FRI0535 NEWLY DETECTED HYPERTHYROIDISM WITH THERAPEUTIC INDICATIONS IN RHEUMATIC DISEASE PATIENTS AND HEALTHY CONTROLS IN JAPAN: A RETROSPECTIVE COHORT STUDY

Background:

Thyroid disorders are known as common comorbidities of rheumatic diseases(RD) [1]. However, data regarding prevalence of hyperthyroidism with treatment indication in RD patients are limited.

Objectives:

This study aims to reveal and compare the frequency of newly developed hyperthyroidism with treatment indication between RD patients and healthy controls (HC), and identify risk factors to identify patients whose thyroid function should be followed up carefully.

Methods:

We retrospectively reviewed charts of RD patients and HC who had thyroid stimulating hormone (TSH) measured at least once between 2004 and 2018 from immuno-rheumatology center and preventive medicine center in St. Luke’s International Hospital, Japan. We compared frequency of hyperthyroidism requiring treatment (TSH ≦ 0.1μU/mL or for which physicians started treatment) with Kaplan-Meier curve and log rank test. Cox regression multivariate analysis was performed to reveal risk factors for the new onset of hyperthyroidism with treatment indication in participants without treatment-indicated hyperthyroidism at initial assessments.

Results:

Overall, 2307 RD patients and 78251 HC were included. Newly detected hyperthyroidism with treatment indication were significantly more frequent in RD patients at initial assessment (1.3% vs 0.5 %, p < 0.001) and in total (2.9% vs 1.7%, p<0.001) (Table 1, Figure 1). Cox regression multivariate analysis revealed systemic lupus erythematosis (SLE), polymyositis dermatomyositis (PMDM), mixed connective tissue disease (MCTD) as significant risk factors of new developments of hyperthyroidism during follow up after adjusting confounders. (Table 2)

Table 1.

Patients characteristics and results of hyperthyroidism

Rheumatic Disease (n = 2307)Control (n = 78251)p.valueAge(yr)53.7 (16.2)46.1 (11.9)<0.001Female (%)1826 (79.2)38632 (49.4)<0.001 Rheumatoid arthritis (%)1091 (47.3)-NA Spondyloarthritis161 (7.0)-NA ANA associated disease (%)944 (40.9)-NA  SLE(%)363 (15.7)-NA  SS (%)396 (17.2)-NA  PMDM(%)104 (4.5)-NA  SSc (%)222 (9.6)-NA  MCTD (%)43 (1.9)-NA Vasculitis (%)202 (8.8)-NA Others (%)244 (10.6)-NATimes of TSH measurement2.0 [1.0, 5.0]5.0 [3.0, 9.0]<0.001Follow up of TSH (days)258.00 [0, 1315]1992 [958, 3632]<0.001Baseline TSH (μU/mL)2.28 (3.21)2.15 (4.07)0.137 ≦0.45 μU/mL (%)86 (3.7)1371 (1.8)<0.001 ≦0.1 μU/mL (%)29 (1.3)389 (0.5)<0.001Baseline FreeT4 (μU/mL)1.16 (0.24)1.30 (0.20)<0.001≧1.65 μU/mL (%)17 (0.8)2355 (3.0)<0.001TSH level in follow up ≦0.45 μU/mL (%)231 (0.0)3926 (5.0)<0.001 ≦0.1 μU/mL (%)84 (3.6)1388 (1.8)<0.001Newly detected hyperthyroidism with treatment indication (%)68 (2.9)1350 (1.7)<0.001 At initial assessment (%)29 (1.3)389 (0.5)<0.001 In follow up (%)39 (1.6)961 (1.2)<0.001Treatment for hyperthyroidism (%)21 (0.9)325 (0.4)0.002Figure 1.

Hyperthyroidism with treatment indication in rheumatic patients and control

Table 2.

Risk factors for newly detected hyperthyroidism with treatment indication

Adjusted HRp valueAge0.99 (0.98-0.99)< 0.001Female2.68 (2.31-3.12)< 0.001BMI1.04 (1.02-1.06)< 0.001Baseline TSH ≦ 0.455.71 (4.47-7.30)< 0.001Baseline Free T4 ≧ 1.651.16 (0.79-1.69)0.45Rheumatoid arthritis1.05 (0.50-2.21)0.90ANA associated diseases-- SLE2.29 (1.11-4.71)0.025 SS1.91 (0.91-4.01)0.089 PMDM12.90 (5.50-30.22)< 0.001 SSc0.67 (0.18-2.43)0.541 MCTD8.02 (2.62-24.51)< 0.001Vasculitis1.44 (0.35-5.92)0.610Spondyloarthritis3.04 (0.74-12.52)0.120Others1.98 (0.67-5.81)0.214

Conclusion:

Hyperthyroidism with therapeutic indications are considerably more frequent in RD patients (particularly with SLE, PMDM and MCTD) both at initial assessment and during follow up. We recommend routine screening at initial assessment and careful follow up of thyroid function test in those patients.

