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RELATIONSHIP BETWEEN PLASMA GHRELIN LEVELS AND SARCOPENIA IN ELDERLY SUBJECTS: A CROSS-SECTIONAL STUDY M. SERRA-PRAT1,2, M. PAPIOL3, R. MONTEIS4, E. PALOMERA1, M. CABRÉ4 1. Research Unit, Consorci Sanitari del Maresme, Mataró, Barcelona (Spain); 2. Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Instituto de Salud Carlos III, Madrid (Spain); 3. Àrea Bàsica de Salut (ABS) Argentona, Consorci Sanitari del Maresme, Mataró, Barcelona (Spain); 4. Service of Internal Medicine, Hospital de Mataró, Consorci Sanitari del Maresme, Mataró, Barcelona (Spain). Corresponding author: Mateu Serra-Prat, MD, PhD, Research Unit, Hospital de Mataró, Carretera de Cirera s/n, E-08304 Mataró, Barcelona, Spain. Tel.: +34 93 7417730, fax: +34 93 7573321, e-mail: [email protected]
Abstract: Objective: The aim of this study was to investigate the relationship between plasma ghrelin levels and sarcopenia in elderly people. Design: Cross-sectional study. Setting: Health consortium medical centers in the Maresme region, Barcelona (Spain). Participants: Two groups of subjects: persons ≥ 70 years (elderly group) and persons 25-65 years (young adults). Measurements: Sarcopenia, diagnosed according to the EWGSOP definition, fasting and postprandial plasma ghrelin levels, body composition, hand grip, Barthel score, and frailty using Fried criteria. Results: Fifty-five elderly subjects and 33 young adults were recruited. In both age groups, mean ghrelin levels were significantly higher in women than in men. However, mean ghrelin levels were similar in elderly and young men (716 vs. 752 pg mL-1, P = 0.763) as well as in elderly and young women (859 vs. 995 pg mL-1, P = 0.190). In the elderly group, subjects with sarcopenia showed significantly lower ghrelin levels than those without sarcopenia (650 vs. 899 pg mL-1, P = 0.036), but these differences disappeared when stratifying by gender. Elderly subjects without sarcopenia had the same ghrelin levels as young adults (899.3 vs. 899.6 pg mL-1). In young women, ghrelin levels correlated with fat free mass (rs = 0.58, P = 0.007) and muscular mass (rs = 0.54, P = 0.015) but these correlations were not observed in men nor in elderly women. Conclusion: This cross-sectional study does not allow a definitive conclusion about the relationship between ghrelin levels and sarcopenia. Further large prospective studies are needed to test this hypothesis. Key words: Body composition, elderly, frailty, functional capacity, ghrelin, sarcopenia.
Introduction Sarcopenia, characterized by progressive and generalized loss of muscle mass and function associated with aging (1), is emerging as a major health concern (2-6) and the mechanisms that cause sarcopenia are still poorly understood (7-16). Ghrelin is a gastrointestinal peptide that increases appetite and food intake, regulates energy balance (17, 18), stimulates growth hormone-insulin-like growth factor (GH/IGF-1) axis, and inhibits various inflammatory cytokines (19). A decline in ghrelin plasma levels with age has been reported (20, 21), which may indicate a role of this peptide in the pathogenesis of sarcopenia and frailty in the elderly. Ghrelin agonists improve appetite, release of GH and IGF-1, and weight and fat-free mass gains, suggesting its usefulness in the treatment of anorexia-cachexia syndrome (22-24). Low physiological levels of ghrelin in the elderly may determine poor nutritional status and functional capacity (25) but the relation of ghrelin levels with sarcopenia and frailty in older people remains to be established. The aim of this study was to assess the relationship of fasting and postprandial plasma ghrelin levels with sarcopenia, frailty, and body composition in elderly subjects. Methods A cross-sectional observational study was designed, in which two study groups were included: a) elderly subjects (≥ Received February 13, 2014 Accepted for publication April 8, 2014
