The Acute, Short-, and Long-Term Effects of Endurance Exercise on Skeletal Muscle Transcriptome Profiles.

A better understanding of the cellular and molecular mechanisms that are involved in skeletal muscle adaptation to exercise is fundamentally important to take full advantage of the enormous benefits that exercise training offers in disease prevention and therapy. The aim of this study was to elucidate the transcriptional signatures that distinguish the endurance-trained and untrained muscles in young adult males (24 ± 3.5 years). We characterized baseline differences as well as acute exercise-induced transcriptome responses in vastus lateralis biopsy specimens of endurance-trained athletes (ET; n = 8; VO2max, 67.2 ± 8.9 mL/min/kg) and sedentary healthy volunteers (SED; n = 8; VO2max, 40.3 ± 7.6 mL/min/kg) using microarray technology. A second cohort of SED volunteers (SED-T; n = 10) followed an 8-week endurance training program to assess expression changes of selected marker genes in the course of skeletal muscle adaptation. We deciphered differential baseline signatures that reflected major differences in the oxidative and metabolic capacity of the endurance-trained and untrained muscles. SED-T individuals in the training group displayed an up-regulation of nodal regulators of oxidative adaptation after 3 weeks of training and a significant shift toward the ET signature after 8 weeks. Transcriptome changes provoked by 1 h of intense cycling exercise only poorly overlapped with the genes that constituted the differential baseline signature of ETs and SEDs. Overall, acute exercise-induced transcriptional responses were connected to pathways of contractile, oxidative, and inflammatory stress and revealed a complex and highly regulated framework of interwoven signaling cascades to cope with exercise-provoked homeostatic challenges. While temporal transcriptional programs that were activated in SEDs and ETs were quite similar, the quantitative divergence in the acute response transcriptomes implicated divergent kinetics of gene induction and repression following an acute bout of exercise. Together, our results provide an extensive examination of the transcriptional framework that underlies skeletal muscle plasticity.

Altered tissue oxygenation in patients with post COVID-19 syndrome.

BACKGROUND: Post COVID-19 syndrome (PCS) is a complex condition with partly substantial impact on patients' social and professional life and overall life quality. Currently, the underlying cause(s) of PCS are unknown. Since PCS-specific symptoms could be associated with systemic alterations in tissue oxygen supply, we aimed to investigate changes in tissue oxygenation in patients with PCS. METHODS: A case-control study including 30 PCS patients (66.6 % males, 48.6 ± 11.2 years, mean time after (first) acute infection: 324 days), 16 cardiologic patients (CVD) (65.5 % males, 56.7 ± 6.3 years) and 11 young healthy controls (55 % males, 28.5 ± 7.4 years) was conducted. Near infrared spectroscopy (NIRS) was used to assess changes in tissue oxygenation during an arterial occlusion protocol on the non-dominant forearm (brachioradialis, 760/850 nm, 5 Hz). The protocol included 10-min rest, a 2-min baseline measurement followed by a 3-min ischemic period (upper-arm cuff, 50 mmHg above resting systolic blood pressure) and a 3-min reoxygenation period. PCS patients were grouped by presence of arterial hypertension and elevated BMI to assess the impact of risk factors. RESULTS: No differences in mean tissue oxygenation in the pre-occlusion phase existed between groups (p ≥ 0.566). During ischemia, comparisons of linear regressions slopes revealed slower oxygen desaturation for PCS patients (-0.064 %/s) compared to CVD patients (-0.08 %/s) and healthy subjects (-0.145 %/s) (p < 0.001). After cuff release, slowest speed for reoxygenation was detected in PCS patients at 0.84 %/s compared to CVD patients (1.04 %/s) and healthy controls (CG: 2.07 %/s) (p < 0.001). The differences between PCS patients and CVD patients during ischemia remained significant also after correction for risk factors. Analyses of complications during acute infection, persistence of PCS symptoms (time after acute infection), or PCS severity (number of lead symptoms) as confounding factors did not reveal a significant effect. CONCLUSIONS: This study provides evidence that the rate of tissue oxygen consumption is persistently altered in PCS and that PCS patients show an even slower decline in tissue oxygenation during occlusion than CVD patients. Our observations may at least partly explain PCS-specific symptoms such as physical impairment and fatigue.

miR-486 attenuates cardiac ischemia/reperfusion injury and mediates the beneficial effect of exercise for myocardial protection.