References:

[1] Rev Bras Rheumatol 2012;52(3):417-430

Disclosure of Interests:

None declared

AB0533 ANTI-NEUTROPHIL CYTOPLASMIC ANTIBODY (ANCA) IN GENERAL POPULATION WITHOUT ANCA ASSOCIATED VASCULITIS

Background:

Currently it is hypothesized that many systemic autoimmune diseases occur due to environmental risk factors in addition to genetic risk factors. Anti-Neutrophil Cytoplasmic Antibody (ANCA) is mainly associated with three systemic autoimmune disease including granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), eosinophilic granulomatosis with polyangiitis (EGPA). It is known that ANCA can be positive before clinical symptoms in patients with known diagnosis of GPA and ANCA titers rise before clinical manifestations appear. However, prevalence of ANCA among general population is not well known. It has not been described as well how many of people with positive ANCA eventually develop clinical manifestations of ANCA associated Vasculitis.

Objectives:

This study aims to estimate prevalence of ANCA in general population without ANCA associated Vasculitis. It also describes natural disease course of people with positive ANCA without ANCA associated Vasculitis. Risk factors for positive ANCA are also analyzed.

Methods:

This is a single center retrospective study at Center for Preventive Medicine of St. Luke’s International Hospital in Tokyo. ANCA was checked among the patients who wished to between 2018 and 2019. St. Luke’s Health Check-up Database (SLHCD) was utilized to collect the data. The patients whose serum was measured for ANCA were identified. The data for basic demographics, social habits, dietary habits and laboratory data were extracted. The charts of the patients with positive ANCA were reviewed.

Results:

Sera of total 1204 people were checked for ANCA. Of these 1204 people, 587 (48.8%) are male and the mean age was 55.8 years (32.6 to 79). There were total 11 patients with positive ANCA. Myeloperoxidase ANCA (MPO-ANCA) was positive for 3 patients and proteinase 3 ANCA (PR3-ANCA) was positive for 8 patients. Of these 11 patients, 5 were male (45.5%) and the mean age was 54.6 years. Two patients had history of autoimmune disease (primary biliary cirrhosis and ulcerative colitis). Five patients were evaluated by rheumatologists with the median follow-up period of 274 days. None of them developed clinical signs and symptoms of ANCA associated Vasculitis. Four out of five patients had ANCA checked later, two of which turned negative. The prevalence of ANCA in this cohort was 0.9% (95% confidence interval [95% CI]: 0.5% to 1.6%). Univariate analysis was performed to identify risk factors of positive ANCA. The variables analyzed include age, gender, body mass index (BMI), smoking habits, alcohol intake, dietary habits (fruits, fish, red meat), hypertension, dyslipidemia, and laboratory data. None of these variables demonstrated statistically significant differences except for positive rheumatoid factor (ANCA positive group: 33 % vs ANCA negative group: 9.1%, p value = 0.044).

Conclusion:

The prevalence of ANCA in this cohort was 0.9% (95% CI: 0.5% to 1.6%). None of them who had a follow-up developed ANCA associated Vasculitis during the follow-up period. Longer follow-up and more patients are necessary to determine natural course of people with positive ANCA.

Disclosure of Interests:

None declared

SAT0525 EFFICACY AND SAFETY OF MZR FOR IgG4-RELATED DISEASE

Background:

IgG4-Related Disease (IgG4RD) is known to cause multiple organ lesions with infiltration of IgG4-positive plasma cells, and patients often have relapses with tapering treatments despite an initial good response to glucocorticoids therapy. Mizoribine (MZR) is an immunosuppressant working as an inhibitor of purine synthesis, which mechanism of action is similar to mycophenolate mofetil. Data regarding the efficacy and safety of MZR on IgG4RD is limited although some previous case reports1showed effectiveness for IgG4RD.

Objectives:

This study aims to assess the efficacy and safety of MZR in patients with IgG4RD.