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70 years) and b) younger adults (25-65 years). Participants were recruited from the Maresme Health Consortium medical centers in Barcelona (Spain). Details of the study design have been previously reported (26). The study was approved by the institutional review board of the ‘Consorci Sanitari del Maresme’, Mataró, Barcelona (Spain). All participants signed an informed consent. Criteria of the European Working Group on Sarcopenia in Older People (EWGSOP) (27) was used for the definition of sarcopenia, in which low muscle mass (< 10.76 kg/ m 2 in men, < 6.76 kg/m 2 in women) was accompanied by low muscle strength (hand grip < 30 kg in men, < 17 kg in women) or low walking speed (≥ 7 seconds/5 meters). The presence of low muscle mass, low muscle strength, and low walking speed defined severe sarcopenia. Muscle mass was assessed by bioimpedance analysis (BIA) (Bioimpedance Analyzer Model BIA101, Akern Srl, Pontassieve, Florence, Italy). Hand grip (non-dominant arm) was measured by a hand held dynamometer (Jamar Hand Dynamometer, Lafayette Instrument Co, Lafayette, IN, USA). Total plasma ghrelin concentrations were measured with a human radioimmunoassay kit (Linco Research Inc, St Charles, MO, USA) at fasting conditions and after 1.5 and 4 hours of a 200 mL standard liquid preparation meal of 400 Kcal. Differences between fasting and 1.5 h and 4 h postprandial plasma ghrelin concentrations were calculated to assess ‘ghrelin response’ and ‘ghrelin recuperation’, respectively (26). Other study variables were socio-demographic characteristics, comorbidities,
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RELATIONSHIP BETWEEN PLASMA GHRELIN LEVELS AND SARCOPENIA and functional capacity assessed by the Barthel score (28). According to Fried criteria (29), a person was considered frail if he/she had three or more of the following five conditions: nonintentional weight loss or body mass index (BMI) < 19 kg/m-2, self-reported exhaustion, poor muscle strength, slow walking speed, and poor physical activity. To assess the relationship of plasma ghrelin levels with sarcopenia, frailty, hand grip, and Barthel score, ghrelin was considered as a continuous variable and as a categorical one (with a cut-off point at the 20th percentile). The chisquare test or the Fisher’s exact test were used for the comparison of proportions, and the Mann-Whitney U test or the Kruskal-Wallis test for the comparison of median values between two or three groups, respectively. The Spearman correlation coefficient (rs) was used to assess relationship between continuous variables and bi- and multivariate linear regression coefficients to assess the effect of ghrelin and other co-variables on body composition (fat-free mass or muscle mass). Logistic regression analysis was used to assess the association of frailty and sarcopenia. Statistical significance was set at P < 0.05. Results Plasma ghrelin levels by age, sex, and BMI A total of 58 elderly subjects (≥ 70 years) and 33 young adults (25-65 years) were recruited. No significant differences in fasting plasma ghrelin levels were observed between the two age groups, neither in men nor in women. In both age groups, mean ghrelin levels were significantly higher in women than in men. Table 1 shows mean plasma ghrelin levels in subjects distributed according to age, sex, and BMI.
Ghrelin and sarcopenia in the elderly Twenty three elderly subjects had sarcopenia (39.6%). Elderly subjects with sarcopenia had lower mean (± standard deviation) fasting plasma ghrelin levels as compared with those without sarcopenia (650.7 ± 196 vs. 899.3 ± 452 pg mL-1, P = 0.036). Also, subjects with severe sarcopenia had lower fasting ghrelin levels than those without severe sarcopenia (615 ± 223 vs. 845 ± 407 pg mL-1, P = 0.067). In the elderly group, severe sarcopenia was present in 45.5% of subjects fasting ghrelin levels below the 20th percentile and in 15.9% of those with ghrelin levels above this cut-off value (P = 0.049). Sarcopenia was more frequent in men (69.2%) than in women (16.7%) (P 30, 20-30, and < 20 kg/m2, showed an odds ratio (OR) of 1.02 (P = 0.712), 10.7 (P = 0.001), and 3.1 (P = 0.097), respectively. Fasting plasma ghrelin levels were similar in the elderly group without sarcopenia (899.3 pg mL-1) than in young adults (899.6 pg mL-1). Also, ghrelin levels showed no relationship with frailty (769 pg mL-1 in frail vs 816 pg mL-1 in non frail, p=0.846), Barthel score (rs=-0.059; p=0.662), and handgrip (rs=-0.221; p=0.096). Subjects with severe sarcopenia showed a poorer ‘ghrelin response’ after a meal test as compared to subjects without severe sarcopenia (difference between fasting and 1.5 h postprandial ghrelin 127.7 vs. -10.1, P = 0.004) but differences at 4 h postprandial levels were not observed.
