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Salty Subjects: Unpacking Racial Differences in Salt-Sensitive Hypertension.
Jeong, S, Hunter, SD, Cook, MD, Grosicki, GJ, Robinson, AT
Current hypertension reports. 2024;(1):43-58
Abstract
PURPOSE OF REVIEW To review underlying mechanisms and environmental factors that may influence racial disparities in the development of salt-sensitive blood pressure. RECENT FINDINGS Our group and others have observed racial differences in diet and hydration, which may influence salt sensitivity. Dietary salt elicits negative alterations to the gut microbiota and immune system, which may increase hypertension risk, but little is known regarding potential racial differences in these physiological responses. Antioxidant supplementation and exercise offset vascular dysfunction following dietary salt, including in Black adults. Furthermore, recent work proposes the role of racial differences in exposure to social determinants of health, and differences in health behaviors that may influence risk of salt sensitivity. Physiological and environmental factors contribute to the mechanisms that manifest in racial differences in salt-sensitive blood pressure. Using this information, additional work is needed to develop strategies that can attenuate racial disparities in salt-sensitive blood pressure.
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The acute effect of passively assisted trunk stretching on central arterial stiffness and blood pressure in middle-aged to older adults.
West, K, Spears, K, Joyner, B, Smith, C, Jenkins, NDM, Grosicki, GJ, Siekirk, NJ
European journal of applied physiology. 2024
Abstract
PURPOSE We examined the effects of acute trunk stretching on central arterial stiffness and central and peripheral blood pressure in middle-aged to older adults. METHODS Twenty-eight middle-aged to older adults (14M/14F, 72 ± 7 years, 28.5 ± 5.3 kg/m2) completed this randomized, controlled, crossover design trial. We measured carotid-femoral pulse wave velocity (cf-PWV) and central and peripheral blood pressures (BP) before and after a single bout of passively assisted trunk stretching (i.e., five rounds of six 30-s stretches) and a time-matched seated control visit (i.e., 30-min). Changes (Δ; post - pre) in cf-PWV and central and peripheral BP were compared between visits and sexes using separate linear mixed-effects models controlling for baseline values. RESULTS Compared with seated control, central (systolic: - 3 ± 7 mmHg; diastolic: - 2 ± 5 mmHg) and peripheral (systolic: - 2 ± 8 mmHg; diastolic: - 1 ± 4 mmHg) BP were reduced following acute trunk stretching (ps ≤ 0.001). Between-visit differences for ∆cf-PWV (stretch: 0.09 ± 0.61 m/s; control: 0.37 ± 0.68 m/s, p = 0.038) were abolished when controlling for change in mean arterial pressure (∆MAP) (p = 0.687). The main effects of sex were detected for changes in systolic BPs (ps ≤ 0.029); more males (n = 13) saw BP reductions than females (n = 7). CONCLUSION These findings demonstrate the superiority of acute trunk stretching over passive sitting of equated duration for BP in middle-aged to older adults, with an appreciable effect in males compared to females.
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Acute beetroot juice reduces blood pressure in young Black and White males but not females.
Grosicki, GJ, Flatt, AA, Cross, BL, Vondrasek, JD, Blumenburg, WT, Lincoln, ZR, Chall, A, Bryan, A, Patel, RP, Ricart, K, et al
Redox biology. 2023;63:102718
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Plain language summary
Cardiovascular (CV) disease is the leading cause of death in the United States. Out of all ethnic groups, CV disease is particularly common in black Americans. High blood pressure (BP) is one of the main contributors to CV disease, and black Americans exhibit a disproportionally higher incident rate of high BP when compared to other ethnic groups. Partly this is due to genetic and physiological differences, yet is also influenced by social, socioeconomic, and environmental factors. One physiological difference that may contribute to higher BP in black adults appears to be a reduced availability of nitric oxide (NO). NO is a gas that is abundant in the human body. It regulates vascular tone and elasticity of the arteries, and therefore helps to manage blood pressure. Nitrates that occur in foods can be converted to NO and thus contribute to NO levels in the body. Beetroot juice (BRJ) is rich in nitrates. This study examined whether BRJ supplementation can reduce resting BP and cardiovascular reactivity in adults. The randomized, placebo-controlled, crossover-design study was completed by 18 black and 20 white young adults, male and female, with an average age of 21. The study monitored heart rate, BP and arterial stiffness in a variety