Epigenetic control of expression of the human L- and M- pigment genes.

Epigenetics alters gene expression by chromatin modification without changing the sequence of DNA. DNA methylation is an essential signal for epigenetic gene regulation. Methylation of cytosine bases at CpG dinucleotides in DNA results in chromatin condensation resulting in suppression of gene expression. DNA methylation has been shown to play important roles in cell differentiation, genomic imprinting and X-chromosome inactivation. We compared the CpG methylation patterns of the promoters of the L-opsin gene (OPN1LW) and the M-opsin gene (OPN1MW), plus a DNase I hypersensitive (DHS) site located about 8 kb (kilobases) upstream of the OPN1LW gene. Comparisons were made using the human retinoblastoma cell line WERI, which expresses the L and M opsin genes when treated with thyroid hormone (T3), and a lymphoblastoid cell line GM06990 that does not express these genes. The results showed that the great majority of the 14 CpGs located within the proximal 200 bp (base pairs) of each promoter, plus 20 bp of the 5'-untranslated region, were hypo-methylated in WERI-Rb-1 cells, whether or not treated with T3, but almost totally methylated in the lymphoblastoid cell line. Three of the CpGs that are located beyond 200 bp from the transcription start site of OPN1LW were hyper-methylated in both WERI and lymphoblastoid cells. Significant differential methylation was also observed within the DHS region (24 CpGs). This DHS region contains a highly conserved motif that binds CCCTC-binding factor (CTCF), referred to as a 'chromatin insulator or boundary element', that has been shown to regulate gene expression at several genome locations. The results suggest that DNA methylation is likely to contribute to regulation of expression of the L- and M-opsin genes during differentiation, as well as to the retinal L:M cone ratio. In addition, thyroid hormone induction of the opsin genes does not appear to alter DNA methylation.

A novel method for measuring human lipoprotein lipase and hepatic lipase activities in postheparin plasma.

The objective of this study was to establish a new lipoprotein lipase (LPL) and hepatic lipase (HL) activity assay method. Seventy normal volunteers were recruited. Lipase activities were assayed by measuring the increase in absorbance at 546 nm due to the quinoneine dye. Reaction mixture-1 (R-1) contained dioleoylglycerol solubilized with lauryldimethylaminobetaine, monoacylglycerol-specific lipase, glycerolkinase, glycerol-3-phosphate oxidase, peroxidase, ascorbic acid oxidase, and apolipoprotein C-II (apoC-II). R-2 contained Tris-HCl (pH 8.7) and 4-aminoantipyrine. Automated assay of lipase activities was performed with an automatic clinical analyzer. In the assay for HL + LPL activity, 160 microl R-1 was incubated at 37 degrees C with 2 microl of sample for 5 min, and 80 microl R-2 was added. HL activities were measured under the same conditions without apoC-II. HL and LPL activities were also measured by the conventional isotope method and for HL mass by ELISA. Lipase activity detected in a 1.6 M NaCl-eluted fraction from a heparin-Sepharose column was enhanced by adding purified apoC-II in a dose-dependent manner, whereas that eluted by 0.8 M NaCl was not. Postheparin plasma-LPL and HL activities measured in the present automated method had high correlations with those measured by conventional activity and mass methods. This automated assay method for LPL and HL activities is simple and reliable and can be applied to an automatic clinical analyzer.

Genetics of apolipoprotein B and apolipoprotein AI and premature coronary artery disease.

Increased low-density lipoprotein (LDL) and decreased high-density lipoprotein cholesterol (HDL-C) predict premature coronary artery disease, as do elevated levels of apolipoprotein B or reduced levels of apolipoprotein AI. Probands were studied of families with common genetic forms of dyslipidaemia to determine if apo B or apo AI define genetic groups and if apo B or apo AI levels relate to premature coronary artery disease risk. Elevated apo B was characteristic of familial hypercholesterolaemia, familial combined hyperlipidaemia (FCHL), and was seen in individuals with elevated Lp(a). Normal apo B levels were seen in familial hypertriglyceridaemia and in 'coronary artery disease with low-HDL cholesterol'. Apo AI levels tended to be low in FCHL and were decreased in 'coronary disease with low-HDL cholesterol'. In familial hypertriglyceraemia, even though HDL-C levels were low, normal apo AI and apo B levels were seen in the absence of premature coronary artery disease. Therefore, in genetic dyslipidaemias elevated apo B levels and reduced apo AI levels (or increased apo B/AI ratio) differ and predict premature coronary artery disease.