Table 1 Fasting ghrelin levels by age, gender and BMI groups N Age and gender * Young males Elderly males Young females Elderly females Gender * Males Females BMI, kg/m2 & 30 Gender * Males Females BMI, kg/m2 & 30
Mean fasting ghrelin
13 752.1 (284.0) 27 716.6 (371.8) 20 995.5 (323.1) 31 859.6 (376.9) Young adults (25-65 years) (N=33) 13 752.1 (284.0) 20 995.5 (323.1) 3 1011.1 (238.3) 28 898.5 (345.3) 2 747.8 (49.2) Elderly subjects (≥ 70 years) (N=58) 27 716.6 (371.8) 31 859.6 (376.9) 5 791.0 (241.9) 40 815.8 (400.6) 12 698.9 (366.3)
* U-Mann Whytney test; & Kruskal-Wallis test
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p 0.763 0.190 0.030 0.153
0.053 0.503
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JNHA: GERIATRIC SCIENCE Table 2 Relationship between ghrelin and body composition Fat-free mass (% of total body weight) rs P value
Correlation *
Young adults (25-65 years) -0.107 0.727 0.583 0.007 Elderly subjects (≥ 70 years) -0.371 0.062 -0.023 0.907
Men Women Men Women Regression &
beta
P value
Young adults (25-65 years) -0.2 0.727 0.7 0.023 0.4 0.141 -0.1 0.724 Elderly subjects (≥ 70 years) -0.4 0.180 -0.02 0.960 -0.2 0.351 -0.4 0.148
Men Women All adjusted by sex All non- adjusted Men Women All adjusted by sex All non-adjusted
Muscle mass (% of total body weight) rs P value 0.016 0.957 0.536 0.015 0.086 0.675 0.205 0.286 beta
P value
-0.2 0.722 0.6 0.032 0.3 0.181 -0.2 0.515 -0.003 0.991 0.1 0.517 0.1 0.641 -0.1 0.670
* Correlation (rs): Spearman correlation coefficient; & Regression: Linear regression analysis
Ghrelin and body composition In young women, ghrelin levels were correlated with the percentage of fat free mass (rs = 0.58, P = 0.007) and muscular mass (rs = 0.54, P = 0.015), although these correlations were not found either in young men or elderly women. Lineal regression analysis showed no effect of ghrelin on fat-free mass and muscle mass in young men but a significant effect on fatfree mass (β = 0.7, P = 0.023) and muscle mass (β = 0.6, P = 0.032) in young women (Table 2). In the elderly group when muscle mass was stratified according to EWGSOP criteria, mean fasting ghrelin was 650.7 pg mL-1 in subjects with poor muscle mass and 899.2 pg mL-1 in those with normal muscle mass (P = 0.036). Sarcopenia and other variables In the elderly group, sarcopenia was also associated with BMI (with 80.0%, 46.2% and 8.3% prevalence for BMI ≤ 20, 20-30 and > 30, respectively; P = 0.012), nutritional impairment (11.1% in well-nourished vs. 48.1% in malnourished or at risk of malnutrition, P = 0.053), and presence of chronic obstructive pulmonary disease (COPD) (66.7% in COPD vs. 28.9% in non-COPD, P = 0.007). Frailty was unrelated to sarcopenia in general, but was related with severe sarcopenia (OR = 4.3, P = 0.036). Discussion Low fasting ghrelin plasma levels were associated with sarcopenia, severe sarcopenia, and poor muscle mass in elderly
subjects. However, sex acted as a potential confounder as it was associated with both fasting ghrelin levels and sarcopenia. Differences in fasting ghrelin among elderly subjects with and without sarcopenia or with poor or normal muscle mass were not statistically significant when stratifying by sex. Some findings suggest that this lack of statistical significance may be explained, almost in part, by the small sample size and the lack of statistical power, rather than by a confusion phenomenon and/or the absence of a relationship between ghrelin and sarcopenia. Firstly, although not statistically significant, differences