Effect of coconut oil on plasma apo A-I levels in WHHL and NZW rabbits

Age-matched Watanabe (WHHL) and New Zealand White (NZW) rabbits were fed a coconut oil-enriched diet (14%, w/w) for 2 weeks. Lipid and apolipoprotein (apo) A-I levels in plasma and lipoprotein fractions were monitored. Within 3 days after the start of the coconut oil diet, plasma apo A-I and high-density lipoprotein (HDL)-apo A-I levels increased 3-fold in the WHHL rabbits. A smaller but significant increase (63%) in apo A-I and HDL-apo A-I levels was also observed in the NZW rabbits. HDL cholesterol levels also increased from 16 +/- 3 mg/dl during a regular diet to 46 +/- 16 mg/dl (288%) during the coconut oil diet in the WHHL rabbits and from 37 +/- 7 mg/dl to 69 +/- 19 mg/dl (186%), respectively, in the NZW rabbits. Apo A-I and HDL cholesterol levels fell sharply to the original levels soon after switching back to a regular diet (within 3 days for WHHL rabbits and within 5 days for NZW rabbits). The fractional catabolic rate calculated from 125I-HDL kinetic studies indicated that the turnover rate for HDL was significantly slower in WHHL rabbits fed the coconut oil diet than the control diet (0.018 +/- 0.004 h-1 vs. 0.027 +/- 0.007 h-1, P less than 0.01). No changes were found in the NZW rabbits fed either diet. Trilaurin, the main component of the coconut oil (46.9%) supplemented diet (6.5%, w/w), was also used in this study. The effect of trilaurin on plasma apo A-I and HDL-cholesterol levels is discussed.     

Dietary coconut oil affects more lipoprotein lipase activity than the mitochondria oxidative capacities in muscles of preruminant calves

The presence of coconut oil in a milk replacer stimulates the growth rate of calves, suggesting a better oxidation of fatty acid in muscles. Because dietary fatty acid composition influences carnitine palmitoyltransferase I (CPT I) activity in rat muscles, this study was designed to examine the effects of a milk replacer containing either tallow (TA) or coconut oil (CO) on fatty acid utilization and oxidation and on the characteristics of intermyofibrillar (IM) and subsarcolemmal (SS) mitochondria in the heart and skeletal muscles of preruminant calves. Feeding CO did not affect palmitate oxidation rate by whole homogenates, but induced higher palmitate oxidation by IM mitochondria (+37%, P < 0.05). CPT I activity did not significantly differ between the two groups of calves. Heart and longissimus thoracis muscle of calves fed CO had higher lipoprotein lipase activity (+27% and 58%, respectively; P < 0.05) but showed no differences in fatty acid binding protein content or activity of oxidative enzymes. Whatever the muscle and the diet, IM mitochondria had higher respiration rates and enzyme activities than those of SS mitochondria (P < 0.05). Furthermore, CPT I activity of the heart was 28-fold less sensitive to malonyl-coenzyme A inhibition in IM mitochondria than in SS mitochondria. In conclusion, dietary CO marginally affected the activity of the two mitochondrial populations and the oxidative activity of muscles in the preruminant calf. In addition, this study showed that differences between IM and SS mitochondria in the heart and muscles were higher in calves than in other species studied so far.     

Enhanced leg exercise endurance with a high-carbohydrate diet and dihydroxyacetone and pyruvate

The effects of dietary supplementation of dihydroxyacetone and pyruvate (DHAP) on metabolic responses and endurance capacity during leg exercise were determined in eight untrained males (20-30 yr). During the 7 days before exercise, a high-carbohydrate diet was consumed (70% carbohydrate, 18% protein, 12% fat; 35 kcal/kg body weight). One hundred grams of either Polycose (placebo) or dihydroxyacetone and pyruvate (treatment, 3:1) were substituted for a portion of carbohydrate. Dietary conditions were randomized, and subjects consumed each diet separated by 7-14 days. After each diet, cycle ergometer exercise (70% of peak oxygen consumption) was performed to exhaustion. Biopsy of the vastus lateralis muscle was obtained before and after exercise. Blood samples were drawn through radial artery and femoral vein catheters at rest, after 30 min of exercise, and at exercise termination. Leg endurance was 66 +/- 4 and 79 +/- 2 min after placebo and DHAP, respectively (P less than 0.01). Muscle glycogen at rest and exhaustion did not differ between diets. Whole leg arteriovenous glucose difference was greater (P less than 0.05) for DHAP than for placebo at rest (0.36 +/- 0.05 vs. 0.19 +/- 0.07 mM) and after 30 min of exercise (1.06 +/- 0.14 vs. 0.65 +/- 0.10 mM) but did not differ at exhaustion. Plasma free fatty acids, glycerol, and beta-hydroxybutyrate were similar during rest and exercise for both diets. Estimated total glucose oxidation during exercise was 165 +/- 17 and 203 +/- 15 g after placebo and DHAP, respectively (P less than 0.05). It is concluded that feeding of DHAP for 7 days in conjunction with a high carbohydrate diet enhances leg exercise endurance capacity by increasing glucose extraction by muscle.     

