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- MARTIN-RINCON, M, et al.
(author)
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Upregulation of nicotinamide n-methyltransferase in skeletal muscle following prolongedexercise and caloric restriction
- 2017
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In: 22nd Annual Congress of the European College of Sport Science. - Cologne, Germany : DTP Publishing. - 9783981841404 ; , s. 186-
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Conference paper (peer-reviewed)abstract
- IntroductionExpression of Nicotinamide (NA) N-methyltransferase (NNMT), the enzyme responsible for the methylation of NA to methylnicotinamide (MNA), is reduced in obese and diabetic mice. In rodent liver, NNMT activity and plasma MNA levels are increased after 90min of swimming.NNMT knockdown in mice white adipose tissue increases energy expenditure, suggesting a protective role against diet-induced obesity and type-2 diabetes. The role that NNMT plays in human metabolism remains unknown. Thus, the aims of the study were 1) to determine in human skeletal muscle (sm) whether NNMT is upregulated by prolonged exercise and 2) to ascertain whether the expression of NNMT in sm is influenced by severe energy deficit.MethodsFifteen overweight men underwent to 4 days of caloric restriction (CR) (0.8 g/kg BW/day) in combination with prolonged exercise (PE) (8h walking + 45min single-arm cranking/day). Three sm biopsies (exercised/non exercised arm and one leg) were obtained before (PRE), after (PE+CR) and following 3 days of control diet (isoenergetic) and reduced exercise (CD) to measure the expression of key metabolic genes (e.g. PDK4, CPT2, PFKFB3, NNMT) (microarray), NNMT protein expression (WB) and circulating plasma MNA levels (LC-MS). Maximal fat oxidation (MFO) (indirect calorimetry) and body composition (DEXA) were measured. ANOVA repeated-measures was used.ResultsDuring PE+CR the energy deficit was 5000 kcal/d reducing fat mass by 2.8 (PE+CR) and 3.8 kg (CD). MFO was increased. CPT2, PDK4, PFKFB3 genes (CHO-to-fat metabolic shift) were differentially expressed (FDR<5%) in at least one sm. Compared to PRE, after CD, NNMT gene expression was upregulated in all sm (~3-5 fold). Protein NNMT increased ~13-fold (p<0.001), ~9-fold (p<0.01) and ~5-fold (p<0.001) for non-exercised and exercised arm (45min/day) and leg (8h/day), respectively. Circulating levels of MNA were augmented two-fold. The increase in NNMT expression from PRE to CD was associated with the increase in MFO (r=0.37, p=0.01,n=45).DiscussionThis findings reveal that NNMT is upregulated in human sm in response to a severe energy deficit, with a simultaneous increase of MNA plasma levels. However, this response was attenuated in the exercised sm. NNMT may have a role in facilitating fat oxidation. Caloric restriction elicits increased sirtuins expression and activity, coupled with the NAD+ breakdown into NA. Overexpression of NNMT probably prevents accumulation of NA, which would otherwise inhibit the sirtuins. Our data suggest sm as a plausible source of MNA, which may act as a myokine with a role in the adaptation to starvation.
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| 3. |
- Parker, James, 1980-
(author)
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Construct validity and test-retest reliability of the force-velocity profile in a golf specific rotation movement
- 2017
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In: Book of Abstracts of the 22nd Annual Congress of the European College of Sport Science – 5th - 8th July 2017, MetropolisRuhr – Germany. - Cologne : European College of Sport Science. - 9783981841404 ; , s. 294-294
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Conference paper (peer-reviewed)abstract
- Introduction: Assessing the isoinertial force-velocity (F-V) and power relationships has previously been found valuable to assist the understanding of the underlying mechanisms responsible for maximal power output. Multiple studies have investigated the F-V profile in the lower body, however, few studies have investigated F-V profiling in rotational movements, in particular, the golf swing. There is a need for isoinertial strength assessment protocols which can relate to final swing performance. The specific objective of the study was to investigate if measurements of force, velocity, and power using five different loads in a golf specific rotational movement are valid and reliable. Methods: 12 elite golfers (handicap -1.5±1.2) 8 men and 4 women performed a golf relevant rotational movement using five different loads (2, 6, 10, 14, and18 kg) in a motorised cable machine (1080 Motion AB, Sweden), measuring exercise peak force (PF), peak velocity (PV), and peak power (PP). In addition, normal-swing driver clubhead speed (CHSnor), and maximum clubhead speed (CHSmax) was measured using radar (Trackman, Denmark). The best of three trials for CHSnor, CHSmax, and the golf rotation was used for further analysis. Test-retest occasions were separated by 7-14 days. Statistical analysis: Change in mean (CIM) individual inter-session coefficient of variation (CV) and intraclass correlation coefficient (ICC) was used to analyze test-retest reliability, a Spearman's correlation between the rotation output variables and the CHS was used to assess construct validity.For reliability, an ICC of >0.70 was considered acceptable and results for correlation was considered excellent (≥0.90), good (0.75–0.89), moderate (0.50–0.74), poor (<0.50).was considered to be acceptable. Results: PF, PV, and PP for all of the five loads, apart from PP with 2 kg (CIM=12.2%, CV=14.1%, &ICC= 0.29) and PP with 18kg (CIM=8.6%, CV=19.1%, & ICC= 0.93), showed good reliability (CIM= 0.05-3.6%, CV=1.4-8.5%, & ICC= 0.84-0.97). PF (r=0.780-0.89 & 0.75-0.88), PV (r=0.76-0.86 & 0.78-0.85), and PP (r=0.75-0.84 & 0.76-0.85) for all loads had statistically significant strong correlations with both CHSnor and CHSmax respectively, apart from PF at 2kg (r=0.33). The average day to day variation among all loads for PF, PV and PP were 17.9 ±13.7 N, 0.30 ± 0.23 m/s, and 135.9 ± 128.1 W respectively. Greatest PP was achieved with the 14 kg load, although PP at 6, 10, and 14kg only differed by 90 W (8%) between these loads. Discussion: Isoinertial force-velocity-power profiling in high-level golfers can be assessed after a familiarization session. The strongest correlation among the rotational tests and CHS was between PF at 10 kg and CHSnor (r=0.89) and in general, the PF, PV, and PP variables had a strong relationship with both CHSnor and CHSmax. Such profiling may provide valuable information insight into the neuromuscular capabilities of high-level golfers and may be used to monitor specific training adaptions.
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