Parathyroid hormone reference ranges in healthy individuals classified by vitamin D status.

PURPOSE: Parathyroid hormone (PTH) concentrations are routinely measured in the diagnosis and management of bone and kidney diseases, but reference ranges can be overestimated if determined in otherwise healthy individuals for whom vitamin D deficiency was not evaluated. We establish PTH reference ranges in apparently healthy, normocalcemic, normophosphatemic individuals categorized by 25-hydroxyvitamin D (25(OH)D) status using the Elecsys® PTH (cobas e 601) and Elecsys® Vitamin D total II electrochemiluminescence immunoassays (cobas e 411). METHODS: This prospective, non-interventional study measured PTH in serum from 653 apparently healthy adults [56.7% female; 68.2% white/Caucasian; 28.6% African American; median age 44 years (range 21-83)] from three diverse geographic sites across the USA during summer and winter months. Subjects were classified by concomitant vitamin D sufficiency (≥ 30 ng/mL), insufficiency (> 20 to < 30 ng/mL) or deficiency (≤ 20 ng/mL). RESULTS: In vitamin D sufficiency, median PTH was 31.9 pg/mL [range (2.5th-97.5th percentile) 17.9-58.6] compared with 35.5 pg/mL (17.0-60.4) for insufficiency, and 39.8 pg/mL (19.5-86.4) for deficiency. A significant inverse relationship was found between PTH and 25(OH)D (P < 0.001). After accounting for vitamin D, potential effects of race or season as covariates were relatively small or absent. CONCLUSIONS: Upper reference limits (URL) for PTH in vitamin D sufficiency/insufficiency were similar and lower than current values. Clinically important PTH elevations were observed in vitamin D deficiency, where revised reference ranges with a higher URL may be appropriate. These data may help to distinguish vitamin D-related PTH elevations from other causes [e.g., primary (normocalcemic) or secondary hyperparathyroidism].

Myosins of secretory tissues.

Myosin has been purified from the principal pancreatic islet of catfish, hog salivary gland, and hog pituitary. Use of the protease inhibitor Trasylol (FBA Pharmaceuticals, New York) was essential in the isolation of pituitary myosin. Secretory tissue myosins were very similar to smooth muscle myosin, having a heavy chain of 200,000 daltons and light chains of 14,000 and 19,000 daltons. Salivary gland myosin cross-reacted with antibodies directed toward both smooth muscle myosin and fibroblast myosin, but not with antiskeletal muscel myosin serum. The specific myosin ATPase activity measured in 0.6 M KCl was present. Tissues associated with secretion of hormone granules contained substantial amounts of this ATPase, rat pancreatic islets having 4.5 times that of rat liver. Activation of low ionic strength myosin ATPase by actin could not be demonstrated despite adequate binding of the myosin to muscle actin and elution by MgATP. The myosins were located primarily in the cytoplasm as determined by cell fractionation and were quite soluble in buffers of low ionic strength.

Muscle actin filaments bind pituitary secretory granules in vitro.

Hog anterior pituitary secretory granules sediment at 3,000 g. When rat or rabbit skeletal muscle actin filaments are present with the granules, the sedimentation decreases markedly. Depolymerized actin or viscous solutions of Ficoll and collagen have no effect on granule sedimentation. With this assay, actin filaments bind secretory granules (consisting of the proteinaceous core plus limiting membrane), secretory granule membranes, mitochondria, artificial lecithin liposomes, and styrene-butadiene microspheres, but have little or no interaction with membrane-free secretory granule cores and albumin microspheres. A secretory granule-actin complex sedimentable between 3,000 g and 25,000 g can be isolated. Metal ions, nucleotides, salts, dithiothreitol, or pretreatment of the granules with trypsin do not destroy the binding, which appears to be a lipophilic interaction.

Regulation of microtubule assembly in cultured fibroblasts.

