Relative fat-free mass deficiency and left ventricular adaptation to obesity: The Strong Heart Study,☆☆

https://doi.org/10.1016/j.ijcard.2012.09.055Get rights and content

Abstract

Background

Relative fat-free mass (FFM) deficiency (RFFMD) can also occur in obesity, but the impact on left ventricular (LV) mass is unknown.

Methods

We assessed relations among reduced FFM, obesity and LV mass in a population with high prevalence of obesity. Echocardiograms were performed in 2625 participants (1694 women, 1199 non-obese) of the Strong Heart Study cohort, free of prevalent cardiovascular disease and kidney failure. FFM was estimated by bioelectric impedance and analyzed in the non-obese subpopulation in relation with sex, BMI and waist-to-hip ratio (WHR). RFFMD was estimated in the obese subpopulation as the percent of observed/predicted FFM < 20th percentile of the non-obese distribution.

Results

RFFMD was more frequent in women than men. LV mass indices (by either height2.7 or FFM) were greater in obese with than in those without RFFMD, even after adjusting for sex and diabetes (both p < 0.0001). The greater LV mass index in obesity with RFFMD was related mostly to increased LV diastolic dimension paralleling increased stroke index and cardiac index, in the presence of normal ejection fraction. RFFMD remained associated with greater LV mass index (p < 0.0001) even independently of older age, greater BMI, higher systolic and lower diastolic blood pressure (all p < 0.007), with negligible effect of sex, waist/hip ratio and diabetes.

Conclusion

In obese SHS participants, RFFMD is associated with higher levels of LV mass, an effect related to adiposity more than central fat distribution and typical of female gender. Biological mechanisms of this association have to be better explored.

Introduction

Bone and muscle growth are influenced by gravity and physical activity stimulating mechanoreceptors regulating production of growth factors [1]. The word “sarcopenia” describes in general the process of age-related muscle loss and the associated frailty condition [2], [3]. Definition of sarcopenia requires studying body composition and is still controversial [3].

A condition of relative loss of fat-free mass, however, has been recently recognized in the presence of obesity and called “sarcopenic obesity” [4]. The phenotype of sarcopenic obesity strongly depends on the adopted definition. Since obese individuals have larger amount of both fat and lean mass, they usually have a “normal” absolute quantity of muscle mass, and therefore they do not appear to be sarcopenic, though their muscle mass might be relatively inadequate for their size [5]. Thus, higher body mass index (BMI) can mask sarcopenia [3]. In general, excess energy intake, physical inactivity, low-grade inflammation, insulin resistance and changes in hormonal milieu are thought to be the main characteristics of sarcopenic obesity [6]. Because sarcopenia is generally considered a characteristic that might increase risk of morbidity in obesity [7], it is of interest to focus on phenotypic characteristics that might be associated with cardiovacular (CV) risk. Because left ventricular (LV) mass is substantially influenced by fat free mass [8], sarcopenia in the obese individual might be thought to be associated with reduced amount of LV mass, which might be protective, as LV hypertrophy is the most potent marker of cardiovascular risk [9]. Specifically, at present, there is little characterization of the CV phenotype of sarcopenia in obese populations. Accordingly, this study has been conceived to assess whether reduced fat-free mass is associated with the magnitude of LV mass, in a population of obese men and women.

Section snippets

Population

The Strong Heart Study (SHS) is a population-based cohort study of CV risk factors and disease in 4549 American Indians from 3 communities in Arizona, 7 in Southwestern Oklahoma and 3 in South and North Dakota, which has been extensively described [10], [11], [12]. For the purpose of the present analysis we analyzed participants to the 2nd exam, which included an echocardiogram (N = 3638, 89% of all living); we excluded participants who had history or signs of prevalent heart failure or coronary

Results

In the group of 1199 non-obese participants, 688 were women (57%), 437 hypertensive (37%) and 435 diabetic (36%). The average BMI was 26.09 ± 2.75 kg/m2, WHR was 0.94 ± 0.06 and FFM was 48.89 ± 9.63 kg. Table 1 displays the equation describing the variability of FFM and the multicollinearity diagnostic. The equation could explain 79% of the variance of FFM with a standard error of the estimate that was < 10% of the mean. Variance inflation factor was < 1.3 for all variables, demonstrating an optimal

Discussion

This is the first observational study evaluating LV adaptation to obesity in relation with relative FFM deficiency, in a large population-based cohort with high prevalence of obesity. Our attention has been especially focused on LV mass, which is considered the most potent (and correctible) marker of cardiovascular risk [9], [22], [23], recently shown to be a bioassay also for other harmful cardiovascular CV characteristics, including LV geometry and function [24].

