The efficacy and safety of pravastatin in patients aged 60 to 85 years with low-density lipoprotein cholesterol > 160 mg/dl.

This study demonstrated that pravastatin 20 mg once daily significantly lowered total cholesterol (by 19%) and LDL cholesterol by 25%.

Physical-chemical behavior of dietary and biliary lipids during intestinal digestion and absorption. 2. Phase analysis and aggregation states of luminal lipids during duodenal fat digestion in healthy adult human beings.

Following the feeding of a triacylglycerol-rich meal to healthy adult human beings, duodenal contents were aspirated for ex vivo chemical and physical-chemical analyses. The aspirates were collected during established lipid digestion and absorption into a "cocktail" of chemical inhibitors that rapidly inhibited ex vivo lipolysis. Following ultracentrifugation, the lipids separated into a floating oil layer, several interfacial layers, a "clear" or turbid "subphase", and a precipitated "pellet". By chemical and phase analyses, the floating layer was composed of oil-in-water emulsion particles with cores of triacylglycerol (TG), diacylglycerols (DG), and cholesteryl esters (CE) emulsified with a surface coat of partially ionized fatty acids (FA), monoacylglycerols (MG), diacylphosphatidylcholine (PL), and bile salts (BS). The interfacial layers contained similar emulsion particles dispersed among excess emulsifier which adopted a lamellar liquid-crystalline structure. Precipitated pellets were composed principally of emulsifying lipids, with smaller amounts of crystalline calcium soaps and BS. Relative lipid compositions of all but three subphases fell within a two-phase region of the condensed ternary phase diagram (Staggers et al., 1990, companion paper) where saturated mixed micelles composed of BS, FA "acid-soaps", MG, PL, cholesterol (Ch), and traces of DG (and TG) coexisted with unilamellar liquid-crystalline vesicles composed of the same lipids. Attempts to achieve clean separation of vesicles from micelles by repeat ultracentrifugation failed. Compared with the structure and sizes of lipid particles in equilibrated model systems (Staggers et al., 1990), quasielastic light scattering (QLS) analysis revealed that ex vivo micellar sizes (mean hydrodynamic radii, Rh) were similar (less than or equal to 40 A), whereas unilamellar vesicle sizes (Rh = 200-600 A) were appreciably smaller. Two-component QLS analysis of the subphases showed that much larger proportions of lipids were solubilized by micelles than were dispersed as unilamellar vesicles. When followed as functions of time, vesicles frequently dissolved spontaneously into mixed micelles, indicating that, in the nonequilibrium in vivo conditions, the constituent micellar phase was often unsaturated with lipids. These results are consistent with the hypothesis that, during hydrolysis of emulsified DG and TG by luminal lipases, unilamellar vesicles originate in lamellar liquid crystals that form at emulsion-water interfaces in the upper small intestine. In a BS-replete environment, unilamellar vesicles probably represent the primary dispersed product phase of human fat digestion and facilitate the dissolution of lipolytic products into unsaturated mixed micelles.(ABSTRACT TRUNCATED AT 400 WORDS)

Physical-chemical behavior of dietary and biliary lipids during intestinal digestion and absorption. 1. Phase behavior and aggregation states of model lipid systems patterned after aqueous duodenal contents of healthy adult human beings.

