Contribution of abdominal adiposity to age-related differences in insulin sensitivity and plasma lipids in healthy nonobese women

WSTĘP. Autorzy sprawdzili słuszność hipotezy zakładającej, że związany z wiekiem przyrost tkanki tłuszczowej trzewnej odpowiada częściowo za ujemny wpływ na insulinowrażliwość i profil lipidowy u kobiet bez otyłości. MATERIAŁ I METODY. Bezpośrednio oceniono: powierzchnię podskórnej i trzewnej tkanki tłuszczowej (tomografia komputerowa), zużycie glukozy (badanie metodą hiperinsulinowej/euglikemicznej klamry metabolicznej), elementy składowe organizmu (metoda absorpcjometrii promieniami X dwoistej energii), profil lipidowy oraz maksymalne zużycie tlenu (VO2max) u 178 kobiet bez otyłości, zakwalifikowanych do odpowiednich grup wiekowych: grupa 1 - 28 &plusmn; 4 lata (n = 88); grupa 2 - 46 &plusmn; 2 lata (n = 38); grupa 3 - 53 &plusmn; 2 lata (n = 31); grupa 4 - 67 &plusmn; 6 lat (n = 21). WYNIKI. Powierzchnia trzewnej tkanki tłuszczowej zwiększa się wraz z wiekiem (2,36 cm2 rocznie, p < 0,0001). Zanotowano związany z wiekiem wzrost stężenia cholesterolu całkowitego (p < 0,0003), triglicerydów (p < 0,0009), cholesterolu frakcji LDL (p < 0,027) i stosunku stężenia cholesterolu całkowitego do cholesterolu frakcji HDL (p < 0,042). Obserwowane różnice w insulinowrażliwości także wiązały się z wiekiem, jednakże w tym przypadku zależność była odmienna. Insulinowrażliwość, wyrażona jako całkowita lub przeliczona na kilogram beztłuszczowej masy ciała, była najniższa w grupie 4, ale nie różniła się istotnie między grupami 1, 2 i 3. Po analizie statystycznej, uwzględniającej powierzchnię tkanki tłuszczowej trzewnej, niższa insulinowrażliwość utrzymywała się, jednocześnie, relatywnie zmniejszyła się różnica w porównaniu z pozostałymi grupami. Wpływ zawartości trzewnej tkanki tłuszczowej na związane z wiekiem zmiany profilu lipidowego był silniejszy. Różnice w powierzchni trzewnej i głębokiej podskórnej tkanki tłuszczowej znosiły wpływ wieku na stężenie cholesterolu całkowitego, triglicerydów i cholesterolu frakcji LDL. Nie obserwowano natomiast wpływu wartości VO2max lub aktywnego wypoczynku na zależne od wieku zmiany w insulinowrażliwości bądź profilu lipidowym. WNIOSKI. 1) Wraz z wiekiem zwiększa się powierzchnia trzewnej tkanki tłuszczowej, podczas gdy zmniejszenie insulinowrażliwości obserwuje się tylko u kobiet starszych; 2) Związane z wiekiem różnice w trzewnej tkance tłuszczowej tylko w niewielkim stopniu odpowiadają za spadek insulinowrażliwości u kobiet bez otyłości; 3) Niepożądane zmiany profilu lipidowego w dużym stopniu wiążą się z zależnym od wieku przyrostem trzewnej tkanki tłuszczowej.INTRODUCTION. We examined the hypothesis that an age-related increase in the compartments of visceral fat would account, in part, for the deleterious changes in insulin sensitivity and blood lipid profile in nonobese women. MATERIAL AND METHODS. We directly assessed visceral and subcutaneous abdominal adipose tissue areas (computed tomography), glucose disposal (hyperinsulinemic-euglycemic clamp), body composition (dual energy X-ray absorptiometry), blood-lipid profile, and aerobic fitness (VO2max) in 178 nonobese women categorized into four age groups: group 1, 28 &plusmn; 4 years, n = 88; group 2, 46 &plusmn; 2 years, n = 38; group 3, 53 &plusmn; 2 years, n = 31; and group 4, 67 &plusmn; 6 years, n = 21. RESULTS. Visceral abdominal adipose tissue area increased with age (2.36 cm2 per year, P < 0.0001). We noted an age-related increase in total cholesterol (P < 0.0003), triglycerides (P < 0.0009), LDL cholesterol (P < 0.027), and the ratio of total cholesterol to HDL cholesterol (P < 0.042). However, agerelated changes in insulin sensitivity exhibited a different age-related pattern. That is, insulin sensitivity, expressed on an absolute basis or indexed per kilogram of fat-free mass, was lowest in group 4 but was not significantly different among groups 1, 2, and 3. After statistical control for visceral fat, lower insulin sensitivity persisted in group 4, although differences were diminished relative to other groups. However, the effect of visceral fat on agerelated changes in the blood-lipid profile was stronger. That is, differences in visceral and deep subcutaneous adipose tissue area abolished age-related differences in total cholesterol, triglycerides, and LDL cholesterol. No independent effects of VO2max or leisure-time physical activity on age-related changes in insulin sensitivity or on the blood-lipid profile were noted. CONCLUSIONS. We conclude that 1) visceral fat shows an increase with advancing age, whereas a decrease in insulin sensitivity was noted only in older women; 2) age-related differences in visceral fat explain only a modest part of the decline in insulin sensitivity in nonobese women; and 3) unfavorable changes in plasma lipids were strongly associated with the age-related increase in visceral abdominal adipose tissue