Influence of diet and carnitine palmitoyltransferase I inhibition on myosin and sarcoplasmic reticulum.

To examine the role of metabolic signals for ventricular myosin expression and activity of the sarcoplasmic reticulum Ca2+ pump, Wistar rats were treated for 7-8 wk with 5 or 50 mg/kg etomoxir, which inhibits fatty acid utilization. The proportion of myosin V1 was increased (P less than 0.05) with 50 mg/kg etomoxir (75 +/- 5% vs. 62 +/- 6% of control rats), whereas both doses increased the rate of Ca2+ uptake. A carbohydrate-rich fat-free diet or 8% sucrose drinking solutions, however, had no effect on myosin and sarcoplasmic reticulum. When rats were fed diets with an increased content (10 or 20%) of sunflower oil, the calorie intake and myosin V1 increased (56 +/- 8 or 64 +/- 8% vs. 44 +/- 6% of control rats). Isocaloric 10% fat diets of varying fatty acid composition (coconut fat, olive oil, or mackerel oil) also induced a higher calorie intake and increased V1 (64 +/- 6, 60 +/- 9, or 65 +/- 8% for the respective oils vs. 44 +/- 6% of control rats) but did not significantly increase rate of Ca2+ uptake. We concluded that calorie-rich diets changed the myosin expression not by affecting the ratio of fatty acid to glucose utilization but via the increased calorie intake.     

Increased energy intake minimizes weight loss in men at high altitude.

The hypothesis that high-altitude weight loss can be prevented by increasing energy intake to meet energy requirement was tested in seven men, 23.7 +/- 4.3 (SD) yr, taken to 4,300 m for 21 days. Energy intake required to maintain body weight at sea level was found to be 3,118 +/- 300 kcal/day, as confirmed by nitrogen balance. Basal metabolic rate (BMR), determined by indirect calorimetry, increased 27% on day 2 at altitude and then decreased and reached a plateau at 17% above the sea level BMR by day 10. Energy expended during strenuous activities was 37% lower at altitude than at sea level. Fecal excretion of energy, nitrogen, total fiber, and total volatile fatty acids was not significantly affected by altitude. Energy intake at altitude was adjusted after 1 wk, on the basis of the increased BMR, to 3,452 +/- 452 kcal/day. Mean nitrogen balance at altitude was negative (-0.25 +/- 0.71 g/day) before energy intake was adjusted but rose significantly thereafter (0.20 +/- 0.71 and 0.44 +/- 0.66 g/day during weeks 2 and 3). Mean body weight decreased 2.1 +/- 1.0 kg over the 3 wk of the study, but the rate of weight loss was significantly diminished after the increase in energy intake (201 +/- 75 vs. 72 +/- 48 g/day). Individual regression lines drawn through 7-day segments of body weight showed that in four of seven subjects the slopes of body weight were not significantly different from zero after the 2nd wk. Thus weight loss ceased in four of seven men in whom increased BMR at altitude was compensated with increased energy intake.(ABSTRACT TRUNCATED AT 250 WORDS)     

Digestibility of a fully hydrogenated tallow for growing pigs

Improved growth performance noted in young pigs fed on a diet supplemented with fully hydrogenated tallow flake prompted further investigation of this fat source by means of a digestibility trial. The apparent digestibility of ether extractives was 0.37 and of gross energy 0.80 for a diet containing 5% of the tallow, compared to 0.66 and 0.89 for a control diet. Faeces from pigs fed on the diet with 5% tallow contained 338 g ether extractives/kg DM while faeces from pigs fed on the control diet contained 71 g ether extractives/kg DM. It is probable that the high proportion of C18:0 fatty acid in the material was responsible for its poor digestibility.     

