Gender-specific association of a perilipin gene haplotype with obesity risk in a white population

The Genetic Basis of Childhood Obesity: A Systematic Review

Overweight and obesity in childhood and adolescence represents one of the most challenging public health problems of our century owing to its epidemic proportions and the associated significant morbidity, mortality, and increase in public health costs. The pathogenesis of polygenic obesity is multifactorial and is due to the interaction among genetic, epigenetic, and environmental factors. More than 1100 independent genetic loci associated with obesity traits have been currently identified, and there is great interest in the decoding of their biological functions and the gene-environment interaction. The present study aimed to systematically review the scientific evidence and to explore the relation of single-nucleotide polymorphisms (SNPs) and copy number variants (CNVs) with changes in body mass index (BMI) and other measures of body composition in children and adolescents with obesity, as well as their response to lifestyle interventions. Twenty-seven studies were included in the qualitative synthesis, which consisted of 7928 overweight/obese children and adolescents at different stages of pubertal development who underwent multidisciplinary management. The effect of polymorphisms in 92 different genes was assessed and revealed SNPs in 24 genetic loci significantly associated with BMI and/or body composition change, which contribute to the complex metabolic imbalance of obesity, including the regulation of appetite and energy balance, the homeostasis of glucose, lipid, and adipose tissue, as well as their interactions. The decoding of the genetic and molecular/cellular pathophysiology of obesity and the gene-environment interactions, alongside with the individual genotype, will enable us to design targeted and personalized preventive and management interventions for obesity early in life.

Sex-Dependent Mediation of Leptin in the Association of Perilipin Polymorphisms with BMI and Plasma Lipid Levels in Children

Variations in the perilipin (PLIN) gene have been suggested to be associated with obesity and its related alterations, but a different nutritional status seems to contribute to differences in these associations. In our study, we examined the association of several polymorphisms at the PLIN locus with obesity and lipid profile in children, and then analyzed the mediation of plasma leptin levels on these associations. The single-nucleotide polymorphisms (SNPs) rs894160, rs1052700, and rs2304795 in PLIN1, and rs35568725 in PLIN2, were analyzed by RT-PCR in 1264 children aged 6–8 years. Our results showed a contrasting association of PLIN1 rs1052700 with apolipoprotein (Apo) A-I levels in boys and girls, with genotype TT carriers showing significantly higher Apo A-I levels in boys and significantly lower Apo A-I levels in girls. Significant associations of the SNP PLIN2 rs35568725 with high-density lipoprotein cholesterol (HDL-cholesterol), Apo A-I, and non-esterified fatty acids (NEFA) were observed in boys but not in girls. The associations of the SNPs studied with body mass index (BMI), NEFA, and Apo A-I in boys and girls were different depending on leptin concentration. In conclusion, we describe the mediation of plasma leptin levels in the association of SNPs in PLIN1 and PLIN2 with BMI, Apo A-I, and NEFA. Different leptin levels by sex may contribute to explain the sex-dependent association of the PLIN SNPs with these variables.

Perilipin Genetic Variation Correlated with Obesity and Lipid Profile in Metabolic Syndrome

BACKGROUND: Perilipin is very important for the regulation of the deposition and mobilization of fats. The human perilipin gene (PLIN) is near the locus for risk of obesity and hypertriglyceridemia. The PLIN gene is thought to be involved in the occurrence of metabolic syndrome. AIM: The aim of this research is to determine the role of variations of the PLIN gene (PLN4 11482 G>A) as a risk factor for component of metabolic syndrome. METHODS: This study involved a total of 160 subjects consisting of 80 with metabolic syndrome and 80 controls. Genotype analysis was done with the polymerase chain reaction-restriction fragment length polymorphism method. The data were analyzed with t-tests to compare the subjects’ characteristics between metabolic syndrome groups and controls. Risk factors of PLIN genotypes were calculated with odds ratio and multivariate regression analysis was used to determine the role of the PLIN gene with each biochemical characteristic. RESULTS: The result was significant differences between the characteristics of the metabolic syndrome subjects with controls (p < 0.05). There was no difference in genotypes between patients with metabolic syndrome and controls. The multivariate analysis of the genetic role with biochemical components showed the PLIN gene in AA carriers as a risk factor for metabolic syndrome compare GA+GG, risk of obesity, and hypercholesterolemia with p < 0.05. CONCLUSION: It can be concluded that PLIN variation has a role in the incidence of metabolic syndrome, especially in relation to obesity and hypercholesterolemia. Further study is needed to determine the role of other gene variations as a risk factor for metabolic syndrome.

