Dietary cholesterol influences cardiac beta-adrenergic receptor adenylate cyclase activity in the marmoset monkey by changes in membrane cholesterol status

High Body Mass Index Is Associated with the Extent of Muscle Damage after Eccentric Exercise

Purpose: The present study aimed to investigate the effects of body mass index (BMI), which is an obesity index, on the change in the muscle damage index after eccentric exercise. Methods: Forty healthy male university students participated in this study and were classified into normal (BMI 18.5⁻22.9 kg/m², n = 20) and high BMI groups (BMI &ge; 25 kg/m², n = 20). For eccentric exercise, a modified preacher curl machine was used. Participants performed two exercise sets with 25 repetitions in each set. With regard to the muscle damage index, maximum strength, muscle soreness, and the creatine kinase (CK) level were measured. Results: Loss of maximum strength, muscle soreness, and the CK level were higher in the high BMI group than in the normal BMI group (p < 0.05, p < 0.05, and p < 0.01, respectively). Conclusions: In conclusion, BMI is one of the potential factors related to muscle damage after eccentric exercise.

Protective effect of lupeol and its ester on cardiac abnormalities in experimental hypercholesterolemia

Hyperlipidemia is a major risk factor for the premature development of coronary heart disease and it has been shown to increase the incidence of myocardial ischemia and cardiac events. Pentacyclic triterpenes possess antiatherosclerotic, antioxidant, anti-inflammatory and cytoprotective effects. To study the effect of plant derived triterpene, lupeol and its ester lupeol linoleate, on lipid status and biochemical changes on heart tissue, male albino Wistar rats were fed high-cholesterol diet (normal rat chow supplemented with 4% cholesterol and 1% cholic acid; HCD) for 30 days. There was a significant (p<0.001) increase in the levels of total cholesterol, triglycerides and phospholipids along with augmented activities of lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase in the heart tissue. Triterpenes treatment reduced the above alterations produced in hypercholesterolemic rats. The transmembrane enzymes, namely Na(+), K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase showed a decrease in their activities. Triterpenes treatment reversed these levels, prevented the hypertrophic cardiac histology and restored the normal ultrastructural architecture. In conclusion, lupeol and lupeol linoleate intervention minimized the lipid abnormalities and abnormal biochemical changes induced by HCD fed rats. This shows that triterpenes possess cardioprotective effects which will be beneficial in hypercholesterolemic condition. Out of these two triterpenes tested, lupeol linoleate appeared to be even more effective than lupeol.

Conceptual foundations of the UCSD Statin Study: a randomized controlled trial assessing the impact of statins on cognition, behavior, and biochemistry

BACKGROUND

Statin cholesterol-lowering drugs are among the most prescribed drugs in the United States. Their cardiac benefits are substantial and well supported. However, there has been persistent controversy regarding possible favorable or adverse effects of statins or of cholesterol reduction on cognition, mood, and behavior (including aggressive or violent behavior).

METHODS

The literature pertaining to the relationship of cholesterol or statins to several noncardiac domains was reviewed, including the link between statins (or cholesterol) and cognition, aggression, and serotonin.

RESULTS

There are reasons to think both favorable and adverse effects of statins and low cholesterol on cognition may pertain; the balance of these factors requires further elucidation. A substantial body of literature links low cholesterol level to aggressive behavior; statin randomized trials have not supported a connection, but they have not been designed to address this issue. A limited number of reports suggest a connection between reduced cholesterol level and reduced serotonin level, but more information is needed with serotonin measures that are practical for clinical use. Whether lipophilic and hydrophilic statins differ in their impact should be assessed.

CONCLUSION

There is a strong need for randomized controlled trial data to more clearly establish the impact of hydrophilic and lipophilic statins on cognition, aggression, and serotonin, as well as on other measures relevant to risks and quality-of-life impact in noncardiac domains.