Three months energy restricted diet does not reduce peripheral insulin resistance in newly diagnosed non insulin dependent diabetics

Sixteen newly diagnosed non insulin dependent diabetic patients were treated for 3 months with an individual energy restricted diet. The effect on weight, hyperglycaemia and insulin response to oral glucose was measured in all subjects, and in 7, peripheral insulin resistance was estimated using a hyperinsulinaemic glucose clamp at two insulin infusion rates (40 and 400 mU m-2 X min-1). After diet, fasting plasma glucose fell from 12.0 +/- 0.7 mmol/l (mean +/- SEM) to 7.4 +/- 0.5 mmol/l (P less than 0.001) and weight fell from 92.9 +/- 4.2 kg to 85.0 +/- 3.1 kg (P less than 0.001). The plasma insulin response to oral glucose was unchanged after diet therapy. Insulin induced glucose disposal (M) was also unaffected by diet at insulin infusion rates of 40 mU m-2 X min-1 (12.5 +/- 1.5 mumol X kg-1 X min-1 vs 15.7 +/- 1.6 mumol X kg-1 X min-1) and 400 mU m-2 X min-1 (49.5 +/- 2.7 mumol X kg-1 X min-1 vs 55.1 +/- 2.5 mumol X kg-1 X min-1). These results show that 3 months reduction of energy consumption with weight loss in newly diagnosed non insulin dependent diabetics improves B-cell responsiveness to glucose but has no effect on liver glucose output or on peripheral insulin action.     

Kidney retention of urea in sheep on a hypoprotein diet: study by retrograde perfusion of urea in the kidney pelvis

In order to study the role of the renal pelvis on urea sparing in sheep fed low protein diets, the pelvis was perfused through the ureter with 1M and 3M urea solutions. Eight ewes were used: four on a regular diet (total nitrogen 188.7 g.kg-1 dry matter) and the other four on a low protein diet (total nitrogen 109.4 g.kg-1 dry matter). On each animal, perfusions were performed on one kidney; the other one was kept as a control. Fractional excretion of urea (TEu) and urea (Cu), inulin, para-aminohippurate and osmolar clearances, were determined during five experimental periods of 30 min each (T = control, 1M = perfusion with 1M urea solution, R1 = first period of recovery, 3M = perfusion with 3M urea solution, R2 = second period of recovery). 1. During control periods sheep on low protein diet have a greater capacity of urea retention than sheep on regular diet, under antidiuretic conditions (inulin U/P = 200). The following data (means +/- S.D.) are all reduced in animals on low protein diet: TEu by 36% (0.38 +/- 0.19 vs. 0.59 +/- 0.28 for normal protein sheep, p less than 0.05), Cu by 55% (0.50 +/- 0.19 vs. 1.15 +/- 0.49 ml.min-1.kg-1 for normal sheep, p less than 0.01) and amount of urea excreted by 80% (2.1 +/- 0.7 vs. 10.4 +/- 2.7 mg.min-1 for normal sheep, p less than 0.01). 2. The linear regression analysis of the relationship between tubular reabsorption of urea and its filtered amount shows that the capacity of urea retention is significantly higher in low protein sheep and that the difference between the two groups is greater as the filtered amount increases. Following 1M and 3M perfusions, the capacity of urea reabsorption by the perfused kidneys is significantly decreased in low protein animals whereas there is no change in the normal ones. The result is that perfused kidneys of the low protein sheep increase the amount of urea excreted during these periods: urine concentration of urea (Uu) increases by 55% during R1 and by 144% during R2, TEu increases by 60% during R1 and by 147% during R2 and Cu increases by 40% during R1 and by 95% during R2, without any variation of urine flow rate. These changes could be understood, provided that an important transfer of the perfused urea to the renal medulla in the low protein sheep would reduce the concentration gradients which enhance urea passive reabsorption from the collecting ducts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reduced stroke volume during exercise in postural tachycardia syndrome.

