Leptin levels do not change acutely with food administration in normal or obese subjects, but are negatively correlated with pituitary-adrenal activity

BACKGROUND

Leptin is a peptide secreted by white adipose tissue which has been shown to have a major influence on body weight regulation, while animal studies have revealed widespread interconnections between leptin and other endocrine systems, especially with insulin. However, its acute regulation has been little studied in the human. We have therefore investigated the effect of a 1000 kcal meal and fasting on the levels of leptin, insulin and cortisol, in both normal and obese subjects.

SUBJECTS AND DESIGN

We have studied the effect of food and fasting on circulating leptin levels in 20 subjects of normal body mass index (BMI range 18-25) and in a group of 12 moderately-severely obese subjects (BMI range 34-61). We also studied the effect of food and fasting in a patient both before and after the successful removal of a pancreatic insulinoma as a model of excess insulin secretion.

RESULTS

Mean leptin levels were significantly higher in the obese than in the lean group (42.7 +/- 3.41 vs 5.35 +/- 1.55 micrograms/l, mean +/- SEM; P < 0.001), and showed a positive correlation with body mass index (r = +0.71; P < 0.001). Frequent (every 20 minutes) sampling for 3 hours after food did not show any acute changes in circulating leptin levels. On the fasting day we observed a small but significant fall in circulating leptin levels in the last 4 hours of a 20-hour fast in our subjects as a group (92 +/- 0.03% of basal, P = 0.03); however, in the lean subjects the fall was greater (86 +/- 0.04% of basal, P = 0.02) than in the obese, where it did not reach statistical significance (96 +/- 0.05% of basal). Pre-meal and peak insulin levels showed a positive correlation with circulating mean leptin levels (r = +0.65; P < 0.001 and r = +0.78; P < 0.001, respectively) in all subjects, while pre-meal and peak serum cortisol levels showed an inverse relation with leptin levels (r = -0.53; P = 0.002 and r = -0.41; P = 0.02, respectively); this effect was independent of BMI in the obese subjects. In the patient with the insulinoma the markedly elevated insulin and leptin levels measured before the operation returned to normal after removal of the tumour, in accord with reports of experimental animal data that long-term insulin excess per se is associated with increased circulating leptin concentrations.

CONCLUSION

Leptin is a robust indicator of BMI and insulin levels, both basal and stimulated, but does not change acutely following food. Fasting causes a proportionately greater decline in leptin levels in lean subjects than in obese subjects. Circulating leptin is inversely correlated with the activity of the hypothalamo-pituitary-adrenal axis: whether this is a direct influence of leptin on hypothalamo-pituitary-adrenal activity, or whether both are indirect indicators of body fat stores, requires further investigation.

Misleading results from immunoassays of serum free thyroxine in the presence of rheumatoid factor

A novel interference with measurements of serum free thyroxine (FT4) caused by rheumatoid factor (RhF) is described. We found misleading, sometimes gross, increases of FT4 results in 5 clinically euthyroid elderly female patients with high RhF concentrations. All 5 patients had high FT4 on Abbott AxSYM or IMx analyzers. "NETRIA" immunoassays gave misleading results in 4 of the 5 patients; Amerlex-MAB in 2 of 4 patients; AutoDELFIA in 2 of the 5; and Corning ACS-180 and Bayer Diagnostics Immuno 1 in 1 of the 5. BM-ES700 system results for FT4 in these women remained within the reference range. Results for serum T4, thyroid-stimulating hormone, free triiodothyronine, thyroid-hormone-binding globulin, and FT4 measured by equilibrium dialysis were normal in all 5 patients. Drugs, albumin-binding variants, and anti-thyroid-hormone antibodies were excluded as interferences. Addition to normal serum of the RhF isolated from each of the 5 patients increased the apparent FT4 (Abbott AxSYM). Screening of 83 unselected patients demonstrated a highly significant positive correlation between FT4 (Abbott AxSYM) and RhF concentrations. Discrepant, apparently increased FT4 with a normal result for thyroid-stimulating hormone should lead to measurement of the patient's RhF concentration.

