Rats enriched with odd-carbon fatty acids: maintenance of liver glycogen during starvation.

In young rats a diet containing triundecanoin as the major source of fat produces substantial enrichment of adipose tissue triglycerides with undecanoate and higher fatty acids with odd-numbered carbons. The terminal three-carbon residues arising from beta-oxidation of these acids are glucogenic and help to counteract the decreases in liver glycogen and serum glucose ordinarily induced by prolonged fasting.

Oxidation of high density lipoproteins: characterization and effects on cholesterol efflux from J774 macrophages.

Oxidative modification of high density lipoproteins (HDL) may alter their capacity to mediate cellular cholesterol efflux. We studied the kinetics of copper-mediated oxidation of HDL and cholesterol efflux mediated by unmodified and oxidized HDL (oxHDL). Oxidation was measured by increases in absorbance at 234 nm (delta A234), production of thiobarbituric acid reactive substances (TBARS) and loss of trinitrobenzene sulfonic acid reactivity. Oxidation was dependent on copper concentration and showed a lag phase and propagation phase. Efflux of cholesterol from J774 macrophages measured by appearance of cellular [3H]cholesterol in the medium was lower by 16% after 4 h and 36% after 24 h with oxHDL compared to HDL. OxHDL-mediated efflux was also lower by 27% to 37% at lipoprotein concentrations of 10 to 200 micrograms protein/ml. Cholesterol efflux correlated negatively with TBARS production (r = -0.97, P < 0.003) and delta A234 (r = -0.77, P < 0.080). There was no difference in efflux mediated by apoproteins prepared from HDL and oxHDL. Efflux measured by change in cholesterol mass in medium was 78% lower with oxHDL. Inhibition of oxidation with butylated hydroxytoluene maintained the capacity of HDL to stimulate efflux. These results suggest that oxidation of HDL may impair its protective role against atherosclerosis.

Suppression of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and of incorporation of acetate into cholesterol in homozygous hypercholesterolemic fibroblasts by ferritin-low density lipoprotein conjugates.

Conjugates of ferritin with low density lipoproteins (LDL) were prepared and separated by sucrose gradient centrifugation. These conjugates, at cholesterol concentration of 100--132 microgram/ml, caused a greater than 90% suppression of hydroxymethylglutaryl coenzyme A reductase activity and of acetate incorporation into cholesterol in cultured skin fibroblasts from a normal subject as well as from a subject with homozygous familial hypercholesterolemia. The half maximal inhibition concentration was approx. 10 microgram/ml cholesterol for LDL and ferritin . (LDL)2 and 5 microgram/ml for (ferritin)2 . LDL in both cell lines. In contrast, native low density lipoproteins have only a minimal inhibitory effect in homozygous cells. The ability of the conjugates to stimulate the incorporation of oleate into cholesteryl esters was also equal in the two cell lines, although the conjugates were only 10% as active as low density lipoproteins in the normal cells. LDL reduced the ferritin . (LDL)2-mediated suppression of hydroxymethylglutaryl-CoA reductase activity in homozygous cells while ferritin . (LDL)2 reduced the LDL-mediated stimulation of cholesteryl ester formation in normal cells.

The effects of triiodothyronine, hydrocortisone and insulin on lipid synthesis by cultured fibroblasts preincubated in a serum-free medium.