Effects of Four Lipid Metabolism-Related Polymorphisms on Body Composition Improvements After 12 Weeks of High-Intensity Interval Training and Dietary Energy Restriction in Overweight/Obese Adult Women: A Pilot Study

Background: Polymorphisms in lipid metabolism-related genes have been associated with obesity and body composition, but these have been scarcely described concerning the magnitude of the response to exercise interventions in the overweight/obese population.

Objective: To evaluate the association of perilipin 1 (PLIN1; rs1052700 and rs2304795), lipoprotein lipase (rs283), and adrenoceptor beta 3 (rs4994) polymorphisms with high and low responders (LoRes) to fat mass reduction after 12 weeks of high-intensity interval training (HIIT) and dietary energy restriction in overweight/obese adult women. In addition, we examined the effect of these genetic variants on body composition changes.

Methods: Forty-three unrelated overweight/obese adult women were incorporated and genotyped, of which 30 women (age = 27.4 ± 7.9 years; BMI = 29.9 ± 3.3 kg/m²) successfully completed the 12-week supervised HIIT program plus an individually prescribed home hypocaloric diet.

Results: An association was observed between the PLIN1 rs1052700 polymorphism with high and LoRes (χ² = 8.138; 2 df; p = 0.01). Moreover, after the intervention, the carriers of TT genotype of PLIN1 rs1052700 as compared to AA and AT showed a greater reduction in absolute fat mass (Δ: −5.1 ± 1.8 vs. − 1.8 ± 1.4 vs. − 2.1 ± 2.3 kg; p = 0.04). The effect size of this fat mass reduction between TT and AT genotypes was a mean difference of −3.01 kg [95%IC − 4.88– − 1.1], and between TT and AA genotypes was −3.29 kg [95%IC − 4.86– − 1.65]. No differences were observed for other polymorphisms investigated.

Conclusion: These results suggest that the rs1052700 (14995A>T) polymorphism of the PLIN1 gene is associated with a differential response to fat mass reduction after a 12-week intervention in overweight/obese adult women. In addition, women with the TT genotype of this genetic variant showed greater changes in fat mass than AA and AT genotypes. However, further studies are needed to confirm these findings.

AA genotype of PLIN1 13041A>G as an unfavourable predictive factor of malnutrition associated with fat mass loss in locally advanced head and neck cancer male patients treated with radiotherapy

Introduction

Malnutrition is a frequently diagnosed condition in head and neck cancer (HNC) patients after radiation therapy (RTH). Malnutrition causes adipose tissue dysfunction associated with intensified lipolysis and disruption of the activity of mechanisms that protect adipose tissue against this process, which include the protective function of perilipin.

Material and methods

The purpose of this study was the evaluation of the predictive value of 13041A>G PLIN1 polymorphism in the development of malnutrition related to adipose tissue loss in a group of 80 patients with locally advanced HNC treated by means of radical radiation therapy.

Results

After the completion of RTH, men with AA genotype had significantly lower fat mass (FM compared to men with G haplotype; FM: 13.84 ± 6.36 kg and 19.06 ± 6.30 kg (p = 0.009). In consequence of RTH, the AA genotype carriers lost an average of 37.01% adipose tissue mass and patients with GA and GG genotypes lost 12.82 and 0.31% (p = 0.035), respectively. AA genotype was also associated with higher chance of ≥ 10%, ≥ 20% and ≥ 30% FM loss in the course of RTH (OR = 13.78; 5.78; 2.28).

Conclusions

The evaluation of such molecular factors as SNP 13041A>G may have higher predictive value in the development of malnutrition associated with severe loss of fat mass than the subjective scales, e.g., SGA and NRS-2002. The presence of AA genotype on men with HNC before RTH may facilitate earlier nutritional intervention and supportive treatment aimed at limiting or preventing body mass and fat mass loss during the applied treatment.

Electronic supplementary material

The online version of this article (10.1007/s00520-020-05675-8) contains supplementary material, which is available to authorized users.