The molecular basis of variation in human color vision.

Common variation in red-green color vision exists among both normal and color-deficient subjects. Differences at amino acids involved in tuning the spectra of the red and green cone pigments account for the majority of this variation. One source of variation is the very common Ser180Ala polymorphism that accounts for two spectrally different red pigments and that plays an important role in variation in normal color vision as well as in determining the severity of defective color vision. This polymorphism most likely resulted from gene conversion by the green-pigment gene. Another common source of variation is the existence of several types of red/green pigment chimeras with different spectral properties. The red and green-pigment genes are arranged in a head-to-tail tandem array on the X-chromosome with one red-pigment gene followed by one or more green-pigment genes. The high homology between these genes has predisposed the locus to relatively common unequal recombination events that give rise to red/green hybrid genes and to deletion of the green-pigment genes. Such events constitute the most common cause of red-green color vision defects. Only the first two pigment genes of the red/green array are expressed in the retina and therefore contribute to the color vision phenotype. The severity of red-green color vision defects is inversely proportional to the difference between the wavelengths of maximal absorption of the photopigments encoded by the first two genes of the array. Women who are heterozygous for red and green pigment genes that encode three spectrally distinct photopigments have the potential for enhanced color vision.

Contribution of hepatic lipase, lipoprotein lipase, and cholesteryl ester transfer protein to LDL and HDL heterogeneity in healthy women.

Hepatic lipase (HL) and cholesteryl ester transfer protein (CETP) have been independently associated with low density lipoprotein (LDL) and high density lipoprotein (HDL) size in different cohorts. These studies have been conducted mainly in men and in subjects with dyslipidemia. Ours is a comprehensive study of the proposed biochemical determinants (lipoprotein lipase, HL, CETP, and triglycerides) and genetic determinants (HL gene [LIPC] and Taq1B) of small dense LDL (sdLDL) and HDL subspecies in a large cohort of 120 normolipidemic, nondiabetic, premenopausal women. HL (P<0.001) and lipoprotein lipase activities (P=0.006) were independently associated with LDL buoyancy, whereas CETP (P=0.76) and triglycerides (P=0.06) were not. The women with more sdLDL had higher HL activity (P=0.007), lower HDL2 cholesterol (P<0.001), and lower frequency of the HL (LIPC) T allele (P=0.034) than did the women with buoyant LDL. The LIPC variant was associated with HL activity (P<0.001), HDL2 cholesterol (P=0.034), and LDL buoyancy (P=0.03), whereas the Taq1B polymorphism in the CETP gene was associated with CETP mass (P=0.002) and HDL3 cholesterol (P=0.039). These results suggest that HL activity and HL gene promoter polymorphism play a significant role in determining LDL and HDL heterogeneity in healthy women without hypertriglyceridemia. Thus, HL is an important determinant of sdLDL and HDL2 cholesterol in normal physiological states as well as in the pathogenesis of various disease processes.

The contribution of intraabdominal fat to gender differences in hepatic lipase activity and low/high density lipoprotein heterogeneity.

Hepatic lipase (HL) hydrolyzes triglyceride and phospholipid in low and high density lipoprotein cholesterol (LDL-C and HDL-C, respectively), and elevated HL activity is associated with small, dense atherogenic LDL particles and reduced HDL2-C. Elevated HL activity is associated with increasing age, male gender, high amounts of intraabdominal fat (IAF), and the HL gene (LIPC) promoter polymorphism (C nucleotide at -514). We investigated the mechanisms underlying the difference in HL activity between men (n = 44) and premenopausal women (n = 63). Men had significantly more IAF (144.5 +/- 80.9 vs. 66.5 +/- 43.2 cm(2), respectively; P < 0.001), higher HL activity (220.9 +/- 94.7 vs.129.9 +/- 53.5 nmol/mL.min; P < 0.001), more dense LDL (Rf, 0.277 +/- 0.032 vs. 0.300 +/- 0.024; P = 0.01), and less HDL2-C (0.19 +/- 0.10 vs. 0.32 +/- 0.16 mmol/L; P < 0.001) than women. After adjusting for IAF and the LIPC polymorphism, men continued to have higher (but attenuated) HL activity (194.5 +/- 80.4 vs.151.0 +/- 45.2, respectively; P = 0.007) and lower HDL2-C (0.23 +/- 0.11 vs. 0.29 +/- 0.14 mmol/L; P = 0.02) than women. Using multiple regression, HL activity remained independently related to IAF (P < 0.001), gender (P < 0.001), and the LIPC genotype (P < 0.001), with these factors accounting for 50% of the variance in HL activity. These data suggest that IAF is a major component of the gender difference in HL activity, but other gender-related differences, perhaps sex steroid hormones, also contribute to the higher HL activity seen in men compared with premenopausal women. The higher HL activity in men affects both LDL and HDL heterogeneity and may contribute to the gender difference in cardiovascular risk.