of settings. The study also assessed socioeconomic status, perceived discrimination, sleep and dietary intake. The main findings from this investigation were that despite young black adults having higher resting BP, acute BRJ supplementation reduced the pressure to a similar extent in young black and white adults, but primarily in males. This reduction correlated with increased levels of circulating nitrites. However, acute BRJ supplementation did not influence resting arterial stiffness. The result also highlighted previously seen racial differences relating to social determinants of health and lifestyle, which may contribute to the elevated BP values seen in black participants. The study demonstrated that dietary nitrate from beetroot juice has the potential to be a cost-effective blood pressure-lowering strategy for young black and white males. Yet the findings also highlighted the complex interplay of social, lifestyle, and underlying physiological factors that influence racial differences when it comes to CV health
Abstract
A complex interplay of social, lifestyle, and physiological factors contribute to Black Americans having the highest blood pressure (BP) in America. One potential contributor to Black adult's higher BP may be reduced nitric oxide (NO) bioavailability. Therefore, we sought to determine whether augmenting NO bioavailability with acute beetroot juice (BRJ) supplementation would reduce resting BP and cardiovascular reactivity in Black and White adults, but to a greater extent in Black adults. A total of 18 Black and 20 White (∼equal split by biological sex) young adults completed this randomized, placebo-controlled (nitrate (NO3-)-depleted BRJ), crossover design study. We measured heart rate, brachial and central BP, and arterial stiffness (via pulse wave velocity) at rest, during handgrip exercise, and during post-exercise circulatory occlusion. Compared with White adults, Black adults exhibited higher pre-supplementation resting brachial and central BP (Ps ≤0.035; e.g., brachial systolic BP: 116(11) vs. 121(7) mmHg, P = 0.023). Compared with placebo, BRJ (∼12.8 mmol NO3-) reduced resting brachial systolic BP similarly in Black (Δ-4±10 mmHg) and White (Δ-4±7 mmHg) adults (P = 0.029). However, BRJ supplementation reduced BP in males (Ps ≤ 0.020) but not females (Ps ≥ 0.299). Irrespective of race or sex, increases in plasma NO3- were associated with reduced brachial systolic BP (ρ = -0.237, P = 0.042). No other treatment effects were observed for BP or arterial stiffness at rest or during physical stress (i.e., reactivity); Ps ≥ 0.075. Despite young Black adults having higher resting BP, acute BRJ supplementation reduced systolic BP in young Black and White adults by a similar magnitude, an effect that was driven by males.
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Racial and ethnic disparities in cardiometabolic disease and COVID-19 outcomes in White, Black/African American, and Latinx populations: Social determinants of health.
Grosicki, GJ, Bunsawat, K, Jeong, S, Robinson, AT
Progress in cardiovascular diseases. 2022;:4-10
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Abstract
Racial and ethnic-related health disparities in the United States have been intensified by the greater burden of Coronavirus Disease 2019 (COVID-19) in racial and ethnic minority populations. Compared to non-Hispanic White individuals, non-Hispanic Black and Hispanic/Latinx individuals infected by COVID-19 are at greater risk for hospitalization, intensive care unit admission, and death. There are several factors that may contribute to disparities in COVID-19-related severity and outcomes in these minority populations, including the greater burden of cardiovascular and metabolic diseases as discussed in our companion review article. Social determinants of health are a critical, yet often overlooked, contributor to racial and ethnic-related health disparities in non-Hispanic Black and Hispanic/Latinx individuals relative to non-Hispanic White individuals. Thus, the purpose of this review is to focus on the essential role of social factors in contributing to health disparities in chronic diseases and COVID-19 outcomes in minority populations. Herein, we begin by focusing on structural racism as a social determinant of health at the societal level that contributes to health disparities through downstream social level (e.g., occupation and residential conditions) and individual level health behaviors (e.g., nutrition, physical activity, and sleep). Lastly, we conclude with a discussion of practical applications and recommendations for future research and public health efforts that seek to reduce health disparities and overall disease burden.
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Single muscle fibre contractile function with ageing.
