- Joined
- Jan 9, 2013
- Messages
- 15,170
- Reaction score
- 2,688
- Points
- 113
[h=1]Effects of an Oral Ghrelin Mimetic on Body Composition and Clinical Outcomes in Healthy Older Adults: A Randomized, Controlled Trial[/h]Ralf Nass, M.D., Suzan S. Pezzoli, B.A., [...], and Michael O. Thorner, M.B., B.S., D.Sc.
Additional article information
[FONT="][h=2]Abstract[/h][h=3]Background[/h]Growth hormone (GH) secretion and muscle mass decline from mid-puberty throughout life culminating in sarcopenia, frailty, decreased function and loss of independence.
[h=3]Objective[/h]Determine if an oral ghrelin mimetic (MK-677) would enhance GH secretion into the young adult range without serious adverse effects, prevent the decline of fat-free mass (FFM), and decrease abdominal visceral fat (AVF) in healthy older adults.
[h=3]Design[/h]Two-year, double-blind, randomized, placebo-controlled, modified-crossover clinical trial.
[h=3]Setting[/h]General Clinical Research Center study performed at a University Hospital.
[h=3]Participants[/h]Sixty-five healthy men and women (on or off hormone replacement therapy) ages 60-81.
[h=3]Intervention[/h]Oral administration of MK-677 (25 mg) or placebo once daily.
[h=3]Measurements[/h]Growth hormone and insulin-like growth factor-I (IGF-I); FFM and AVF were the primary endpoints after one year of treatment. Other endpoints: weight, fat mass, insulin sensitivity, lipid and cortisol levels, bone mineral density, limb lean and fat mass, isokinetic strength, function and quality of life; all endpoints were assessed at baseline and every 6 months.
[h=3]Limitations[/h]Study design (duration and subject number) not sufficient to evaluate functional endpoints in healthy elderly
[h=3]Results[/h]Daily MK-677 significantly increased GH and IGF-I levels to those of healthy young adults without serious adverse effects. With placebo, mean (95% Cl) FFM decreased -0.5 (-1.1 to 0.2) kg, however, FFM increased 1.1 (0.7 to 1.5) kg with MK-677 (P<0.001, MK-677 vs. placebo); body cell mass as reflected by intracellular water decreased -1.0 (-2.1 to 0.2) kg with placebo, but increased 0.8 (-0.1 to 1.6) kg with MK-677 (P=0.021). There were no significant differences in AVF or total fat mass. However, the average increase in limb fat in the MK-677 group (1.1 kg) was greater than with placebo (0.24 kg); P=0.001. Body weight increased 0.8 (-0.3 to 1.8) kg with placebo and 2.7 (2.0 to 3.5) kg with MK-677 (P=0.003). Fasting blood glucose increased an average of 0.3 mmol/L (5 mg/dL) with MK-677 (P=0.015) and insulin sensitivity declined. The most frequent side effects were an increase in appetite that subsided within a few months and transient, mild lower extremity edema and muscle pain. Low density lipoprotein cholesterol decreased -0.14 (-0.27 to -0.01) mmol/L [-5.4 (-10.4 to -0.4) mg/dL] with MK-677 (P=0.026); there were no differences in total or high density lipoprotein cholesterol. Cortisol increased 47 (28 to 71) nmol/L [1.7 (1.0 to 2.6 µg/dL)] with MK-677 (P=0.020). Changes in bone mineral density consistent with increased bone remodeling occurred in MK-677-treated subjects. Increased FFM did not result in changes in strength or function. Two-year exploratory analyses confirmed the 1-year results.
[h=3]Conclusions[/h]The ghrelin mimetic MK-677 enhanced pulsatile GH secretion and significantly increased FFM over 12 months and was generally well tolerated. Long-term functional, and ultimately pharmaco-economic, studies in elderly adults are indicated.
Keywords: Ghrelin, ghrelin mimetic, body composition, aging, sarcopenia, frailty, healthspan, growth hormone, growth hormone secretagogue
[/FONT]
[FONT="][h=2]INTRODUCTION[/h]Aging is an inevitable process across all species. In humans, muscle mass declines following its peak in the third decade of life. Muscle mass is important for physical fitness and metabolic regulation; development of sarcopenia is a major risk factor for developing frailty, loss of independence and physical disability in the elderly (1) and is associated with shortened survival in critically-ill patients (2). With increased lifespan, increasing numbers of adults are becoming frail and dependent upon others, creating challenges for them, their families and society.