in fasting ghrelin between subjects of both sexes with and without sarcopenia can be considered of clinically relevant magnitude, particularly in men. Secondly, the multivariate analysis showed an important effect of categorized ghrelin on sarcopenia (adjusted by age and sex) with an OR = 3.1 and a P value close to significance (P < 0.10). Thirdly, elderly subjects without sarcopenia showed almost exactly the same fasting ghrelin levels than young adults, suggesting that ghrelin secretion is preserved in subjects without sarcopenia but impaired in those with sarcopenia. Finally, a significant effect of ghrelin on muscle mass was observed in the elderly group despite it would be expected that sex would dilute but not maximize such effect (since fasting ghrelin was higher in women than in men). A positive correlation of fasting ghrelin levels with muscle mass and fat free mass was only observed in young women, which suggests a lower weight of ghrelin as anabolic hormone in young men in whom testosterone plays a major role. 671
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RELATIONSHIP BETWEEN PLASMA GHRELIN LEVELS AND SARCOPENIA Gender differences in nutritional and functional decline associated with aging are well established. In the general population, elderly women use to have poorer nutritional and functional status than elderly men. However, in the present study men showed a higher prevalence of sarcopenia than women, probably because it was designed not as an epidemiological but as a physiological one, and sampling process did not consider a random but an opportunistic selection of patients. To solve this question and to assess gender differences, all analyses were performed separately by gender. Lower ghrelin levels were found in elderly subjects with sarcopenia as compared with those without sarcopenia, but this latter group showed the same ghrelin levels than young adults. These results suggest that ghrelin decline does not seem to be dependent on age per se but on an unhealthy or frail aging process. Fasting ghrelin was not associated with hand grip and functional capacity. These results do not support the hypothesis of the present study but are in accordance with most interventional studies that have showed beneficial effects of hormone replacement therapy on muscle mass but not on strength and function (16). Improvement in muscle mass is not sufficient to improve muscle function if it is not accompanied by exercise or training (30). Finally, ghrelin response and recuperation after a standard meal test do not seem to have much relevance as indicators of sarcopenia or functional decline. Some limitations should be considered, including crosssectional design, representativeness of the sample, which was not mandatory for the main purpose of the study but could have affected gender comparisons, and the limited statistical power due to the sample size especially in the gender subgroup or multivariate analyses. The present results are inconclusive regarding the relationship between plasma ghrelin levels and sarcopenia in elderly people. Large prospective studies are required to assess this hypothesis. Acknowledgements: This study was funded by grants from the Spanish Ministry of Health, Instituto de Salud Carlos III, Fondo de Investigación Sanitaria; expedient PI 05/1120 and PI08/0478. We thank Marta Pulido, MD, for editing the manuscript and editorial assistance. Conflict of interest: The authors do not have any conflict of interest to disclose.
