Alterations of the Gut Microbiome in Psoriasis before and after Treated with Secukinumab

Abstract

Background:

Psoriasis is a chronic inflammatory skin disease linked to immune system. Despite its prevalence, the precise aetiology and pathogenesis of psoriasis remain elusive. This study aimed to assess the efficacy and safety of Secukinumab while exploring its impact on the intestinal microbiota in patients with moderate-to-severe plaque psoriasis.

Materials and Methods:

We recruited 60 healthy controls and 110 patients with moderate-to-severe plaque psoriasis who attended outpatient clinics between June 2022 and June 2023. Clinical data (gender, age, BMI, PASI score, PGA, DLQI, Itch NRS, and STAI score) and faecal samples were collected from all groups. Faecal samples underwent PacBio Full-Length Diversity Sequencing and subsequent informatics analysis.

Results:

Patients were randomly assigned to two groups: Before Secukinumab treatment group (BT, n = 55), After 24 weeks of Secukinumab treatment group (AT, n = 55). Control group (Con) consisting of healthy individuals matched for age, sex, and body mass index (n = 60). Following 24 weeks of Secukinumab treatment, significant reductions in PASI score, PGA, DLQI, Itch NRS, and STAI score were observed in psoriatic patients (P < 0.05). The microbial diversity and composition in the AT group exhibited substantial alterations compared to the BT and Con groups, typified by an elevated abundance of Agathobacter and Anaerobutyricum and a diminished presence of Bacteroides and Phocaeicola.

Conclusion:

The changes in gut microbiota occur at a slower pace than cutaneous manifestations, necessitating prolonged follow-up and microbiome-based investigations in Secukinumab-treated psoriasis patients to substantiate its therapeutic efficacy.

Introduction

Psoriasis, an immune-mediated chronic inflammatory dermatosis, arises from a complex interplay of environmental and endogenous factors in genetically predisposed individuals.[1] While non-communicable, its persistent nature and recurring symptoms of skin scaling and erythema render patients susceptible to social discrimination and prejudice, imposing significant social and psychological burdens.[2,3]

In recent years, advancements in understanding of the pathogenesis of psoriasis have led to the emergence of novel treatments. The advent of innovative therapies, such as IL-17A biologics, marks a pivotal shift towards precise targeting in clinical diagnosis and management, revolutionizing the approach to psoriasis treatment.[4] The gut–immune–skin axis delineates the role of gut microbiota in modulating systemic and local inflammation by interacting with the skin through the immune system. Mounting evidence implicates gut microbiota in shaping intestinal immunity in psoriasis patients.[5] Secukinumab is a biologic drug that targets interleukin (IL)-17 and has shown promising efficacy in the treatment of psoriasis.[4] IL-17 inhibitors have been shown to modulate gut microbiome composition in patients with psoriasis.[6,7] Studies have reported sustained clearance of skin lesions for up to 42–52 weeks with Secukinumab in moderate-to-severe plaque psoriasis treatment,[8,9] yet its impact on patients’ intestinal flora remains uncertain.

In this study, PacBio Full-Length Diversity Sequencing was employed to delve into the impact of biologic Secukinumab on the composition of intestinal microbiota in psoriasis patients. Specifically, we compared the characteristics and composition of faecal intestinal microbiota in psoriasis patients before and after Secukinumab treatment, alongside samples from healthy individuals serving as controls. Notably, for the first time, our study unveiled the significant role of probiotic Phocaeicola in the gut flora of psoriasis, offering insights into the aetiology and pathological mechanisms of this condition, and paving the way for targeted and innovative prediction and treatment strategies.

Materials and Methods

Study setting and participant recruitment

Psoriasis patients aged 18–60 years and healthy residents in the vicinity of Xishan People’s Hospital in Wuxi City were recruited. Diagnosis and classification of psoriasis patients were conducted according to the British Association of Dermatologists (BAD) guidelines[10] by two or more dermatologists with attending or above titles.

Subject inclusion criteria: (1) Willingness to participate in the study, understanding of the study protocol, and provision of informed consent; (2) No oral steroid preparations, immunosuppressants, Chinese herbal preparations, or other drugs that may affect the digestive tract flora in the past one year; No topical steroid preparations, immunosuppressants, Chinese herbal preparations, etc., in the past three months; (3) Complete medical history, systematic physical examination, and routine laboratory tests including blood routine, urine routine, stool routine, blood biochemical test, electrocardiogram examination, abdominal routine ultrasound, male urinary system ultrasound, female reproductive system ultrasound, chest X-ray, etc., and were eligible for inclusion in the study. Exclusion criteria: (1) Presence of systemic diseases known to influence intestinal flora, such as gastrointestinal bleeding, diabetes, or hypertension; (2) Recent occurrences of events, such as haemorrhoids or diarrhoea, affecting stool morphology and composition within the past month; (3) Use of antibiotics or oral probiotics in any form within the previous three months; (4) Pregnancy, lactation, or within the postpartum period.