Hepatic lipase as a focal point for the development and treatment of coronary artery disease.

Recent epidemiological evidence suggests that although lowering low-density lipoprotein (LDL) cholesterol is important in decreasing cardiovascular disease morbidity and mortality, it accounts only for part of the coronary artery disease (CAD) improvement with lipid-lowering therapy. In the last decade, it has become evident that the atherogenicity of LDL particles is associated not only with their plasma levels, but also with their size and density. The presence of small, dense LDL particles is associated with a three fold increase in CAD risk. Hepatic lipase (HL), a key enzyme in the formation of small, dense LDL particles, modulates their phospholipid and triglyceride contents. The higher the HL activity, the smaller, denser, and more atherogenic the resulting lipoprotein particle. It is, therefore, plausible to hypothesize that at least part of the CAD benefits observed in the recent CAD-prevention pharmacological trials, which are not accounted for by the decrease in LDL-C (LDL-cholesterol), might be explained by a pharmacological effect on LDL size and density, possibly mediated by changes in hepatic lipase activity. By studying patients with dyslipidemia and CAD, we have been able to provide strong evidence that regression of coronary atherosclerosis results from at least two independent effects of lipid-lowering therapy on lipoprotein metabolism: the well known one that leads to changes in LDL-C and apo B levels, and a new pathway of HL-mediated improvement in LDL buoyancy. Finally, HL activity and LDL density appear to be significantly affected by the presence of a common C-->T substitution at position -514 with respect to the transcription start site of the HL gene, raising the possibility that the -514 C-->T polymorphism may significantly contribute to differences in individual CAD response to lipid-lowering treatment, as seen in the recent major primary and secondary CAD-prevention clinical trials.

Common hepatic lipase gene promoter variant determines clinical response to intensive lipid-lowering treatment.

BACKGROUND: The common -514 C-->T polymorphism in the promoter region of the hepatic lipase (HL) gene affects HL activity. The C allele is associated with higher HL activity, more dense and atherogenic LDL, and lower HDL(2) cholesterol. Intensive lipid-lowering therapy lowers HL activity, increases LDL and HDL buoyancy, and promotes coronary artery disease (CAD) regression. We tested the hypothesis that subjects with the CC genotype and a more atherogenic lipid profile experience the greatest CAD regression from these favorable effects. METHODS AND RESULTS: Forty-nine middle-aged men with dyslipidemia and established CAD who were undergoing intensive lipid-lowering therapy were studied. Change in coronary stenosis was assessed by quantitative angiography, HL polymorphism by polymerase chain reaction amplification, HL activity by (14)C-labeled substrate, and LDL buoyancy by density-gradient ultracentrifugation. The response to lipid-lowering therapy was significantly different among subjects with different HL promoter genotypes. Subjects with the C:C genotype had the greatest decrease in HL activity (P<0.005 versus TC and TT by ANOVA) and the greatest improvement in LDL density (P<0.005) and HDL(2)-C (P<0.05) with therapy. These subjects had the greatest angiographic improvement, with 96% of them experiencing CAD regression, compared with 60% of TC and none of the TT patients (P:<0.001). CONCLUSIONS: -In middle-aged men with established CAD and dyslipidemia, the HL gene -514 C-->T polymorphism significantly predicts changes in coronary stenosis with lipid-lowering treatment that appear to involve an HL-associated effect on LDL metabolism. This study identifies a gene polymorphism that strongly influences the lipid and clinical response to lipid-lowering drugs.

In vivo evidence of a role for hepatic lipase in human apoB-containing lipoprotein metabolism, independent of its lipolytic activity.

