Arachidonic acid inhibition of the NLRP3 inflammasome is a mechanism to explain the anti-inflammatory effects of fasting.

Elevated interleukin (IL)-1ß levels, NLRP3 inflammasome activity, and systemic inflammation are hallmarks of chronic metabolic inflammatory syndromes, but the mechanistic basis for this is unclear. Here, we show that levels of plasma IL-1ß are lower in fasting compared to fed subjects, while the lipid arachidonic acid (AA) is elevated. Lipid profiling of NLRP3-stimulated mouse macrophages shows enhanced AA production and an NLRP3-dependent eicosanoid signature. Inhibition of cyclooxygenase by nonsteroidal anti-inflammatory drugs decreases eicosanoid, but not AA, production. It also reduces both IL-1ß and IL-18 production in response to NLRP3 activation. AA inhibits NLRP3 inflammasome activity in human and mouse macrophages. Mechanistically, AA inhibits phospholipase C activity to reduce JNK1 stimulation and hence NLRP3 activity. These data show that AA is an important physiological regulator of the NLRP3 inflammasome and explains why fasting reduces systemic inflammation and also suggests a mechanism to explain how nonsteroidal anti-inflammatory drugs work.

Canakinumab in patients with COVID-19 and type 2 diabetes - A multicentre, randomised, double-blind, placebo-controlled trial.

Background: Patients with type 2 diabetes and obesity have chronic activation of the innate immune system possibly contributing to the higher risk of hyperinflammatory response to SARS-CoV2 and severe COVID-19 observed in this population. We tested whether interleukin-1ß (IL-1ß) blockade using canakinumab improves clinical outcome. Methods: CanCovDia was a multicenter, randomised, double-blind, placebo-controlled trial to assess the efficacy of canakinumab plus standard-of-care compared with placebo plus standard-of-care in patients with type 2 diabetes and a BMI > 25 kg/m2 hospitalised with SARS-CoV2 infection in seven tertiary-hospitals in Switzerland. Patients were randomly assigned 1:1 to a single intravenous dose of canakinumab (body weight adapted dose of 450-750 mg) or placebo. Canakinumab and placebo were compared based on an unmatched win-ratio approach based on length of survival, ventilation, ICU stay and hospitalization at day 29. This study is registered with ClinicalTrials.gov, NCT04510493. Findings: Between October 17, 2020, and May 12, 2021, 116 patients were randomly assigned with 58 in each group. One participant dropped out in each group for the primary analysis. At the time of randomization, 85 patients (74·6 %) were treated with dexamethasone. The win-ratio of canakinumab vs placebo was 1·08 (95 % CI 0·69-1·69; p = 0·72). During four weeks, in the canakinumab vs placebo group 4 (7·0%) vs 7 (12·3%) participants died, 11 (20·0 %) vs 16 (28·1%) patients were on ICU, 12 (23·5 %) vs 11 (21·6%) were hospitalised for more than 3 weeks, respectively. Median ventilation time at four weeks in the canakinumab vs placebo group was 10 [IQR 6.0, 16.5] and 16 days [IQR 14.0, 23.0], respectively. There was no statistically significant difference in HbA1c after four weeks despite a lower number of anti-diabetes drug administered in patients treated with canakinumab. Finally, high-sensitive CRP and IL-6 was lowered by canakinumab. Serious adverse events were reported in 13 patients (11·4%) in each group. Interpretation: In patients with type 2 diabetes who were hospitalised with COVID-19, treatment with canakinumab in addition to standard-of-care did not result in a statistically significant improvement of the primary composite outcome. Patients treated with canakinumab required significantly less anti-diabetes drugs to achieve similar glycaemic control. Canakinumab was associated with a prolonged reduction of systemic inflammation. Funding: Swiss National Science Foundation grant #198415 and University of Basel. Novartis supplied study medication.

Altered miR-29 Expression in Type 2 Diabetes Influences Glucose and Lipid Metabolism in Skeletal Muscle.