Microtubule assembly in diploid human skin fibroblasts was studied by [3H]colchicine binding to disaggregated microtubule subunits and to total cell tubulin. Microtubule content per milligram of cell protein was critically dependent upon cell density. As cultures neared confluence, microtubules increased and total cell tubulin decreased; the percent of tubulin assembled into microtubules increased from 5.3 in spare cultures to 58.3 in confluent cultures. Microtubules disappeared with a half-time of 2 min in response to 0 degree C incubation and reformed upon rewarming. Brief treatment of intact cells with concanavalin A or cytochalasin A depolymerized microtubules to 55 or 56% of control levels. The effect of concanavalin A was prevented by alpha-methylmannoside. Fibroblast microtubule assembly was not significantly altered by cyclic nucleotides, ascorbate, glucose, insulin, medium calcium concentration, or calcium ionophore A23187.

Role of microtubules in low density lipoprotein processing by cultured cells.

The effect of the microtubule inhibitor colchicine on the metabolism of (125)I-low density lipoprotein (LDL) by cultured human skin fibroblasts and aortic medial cells was studied in vitro. Colchicine did not alter the binding of LDL to cell surface receptors. However, the rate of LDL endocytosis was reduced to 58% of that expected. Despite diminished endocytosis, LDL was found to accumulate within the cells to 165% of that expected, whereas the release of LDL protein degradation products into the medium was reduced to 34% of control, findings consistent with a reduced rate of intracellular LDL breakdown. Colchicine did not alter cell content of the acid protease which degrades LDL, nor did [(3)H]colchicine accumulate in lysosomal fractions. However, colchicine did alter the intracellular distribution of both fibroblast lysosomes and endosomes. After colchicine, lysosomes tended to accumulate in the perinuclear region, whereas endosomes were found at the cell periphery. These findings are consistent with the hypothesis that ingested LDL is less available to lysosomal enzymes in the presence of colchicine. The actions of colchicine appear to be a result of destruction of cell microtubules. Lumicolchicine, a mixture of colchicine isomers which (unlike the parent compound) does not bind to the subunit of microtubules, was without effect. The uptake and degradation of LDL by cultured cells consists of both a receptor-specific component and nonspecific pinocytosis. Important differences must exist between these processes because even large amounts of LDL taken up and degraded by the nonspecific route fail to regulate key aspects of intracellular cholesterol metabolism. Colchicine selectively inhibited receptor-mediated LDL degradation. No effect was demonstrable on the nonspecific degradation of LDL by familial hypercholesterolemia fibroblasts grown in medium containing serum and added sterols. The degradation of bovine albumin by normal cells was also unaffected. Colchicine sensitivity appears to be a biochemical marker for the LDL receptor-specific metabolic pathway. Cytochalasins inhibit crosslinking and polymerization of cell microfilaments (although other important cell effects also occur). Cytochalasin D reduced LDL degradation to 44% of that expected. This result and the actions of colchicine suggest that cytoskeletal components such as microtubules and possibly microfilaments facilitate normal LDL metabolism.

Structure, immunology, and cell reactivity of low density lipoprotein from umbilical vein of a newborn type II homozygote.

