FormalPara Key Summary Points

Why carry out this study?

Due to the high frequency of cardiometabolic complications in psoriatic patients, it is crucial to look for markers of such disorders and tailor the patient’s treatment.

Metabolic complication biomarkers in urine have been very poorly studied in psoriatics so far, even though they would be of high value due to their non-invasive character.

What was learned from the study?

Serum tumor necrosis factor alpha (TNFα), endothelin 1 (ET-1) and α1-acid glycoprotein (α1AGP) seem to be useful biomarkers of metabolic syndrome in psoriatics.

ET-1 could perhaps become a urinary marker of metabolic disorders in psoriatics. Urinary TNFα assessment does not seem to be useful for screening for metabolic disorders in psoriatics. The utility of urinary α1AGP as a marker seems to be uncertain and requires further verification.

Introduction

Psoriasis is a very frequent dermatosis in daily dermatological practice. In addition to skin involvement, it can lead to many serious complications. Currently, there is an idea that psoriasis is a kind of systemic disease that affects many organs [1]. One of the most documented and well-known associations is that between psoriasis and cardiometabolic disorders [1, 2]. It must be highlighted that due to cardiovascular diseases (CVD), psoriatics live approximately 5 years shorter than subjects without this dermatosis [2]. This observation prompted doctors to look for how to avoid such complications.

Psoriasis has been widely investigated with regard to the possible clinical application of different markers. Serum, tissue, and even genetic markers have been proposed [3]; however, they are characterized by various sensitivities and specificities and need validation [4]. Not only may they be useful in the prediction of comorbidities, they may also be used to predict the response to therapy or prognosis, and to make diagnoses in doubtful cases [4].

Attempts have been made to look for markers of conditions associated with metabolic syndrome in urine. Some of those markers were tumor necrosis factor alpha (TNFα), endothelin 1 (ET-1), and alpha-1-acid glycoprotein (α1AGP), which are related to endothelial dysfunction and a sustained inflammatory condition observed in different metabolic syndrome components [5, 6]. It is well known that psoriasis is associated with systemic inflammation. Chronic inflammation in this dermatosis leads to insulin resistance and then to endothelial dysfunction and atherosclerosis, which is bilaterally associated with metabolic syndrome components. This sequence is called a ‘psoriatic march’ [7]. To highlight the relationship between inflammation and metabolic disorders, the term ‘metaflammation’ has been introduced [7].

The TNFα molecule is a cone-shaped trimer that was discovered in 1975. It is a proinflammatory cytokine secreted by dendritic cells, T lymphocytes, or macrophages [8]. TNFα plays several important roles in health maintenance and pathological conditions. On the one hand, it provides an inflammatory immune response, e.g., during infections, and possesses anti-tumor properties [9]. On the other hand, it is involved in the pathogenesis of many diseases, such as rheumatoid arthritis, Crohn’s disease, or graft vs. host disease [9, 10]. The engagement of TNFα in psoriasis has been well documented. First, TNFα is secreted by dendritic cells and leads to the gathering of CD4 and CD8 T lymphocytes. Moreover, it stimulates keratinocyte proliferation and promotes the secretion of other cytokines from dendritic cells [8]. Serum TNFα has already been investigated in psoriatics and was found to be elevated [8]. Antipsoriatic biological agents—TNFα inhibitors, such as adalimumab or infliximab—show great efficacy in psoriasis treatment, thus further confirming the role of TNFα in psoriasis [8]. As far as we are aware, TNFα has never been studied in psoriatics’ urine.

ET-1 is primarily secreted by endothelium, but also by keratinocytes or kidney mesangial cells [11]. It has numerous properties: vasoconstriction, bronchoconstriction, and an increase in vascular permeability or neurotransmission [12]. Increased serum ET-1 concentrations have been observed in subjects with atherosclerosis, obesity, arterial hypertension, ischemic heart disease, and diabetes mellitus (DM) [13]. What is more, ET-1 is considered a negative prognostic factor for CVD [13]. On the other hand, decreased expression of ET-1 has been observed in atheromas [14]. ET-1 is also an autocrine growth factor for keratinocytes [15]. It is secreted by psoriatic keratinocytes and inhibits apoptosis. Under inflammatory condition, secretion of ET-1 increases, which leads to the stimulation of keratinocyte proliferation [16]. ET-1 has already been evaluated in the blood of patients with psoriasis, and its concentration was increased compared to the control group [11, 17, 18]. ET-1 has also been proposed as a therapeutic target for psoriasis [19]. As far as we are aware, it has never been studied in psoriatics’ urine.