Methods:

We retrospectively reviewed charts of IgG4RD patients who used MZR between January 2004 and December 2019 at Immuno-Rheumatology Center in St. Luke’s International Hospital, Tokyo, Japan. We investigated basic demographics, involved organs, results of blood tests including IgG and IgG4 titer, and medications used including glucocorticoid and other immunosuppressants (IS). We followed IgG4 titer, dose of glucocorticoid, flare of disease and retention of MZR at the beginning, 6 and 12months after starting MZR. We compared changes in PSL (prednisolone) doses and IgG4 titers over time using Friedman test with Bonferroni correction. We also checked adverse events during follow up.

Results:

Twenty-two patients with IgG4RD who used MZR were included. Median age was 62 years old, and 15 (68.2%) patients are male. Lacrimal and salivary glands, pancreatitis and retroperitoneal fibrosis were common lesions. All patients were initially treated with glucocorticoids. Flare was observed in 5 (22.7 %) patients before initiation of MZR. The number of patients who continued MZR without flare are 19 (86.4 %) at 6 months, and 14 (73.7 %) at 12 months. IgG4 titer significantly declined at 6 and 12 months from baseline although significant consecutive decrease in PSL dose (Figure 1, 2). Liver dysfunctions are commonest adverse events (n=16, 72.7%) but mild (grade1; n=15, 68.2%) and most cases are apparently due to other reasons. Serious infection (SI) occurred in 3 (13.6%) patients in total follow up, however no SI were observed during 1 year after MZR treatment.

Conclusion:

MZR can be safely used in patients of IgG4RD with high retention rate, and seemed to have steroid-sparing effect. Prospective comparative studies are needed.

References:

[1]Nanke Y, Kobashigawa T, Yago T, Kamatani N, Kotake S. A case of Mikulicz’s disease, IgG4-related plasmacytic syndrome, successfully treated by corticosteroid and mizoribine, and then by mizoribine alone. Intern Med 49: 1449-1453, 2010.

Table 1.

Patient characteristics

    Table 2.

Disease and treatment status before and after initiation of MZR

    Figure 1.

Serum IgG4 level changes

Figure 2.

Changes in the PSL dose over time

Disclosure of Interests:

None declared

AB0198 SMOKING AND POSITIVITY OF RHEUMATOID FACTOR AND ANTI-CYCLIC CITRULLINATED PEPTIDE ANTIBODY IN THE GENERAL POPULATION

Background:

It is well known that rheumatoid arthritis (RA) occurs due to environmental risk factors in addition to genetic risk factors. Rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibody (ACPA) are strongly associated with RA, and these biomarkers could turn to be positive before development of clinical symptoms. While smoking, particularly Brinkman index (BI) is well known as a risk factor for RA and ACPA positivity, it is still unclear whether smoking intensity or smoking duration contribute more to positive RF and ACPA.

Objectives:

This study aims to evaluate risk factors for RF and ACPA positivity in the general population. It also describes whether smoking intensity, duration, and BI are significant.

Methods:

This is a cross-sectional, observational, single center study. We reviewed the baseline characteristics of the general population who checked RF and ACPA at Preventive Medicine Center in St. Luke’s International Hospital, Tokyo, Japan from January 2004 to December 2018.

The data for basic demographics, dietary habit, smoking intensity, smoking duration, BI, and blood tests including RF and ACPA were extracted. The data was analyzed statistically.

Results:

A total of 127472 people who checked RF are included. Of these 127472 people, 64504 (50.6%) are male and the mean age was 44.9 years. RF was positive in 11477 people (9.0%). Among these, 1667 (1.2%) were checked for ACPA, and 21 people (1.3%) had positive ACPA. None of variables demonstrated significant association with RF positivity. In contrast, BI and smoking duration was significantly associated with an increased risk of ACPA positivity (13.3 years vs 7.49 years, p value = 0.023), although the number of cigarettes smoked was not. The smoking duration for 10 years or more was associated with an increased risk of ACPA positivity even after adjusted for age and sex (adjusted hazard ratio: 2.47 [95% confidence interval: 1.04-5.87]; p=0.04).

Conclusion:

In this study, no significant risk factor for positive RF was found. Even smoking was not associated with RF positivity. On the other hand, smoking duration, not smoking intensity was significantly associated with an increased risk of ACPA positivity.

References:

[1]Verpoort KN. Association of smoking with the constitution of the anti-cyclic citrullinated peptide response in the absence of HLA-DRB1 shared epitope alleles. Arthritis Rheum 2007;56:29138.