In this report we compare the cord blood lipoproteins of a newborn boy homozygote who has low density lipoprotein (LDL) receptor-defective familial hypercholesterolemia (FH) with the lipoproteins from cord blood of normal newborns. Plasma LDL-cholesterol and apoprotein (Apo)B were 612 and 233 mg/dl (vs. 31+/-16 and 24+/-12 mg/dl, respectively, for normals, n = 21). LDL-cholesterol/ApoB ratio was 2.6 vs. 1.4+/-0.5. Levels of ApoA-I, ApoA-II, and HDL-cholesterol were similar to normal cord plasma. Thus, the lipoprotein abnormality is apparent at birth and is definitely present in LDL. Abnormalities in other lipoprotein, lipid, and in plasma apoprotein levels were not detected. On zonal ultracentrifugation, FH LDL was comprised of two populations (LDL(a) and LDL(b)), both faster floating than normal cord LDL (LDL(c)). This difference was due to the larger diameters of the particles on electron microscopy (LDL(a) = 276A+/-32 and LDL(b) = 260A+/-38 vs. LDL(c) = 237A+/-26, n = 200 each, mean+/-1 SD), and their higher contents of lipids relative to protein (86 and 82% vs. 74%, LDL(a), LDL(b), and LDL(c), respectively). More than 94% of the protein in both the FH and the normal preparations consisted of ApoB. FH LDL were more effective than control LDL in competing with (125)I-LDL (adult) for limiting amounts of anti-LDL antibodies in radioimmunoassay. FH LDL also competed more effectively for binding to LDL receptors on cultured fibroblasts at 4 degrees C, and FH LDL also delivered more cholesterol into the cells. Cells grown in lipoprotein-deficient serum contained 44+/-2 mug cholesterol/mg cell protein, incubation of cells for 18 h at 37 degrees C in 5 mug/ml FH LDL (protein) or in normal LDL raised cellular cholesterol levels to 75+/-2 and 60+/-2 mug/mg, respectively.LDL isolated from the FH patient's plasma at 6 mo of age and from his brother's plasma (a 5-yr-old boy FH homozygote) were similar to LDL isolated from normolipemic subjects in flotation properties, chemical composition, and immunochemical and cell reactivity. The fact that differences between normal cord LDL and FH cord LDL were present at birth, but that the differences between control and FH LDL were no longer present postnatally suggests that the altered immunologic and cell interactive properties of FH cord LDL were probably related to its unusually high contents of core lipids.

Diversity in expression of heterozygous familial hypercholesterolemia. Characterization of a unique kindred.

Clinical and biochemical characteristics of familial hypercholesterolemia (FH) heterozygotes possessing an abnormally high molecular weight low density lipoprotein receptor (HMWR) are reported. The disorder is transmitted as an autosomal dominant trait and is not distinguishable from classic heterozygous FH on clinical grounds. The average plasma low density lipoprotein (LDL) level is 360 mg/dl and tendon xanthomata and early coronary disease are present. LDL receptor activity is higher than expected. In skin fibroblast cultures two types of functional LDL receptors are present, one with a normal apparent native molecular weight of 140,000, and the other of 176,000. When immobilized on nitrocellulose paper both receptors bind LDL. Maximum 125I-LDL binding capacity of fibroblast monolayers is reduced only 20%, compared with 50% in typical heterozygous FH. Affinity for 125I-LDL is increased and a 38% reduction in the Michaelis constant for LDL is observed. When autologous 125I-LDL was injected intravenously, the fractional catabolic rate of LDL was 205% and the LDL apoprotein B production rate was 328% of that found in a typical heterozygous FH subject. Thus, both in vitro and in vivo testing indicated only a modest deficiency of LDL receptor activity. Kindred members possessing the HMWR had an associated abnormality of cholesterol biosynthesis. Cholesterol balance studies in three individuals with the HMWR trait demonstrated elevated cholesterol biosynthesis of two to three times the mean of normal subjects. These findings suggest that increased LDL production and increased cholesterol production may assume a significant role in the pathologic manifestations of heterozygous FH. Functional abnormalities in LDL receptor activity as measured in fibroblast culture may be relatively small.

Familial hypercholesterolemia. Evidence for a newly recognized mutation determining increased fibroblast receptor affinity but decreased capacity for low density lipoprotein in two siblings.