The decline in fat-free mass (FFM) correlates with the aging-associated decline of growth hormone (GH) secretion (3, 4). Rudman et al. noted that aging adults show similar declines in FFM and GH secretion as seen in GH-deficient young adults (5). By the 8th decade, men and women have lost about 7 and 3.8 kg of muscle mass, respectively (3), with an increase in intra-abdominal fat (6, 7).
Previous trials using GH in the elderly were small, poorly controlled and/or too short (8); in addition, GH replacement does not restore pulsatile GH secretion. MK-677, the first orally-active ghrelin mimetic (GH secretagogue; GH secretagogue-receptor agonist), increases pulsatile GH secretion in older adults to that observed in young adults (9, 10). The primary objectives were to determine if oral MK-677 (25 mg daily) in healthy older adults would increase GH and IGF-I levels, prevent the decline of FFM and decrease abdominal visceral fat (AVF) with acceptable tolerability.
[/FONT]
[FONT="][h=2]METHODS[/h][h=3]Study Design[/h]This study was approved by the General Clinical Research Center (GCRC) and the University of Virginia Institutional Review Boards under IND # 54,041. All subjects gave written informed consent. A two-year, randomized, double-blind, modified-crossover trial of once-daily oral administration of 25 mg MK-677 or placebo (2:1 ratio) to healthy older adults (men, women on and women off hormone replacement therapy) was performed. After 1 year, MK-677-treated subjects were randomized to continue on MK-677 (Group 1) or change to placebo (Group 2); the placebo-treated subjects were given MK-677 during year 2 (Group 3). A schematic of the study design is provided in APPENDIX FIGURE 1.
[h=3]Setting and Participants[/h]Healthy older volunteers ≥ 60 years were recruited from the general population by advertisement and were screened by medical history, physical examination and laboratory testing to rule out underlying disease. Exclusion criteria included body mass index ≥ 35 kg/m2, strenuous exercise > 60 minutes per day, smoking, diabetes, history of malignancy (other than some skin cancers), untreated hypertension, thyroid disease or medications known to affect GH secretion. Participants were asked to maintain their typical diet and exercise throughout the study and to report any illnesses, medical procedures or adverse effects. All subjects were Caucasian, with the exception of 1 Hispanic and 1 African-American man.
At baseline and every 6 months for 2 years, subjects were admitted to the GCRC for body composition, body water, lipid and bone mineral density measurements, frequent blood sampling and completion of quality of life questionnaires. Tests of strength and function also were performed. During GCRC admissions, meals were standardized for caloric and nutrient content. Blood samples for GH were drawn from an indwelling venous cannula every 10 minutes for 24 hours; subjects were allowed to sleep after 21:00.
[h=3]Randomization and Intervention[/h]Blinded supplies of MK-677 and placebo tablets were provided by Merck Research Laboratories, Inc., stored by a research pharmacist, and were dispensed in a blinded manner according to a randomization table with stratification for gender and hormone replacement therapy. Ten mg tablets were provided for blind back-titration. Placebo or MK-677 (25 mg) tablets were taken once daily between 7 and 9:00 AM (at 9:00 AM during admissions). All research staff and the volunteers remained blinded throughout the study and during data verification. Compliance was monitored by pill counts.
[h=3]Outcome Measures[/h][h=4]Growth Hormone and IGF-I[/h]Serum GH and IGF-I levels were measured in duplicate in the GCRC Core Laboratory. 24-h mean GH and endogenous GH secretory dynamics were assessed by Cluster (11) and an automated (12) multiple-parameter deconvolution method (9). Details of all assay methods are provided in APPENDIX 1.
[h=4]Body Composition and Bone Mineral Density[/h]FFM and total body fat were evaluated by a 4-compartment (4-C) model (13) and by dual x-ray absorptiometry (DXA) on a Hologic QDR-2000 (Hologic Inc., Bedford MA) in pencil beam mode (14). DXA measurements included: i. appendicular lean soft tissue of the arms and legs as an estimate of total appendicular skeletal muscle mass (TASM) (15); ii. appendicular fat; iii. bone mineral density of the femoral neck, spine (L2-4) and total hip.
