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Biomedical subjects

J A Kanaley

Publications and source records attributed to J A Kanaley.

28 records · Page 2Linked to original sources
PubMed1995

Fatty acid kinetic responses to running above or below lactate threshold.

During running exercise above the lactate threshold (LT), it is unknown whether free fatty acid (FFA) mobilization can meet the energy demands for fatty acid oxidation. This study was performed to determine whether FFA availability is reduced during running exercise above compared with below the LT and to assess whether the level of endurance training influences FFA mobilization. Twelve marathon runners and 12 moderately trained runners ran at a workload that was either above or below their individual LT. Fatty acid oxidation (indirect calorimetry) and FFA release ([1-14C]palmitate) were measured at baseline, throughout exercise, and at recovery. The plasma FFA rate of appearance increased during exercise in both groups; running above or below the LT, but the total FFA availability for 30 min of exercise was greater (P < 0.01) in the below LT group (marathon, 23 +/- 2 mmol; moderate, 21 +/- 2 mmol) than in the above LT group (18 +/- 3 and 13 +/- 3 mmol, respectively). Total fatty acid oxidation (indirect calorimetry) greatly exceeded circulating FFA availability, regardless of training or exercise group (P < 0.01). No statistically significant exercise intensity or training differences in fatty acid oxidation were found (above LT: marathon, 71 +/- 12, moderate, 64 +/- 17 mmol/30 min; below LT: marathon 91 +/- 12, moderate, 60 +/- 5 mmol/30 min). In conclusion, during exercise above or below LT, circulating FFA cannot meet the oxidative needs and intramuscular triglyceride stores must be utilized. Further marathon training does not enhance effective adipose tissue lipolysis during exercise compared with moderate endurance training.

Adipose Tissue↗
PubMed1993

Assessment of body composition with use of dual-energy x-ray absorptiometry: evaluation and comparison with other methods.

Dual-energy x-ray absorptiometry (DEXA) is a relatively new method of assessing body composition in humans. In the current study, DEXA was analyzed for accuracy and precision by using both anthropomorphic phantoms and a combination of body composition techniques in humans. Satisfactory precision for measurement of total body fat, fat-free mass, and total body bone mineral could be demonstrated in vivo and in vitro. Predictions of lean body mass in humans on the basis of DEXA, total body water, and total body potassium were significantly different. The results of multiple regression analysis suggested that a component of total body water was related to body potassium, and another component was predicted by body fat. In addition, extracellular fluid volume, as measured by the bromide space technique, was significantly associated with both fat-free mass and fat mass as measured by DEXA. These findings have implications for the interpretation of body composition data in humans.

Absorptiometry, Photon↗
PubMed1993

Differential health benefits of weight loss in upper-body and lower-body obese women.

Upper-body obesity (UB Ob) is more strongly associated with adverse health consequences; however, few obesity-treatment studies have examined outcome according to body-fat distribution. To examine whether diet and formal- or informal-exercise instruction causes differential changes in health and lipid profiles, ten LB Ob and nine UB Ob premenopausal women received dietary intervention (2.1 MJ-deficit/d for 16 wk) and were randomly assigned to either formal- or informal-exercise instruction. Weight loss was similar between groups (approximately 8 kg), and no change occurred in lean body mass or basal metabolic rate. Baseline cholesterol and triglycerides were greater (P < 0.01) in UB Ob than LB Ob women and decreased more (P < 0.01) in response to treatment in UB Ob women. Formal exercise instruction increased high-density-lipoprotein cholesterol (P < 0.05) especially in UB Ob women. Future studies on treatment of obesity should include consideration of regional fat distribution.

Adipose Tissue↗
PubMed1993

Effects of exercise and weight loss on leucine turnover in different types of obesity.

These studies were performed to determine whether protein turnover during exercise and after weight loss is influenced by obesity and body fat distribution. Leucine carbon flux was measured before, during, and after 2.5 h of bicycle exercise in 10 upper body obese, 9 lower body obese, and 6 nonobese, age-matched, premenopausal women. The obese women then followed an energy-restricted diet for 16 wk, resulting in approximately 8 kg weight loss. Baseline leucine carbon flux was greater (P < 0.01) in obese women than in nonobese women but decreased in a similar fashion in response to exercise in all groups. There were no differences between upper body and lower body obese women during exercise. After weight loss, baseline leucine carbon flux decreased (P < 0.05) similarly in both groups of obese women and was further suppressed by exercise. Thus obesity phenotype has no specific effect on either baseline protein turnover or the antiproteolytic response to moderate intensity exercise or weight loss. We conclude that the previously observed defect in insulin suppression of leucine flux in upper body obese women appears related to insulin resistance and does not represent an inherent abnormality of protein metabolism.