Postural tachycardia syndrome (POTS) is characterized by excessive tachycardia without hypotension during orthostasis. Most POTS patients also report exercise intolerance. To assess cardiovascular regulation during exercise in POTS, patients (n = 13) and healthy controls (n = 10) performed graded cycle exercise at 25, 50, and 75 W in both supine and upright positions while arterial pressure (arterial catheter), heart rate (HR; measured by ECG), and cardiac output (open-circuit acetylene breathing) were measured. In both positions, mean arterial pressure, cardiac output, and total peripheral resistance at rest and during exercise were similar in patients and controls (P > 0.05). However, supine stroke volume (SV) tended to be lower in the patients than controls at rest (99 +/- 5 vs. 110 +/- 9 ml) and during 75-W exercise (97 +/- 5 vs. 111 +/- 7 ml) (P = 0.07), and HR was higher in the patients than controls at rest (76 +/- 3 vs. 62 +/- 4 beats/min) and during 75-W exercise (127 +/- 3 vs. 114 +/- 5 beats/min) (both P < 0.01). Upright SV was significantly lower in the patients than controls at rest (57 +/- 3 vs. 81 +/- 6 ml) and during 75-W exercise (70 +/- 4 vs. 94 +/- 6 ml) (both P < 0.01), and HR was much higher in the patients than controls at rest (103 +/- 3 vs. 81 +/- 4 beats/min) and during 75-W exercise (164 +/- 3 vs. 131 +/- 7 beats/min) (both P < 0.001). The change (upright - supine) in SV was inversely correlated with the change in HR for all participants at rest (R(2) = 0.32), at 25 W (R(2) = 0.49), 50 W (R(2) = 0.60), and 75 W (R(2) = 0.32) (P < 0.01). These results suggest that greater elevation in HR in POTS patients during exercise, especially while upright, was secondary to reduced SV and associated with exercise intolerance.     

Inherent capacity for lipogenesis or dietary fat retention is not increased in obesity-prone rats

Obesity results from positive energy balance and, perhaps, abnormalities in lipid and glycogen metabolism. The purpose of this study was to determine whether differences in lipogenesis, retention of dietary fat, and/or glycogenesis influenced susceptibility to dietary obesity. After 1 wk of free access to a high-fat diet (HFD; 45% fat by energy) rats were separated on the basis of 1 wk body weight gain into obesity-prone (OP; > or =48 g) or obesity-resistant groups (OR; < or =40 g). Rats were either studied at this time (OR1, OP1) or continued on the HFD for an additional 4 wk (OR5, OP5). Weight gain and energy intake were greater (P < or = 0.05) in OP vs. OR at both 1 (53 +/- 2 vs. 34 +/- 1 g; 892 +/- 27 vs. 755 +/- 14 kcal) and 5 (208 +/- 7 vs. 170 +/- 7 g; 4,484 +/- 82 vs. 4,008 +/- 72 kcal) wk, respectively. Rats were injected with (3)H(2)O and were either provided free access to an HFD meal containing labeled fatty acids (fed; n = 10 or 11/group) or were fasted (n = 10/group) overnight. The amount of food or (14)C tracer eaten overnight was equivalent between OP and OR rats. In liver, the fraction of (3)H retained in glycogen or lipid was not significantly different between OR and OP groups. Retention of dietary fat in the liver was not increased in OP rats. In adipose tissue, retention of (3)H was approximately 49% greater (P < or = 0.05) in OP1 vs. OR1 and approximately 30% greater in OP5 vs. OR5, but retention of dietary fat was not elevated in OP vs. OR. At the same time, fat pad weight (sum of epididymal, retroperitoneal, mesenteric) was 49% greater in OP1 rats vs. OR1 rats and 65% greater in OP5 vs. OR5 rats (P < or = 0.05). Thus a greater capacity for lipogenesis or retention of dietary fat does not appear to be included in the OP phenotype. The characteristic increase in energy intake associated with OP rats appears to be necessary and critical to accelerated weight and fat gain.     

