Distinctive exercise-induced inflammatory response and exerkine induction in skeletal muscle of people with type 2 diabetes.

Mechanistic insights into the molecular events by which exercise enhances the skeletal muscle phenotype are lacking, particularly in the context of type 2 diabetes. Here, we unravel a fundamental role for exercise-responsive cytokines (exerkines) on skeletal muscle development and growth in individuals with normal glucose tolerance or type 2 diabetes. Acute exercise triggered an inflammatory response in skeletal muscle, concomitant with an infiltration of immune cells. These exercise effects were potentiated in type 2 diabetes. In response to contraction or hypoxia, cytokines were mainly produced by endothelial cells and macrophages. The chemokine CXCL12 was induced by hypoxia in endothelial cells, as well as by conditioned medium from contracted myotubes in macrophages. We found that CXCL12 was associated with skeletal muscle remodeling after exercise and differentiation of cultured muscle. Collectively, acute aerobic exercise mounts a noncanonical inflammatory response, with an atypical production of exerkines, which is potentiated in type 2 diabetes.

Changes in Vitamin D Status in Overweight Middle-Aged Adults with or without Impaired Glucose Metabolism in Two Consecutive Nordic Summers.

BACKGROUND: Sun exposure is the main driver of vitamin D synthesis. High latitude, obesity, and type 2 diabetes mellitus (T2DM) are all risk factors for vitamin D deficiency. However, the seasonal variation in vitamin D concentrations (25[OH]D) in such populations before and after sun exposure during the summer is unknown. Therefore, we investigated 25[OH]D status before and after two consecutive summers in high latitude and its associations with body fat, sex, and glucose metabolism. METHODS: 158 participants from Sweden (87 women, 71 men; mean age, 60 ± 5 y; body mass index ≥ 25 kg/m2) and 25[OH]D were measured and evaluated in relation to normal or impaired glucose tolerance, body composition, and dietary habits during summer season. RESULTS: Eighty-four percent of the participants were categorized with low to deficient 25[OH]D values before summer (55.1 ± 21.7 nmol·L-1), with a significant increase after the summer season (66.3 ± 21.0 nmol·L-1; P < 0.001). However, the values remained below the recommended range (76-250 nmol·L-1) in 66% of the participants. These findings were verified in a subgroup of the study population during the subsequent summer. Participants who reported use of vitamin D supplements had higher initial concentrations (64.2 ± 20.1 nmol·L-1) compared to nonusers (53.7 ± 21.7 nmol·L-1; P=0.04). Further, 25[OH]D values correlated negatively with fat mass (kg) prior to summer only in the female population (r=-0.29, P=0.008). CONCLUSIONS: In the present study, sun exposure had a beneficial but insufficient effect on 25[OH]D levels, and the same levels were documented in two consecutive summer seasons, confirming that vitamin D supplementation in both summer and winter should be considered in this population.

Afternoon exercise is more efficacious than morning exercise at improving blood glucose levels in individuals with type 2 diabetes: a randomised crossover trial.

AIMS/HYPOTHESIS: Exercise is recommended for the treatment and prevention of type 2 diabetes. However, the most effective time of day to achieve beneficial effects on health remains unknown. We aimed to determine whether exercise training at two distinct times of day would have differing effects on 24 h blood glucose levels in men with type 2 diabetes. METHODS: Eleven men with type 2 diabetes underwent a randomised crossover trial. Inclusion criteria were 45-68 years of age and BMI between 23 and 33 kg/m2. Exclusion criteria were insulin treatment and presence of another systemic illness. Researchers were not blinded to the group assignment. The trial involved 2 weeks of either morning or afternoon high-intensity interval training (HIIT) (three sessions/week), followed by a 2 week wash-out period and a subsequent period of the opposite training regimen. Continuous glucose monitor (CGM)-based data were obtained. RESULTS: Morning HIIT increased CGM-based glucose concentration (6.9 ± 0.4 mmol/l; mean ± SEM for the exercise days during week 1) compared with either the pre-training period (6.4 ± 0.3 mmol/l) or afternoon HIIT (6.2 ± 0.3 mmol/l for the exercise days during week 1). Conversely, afternoon HIIT reduced the CGM-based glucose concentration compared with either the pre-training period or morning HIIT. Afternoon HIIT was associated with elevated thyroid-stimulating hormone (TSH; 1.9 ± 0.2 mU/l) and reduced T4 (15.8 ± 0.7 pmol/l) concentrations compared with pre-training (1.4 ± 0.2 mU/l for TSH; 16.8 ± 0.6 pmol/l for T4). TSH was also elevated after morning HIIT (1.7 ± 0.2 mU/l), whereas T4 concentrations were unaltered. CONCLUSIONS/INTERPRETATION: Afternoon HIIT was more efficacious than morning HIIT at improving blood glucose in men with type 2 diabetes. Strikingly, morning HIIT had an acute, deleterious effect, increasing blood glucose. However, studies of longer training regimens are warranted to establish the persistence of this adverse effect. Our data highlight the importance of optimising the timing of exercise when prescribing it as treatment for type 2 diabetes.