Development of enzyme immunoassay for endogenous ouabain-like compound in human plasma

Widespread evidence supports the existence of an endogenous digitalis-like compound in mammals. We report here the development of a novel enzyme immunoassay for ouabain that, in conjunction with a detailed HPLC study, identifies a ouabain-like compound (OLC) in extracted human plasma. The assay is sensitive-minimum detection limit for OLC 37 pmol/L (11 pmol/L in plasma)-and has a working range (between-assay CV < 10%) of 180-10000 pmol/L (54-3000 pmol/L in plasma). Mean recoveries of ouabain added to plasma ranged from 90% to 100%, and plasma extracts diluted in parallel to the standard curve. Plasma OLC concentrations in 10 healthy volunteers averaged 92 pmol/L (range 55-168), assuming 100% cross-reactivity of OLC in the ouabain assay. HPLC analysis with two distinct chromatographic conditions demonstrated that endogenous human plasma OLC co-eluted with authentic ouabain. The enzyme immunoassay is rapid and easy to perform and will support further investigation of the nature of this controversial endogenous steroid.

Insulin-like growth factor-I and- II in combination inhibit the release of growth hormone-releasing hormone from the rat hypothalamus in vitro

This study was designed to investigate the feedback loop between insulin-like growth factor-I (IGF-I) and IGF-II and the hypothalamic hormones growth hormone-releasing hormone (GHRH) and somatostatin (SS) using an in vitro rat hypothalamic model. IGF-I and, to lesser extent, IGF-II, both activate type 1 IGF receptors, while type 2 receptors are activated by IGF-II alone. IGF-I, IGF-II, their various specific analogues (Des[1-3]IGF-I, [Arg54/Arg55]IGF-II and [Leu27]IGF-II), insulin and the type 2 receptor antagonist beta-galactosidase were used on their own or in combination to study their effect on GHRH and SS release. Our results suggest that the simultaneous activation of type 1 and type 2 IGF receptors is needed for the negative feedback effect of IGFs on GHRH release in this in vitro system, in agreement with earlier findings in vivo. Somatostatin was not altered by any combination of peptides.

Sex difference in high density lipoprotein cholesterol in six countries

It is known that women have higher levels of high density lipoprotein (HDL) cholesterol than men. The authors examined the association between HDL cholesterol and biologic sex in 8,631 women and 10,690 men aged 45-54 years from six countries studied between 1972 and 1989. The variation in the sex difference for HDL cholesterol was significant; the smallest difference (0.06 mmol/liter) was seen in China and the largest (0.40 mmol/liter) in Canada. Adjustment for differences in body mass index, smoking, alcohol use, and heart rate reduced but did not eliminate the variability. The sex difference in HDL cholesterol levels, usually assumed to be due to biologic factors, differs across cultures and may be related to environmental factors.

An enzyme immunoassay for 6-sulphatoxy-melatonin in human urine

We describe a newly developed enzyme immunoassay (EIA) for the determination of 6-sulphatoxy-melatonin (aMT6s) in human urine, using a aMT6s-bovine serum albumin-horseradish peroxidase (aMt6s-BSA-HRP) conjugate as the enzyme label. The assay incorporates a highly specific antibody raised in rabbits. The EIA has a sensitivity of 2 pg/well (40 pg/ml) with intraassay coefficients of variation of 2.3-6.1% in the range of the assay. The material with the highest level of cross-reactivity was N-acetyl serotonin sulphate, with a relative potency of 0.000078%. One hundred thirty-four urine samples from children and adults at different time points were assayed and the results compared with those from an established radioimmunoassay (RIA) and with a newly developed RIA using the same antibody as the EIA. The correlation coefficient, r, comparing the two RIA's was 0.9869, and the regression equation was log (kit) = 0.9340 log (new) + 0.1213. The correlation coefficient, r, comparing the EIA with the newly developed RIA, was 0.9686, and regression equation log (new) = 0.9674 log (EIA) + 0.0600. The EIA for the measurement of aMT6s in urine represents a new approach in the investigation of pineal function.