Exercise and its regulated molecules have myocardial protective effects against cardiac ischemia/reperfusion (I/R) injury. The muscle-enriched miR-486 was previously identified to be upregulated in the exercised heart, which prompted us to investigate the functional roles of miR-486 in cardiac I/R injury and to further explore its potential in contributing to exercise-induced protection against I/R injury. Our data showed that miR-486 was significantly downregulated in the heart upon cardiac I/R injury. Both preventive and therapeutic interventions of adeno-associated virus 9 (AAV9)-mediated miR-486 overexpression could reduce cardiac I/R injury. Using AAV9 expressing miR-486 with a cTnT promoter, we further demonstrated that cardiac muscle cell-targeted miR-486 overexpression was also sufficient to protect against cardiac I/R injury. Consistently, miR-486 was downregulated in oxygen-glucose deprivation/reperfusion (OGDR)-stressed cardiomyocytes, while upregulating miR-486 inhibited cardiomyocyte apoptosis through PTEN and FoxO1 inhibition and AKT/mTOR activation. Finally, we observed that miR-486 was necessary for exercise-induced protection against cardiac I/R injury. In conclusion, miR-486 is protective against cardiac I/R injury and myocardial apoptosis through targeting of PTEN and FoxO1 and activation of the AKT/mTOR pathway, and mediates the beneficial effect of exercise for myocardial protection. Increasing miR-486 might be a promising therapeutic strategy for myocardial protection.

Effects of Training Status and Exercise Mode on Global Gene Expression in Skeletal Muscle.

The aim of this study was to investigate differences in skeletal muscle gene expression of highly trained endurance and strength athletes in comparison to untrained individuals at rest and in response to either an acute bout of endurance or strength exercise. Endurance (ET, n = 8, VO2max 67 ± 9 mL/kg/min) and strength athletes (ST, n = 8, 5.8 ± 3.0 training years) as well as untrained controls (E-UT and S-UT, each n = 8) performed an acute endurance or strength exercise test. One day before testing (Pre), 30 min (30'Post) and 3 h (180'Post) afterwards, a skeletal muscle biopsy was obtained from the m. vastus lateralis. Skeletal muscle mRNA was isolated and analyzed by Affymetrix-microarray technology. Pathway analyses were performed to evaluate the effects of training status (trained vs. untrained) and exercise mode-specific (ET vs. ST) transcriptional responses. Differences in global skeletal muscle gene expression between trained and untrained were smaller compared to differences in exercise mode. Maximum differences between ET and ST were found between Pre and 180'Post. Pathway analyses showed increased expression of exercise-related genes, such as nuclear transcription factors (NR4A family), metabolism and vascularization (PGC1-α and VEGF-A), and muscle growth/structure (myostatin, IRS1/2 and HIF1-α. The most upregulated genes in response to acute endurance or strength exercise were the NR4A genes (NR4A1, NR4A2, NR4A3). The mode of acute exercise had a significant effect on transcriptional regulation Pre vs. 180'Post. In contrast, the effect of training status on human skeletal muscle gene expression profiles was negligible compared to strength or endurance specialization. The highest variability in gene expression, especially for the NR4A-family, was observed in trained individuals at 180'Post. Assessment of these receptors might be suitable to obtain a deeper understanding of skeletal muscle adaptive processes to develop optimized training strategies.

Cardiac endurance training alters plasma profiles of circular RNA MBOAT2.

Marathon running is an extreme physical activity, which determines cardiopulmonary adaption of athletes. Circular RNAs (circRNAs) as potential biomarkers in the blood stream have so far not been tested after such strenuous activities. In silico approaches were performed to identify the potential candidate circRNA MBOAT2. Next, we demonstrated high stability and conservation of circRNA MBOAT2 as well as its abundancy in human plasma. In addition to Sanger sequencing of the circRNA specific head-to-tail junction, or back-splice site, we established a synthetic plasmid standard which allowed exact copy number calculations of circRNA MBOAT2. We then analyzed plasmatic circRNA MBOAT2 and observed a significantly lower level 24 h after the marathon. Such alterations were correlated to physical exercise parameters confirming the role of circRNA MBOAT2 as a promising noncoding RNA biomarker detecting cardiopulmonary adaption.NEW & NOTEWORTHY In brief, we herein report a timeline of circulating circular RNA (circRNA) MBOAT2 in a cohort of marathon runners. Time-course analysis of plasmatic circRNA MBOAT2 demonstrated a significantly lowered level 24 h after the marathon. Abundancy of circRNA was correlated to physical exercise parameters highlighting the role of circRNA MBOAT2 as a valuable noncoding RNA biomarker detecting and following up cardiopulmonary adaption.