Effect of Endurance Training on Gross Energy Expenditure during Exercise

We compared the effect of endurance exercise training on gross energy expenditure (GEE) during steady-state exercise in 20 younger men (31.2 ± 0.6 years) and 20 middle-aged men (49.2 ±1.1 years). The subjects trained for eight months. The training program consisted of three 45-min walking and jogging exercise sessions per week at an intensity of approximately 60-85% of the heart rate at peak VO2, We administered bicycle ergometer tests at 0, 4, and 8 months into training. Participants exercised at a power output of 100 W for 10 min using a pedaling frequency of 50 rpm. We determined GEE (kcal/min) by measuring the oxygen consumption and respiratory exchange ratio. We found a significant reduction (p \u3c 0.05) in GEE (0.7-1.3 kcal/min) following 4 months of endurance training in both age groups, with a further reduction (p \u3c 0.05) noted in only the middle-aged group at month 8. We found no difference (p \u3e 0.05) in GEE between the younger and middle-aged men. We conclude that chronic exercise may modify GEE during a submaximal exercise bout and that this adaptation is similar in magnitude in younger and middle-aged men

No effect of the Trp64Arg β3-adrenoceptor gene variant on weight loss, body composition, or energy expenditure in obese, Caucasian postmenopausal women

The Trp64Arg polymorphism in the β3-adrenoceptor gene has been associated with increased prevalence of obesity, type 2 diabetes, and low rates of energy expenditure, although these findings are not unanimous. It is currently unknown if the presence of the Trp64Arg gene variant impedes the loss of body weight in obese, postmenopausal women via a reducing effect on energy expenditure. The objective of this study was to compare body composition and energy expenditure in carriers and noncarriers of the Trp64Arg variant in the β3-adrenoceptor before and after weight loss. We measured body composition, total daily energy expenditure (TEE), resting metabolic rate (RMR), physical activity energy expenditure (PAEE), thermic effect of feeding (TEF), and respiratory quotient (RQ) in 34 obese, postmenopausal women (19 carriers and 15 noncarriers for the Trp64Arg variant) before and after a weight loss intervention. There were no differences in body composition or daily energy expenditure and its components between the 2 groups at baseline. There were significant reductions in body mass, body mass index (BMI), percent body fat, fat-free mass, and fat mass (main effect, all P \u3c .0001) when analyzed with the 2 genotypes combined, but no significant differences between carriers and noncarriers with respect to change in these variables (group × time interaction term, all P \u3e .05). Total energy expenditure tended to be reduced (490 kJ.d-1, P = .13) in both groups following weight loss, but there was no significant group × time interaction term (P = .78), indicating no difference in the response of the 2 genotypes. There was a 9% reduction in RMR (611 kJ.d-1, P \u3c .001) when both groups were considered together, but no significant group × time interaction term (P = .84), suggesting that both groups responded in a similar manner to the weight loss intervention. PAEE and the TEF were not different following weight loss (both P \u3e .60). There was a trend for RQ to be reduced after weight loss (P = .07), but there was no difference between carriers or noncarriers of the Trp64Arg variant (P = .58). In summary, we found that obese postmenopausal women who carry the Trp64Arg variant in the β3-adrenoceptor had similar changes in body composition and energy expenditure to noncarriers of the variant in response to prolonged caloric restriction. These results suggest that the presence of the Trp64Arg variant in the β3-adrenoceptor should not be a hindrance to weight reduction. Copyright 2002, Elsevier Science (USA). All rights reserved

Understanding and Using the Implicit Association Test: III. Meta-Analysis of Predictive Validity.

This review of 122 research reports (184 independent samples, 14,900 subjects) found average r = .274 for prediction of behavioral, judgment, and physiological measures by Implicit Association Test (IAT)measures. Parallel explicit (i.e., self-report) measures, available in 156 of these samples (13,068 subjects), also predicted effectively (average r = .361), but with much greater variability of effect size. Predictive validity of self-report was impaired for socially sensitive topics, for which impression management may distort self-report responses. For 32 samples with criterion measures involving Black–White interracial behavior, predictive validity of IAT measures significantly exceeded that of self-report measures. Both IAT and self-report measures displayed incremental validity, with each measure predicting criterion variance beyond that predicted by the other. The more highly IAT and self-report measures were intercorrelated, the greater was the predictive validity of each.Psycholog