The associations of cholesterol metabolism and plasma plant sterols with all-cause and cardiovascular mortality

Moderately elevated levels of plasma plant sterols have been suspected to be causally involved in atherosclerosis. The aim of this study was to investigate whether plant sterols and other markers of sterol metabolism predicted all-cause and cardiovascular mortality in participants of the Ludwigshafen Risk and Cardiovascular health (LURIC) study. A total of 1,257 individuals who did not use statins and at baseline had a mean (± SD) age of 62.8 (± 11.0) years were included in the present analysis. Lathosterol, cholestanol, campesterol, and sitosterol were measured to estimate cholesterol synthesis and absorption. The mean (± SD) time of the follow-up for all-cause and cardiovascular mortality was 7.32 (± 2.3) years. All-cause (P = 0.001) and cardiovascular (P = 0.006) mortality were decreased in the highest versus the lowest lathosterol to cholesterol tertile. In contrast, subjects in the third cholestanol to cholesterol tertile had increased all-cause (P < 0.001) and cardiovascular mortality (P = 0.010) compared with individuals in the first tertile. The third campesterol to cholesterol tertile was associated with increased all-cause mortality (P = 0.025). Sitosterol to cholesterol tertiles were not significantly related to all-cause or cardiovascular mortality. The data suggest that high absorption and low synthesis of cholesterol predict increased all-cause and cardiovascular mortality in LURIC participants.     

In Vivo Effects of Free Form Astaxanthin Powder on Anti-Oxidation and Lipid Metabolism with High-Cholesterol Diet

Astaxanthin extracted from Pomacea canaliculata eggs was made into free-form astaxanthin powder (FFAP) and its effects on lipid metabolism, liver function, antioxidants activities and astaxanthin absorption rate were investigated. 45 hamsters were split into 5 groups and fed with normal diet, high-cholesterol control (0.2% cholesterol), 1.6FFAP (control+1.6% FFAP), 3.2FFAP (control+3.2% FFAP) and 8.0FFAP (control+8.0% FFAP), respectively, for 6 weeks. FFAP diets significantly decreased the liver total cholesterol, triglyceride levels and increased liver fatty acids (C20:5n3; C22:6n3) compositions. It decreased plasma alanine aminotransferase and aspartate aminotransferase. In terms of anti-oxidative activities, we found 8.0 FFAP diet significantly decreased plasma and liver malonaldehyde (4.96±1.96 μg TEP eq./mL and 1.56±0.38 μg TEP eq./g liver) and liver 8-isoprostane levels (41.48±13.69 μg 8-ISOP/g liver). On the other hand, it significantly increased liver catalase activity (149.10±10.76 μmol/min/g liver), Vitamin C (2082.97±142.23 μg/g liver), Vitamin E (411.32±81.67 μg/g liver) contents, and glutathione levels (2.13±0.42 mg GSH eq./g liver). Furthermore, 80% of astaxanthin absorption rates in all FFAP diet groups suggest FFAP is an effective form in astaxanthin absorption. Finally, astaxanthin was found to re-distribute to the liver and eyes in a dose dependent manner. Taken together, our results suggested that the appropriate addition of FFAP into high cholesterol diets increases liver anti-oxidative activity and reduces the concentration of lipid peroxidase and therefore, it may be beneficial as a material in developing healthy food.     

Insulin sensitivity regulates cholesterol metabolism to a greater extent than obesity: lessons from the METSIM Study