Studies of lipid metabolism in cell cultures are usually carried out after preincubation of cells in media containing lipoprotein-deficient or delipidated serum. The artifacts produced during delipidation prevent the standardization of assays and the study of the role of hormones on lipid metabolism. We studied the effects of triiodothyronine, hydrocortisone, insulin and their combination on cholesterol and fatty acid synthesis in cultured human skin fibroblasts preincubated for 24 h in an artificial medium (medium A) consisting of equal volumes of Dulbecco's modified Eagle's and Ham's F-12 media enriched with transferrin, biotin and calcium pantothenate. In cells preincubated in medium A the incorporation of acetate to cholesterol and the activity of hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase were much lower than in cells preincubated in standard medium containing lipoprotein-deficient serum. Addition of the three hormones caused a marked stimulation of the incorporation of acetate to cholesterol (from 3.1 to 17.7 pmol/min per mg protein), an activity similar to that in cells preincubated in lipoprotein-deficient serum plus hormones. The stimulatory effect of the hormones on HMG-CoA reductase activity was smaller, from 11 to 26 pmol/min per mg protein compared to 83 pmol/min per mg protein in cells preincubated in lipoprotein-deficient serum plus hormones. Most of the stimulatory effect was due to insulin. The lack of coordinate response between these two parameters in cells preincubated in artificial medium could not be explained by (a) stimulation of a post-mevalonate step as measured by the incorporation of mevalonate to cholesterol; (b) the in vitro inactivation of HMG-CoA reductase by phosphorylation: incubation of fibroblast microsomes with Escherichia coli alkaline phosphatase resulted in a decrease in HMG-CoA reductase activity, in contrast to an increase in hepatic microsomes; (c) the presence of inhibitors of HMG-CoA reductase in the microsomal extract. In cells preincubated in medium A the incorporation of acetate to fatty acids and the activities of acetyl-CoA carboxylase and fatty acid synthetase were approximately equal to that of cells preincubated in standard medium containing lipoprotein-deficient serum. Hormones added to medium A caused a stimulation of incorporation of acetate to fatty acids (from 5.1 to 19.8 pmol/min per mg protein), the activity of acetyl-CoA carboxylase (from 494 to 820 pmol/min per mg protein) and of fatty acid synthetase (from 300 to 678 pmol/mg protein). These values were significantly higher than those obtained in cells preincubated with lipoprotein-deficient serum with or without hormones.(ABSTRACT TRUNCATED AT 400 WORDS)

Ten-year experience with an exercise-based outpatient life-style modification program in the treatment of diabetes mellitus.

Exercise is frequently recommended in the treatment of diabetes mellitus. Nevertheless, its use has been limited in clinical practice, and concerns about safety and efficacy persist. We have reviewed a 10-yr experience with 255 patients enrolled in a comprehensive diabetes program that emphasized physical training. A low maximal oxygen uptake (VO2max) was found in patients with non-insulin-dependent diabetes mellitus compared with sedentary control subjects. This was not accounted for by autonomic neuropathy and is unlikely to be due to subtle differences in life-style. Exercise-related proteinuria was common and occurred in 29% of patients and was associated with higher blood pressure levels at rest and during exercise, impaired VO2max, and decreased R-R interval variation. Regular exercise was associated with a modest decrease in resting and exercise blood pressure. Glycosylated hemoglobin levels and plasma triglycerides improved only in patients with non-insulin-dependent diabetes mellitus. Insulin requirements were significantly reduced in patients with insulin-dependent diabetes mellitus. Compliance for up to 3 mo in the program was acceptable but longer-term compliance was poor. Serious complications during the program were rare. Our experience suggests a program of regular aerobic training can be safely and effectively used in an outpatient population with diabetes mellitus for up to 3 mo.

Effects of dietary vitamin C and E supplementation on the copper mediated oxidation of HDL and on HDL mediated cholesterol efflux.

Copper mediated oxidative modification of high density lipoprotein (HDL) diminishes its capacity to promote cholesterol efflux from cells in culture. In the present study, HDL was isolated from eight subjects before and after a 10 day administration of the antioxidant vitamins C and E. After incubation HDL (1.25 mg protein/ml) with 10 microM copper for 0-4 h or with 0-20 microM copper for 4 h, thiobarbituric acid reactive substances (TBARS) production was significantly decreased following vitamin administration suggesting that the vitamins decreased the susceptibility of HDL to oxidation. However, two other assays of lipoprotein oxidation, trinitrobenzene sulfonic acid reactivity and conjugated diene formation, did not show a consistent effect of vitamin administration. To study cholesterol efflux, J774 macrophages were labeled with 3H cholesterol (0.1 microCi/ml, 50 micrograms/ml) and incubated with HDL or oxidized HDL (100 micrograms protein/ml) for 24 h. HDL isolated before vitamins and oxidized in vitro was 39% less effective in mediating efflux compared to unmodified HDL, while HDL isolated after vitamins and oxidized was 22% less effective (before vs. after vitamins, P < 0.015). HDL oxidation determined by measuring TBARS production correlated with decreased cholesterol efflux (r = 0.37, P < 0.050). These data suggest that oxidation of HDL interferes with its role in reverse cholesterol transport and that antioxidant vitamins have a protective effect.

