Biomedical subjects

Bret H Goodpaster

Publications and source records attributed to Bret H Goodpaster.

At least 19 recordsLinked to original sources

PubMed2006

Daily activity energy expenditure and mortality among older adults.

CONTEXT: Exercise is associated with mortality benefits but simply expending energy through any activity in an individual's free-living environment may confer survival advantages. OBJECTIVE: To determine whether free-living activity energy expenditure is associated with all-cause mortality among older adults. DESIGN, SETTING, AND PARTICIPANTS: Free-living activity energy expenditure was assessed in 302 high-functioning, community-dwelling older adults (aged 70-82 years). Total energy expenditure was assessed over 2 weeks using doubly labeled water. Resting metabolic rate was measured using indirect calorimetry and the thermic effect of meals was estimated at 10% of total energy expenditure. Free-living activity energy expenditure was calculated as: (total energy expenditure x 0.90) - resting metabolic rate. Participants were followed up over a mean of 6.15 years (1998-2006). MAIN OUTCOME MEASURES: Free-living activity energy expenditure (3 tertiles: low, <521 kcal/d; middle, 521-770 kcal/d; high, >770 kcal/d) and all-cause mortality. RESULTS: Fifty-five participants (18.2%) died during follow-up. As a continuous risk factor, an SD increase in free-living activity energy expenditure (287 kcal/d) was associated with a 32% lower risk of mortality after adjusting for age, sex, race, study site, weight, height, percentage of body fat, and sleep duration (hazard ratio, 0.68; 95% confidence interval, 0.48-0.96). Using the same adjustments, individuals in the highest tertile of free-living activity energy expenditure were at a significantly lower mortality risk compared with the lowest tertile (hazard ratio, 0.31; 95% confidence interval, 0.14-0.69). Absolute risk of death was 12.1% in the highest tertile of activity energy expenditure vs 24.7% in the lowest tertile; absolute risks were similar to these for tertiles of physical activity level. The effect of free-living activity energy expenditure changed little after further adjustment for self-rated health, education, prevalent health conditions, and smoking behavior. According to self-reports, individuals expending higher levels of free-living activity energy were more likely to work for pay (P = .004) and climb stairs (P = .01) but self-reported high-intensity exercise, walking for exercise, walking other than for exercise, volunteering, and caregiving did not differ significantly across the activity energy expenditure tertiles. CONCLUSIONS: Objectively measured free-living activity energy expenditure was strongly associated with lower risk of mortality in healthy older adults. Simply expending energy through any activity may influence survival in older adults.

Activities of Daily Living↗

PubMed2006

Adipocytokines and incident diabetes mellitus in older adults: the independent effect of plasminogen activator inhibitor 1.

BACKGROUND: Adipose tissue produces "adipocytokines" of uncertain clinical significance. METHODS: We analyzed the relationships among adiposity, adipocytokines, glycemia, and incident diabetes mellitus in 2356 white and black adults aged 70 to 79 years in the Health, Aging, and Body Composition Study who did not have diabetes at baseline. We measured the levels of adipocytokines adiponectin, leptin, interleukin 6, tumor necrosis factor alpha, and plasminogen activator inhibitor 1. Regional fat area was determined by means of computed tomography. New diabetes was defined as a self-reported diagnosis of diabetes or as a fasting plasma glucose level of 126 mg/dL or greater (>/=7.0 mmol/L) at the second, fourth, or sixth annual examination. RESULTS: A total of 143 participants (14.1 cases per 1000 person-years) developed diabetes across 5 years. Visceral fat area (odds ratio [OR], 1.33; 95% confidence interval [CI], 1.10-1.60 per standard deviation increase) and body mass index (white individuals: OR, 1.65; 95% CI, 1.26-2.15 per standard deviation increase; black individuals: OR, 1.22; 95% CI, 0.99-1.51 per standard deviation increase) independently predicted incident diabetes. Adiponectin, leptin, and plasminogen activator inhibitor 1 attenuated the relationship between adiposity and diabetes. After controlling for body mass index, visceral fat, fasting glucose, fasting insulin, high-density lipoprotein cholesterol, triglycerides, and hypertension at baseline, plasminogen activator inhibitor 1 was the only adipocytokine independently associated with increased odds of diabetes (OR, 1.35; 95% CI, 1.01-1.81). Fasting glucose level at baseline remained a strong predictor of incident diabetes, whereas associations with body mass index and visceral fat were attenuated. CONCLUSIONS: Adipocytokines and glycemia partially account for the relationship between adiposity and risk of type 2 diabetes due to adiposity. Plasminogen activator inhibitor 1 may be a useful predictor of diabetes in addition to measurements of body fat.