Moderating effect of PLIN4 genetic variant on impulsivity traits in 5-year-old-children born small for gestational age

Poor fetal growth is associated with long-term behavioral, metabolic and psychiatric alterations, including impulsivity, insulin resistance, and mood disorders. However, the consumption of omega-3 polyunsaturated fatty acid (n-3 PUFA) seems to be protective for this population, improving inhibitory control and behavioral reactivity. We investigated whether the presence of the A allele of rs8887 SNP (PLIN4 gene), known to be associated with increased sensitivity to the consumption of n-3 PUFAs, interacts with fetal growth influencing inhibitory control. 152 five-year-old children were genotyped and performed the Stop Signal Task (SSRT). There was a significant interaction between birth weight and the presence of the A allele on SSRT performance, in which lower birth weight associated with poorer inhibitory control only in non-carriers. These results suggest that a higher responsiveness to n-3 PUFAS protects small for gestational age children from developing poor response inhibition, highlighting that optimizing n-3 PUFA intake may benefit this population.

The Perilipins: Major Cytosolic Lipid Droplet-Associated Proteins and Their Roles in Cellular Lipid Storage, Mobilization, and Systemic Homeostasis

The discovery by Dr. Constantine Londos of perilipin 1, the major scaffold protein at the surface of cytosolic lipid droplets in adipocytes, marked a fundamental conceptual change in the understanding of lipolytic regulation. Focus then shifted from the enzymatic activation of lipases to substrate accessibility, mediated by perilipin-dependent protein sequestration and recruitment. Consequently, the lipid droplet became recognized as a unique, metabolically active cellular organelle and its surface as the active site for novel protein-protein interactions. A new area of investigation emerged, centered on lipid droplets' biology and their role in energy homeostasis. The perilipin family is of ancient origin and has expanded to include five mammalian genes and a growing list of evolutionarily conserved members. Universally, the perilipins modulate cellular lipid storage. This review provides a summary that connects the perilipins to both cellular and whole-body homeostasis.

Genetic Predictors of ≥5% Weight Loss by Multidisciplinary Advice to Severely Obese Subjects

BACKGROUND

Weight loss success is determined by genetic factors, which may differ according to treatment strategy.

METHODS

From a multidisciplinary obesity treatment program involving dietary advice, psychological counseling, and increased physical activity, 587 subjects (68% female; 46.1 ± 12.4 years; BMI 39.9 ± 6.3) were recruited. At baseline, a blood sample was drawn for DNA isolation. Genotypes were determined for 30 polymorphisms in 25 candidate genes. The association between genotypes and weight loss was assessed after 3 months (short-term) and after 12 months of treatment (long-term). Weight loss was categorized as ≥5% or <5% of initial weight.

RESULTS

The G/G genotype of PLIN1 (rs2289487) and PLIN1 (rs2304795), the T/T genotype of PLIN1 (rs1052700), and the C/C genotype of MMP2 predicted ≥5% weight loss in the first 3 months. The C/G-G/G genotype of PPARγ (rs1801282) and the T/C genotype of TIMP4 (rs3755724) predicted ≥5% weight loss after 12 months. Subjects with the combination of PPARγ (rs1801282) C/G-G/G and TIMP4 (rs3755724) T/C lost even more weight.

CONCLUSION

Polymorphisms in genes related to regulation of fat storage and structural adaptation of the adipocytes are predictors for weight loss success with different genes being relevant for short-term and long-term weight loss success.

Perilipin polymorphisms are risk factors for the development of obesity in adolescents? A case-control study

Background

The variations in perilipin gene (PLIN) were previously associated with obesity. We examined the association of polymorphisms at the PLIN locus in adolescents with obesity and their connection with serum adipokines.

Methods

A total of 308 children (206 obese, 66.8% and 102 healthy control, 33.2%) between the ages of 10-18 years were included into the study. PLIN gene analysis [PLIN 1, PLIN 4, PLIN 6, PLIN 5’UTR-1234 C > G and PLIN 10171 A/T] were studied by Real Time-PCR. Serum leptin, adiponectin, resistin and ghrelin levels were studied by ELISA method in both groups and their link with perilipin polymorphisms were analyzed.

