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Pergande MR, Osterbauer KJ, Buck KM, Roberts DS, Wood NN, Balasubramanian P, Mann MW, Rossler KJ, Diffee GM, Colman RJ, Anderson RM, Ge Y. Mass Spectrometry-Based Multiomics Identifies Metabolic Signatures of Sarcopenia in Rhesus Monkey Skeletal Muscle. J Proteome Res 2023:10.1021/acs.jproteome.3c00474. [PMID: 37991985 PMCID: PMC11109024 DOI: 10.1021/acs.jproteome.3c00474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2023]
Abstract
Sarcopenia is a progressive disorder characterized by age-related loss of skeletal muscle mass and function. Although significant progress has been made over the years to identify the molecular determinants of sarcopenia, the precise mechanisms underlying the age-related loss of contractile function remains unclear. Advances in "omics" technologies, including mass spectrometry-based proteomic and metabolomic analyses, offer great opportunities to better understand sarcopenia. Herein, we performed mass spectrometry-based analyses of the vastus lateralis from young, middle-aged, and older rhesus monkeys to identify molecular signatures of sarcopenia. In our proteomic analysis, we identified proteins that change with age, including those involved in adenosine triphosphate and adenosine monophosphate metabolism as well as fatty acid beta oxidation. In our untargeted metabolomic analysis, we identified metabolites that changed with age largely related to energy metabolism including fatty acid beta oxidation. Pathway analysis of age-responsive proteins and metabolites revealed changes in muscle structure and contraction as well as lipid, carbohydrate, and purine metabolism. Together, this study discovers new metabolic signatures and offers new insights into the molecular mechanisms underlying sarcopenia for the evaluation and monitoring of a therapeutic treatment of sarcopenia.
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Affiliation(s)
- Melissa R. Pergande
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Katie J. Osterbauer
- Department of Medicine, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Kevin M. Buck
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - David S. Roberts
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Nina N. Wood
- Department of Medicine, University of Wisconsin-Madison, Madison, WI 53705, USA
| | | | - Morgan W. Mann
- Department of Medicine, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Kalina J. Rossler
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Gary M. Diffee
- Department of Kinesiology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Ricki J. Colman
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705, USA
- Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, WI 53715, USA
| | - Rozalyn M. Anderson
- Department of Medicine, University of Wisconsin-Madison, Madison, WI 53705, USA
- Geriatric Research Education and Clinical Center, William S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA
| | - Ying Ge
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705, USA
- Department of Medicine, University of Wisconsin-Madison, Madison, WI 53705, USA
- Human Proteomics Program, University of Wisconsin-Madison, Madison, WI 53705, USA
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Koirala B, Concas A, Sun Y, Gladden LB, Lai N. Relationship between muscle venous blood oxygenation and near-infrared spectroscopy: quantitative analysis of the Hb and Mb contributions. J Appl Physiol (1985) 2023; 134:1063-1074. [PMID: 36927143 PMCID: PMC10125031 DOI: 10.1152/japplphysiol.00406.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 02/22/2023] [Accepted: 03/13/2023] [Indexed: 03/18/2023] Open
Abstract
A linear relationship between skeletal muscle venous ([Formula: see text]) and oxygenated (ΔHbMbO2,N) or deoxygenated (ΔHHbMbN) near-infrared spectroscopy (NIRS) signals suggest a main hemoglobin (Hb) contribution to the NIRS signal. However, experimental, and computational evidence supports a significant contribution of myoglobin (Mb) to the NIRS. Venous and NIRS measurements from a canine model of muscle oxidative metabolism (Sun Y, Ferguson BS, Rogatzki MJ, McDonald JR, Gladden LB. Med Sci Sports Exerc 48(10):2013-2020, 2016) were integrated into a computational model of muscle O2 transport and utilization to evaluate whether the relationship between venous and NIRS oxygenation can be affected by a significant Mb contribution to the NIRS signals. The mathematical model predicted well the measure of the changes of [Formula: see text] and NIRS signals for different O2 delivery conditions (blood flow, arterial O2 content) in muscle at rest (T1, T2) and during contraction (T3). Furthermore, computational analysis indicates that for adequate O2 delivery, Mb contribution to NIRS signals was significant (20%-30%) even in the presence of a linear [Formula: see