Exercise training reduces circulating cytokines in male patients with coronary artery disease and type 2 diabetes: A pilot study.

Low-grade inflammation is central to coronary artery disease (CAD) and type 2 diabetes (T2D) and is reduced by exercise training. The objective of this study was to compare the anti-inflammatory potential of moderate-to-vigorous intensity continuous training (MICT) and high-intensity interval training (HIIT) in patients with CAD with or without T2D. The design and setting of this study is based on a secondary analysis of registered randomized clinical trial NCT02765568. Male patients with CAD were randomly assigned to either MICT or HIIT, with subgroups divided according to T2D status (non-T2D-HIIT n = 14 and non-T2D-MICT n = 13; T2D-HIIT n = 6 and T2D-MICT n = 5). The intervention was a 12-week cardiovascular rehabilitation program consisting of either MICT or HIIT (twice weekly sessions) and circulating cytokines measured pre- and post-training as inflammatory markers. The co-occurrence of CAD and T2D was associated with increased plasma IL-8 (p = 0.0331). There was an interaction between T2D and the effect of the training interventions on plasma FGF21 (p = 0.0368) and IL-6 (p = 0.0385), which were further reduced in the T2D groups. An interaction between T2D, training modalities, and the effect of time (p = 0.0415) was detected for SPARC, with HIIT increasing circulating concentrations in the control group, while lowering them in the T2D group, and the inverse occurring with MICT. The interventions also reduced plasma FGF21 (p = 0.0030), IL-6 (p = 0.0101), IL-8 (p = 0.0087), IL-10 (p < 0.0001), and IL-18 (p = 0.0009) irrespective of training modality or T2D status. HIIT and MICT resulted in similar reductions in circulating cytokines known to be increased in the context of low-grade inflammation in CAD patients, an effect more pronounced in patients with T2D for FGF21 and IL-6.

BPA exposure in L6 myotubes increased basal glucose metabolism in an estrogen receptor-dependent manner but induced insulin resistance.

Exposure to bisphenol A (BPA) is associated with insulin resistance and type 2 diabetes (T2D). Since muscle insulin resistance is the primary defect in T2D, we aimed to determine whether BPA alters glucose metabolism in L6 muscle cells. L6 or L6-GLUT4-myc cells were exposed to 1-104 nM BPA or the vehicle (0.1% DMSO) for 7 days. BPA at 103-104 nM significantly decreased the levels of the muscle differentiation markers troponin- T and myosin heavy chain 3. Insulin-stimulated phosphorylation of Akt and GSK3, insulin-stimulated glucose uptake, and insulin-stimulated GLUT4 translocation were significantly decreased with 103-104 nM BPA. Basal glucose uptake and glycolysis (extracellular acidification rates measured by Seahorse XFe96) were increased with 103-104 nM BPA. Levels of ROS detoxifying enzymes were increased with BPA >10 nM, while catalase activity was increased with 103-104 nM BPA. However, BPA did not induce oxidative stress (measured by protein carbonylation and lipid peroxidation) nor mitochondrial dysfunction. The effects of BPA on basal glucose uptake and catalase activity, but not on insulin sensitivity, were restored when estrogen receptors (ERs) were inhibited with ICI. These findings suggest that high concentrations of BPA increase muscle glucose uptake through the ERs but induce insulin resistance through another pathway.

Placental superoxide dismutase 3 mediates benefits of maternal exercise on offspring health.

Poor maternal diet increases the risk of obesity and type 2 diabetes in offspring, adding to the ever-increasing prevalence of these diseases. In contrast, we find that maternal exercise improves the metabolic health of offspring, and here, we demonstrate that this occurs through a vitamin D receptor-mediated increase in placental superoxide dismutase 3 (SOD3) expression and secretion. SOD3 activates an AMPK/TET signaling axis in fetal offspring liver, resulting in DNA demethylation at the promoters of glucose metabolic genes, enhancing liver function, and improving glucose tolerance. In humans, SOD3 is upregulated in serum and placenta from physically active pregnant women. The discovery of maternal exercise-induced cross talk between placenta-derived SOD3 and offspring liver provides a central mechanism for improved offspring metabolic health. These findings may lead to novel therapeutic approaches to limit the transmission of metabolic disease to the next generation.