Diagnosis of familial hypercholesterolemia by measurement of sterol synthesis in cultured skin fibroblasts.

The incorporation of radioactive acetate into the digitonin precipitable fraction (cholesterol) was measured in monolayers of primary cultures of skin fibroblasts. Mean incorporation was increased approximately 20-fold in 4 subjects homozygous for familial hypercholesterolemia (FH) and 4-fold in 6 heterozygotes derived from the immediate family of homozygotes. Incorporation was normal in 4 subjects with Type IV and V hyperlipoproteinemia. In cells that had been preincubated in lipid free medium, incorporation by cells from homozygotes was equal to controls, denoting a derangement in the feedback inhibition of cholesterol synthesis by medium lipids in paralleled the values obtained for sterol synthesis. The assay described could be useful in making an "etiologic" diagnosis of familial hypercholesterolemia and could possible identify variants of monogenic hyperbetalipoproteinemia.

Stimulation of low-density lipoprotein oxidation by insulin and insulin like growth factor I.

Hyperinsulinemia has been implicated as an independent risk factor for atherosclerosis. We measured the effect of insulin and related hormones on the oxidation of low density lipoproteins (LDL) and superoxide anion production by peripheral blood mononuclear cells (MC). LDL oxidation was measured by the production of thiobarbituric acid reactive substances (TBARS). Insulin and IGF-I at 10(-7) M caused a 33% and 48% increase in TBARS production, respectively. At 10(-6) M the corresponding values were 63% and 67%. Proinsulin and IGF-II at 10(-6) M had no effect. Glucose caused a concentration dependent (up to 10 mM) stimulation of LDL oxidation reaching 85% and 77% at insulin concentrations of 10(-7) M and 10(-6) M, respectively. The stimulatory effect of insulin was confirmed by measurements of other indices of LDL oxidation, i.e. absorbance at 234 nm, trinitrobenzene sulfonic acid reactivity and electrophoretic mobility. Insulin-stimulated LDL oxidation was inhibited by superoxide dismutase (SOD), but insulin had no effect on MC superoxide production. MC were isolated from five subjects before and after a 5 h hyperinsulinemic, euglycemic clamp. Insulin infusion had no effect on TBARS or superoxide production by MC. Our in vitro experiments suggest that high levels of insulin and IGF-I stimulate MC-mediated oxidation of LDL, an effect that is potentially atherogenic.

The effects of polyoxyethylated cholesterol feeding on hepatic cholesterol synthesis and intestinal cholesterol absorption in rats.

Adduction of ethylene glycol moieties to the 3-hydroxy position of cholesterol produces polyoxyethylated cholesterol (POEC), a water-soluble compound that suppresses cholesterol synthesis and esterification in cultured human fibroblasts. Feeding Sprague-Dawley rats a diet containing 2% (wt/wt) POEC with 10 ethoxy groups resulted in a 3-fold increase in hepatic 3-hydroxy-3-methylglutaryl-CoA reductase activity compared to activity in rats pair-fed a diet of standard rat chow. POEC with an average of 20 ethoxy groups (POEC-20) caused comparable changes in hepatic [2-14C]acetate incorporation into non-saponifiable lipids under ad libitum feeding conditions, significantly reduced cholesterol absorption (18% vs 57%), and increased fecal excretion of neutral steroids (5.1 vs 2.0 mg/g food intake). POEC-20 also reduced cholesterol absorption in rats fed a diet enriched with 2% cholesterol (11% vs 31%). Histologic studies of intestinal mucosa and hepatic tissues from rats fed POEC showed no pathologic changes. These experiments indicate that POEC reduces cholesterol absorption and causes compensatory increases in hepatic cholesterol synthesis.