Adult↗
PubMed1993

Fatty acid kinetic responses to exercise. Effects of obesity, body fat distribution, and energy-restricted diet.

UNLABELLED: Upper body obesity (UB Ob) is associated with a reduced net free fatty acid (FFA) response to epinephrine compared with nonobese (Non Ob) and lower-body obese (LB Ob) women. Because catecholamines regulate some of the metabolic responses to exercise, we hypothesized that UB Ob would have a reduced net FFA response to exercise. Plasma FFA rate of appearance (Ra) ([1-14C]palmitate) and fatty acid oxidation (indirect calorimetry) were therefore measured during 2.5 h of stationary bicycle exercise (45% VO2 peak) in 13 UB Ob, 11 LB Ob, and 8 Non Ob premenopausal women. 10 UB Ob and 8 LB Ob women were retested after an approximately 8-kg weight loss. RESULTS: During exercise Non Ob and LB Ob women had greater increments in FFA availability (51 +/- 7 and 53 +/- 8 mmol, respectively) than UB Ob women (27 +/- 4 mmol, P < 0.05). Total exercise FFA availability and fatty acid oxidation were not different between Non Ob, LB Ob, and UB Ob women, however. Following weight loss (approximately 8 kg), the FFA response to exercise increased (P < 0.01) and remained greater (P < 0.05) in LB Ob than in UB Ob women. In conclusion, the FFA response to exercise was reduced in UB Ob women before and after weight loss, but no effects on fatty acid oxidation were apparent.

Body Composition↗
PubMed1992

Cortisol levels during prolonged exercise: the influence of menstrual phase and menstrual status.

The purpose of this study was to determine the influence of menstrual phase and menstrual status on the cortisol response during 90 minutes of treadmill running at 60% VO2max. Eight eumenhorrheic athletes were tested in the early follicular (EF) (day 3-5), late follicular (LF) (day 13-15) and mid-luteal (ML) (day 22-24) phases. Six amenorrheic athletes were tested on two separate occasions. The resting cortisol levels were similar in each menstrual phase and overall a decreasing pattern of cortisol response to exercise was observed in all menstrual phases (P greater than .05). The amenorrheic athletes had a significantly greater (P less than .01) pattern of cortisol response than was observed in eumenorrheic athletes. The net increment in cortisol levels during exercise were distinctly greater (P less than .01) in amenorrheic than eumenorrheic athletes (amenorrheic: 413.8 +/- 113.1, eumenorrheic: EF: -482.8 +/- 88.3, LF: -311.8 +/- 102.1, ML: -386.3 +/- 146.2 nmol.l-1). In conclusion the cortisol levels are independent of menstrual phase. Also a larger cortisol increment is observed in amenorrheic athletes in response to prolonged submaximal exercise. The elevated cortisol levels in amenorrheics at rest and throughout exercise provides further evidence that disturbances in the hypothalamic-pituitary-adrenal function are associated with exercise-induced amenorrhea, although the site(s) of physiological disturbance have not been identified.

Adult↗
PubMed1992

Insulin regulation of insulin-like growth factor binding protein-1 in obese and nonobese humans.