Adiponectin↗

PubMed2006

Strength, but not muscle mass, is associated with mortality in the health, aging and body composition study cohort.

BACKGROUND: Although muscle strength and mass are highly correlated, the relationship between direct measures of low muscle mass (sarcopenia) and strength in association with mortality has not been examined. METHODS: Total mortality rates were examined in the Health, Aging and Body Composition (Health ABC) Study in 2292 participants (aged 70-79 years, 51.6% women, and 38.8% black). Knee extension strength was measured with isokinetic dynamometry, grip strength with isometric dynamometry. Thigh muscle area was measured by computed tomography (CT) scan, and leg and arm lean soft tissue mass were determined by dual energy x-ray absorptiometry (DXA). Both strength and muscle size were assessed as in gender-specific Cox proportional hazards models, with age, race, comorbidities, smoking status, level of physical activity, fat area by CT or fat mass by DXA, height, and markers of inflammation, including interleukin-6, C-reactive protein, and tumor necrosis factor-alpha considered as potential confounders. RESULTS: There were 286 deaths over an average of 4.9 (standard deviation = 0.9) years of follow-up. Both quadriceps and grip strength were strongly related to mortality. For quadriceps strength (per standard deviation of 38 Nm), the crude hazard ratio for men was 1.51 (95% confidence interval, 1.28-1.79) and 1.65 (95% confidence interval, 1.19-2.30) for women. Muscle size, determined by either CT area or DXA regional lean mass, was not strongly related to mortality. In the models of quadriceps strength and mortality, adjustment for muscle area or regional lean mass only slightly attenuated the associations. Further adjustment for other factors also had minimal effect on the association of quadriceps strength with mortality. Associations of grip strength with mortality were similar. CONCLUSION: Low muscle mass did not explain the strong association of strength with mortality, demonstrating that muscle strength as a marker of muscle quality is more important than quantity in estimating mortality risk. Grip strength provided risk estimates similar to those of quadriceps strength.

Age Factors↗

PubMed2006

The loss of skeletal muscle strength, mass, and quality in older adults: the health, aging and body composition study.

BACKGROUND: The loss of muscle mass is considered to be a major determinant of strength loss in aging. However, large-scale longitudinal studies examining the association between the loss of mass and strength in older adults are lacking. METHODS: Three-year changes in muscle mass and strength were determined in 1880 older adults in the Health, Aging and Body Composition Study. Knee extensor strength was measured by isokinetic dynamometry. Whole body and appendicular lean and fat mass were assessed by dual-energy x-ray absorptiometry and computed tomography. RESULTS: Both men and women lost strength, with men losing almost twice as much strength as women. Blacks lost about 28% more strength than did whites. Annualized rates of leg strength decline (3.4% in white men, 4.1% in black men, 2.6% in white women, and 3.0% in black women) were about three times greater than the rates of loss of leg lean mass ( approximately 1% per year). The loss of lean mass, as well as higher baseline strength, lower baseline leg lean mass, and older age, was independently associated with strength decline in both men and women. However, gain of lean mass was not accompanied by strength maintenance or gain (ss coefficients; men, -0.48 +/- 4.61, p =.92, women, -1.68 +/- 3.57, p =.64). CONCLUSIONS: Although the loss of muscle mass is associated with the decline in strength in older adults, this strength decline is much more rapid than the concomitant loss of muscle mass, suggesting a decline in muscle quality. Moreover, maintaining or gaining muscle mass does not prevent aging-associated declines in muscle strength.

Aged↗

PubMed2006

Effects of exercise on mitochondrial content and function in aging human skeletal muscle.