text]-NIRS relationship; for a reduced O2 delivery the nonlinearity of the [Formula: see text]-NIRS relationship was related to the Mb contribution (50%). In this case (T3), the deviation from linearity is observed when O2 delivery is reduced from 1.3 to 0.7 L kg-1·min-1 ([Formula: see text] < 10 mLO2 100 mL-1) and Mb saturation decreased from 85% to 40% corresponding to an increase of the Mb contribution to ΔHHbMbN from 15% to 50% and the contribution to ΔHbMbO2,N from 0% to 30%. In contrast to a common assumption, our model indicates that both NIRS signals (ΔHHbMbN and ΔHbMbO2,N are significantly affected by Hb and Mb oxygenation changes.NEW & NOTEWORTHY Within the near-infrared spectroscopy (NIRS) signal, the contribution from hemoglobin is indistinguishable from that of myoglobin. A computation analysis indicates that a linear relationship between muscle venous oxygen content and NIRS signals does not necessarily indicate a negligible myoglobin contribution to the NIRS signal. A reduced oxygen delivery increases the myoglobin contribution to the NIRS signal. The integrative approach proposed is a powerful way to assist in interpreting the elements from which the NIRS signals are derived.
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Affiliation(s)
- Bhabuk Koirala
- Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia United States
- Biomedical Engineering Institute, Old Dominion University, Norfolk, Virginia, United States
| | - Alessandro Concas
- Department of Mechanical, Chemical and Materials Engineering, University of Cagliari, Italy
| | - Yi Sun
- Key Laboratory of Adolescent Health Assessment and Exercise Intervention of Ministry of Education, East China Normal University, Shanghai, China
- School of Physical Education & Health Care, East China Normal University, Shanghai, People's Republic of China
| | - L Bruce Gladden
- School of Kinesiology, Auburn University, Auburn, Alabama United States
| | - Nicola Lai
- Department of Mechanical, Chemical and Materials Engineering, University of Cagliari, Italy
- Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia United States
- Biomedical Engineering Institute, Old Dominion University, Norfolk, Virginia, United States
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Koirala B, Concas A, Sun Y, Gladden LB, Lai N. Blood volume versus deoxygenated NIRS signal: computational analysis of the effects muscle O 2 delivery and blood volume on the NIRS signals. J Appl Physiol (1985) 2021; 131:1418-1431. [PMID: 34528461 DOI: 10.1152/japplphysiol.00105.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Near-infrared spectroscopy (NIRS) signals quantify the oxygenated (ΔHbMbO2) and deoxygenated (ΔHHbMb) heme group concentrations. ΔHHbMb has been preferred to ΔHbMbO2 in evaluating skeletal muscle oxygen extraction because it is assumed to be less sensitive to blood volume (BV) changes, but uncertainties exist on this assumption. To analyze this assumption, a computational model of oxygen transport and metabolism is used to quantify the effect of O2 delivery and BV changes on the NIRS signals from a canine model of muscle oxidative metabolism (Sun Y, Ferguson BS, Rogatzki MJ, McDonald JR, Gladden LB. Med Sci Sports Exerc 48: 2013-2020, 2016). The computational analysis accounts for microvascular (ΔHbO2, ΔHHb) and extravascular (ΔMbO2, ΔHMb) oxygenated and deoxygenated forms. Simulations predicted muscle oxygen uptake and NIRS signal changes well for blood flows ranging from resting to contracting muscle. Additional NIRS signal simulations were obtained in the absence or presence of BV changes corresponding to a heme groups concentration changes (ΔHbMb = 0-48 µM). Under normal delivery (Q = 1.0 L·kg-1·min-1) in contracting muscle, capillary oxygen saturation (So2) was 62% with capillary ΔHbO2 and ΔHHb of ± 41 µΜ for ΔHbMb = 0. An increase of BV (ΔHbMb = 24 µΜ) caused a ΔHbO2 decrease (16µΜ) almost twice as much as the increase observed for ΔHHb (9 µΜ). When So2 increased to more than 80%, only ΔHbO2 was significantly affected by BV changes. The analysis indicates that microvascular So2 is a key factor in determining the sensitivity of ΔHbMbO2 and deoxygenated ΔHHbMb to BV changes. Contrary to a common assumption, the ΔHHbMb is affected by BV changes in normal contracting muscle and even more in the presence of impaired O2 delivery.NEW & NOTEWORTHY Deoxygenated is preferred to the oxygenated near-infrared spectroscopy signal in evaluating skeletal muscle oxygen extraction because it is assumed to be insensitive to blood volume changes. The quantitative analysis proposed in this study indicates that even in absence of skin blood flow effects, both NIRS signals in presence of either normal or reduced oxygen delivery are affected by blood volume changes. These changes should be considered to properly quantify muscle oxygen extraction by NIRS methods.
