Variants of the Solute Carrier SLC16A1 Gene (MCT1) Associated With Metabolic Responses During a Long-Graded Test in Road Cyclists

The interactions between monocarboxylate transporter genes MCT1, MCT2, and MCT4 and the kinetics of blood lactate production and removal after high-intensity efforts in elite males: a cross-sectional study

BACKGROUND

This cross-sectional study investigated the relationship between genetic variations in monocarboxylate transporter genes and blood lactate production and removal after high-intensity efforts in humans. The study was conducted to explore how genetic variations in the MCT1, MCT2, and MCT4 genes influenced lactate dynamics and to advance the field of sports genetics by pinpointing critical genetic markers that can enhance athletic performance and recovery.

METHODS

337 male athletes from Poland and the Czech Republic underwent two intermittent all-out Wingate tests. Before the tests, DNA samples were taken from each participant, and SNP (single nucleotide polymorphism) analysis was carried out. Two intermittent all-out tests were implemented, and lactate concentrations were assessed before and after these tests.

RESULTS

Sprinters more frequently exhibited the haplotype TAC in the MCT2 gene, which was associated with an increase in the difference between maximum lactate and final lactate concentration. Additionally, this haplotype was linked to higher maximum lactate concentration and was more frequently observed in sprinters. The genotypic interactions AG/T- and GGxT- (MCT1 rs3789592 x MCT4 rs11323780), TTxTT (MCT1 rs12028967 x MCT2 rs3763979), and MCT1 rs7556664 x MCT4 rs11323780 were all associated with an increase in the difference between maximum lactate concentration and final lactate concentration. Conversely, the AGxGG (MCT1 rs3789592 x MCT2 rs995343) interaction was linked to a decrease in this difference. The relationship between maximum lactate concentration and genotypic interactions can be observed as follows: when ATxTT (MCT2 rs3763980 x MCT4 rs11323780) or CTxCT (MCT1 rs10857983 x MCT2 rs3763979) genotypic combinations are present, it leads to a decrease in maximum lactate concentration. Similarly, the combination of CTxCT (MCT1 rs4301628 x MCT2 rs3763979), CT x TT (MCT1 rs4301628 x MCT4 rs11323780), and CTxTT (MCT1 rs4301628 x MCT2 rs3763979) results in decreased maximum lactate concentration.

CONCLUSIONS

The TAC haplotype (rs3763980, rs995343, rs3763979) in the MCT2 gene is associated with altered lactate clearance in sprinters, potentially affecting performance and recovery by elevating post-exercise lactate concentrations. While MCT4 rs11323780 is also identified as a significant variant in lactate metabolism, suggesting its role as a biomarker for sprinting performance, further investigation is necessary to clarify underlying mechanisms and consider additional factors. Based on elite male athletes from Poland and the Czech Republic, the study may not generalize to all sprinters or diverse athletic populations. Although genetic variants show promise as biomarkers for sprinting success, athletic performance is influenced by a complex interplay of genetics, environment, and training extending beyond MCT genes.

Targeting monocarboxylate transporters (MCTs) in cancer: How close are we to the clinics?

As a result of metabolic reprogramming, cancer cells display high rates of glycolysis, causing an excess production of lactate along with an increase in extracellular acidity. Proton-linked monocarboxylate transporters (MCTs) are crucial in the maintenance of this metabolic phenotype, by mediating the proton-coupled lactate flux across cell membranes, also contributing to cancer cell pH regulation. Among the proteins codified by the SLC16 gene family, MCT1 and MCT4 isoforms are the most explored in cancers, being overexpressed in many cancer types, from solid tumours to haematological malignancies. Similarly to what occurs in particular physiological settings, MCT1 and MCT4 are able to mediate lactate shuttles among cancer cells, and also between cancer and stromal cells in the tumour microenvironment. This form of metabolic cooperation is responsible for important cancer aggressiveness features, such as cell proliferation, survival, angiogenesis, migration, invasion, metastasis, immune tolerance and therapy resistance. The growing understanding of MCT functions and regulation is offering a new path to the design of novel inhibitors that can be foreseen in clinical practices. This review provides an overview of the role of MCT isoforms in cancer and summarizes the recent advances in their pharmacological targeting, highlighting the potential of new potent and selective MCT1 and/or MCT4 inhibitors in cancer therapeutics, and anticipating its inclusion in clinical practice.