Cultured skin fibroblasts were obtained from two siblings with classic clinical features of homozygous familial hypercholesterolemia. Plasma cholesterol values were 970 and 802 mg/100 ml in the siblings, 332 mg/100 ml in the mother, and 426 mg/100 ml in the father. Fibroblast receptor-specific capacity for binding and degradation of (125)I-low density lipoprotein (LDL) at 37 degrees C was 11% of normal, consistent with the diagnosis of "homozygous LDL receptor-defective" hypercholesterolemia, a disorder in which LDL binding activity is low but detectable. The residual LDL receptor activity was clearly qualitatively abnormal. The Michaelis constant (K(m)) for (125)I-LDL was reduced to 20-40% of normal, indicating a substantially increased affinity for LDL. Increased affinity and reduced capacity for (125)I-LDL are also found when normal fibroblasts are assayed at 4 degrees C. As the temperature is raised to 37 degrees C surface LDL binding affinity decreases while capacity increases. At 4 degrees C the fibroblasts of our subjects had an affinity for LDL indistinguishable from normal cells assayed at that temperature and a binding capacity 23% of normal. However, only small changes in affinity and capacity occurred upon increasing the temperature to 37 degrees C. When (125)I-apoprotein E-phospholipid vesicles were bound at 37 degrees C the receptor deficiency appeared only half as severe as when (125)I-LDL was used as ligand.A family study suggests that the siblings are genetic compounds rather than homozygotes, having inherited a mutant maternal gene causing absent or silent LDL receptors and a mutant paternal gene resulting in qualitatively altered LDL receptors. It is not clear whether these defects are present at the same or different genetic loci. The altered receptors are characterized by increased affinity and moderately reduced capacity for LDL at 37 degrees C and are accompanied by hypercholesterolemia at least as severe as that associated with familial hypercholesterolemia with absent or nonfunctional LDL receptors.

The purification and quantitation of myosin from cultured cells.

Myosin has been purified from the following cultured cell lines: normal rat kidney fibroblast (NRK), HeLa-Rhino (HeLa), human choriocarcinoma, human acute lymphoblastic leukemia, rat hepatoma (HTC), monkey kidney (VERO), pigmented mouse melanoma, Y-1 rat adrenal cortex, and growth hormone-secreting GH-1. Myosin constitutes 0.5-5.4% of the protein of these cells. It was not detected in washed human erythrocytes or in two types of mouse plasmacytoma cells. Two methods for the purification of myosin from cultured cells have been employed. With Method I highly purified myosin was prepared by Sepharose 4B and DEAE-cellulose chromatography from 10(10) L-929 cells as well as from mouse uterus. Those myosins have similar molecular and subunit weights as well as ATPase activity but are immunologically distinct. Method II involving ultracentrifugation and Sepharose 4B chromatography, is suitable for the production of moderately pure myosin in good yield from as few as 5-10(7) cells (five 100-mm Petrie dishes).

Contractile proteins and pancreatic beta-cell secretion.

Much indirect evidence suggests, but does not prove, that insulin secretion depends on contractile proteins similar to those of skeletal muscle and cilia. Such proteins constitute a molecular basis for the emiocytotic extrusion of insulin granules. It is likely that the secretory machinery is complex, requiring over eight proteins. The available evidence is consistent with a model of saltatory granule movement oriented by microtubules and powered by actomyosin contraction in response to elevations in cytosol calcium. Because most diabetics secrete some insulin and because relatively little of the stored B-cell insulin is released in response to hyperglycemia, further research into the molecular mechanism of insulin granule release is needed.

Increased low density lipoprotein receptor expression mediated through the insulin-like growth factor-I receptor in cultured fibroblasts.

Plasma insulin-like growth factor-I (IGF-I) levels are inversely correlated with apolipoprotein B and low density lipoprotein (LDL) cholesterol in humans. To identify a molecular basis for this observation, the effects of IGF-I on LDL receptor expression in fibroblasts were studied. IGF-I increased LDL receptors in cultured human skin fibroblasts at concentrations greater than 25 ng/ml. However, IGF-I effects were not easily quantitated due to secretion of inhibitory IGF-binding proteins by the cells. To circumvent this difficulty, QAYL, an IGF-I analog that binds to the IGF-I receptor but not to IGF-binding proteins, was used. QAYL increased LDL receptor number 56-72% with half-maximum effect at 0.6 ng/ml. alpha-IR3, a monoclonal antibody directed toward the IGF-I receptor, blocked this effect. QAYL treatment increased synthesis of LDL receptor protein without increasing LDL receptor mRNA levels or altering protein stability. Both QAYL and IGF-I increased LDL receptors prominently in cells that had been treated with physiological amounts of LDL cholesterol. IGF-I, acting through the IGF-I receptor and modulated by IGF-binding proteins, may contribute to the regulation of LDL metabolism by increasing translation of LDL receptor message.