[h=4]T-score for TASM/ht2[/h]The DXA TASM estimates were divided by height squared in meters [TASM (kg)/ht2] (15). This index of relative limb muscle mass was used to compute a t-score for each individual, relating the TASM/ht2 to those of gender-concordant young adults (16). Sarcopenia was defined as ≤ 2 SD below young, gender-specific reference populations (17, 18).
[h=4]Computed Tomography[/h]Cross-sectional computed tomography images were used to measure the areas (cm2) of abdominal visceral (AVF) and subcutaneous fat, and mid-thigh skeletal muscle at pre-defined anatomic locations (19); data were not included when the subsequent scan location differed or there were technical difficulties [N=4 placebo, N=3 MK-677].
DXA and CT scans were analyzed by a single blinded observer (J.L.C.)
[h=4]Body Water[/h]Total body water, using the deuterium oxide (D2O) dilution technique (20), and extracellular water by bromide dilution (21) were measured. Intracellular water was assessed as the difference between total body water and extracellular water. To determine the relative relationships of total-, extra- and intra-cellular water, each component (in kg) was expressed per kg of FFM at each time point. The scale of measure used in the analysis was chosen a priori; the raw data also were analyzed and are reported in typical units for comparison.
[h=4]Isokinetic Muscle Strength[/h]Concentric force during flexion and extension of the knee and shoulder were determined every 6 months using an isokinetic dynamometer (Cybex II, CSM, Inc., Boston, MA). Six repetitions of maximal effort over 90 degrees at 60 degrees/second were performed with the mean of the last 5 repetitions computed by proprietary software (22). Total work (Newton.metres) was calculated by multiplying the mean per repetition by 5.
[h=4]Function[/h]Function tests performed every 6 months included walking 30 meters as quickly as possible (best of 2 trials), walking as far as possible in 6 minutes on an indoor track, descending and ascending 4 flights of stairs, and rising and sitting 5 times from an armless chair with an 18” seat height.
[h=4]Correction for Height and Gender[/h]To compensate for differences in muscle mass between men and women, all strength and function measurements were analyzed per kg of baseline appendicular skeletal muscle (lean) from DXA. Arm lean and leg lean were used for shoulder and knee strength, respectively; baseline TASM (sum of arms and legs) was used for the function tests. The scale of measure used in the analysis was chosen a priori; the raw data also are reported.
[h=4]Quality of Life Assessments[/h]Subjects completed 4 questionnaires every 6 months to assess quality of life and general wellbeing: the 20-item Short Form Health Survey; Beck Depression Inventory; Pittsburgh Sleep Quality Index; and the Body Cathexis Scale.
Additional details of quality of life, muscle strength and function assessments are provided in APPENDIX 1.
[h=4]Clinical Outcomes[/h]Every 6 months, cholesterol, cortisol and insulin sensitivity, estimated by fasting insulin and glucose using the Quicki Index method of Katz et al. (23), were measured.
[h=4]Exploratory 2-year Outcomes[/h]To determine if the effects of MK-677 treatment were sustained over 2 years, or reversed when changed to placebo, several endpoints were analyzed in a subgroup of subjects who completed 24 months in each of the 3 treatment groups; FIGURE 1.
FIGURE 1
Participant Flow Through the Study
[h=3]Monitoring for Adverse Effects[/h]Each year volunteers were seen monthly for the first 3 months and every 3 months thereafter for a physical examination, documentation of medications and vital signs, and questioning for side effects and overall well being. A complete blood count, chemistry panel, hemoglobin A1c (HbA1c), fasting blood glucose, and prostate-specific antigen and testosterone levels in men were monitored. Women had annual pap smears and mammograms.
[h=3]Statistical Analysis[/h]The two primary endpoints were FFM and AVF. The study was powered for the pivotal first 12 months; the power analysis is described in detail in APPENDIX 1. It was unknown whether there would be differences in responses among men, women on and women off hormone replacement therapy. Consequently, the randomization was conducted a priori so that equal numbers of these 3 populations would be randomly assigned to MK-677 and to placebo. Therefore, the power analyses were focused on the pivotal 12-month change comparison between the 2 treatment groups as a whole and did not focus on specific subgroup comparisons (gender or hormone replacement therapy).