Assessing the observed relationship between low cholesterol and violence-related mortality. Implications for suicide risk

Health advocacy groups advise all Americans to restrict their dietary intake of saturated fat and cholesterol as an efficacious and safe way to lower plasma cholesterol concentrations and thus reduce the risk of coronary heart disease and other atherosclerotic disorders. However, accumulating evidence suggests that naturally low or clinically reduced cholesterol is associated with increased nonillness mortality (principally suicide and accidents). Other evidence suggests that such increases in suicide and traumatic death may be mediated by the adverse changes in behavior and mood that sometimes accompany low or reduced cholesterol. These observations provided the rationale for an ongoing series of studies in monkeys designed to explore the hypothesis that alterations in dietary or plasma cholesterol influence behavior and that such effects are potentiated by lipid-induced changes in brain chemistry. In fact, the investigations in monkeys reveal that reductions in plasma cholesterol increase the tendency to engage in impulsive or violent behavior through a mechanism involving central serotonergic activity. It is speculated that the cholesterol-serotonin-behavior association represents a mechanism evolved to increase hunting or competitive foraging behavior in the face of nutritional threats signaled by a decline in total serum cholesterol (TC). The epidemiological and experimental data could be interpreted as having two implications for public health: (1) low-cholesterol may be a marker for risk of suicide or traumatic death and (2) cholesterol lowering may have adverse effects for some individuals under some circumstances.

Decrease in myocardial Na(+)-K(+)-ATPase activity and ouabain binding sites in hypercholesterolemic rabbits

OBJECTIVES

The purpose of this study was to explore the effect of high dietary cholesterol on the lipid composition, Na(+)-K(+)-ATPase activity and ouabain receptor property of the myocardial sarcolemma.

METHODS

Male New Zealand white rabbits were fed with standard chow or standard chow supplemented with 0.5% (w/w) cholesterol and 10% (w/w) coconut oil to induce hypercholesterolemia. After 8 weeks, the rabbits were sacrificed; a myocardial sarcolemma fraction was then prepared from the left ventricular myocardium and analyzed for lipid composition. Assay of Na(+)-K(+)-ATPase activity and 3H-ouabain binding studies were performed in the myocardial sarcolemma from the control and cholesterol-fed rabbits.

RESULTS

The cholesterol content, but not the phospholipid content, of the sarcolemma was significantly greater in the cholesterol-fed group, thus, resulting in an increased cholesterol/phospholipid molar ratio in the cholesterol-fed group. In addition, a decrease in Na(+)-K(+)-ATPase activity was also found in this group. The decrease in Na(+)-K(+)-ATPase activity was selective, since the Mg(++)-ATPase and 5'-nucleotidase activities remained unchanged. In the 3H-ouabain binding study, a decrease in the number of maximum binding sites, but not the binding affinity, for 3H-ouabain was found in the cholesterol-fed group.

CONCLUSIONS

High dietary cholesterol induces higher levels of cholesterol not only in the plasma, but also in the myocardial sarcolemma. These changes result in decreased myocardial Na(+)-K(+)-ATPase activity mediated by a reduction in the maximum number of binding sites for ouabain but not a change in binding affinity.

The influence of dietary cholesterol on cardiac and hepatic Beta-adrenergic receptors in egyptian sand rats

We examined the effects of dietary cholesterol on cardiac and hepatic beta-adrenergic receptor functioning. Age-matched adult desert rodents (Psammomys obesus) were randomized to either a 5% cholesterol diet (CD, n = 20), or normal rabbit chow (RC, n = 18). After a 2-month exposure to the diets, animals were sacrificed and tissue from both heart and liver were retained for radioligand bindings studies. In heart tissue, cholesterol fed animals, relative to controls, showed an increased production of adenosine 3,5>-cyclic monophosphate (cAMP) in response to isoproterenol. Cholesterol supplementation was not associated with an increase in heart beta-adrenergic receptor number. Animals fed the 5% cholesterol diet showed significant increases in the number of beta-adrenergic receptor sites in hepatic tissue (M = 13.2 vs. 10.4 pmol/mg protein, CD and RC, respectively). The increased number of receptor sites in the liver was accompanied by a significant increase in isoproterenol-stimulated cAMP production. Results are supportive of the hypothesis that dietary cholesterol contributes to an upregulation of beta-adrenergic receptor function in cardiac, as well as hepatic tissue. These findings may be relevant to the observations of excessive stress-induced cardiovascular reactivity in persons with high cholesterol levels.