The α1AGP (orosomucoid) molecule is characterized by a very high content of carbohydrates, which are attached as five complex-type N-linked glycans [20]. It was first described in 1950 [20]. It is primarily secreted in the liver, but also in the heart or gastrointestinal tract [20]. α1AGP serves as an acute-phase protein, and its secretion is stimulated by inflammation or infection [21, 22]. It exerts immunomodulatory properties and takes part in drug transport [23]. It has been shown to prevent neutrophil chemotaxis, lymphocyte proliferation, and platelet aggregation [23]. α1AGP has been reported to be associated with metabolic syndrome [22]. It has already been studied in psoriatic serum and urine, and it was found to be elevated in both fluids [24].

In this study, we took on the challenge of looking for a non-invasive marker of metabolic disorders in psoriatics. First, we evaluated potential markers in serum and then in urine. To the best of our knowledge, with the exception of orosmucoid, the selected markers have never been assessed in urine in psoriatic patients. Moreover, we analyzed them with regard to clinical and demographic variables.

Methods

Our team has searched for different metabolic markers in psoriatics for a long time. So far, we have only used serum or plasma as a biological material. However, we know for a fact that patients are not always willing to donate blood for the purpose of the study or even for screening measures that could serve their health. Hence, we decided to investigate not only blood, but also urine. We chose urine because it is painless and easy to collect.

The study included 60 patients (21 women and 39 men) with exacerbation of plaque psoriasis who had a mean age of The basic characteristics of patients and 50 ± 2.34 years old and 30 subjects without dermatoses and with a negative family history of psoriasis. All participants signed an informed consent before enrollment into the study. The exclusion criteria for the study were: age under 18 years old, pregnancy, types of psoriasis other than plaque, dietary restrictions, intake of oral medications at least 3 months prior to the study, infectious diseases, autoimmune diseases (other than psoriasis), renal impairment and malignancies. The enrolled patients had never been treated with biological agents. The severity of psoriatic skin lesions was assessed using the psoriasis area and severity index (PASI) and was always performed by the same dermatologist. The group of patients was divided into three subgroups depending on the severity of the disease: PASI I (PASI < 10)—mild psoriasis, PASI II (PASI 10–20)—moderate psoriasis, and PASI III (PASI > 20)—severe psoriasis. Moreover, they were divided into two subgroups according to psoriasis duration—more or less than 15 years. Body mass index (BMI) was calculated as weight/height2. Laboratory tests, including complete blood count, serum fasting glucose, lipid profile, and indicators of liver and kidney function, were performed before the study. The study was approved by the Bioethics Committee of the Medical University of Bialystok (number: APK.002.19.2020) and was conducted in accordance with the principles of the Declaration of Helsinki [25].

Serum and Urine Collection

Fasting blood samples were taken using vacuum tubes. They were left to clot for 30 min before centrifugation for 10 min at 2000g. Urine samples were taken as first morning specimens from mid-stream. They were centrifugated for 10 min at 2000g. The obtained serum and urine were stored at − 80 °C until further analysis. Laboratory parameters were measured using routine techniques. TNFα, α1AGP and ET-1 concentrations were measured with an enzyme-linked immunosorbent assay (ELISA) provided by Cloud Clone® (SEA133Hu, SEA816Hu, CEA482Hu). Optical density was read at a wavelength of 450 nm. The concentrations were assessed by interpolation from calibration curves prepared with standard samples provided by the manufacturer. All laboratory tests were performed by the same person in standardized laboratory settings.