All statistical analyses were conducted under the guidelines of the intention-to-treat principle and missing data points were not imputed. The analyses were performed on the baseline and the 6- and 12-month primary and secondary outcomes and the data analysis plan was decided a priori. The primary outcome data for the 6- and 12-month changes in FFM and AVF as well as for IGF-I and GH were analyzed via repeated measures analysis of covariance (ANCOVA). For each ANCOVA, treatment (MK-677 or placebo) and time (6- or 12-months) were considered potential sources of variability, as was treatment by time interaction. The subjects' baseline measurements were treated as the ANCOVA covariate. The FFM and AVF data were analyzed on the same scale on which they were measured and are reported as a difference between arithmetic means. The GH and IGF-I data were transformed to the natural logarithmic scale before conducting the statistical analyses so that the variance and normality assumptions of the linear model were not violated; results are reported as a ratio of geometric means (fold change).
To estimate the mean within-subject change in the response at 6 and at 12 months, linear contrasts were constructed. Similarly, linear contrasts were constructed to estimate the baseline-adjusted difference in changes in the response at 6 and 12 months between the MK-677 and placebo groups. For the pivotal 12-month comparison (MK-677 versus placebo), the null hypothesis of equality of means was rejected if the p-value of the F-statistic was ≤ 0.05. For the 6-month between-group comparison, the null hypothesis was rejected if the p-value of the F-statistic was ≤ 0.05 after implementing the Bonferonni post-hoc test correction. For the 12-month comparison, the 95% confidence interval was constructed based on the Students' t-distribution quantile values at the 2.5 and 97.5 percentiles, while the 6-month comparison was based on the 1.25 and 98.75 percentiles of the distribution. With the exception of the quality of life data, all secondary outcome data were analyzed via repeated measure ANCOVA and are reported exactly as the primary outcome data. For the quality of life data, a Factor Analysis (24) of the different scales of the questionnaires was performed to create an overall wellbeing factor; this is described in detail in APPENDIX 1.
The effects of year-2 treatment were designed as exploratory. To determine whether the effects were maintained or reversed, a separate post hoc analysis of endpoints based on responses in year 1, was performed in subjects who had complete data at baseline, 12 and 24 months. Only the change from baseline to 24 months was analyzed, in exactly the same way as the year 1 data; a post hoc correction for the 3 treatment groups was implemented. The software of SAS version 9.1 (SAS Institute Inc, Cary NC) was used to conduct the statistical analyses.
[h=3]Role of Funding Source[/h]This was an investigator-initiated GCRC study funded by the NIH; it was conducted and analyzed at the University of Virginia.
[/FONT]
[FONT="][h=2]RESULTS[/h][h=3]Characteristics of the participants[/h]FIGURE 1 shows the flow of study participants and baseline demographics are shown in TABLE 1.
TABLE 1
DEMOGRAPHICS
Treatment occurred between September 1998 and November 2003. Because the study drug expired in November 2003, 6 subjects were treated for only 18 months (2 on placebo, 4 on MK-677) and 1 for only 12 months (on placebo). Seventy-one volunteers were randomized and 65 completed year 1 (dropout rate, 8.5%); 23 men and 42 women (25 on and 17 not on hormone replacement therapy). The treatment groups were well-matched at baseline, with no significant differences between groups. Fifty-nine subjects completed 18 months and 53 completed 24 months (FIGURE 1).
[h=4]Back titration[/h]In 4 subjects, the dose of study drug was blindly back titrated to 10 mg daily because of: increased fasting glucose after crossover from placebo to MK-677 in year 2 (81-year-old man, completed 2 years); increased fasting glucose in 1 woman on MK-677 (withdrawn after 3 months); and increased joint pain in 2 women on MK-677 (withdrew after 12 months).
Additional methods, baseline data and all results are presented in supplementary appendix materials. Data presented are mean (95% confidence limits). All statistical comparisons at 6 and 12 months are between MK-677 and placebo.
[h=3]Growth Hormone and IGF-I Levels[/h]The effects of treatment in the pivotal year 1 are shown in FIGURE 2. After 12 months of MK-677 treatment, there was a 1.8 (1.56 to 2.0) -fold increase from baseline in 24-h mean GH (P<0.001). This was accounted for by enhanced pulsatile GH secretion (APPENDIX TABLE 1), as shown in a representative subject, FIGURE 2C. Serum IGF-I levels also were increased by 1.5 (1.4 to 1.6) -fold, P<0.001. In 22/43 subjects, IGF-I levels were sustained in the normal range for young adults; individual IGF-I results are shown in APPENDIX FIGURE 2.
