Browsing by Subject "Fiber type"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Dietary nitrate-induced increases in human muscle power: high versus low responders
    (Wiley, 2018-01) Coggan, Andrew R.; Broadstreet, Seth R.; Mikhalkova, Deana; Bole, Indra; Leibowitz, Joshua L.; Kadkhodayan, Ana; Park, Soo; Thomas, Deepak P.; Thies, Dakkota; Peterson, Linda R.; Kinesiology, School of Physical Education and Tourism Management
    Maximal neuromuscular power is an important determinant of athletic performance and also quality of life, independence, and perhaps even mortality in patient populations. We have shown that dietary nitrate (NO3- ), a source of nitric oxide (NO), improves muscle power in some, but not all, subjects. The present investigation was designed to identify factors contributing to this interindividual variability. Healthy men (n = 13) and women (n = 7) 22-79 year of age and weighing 52.1-114.9 kg were studied using a randomized, double-blind, placebo-controlled, crossover design. Subjects were tested 2 h after ingesting beetroot juice (BRJ) either containing or devoid of 12.3 ± 0.8 mmol of NO3- . Plasma NO3- and nitrite (NO2- ) were measured as indicators of NO bioavailability and maximal knee extensor speed (Vmax ), power (Pmax ), and fatigability were determined via isokinetic dynamometry. On average, dietary NO3- increased (P < 0.05) Pmax by 4.4 ± 8.1%. Individual changes, however, ranged from -9.6 to +26.8%. This interindividual variability was not significantly correlated with age, body mass (inverse of NO3- dose per kg), body mass index (surrogate for body composition) or placebo trial Vmax or fatigue index (in vivo indicators of muscle fiber type distribution). In contrast, the relative increase in Pmax was significantly correlated (r = 0.60; P < 0.01) with the relative increase in plasma NO2- concentration. In multivariable analysis female sex also tended (P = 0.08) to be associated with a greater increase in Pmax. We conclude that the magnitude of the dietary NO3- -induced increase in muscle power is dependent upon the magnitude of the resulting increase in plasma NO2- and possibly female sex.
  • Thumbnail Image
    Item
    Dietary nitrate‐induced increases in human muscle power: high versus low responders
    (Wiley, 2018-01-25) Coggan, Andrew R.; Broadstreet, Seth R.; Mikhalkova, Deana; Bole, Indra; Leibowitz, Joshua L.; Kadkhodayan, Ana; Park, Soo; Thomas, Deepak P.; Thies, Dakkota; Peterson, Linda R.; Kinesiology, School of Health and Human Sciences
    Maximal neuromuscular power is an important determinant of athletic performance and also quality of life, independence, and perhaps even mortality in patient populations. We have shown that dietary nitrate (NO 3 −), a source of nitric oxide (NO), improves muscle power in some, but not all, subjects. The present investigation was designed to identify factors contributing to this interindividual variability. Healthy men (n = 13) and women (n = 7) 22–79 year of age and weighing 52.1–114.9 kg were studied using a randomized, double‐blind, placebo‐controlled, crossover design. Subjects were tested 2 h after ingesting beetroot juice (BRJ) either containing or devoid of 12.3 ± 0.8 mmol of NO 3 −. Plasma NO 3 − and nitrite (NO 2 −) were measured as indicators of NO bioavailability and maximal knee extensor speed (V max), power (P max), and fatigability were determined via isokinetic dynamometry. On average, dietary NO 3 − increased (P < 0.05) P max by 4.4 ± 8.1%. Individual changes, however, ranged from −9.6 to +26.8%. This interindividual variability was not significantly correlated with age, body mass (inverse of NO 3 − dose per kg), body mass index (surrogate for body composition) or placebo trial V max or fatigue index (in vivo indicators of muscle fiber type distribution). In contrast, the relative increase in Pmax was significantly correlated (r = 0.60; P < 0.01) with the relative increase in plasma NO 2 − concentration. In multivariable analysis female sex also tended (P = 0.08) to be associated with a greater increase in Pmax. We conclude that the magnitude of the dietary NO 3 −‐induced increase in muscle power is dependent upon the magnitude of the resulting increase in plasma NO 2 − and possibly female sex.
  • Thumbnail Image
    Item
    Insulin Resistance Is Not Sustained Following Denervation in Glycolytic Skeletal Muscle
    (MDPI, 2021-05-06) McMillin, Shawna L.; Stanley, Erin C.; Weyrauch, Luke A.; Brault, Jeffrey J.; Kahn, Barbara B.; Witczak, Carol A.; Anatomy and Cell Biology, School of Medicine
    Denervation rapidly induces insulin resistance (i.e., impairments in insulin-stimulated glucose uptake and signaling proteins) in skeletal muscle. Surprisingly, whether this metabolic derangement is long-lasting is presently not clear. The main goal of this study was to determine if insulin resistance is sustained in both oxidative soleus and glycolytic extensor digitorum longus (EDL) muscles following long-term (28 days) denervation. Mouse hindlimb muscles were denervated via unilateral sciatic nerve resection. Both soleus and EDL muscles atrophied ~40%. Strikingly, while denervation impaired submaximal insulin-stimulated [3H]-2-deoxyglucose uptake ~30% in the soleus, it enhanced submaximal (~120%) and maximal (~160%) insulin-stimulated glucose uptake in the EDL. To assess possible mechanism(s), immunoblots were performed. Denervation did not consistently alter insulin signaling (e.g., p-Akt (Thr308):Akt; p-TBC1D1 [phospho-Akt substrate (PAS)]:TBC1D1; or p-TBC1D4 (PAS):TBC1D4) in either muscle. However, denervation decreased glucose transporter 4 (GLUT4) levels ~65% in the soleus but increased them ~90% in the EDL. To assess the contribution of GLUT4 to the enhanced EDL muscle glucose uptake, muscle-specific GLUT4 knockout mice were examined. Loss of GLUT4 prevented the denervation-induced increase in insulin-stimulated glucose uptake. In conclusion, the denervation results sustained insulin resistance in the soleus but enhanced insulin sensitivity in the EDL due to increased GLUT4 protein levels.