Skeletal muscle mitochondria are implicated with age-related loss of function and insulin resistance. We examined the effects of exercise on skeletal muscle mitochondria in older (age = 67.3 +/- 0.6 years) men (n = 5) and women (n = 3). Similar increases in (p <.01) cardiolipin (88.2 +/- 9.0 to 130.6 +/- 7.5 microg/mU creatine kinase activity [CK]) and the total mitochondrial DNA (1264 +/- 170 to 1895 +/- 273 copies per diploid of nuclear genome) reflected increased mitochondria content. Succinate oxidase activity, complexes 2-4 of the electron transport chain (ETC), increased from 0.13 +/- 0.02 to 0.20 +/- 0.02 U/mU CK (p <.01). This improvement was more pronounced (p <.05) in subsarcolemmal (127 +/- 48%) compared to intermyofibrillar (56 +/- 12%) mitochondria. NADH oxidase activity, representing total ETC activity, increased from 0.51 +/- 0.09 to 1.00 +/- 0.09 U/mU CK (p <.01). In conclusion, exercise enhances mitochondria ETC activity in older human skeletal muscle, particularly in subsarcolemmal mitochondria, which is likely related to the concomitant increases in mitochondrial biogenesis.

Aged↗

PubMed2006

Assessment of intramuscular triglycerides: contribution to metabolic abnormalities.

PURPOSE OF REVIEW: The purpose of this review is to highlight recent methodological advances that have helped us to understand the role of intramuscular triglycerides in human health as well as prevention and treatment of disease. In addition to both invasive (muscle biopsy) and noninvasive methods, techniques to assess other lipids within muscle will be reviewed. RECENT FINDINGS: In addition to intramuscular triglycerides, other lipids contained within skeletal muscle such as diacylglycerol and ceramides may have an important role in human metabolic disease. Both ex-vivo and in-vivo methods to obtain serial measurements of these muscle lipids as a result of experimental perturbation have recently provided unique insight into their respective roles in human metabolism. SUMMARY: Triglyceride accumulation within skeletal muscle has received considerable interest due to its potential role in insulin resistance and fatty acid metabolism of obesity, aging and type 2 diabetes. Observations that triglycerides themselves may be used as a fuel source for exercising muscle, and thus may not be detrimental in all circumstances, has in part prompted the development and implementation of analytical methods to quantify the fatty acid composition of muscle triglycerides as well as other lipid species within muscle, e.g. diacylglycerol and ceramides. In addition, noninvasive computed tomography, magnetic resonance spectroscopy and magnetic resonance imaging methods have been applied to examine the serial effects of intervention on muscle triglycerides.

Absorptiometry, Photon↗

PubMed2006

Decreased muscle strength and quality in older adults with type 2 diabetes: the health, aging, and body composition study.

Adequate skeletal muscle strength is essential for physical functioning and low muscle strength is a predictor of physical limitations. Older adults with diabetes have a two- to threefold increased risk of physical disability. However, muscle strength has never been investigated with regard to diabetes in a population-based study. We evaluated grip and knee extensor strength and muscle mass in 485 older adults with diabetes and 2,133 without diabetes in the Health, Aging, and Body Composition study. Older adults with diabetes had greater arm and leg muscle mass than those without diabetes because they were bigger in body size. Despite this, muscle strength was lower in men with diabetes and not higher in women with diabetes than corresponding counterparts. Muscle quality, defined as muscle strength per unit regional muscle mass, was significantly lower in men and women with diabetes than those without diabetes in both upper and lower extremities. Furthermore, longer duration of diabetes (>or=6 years) and poor glycemic control (HbA(1c) >8.0%) were associated with even poorer muscle quality. In conclusion, diabetes is associated with lower skeletal muscle strength and quality. These characteristics may contribute to the development of physical disability in older adults with diabetes.

Aged↗

PubMed2006

Diabetes, inflammation, and functional decline in older adults: findings from the Health, Aging and Body Composition (ABC) study.

