bims-exemet Biomed News
on Exercise metabolism
Issue of 2021‒03‒21
thirteen papers selected by
Javier Botella Ruiz
Victoria University

  1. Exerc Sport Sci Rev. 2021 Apr 01. 49(2): 67-76
      Exercise stimulates the biogenesis of mitochondria in muscle. Some literature supports the use of pharmaceuticals to enhance mitochondria as a substitute for exercise. We provide evidence that exercise rejuvenates mitochondrial function, thereby augmenting muscle health with age, in disease, and in the absence of cellular regulators. This illustrates the power of exercise to act as mitochondrial medicine in muscle.
  2. Cell Metab. 2021 Mar 13. pii: S1550-4131(21)00102-9. [Epub ahead of print]
      Exercise training positively affects metabolic health through increased mitochondrial oxidative capacity and improved glucose regulation and is the first line of treatment in several metabolic diseases. However, the upper limit of the amount of exercise associated with beneficial therapeutic effects has not been clearly identified. Here, we used a training model with a progressively increasing exercise load during an intervention over 4 weeks. We closely followed changes in glucose tolerance, mitochondrial function and dynamics, physical exercise capacity, and whole-body metabolism. Following the week with the highest exercise load, we found a striking reduction in intrinsic mitochondrial function that coincided with a disturbance in glucose tolerance and insulin secretion. We also assessed continuous blood glucose profiles in world-class endurance athletes and found that they had impaired glucose control compared with a matched control group.
    Keywords:  athletes; continuous glucose monitoring; exercise; exercise adaptations; glucose tolerance; high-intensity interval training; insulin resistance; metabolic dysfunction; mitochondria; mitochondrial dynamics; mitochondrial dysfunction
  3. Med Sci Sports Exerc. 2021 Feb 18.
      INTRODUCTION: Exercise-induced microRNAs (miRNAs) expression has been implicated in the regulation of skeletal muscle plasticity. However, the specificity and acute time course in miRNA expression following divergent exercise modes are unknown. In a randomized cross-over design, we compared the acute expression profile of eight skeletal muscle miRNAs previously reported to be involved in skeletal muscle development, growth and maintenance following a bout of either resistance exercise (RE), high intensity interval exercise (HIIE) and concurrent resistance and high intensity interval exercises (CE).METHODS: Nine untrained young men (23.9±2.8y, 70.1±14.9kg, 177.2±3.0cm, 41.4±5.2ml·kg-1·min-1) underwent a counter-balanced cross-over design in which they performed bouts of RE (2x10 repetitions maximum 45°Leg Press and Leg Extension exercises), HIEE (12x1 min sprints at VO2peak with 1min rest intervals between sprints) and CE (RE followed by HIIE), separated by one week. Vastus lateralis biopsies were harvested immediately before (Pre), and immediately (0h), 4h and 8h after each exercise bout.
    RESULTS: There were similar increases (main effect of time; P<0.05) in miR-1-3p,-133a-3p,-133b, -181a-3p, and -486 expression at 8h from Pre with all exercise modes. Besides a main effect of time, miR-23a-3p and -206 presented a main effect of condition with lower expression after HIIE compared to RE and CE.
    CONCLUSIONS: Select miRNAs (miR-1-3p, -133a-3p,-133b,-23a-3p,-181a-3p,-206,-486) do not exhibit an expression specificity in the acute recovery period following a single bout of either RE, HIIE or CE in skeletal muscle. Our data also indicate that RE has a higher effect on the expression of miR-23a-3p and -206 than HIIE. As upregulation of these miRNAs appears to be confined to the 8h period post-exercise, this may subsequently impact the expression patterns of target mRNAs forming the basis of exercise-induced adaptive responses.