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Cruz-Jentoft AJ, Baeyens JP, Bauer JM, Boirie Y, Cederholm T, Landi F, Martin FC, Michel JP, Rolland Y, Schneider SM, Topinková E, Vandewoude M, Zamboni M. Sarcopenia: European consensus on definition and diagnosis: Report of the European Working Group on Sarcopenia in Older People. Age Ageing 2010;39:412-423. doi: 10.1093/ageing/afq034. Mahoney FI, Barthel DW. Functional evaluation: the Barthel index. Md State Med J 1965; 14: 61-5. Fried LP, Tangen CM, Walston J, Newman AB, Hirsch C, Gottdiener J, Seeman T, Tracy R, Kop WJ, Burke G, McBurnie MA. Frailty in older adults: evidence for a phenotype. J Gerontol A Biol Sci Med Sci 2001;56:M146-M156. Burton LA, Sumukadas D Optimal management of sarcopenia. Clin Interv Ageing 2010;5:217-228.
RELATIONSHIP BETWEEN PLASMA GHRELIN LEVELS AND SARCOPENIA IN ELDERLY SUBJECTS: A CROSS-SECTIONAL STUDY M. SERRA-PRAT1,2, M. PAPIOL3, R. MONTEIS4, E. PALOMERA1, M. CABRÉ4 1. Research Unit, Consorci Sanitari del Maresme, Mataró, Barcelona (Spain); 2. Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Instituto de Salud Carlos III, Madrid (Spain); 3. Àrea Bàsica de Salut (ABS) Argentona, Consorci Sanitari del Maresme, Mataró, Barcelona (Spain); 4. Service of Internal Medicine, Hospital de Mataró, Consorci Sanitari del Maresme, Mataró, Barcelona (Spain). Corresponding author: Mateu Serra-Prat, MD, PhD, Research Unit, Hospital de Mataró, Carretera de Cirera s/n, E-08304 Mataró, Barcelona, Spain. Tel.: +34 93 7417730, fax: +34 93 7573321, e-mail: [email protected]
Abstract: Objective: The aim of this study was to investigate the relationship between plasma ghrelin levels and sarcopenia in elderly people. Design: Cross-sectional study. Setting: Health consortium medical centers in the Maresme region, Barcelona (Spain). Participants: Two groups of subjects: persons ≥ 70 years (elderly group) and persons 25-65 years (young adults). Measurements: Sarcopenia, diagnosed according to the EWGSOP definition, fasting and postprandial plasma ghrelin levels, body composition, hand grip, Barthel score, and frailty using Fried criteria. Results: Fifty-five elderly subjects and 33 young adults were recruited. In both age groups, mean ghrelin levels were significantly higher in women than in men. However, mean ghrelin levels were similar in elderly and young men (716 vs. 752 pg mL-1, P = 0.763) as well as in elderly and young women (859 vs. 995 pg mL-1, P = 0.190). In the elderly group, subjects with sarcopenia showed significantly lower ghrelin levels than those without sarcopenia (650 vs. 899 pg mL-1, P = 0.036), but these differences disappeared when stratifying by gender. Elderly subjects without sarcopenia had the same ghrelin levels as young adults (899.3 vs. 899.6 pg mL-1). In young women, ghrelin levels correlated with fat free mass (rs = 0.58, P = 0.007) and muscular mass (rs = 0.54, P = 0.015) but these correlations were not observed in men nor in elderly women. Conclusion: This cross-sectional study does not allow a definitive conclusion about the relationship between ghrelin levels and sarcopenia. Further large prospective studies are needed to test this hypothesis. Key words: Body composition, elderly, frailty, functional capacity, ghrelin, sarcopenia.