Cholesterol synthesis is upregulated and absorption downregulated in insulin resistance and in type 2 dia-betes. We investigated whether alterations in cholesterol metabolism are observed across the glucose tolerance status, from normoglycemia through impaired glucose tolerance to type 2 diabetes, in 781 randomly selected men 45 to 70 years of age from a population-based Metabolic Syndrome in Men Study. Cholesterol metabolism was assayed using surrogate serum markers, squalene, and noncholesterol sterols. The study population was classified into subgroups according to glucose tolerance as follows: normoglycemia, impaired fasting glucose, impaired glucose tolerance, and type 2 diabetes. LDL cholesterol did not differ between the groups. Cholesterol synthesis markers were lowest and absorption markers highest in normoglycemia. Sitosterol was lower in subjects with impaired fasting glucose compared with normoglycemic subjects (113 ± 7 vs. 136 ± 3 10² μmol/mmol of cholesterol, P < 0.05). LDL cholesterol was not associated with lathosterol/sitosterol ratio, a marker of cholesterol metabolism. Peripheral insulin sensitivity evaluated by the Matsuda index was associated with the lathosterol/sitosterol ratio in the entire population (r = −0.457, P < 0.001) and with that of lathosterol/cholestanol independently of obesity. In conclusion, cholesterol metabolism was altered already from subjects with impaired fasting glucose. Upregulated cholesterol synthesis was associated with peripheral insulin resistance independent of obesity.     

ABCG5/G8 polymorphisms and markers of cholesterol metabolism: systematic review and meta-analysis

Genetic variation at the ABCG5/G8 locus has been associated with markers of cholesterol homeostasis. As data originate from small-scale studies, we performed a meta-analysis to study these associations in a large dataset. We first investigated associations between five common ABCG5/G8 polymorphisms (p.Q604E, p.D19H, p.Y54C, p.T400K, and p.A632V) and plasma sterol levels in 245 hypercholesterolaemic individuals. No significant associations were found. Subsequently, our data were pooled into a meta-analysis that comprised 3,364 subjects from 16 studies (weighted mean age, 46.7 ± 10.5 years; BMI, 23.9 ± 3.5 kg/m²). Presence of the minor 632V allele correlated with reduced LDL-C concentrations (n = 367) compared with homozygosity for the 632A variant [n = 614; −0.11 mmol/l (95% CI, range: −0.20 to −0.02 mmol/l); P = 0.01]. The remaining polymorphisms were not associated with plasma lipid levels. Carriers of the 19H allele exhibited lower campesterol/TC (n = 83; P < 0.001), sitosterol/TC (P < 0.00001), and cholestanol/TC (P < 0.00001), and increased lathosterol/TC ratios (P = 0.001) compared with homozygous 19D allele carriers (n = 591). The ABCG8 632V variant was associated with a clinically irrelevant LDL-C reduction, whereas the 19H allele correlated with decreased cholesterol absorption and increased synthesis without affecting the lipid profile. Hence, associations between frequently studied missense ABCG5/G8 polymorphisms and markers of cholesterol homeostasis are modest at best.     

Elevated serum squalene and cholesterol synthesis markers in pregnant obese women with gestational diabetes mellitus

We examined serum cholesterol synthesis and absorption markers and their association with neonatal birth weight in obese pregnancies affected by gestational diabetes mellitus (GDM). Pregnant women at risk for GDM (BMI >30 kg/m²) were enrolled from maternity clinics in Finland. GDM was determined from the results of an oral glucose tolerance test. Serum samples were collected at six time-points, one in each trimester of pregnancy, and at 6 weeks, 6 months, and 12 months postpartum. Analysis of serum squalene and noncholesterol sterols by gas-liquid chromatography revealed that in subjects with GDM (n = 22), the serum Δ8-cholestenol concentration and lathosterol/sitosterol ratio were higher (P < 0.05) than in the controls (n = 30) in the first trimester, reflecting increased cholesterol synthesis. Also, subjects with GDM had an increased ratio of squalene to cholesterol (100 × μmol/mmol of cholesterol) in the second (11.5 ± 0.5 vs. 9.1 ± 0.5, P < 0.01) and third (12.1 ± 0.8 vs. 10.0 ± 0.7, P < 0.05) trimester. In GDM, the second trimester maternal serum squalene concentration correlated with neonatal birth weight (r = 0.70, P < 0.001). In conclusion, in obesity, GDM associated with elevated serum markers of cholesterol synthesis. Correlation of maternal serum squalene with neonatal birth weight suggests a potential contribution of maternal cholesterol synthesis to newborn weight in GDM.     