  4. Front Physiol. 2021 ;12 564862
      This study aimed to determine the expression of omentin and vaspin, inflammatory markers, body composition, and lipid profile in diet-induced obese rats and high-intensity interval training (HIIT). Forty Wistar rats were divided into four groups: untrained normal diet, trained normal diet (T-ND), untrained high-fat diet (Unt-HFD), and trained high-fat diet (T-HFD). For the animals of the Unt-HFD and T-HFD groups, a high-fat diet was offered for 4 weeks. After that, all the animals in the T-ND and T-HFD groups were submitted to HITT, three times per week, for 10 weeks (2 weeks of adaptation and 8 weeks of HIIT). Muscle (gastrocnemius), liver, epididymal adipose tissue, retroperitoneal adipose tissue, visceral adipose tissue (VAT), and serum were collected to analyze TNF-α, IL-6, PCR, IL-8, IL-10, IL-4, vaspin, and omentin. A body composition analysis was performed before adaptation to HIIT protocol and after the last exercise session using dual-energy X-ray absorptiometry. Omentin and vaspin in the VAT were quantified using Western blotting. The results showed that, when fed a high-fat diet, the animals obtained significant gains in body fat and elevated serum concentrations of vaspin and blood triglycerides. The HIIT was able to minimize body fat gain but did not reduce visceral fat despite the increase in maximum exercise capacity. Moreover, there was a reduction in the serum levels of adiponectin, IL-6, and IL-10. Finally, we concluded that, although the training protocol was able to slow down the weight gain of the animals, there was no reduction in visceral fat or an improvement in the inflammatory profile, including no changes in omentin and vaspin.
    Keywords:  body composition; high fat diet; high-intensity interval training; obesity; omentin; vaspin; visceral adipose tissue
  5. Front Physiol. 2021 ;12 629914
      High-intensity interval training (HIIT) is reported to be beneficial to brain-derived neurotrophic factor (BDNF) biosynthesis. A key element in this may be the existence of lactate, the most obvious metabolic product of exercise. In vivo, this study investigated the effects of a 6-week HIIT on the peripheral and central lactate changes, mitochondrial quality control system, mitochondrial function and BDNF expression in mouse hippocampus. In vitro, primary cultured mice hippocampal cells were used to investigate the role and the underlying mechanisms of lactate in promoting mitochondrial function during HIIT. In vivo studies, we firstly reported that HIIT can potentiate mitochondrial function [boost some of the mitochondrial oxidative phosphorylation (OXPHOS) genes expression and ATP production], stimulate BDNF expression in mouse hippocampus along with regulating the mitochondrial quality control system in terms of promoting mitochondrial fusion and biogenesis, and suppressing mitochondrial fission. In parallel to this, the peripheral and central lactate levels elevated immediately after the training. In vitro study, our results revealed that lactate was in charge of regulating mitochondrial quality control system for mitochondrial function and thus may contribute to BDNF expression. In conclusion, our study provided the mitochondrial mechanisms of HIIT enhancing brain function, and that lactate itself can mediate the HIIT effect on mitochondrial quality control system in the hippocampus.
    Keywords:  BDNF; High-intensity interval training; lactate; mitochondrial quality control system; mouse hippocampus
  6. J Exp Biol. 2021 Mar 18. pii: jeb234237. [Epub ahead of print]224(Pt 6):
      Regular exercise induces a broad spectrum of adaptation reactions in a variety of tissues and organs. However, the respective mechanisms are incompletely understood. In the context of their analysis, animal model systems, specifically rodent treadmill running protocols, play an important role. However, few researchers have studied different aspects of adaptation, such as cardiorespiratory and skeletal muscle training effects, within one set of experiments. Here, we analyzed physiological adaptation to 10 weeks of regular, moderate-intensity, uphill treadmill running in mice, a widely used model for endurance exercise training. To study the effects of reactive oxygen species (ROS), which have been suggested to be major regulators of training adaptation, a subgroup of mice was treated with the ROS scavenger PDTC (pyrrolidine dithiocarbamate). We found that mass gain in mice that exercised under PDTC treatment lagged behind that of all other experimental groups. In addition, both exercise and PDTC significantly and additively decreased resting heart rate. Furthermore, there was a trend towards an enhanced proportion of type 2A skeletal muscle fibers and differential expression of metabolism-associated genes, indicating metabolic and functional adaptation of skeletal muscle fibers. By contrast, there were no effects on grip strength and relative mass of individual muscles, suggesting that our protocol of uphill running did not increase skeletal muscle hypertrophy and strength. Taken together, our data suggest that a standard protocol of moderate-intensity uphill running induces adaptation reactions at multiple levels, part of which might be modulated by ROS, but does not enhance skeletal muscle hypertrophy and force.