The renal response of sheep to a low dietary nitrogen intake

Renal functions were tested in sheep fed on a low nitrogen diet (LN sheep), with a daily N intake of 4.7 g (gross energy 17.76 . 10(6) J). Sheep given a high nitrogen diet (HN sheep) with 21.2 g N (24.12 . 10(6) J) acted as the control. The functions of the left kidney were measured in anaesthetized animals by the standard clearance technique. A comparison of HN and LN sheep showed that a low nitrogen intake led to a drop in the plasma urea level (from 5.91 +/- 0.35 to 2.87 +/- 0.36 mmol.1-1, (P less than 0.001), the glomerular filtration rate (GFR, from 36.6 +/- 3.6 to 20.7 +/- 2.4 ml.min-1, P less than 0.005), amount of urea excreted (from 106.7 +/- 18.1 to 15.7 +/- 3.3 mumol.min-1, P less than 0.001), fractional urea excretion (from 51.0 +/- 3.0 to 24.6 +/- 3.1 %, P less than 0.001) and the absolute tubular reabsorption of urea (Reaburea/GFR (from 3.06 +/- 0.27 to 2.12 +/- 0.28 mumol.ml-1, P less than 0.05), without a significant change in the effective renal plasma flow (182.6 +/- 20.0 and 138.5 +/- 21.0 ml.min-1, non-significant - N.S.) and in sodium and potassium excretory function. Free water clearance rose in LN sheep (from -0.53 +/- 0.11 to -0.19 +/- 0.06 ml.min-1, P less than 0.05) owing to inhibited urea excretion. A regression analysis of the relationship of the tubular reabsorption of urea to the amount of filtered urea (both normalized to the GFR) showed that the urea transport capacity of the tubules of LN sheep was significantly higher.(ABSTRACT TRUNCATED AT 250 WORDS)     

Enhanced exercise-induced rise of aldosterone and vasopressin preceding mountain sickness

A possible contribution of exercise to the fluid retention associated with acute mountain sickness (AMS) was investigated in 17 mountaineers who underwent an exercise test for 30 min on a bicycle ergometer with a constant work load of 148 +/- 9 (SE) W at low altitude (LA) and with 103 +/- 6 W 4-7 h after arrival at 4,559 m or high altitude (HA). Mean heart rates during exercise at both altitudes and during active ascent to HA were similar. Exercise-induced changes at LA did not differ significantly between the eight subjects who stayed well and the nine subjects who developed AMS during a 3-day sojourn at 4,559 m. At HA, O2 saturation before (71 +/- 2 vs. 83 +/- 2%, P less than 0.01) and during exercise (67 +/- 2 vs. 72 +/- 1%, P less than 0.025) was lower and exercise-induced increase of plasma aldosterone (617 +/- 116 vs. 233 +/- 42 pmol/l, P less than 0.025) and plasma antidiuretic hormone (23.8 +/- 14.4 vs. 3.4 +/- 1.8 pmol/l, P less than 0.05) was greater in the AMS group, whereas exercise-induced rise of plasma atrial natriuretic factor and changes of hematocrit, potassium, and osmolality in plasma were similar in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of a menhaden oil diet on cercarial penetration of Schistosoma mansoni.

The ability of a menhaden oil (MO) diet to influence cercarial penetration into mouse tail skin was evaluated. Male CD-1 mice 4-6 wk old (15.2 g average weight) were fed a 0, 10%, or 20% MO-supplemented diet for 2 wk. After this time mice were infected with either 65 +/- 3 or 145 +/- 3 [35S]methionine/cysteine-labeled cercariae for 1 hr by tail immersion. Twenty-four hours and 7 days later groups of mice were killed and their tail skin removed and autoradiographed. At 24 hr postinfection, mice fed a 20% MO diet had significantly higher cercarial penetration than controls and 10% MO diets (56% +/- 5.2 vs. 44% +/- 2.9, P = 0.02, 1-tailed t-test). After 7 days mice fed a 20% MO diet retained more radioactive foci than controls or 10% MO diets (21% +/- 2.0 vs. 15% +/- 1.3, P = 0.01, 1-tailed t-test).     