Plasma lipids in patients with type I diabetes mellitus. Influence of race, gender, and plasma glucose control: lipids do not correlate with glucose control in black women.

Plasma lipids and hemoglobin A1 were measured in 544 type I diabetic patients. Hemoglobin A1 was positively correlated with the levels of total plasma cholesterol, total triglycerides, and low-density lipoprotein cholesterol and negatively correlated with the level of high-density lipoprotein cholesterol in the entire biracial group. These relationships between plasma lipids and hemoglobin A1 were not present in black women. In the white diabetic population a reduction in hemoglobin A1 of one percentage point was statistically associated with a decrease of 0.16 to 0.17 mmol/L in total plasma cholesterol, a decrease of 0.10 to 0.13 mmol/L in low-density lipoprotein cholesterol, and a reduction of 0.12 to 0.14 mmol/L in triglycerides. These findings suggest that race and gender are important determinants of the response of plasma lipids to glucose control in type I diabetes mellitus.

Quantitative relationship between plasma lipids and glycohemoglobin in type I patients. Longitudinal study of 212 patients.

Plasma cholesterol, triglycerides, glycohemoglobin, and other covariates were measured in 212 type I (insulin-dependent) diabetic subjects on entry into a longitudinal study of diabetes and again after an average interval of 3.7 yr. Changes in individual cholesterol and triglyceride values over time were significantly correlated with changes in glycohemoglobin. After adjustment for potentially confounding covariates, plasma cholesterol declined by 2.2% (0.1 mM) for each percentage-point reduction in glycohemoglobin and plasma triglycerides declined by 8% (0.08 mM) per percentage point glycohemoglobin. Increased insulin dose was independently associated with increased plasma triglycerides, after adjusting for glycohemoglobin level and other covariates. However, insulin dose diabetic metabolic control, measured as declining glycohemoglobin, is the variable most closely associated with reduced plasma lipids in a population of typical type I diabetic patients.

Effect of pinitol treatment on insulin action in subjects with insulin resistance.

OBJECTIVE: Endogenous low-molecular-weight glycans containing pinitol (3-O-methyl-D-chiro-inositol) and D-chiro-inositol are thought to mediate certain actions of insulin. We tested the hypothesis that oral administration of soybean-derived pinitol would improve insulin sensitivity in obese subjects (BMI = 36.6 kg/m2) with diet-treated type 2 diabetes or glucose intolerance (HbA1c = 6.8%). RESEARCH DESIGN AND METHODS: There were 22 subjects randomized to receive either pinitol 20 mg x kg(-1) x day(-1) (n = 12) or placebo (n = 10) in a 28-day double-blinded trial. RESULTS: No toxicity due to the pinitol was observed during the study The sensitivity of glucose and lipid metabolism to insulin were assessed by measurement of whole-body glucose, palmitate, and glycerol kinetics during basal conditions and a hyperinsulinemic-euglycemic clamp. Metabolic measurements were made at baseline and again at the end of the study Final plasma levels of pinitol were 48-fold (1.06 +/- 0.15 vs. 0.02 +/- 0.01 micromol/l, P < 0.0001) and D-chiro-inositol levels 14-fold (0.56 +/- 0.08 vs. 0.04 +/- 0.02 micromol/l, P < 0.0001) greater in the pinitol group compared with placebo. CONCLUSIONS: Four weeks of pinitol treatment did not alter baseline glucose production, insulin-mediated glucose disposal, or rates of appearance of free fatty acids and glycerol in plasma. We conclude that plasma levels of both pinitol and D-chiro-inositol are very responsive to pinitol ingestion, but insulin sensitivity does not increase after pinitol treatment in individuals with obesity and mild type 2 diabetes.

Acute stimulated hormone release from cultured GH3 pituitary cells.

