João Victor Del Conti Esteves

Insulin acutely triggers transcription of Slc2a4 gene: Participation of the AT-rich, E-box and NFKB-binding sites

AIMS The insulin-sensitive glucose transporter protein GLUT4 (solute carrier family 2 member 4 (Slc2a4) gene) plays a key role in glycemic homeostasis. Decreased GLUT4 expression is a current feature in insulin resistant conditions such as diabetes, and the restoration of GLUT4 content improves glycemic control. This study investigated the effect of insulin upon Slc2a4/GLUT4 expression, focusing on the AT-rich element, E-box and nuclear factor NF-kappa-B (NFKB) site. MAIN METHODS Rat soleus muscles were incubated during 180 min with insulin, added or not with wortmannin (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit gamma isoform (PI3K)-inhibitor), ML9 (serine/threonine protein kinase (AKT) inhibitor) and tumor necrosis factor (TNF, GLUT4 repressor), and processed for analysis of GLUT4 protein (Western blotting); Slc2a4, myocyte enhancer factor 2a/d (Mef2a/d), hypoxia inducible factor 1a (Hif1a), myogenic differentiation 1 (Myod1) and nuclear factor of kappa light polypeptide gene enhancer in B-cells 1 (Nfkb1) messenger ribonucleic acids (mRNAs) (polymerase chain reaction (PCR)); and AT-rich- (myocyte-specific enhancer factor 2 (MEF2)-binding site), E-box- (hypoxia inducible factor 1 alpha (HIF1A)- and myoblast determination protein 1 (MYOD1)-binding site), and NFKB-binding activity (electrophoretic mobility assay). KEY FINDINGS Insulin increased Slc2a4 mRNA expression (140%) and nuclear proteins binding to AT-rich and E-box elements (~90%), all effects were prevented by wortmannin and ML9. Insulin also increased Mef2a/d and Myod1 mRNA expression, suggesting the participation of these transcriptional factors in the Slc2a4 enhancing effect. Conversely, insulin decreased Nfkb1 mRNA expression and protein binding to the NFKB-site (~50%). Furthermore, TNF-induced inhibition of GLUT4 expression (~40%) was prevented by insulin in an NFKB-binding repressing mechanism. GLUT4 protein paralleled the Slc2a4 mRNA regulations. SIGNIFICANCE Insulin enhances the Slc2a4/GLUT4 expression in the skeletal muscle by activating AT-rich and E-box elements, in a PI3K/AKT-dependent mechanism, and repressing NFKB-site activity as well. These results unravel how post-prandial increase of insulin may guarantee GLUT4 expression, and how the insulin signaling impairment can participate in insulin resistance-induced repression of GLUT4.

MicroRNAs-Mediated Regulation of Skeletal Muscle GLUT4 Expression and Translocation in Insulin Resistance

The solute carrier family 2 facilitated glucose transporter member 4 (GLUT4) plays a key role in the insulin-induced glucose uptake by muscle and adipose tissues. In prediabetes and diabetes, GLUT4 expression/translocation has been detected as reduced, participating in mechanisms that impair glycemic control. Recently, a class of short endogenous noncoding RNAs named microRNAs (miRNAs) has been increasingly described as involved in the posttranscriptional epigenetic regulation of gene expression. The present review focuses on miRNAs potentially involved in the expression of GLUT4 expression, and proteins related to GLUT4 and translocation in skeletal muscle, seeking to correlate them with insulin resistance and diabetes. So far, miR-21a-5p, miR-29a-3p, miR-29c-3p, miR-93-5p, miR-106b-5p, miR-133a-3p, miR-133b-3p, miR-222-3p, and miR-223-3p have been reported to directly and/or indirectly regulate the GLUT4 expression; and their expression is altered under diabetes-related conditions. Besides, some miRNAs that have been linked to the expression of proteins involved in GLUT4 translocation machinery in muscle could also impact glucose uptake. That makes these miRNAs promising targets for preventive and/or therapeutic approaches, which could improve glycemic control, thus deserving future new investigations.