Prostate secretory protein 94 inhibits sterol binding and export by the mammalian CAP protein CRISP2 in a calcium-sensitive manner

Members of the CAP protein superfamily are present in all kingdoms of life and have been implicated in many different processes, including pathogen defense, immune evasion, sperm maturation, and cancer progression. Most CAP proteins are secreted glycoproteins and share a unique conserved αβα sandwich fold. The precise mode of action of this class of proteins, however, has remained elusive. Saccharomyces cerevisiae has three CAP family members, termed pathogen related in yeast (Pry). We have previously shown that Pry1 and Pry2 export sterols in vivo and that they bind sterols in vitro. This sterol binding and export function of yeast Pry proteins is conserved in the mammalian CRISP proteins and other CAP superfamily members. CRISP3 is an abundant protein of the human seminal plasma and interacts with prostate secretory protein of 94 amino acids (PSP94), another major protein component in the seminal plasma. Here we examine whether the interaction between CRISP proteins and PSP94 affects the sterol binding function of CAP family members. We show that coexpression of PSP94 with CAP proteins in yeast abolished their sterol export function and the interaction between PSP94 and CAP proteins inhibits sterol binding in vitro. In addition, mutations that affect the formation of the PSP94–CRISP2 heteromeric complex restore sterol binding. Of interest, we found the interaction of PSP94 with CRISP2 is sensitive to high calcium concentrations. The observation that PSP94 modulates the sterol binding function of CRISP2 in a calcium-dependent manner has potential implications for the role of PSP94 and CRISP2 in prostate physiology and progression of prostate cancer.     

In vivo tissue cholesterol efflux is reduced in carriers of a mutation in APOA1

Atheroprotection by high density lipoprotein (HDL) is considered to be mediated through reverse cholesterol transport (RCT) from peripheral tissues. We investigated in vivo cholesterol fluxes through the RCT pathway in patients with low plasma high density lipoprotein cholesterol (HDL-c) due to mutations in APOA1. Seven carriers of the L202P mutation in APOA1 (mean HDL-c: 20 ± 19 mg/dl) and seven unaffected controls (mean HDL-c: 54 ± 11 mg/dl, P < 0.0001) received a 20 h infusion of ¹³C₂-cholesterol (¹³C-C). Enrichment of plasma and erythrocyte free cholesterol and plasma cholesterol esters was measured. With a three-compartment SAAM-II model, tissue cholesterol efflux (TCE) was calculated. TCE was reduced by 19% in carriers (4.6 ± 0.8 mg/kg/h versus 5.7 ± 0.7 mg/kg/h in controls, P = 0.02). Fecal ¹³C recovery and sterol excretion 7 days postinfusion did not differ significantly between carriers and controls: 21.3 ± 20% versus 13.3 ± 6.3% (P = 0.33), and 2,015 ± 1,431 mg/day versus 1456 ± 404 mg/day (P = 0.43), respectively. TCE is reduced in carriers of mutations in APOA1, suggesting that HDL contributes to efflux of tissue cholesterol in humans. The residual TCE and unaffected fecal sterol excretion in our severely affected carriers suggest, however, that non-HDL pathways contribute to RCT significantly.     

