The Effect of Geranylgeraniol on Satellite Cells Myogenic State in Type 2 Diabetic Rats

Type 2 Diabetes (T2D) is associated with chronic inflammation, which can contribute to impaired satellite cells (SC) myogenic state that may result in muscle atrophy. Geranylgeraniol (GGOH) has shown to prevent muscle atrophy, reduce inflammatory markers, and increase SC content; however, the effect of GGOH on SC myogenic state in T2D rats is not known. PURPOSE: To examine the effects of GGOH on SC myogenic state and muscle cross-sectional area (CSA) in T2D rats. METHODS: 21 Sprague-Dawley rats were fed a control diet (CON; n=7), a high-fat diet with 35 mg/kg of streptozotocin (HFD; n=7), and HFD with 800mg/kg body weight of GGOH (GG; n=7). In the 8th week, the right soleus muscle was analyzed for protein expression for Pax7, MyoD, myostatin, and GAPDH, and protein content was normalized to GAPDH. The left soleus muscle was co-stained with Pax7, MyoD, and myostatin using immunohistochemistry and analyzed for muscle CSA. Counted SC were normalized to 100 fibers. RESULTS: A significant (p \u3c 0.05) condition effect was observed for MyoD and myostatin protein expression. For MyoD, HFD (1.41 ± 0.09 A.U.) was lower than CON (2.24 ± 0.21 A.U.) and GG (2.62 ± 0.43 A.U.). For myostatin, HFD (0.42 ± 0.06 A.U.) was lower than CON (0.91 ± 0.09 A.U.). Additionally, a significant condition effect was observed for the number of cells that presented Pax7+/MyoD- and Pax7+/myostatin+. For Pax7+/MyoD-, HFD (0.039 ± 0.004) and GG (0.035 ± 0.004) had lower cell counts than CON (0.064 ± 0.010). For Pax7+/myostatin+, HFD (0.034 ± 0.003) had lower cell counts than GG (0.065 ± 0.010) and CON (0.057 ± 0.004). A significant condition effect was observed for CSA where CON (7099.89 ± 187.33 μm2) was larger than HFD (4351.02 ± 127.46 μm2) and GG (5584.61 ± 208.01 μm2), while GG (5584.61 ± 208.01 μm2) was larger than HFD (4351.02 ± 127.46 μm2). CONCLUSION: GGOH supplementation to T2D rats mitigated muscle mass loss (increased MyoD expression with no change in MyoD+ SC). Despite no differences in SC myogenic state (proliferative and differentiation) among groups, GGOH appeared to mitigate the reduction in the quiescent SC pool (Pax7+/myostatin+) observed in HFD. Given the importance of quiescent SC pool on retaining myogenic potential, which is essential for muscle hypertrophy and regeneration, supplementing GGOH to T2D rats could improve muscle health

Sleep Duration is Increased Following Muscle Damaging Exercise in Hot Environmental Conditions

