Association of Baseline Serum Soluble Tumour Necrosis Factor Receptor Levels with the Response of Rheumatoid Arthritis to Janus Kinase Inhibitor Therapy.

Aim: The aim of this study was to investigate whether cytokines associated with tumour necrosis factor- (TNF-) α and interleukin- (IL-) 6 signalling could predict rheumatoid arthritis (RA) clinical remission (CR) with Janus kinase inhibitor (JAKinib) treatment using the Simplified Disease Activity Index (SDAI). Methods: Eighty-nine patients with RA treated with JAKinibs were enrolled, and their clinical data were collected retrospectively. CR was defined as an SDAI ≤ 3.3 after 6 months of treatment with JAKinib. The serum samples of 89 patients were analysed for IL-6, soluble IL-6 receptor (sIL-6R), soluble gp130 (spg130), and soluble TNF receptor- (sTNFR-) I and sTNFR-II titres. Results: There were no significant differences in the baseline clinical parameters between the CR and non-CR groups. Serum levels of IL-6, sIL-6R, and sgp130 were not significantly different; whereas, the serum sTNFR-I and sTNFR-II levels were significantly lower in the CR group. Univariate and multivariate logistic regression analysis showed that the baseline log sTNFR II values (OR: 0.002; p = 0.034) were predictors of CR. Conclusions: Patients with RA can be stratified prior to JAKinib administration using serum sTNFR-I and sTNFR-II levels but not serum IL-6 axis cytokine levels (IL-6, sIL-6R, and sgp130).

Pedicled Omentoplasty for Treatment of Rheumatoid Nodule Pneumothorax: A Case Report.

Background No consensus exists regarding surgical intervention for rheumatoid nodule-related pneumothorax. Clinical policy decisions rely on individual clinicians' experience and are usually intractable. Case Description A 50-year-old man with a difficult-to-treat rheumatoid arthritis-related pneumothorax was successfully treated with pedicle omentoplasty without recurrence at approximately 2 years posttreatment. To the best of our knowledge, this is the first report of a patient where pneumothorax did not recur due to firm adhesions despite fluctuating postoperative rheumatoid nodules, as captured by regular computed tomography imaging follow-ups. Conclusion Pedicled omentoplasty is effective for rheumatoid nodule-related pneumothorax as it reduces pneumothorax recurrence.

Involvement of YKL-40-positive macrophages commonly identified in polymyositis and dermatomyositis in the pathogenesis of myositis: a retrospective study.

YKL-40 is implicated in inflammation and tissue repair, but no reports have investigated its involvement in myositis in polymyositis (PM) and dermatomyositis (DM). Therefore, we aimed to investigate the relationship between YKL-40 and PM/DM. We retrospectively enrolled 35 patients diagnosed with PM/DM along with 26 healthy controls (HCs). Both PM and DM were diagnosed according to Bohan and Peter's criteria. Serum YKL-40 levels were measured, age-corrected to YKL-40 percentile values, and compared to HCs. Patients with myositis without interstitial lung disease were also enrolled and compared to HCs. Immunofluorescence staining was performed to identify YKL-40-positive inflammatory cells in muscle biopsy samples from two patients each with PM and DM. Age-corrected serum YKL-40 levels were significantly higher in patients with PM/DM compared to HCs with and without lung disease; however, these levels decreased significantly after treatment. Immunohistochemical analysis showed infiltration of YKL-40-positive inflammatory cells into the intramuscular sheath and perimuscular membrane. Immunofluorescence staining showed CD68 expression in YKL-40-positive inflammatory cells, suggesting that these cells were macrophages. To the best of our knowledge, this is the first study to demonstrate that YKL-40-positive macrophages are present in PM and DM, indicating that YKL-40 may be involved in PM/DM.

[COMPONENT ANALYSIS OF THREE ANISAKIASIS ALLERGY CASES IN OUR DEPARTMENT].