Resveratrol Improves Glycemic Control in Type 2 Diabetic Obese Mice by Regulating Glucose Transporter Expression in Skeletal Muscle and Liver

Insulin resistance participates in the glycaemic control disruption in type 2 diabetes mellitus (T2DM), by reducing muscle glucose influx and increasing liver glucose efflux. GLUT4 (Slc2a4 gene) and GLUT2 (Slc2a2 gene) proteins play a fundamental role in the muscle and liver glucose fluxes, respectively. Resveratrol is a polyphenol suggested to have an insulin sensitizer effect; however, this effect, and related mechanisms, have not been clearly demonstrated in T2DM. We hypothesized that resveratrol can improve glycaemic control by restoring GLUT4 and GLUT2 expression in muscle and liver. Mice were rendered obese T2DM in adult life by neonatal injection of monosodium glutamate. Then, T2DM mice were treated with resveratrol for 60 days or not. Glycaemic homeostasis, GLUT4, GLUT2, and SIRT1 (sirtuin 1) proteins (Western blotting); Slc2a4, Slc2a2, and Pck1 (key gluconeogenic enzyme codifier) mRNAs (RT-qPCR); and hepatic glucose efflux were analysed. T2DM mice revealed: high plasma concentration of glucose, fructosamine, and insulin; insulin resistance (insulin tolerance test); decreased Slc2a4/GLUT4 content in gastrocnemius and increased Slc2a2/GLUT2 content in liver; and increased Pck1 mRNA and gluconeogenic activity (pyruvate tolerance test) in liver. All alterations were restored by resveratrol treatment. Additionally, in both muscle and liver, resveratrol increased SIRT1 nuclear content, which must participate in gene expression regulations. In sum, the results indisputably reveals that resveratrol improves glycaemic control in T2DM, and that involves an increase in muscle Slc2a4/GLUT4 and a decrease in liver Slc2a2/GLUT2 expression. This study contributes to our understanding how resveratrol might be prescribed for T2DM according to the principles of evidence-based medicine.

The Effects of Hyperbaric Oxygen Therapy on Post-Training Recovery in Jiu-Jitsu Athletes

Objectives The present study aimed to evaluate the effects of using hyperbaric oxygen therapy during post-training recovery in jiu-jitsu athletes. Methods Eleven experienced Brazilian jiu-jitsu athletes were investigated during and following two training sessions of 1h30min. Using a cross-over design, the athletes were randomly assigned to passive recovery for 2 hours or to hyperbaric oxygen therapy (OHB) for the same duration. After a 7-day period, the interventions were reversed. Before, immediately after, post 2 hours and post 24 hours, blood samples were collected to examine hormone concentrations (cortisol and total testosterone) and cellular damage markers [creatine kinase (CK), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH)]. Moreover, the rating of perceived exertion (RPE) and recovery (RPR) scales were applied. Results Final lactate [La] values (control: 11.9 ± 1.4 mmol/L, OHB: 10.2 ± 1.4 mmol/L) and RPE [control: 14 (13–17 a.u.), OHB: 18 (17–20 a.u.)] were not significantly different following the training sessions. Furthermore, there was no difference between any time points for blood lactate and RPE in the two experimental conditions (P>0.05). There was no effect of experimental conditions on cortisol (F1,20 = 0.1, P = 0.793, η2 = 0.00, small), total testosterone (F1,20 = 0.03, P = 0.877, η2 = 0.00, small), CK (F1,20 = 0.1, P = 0.759, η2 = 0.01, small), AST (F1,20 = 0.1, P = 0.761, η2 = 0.01, small), ALT (F1,20 = 0.0, P = 0.845, η2 = 0.00, small) or LDH (F1,20 = 0.7, P = 0.413, η2 = 0.03, small). However, there was a difference between the two experimental conditions in RPR with higher values at post 2 h and 24 h in OHB when compared to the control condition (P<0.05). Conclusions Thus, it can be concluded that OHB exerts no influence on the recovery of hormonal status or cellular damage markers. Nonetheless, greater perceived recovery, potentially due to the placebo effect, was evident following the OHB condition.

Comment on: “Effect of High-Intensity Interval Training on Total, Abdominal and Visceral Fat Mass: A Meta-Analysis”