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Affiliation(s)
- B Koirala
- Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia.,Biomedical Engineering Institute, Old Dominion University, Norfolk, Virginia
| | - A Concas
- Center for Advanced Studies, Research and Development in Sardinia (CRS4), Cagliari, Italy
| | - Yi Sun
- Key Laboratory of Adolescent Health Assessment and Exercise Intervention of Ministry of Education, East China Normal University, Shanghai, China.,School of Physical Education & Health Care, East China Normal University, Shanghai, China
| | - L B Gladden
- School of Kinesiology, Auburn University, Auburn, Alabama
| | - N Lai
- Department of Mechanical, Chemical and Materials Engineering, University of Cagliari, Cagliari, Italy.,Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia.,Biomedical Engineering Institute, Old Dominion University, Norfolk, Virginia
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Sambashivaiah S, Harridge SDR, Sharma N, Selvam S, Rohatgi P, Kurpad AV. Asian Indians With Prediabetes Have Similar Skeletal Muscle Mass and Function to Those With Type 2 Diabetes. Front Nutr 2019; 6:179. [PMID: 31828076 PMCID: PMC6892303 DOI: 10.3389/fnut.2019.00179] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 11/12/2019] [Indexed: 12/16/2022] Open
Abstract
Background: Type 2 Diabetes (T2D) is a major concern among Asian Indians, not least because many develop T2D at despite having a normal BMI (body mass index), and with relatively low body fat. Asian Indians are also generally considered to have relatively low skeletal muscle mass and strength, this has not been explored in the context of T2D. Aim: The present study aimed to compare skeletal muscle mass, function and contractile quality (strength/mass) between healthy controls, those with prediabetes (PD) as well as T2D middle-aged non-obese Asian Indians. Methods: Adult males between the age of 20–50 years, consisting of healthy controls (n = 44), PD (n = 125) and T2D (n = 55) were studied. Skeletal muscle mass was measured using Dual X-ray Absorptiometry (DXA). Isometric and dynamic muscle function was measured using an isokinetic dynamometer (at 0, 60, 120, 180 degree/s). Muscle contractile quality was derived by dividing the peak muscle torque with the respective LMM (lower limb muscle mass). Fasting blood glucose (FBG) and insulin were used to derive insulin resistance (HOMA-IR). Results: The control group was on average 10 years younger than the other two groups (p < 0.01). The LMM was similar across the three study groups. However, the age-adjusted mean muscle torque was significantly lower in both absolute and normalized isometric and isokinetic strength in PD and T2D groups compared to controls (p ≤ 0.01), with the difference persisting even after adjusting for age and other covariates. However, there was no difference in muscle strength and contractile quality between the PD and T2D study groups. Conclusions: Muscle strength and contractile quality would appear to be sensitive and early indices of the trajectory toward diabetes in Asian Indians and more so than skeletal muscle mass. It is thus important to recognize the importance of functional measurements among this population when considering the role of muscle in diabetes. The data also would suggest that specific muscle conditioning (e.g., resistance training) might have efficacy in improving function as well as muscle mass, and thus aiding in the prevention of the trajectory toward the development of T2D.