Effects of tiadenol and clofibrate on plasma post heparin lipolytic hepatic, extrahepatic and monoglyceride hydrolase activities in rats with hypertriglyceridemia induced by a sucrose rich diet

Normal rats fed an isocaloric sucrose-rich diet (SRD) for 3 weeks developed high levels of triacylglycerol in plasma (P) (mmol triacylglycerol I-1) heart (H) and liver (L) tissues (mumol triacylglycerol mg DNA-1) as compared to control rats fed the standard chow (STD) (X +/- SEM; P: SRD 1.32 +/- 0.06 vs STD 0.49 +/- 0.05, P less than 0.001; H: SRD 2.1 +/- 0.17 vs STD 0.94 +/- 0.01, P less than 0.001; L: SRD 8.48 +/- 1.47 vs STD 1.71 +/- 0.12, P less than 0.001). A simultaneous drop in the activities (mumol glycerol ml-1 hr-1) of several plasma post heparin lipolytic enzymes was observed; total triglyceride lipase (T-TGL): SRD 5.32 +/- 0.34 vs STD 7.48 +/- 0.64, P less than 0.01; lipoprotein lipase (LPL): SRD 1.61 +/- 0.26 vs STD 2.42 +/- 0.41, P less than 0.05; hepatictriglyceride lipase (H-TGL): SRD 3.71 +/- 0.28 vs STD 5.05 +/- 0.69, P less than 0.05 and monoglyceride hydrolase (MGH) (mumol glycerol I-1 min-1): SRD 558 +/- 108 vs STD 1165 +/- 45, P less than 0.001. Rats fed the SRD presented glucose intolerance after i.v. glucose (Kg X 10(-2); 1.06 +/- 0.09 vs 2.61 +/- 0.14 of STD, P less than 0.001) in spite of the presence of hyperinsulinism (sigma plasma IRI microU/ml from 0 to 30 min: 184.6 +/- 23.6 vs 100.5 +/- 9.7 of STD, P less than 0.01) suggesting that a state of insulin resistance had developed.(ABSTRACT TRUNCATED AT 250 WORDS)     

VO(2) kinetics reveal a central limitation at the onset of subthreshold exercise in heart transplant recipients.

Because the cardiocirculatory response of heart transplant recipients (HTR) to exercise is delayed, we hypothesized that their O(2) uptake (VO(2)) kinetics at the onset of subthreshold exercise are slowed because of an impaired early "cardiodynamic" phase 1, rather than an abnormal subsequent "metabolic" phase 2. Thus we compared the VO(2) kinetics in 10 HTR submitted to six identical 10-min square-wave exercises set at 75% (36 +/- 5 W) of the load at their ventilatory threshold (VT) to those of 10 controls (C) similarly exercising at the same absolute (40 W; C40W group) and relative load (67 +/- 14 W; C67W group). Time-averaged heart rate, breath-by-breath VO(2), and O(2) pulse (O(2)p) data yielded monoexponential time constants of the VO(2) (s) and O(2)p increase. Separating phase 1 and 2 data permitted assessment of the phase 1 duration and phase 2 VO(2) time constant (). The VO(2) time constant was higher in HTR (38.4 +/- 7.5) than in C40W (22.9 +/- 9.6; P < or = 0. 002) or C67W (30.8 +/- 8.2; P < or = 0.05), as was the O(2)p time constant, resulting from a lower phase 1 VO(2) increase (287 +/- 59 vs. 349 +/- 66 ml/min; P < or = 0.05), O(2)p increase (2.8 +/- 0.6 vs. 3.6 +/- 1.0 ml/beat; P < or = 0.0001), and a longer phase 1 duration (36.7 +/- 12.3 vs. 26.8 +/- 6.0 s; P < or = 0.05), whereas the was similar in HTR and C (31.4 +/- 9.6 vs. 29.9 +/- 5.6 s; P = 0.85). Thus the HTR have slower subthreshold VO(2) kinetics due to an abnormal phase 1, suggesting that the heart is unable to increase its output abruptly when exercise begins. We expected a faster in HTR because of their prolonged phase 1 duration. Because this was not the case, their muscular metabolism may also be impaired at the onset of subthreshold exercise.     