Much debate is still ongoing

Acknowledgments

The authors wish to thank the Indian Health Service, the Strong Heart Study Participants, the Participating Tribal Communities and the Strong Heart Study Center Coordinators for their help in the realization of this project.

Views expressed in this paper are those of the authors and do not necessarily reflect those of the Indian Health Service or the Federal Government.

References (44)

  • Y. Ohira et al.

    Role of gravity in mammalian development: effects of hypergravity and/or microgravity on the development of skeletal muscles

    Biol Sci Space

    (2004)
  • A.M. Kenny et al.

    Prevalence of sarcopenia and predictors of skeletal muscle mass in nonobese women who are long-term users of estrogen-replacement therapy

    J Gerontol A Biol Sci Med Sci

    (2003)
  • A.B. Newman et al.

    Sarcopenia: alternative definitions and associations with lower extremity function

    J Am Geriatr Soc

    (2003)
  • R. Roubenoff

    Sarcopenic obesity: the confluence of two epidemics

    Obes Res

    (2004)
  • S. Stenholm et al.

    Sarcopenic obesity: definition, cause and consequences

    Curr Opin Clin Nutr Metab Care

    (2008)
  • L.J. Dominguez et al.

    The cardiometabolic syndrome and sarcopenic obesity in older persons

    J Cardiometab Syndr

    (2007)
  • G. de Simone et al.

    Influence of fat-free mass on detection of appropriateness of left ventricular mass: the HyperGEN Study

    J Hypertens

    (2003)
  • D. Levy et al.

    Prognostic implications of echocardiographically determined left ventricular mass in the Framingham Heart Study

    N Engl J Med

    (1990)
  • E.T. Lee et al.

    The Strong Heart Study – A study of cardiovascular disease in American Indians: Design and methods

    Am J Epidemiol

    (1990)
  • B.V. Howard et al.

    Coronary heart disease prevalence and its relation to risk factors in American Indians. The Strong Heart Study

    Am J Epidemiol

    (1995)
  • R.B. Devereux et al.

    Impact of diabetes on cardiac structure and function: the strong heart study

    Circulation

    (2000)
  • B.V. Howard et al.

    Rising tide of cardiovascular disease in American Indians. The Strong Heart Study

    Circulation

    (1999)
  • Cited by (25)

    • Low relative muscle mass and left ventricular diastolic dysfunction in middle-aged adults

      2018, International Journal of Cardiology
      Citation Excerpt :

      Although the relationships between obesity and LVDD and LV structure have been investigated in some studies [17,18] and muscular mass or strength is related to better prognosis in groups with HF [19,20], the literature is sparse with regard to the relationship between relative skeletal muscle mass and LVDD or LVM. The Strong Heart Study, which was conducted among Native Americans, showed that relative fat-free mass deficiency in an obese population was associated with higher LVM [21]. A population-based study in Korea revealed that a relative decrease in skeletal muscle mass along with visceral adiposity was associated with slight impairment of LV diastolic function and greater LVMI [22].

    • Echocardiographic findings in patients with eating disorders: Acase-control study

      2015, Nutrition, Metabolism and Cardiovascular Diseases
    • Preliminary evaluation of the prevalence of sarcopenia in obese patients from Southern Italy

      2015, Nutrition
      Citation Excerpt :

      On the other hand, the FM increase is considered as an independent risk factor for physical disability, therefore, in obese individuals, low physical performance could not depend on the presence of sarcopenia [1,3,4,6,26,28]. Interestingly, sarcopenia in obesity has been defined as a “relative fat-free mass deficiency” because, due to the FFM increase in obesity, the assessment of sarcopenia based on the raw evaluation of FFM (or SM) could be misleading [28]. In fact, in the context of obesity, sarcopenia should be considered a condition of abnormal body composition, with an altered balance between fat and FFM [28].

    View all citing articles on Scopus

    This work has been supported by grants HL41642, HL41652, HL41654, HL65521 and M10RR0047-34 (GCRC) from the National Institutes of Health, Bethesda, MD.

    ☆☆

    All authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.

    View full text