Sleep and recovery measures are typically negatively affected by a muscle-damaging bout of exercise. However, it remains unknown if the additive effects of hot environmental conditions, resulting in increased core temperature and other thermoregulatory responses during the exercise bout, further progress changes in quantity and performance quality of sleep duration. PURPOSE: To investigate the effect of muscle-damaging exercise in the heat, compared to a thermoneutral condition, on sleep and recovery measures. METHODS: Ten healthy males (age: 23 ± 3yr; body mass: 78.7 ± 11.5kg; height: 176.9 ± 5cm; lactate threshold [LT]: 9.7 ± 1.0km.hr-1) performed two protocols in a randomized, counterbalanced order of downhill running (DHR) for 30-minutes at the LT in either a thermoneutral (ambient temperate [Tamb], 20°C; relative humidity [RH], 20%) or hot environmental condition (Tamb, 35°C; RH, 40%) at a -10% gradient. Sleep and recovery measures were collected from a wearable sleep device participants wore the night after the DHR. Differences in sleep and recovery measures following DHR in the heat compared to a thermoneutral condition were analyzed using paired samples T-tests. RESULTS: Sleep hours, restorative sleep hours, rapid eye movement (REM) sleep hours, and slow wave sleep (SWS) hours were all greater following the heat condition (mean ± SD; sleep hours: 6.70 ± 0.74hr, p = 0.040; restorative sleep hours: 3.31 ± 0.90hr, p = 0.012; REM sleep hours: 1.70 ± 0.64hr, p = 0.046; SWS hours: 1.61 ± 0.35hr, p = 0.015) compared to the thermoneutral condition (sleep hours: 5.24 ± 1.75hr; restorative sleep hours: 2.45 ± 1.11hr; REM sleep hours: 1.23 ± 0.68hr; SWS: 1.22 ± 0.53hr). Also, recovery was higher following the heat condition (recovery: 75.88 ± 15.31, p = 0.023) compared to the thermoneutral condition (recovery: 50.75 ± 21.46). Sleep efficiency, sleep disturbance, sleep deprivation, sleep score, %REM, %SWS, light sleep, resting heart rate, and heart rate variability were not different between conditions (ps \u3e 0.05). CONCLUSION: Following muscle-damaging exercise in the heat, sleep and recovery duration measures were increased compared to a thermoneutral condition. These findings suggest that performing muscle-damaging exercises in hot conditions may require a greater amount of sleep for optimal recovery

Relationships between Morning and Afternoon WUT (Weight, Urine Color, and Thirst) Criteria and Hydration Markers

A Venn diagram decision tool consisting of weight, urine color, and thirst (WUT) is suggested to measure hydration status. The WUT Venn diagram has been used as a practical hydration status assessment tool; however, this relationship has only been investigated using a first-morning urine sample. PURPOSE: To investigate relationships between morning and afternoon WUT criteria, blood and urine markers. METHODS: Eight men (age: 21 ± 3; mass: 76.3 ± 15.6 kg) and five women (age: 22 ± 2; mass: 60.5 ± 13.6 kg) completed the study. Body mass, urine color, urine specific gravity (USG), urine osmolality (UOSM), thirst level, and plasma osmolality (POSM) were collected as a first-morning and afternoon spot urine (2:00-4:00 CST) for 3 consecutive days in a free-living situation and 3 consecutive days in a euhydrated state. Body mass loss \u3e1%, urine color \u3e5, and thirst level ≥5 were used as dehydration thresholds. The number of markers that indicated dehydration levels were counted and categorized into either 3, 2, 1, or 0 WUT markers indicating dehydration (defined by either USG, UOSM, or POSM). One-way ANOVA with Tukey pairwise comparisons were used to assess differences in USG, UOSM, and POSM between different numbers of WUT markers. Receiver operating characteristics analysis was performed to calculate the predictive value of 0, 1, 2, or 3 hydration markers in detecting a dehydrated or euhydrated state. RESULTS: Morning and afternoon 1, 2, and 3 WUT markers were not significantly different (ps \u3e .05) for USG and POSM. Morning and afternoon 0, 2, and 3 WUT markers were not significantly different for UOSM. Morning and afternoon 3 WUT resulted in a specificity of 0.984 and 1.000, 0.984 and 1.000, and 0.956 and 0.981 for USG \u3e 1.020, UOSM \u3e 700mOsm, and POSM \u3e 290mOsm, respectively. Meeting at 2 WUT for morning and afternoon resulted in a specificity of 0.820 and 0.985, and 0.806 and 0.984 for USG and UOSM, respectively. Meeting at 1 WUT for morning and afternoon resulted in a sensitivity of 1.000 and 0.813 for UOSM. CONCLUSION: These results suggest that when 2 or 3 WUT markers are met, urine and blood hydration markers indicate dehydration, and when 1 WUT marker is met, UOSM indicates not dehydrated. The WUT Venn diagram can assess hydration status when an afternoon spot urine sample is used

Characterization of Physical and Cognitive Performance and Hydration in Older Adults