Table 1.

Patient characteristics with RF and ACPA positivity

RF positive (n=11477)RF negative (n=115995)p valueACPA positive (n=21)ACPA negative (n=1646)p valueAge44.86 (12.32)44.94 (12.47)0.5437.90 (9.07)45.26 (12.58)0.008Male (%)5659 (49.3)57309 (49.4)0.84511 (52.4)834 (50.7)1Body Mass Index22.33 (3.38)22.35 (3.40)0.52121.64 (3.28)22.34 (3.37)0.346Smoker, total (%)4509 (39.3)45738 (39.4)0.77212 (57.1)642 (39.0)0.115Current smoker (%)1959 (17.1)20483 (17.7)0.1148 (38.1)277 (16.8)0.017Previous smoker (%)2550 (22.2)25255 (21.8)0.2714 (19.0)365 (22.2)1Brinkman index144.8 (299.3)145.2 (313.8)0.897280.9 (409.7)145.3 (300.3)0.041Number of cigarettes (/day)17.7 (18.5)17.4 (13.3)0.16619.8 (12.0)17.4 (12.1)0.511Smoking Duration (years)7.43 (11.68)7.45 (11.66)0.85113.33 (14.11)7.49 (11.68)0.023Alcohol Drinker (%)6972 (60.7)70010 (60.4)0.41810 (47.6)1005 (61.1)0.261Alcohol Intake (g/day)13.67 (21.88)13.58 (21.32)0.67616.70 (26.89)14.06 (22.16)0.59Exercise ≧3 times/week (%)2792 (24.3)28293 (24.4)0.8825 (23.8)402 (24.4)1White blood cell (103/μL)5.32 (1.46)5.35 (1.50)0.135.59 (2.05)5.37 (1.54)0.52Hemoglobin (g/dL)13.82 (1.44)13.82 (1.45)0.75314.12 (1.03)13.83 (1.43)0.36Creatinine (mg/dL)0.73 (0.20)0.73 (0.25)0.1940.76 (0.16)0.73 (0.18)0.586AST (U/L)21.89 (9.39)21.93 (11.65)0.78220.95 (6.02)21.68 (8.29)0.69LDL cholesterol (mg/dL)115.41 (30.90)115.48 (30.77)0.815112.62 (33.26)115.36 (31.03)0.688Triglyceride (mg/dL)97.63 (78.46)97.70 (80.36)0.929100.57 (63.40)97.85 (78.37)0.874Uric Acid (mg/dL)5.32 (1.42)5.33 (1.42)0.6235.76 (1.34)5.34 (1.42)0.172

Disclosure of Interests:

None declared

Manufactural impact of the solid-state saccharification process in rice-flavor baijiu production

Rice-flavor baijiu is a traditional Chinese liquor that is manufactured using a solid-state saccharification process. In the present study, we investigated the role of the process in making of rice-flavor baijiu using chemical and biological quantitative analysis approaches. More than 70% of starch in rice decomposed to glucose after saccharification. In addition, the number of fungal cells, saccharification activity, and lactic acid concentration increased. Rhizopus oryzae was identified as the major fungus proliferating under saccharification based on denaturing gradient gel electrophoresis analysis targeting the internal spacer transcribed region. Lactic acid bacteria were not detected by 16S rRNA gene-based next-generation sequencing analysis during saccharification. Conversely, R. oryzae, isolated from xiaoqu, exhibited a capacity to produce lactic acid. The results imply that the solid-state saccharification is essential not only for saccharification but also for the culture of R. oryzae, which promote saccharification activity and lactic acid production. We also investigated the most appropriate temperature for solid-state saccharification and 35°C was the optimum temperature for R. oryzae cultivation, enzyme production, and saccharification. The results could facilitate the efficient and stable manufacture of rice-flavor baijiu.