Metabolic persistence of fetal hemoglobin

Hereditary persistence of fetal hemoglobin (HPFH) has typically been ascribed to mutations in the beta-globin gene cluster. Pharmacologic agents, including the short-chain fatty acid butyrate, have been shown to upregulate fetal and embryonic globin gene expression. In this report we investigate the possibility that metabolic derangements characterized by an inability to metabolize another short-chain fatty acid, propionate, could be associated with a persistence of fetal hemoglobin unrelated to alterations in the beta-globin cluster. Embryonic globin gene upregulation in a murine adult erythroid cell culture was shown by RNase protection after induction with three short-chain fatty acids (C2-C5). Chart reviews and measurement of fetal hemoglobin in five patients with abnormalities in propionate (C3) metabolism were undertaken; SSCP/dideoxy fingerprint analysis of the gamma-globin gene promoters was done in three of these five patients. Twelve patients with other metabolic derangements served as controls. Only the four patients with clinically severe abnormalities in propionate metabolism (ages 2 to 11), but without anemia, showed a sustained elevation in fetal hemoglobin (3% to 10%). The level of elevation of fetal hemoglobin in these patients, who lack erythropoietic stress, suggests that propionic acid and/or its metabolites are potent stimulators of fetal hemoglobin expression. Study of this group of patients should allow unique insights into the long-term effects of sustained exposure to elevations of short-chain fatty acid levels.

An experimental comparison of equivalent terminal and rotational crossbreeding systems in swine: pig performance

Eleven thousand forty-nine pigs produced from 934 litters using 262 rotational and F1 crossbred sows were used to study differences in pig weights, survival rates and pen average daily gain, daily feed intake, and feed conversion between pigs from equivalent three-breed rotational and three-breed terminal crossbreeding systems using Duroc, Yorkshire, and Landrace breeds. Pig weights at birth and 21 and 56 d and days to reach 100 kg did not differ (P > .10) between the terminal and rotational crossbreeding systems. However, ultrasound backfat thickness of pigs from the terminal crossbreeding system was .04 cm greater (P < .007) than that of pigs from the rotational crossbreeding system. Survival rate from 56 d to 100 kg was .8% greater (P < .01) for pigs from the terminal crossbreeding system than for those from the rotational crossbreeding system. The crossbreeding system had no effect (P > .10) on survival rate at birth, from birth to 21 d, from 21 to 56 d, or from birth to 100 kg. Differences between the two crossbreeding systems were nonsignificant (P > .20) for pen average daily gain, daily feed intake, and feed conversion. Breed composition of pigs was an important source of variation (P < .01) for pig weights at birth and at 56 d. Similarly, breed composition of the pig also affected ultrasound backfat thickness at 100 kg (P < .01), but not days required to reach 100 kg (P > .10). For survival traits, only survival rate from 56 d to 100 kg was influenced by breed composition of the pig.(ABSTRACT TRUNCATED AT 250 WORDS)

An experimental comparison of equivalent terminal and rotational crossbreeding systems in swine: sow and litter performance

Two hundred sixty-two rotational and F1 sows were mated to Duroc, Yorkshire, or Landrace boars to study performance differences between equivalent three-breed rotational and three-breed terminal crossbreeding systems. Matings were made to maximize heterosis. The sows were fed either 1.8 or 2.7 kg/d (2.25 and 3.15 kg/d in winter months) during gestation. These matings produced 934 litters to determine the effect of crossbreeding system, breed composition within crossbreeding system, and gestation feeding level on litter sizes and weights, sow weight and backfat thickness at weaning, daily feed intake of the sow during lactation, interval from weaning to estrus, and farrowing rate. Feeding level during gestation was not an important source of variation for any of the traits except litter birth weight and daily feed intake of the sow during lactation. Litter size marketed was .37 pigs/litter greater (P < .05) for the terminal-cross sows than those sows from the rotational crossbreeding system. Litter weights at birth and 56 d were .8 and 6.5 kg heavier (P < .02, .03), respectively, for the terminal crossbreeding system than for the rotational crossbreeding system. Sow weight and backfat thickness at weaning, daily feed intake during lactation, and farrowing rate were not affected (P > .10) by crossbreeding system. Weaning-to-estrus interval was 1.3 d shorter (P < .03) for sows in the terminal crossbreeding system than for those in the rotational system.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of disulfide-linked apolipoprotein species in human lipoproteins