Circulating Exosomal miR-20b-5p Is Elevated in Type 2 Diabetes and Could Impair Insulin Action in Human Skeletal Muscle.

miRNAs are noncoding RNAs representing an important class of gene expression modulators. Extracellular circulating miRNAs are both candidate biomarkers for disease pathogenesis and mediators of cell-to-cell communication. We examined the miRNA expression profile of total serum and serum-derived exosome-enriched extracellular vesicles in people with normal glucose tolerance or type 2 diabetes. In contrast to total serum miRNA, which did not reveal any differences in miRNA expression, we identified differentially abundant miRNAs in patients with type 2 diabetes using miRNA expression profiles of exosome RNA (exoRNA). To validate the role of these differentially abundant miRNAs on glucose metabolism, we transfected miR-20b-5p, a highly abundant exoRNA in patients with type 2 diabetes, into primary human skeletal muscle cells. miR-20b-5p overexpression increased basal glycogen synthesis in human skeletal muscle cells. We identified AKTIP and STAT3 as miR-20b-5p targets. miR-20b-5p overexpression reduced AKTIP abundance and insulin-stimulated glycogen accumulation. In conclusion, exosome-derived extracellular miR-20b-5p is a circulating biomarker associated with type 2 diabetes that plays an intracellular role in modulating insulin-stimulated glucose metabolism via AKT signaling.

Outcome of extremely preterm infants after iatrogenic or spontaneous birth.

INTRODUCTION: The risks of preterm birth are known. We investigated the perinatal and infant mortality and morbidity after iatrogenic or spontaneous onset of extremely preterm birth. MATERIAL AND METHODS: The present study used data from the population-based EXPRESS study comprising all infants delivered before 27+0 gestational weeks in Sweden between 2004 and 2007. All fetuses alive at admission and with known mode of onset of delivery were included (682 live-born infants; 65 intrapartum deaths). Four multivariate regression models were applied with adjustments for gestational age, fetal gender, multiple pregnancy, and birthweight. RESULTS: After adjustment for gestational age, no significant differences were found between iatrogenic and spontaneous onsets of birth regarding intrapartum death, early neonatal death (0-6 d), or death within 364 days. In the group with iatrogenic onset of delivery, there was an increased risk for severe morbidity (odds ratio [OR] 1.86, 95% confidence interval [95% CI] 1.15-3.02), severe bronchopulmonary dysplasia (OR 1.90, 95% CI 1.10-3.26), and retinopathy of prematurity (OR 1.99, 95% CI 1.21-3.27) after adjustment for gestational age, fetal gender, and multiple pregnancy. After additional adjustment for weight z-scores at 36 gestational weeks, the associations were not significant. Within the group with spontaneous onset of delivery, fetuses with preterm prelabor rupture of membranes had increased mortality risk. CONCLUSIONS: No evidence was found for mode of onset of delivery (iatrogenic vs spontaneous) having an impact on neonatal or infant mortality or morbidity in extremely preterm infants. Instead, gestational age and growth deviation at birth seem to be associated with the outcome.

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.

Influence of physical activity and gender on arterial function in type 2 diabetes, normal and impaired glucose tolerance.