OBJECTIVE: Age, diabetes, and elevated inflammatory markers independently increase the risk of functional decline. We examined the effect of C-reactive protein (CRP) and interleukin-6 (IL-6) on the incident mobility limitation in older adults with and without diabetes. RESEARCH DESIGN AND METHODS: We analyzed data from a cohort of 2,895 well-functioning adults aged 70-79 years, followed for development of persistent functional limitation over 3.5 years. Participants were assessed for the presence of diabetes according to fasting glucose and/or hypoglycemic medication use and were divided into three equal groups (tertiles) according to level of CRP or IL-6. Persistent functional limitation was defined as difficulty climbing 10 steps or walking one-quarter mile on two consecutive semiannual assessments. RESULTS: At baseline, 702 participants (24%) had diabetes. CRP values were (median +/- SD) 2.8 +/- 4.4 versus 3.7 +/- 5.4 for those with normal glucose and diabetes, respectively (P < 0.001). The unadjusted incidence of functional limitation associated with increased levels of CRP and IL-6 was greater among participants with diabetes. After adjusting for clinical and demographic covariates, persistent functional limitation for the highest tertile was greater compared with that for the lowest tertile of CRP or IL-6 for those with and without diabetes. CRP hazard ratios (HRs) were 1.7 (95% CI 1.2-2.3) versus 1.4 (1.1-1.6), respectively. IL-6 HRs were 1.8 (1.3-2.5) versus 1.6 (1.4-2.0), respectively. CONCLUSIONS: In initially high-functioning older adults, those with diabetes and higher inflammatory burden had an increased risk of functional decline. Interventions at early stages to reduce inflammation may preserve function in these individuals.

Aged↗

PubMed2005

Increased intramuscular lipid storage in the insulin-resistant and endurance-trained state.

Numerous studies have reported a strong correlation between intramuscular triacylglycerol (IMTG) content and insulin resistance. However, the proposed relationship between IMTG accumulation and skeletal muscle insulin resistance is not unambiguous, as trained athletes have been shown to be markedly insulin sensitive despite an elevated IMTG storage. Though the latter has often been attributed to differences in muscle fibre type composition and/or structural characteristics of the intramyocellular lipid deposits, recent studies have failed to provide such evidence. The greater insulin sensitivity despite an elevated IMTG deposition in the endurance-trained state has often been described as a metabolic paradox. However, divergent metabolic events are responsible for the greater IMTG content in the endurance-trained versus insulin-resistant states. The greater IMTG storage in the trained athlete represents an adaptive response to endurance training, allowing a greater contribution of the IMTG pool as a substrate source during exercise. In contrast, elevated IMTG stores in the obese and/or type 2 diabetes patient seem to be secondary to a structural imbalance between plasma free fatty acid availability, fatty acid (FA) storage and oxidation. Therefore, the reported correlation between IMTG content and insulin resistance does not represent a functional relationship, as it is strongly influenced by training status and/or habitual physical activity. It can be argued that the ratio between IMTG content and muscle oxidative capacity represents a more accurate marker of insulin resistance. Interventions to augment mitochondrial density and/or function are likely to improve the balance between FA uptake and oxidation and should be applied to prevent and/or treat insulin resistance.

Humans↗

PubMed2005

Angiotensin-converting enzyme insertion/deletion genotype, exercise, and physical decline.

CONTEXT: Physical performance in response to exercise appears to be influenced by the angiotensin-converting enzyme (ACE) insertion (I)/deletion (D) genotype in young adults, but whether this relationship could help explain variation in older individuals' response to exercise has not been well studied. OBJECTIVE: To determine whether the ACE genotype interacts with significant physical activity to affect the incidence of mobility limitation in well-functioning older adults. DESIGN, SETTING, AND PARTICIPANTS: The Health Aging and Body Composition (Health ABC) Cohort Study, conducted in the metropolitan areas of Memphis, Tenn, and Pittsburgh, Pa. A total of 3075 well-functioning community-dwelling adults aged 70 through 79 years were enrolled from 1997 to 1998 and had a mean of 4.1 years of follow-up. MAIN OUTCOME MEASURE: Incident mobility limitation defined as the report of difficulty walking a quarter of a mile (0.4 km) or walking up 10 steps on 2 consecutive semiannual interviews (n = 1204). RESULTS: Physically active participants (those reporting expending > or =1000 kcal/wk in exercise, walking, and stair climbing) were less likely to develop mobility limitation regardless of genotype. However, activity level interacted significantly with the ACE genotype (P = .002). In the inactive group, the ACE genotype was not associated with limitation (P = .46). In the active group, those with the II genotype were more likely to develop mobility limitation after adjusting for potential confounders compared with those with ID/DD genotypes (adjusted rate ratio, 1.45, 95% confidence interval, 1.08-1.94). The gene association was especially strong among participants reporting weightlifting. Exploration of possible physiological correlates revealed that among active participants, those with the II genotype had higher percentage of body fat (P = .02) and more intermuscular thigh fat (P = .02) but had similar quadriceps strength as those with ID/DD. CONCLUSIONS: Among older individuals who exercised, those with the ACE DD or ID genotypes were less likely to develop mobility limitation than those with the II genotype. Regardless of genotype, individuals who exercised were less likely to develop mobility limitation than those who did not exercise.