Statistical Analysis

Shapiro–Wilk’s W test of normality was used for data distribution analysis. The normally distributed data were analyzed using Student’s t-test or one-way analysis of variance (ANOVA) and shown as mean ± SD. The non-Gaussian data were presented as median (full range) and analyzed using the non-parametric Mann–Whitney test or Kruskal–Wallis test. The relationships between the examined parameters were assessed with Spearman’s rank test. Statistical analysis was conducted using GraphPad Prism 9.4 software. The differences were deemed statistically significant when p < 0.05.

Results

The basic characteristics of patients and controls are presented in Table 1. 60 patients (21 women and 39 men) with active plaque psoriasis and a mean age of 50 ± 2.34 years old participated in the study, along with 30 volunteers (10 women and 20 men) without dermatoses and with a negative family history of psoriasis who had a mean age of 48 ± 2.45 years old.

Table 1 Basic characteristics of the patients and controls
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There was no statistically significant difference between the patients and controls in terms of age, gender or BMI (NS).

Tumor Necrosis Factor α

The serum concentration of TNFα was significantly higher in patients than in controls (p < 0.001) (Fig. 1), whereas urine concentrations were undetectable in more than half of the patients, so we gave up on further analysis of this parameter.

Fig. 1
figure 1

Serum concentrations of TNFα in patients and controls. ***Difference compared to the control group is statistically significant (p < 0.001)

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After the division of patients according to psoriasis duration (more or less than 15 years), TNFα concentrations were higher in subjects who had suffered from psoriasis for a shorter period, although the difference was not significant (NS) (Fig. 2).

Fig. 2
figure 2

TNFα serum concentrations according to psoriasis duration. */***Difference compared to the control group is statistically significant (p < 0.05/0.001, respectively)

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After division into three subgroups according to PASI, there were no differences in TNFα serum concentration between the subgroups (NS) (Fig. 3).

Fig. 3
figure 3

TNFα serum concentrations in subgroups according to psoriasis severity. */**Difference compared to the control group is statistically significant (p < 0.05/0.01, respectively)

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We noticed a positive correlation between TNFα serum concentrations and triglycerides (R = 0.3, p = 0.04) and total cholesterol concentrations (R = 0.32, p = 0.024), as well as a negative correlation with ALT activity (R =  − 0.3, p = 0.027) (Fig. 4). We did not observe any correlation between serum TNFα and age or sex of the patient.

Fig. 4
figure 4

Correlations between the investigated serum proteins and laboratory parameters. TGs triglycerides, ALT alanine transaminase, AST asparagine transaminase, GLU fasting glucose, Chol total cholesterol, HDL high-density lipoprotein, LDL low-density lipoprotein, RBC red blood cells, WBC white blood cells, PLT platelets, HGB hemoglobin, UAC uric acid, CR creatinine

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Endothelin 1

The serum concentration of ET-1 was significantly higher in patients than in controls (p < 0.05) (Fig. 5a), whereas the absolute urine concentration was not significantly different between the groups (NS) (Fig. 5b), and the urine ET-1/creatinine concentration ratio (Fig. 5c) was significantly lower in psoriatics than controls (p < 0.001).

Fig. 5
figure 5

Serum ET-1 concentration (a), absolute urine ET-1 concentration (b), and urine ET-1/creatinine concentration ratio (c) in patients and controls. */***Difference compared to the control group is statistically significant (p < 0.05/0.001, respectively)

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After the division of patients according to psoriasis duration, serum ET-1 concentrations were higher in subjects who suffered from psoriasis shorter (Fig. 6).

Fig. 6
figure 6

Serum ET-1 concentration after division according to psoriasis duration. *Difference compared to the control group is statistically significant (p < 0.05)

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After division into three subgroups according to PASI, there were no differences in ET-1 serum concentration between the groups (Fig. 7).

Fig. 7
figure 7

Serum ET-1 concentration after division according to PASI (psoriasis activity and severity index)

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We did not notice any significant correlations between ET-1 serum concentration and the laboratory parameters, age, or sex of the patient.

We did not find any significant correlations between urinary ET-1 and laboratory parameters, PASI, age, sex, or psoriasis duration of the patient.