In addition, we evaluated the differences in PASI, CRP, PGA, DLQI, STAI, and NRS scores in the two groups to analyse the relationship between clinical indicators and intestinal microbiota. This study is an exploratory case–control study designed to provide lead data for future studies in the same population. A total of 110 patients with moderate-to-severe psoriasis and 60 healthy controls participated in the study. Psoriasis patients were randomly divided into Before Secukinumab treatment group (BT, n = 55), After 24 weeks of Secukinumab treatment group (AT, n = 55). Faecal samples were frozen within two hours and stored at −80°C after collection until analysis. Ethical approval for this study was obtained from the Ethics Committee of Xishan People’s Hospital of Wuxi City (Ethics Approval Number: xs2021ky017).

Microbiome analysis

DNA extraction and PCR amplification

Microbial DNA was extracted from Stool samples using the E.Z.N.A.^® Soil DNA Kit (Omega Bio-tek, Norcross, GA, USA), following the manufacturer’s protocols. PCR amplification targeted the V1–V9 region of the bacterial 16S ribosomal RNA gene (95°C for 2 min, followed by 27 cycles at 95°C for 30 s, 55°C for 30 s, and 72°C for 60 s and a final extension at 72°C for 5 min) using primers 27F 5’-AGRGTTYGATYMTGGCTCAG-3’ and 1492R5’- RGYTACCTTGTTACGACTT-3’, where barcode is an eight-base sequence unique to each sample. PCR reactions were performed in triplicate 20 μL mixture containing 4 μL of 5 × FastPfu Buffer, 2 μL of 2.5 mM dNTPs, 0.8 μL of each primer (5 μM), 0.4 μL of FastPfu Polymerase, and 10 ng of template DNA. Amplicons were extracted from 2% agarose gels and purified using the AxyPrep DNA Gel Extraction Kit (Axygen Biosciences, Union City, CA, USA) according to the manufacturer’s instructions.

Library construction and sequencing

SMRTbell libraries were prepared from the amplified DNA via blunt ligation according to the manufacturer’s instructions (Pacific Biosciences). Purified SMRTbell libraries from the Zymo and HMP mock communities were sequenced on dedicated PacBio Sequel II 8M cells using the Sequencing Kit 2.0 chemistry. Purified SMRTbell libraries from the pooled and barcoded samples were sequenced on a single PacBio Sequel II cell. All amplicon sequencing was performed by Shanghai Biozeron Biotechnology Co. Ltd (Shanghai, China). OTUs were clustered with 98.65% similarity cut-off using UPARSE (version 7.1 http://drive5.com/uparse/) and chimeric sequences were identified and removed using UCHIME. The phylogenetic affiliation of each 16S rRNA gene sequence was analysed by RDP Classifier (http://rdp.cme.msu.edu/) against the silva (SSU132) 16S rRNA database using confidence threshold of 70%.

Statistical analysis

The basic clinical information of patients was presented as mean ± standard deviation (SD). For the highly dimensional colonic bacteria results obtained via PacBio Full-Length Diversity Sequencing, LEfSe analysis was conducted, followed by Kruskal–Wallis sum-rank test to examine changes and dissimilarities among classes, with LDA analysis used to determine the size effect of each distinctively abundant taxa. Gender was expressed as percentages (%), while age, BMI, PASI, PGA, and DLQI were expressed as mean ± SD. Chi-square tests were applied for categorical data, with statistical significance set at P < 0.05.

Results

Participant demographics and clinical characteristics

Table 1 summarizes the socio-demographic characteristics and psoriasis diagnostic data. Stool samples were collected from 110 patients before and after treatment, as well as from 60 healthy controls. No significant differences were observed in age, sex, or BMI between groups. PASI score, PGA, DLQI, Itch NRS, and STAI were significantly decreased between AT group and BT group, and there were significant differences in statistical analysis [Table 1]. After 24 weeks of treatment with Secukinumab, significant improvement in skin lesions was observed, and both PASI and PGA scores were significantly lower (P < 0.001) [Figure 1a and c]. There was no significant difference in CRP levels among the three groups [Figure 1b]. Before treatment, both DLQI scores and pruritus NRS scores were out of the normal range, but after treatment, both DLQI and pruritus NRS scores decreased significantly (P < 0.0001). STAI scores were reduced after treatment (P < 0.0001) [Figure 1e]. There were no serious adverse reactions after six months of treatment.

