Acute decrease in serum triglycerides with exercise: Is there a threshold for an exercise effect?

Acute reductions in triglycerides and low density lipoprotein (LDL) cholesterol concentrations have been demonstrated in endurance athletes after prolonged exercise. To determine if similar changes occur in untrained subjects and to determine the duration of exercise necessary for such changes, we measured serum lipids and lipoproteins in 10 sedentary men after 1 hour of exercise at their anaerobic threshold. Findings in sedentary men were compared with those of 9 competitive cyclists after 1 and 2 hr of exercise. LDL cholesterol increased in the cyclists immediately after 1 and 2 hours of exercise. Total cholesterol and high density lipoprotein (HDL) cholesterol also increased in the cyclists immediately after the 2 hr session. These increases were transient and not significant when corrected for changes in plasma volume. Serum triglycerides were unchanged for 4 hr after exercise. By 24 hr, however, triglycerides had decreased in both the trained (17%) and untrained men (22%) after the 1 hr session and in the trained men (33% p < 0.01) after the 2 hr session. These results demonstrate a delayed decrease in triglyceride concentration that is related to the duration of exercise and probably has no distinct threshold. The lower level of triglycerides in endurance athletes and in sedentary subjects after exercise training is due at least in part to an acute exercise effect.     

The effects of caloric restriction or exercise cessation on the serum lipid and lipoprotein concentrations of endurance athletes

The interaction of exercise and diet in determining the lipid profiles of endurance athletes is poorly defined. Since active men consume more calories than sedentary individuals, we examined the effects of caloric restriction alone or in combination with exercise cessation on the serum lipid levels of men running 16 km daily. For seven days before each study, subjects consumed diets composed of 15% protein, 32% fat, and 53% carbohydrate. During ten-day experimental periods, one group (n = 10) continued running and consumed the same diet containing 3670 kcal/day, while two other groups consumed an identical diet containing 20% fewer calories and either continued (n = 16) or stopped (n = 15) exercise training. High-density lipoprotein cholesterol (HDL-C) concentrations decreased 1% to 5% in all groups during the seven-day preliminary diet. Additional reductions in total HDL-C concentrations were similar in the control and exercise cessation groups, but HDL2-C level decreased 15% during exercise cessation. During caloric restriction and continued running, in contrast, HDL-C concentration increased 8% and the HDL2-C subfraction increased 23%. There was little change in levels of apolipoprotein A-I concentrations during any of the protocols, demonstrating that changes in HDL-C are not necessarily attended by changes in the major HDL apoprotein. Low-density lipoprotein cholesterol (LDL-C) level decreased 10% to 15% in all groups during the preliminary period. Only small additional reductions occurred in men who continued running. Exercise cessation, however, was associated with a 10% increase in LDL-C level after only two days of inactivity.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of high-carbohydrate and high-fat diets on the serum lipid and lipoprotein concentrations of endurance athletes

We examined the effects of high-carbohydrate and high-fat diets on the serum lipid levels of distance runners. For seven days before each study, subjects consumed a diet containing 15% protein, 32% fat, and 53% carbohydrate. During 14-day experimental periods, a control group (n = 10) continued the same diet while two other groups consumed 69% of their calories as either carbohydrate (n = 13) or fat (n = 14). High-density lipoprotein (HDL)-cholesterol decreased 9% during the high-carbohydrate diet because of a 26% fall in the HDL2 fraction (1.063 to 1.125 g/mL). These changes were not accompanied by changes in the levels of apolipoproteins (apo) A-I or A-II. Total and low-density lipoprotein (LDL)-cholesterol initially decreased but subsequently exceeded pre-diet values while triglyceride concentrations increased 30% to 50%. Postheparin lipoprotein lipase activity (LPLA) fell 20%. Despite these dietary effects, HDL and HDL2 cholesterol concentrations in the athletes remained above values typical of sedentary men. The high-fat diet produced different effects on the serum lipids and lipoprotein levels of the athletes. HDL levels changed little during the study although HDL-cholesterol and apo A-I on the last diet day were both slightly above initial values. The high-fat diet provided 111 g of saturated fat per day but had surprisingly little effect on total and LDL-cholesterol whereas serum triglycerides fell by 10% to 20%. Postheparin LPLA increased 30% with fat feeding and the changes in LPLA correlated with alterations in triglyceride levels (r = -0.53, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of potassium loading on metabolism of aldosterone in rats