APPENDIX TABLE 1
EFFECTS OF TREATMENT ON 24-H MEAN GH AND IGF-I AND GH SECRETORY DYNAMICS
FIGURE 2
Serum 24-h mean GH and IGF-I results in pivotal year 1
[/FONT]
Additional article information
[FONT="][h=2]Abstract[/h][h=3]Background[/h]Growth hormone (GH) secretion and muscle mass decline from mid-puberty throughout life culminating in sarcopenia, frailty, decreased function and loss of independence.
[h=3]Objective[/h]Determine if an oral ghrelin mimetic (MK-677) would enhance GH secretion into the young adult range without serious adverse effects, prevent the decline of fat-free mass (FFM), and decrease abdominal visceral fat (AVF) in healthy older adults.
[h=3]Design[/h]Two-year, double-blind, randomized, placebo-controlled, modified-crossover clinical trial.
[h=3]Setting[/h]General Clinical Research Center study performed at a University Hospital.
[h=3]Participants[/h]Sixty-five healthy men and women (on or off hormone replacement therapy) ages 60-81.
[h=3]Intervention[/h]Oral administration of MK-677 (25 mg) or placebo once daily.
[h=3]Measurements[/h]Growth hormone and insulin-like growth factor-I (IGF-I); FFM and AVF were the primary endpoints after one year of treatment. Other endpoints: weight, fat mass, insulin sensitivity, lipid and cortisol levels, bone mineral density, limb lean and fat mass, isokinetic strength, function and quality of life; all endpoints were assessed at baseline and every 6 months.
[h=3]Limitations[/h]Study design (duration and subject number) not sufficient to evaluate functional endpoints in healthy elderly
[h=3]Results[/h]Daily MK-677 significantly increased GH and IGF-I levels to those of healthy young adults without serious adverse effects. With placebo, mean (95% Cl) FFM decreased -0.5 (-1.1 to 0.2) kg, however, FFM increased 1.1 (0.7 to 1.5) kg with MK-677 (P<0.001, MK-677 vs. placebo); body cell mass as reflected by intracellular water decreased -1.0 (-2.1 to 0.2) kg with placebo, but increased 0.8 (-0.1 to 1.6) kg with MK-677 (P=0.021). There were no significant differences in AVF or total fat mass. However, the average increase in limb fat in the MK-677 group (1.1 kg) was greater than with placebo (0.24 kg); P=0.001. Body weight increased 0.8 (-0.3 to 1.8) kg with placebo and 2.7 (2.0 to 3.5) kg with MK-677 (P=0.003). Fasting blood glucose increased an average of 0.3 mmol/L (5 mg/dL) with MK-677 (P=0.015) and insulin sensitivity declined. The most frequent side effects were an increase in appetite that subsided within a few months and transient, mild lower extremity edema and muscle pain. Low density lipoprotein cholesterol decreased -0.14 (-0.27 to -0.01) mmol/L [-5.4 (-10.4 to -0.4) mg/dL] with MK-677 (P=0.026); there were no differences in total or high density lipoprotein cholesterol. Cortisol increased 47 (28 to 71) nmol/L [1.7 (1.0 to 2.6 µg/dL)] with MK-677 (P=0.020). Changes in bone mineral density consistent with increased bone remodeling occurred in MK-677-treated subjects. Increased FFM did not result in changes in strength or function. Two-year exploratory analyses confirmed the 1-year results.
[h=3]Conclusions[/h]The ghrelin mimetic MK-677 enhanced pulsatile GH secretion and significantly increased FFM over 12 months and was generally well tolerated. Long-term functional, and ultimately pharmaco-economic, studies in elderly adults are indicated.
Keywords: Ghrelin, ghrelin mimetic, body composition, aging, sarcopenia, frailty, healthspan, growth hormone, growth hormone secretagogue
[/FONT]
[FONT="][h=2]INTRODUCTION[/h]Aging is an inevitable process across all species. In humans, muscle mass declines following its peak in the third decade of life. Muscle mass is important for physical fitness and metabolic regulation; development of sarcopenia is a major risk factor for developing frailty, loss of independence and physical disability in the elderly (1) and is associated with shortened survival in critically-ill patients (2). With increased lifespan, increasing numbers of adults are becoming frail and dependent upon others, creating challenges for them, their families and society.