MicroRNAs have emerged as important regulators of glucose and lipid metabolism in several tissues; however, their role in skeletal muscle remains poorly characterized. We determined the effects of the miR-29 family on glucose metabolism, lipid metabolism, and insulin responsiveness in skeletal muscle. We provide evidence that miR-29a and miR-29c are increased in skeletal muscle from patients with type 2 diabetes and are decreased following endurance training in healthy young men and in rats. In primary human skeletal muscle cells, inhibition and overexpression strategies demonstrate that miR-29a and miR-29c regulate glucose uptake and insulin-stimulated glucose metabolism. We identified that miR-29 overexpression attenuates insulin signaling and expression of insulin receptor substrate 1 and phosphoinositide 3-kinase. Moreover, miR-29 overexpression reduces hexokinase 2 expression and activity. Conversely, overexpression of miR-29 by electroporation of mouse tibialis anterior muscle decreased glucose uptake and glycogen content in vivo, concomitant with decreased abundance of GLUT4. We also provide evidence that fatty acid oxidation is negatively regulated by miR-29 overexpression, potentially through the regulation of peroxisome proliferator-activated receptor γ coactivator-1α expression. Collectively, we reveal that miR-29 acts as an important regulator of insulin-stimulated glucose metabolism and lipid oxidation, with relevance to human physiology and type 2 diabetes.

Exercise in vivo marks human myotubes in vitro: Training-induced increase in lipid metabolism.

BACKGROUND AND AIMS: Physical activity has preventive as well as therapeutic benefits for overweight subjects. In this study we aimed to examine effects of in vivo exercise on in vitro metabolic adaptations by studying energy metabolism in cultured myotubes isolated from biopsies taken before and after 12 weeks of extensive endurance and strength training, from healthy sedentary normal weight and overweight men. METHODS: Healthy sedentary men, aged 40-62 years, with normal weight (body mass index (BMI) < 25 kg/m2) or overweight (BMI ≥ 25 kg/m2) were included. Fatty acid and glucose metabolism were studied in myotubes using [14C]oleic acid and [14C]glucose, respectively. Gene and protein expressions, as well as DNA methylation were measured for selected genes. RESULTS: The 12-week training intervention improved endurance, strength and insulin sensitivity in vivo, and reduced the participants' body weight. Biopsy-derived cultured human myotubes after exercise showed increased total cellular oleic acid uptake (30%), oxidation (46%) and lipid accumulation (34%), as well as increased fractional glucose oxidation (14%) compared to cultures established prior to exercise. Most of these exercise-induced increases were significant in the overweight group, whereas the normal weight group showed no change in oleic acid or glucose metabolism. CONCLUSIONS: 12 weeks of combined endurance and strength training promoted increased lipid and glucose metabolism in biopsy-derived cultured human myotubes, showing that training in vivo are able to induce changes in human myotubes that are discernible in vitro.

Insulin and Glucose Alter Death-Associated Protein Kinase 3 (DAPK3) DNA Methylation in Human Skeletal Muscle.

DNA methylation is altered by environmental factors. We hypothesized that DNA methylation is altered in skeletal muscle in response to either insulin or glucose exposure. We performed a genome-wide DNA methylation analysis in muscle from healthy men before and after insulin exposure. DNA methylation of selected genes was determined in muscle from healthy men and men with type 2 diabetes before and after a glucose tolerance test. Insulin altered DNA methylation in the 3' untranslated region of the calcium pump ATP2A3 gene. Insulin increased DNA methylation in the gene body of DAPK3, a gene involved in cell proliferation, apoptosis, and autophagy. DAPK3 methylation was reduced in patients with type 2 diabetes. Carbohydrate ingestion reduced DAPK3 DNA methylation in healthy men and men with type 2 diabetes, suggesting glucose may play a role. Supporting this, DAPK3 DNA methylation was inversely correlated with the 2-h glucose concentration. Whereas glucose incorporation to glycogen was unaltered by small interfering RNA against DAPK3, palmitate oxidation was increased. In conclusion, insulin and glucose exposure acutely alter the DNA methylation profile of skeletal muscle, indicating that DNA methylation constitutes a rapidly adaptive epigenetic mark. Furthermore, insulin and glucose modulate DAPK3 DNA methylation in a reciprocal manner, suggesting a feedback loop in the control of the epigenome.

High-fat diet reprograms the epigenome of rat spermatozoa and transgenerationally affects metabolism of the offspring.