Omapatrilat,an Angiotensin-Converting Enzyme and Neutral Endopeptidase Inhibitor,Attenuates Early Atherosclerosis in Diabetic and in Nondiabetic Low-Density Lipoprotein Receptor–Deficient Mice

Omapatrilat inhibits both angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP). ACE inhibitors have been shown to inhibit atherosclerosis in apoE-deficient mice and in several other animal models but failed in low-density lipoprotein (LDL) receptor– deficient mice despite effective inhibition of the reninangiotensin- aldosterone system. The aim of the present study was to examine the effect of omapatrilat on atherogenesis in diabetic and nondiabetic LDL receptor–deficient mice. LDL receptor–deficient male mice were randomly divided into 4 groups (n = 11 each). Diabetes was induced in 2 groups by low-dose STZ, the other 2 groups served as nondiabetic controls. Omapatrilat (70 mg/kg/day) was administered to one of the diabetic and to one of the nondiabetic groups. The diabetic and the nondiabetic mice were sacrificed after 3 and 5 weeks, respectively. The aortae were examined and the atherosclerotic plaque area was measured. The atherosclerotic plaque area was significantly smaller in the omapatrilat-treated mice, both diabetic and nondiabetic, as compared to nontreated controls. The mean plaque area of omapatrilattreated nondiabetic mice was 9357 ± 7293 μm², versus 71977 ± 34610 μm² in the nontreated mice (P = .002). In the diabetic animals, the plaque area was 8887 ± 5386 μm² and 23220 ± 10400 μm², respectively for treated and nontreated mice (P = .001). Plasma lipids were increased by omapatrilat: Meanplasma cholesterol in treated mice, diabetic and nondiabetic combined, was 39.31 ± 6.00 mmol/L, versus 33.12 ± 7.64 mmol/L in the nontreated animals (P = .008). The corresponding combined mean values of triglycerides were 4.83 ± 1.93 versus 3.00 ± 1.26 mmol/L (P = .02). Omapatrilat treatment did not affect weight or plasma glucose levels. Treatment with omapatrilat inhibits atherogenesis in diabetic as well as nondiabetic LDL receptor–deficient mice despite an increase in plasma lipids, suggesting a direct effect on the arterial wall.     

Discovery of an ergosterol-signaling factor that regulates Trypanosoma brucei growth

Ergosterol biosynthesis and homeostasis in the parasitic protozoan Trypanosoma brucei was analyzed by RNAi silencing and inhibition of sterol C24β-methyltransferase (TbSMT) and sterol 14α-demethylase [TbSDM (TbCYP51)] to explore the functions of sterols in T. brucei growth. Inhibition of the amount or activity of these enzymes depletes ergosterol from cells at <6 fg/cell for procyclic form (PCF) cells or <0.01 fg/cell for bloodstream form (BSF) cells and reduces infectivity in a mouse model of infection. Silencing of TbSMT expression by RNAi in PCF or BSF in combination with 25-azalanosterol (AZA) inhibited parasite growth and this inhibition was restored completely by adding synergistic cholesterol (7.8 μM from lipid-depleted media) with small amounts of ergosterol (1.2 μM) to the medium. These observations are consistent with the proposed requirement for ergosterol as a signaling factor to spark cell proliferation while imported cholesterol or the endogenously formed cholesta-5,7,24-trienol act as bulk membrane components. To test the potential chemotherapeutic importance of disrupting ergosterol biosynthesis using pairs of mechanism-based inhibitors that block two enzymes in the post-squalene segment, parasites were treated with AZA and itraconazole at 1 μM each (ED₅₀ values) resulting in parasite death. Taken together, our results demonstrate that the ergosterol pathway is a prime drug target for intervention in T. brucei infection.     

Plasma Biomarker of Dietary Phytosterol Intake

BackgroundDietary phytosterols, plant sterols structurally similar to cholesterol, reduce intestinal cholesterol absorption and have many other potentially beneficial biological effects in humans. Due to limited information on phytosterol levels in foods, however, it is difficult to quantify habitual dietary phytosterol intake (DPI). Therefore, we sought to identify a plasma biomarker of DPI.ConclusionThe ratio of plasma campesterol to the coordinately regulated endogenous cholesterol metabolite 5-α-cholestanol is a biomarker of dietary phytosterol intake. Conversely, plasma phytosterol levels alone are not ideal biomarkers of DPI because they are confounded by large inter-individual variation in absorption and turnover of non-cholesterol sterols. Further work is needed to assess the relation between non-cholesterol sterol metabolism and associated cholesterol transport in the genesis of coronary heart disease.     