Combined effects of moderate exercise and short-term fasting on markers of immune function in healthy human subjects.

This study aimed to investigate the effects of a short-term (36 h) fasting period combined with an acute bout of exercise on markers of immune function and inflammation in healthy human subjects. Fourteen moderately trained male subjects (aged 19-39 yr) participated in a 36-h fasting trial (FA-T), followed by an acute bout of moderate exercise (60% V̇o2max). After 1 wk, the same subjects, as their own control, participated in a nonfasting trial (NFA-T) in which they performed an exercise trial of the same duration and intensity. Blood samples were taken before, immediately after, and 1 h after each exercise bout and analyzed for several immunological and metabolic markers. At baseline, fasting subjects showed lower levels of T cell apoptosis, lymphocyte-proliferative responses, IL-6, monocyte chemoattractant protein-1 (MCP-1), insulin, and leptin (P < 0.05) as well as higher levels of neutrophil oxidative burst and thiobarbituric acid reactive substances (TBARS) than those in the NFA-T (P < 0.05). After the exercise protocol, fasted subjects revealed higher T cell apoptosis, neutrophil oxidative burst, TBARS, TNFα, and MCP-1 levels as well as lower levels of lymphocyte-proliferative response, IL-6, insulin, and leptin than those in the NFA-T (P < 0.05). Short-term fasting aggravates perturbations in markers of immune function, and inflammation was induced by an acute moderate-intensity exercise protocol.

Exercise training reverses inflammation and muscle wasting after tobacco smoke exposure.

Long-term cigarette smoking induces inflammatory processes in the pulmonary system that are suggested to "spill over" into systemic inflammation. Regular exercise has been shown to have anti-inflammatory properties. The aim of the study was to investigate the effects of therapeutic exercise on inflammation and muscle wasting in smoke-exposed mice. C57BL/6J mice ( n = 30) were separated into three groups to receive either 1) no specific treatment (control group), 2) 8-mo exposure to cigarette smoke [smoke-exposed (SE) group], or 3) 8 mo of cigarette smoke combined with exercise training during the last 2 mo (SEex group). The inflammatory status was analyzed by quantifying levels of various plasma proteins using multiplex ELISA and detection of lymphocyte surface markers by flow cytometry. Muscle tissue was analyzed by histological techniques and measurements of RNA/protein expression. SE led to decreased maximal O2 uptake (V̇o2max) and maximal running speed ( Vmax), which was reversed by exercise ( P < 0.05). Expression of ICAM-1, VCAM-1, and CD62L on T cells increased and was reversed by exercise ( P < 0.05). Similarly, SE induced an increase of various inflammatory cytokines, which were downregulated by exercise. In muscle, exercise improved the structure, oxidative capacity, and metabolism by reducing ubiquitin proteasome system activation, stimulating insulin-like growth factor 1 expression, and the SE-induced inhibition of mammalian target of rapamycin signaling pathway ( P < 0.05). Exercise training reverses smoke-induced decline in exercise capacity, systemic inflammation, and muscle wasting by addressing immune-regulating, anabolic, and metabolic pathways.

Low-to-moderate intensity aerobic exercise training modulates irritable bowel syndrome through antioxidative and inflammatory mechanisms in women: Results of a randomized controlled trial.

Our aim was to explore the putative beneficial effects of low-to-moderate intensity exercise training program in patients with irritable bowel syndrome (IBS). This study evaluated the changes in blood oxidative stress status, inflammatory biomarkers and IBS severity symptoms following 24 weeks of moderate aerobic exercise in sedentary IBS patients. A total of 109 female volunteers (aged 18-41 yrs) who fulfilled Rome III criteria for the diagnosis of IBS were screened and 60 were randomized to exercise (EX, n = 30) and non-exercise (NON-EX, n = 30) groups. Exercise intervention favorably attenuated inflammation as indicated by plasma cytokines (IL-1ß, IL-6, IL-8, IL-10 and TNF-α), adenosine deaminase, oxidative stress (XO, MDA and NO) and enhanced antioxidants (SOD, CAT and GSH-Px) (P < .05), and these alterations correlate with promising improvements in IBS symptoms (P < .05). Taken together, low-to-moderate intensity exercise training program attenuates symptoms in IBS. Symptom improvement was associated with a reversal of the ratio of anti- to pro-inflammatory cytokines as well as facilitating blood redox homeostasis, suggesting an immune- and redox modulating function for exercise training.

