Influence of age and sex on composition and lipid fluidity in miniature swine plasma lipoproteins

Sex as a Biological Variable in Atherosclerosis

Atherosclerosis is a chronic inflammatory vascular disease and the predominant cause of heart attack and ischemic stroke. Despite the well-known sexual dimorphism in the incidence and complications of atherosclerosis, there are relatively limited data in the clinical and preclinical literature to rigorously address mechanisms underlying sex as a biological variable in atherosclerosis. In multiple histological and imaging studies, overall plaque burden and markers of inflammation appear to be greater in men than women and are predictive of cardiovascular events. However, while younger women are relatively protected from cardiovascular disease, by the seventh decade, the incidence of myocardial infarction in women ultimately surpasses that of men, suggesting an interaction between sex and age. Most preclinical studies in animal atherosclerosis models do not examine both sexes, and even in those that do, well-powered direct statistical comparisons for sex as an independent variable remain rare. This article reviews the available data. Overall, male animals appear to have more inflamed yet smaller plaques compared to female animals. Plaque inflammation is often used as a surrogate end point for plaque vulnerability in animals. The available data support the notion that rather than plaque size, plaque inflammation may be more relevant in assessing sex-specific mechanisms since the findings correlate with the sex difference in ischemic events and mortality and thus may be more reflective of the human condition. Overall, the number of preclinical studies directly comparing plaque inflammation between the sexes is extremely limited relative to the vast literature exploring atherosclerosis mechanisms. Failure to include both sexes and to address age in mechanistic atherosclerosis studies are missed opportunities to uncover underlying sex-specific mechanisms. Understanding the mechanisms driving sex as a biological variable in atherosclerotic disease is critical to future precision medicine strategies to mitigate what is still the leading cause of death of men and women worldwide.

Effect of Age on Diabetogenicity of Alloxan in Ossabaw Miniature Swine

According to a single study in dogs that was conducted in 1949, the diabetic effects of the β-cell toxin alloxan are dependent on age. The current study examined whether this age-dependence of alloxan is present in the clinically relevant Ossabaw miniature swine (Sus scrofa domestica) model of metabolic syndrome. Juvenile swine (n = 8; age, 4.3 ± 0.2 mo) and adult swine (n = 8; age, 7.4 ± 0.2 mo) received alloxan (average dosage, 140 mg/kg IV) and were placed on a hypercaloric, atherogenic diet for 6 mo. The metabolic syndrome profile was confirmed by measuring body weight, cholesterol, and triglycerides. Intravenous glucose tolerance testing was used to assess glucose clearance and peripheral plasma insulin levels. The β-cell mass was calculated by immunohistochemical staining of pancreatic tissue. Although juvenile and adult swine exhibited comparable severity of metabolic syndrome, adult swine developed impaired glucose clearance and elevated fasting blood glucose levels at 6 mo after alloxan administration on the atherogenic diet. Peripheral plasma insulin levels in juvenile and adult swine were comparable at all time points and lower than in nonalloxan-treated age-matched controls, which is reflected in the lower pancreatic β-cell mass of the 2 treated groups. However, compared with adult pigs, juvenile swine exhibited greater insulin response recovery (complete or partial restoration of peripheral insulin levels to reference values) at 6 mo after alloxan administration. Overall, these results indicate that youth can confer some protection against the diabetogenic effects of alloxan in swine, potentially due in part to the greater insulin response recovery of young pigs. This study supports previous research that the effects of alloxan are dependent on the developmental maturity of the animal.

Cholesterol-lowering properties of Ganoderma lucidum in vitro, ex vivo, and in hamsters and minipigs

INTRODUCTION

There has been renewed interest in mushroom medicinal properties. We studied cholesterol lowering properties of Ganoderma lucidum (Gl), a renowned medicinal species.

RESULTS

Organic fractions containing oxygenated lanosterol derivatives inhibited cholesterol synthesis in T9A4 hepatocytes. In hamsters, 5% Gl did not effect LDL; but decreased total cholesterol (TC) 9.8%, and HDL 11.2%. Gl (2.5 and 5%) had effects on several fecal neutral sterols and bile acids. Both Gl doses reduced hepatic microsomal ex-vivo HMG-CoA reductase activity. In minipigs, 2.5 Gl decreased TC, LDL- and HDL cholesterol 20, 27, and 18%, respectively (P < 0.05); increased fecal cholestanol and coprostanol; and decreased cholate.

CONCLUSIONS

Overall, Gl has potential to reduce LDL cholesterol in vivo through various mechanisms. Next steps are to: fully characterize bioactive components in lipid soluble/insoluble fractions; evaluate bioactivity of isolated fractions; and examine human cholesterol lowering properties. Innovative new cholesterol-lowering foods and medicines containing Gl are envisioned.