Reactivity to an anisakis allergen component was examined in three patients with a history of an anisakiasis anaphylaxis. Case 1, a 38-year-old man, allergic symptoms appeared 0.5 hours after ingestion, and the component Ani s 1 and 3 were positive. Case 2, a 44-year-old woman, allergic symptoms appeared 4 hours after ingestion, and components Ani s 3 and 12 were positive. Case 3, a 36-year-old woman, developed allergic symptoms 7 hours after ingestion of fish and shellfish, and tested positive for Ani s 1, 4, and 12. Case 3 reacted strongly to both heated and unheated Anisakis extract, while cases 1 and 2 reacted weakly to heated Anisakis extract. The most common allergen was Ani s 12, followed by Ani s 1, when analyzed in conjunction with existing reports on 10 cases. Anisakis IgE was class 3 or higher in all cases. Analysis of 13 cases showed 2 cases sensitized to Ani s 4 and moderate or higher anaphylaxis, while Ani s 4-sensitized patients were reported to be more likely to develop severe disease. It is possible that the patients sensitized to Ani s 4 need to be careful about the severity of their allergic symptoms.

Tocilizumab suppresses NF-kappa B activation via toll-like receptor 9 signaling by reducing cell-free DNA in rheumatoid arthritis.

Endogenous DNA is released into the bloodstream as cell-free DNA (cfDNA) following cell death and is associated with various pathological conditions. However, their association with therapeutic drugs against rheumatoid arthritis (RA) remains unknown. Therefore, we investigated the significance of cfDNA in RA treated with tocilizumab and tumour necrosis factor inhibitor (TNF-I). Biological DMARDs (bDMARDs), including tocilizumab and TNF-I, were administered to 77 and 59 RA patients, respectively. Plasma cfDNA levels were measured at weeks 0, 4, and 12 by quantitative polymerase chain reaction. Disease activity was evaluated at the same time point using DAS28ESR. cfDNA levels from RA synovial cells treated with tocilizumab or etanercept for 24 h were measured. Human toll-like receptor 9 (hTLR9)-expressing HEK293 cells, which release secreted embryonic alkaline phosphatase (SEAP) upon NF-κB activation, were stimulated by cfDNA from RA patients, and subsequently, SEAP levels were determined. NF-κB translocation was evaluated by immunofluorescence staining with or without tocilizumab. The DAS28ESR significantly improved in both bDMARD groups at week 12. However, plasma cfDNA levels significantly decreased in the tocilizumab group at week 12 compared to that in week 0. cfDNA levels correlated with DAS28ESR in biological treatment-naïve patients administered tocilizumab. cfDNA levels in synovial cells were significantly suppressed by tocilizumab treatment and unaltered with etanercept. HEK293 cells released SEAP upon cfDNA stimulation, and the observed NF-κB nuclear translocation was suppressed by tocilizumab. Tocilizumab suppressed inflammation via the TLR9 pathway by decreasing cfDNA levels. Regulation of cfDNA may be a therapeutic target for RA.

Thoracoscopic and laparoscopic approach for pleuroperitoneal communication under peritoneal dialysis: a report of four cases.

BACKGROUND: Pleuroperitoneal communication (PPC) is a rare complication of continuous ambulatory peritoneal dialysis (CAPD) and often forces patients to switch to hemodialysis. Some efficiencies of video-assisted thoracic surgery (VATS) for PPC have been reported recently; however, there is no standard approach for these complications. In this case series, we present a combined thoracoscopic and laparoscopic approach for PPC in four patients to better assess its feasibility and efficiency. CASE PRESENTATION: Clinical characteristics, perioperative findings, surgical procedures, and clinical outcomes were retrospectively analyzed. We combined VATS with a laparoscopic approach to detect and repair the diaphragmatic lesions responsible for PPC. We first performed pneumoperitoneum in all patients following thoracoscopic exploration. In two cases, we found bubbles gushing out of a small pore in the central tendon of the diaphragm. The lesions were closed with 4-0 non-absorbable monofilament sutures, covered with a sheet of absorbable polyglycolic acid (PGA) felt, and sprayed with fibrin glue. In the other two cases without bubbles, a laparoscope was inserted, and we observed the diaphragm from the abdominal side. In one of the two cases, two pores were detected on the abdominal side. The lesions were closed using sutures and reinforced using the same procedure. In one case, we failed to detect a pore using VATS combined with the laparoscopic approach. Therefore, we covered the diaphragm with only a sheet of PGA felt and fibrin glue. There was no recurrence of PPC, and CAPD was resumed at an average of 11.3 days. CONCLUSIONS: The combined thoracoscopic and laparoscopic approach is an effective treatment for detecting and repairing the lesions responsible for PPC.