Introduction Sarcopenia, characterized by progressive and generalized loss of muscle mass and function associated with aging (1), is emerging as a major health concern (2-6) and the mechanisms that cause sarcopenia are still poorly understood (7-16). Ghrelin is a gastrointestinal peptide that increases appetite and food intake, regulates energy balance (17, 18), stimulates growth hormone-insulin-like growth factor (GH/IGF-1) axis, and inhibits various inflammatory cytokines (19). A decline in ghrelin plasma levels with age has been reported (20, 21), which may indicate a role of this peptide in the pathogenesis of sarcopenia and frailty in the elderly. Ghrelin agonists improve appetite, release of GH and IGF-1, and weight and fat-free mass gains, suggesting its usefulness in the treatment of anorexia-cachexia syndrome (22-24). Low physiological levels of ghrelin in the elderly may determine poor nutritional status and functional capacity (25) but the relation of ghrelin levels with sarcopenia and frailty in older people remains to be established. The aim of this study was to assess the relationship of fasting and postprandial plasma ghrelin levels with sarcopenia, frailty, and body composition in elderly subjects. Methods A cross-sectional observational study was designed, in which two study groups were included: a) elderly subjects (≥ Received February 13, 2014 Accepted for publication April 8, 2014
669
70 years) and b) younger adults (25-65 years). Participants were recruited from the Maresme Health Consortium medical centers in Barcelona (Spain). Details of the study design have been previously reported (26). The study was approved by the institutional review board of the ‘Consorci Sanitari del Maresme’, Mataró, Barcelona (Spain). All participants signed an informed consent. Criteria of the European Working Group on Sarcopenia in Older People (EWGSOP) (27) was used for the definition of sarcopenia, in which low muscle mass (< 10.76 kg/ m 2 in men, < 6.76 kg/m 2 in women) was accompanied by low muscle strength (hand grip < 30 kg in men, < 17 kg in women) or low walking speed (≥ 7 seconds/5 meters). The presence of low muscle mass, low muscle strength, and low walking speed defined severe sarcopenia. Muscle mass was assessed by bioimpedance analysis (BIA) (Bioimpedance Analyzer Model BIA101, Akern Srl, Pontassieve, Florence, Italy). Hand grip (non-dominant arm) was measured by a hand held dynamometer (Jamar Hand Dynamometer, Lafayette Instrument Co, Lafayette, IN, USA). Total plasma ghrelin concentrations were measured with a human radioimmunoassay kit (Linco Research Inc, St Charles, MO, USA) at fasting conditions and after 1.5 and 4 hours of a 200 mL standard liquid preparation meal of 400 Kcal. Differences between fasting and 1.5 h and 4 h postprandial plasma ghrelin concentrations were calculated to assess ‘ghrelin response’ and ‘ghrelin recuperation’, respectively (26). Other study variables were socio-demographic characteristics, comorbidities,
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RELATIONSHIP BETWEEN PLASMA GHRELIN LEVELS AND SARCOPENIA and functional capacity assessed by the Barthel score (28). According to Fried criteria (29), a person was considered frail if he/she had three or more of the following five conditions: nonintentional weight loss or body mass index (BMI) < 19 kg/m-2, self-reported exhaustion, poor muscle strength, slow walking speed, and poor physical activity. To assess the relationship of plasma ghrelin levels with sarcopenia, frailty, hand grip, and Barthel score, ghrelin was considered as a continuous variable and as a categorical one (with a cut-off point at the 20th percentile). The chisquare test or the Fisher’s exact test were used for the comparison of proportions, and the Mann-Whitney U test or the Kruskal-Wallis test for the comparison of median values between two or three groups, respectively. The Spearman correlation coefficient (rs) was used to assess relationship between continuous variables and bi- and multivariate linear regression coefficients to assess the effect of ghrelin and other co-variables on body composition (fat-free mass or muscle mass). Logistic regression analysis was used to assess the association of frailty and sarcopenia. Statistical significance was set at P < 0.05. Results Plasma ghrelin levels by age, sex, and BMI A total of 58 elderly subjects (≥ 70 years) and 33 young adults (25-65 years) were recruited. No significant differences in fasting plasma ghrelin levels were observed between the two age groups, neither in men nor in women. In both age groups, mean ghrelin levels were significantly higher in women than in men. Table 1 shows mean plasma ghrelin levels in subjects distributed according to age, sex, and BMI.