We wished to determine whether apolipoprotein C-IIToronto, a mutant form of apolipoprotein C-II that contains a C-terminal cysteine residue, exists as a monomeric species or as multiple disulfide-linked species in plasma lipoproteins. The plasma lipoproteins from a heterozygous carrier and two homozygous carriers of apoC-IIToronto were investigated. The mutant apolipoprotein was found in homodimeric form and as heterodimers with apolipoprotein A-II, apolipoprotein B-100, and apolipoprotein E. Of particular interest was the demonstration of the existence of the disulfide-linked species apolipoprotein B-100:A-II and B-100:C-IIToronto in the very low density and low density lipoproteins in subjects who were carriers of apoC-IIToronto. We also observed that apoE3:C-IIToronto and apoE3:A-II dimers were present in the chylomicrons and very low density lipoproteins of these subjects. The observation of the existence of apolipoprotein B-100:A-II was extended to other hypercholesterolemic and hypertriglyceridemic subjects. The highest proportion of apolipoprotein B-100:A-II was observed in the very low density lipoproteins of hypertriglyceridemic subjects. The concentration of this species was significantly higher in hyperlipidemic subjects than in normolipidemic controls. These results demonstrate that the molecular species of cysteine-containing apolipoproteins are complex and should be considered in studies of human lipoprotein composition and function.

Beta-VLDL in hepatic lipase deficiency induces apoE-mediated cholesterol ester accumulation in macrophages

Hepatic lipase-deficient subjects in the Ontario kindred are compound heterozygotes for hepatic lipase mutations (Ser267-->Phe and Thr383-->Met). Cholesteryl ester-rich beta-very-low-density lipoprotein (beta-VLDL) accumulates in plasma and such subjects have premature atherosclerosis. To determine a possible mechanism, we hypothesized that hepatic lipase-deficient beta-VLDL, homozygous for apolipoprotein (apo) E3, would cause cholesteryl ester accumulation and foam cell formation in macrophages. beta-VLDL and pre-beta-VLDL were isolated by Pevikon electrophoresis and incubated with J774 macrophages, cells that do not secrete apoE. beta-VLDL increased cellular cholesteryl ester content 13-fold, whereas pre-beta-VLDL increased cholesteryl ester sevenfold. beta-VLDL increased acyl CoA:cholesterol acyltransferase activity fourfold (measured as [14C]oleate incorporation into cholesteryl ester). Preincubation of hepatic lipase-deficient beta-VLDL with the anti-apoE monoclonal antibody 1D7, which inhibits binding of apoE to low-density lipoprotein receptors, inhibited cellular cholesteryl ester accumulation by 75%, whereas the anti-apoB blocking monoclonal antibody 5E11 failed to inhibit cellular cholesteryl ester accumulation. In contrast to hepatic lipase deficiency, beta-VLDL from type III subjects (E2/E2) failed to increase cellular cholesteryl ester or acyl CoA:cholesterol acyltransferase more than 1.5-fold. Thus, hepatic lipase-deficient beta-VLDL readily induces cholesteryl ester accumulation in J774 macrophages, a process mediated by functional apoE3. This may explain the premature atherosclerosis observed in this kindred.

Hepatic lipase deficiency. Clinical, biochemical, and molecular genetic characteristics

Hepatic lipase (HL) is an important enzyme in the metabolism of triglyceride-rich lipoproteins and high density lipoproteins. The clinical syndrome of HL deficiency is rare and difficult to identify. We studied carriers of mutant HL to ascertain whether there are distinctive clinical and/or biochemical characteristics of the heterozygous state. In an Ontario kindred, compound heterozygosity for two HL mutations, S267F and T383M, underlies the clinical syndrome of complete HL deficiency. We report that simple heterozygotes for either HL mutant do not have a discrete lipoprotein abnormality, except for relative triglyceride enrichment of lipoprotein fractions with d > 1.006 g/mL. Postheparin HL activity is depressed to a greater degree in carriers of S267F compared with carriers of T383M. Retinyl palmitate loading studies in a compound heterozygote revealed impaired clearance of chylomicron remnants. The dyslipoproteinemia in a compound heterozygote was ameliorated by lovastatin. There was no difference in the quantity and distribution of HL mRNA in the liver of a compound heterozygote when compared with that of a normal subject. Thus, HL deficiency associated with structural variation of the HL gene is characterized by premature atherosclerosis, triglyceride enrichment of lipoprotein fractions with d > 1.006 g/mL, the presence of circulating beta-very low density lipoproteins, and abnormal catabolism of postprandial triglyceride-rich lipoproteins.