To determine whether Nordic walking improves cardiovascular function in middle-aged women and men, we included 121 with normal glucose tolerance, 33 with impaired glucose tolerance and 47 with Type 2 diabetes mellitus in a randomized controlled study. The intervention group added Nordic walking 5 h/week for 4 months to their ordinary activities. Aortic pulse wave velocity, aortic augmentation index, stiffness index, reflection index, intima-media thickness in the radial and carotid arteries, echogenicity of the carotid intima-media and systemic vascular resistance were measured. While baseline blood pressure did not differ by gender or diagnosis, aortic augmentation index was found to be higher in women in all groups. Vascular function was unchanged with intervention, without differences by gender or diagnosis. In conclusion, 4 months of Nordic walking is an insufficient stimulus to improve vascular function. Future studies should consider hard endpoints in addition to measures of vascular health, as well as larger population groups, long-term follow-up and documented compliance to exercise training.

Changes in gene expression in responders and nonresponders to a low-intensity walking intervention.

OBJECTIVE: Daily physical activity remains an effective strategy to prevent obesity and type 2 diabetes. However, the metabolic response to exercise training is variable, and the precise clinical and molecular determinants that mark the metabolic improvements remain unknown. We tested the hypothesis that clinical improvements in glucose control after low-intensity exercise in individuals with impaired glucose tolerance (IGT) are coupled to alterations in skeletal muscle gene expression. RESEARCH DESIGN AND METHODS: We investigated 14 overweight individuals with IGT before and after a 4-month low-intensity unsupervised walking exercise intervention. Clinical and anthropometric measurements and glucose tolerance were determined before and after the intervention. Skeletal muscle biopsy specimens were obtained for mRNA expression analysis. RESULTS: Waist circumference and work capacity during cycle ergometry were improved in individuals who achieved normal glucose tolerance (NGT) after exercise training (IGT-NGT; n = 9) but in not individuals who remained IGT (IGT-IGT; n = 5). Pretraining glycemic control was better in IGT-NGT compared with IGT-IGT. mRNA expression of mitochondrial markers and transcription factors was increased in IGT-NGT after exercise intervention and normalized to levels measured in a separate cohort of nonexercised individuals with NGT. Conversely, these markers were unaltered after exercise intervention in IGT-IGT. CONCLUSIONS: Normalization of metabolic control can be achieved after low-intensity exercise in individuals with IGT. This can be tracked with increased mRNA expression of mitochondrial and metabolic genes in skeletal muscle. However, for individuals presenting with a greater derangement in glycemia, the potential for clinical and metabolic improvements after this low-intensity unsupervised exercise protocol appears to be limited.

Acute exercise remodels promoter methylation in human skeletal muscle.

DNA methylation is a covalent biochemical modification controlling chromatin structure and gene expression. Exercise elicits gene expression changes that trigger structural and metabolic adaptations in skeletal muscle. We determined whether DNA methylation plays a role in exercise-induced gene expression. Whole genome methylation was decreased in skeletal muscle biopsies obtained from healthy sedentary men and women after acute exercise. Exercise induced a dose-dependent expression of PGC-1α, PDK4, and PPAR-δ, together with a marked hypomethylation on each respective promoter. Similarly, promoter methylation of PGC-1α, PDK4, and PPAR-δ was markedly decreased in mouse soleus muscles 45 min after ex vivo contraction. In L6 myotubes, caffeine exposure induced gene hypomethylation in parallel with an increase in the respective mRNA content. Collectively, our results provide evidence that acute gene activation is associated with a dynamic change in DNA methylation in skeletal muscle and suggest that DNA hypomethylation is an early event in contraction-induced gene activation.

Mitochondrial regulators of fatty acid metabolism reflect metabolic dysfunction in type 2 diabetes mellitus.

The delicate homeostatic balance between glucose and fatty acid metabolism in relation to whole-body energy regulation is influenced by mitochondrial function. We determined expression and regulation of mitochondrial enzymes including pyruvate dehydrogenase kinase (PDK) 4, PDK2, carnitine palmitoyltransferase 1b, and malonyl-coenzyme A decarboxylase in skeletal muscle from people with normal glucose tolerance (NGT) or type 2 diabetes mellitus (T2DM). Vastus lateralis biopsies were obtained from NGT (n = 79) or T2DM (n = 33) men and women matched for age and body mass index. A subset of participants participated in a 4-month lifestyle intervention program consisting of an unsupervised walking exercise. Muscle biopsies were analyzed for expression and DNA methylation status. Primary myotubes were derived from biopsies obtained from NGT individuals for metabolic studies. Cultured skeletal muscle was exposed to agents mimicking exercise activation for messenger RNA (mRNA) expression analysis. The mRNA expression of PDK4, PDK2, and malonyl-coenzyme A decarboxylase was increased in skeletal muscle from T2DM patients. Methylation of the PDK4 promoter was reduced in T2DM and inversely correlated with PDK4 expression. Moreover, PDK4 expression was positively correlated with body mass index, blood glucose, insulin, C peptide, and hemoglobin A(1c). A lifestyle intervention program resulted in increased PDK4 mRNA expression in NGT individuals, but not in those with T2DM. Exposure to caffeine or palmitate increased PDK4 mRNA in a cultured skeletal muscle system. Our findings reveal that skeletal muscle expression of PDK4 and related genes regulating mitochondrial function reflects alterations in substrate utilization and clinical features associated with T2DM. Furthermore, hypomethylation of the PDK4 promoter in T2DM coincided with an impaired response of PDK4 mRNA after exercise.