The decline in fat-free mass (FFM) correlates with the aging-associated decline of growth hormone (GH) secretion (3, 4). Rudman et al. noted that aging adults show similar declines in FFM and GH secretion as seen in GH-deficient young adults (5). By the 8th decade, men and women have lost about 7 and 3.8 kg of muscle mass, respectively (3), with an increase in intra-abdominal fat (6, 7).
Previous trials using GH in the elderly were small, poorly controlled and/or too short (8); in addition, GH replacement does not restore pulsatile GH secretion. MK-677, the first orally-active ghrelin mimetic (GH secretagogue; GH secretagogue-receptor agonist), increases pulsatile GH secretion in older adults to that observed in young adults (9, 10). The primary objectives were to determine if oral MK-677 (25 mg daily) in healthy older adults would increase GH and IGF-I levels, prevent the decline of FFM and decrease abdominal visceral fat (AVF) with acceptable tolerability.
[/FONT]
[FONT="][h=2]METHODS[/h][h=3]Study Design[/h]This study was approved by the General Clinical Research Center (GCRC) and the University of Virginia Institutional Review Boards under IND # 54,041. All subjects gave written informed consent. A two-year, randomized, double-blind, modified-crossover trial of once-daily oral administration of 25 mg MK-677 or placebo (2:1 ratio) to healthy older adults (men, women on and women off hormone replacement therapy) was performed. After 1 year, MK-677-treated subjects were randomized to continue on MK-677 (Group 1) or change to placebo (Group 2); the placebo-treated subjects were given MK-677 during year 2 (Group 3). A schematic of the study design is provided in APPENDIX FIGURE 1.
[h=3]Setting and Participants[/h]Healthy older volunteers ≥ 60 years were recruited from the general population by advertisement and were screened by medical history, physical examination and laboratory testing to rule out underlying disease. Exclusion criteria included body mass index ≥ 35 kg/m2, strenuous exercise > 60 minutes per day, smoking, diabetes, history of malignancy (other than some skin cancers), untreated hypertension, thyroid disease or medications known to affect GH secretion. Participants were asked to maintain their typical diet and exercise throughout the study and to report any illnesses, medical procedures or adverse effects. All subjects were Caucasian, with the exception of 1 Hispanic and 1 African-American man.
At baseline and every 6 months for 2 years, subjects were admitted to the GCRC for body composition, body water, lipid and bone mineral density measurements, frequent blood sampling and completion of quality of life questionnaires. Tests of strength and function also were performed. During GCRC admissions, meals were standardized for caloric and nutrient content. Blood samples for GH were drawn from an indwelling venous cannula every 10 minutes for 24 hours; subjects were allowed to sleep after 21:00.
[h=3]Randomization and Intervention[/h]Blinded supplies of MK-677 and placebo tablets were provided by Merck Research Laboratories, Inc., stored by a research pharmacist, and were dispensed in a blinded manner according to a randomization table with stratification for gender and hormone replacement therapy. Ten mg tablets were provided for blind back-titration. Placebo or MK-677 (25 mg) tablets were taken once daily between 7 and 9:00 AM (at 9:00 AM during admissions). All research staff and the volunteers remained blinded throughout the study and during data verification. Compliance was monitored by pill counts.
[h=3]Outcome Measures[/h][h=4]Growth Hormone and IGF-I[/h]Serum GH and IGF-I levels were measured in duplicate in the GCRC Core Laboratory. 24-h mean GH and endogenous GH secretory dynamics were assessed by Cluster (11) and an automated (12) multiple-parameter deconvolution method (9). Details of all assay methods are provided in APPENDIX 1.
[h=4]Body Composition and Bone Mineral Density[/h]FFM and total body fat were evaluated by a 4-compartment (4-C) model (13) and by dual x-ray absorptiometry (DXA) on a Hologic QDR-2000 (Hologic Inc., Bedford MA) in pencil beam mode (14). DXA measurements included: i. appendicular lean soft tissue of the arms and legs as an estimate of total appendicular skeletal muscle mass (TASM) (15); ii. appendicular fat; iii. bone mineral density of the femoral neck, spine (L2-4) and total hip.
[h=4]T-score for TASM/ht2[/h]The DXA TASM estimates were divided by height squared in meters [TASM (kg)/ht2] (15). This index of relative limb muscle mass was used to compute a t-score for each individual, relating the TASM/ht2 to those of gender-concordant young adults (16). Sarcopenia was defined as ≤ 2 SD below young, gender-specific reference populations (17, 18).