Administration of antioxidant vitamins does not alter plasma fibrinolytic activity in subjects with central obesity.

In vitro studies suggest that oxidized low density lipoprotein inhibits fibrinolysis by stimulating the production of plasminogen activator inhibitor -1 (PAI). We assessed the effects of dietary antioxidant vitamins for four weeks on three indices of copper mediated oxidation of very low and low density lipoproteins (VLDL+LDL) and plasma fibrinolytic activities in 15 male subjects with central obesity, a condition associated with increased PAI activity. Vitamin administration resulted in a decrease in production of thiobarbituric acid reactive substances from 29.3 +/- 3.9 to 13.6 +/- 3.5 nmoles/mg VLDL + LDL protein (mean +/- SE, p <0.003), an increase in the lag phase of conjugated diene formation from 94.8 +/- 5.5 to 225.0 +/- 31.9 min (p <0.001) and an increase in reactivity of lysine residues from 73.6% +/- 4.8% to 86.8% +/- 3.6% (p <0.034) demonstrating a reduction in the susceptibility of the lipoproteins to oxidation. However, antioxidant vitamins had no effect on plasma PAI activity, PAI antigen, tissue-type plasminogen activator activity and antigen, fibrinogen and fibrin degradation products. These results do not support the hypothesis that lipoprotein oxidation is a significant cause of impaired fibrinolysis in men with central obesity.

The inhibition of low-density lipoprotein oxidation by 17-beta estradiol.

The antioxidant activities of 17-beta-estradiol (E2) and other steroid hormones were studied by determining their effect on copper-catalyzed (cell-free) and mononuclear cell-mediated oxidation of low-density lipoproteins (LDL), as measured by the production of thiobarbituric acid-reactive substances (TBARS). The oxidation of LDL increased linearly with copper concentrations ranging from 0 to 10 mumol/L. E2 at a concentration of 1 mumol/L inhibited LDL oxidation by 37% to 62% at the various concentrations of copper. In a time-course study, E2 at 1 mumol/L delayed the onset of LDL oxidation in the presence of 5 mumol/L copper. E2 (1 mumol/L) inhibited TBARS production catalyzed by 5 mumol/L copper by 54%, compared with 60% inhibition by 1 mumol/L butylated hydroxytoluene (BHT), a known inhibitor of lipid peroxidation. Estriol at 5 mumol/L decreased LDL oxidation by 49%. Dehydroepiandrosterone (DHEA), testosterone, and estrone had no significant effects. E2 was also an effective inhibitor of mononuclear cell (MNC)-mediated oxidation of LDL, but had no effect on superoxide production by these cells. The onset of TBARS formation from cell-mediated LDL oxidation was also delayed by incubation with 1 mumol/L E2. The results indicate that estrogen may protect against atherosclerosis by inhibiting lipoprotein oxidation.

Impaired adrenergic response to prolonged exercise in type I diabetes.

Patients with type I diabetes mellitus commonly experience hypoglycemia related to physical activity. We investigated the metabolic and hormonal response to exercise in type I diabetics, normal controls, and controls exercising under hypoglycemic conditions. All subjects exercise for 60 minutes at 60% to 65% of their VO2max while insulin concentrations were clamped at basal or hyperinsulinemic levels. With low-dose insulin infusion, despite similar free insulin levels, diabetics had a greater decrease in plasma glucose concentrations during exercise than controls. Nevertheless, the increments of epinephrine (E) and norepinephrine (NE) during exercise tended to be less in the diabetic subjects. Circulating levels of free fatty acids (FFA) were lower in diabetics, especially during early recovery from exercise. To better compare responses, a group of normal controls exercised during an infusion of insulin, which resulted in a similar decrease in plasma glucose to that of exercising diabetics. While exercising during a similar degree of hypoglycemia, diabetics had a significantly smaller increment of E and NE compared with controls. Increments of glucagon (GL) and growth hormone (GH) were not different. These studies suggest that there is a subnormal catecholamine response to exercise under hypoglycemic conditions in some patients with type I diabetes. The hypoglycemia during and after exercise in these individuals is probably the result of multiple factors, including relative hyperinsulinemia, decreased increment in catecholamines, and decreased availability of FFA.