Grosicki, GJ, Zepeda, CS, Sundberg, CW
The Journal of physiology. 2022;(23):5005-5026
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Abstract
Ageing is accompanied by decrements in the size and function of skeletal muscle that compromise independence and quality of life in older adults. Developing therapeutic strategies to ameliorate these changes is critical but requires an in-depth mechanistic understanding of the underlying physiology. Over the past 25 years, studies on the contractile mechanics of isolated human muscle fibres have been instrumental in facilitating our understanding of the cellular mechanisms contributing to age-related skeletal muscle dysfunction. The purpose of this review is to characterize the changes that occur in single muscle fibre size and contractile function with ageing and identify key areas for future research. Surprisingly, most studies observe that the size and contractile function of fibres expressing slow myosin heavy chain (MHC) I are well-preserved with ageing. In contrast, there are profound age-related decrements in the size and contractile function of the fibres expressing the MHC II isoforms. Notably, lifelong aerobic exercise training is unable to prevent most of the decrements in fast fibre contractile function, which have been implicated as a primary mechanism for the age-related loss in whole-muscle power output. These findings reveal a critical need to investigate the effectiveness of other nutritional, pharmaceutical or exercise strategies, such as lifelong resistance training, to preserve fast fibre size and function with ageing. Moreover, integrating single fibre contractile mechanics with the molecular profile and other parameters important to contractile function (e.g. phosphorylation of regulatory proteins, innervation status, mitochondrial function, fibre economy) is necessary to comprehensively understand the ageing skeletal muscle phenotype.
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Evidence for the Contribution of Gut Microbiota to Age-Related Anabolic Resistance.
Watson, MD, Cross, BL, Grosicki, GJ
Nutrients. 2021;(2)
Abstract
Globally, people 65 years of age and older are the fastest growing segment of the population. Physiological manifestations of the aging process include undesirable changes in body composition, declines in cardiorespiratory fitness, and reductions in skeletal muscle size and function (i.e., sarcopenia) that are independently associated with mortality. Decrements in muscle protein synthetic responses to anabolic stimuli (i.e., anabolic resistance), such as protein feeding or physical activity, are highly characteristic of the aging skeletal muscle phenotype and play a fundamental role in the development of sarcopenia. A more definitive understanding of the mechanisms underlying this age-associated reduction in anabolic responsiveness will help to guide promyogenic and function promoting therapies. Recent studies have provided evidence in support of a bidirectional gut-muscle axis with implications for aging muscle health. This review will examine how age-related changes in gut microbiota composition may impact anabolic response to protein feeding through adverse changes in protein digestion and amino acid absorption, circulating amino acid availability, anabolic hormone production and responsiveness, and intramuscular anabolic signaling. We conclude by reviewing literature describing lifestyle habits suspected to contribute to age-related changes in the microbiome with the goal of identifying evidence-informed strategies to preserve microbial homeostasis, anabolic sensitivity, and skeletal muscle with advancing age.
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Application of Cut-Points for Low Muscle Strength and Lean Mass in Mobility-Limited Older Adults.
Grosicki, GJ, Travison, TG, Zhu, H, Magaziner, J, Binder, EF, Pahor, M, Correa-de-Araujo, R, Cawthon, PM, Bhasin, S, Orwig, D, et al
Journal of the American Geriatrics Society. 2020;(7):1445-1453
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Abstract
BACKGROUND The Sarcopenia Definitions and Outcomes Consortium (SDOC) is a collaborative initiative seeking to develop and evaluate cut-points for low muscle strength and lean mass that predict an increased risk for slowness (usual walking speed <.8 m/s) among older adults. OBJECTIVES The goal of the present study was to provide clinicians and researchers with an understanding of the diagnostic implications of using SDOC variables and cut-points in mobility-limited older adults. Using data from older individuals with specific conditions that render them at increased risk for mobility limitation, we evaluated the performance characteristics (ie, sensitivity and specificity) of five putative sarcopenia parameters and then compared these values with previously recommended diagnostic criteria for sarcopenia. DESIGN Retrospective analysis of six randomized controlled trials enriched in persons at risk for mobility limitation. SETTING National and international geriatric clinical research centers. PARTICIPANTS A total of 925 mobility-limited older adults (≥55 years of age; 58% women) were included in the analysis. MEASUREMENTS The prevalence of low muscle strength and lean mass were assessed using five candidate metrics discriminative of slowness. Analyses of sensitivity and specificity were used to compare muscle weakness criteria with published diagnostics for sarcopenia. RESULTS Odds ratios (ORs) supported maximal grip strength (Grip max <35.5 and 20.0 in men and women, respectively) as the most discriminative of slowness in both men and women (OR = 3.66 and 3.53, respectively). More men (58%) than women (30%) fell below sex-specific maximal grip cut-points. When applying previously recommended sarcopenia component definitions in our population, we found that fewer individuals met those criteria (range = 6%-32%). CONCLUSION A greater number of individuals fall below SDOC Grip max cut-points compared with previous recommendations. Clinicians and researchers working with older adults may consider these thresholds as an inclusive means to identify candidates for low-risk lifestyle promyogenic and function-promoting therapies. J Am Geriatr Soc 68:1445-1453, 2020.