Essential and distinct roles of phosphatidylinositol 4-kinases, Pik1p and Stt4p, in yeast autophagy

Autophagy is a degradative cellular pathway that protects eukaryotic cells from starvation/stress. Phosphatidylinositol 4-kinases, Pik1p and Stt4p, are indispensable for autophagy in budding yeast, but participation of PtdIns-4 kinases and their product, phosphatidylinositol 4-phosphate [PtdIns(4)P], is not understood. Nanoscale membrane lipid distribution analysis showed PtdIns(4)P is more abundant in yeast autophagosomes in the luminal leaflet than the cytoplasmic leaflet. PtdIns(4)P is confined to the cytoplasmic leaflet of autophagosomal inner and outer membranes in mammalian cells. Using temperature-conditional single PIK1 or STT4 PtdIns 4-kinase mutants, autophagic bodies in the vacuole of PIK1 and STT4 mutant cells dramatically decreased at restrictive temperatures, and the number of autophagosomes in the cytosol of PIK1 mutants cells was also decreased, whereas autophagosome levels of STT4 mutant cells were comparable to that of wild-type and STT4 mutant cells at permissive temperatures. Localization of PtdIns(4)P in the luminal leaflet in the biological membrane is a novel finding, and differences in PtdIns(4)P distribution suggest substantial differences between yeast and mammals. We also demonstrate in this study that Pik1p and Stt4p play essential roles in autophagosome formation and autophagosome-vacuole fusion in yeast cells, respectively.

Shochu slop is an excellent medium for Escherichia coli K-12

We found that shochu slop, the residue generated during the production of distilled shochu liquor, which must be treated as industrial waste, can be used as an excellent medium for Escherichia coli culture. LB medium is generally used in laboratories for culturing E. coli. However, it is not the optimal medium for E. coli culture because the bacterial cells cannot grow to very high densities in LB medium. On the other hand, E. coli can grow to higher densities in Terrific broth and this medium is used when researchers want to grow E. coli to high density or to obtain a protein with high yield. In this study, we removed solid matter from shochu slop, adjusted the pH of the mixture to 7 and subsequently used the slop for E. coli culture. The ability of shochu slop to support E. coli growth was compared with those of LB Miller medium and Terrific broth. The results indicate that sweet potato shochu slop as culture medium for E. coli is comparable to Terrific broth and much better than LB Miller medium in terms of supporting cell proliferation, and plasmid and enzyme production. SIGNIFICANCE AND IMPACT OF THE STUDY: Shochu manufacturers incur a cost to dispose shochu slop, which is recognized as food manufactural residues. Escherichia coli has been used in laboratories and in industry. However, culture media used in the laboratories are expensive and those used in industry are expensive because of their large scale. We found that sweet potato shochu slop is an excellent culture medium for E. coli. This finding is not only useful for laboratories and industry, but also beneficial to the effective utilization of this renewable resource to create a sustainable society.

Characterization of amylolytic enzyme overproducing mutant of Aspergillus luchuensis obtained by ion beam mutagenesis

Aspergillus luchuensis is a kuro (black) koji fungus that has been used as a starch degrader for the awamori- and shochu-making industries in Japan. In this study, we investigated the effect of ion beam irradiation on A. luchuensis RIB2601 and obtained a high starch-degrading mutant strain U1. Strain U1 showed reduced growth rate, whereas it showed higher α-amylase, glucoamylase, and α-glucosidase activities on a mycelial mass basis than the wild type (wt) strain both on agar plates and in rice koji. In addition, strain U1 showed higher N-acetylglucosamine content in the cell wall and higher sensitivity to calcofluor white, suggesting a deficiency in cell wall composition. Interestingly, produced protein showed higher expression of acid-labile α-amylase (AmyA) and glucoamylase (GlaA) in strain U1, although real-time RT-PCR indicated no significant change in the transcription of the amyA or glaA gene. These results suggested that the high amylolytic activity of strain U1 is attributable to a high AmyA and GlaA production level, but the elevated production is not due to transcriptional regulation of the corresponding genes. Furthermore, RNA-seq analysis indicated that strain U1 shows transcriptional changes in at least 604 genes related to oxidation-reduction, transport, and glucosamine-containing compound metabolic processes, which may be involved in the deficient cell wall composition of strain U1.

Multi-gene phylogenetic analysis reveals that shochu-fermenting Saccharomyces cerevisiae strains form a distinct sub-clade of the Japanese sake cluster