Direct effects of FGF21 on glucose uptake in human skeletal muscle: implications for type 2 diabetes and obesity.

BACKGROUND: Fibroblast growth factor (FGF) 21, a novel member of the FGF family, plays a role in a variety of endocrine functions, including regulation of glucose and lipid metabolism. The role of FGF21 in skeletal muscle is currently not known. METHODS: Serum levels and skeletal muscle mRNA of FGF21 were determined in normal glucose tolerant (n = 40) and type 2 diabetic (T2D; n = 40) subjects. We determined whether FGF21 has direct effects on glucose metabolism in cultured myotubes (n = 8) and extensor digitorum longus skeletal muscle. RESULTS: Serum FGF21 levels increased 20% in T2D versus normal glucose tolerant subjects (p < 0.05), whereas skeletal muscle mRNA expression was unaltered. Fasting insulin, homeostatic model assessment of insulin resistance (HOMA-IR), waist circumference, and body mass index (BMI) significantly correlated with serum FGF21 levels in T2D (p < 0.01), but not in normal glucose tolerant subjects. Serum FGF21 concentrations were greater in T2D patients in the highest tertile of fasting insulin (p < 0.05) and BMI (p < 0.05). Stepwise regression analysis identified BMI as the strongest independent variable correlating with FGF21. FGF21 exposure increased basal and insulin-stimulated glucose uptake in human myotubes, coincident with increased glucose transporter 1 mRNA, and enhanced glucose transporter 1 abundance at the plasma membrane. In isolated extensor digitorum longus muscle, FGF21 potentiated insulin-stimulated glucose transport, without altering phosphorylation of Akt or AMP-activated protein kinase. CONCLUSIONS: Plasma FGF21 is increased in T2D patients, and positively correlated with fasting insulin and BMI. However, FGF21 has direct effects in enhancing skeletal muscle glucose uptake, providing additional points of regulation that may contribute to the beneficial effects of FGF21 on glucose homeostasis. Whether increased plasma FGF21 in T2D is a compensatory mechanism to increase glucose metabolism remains to be determined.

Non-CpG methylation of the PGC-1alpha promoter through DNMT3B controls mitochondrial density.

Epigenetic modification through DNA methylation is implicated in metabolic disease. Using whole-genome promoter methylation analysis of skeletal muscle from normal glucose-tolerant and type 2 diabetic subjects, we identified cytosine hypermethylation of peroxisome proliferator-activated receptor gamma (PPARgamma) coactivator-1 alpha (PGC-1alpha) in diabetic subjects. Methylation levels were negatively correlated with PGC-1alpha mRNA and mitochondrial DNA (mtDNA). Bisulfite sequencing revealed that the highest proportion of cytosine methylation within PGC-1alpha was found within non-CpG nucleotides. Non-CpG methylation was acutely increased in human myotubes by exposure to tumor necrosis factor-alpha (TNF-alpha) or free fatty acids, but not insulin or glucose. Selective silencing of the DNA methyltransferase 3B (DNMT3B), but not DNMT1 or DNMT3A, prevented palmitate-induced non-CpG methylation of PGC-1alpha and decreased mtDNA and PGC-1alpha mRNA. We provide evidence for PGC-1alpha hypermethylation, concomitant with reduced mitochondrial content in type 2 diabetic patients, and link DNMT3B to the acute fatty-acid-induced non-CpG methylation of PGC-1alpha promoter.

Low-intensity exercise increases skeletal muscle protein expression of PPARdelta and UCP3 in type 2 diabetic patients.