The effects of bisphenol A and bisphenol S on adipokine expression and glucose metabolism in human adipose tissue.

PURPOSE: The environmental endocrine disruptors, bisphenol A (BPA) and bisphenol S (BPS) are associated with the development of type 2 diabetes. We aim to study the effects of BPA or BPS exposure on adipokine expression in human adipose tissue and on adipocyte glucose uptake. METHODS: Human subcutaneous adipose tissue was treated for 24 or 72 h with environmentally-relevant and supraphysiological concentrations of BPA or BPS (1-104 nM). Following exposure, gene expression of proinflammatory cytokines, adipokines, and estrogen receptors was measured in adipose tissue. Glucose uptake and the insulin signalling pathway were analyzed in isolated adipocytes following adipose tissue culture with BPA for 24 h. RESULTS: Adipose tissue treated with BPA for 24 h had reduced expression of the proinflammatory genes (IL6, IL1B, TNFA) and adipokines (ADIPOQ, FABP4). BPA and BPS had no effect on the expression of other proinflammatory genes (IL33), adipokines (LEP), or receptors (ESR1, ESR2) after 72-h exposure. Adipose tissue treated with environmentally-relevant concentrations of BPA for 24 h had reduced insulin-stimulated glucose uptake, without altered gene and protein levels of key insulin signalling pathway markers. CONCLUSIONS: We found that human adipose tissue treated with environmentally-relevant concentrations of BPA for 24 h, but not BPS, reduced expression of proinflammatory genes and adipokines. Furthermore, BPA reduced glucose uptake in adipocytes independently of insulin signalling. Such mechanisms can contribute to the development of insulin resistance associated with BPA exposure.

Plasma Myokine Concentrations After Acute Exercise in Non-obese and Obese Sedentary Women.

Exercise and physical activity levels influence myokine release from skeletal muscle and contribute to circulating concentrations. Indeed, many myokines, including interleukin (IL)-6, IL-15, secreted protein acidic rich in cysteine (SPARC), and fibroblast growth factor (FGF) 21 are higher in the circulation after an exercise bout. Since these peptides modulate muscle metabolism and can also be targeted toward other tissues to induce adaptations to energy demand, they are of great interest regarding metabolic diseases. Therefore, we set out to compare, in six women with obesity (BMI ≥30 kg/m2) and five healthy women (BMI 22-29.9 kg/m2), the effect of an acute bout of moderate-intensity, continuous cycling exercise (60 min, 60% VO2peak) on the release of myokines (IL-6, IL-8, IL-10, IL-13, IL-15, SPARC, and FGF21) in plasma for a 24-h time course. We found that plasma IL-8 and SPARC levels were reduced in the group of women with obesity, whereas plasma IL-13 concentrations were elevated in comparison to non-obese women both before and after the exercise bout. We also found that plasma FGF21 concentration during the 24 h following the bout of exercise was regulated differently in the non-obese in comparison to obese women. Plasma concentrations of FGF21, IL-6, IL-8, IL-15, and IL-18 were regulated by acute exercise. Our results confirm the results of others concerning exercise regulation of circulating myokines while providing insight into the time course of myokine release in circulation after an acute exercise bout and the differences in circulating myokines after exercise in women with or without obesity.

The effects of acute BPA exposure on skeletal muscle mitochondrial function and glucose metabolism.