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Affiliation(s)
| | - Stephen D R Harridge
- Centre for Human and Applied Physiological Sciences, King's College London, London, United Kingdom
| | - Nidhi Sharma
- Division of Nutrition, St. John's Research Institute, Bengaluru, India
| | - Sumithra Selvam
- Division of Epidemiology and Biostatistics, St. John's Research Institute, Bengaluru, India
| | | | - Anura V Kurpad
- Department of Physiology, St. John's Medical College, Bengaluru, India.,Division of Nutrition, St. John's Research Institute, Bengaluru, India
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Skeletal muscle excitation-metabolism coupling. Arch Biochem Biophys 2019; 664:89-94. [DOI: 10.1016/j.abb.2019.01.037] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 01/30/2019] [Accepted: 01/31/2019] [Indexed: 01/17/2023]
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Lai N, Martis A, Belfiori A, Tolentino-Silva F, Nasca MM, Strainic J, Cabrera ME. Gender differences in V˙O2 and HR kinetics at the onset of moderate and heavy exercise intensity in adolescents. Physiol Rep 2016; 4:4/18/e12970. [PMID: 27655810 PMCID: PMC5037918 DOI: 10.14814/phy2.12970] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 08/22/2016] [Indexed: 11/24/2022] Open
Abstract
The majority of the studies on V˙O2 kinetics in pediatric populations investigated gender differences in prepubertal children during submaximal intensity exercise, but studies are lacking in adolescents. The purpose of this study was to test the hypothesis that gender differences exist in the V˙O2 and heart rate (HR) kinetic responses to moderate (M) and heavy (H) intensity exercise in adolescents. Twenty-one healthy African-American adolescents (9 males, 15.8 ± 1.1 year; 12 females, 15.7 ± 1 year) performed constant work load exercise on a cycle ergometer at M and H. The V˙O2 kinetics of the male group was previously analyzed (Lai et al., Appl. Physiol. Nutr. Metab. 33:107-117, 2008b). For both genders, V˙O2 and HR kinetics were described with a single exponential at M and a double exponential at H. The fundamental time constant (τ1) of V˙O2 was significantly higher in female than male at M (45 ± 7 vs. 36 ± 11 sec, P < 0.01) and H (41 ± 8 vs. 29 ± 9 sec, P < 0.01), respectively. The functional gain (G1) was not statistically different between gender at M and statistically higher in females than males at H: 9.7 ± 1.2 versus 10.9 ± 1.3 mL min-1 W-1, respectively. The amplitude of the slow component was not significantly different between genders. The HR kinetics were significantly (τ1, P < 0.01) slower in females than males at M (61 ± 16 sec vs. 45 ± 20 sec, P < 0.01) and H (42 ± 10 sec vs. 30 ± 8 sec, P = 0.03). The G1 of HR was higher in females than males at M: 0.53 ± 0.11 versus 0.98 ± 0.2 bpm W-1 and H: 0.40 ± 0.11 versus 0.73 ± 0.23 bpm W-1, respectively. Gender differences in the V˙O2 and HR kinetics suggest that oxygen delivery and utilization kinetics of female adolescents differ from those in male adolescents.