    Keywords:  Cardiorespiratory adaptation; Exercise; Metabolic adaptation; Reactive oxygen species
  7. Life Sci. 2021 Mar 11. pii: S0024-3205(21)00325-8. [Epub ahead of print] 119340
      AIMS: Hypoxic training promotes human cardiopulmonary function and exercise performance efficiently, but the myocellular mechanism has been less studied. We aimed to examine the effects of hypoxic trainings on mitochondrial turnover and vascular remodeling of skeletal muscle.MAIN METHODS: C57BL/6 J mice were divided into control, hypoxic exposure, exercise training, "live high-train low" (LHTL), and "live low-train high" (LLTH) groups (n = 8/group). Western blot and immunohistochemistry were used to evaluate mitochondrial turnover of gastrocnemius and angiogenesis of quadriceps after six weeks interventions.
    KEY FINDINGS: Compared with control group, both LHTL and LLTH increased phosphorylation levels of p38 MAPK markedly (p < 0.05). LLTH also elevated PGC-1α protein expression significantly (p < 0.05). All interventions did not influence Bnip3 and Drp-1 proteins levels (p > 0.05), while LLTH enhanced Parkin and Mff protein contents significantly (p < 0.05). Immunohistochemical analysis showed both LHTL and LLTH promoted CD31 and VEGF expressions (p < 0.05). ATP content, citrate synthase activities of gastrocnemius were robustly elevated in LHTL and LLTH groups (p < 0.01). The exercise training increased Mff protein and ATP content in gastrocnemius as well as VEGF expression in quadriceps (p < 0.05). The hypoxic exposure also increased ATP content, citrate synthase, and ATP synthase activities in gastrocnemius as well as VEGF expression in quadriceps (p < 0.01).
    SIGNIFICANCE: Our results suggested that hypoxic trainings, especially LLTH, promoted mitochondrial turnover and angiogenesis of skeletal muscle, which may be an underlying mechanism of hypoxic training-induced exercise capacity.
    Keywords:  Exercise; Hypoxic training; Mitochondrial biogenesis; Mitophagy
  8. Biochim Biophys Acta Mol Basis Dis. 2021 Mar 12. pii: S0925-4439(21)00059-4. [Epub ahead of print] 166126
      Mitochondrial-derived peptide (MOTS-c) has gained increasing attention as a promising therapeutic or prevention strategy for obesity and diabetes mellitus. MOTS-c targets the folate cycle, leading to an accumulation of 5-aminomidazole-4-carboxamide ribonucleotide (AICAR) as well as AMPK activation. AMPK is a well-known upstream regulator of the proliferation-activated receptor co-activator 1 (PGC-1α), which can improve mitochondrial biogenesis via co-transcriptional modifications. We hypothesized that AMPK can induce the expression of MOTS-c through PGC-1α. Our study aimed to explore whether MOTS-c and/or exercise can regulate MOTS-c expression, attenuate insulin resistance and enhance glucose metabolism both in vitro and in vivo. It was found that C2C12 myotubes exposed to Compound C (an AMPK inhibitor) had deceases in the protein and mRNA expressions of PGC-1α and MOTS-c. PGC-1α knockdown downregulated the protein and mRNA expressions of MOTS-c in C2C12 myotubes, whereas both PGC-1α overexpression and recombinant MOTS-c supplementation upregulated the protein and mRNA expressions of MOTS-c in C2C12 myotubes. Furthermore, the skeletal muscle and plasma levels of MOTS-c were markedly reduced in high-fat diet-induced obese mice. Treadmill training remarkably upregulated the protein levels of MOTS-c, PGC-1α and GLUT4, along with the phosphorylation levels of AMPK and ACC. Altogether, these results indicate that AMPK/PGC-1α pathway can mediate the secretion and/or production of MOTS-c in skeletal muscle, implying the possible roles of exercise intervention and recombinant MOTS-c in treating obesity and diabetes mellitus.