Bisphenol A (BPA) is an environmental pollutant that has been associated with adverse health effects including skeletal muscle insulin resistance, a major contributor to the pathogenesis of type 2 diabetes (T2D). Early mitochondrial dysfunction and oxidative stress are linked to impaired glucose metabolism in skeletal muscle. In this study, we investigated the effects of BPA on skeletal muscle mitochondrial function and insulin sensitivity. L6 myotubes were treated with BPA (1 nM-105 nM) during the last 24 h of differentiation. Following exposure to 105 nM of BPA, resting and maximal oxygen consumption rates were decreased, whereas mitochondrial proton leak was increased. Overall metabolic activity, measured by redox ability, was decreased in L6 myotubes exposed to 105 nM of BPA. At this concentration, insulin-stimulated glucose uptake was increased, which corresponded to an increased phosphorylation of the insulin signaling protein Akt, and increased glycolysis measured by extracellular acidification rate (ECAR). Acute BPA exposure did not alter levels of oxidative stress markers in muscle cells, but significantly increased mitochondrial proton leak, which is known to be involved in decreased ROS production. The effects of BPA on glucose uptake, but not mitochondrial function, were reversed by the use of an estrogen receptor antagonist. These results suggest that acute exposure of L6 myotubes at only high concentrations of BPA alters glucose metabolism, which is likely a compensatory response to reduced mitochondrial energy production capacity.

A role for maternally derived myokines to optimize placental function and fetal growth across gestation.

Exercise during pregnancy is associated with improved health outcomes for both mother and baby, including a reduced risk of future obesity and susceptibility to chronic diseases. Overwhelming evidence demonstrates a protective effect of maternal exercise against fetal birth weight extremes, reducing the rates of both large- and small-for-gestational-age infants. It is speculated that this protective effect is mediated in part through exercise-induced regulation of maternal physiology and placental development and function. However, the specific mechanisms through which maternal exercise regulates these changes remain to be discovered. We hypothesize that myokines, a collection of peptides and cytokines secreted from contracting skeletal muscles during exercise, may be an important missing link in the story. Myokines are known to reduce inflammation, improve metabolism and enhance macronutrient transporter expression and activity in various tissues of nonpregnant individuals. Little research to date has focused on the specific roles of the myokine secretome in the context of pregnancy; however, it is likely that myokines secreted from exercising skeletal muscles may modulate the maternal milieu and directly impact the vital organ of pregnancy-the placenta. In the current review, data in strong support of this potential role of myokines will be presented, suggesting myokine secretion as a key mechanism through which maternal exercise optimizes fetal growth trajectories. It is clear that further research is warranted in this area, as knowledge of the biological roles of myokines in the context of pregnancy would better inform clinical recommendations for exercise during pregnancy and contribute to the development of important therapeutic interventions.

Galactose enhances oxidative metabolism and reveals mitochondrial dysfunction in human primary muscle cells.

BACKGROUND: Human primary myotubes are highly glycolytic when cultured in high glucose medium rendering it difficult to study mitochondrial dysfunction. Galactose is known to enhance mitochondrial metabolism and could be an excellent model to study mitochondrial dysfunction in human primary myotubes. The aim of the present study was to 1) characterize the effect of differentiating healthy human myoblasts in galactose on oxidative metabolism and 2) determine whether galactose can pinpoint a mitochondrial malfunction in post-diabetic myotubes. METHODOLOGY/PRINCIPAL FINDINGS: Oxygen consumption rate (OCR), lactate levels, mitochondrial content, citrate synthase and cytochrome C oxidase activities, and AMPK phosphorylation were determined in healthy myotubes differentiated in different sources/concentrations of carbohydrates: 25 mM glucose (high glucose (HG)), 5 mM glucose (low glucose (LG)) or 10 mM galactose (GAL). Effect of carbohydrates on OCR was also determined in myotubes derived from post-diabetic patients and matched obese non-diabetic subjects. OCR was significantly increased whereas anaerobic glycolysis was significantly decreased in GAL myotubes compared to LG or HG myotubes. This increased OCR in GAL myotubes occurred in conjunction with increased cytochrome C oxidase activity and expression, as well as increased AMPK phosphorylation. OCR of post-diabetic myotubes was not different than that of obese non-diabetic myotubes when differentiated in LG or HG. However, whereas GAL increased OCR in obese non-diabetic myotubes, it did not affect OCR in post-diabetic myotubes, leading to a significant difference in OCR between groups. The lack of an increase in OCR in post-diabetic myotubes differentiated in GAL was in relation with unaltered cytochrome C oxidase activity levels or AMPK phosphorylation. CONCLUSIONS/SIGNIFICANCE: Our results indicate that differentiating human primary myoblasts in GAL enhances aerobic metabolism. Because this cell culture model elicited an abnormal response in cells from post-diabetic patients, it may be useful in further studies of the molecular mechanisms of mitochondrial dysfunction.