Ghrelin and sarcopenia in the elderly Twenty three elderly subjects had sarcopenia (39.6%). Elderly subjects with sarcopenia had lower mean (± standard deviation) fasting plasma ghrelin levels as compared with those without sarcopenia (650.7 ± 196 vs. 899.3 ± 452 pg mL-1, P = 0.036). Also, subjects with severe sarcopenia had lower fasting ghrelin levels than those without severe sarcopenia (615 ± 223 vs. 845 ± 407 pg mL-1, P = 0.067). In the elderly group, severe sarcopenia was present in 45.5% of subjects fasting ghrelin levels below the 20th percentile and in 15.9% of those with ghrelin levels above this cut-off value (P = 0.049). Sarcopenia was more frequent in men (69.2%) than in women (16.7%) (P 30, 20-30, and < 20 kg/m2, showed an odds ratio (OR) of 1.02 (P = 0.712), 10.7 (P = 0.001), and 3.1 (P = 0.097), respectively. Fasting plasma ghrelin levels were similar in the elderly group without sarcopenia (899.3 pg mL-1) than in young adults (899.6 pg mL-1). Also, ghrelin levels showed no relationship with frailty (769 pg mL-1 in frail vs 816 pg mL-1 in non frail, p=0.846), Barthel score (rs=-0.059; p=0.662), and handgrip (rs=-0.221; p=0.096). Subjects with severe sarcopenia showed a poorer ‘ghrelin response’ after a meal test as compared to subjects without severe sarcopenia (difference between fasting and 1.5 h postprandial ghrelin 127.7 vs. -10.1, P = 0.004) but differences at 4 h postprandial levels were not observed.
Table 1 Fasting ghrelin levels by age, gender and BMI groups N Age and gender * Young males Elderly males Young females Elderly females Gender * Males Females BMI, kg/m2 & 30 Gender * Males Females BMI, kg/m2 & 30
Mean fasting ghrelin
13 752.1 (284.0) 27 716.6 (371.8) 20 995.5 (323.1) 31 859.6 (376.9) Young adults (25-65 years) (N=33) 13 752.1 (284.0) 20 995.5 (323.1) 3 1011.1 (238.3) 28 898.5 (345.3) 2 747.8 (49.2) Elderly subjects (≥ 70 years) (N=58) 27 716.6 (371.8) 31 859.6 (376.9) 5 791.0 (241.9) 40 815.8 (400.6) 12 698.9 (366.3)
* U-Mann Whytney test; & Kruskal-Wallis test
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p 0.763 0.190 0.030 0.153
0.053 0.503
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JNHA: GERIATRIC SCIENCE Table 2 Relationship between ghrelin and body composition Fat-free mass (% of total body weight) rs P value
Correlation *
Young adults (25-65 years) -0.107 0.727 0.583 0.007 Elderly subjects (≥ 70 years) -0.371 0.062 -0.023 0.907
Men Women Men Women Regression &
beta
P value
Young adults (25-65 years) -0.2 0.727 0.7 0.023 0.4 0.141 -0.1 0.724 Elderly subjects (≥ 70 years) -0.4 0.180 -0.02 0.960 -0.2 0.351 -0.4 0.148
Men Women All adjusted by sex All non- adjusted Men Women All adjusted by sex All non-adjusted
Muscle mass (% of total body weight) rs P value 0.016 0.957 0.536 0.015 0.086 0.675 0.205 0.286 beta
P value
-0.2 0.722 0.6 0.032 0.3 0.181 -0.2 0.515 -0.003 0.991 0.1 0.517 0.1 0.641 -0.1 0.670
* Correlation (rs): Spearman correlation coefficient; & Regression: Linear regression analysis
Ghrelin and body composition In young women, ghrelin levels were correlated with the percentage of fat free mass (rs = 0.58, P = 0.007) and muscular mass (rs = 0.54, P = 0.015), although these correlations were not found either in young men or elderly women. Lineal regression analysis showed no effect of ghrelin on fat-free mass and muscle mass in young men but a significant effect on fatfree mass (β = 0.7, P = 0.023) and muscle mass (β = 0.6, P = 0.032) in young women (Table 2). In the elderly group when muscle mass was stratified according to EWGSOP criteria, mean fasting ghrelin was 650.7 pg mL-1 in subjects with poor muscle mass and 899.2 pg mL-1 in those with normal muscle mass (P = 0.036). Sarcopenia and other variables In the elderly group, sarcopenia was also associated with BMI (with 80.0%, 46.2% and 8.3% prevalence for BMI ≤ 20, 20-30 and > 30, respectively; P = 0.012), nutritional impairment (11.1% in well-nourished vs. 48.1% in malnourished or at risk of malnutrition, P = 0.053), and presence of chronic obstructive pulmonary disease (COPD) (66.7% in COPD vs. 28.9% in non-COPD, P = 0.007). Frailty was unrelated to sarcopenia in general, but was related with severe sarcopenia (OR = 4.3, P = 0.036). Discussion Low fasting ghrelin plasma levels were associated with sarcopenia, severe sarcopenia, and poor muscle mass in elderly