Shochu is a traditional Japanese distilled spirit. The formation of the distinguishing flavour of shochu produced in individual distilleries is attributed to putative indigenous yeast strains. In this study, we performed the first (to our knowledge) phylogenetic classification of shochu strains based on nucleotide gene sequences. We performed phylogenetic classification of 21 putative indigenous shochu yeast strains isolated from 11 distilleries. All of these strains were shown or confirmed to be Saccharomyces cerevisiae, sharing species identification with 34 known S. cerevisiae strains (including commonly used shochu, sake, ale, whisky, bakery, bioethanol and laboratory yeast strains and clinical isolate) that were tested in parallel. Our analysis used five genes that reflect genome-level phylogeny for the strain-level classification. In a first step, we demonstrated that partial regions of the ZAP1, THI7, PXL1, YRR1 and GLG1 genes were sufficient to reproduce previous sub-species classifications. In a second step, these five analysed regions from each of 25 strains (four commonly used shochu strains and the 21 putative indigenous shochu strains) were concatenated and used to generate a phylogenetic tree. Further analysis revealed that the putative indigenous shochu yeast strains form a monophyletic group that includes both the shochu yeasts and a subset of the sake group strains; this cluster is a sister group to other sake yeast strains, together comprising a sake-shochu group. Differences among shochu strains were small, suggesting that it may be possible to correlate subtle phenotypic differences among shochu flavours with specific differences in genome sequences. Copyright © 2017 John Wiley & Sons, Ltd.

Key volatile compounds in red koji-shochu, a Monascus-fermented product, and their formation steps during fermentation

Red koji, which refers the solid culture grown koji mold on the steamed rice, is one of the ingredients of Asian fermented foods including the Japanese spirit shochu. This study was aimed at elucidating the characteristic flavor and key volatile compounds of red koji-shochu as well as the mechanism of their formation. Sensory evaluation showed that red koji-shochu has the distinctive flavors cheese, sour, milky, and oily. Fifteen key volatile compounds of red koji-shochu were identified by gas chromatography-mass spectrometry and high-performance liquid chromatography, and by comparison between red koji-shochu and white koji-shochu, as another typical shochu. The mash analysis revealed that ketone compounds and short-chain acids derive from red koji. Furthermore, although other key compounds were produced by yeast, it is highly likely that their concentrations were affected directly or indirectly by the high activities of protease and lipase in red koji.

Effect of electrical stimulation-induced muscle force and streptomycin treatment on muscle and trabecular bone mass in early-stage disuse musculoskeletal atrophy

OBJECTIVES

The aim was to determine whether daily muscle electrical stimulation (ES) and streptomycin treatment would have positive or negative effects on trabecular bone mass in disuse rats.

METHODS

Seven-week-old male F344 rats were randomly divided into five groups of eight animals each: an age-matched control group (CON); a sciatic denervation group (DN); a DN + direct electrical stimulation group (DN+ES); a DN + streptomycin treatment group (DN+SM); and a DN+ES+SM group. The tibialis anterior (TA) muscles in all ES groups were stimulated with 16mA at 10Hz for 30 min/day, six days/week, for one week. Bone volume and structure were evaluated using micro-CT, and histological examinations of the tibiae were performed.

RESULTS

Direct ES significantly reduced the disuse-induced trabecular bone loss. Osteoid thickness were also significantly greater in the ES groups than in the DN group. Micro CT and histomorphological parameters were significantly lower in the DN+ES+SM group than in the DN+ES group, while there were no significant differences between the DN and DN+SM groups.

CONCLUSIONS

These results suggest that ES-induced muscle force reduced trabecular bone loss, and streptomycin treatment did not induce bone loss, but attenuated the effects of ES-induced muscle force on reducing the loss of disused bone.

Electrical stimulation of denervated rat skeletal muscle retards trabecular bone loss in early stages of disuse musculoskeletal atrophy

OBJECTIVES

We aimed to determine the intensity of muscle stimulation required to prevent structural failure as well as bone and skeletal muscle loss after denervation-induced disuse.

METHODS

Seven-week-old rats (weight, 198-225 g) were randomly assigned to age-matched groups comprising control (CON), sciatic nerve denervation (DN) or direct electrical stimulation (ES) one day later [after denervation] with 4, 8 and 16 mA at 10 Hz for 30 min/day, six days/week, for one or three weeks. Bone architecture and mean osteoid thickness in histologically stained tibial sections and tension in tibialis anterior muscles were assessed at one and three weeks after denervation.

RESULTS

Direct ES with 16 mA generated 23-30% maximal contraction force. Denervation significantly decreased trabecular bone volume fraction, thickness and number, connectivity density and increased trabecular separation in the DN group at weeks one and three. Osteoid thickness was significantly greater in the ES16 group at week one than in the DN and other ES groups. Trabecular bone volume significantly correlated with muscle weight.

CONCLUSIONS

Relatively low-level muscle contraction induced by low-frequency, high-intensity electrical muscle stimulation delayed trabecular bone loss during the early stages (one week after DN) of musculoskeletal atrophy due to disuse.