Glutathionylation acts as a control switch for uncoupling proteins UCP2 and UCP3.

The mitochondrial uncoupling proteins 2 and 3 (UCP2 and -3) are known to curtail oxidative stress and participate in a wide array of cellular functions, including insulin secretion and the regulation of satiety. However, the molecular control mechanism(s) governing these proteins remains elusive. Here we reveal that UCP2 and UCP3 contain reactive cysteine residues that can be conjugated to glutathione. We further demonstrate that this modification controls UCP2 and UCP3 function. Both reactive oxygen species and glutathionylation were found to activate and deactivate UCP3-dependent increases in non-phosphorylating respiration. We identified both Cys(25) and Cys(259) as the major glutathionylation sites on UCP3. Additional experiments in thymocytes from wild-type and UCP2 null mice demonstrated that glutathionylation similarly diminishes non-phosphorylating respiration. Our results illustrate that UCP2- and UCP3-mediated state 4 respiration is controlled by reversible glutathionylation. Altogether, these findings advance our understanding of the roles UCP2 and UCP3 play in modulating metabolic efficiency, cell signaling, and oxidative stress processes.

A 5-month weight-reduction programme has a positive effect on body composition, aerobic fitness, and habitual physical activity of severely obese girls: a pilot evaluation study.

In this pilot study, we wished to determine whether a 5-month multidisciplinary programme of a combined dietary-nutritional education-exercise intervention would have favourable effects on the health status of 18 obese adolescent girls. Before and after the clinical intervention, body composition and habitual physical activity were assessed by bioelectrical impedance and accelerometry, respectively. Aerobic fitness and substrate utilization were determined by gas exchange using an incremental field test that mimics habitual conditions. Despite a significantly (P < 0.001) greater loss of fat mass (-8.7 +/- 4.1 kg) compared with fat-free mass (-2.8 +/- 2.2 kg), energy expenditure at rest decreased by 9% following the intervention. Maximal oxygen consumption [Vdot]O2max related to fat-free mass increased by 7% (P < 0.05), whereas substrate utilization during exercise did not change following the intervention. Moderate and intense physical activity increased by 15% (+20 min . day(-1); P < 0.05) and 45% (+25 min . day(-1); P < 0.01), respectively. A significant relationship was observed between change in habitual physical activity and change in .[Vdot]O2max fat-free mass (r = 0.56, P = 0.01). The present multidisciplinary programme enhanced the loss of fat mass relative to fat-free mass but not sufficiently so to prevent a decline in metabolic rate during rest. Our results suggest a coupling in the improvement of aerobic fitness and habitual physical activity in obese adolescent girls, and hence an improvement in behaviour in relation to physical activity.

Lipid content and response to insulin are not invariably linked in human muscle cells.

In type 2 diabetes, a strong correlation between intramyocellular lipid accumulation and insulin resistance exists but whether intramyocellular accumulation is a cause or a consequence of insulin resistance is not clear. Lipid accumulation and response to insulin were evaluated in primary human myotubes derived from non-diabetic subjects and type 2 diabetic patients. Myotubes derived from type 2 diabetic patients had a defective response to insulin without showing a significant increase in lipid accumulation compared to myotubes derived from non-diabetic subjects. In myotubes derived from non-diabetic subjects, response to insulin stimulation (Akt phosphorylation) was abrogated and lipid content was increased after palmitate treatment. However, chronic exposure to insulin or inhibition of mitochondrial activity by antimycin led to independent changes of lipid content and response to insulin in myotubes derived from non-diabetic subjects. Altogether these results suggest that lipid accumulation and response to insulin are not invariably linked.