The Relationship Between Cholesterol Absorption and Intestinal Cholesterol Synthesis in the Diabetic Rat Model

The chylomicron remnant particle is thought to be particularly atherogenic and we have previously shown alterations in post-prandial lipoproteins which could contribute to their atherogenicity. Cholesterol metabolism is disturbed in diabetes, yet the effect of diabetes on intestinal cholesterol synthesis and absorption has rarely been investigated. The aim of this study was to examine cholesterol absorption and intestinal synthesis of cholesterol in the streptozotocin diabetic rat. Twelve diabetic rats were paired with 12 control rats. [¹⁴C]-Cholesterol emulsion was administered and the lymph duct was canulated. Lymph was collected for 4 h. At sacrifice blood was taken for plasma lipoprotein measurements. Chylomicrons were prepared from the lymph by ultracentrifugation and [¹⁴C]-cholesterol content was determined by liquid scintillation counting. Lymph apolipoprotein B48 was isolated by gradient gel electrophoresis, and quantified by densitometric scanning. Serum triglyceride and cholesterol were greatly elevated in diabetic compared to control animals (260 ± 90 and 9.8 ± 8.0 mg/ml vs. 1.0 ± 0.4 and 0.6 ± 0.3 mg/ml, p < 0.0001 respectively). Lymph chylomicron apo B48 was similar in the two groups. Cholesterol absorption was not significantly different in diabetic compared to control rats but cholesterol synthesis was significantly, higher in the diabetic animals (550 ± 352 vs. 322 ± 113 μg/h p < 0.03). There was a positive correlation between apo B48 and cholesterol absorption (r = 0.70, p < 0.01) in the diabetic rats and control rats (r = 0.71, p < 0.01) but no correlation between apo B48 and cholesterol synthesis in either group. This study demonstrates that cholesterol synthesis was increased in diabetes whereas cholesterol absorption was unaffected suggesting that intestinal cholesterol synthesis made an important contribution to the hypercholesterolaemia seen in the diabetic animals.     

Plasma non-cholesterol sterols in patients with non-insulin dependent diabetes mellitus.

Plasma plant sterol concentrations (an index of cholesterol absorption efficiency) and plasma lathosterol concentration (an index of cholesterol synthesis rate) were measured in 52 patients with non-insulin dependent diabetes mellitus (NIDDM) and 36 non-diabetic controls. Plasma plant sterol concentrations were significantly (P less than 0.01) lower in diabetic patients (campesterol: men -36%, women -48%; betasitosterol: men -35%, women -42%). Fasting serum insulin levels were inversely correlated with plasma plant sterol concentrations in diabetic patients (campesterol: r = -0.347, P = 0.012; betasitosterol: r = -0.345, P = 0.012) and in non-diabetic men (campesterol: r = -0.578, P = 0.039; betasitosterol: r = -0.702, P = 0.008). Serum insulin levels were also correlated significantly with plasma lathosterol concentration in diabetic patients (r = 0.295, P = 0.034). The results of this study suggest that absorption of plant sterols and possibly cholesterol from the diet may be reduced in hyperinsulinemic diabetics.     

Changes in Sterol Composition during Greening of Etiolated Barley Shoots

The following sterols were identified in barley shoots: stigmasterol, β-sitosterol, campesterol, and cholesterol. The total sterol content of green and etiolated tissue was 2.84 and 3.20 milligrams per gram dry weight, respectively. The free sterols accounted for most of the difference in total sterol content. The sterol ester, sterol glycoside, and acylated sterol glycoside contents of green and etiolated barley shoots were essentially the same. Etiolated tissue had twice as much total β-sitosterol as stigmasterol, while green tissue had equal amounts of these two sterols. The campesterol and cholesterol content was the same in green and etiolated tissue. This same sterol composition pattern held true for the free, glycosidic, and acylated glycosidic sterols; however, the sterol ester fraction had a completely different composition pattern. The esterified stigmasterol content was quite low in green and etiolated tissue, and campesterol was the second largest esterfied sterol component in etiolated tissue. Etiolated barley seedlings exposed to light had a shift in the ratio of free stigmasterol to β-sitosterol in favor of stigmasterol; however, no correlation was observed between chlorophyll synthesis and shift in sterol composition.     