We developed equilibrium phase diagrams corresponding to aqueous lipid compositions of upper small intestinal contents during lipid digestion and absorption in adult human beings. Ternary lipid systems were composed of a physiological mixture of bile salts (BS), mixed intestinal lipids (MIL), principally partially ionized fatty (oleic) acid (FA) plus racemic monooleylglycerol (MG), and cholesterol (Ch), all at fixed aqueous-electrolyte concentrations, pH, temperature, and pressure. The condensed phase diagram for typical physiological conditions (1 g/dL total lipids, FA:MG molar ratio of 5:1, pH 6.5, 0.15 M Na+ at 37 degrees C) was similar to that of a dilute model bile [BS/lecithin (PL)/Ch] system [Carey, M. C., & Small, D. M. (1978) J. Clin. Invest. 61, 998-1026]. We identified two one-phase zones composed of mixed micelles and lamellar liquid crystals, respectively, and two two-phase zones, one composed of Ch monohydrate crystals and Ch-saturated micelles and the other of physiologic relevance composed of Ch- and MIL-saturated mixed micelles and unilamellar vesicles. A single large three-phase zone in the system was composed of Ch-saturated micelles, Ch monohydrate crystals, and liquid crystals. Micellar phase boundaries for otherwise typical physiological conditions were expanded by increases in total lipid concentration (0.25-5 g/dL), pH (5.5-7.5), and FA:MG molar ratio (5-20:1), resulting in a reduction of the size of the physiological two-phase zone. Mean particle hydrodynamic radii (Rh), measured by quasielastic light scattering (QLS), demonstrated an abrupt increase from micellar (less than 40 A) to micelle plus vesicle sizes (400-700 A) as this two-phase zone was entered. With relative lipid compositions within this zone, unilamellar vesicles formed spontaneously following coprecipitation, and their sizes changed markedly as functions of time, reaching equilibrium values only after 4 days. Further, vesicle Rh values were influenced appreciably by MIL:mixed bile salt (MBS) ratio, pH, total lipid concentration, and FA:MG ratio, but not by Ch content. In comparison, micellar systems equilibrated rapidly, and their Rh values only slightly influenced by physical-chemical variables of physiological importance. In contrast to the BS-PL-Ch system [Mazer, N. A., & Carey, M. C. (1983) Biochemistry 22, 426-442], no divergence in micellar sizes occurred as the micellar phase boundary was approached. The ionization state of FA at simulated "intestinal" pH values (5.5-7.5) in the micellar and physiologic two-phase zones was principally that of 1:1 sodium hydrogen dioleate, an insoluble swelling "acid soap" compound. By phase separation and analysis, tie-lines for the constituent phase in the two-phase zone demonstrated that the mixed micelles were saturated with MIL and Ch and the coexisting vesicles were saturated with MBS, but not with Ch.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of simvastatin and probucol in hypercholesterolemia (Simvastatin Multicenter Study Group II).

This 12-week, randomized, double-blind, multicenter study compared the efficacy, tolerability and safety of simvastatin (a potent HMG-CoA reductase inhibitor) and probucol. Two doses of simvastatin, 20 or 40 mg once daily, were compared to probucol, 500 mg twice daily. Both simvastatin doses were significantly more effective than probucol in improving the plasma lipid profile. Mean reduction in low density lipoprotein (LDL) cholesterol was 34% with 20-mg simvastatin and 40% with the 40-mg dosage, compared to a mean reduction of 8% with probucol. Simvastatin significantly decreased total cholesterol, triglycerides and apolipo-protein B, and increased high density lipoprotein (HDL) cholesterol and apolipoprotein A-I. Probucol caused some reduction in LDL cholesterol but significantly decreased HDL cholesterol. Both simvastatin and probucol were well tolerated and no serious drug-related events occurred. Simvastatin appears to be a well-tolerated and effective new agent used once-a-day as an adjunct to diet in the management of patients with hypercholesterolemia.

Occurrence of beta-hydroxylated asparagine residues in non-vitamin K-dependent proteins containing epidermal growth factor-like domains.

Vitamin K-dependent bovine protein S has been shown to contain a posttranslationally hydroxylated asparagine within a conserved sequence in three of its epidermal growth factor (EGF)-like domains. In a review of amino acid sequences deduced from cDNA data, we have observed that a conserved sequence containing a potential asparagine hydroxylation site exists within EGF-like domains of a variety of functionally diverse proteins. We have studied a number of these and report the presence of erythro-beta-hydroxyasparagine (e-beta Hyn) in three non-vitamin K-dependent proteins: the plasma complement proteins C1r and C1s (where overbar indicates activated form) and the urinary protein uromodulin. For each protein, e-beta Hyn was identified in enzyme digests following the initial observation of erythro-beta-hydroxyaspartic acid (e-beta Hya) in acid hydrolysates of the proteins. e beta Hya and e-beta Hyn residues are detected by a postcolumn derivatization cation-exchange HPLC method herein described. HPLC isolation of the presumptive e-beta Hyn residue from enzyme digests of intact C1r allowed confirmation of its structure by GC/MS. Based upon available cDNA sequence data and observation of e-beta Hya in acid hydrolysates, we suggest other proteins in which e-beta Hyn may occur.

Effects of pH and exocyclic substitution on flavosemiquinone reactivity with redox proteins and inorganic oxidants.

