Genetic variation at the hormone sensitive lipase: gender-specific association with plasma lipid and glucose concentrations

Habitual nappers and non-nappers differ in circadian rhythms of LIPE expression in abdominal adipose tissue explants

Background and purpose

Napping is a widespread practice worldwide and has in recent years been linked to increased abdominal adiposity. Lipase E or LIPE encodes the protein hormone-sensitive lipase (HSL), an enzyme that plays an important role in lipid mobilization and exhibits a circadian expression rhythm in human adipose tissue. We hypothesized that habitual napping may impact the circadian expression pattern of LIPE, which in turn may attenuate lipid mobilization and induce abdominal fat accumulation.

Methods

Abdominal adipose tissue explants from participants with obesity (n = 17) were cultured for a 24-h duration and analyzed every 4 h. Habitual nappers (n = 8) were selected to match non-nappers (n = 9) in age, sex, BMI, adiposity, and metabolic syndrome traits. Circadian LIPE expression rhythmicity was analyzed using the cosinor method.

Results

Adipose tissue explants exhibited robust circadian rhythms in LIPE expression in non-nappers. In contrast, nappers had a flattened rhythm. LIPE amplitude was decreased in nappers as compared with non-nappers (71% lower). The decrease in amplitude among nappers was related to the frequency of napping (times per week) where a lower rhythm amplitude was associated with a higher napping frequency (r = -0.80; P = 0.018). Confirmatory analyses in the activity of LIPE's protein (i.e., HSL) also showed a significant rhythm in non-nappers, whereas significance in the activity of HSL was lost among nappers.

Conclusion

Our results suggest that nappers display dysregulated circadian LIPE expression as well as dysregulated circadian HSL activity, which may alter lipid mobilization and contribute to increased abdominal obesity in habitual nappers.

Identification of the bovine HSL gene expression profiles and its association with fatty acid composition and fat deposition traits

Hormone-sensitive lipase (HSL) is an intracellular neutral lipase capable of hydrolysing a variety of esters and is considered to be a candidate gene affecting fat deposition traits. Gene expression profiles of HSL were analysed in various adipose tissues of cattle, and the effect of HSL on lipid metabolism genes was analysed by a PCR array. Novel polymorphisms were identified within the HSL regulatory domain by sequencing, and the relationship between HSL variants and fat deposition traits was analysed. HSL mRNA was highly expressed in the subcutaneous and visceral fat of cattle. CPT1B/CPT1C and other lipocatabolic genes were upregulated, and lipogenesis-related genes (FASN, LPL and ACOT12) were downregulated by HSL overexpression in BFFs. Five novel variants in the HSL functional domain were significantly associated with fat deposition traits, including FCR, LBT, MFW and fatty acid composition. HSL plays a pivotal role in the regulation of lipolysis and fatty acid biosynthesis in beef cattle.

Mechanisms mediating environmental chemical-induced endocrine disruption in the adrenal gland

Humans are continuously exposed to hundreds of man-made chemicals that pollute the environment in addition to multiple therapeutic drug treatments administered throughout life. Some of these chemicals, known as endocrine disruptors (EDs), mimic endogenous signals, thereby altering gene expression, influencing development, and promoting disease. Although EDs are eventually removed from the market or replaced with safer alternatives, new evidence suggests that early-life exposure leaves a fingerprint on the epigenome, which may increase the risk of disease later in life. Epigenetic changes occurring in early life in response to environmental toxicants have been shown to affect behavior, increase cancer risk, and modify the physiology of the cardiovascular system. Thus, exposure to an ED or combination of EDs may represent a first hit to the epigenome. Only limited information is available regarding the effect of ED exposure on adrenal function. The adrenal gland controls the stress response, blood pressure, and electrolyte homeostasis. This endocrine organ therefore has an important role in physiology and is a sensitive target of EDs. We review herein the effect of ED exposure on the adrenal gland with particular focus on in utero exposure to the plasticizer di(2-ethylehyl) phthalate. We discuss the challenges associated with identifying the mechanism mediating the epigenetic origins of disease and availability of biomarkers that may identify individual or population risks.

Risk interaction of obesity, insulin resistance and hormone-sensitive lipase promoter polymorphisms (LIPE-60 C > G) in the development of fatty liver

Background

Hormone sensitive lipase (HSL) promoter (LIPE-60 C > G) polymorphism has been found to be involved in hepatic steatosis, obesity, diabetes and dyslipidemia. The precise interactions between these risk factors and genetic susceptibility that may affect non-alcoholic fatty liver disease (NAFLD) are still not fully determined.