Insulin is the principal regulator of hepatic insulin-like growth factor binding protein-1 (IGFBP-1) production, mediating the rapid decrease in plasma IGFBP-1 in response to nutritional intake. In this study, we defined IGFBP-1 regulation by insulin in upper and lower body obesity, conditions associated with insulin resistance and chronic hyperinsulinemia. Overnight postabsorptive IGFBP-1 levels in obese and nonobese women showed an inverse, nonlinear relationship with plasma insulin concentrations. Maximum suppression of IGFBP-1 was seen at 70-90 pmol/L plasma insulin. Both groups of obese women had mean fasting plasma insulin concentrations above this threshold level and, consequently, markedly suppressed IGFBP-1 levels. To assess the dynamics of insulin regulated IGFBP-1, 10 obese and 8 nonobese women were studied during sequential saline infusion (0-90 min), hyperinsulinemia (insulin infusion; 90-210 min) and hypoinsulinemia (somatostatin + GH infusion; 210-330 min). Insulin infusion rapidly decreased plasma IGFBP-1 levels in nonobese subjects (60% decrease in 2 h), but had little or no further suppressive effect in obese subjects. Complete insulin withdrawal resulted in a significant rise in plasma IGFBP-1 concentrations in all subjects, but the response was blunted in obese compared to nonobese groups. In contrast to plasma IGFBP-1, IGF-I concentrations did not vary during hyper- and hypoinsulinemic infusion periods and were not significantly different between groups. Basal GH levels were significantly higher in nonobese when compared to obese women, but did not change with infusions. In conclusion, low IGFBP-1 levels in obesity are related to elevated insulin levels which are, in turn, related to body fat distribution and insulin resistance. The chronically depressed levels of IGFBP-1 may promote IGF bioactivity as well as its feedback regulation of GH secretion, thus contributing to the metabolic and mitogenic consequences of obesity. In addition, our findings imply that hepatic insulin sensitivity in terms of IGFBP-1 production is preserved despite peripheral insulin resistance in obesity.

Adult↗
PubMed1992

Substrate oxidation and GH responses to exercise are independent of menstrual phase and status.

The purpose of this study was to determine the extent to which growth hormone (GH) and energy substrate utilization are influenced by basal sex steroid levels during prolonged submaximal exercise across menstrual phase and status. Also the 17 beta-estradiol (E2) and progesterone responses during prolonged exercise were compared according to menstrual phase and menstrual status. Six amenorrheic (AMc) athletes and seven eumenorrheic (EUc) athletes ran at 60% VO2max for 90 min and serial blood samples were taken at rest, every 10 min throughout exercise, and 5 and 15 min post-exercise. The EUc athletes were tested in the early follicular phase (EF) (days 3-5), the late follicular phase (LF) (days 14-16) and the mid-luteal phase (ML) (days 22-25). The incremental GH response to exercise, measured by area under the curve, was consistent with previous reposts and was not altered according to menstrual phase or status (EF-37.5 +/- 11.5, LF-61.9 +/- 11.5, ML-48.1 +/- 12.8 micrograms.1-1.90 min-1). Furthermore, carbohydrate and fat utilization during exercise were not influenced by basal sex steroid levels associated with menstrual phase or status. The incremental E2 response to exercise in AMc athletes was significantly smaller than seen in EUc athletes (AMc-208.1 +/- 44.0, EF-383.0 +/- 116.4, LF-204.7 +/- 84.1, ML-45.1 +/- 18.4 pmol.1(-1).90 min-1), although the pattern of release is similar between groups. In conclusion, GH levels and substrate utilization are independent of both menstrual phase and status; hence, menstrual phase has no negative ramifications on metabolism during exercise. Amenorrhea does not result in metabolic consequences during prolonged exercise by influencing substrate utilization.

Adolescent↗
PubMed1991

Antioxidant enzyme activity during prolonged exercise in amenorrheic and eumenorrheic athletes.

Exogenous 17 beta-estradiol (E2) has been shown to be associated with elevated levels of erythrocyte glutathione peroxidase (GPX) activity. The purpose of this study was to examine the influence of endogenous E2, as defined by menstrual status (amenorrhea v eumenorrhea), on activity of blood antioxidant enzymes at rest and during prolonged exercise. Six amenorrheic (AMc) and six eumenorrheic (EUc) athletes were subjected to a treadmill running test at 60% VO2max for 90 minutes. Serial blood samples were taken from a forearm vein at rest, 30, 60, and 90 minutes during exercise, and 15 minutes into recovery. Resting estrogen levels were significantly lower in AMc athletes at rest and during exercise as compared with EUc athletes, whereas plasma cortisol levels in AMc were significantly higher. GPX activity was significantly higher in AMc than EUc at rest (46.9 +/- 7.7 v 30.2 +/- 2.2 nmol/min x mg Hb, P less than .05, respectively) and throughout exercise. Glutathione reductase (GR) activity was similar between the two groups at rest and was significantly higher (P less than .01) in AMc than EUc during exercise. Plasma lipid peroxidation and catalase activity did not change significantly in response to exercise, nor were they different between AMc and EUc athletes. GPX activity was found to be negatively correlated with E2 (r = -.64, P less than .01) and positively correlated with cortisol (r = .69, P less than .01). It is tentatively concluded that the alteration of hormonal status in amenorrhea has an influence on the blood antioxidant enzyme system.

Adult↗