In younger adults, dehydration has been shown to impair physical and cognitive performance. Older adults are habitually hypohydrated alongside experiencing physical and cognitive performance deficits. Despite these deficits, the link between these factors remains unexplored. Purpose: To examine the effect of hydration status on physical and cognitive performance in older adults. Methods: Sixteen (5 men and 11 women) community-dwelling adults (74±7yr; 78.2±15.0kg; 161±11cm) completed measurements of hydration status (urine specific gravity [USG], urine color), bioelectrical impedance analysis (lean mass, fat mass, total body fluid, intracellular to extracellular fluid ratio [ICF: ECF]), blood pressure, physical performance (handgrip strength test, sit-to-stand test, and a timed-up-and-go test), and reaction time (Flanker task). Hierarchical cluster analysis was performed on the distance matrix of USG and urine color to group participants. One-way ANOVAs were performed to determine differences among groups. Results: Hierarchical cluster analysis assigned participants to 4 groups (group1, n=3; group2, n=4; group3, n=5; group4,n=4). Consistent with the cluster analysis, each group had significantly (p1: 1.0±0.0, group2: 2.3±0.3, group3: 4.2±0.4, group4, 6.0±0.0). In addition, the reaction time was significantly different among groups. For group1, compatible and incompatible tasks (compatible: 1116±71.7s, p=0.049; incompatible: 1205±13.4ms, p=0.042) had a longer response time compared to group2(compatible: 640±67.5ms; incompatible: 688±74.0ms), group3 (compatible: 725±67.4ms; incompatible: 796±174.2ms), and group4 (compatible: 731±139.8ms; incompatible: 782±122.7ms). No significant differences were observed for lean mass, fat mass, total body fluid, ICF:ECF, blood pressure, handgrip strength, sit-to-stand test, and time-up-and-go test. Conclusion: Despite grouping by USG and urine color, no relationship was observed between body composition and physical performance. Surprisingly, hydrated individuals performed poorly cognitively compared to less hydrated individuals. We suggest these differences may reflect varying individual cognitive functions, not hydration status, among free-living older adults

The Effect of Dehydration and High-Volume Resistance Exercise on Intracellular and Local Muscular Fluid Shifts - A Pilot Study

Hypertonic hypovolemia (dehydration) could disrupt the balance between extracellular water (ECW) and intracellular water (ICW). Notably, high-volume resistance exercise (RE) accumulates metabolites resulting in acute muscle swelling (increased ICF). However, the impact of hypertonic hypovolemia state on ECW and ICW distribution after RE is not known. PURPOSE: To determine the effect of acute dehydration on fluid balance after RE. METHODS: 7 resistance-trained males completed two identical high-volume RE, separated by two weeks (bilateral leg press and knee extensions exercises [5 sets of 10 repetitions at 80% of 1 repetition maximum]) either in a euhydrated (EH; urine specific gravity [USG] \u3c 1.020) or dehydrated state (DH; USG ≥ 1.020; 24hr fluid fast). Total body water (TBW) and the ratio of ICW to ECW (ICW/ECW) were measured using bioelectrical impedance spectroscopy before (PRE), 1h, and 3h after RE. The rectus femoris thickness (RFT) was imaged using ultrasound at PRE, immediately (IP), 10m, 15m, and 30m after RE. Vastus lateralis samples were collected at PRE, 1h, and 3h and were immediately weighed (Wt) before and after heating at 80°C for 55 minutes. Repeated measures ANOVAs were used to identify the differences, and effect sizes were calculated if p values were trending. RESULTS: A significant (p \u3c 0.05) condition effect was observed for TBW, while a time effect was observed for ICW/ECW and RFT. For TBW, EH (1.00±0.06L) was greater than DH (0.95±0.05L). For ICW/ECW, PRE (1.00±0.00L) was lower than 1h (1.05±0.10L) and 3h (1.03±0.05L), while 1h was greater than PRE and 3h. For RFT, PRE (17.1±0.9mm) was less thick than IP (23.7±0.9mm), 10m (22.3±1.0mm), 15m (22.0±0.9mm), and 30m (21.5±1.0mm) while IP was thicker than all time points. Furthermore, EH (22.8±1.4mm) trended to have thicker RFT than DH (19.9±0.8mm; p=0.082; Cohen’s f = 0.85; large effect size). Additionally, a significant condition x time effect was observed for Wt. For Wt, EH (1.07±0.04mg) had a greater change in muscle weight than DH (1.01±0.06mg) at 1h. CONCLUSION: These results suggest that high volume RE can cause fluid shift from the extracellular to the intracellular compartment (i.e., increase ICW/ECF and RFT) regardless of the hydration status. Intriguingly, at the intramuscular level, it appears that the intramuscular water content after RE is less in dehydrated than euhydrated state (i.e., less changes in Wt)