Thirty minutes after subcutaneous injection of ³H-aldosterone, the distribution of ³H radioactivity in the liver, kidney, small intestine, and plasma of rats who had been potassium-loaded for 2 or 4 days was demonstrated to be significantly altered. The total radioactivity (disintegrations per minute per gram) in both the homogenate and cytosol fractions of both the liver and kidney were markedly increased in rats maintained on the high-potassium diet. Of marked interest, both the quantities and percentages of nonextractable polar derivatives of aldosterone were significantly increased in these tissues during the 4 days of potassium loading. However, significantly smaller quantities of ³H radioactivity were demonstrated to be present in the small intestine of the potassium-loaded rats. Total plasma radioactivity and the quantities of the polar metabolites of aldosterone in the plasma were also significantly elevated in the potassium-loaded rats. The percentage of nonextractable radioactivity in the plasma also increased from 42% to 54% by 4 days of potassium loading. Interestingly, the halflife for aldosterone in the plasma, 11 min, was not altered following the potassium loading. The rates of biliary excretion of radiometabolites of aldosterone were not different from those of the control rats. These preliminary findings suggest that the overall metabolism of aldosterone is altered in potassium-loaded rats, leading to increased quantities of the polar metabolites of aldosterone in the plasma, the liver, and particularly in the target tissue, the kidney. These findings might indicate a relationship between the alteration in the metabolism of aldosterone and the increased secretion of potassium ions by the kidney when adaptation to potassium loading occurs in rats.     

Effect of exercise training on the untrained limb exercise performance of men with angina pectoris

This study examined the exercise capacity of trained and untrained limbs in men with angina pectoris before and after 8 weeks of arm (n = 4) or leg (n = 7) physical training or a control (n = 4) period. Time to angina (mean ± standard deviation) increased 3.6 ± 2.7 minutes (p < 0.01) during trained limb and 1.6 ± 1.2 minutes (p < 0.01) during untrained limb exercise. Myocardial oxygen demand at angina estimated by the product of heart rate and systolic blood pressure did not change with training. At a constant subanginal work load, rate-pressure product × 10^?2 was reduced by 35 ± 22 (p < 0.001) during trained limb and by 18 ± 27 (p < 0.05) during untrained limb exercise. The decrease in rate-pressure product with both trained and untrained limbs was greatest in subjects with the highest rate-pressure product at angina before training. Control subjects showed no change in any exercise measurement.Exercise training increases the exercise capacity of untrained limbs in patients with angina pectoris by a generalized training effect not dependent on adaptations In trained skeletal muscle. The improvement for both trained and untrained limbs results from a reduced rate-pressure product at subanginal work loads rather than from an increase in myocardial oxygen delivery. Subjects with the highest pretraining coronary arterial oxygen supply at the onset of angina benefit most from physical training.     

Exercise-induced coronary spasm with S-T segment depression and normal coronary arteriography

The unique association of both exercise-induced coronary arterial spasm and S-T segment depression with normal findings on selective coronary arterlography is described. The patient had a prior history of typical effort angina that had recently progressed to angina at rest. Despite the change In anginal pattern, the electrocardiogram disclosed S-T segment depression that was consistent with subendocardial Ischemia, during both exercise testing and spontaneous chest pain. Exercise thallium-201 sclntigraphy demonstrated the presence of large perfusion defects of the anterior and septal walls of the left ventricle. Coronary arteriographie findings, in the absence of symptoms, were entirely normal. Severe localized, reversible coronary spasm of the proximal left anterior descending coronary artery was subsequently demonstrated during spontaneous angina, Isometric arm exercise and after the administration of ergonovine maleate. After treatment with isosorblde dlnitrate and nifediplne, the patient had no further chest pain or electrocardiographic changes, and a repeated thallium-201 stress test revealed nomal findings and greatly Improved exercise tolerance.     

Cost-effective application of the Centers for Disease Control Guideline for Prevention of Nosocomial Pneumonia

Some parts of the Guideline are clearly cost-effective. Abandoning routine cultures of respiratory therapy equipment is cost-effective and should be adopted by any hospitals that have not done so already. Other practices such as the use of preoperative and postoperative instructions regarding deep breathing and incentive spirometry, and the policy of never reusing respiratory therapy equipment items that are intended for single use probably warrant further cost-benefit analysis. Finally, there is increasing evidence that changing ventilator tubing every 24 hours is not cost-effective. Changing tubing every 48 hours appears to be safe and can save hospitals substantial sums of money.     