Stimulation of cholesterol and lipid synthesis by insulin in familial hypercholesterolemic fibroblasts.

Cultured skin fibroblasts from two patients with homozygous familial hypercholesterolemia and three normal subjects were preincubated for 24 hours in medium containing 10% delipidated serum with insulin concentrations of 0.4, 4, or 40 ng/mL. [14C]acetate incorporation into total lipids, cholesterol, and phospholipids was significantly increased in familial hypercholesterolemic cells at insulin concentrations of 0.4 and 4 ng/mL, which had no effect in normal cells. When the data were normalized as percent stimulation over control for individual experiments, [14C]acetate incorporation into cholesterol was comparable at 40 ng/mL in both cell types. Similar results were obtained in cells preincubated in serum free artificial medium. Coordinate increases in the activity of 3-hydroxy-3-methylglutaryl CoA reductase in response to insulin were not found. These studies show that familial hypercholesterolemic cells have an altered lipogenic response to low concentrations of insulin.

Impaired fibrinolytic response to exercise in type II diabetes: effects of exercise and physical training.

We studied the effects of exercise and physical training on coagulation parameters and fibrinolytic activity in 16 sedentary non-insulin-dependent diabetics and nine control subjects matched for prior physical activity. Parameters were measured at rest and after 30 minutes of bicycle exercise at 70% to 75% of maximal oxygen uptake before and after 6 weeks of thrice-weekly physical training. In the untrained state, fibrinolytic activity was impaired in diabetics compared with controls (1.26 +/- 0.19 v 2.20 +/- 0.34 U; P less than .03), and resting levels of plasma fibrinogen (329 +/- 21 v 266 +/- 17 mg/dL; P less than .01) and the prothrombin time (PT) maximal velocity (Vmax) (4.9 +/- 0.5 v 2.9 +/- 0.5; P less than .05) were increased. The activated partial thromboplastin time (APTT) Vmax was also increased but this did not reach statistical significance (3.6 +/- 0.2 v 2.3 +/- 0.5; P less than 0.10). Activation of fibrinolysis occurred following exercise in both groups but the peak activity and increment were less in diabetics. Physical training for 6 weeks had no effect on plasma fibrinogen levels but significantly improved the resting and postexercise APTT Vmax and resting fibrinolytic activity in diabetics. The exercise-induced increment in fibrinolytic activity following training remained depressed compared with normal controls. The changes in APTT Vmax correlated with changes in the indices of blood glucose control. The relevance of these findings to possible antiatherogenic effects of exercise and the mechanism by which exercise produces these effects remain to be established.

Glycation of high-density lipoprotein does not increase its susceptibility to oxidation or diminish its cholesterol efflux capacity.

In vitro oxidation of high-density lipoprotein (HDL) diminishes its capacity to mediate cholesterol efflux from J774 macrophages. To investigate the possible role of HDL glycation in the increased atherosclerotic risk in diabetes, we studied the effects of in vitro glycation of HDL on its susceptibility to oxidation and capacity to mediate cholesterol efflux. HDL isolated from normal volunteers was incubated with 25 mmol/L glucose for 70 hours, resulting in 6.1% additional derivatization of apoproteins as determined by trinitrobenzene sulfonic acid (TNBS) reactivity. Unmodified HDL and glycated HDL (glyHDL) were tested for susceptibility to oxidation by incubation with various concentrations of copper and three assays of lipid oxidation. GlyHDL produced 51% to 64% less lipid peroxide than HDL as determined by reaction with xylenol orange (P < .02), indicating decreased susceptibility to oxidation. However, glycation of HDL did not result in significant changes in the formation of conjugated dienes or thiobarbituric acid-reactive substances (TBARS), two other indices of oxidation. To study cholesterol efflux, J774 macrophages were labeled with 3H-cholesterol followed by incubation with the various HDL preparations. HDL and glyHDL had a similar capacity to mediate efflux. The efflux mediated by oxidized HDL (oxHDL) and oxidized glyHDL was reduced to a similar extent compared with the efflux mediated by HDL and glyHDL. These data indicate that in vitro glycation of HDL does not increase its susceptibility to oxidation and does not diminish its capacity to mediate cholesterol efflux.