Low energy availability, not exercise stress, suppresses the diurnal rhythm of leptin in healthy young women

Because the effect of exercise on leptin was not established, we controlled energy intake (I) and exercise energy expenditure (E) to distinguish the independent effects of energy availability (A = I - E) and exercise stress (everything associated with exercise except its energy cost) on the diurnal leptin rhythm in healthy young women. In random order, we set A = 45 and 10 kcal. kg lean body mass(-1) (LBM) x day(-1) for 4 days during the early follicular phase of separate menstrual cycles in sedentary (S, n = 7) and exercising (X, n = 9: E = 30 kcal x kg LBM(-1) x day(-1)) women. Low energy availability suppressed the 24-h mean (P < 10(-6)) and amplitude (P < 10(-5)), whereas exercise stress did not (both P > 0.2). Suppressions of the 24-h mean (-72 +/- 3 vs. -53 +/- 3%, P < 0.001) and amplitude (-85 +/- 3 vs. -58 +/- 6%, P < 0.001) were more extreme in S vs. X than previously reported effects on luteinizing hormone pulsatility and carbohydrate availability. Thus the diurnal rhythm of leptin depends on energy, or carbohydrate, availability, not intake, and exercise has no suppressive effect on the diurnal rhythm of leptin beyond the impact of its energy cost on energy availability.     

Effect of sodium intake on aldosterone and corticosterone production, the serum sodium concentration and body weight in infant rats during weaning period.

1. The effect of a low salt (LS, 0.3% NaC1) and control (HS, 1% NaC1) diet on in vitro aldosterone and corticosterone production, the serum corticosterone level, the serum sodium concentration and adrenal and body weight was studied in 30-day-old male rats, some of which were weaned prematurely at the age of 15 days (PW) and some left with the female up to the end of the experiment (NW). 2. Aldosterone production in the control (HS-NW) animals was 1.07+/-0.07 mug/100 mg adrenal/hour (mean +/-S.E.M.), in HS-PW animals 0.6+/-0.07 (P less than 0.01), while in LS-NW and LS-PW animals it rose to 1.59+/-0.1 and 1.81+/-0.14 respectively. The effect of the salt regimen was significant in both the NW group (P less than 0.01) and the PW group (P less than 0.01). Premature weaning did not inhibit aldosterone production in LS-PW animals. 3. Corticosterone production in animals fed on the control diet was 1.81+/-0.16 mug corticosterone/100 mg adrenal/hour in HS-NW rats and 0.91+/-0.09 in the HS-PW group (P less than 0.01). On the low salt diet it fell to 1.4+/-0.11 in LS-NW rats (HW-NW) vs LS-NW: P less than 0.01) and to 0.4+/-0.06 in LS-PW animals (HS-PW vs LS-PW: P less than 0.01). The difference between LS-NW and LS-PW was likewise statistically significant (P less than 0.01). Changes in production were not accompanied by parallel changes in the serum corticosterone level, where an analysis of variance showed no significant difference. 4. The low salt diet reduced the serum sodium concentration in both NW and PW animals (HS-NW 132.9+/-0.86 mEd HS-PW 132+/-0.86, LS-PW 128.5+/-1.16: P less than 0.01). The differences between NW and PW animals were not significant. 5. A low salt intake also reduced the body weight both of animals left with the female (HS-NW vs LS-NW: P less than 0.01) and of prematurely weaned animals (HS-PW vs LS-PW: P less than 0.01). Early weaning significantly affected body weight in LS animals only, the body weight of LS-PW animals being significantly lower than that of LS-NW animals (P less than 0.02). 6. The results show that infant rats are hypersensitive to a low salt intake at the end of the weaning period and that this phenomenon is not mediated by lower reactivity of the zona glomerulosa and of its regulation.     

Effect of exercise on epinephrine turnover in trained and untrained male subjects

The kinetics underlying plasma epinephrine concentrations were studied. Six athletes (T) and six sedentary males (C) were given intravenous infusions of 3H-labeled epinephrine, after which arterial blood was drawn. They rested sitting and bicycled continuously to exhaustion (60 min at 125 W, 60 min at 160 W, 40 min at 200 W, and 240 W to the end). Work time was 154 +/- 13 (SE) (T) and 75 +/- 6 (C) min. At rest, epinephrine clearance was identical [28.4 +/- 1.3 (T) vs. 29.2 +/- 1.8 (C) ml . kg-1 . min-1], but plasma concentration [1.42 +/- 0.27 (T) vs. 0.71 +/- 0.16 (C) nmol . l-1] and, accordingly, secretion [2.9 +/- 0.7 vs. 1.5 +/- 0.4 nmol . min-1] were higher (P less than 0.05) in T than C subjects. Epinephrine clearance was closely related to relative work load, decreasing from 15% above the basal level at 30% of maximal O2 uptake (VO2 max) to 22% below at 76% of VO2 max. Epinephrine concentrations increased much more with work intensity than could be accounted for by changes in clearance and were, at exhaustion, higher (P less than 0.05) in T (7.2 +/- 1.6) than in C (2.5 +/- 0.7 nmol . l-1) subjects despite similar glucose, heart rate, and hematocrit values. At a given load, epinephrine clearance rapidly became constant, whereas concentration increased continuously. Forearm extraction of epinephrine invalidated use of blood from a cubital vein or a hand vein arterialized by hot water in turnover measurements. During exercise, changes in epinephrine concentrations reflect changes in secretion rather than in clearance. Training may increase adrenal medullary secretory capacity.     