Serum B cell activating factor (BAFF) as a biomarker for induction of remission with rituximab in ANCA-associated vasculitis.

We examined whether serum B cell activating factor (BAFF) is useful for predicting the remission of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) following rituximab treatment. We used the Birmingham Vasculitis Activity Score (BVAS) 2008 version 3 for the evaluation of 27 patients with AAV 6 months after rituximab treatment. Those with BVAS = 0 achieved remission, whereas those with BVAS score > 0 did not achieve remission. We considered changes in serum BAFF before rituximab treatment, 1 month after treatment, and 6 months after treatment. In the remission group, the serum BAFF increased consistently. In the non-achieved group, serum BAFF was within the normal range. In addition, there was no statistically significant difference between the two groups in terms of serum BAFF before and 1 month after rituximab treatment. However, the serum BAFF level at 6 months after rituximab treatment was significantly higher in the remission group than in the non-achieved group. If serum BAFF does not increase after 6 months of rituximab in AAV, it may be assumed that there are residual B cells and plasma cells in the tissues. Enhanced treatment targeting B cells, including re-administration of rituximab or the addition of other immunosuppressive drugs, should be considered.

Relationship between anti-acetylcholine receptor antibodies and the development of post-thymectomy myasthenia gravis in patients with thymoma: a single-center experience.

BACKGROUND: Approximately 15-29.6% of patients with thymoma have myasthenia gravis (MG). Some of these patients develop MG after thymectomy despite having no history of MG or related symptoms. Few previous studies have examined the risk factors for the development of post-thymectomy MG in patients with thymoma. Herein, we retrospectively reviewed our institutional experience with patients with thymoma who developed MG after thymectomy. METHODS: Twenty-six patients with thymoma but without MG, who were tested preoperatively for anti-acetylcholine receptor antibody (anti-AChR-Ab) levels, underwent surgical resection at our hospital between 2013 and 2020. Patients with thymic carcinoma were excluded from the study. We evaluated the association of outcomes with preoperative anti-AChR-Ab levels and post-thymectomy MG. We performed a χ2 test for bivariate analysis of categorical data. Differences were considered significant at P<0.05. RESULTS: The characteristics of the 26 patients (median age: 62 years; 8 men, 18 women) were as follows: World Health Organization (WHO) classifications AB (n=8), B1 (n=9), B2 (n=6), B3 (n=1), and others (n=2) and Masaoka stage I (n=12), II (n=9), III (n=3), and IVa (n=2). Among the 26 patients, only five had high (>0.3 nmol/L) preoperative anti-AChR-Ab levels. Post-thymectomy MG occurred in two of the five patients (40%) with high preoperative anti-AChR-Ab levels. A high preoperative serum anti-AChR-Ab titer was significantly associated with post-thymectomy MG (P=0.0267). The anti-AChR-Ab titer was also measured postoperatively in four of the five (80%) patients with high preoperative levels. The anti-AChR-Ab titer decreased in two of these four patients, and neither developed postoperative MG. CONCLUSIONS: Preoperative and postoperative anti-AChR-Ab positivity might be associated with post-thymectomy MG. Therefore, regular measurement of anti-AChR-Ab levels after thymectomy is required.

Cell-Free DNA in Rheumatoid Arthritis.