Abnormal glucoregulation during exercise in type II (non-insulin-dependent) diabetes.

We studied the effects of exercise on the levels of plasma glucose and glucoregulatory hormones before and after 6 weeks of thrice-weekly physical training in 20 sedentary type II (non-insulin-dependent) diabetic patients and 11 control subjects matched for previous physical activity. Parameters were measured at rest, after 30 minutes of bicycle exercise at 70% to 75% of maximal oxygen uptake, and after 30 minutes of recovery. In the untrained state exercise resulted in a decrease in plasma glucose levels in diabetics but not in controls (-12 +/- 5 v + 4 +/- 2 mg/dL, P less than .01) and the expected drop in plasma insulin level was absent in diabetics. These differences in glucose and insulin response persisted after physical training. There was a tendency for patients with diabetes to have a smaller R-R interval variation during deep breathing, an abnormal resting heart rate response to physical training, and a lesser increment in plasma epinephrine levels following exercise, findings consistent with autonomic dysfunction. Physical training resulted in a blunting of the exercise-induced increment of plasma epinephrine, growth hormone, and lactate levels in control subjects, but not in diabetics. Our data demonstrate a hypoglycemic effect of exercise in mildly hyperglycemic nonobese type II diabetics. Possible causative factors include: hyperglycemia per se, a lack of physiologic suppression of plasma insulin, and abnormalities of autonomic or hypothalamic regulatory function.

Effects of ketanserin, a 5-HT2-receptor antagonist, on the blood flow response to temperature changes in the diabetic foot.

We studied the effect of ketanserin, a relatively specific antagonist for 5-hydroxytryptamine2-serotonergic receptors, on the total blood flow to the foot of patients with diabetes using a computerized pulse volume plethysmograph and a temperature controlled foot chamber. Ketanserin was administered intravenously as a bolus of 10 mg over four minutes followed by a constant infusion at the rate of 5 mg/hr. Saline infusion served as a control in each subject. Sixteen patients with type II diabetes and two patients with type I diabetes were studied. Mean age was 58.5 +/- 1.6 years and mean duration of diabetes was 10 +/- 2 years. Basal blood flow (mean +/- SEM, mL/100 mL/min) at room temperature was 3.77 +/- 0.99 with saline and 12.07 +/- 1.81 with ketanserin. At 38 to 40 degrees C, the values were 4.84 +/- 1.09 and 16.93 +/- 1.83. Reactive hyperemia was measured following three minutes of arterial occlusion; at 38 to 40 degrees C the flow rate was 20.67 +/- 2.45 with saline and 30.86 +/- 3.02 with ketanserin, while at 8 to 10 degrees C the corresponding values were 15.63 +/- 2.01 and 27.16 +/- 2.03. All differences between saline and ketanserin had a P less than .01. Venous distensibility (vol% at 50 mm Hg) at 8 to 10 degrees C was 0.55 +/- 0.05 with saline and 0.90 +/- 0.15 with ketanserin, P less than .05. Our findings are consistent with the hypothesis that serotonin is involved in the limitation of blood flow to the foot in diabetes and that ketanserin may play a potential role in therapy.

Comparison of fixed-ratio versus variable-ratio regular and NPH semisynthetic human insulin in insulin-requiring diabetic patients.