[h=4]Computed Tomography[/h]Cross-sectional computed tomography images were used to measure the areas (cm2) of abdominal visceral (AVF) and subcutaneous fat, and mid-thigh skeletal muscle at pre-defined anatomic locations (19); data were not included when the subsequent scan location differed or there were technical difficulties [N=4 placebo, N=3 MK-677].
DXA and CT scans were analyzed by a single blinded observer (J.L.C.)
[h=4]Body Water[/h]Total body water, using the deuterium oxide (D2O) dilution technique (20), and extracellular water by bromide dilution (21) were measured. Intracellular water was assessed as the difference between total body water and extracellular water. To determine the relative relationships of total-, extra- and intra-cellular water, each component (in kg) was expressed per kg of FFM at each time point. The scale of measure used in the analysis was chosen a priori; the raw data also were analyzed and are reported in typical units for comparison.
[h=4]Isokinetic Muscle Strength[/h]Concentric force during flexion and extension of the knee and shoulder were determined every 6 months using an isokinetic dynamometer (Cybex II, CSM, Inc., Boston, MA). Six repetitions of maximal effort over 90 degrees at 60 degrees/second were performed with the mean of the last 5 repetitions computed by proprietary software (22). Total work (Newton.metres) was calculated by multiplying the mean per repetition by 5.
[h=4]Function[/h]Function tests performed every 6 months included walking 30 meters as quickly as possible (best of 2 trials), walking as far as possible in 6 minutes on an indoor track, descending and ascending 4 flights of stairs, and rising and sitting 5 times from an armless chair with an 18” seat height.
[h=4]Correction for Height and Gender[/h]To compensate for differences in muscle mass between men and women, all strength and function measurements were analyzed per kg of baseline appendicular skeletal muscle (lean) from DXA. Arm lean and leg lean were used for shoulder and knee strength, respectively; baseline TASM (sum of arms and legs) was used for the function tests. The scale of measure used in the analysis was chosen a priori; the raw data also are reported.
[h=4]Quality of Life Assessments[/h]Subjects completed 4 questionnaires every 6 months to assess quality of life and general wellbeing: the 20-item Short Form Health Survey; Beck Depression Inventory; Pittsburgh Sleep Quality Index; and the Body Cathexis Scale.
Additional details of quality of life, muscle strength and function assessments are provided in APPENDIX 1.
[h=4]Clinical Outcomes[/h]Every 6 months, cholesterol, cortisol and insulin sensitivity, estimated by fasting insulin and glucose using the Quicki Index method of Katz et al. (23), were measured.
[h=4]Exploratory 2-year Outcomes[/h]To determine if the effects of MK-677 treatment were sustained over 2 years, or reversed when changed to placebo, several endpoints were analyzed in a subgroup of subjects who completed 24 months in each of the 3 treatment groups; FIGURE 1.
FIGURE 1Participant Flow Through the Study
[h=3]Monitoring for Adverse Effects[/h]Each year volunteers were seen monthly for the first 3 months and every 3 months thereafter for a physical examination, documentation of medications and vital signs, and questioning for side effects and overall well being. A complete blood count, chemistry panel, hemoglobin A1c (HbA1c), fasting blood glucose, and prostate-specific antigen and testosterone levels in men were monitored. Women had annual pap smears and mammograms.
[h=3]Statistical Analysis[/h]The two primary endpoints were FFM and AVF. The study was powered for the pivotal first 12 months; the power analysis is described in detail in APPENDIX 1. It was unknown whether there would be differences in responses among men, women on and women off hormone replacement therapy. Consequently, the randomization was conducted a priori so that equal numbers of these 3 populations would be randomly assigned to MK-677 and to placebo. Therefore, the power analyses were focused on the pivotal 12-month change comparison between the 2 treatment groups as a whole and did not focus on specific subgroup comparisons (gender or hormone replacement therapy).
All statistical analyses were conducted under the guidelines of the intention-to-treat principle and missing data points were not imputed. The analyses were performed on the baseline and the 6- and 12-month primary and secondary outcomes and the data analysis plan was decided a priori. The primary outcome data for the 6- and 12-month changes in FFM and AVF as well as for IGF-I and GH were analyzed via repeated measures analysis of covariance (ANCOVA). For each ANCOVA, treatment (MK-677 or placebo) and time (6- or 12-months) were considered potential sources of variability, as was treatment by time interaction. The subjects' baseline measurements were treated as the ANCOVA covariate. The FFM and AVF data were analyzed on the same scale on which they were measured and are reported as a difference between arithmetic means. The GH and IGF-I data were transformed to the natural logarithmic scale before conducting the statistical analyses so that the variance and normality assumptions of the linear model were not violated; results are reported as a ratio of geometric means (fold change).