Aged↗

PubMed2005

Obesity, regional body fat distribution, and the metabolic syndrome in older men and women.

BACKGROUND: The metabolic syndrome is a disorder that includes dyslipidemia, insulin resistance, and hypertension and is associated with an increased risk of diabetes and cardiovascular disease. We determined whether patterns of regional fat deposition are associated with metabolic syndrome in older adults. METHODS: A cross-sectional study was performed that included a random, population-based, volunteer sample of Medicare-eligible adults within the general communities of Pittsburgh, Pa, and Memphis, Tenn. The subjects consisted of 3035 men and women aged 70 to 79 years, of whom 41.7% were black. Metabolic syndrome was defined by Adult Treatment Panel III criteria, including serum triglyceride level, high-density lipoprotein cholesterol level, glucose level, blood pressure, and waist circumference. Visceral, subcutaneous abdominal, intermuscular, and subcutaneous thigh adipose tissue was measured by computed tomography. RESULTS: Visceral adipose tissue was associated with the metabolic syndrome in men who were of normal weight (odds ratio, 95% confidence interval: 2.1, 1.6-2.9), overweight (1.8, 1.5-2.1), and obese (1.2, 1.0-1.5), and in women who were of normal weight (3.3, 2.4-4.6), overweight (2.4, 2.0-3.0), and obese (1.7, 1.4-2.1), adjusting for race. Subcutaneous abdominal adipose tissue was associated with the metabolic syndrome only in normal-weight men (1.3, 1.1-1.7). Intermuscular adipose tissue was associated with the metabolic syndrome in normal-weight (2.3, 1.6-3.5) and overweight (1.2, 1.1-1.4) men. In contrast, subcutaneous thigh adipose tissue was inversely associated with the metabolic syndrome in obese men (0.9, 0.8-1.0) and women (0.9, 0.9-1.0). CONCLUSION: In addition to general obesity, the distribution of body fat is independently associated with the metabolic syndrome in older men and women, particularly among those of normal body weight.

Adipose Tissue↗

PubMed2005

Skeletal muscle fatigue, strength, and quality in the elderly: the Health ABC Study.

We examined the muscle fatigue characteristics in older men and women and determined whether these were related to the size, strength, or quality of muscle. A total of 1,512 men and women aged 70-79 yr from the Health, Aging, and Body Composition Study participated in this study. Muscle cross-sectional area and attenuation were determined with computed tomography. Skeletal muscle fatigue and strength (peak torque) of the knee extensors and flexors were measured using isokinetic dynamometry. Men were more fatigue resistant than women for both knee extension (fatigue index: 70.4 +/- 15.3 vs. 66.9 +/- 14.3%; P < 0.05) and knee flexion (67.9 +/- 16.4 vs. 64.9 +/- 17.6%; P < 0.05). Peak torque and muscle quality (specific torque) were higher in men than women for knee extension (99.6 +/- 28.2 vs. 63.0 +/- 16.8 N x m and 1.62 +/- 0.43 vs. 1.51 +/- 0.39 N x m/cm2; both P < 0.05) and for knee flexion (74.0 +/- 26.4 vs. 49.6 +/- 15.9 N x m and 2.47 +/- 1.29 vs. 2.22 +/- 0.78 N x m/cm2; both P < 0.05). Total work and power output was greater in men compared with women for both the quadriceps (1,353 +/- 451 vs. 832 +/- 264 J and 87.7 +/- 33.5 vs. 53.3 +/- 19.2 W; both P < 0.05) and the hamstrings (741 +/- 244 vs. 510 +/- 141 J and 35.4 +/- 16.0 vs. 23.7 +/- 10.2 W; both P < 0.05). In both genders, the quadriceps was able to perform more work with greater power compared with the hamstrings. Those who were stronger actually had greater fatigue after adjusting for age, race, physical activity, and total body fat. In conclusion, older men were more fatigue resistant than women, although in both men and women greater fatigue was not related to muscle weakness.

Aged↗

PubMed2005

Lower serum albumin concentration and change in muscle mass: the Health, Aging and Body Composition Study.