Hepatic lipase (HL) is a key player in lipoprotein metabolism by modulating, through its lipolytic activity, the triglyceride (TG) and phospholipid content of apolipoprotein B (apoB)-containing lipoproteins and of high density lipoproteins (HDL), thereby affecting their size and density. A new and separate role has been suggested for HL in cellular lipoprotein metabolism, in which it serves as a ligand promoting cellular uptake of apoB-containing remnant lipoproteins and HDL. We tested the hypothesis that HL has both a lipolytic and a nonlipolytic role in human lipoprotein metabolism, by measuring lipid plasma concentrations, lipoprotein density distribution by density gradient ultracentrifugation, and lipoprotein composition, in three subjects with HL deficiency: two of the patients (S-1 and S-3) were characterized as having neither plasma HL activity nor detectable HL protein; the third subject (S-2) had no plasma HL activity but a detectable amount (35.5 ng/ml) of HL protein. All HL-deficient subjects showed a severalfold increase in lipoprotein TG content across the lipoprotein density spectrum [very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL), low density lipoprotein (LDL), and HDL] as compared with control subjects. They also had remarkably more buoyant LDL particles (LDL-R(f) = 0.342;-0.394) as compared with the control subjects (LDL-R(f) = 0.303). Subjects S-1 and S-3 (no HL activity or protein) presented with a distinct increase in cholesterol and apoB levels in the IDL and VLDL density range as compared with patient S-2, with detectable HL protein, and the control subjects. This study provides evidence in humans that HL indeed plays an important role in lipoprotein metabolism independent of its enzymatic activity: in particular, inactive HL protein appears to affect VLDL and IDL particle concentration, whereas HL enzymatic activity seems to influence VLDL-, IDL-, LDL-, and HDL-TG content and their physical properties.

G-250A substitution in promoter of hepatic lipase gene is associated with dyslipidemia and insulin resistance in healthy control subjects and in members of families with familial combined hyperlipidemia.

Low activity of hepatic lipase (HL) has been associated with high levels of triglycerides and high density lipoproteins, but the association of the HL promoter variants with insulin sensitivity has not been investigated. Therefore, in this study, the relationship of the G-250A promoter variant of the HL gene to the rates of insulin-stimulated glucose uptake measured by the hyperinsulinemic euglycemic clamp was investigated in 110 control subjects (82 men and 28 women, aged 50.7+/-7.6 [mean+/-SD] years, body mass index 26. 1+/-3.6 kg/m(2)) and in 105 first-degree relatives (65 men and 40 women, aged 47.8+/-16.0 years, body mass index 26.9+/-5.3 kg/m(2)) of 34 families with familial combined hyperlipidemia (FCHL). The A-250 allele of the HL promoter was associated with low rates of insulin-stimulated whole-body nonoxidative glucose disposal in control subjects (41.1+/-12.7 micromol. kg(-1). min(-1) in subjects with the G-250G genotype, 36.9+/-13.1 micromol. kg(-1). min(-1) in subjects with the G-250A genotype, and 29.9+/-13.5 micromol. kg(-1). min(-1) in subjects with the A-250A genotype; P=0.012 adjusted for age and sex) and with low rates of insulin-stimulated whole-body glucose oxidation in FCHL family members (16.7+/-4.2 versus 15.0+/-4. 4 versus 14.1+/-4.4 micromol. kg(-1). min(-1), P=0.024). In addition, the A-250 allele was associated with high levels of fasting insulin (P=0.047), very low density lipoprotein cholesterol (P=0.007), and total (P=0.009) and very low density lipoprotein (P=0.005) triglycerides in control subjects and with high levels of low density lipoprotein triglycerides (P=0.001) in FCHL family members (n=340). We conclude that the G-250A promoter variant of the HL gene is associated with dyslipidemia and insulin resistance. Mechanisms via which this polymorphism could affect insulin sensitivity remain to be elucidated.

RINX(VSX1), a novel homeobox gene expressed in the inner nuclear layer of the adult retina.