subjects. However, sex acted as a potential confounder as it was associated with both fasting ghrelin levels and sarcopenia. Differences in fasting ghrelin among elderly subjects with and without sarcopenia or with poor or normal muscle mass were not statistically significant when stratifying by sex. Some findings suggest that this lack of statistical significance may be explained, almost in part, by the small sample size and the lack of statistical power, rather than by a confusion phenomenon and/or the absence of a relationship between ghrelin and sarcopenia. Firstly, although not statistically significant, differences in fasting ghrelin between subjects of both sexes with and without sarcopenia can be considered of clinically relevant magnitude, particularly in men. Secondly, the multivariate analysis showed an important effect of categorized ghrelin on sarcopenia (adjusted by age and sex) with an OR = 3.1 and a P value close to significance (P < 0.10). Thirdly, elderly subjects without sarcopenia showed almost exactly the same fasting ghrelin levels than young adults, suggesting that ghrelin secretion is preserved in subjects without sarcopenia but impaired in those with sarcopenia. Finally, a significant effect of ghrelin on muscle mass was observed in the elderly group despite it would be expected that sex would dilute but not maximize such effect (since fasting ghrelin was higher in women than in men). A positive correlation of fasting ghrelin levels with muscle mass and fat free mass was only observed in young women, which suggests a lower weight of ghrelin as anabolic hormone in young men in whom testosterone plays a major role. 671
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RELATIONSHIP BETWEEN PLASMA GHRELIN LEVELS AND SARCOPENIA Gender differences in nutritional and functional decline associated with aging are well established. In the general population, elderly women use to have poorer nutritional and functional status than elderly men. However, in the present study men showed a higher prevalence of sarcopenia than women, probably because it was designed not as an epidemiological but as a physiological one, and sampling process did not consider a random but an opportunistic selection of patients. To solve this question and to assess gender differences, all analyses were performed separately by gender. Lower ghrelin levels were found in elderly subjects with sarcopenia as compared with those without sarcopenia, but this latter group showed the same ghrelin levels than young adults. These results suggest that ghrelin decline does not seem to be dependent on age per se but on an unhealthy or frail aging process. Fasting ghrelin was not associated with hand grip and functional capacity. These results do not support the hypothesis of the present study but are in accordance with most interventional studies that have showed beneficial effects of hormone replacement therapy on muscle mass but not on strength and function (16). Improvement in muscle mass is not sufficient to improve muscle function if it is not accompanied by exercise or training (30). Finally, ghrelin response and recuperation after a standard meal test do not seem to have much relevance as indicators of sarcopenia or functional decline. Some limitations should be considered, including crosssectional design, representativeness of the sample, which was not mandatory for the main purpose of the study but could have affected gender comparisons, and the limited statistical power due to the sample size especially in the gender subgroup or multivariate analyses. The present results are inconclusive regarding the relationship between plasma ghrelin levels and sarcopenia in elderly people. Large prospective studies are required to assess this hypothesis. Acknowledgements: This study was funded by grants from the Spanish Ministry of Health, Instituto de Salud Carlos III, Fondo de Investigación Sanitaria; expedient PI 05/1120 and PI08/0478. We thank Marta Pulido, MD, for editing the manuscript and editorial assistance. Conflict of interest: The authors do not have any conflict of interest to disclose.
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