Results

Serum leptin level was found significantly high in obese adolescents. Other adipokine levels were similar in both groups. The incidence of PLIN 1, PLIN 4, PLIN 5’UTR-1234 C > G and PLIN 10171 A/T minor and major alleles was similar in both groups. PLIN 6 T/T allele was determined significantly high in obese adolescents compared to that of control group. No correlation was detected between perilipin polymorphism and serum levels of adipokines.

Conclusion

The PLIN 6 polymorphism of the perilipin gene may influence the risk of the obesity during adolescence.

Trial registration

Retrospectively registered.

Lunch eating predicts weight-loss effectiveness in carriers of the common allele at PERILIPIN1: the ONTIME (Obesity, Nutrigenetics, Timing, Mediterranean) study

BACKGROUND

We propose that eating lunch late impairs the mobilization of fat from adipose tissue, particularly in carriers of PERILIPIN1 (PLIN1) variants.

OBJECTIVE

The aim was to test the hypothesis that PLIN1, a circadian lipid-stabilizing protein in the adipocyte, interacts with the timing of food intake to affect weight loss.

DESIGN

A total of 1287 overweight and obese subjects [229 men and 1058 women; mean ± SD body mass index (in kg/m²): 31 ± 5] who attended outpatient obesity clinics were enrolled in the ONTIME (Obesity, Nutrigenetics, Timing, Mediterranean) study. Timing of food intake was estimated with a validated questionnaire. Anthropometric variables and PLIN1 genotypes were analyzed, including 6209T>C (rs2289487), 11482G>A (rs894160), 13041A>G (rs2304795), and 14995A>T (rs1052700). The main outcomes were effectiveness of the program and weight-loss progression during 28 wk of treatment.

RESULTS

The PLIN1 locus was associated with variability in response to a weight-loss program. Specifically, carrying the minor C allele at the PLIN1 6209T>C was associated with better weight-loss response (P = 0.035). The probability of being a better responder [percentage of weight loss ≥7.5% (median)] was 33% higher among C than among TT carriers (OR: 1.32; 95% CI: 1.05, 1.67; P = 0.017). We found an interaction of PLIN1 × food timing between the 14995A>T variant and timing of lunch eating for total weight loss (P = 0.035). Among AA carriers, eating late was associated with less weight loss (P < 0.001), whereas time of eating did not influence weight loss among TT carriers (P = 0.326).

CONCLUSIONS

Variability at the PLIN1 locus is associated with variability in weight loss. Moreover, eating late is related to lower weight-loss effectiveness among carriers of the AA genotype at the PLIN1 14995A>T variant. These results contribute to our ability to implement more precise and successful obesity treatments. The ONTIME study was registered at clinicaltrials.gov as NCT02829619.

An Improved PCR-RFLP Assay for the Detection of a Polymorphism rs2289487 of PLIN1 Gene

BACKGROUND

In recent research, it has been shown that rs2289487 within the PLIN1 gene has different variants that have been associated with obesity, type 2 diabetes, and other diseases. However, the isochizomers such as the BsmI enzyme required for detection of this polymorphism through polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method are expensive. In this study, we aimed to explore a novel PCR-RFLP method for identifying the single-nucleotide polymorphism (SNP) of rs2289487 of PLIN1 gene.

METHODS

A new restriction enzyme site was created through created restriction site PCR. In the forward primer, a deoxynucleotide A was substituted with C, and after PCR a new restriction enzyme site for BstUI was introduced into the PCR products. A total of 108 samples from Han Chinese were tested to evaluate this new method.

RESULTS

Allele frequencies in the Asian population were 0.326 for allele A and 0.674 for allele G, and the genotype frequencies were 12.8% for AA, 39.5% for AG, and 47.7% for GG.

CONCLUSION

The PCR-RFLP with new site for detecting the SNP of rs2289487 is an improved method with low cost and high accuracy.

