Running title: Carnosine and β-alanine in exercise and training Word count: 6227 2 Acknowledgements:

This multicentre, international study showed moderate reliability of simple capillaroscopic definitions for describing morphology of capillaries by rheumatologists with varying levels of expertise. Novices were capable of distinguishing normal from abnormal capillaries by means of a 1-h training session. In future studies, the class not evaluable may be obsolete.

IntroductionMicroscopic bowel inflammation is present in up to 50% of patients with spondyloarthritis (SpA) and is associated with more severe disease. Currently no reliable biomarkers exist to identify patients at risk. Calprotectin is a sensitive marker of neutrophilic inflammation, measurable in serum and stool.ObjectivesTo assess whether serum and faecal calprotectin in addition to C-reactive protein (CRP) can be used to identify patients with SpA at risk of microscopic bowel inflammation.MethodsSerum calprotectin and CRP were measured in 125 patients with SpA. In 44 of these patients, faecal samples were available for calprotectin measurement. All 125 patients underwent an ileocolonoscopy to assess the presence of microscopic bowel inflammation.ResultsMicroscopic bowel inflammation was present in 53 (42.4%) patients with SpA. Elevated serum calprotectin and CRP were independently associated with microscopic bowel inflammation. Faecal calprotectin was also significantly higher in patients with microscopic bowel inflammation. Patients with CRP and serum calprotectin elevated had a frequency of bowel inflammation of 64% vs 25% in patients with low levels of both. When either CRP or serum calprotectin was elevated, the risk was intermediate (40%) and measuring faecal calprotectin provided further differentiation. Hence we suggest a screening approach where initially serum calprotectin and CRP are assessed and, if necessary, faecal calprotectin. The model using this scenario provided an area under the ROC curve of 74.4% for detection of bowel inflammation.ConclusionsCalprotectin measurements in stool and serum, in addition to CRP, may provide a promising strategy to identify patients with SpA at risk of bowel inflammation and could play a role in overall patient stratification.

Carnosine is an abundant dipeptide in human skeletal muscle with proton buffering capacity. There is controversy as to whether training can increase muscle carnosine and thereby provide a mechanism for increased buffering capacity. This study investigated the effects of 5 weeks sprint training combined with a vegetarian or mixed diet on muscle carnosine, carnosine synthase mRNA expression and muscle buffering capacity. Twenty omnivorous subjects participated in a 5 week sprint training intervention (2-3 times per week). They were randomized into a vegetarian and mixed diet group. Measurements (before and after the intervention period) included carnosine content in soleus, gastrocnemius lateralis and tibialis anterior by proton magnetic resonance spectroscopy ((1)H-MRS), true-cut biopsy of the gastrocnemius lateralis to determine in vitro non-bicarbonate muscle buffering capacity, carnosine content (HPLC method) and carnosine synthase (CARNS) mRNA expression and 6 × 6 s repeated sprint ability (RSA) test. There was a significant diet × training interaction in soleus carnosine content, which was non-significantly increased (+11%) with mixed diet and non-significantly decreased (-9%) with vegetarian diet. Carnosine content in other muscles and gastrocnemius buffer capacity were not influenced by training. CARNS mRNA expression was independent of training, but decreased significantly in the vegetarian group. The performance during the RSA test improved by training, without difference between groups. We found a positive correlation (r = 0.517; p = 0.002) between an invasive and non-invasive method for muscle carnosine quantification. In conclusion, this study shows that 5 weeks sprint training has no effect on the muscle carnosine content and carnosine synthase mRNA.