Endogenous DNA derived from the nuclei or mitochondria is released into the bloodstream following cell damage or death. Extracellular DNA, called cell-free DNA (cfDNA), is associated with various pathological conditions. Recently, multiple aspects of cfDNA have been assessed, including cfDNA levels, integrity, methylation, and mutations. Rheumatoid arthritis (RA) is the most common form of autoimmune arthritis, and treatment of RA has highly varied outcomes. cfDNA in patients with RA is elevated in peripheral blood and synovial fluid and is associated with disease activity. Profiling of cfDNA in patients with RA may then be utilized in various aspects of clinical practice, such as the prediction of prognosis and treatment responses; monitoring disease state; and as a diagnostic marker. In this review, we discuss cfDNA in patients with RA, particularly the sources of cfDNA and the correlation of cfDNA with RA pathogenesis. We also highlight the potential of analyzing cfDNA profiles to guide individualized treatment approaches for RA.

Increased Circulating Cell-Free DNA in Eosinophilic Granulomatosis With Polyangiitis: Implications for Eosinophil Extracellular Traps and Immunothrombosis.

Background: Endogenous DNA derived from nuclei or mitochondria is released into the blood circulation as cell-free DNA (cfDNA) following cell damage or death. cfDNA is associated with various pathological conditions; however, its clinical significance in antineutrophil cytoplasmic antibody-associated vasculitis (AAV) remains unclear. This study aimed to evaluate the clinical significance of cfDNA in AAV. Methods: We enrolled 35 patients with AAV, including 10 with eosinophilic granulomatosis with polyangiitis (EGPA), 13 with microscopic polyangiitis, and 12 with granulomatosis with polyangiitis. Serum cf-nuclear DNA (cf-nDNA) and cf-mitochondrial DNA (cf-mtDNA) levels were measured by quantitative polymerase chain reaction before and after the initiation of immunosuppressive therapy. Tissue samples from EGPA patients were examined by immunofluorescence and transmission electron microscopy. The structure of eosinophil extracellular traps (EETs) and neutrophil extracellular traps (NETs) and stability against DNase were assessed in vitro. Platelet adhesion of EETs were also assessed. Results: Serum cf-nDNA and cf-mtDNA levels were significantly higher in AAV than in healthy controls, with the highest levels in EGPA; however, serum DNase activities were comparable among all groups. cf-nDNA and cf-mtDNA decreased after treatment and were associated with disease activity only in EGPA. Blood eosinophil count and plasma D-dimer levels were significantly correlated with cf-nDNA in EGPA and cf-mtDNA. EGPA tissue samples showed lytic eosinophils and EETs in small-vessel thrombi. The structure of EETs showed bolder net-like chromatin threads in vitro and EETs showed greater stability against DNase than NETs. EETs provided a scaffold for platelet adhesion. Conclusion: cfDNA was increased in EGPA, associated with disease activity. The presence of DNase-resistant EETs in small-vessel thrombi might contribute to higher concentration of cfDNA and the occurrence of immunothrombosis in EGPA.

Expressions of circadian clock genes represent disease activities of RA patients treated with biological DMARDs.

Objectives: Rheumatoid Arthritis (RA) is the autoimmune disease representing the circadian variations of symptoms such as morning stiffness of joints or increased production of cytokines around midnight. Clock genes have been reported to affect on the pathogenesis of RA, however, the detailed relation between clock genes and disease activities of RA has remained unclear.Methods: In this study, 15 RA patients treated with biological disease modifying anti-rheumatic drugs (bDMARDs) were enrolled (TNF inhibitor, 5; IL-6 inhibitor, 5; CTLA4-IgG, 5). Blood samples were collected from RA patients before treatment and at the study end-point fulfilling DAS28-ESR < 3.2. Total RNA was extracted from leukocytes to examine the expressions of the clock genes. We then evaluated the correlation of the clock gene expression with disease activity and the diagnostic values of the clock genes.Results: The expressions of the clock genes were significantly modulated by bDMARDs treatments. Disease activities were significantly correlated with the clock genes expressions, and disease remission/low disease activity could be distinguished from moderate/high disease activity due to the sensitivities, the specificities and the areas under the curves of that.Conclusion: The expressions of the clock genes in leukocytes could be useful as novel biomarkers predicting disease activities and therapeutic efficacies for bDMARDs in RA treatments.