To estimate the mean within-subject change in the response at 6 and at 12 months, linear contrasts were constructed. Similarly, linear contrasts were constructed to estimate the baseline-adjusted difference in changes in the response at 6 and 12 months between the MK-677 and placebo groups. For the pivotal 12-month comparison (MK-677 versus placebo), the null hypothesis of equality of means was rejected if the p-value of the F-statistic was ≤ 0.05. For the 6-month between-group comparison, the null hypothesis was rejected if the p-value of the F-statistic was ≤ 0.05 after implementing the Bonferonni post-hoc test correction. For the 12-month comparison, the 95% confidence interval was constructed based on the Students' t-distribution quantile values at the 2.5 and 97.5 percentiles, while the 6-month comparison was based on the 1.25 and 98.75 percentiles of the distribution. With the exception of the quality of life data, all secondary outcome data were analyzed via repeated measure ANCOVA and are reported exactly as the primary outcome data. For the quality of life data, a Factor Analysis (24) of the different scales of the questionnaires was performed to create an overall wellbeing factor; this is described in detail in APPENDIX 1.
The effects of year-2 treatment were designed as exploratory. To determine whether the effects were maintained or reversed, a separate post hoc analysis of endpoints based on responses in year 1, was performed in subjects who had complete data at baseline, 12 and 24 months. Only the change from baseline to 24 months was analyzed, in exactly the same way as the year 1 data; a post hoc correction for the 3 treatment groups was implemented. The software of SAS version 9.1 (SAS Institute Inc, Cary NC) was used to conduct the statistical analyses.
[h=3]Role of Funding Source[/h]This was an investigator-initiated GCRC study funded by the NIH; it was conducted and analyzed at the University of Virginia.
[/FONT]
[FONT="][h=2]RESULTS[/h][h=3]Characteristics of the participants[/h]FIGURE 1 shows the flow of study participants and baseline demographics are shown in TABLE 1.
DEMOGRAPHICS
Treatment occurred between September 1998 and November 2003. Because the study drug expired in November 2003, 6 subjects were treated for only 18 months (2 on placebo, 4 on MK-677) and 1 for only 12 months (on placebo). Seventy-one volunteers were randomized and 65 completed year 1 (dropout rate, 8.5%); 23 men and 42 women (25 on and 17 not on hormone replacement therapy). The treatment groups were well-matched at baseline, with no significant differences between groups. Fifty-nine subjects completed 18 months and 53 completed 24 months (FIGURE 1).
[h=4]Back titration[/h]In 4 subjects, the dose of study drug was blindly back titrated to 10 mg daily because of: increased fasting glucose after crossover from placebo to MK-677 in year 2 (81-year-old man, completed 2 years); increased fasting glucose in 1 woman on MK-677 (withdrawn after 3 months); and increased joint pain in 2 women on MK-677 (withdrew after 12 months).
Additional methods, baseline data and all results are presented in supplementary appendix materials. Data presented are mean (95% confidence limits). All statistical comparisons at 6 and 12 months are between MK-677 and placebo.
[h=3]Growth Hormone and IGF-I Levels[/h]The effects of treatment in the pivotal year 1 are shown in FIGURE 2. After 12 months of MK-677 treatment, there was a 1.8 (1.56 to 2.0) -fold increase from baseline in 24-h mean GH (P<0.001). This was accounted for by enhanced pulsatile GH secretion (APPENDIX TABLE 1), as shown in a representative subject, FIGURE 2C. Serum IGF-I levels also were increased by 1.5 (1.4 to 1.6) -fold, P<0.001. In 22/43 subjects, IGF-I levels were sustained in the normal range for young adults; individual IGF-I results are shown in APPENDIX FIGURE 2.
EFFECTS OF TREATMENT ON 24-H MEAN GH AND IGF-I AND GH SECRETORY DYNAMICS
FIGURE 2Serum 24-h mean GH and IGF-I results in pivotal year 1
[/FONT]