Table 1.

Socio-demographic and psoriasis-specific characteristics of participants

Variables (mean±SD)	Control (n=60)	Psoriasis group		P
		BT (n=55)	AT (n=55)
Ages (years)	40.5±11.55	42.13±10.19	40.15±13.01	0.7949
Gender/male, n (%)	16 (53.33%)	15 (50.00%)	11 (55.00%)	0.9354
BMI	23.16±1.59	23.87±1.91	23.63±1.35	0.2574
PASI score	-	15.78±1.92	4.19±2.32	<0.0001
CRP (mg/L)	3.26±1.12	3.56±1.98	3.04±1.23	0.5497
PGA	-	3.53±0.51	1.40±0.50	<0.0001
DLQI	-	19.67±4.49	7.15±5.70	<0.0001
Itch NRS	-	8.13±0.90	2.60±1.35	<0.0001
STAI	-	68.70±5.46	49.45±15.62	<0.0001

BMI=Body mass index, PASI=Psoriasis area and severity index, BT=Before Secukinumab treatment group, AT=After Secukinumab treatment group

Figure 1.

The severity of skin lesions and depression scores before and after psoriasis treatment. PASI score (a), CRP levels (b), PGA score (c), DLQI score (d), STAI score (e) and NRS score (f) changed before (BT) and after treatment (AT). **** represents P < 0.0001

Gut microbial α-diversity in psoriasis BT group and AT group compared to the normal controls

We investigated alterations in faecal microbial diversity among psoriasis patients before and after Secukinumab treatment and healthy controls. The adequacy of the sequence collection to encompass the majority of species was validated through species accumulation and rarefaction curves [Figure S1 ^{(120.9KB, tif)} ]. The α-diversity of the gut microbial communities across the three groups was evaluated using richness estimators, including the Observed species, Chao index, Shannon index, and Simpson index [Figure 2a–c]. No significant differences were observed between BT and Con in terms of Observed species, Chao index, Shannon index, and Simpson (P > 0.05), nor between BT and AT (P > 0.05). Notably, there was a significant difference in Observed species and Shannon index of AT and Con (P = 0.013, P = 0.02), although Chao index and Simpson index showed no significant difference between AT and Con (P > 0.05).

Figure 2.

The relative abundance of specific gut microbial taxa in AT, CT, and Con groups. The richness of faecal microbiota and structural differences were analysed by Observed species, Chao index, and Shannon index (a) BT vs Con; (b) AT vs Con; (c) AT vs BT. Data are representing 25–75% interquartile range of the median (P < 0.05)

Altered composition of genus gut microbiota in BT group and AT group compared to the normal controls

We then aimed to identify the most relevant taxa whose abundance altered after the treatment (week 24) to explore the effect of Secukinumab on the composition of gut microbiota. The levels of Bacteroides and Phocaeicola were no significant difference between BT and AT (BT vs AT, Bacteroides: P = 0.1740, BT vs AT, Phocaeicola: P = 0.1477) [Figure 3c and f]. Compared with the Con group, levels of Bacteroides and Phocaeicola in BT and AT groups were significantly reduced (Bacteroides: BT vs Con: P = 0.0002, AT vs Con: P = 0.001; Phocaeicola: BT vs Con: P = 0.0005, AT vs Con: P = 0.0003) [Figure 3a, b, d and e]. There was no significant difference in β diversity between BT and AT [Figure S3 ^{(232.7KB, tif)} ]. The differences in relative abundance of the top 10 species in different groups are shown in Figures S2 ^{(218.7KB, tif)} –S4 ^{(213.4KB, tif)} .

Figure 3.