BACKGROUND: Low albumin concentrations in older persons increase the risk of poor health outcomes, including functional decline. OBJECTIVE: The aim of the study was to investigate the association between serum albumin concentration and skeletal muscle loss (sarcopenia) in old age. DESIGN: Serum albumin concentration was measured in 1882 black and white men and women aged 70-79 y participating in the Health, Aging and Body Composition Study. Five-year changes in appendicular skeletal muscle mass (ASMM), total-body fat-free mass (FFM), and trunk lean mass (TLM) were measured by using dual-energy X-ray absorptiometry. Confounders included health and lifestyle factors, which are markers of inflammation and protein intake. RESULTS: A low albumin concentration (< 38 g/L) was observed in 21.2% of the study participants. After adjustment for confounders, the mean (+/-SE) change in ASMM was -82 +/- 26 g per 3-g/L lower albumin concentration (P = 0.002). This association remained after persons with a low albumin concentration (< 38 g/L) were excluded. The decline in ASMM in subjects with low albumin concentrations was almost 30% higher (-930 +/- 56 g) than that in those with albumin concentrations > or = 42 g/L (-718 +/- 38 g; P < 0.01). The association between albumin and change in ASMM remained after additional adjustment for weight change. A weak association was observed for FFM, whereas no association was observed for TLM, which suggests a specific role of albumin in skeletal muscle change. CONCLUSIONS: Lower albumin concentrations, even above the clinical cutoff of 38 g/L, are associated with future loss of ASMM in older persons. Low albumin concentration may be a risk factor for sarcopenia.

Absorptiometry, Photon↗

PubMed2005

Weight change and the conservation of lean mass in old age: the Health, Aging and Body Composition Study.

BACKGROUND: Weight loss may contribute to the loss of lean mass with age. OBJECTIVE: The objective was to evaluate the relation between weight loss or weight gain and changes in lean mass and fat mass in older adults. DESIGN: We observed changes in weight and body composition during a 4-y period in 2163 men (47%) and women (53%) aged 70-79 y in the Health, Aging and Body Composition Study cohort. Whole-body and appendicular bone-free lean mass and fat mass were measured by using dual-energy X-ray absorptiometry. RESULTS: Weight loss and weight gain were common. In both weight losers and weight gainers, changes in lean mass as a percentage of initial lean mass were substantially smaller than changes in fat mass as a percentage of initial fat mass. However, the difference between the change in lean mass and that in fat mass was more pronounced with weight gain than with weight loss, especially in men. Small amounts of lean loss and fat gain were noted with weight stability. In multivariate models, weight loss was strongly associated with lean mass loss in both men and women, especially in men whose weight loss was concurrent with a hospitalization. CONCLUSIONS: With weight change, a greater proportion of lean mass than of fat mass was conserved, but, especially in older men, significantly more lean mass was lost with weight loss than was gained with weight gain. These findings suggest that weight loss, even with regain, could accelerate sarcopenia in older adults.

Absorptiometry, Photon↗

PubMed2005

Muscle mass, muscle strength, and muscle fat infiltration as predictors of incident mobility limitations in well-functioning older persons.

BACKGROUND: Lower muscle mass has been correlated with poor physical function; however, no studies have examined this relationship prospectively. This study aims to investigate whether low muscle mass, low muscle strength, and greater fat infiltration into the muscle predict incident mobility limitation. METHODS: Our study cohort included 3075 well-functioning black and white men and women aged 70-79 years participating in the Health, Aging, and Body Composition study. Participants were followed for 2.5 years. Muscle cross-sectional area and muscle tissue attenuation (a measure of fat infiltration) were measured by computed tomography at the mid-thigh, and knee extensor strength by using a KinCom dynamometer. Incident mobility limitation was defined as two consecutive self-reports of any difficulty walking one-quarter mile or climbing 10 steps. RESULTS: Mobility limitations were developed by 22.3% of the men and by 31.8% of the women. Cox's proportional hazards models, adjusting for demographic, lifestyle, and health factors, showed a hazard ratio of 1.90 [95% confidence interval (CI), 1.27-2.84] in men and 1.68 (95% CI, 1.23-2.31) in women for the lowest compared to the highest quartile of muscle area (p <.01 for trend). Results for muscle strength were 2.02 (95% CI, 1.39-2.94) and 1.91 (95% CI, 1.41-2.58), p <.001 trend, and for muscle attenuation were 1.91 (95% CI, 1.31-2.83) and 1.68 (95% CI, 1.20-2.35), p <.01 for trend. When included in one model, only muscle attenuation and muscle strength independently predicted mobility limitation (p < .05). Among men and women, associations were similar for blacks and whites. CONCLUSION: Lower muscle mass (smaller cross-sectional thigh muscle area), greater fat infiltration into the muscle, and lower knee extensor muscle strength are associated with increased risk of mobility loss in older men and women. The association between low muscle mass and functional decline seems to be a function of underlying muscle strength.