    Keywords:  AMPK; Exercise; Insulin resistance; MOTS-c; PGC-1α; Skeletal muscle
  9. Scand J Med Sci Sports. 2021 Mar 17.
      The purpose of the study was to determine if concurrent training (endurance and resistance in a single session) elicits leg muscular adaptations beyond the ones obtained by endurance training alone in sedentary individuals with metabolic syndrome (MetS). Sixty-six MetS individuals (37% women, age 56±7 years, BMI 32±5 kg·m-2 and 3.8±0.8 MetS factors) were randomized to undergo one of the following 16-week isocaloric exercise programs: i) 4+1 bouts of 4-min at 90% of HRMAX of intense aerobic cycling (IAC+IAC group; n=33), ii) 4 IAC bouts followed by 3 sets of 12 repetitions of 3 lower limb free-weight exercises (IAC+RT group; n=33). We measured the effects of training on maximal cycling power, leg press maximum strength (1RM), countermovement jump height (CMJ) and mean propulsive velocity (MPV) at workloads ranging from 10-100% of baseline 1RM leg press. After intervention, MetS components (Z-score) improved similarly in both groups (P=0.002). Likewise, maximal cycling power during a ramp test improved similarly in both groups (time effect P<0.001). However, leg press 1RM improved more in IAC+RT than in IAC+IAC (47±5 vs 13±5 kg, respectively, interaction P<0.001). CMJ only improved with IAC+RT (0.8±0.2 cm, P=0.001). Leg press MPV at heavy loads (i.e., 80-100% 1RM) improved more with concurrent training (0.12±0.01 vs. 0.06±0.02 m·s-1 , interaction P=0.013). In conclusion, in unconditioned MetS individuals, intense aerobic cycling alone improves leg muscle performance. However, substituting 20% of intense aerobic cycling by resistance training further improves 1RM leg press, MPV at high loads and jumping ability while providing similar improvement in MetS components.
    Keywords:  Metabolic syndrome; muscular adaptations; concurrent training; intense aerobic cycling; resistance training
  10. Sci Rep. 2021 Mar 19. 11(1): 6453
      This study examined acute molecular responses to concurrent exercise involving different muscles. Eight men participated in a randomized crossover-trial with two sessions, one where they performed interval cycling followed by upper body resistance exercise (ER-Arm), and one with upper body resistance exercise only (R-Arm). Biopsies were taken from the triceps prior to and immediately, 90- and 180-min following exercise. Immediately after resistance exercise, the elevation in S6K1 activity was smaller and the 4E-BP1:eIF4E interaction greater in ER-Arm, but this acute attenuation disappeared during recovery. The protein synthetic rate in triceps was greater following exercise than at rest, with no difference between trials. The level of PGC-1α1 mRNA increased to greater extent in ER-Arm than R-Arm after 90 min of recovery, as was PGC-1α4 mRNA after both 90 and 180 min. Levels of MuRF-1 mRNA was unchanged in R-Arm, but elevated during recovery in ER-Arm, whereas MAFbx mRNA levels increased slightly in both trials. RNA sequencing in a subgroup of subjects revealed 862 differently expressed genes with ER-Arm versus R-Arm during recovery. These findings suggest that leg cycling prior to arm resistance exercise causes systemic changes that potentiate induction of specific genes in the triceps, without compromising the anabolic response.
  11. Autophagy. 2021 Mar 17.
      CREG1 (cellular repressor of E1A-stimulated genes 1) is involved in tissue homeostasis and influences macroautophagy/autophagy to protect cardiovascular function. However, the physiological and pathological role of CREG1 in the skeletal muscle is not clear. Here, we established a skeletal muscle-specific creg1 knockout mouse model (creg1;Ckm-Cre) by crossing the Creg1-floxed mice (Creg1fl/fl) with a transgenic line expressing Cre recombinase under the muscle-specific Ckm (creatine kinase, muscle) promoter. In creg1;Ckm-Cre mice, the exercise time to exhaustion and running distance were significantly reduced compared to Creg1fl/fl mice at the age of 9 months. In addition, the administration of recombinant (re)CREG1 protein improved the motor function of 9-month-old creg1;Ckm-Cre mice. Moreover, electron microscopy images of 9-month-old creg1;Ckm-Cre mice showed that the mitochondrial quality and quantity were abnormal and associated with increased levels of PINK1 (PTEN induced putative kinase 1) and PRKN/PARKIN (parkin RBR E3 ubiquitin protein ligase) but reduced levels of the mitochondrial proteins PTGS2/COX2, COX4I1/COX4, and TOMM20. These results suggested that CREG1 deficiency accelerated the induction of mitophagy in the skeletal muscle. Mechanistically, gain-and loss-of-function mutations of Creg1 altered mitochondrial morphology and function, impairing mitophagy in C2C12 cells. Furthermore, HSPD1/HSP60 (heat shock protein 1) (401-573 aa) interacted with CREG1 (130-220 aa) to antagonize the degradation of CREG1 and was involved in the regulation of mitophagy. To the best of our knowledge, this was the first time to demonstrate that CREG1 localized to the mitochondria and played an important role in mitophagy modulation that determined skeletal muscle wasting during the growth process or disease conditions.
    Keywords:  CREG1; HSPD1; mitochondria; mitophagy; skeletal muscle