Gas chromatographic profiles of plasma total lipids as indicators of dietary history. Correlation with carbohydrate and alcohol intake based on 24-h dietary recall

Quantitative gas chromatographic estimates of the major lipid classes and molecular species in fasting plasma were correlated with total carbohydrate, starch, fibre, sucrose and alcohol intake based on 24-h dietary recall. Spearman coefficients (rs) and tests of significance (P) were obtained for groups of 775 males and 471 females aged 20-59 years from a Toronto-McMaster Lipid Research Clinics Population Study. The most significant correlations varying from rs 0.1 to 0.2 and P 0.001 to 0.0005 (n = 400-773) were between increased intake of alcohol and increased ratios of C50/C54 triacylglycerols, C34/C36 phosphatidylcholines and phosphatidylcholine/free cholesterol (PC/FC) of plasma. Increase in total dietary carbohydrate, starch and fibre correlated with decreasing C50/C54 triacylglycerol, C34/C36 phosphatidylcholine and PC/FC ratios (rs = -0.1-0.2; P less than 0.002-0.04; n = 400-773). In contrast, consumption of high levels of alcohol was associated with increasing C50/C54 triacylglycerol, C34/C36 phosphatidylcholine and PC/FC ratios. A high intake of alcohol (50-150 ml per day) distinguished itself from other simple carbohydrate-induced lipid profiles by its marked effect on increased C50/C52 triacylglycerol and PC/FC ratio.

Plasma lipids and lipoproteins and the prevalence of risk for coronary heart disease in Canadian adults. Canadian Heart Health Surveys Research Group

OBJECTIVE

To report population reference values for blood lipids, to determine the prevalence of lipid risk factors and to assess their association with other risk factors.

DESIGN

Population-based cross-sectional surveys. Survey participants were interviewed at home and provided a blood sample at a clinic. All blood lipid analyses were done in the Lipid Research Laboratory, University of Toronto. The laboratory is standardized in the National Heart, Lung Blood Institute-Centres for Disease Control Standardization Program.

SETTING

Nine Canadian provinces, from 1986 to 1990.

PARTICIPANTS

A probability sample of 26,293 men and women aged 18 to 74 was selected from the health insurance registers for each province. Blood samples were obtained from 16,924 participants who had fasted 8 hours or more.

OUTCOME MEASURES

Concentration of total plasma cholesterol, triglycerides and high density lipoprotein (HDL) and low density lipoprotein (LDL) cholesterol in blood samples from fasting participants.

MAIN RESULTS

Of the study population, 46% had total plasma cholesterol levels above 5.2 mmol/L, 15% had LDL-cholesterol levels above 4.1 mmol/L, 15% had triglyceride levels above 2.3 mmol/L and 8% had HDL-cholesterol levels below 0.9 mmol/L. Total plasma cholesterol, LDL-cholesterol and triglyceride levels rose with age in men to a maximum in the 45-54 age group; in women there was little change with age up to ages 45 to 54, at which time the level of each of these lipids increased appreciably. The age-standardized prevalence of obesity was positively associated with elevation of total plasma cholesterol.

CONCLUSION

The results suggest the need for a multifactorial approach in health promotion efforts to lower blood cholesterol levels and reduce other risk factors in the population. A considerable number of adults were found to be at risk at all ages in both sexes. In the short term, men aged 34 and older and women aged 45 and older might benefit most from prevention programs.

5'-flanking sequences mediate butyrate stimulation of embryonic globin gene expression in adult erythroid cells

A stable transfection assay was used to test the mechanism by which embryonic globin gene transcription is stimulated in adult erythroid cells exposed to butyric acid and its analogs. To test the appropriate expression and inducibility of chicken globin genes in murine erythroleukemia (MEL) cells, an adult chicken beta-globin gene construct was stably transfected. The chicken beta-globin gene was found to be coregulated with the endogenous adult mouse alpha-globin gene following induction of erythroid differentiation of the transfected MEL cells by incubation with either 2% dimethyl sulfoxide (DMSO) or 1 mM sodium butyrate (NaB). In contrast, a stably transfected embryonic chicken beta-type globin gene, rho, was downregulated during DMSO-induced MEL cell differentiation. However, incubation with NaB, which induces MEL cell differentiation, or alpha-amino butyrate, which does not induce differentiation of MEL cells, resulted in markedly increased levels of transcription from the stably transfected rho gene. Analysis of histone modification showed that induction of rho gene expression was not correlated with increased bulk histone acetylation. A region of 5'-flanking sequence extending from -569 to -725 bp upstream of the rho gene cap site was found to be required for both downregulation of rho gene expression during DMSO-induced differentiation and upregulation by treatment with NaB or alpha-amino butyrate. These data are support for a novel mechanism by which butyrate compounds can alter cellular gene expression through specific DNA sequences. The results reported here are also evidence that 5'-flanking sequences are involved in the suppression of embryonic globin gene expression in terminally differentiated adult erythroid cells.