Treatment of cultured rat pituitary GH3 cells with 50 mM KCl in growth medium released 33% of cell PRL and 18% of cell GH with a half-time of 5 min. Hormone in the culture medium was increased 2- to 4-fold over unstimulated levels. The response required calcium; barium and strontium, but not magnesium, could substitute for calcium. Low temperature completely inhibited hormone release, which was also reduced significantly by inhibitors of energy metabolism and by nitrogen. This acute response was similar in ionic requirements, hormones released, and time course to the acute effect of TRH. Like potassium stimulation, TRH resulted in acute release of both PRL and GH. This contrasts with the finding that chronic TRH treatment reduced GH synthesis in GH3 cells. After a 10-min preincubation with potassium, subsequent short incubations with potassium released little hormone unless the cells were allowed to recover by incubation in normal medium for at least 2 h. This acutely releasable hormone pool seems to be located in a membrane-bound subcellular fraction, since GH3 cells did not discharge the cytoplasmic marker enzyme, lactate dehydrogenase, during potassium-stimulated hormone release.

The low density lipoprotein receptor on human peripheral blood monocytes and lymphocytes: visualization by ligand blotting and immunoblotting techniques.

Western blotting and immunoprecipitation techniques were used to study low density lipoprotein (LDL) receptors from cultured human monocytes, lymphocytes, and fibroblasts. After incubation in lipoprotein-deficient media to allow induction, receptors were solubilized, subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transferred to nitrocellulose paper, and detected by incubation with apolipoprotein B-containing lipoproteins followed by radiolabeled antiapolipoprotein B antibody. LDL receptors of identical apparent mol wt were demonstrated in monocyte and lymphocyte cell extracts; the receptors bound LDL as well as human post-prandial lipoprotein (density, less than 1.0063) on Western blots, but did not bind acetyl-LDL. LDL receptors in mononuclear cells could also be detected by immunoblotting using immunoglobulin G-C7, a monoclonal antibody raised against the bovine LDL receptor. When cell extracts were blotted, the mononuclear cell receptors had a lower mol wt than the fibroblast receptor in unreduced sodium dodecyl sulfate-polyacrylamide gels, with an apparent mol wt difference of 5,000 [134,000 +/- 1,400 (+/- SE) for mononuclear cells vs. 139,000 +/- 1600 for fibroblasts]. Immunoprecipitation and electrophoresis of L-[35S]methionine-labeled cell extracts revealed more rapid conversion of the receptor precursor to the mature receptor in monocytes than in fibroblasts. Western blotting of mononuclear cells from a patient with an abnormally high mol wt receptor characterized in fibroblasts demonstrated that the same mutation was expressed in monocytes and lymphocytes. This report represents the first visualization of human mononuclear cell LDL receptors by Western blotting and immunoprecipitation. These techniques may find application in population screening for LDL receptor variability.

Relation between plasma leptin concentration and body fat, gender, diet, age, and metabolic covariates.

We measured plasma leptin concentrations by RIA in 204 normal weight and obese subjects, aged 18-80 yr, using full-length recombinant human leptin as a standard. Fasting levels between 1.2-97.9 ng/mL were observed. The plasma leptin concentration was highly correlated with percent body fat (r = 0.710; P < 0.0001) and was 3 times as high in women as in men (17.1 vs. 5.8 ng/mL; P < 0.0001). Circulating leptin was inversely related to age and was reduced 53% in subjects over age 60 yr. A statistical model containing percent body fat, gender, and age accounted for 65% of the variance in plasma leptin levels. Leptin was not independently related to abdominal fat distribution, plasma lipids and lipoproteins, chronic energy intake, diet composition, plasma insulin, or maximum oxygen consumption. However, plasma leptin was reduced by 26% in 5 obese subjects who consumed a 1000-Cal diet for 10 days (P = 0.004). We conclude that circulating leptin rises continuously with increasing adiposity. Gender, age, and short term caloric restriction may be important secondary regulators of plasma leptin.

Sitostanol administered in lecithin micelles potently reduces cholesterol absorption in humans.