BACKGROUND: Physical exercise provides health benefits for people with type 2 diabetes mellitus, partly by enhancing skeletal muscle insulin action. We tested the hypothesis that changes in expression of key genes in skeletal muscles relate to exercise-induced improvements in type 2 diabetic patients. METHODS: We determined mRNA expression of 20 selected genes following a self-supervised program of walking (> 150 min per week) over a 4-month period. RESULTS: This level of physical activity improved clinical parameters in approximately half the participants, as determined by reduced hypertension and enhanced insulin sensitivity (defined by reduced plasma-insulin levels and improved homeostasis model assessment (HOMA)). Skeletal muscle mRNA expression of Cbl-associated protein (CAP), diacylglycerol kinase (DGK)delta, uncoupling protein (UCP) 3, nuclear respiratory factor (NRF)-1, and peroxisome proliferator-activated receptor (PPAR)delta tended to increase in type 2 diabetic patients with an improved clinical profile. Skeletal muscle protein expression of PPARdelta and UCP3 was increased significantly after physical exercise in patients with an improved clinical profile, but were unchanged in patients who did not show exercise-mediated improvements in clinical parameters. CONCLUSIONS: This study provides clinical evidence that improvements in insulin sensitivity can be achieved in type 2 diabetic patients after individually executed low-intensity exercise training. Moreover, the positive clinical response to exercise is correlated with changes in skeletal muscle proteins involved in the regulation of mitochondrial biogenesis and metabolism. These changes in skeletal muscle gene expression offer a possible molecular explanation for the improvements in clinical outcomes.

Walking for exercise--does three times per week influence risk factors in type 2 diabetes?

In order to assess the effects of regular walking on metabolic control and cardiovascular risk factors in type 2 diabetes 26 patients from one primary care clinic, aged 60.0+/-7.3 years, participated in a walking program during 4 months. Prescribed exercise was walking for 45-60 min three times weekly. A control group of 26 patients from a neighboring primary care clinic, aged 59.3+/-6.2 years, received no exercise instructions. Thus, randomization was not performed. There were no improvements of blood pressure, body mass index, physical fitness, glycated hemoglobin A1c, fasting plasma glucose or insulin by intention-to-treat analysis. Seventeen patients in the intervention group increased their physical activity and improved systolic blood pressure; -7.6 mmHg (-15 to -0.2), diastolic blood pressure; -4.3 mmHg (-7.4 to -1.2), body mass index; -0.6 kg/m2 (-1.1 to -0.1) and total plasma cholesterol; -0.6 mmol/l (-0.9 to -0.3), (mean difference, with 95% CI). We could observe no effects on glucose metabolism in either group. Our results suggest that an increase of regular physical activity equivalent to 45 min of walking 3 days/week may suffice to improve systolic and diastolic blood pressure, lipid metabolism and BMI in patients with type 2 diabetes.

Gender differences in risk factor control and treatment profile in diabetes: a study in 229 swedish primary health care centres.

OBJECTIVE: To measure the risk factors and treatment profile of diabetes patients treated in primary health care (PHC) in order to evaluate potential gender differences. DESIGN: Cross-sectional survey of consecutive diabetes patients. SETTING: 229 PHC centres in Sweden. SUBJECTS: 5082 men and 4293 women with diabetes were investigated (1998-2001). MAIN OUTCOME MEASURES: Glycaemic control (HbA1c), blood pressure, lipid levels, prevalence of left ventricular hypertrophy and microalbuminuria. Proportions of patients with previous ischaemic heart disease (IHD) and specific drug treatment. RESULTS: Male patients generally had better blood pressure ( < 140 and/or 85 mmHg) and glycaemic (HbA1c < 6.5%) control than corresponding female patients (44% and 59%, versus 40% and 54% in the 60-75 year age group; p < 0.01). Females showed higher levels of total (p < 0.01) and HDL cholesterol (p < 0.05) than males in all age groups. No gender difference was detected for LDL cholesterol levels in the younger or elderly patients, but in the age group 60-75 years female patients had significantly higher mean LDL cholesterol level than male patients (3.3 vs 3.2 mmol/L; p < 0.05). Previously known manifestations of IHD were more common (p < 0.01) in male patients. CONCLUSION: Elderly male patients with diabetes had a more favourable risk factor control than corresponding female patients.