Membrane interaction of calcium channel antagonists modulated by cholesterol. Implications for drug activity

The interactions of lipophilic calcium channel antagonists with the membrane lipid bilayer are complex and highly dependent on membrane composition and structure. Variability in membrane lipid composition (e.g. cholesterol content, acyl chain saturation) can dramatically affect the membrane partitioning of calcium channel antagonists. The membrane binding properties of these drugs did not correlate with traditional measurements of drug lipophilicity, such as a simple hydrocarbon system (Table 2). These data indicate the need for directly measuring the binding of drug molecules to membranes in order to understand better certain pharmacological parameters, including bioavailability, under both normal and pathological conditions in which membrane composition is altered. The interaction of certain lipophilic amphipathic drugs with the membrane lipid bilayer may be an important component of their overall receptor binding mechanism. Specifically, the membrane bilayer may serve to concentrate and orient these drug molecules with respect to a hydrophobic receptor site at the protein receptor/membrane bilayer interface. Thus, the design of drugs which target membrane bound receptors should take into consideration the interaction of the drug molecule with the membrane lipid compartment. This understanding of drug/membrane interactions may lead to the development of drugs with more desirable pharmacokinetics, greater efficacy, and reduced side effects.

Influence of aging on fluidity and coupling between beta-receptors and G-proteins in rat lung membranes

We tested the hypothesis that in rat lung membranes, the age-related decline in the percentage of beta-receptors coupled with high affinity to G-proteins, is due to limitation of the diffusion caused by a decrease in membrane fluidity. We measured both parameters simultaneously in a crude membrane preparation from lungs of rat of different age. In contrast to what is found in crude membrane preparations from rat liver and brain, in rat lung fluidity was increased upon aging. We conclude that the age-related alteration in coupling between receptor and G-protein is difficult to explain by alterations of membrane fluidity.

Lipids in psychological research: the last decade

We review the recent literature examining lipid changes during stressful experiences, and the psychological and constitutional differences that influence lipid levels at rest and that may modulate lipid response to stress. Mild forms of chronic or episodic stress are apparently not associated with alterations in lipids and lipoproteins, but severe forms of real or perceived stress do appear to alter lipid levels. Acute laboratory stress is frequently associated with short-term alterations in lipids and lipoproteins, but the significance of these changes is unclear. Several individual characteristics, such as heightened neuroendocrine or autonomic reactivity to stressors, Type A component behavior, and other aspects of personality, appear to be associated with an atherogenic lipid profile. Stress may influence lipid concentrations and metabolism through a variety of physiological and behavioral mechanisms, but none have been clearly elucidated. Future research should concentrate on understanding these mechanisms.

Cholesterol-rich rabbit serum modulates beta-adrenergic receptor density of human lymphocytes. A possible role of LDL-cholesterol

The effect of in vitro treatment of human lymphocytes with rabbit cholesterol-rich serum (RCS) on the membrane microviscosity as well as on the beta-adrenergic receptor density has been investigated. RCS treatment of cells resulted in a 30% decrease of receptor density without any effect on membrane microviscosity. A complete recovery was observed incubating the RCS cells either with the "Active Lipids" (AL) or with heparin. The AL are a mixture of neutral lipids, phosphatidylcholine and phosphatidylethanolamine from hen egg yolk known to fluidify the cell membrane. The AL modified membrane microviscosity of control lymphocytes without altering their beta-receptor number. These observations support the proposition that beta-receptor density of human lymphocytes is not regulated by membrane microviscosity and suggest that probably low density lipoprotein-cholesterol complex is involved in such a regulation.