Alpha-1 Acid Glycoprotein

The serum and absolute urine concentrations of α1AGP were significantly higher in patients than in controls (p < 0.001) (Fig. 8a, b), whereas the α1AGP/creatinine concentration ratio was not significantly different between the groups (NS) (Fig. 8c).

Fig. 8
figure 8

Serum α1AGP concentration (a), absolute urine α1AGP concentration (b), and urine α1AGP/creatinine concentration ratio (c) in patients and controls. ***Difference compared to the control group is statistically significant (p < 0.001)

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After the division of the patients according to psoriasis duration, α1AGP concentrations were higher in subjects who had suffered from psoriasis for a shorter period (Fig. 9).

Fig. 9
figure 9

Serum α1AGP concentration after division according to psoriasis duration. ***Difference compared to the control group is statistically significant (p < 0.001)

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After the division of patients according to PASI, α1AGP concentrations were higher in subjects with more severe psoriasis (Fig. 9).

We noticed a negative correlation between α1AGP serum concentration and HDL cholesterol concentration (R = − 0.46, p = 0.02) (Fig. 4). We did not observe any correlation between serum α1AGP and patient age. Serum α1AGP was significantly higher in male patients compared to male controls (p < 0.01), whereas there was no difference in women (NS) (Fig. 10).

Fig. 10
figure 10

Serum α1AGP concentration after division according to PASI. *Difference compared to the control group is statistically significant (p < 0.05)

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We did not find any significant correlations between urinary α1AGP and laboratory parameters, PASI, age, sex, or psoriasis duration of the patient.

Discussion

Metabolic disorders in psoriasis are undeniable, so there is a need to search for markers allowing the early detection of complications. The ideal marker would be non-invasive and painless to collect, so we focused on urine. Encouraged by the results of other teams [6, 24] who found inflammatory and metabolic-related markers in urine to be reliable, we decided to investigate them in psoriasis and check their application in this specific group of patients. The development of markers of complications related to psoriasis would enable treatment to be personalized for each patient depending on the type of risk the patient is exposed to, the specific therapy applied, and its side effects [26].

The biggest obstacle to the use of urine for screening is the fact that the kidney function of every patient is different. Moreover, it was documented that psoriatics may have impaired kidney function due to the disease itself (through an immune-mediated mechanism), but also due to the administered antipsoriatic drugs, especially cyclosporin A [27]. Therefore, in our study, we presented absolute values of marker concentrations as well as their ratios to urine creatinine to obtain reliable results.

However, the serum concentrations of the investigated markers were, as expected, significantly higher in patients than controls, which clearly indicates an increased risk of metabolic complications in psoriatics, but the urine concentrations were not often significantly different.

For TNFα, the serum concentration was significantly higher in psoriatics than in controls. Moreover, it was negatively correlated with triglycerides and total cholesterol, which confirms its usefulness in the prediction of metabolic complications—especially hyperlipidemia in this case. TNFα is documented to increase leptin concentrations, leading to insulin resistance [28]. At the same time, we know that psoriasis is characterized by increases in the serum concentration and tissue expression of leptin [29]. Serum TNFα was also not associated directly with psoriasis severity in PASI, so it cannot be used as a predictive tool for skin lesion severity.

Unexpectedly, the urinary concentrations of this cytokine were undetectable in half of the patients, in contrast to the observation by Singh et al. that TNFα was significantly higher in obese subjects [6]. Urinary TNFα has also been documented to be elevated in subjects with arterial hypertension, which leads to other complications, such as stroke or ischemic heart disease [28]. As far as we are aware, this study is the first attempt to assess TNFα in psoriatic patients’ urine. Our outcomes indicate that the assessment of urinary TNFα probably has no value with regards to detecting metabolic complications in psoriasis. Nevertheless, future observations are welcome to further investigate this issue.