The MCT1 gene Glu490Asp polymorphism (rs1049434) is associated with endurance athlete status, lower blood lactate accumulation and higher maximum oxygen uptake

The purpose of this study was to explore the association of the MCT1 gene Glu490Asp polymorphism (rs1049434) with athletic status and performance of endurance athletes. A total of 1,208 Brazilians (318 endurance athletes and 890 non-athletes) and 867 Europeans (315 endurance athletes and 552 non-athletes) were evaluated in a case-control approach. Brazilian participants were classified based on self-declared ethnicity to test whether the polymorphism was different between Caucasians and Afro-descendants. Moreover, 66 Hungarian athletes underwent an incremental test until exhaustion to assess blood lactate levels, while 46 Russian athletes had their maximum oxygen uptake ( V ⋅ O 2 max ) compared between genotypes. In the Brazilian cohort, the major T-allele was more frequent in Caucasian top-level competitors compared to their counterparts of lower competitive level (P = 0.039), and in Afro-descendant athletes compared to non-athletes (P = 0.015). Similarly, the T-allele was more frequent in European athletes (P = 0.029). Meta-analysis of the Brazilian and European cohorts confirmed that the T-allele is over-represented in endurance athletes (OR: 1.48, P = 0.03), especially when Afro-descendant athletes were included in the meta-analysis (OR: 1.58, P = 0.005). Furthermore, carriers of the T/T genotype accumulated less blood lactate in response to intense effort (P < 0.01) and exhibited higher V ⋅ O 2 max (P = 0.04)_. In conclusion, the Glu490Asp polymorphism was associated with endurance athletic status and performance. Our findings suggest that, although ethnic differences may exist, the presence of the major T-allele (i.e., the Glu-490 allele) favours endurance performance more than the mutant A-allele (i.e., the 490-Asp allele).

Monocarboxylate transporters in cancer

Background

Tumors are highly plastic metabolic entities composed of cancer and host cells that can adopt different metabolic phenotypes. For energy production, cancer cells may use 4 main fuels that are shuttled in 5 different metabolic pathways. Glucose fuels glycolysis that can be coupled to the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) in oxidative cancer cells or to lactic fermentation in proliferating and in hypoxic cancer cells. Lipids fuel lipolysis, glutamine fuels glutaminolysis, and lactate fuels the oxidative pathway of lactate, all of which are coupled to the TCA cycle and OXPHOS for energy production. This review focuses on the latter metabolic pathway.

Scope of review

Lactate, which is prominently produced by glycolytic cells in tumors, was only recently recognized as a major fuel for oxidative cancer cells and as a signaling agent. Its exchanges across membranes are gated by monocarboxylate transporters MCT1-4. This review summarizes the current knowledge about MCT structure, regulation and functions in cancer, with a specific focus on lactate metabolism, lactate-induced angiogenesis and MCT-dependent cancer metastasis. It also describes lactate signaling via cell surface lactate receptor GPR81.

Major conclusions

Lactate and MCTs, especially MCT1 and MCT4, are important contributors to tumor aggressiveness. Analyses of MCT-deficient (MCT^+/- and MCT^−/-) animals and (MCT-mutated) humans indicate that they are druggable, with MCT1 inhibitors being in advanced development phase and MCT4 inhibitors still in the discovery phase. Imaging lactate fluxes non-invasively using a lactate tracer for positron emission tomography would further help to identify responders to the treatments.

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In cancer, hypoxia and cell proliferation are associated to lactic acid production.

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Lactate exchanges are at the core of tumor metabolism.

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Transmembrane lactate trafficking depends on monocarboxylate transporters (MCTs).

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MCTs are implicated in tumor development and aggressiveness.

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Targeting MCTs is a therapeutic option for cancer treatment.

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).