The locus control region (LCR) of the human red and green visual pigment genes is critical for the formation of functional red and green cones in the retina. A 37-bp core of the LCR is perfectly conserved among mammals and binds specific retinal nuclear proteins. Here, we employed a yeast one-hybrid screen of an adult retinal cDNA library to clone and characterize these proteins. We identified clones encoding homeodomain (HD) transcription factors Pax6, Rx, and Chx10 and a novel paired-like HD protein, RINX. In the adult retina, RINX is exclusively expressed in a subset of cells (likely to be bipolar cells) of the retinal inner nuclear layer (INL). RINX is closely related to Chx10, which is also exclusively expressed in the INL of the adult retina and is critical for retinal development. The RINX gene is expressed in two classes of mRNA. One class encodes proteins that lack either part of or all of the HD, but retain the transcriptional activation domain. The RINX gene maps to chromosome 20p11.2 to which no retinal disease has been assigned. In conclusion, the LCR contains two adjacent motifs that are targets for binding of HD proteins that may specify the development and differentiation of cone photoreceptors and a subset of INL bipolar cells. Mutations in the related human CHX10 gene cause microphthalmia in a subset of families, and, therefore, the RINX gene is a candidate for this phenotype in another subset of patients. Since the RINX gene is likely an ortholog of the goldfish Vsx1 gene, it has been named VSX1 by the Human Gene Nomenclature Committee.

Impact of the Peroxisome Proliferator Activated Receptor gamma2 Pro12Ala polymorphism on adiposity, lipids and non-insulin-dependent diabetes mellitus.

OBJECTIVE: The Pro12Ala polymorphism of the Peroxisome Proliferator Activated Receptor gamma2 (PPARgamma2) gene has been inconsistently associated with body mass index variations and non-insulin-dependent diabetes mellitus (NIDDM). We investigated the impact of this polymorphism on obesity markers, lipid and glucose variables in a sample of French subjects and evaluated its possible role in the onset of NIDDM. DESIGN AND SUBJECTS: Within the framework of the WHO-MONICA project, a population study composed of 1195 subjects aged 35-64 y was randomly sampled from the electoral rolls of the urban community of Lille, in northern France. Subjects receiving medical treatment for hypercholesterolemia, hypertension or diabetes mellitus were excluded for the analyses, to avoid any interferences between medical treatment and biological variables. This resulted in a sample size of 839 subjects (421 men/418 women, age=49.4+/-8.1 y, body mass index (BMI)=25.7+/-4.4 kg/m2). To evaluate the role of the Pro12Ala polymorphism in the onset of NIDDM, we evaluated its distribution in 170 Caucasian NIDDM subjects from a clinical series (117 men/53 women, age=62.3+/-9.0 y, BMI=30.1+/-3.6 kg/m2). MEASUREMENTS: The PPARgamma2 Pro12Ala polymorphism genotyping was carried out with allele specific oligonucleotides hybridisation. Data were statistically analysed for association with various obesity markers (body weight (BW), BMI, waist-to-hip ratio (WHR), plasma leptin concentrations, lipid and glucose variables. RESULTS: In the WHO-MONICA population, the Ala allele frequency was 0.11. The presence of the Ala allele was significantly associated with higher body weight (P=0.002), BMI (P=0.02), height (P=0.02) and waist circumference (P=0.04). Increased plasma concentrations of total cholesterol (P=0.01), LDL-cholesterol (P=0.004) and apolipoprotein B (P=0.01) were also detected in Ala allele bearers. The distribution of the Pro12Ala polymorphism was similar in NIDDM subjects (Ala allele frequency: 0.10) and in the WHO-MONICA population subjects. CONCLUSION: Our results suggest that genetic variability of PPARgamma2 affects body weight control and lipid homeostasis in humans and do not support a significant role for the PPARgamma2 Pro12Ala polymorphism in the aetiology of NIDDM. International Journal of Obesity (2000) 24, 195-199

Interindividual and topographical variation of L:M cone ratios in monkey retinas.

We analyzed the ratio of L:M cone photopigment mRNA in the retinas of Old World monkeys, using the method of rapid polymerase chain reaction-single-strand conformation polymorphism. The L:M cone pigment mRNA ratio in whole retina ranged from 0.6 to 7.0, with a mean of approximately 1.6 (standard deviation, +/- 0.56; n = 26). There was no change in this ratio with eccentricity up to 9 mm (approximately 45 degrees), though the ratio was approximately 30% greater in temporal than in nasal retina. The mRNA ratios are in good agreement with the L:M cone ratio in these same retinas, inferred from electrophysiological recordings of cone signal gain in horizontal cell interneurons. The correlation between mRNA ratios and physiological cone gain ratio supports the conclusion that both measures reflect the relative number of L and M cones.

Hypoxia induces hexokinase II gene expression in human lung cell line A549.