The relative genus abundance of Bacteroides gut microbial taxa of (a) BT vs Con; (b) AT vs Con; (c) AT vs BT. The relative genus abundance of Phocaeicola gut microbial taxa of (d) BT vs Con; (e) AT vs Con; (f) AT vs BT. Data are shown at each time point as box plots and represent 25–75% interquartile range of the median (*P < 0.05, **P < 0.005)

Changes in gut microbiota in BT group psoriasis patients and AT group patients compared with normal controls

PCoA analysis, also known as principal ordinates analysis, is a non-binding data dimensionality reduction analysis method, which can be used to study the similarity or difference of sample community composition, similar to PCA analysis. While PCA is based on Euclidean distance, PCoA employs alternative distance metrics for dimensionality reduction to identify potential principal components influencing differences in sample community composition. PCoA analysis showed that intestinal bacterial communities were obviously clustered among the three groups [Figure 4a].

Figure 4.

(a) PCoA analysis of the AT, BT, and Con groups. (b) The top taxonomic profiles in the AT, BT, and Con groups at the genus level. (c) Total OTU analysis (≥97% identity level) the number shows the total number of OTUs in the AT, BT, and Con groups

At the genus level, we compared the abundance of bacteria in AT, BT, and Con groups, revealing alterations in relative abundance. In psoriasis patients (BT and AT), there was a significant increase in the relative abundances of Agathobacter and Anaerobutyricum, while the relative abundances of Bacteroides, Megamonas, and Phocaeicola were significantly reduced. There was no significant difference in the relative abundance of intestinal bacteria between BT group and AT group [Figure 4b].

Common species identification analysis was performed on the groups and samples, identifying OTUs (core OTUs) detected across all groups/samples. Subsequently, relative abundance variation rule, inter-group difference test, taxonomic composition statistics, and other analysis contents were carried out. The results were displayed using Venn diagram. There were 41,013 OTUs obtained in three groups. The analysis showed 2,708 overlapping genera among the three groups. BT and Con illustrated 7,342 overlapping genera, and 20,147 (BT) and 7,990 (Con) specific genera, respectively. BT and AT showed 6,984 overlapping genera and 20,505 (BT) and 7,175 (AT) unique genera, respectively [Figure 4c].

Discussion

Psoriasis is a disease related to the immune system with complicated inducement, and its pathogenesis remains to be fully elucidated in the medical field.[11,12,13] Probiotics, inhabiting the human intestinal tract and reproductive system, enhance the host’s microecological balance. Traditional probiotics, including lactobacilli, bifidobacterial, clostridium casei, Lactobacillus acidophilus, actinomycetes, yeasts, have been succeeded by next-generation probiotics (NGP), such as Faecalibacterium or Akkermansia, with advancements in second-generation sequencing technology.[14] However, there are few studies on the effects of biologics on the intestinal flora of psoriasis patients, the objective of this study was to explore the effects of Secukinumab on the gut microbiota in patients with psoriasis.

Studies have confirmed that gut flora is associated with autoimmune diseases, such as obesity, rheumatoid arthritis, psoriasis, and enteritis, and that some flora can regulate the body’s metabolism, inhibit the settlement of pathogenic bacteria, and reduce intestinal inflammation.[15,16,17] However, few studies have investigated clinical information and gut microbiota characteristics before and after the treatment of plaque psoriasis with the biologic agent Secukinumab. In this study, clinically informative faecal specimens were collected from 110 cases of plaque psoriasis before and after Secukinumab treatment (BT and AT) and 60 healthy controls using the PacBio Full-Length Diversity Sequencing method. We identified a significant decrease in a bacterium called Phocaeicola in psoriasis patients both before and after treatment, suggesting its potential role in psoriasis treatment as a new generation of potential probiotic bacteria. This is the first study to demonstrate altered β diversity in the gut microbiome and reduced abundance of the probiotic Phocaeicolao in patients treated with Secukinumab for 24 weeks.

Psoriasis patients commonly experience pruritus, overweight, depression, anxiety, suicide, and some metabolic syndromes,[18,19] which may exacerbate skin inflammation. Secukinumab is the first IL-17A antagonist that receives FDA approval for moderate-to-severe plaque psoriasis and the only fully human IL-17A inhibitor, which can precisely target the core pathogenic factor of psoriasis.[4,20,21] Our study confirmed significant improvements in patients’ conditions after Secukinumab treatment, with reduced PASI and PGA scores. Study shows that IL-17A plays an important role in comorbid depression, where both NF-κB and p38MAPK pathways play significant roles via upregulation of inflammatory mediators in the brain.[22] In our study, all patients experienced a reduction in itching NRS score after 24-week treatment, and some experienced complete remission. The DLQI score and STAI score also decreased significantly after treatment, there were no significant changes in BMI and CRP before and after treatment.