Sterol absorption by the small intestine

PURPOSE OF REVIEW: Cholesterol absorption is a selective process in that plant sterols and other non-cholesterol sterols are absorbed poorly or not at all. Recent research on the sterol efflux pumps adenosine triphosphate-binding cassette transporter G5 and adenosine triphosphate-binding cassette transporter G8 has not only provided an explanation for this selectivity, but also, together with the discovery of a new class of cholesterol absorption inhibitor, has yielded new insights into the mechanisms that potentially regulate the flux of cholesterol across the enterocyte. This review discusses these recent developments and their importance to the regulation of whole body cholesterol homeostasis. RECENT FINDINGS: Adenosine triphosphate-binding cassette transporters G5/8 regulate plant sterol absorption and also the secretion into bile of cholesterol and non-cholesterol sterols. Loss of adenosine triphosphate-binding cassette transporter G5/8 function results in sitosterolemia. Ezetimibe, a novel, potent and selective inhibitor of cholesterol absorption which is effective in milligram doses, lowers plasma plant sterol concentrations in sitosterolemic subjects, thus suggesting that this drug might be inhibiting the activity of a putative sterol permease in the brush border membrane of the enterocyte that actively facilitates the uptake of cholesterol as well as other non-cholesterol sterols. SUMMARY: Intestinal cholesterol absorption represents a major route for the entry of cholesterol into the body's miscible pools and therefore can potentially impact the plasma LDL-cholesterol concentration. The combined use of agents that inhibit the absorption and synthesis of cholesterol provides a powerful new approach to the prevention and treatment of atherosclerosis.     

Intestinal helminths as predictors of some malaria clinical outcomes and IL-1β levels in outpatients attending two public hospitals in Bamenda,North West Cameroon

This study aimed at determining the impact of intestinal helminths on malaria parasitaemia, anaemia and pyrexia considering the levels of IL-1β among outpatients in Bamenda. A cohort of 358 consented participants aged three (3) years and above, both males and females on malaria consultation were recruited in the study. At enrolment, patients’ axillary body temperatures were measured and recorded. Venous blood was collected for haemoglobin concentration and malaria parasitaemia determination. Blood plasma was used to measure human IL-1β levels using Human ELISA Kit. The Kato-Katz technique was used to process stool samples. Five species of intestinal helminths Ascaris lumbricoides (6.4%), Enterobius vermicularis (5.0%), Taenia species (4.2%), Trichuris trichiura (1.1%) and hookworms (0.8%) were identified. The overall prevalence of Plasmodium falciparum and intestinal helminths was 30.4% (109/358) and 17.6% (63/358) respectively. The prevalence of intestinal helminths in malaria patients was 17.4% (19/109). Higher Geometric mean parasite density (GMPD ±SD) (malaria parasitaemia) was significantly observed in patients co-infected with Enterobius vermicularis (5548 ± 2829/μL, p = 0.041) and with Taenia species (6799 ± 4584/μL, p = 0.020) than in Plasmodium falciparum infected patients alone (651 ± 6076/ μL). Higher parasitaemia of (1393 ± 3031/μL) and (3464 ± 2828/μL) were recorded in patients co-infected with Ascaris lumbricoides and with hookworms respectively but the differences were not significant (p > 0.05). Anaemia and pyrexia prevalence was 27.1% (97/358) and 33.5% (120/358) respectively. Malaria patients co-infected with Enterobius vermicularis and Ascaris lumbricoides had increased risk of anaemia (OR = 13.712, p = 0.002 and OR = 16.969, p = 0.014) respectively and pyrexia (OR = 18.07, p = 0.001 and OR = 22.560, p = 0.007) respectively than their counterparts. Increased levels of IL-1β were significantly observed in anaemic (148.884 ± 36.073 pg/mL, t = 7.411, p = 0.000) and pyretic (127.737 ± 50.322 pg/mL, t = 5.028, p = 0.000) patients than in non-anaemic (64.335 ± 38.995pg/mL) and apyretic patients (58.479 ± 36.194pg/mL). Malaria patients co-infected with each species of intestinal helminths recorded higher IL-1β levels (IL-1β > 121.68 ± 58.86 pg/mL) and the overall mean (139.63 ± 38.33pg/mL) was higher compared with levels in malaria (121.68 ± 58.86 pg/mL) and helminth (61.78 ± 31.69pg/mL) infected patients alone. Intestinal helminths exacerbated the clinical outcomes of malaria in the patients and increased levels of IL-1β were observed in co-infected patients with anaemia, pyrexia and higher parasitaemia.     