Inferoseptal myocardial infarction: Another cause of precordial ST-segment depression in transmural inferior wall myocardial infarction?

Electrocardiographic ST-segment depression in the anterior precordial leads is a frequent observation during the initial hospital phase of acute transmural inferior myocardial infarction (MI), but is of uncertain significance. No available clinical studies have examined the prevalence of inferoseptal necrosis complicating inferior MI. Therefore, the clinical course, electrocardiographic features, radionuclide angiograms and cardiac enzyme changes in 57 patients with transmural inferior MI who did not have prior anterior or concomitant "true posterior" MI, associated anterior or posterolateral asynergy by radionuclide ventriculography, or left or right bundle branch block were reviewed retrospectively. Patients were categorized according to the presence (group A) or absence (group B) of precordial ST-segment depression and according to the presence (group I) or absence (group II) of radionuclide septal wall motion abnormalities. There were no significant differences in global left ventricular ejection fraction (group A, 49 +/- 8, group B, 52 +/- 41; group I, 51 +/- 7, group II, 51 +/- 6), right ventricular ejection fraction (group A, 45 +/- 9, group B, 42 +/- 7; group I, 43 +/- 8, group II, 41 +/- 8), or clinical outcome in the hospital. However, chi-square analysis revealed a significant (p less than 0.05) association between the presence or absence of septal asynergy and the presence or absence of precordial ST depression. In addition, average peak creatine kinase elevation (group I, 761 +/- 164 IU; group II, 698 +/- 178 IU) attained marginal significance by paired t test (p = 0.06). Precordial ST-segment depression during transmural inferior MI is frequently associated with septal asynergy by gated radionuclide angiography (15 of 26 patients, 58%).(ABSTRACT TRUNCATED AT 250 WORDS)     

Hemodynamic correlates of right ventricular ejection fraction measured with gated radionuclide angiography

Right ventricular function was studied in 60 patients with equilibrium gated radionuclide angiography. The mean (± standard deviation) right ventricular ejection fraction in 20 normal subjects was 53 ± 6 percent, a value in agreement with previous data from both radionuclide and contrast angiographie studies. This value was similar (55 ± 7 percent) in 11 patients with coronary artery disease but normal left ventricular function.Radionuclide measurements of right ventricular ejection fraction were correlated with right heart hemodynamics. There was a significant negative linear correlation between right ventricular ejection fraction and mean pulmonary arterial pressure (r = ?0.82) and between right ventricular ejection fraction and right ventricular end-diastolic pressure (r = ?0.67). Furthermore, patients with elevated right ventricular enddiastolic pressure and mean pulmonary arterial pressure had a more severely depressed ejection fraction than did those with an elevated mean pulmonary arterial pressure alone.Thus, an abnormal value for right ventricular ejection fraction by gated radionuclide angiography in the absence of primary right ventricular volume overload suggests abnormal right heart pressures, whereas a normal value excludes severe pulmonary arterial hypertension or an elevated right ventricular end-diastolic pressure.     

Aldosterone: current concepts

Since the discovery of aldosterone, the mechanism by which this hormone regulates electrolyte balance in the kidney and in its other target tissues has been intensively studied. Increased interest in aldosterone has resulted from the realization of the significant role it plays in the fluid and electrolyte abnormalities associated with congestive heart failure, hypertension, cirrhosis, and a variety of diseases of the kidney and heart. Recently, attention has been given to the biochemical events that occur during the latent period prior to the physiologic effects of aldosterone. In this review, evidence is presented to show that the antinatriuretic and kaliuretic components of the physiologic response to aldosterone appear to be separable effects. The possibility is discussed that the lag times prior to each of these physiologic components might be comprised of separate and distinct sets of biochemical events. The importance of aldosterone protein receptors and the protein synthetic responses thought to be necessary to elicit some of the aldosterone effects is also discussed. The metabolism of aldosterone also appears to be important in the regulation of the physiologic effects of this hormone and the lag times prior to the effects. The kaliuretic component, particularly, appears to be a possible consequence of this metabolism.     