Bacteroides has garnered attention as a candidate for the next generation of probiotics. Phocaeicola is a new genus from the genus bacteroidetes, which was divided into bacteroidetes in 2009. With the bacteroidetes (bacteroidetes, alistipes parabacteroides, prevotella) of other similar, some types of Phocaeicola have been shown to have a close relationship with inflammatory diseases. The study has shown that oral Phocaeicola vulgatus could help maintain the epithelial barrier by regulating cytokine levels and secreting short-chain fatty acid ameliorates dextran sulphate sodium-induced colitis in Mice.[23] A recent study showed that Secukinumab enhanced the richness and altered the diversity of gut microbiota, as indicated by changes in gut microbiota composition.[24] Our findings revealed a significant decrease in the abundance of Bacteroides and Phocaeicola in both before and after treatment groups compared to the control group.

Phocaeicola vulgatus is known to be associated with succinic acid and propionic acid short-chain fatty acids in the human gut,[25] playing a crucial role in degrading complex heteropolysaccharides into short-chain fatty acids and synthesizing vitamins and other bioactive compounds.[25,26] Therefore, through the reduction of Phocaeicola in the psoriatic gut, we speculate that the balance between the gut microbiome and the body is disrupted in psoriatic patients, and the microbiome can affect the health of the host through various pathways, such as energy absorption, short-chain fatty acids, choline, bile acid metabolism, and brain–gut axis. Furthermore, due to the vital protective effect of beneficial bacteria on the intestinal mucosa, damage to the intestinal mucosa can lead to increased permeability, allowing allergens and toxic bacteria to enter the bloodstream and other organs, potentially triggering psoriasis.

In summary, our findings suggest that Phocaeicola of patients with psoriasis is significantly lower in psoriasis patients than in healthy individuals before and after 24 weeks of Secukinumab treatment. This indirectly indicates that 24 weeks of treatment with Secukinumab still failed to restore intestinal flora to a normal state. Previous studies have reported that Phocaeicola plays an important role in the treatment of enteritis, Phocaeicola may play an important role in the treatment of psoriasis by inhibiting inflammatory factors and restoring the intestinal barrier.

Data availability

All data are available in the main text or Supplementary Materials. Shannon–Wiener curves are available as Supplementary Figure S1 ^{(120.9KB, tif)} and differences in relative abundance of the top 10 species in genus are available as Supplementary Figures S1 ^{(120.9KB, tif)} –4 ^{(213.4KB, tif)} .

Conflicts of interest

There are no conflicts of interest.

Supplementary Materials

Alterations of the Gut Microbiome in Psoriasis before and after treated with Secukinumab

Shannon-Wiener is an index reflecting the microbial diversity of samples. A curve was constructed by using the microbial diversity index of each sample at different sequencing depths to reflect the microbial diversity of each sample at different sequencing quantities. The curve tends to be flat, it indicates that the sequencing data is large enough. (Figure S1 ^{(120.9KB, tif)} ).

Differences in relative abundance of the top 10 species in genus (BT vs Con) showed that compared with the Con group, levels of bacteroides and phocaeicola in BT groups were significantly reduced (bacteroides: P = 0.0002, phocaeicola: P = 0.0005), there were no statistical differences in other species. (Figure S2 ^{(218.7KB, tif)} ).

Differences in relative abundance of the top 10 species in genus (AT vs BT) showed that there was no significant difference in two groups. (Figure S3 ^{(232.7KB, tif)} ).

Differences in relative abundance of the top 10 species in genus (AT vs Con) showed that compared with the Con group, levels of bacteroides and phocaeicola in AT groups were significantly reduced (bacteroides: P = 0.0010, phocaeicola: P = 0.0003), there were no statistical differences in other species. (Figure S4 ^{(213.4KB, tif)} ).

Figure S1

Shannon-Wiener curves for different groups. (a) Con group; (b) BT group; (c) AT group

Figure S2

Differences in relative abundance of the top 10 species in genus (BT vs Con)

Figure S3

Differences in relative abundance of the top 10 species in genus (AT vs BT)

Figure S4

Differences in relative abundance of the top 10 species in genus (CT vs Con)

Funding Statement

This research was supported by the Scientific Research Program of Wuxi Health Commission (Grant Q202166 and Z202015), the Top Talent Support Program for Young and Middle-aged Individuals of Wuxi Health Committee (Grant HB2023115), and the National Natural Science Foundation of China (Grant 82302562). The authors extend sincere gratitude to all patients with psoriasis and control subjects for their participation in this study.