The Effect of Hydration Status on Sleep Quality: A Pilot Study

Sleep improves muscle recovery and cognitive health and can be impaired by physiological and mental stress. Dehydration can induce stress which leads to sleep impairment and thus could affect the readiness for and recovery from exercise. However, no study has examined the effect of hydration on sleep before and after resistance exercise (RE). PURPOSE: To examine the effect of hydration status on sleep before and after RE. METHODS: 7 resistance-trained men completed two identical RE consisting of bilateral leg press and knee extensions (5 sets of 10 repetitions at 80% of 1 repetition maximum) in a euhydrated state (EU; urine specific gravity (USG) \u3c 1.020) and in a dehydrated state (DE: USG ≥ 1.020). The two conditions were separated by 2 weeks in random order. During DE, participants underwent a 24-hr fluid restriction the day before RE and consumed only 1.5 L water following RE throughout the day. Participants wore a wearable sleep device, and sleep efficiency (SE), light sleep (LS), rapid eye movement (REM), and slow wave sleep (SWS) were measured the night before (PRE) and the night after (POST) RE. A 2X2 ANOVA and effect sizes (ES) were used to detect differences. RESULTS: No significant (p \u3e 0.05) condition x time effect was observed for any sleep parameters. At PRE, a small ES was observed for SE (1.1%; η2 = 0.05) where EU was more efficient than DE. Additionally, a medium ES was observed for LS (26.2%; η2 = 0.09) and SWS (8%; η2 = 0.08) where EU spent more time in these phases than DE, while EU spent less time in the REM phase (-16.4%; η2 = 0.07) than DE. At POST, a small ES was observed for SE (1.3%; η2 = 0.05) where EU was more efficient than DE. Additionally, a medium ES was observed for REM (-35.7%; η2 = 0.07) and SWS (-8.4%; η2 = 0.08) where EU spent less time in these phases than DE, while EU spent more time in the LS phase (18.7%; η2 = 0.09) than DE. CONCLUSION: The pilot data suggests hydration status could influence sleep. Proper fluid intake could help with sleep efficiency and increase time spent in LS and SWS, which are beneficial for muscle and tissue recovery. Intriguingly, inadequate fluid intake could increase the time spent in REM, which might be due to the mental and physical stresses from dehydration and RE. Combined, these data suggest that hydration status could affect the readiness for and recovery from physical stress

The Effects of Hydration Status on Heart Rate Variability Following Supramaximal Intensity Exercise