Methotrexate upregulates circadian transcriptional factors PAR bZIP to induce apoptosis on rheumatoid arthritis synovial fibroblasts.

BACKGROUND: Effects of methotrexate (MTX) on the proliferation of rheumatoid arthritis (RA) synovial fibroblasts are incompletely understood. We explored actions of MTX in view of circadian transcriptions of synovial fibroblasts. METHODS: Under treatment with MTX, expression of core circadian clock genes, circadian transcriptional factor proline and acidic amino acid-rich basic leucine zipper (PAR bZIP), and proapoptotic molecule Bcl-2 interacting killer (Bik) was examined by real-time polymerase chain reaction. Protein expression of circadian clock gene PERIOD2 (PER2) and CYTOCHROME C was also examined by western blotting and ELISA. Promoter activities of Per2 and Bik were measured by Luciferase assay. Expression of PER2, BIK, and CYTOCHROME C and morphological changes of the nucleus were observed by fluorescent immunostaining. Synovial fibroblasts were transfected with Per2/Bik small interfering RNA, and successively treated with MTX to determine cell viabilities. Finally, synovial fibroblasts were treated with MTX according to the oscillation of Per2/Bik expression. RESULTS: MTX (10 nM) significantly decreased cell viabilities, but increased messenger RNA expression of Per2, Bik, and PAR ZIP including D site of the albumin promoter binding protein (Dbp), hepatic leukemia factor (Hlf), and thyrotroph embryonic factor (Tef). MTX also increased protein expression of PER2 and CYTOCHROME C, and promoter activities of Per2 and Bik via D-box. Under fluorescent observations, expression of PER2, BIK, and CYTOCHROME C was increased in apoptotic cells. Cytotoxicity of MTX was attenuated by silencing of Per2 and/or Bik, and revealed that MTX was significantly effective in situations where Per2/Bik expression was high. CONCLUSIONS: We present here novel unique action of MTX on synovial fibroblasts that upregulates PAR bZIP to transcribe Per2 and Bik, resulting in apoptosis induction. MTX is important in modulating circadian environments to understand a new aspect of pathogenesis of RA.

TNF-α induces expression of the circadian clock gene Bmal1 via dual calcium-dependent pathways in rheumatoid synovial cells.

Tumor necrosis factor (TNF)-α is responsible for expressions of several clock genes and affects joint symptoms of rheumatoid arthritis (RA) with diurnal fluctuation. We tried to determine the mechanism involved in over-expression of Bmal1, induced by TNF-α, in primary cultured rheumatoid synovial cells. Cells were incubated with intra-cellular Ca2+ chelator BAPTA-AM, calcineurin inhibitor FK506 and p300/CBP (CREB binding protein) inhibitor C646, respectively, or transfected with p300 and CBP small interfering RNA (siRNA) before stimulation with TNF-α. Oscillation phase and amplitude of Bmal1, transcriptional activator Rorα, transcriptional repressor Rev-erbα, and histone acetyltransferases (p300 and Cbp) were evaluated by quantitative real-time PCR. As results, TNF-α did not influence the oscillation phase of Rev-erbα, while enhanced those of Rorα, resulting in over-expression of Bmal1. When Ca2+ influx was inhibited by BAPTA-AM, TNF-α-mediated up-regulation of Rorα was cancelled, however, that of Bmal1 was still apparent. When we further explored another pathway between TNF-α and Bmal1, TNF-α suppressed the expression of Rev-erbα in the absence of Ca2+ influx, as well as those of p300 and Cbp genes. Finally, actions of TNF-α, in increasing Bmal1/Rorα and decreasing Rev-erbα, were cancelled by C646 treatment or silencing of both p300 and Cbp. In conclusion, we determined a novel role of TNF-α in inducing Bmal1 via dual calcium dependent pathways; Rorα was up-regulated in the presence of Ca2+ influx and Rev-erbα was down-regulated in the absence of that. Results proposed that inhibition of p300/CBP could be new therapeutic targets for RA.