Cinnamaldehyde supplementation prevents fasting-induced hyperphagia, lipid accumulation, and inflammation in high-fat diet-fed mice

Cinnamaldehyde, a bioactive component of cinnamon, is increasingly gaining interest for its preventive and therapeutic effects against metabolic complications like type-2 diabetes. This study is an attempt to understand the effect of cinnamaldehyde in high-fat diet (HFD)-associated increase in fasting-induced hyperphagia and related hormone levels, adipose tissue lipolysis and inflammation, and selected cecal microbial count in mice. Cinnamaldehyde, at 40 µM dose, prevented lipid accumulation and altered gene expression toward lipolytic phenotype in 3T3-L1 preadipocyte cell lines. In vivo, cinnamaldehyde coadministration prevented HFD-induced body weight gain, decreased fasting-induced hyperphagia, as well as circulating leptin and leptin/ghrelin ratio. In addition to that, cinnamaldehyde altered serum biochemical parameters related to lipolysis, that is, glycerol and free fatty acid levels. At transcriptional level, cinnamaldehyde increased anorectic gene expression in hypothalamus and lipolytic gene expression in visceral white adipose tissue. Furthermore, cinnamaldehyde also decreased serum IL-1β and inflammatory gene expression in visceral white adipose tissue. However, cinnamaldehyde did not modulate the population of selected gut microbial (Lactobacillus, Bifidibaceria, and Roseburia) count in cecal content. In conclusion, cinnamaldehyde increased adipose tissue lipolysis, decreased fasting-induced hyperphagia, normalized circulating levels of leptin/ghrelin ratio, and reduced inflammation in HFD-fed mice, which augurs well for its antiobesity role.

Unraveling the roles of PLIN5: linking cell biology to physiology

The discovery of perilipin (PLIN) 1 provided a major conceptual shift in the understanding of adipose tissue lipolysis and generated intense interest in lipid droplet biology research. The subsequent discovery of other PLIN proteins revealed unique tissue distribution profiles, subcellular locations, and lipid-binding properties and divergent cellular functions. PLIN5 is highly expressed in oxidative tissues such as skeletal muscle, liver, and heart and is central to lipid homeostasis in these tissues. Studies in cell systems have ascribed several metabolic roles to PLIN5 and demonstrated interactions with other proteins that are requisite for these functions. We examine recent in vivo studies and ask whether the evidence from the cell biology approaches is consistent with the physiological roles of PLIN5.

Association between three genetic variants of the Perilipin Gene (PLIN) and glucose metabolism: results from a replication study among Chinese adults and a meta-analysis

OBJECTIVE

This study was aimed to replicate the associations between three Perilipin Gene (PLIN) variants (rs894160, rs1052700, and rs2304796) and diabetes risks and to evaluate the overall effects of these variants on diabetes risk and obesity risk.

METHODS

We conducted a cross-sectional study among 993 Chinese Han adults. We also made a meta-analysis to estimate associations between these variants and diabetes risk and obesity risk.

RESULTS

In the sample of all participants, all three single-nucleotide polymorphisms (SNPs) were not significantly associated with diabetes risks. The PLIN polymorphisms significantly interacted with central obesity in relation to diabetes risk (P for interaction = 0.036, 0.033, and 0.042 for rs1052700, rs894160, and rs2304796, respectively). In those with allele T of rs1052700 or allele A of rs894160, fasting glucose concentration and diabetes risk increased significantly with the increment of waist circumference. Only association between rs894160 and obesity risk was available for meta-analysis. The meta-analysis indicated the overall estimation of obesity risk for rs894160 was 0.97 (0.78, 1.16) among participants with allele A versus people with genotype GG and 1.46 (0.99, 1.93) among those with genotype AA versus allele G carriers.

CONCLUSION

Chinese adults with high waist circumference may have a high risk of diabetes, especially among those with allele T in rs1052700 or with allele A in rs894160. People with genotype AA (rs894160) may have a high risk of obesity.

Genetic determinants of obesity and related vascular diseases

Obesity is one of the major risk factors of vascular diseases, and its prevalence is increasing worldwide. In the past decade, progress has been made in the understanding of genetic determinants of obesity and obesity-associated diseases. Genome-wide association studies identified a number of genetic variants associated with obesity. In addition to common variants, FTO and MC4R, new loci, such as TMEM18, KCTD15, GNPDA2, SH2B1, MTCH2, and NEGR1 have been detected. In the past years, abdominal obesity has been shown to be a more important vascular risk factor than the body mass index. In the context of vascular risk assessment, identification of genetic polymorphisms associated with accumulation of visceral fat is of special importance. Some polymorphisms associated with abdominal obesity, such as variants of gene encoding microsomal triglyceride transfer protein, have been already discovered. In this chapter, we provide a review of genetic determinants of obesity and discuss their role in obesity-related vascular diseases.