During adaptation to hypoxic and hyperoxic conditions, the genes involved in glucose metabolism are upregulated. To probe involvement of the transcription factor hypoxia-induced factor-1 (HIF-1) in hexokinase (HK) II expression in human pulmonary cells, A549 cells and small-airway epithelial cells (SAECs) were exposed to stimuli such as hypoxia, deferoxamine (DFO), and metal ions. The largest increase in HK-II (20-fold for mRNA and 2.5-fold for enzymatic activity) was observed in A549 cells when exposed to DFO. All stimuli selectively increased the 5.5-kb rather than 4-kb transcript in A549 cells. Cycloheximide and actinomycin D inhibited these responses. In addition, cells were transfected with luciferase reporter constructs driven by the full-length HK-II 5'-regulatory region (4.0 kb) or various deletions of that region. A549 cells transfected with the 4.0-kb construct and exposed to hypoxia or DFO increased their luciferase activity 7- and 10-fold, respectively, indicating that HK-II induction is, at least in part, due to increased gene transcription. Sixty percent of the inducible activity of the 4.0-kb construct was shown to reside within the proximal 0.5 kb. Additionally, cotransfection with a stable HIF-1 mutant and the 4.0-kb promoter construct resulted in increased luciferase activity under normoxic conditions. These results strongly suggest that HK-II is selectively regulated in pulmonary cells by a HIF-1-dependent mechanism.

Mouse hexokinase II gene: structure, cDNA, promoter analysis, and expression pattern.

In mammalian tissues, the phosphorylation of intracellular glucose to glucose-6-phosphate (Glu-6-P) is facilitated by four distinct hexokinase (HK) isoenzymes, designated as HKI-IV. Because of the role of HKII as a leading glycolytic enzyme in insulin-sensitive tissues such as skeletal muscle, heart, and adipose tissue, defects in HKII function could contribute to the development of insulin resistance and perhaps Type 2 diabetes. As a first step towards elucidation of the physiological role of HKII in insulin resistance and type 2 diabetes using mouse knock-out models, we determined the genomic structure, sequence of the cDNA and of 4.8 kb of the 5' regulatory region, and tissue-specific expression of the mouse HKII gene. The gene comprises 18 exons that span approximately 50 kb of DNA. Nucleotide sequence of the proximal promoter revealed a number of conserved putative transcription factor binding motifs. We also found numerous repeat elements throughout the mouse HKII gene. The mouse HKII cDNA is approximately 5.5 kb in length and contains an open reading frome of 2751 bp encoding a protein of 917 amino acids. The mouse HKII gene is predominantly expressed in skeletal muscle, heart, and adipose tissue. The transcription initiation and polyadenylation sites for the mouse HKII mRNA were similar to those of the rat and human genes.

The C-514T polymorphism in the human hepatic lipase gene promoter diminishes its activity.

Four common polymorphisms in the promoter of the hepatic lipase gene (LIPC) that are in almost complete linkage disequilibrium have been described in different ethnic groups. The T and A alleles at positions -514 and -250, respectively, were observed to be associated with decreased hepatic lipase (HL) activity and increased triglyceride content of HDL and LDL particles. We investigated whether these polymorphisms have any effect on transcriptional activity of the proximal promoter (-639 to +29) in transient transfection assays. We found that the promoter with T at position -514 had approximately 30% lower activity than the one with C at the same position (P < 0.0005) regardless of the genotype at position -250. In conclusion, these data indicate that the -514T allele may contribute significantly to decreased HL activity and the resultant increase in plasma levels of triglyceride-rich HDL(2) and large buoyant LDL particles. In addition, this promoter variant may explain the finding that its presence attenuates the increase in HL activity with increasing intra-abdominal fat in women.

Polymorphisms at the Werner locus: II. 1074Leu/Phe, 1367Cys/Arg, longevity, and atherosclerosis.