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Affiliation(s)
- Nicola Lai
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio Department of Pediatrics Cardiology, Case Western Reserve University, Cleveland, Ohio Center for Modeling Integrated Metabolic Systems, Cleveland, Ohio Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia Biomedical Engineering Institute, Old Dominion University, Norfolk, Virginia
| | - Alessandro Martis
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
| | - Alfredo Belfiori
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
| | | | - Melita M Nasca
- Department of Pediatrics Cardiology, Case Western Reserve University, Cleveland, Ohio Rainbow Babies and Children's Hospital, Cleveland, Ohio
| | - James Strainic
- Department of Pediatrics Cardiology, Case Western Reserve University, Cleveland, Ohio Rainbow Babies and Children's Hospital, Cleveland, Ohio
| | - Marco E Cabrera
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio Department of Pediatrics Cardiology, Case Western Reserve University, Cleveland, Ohio Center for Modeling Integrated Metabolic Systems, Cleveland, Ohio Rainbow Babies and Children's Hospital, Cleveland, Ohio
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Asiedu-Gyekye IJ, Seidu MA, N'guessan BB, Frimpong-Manso S, Sarkodie JE, Adjei S, Kutu S, Osei-Little J, Nyarko AK, Debrah P. A dietary strategy for the management of artemether-lumefantrine-induced cardiovascular and renal toxicity. BMC COMPLEMENTARY AND ALTERNATIVE MEDICINE 2016; 16:348. [PMID: 27599802 PMCID: PMC5012013 DOI: 10.1186/s12906-016-1334-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 08/31/2016] [Indexed: 02/08/2023]
Abstract
BACKGROUND Unsweetened natural cocoa has antimalarial properties. Unsweetened natural cocoa powder (UNCP), obtained as a result of the removal of cocoa butter from a cocoa bean protects against malaria episodes. Cocoa powder, which is prepared after removal of the cocoa butter, contains about 1.9 % theobromine and 0.21 % caffeine. Concomitant consumption of cocoa and artemether/lumefantrine (A/L) is a common practice in Ghana, West Africa. This study seeks to determine the elemental composition of UNCP and its protective effect on the heart and kidney against (A/L) administration. METHODS Energy dispersive x-ray fluorescence spectroscopy was used to detect the quality and quantity of the elemental composition in UNCP. Thereafter, 30 nonmalarious male guinea pigs were divided into five groups of six animals each. One group was administered with 75 mg/kg body weight A/L only and another group distilled water (control group). The rest received 300 mg/kg, 900 mg/kg and 1500 mg/kg body weight UNCP for 14 days orally and A/L for the last 3 days (ie day 11 to day 14). Biochemical and histopathological examinations were carried out after euthanisation of the animals. RESULTS A total of thirty-eight (38) micro and macro elements were detected with the ED-XRF. Macro elements like sodium (Na), magnesium (Mg), aluminium (Al), phosphorus (P), chlorine (Cl), potassium (K), calcium (Ca), manganese (Mn) and iron (Fe) and micro elements like chromium (Cr), copper (Cu), zinc (Zn), arsenic (As), and lead (Pb) were identified and evaluated. Biochemical analysis revealed increases in HDL levels (p>0.05) while there were decreases in LDL levels (p>0.05), creatine kinase and AST levels (P<0.05) in animals that received UNCP compared to A/L only administered group. Urea levels reduced significantly by 53 % (p<0.05) in group that received 1500 mg/kg UNCP. Histopathological examinations of the heart and kidney buttressed the protective effects of cocoa administration. CONCLUSION The percentage of recommended daily allowance of UNCP for chromium is 3750 % for men and 5250 % for women while % RDA for copper corresponds to 103.6 % in both sexes. UNCP proved to possess cardioprotective and renoprotective potential during artemether-lumefantrine administration.
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Affiliation(s)
- Isaac Julius Asiedu-Gyekye
- Department of Pharmacology and Toxicology, College of Health Sciences, University of Ghana School of Pharmacy, P. O. Box LG 43, Legon, Ghana.