Update on perilipin polymorphisms and obesity

Perilipin proteins were discovered in the adipocyte, where they regulate lipid storage and lipolysis. Animal knockout models provided initial evidence of the critical role of perilipin 1, the most abundant of the adipocyte proteins, in energy and glucose metabolism. During a decade of study, genetic variation in perilipin 1 has been consistently but not invariably associated with body weight and obesity-related complications. Related phenotypes such as postprandial lipid metabolism and aerobic fitness are also modulated by perilipin 1 genotype, consistent with earlier metabolic studies. Investigations of gene-diet interactions, together with gene expression studies, have yielded increased understanding, but important questions about causal variants and mechanisms remain. The newest work examines perilipin 4, an adipocyte regulator of triglyceride synthesis and packaging. The novel discovery that a perilipin 4 variant creates a binding site for regulation of the perilipin gene (PLIN) by microRNA suggests intriguing new possibilities for additional mechanistic investigations of other perilipin proteins.

Perilipin family members preferentially sequester to either triacylglycerol-specific or cholesteryl-ester-specific intracellular lipid storage droplets

Perilipin family proteins (Plins) coat the surface of intracellular neutral lipid storage droplets in various cell types. Studies across diverse species demonstrate that Plins regulate lipid storage metabolism through recruitment of lipases and other regulatory proteins to lipid droplet surfaces. Mammalian genomes have distinct Plin gene members and additional protein forms derived from specific mRNA splice variants. However, it is not known if the different Plins have distinct functional properties. Using biochemical, cellular imaging and flow cytometric analyses, we now show that within individual cells of various types, the different Plin proteins preferentially sequester to separate pools of lipid storage droplets. By examining ectopically expressed GFP fusions and all endogenous Plin protein forms, we demonstrate that different Plins sequester to different types of lipid droplets that are composed of either triacylcerides or cholesterol esters. Furthermore, Plins with strong association preferences to triacylceride (or cholesterol ester) droplets can re-direct the relative intracellular triacylceride-cholesterol ester balance toward the targeted lipid. Our data suggest diversity of Plin function, alter previous assumptions about shared collective actions of the Plins, and indicate that each Plin can have separate and unique functions.

A Polymorphism in a gene encoding Perilipin 4 is associated with height but not with bone measures in individuals from the Framingham Osteoporosis Study

There is increasing interest in identifying new pathways and candidate genes that confer susceptibility to osteoporosis. There is evidence that adipogenesis and osteogenesis may be related, including a common bone marrow progenitor cell for both adipocytes and osteoblasts. Perilipin 1 (PLIN1) and Perilipin 4 (PLIN4) are members of the PATS family of genes and are involved in lipolysis of intracellular lipid deposits. A previous study reported gender-specific associations between one polymorphism of PLIN1 and bone mineral density (BMD) in a Japanese population. We hypothesized that polymorphisms in PLIN1 and PLIN4 would be associated with bone measures in adult Caucasian participants of the Framingham Osteoporosis Study (FOS). We genotyped 1,206 male and 1,445 female participants of the FOS for four single-nucleotide polymorphism (SNPs) in PLIN1 and seven SNPs in PLIN4 and tested for associations with measures of BMD, bone ultrasound, hip geometry, and height. We found several gender-specific significant associations with the measured traits. The association of PLIN4 SNP rs8887, G>A with height in females trended toward significance after simulation testing (adjusted P = 0.07) and remained significant after simulation testing in the combined-sex model (adjusted P = 0.033). In a large study sample of men and women, we found a significant association between one SNP in PLIN4 and height but not with bone traits, suggesting that PATS family genes are not important in the regulation of bone. Identification of genes that influence human height may lead to a better understanding of the processes involved in growth and development.