Probing depth is an independent risk factor for HbA1c levels in diabetic patients under physical training: a cross-sectional pilot-study.

BACKGROUND: This cross-sectional study investigates the potential association between active periodontal disease and high HbA1c levels in type-2-diabetes mellitus subjects under physical training. METHODS: Women and men with a diagnosis of non-insulin-dependent diabetes mellitus and ongoing physical and an ongoing exercise program were included. Periodontal conditions were assessed according to the CDC-AAP case definitions. Venous blood samples were collected for the quantitative analysis of HbA1c. Associations between the variables were examined with univariate and multivariate regression models. RESULTS: Forty-four subjects with a mean age of 63.4 ± 7.0 years were examined. Twenty-nine subjects had no periodontitis, 11 had a moderate and 4 had a severe form of periodontal disease. High fasting serum glucose (p < 0.0001), high BMI scores (p = 0.001), low diastolic blood pressure (p = 0.030) and high probing depth (p = 0.036) were significantly associated with high HbA1c levels. CONCLUSIONS: Within the limitations of this study HbA1c levels are positively associated with high probing pocket depth in patients with non-insulin-dependent diabetes mellitus under physical exercise training. Control and management of active periodontal diseases in non-insulin-dependent patients with diabetes mellitus is reasonable in order to maximize therapeutic outcome of lifestyle interventions.

Forced exercise-induced osteoarthritis is attenuated in mice lacking the small leucine-rich proteoglycan decorin.

OBJECTIVE: Interterritorial regions of articular cartilage matrix are rich in decorin, a small leucine-rich proteoglycan and important structural protein, also involved in many signalling events. Decorin sequesters transforming growth factor ß (TGFß), thereby regulating its activity. Here, we analysed whether increased bioavailability of TGFß in decorin-deficient (Dcn-/-) cartilage leads to changes in biomechanical properties and resistance to osteoarthritis (OA). METHODS: Unchallenged knee cartilage was analysed by atomic force microscopy (AFM) and immunohistochemistry. Active transforming growth factor ß-1 (TGFß1) content within cultured chondrocyte supernatants was measured by ELISA. Quantitative real-time (RT)-PCR was used to analyse mRNA expression of glycosaminoglycan (GAG)-modifying enzymes in C28/I2 cells following TGFß1 treatment. In addition, OA was induced in Dcn-/- and wild-type (WT) mice via forced exercise on a treadmill. RESULTS: AFM analysis revealed a strikingly higher compressive stiffness in Dcn-/- than in WT cartilage. This was accompanied by increased negative charge and enhanced sulfation of GAG chains, but not by alterations in the levels of collagens or proteoglycan core proteins. In addition, decorin-deficient chondrocytes were shown to release more active TGFß1. Increased TGFß signalling led to enhanced Chst11 sulfotransferase expression inducing an increased negative charge density of cartilage matrix. These negative charges might attract more water resulting in augmented compressive stiffness of the tissue. Therefore, decorin-deficient mice developed significantly less OA after forced exercise than WT mice. CONCLUSIONS: Our study demonstrates that the disruption of decorin-restricted TGFß signalling leads to higher stiffness of articular cartilage matrix, rendering joints more resistant to OA. Therefore, the loss of an important structural component can improve cartilage homeostasis.

Consensus Statement Immunonutrition and Exercise.

In this consensus statement on immunonutrition and exercise, a panel of knowledgeable contributors from across the globe provides a consensus of updated science, including the background, the aspects for which a consensus actually exists, the controversies and, when possible, suggested directions for future research.

A randomized controlled trial examining the effects of 16 weeks of moderate-to-intensive cycling and honey supplementation on lymphocyte oxidative DNA damage and cytokine changes in male road cyclists.

The aim of this study was to investigate whether honey supplementation (70g, ninety minutes before each training session) attenuates changes in lymphocyte counts, DNA damage, cytokines, antioxidative and peroxidative biomarkers following moderate-to-intensive exercise training in male road cyclists. Healthy nonprofessional cyclists (n=24, aged 17-26years) were randomly assigned to exercise+supplement (EX+S, n=12) and exercise (EX, n=12) groups for an experimental period of 16weeks. Moderate-to-intensive exercise training increased lymphocytes DNA damage, cytokines and peroxidative biomarkers as well as decreased antioxidative biomarkers in the EX group. These changes were significantly attenuated in the EX+S group. Furthermore, for both groups the observed changes in peroxidative and antioxidative biomarkers could be correlated positively and negatively, respectively, with lymphocyte DNA damage and cytokines. Findings suggest that honey attenuates oxidative stress and lymphocyte DNA damage after exercise, activities that are most likely attributable to its high antioxidant capacity.