BACKGROUND: Phytosterol feeding in human clinical trials has had generally small and inconsistent effects on serum cholesterol concentrations, raising doubts about the importance of phytosterols in natural diets and supplements. OBJECTIVE: The hypothesis tested was that the low intestinal bioavailability of purified phytosterols can be increased by formulation with lecithin. DESIGN: The ability of sitostanol to reduce cholesterol absorption was measured directly by including hexadeuterated cholesterol tracer in a standard test breakfast and measuring plasma tracer concentration 4 and 5 d later by gas chromatography-negative ion mass spectrometry. The tracer amount after a test meal containing sitostanol was compared with that after an identical meal containing placebo. Each subject served as his or her own control and the order of testing was random. Sitostanol was formulated either as a powder or as a sonicated micellar solution with lecithin. A total of 38 single-meal tests were performed in 6 healthy subjects. RESULTS: Sitostanol powder (1 g) reduced cholesterol absorption by only 11.3 +/- 7.4% (P = 0.2), confirming in vitro data showing poor solubility of sitostanol powder in artificial bile. In contrast, sitostanol in lecithin micelles reduced cholesterol absorption by 36.7 +/- 4.2% (P = 0.003) at a dose of 700 mg and by 34.4 +/- 5.8% (P = 0.01) at a dose of 300 mg. CONCLUSIONS: Sitostanol reduced cholesterol absorption at doses lower than reported previously, but only if presented in lecithin micelles. Properly formulated sitostanol as well as naturally occurring complexes of phytosterol and phospholipid might be therapeutically useful for cholesterol lowering.

Effect of exercise training on plasma cholesterol and cholesterol kinetics in adult female rats.

Adult female rats fed laboratory chow of low cholesterol content were trained by swimming for 77 days. Plasma cholesterol concentration decreased 38% compared to sedentary controls. Whole body cholesterol metabolism was studied by injection of [14C]cholesterol tracer and determination of the plasma cholesterol-specific activity during the last 49 days of the experiment. The rate constant for elimination of cholesterol from the body was 31% higher in swimming than in sedentary animals, and the size of the rapidly-exchanging cholesterol pool was 28% smaller. These results suggest that enhanced cholesterol excretion or catabolism accompanies exercise training in the rat.

Apolipoprotein E-rich HDL in patients with homozygous familial hypercholesterolemia.

Ordinarily, HDL1, a fraction of HDL enriched in apoE, is a minor fraction of plasma, but in human subjects and experimental animals eating diets high in fat and cholesterol and in patients with homozygous familial hypercholesterolemia (HFH) or CETP deficiency, HDL1 (or HDLc) concentrations in plasma are increased. However, little is known about the structures, compositions and metabolic sources of HDL1 in HFH patients. To obtain HDL1 for the study, we surveyed several fractions in the HDL density range for apoE by SDS-PAGE. The ratio of apoE to apoAI in the HDL (d = 1.063-1.21 g/ml) of 8 HFH patients was 0.14 +/- 0.03 compared to 0.03 +/- 0.005 in a control group of 8 normolipidemic subjects (P less than 0.001) suggesting that an apoE-rich fraction indeed was present in increased amounts. ApoE/apoAI ratios of lipoproteins of the density range 1.050-1.090 were even higher at 1.5 and 2.0 in 2 patients compared to 0.4 +/- 0.1 in controls, indicating that this density fraction may be particularly enriched with apoE-rich lipoproteins. By contrast, d = 1.020-1.050 g/ml and d greater than 1.090 fractions contained very little apoE. Therefore, we further characterized the d = 1.050-1.090 g/ml lipoproteins of HFH patients and controls. Fractionation of an d = 1.050-1.090 fraction by concanavalin-A chromatography (CONA) yielded an unbound apoE-rich fraction that contained apoE, apoAI and apoC but no apoB, and a bound LDL-like fraction that contained mostly apoB-100, as determined by SDS-PAGE and by solid phase immunoassays, containing monoclonal antibodies directed against apoB, apoE and apoAI. The apoE/apoAI ratio of the CONA unbound fraction of HFH patients was greater, and the fraction also contained more free cholesterol and phospholipids than the fraction of control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)