The effect of dietary supplementation with eicosapentaenoic acid on the phospholipid and fatty acid composition of erythrocytes of marmoset

Adult male marmoset monkeys were fed eicosapentaenoic acid (20:5n-3) as the ethyl ester in diets containing either 32% (reference diet, no added cholesterol) or 7% (atherogenic diet with 0.2% added cholesterol) linoleic acid (18:2n-6) for 30 wk. No changes were seen in the level of phosphatidylcholine (PC) or phosphatidylethanolamine (PE) but minor changes were observed in both the sphingomyelin (SPM) and phosphatidylinositol plus phosphatidylserine (PI+PS) fractions of erythrocyte lipids. The extent of total n-3 fatty acid incorporation into membrane lipids was higher in atherogenic diets (polyunsaturated/monounsaturated/saturated (P/M/S) ratio 0.2:0.6:1.0) than reference diets (P/M/S ratio 1:1:1) and this was true for both PE (33.4 +/- 1.0% vs 24.3 +/- 1.1%) and PC (9.3 +/- 0.5% vs 4.9 +/- 0.3%). Although suitable controls for cholesterol effects were not included in the study, earlier results obtained with marmosets lead us to believe such effects were probably small. Regardless of basic diet (atherogenic, reference), 20:5n-3 was preferentially incorporated into PE (10.8 +/- 0.2%, 6.0 +/- 0.02%) while smaller amounts were incorporated into PC (6.9 +/- 0.4%, 3.2 +/- 0.2%). The major n-3 polyunsaturated fatty acid found in PE in response to dietary 20:5n-3 was the elongation metabolite 22:5n-3 in both the atherogenic (17.7 +/- 0.7%) and reference (14.3 +/- 1.0%) dietary groups; 22:6n-3 levels were less affected by diet (4.7 +/- 0.3% and 3.9 +/- 0.2%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Food restriction slows down age-related changes in cell membrane parameters

The effect of undernutrition on some plasma membrane parameters has been analyzed. Diet restriction was applied to female Wistar rats on every-other-day schedule (EOD), starting from the age of 3.5 months. Membrane microviscosity of splenic lymphocytes was lower in EOD rats than in the ad libitum (AL) fed ones even if one assumes a decrease of body temperature of 2 degrees C. The decrease of membrane microviscosity due to diet restriction ran parallel with the improvement of proliferative response of lymphocytes. The analysis of Arrhenius plots of 1,6-diphenyl-1,3,5-hexatriene as well as of 5'-nucleotidase activity showed a diet-dependent improvement of membrane properties also of liver plasma membranes. Diet restriction was able to partially recover the age-dependent decrease of beta-adrenoceptor density of cerebellar membranes. On the contrary, beta-adrenoceptor density of lymphocytes, which did not show any age-dependent alteration, was not influenced by diet restriction. Present results support that undernutrition exerted a protective effect on cell membranes of old animals and it was able to improve those alterations which are related to aging.

Differential alteration of vascular reactivity in rabbit aorta with modest elevation of serum cholesterol

The effect of diet-induced, moderate elevation of serum cholesterol on vascular reactivity in isolated rabbit abdominal aortic rings was examined by using a series of vasoconstrictor and vasodilator agonists. Serum cholesterol of rabbits that were fed a cholesterol-free, casein-rich diet for 10 weeks was elevated approximately 4.5-fold compared with values found in control rabbits that were fed standard lab chow (223 +/- 41 versus 51 +/- 5 mg/dl, respectively). Relaxation responses to carbamylcholine chloride and (+/-)-isoproterenol hydrochloride in vessels from hypercholesterolemic rabbits were markedly inhibited in the presence of norepinephrine, prostaglandin F2 alpha, 5-hydroxytryptamine, and angiotensin II but not in the presence of phorbol 12,13-dibutyrate. The depressed vasodilation in hypercholesterolemic vessels appeared to depend on the agonist initiating the contraction. Sodium nitroprusside-induced relaxations were unchanged in rings from hypercholesterolemic rabbits compared with rings from control rabbits for all contractile agonists except KCl. Isolated aortic rings from hypercholesterolemic rabbits exhibited a slight but significantly increased vasoconstrictor sensitivity to 5-hydroxytryptamine and KCl but not to norepinephrine, prostaglandin F2 alpha, angiotensin II, or phorbol 12,13-dibutyrate compared with aortic rings from control rabbits. These results demonstrate that modest elevation of serum cholesterol is sufficient to depress vasodilator and enhance vasoconstrictor responses to certain agonists. Vasodilator effects are impaired to a greater extent by a small increase in serum cholesterol than are responses to vasoconstrictor agonists. It is postulated that the induction of differential alterations in vascular reactivity with moderate increase in serum cholesterol may represent important early events predisposing arteries to vasospasm.