Effects of Acute Endurance Exercise on Plasma Protein Profiles of Endurance-Trained and Untrained Individuals over Time.

Acute physical exercise and repeated exercise stimuli affect whole-body metabolic and immunologic homeostasis. The aim of this study was to determine plasma protein profiles of trained (EET, n = 19) and untrained (SED, n = 17) individuals at rest and in response to an acute bout of endurance exercise. Participants completed a bicycle exercise test at an intensity corresponding to 80% of their VO2max. Plasma samples were taken before, directly after, and three hours after exercise and analyzed using multiplex immunoassays. Seventy-eight plasma variables were included in the final analysis. Twenty-nine variables displayed significant acute exercise effects in both groups. Seven proteins differed between groups, without being affected by acute exercise. Among these A2Macro and IL-5 were higher in EET individuals while leptin showed elevated levels in SED individuals. Fifteen variables revealed group and time differences with elevated levels for IL-3, IL-7, IL-10, and TNFR2 in EET individuals. An interaction effect could be observed for nine variables including IL-6, MMP-2, MMP-3, and muscle damage markers. The proteins that differ between groups indicate a long-term exercise effect on plasma protein concentrations. These findings might be of importance in the development of exercise-based strategies in the prevention and therapy of chronic metabolic and inflammatory diseases and for training monitoring.

Magnesium and disturbances in carbohydrate metabolism.

Magnesium is actively involved in a number of metabolic reactions as an important co-factor, with special emphasis on carbohydrate metabolism. After a brief overview of the regulation of intra- and extracellular magnesium, the present review first describes the regulatory role of magnesium in important metabolic pathways involved in energy metabolism and glycaemic control. Next the clinical significance of hypomagnesaemic conditions with regard to the management of glucose in prediabetic stages, such as insulin resistance/impaired glucose tolerance and in type 2 diabetes mellitus are characterized. Cross-sectional as well as longitudinal studies suggest that a reduced dietary magnesium intake serves as a risk factor for the incidence of both impaired glucose regulation and type 2 diabetes. Mechanisms that might be responsible for diabetes-associated hypomagnesaemia are discussed. Furthermore, the role of hypomagnesaemia in the development and progression of chronic diabetic complications are addressed. Finally, the available literature on the effects of magnesium supplementation on glycaemic control parameters during prediabetic conditions (preventive approach) as well as type 2 diabetes mellitus (therapeutic approach) are reviewed systematically. There is considerable evidence that chronic magnesium supplementation may delay the progression from impaired glucose regulation to type 2 diabetes; however, the effects of oral magnesium supplementation as an adjunct therapy for type 2 diabetes are quite heterogeneous with respect to the various measures of glycaemic control. The results of this review suggest a requirement for critical consideration of the pros and cons of magnesium replacement therapy, based on variables such as magnesium status, stage of disease and glycaemic control.

Metabolic signals and innate immune activation in obesity and exercise.

The combination of a sedentary lifestyle and excess energy intake has led to an increased prevalence of obesity which constitutes a major risk factor for several co-morbidities including type 2 diabetes and cardiovascular diseases. Intensive research during the last two decades has revealed that a characteristic feature of obesity linking it to insulin resistance is the presence of chronic low-grade inflammation being indicative of activation of the innate immune system. Recent evidence suggests that activation of the innate immune system in the course of obesity is mediated by metabolic signals, such as free fatty acids (FFAs), being elevated in many obese subjects, through activation of pattern recognition receptors thereby leading to stimulation of critical inflammatory signaling cascades, like IκBα kinase/nuclear factor-κB (IKK/NF- κB), endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) and NOD-like receptor P3 (NLRP3) inflammasome pathway, that interfere with insulin signaling. Exercise is one of the main prescribed interventions in obesity management improving insulin sensitivity and reducing obesity- induced chronic inflammation. This review summarizes current knowledge of the cellular recognition mechanisms for FFAs, the inflammatory signaling pathways triggered by excess FFAs in obesity and the counteractive effects of both acute and chronic exercise on obesity-induced activation of inflammatory signaling pathways. A deeper understanding of the effects of exercise on inflammatory signaling pathways in obesity is useful to optimize preventive and therapeutic strategies to combat the increasing incidence of obesity and its comorbidities.

Exercise, skeletal muscle and inflammation: ARE-binding proteins as key regulators in inflammatory and adaptive networks.