Interaction between variant apolipoproteins C-II and E that affects plasma lipoprotein concentrations

The genes for apolipoprotein (apo) C-II, a cofactor for activation of lipoprotein lipase, and apo E, a ligand for receptor-mediated uptake of triglyceride-rich lipoproteins, are physically linked on chromosome 19q13.1. In a large Caribbean Caucasian family, several individuals had clinical features of the complete absence of lipoprotein lipase activity and were homozygous for a DNA frameshift mutation of apo C-II, imparting functional inactivity to the mutant protein. Plasma from heterozygous carriers of this mutation, when compared with plasma from relatives who were noncarriers, had significantly diminished capacity to activate lipoprotein lipase in vitro. We also observed in heterozygotes for this mutation a wide range of serum lipid and lipoprotein levels. When age and sex were taken into account, the presence of a single apo E allele encoding the E4 isoform occurring in individuals with a single mutant apo C-II allele was strongly associated with higher levels of cholesterol, triglycerides, very low density lipoprotein cholesterol, and non-high density lipoprotein cholesterol when compared with those of relatives who carried neither or only one variant allele. This suggests that a single genetic mutation that usually has a recessive effect on lipoprotein metabolism can have an interactive effect on lipid phenotype when it is coinherited with a single mutation at another gene whose product affects the same metabolic pathway.

Compound heterozygosity for mutant hepatic lipase in familial hepatic lipase deficiency

In a kindred with three hyperlipidemic subjects who had premature atherosclerosis and complete deficiency of hepatic lipase activity, we had previously identified a novel structural hepatic lipase gene variant. We now report the identification of three more hepatic lipase gene mutations in this family and demonstrate that compound heterozygosity for two hepatic lipase mutations (designated S267F and T383M) underlies hepatic lipase deficiency.

Gas chromatographic profiles of plasma total lipids as indicators of dietary history. Correlation with fat intake based on 24-h dietary recall

Fasting plasma total lipid profiles were determined by high-temperature gas chromatography on a total of 1246 free living urban subjects, ages 20-59 years, from the Toronto-McMaster Lipid Research Clinic Population Study. Quantitative estimates of the major molecular species, lipid classes and lipid class ratios were correlated with a total of twelve dietary lipid components, including total saturated and unsaturated fats. oleic and linoleic acids, and cholesterol, to give appropriate Spearman coefficients (rS) and tests of significance (P) for groups of 775 males and 471 females. The intake of the various nutrients was derived from a 24-h dietary recall. The most significant correlations varying from rs +/- 0.1-0.4 and P less than 0.0001-0.0005 were between the intake of total fat, individual saturated and unsaturated fats, and the ratios of C50/C54 triacylglycerols and the C34/C36 phosphatidylcholines, which reflected the nature and quantity of the dietary fat consumed. Increases in dietary cholesterol and saturated fat produced small increases in plasma cholesterol and saturated triacylglycerols, while unsaturated dietary fat produced small decreases in saturated and increases in unsaturated plasma triacylglycerols. These changes in the plasma lipid parameters are consistent with those observed previously in much more limited dietary experiments with accurately known composition of ingested fats. It is, therefore, concluded that direct gas chromatographic profiling of plasma total lipids provides a simple and rapid method of verifying the overall correctness of the dietary recall.

An apolipoprotein CII mutation, CIILys19----Thr' identified in patients with hyperlipidemia

Five hyperlipidemic patients (one with Type III, three with Type IV, and one with Type V hyperlipoproteinemia) were found on isoelectric focusing to have both the normal isoform of apolipoprotein CII and a second isoform whose isoelectric point was consistent with a single charge change. The structure of the apolipoprotein CII variant was determined to be the same as normal apolipoprotein CII except for replacement of the normal Lys at amino acid residue 19 by Thr (C2K19T). The mutation was absent from 160 apoCII alleles screened from normolipemic subjects. The C2K19T substitution occurs in a domain of apolipoprotein CII postulated to contain a lipid-binding amphipathic alpha-helix. The presence of C2K19T in unrelated hyperlipidemic patients of various racial backgrounds suggests that, in combination with other factors such as mutations in apolipoprotein E, it plays a role in the development of hyperlipoproteinemias.