The efficacy and safety of a fixed combination of semisynthetic human insulin (Novolin) providing a 70:30 ratio of NPH to regular insulin versus a varying ratio of semisynthetic human insulin, regular and NPH (control group), were compared in adult insulin-dependent and noninsulin-dependent diabetic patients whose glycemic control had been stable on customized split-mix regimens of animal insulin. Seventy-eight patients were enrolled, of whom 72 were evaluated for efficacy of the respective regimens. Although the baseline fasting serum glucose concentrations were significantly higher in the fixed-ratio group than in the control group, mean serum glucose and glycosylated hemoglobin values throughout the 12 weeks of experimental treatment were not significantly different between groups. The mean serum glucose and glycosylated hemoglobin values in the fixed-ratio group also did not differ significantly from baseline; however, statistically significant increases were observed in the control group at weeks 4 and 8, but not at week 12. Total daily insulin dosages were comparable between the two groups, and body weight did not change significantly in either group. At the end of the study, the investigators judged 90% of the patients in the fixed-ratio group and 88% of the patients in the control group to be either improved or unchanged with respect to glycemic control. The frequency of hypoglycemic episodes and other clinical events did not change significantly from baseline in either group or differ significantly between the two groups at any time. The results of this study suggest that stable diabetic patients receiving animal insulin can safely be transferred to semisynthetic human insulin and that the majority of patients can maintain acceptable glycemic control with a fixed 70:30 ratio of NPH to regular semisynthetic human insulin.

Identification of 5 alpha-stanols in patients with sitosterolemia and xanthomatosis: stereochemistry of the protonolysis of steroidal organoboranes.

Plasma and fecal sterols of patients who exhibited tendon xanthomas with normal plasma cholesterol levels were studied. Plasma levels were (mg/dl mean +/- SD): cholesterol 232 +/- 36; cholestanol 5.9 +/- 2.1 (normal less than 0.6); sitosterol 18 +/- 5.6 (normal less than 1.0); campesterol 11 +/- 3.3 (normal less than 1.0). Other sterols such as sitostanol and campestanol (the 5 alpha-dihydro derivatives of sitosterol and campesterol) were also present in large amounts. Examination of the feces from these subjects showed cholesterol, sitosterol, campesterol and their 5 beta-saturated derivatives. Presence of 5 alpha-stanols in the plasma, and their absence in the feces indicates that the 5 alpha-stanols are synthesized endogenously within the body rather than in the intestine by colonic bacteria. The absolute identification of the structures of these 5 alpha-stanols was elucidated via hydroboration of their corresponding unsaturated sterols coupled with protonolysis of the resultant organoboranes.

The effects of polyoxyethylated cholesterol on fecal bile acids and nitrogen and on cholesterol balance in rats.

Polyoxyethylated cholesterol (POEC) is a water soluble derivative of cholesterol which decreases cholesterol absorption in rats without affecting body weight, fatty acid excretion, or intestinal histology. In the present study rat feces were analyzed for cholic, deoxycholic, chenodeoxycholic, muricholic and lithocholic acid following 3 months of feeding a standard or a 2% enriched cholesterol diet with or without 1.5% POEC. In rats maintained on the cholesterol free diet, POEC increased total bile acids (mg/day) by 50% from 14 +/- 3 to 21 +/- 3 (mean +/- SEM) but only the increase in chenodeoxycholic acid was significant (P less than 0.05). The corresponding POEC effect in the 2% cholesterol diet was 31% (70 +/- 8 to 93 +/- 3, P less than 0.01). Fecal nitrogen and serum cholesterol did not vary among groups. Comparing these data with neutral steroid excretion previously determined showed that POEC in the cholesterol-free diet increased the negative cholesterol balance more than three-fold (34 +/- 7 vs 118 +/- 13 P less than 0.01). In rats fed 2% cholesterol, POEC caused a negative cholesterol balance of 222 +/- 8 compared to the control of 27 +/- 52 (P less than 0.01). The data indicate that POEC exerts complex effects in the intestinal tract which increase both bile acid and cholesterol excretion.