OBJECTIVES: Chronic and high consumption of fat constitutes an environmental stress that leads to metabolic diseases. We hypothesized that high-fat diet (HFD) transgenerationally remodels the epigenome of spermatozoa and metabolism of the offspring. METHODS: F0-male rats fed either HFD or chow diet for 12 weeks were mated with chow-fed dams to generate F1 and F2 offspring. Motile spermatozoa were isolated from F0 and F1 breeders to determine DNA methylation and small non-coding RNA (sncRNA) expression pattern by deep sequencing. RESULTS: Newborn offspring of HFD-fed fathers had reduced body weight and pancreatic beta-cell mass. Adult female, but not male, offspring of HFD-fed fathers were glucose intolerant and resistant to HFD-induced weight gain. This phenotype was perpetuated in the F2 progeny, indicating transgenerational epigenetic inheritance. The epigenome of spermatozoa from HFD-fed F0 and their F1 male offspring showed common DNA methylation and small non-coding RNA expression signatures. Altered expression of sperm miRNA let-7c was passed down to metabolic tissues of the offspring, inducing a transcriptomic shift of the let-7c predicted targets. CONCLUSION: Our results provide insight into mechanisms by which HFD transgenerationally reprograms the epigenome of sperm cells, thereby affecting metabolic tissues of offspring throughout two generations.

Direct effects of exercise on kynurenine metabolism in people with normal glucose tolerance or type 2 diabetes.

BACKGROUND: Systemic kynurenine levels are associated with resistance to stress-induced depression and are modulated by exercise. Tryptophan is a precursor for serotonin and kynurenine synthesis. Kynurenine is transformed into the neuroprotective catabolite kynurenic acid by kynurenine aminotransferases (KATs). PGC-1α1 increases KAT mRNA and induces kynurenic acid synthesis. We tested the hypothesis that skeletal muscle PGC-1α1/KAT-kynurenine pathway is altered by exercise and type 2 diabetes. METHOD: Skeletal muscle and plasma from men with normal glucose tolerance (n = 12) or type 2 diabetes (n = 12) was studied at rest, after acute exercise and during recovery. Tryptophan, Kynurenine and kynurenic acid plasma concentration were measured as well as mRNA of genes related to exercise and kynurenine metabolism. RESULTS: mRNA expression of KAT1, KAT2 and PPARα was modestly reduced in type 2 diabetic patients. In response to exercise, mRNA expression of KAT4 decreased and PGC-1α1 increased in both groups. Exercise increased plasma kynurenic acid and reduced kynurenine in normal glucose tolerance and type 2 diabetic participants. Plasma tryptophan was reduced and the ratio of [kynurenic acid] * 1000/[kynurenine] increased in both groups at recovery, suggesting an improved balance between neurotoxic and neuroprotective influences. Tryptophan and kynurenine correlated with body mass index, suggesting a relationship with obesity. CONCLUSIONS: Acute exercise directly affects circulating levels of tryptophan, kynurenine and kynurenic acid, providing a potential mechanism for the anti-depressive effects of exercise. Furthermore, exercise-mediated changes in kynurenine metabolism are preserved in type 2 diabetic patients. Copyright © 2016 John Wiley & Sons, Ltd.

TWIST1 and TWIST2 regulate glycogen storage and inflammatory genes in skeletal muscle.

TWIST proteins are important for development of embryonic skeletal muscle and play a role in the metabolism of tumor and white adipose tissue. The impact of TWIST on metabolism in skeletal muscle is incompletely studied. Our aim was to assess the impact of TWIST1 and TWIST2 overexpression on glucose and lipid metabolism. In intact mouse muscle, overexpression of Twist reduced total glycogen content without altering glucose uptake. Expression of TWIST1 or TWIST2 reduced Pdk4 mRNA, while increasing mRNA levels of Il6, Tnfα, and Il1ß. Phosphorylation of AKT was increased and protein abundance of acetyl CoA carboxylase (ACC) was decreased in skeletal muscle overexpressing TWIST1 or TWIST2. Glycogen synthesis and fatty acid oxidation remained stable in C2C12 cells overexpressing TWIST1 or TWIST2. Finally, skeletal muscle mRNA levels remain unaltered in ob/ob mice, type 2 diabetic patients, or in healthy subjects before and after 3 months of exercise training. Collectively, our results indicate that TWIST1 and TWIST2 are expressed in skeletal muscle. Overexpression of these proteins impacts proteins in metabolic pathways and mRNA level of cytokines. However, skeletal muscle levels of TWIST transcripts are unaltered in metabolic diseases.