Influence of ascorbic acid on the thermic effect of feeding in overweight and obese adult humans

The thermic effect of feeding (TEF: increase in energy expenditure following acute energy intake) is an important physiological determinant of total daily energy expenditure and thus energy balance. Approximately 40% of TEF is believed to be mediated by sympathoadrenal activation and consequent beta-adrenergic receptor stimulation of metabolism. In sedentary adults, acute administration of ascorbic acid, a potent antioxidant, augments the thermogenic response to beta-adrenergic stimulation. We hypothesized that acute ascorbic acid administration augments TEF in sedentary overweight and obese adults. Energy expenditure was determined (ventilated hood technique) before and 4 h after consumption of a liquid-mixed meal (caloric equivalent 40% of resting energy expenditure (REE)) in 11 sedentary, overweight/obese adults (5 men, 6 women; age: 24 +/- 2 years; BMI: 28.5 +/- 1.0 kg/m(2) (mean +/- s.e.)) on two separate, randomly ordered occasions: during continuous intravenous administration of saline (placebo control) and/or ascorbic acid (0.05 g/kg fat-free mass). Acute ascorbic acid administration prevented the increase in plasma concentration of oxidized low-density lipoprotein in the postprandial state (P = 0.04), but did not influence REE (1,668 +/- 107 kcal/day vs.1,684 +/- 84 kcal/day; P = 0.91) or the area under the TEF response curve (33.4 +/- 2.4 kcal vs. 30.5 +/- 3.6 kcal; P = 0.52) (control vs. ascorbic acid, respectively). Furthermore, acute ascorbic acid administration had no effect on respiratory exchange ratio, heart rate, or arterial blood pressure in the pre- and postabsorptive states (all P > 0.64). These data imply that the attenuated TEF commonly observed with sedentary lifestyle and obesity is not modulated by ascorbic acid-sensitive oxidative stress.     

HUM5007, a novel combination of thermogenic compounds, and 3-acetyl-7-oxo-dehydroepiandrosterone: each increases the resting metabolic rate of overweight adults

This study tested the hypothesis that 3-acetyl-7-oxo-dehydroepiandrosterone alone (7-Keto) and in combination with calcium citrate, green tea extract, ascorbic acid, chromium nicotinate and cholecalciferol (HUM5007) will increase the resting metabolic rate (RMR) of overweight subjects maintained on a calorie-restricted diet. In this randomized, double-blind, placebo-controlled, crossover trial, overweight adults on a calorie-restricted diet were randomized to three 7-day treatment periods with 7-Keto, HUM5007 or placebo. Resting metabolic rate was measured by indirect calorimetry at the beginning and end of each treatment period with a 7-day washout between testing periods. Of 45 subjects enrolled, 40 completed the study (30 women, 10 men; mean age, 38.5 years; mean mass index, 32.0 kg/m(2)). During the placebo treatment, RMR decreased by 3.9% (75+/-111 kcal/day; mean+/-S.D.); however, RMR increased significantly by 1.4% (21+/-115 kcal/day) and 3.4% (59+/-118 kcal/day) during the 7-Keto and HUM5007 treatment periods, respectively (each compared to placebo, P=.001). No significant differences were found between the treatment periods with respect to compliance or adverse events. In this study, the administration of HUM5007 or 7-Keto reversed the decrease in RMR normally associated with dieting. HUM5007 and 7-Keto increased RMR above basal levels and may benefit obese individuals with impaired energy expenditure. HUM5007 and 7-Keto were generally well tolerated and no serious adverse events were reported.