Circulating cell free DNA: a marker to predict the therapeutic response for biological DMARDs in rheumatoid arthritis.

AIM: To evaluate the correlation between circulating cell-free DNA (ccfDNA) in plasma and clinical disease activities in patients with rheumatoid arthritis (RA). METHOD: The study group included 30 patients with RA who started biological disease-modifying anti-rheumatic drugs (DMARDs) therapy. The concentration of ccfDNA in plasma was measured by quantitative real-time polymerase chain reaction at baseline to 24 weeks in every 4-week period from 30 patients and 21 healthy individuals. We also evaluated the correlation between ccfDNA and the clinical activity or the therapeutic response for biological DMARDs, using the simplified disease activity index (SDAI), Disease Activity Score of 28 joints (erythrocyte sedimentation rate) and the European League Against Rheumatism (EULAR) response criteria. Synovial fluid samples of knee joints were collected from 13 patients with RA and 12 with osteoarthritis (OA) to measure ccfDNA. RESULT: The concentration of ccfDNA in RA patients at baseline was higher than healthy controls (P = 0.016). After introducing biological DMARDs, ccfDNA was increased until 8 weeks from the baseline, and decreased after 12 weeks. The average of SDAI was improved in all patients enrolled. At 12 weeks after treatment, 15 patients were good responders to the EULAR response criteria, nine showed moderate response and six showed no response. ccfDNA in good responders was increased until 8 weeks, while those of moderate or no response were not (P = 0.042). In joint fluid of RA patients, ccfDNA was remarkably increased as compared to those from OA (P = 0.00011). CONCLUSION: After introducing biological DMARDs, increase of ccfDNA at 8 weeks was associated with improvement of disease activities. Compared with biomarkers reported, ccfDNA is able to predict the early therapeutic effects of biological DMARDs in RA patients.

Involvement of the circadian rhythm and inflammatory cytokines in the pathogenesis of rheumatoid arthritis.

Among the symptoms of patients with rheumatoid arthritis (RA), joint stiffness is influenced by diurnal rhythm and reaches peak in the morning, which is a common complaint and reflects the circadian nature of disease manifestation. In addition, inflammatory cytokines, which reach peak secretion early in the morning are major players causing the morning stiffness. In this review, we explore the link between the circadian clock and inflammation, focusing on the interactions of various clock genes with the immune-pathways underlying the pathology of rheumatoid arthritis.

Shorter disease duration is important for tocilizumab to achieve Boolean remission.

OBJECTIVE: To determine the optimal conditions for inducing rheumatoid arthritis (RA) into disease remission by tocilizumab (TCZ), we analyzed the TCZ therapy carried out in our facility. METHOD: The study group comprised 116 patients with RA who started TCZ therapy at Kobe University Hospital and Konan-Kakogawa Hospital. The clinical response to TCZ was evaluated by the 2011 Boolean definition and the disease activity score of 28 joints erythrocyte sedimentation rate 4 (DAS28-ESR4). RESULTS: After 24 weeks of TCZ therapy, 25.9% of the patients achieved a Boolean-defined disease remission (Boolean remission). DAS28-ESR4 was improved from 5.25 ± 1.15 at week 0 to 2.75 ± 1.34 at week 24 (mean ± SD, P < 0.0001), and 57.8% patients achieved DAS28 remission. Analysis of the relationship between disease duration and remission showed that this odds ratio peaked at 3.0 years. Univariate analyses showed that Boolean remission was associated with baseline ESR levels, Steinbrocker's class and stage, and patient global assessment of disease activity (PGA). Accordingly, we categorized and compared the patient groups referring to the 3.0-year peak. We found significant differences in Steinbrocker's class and stage. CONCLUSION: TCZ therapy leading to Boolean disease remission is optimal when initiated less than 3.0 years after disease onset.

Nicotinamide adenine dinucleotide extends the lifespan of Caenorhabditis elegans mediated by sir-2.1 and daf-16.