Heart rate variability (HRV) is a non-invasive method used to monitor physiological stress via assessment of sympathetic and parasympathetic regulations and can indicate an individual’s recovery and readiness to exercise. Evidence suggests dehydration negatively impacts HRV; however, the influence of hydration status on HRV following supramaximal resistance exercise (RE) is unknown. PURPOSE: To investigate the effect of hydration status on HRV indices following supramaximal intensity RE. METHODS: 14 recreationally resistance-trained men (age, 21 ± 2 years; height, 176.25 ± 5.84 cm; weight, 81.31 ± 12.77 kg) participated in this study. In a randomized, counterbalanced order, participants performed a supramaximal intensity RE protocol in a euhydrated (EUH; urine specific gravity [USG] \u3c 1.020) and a dehydrated (DEH; USG \u3e 1.020) state, with conditions separated by 2 weeks. HRV indices (standard deviation of normal sinus beats [SDNN], root mean square of successive differences between normal heartbeats [RMSSD], high frequency power [HF], low frequency power [LF], LF:HF ratio, standard deviation of Poincaré plot perpendicular to [SD1] and along the line of identity [SD2]) were measured with participants lying in a supine position for 5 minutes in a dark room at baseline, immediately post-, 1hr-, 2hr-, and 3hr post-RE. Repeated measure analysis of variance was used to determine the effect of hydration status on HRV indices at each timepoint, with Bonferroni corrections for post-hoc analysis. RESULTS: RMSSD was significantly higher 1hr post-exercise in EUH (30.69 ± 7.09 ms) compared to DEH (16.31 ± 2.44 ms; p = 0.04). Similarly, HF power was significantly higher 1hr post-exercise in EUH (32.49 ± 4.12 %) compared to DEH (16.63 ± 2.71 %; p \u3c 0.01). In contrast, LF power was lower 1hr post-exercise in EUH (57.74 ± 3.62 %) compared to DEH (75.95 ± 3.42 %; p = 0.02), with LF:HF ratio significantly lower in EUH (2.36 ± 0.62) than DEH (6.21 ± 1.34; p = 0.01). SD1 was significantly greater 1hr post-exercise in EUH (21.74 ± 5.03 ms) than DEH (11.54 ± 1.73 ms; p = 0.04). No significant condition by time effects were observed for SDNN and SD2, or at remaining timepoints. CONCLUSION: These findings indicate that recovery and readiness to exercise are impaired 1hr following supramaximal intensity RE in a dehydrated state. However, impairments were ameliorated 2-3hrs proceeding the RE bout

The Effect of Hydration on Readiness and Recovery Before and After Resistance Exercise- A Pilot Study

Dehydration can disturb sleep which is essential for the readiness and recovery process. However, the role of hydration on readiness and recovery indicated by low resting heart rate (RHR) and high heart rate variability (HRV) before and after resistance exercise (RE) is not known. PURPOSE: The purpose of this study was to examine the effect of hydration status on readiness and recovery before and after RE. METHODS: Seven resistance-trained men (age: 21±1 years; weight: 77.8±11.0 kg; height: 177.4±5.3 cm) performed a series of RE that included bilateral leg press and knee extensions (5 sets of 10 repetitions at 80% of 1 repetition maximum). Participants completed the same RE twice with 2 weeks in between. Participants completed one trial in a euhydrated state (EUH; urine specific gravity (USG) \u3c 1.020) and the other in a dehydrated state (DEH: USG ≥ 1.020). For the DEH trial, participants were restricted from consuming fluids for 24 hours prior to the RE and were only permitted to drink 1.5 L of water post-exercise for the remainder of the day. For the EUH trial, participants were instructed to consume fluid throughout the day before and the day of RE to maintain euhydration. Data was collected from a wearable sleep device that participants wore to determine recovery by assessing RHR and HRV. Repeated measures ANOVAs were used to identify the differences, and effect size (ES), resulting effects identified as either small (0.2-0.49), medium (0.5-0.79), or large (\u3e0.8) effects, was calculated. RESULTS: There were no differences in RHR between EUH and DEH on the night before (EUH, 63±13 bpm; DEH, 61±11 bpm; ES=0.16) and after RE (EUH, 59±14 bpm; DEH, 58±9 bpm; ES=0.12; p=0.806). No significant difference was found in recovery between EUH and DEH on the night before (EUH, 37±30 au; DEH, 39±25 au; ES=0.05) or the night after (EUH, 38±29 au; DEH, 42±22 au; ES=0.42; p=0.821) RE. HRV were not different between EUH and DEH on the night before (EUH, 55±27 ms; DEH, 60±32 ms; ES=0.16) and after (EUH, 67±38 ms; DEH, 71±23 ms; ES=0.12; p=0947). CONCLUSION: This pilot study showed hydration status did not impact readiness and recovery before and after RE. However, this could be because the few participants resulted in a low statistical power. Therefore, further studies with more participants could be conducted to better determine how hydration affects readiness and recovery