Methods

A cross-sectional study was conducted in 1056 men. To avoid the confounding effect of plasma glucose, the study population was classified into normal glucose tolerance (NGT, n = 729) and glucose intolerance (GI, n = 299) groups. NAFLD was diagnosed by abdominal ultrasound after ruling out any history of alcohol abuse. A multivariate regression model was used to estimate the impact of these factors on NAFLD.

Results

In the NGT group, subjects with NAFLD often have complicated metabolic abnormalities. The coexistence of NAFLD and GI has been demonstrated to have a synergistic effect raising BMI, serum insulin and HOMA-insulin resistance (HOMA-IR). BMI and adipose-insulin resistance (Adipo-IR), but not HOMA-IR, significantly contributed to a greater risk of developing NAFLD. Serum triglyceride was significantly up-regulated in men with the (CG + GG) genotype of HSL promoter polymorphism, NAFLD and Adiopo-IR in sequence.

Conclusion

Adipo-IR, rather than HOMA-IR, appears to be a consistent insulin resistance index in the study of NAFLD. G allele of the HSL promoter polymorphism may contribute the greatest impact raising serum triglyceride in a state of glucose intolerance.

The Human Obesity Gene Map: The 2004 Update

This paper presents the eleventh update of the human obesity gene map, which incorporates published results up to the end of October 2004. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTLs) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2004, 173 human obesity cases due to single-gene mutations in 10 different genes have been reported, and 49 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 166 genes which, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 221. The number of human obesity QTLs derived from genome scans continues to grow, and we have now 204 QTLs for obesity-related phenotypes from 50 genome-wide scans. A total of 38 genomic regions harbor QTLs replicated among two to four studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably with 358 findings of positive associations with 113 candidate genes. Among them, 18 genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, >600 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful publications and genomic and other relevant sites can be found at http://obesitygene.pbrc.edu.

Genetic variation at the goat hormone-sensitive lipase (LIPE) gene and its association with milk yield and composition

Hormone-sensitive lipase (LIPE) plays a fundamental role in the regulation of energy balance by releasing free fatty acids from adipose triacylglycerol stores. These fatty acids can be subsequently transferred to other body compartments to be oxidized or employed in other biochemical reactions. This enzymic function is particularly important in lactating animals because the synthesis of milk components involves the mobilization of lipid depots to satisfy the large energy demands of the mammary gland. In the current study, we partially sequenced the goatLIPEgene in several individuals. In doing so, we identified two synonymous polymorphisms at exons 2 (c.327C>A>T, triallelic polymorphism) and 3 (c.558C>T). Moreover, we found a mis-sense polymorphism at exon 6 (c.1162G>T) that involves an alanine to serine substitution at position 388. Analysis with Polyphen and Panther softwares revealed that this amino acid replacement is expected to be neutral. Performance of an association analysis with a variety of milk traits revealed that goatLIPEgenotype has highly suggestive effects on milk yield (P=0·0032) as well as on C18:3 n-6g (P=0·0051),trans-10cis-12 CLA (P=0·007) and C12:0 (P=0·0084) milk contents. These associations are concordant with the preference of LIPE to selectively mobilize medium-chain and unsaturated fatty acids.

Genetic variance in the adiponutrin gene family and childhood obesity

Aim

The adiponutrin gene family consists of five genes (PNPLA1-5) coding for proteins with both lipolytic and lipogenic properties. PNPLA3 has previously been associated with adult obesity. Here we investigated the possible association between genetic variants in these genes and childhood and adolescent obesity.

Methods/Results

Polymorphisms in the five genes of the adiponutrin gene family were selected and genotyped using the Sequenom platform in a childhood and adolescent obesity case-control study. Six variants in PNPLA1 showed association with obesity (rs9380559, rs12212459, rs1467912, rs4713951, rs10947600, and rs12199580, p<0.05 after adjustment for age and gender). Three variants in PNPLA3 showed association with obesity before, but not after, adjustment for age and gender (rs139051, rs12483959, and rs2072907, p>0.05). When analyzing these SNPs in relation to phenotypes, two SNPs in the PNPLA3 gene showed association with insulin sensitivity (rs12483959: β = −0.053, p = 0.016, and rs2072907: β = −0.049, p = 0.024). No associations were seen for PNPLA2, PNPLA4, and PNPLA5.

