Energy metabolism and oxidative stress: impact on the metabolic syndrome and the aging process

Aging can be defined as a progressive decline in the ability of the organism to resist stress, damage, and diseas. Although there are currently over 300 theories to explain the aging phenomenon, it is still not well understood why organisms age and why the aging process can vary so much in speed and quality from individual to individual. The oxidative stress hypothesis is one of the prevailing theories of aging. This theory states that free radicals produced during cellular respiration damage lipids, proteins, and DNA thereby accelerating the aging process and increasing disease risk. Under normal conditions, the electron transport chain is the primary producer of the superoxide anion, which is precursor to other highly reactive species such as hydrogen peroxide and the hydroxyl radical. Oxidative stress accumulates when prooxidants overwhelm the antioxidant defense mechanisms. This is dependent on a number of factors including free radical production, susceptibility of tissue to stress, and strength of the defense and repair system. Oxidative stress has been implicated in a number of chronic disease states usually grouped under the umbrella of the metabolic syndrome and is thought to contribute to the aging process. It has been hypothesized that the production of free radicals is dependent on resting metabolic rate and this may have an impact on the aging process. However, other factors, such as mitochondrial function, may be important in the production of free radicals and the subsequent effect on aging and disease states.     

Effect of a dietary herbal supplement containing caffeine and ephedra on weight, metabolic rate, and body composition

OBJECTIVE: To evaluate the effect of a dietary supplement containing herbal caffeine (70 mg/dose) and ephedra (24 mg/dose; C&E) on metabolic rate, weight loss, body composition, and safety parameters. RESEARCH METHODS AND PROCEDURES: In phase I, 12 healthy subjects with a BMI of 25 to 35 kg/m2 had resting metabolic rate (RMR) measured for 2 hours after ingesting C&E or a placebo on two occasions 1 week apart, followed by a 1-week washout before phase II. In phase II, these 12 and 28 additional subjects were randomized to a 12-week, double-blind trial comparing C&E (3 times/day) to placebo. In phase III, the C&E group was given open-label C&E for 3 months, and the placebo group was given C&E for 6 months. RESULTS: In phase I, C&E gave an average 8 +/- 0.1% (SE) rise in RMR over 2 hours compared with placebo (p < 0.01). In phase II, weight loss at 12 weeks was 3.5 +/- 0.6 kg with C&E compared with 0.8 +/- 0.5 kg with placebo (p < 0.02). The percentage fat lost, shown by DXA, was 7.9 +/- 2.9% with C&E and 1.9 +/- 1.1% with placebo (p < 0.05). Pulse decreased more in the placebo group that in the C&E group (p < 0.03). There were no differences in lipid levels or blood pressure. In phase III, there was a 6-month loss of 7.3% and 7.8% of initial body weight for the groups on placebo and C&E during phase II, respectively. There were no serious adverse events. DISCUSSION: C&E increased RMR significantly by 8% compared with placebo, promoted more weight and fat loss than placebo, and was well tolerated.     

Comparison of methods to assess body composition changes during a period of weight loss

OBJECTIVE: To assess the accuracy of body composition measurements by air displacement plethysmography and bioelectrical impedance analysis (BIA) compared with DXA during weight loss. RESEARCH METHODS AND PROCEDURES: Fifty-six healthy but overweight participants, 34 women and 22 men (age, 52 +/- 8.6 years; weight, 92.2 +/- 11.6 kg; BMI, 33.3 +/- 2.9 kg/m(2)) were studied in an outpatient setting before and after 6 months of weight loss (weight loss, 5.6 +/- 5.5 kg). Subjects were excluded if they had initiated a new drug therapy within 30 days of randomization, were in a weight loss program, or took a weight loss drug within 90 days of randomization. Subjects were randomly assigned either to a self-help program, consisting of two 20-minute sessions with a nutritionist and provision of printed materials and other self-help resources, or to attendance at meetings of a commercial program (Weight Watchers). Body composition was examined by each of the methods before and after weight loss. RESULTS: BIA (42.4 +/- 5.8%) underestimated percentage fat, whereas the BodPod (Siri = 51.7 +/- 6.9%; Brozek = 48.5 +/- 6.5%) overestimated percentage fat compared with DXA (46.1 +/- 7.9%) before weight loss. Correlation coefficients for detecting changes in body composition between DXA and the other methods were relatively high, with Brozek Deltafat mass (FM; r(2) = 0.63), Siri FM (r(2) = 0.65), tetrapolar BIA percentage fat (r(2) = 0.57), and Tanita FM (r(2) = 0.61) being the highest. DISCUSSION: In conclusion, all of the methods were relatively accurate for assessing body composition compared with DXA, although there were biases. Furthermore, each of the methods was sensitive enough to detect changes with weight loss.     

Physical activity level and physical functionality in nonagenarians compared to individuals aged 60-74 years

BACKGROUND: Functional dependence and the risks of disability increase with age. The loss of independence is thought to be partially due to a decrease in physical activity. However, in populations, accurate measurement of physical activity is challenging and may not provide information on functional impairment. METHODS: This study therefore assessed physical functionality and physical activity level in a group of nonagenarians (11 men/11 women; 93+/-1 years, 66.6+/-2.4 kg, body mass index [BMI]=24+/-1 kg/m2) and a group of participants aged 60-74 years (17 men/15 women; 70+/-1 years, 83.3+/-3.0 kg, BMI=29+/-1 kg/m2) from the Louisiana Healthy Aging Study. Physical activity level was calculated from total energy expenditure (TEE) and resting metabolic rate (RMR). Physical functionality was assessed using the Reduced Continuous Scale Physical Functional Performance Test (CS-PFP10). RESULTS: Nonagenarians had lower absolute (p<.001) and adjusted (p<.007) TEE compared to participants aged 60-74 years which was attributed to a reduction in both RMR and physical activity level. Nonagenarians also had reduced functional performance (p<.001) which was correlated with activity level (r=0.68, p<.001). CONCLUSIONS: When compared to individuals aged 60-74 years, 73% of the reduction in TEE in nonagenarians can be attributed to a reduction in physical activity level, the remaining being accounted for by a reduction in RMR. The reduced physical activity in nonagenarians is associated with less physical functionality. This study provides the first objective comparison of physical functionality and actual levels of physical activity in older individuals.     

Aging, resting metabolic rate, and oxidative damage: results from the Louisiana Healthy Aging Study

BACKGROUND: The aging process occurs at variable rates both among and within species and may be related to the variability in oxygen consumption and free radical production impacting oxidative stress. The current study was designed to test whether nonagenarians have a relatively low metabolic rate and whether it is associated with low levels of oxidative stress relative to age. METHODS: Resting metabolic rate (RMR) and markers of oxidative stress to lipids, proteins, and DNA were measured in three groups of individuals aged 20-34 (n=47), 60-74 (n=49), and>or=90 years (n=74). RESULTS: RMR, adjusted for fat-free mass, fat mass, and sex, was lower in both older groups when compared to the young group (p相似文献