The role of inflammation in skeletal muscle adaptation to exercise is complex and has hardly been elucidated so far. While the acute inflammatory response to exercise seems to promote skeletal muscle training adaptation and regeneration, persistent, low-grade inflammation, as seen in a multitude of chronic diseases, is obviously detrimental. The regulation of cytokine production in skeletal muscle cells has been relatively well studied, yet little is known about the compensatory and anti-inflammatory mechanisms that resolve inflammation and restore tissue homeostasis. One important strategy to ensure sequential, timely and controlled resolution of inflammation relies on the regulated stability of mRNAs encoding pro-inflammatory mediators. Many key transcripts in early immune responses are characterized by the presence of AU-rich elements (AREs) in the 3'-untranslated regions of their mRNAs, allowing efficient fine-tuning of gene expression patterns at the post-transcriptional level. AREs exert their function by recruiting particular RNA-binding proteins, resulting, in most cases, in de-stabilization of the target transcripts. The best-characterized ARE-binding proteins are HuR, CUGBP1, KSRP, AUF1, and the three ZFP36 proteins, especially TTP/ZFP36. Here, we give a general introduction into the role of inflammation in the adaptation of skeletal muscle to exercise. Subsequently, we focus on potential roles of ARE-binding proteins in skeletal muscle tissue in general and specifically exercise-induced skeletal muscle remodeling. Finally, we present novel data suggesting a specific function of TTP/ZFP36 in exercise-induced skeletal muscle plasticity.

Preventive strength training improves working ergonomics during welding.

To investigate the effect of a preventive strength training program on cardiovascular, metabolic and muscular strains during welding. Welders are one of the occupation groups which typically have to work in extended forced postures which are known to be an important reason for musculoskeletal disorders. Subjects (exercise group) accomplished a 12-week strength training program, while another group served as controls (control group). Pre and post training examinations included the measurements of the one repetition maximum and an experimental welding test. Local muscle activities were analysed by surface electromyography. Furthermore, heart rate, blood pressure, lactate and rating of perceived exertion were examined. In the exercise group, strength training lead to a significant increase of one repetition maximum in all examined muscles (p<.05). During the experimental welding test muscle activities of trunk and shoulder muscles and arm muscles were significantly reduced in the exercise group after intervention (p<.05). While no changes of neither cardiovascular nor metabolic parameters were found, subjects of the exercise group rated a significantly decreased rate of perceived exertion welding (p<.05). Effects of strength training can be translated in an improved working ergonomics and tolerance against the exposure to high physical demands at work.

Effect of magnesium supplementation and depletion on the onset and course of acute experimental pancreatitis.

BACKGROUND AND OBJECTIVE: High calcium concentrations are an established risk factor for pancreatitis. We have investigated whether increasing magnesium concentrations affect pathological calcium signals and premature protease activation in pancreatic acini, and whether dietary or intraperitoneal magnesium administration affects the onset and course of experimental pancreatitis. METHODS: Pancreatic acini were incubated with up to 10 mM magnesium; [Ca(2+)](i) (fura-2AM) and intracellular protease activation (fluorogenic substrates) were determined over 60 min. Wistar rats received chow either supplemented or depleted for magnesium (<300 ppm to 30 000 ppm) over two weeks before pancreatitis induction (intravenous caerulein 10 µg/kg/h/4 h); controls received 1 µg/kg/h caerulein or saline. C57BL6/J mice received four intraperitoneal doses of magnesium (NaCl, Mg(2+) 55 192 or 384 mg/kg bodyweight) over 72 h, then pancreatitis was induced by up to eight hourly supramaximal caerulein applications. Pancreatic enzyme activities, protease activation, morphological changes and the immune response were investigated. RESULTS: Increasing extracellular Mg(2+) concentration significantly reduced [Ca(2+)](i) peaks and frequency of [Ca(2+)](i) oscillations as well as intracellular trypsin and elastase activity. Magnesium administration reduced pancreatic enzyme activities, oedema, tissue necrosis and inflammation and somewhat increased Foxp3-positiv T-cells during experimental pancreatitis. Protease activation was found in animals fed magnesium-deficient chow-even with low caerulein concentrations that normally cause no damage. CONCLUSIONS: Magnesium supplementation significantly reduces premature protease activation and the severity of pancreatitis, and antagonises pathological [Ca(2+)](i) signals. Nutritional magnesium deficiency increases the susceptibility of the pancreas towards pathological stimuli. These data have prompted two clinical trials on the use of magnesium in patients at risk for pancreatitis.