Conclusions

Genetic variation in the adiponutrin gene family does not seem to contribute strongly to obesity in children and adolescents. PNPLA1 exhibited a modest effect on obesity and PNPLA3 on insulin sensitivity. These data, however, require confirmation in other cohorts and ethnic groups.

LIPE C-60G influences the effects of physical activity on body fat and plasma lipid concentrations: the Quebec Family Study

A large body of evidence suggests that the environment plays an important role in the development of obesity. The hormone-sensitive lipase (encoded by the LIPE gene) is an intracellular enzyme that mobilises fat stores in a hormone-stimulated manner. The aim of the present study was to determine the effects of the LIPE C-60G polymorphism on body fat and plasma lipid and lipoprotein concentrations, and to test for its interaction with physical activity. The LIPE C-60G polymorphism was genotyped in 862 subjects from the Quebec Family Study. Body mass index (BMI), fat mass, percentage body fat, abdominal fat areas assessed by computed tomography, and detailed fasting plasma lipid and lipoprotein profiles were measured. Levels of physical activity were estimated using a three-day diary, and a moderate to strenuous physical activity score was retained for this study. The main effects of the LIPE C-60G polymorphism, physical activity and their interaction were determined by regression analyses separately in men and women using the MIXED model procedure. In men, we observed significant gene-physical activity interactions for BMI (p = 0.006), fat mass (p = 0.04), abdominal visceral fat area (p = 0.005) and plasma cholesterol (C) high-density lipoprotein cholesterol (HDL-C) ratio (p = 0.003). A high level of physical activity was associated with reduced adiposity and a lower plasma-C/HDL-C ratio, but only in non-carriers of the genetic variant (G-60 allele). In women, no evidence of a gene by physical activity interaction was observed, except for subcutaneous abdominal fat (p = 0.05). These results suggest that the associations between physical activity and body fat and plasma lipoprotein/lipid concentrations in men are dependent on the LIPE C-60G polymorphism, and highlight the importance of taking into account the role of gene-physical activity interactions in candidate gene studies of obesity and obesity-related traits.

K45R variant of squalene synthase increases total cholesterol levels in two study samples from a French Canadian population

Squalene synthase is an important component of the cholesterol biosynthetic pathway, and inhibitors of this enzyme have been shown to lower plasma cholesterol levels. Previously, we sequenced the squalene synthase gene, FDFT1 (farnesyl-diphosphate farnesyltransferase), and identified several SNPs, including a nonsynonymous variant, rs11549147:A>G (K45R). To examine the possible association of K45R with plasma lipid traits, we tested 887 individuals from 149 families from the founder population of Saguenay-Lac St. Jean (SLSJ), Quebec. K45R was associated with increased total cholesterol (TC) (P=0.035) and non-high-density lipoprotein cholesterol (non-HDL-C) (P=0.01). These results were replicated in an independent sample of unrelated individuals (P=0.0008 for TC, P=0.004 for non-HDL-C). This SNP also influenced low-density lipoprotein cholesterol (P=0.042) and HDL-C (P=0.025) in the family-based sample, and triglycerides (TG) (P=0.007) in the unrelated subjects. The lysine (K) in codon 45 is conserved across 11 mammals and lies in a potential exonic splicing enhancer (ESE) site. These results suggest that this coding variant in the squalene synthase gene influences plasma cholesterol levels, possibly by affecting the intracellular production of cholesterol.

Blunted beta-adrenoceptor-mediated fat oxidation in overweight subjects: a role for the hormone-sensitive lipase gene

Obesity is associated with blunted beta-adrenoceptor-mediated lipolysis and fat oxidation, which persist after weight reduction. We investigated whether dinucleotide (CA)(n) repeat polymorphisms in intron 6 (i6) or 7 (i7) and a C-60G promoter substitution of the hormone-sensitive lipase (HSL) gene are associated with a blunted in vivo beta-adrenoceptor-mediated increase in circulating fatty acids and glycerol (estimation of lipolytic response) and fat oxidation in overweight-obese subjects. A total of 103 overweight (25 kg/m(2) < or = body mass index < 30 kg/m(2)) and obese (body mass index > or =30 kg/m(2)) subjects (62 men, 41 women) were included. Energy expenditure, respiratory quotient (RQ), and circulating fatty acid and glycerol were determined after stepwise infusion of increasing doses of the nonselective beta-agonist isoprenaline. The i6, i7 (CA)(n) repeat polymorphisms were determined by size-resolved capillary electrophoresis; and a C-60G promoter substitution was determined by restriction enzyme digestion assay. Female noncarriers of allele 184 i7 (n = 18) and female carriers of allele 240 i6 (n = 12) showed an overall reduced fat oxidation (as indicated by changes in RQ) after beta-adrenoceptor-mediated stimulation, explaining, respectively, 6.9% and 20.8% of the variance in RQ. These effects were not seen in male subjects. In conclusion, our results suggest that variation in i7 and i6 of the HSL gene might be associated with a physiological effect on in vivo beta-adrenoceptor-mediated fat oxidation, at least in overweight-obese female subjects.

