Exercise influence on monocarboxylate transporter 1 (MCT1) and 4 (MCT4) in the skeletal muscle: A systematic review

This review aims to systematically analyze the effect of exercise on muscle MCT protein levels and mRNA expression of their respective genes, considering exercise intensity, and duration (single-exercise session and training program) in humans and rodents, to observe whether both models offer aligned results. The review also aims to report methodological aspects that need to be improved in future studies. A systematic search was conducted in the PubMed and Web of Science databases, and the Preferred Reporting Items for Systematic review and Meta-Analyses (PRISMA) checklist was followed. After applying inclusion and exclusion criteria, 41 studies were included and evaluated using the Cochrane collaboration tool for risk of bias assessment. The main findings indicate that exercise is a powerful stimulus to increase MCT1 protein content in human muscle. MCT4 protein level increases can also be observed after a training program, although its responsiveness is lower compared to MCT1. Both transporters seem to change independently of exercise intensity, but the responses that occur with each intensity and each duration need to be better defined. The effect of exercise on muscle mRNA results is less defined, and more research is needed especially in humans. Moreover, results in rodents only agree with human results on the effect of a training program on MCT1 protein levels, indicating increases in both. Finally, we addressed important and feasible methodological aspects to improve the design of future studies.

Role of the monocarboxylate transporter MCT1 in the uptake of lactate during active recovery

PURPOSE

We assessed the role of monocarboxylate transporter 1 (MCT1) on lactate clearance during an active recovery after high-intensity exercise, by comparing genetic groups based on the T1470A (rs1049434) MCT1 polymorphism, whose influence on lactate transport has been proven.

METHODS

Sixteen young male elite field hockey players participated in this study. All of them completed two 400 m maximal run tests performed on different days, followed by 40 min of active or passive recovery. Lactate samples were measured immediately after the tests, and at min 10, 20, 30 and 40 of the recoveries. Blood lactate decreases were calculated for each 10-min period. Participants were distributed into three groups according to the T1470A polymorphism (TT, TA and AA).

RESULTS

TT group had a lower blood lactate decrease than AA group during the 10-20 min period of the active recovery (p = 0.018). This period had the highest blood lactate for the whole sample, significantly differing from the other periods (p ≤ 0.003). During the passive recovery, lactate declines were constant except for the 0-10-min period (p ≤ 0.003), suggesting that liver uptake is similar in all the genetic groups, and that the difference seen during the active recovery is mainly due to muscle lactate uptake.

CONCLUSIONS

These differences according to the polymorphic variant T1470A suggest that MCT1 affects the plasma lactate decrease during a crucial period of active recovery, where the maximal lactate amount is cleared (i.e. 10-20 min period).

Influence of ADRB2 Gln27Glu and ADRB3 Trp64Arg polymorphisms on body weight and body composition changes after a controlled weight-loss intervention

The β-2 and β-3 adrenergic receptors (ADRB2 and ADRB3) are thought to play a role in energy expenditure and lipolysis. However, the effects of the ADRB2 glutamine (Gln) 27 glutamic acid (glutamate) (Glu) and ADRB3 tryptophan (Trp) 64 arginine (Arg) polymorphisms on weight loss remain controversial. The aim of this study was to investigate the effect of these polymorphisms on changes in weight and body composition during a controlled weight-loss program. One hundred seventy-three healthy overweight and obese participants (91 women, 82 men) aged 18-50 years participated in a 22-week-long intervention based on a hypocaloric diet and exercise. They were randomly assigned to 1 of 4 groups: strength, endurance, strength and endurance combined, and physical activity recommendations only. Body weight, body mass index (BMI), and body composition variables were assessed before and after the intervention. Genetic analysis was carried out according to standard protocols. No effect of the ADRB2 gene was shown on final weight, BMI, or body composition, although in the supervised male group, Glu27 carriers tended to have greater weight (p = 0.019, 2.5 kg) and BMI (p = 0.019, 0.88 kg/m(2)) reductions than did noncarriers. There seems to be an individual effect of the ADRB3 polymorphism on fat mass (p = 0.004) and fat percentage (p = 0.036), in addition to an interaction with exercise for fat mass (p = 0.038). After the intervention, carriers of the Arg64 allele had a greater fat mass and fat percentage than did noncarriers (p = 0.004, 2.8 kg). In conclusion, the ADRB2 Gln27Glu and ADRB3 Trp64Arg polymorphisms may influence weight loss and body composition, although the current evidence is weak; however, further studies are necessary to clarify their roles.

Sequence structure and population data of two X-linked markers: DXS7423 and DXS8377

DXS7423 and DXS8377 are two microsatellite markers located in the q28 band of chromosome X. We developed a protocol to amplify both markers in a single reaction, sequenced the most common alleles and studied allele frequencies in a Spanish population sample. DXS7423 allele variability was due to different numbers of (TCCA) repeats and five different alleles were found with apparent sizes between 181 and 197 bp. The probability of discrimination (PD) was 87% for female samples, and the expected probability of exclusion (PE) was 71%. DXS8377 appeared as a highly polymorphic marker with variable numbers of (CTC), (TCC) and (TTC) repeats. We found 18 alleles of different sizes (204-258 bp) and the PD and PE were 99% and 93%, respectively. These data suggest that DXS7423 and DXS8377 can be very useful markers for genetic forensic studies.

A new pentaplex system to study short tandem repeat markers of forensic interest on X chromosome

A new method has been optimised to amplify five X chromosome short tandem repeat (STR) markers of interest in forensic medicine: human phosphoribosyl transferase (HPRTB), DXS101, androgen receptor (ARA), DXS7423 and DXS8377. Markers were conveniently amplified in a single PCR reaction with fluorochrome-labelled primers, which allowed the analysis of fragment sizes after injection into a capillary electrophoresis system. The most common alleles of each locus were sequenced and used in a control ladder to type unknown samples.