We would like to congratulate Maillard et al. [1] on their review, Effect of High-Intensity Interval Training on Total, Abdominal and Visceral Fat Mass: A Meta-Analysis, published recently in Sports Medicine [1]. This is an extremely relevant topic since obesity is a pandemic health problem [2, 3] and high-intensity interval training (HIIT) has been shown to be an effective training method for the improvement of several physiological parameters [4, 5], including the body composition of overweight/obese individuals [6]. The results presented by Maillard et al. [1] contribute tremendously to this area of research. However, we feel the data should be interpreted with caution and would like to address five crucial points of concern. The first of these points is the ambiguous description and analysis of certain studies included in the meta-analysis. For example, we highlight the reported lengths of the exercise sessions. In Table 2, Maillard et al. [1] demonstrate that, in the study by Shepherd et al. [7], the HIIT protocol ranged between ‘‘18–25’: [15–60 s (90% HRmax)/45–120 s active R])’’ during the follow-up; however, the HIIT protocol actually ranged between 8–15’. This difference is due to the warm-up (5-min) and cooldown (5-min) periods of the exercise session, overestimating, at times, the length of the session by more than 100%. Similarly, in another study [8], the warm-up (6min) was also included in the length of the exercise session. Furthermore, the analysis of the effect of HIIT on abdominal fat mass needs to be clarified (Fig. 3). Maillard et al. [1] consider certain studies to have had more than one HIIT protocol, but some of these HIIT protocols are nonexistent. For example, the authors reported that Heydari et al. [9] had four protocols and that Trapp et al. [10] and Kong et al. [11] had two protocols, but only one HIIT protocol was observed in each of these studies. The second point of concern is the inclusion of studies with potential confounding factors, such as protocols in which the HIIT intervention group also received another type of intervention. For example, in the studies by Cassidy et al. [12] and Hallsworth et al. [13], the participants performed 60 s of band-resisted upper-body exercise during the 3-min recovery periods between effort intervals. In the study conducted by Hornbuckle et al. [14], which consisted of a 16-week intervention in the HIIT group, the subjects only performed continuous effort at an intensity corresponding to 60–70% maximum heart rate (HRmax) for 4 weeks, but Maillard et al. [1] did not mention this. Furthermore, in the studies by Hutchison et al. [15] and Terada et al. [16], the individuals from the HIIT group performed moderate-intensity continuous training (60’ at 70% maximal oxygen consumption—VO2max and 30–60’ at 40% oxygen consumption reserve [VO2R]) for 1 day each week. The third point of concern is the inclusion of studies that did not meet the proposed eligibility criteria: the metaanalysis should involve only HIIT protocols, as these protocols have a ‘‘target intensity ‘near the maximal’ effort (i.e., between 80 and 100% of the peak heart rate [PHR]),’’ and will exclude studies that involve sprint interval training & Leonardo Vidal Andreato vidal.leo@hotmail.com

Advanced glycation end products-induced insulin resistance involves repression of skeletal muscle GLUT4 expression

Little is known about advanced glycation end products (AGEs) participation in glucose homeostasis, a process in which skeletal muscle glucose transporter GLUT4 (Scl2a4 gene) plays a key role. This study investigated (1) the in vivo and in vitro effects of AGEs on Slc2a4/GLUT4 expression in skeletal muscle of healthy rats, and (2) the potential involvement of endoplasmic reticulum and inflammatory stress in the observed regulations. For in vivo analysis, rats were treated with advanced glycated rat albumin (AGE-albumin) for 12 weeks; for in vitro analysis, soleus muscles from normal rats were incubated with bovine AGE-albumin for 2.5 to 7.5 hours. In vivo, AGE-albumin induced whole-body insulin resistance; decreased (~30%) Slc2a4 mRNA and GLUT4 protein content; and increased (~30%) the nuclear content of nuclear factor NF-kappa-B p50 subunit (NFKB1), and cellular content of 78 kDa glucose-regulated protein (GRP78). In vitro, incubation with AGE-albumin decreased (~50%) the Slc2a4/GLUT4 content; and increased cellular content of GRP78/94, phosphorylated-IKK-alpha/beta, nuclear content of NFKB1 and RELA, and the nuclear protein binding into Slc2a4 promoter NFKB-binding site. The data reveal that AGEs impair glucose homeostasis in non-diabetic states of increased AGEs concentration; an effect that involves activation of endoplasmic reticulum- and inflammatory-stress and repression of Slc2a4/GLUT4 expression.

Time-course of time-motion, physiological, perceived exertion and neuromuscular responses during simulated judo matches

ABSTRACT The objective of the present study was to describe the physiological, perceived exertion, time-motion and neuromuscular responses in judo matches with different durations. Twelve male brown and black belt judo athletes (74.3 ± 10.5 kg, 175.1 ± 5.3 cm) performed five matches with different durations (1, 2, 3, 4 and 5 min) randomly determined, against the same opponent, in different days and blinded to the time duration. Data from matches were analyzed concerning: rating of perceived recovery, rating of perceived exertion (RPE), heart rate, delta of blood lactate concentrations [La] (the highest minus the rest values), rate of the increment in RPE and [La] per minute of match, maximal isometric strength in dominant and non-dominant hands, leg power and dynamic strength-endurance. After the match, decreases in dynamic strength-endurance and non-dominant isometric strength were observed, dominant hand isometric strength was maintained, while leg power increased. The rate of the physiological and perceptual responses per minute of match changes decreased throughout the course of the match, with the highest changes occurring at the beginning of match and none time-motion variable has been modified throughout the course of the match.