levels in babies whose mothers received antenatal steroids might have been due to fetal inflammation on resistin levels. The findings of our study reported herein support the role of resistin in the regulation of inflammatory responses in premature newborns. However, no research showing its relationship with inflammation in neonates has been carried out. Similarly, there are limited data in the literature on resistin levels of premature newborns with sepsis. Recently, Cekmez et al11 investigated the predictive value of resistin in near-term and term babies with sepsis and they showed that resistin could be used in the diagnosis of neonatal sepsis with a similar efficacy as other markers such as CRP, PCT, and IL-6. In adult patients with sepsis, resistin has been proposed as a powerful indicator of sepsis severity, as well as a predictor of survival of critically ill patients. Johansson et al9 investigated the resistin levels in adult patients with severe sepsis and septic shock, and they showed that resistin is a marker of severity of disease and possibly a mediator of the prolonged inflammatory state seen in infected critically ill patients. Similarly, in the study by Koch and co-workers,21 serum resistin levels were investigated in critically ill adult patients, and the authors highlighted that resistin has a role as an acute-phase protein in critical-care circumstances. In the same study, they also observed a strong correlation between resistin levels and CRP, IL-6, and tumor necrosis factor-a. However, we could not find any association between resistin and these parameters except for IL-6. It is believed that PCT is produced by the liver and peripheral blood mononuclear
Table 2 C-reactive protein, procalcitonin, interleukin-6, and plasma resistin levels in babies with sepsis (on the 1st day) compared with control.
CRP (mg/L) PCT (ng/mL) IL-6 (pg/mL) Resistin (ng/mL)
Control group (n Z 43)
Study group (n Z 43)
p
0.1 0.1 17.7 29.9
2.32 1.80 342.7 85.9
0.000 0.000 0.001 0.001
(0.1e5.7) (0.1e3.18) (2e2500) (7.2e176.7)
Data are presented as median (minemax values). CRP Z C-reactive protein; IL-6 Z interleukin-6; PCT Z procalcitonin.
(0.1e23.1) (0.1e90) (2e3184) (17.5e229.9)
56
D. Aliefendioglu et al cells, modulated by lipopolysaccharides and sepsis-related cytokines.22 Cytokines such as IL-6 and IL-8 are also induced by lipopolysaccharides or other bacterial compounds and are potentially valuable parameters in the early diagnosis of bacterial sepsis as their levels are increased even before infants develop any clinical symptoms and routine laboratory tests become positive.23 The CRP, which is widely used as a parameter in the diagnosis of sepsis is also synthesized by the liver, mainly in response to IL-6. IL-6 drives the acute-phase response based on IL-6-response elements within the promoter region of CRP and thus the increase in CRP follows that of IL-6. Interestingly, in our study, the correlation between IL-6 and CRP was observed on the 3rd day of sepsis, while the correlation with PCT was observed on the 1st day of sepsis. However, although both are diagnostic markers of infection, PCT increased and returned to the normal range quicker than CRP, suggesting that PCT may be an early marker of a favorable outcome.24 It has been reported that PCT is a better diagnostic marker of sepsis than CRP in a study comparing area under the ROC curve, optimum predictive values, and optimum diagnostic cutoff values for PCT and CRP.25 The diagnosis of sepsis is difficult in neonates who are admitted to the NICU due to nonspecific clinical signs. Therefore, reliable indicators of sepsis would be helpful in an accurate diagnosis, resulting in a decrease in the unnecessary use of antibiotics. In this study, we investigated the practical use of resistin in the diagnosis of neonatal sepsis and compared it with the other markers. The cutoff value for resistin that can be used to discriminate the babies with sepsis from healthy babies was found to be 50 ng/ mL. The sensitivity, specificity, positive, and negative predictive values for this cutoff value were found to be 74%, 46%, 68%, and 52%, respectively. The area under the curve was 0.74 for resistin; however, the values for the remaining parameters, such as CRP, PCT, and IL-6 were 0.94, 0.86, and 0.83, respectively. As can be seen here, these markers, which are frequently used in the diagnosis of neonatal sepsis, have more priority for the diagnosis. In conclusion, plasma resistin levels were significantly increased in premature babies with sepsis. Increased levels of resistin and also correlations found with the IL-6 levels (which is a frequently used marker of neonatal sepsis) suggest that resistin may be used as an indicator of sepsis in preterm babies. However, it has a limited value compared with other inflammatory markers, including CRP, PCT, and IL-6.
Conflicts of Interest The authors declare that they have no financial or nonfinancial conflicts of interest related to the subject matter or materials discussed in the manuscript.
Figure 1 Correlations between plasma resistin and interleukin-6 (IL-6) levels in the patients with sepsis (A) on the 1st day of sepsis (r Z 0.46, p Z 0.003); (B) on the 3rd day (r Z 0.55, p Z 0.002); and (C) on the 7th day (r Z 0.52, p Z 0.01).
Acknowledgments This study was supported by the Mother and Child Health Foundation, Istanbul, Turkey.
Resistin in neonatal sepsis
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