Effect of lovastatin on lipoprotein fluidity in patients with hypercholesterolaemia

Lovastatin was administered to six hypercholesterolaemic patients (mean plasma cholesterol 450 mg dl-1). Plasma lipoproteins (VLDL, LDL, and HDL) were separated before and following 7 and 12 weeks treatment with lovastatin. Fluidity was quantified by fluorescence polarization measurements using 1,6-diphenyl 1,3,5 hexatriene (DPH) as the fluorescent probe. Lovastatin treatment resulted in a significant reduction of total plasma cholesterol, LDL cholesterol and VLDL cholesterol (-41%, -44%, -68%, respectively). Fluidity measurements showed significant (p < 0.01) increase in LDL fluidity by 11% and 21% after 7 and 12 weeks of lovastatin treatment, whereas, VLDL fluidity was increased by 27% after 12 weeks of therapy. HDL fluidity was not altered. These alterations in the fluidity of the atherogenic lipoproteins (LDL and VLDL) in hypercholesterolaemic patients may prove to be of significance in reducing the risk of atherosclerosis.

Plasma and red blood cell fatty acid values as indexes of essential fatty acids in the developing organs of infants fed with milk or formulas

The dietary requirement of n-6 and n-3 fatty acids for normal biochemical and functional development of the central nervous system (CNS) is an important, unresolved issue in infant nutrition. High levels of arachidonic acid (AA; 20:4n-6) and docosahexaenoic acid (DHA; 22:6n-3) are found in the CNS and are important to normal learning and visual function. Dietary fatty acids may be desaturated and elongated to AA and DHA, respectively, but may also be oxidized for energy. Synthesis of AA and DHA in the young infant, therefore, depends on adequate desaturase enzyme activity, as well as an adequate supply of dietary 18:2n-6, 18:3n-3, and energy. Levels of AA and DHA are lower in the plasma and red blood cell (RBC) lipids of infants fed formula rather than human milk and are not increased with increased formula 18:2n-6 or 18:3n-3 supply. The decline in AA and DHA in infants fed formula becomes evident in the order plasma phospholipid greater than RBC phosphatidylcholine greater than RBC phosphatidylethanolamine. As in infants, piglets fed formula rather than natural milk have lower plasma and RBC AA and DHA concentrations. Despite lower levels in the plasma and RBC, analyses of CNS lipids demonstrated adequate AA and DHA in piglets fed formula with greater than 7% kcal 18:2n-6 and greater than 0.3% kcal 18:3n-3. This finding suggests that circulating lipid fatty acids are not specific indexes of organ deficiency. The rapid decrease in circulating lipid AA and DHA concentrations experienced by premature infants during early postnatal parenteral and enteral nutrition, however, may be related to oxidation of 18:2n-6 and 18:3n-3, rather than equilibrium of circulating lipids with the dietary fatty acids. Arachidonic acid and DHA may be conditionally essential nutrients for these infants because of oxidation of 18:2n-6 and 18:3n-3 for energy during periods of negative energy balance.

Dietary fat and hormonal influences on lipoprotein fluidity and composition in premenopausal women

LDL and HDL became more fluid when health, free-living, premenopausal women were fed reduced fat diets with higher proportions of polyunsaturated fatty acids. Lipoproteins were isolated from plasma of 31 female subjects fed one of two sets of diets from typical U.S.A. foods with P/S ratios of 0.3 or 1.0. All subjects were fed high-fat diets (40% of energy) for the duration of four menstrual cycles followed by low-fat diets (20% of energy) for the next four cycles. Blood samples were collected during mid-follicular and mid-luteal phases of the fourth menstrual cycle of each diet period to assess interactive dietary and hormonal control of lipoprotein fluidity. LDL was significantly more fluid, as determined by DPH fluorescence, upon reducing fat consumption from 40 to 20% of energy for subjects eating foods with P/S = 1.0 or 0.3. Generally LDL was more fluid during the follicular phase than the luteal phase of the cycles, thus indicating hormonal influences on LDL fluidity. HDL results were similar but not as pronounced as with LDL. Lipoprotein phospholipid (PL) and cholesteryl ester (CE) fatty acyl compositions were also subject to dietary and hormonal influences. Effects were noted in several fatty acids depending upon diet and hormonal state; however, generally diet fat reduction resulted in reduced linoleate and increased oleate contents. Regression analyses showed that fluidity was more dependent upon the lipoprotein cholesterol content than upon fatty acyl composition.

Dietary fat and cholesterol induced modification of minipig lipoprotein fluidity and composition

1. Miniature swine were fed a low (2.7%) fat control stock diet alone or supplemented with either 20% lard plus 1% cholesterol or 20% lard alone for periods of up to 6 months. 2. Cholesterol feeding reduced VLDL fluidity drastically and LDL fluidity minimally but had no effect on HDL fluidity. 3. Lard feeding had no effect on lipoprotein fluidity. 4. The rigid VLDL produced by cholesterol feeding was enriched in cholesterol and phospholipid contents, similar to beta-VLDL. 5. Plasma cholesterol concentrations were increased by 1.5 to 5-fold in pigs fed stock diets supplemented with 20% lard, with or without added cholesterol, but plasma triacylglycerol concentrations were not affected by either diet modification. 6. Diet effects were complete within 4 weeks with no further changes for periods up to 6 months. 7. Regression of the induced hypercholesterolemia was also accomplished within one month of removing cholesterol from the diet.