A hepatic lipase gene mutation associated with heritable lipolytic deficiency

Absent hepatic lipase (HL) activity results in dyslipidemia and premature atherosclerosis. DNA sequencing of the HL gene from subjects with heritable HL deficiency identified a new C to T substitution within exon 8 that in the mature enzyme caused a threonine to methionine change at position 383 (T383M). With a rapid DNA detection method we observed that all 6 individuals with complete HL deficiency from 2 families had the T383M mutation. None of 50 random unrelated unaffected subjects had this mutation. We propose that T383M is specific to families with heritable HL deficiency. Furthermore, structural variation at the HL gene, possibly in combination with other factors, appears to be etiologic in HL deficiency.

Plasma lipoproteins in familial hepatic lipase deficiency

We have studied the lipoproteins, apolipoproteins, and postheparin lipase activities in an extended pedigree with familial hepatic lipase deficiency. A deficiency of hepatic lipase was found in three of five brothers and in one of their children. Triglyceride enrichment of low density and high density lipoproteins was identified as the constitutive phenotype. beta-very low density lipoprotein was observed in hepatic lipase-deficient subjects, but it was absent when the plasma triglyceride concentration was less than 1 mM/l. The hepatic lipase-deficient subjects had normal or elevated low density lipoprotein cholesterol and high density lipoprotein cholesterol concentrations. Hyperprebetalipoproteinemia, hyperbetalipoproteinemia, and hyperalphalipoproteinemia were observed in both affected and unaffected family members. Compared with the unaffected family members, the hepatic lipase-deficient subjects had no significant differences in very low density lipoprotein cholesterol, very low density lipoprotein triglyceride, or low density lipoprotein cholesterol. These observations are consistent with the presence of additional genes causing hyperlipidemia in this family, independent of the deficiency of hepatic lipase.

Comparisons of specific crosses from Duroc-Landrace, Yorkshire-Landrace and Hampshire-Landrace sows managed in two types of gestation systems: pig performance

Ten thousand one hundred sixty-nine pigs were farrowed in 844 litters that were produced by mating Duroc (D), Yorkshire (Y) and Hampshire (H) boars to Duroc-Landrace (DL), Yorkshire-Landrace (YL) and Hampshire-Landrace (HL) sows to study the effect of sire breed, dam breeding and gestation environment (pasture lots vs confinement stalls) on pig weights, survival rates and feed efficiency. Pigs sired by H boars were .05 kg heavier at birth than Y-sired pigs and .2 kg heavier at 21 d than Y- and D-sired pigs, but they were .6 kg smaller at 56 d. D-sired pigs grew .028 kg/d faster from 56 d to 100 kg and reached 100 kg approximately 5 d sooner than the Y- and the H-sired pigs. At birth, pigs out of DL sows were .21 kg heavier than pigs out of YL sows. Pigs out of HL sows grew .025 and .021 kg/d slower from 56 d to 100 kg compared with pigs out of DL and YL sows, respectively. Sows in the pasture gestation system produced pigs that were .05 kg heavier at birth than pigs out of sows in gestation stalls. Three-breed-cross pigs were .9 kg heavier at 56 d, grew .039 kg/d faster and took 7.9 fewer days to reach 100 kg than backcross pigs. The H sire breed had lower survival rates of pigs at 21 d and to 100 kg of those born alive (P less than .10), compared with pigs sired by D and Y boars. Pigs out of HL dams had the highest survival rates, whereas pigs out of YL sows had the lowest survival rates at birth, 21 d and at 100 kg. Three-breed-cross pigs averaged .025, .028 and .035 greater survival rates at birth, 21 d and 56 d than backcross pigs. Feed efficiency was most desirable in pens of pigs sired by H and D boars compared with pens of pigs sired by Y boars. However, pens of pigs with YL dams were more efficient than pens of pigs with HL dams.