Food restriction in female Wistar rats. II. β-adrenoceptor density in the cerebellum and in the splenic lymphocytes

The effect of diet restriction, applied on an every-other-day schedule from 3.5 months of age on, has been investigated on the beta-adrenoceptor density in the cerebellum and in the splenic lymphocytes of old female Wistar rats. Comparing animals 6 months and 24 months old fed ad libitum, a 75% age-dependent reduction in specific binding of the agonist dihydroalprenolol was observed in cerebellar membrane preparations, while the beta-adrenoceptor density of lymphocytes remained unaltered. Diet restriction induced a partial recovery of the age-related decrease of this parameter in the cerebellum without affecting the receptor density of lymphocytes. Present results suggest that undernutrition delays the appearance of those alterations related to aging.

Incorporation and effects of dietary eicosapentaenoate (20:5(n-3)) on plasma and erythrocyte lipids of the marmoset following dietary supplementation with differing levels of linoleic acid

The effect of dietary eicosapentaenoic acid (EPA, 20:5(n-3), as the ethyl ester) on plasma lipid levels and the incorporation of EPA into erythrocyte and plasma lipids were investigated in the marmoset monkey. Marmosets were fed high mixed-fat diets (14.5% total fat) supplemented with or without 0.8% EPA for 30 weeks. Markedly elevated plasma cholesterol (16.4 mmol/l) was induced by an atherogenic-type diet but with EPA supplementation, plasma cholesterol increased to only 6.6 mmol/l. Plasma triacylglycerol levels were not elevated with an atherogenic type diet. Substantial EPA incorporation was evident for plasma phospholipid, triacylglycerol and cholesterol ester fractions. The proportion of docosapentaenoic acid (22:5(n-3)) but not docosahexaenoic acid (22:6(n-3)) was also elevated in these plasma lipid fractions. Greatest incorporation of EPA occurred when it was administered with an atherogenic type diet having a P:M:S (polyunsaturated:monounsaturated:saturated) fatty acid ratio of about 0.2:0.6:1.0 in comparison to the control diet of 1.0:1.0:1.0. Incorporation of EPA and 22:5(n-3)) into erythrocyte phospholipids was also apparent and this was at the expense of linoleic acid (18:2(n-6)). These results in the marmoset highlight both the cholesterol-lowering properties of EPA and the extent of its incorporation into plasma lipids and erythrocyte membrane phospholipids with far greater incorporation occurring when the level of dietary linoleic acid was reduced.

Effects of dietary eicosapentaenoate (20:5 n-3) on cardiac beta-adrenergic receptor activity in the marmoset monkey

Eicosapentaenoic acid (EPA; 20:5 n-3; ethyl ester) in combination with atherogenic or non-atherogenic high fat diets was fed to young adult male marmoset monkeys for a period of 30 weeks. EPA markedly reduced the raised plasma cholesterol level evident when feeding an atherogenic diet but did not influence the cardiac membrane cholesterol-to-phospholipid ratio. EPA and its elongation product 22:5 n-3 was incorporated into cardiac membrane phospholipids at the expense of linoleic and arachidonic acids. Dietary EPA increased cardiac beta-AR affinity and reversed the decreased beta-AR affinity evident when feeding an atherogenic diet.