| | - Mahmood Abdulai Seidu
- Department of Medical Laboratory Sciences, College of Health Sciences, School of Biomedical and Allied Health Sciences, Legon, Ghana
| | - Banga Benoit N'guessan
- Department of Pharmacology and Toxicology, College of Health Sciences, University of Ghana School of Pharmacy, P. O. Box LG 43, Legon, Ghana
| | - Samuel Frimpong-Manso
- Department of Pharmaceutical Chemistry, College of Health Sciences, University of Ghana School of Pharmacy, Legon, Ghana
| | - Joseph Edusei Sarkodie
- Department of Pharmacognosy and Herbal Medicine, College of Health Sciences, University of Ghana School of Pharmacy, Legon, Accra, Ghana
| | - Samuel Adjei
- Department of animal experimentation unit, College of Health Sciences, Noguchi Memorial Institute for Medical Research, Legon, Accra, Ghana
| | - Schevadnazy Kutu
- Department of Pharmacology and Toxicology, College of Health Sciences, University of Ghana School of Pharmacy, P. O. Box LG 43, Legon, Ghana
| | - Joseph Osei-Little
- Department of Pharmacology and Toxicology, College of Health Sciences, University of Ghana School of Pharmacy, P. O. Box LG 43, Legon, Ghana
| | - Alexander Kwadwo Nyarko
- Department of Pharmacology and Toxicology, College of Health Sciences, University of Ghana School of Pharmacy, P. O. Box LG 43, Legon, Ghana
| | - Philip Debrah
- Department of Pharmaceutics and Microbiology, College of Health Sciences, University of Ghana School of Pharmacy, Legon, Ghana
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Lai N, Tolentino-Silva F, Nasca MM, Silva MA, Gladden LB, Cabrera ME. Exercise intensity and oxygen uptake kinetics in African-American and Caucasian women. Eur J Appl Physiol 2011; 112:973-82. [PMID: 21717119 DOI: 10.1007/s00421-011-2054-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Accepted: 06/18/2011] [Indexed: 11/24/2022]
Abstract
The effect of exercise intensity on the on- and off-transient kinetics of oxygen uptake (VO(2)) was investigated in African American (AA) and Caucasian (C) women. African American (n = 7) and Caucasian (n = 6) women of similar age, body mass index and weight, performed an incremental test and bouts of square-wave exercise at moderate, heavy and very heavy intensities on a cycle ergometer. Gas exchange threshold (LT(GE)) was lower in AA (13.6 ± 2.3 mL kg(-1) min(-1)) than C (18.6 ± 5.6 mL kg(-1) min(-1)). The dynamic exercise and recovery VO(2) responses were characterized by mathematical models. There were no significant differences in (1) peak oxygen uptake (VO(2peak)) between AA (28.5 ± 5 mL kg(-1) min(-1)) and C (31.1 ± 6.6 mL kg(-1) min(-1)) and (2) VO(2) kinetics at any exercise intensity. At moderate exercise, the on- and off- VO(2) kinetics was described by a monoexponential function with similar time constants τ (1,on) (39.4 ± 12.5; 38.8 ± 15 s) and τ (1,off) (52.7 ± 10.1; 40.7 ± 4.4 s) for AA and C, respectively. At heavy and very heavy exercise, the VO(2) kinetics was described by a double-exponential function. The parameter values for heavy and very heavy exercise in the AA group were, respectively: τ (1,on) (47.0 ± 10.8; 44.3 ± 10 s), τ (2,on) (289 ± 63; 219 ± 90 s), τ (1,off) (45.9 ± 6.2; 50.7 ± 10 s), τ (2,off) (259 ± 120; 243 ± 93 s) while in the C group were, respectively: τ (1,on) (41 ± 12; 43.2 ± 15 s); τ (2, on) (277 ± 81; 215 ± 36 s), τ (1,off) (40.2 ± 3.4; 42.3 ± 7.2 s), τ (2,off) (215 ± 133; 228 ± 64 s). The on- and off-transients were symmetrical with respect to model order and dependent on exercise intensity regardless of race. Despite similar VO(2) kinetics, LT(GE) and gain of the VO(2) on-kinetics at moderate intensity were lower in AA than C. However, generalization to the African American and Caucasian populations is constrained by the small subject numbers.
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Affiliation(s)
- Nicola Lai
- Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Avenue, Wickenden Bldg. Rm 524, Cleveland, OH 44106-7207, USA.
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