Multiple genetic determinants of plasma lipid levels in Caribbean Hispanics

OBJECTIVES

To identify candidate genes in relation to plasma lipid levels in Caribbean Hispanics.

DESIGN AND METHODS

A total of 114 single nucleotide polymorphisms (SNPs) at 17 lipid-related genes were genotyped in 477 Caribbean Hispanics from the Northern Manhattan Study (NOMAS). Analyses for each SNP and haplotype were performed to evaluate the associations with four lipid traits: high- and low-density lipoprotein cholesterol (HDL-C, LDL-C), triglyceride (TG) and total cholesterol (TC).

RESULTS

We identified 19 SNPs at 10 genes that were significantly related to lipids (p<0.01), including nine involved in the reverse cholesterol transport pathway, and one involved in bile acid synthesis. Three genes, namely the apolipoprotein A5, apolipoprotein B and cytochrome p450 polypeptide 7A1 genes, accounted for the largest proportion of variation in HDL-C/TG, TC and LDL-C respectively.

CONCLUSIONS

The cumulative effects of multiple genetic variants led to a substantially better prediction of inter-individual variations in lipid levels.

The hormone-sensitive lipase C-60G promoter polymorphism is associated with increased waist circumference in normal-weight subjects

OBJECTIVE

Hormone-sensitive lipase (HSL) is a key enzyme in the mobilization of fatty acids from triglyceride stores in adipocytes. The aim of the present study was to investigate the role of the HSL gene promoter variant C-60G, a polymorphism which previously has been associated with reduced promoter activity in vitro, in obesity and type 2 diabetes.

DESIGN

We genotyped two materials consisting of obese subjects and non-obese controls, one material with offspring-parents trios, where the offspring was abdominally obese and one material with trios, where the offspring had type 2 diabetes or impaired glucose homeostasis. HSL promoter containing the HSL C-60G G-allele was generated and tested against a construct with the C-allele in HeLa cells and primary rat adipocytes. HSL mRNA levels were quantified in subcutaneous and visceral fat from 33 obese subjects.

RESULTS

We found that the common C-allele was associated with increased waist circumference and WHR in lean controls, but there was no difference in genotype frequency between obese and non-obese subjects. There was a significant increased transmission of C-alleles to the abdominally obese offspring but no increased transmission of C-alleles was observed to offspring with impaired glucose homeostasis. The G-allele showed reduced transcription in HeLa cells and primary rat adipocytes. HSL mRNA levels were significantly higher in subcutaneous compared to visceral fat from obese subjects.

CONCLUSION

The HSL C-60G polymorphism is associated with increased waist circumference in non-obese subjects.

Gene expression and adiposity are modified by soy protein in male Zucker diabetic fatty rats

It has earlier been demonstrated that soy protein diets ameliorate the diabetic phenotype in obese Zucker rats. In this study, we further investigated physiological changes related to adiposity in male Zucker diabetic fatty rats consuming soy-based diets and compared these diets with the insulin-sensitizing drug, rosiglitazone. Transcript abundance of known genes was assessed in the livers to identify potential molecular connections between soy diets and adiposity. Male Zucker diabetic fatty rats were assigned to casein (C) protein, low-isoflavone soy (LIS) protein, high-isoflavone soy (HIS) protein, or C + rosiglitazone (CR) diets. Compared with the C diet, the LIS diet decreased plasma lipids and increased body weight, but did not change liver weight or carcass adiposity. HIS decreased plasma lipids, liver weight, and body weight. CR decreased plasma lipids and increased carcass adiposity and body weight with no effect on liver weight. In LIS livers, 15 genes involved in signaling and lipid metabolism were up-regulated 2-fold or higher. In HIS livers, seven genes had a 2-fold or higher change in abundance. However, in CR livers, none of the genes was significantly changed compared with the C diet. There appears to be a distinct change in gene expression associated with soy diets as compared with C-based diets and rosiglitazone treatment.