It is well understood that sir2 (sirtuin), an NAD-dependent deacetylase, is essential for the extension of lifespan under caloric restriction. However, the mechanism underlying activation of sir2 is unclear. Life extension through caloric restriction requires the sir2 ortholog sir-2.1 in nematodes but occurs independently of the forkhead-type transcription factor DAF-16. We aimed here to elucidate the correlation between life extension in nematodes and NAD-dependent activation of sirtuin by analyzing the relationship between NAD and DAF-16. Lifespan was extended when Caenorhabditis elegans were bred using medium containing NAD. An RNA interference experiment revealed that life extension by NAD was sir-2.1 dependent. However, life extension by NAD did not occur in daf-16-RNAi nematodes, suggesting that NAD-dependent longevity requires daf-16. This result suggested that different signaling pathways are involved in life extension resulting from caloric restriction and from NAD addition. Expression of sod-3, a target gene of daf-16, and increased oxidative-stress resistance and adiposity were observed in response to NAD addition, indicating that NAD activated daf-16 in each phenotype. These results suggest that NAD affected lifespan through the activation of SIR-2.1 and DAF-16 along a signaling pathway, namely insulin-like signalling pathway (at least parts of it), different from that associated with caloric restriction.

Fat accumulation in Caenorhabditis elegans is mediated by SREBP homolog SBP-1.

Research into the metabolism of fats may reveal potential targets for developing pharmaceutical approaches to obesity and related disorders. Such research may be limited, however, by the cost and time involved in using mammalian subjects or developing suitable cell lines. To determine whether invertebrates could be used to carry out such research more efficiently, we investigated the ability of Caenorhabditis elegans (C. elegans) to accumulate body fat following the consumption of excess calories and the mechanisms it uses to metabolize fat. C. elegans worms were grown on media containing various sugars and monitored for changes in body fat and expression of sbp-1, a homolog of the mammalian transcription factor SREBP-1c, which facilitates fat storage in mammals. The fat content increased markedly in worms exposed to glucose. In situ analysis of gene expression in transgenic worms carrying the GFP-labeled promoter region of sbp-1 revealed that sbp-1 mRNA was strongly expressed in the intestine. An sbp-1 knockdown caused a reduction in body size, fat storage, and egg-laying activity. RT-PCR analysis revealed a considerable decrease in the expression of fatty acid synthetic genes (including elo-2, fat-2, and fat-5) and a considerable increase of starvation-inducible gene acs-2. Normal egg-laying activity and acs-2 expression were restored on exposure to a polyunsaturated fatty acid. These findings suggest that SBP-1 and SREBP regulate the amount and composition of fat and response to starvation in a similar manner. Thus, C. elegans may be an appropriate subject for studying the metabolism of fats.

Elongation and desaturation of fatty acids are critical in growth, lipid metabolism and ontogeny of Caenorhabditis elegans.

Recently, it was reported that a deficit in the mouse stearoyl-CoA desaturase 1 gene decreases biosynthesis and accumulation of fatty acid and revitalizes the beta-oxidation of fatty acid. To examine the physiological role of fatty acid desaturase (FAT) and elongase (ELO)-gene transduction in ontogeny, fatty acid accumulation and individual lifespan, we performed bacteria-mediated RNA interference (RNAi) in the nematode Caenorhabditis elegans. Suppression of the expression of FAT-2 gene mRNA caused a drastic decrease in the amount of body fat and defects in egg-hatching. The amount of body fat was markedly decreased, and body size reduced, by down regulation of FAT-6 and FAT-7, whereas lifespan was drastically reduced. RNAi of the FAT-2 gene caused a remarkable increase of the beta-oxidation-related gene expression and the DAF-16 transcriptional activity, whereas, ELO-2 RNAi caused a remarkable decrease in fatty acid biosynthesis-related gene expression. Additionally, RNAi of FAT-6 decreased the mRNA levels of the genes involved in fatty acid synthesis, and FAT-7 RNAi increased the mRNA levels of beta-oxidation system genes. These results indicated that the elongation and desaturation of fatty acids are integral to various phenomena such as ontogeny and lifespan and play important roles in fatty acid accumulation and consumption.