Sterol Composition of the Corn Cyst Nematode,Heterodera zeae,and Corn Roots

Sterols from free sterol and steryl ester fractions from Heterodera zeae and from total lipids of Zea mays roots were analyzed by gas-liquid chromatography (GLC) and by GLC-mass spectrometry. The major free sterols of H. zeae were 24-ethylcholesterol (54.4% of total free sterol), 24-ethylcholesta-5,22-dien-3β-ol (13.3%), 24-methylcholesterol (12.5%), and cholesterol (7.2%). The same four sterols comprised 34.6%, 7.2%, 30.3%, and 18.6%, respectively, of the esterified sterols of H. zeae. Corn root sterols included 46.6% 24-ethylcholesta-5,22-dien-3β-ol, 16.7% methylcholesterol, 16.4% cycloartenol, 12.7% 24-ethylcholesterol, and 0.5% cholesterol. The sterol 24-composition of H. zeae differed greatly from that of the only other cyst nematode previously investigated, Globodera solanacearum.     

Recent Developments in Nematode Steroid Biochemistry

Current knowledge of steroid nutrition, metabolism, and function in free-living, plant-parasitic and animal-parasitic nematodes is reviewed, with emphasis upon recent investigation of Caenorhabditis elegans. A number of 4-desmethylsterols with a trans-A/B ring configuration can satisfy the steroid nutritional requirement in C. elegans, but sterols with a cis-A/B ring configuration or trans-A/B sterols with a 4-methyl group cannot. C. elegans removes methyl or ethyl substituents at C-24 of the plant sterols sitosterol, campesterol, stigmasterol, stigmastanol, and 24-methylene-cholesterol to produce various sterols with structures partially dependent upon that of the dietary sterol. Additional metabolic steps in C. elegans include reduction of Δ²²- and Δ⁵-bonds, C-7 dehydrogenation, isomerization of a Δ⁷-bond to a Δ⁸⁽¹⁴⁾-bond, and 4α-methylation. An azasteroid and several long-chain alkyl amines interfere with the dealkylation pathway in C. elegans by inhibiting the Δ²⁴-sterol reductase; these compounds also inhibit growth and reproduction in various plant-parasitic and animal-parasitic nematodes. A possible hormonal role for various steroids identified in nematodes is discussed.     

