Mechanisms of anti-atherosclerotic functions of soy-based diets

Soy-based diets have been reported to protect against the development of atherosclerosis. However, the underlying mechanism(s) for this protection remains unknown. Although atherosclerosis was traditionally considered a disease associated with impaired lipid metabolism, in recent years the inflammatory components of atherosclerosis have been explored. Recent studies have convincingly delineated that uncontrolled chronic inflammation is the principal contributing factor for the initiation and progression of atherosclerosis. Interaction between activated monocytes and vascular endothelial cells is an early event in atherogenesis. The adhesion of leukocytes, including monocytes, to the inflamed-vascular endothelium and their transmigration into intima initiate the inflammatory processes. Following transmigration, monocytes in the intima are transformed to macrophages, which take up oxidized-LDL (oxLDL) to generate lipid-laden macrophages, also known as foam cells. Hence, in this review article the inflammatory processes associated with atherosclerosis and possible anti-inflammatory functions of soy-based diets contributing to the prevention of atherosclerosis are presented.     

Nif-hybrids of Enterobacter: selection for nif gene integration with chlorate

The nif gene group from Klebsiella can be transferred into Enterobacter cloacae by conjugation using Escherichia coli donor cells carrying the composite self-transmissible nif-plasmid pRD1. A small fraction of the hybrids obtained is stable upon prolonged passaging without selection. Their stability is due to integration of pRD1 into the chromosome. Such integration hybrids were chlorate resistant, and nitrate reductase negative, which indicated that integration preferentially occurred within one of the genes for the production or functioning of this enzyme. Chlorate resistance could, therefore, be used to select for additional nitrate reductase-negative sublines with pRD1 in their chromosome. Such sublines have been analyzed further for the presence of nif genes, other pRD1 markers, and for stability. In all except one the complete plasmid seems to have been integrated. Some tend to revert to nitrate utilisation (chlorate sensitivity).     

Hepatic glycogen metabolism in the db/db mouse

Summary Knowledge of the metabolic changes that occur in insulin-resistant type 2 diabetes is relatively lacking compared to insulin-deficient type 1 diabetes. This paper summarizes the importance of the C57BL/KsJ-db/db mouse as a model of type 2 diabetes, and illustrates the effects that insulin-deficient and insulin-resistant states have on hepatic glycogen metabolism. A longitudinal study of db/db mice of ages 2–15 weeks revealed that significant changes in certain parameters of hepatic glycogen metabolism occur during this period. The liver glycogen levels were similar between diabetic and control mice. However, glycogen particles from db/db mice were on average smaller in mass and had shorter exterior and interior chain lengths. Total phosphorylase and phosphorylase a activities were elevated in the genetically diabetic mice. This was primarily due to an increase in the amount of enzymic protein apparently the result of a decreased rate of degradation. It was not possible to find a consistent alteration in glycogen synthase activity in the db/db mice. Glycogen synthase and phosphorylase from diabetic liver revealed some changes in kinetic properties in the form of a decrease in V_max, and altered sensitivity to inhibitors like ATP. The altered glycogen structure in db/db mice may have contributed to changes in the activities and properties of glycogen synthase and phosphorylase. The exact role played by hormones (insulin and glucagon) in these changes is not clear but further studies should reveal their contributions. The db/db mouse provides a good model for type 2 diabetes and for fluctuating insulin and glucagon ratios. Its use should clarify the regulation of hepatic glycogen metabolism and other metabolic processes known to be controlled by these hormones. The other animal models of type 2 diabetes, ob/ob mouse and fatty Zucker (fa/fa) rat, show similar impairment of hepatic glycogen metabolism. The concentrations of glycogen metabolizing enzymes are high and in vitro studies indicate enhanced rate of glycogen synthesis and breakdown. However, streptozotocin-induced diabetic animals and BB rats which resemble insulin-deficient type 1 diabetes are characterized by decreased glycogen turnover as a result of reduction in the levels of glycogen metabolizing enzymes.     

Effect of cycloheximide and growth factors on gene expression in quiescent mouse embryo fibroblasts

Gene expression in quiescent mouse embryo fibroblasts was studied by labelling the cells with [14C] amino acids and analysing the proteins by electrophoresis in polyacrylamide gradient gels containing sodium dodecyl sulfate. Cycloheximide (CH) pretreatment of the cells was found to induce the synthesis of four proteins of molecular weights 72,000, 68,000, 42,000, and 29,000. These proteins were induced by CH both in serum-arrested and serum-stimulated cells. Addition of platelet-derived growth factor to serum-arrested quiescent cells also induced the synthesis of these proteins. Addition of CH and fetal calf serum (20%) to quiescent cells resulted in a dramatic increase in the synthesis of actin and another protein of molecular weight 29,000. The 29,000-dalton protein was present in higher quantities in the nuclei of induced cells. This protein appeared to be an early protein whose synthesis was transiently induced in quiescent cells within 3 hours of addition of 20% fetal calf serum (FCS). The synthesis of this protein was virtually turned off at 5-6 hours after the addition of serum. However, if CH or a combination of CH and FCS was present, a continuous synthesis of the 29 K protein was observed.     