Aged↗

PubMed2005

Skeletal muscle lipid and its association with insulin resistance: what is the role for exercise?

Skeletal muscle lipid content has been associated with insulin resistance and type 2 diabetes. However, intramuscular triglycerides can also be a fuel source for healthy muscle during exercise. The balance between storage and use of muscle triglycerides is likely a key to the interaction between dysregulated fat and glucose metabolism by healthy and insulin resistant muscle.

Adipose Tissue↗

PubMed2005

Estrogen replacement, muscle composition, and physical function: The Health ABC Study.

PURPOSE: Although the beneficial effects of estrogen use on cardiovascular and cognitive function in postmenopausal women have been recently discredited, controversy remains regarding its usefulness for maintaining skeletal muscle mass or strength. Therefore, the purpose of this study was to determine whether estrogen use is associated with enhanced muscle composition and, if so, whether this translates into improved strength and physical function. METHODS: Cross-sectional analysis of 840 well-functioning community-dwelling white women (current estrogen replacement therapy (ERT) users = 259, nonusers = 581) aged 70-79 yr participating in the Health, Aging and Body Composition Study. Muscle composition of the midthigh by computed tomography included cross-sectional area (CSA) of the quadriceps, hamstrings, intermuscular fat and subcutaneous fat, and muscle attenuation in Hounsfield units (HU) as a measure of muscle density. Isometric hand grip and isokinetic knee extensor strength were assessed by dynamometry. Physical function was assessed using a summary scale that included usual 6-m walk and narrow walk speed, repeated chair stands, and standing balance. RESULTS: In analyses of covariance adjusted for relevant confounders, quadriceps muscle CSA and HU were greater in current ERT than non-ERT women (P < 0.05). Grip strength was also greater (P < 0.05) in women taking ERT while knee extensor strength approached significance (P < 0.10). However, differences in muscle composition and strength were modest at < or =3.3%. There was no difference by ERT status for the hamstring muscles, fat CSA, or for physical function. CONCLUSION: The associations between ERT and muscle composition and strength were minor and did not translate into improved physical function. Initiation of ERT for preservation of muscle composition and function may not be indicated.

Aged↗

PubMed2005

Deficiency of subsarcolemmal mitochondria in obesity and type 2 diabetes.

The current study addresses a novel hypothesis of subcellular distribution of mitochondrial dysfunction in skeletal muscle in type 2 diabetes. Vastus lateralis muscle was obtained by percutaneous biopsy from 11 volunteers with type 2 diabetes; 12 age-, sex-, and weight-matched obese sedentary nondiabetic volunteers; and 8 lean volunteers. Subsarcolemmal and intermyofibrillar mitochondrial fractions were isolated by differential centrifugation and digestion techniques. Overall electron transport chain activity was similar in type 2 diabetic and obese subjects, but subsarcolemmal mitochondria electron transport chain activity was reduced in type 2 diabetic subjects (0.017 +/- 0.003 vs. 0.034 +/- 0.007 units/mU creatine kinase [CK], P = 0.01) and sevenfold reduced compared with lean subjects (P < 0.01). Electron transport chain activity in intermyofibrillar mitochondria was similar in type 2 diabetic and obese subjects, though reduced compared with lean subjects. A reduction in subsarcolemmal mitochondria was confirmed by transmission electron microscopy. Although mtDNA was lower in type 2 diabetic and obese subjects, the decrement in electron transport chain activity was proportionately greater, indicating functional impairment. Because of the potential importance of subsarcolemmal mitochondria for signal transduction and substrate transport, this deficit may contribute to the pathogenesis of muscle insulin resistance in type 2 diabetes.

Adult↗