The effect of pH on the reaction of free flavosemiquinone analogs generated by laser-flash photolysis with oxidized Chromatium vinosum high-potential iron-sulfur protein, other iron-containing redox proteins, and nonbiological one-electron oxidants has been investigated. The results demonstrate that the second-order rate constant for the oxidation of lumiflavin flavosemiquinone increases dramatically with increasing pH for the redox proteins and some of the other oxidants. The pH-rate constant profiles for the redox proteins closely follow the ionization of the proton at the N-5 position of the neutral lumiflavin flavosemiquinone, suggesting a higher intrinsic reactivity for the anionic lumiflavin flavosemiquinone. This increased reactivity apparently results from changes in the redox potential and in the electron spin density distribution between the two protonic forms of the semiquinone. Similar pH dependencies are observed for a number of other flavin structural analogs, yielding estimates of the N-5 pK values for these analogs. The data are consistent with the involvement of both the N-5-dimethylbenzene ring portion and the C-4a position of the flavin macrocycle in flavosemiquinone oxidation by one-electron oxidants.

Studies on fat digestion, absorption, and transport in the suckling rat. III. Composition of bile and evidence for enterohepatic circulation of bile salts.

Biliary secretions from suckling rats (10-15 days old) were characterized: bile flow rate was 197.3 microliters/hr per 100 g; bile salt pool size was 19.0 mumol/100 g; secretion rate was 14.5 mumol/hr per 100 g; synthesis rate was 12.0 mumol/day; and the daily turnover frequency was 18.3. Phospholipid and cholesterol secretion rates were 2.3 mumol/hr per 100 g and 0.17 mumol/hr per 100 g, respectively. The bile salt concentration in portal plasma was 0.17 mumol/ml. The fatty acid composition of biliary phosphatidylcholine and ethanolamine, as well as the stereospecific distribution of fatty acids in the former, were similar to that found in phospholipids from adult rat bile. Compositional analysis of bile acids showed greater than 98% taurine conjugates consisting of approximately 54% cholic acid, 40% beta-muricholic acid, 2% chenodeoxycholic acid, and 1% each of deoxycholic and hyodeoxycholic acids. Through the use of intestinal and liver perfusion experiments, we have obtained evidence for enterohepatic circulation of taurocholate in neonatal rats. The level of bile salts found in intestinal contents (49.5 mumol/g), and the biliary phospholipid concentration (11.8 mM) both exceed adult values (6-10 mumol/g and 6.3 mM, respectively) and may be important for the utilization of the large amount of milk triacylglycerols ingested during the suckling period.

Studies on fat digestion, absorption, and transport in the suckling rat. II. Triacylglycerols: molecular species, stereospecific analysis, and specificity of hydrolysis by lingual lipase.

Triacylglycerols (TG) of rat milk supply about two-thirds of the energy consumed by suckling rat pups. The present studies were undertaken to determine stereospecific fatty acid composition and molecular species distribution of milk TG and TG produced during digestion, transported in lymph and blood, and present in the liver of 9-- 10-day-old pups. Results support non-random stereochemical fatty acid and molecular species distribution for all TG's analyzed. Stereospecific compositional results show loss of medium chain fatty acids (MCFA) during digestion, producing a shift to a larger average molecular weight TG than present in milk. These MCFA are esterified primarily at the sn-3 position of milk TG and appear to be hydrolyzed by the action of lingual lipase in the stomach. In vitro incubation of milk with tongue homogenate yields free fatty acids and glyceride products that resemble those found in suckling stomach contents. Further TG metabolism appears to involve redistribution of the long chain fatty acids that remain esterified in TG following gastric lipolysis and release of MCFA.

Studies on fat digestion, absorption, and transport in the suckling rat. I. Fatty acid composition and concentrations of major lipid components.

The lipids of rat milk, the contents of 9-- 10-day-old rat stomach and intestine, lymph, plasma, and liver were quantitated and their fatty acids were analyzed. Rat milk consists of 97% triacylglycerols, of which 35% of the fatty acids are of medium chain length (C8-C12). However, stomach triacylglycerols show a 25% reduction in medium chain fatty acids, which indicates preferential hydrolysis of medium chain fatty acids in the stomach. The intestinal lumen free fatty acid composition shows decreased medium chain fatty acids compared to long chain fatty acids, indicating preferential absorption of the former. Lymph was shown to contain a significant amount (approximately 22%) of medium chain fatty acids. The decreased content of medium chain fatty acids in vena cava blood compared to portal blood, and also the lower concentration of medium chain fatty acids in liver compared to blood, indicates preferential use of these fatty acids by the liver.