Werner syndrome (WS) is a progeroid syndrome caused by autosomal recessive null mutations at the WRN locus. The WRN gene encodes a nuclear protein of 180 kD that contains both exonuclease and helicase domains. WS patients develop various forms of arteriosclerosis, particularly atherosclerosis, and medial calcinosis. The most common cause of death in Caucasian subjects with WS is myocardial infarction. Previous studies have identified specific polymorphisms within WRN that may modulate the risk of atherosclerosis. Population studies of the 1074Leu/Phe and 1367Cys/Arg polymorphisms were undertaken to evaluate the role of WRN in atherogenesis. Frequencies of the 1074Leu/Phe polymorphisms in Finnish and Mexican populations revealed an age-dependent decline of 1074Phe/Phe genotype. In Mexican newborns, but not in Finnish newborns, the 1074Leu/Phe and 1367Cys/ Arg polymorphisms were in linkage disequilibrium. Among coronary artery disease subjects, there was a tendency for the 1074Phe allele to be associated with coronary stenosis in a gene dose-dependent manner. Furthermore, the 1367Arg/Arg genotype predicted a lower degree of coronary artery occlusion, as measured by NV50, when compared to the 1367Cys/Cys or 1367Cys/Arg genotypes. However, these tendencies did not achieve statistical significance. Samples from Mexican patients with ischemic stroke showed a trend of haplotype frequencies different from that in a control group of Mexican adults. These data support the hypothesis that WRN may mediate not only WS, but may also modulate more common age-related disorders and, perhaps, a basic aging process.

A hepatic lipase gene promoter polymorphism attenuates the increase in hepatic lipase activity with increasing intra-abdominal fat in women.

High hepatic lipase (HL) activity is associated with an atherogenic lipoprotein profile of small, dense LDL particles and lower HDL(2)-C. Intra-abdominal fat (IAF) is positively associated with HL activity. A hepatic lipase gene (LIPC) promoter variant (G-->A(-250)) is associated with lower HL activity, higher HDL(2)-C, and less dense LDL particles. To determine whether the LIPC promoter polymorphism acts independently of IAF to regulate HL, 57 healthy, premenopausal women were studied. The LIPC promoter A allele was associated with significantly lower HL activity (GA/AA=104+/-34 versus GG=145+/-57 nmoles x mL(-1) x min(-1), P=0.009). IAF was positively correlated with HL activity (r=0.431, P<0.001). Multivariate analysis revealed a strong relationship between both the LIPC promoter genotype (P=0. 001) and IAF (P<0.001) with HL activity. The relationship between IAF and HL activity for carriers and noncarriers of the A allele was curvilinear with the carriers having a lower apparent maximum level of plasma HL activity compared with noncarriers (138 versus 218 nmoles x mL(-1) x min(-1), P<0.001). In addition, the LIPC A allele was associated with a significantly higher HDL(2)-C (GA/AA=16+/-7 versus GG=11+/-5 mg/dL, P=0.003). We conclude that the LIPC promoter A allele attenuates the increase in HL activity due to IAF in premenopausal women.

Two polymorphisms in the peroxisome proliferator-activated receptor-gamma gene are associated with severe overweight among obese women.

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a nuclear receptor that regulates adipocyte differentiation. Variations in the PPARgamma gene may affect the function of the PPARgamma and, therefore, body adipocity. We investigated the frequencies of the Pro12Ala polymorphism in exon B and the silent CAC478CAT polymorphism in exon 6 of the PPARgamma gene and their effects on body weight, body composition, and energy expenditure in obese Finns. One hundred and seventy obese subjects [29 men and 141 women; body mass index (BMI), 35.7 +/- 3.8 kg/m2; age, 43 +/- 8 yr; mean +/- SD) participated in the study. The frequencies of the Ala12 allele in exon B and CAT478 allele in exon 6 were not significantly different between the obese and population-based control subjects (0.14 vs. 0.13 and 0.19 vs. 0.21, respectively). The polymorphisms were associated with increased BMI [Pro12Pro, 34.5 +/- 3.8; Pro12Ala, 34.8 +/- 3.1; Ala12Ala, 39.2 +/- 4.6 kg/m2 (P = 0.011); CAC478CAC, 34.5 +/- 3.8; CAC478CAT, 34.5 +/- 3.3; CAT478CAT, 37.7 +/- 4.1 kg/m2 (P = 0.046)]. In addition, the women with both Ala12Ala and CAT478CAT genotypes (n = 5) were significantly more obese compared with the women having both Pro12Pro and CAC478CAC genotypes (n = 85; BMI, 40.6 +/- 3.3 vs. 34.4 +/- 3.9 kg/m2; P = 0.001), and they had increased fat mass (46.8 +/- 9.1 vs. 36.8 +/- 7.5 kg; P = 0.005). In conclusion, the Pro12Ala and CAC478CAT polymorphisms in the PPARgamma gene are associated with severe overweight and increased fat mass among obese women.