Measurement of normal left atrial function with gated radionuclide angiography

A method is described for measuring relative left atrial volume changes with gated radionuclide angiography, using an approximate computer-generated functional image to locate the atrial region of interest. M mode echocardiographic measurements of left atrial and left ventricular distances from the chest wall allowed calculation of a correction factor for the differential attenuation of atrial and ventricular photons. Background-corrected left atrial time-activity curves obtained from normal subjects exhibited excellent temporal resolution and were used to identify and quantitate the reservoir and contractile phases of left atrial volume change. In 20 normal subjects, the mean (+/- standard deviation) value for left atrial fractional emptying was 0.39 +/- 0.07. Expressed as fractions of the left ventricular stroke volume, mean values of the specific phases of atrial volume change were (1) reservoir volume 0.25 +/- 0.09, (2) contractile volume 0.29 +/- 0.10, and (3) conduit volume 0.46 +/- 0.12.     

Gated radionuclide angiographic evaluation of valve regurgitation

Gated radionuclide angiography is a new noninvasive technique that can be used to calculate the ratio of left and right ventricular stroke volumes. This stroke volume ratio, which must be unity in normal subjects, increases in patients with aortic or mitral regurgitation in direct proportion to the degree of left ventricular volume overload, provided no shunts or regurgitant right heart lesions are present. In 22 patients with aortic or mitral regurgitation there was excellent correlation between the stroke volume ratio determined with gated radionuclide angiography and with standard quantitative catheterization methods (r = 0.79). Measurement of valve regurgitation with this radionuclide method also correlated well with data obtained from semiquantitative aortic root or left ventricular cineangiography (r = 0.72). Twenty-one of the 22 patients with valve regurgitation had an abnormally elevated stroke volume ratio, thereby suggesting that gated radionuclide angiography may be useful in detecting or excluding hemodynamically significant valve regurgitation.     

Acute effects of prolonged exercise on serum lipids

The acute effects of a single prolonged exercise session on the serum concentrations of cholesterol, triglycerides (TG), glycerol, high density lipoprotein (HDL) cholesterol, and the major HDL protein, apolipoprotein A-I (apoA-I), were examined in 12 trained male runners participating in a 42-km footrace. Serum TG levels were unchanged up to 4 h after the race, but at 18, 42, and 66 hr mean reductions of 65%, 39%, and 32% were observed. Free glycerol concentrations were increased fivefold immediately after the race, but did not differ from prerace levels by 4 hr. Total cholesterol concentration did not change immediately after exercise, but unexpected significant reductions of 6%–10% were found at 4–66 hr. Only small and transient increases in HDL cholesterol and apoA-I levels were noted after exercise. These results suggest that prolonged exercise acutely lowers TG and total cholesterol, but has little effect on HDL mass.     

Sex dependence of aldosterone response in rats

The dose/response relationship of aldosterone as measured by the urinary $\text{Na}{}^{\mathrm{+}}\text{K}{}^{\mathrm{+}}$ ratio was significantly different in male and female adrenalectomized rats: the males showing a greater physiologic response to aldosterone than females. This sex dependence also existed when the components of the physiologic response, antinatriuresis and kaliuresis, were determined individually. The correlation is made between the higher physiologic response to aldosterone and the greater metabolism of aldosterone in male rats.     

Exercise activation of myocardial lipoprotein lipase in male and estrogen-treated female rats

Lipoprotein lipase (LPL) is the rate-limiting enzyme in the utilization of plasma triglycerides by extrahepatic tissues. The present study examined the effect of estrogen upon the circadian rhythm of rat myocardial LPL and upon the endothelial-bound and tissue components of rat myocardial LPL immediately after exhaustive exercise. Female rats were ovariectomized at 28 days. Estrogen replaced female rats (ER) received 17-beta-estradiol in sunflower oil (200 micrograms/100 g body weight/week for 4 weeks). Oil-injected female rats (OI) received sunflower oil (0.1 mL/100 g body weight/week for 4 weeks). Normal male rats (M) were studied for comparison. ER, OI, and M animals were killed every four hours starting at 8 AM. Estrogen treatment did not alter the circadian rhythm of LPL activity. A second group of animals were run to exhaustion on a motorized treadmill, starting at 9 AM. ER animals performed significantly more work (P less than 0.05) than OI or M rats. Liver glycogen concentration was reduced 96.8% to 97.8% from control in all three groups after exercise. Both the tissue and endothelial fractions of LPL activity were elevated after exercise in all three groups. Exercised ER females (116.3 +/- 9.0 units) had significantly higher cardiac tissue enzyme activity than exercised males (85.0 +/- 9.4 units). Heparin-releasable LPL activity in exercised ER rats (65.3 +/- 5.7 units) was 43% higher than in exercised M rats (45.5 +/- 5.6 units) and 53% higher than in OI female rats (42.6 +/- 8.1 units).(ABSTRACT TRUNCATED AT 250 WORDS)     