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Circulating Interleukin-6 Is Associated with Skeletal Muscle Strength, Quality, and Functional Adaptation with Exercise Training in Mobility-Limited Older Adults.
Grosicki, GJ, Barrett, BB, Englund, DA, Liu, C, Travison, TG, Cederholm, T, Koochek, A, von Berens, Å, Gustafsson, T, Benard, T, et al
The Journal of frailty & aging. 2020;(1):57-63
Abstract
BACKGROUND Human aging is characterized by a chronic, low-grade inflammation suspected to contribute to reductions in skeletal muscle size, strength, and function. Inflammatory cytokines, such as interleukin-6 (IL-6), may play a role in the reduced skeletal muscle adaptive response seen in older individuals. OBJECTIVES To investigate relationships between circulating IL-6, skeletal muscle health and exercise adaptation in mobility-limited older adults. DESIGN Randomized controlled trial. SETTING Exercise laboratory on the Health Sciences campus of an urban university. PARTICIPANTS 99 mobility-limited (Short Physical Performance Battery (SPPB) ≤9) older adults. INTERVENTION 6-month structured physical activity with or without a protein and vitamin D nutritional supplement. MEASUREMENTS Circulating IL-6, skeletal muscle size, composition (percent normal density muscle tissue), strength, power, and specific force (strength/CSA) as well as physical function (gait speed, stair climb time, SPPB-score) were measured pre- and post-intervention. RESULTS At baseline, Spearman's correlations demonstrated an inverse relationship (P<0.05) between circulating IL-6 and thigh muscle composition (r = -0.201), strength (r = -0.311), power (r = -0.210), and specific force (r = -0.248), and positive association between IL-6 and stair climb time (r = 0.256; P<0.05). Although the training program did not affect circulating IL-6 levels (P=0.69), reductions in IL-6 were associated with gait speed improvements (r = -0.487; P<0.05) in "higher" IL-6 individuals (>1.36 pg/ml). Moreover, baseline IL-6 was inversely associated (P<0.05) with gains in appendicular lean mass and improvements in SPPB score (r = -0.211 and -0.237, respectively). CONCLUSIONS These findings implicate age-related increases in circulating IL-6 as an important contributor to declines in skeletal muscle strength, quality, function, and training-mediated adaptation. Given the pervasive nature of inflammation among older adults, novel therapeutic strategies to reduce IL-6 as a means of preserving skeletal muscle health are enticing.
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Progressive Resistance Training Improves Torque Capacity and Strength in Mobility-Limited Older Adults.
Englund, DA, Price, LL, Grosicki, GJ, Iwai, M, Kashiwa, M, Liu, C, Reid, KF, Fielding, RA
The journals of gerontology. Series A, Biological sciences and medical sciences. 2019;(8):1316-1321
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Abstract
BACKGROUND Progressive resistance training (PRT) is consistently shown to improve muscle strength in older adults. The efficacy of PRT to improve muscle fatigue in older adults with demonstrated mobility limitations remains unclear. METHODS Mobility-limited (Short Physical Performance Battery [SPPB] ≤ 9) older adults (age 70-92 years) were recruited for this study and randomized to either PRT or home-based flexibility (FLEX) 3 d/wk for 12 weeks. Muscle fatigue and strength outcomes were assessed at baseline and 12 weeks. The primary outcome was torque capacity, a composite measure of strength and fatigue, defined as the sum of peak torques from an isokinetic fatigue test. RESULTS Seventy participants were randomized (mean [SD] age 78.9 [5.4] years; 60% female; mean [SD] SPPB 7.5 [1.6]). At follow-up, the PRT group improved significantly in torque capacity, mean between-group difference (95% confidence interval) 466.19 (138.4, 793.97) Nm (p = .006), and maximal strength 127.3 (60.96, 193.61) Nm (p = .0003), when compared with FLEX group. Neither group demonstrated significant changes in muscle fatigue or torque variability. CONCLUSION Twelve weeks of PRT improved torque capacity, as well as strength in mobility-limited older adults. These results demonstrate PRT improves multiple age-related muscular impairments.