As for ET-1, its serum concentration was also significantly higher, making it a good candidate for a metabolic biomarker. Note that ET-1 upregulation is stimulated by leptin, the concentration of which is well known to be increased in psoriatics’ blood and skin, as we have previously mentioned [29, 30]. On the other hand, ET-1 has the ability to indirectly inhibit adiponectin [30], the concentration of which was found to be decreased in the blood and skin of subjects with psoriasis [29]. The absolute urine concentration was insignificantly lower but the ET-1/creatinine ratio was significantly lower. This suggests that ET-1 could actually be useful for the detection of psoriatics with metabolic disorders. Perhaps, in addition to serum measurements, a decreased urine concentration could become a marker. In contrast to our results, an increased urinary ET-1 concentration has been observed in adolescents with insulin-dependent DM, and it has been positively correlated with microalbuminuria [6], but that study was conducted on a non-adult population. Hence, this issue requires more in-depth research. In psoriatics, we are not aware of any other urinary ET-1 studies.

We did not find an association between serum ET-1 and psoriasis severity (similar to Yildiz and Borska et al. [16, 17]). We did not find urinary ET-1 to be correlated with PASI either, so this molecule will probably not be useful for predicting the course of psoriasis. However, this work is the first attempt to assess the clinical utility of urinary ET-1, so we have no data from the literature to compare with. Similar to two other studies, we did not find any correlation between serum ET-1 concentration and the age or gender of the patient [11, 17], so it would probably be useful in both women and men, regardless of their age.

Serum α1AGP concentration was significantly higher in psoriatics, which again confirms its utility as a marker. However, we did not find any correlation of this glycoprotein with the PASI score, so it does not seem to be predictive of psoriasis severity. Only the absolute concentration in urine was significantly higher, with no difference observed when we used the ratio of α1AGP to creatinine. That slightly limits its use as a urine marker, as the use of only absolute values could be confusing considering that kidney function differs between patients. Nevertheless, it is an interesting target and requires further research to determine its true application in clinical practice with regard to CVD, especially since urinary α1AGP is believed to be a more sensitive marker than its serum concentration [31]. Interestingly, it is suspected that elevated secretion of α1AGP into the urine is associated with the activation of the immune system and is observed in other autoimmune conditions [31]. Moreover, some scientists have found that both the absolute α1AGP concentration and and the α1AGP to creatinine ratio in urine are elevated in psoriatics [24, 31, 32]. Similar results were obtained by Singh et al. [6]. Importantly, one study revealed a correlation between α1AGP and CVD risk based on the QRISK score [24]. As for metabolic parameters, in our study, we observed a negative correlation between α1AGP and HDL, which indicates a negative impact of this protein on lipidemia and CVD risk. Based on the study by Nemeth et al. and ours, there seems to be no correlation, though, between psoriasis severity and urinary α1AGP [24], contrary to what Khalid et al. observed. Their team found a positive correlation with PASI score [31]; however, their study was performed on a small sample.

Surprisingly, all markers were higher (although insignificantly) in patients with psoriasis lasting less than 15 years. Perhaps this is due to high-grade inflammation and no treatment or inadequate therapy at the beginning of the disease. Unfortunately, we were not able to find any data in the literature to compare our outcomes with.

Limitations

Finally, we would like to list the limitations of our study and possible future directions. First, the study was performed on a relatively small sample size of only one ethnicity originating from only one city. In further studies, we would like to investigate the role of other acute-phase proteins in psoriatics, as well as some of their receptors. Moreover, we plan to analyze the influence of systemic antipsoriatic treatment on these parameters. Perhaps some markers would be valuable when choosing a particular therapy and adjusting a tailored treatment.

Conclusions

In this study, we took up the challenge of looking for not only serum markers but also non-invasive markers of metabolic disorders in psoriatics. We chose urine because it is painless, cheap, and easy to collect. The use of urine in daily clinical practice would surely be much appreciated by the patients. All three molecules seem useful as serum biomarkers of metabolic complications in psoriatics. Moreover, ET-1 could perhaps become a new urine marker of metabolic disorders in these patients, so further studies are required to confirm that a decreased urine concentration of ET-1 is a reliable predictive tool. Based on our and previous studies, attention should be also paid in the future to the urinary α1AGP as a marker of metaflammation. TNFα urine assessment does not seem to be useful for screening for metabolic disorders in psoriatics.