Combined deficiency of apolipoprotein C-II and lipoprotein lipase in familial hyperchylomicronemia

The underlying pathophysiological defect was studied in four siblings with familial hyperchylomicronemia. Deficiency of apolipoprotein C-II and E-3 was identified. In addition, these subjects had markedly decreased LPL activity in postheparin plasma. Addition of normal plasma to the assay as source for apoC-II enhanced LPL activity only to a limited extent. In contrast with previously reported patients with apoC-II deficiency, a far less pronouced effect of intravenous infusion of normal plasma was seen in one of the siblings, probably due to the combined deficiency of apoC-II and LPL. Plasma VLDL-TG turnover rate was not decreased in one of the siblings with apoC-II and LPL deficiency, suggesting different metabolic pathways for chylomicrons and VLDL. Family study confirmed an autosomal recessive mode of inheritance both for apoC-II and for apoE-3 deficiency. The mode of inheritance for LPL deficiency could not be established exactly.     

Chronic hyperglucagonemia in rats: effects on insulin, substrates, and hepatic enzymes of intermediary metabolism

The effects of chronic exogenous hyperglucagonemia were evaluated in 120–140 g rats given 0.8 or 0.4 mg glucagon per day for seven days by constant infusion through the use of subcutaneously implanted, osmotically driven minipumps. Untreated animals, with and without dietary restriction, served as controls. Glucagon infusion resulted in plasma glucagon concentrations ranging from 1000 to more than 4000 pg/mL. The experimental animals had decreased food intake resulting in poor weight gain. Plasma insulin, glucose, and β-hydroxybutyrate concentrations were unchanged in the experimental animals. Glucagon administration was associated with generalized hypoaminoacidemia (75% reduction from the control mean total amino acid concentration). Hepatic glycogen content decreased to the level seen in the dietary-restricted animals, which were matched for weight gain. In vitro activities of total hepatic glycogen phosphorylase, pyruvate kinase (measured at saturating PEP concentrations), acetyl-CoA carboxylase and fatty acid synthase were decreased in the experimental animals. Total glycogen synthase and PEP carboxykinase activities increased. These results are not consistent with previously described effects of glucagon mediated through enzyme phosphorylation and are interpreted as suggesting changes in total enzyme content. From these studies we conclude that chronic hyperglucagonemia of 1 week's duration in young rats has persistent metabolic effects. It does not, however, result in persistent changes in plasma glucose or β-hydroxybutyrate concentrations when insulin secretion is preserved. The observed hypoaminoacidemia is analogous to that seen in the glucagonoma syndrome. Long-term effects of glucagon on in vitro hepatic enzyme activities are possibly due to changes in enzyme protein content and not protein phosphorylation.     

Decline of postheparin plasma lipoprotein lipase in acromegalic patients

Lipoprotein lipase and hepatic triglyceride lipase in postheparin plasma were measured in seven patients with active acromegaly by an immunochemical method utilizing antiserum prepared against hepatic triglyceride lipase. A mild or moderate hypertriglyceridemia was shown, with plasma triglyceride concentrations between 156 and 544 mg/dl. Lipoprotein lipase was found to be decreased in all patients (p < 0.001). Hepatic triglyceride lipase was also low in these patients (p < 0.001). We speculate that acromegalic hypertriglyceridemia is mediated, at least in part, by the decline in lipoprotein lipase and possibly by the decline in hepatic triglyceride lipase activities.     

Adipose tissue lipoprotein lipase activity in type III hyperlipoproteinemia.

An impairment in the catabolism of chylomicron and very low density lipoprotein remnants appears to cause the lipid abnormalities in type III hyperlipoproteinemia. A reduction in the activity of lipoprotein lipase (LPL) has been suggested as the catabolic defect. Results in this study indicate that the activity of adipose tissue LPL measured in the fasted and fed states are in the normal range in type III hyperlipoproteinemia (fasted: type III = 2.7 +/- 1.8 mU/10(6) cells, N = 8; normals = 3.4 +/- 2.5, N = 23, p, not significant; fed: type III = 3.6 +/- 2.1, N = 7; normals = 4.8 +/- 1.8, N = 12, p, not significant). This suggests that perhaps another mechanism, such as the interaction between LPL and its lipid substrate, is abnormal, or that the activity of LPL derived from another tissue source is deficient.