Human breast milk stimulates prostaglandin synthesis in cultured human skin fibroblasts

Effect of human breast milk or its fractions on prostaglandin synthesis was investigated in cultured human skin fibroblasts. Prostaglandins released into the media were measured by radioimmunoassay. Incorporation of breast milk (2% level) into 10% fetal calf serum media (for 48 hours) stimulated the synthesis of 6-keto-PGF1 alpha (stable product of prostacyclin) by 800%. This stimulating effect of milk persisted after cold acetone extraction to remove phospholipids and potentiated further after dialysis. Stimulation by one of the commercial formulas (Similac) was less than 50% of the milk effect. Milk also stimulated PGE2 synthesis, although to a much lesser degree. These studies show for the first time that a) human breast milk contains potent factor(s) capable of influencing prostaglandin synthesis and suggest that b) these factors might have a role in the development of lipid synthetic pathways during early life.     

Ontogeny of guinea pig liver cholesterol 7 alpha-hydroxylase: unexpected inverse correlation of enzyme activity with expanding bile acid pool

Changes in the activity of guinea pig liver cholesterol 7 alpha-hydroxylase (rate limiting enzyme of cholesterol catabolism) from birth to adult life was investigated using a microsomal acetone extraction method (to remove endogenous cholesterol). Contrary to the previously held notion, it was noted that while the total bile acid pool increased progressively with age after birth, hepatic cholesterol 7 alpha-hydroxylase specific activity declined. Neonatal hepatic cholesterol 7 alpha-hydroxylase showed an increase in enzyme activity in response to cell supernatant factors (100,000 xg supernatant) from neonatal livers, but not from adult livers.     

Cloning of hydrogenase genes and fine structure analysis of an operon essential for H2 metabolism in Escherichia coli.

Escherichia coli has two unlinked genes that code for hydrogenase synthesis and activity. The DNA fragments containing the two genes (hydA and hydB) were cloned into a plasmid vector, pBR322. The plasmids containing the hyd genes (pSE-290 and pSE-111 carrying the hydA and hydB genes, respectively) were used to genetically map a total of 51 mutant strains with defects in hydrogenase activity. A total of 37 mutants carried a mutation in the hydB gene, whereas the remaining 14 hyd were hydA. This complementation analysis also established the presence of two new genes, so far unidentified, one coding for formate dehydrogenase-2 (fdv) and another producing an electron transport protein (fhl) coupling formate dehydrogenase-2 to hydrogenase. Three of the four genes, hydB, fhl, and fdv, may constitute a single operon, and all three genes are carried by a 5.6-kilobase-pair chromosomal DNA insert in plasmid pSE-128. Plasmids carrying a part of this 5.6-kilobase-pair DNA (pSE-130) or fragments derived from this DNA in different orientations (pSE-126 and pSE-129) inhibited the production of active formate hydrogenlyase. This inhibition occurred even in a prototrophic E. coli, strain K-10, but only during an early induction period. These results, based on complementation analysis with cloned DNA fragments, show that both hydA and hydB genes are essential for the production of active hydrogenase. For the expression of active formate hydrogenlyase, two other gene products, fhl and fdv are also needed. All four genes map between 58 and 59 min in the E. coli chromosome.     

Regulation of hydrogenase activity in vegetative cells of Anabaena variabilis.

Heterocyst-free (NH4+-grown) cultures of the cyanobacterium Anabaena variabilis produce a hydrogenase which is reversibly inhibited by light and O2. White or red light at an intensity of 5,000 lx inhibited greater than 95% of the activity. Oxygen at concentrations as low as 0.5% inhibited more than 85% of the hydrogenase in the vegetative cells of CO2-NH4+-grown cultures. The vegatative cell hydrogenase is also sensitive to strong oxidants like ferricyanide. In the presence of strong reductants like S2O4(2-), hydrogenase activity was not inhibited by light. However, hydrogenase activity in the heterocysts was insensitive to both light (greater than 5,000 lx) and O2 (10%). Heterocysts and light-insensitive hydrogenase activity appear simultaneously during differentiation of the vegetative cells into heterocysts (an NH4+-grown culture transferred to NH4+-free, N2-containing medium). This light-insensitive hydrogenase activity was detected several hours before the induction of nitrogenase activity. These results suggest a mode of regulation of hydrogenase in the vegetative cells of A. variabilis that is similar to "redox control" of hydrogenase and other "anaerobic" proteins in enteric bacteria like Escherichia coli.