Control of sterol metabolism in rat adrenal mitochondria

Steroidogenesis by adrenal mitochondria from endogenous precursors is stimulated by corticotropin (ACTH) and is sensitive to the protein-synthesis inhibitor cycloheximide. In the present investigation the effect of cycloheximide treatment on the metabolism of a number of analogues of the normal steroidogenic substrate, i.e. cholesterol, by rat adrenal mitochondria was studied. It was observed that the metabolism of analogues such as desmosterol, 26-norcholest-5-en-3β-ol and 5-cholen-3β-ol (that is with non-polar alkyl side chains like cholesterol), was sensitive to cycloheximide treatment. By contrast, the metabolism of those analogues with polar groupings on the side chain, i.e., 20α-, 24-, 25- and 26-hydroxycholesterols was insensitive to pretreatment with cycloheximide. The binding of added sterol to the cytochrome P-450 component of the mitochondrial sterol desmolase was studied. Similar studies on the equilibration time on addition of exogenous sterols to achieve maximum rates of pregnenolone production were also made. Both studies show that cholesterol, a non-polar sterol, penetrated slowly through the mitochondrial milieu to reach the cytochrome P-450 reaction centre whereas 24- and 26-hydroxycholesterols rapidly attained the enzymic environment. The cycloheximide-sensitive process in sterol metabolism appeared related to the transfer of non-polar sterols such as cholesterol within the mitochondria to a region in close proximity to the enzyme. The importance, and possible mechanism of action, of the cycloheximide-sensitive factor in the control of adrenal steroidogenesis is discussed.     

Higher Urinary Bisphenol A Concentration Is Associated with Unexplained Recurrent Miscarriage Risk: Evidence from a Case-Control Study in Eastern China

BackgroundEvidence about the association between Bisphenol A (BPA) and the risk of recurrent miscarriage (RM) in human being is still limited.ObjectiveWe evaluated the association of urinary BPA concentrations with RM in human being.MethodsA hospital-based 1:2 matched case-control study on RM was carried out in Suzhou and Kunshan in Jiangsu Province in China between August 2008 and November 2011. Total urinary BPA concentrations in 264 eligible urine samples (102 RM patients and 162 controls) were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The Wilcoxon test and conditional logistic regression were used to estimate the differences between the groups and odds ratios (OR) with 95% confidence intervals (CI), respectively.ResultsThe median ± IQR (interquartile range) (P₇₅-P₂₅) values of non-creatinine-adjusted total urinary BPA levels in the RM patients and the controls were 1.66±3.69ng/ml and 0.58±1.07ng/ml, respectively (0.98±2.67μg/g Cr (creatinine) and 0.40±0.77μg/g Cr. The adjusted BPA level was significantly higher in the RM patients than in the controls (Wilcoxon test, Z = 4.476, P<0.001). Higher level of urinary BPA was significantly associated with an increased risk of RM (P-trend <0.001). Compared to the groups with urinary BPA levels less than 0.16μg/g Cr, the women with levels of 0.40–0.93μg/g Cr and 0.93μg/g Cr or above had a significantly higher risk of RM (OR = 3.91, 95%CI: 1.23–12.45 and OR = 9.34, 95%CI: 3.06–28.44) that persisted after adjusting for confounding factors. The time from recently RM date to recruitment does not significantly influence the urinary BPA level (P = 0.090).ConclusionExposure to BPA may be associated with RM risk.     

Sterol distribution in intracellular organelles isolated from tobacco leaves

All membrane-containing fractions isolated from tobacco leaves contained free sterols, sterol glycosides, and sterol esters. The three sterol forms increased, on a dry weight basis, with a decrease in particle size. The supernatant fraction contained only trace amounts of sterol. The major sterols in all cellular fractions, in the order of decreasing amounts, were: stigmasterol, β-sitosterol, campesterol, and cholesterol. The 500g pellet contained the largest percentage of free sterol, while the 46,000g pellet contained the largest percentage of esterified sterol. The individual sterol composition of the free sterol and sterol glycoside fraction was very similar; however, the composition of the sterol ester fraction varied widely among intracellular fraction. The intracellular distribution pattern of cholesterol-¹⁴C added to the isolation medium provided evidence that the intracellular sterol distribution pattern is not an artifact. These results support the suggestion that sterols in plant cells may have a physiological function associated with membranes.