The PLIN4 variant rs8887 modulates obesity related phenotypes in humans through creation of a novel miR-522 seed site

PLIN4 is a member of the PAT family of lipid storage droplet (LSD) proteins. Associations between seven single nucleotide polymorphisms (SNPs) at human PLIN4 with obesity related phenotypes were investigated using meta-analysis followed by a determination if these phenotypes are modulated by interactions between PLIN4 SNPs and dietary PUFA. Samples consisted of subjects from two populations of European ancestry. We demonstrated association of rs8887 with anthropometrics. Meta-analysis demonstrated significant interactions between the rs8887 minor allele with PUFA n3 modulating anthropometrics. rs884164 showed interaction with both n3 and n6 PUFA modulating anthropometric and lipid phenotypes. In silico analysis of the PLIN4 3′UTR sequence surrounding the rs8887 minor A allele predicted a seed site for the human microRNA-522 (miR-522), suggesting a functional mechanism. Our data showed that a PLIN4 3′UTR luciferase reporter carrying the A allele of rs8887 was reduced in response to miR-522 mimics compared to the G allele. These results suggest variation at the PLIN4 locus, and its interaction with PUFA as a modulator of obesity related phenotypes, acts in part through creation of a miR-522 regulatory site.

Preliminary findings on the role of PLIN1 polymorphisms on body composition and energy metabolism response to energy restriction in obese women

The aim of the present study was to investigate the association of PLIN1 11482G>A (rs894160) and PLIN1 13041A>G (rs2304795) polymorphisms with body composition, energy and substrate metabolism, and the metabolic response to a 12-week energy-restricted diet in obese women. The study comprised a total of seventy-eight obese (BMI 34·0 (SD 2·8) kg/m(2)) women (age 36·7 (SD 7) years). We measured weight, height and waist circumference before and after a 12-week controlled energy-restricted diet intervention. Body fat mass and lean mass were measured by dual-energy X-ray absorptiometry. RMR and lipid oxidation rate were measured by indirect calorimetry. We also analysed fasting plasma glucose, insulin, cholesterol and leptin. Women carrying the 11482A allele had a lower reduction in waist circumference than non-A allele carriers (3·2 (SD 0·5) v. 4·6 (SD 0·6) %, respectively, P = 0·047; P for gene-diet interaction = 0·064). Moreover, women with the 11482A allele had a higher decrease in lipid oxidation rate than non-A allele carriers (58·9 (SD 6·7) v. 31·3 (SD 8·2) %, respectively, P = 0·012; P for gene-diet interaction = 0·004). There was no interaction effect between the 13041A>G polymorphism and diet-induced changes on the outcome variables (all P>0·1). These results confirm and extend previous findings suggesting that the PLIN1 11482G>A polymorphism plays a modulating role on diet-induced changes in body fat and energy metabolism in obese women.

Not just fat: the structure and function of the lipid droplet

Lipid droplets (LDs) are independent organelles that are composed of a lipid ester core and a surface phospholipid monolayer. Recent studies have revealed many new proteins, functions, and phenomena associated with LDs. In addition, a number of diseases related to LDs are beginning to be understood at the molecular level. It is now clear that LDs are not an inert store of excess lipids but are dynamically engaged in various cellular functions, some of which are not directly related to lipid metabolism. Compared to conventional membrane organelles, there are still many uncertainties concerning the molecular architecture of LDs and how each function is placed in a structural context. Recent findings and remaining questions are discussed.

Perilipin 1 and perilipin 2 protein localization and gene expression study in skeletal muscles of European cross-breed pigs with different intramuscular fat contents

This study investigated the lipid droplet coat proteins perilipin 1 (PLIN1) and perilipin 2 (PLIN2) localization in pig skeletal muscle and their relationship with intramuscular fat (IMF) content. PLIN1 and PLIN2 proteins were immunostained in semimembranosus muscle cross-sections from two groups of samples divergent for IMF and the gene expression was quantified. PLIN1 localized in the periphery of intramuscular adipocytes, whereas PLIN2 localized within myofibers with high lipid content. The high IMF group showed higher total cross-sectional area of PLIN1-stained adipocytes compared with the low IMF group (P<0.05), while the cross-sectional area and percentage of PLIN2-positive myofibers did not differ between IMF-divergent groups. This suggested that IMF content is mainly determined by extra-myocellular lipids. At mRNA level, PLIN2 expression was higher in high IMF muscles (P<0.05). The results indicate for the first time that in pig muscle PLIN1 and PLIN2 proteins are localized in correspondence with extra and intra-myocellular lipids, respectively.

Association of common polymorphisms in the fractalkine receptor (CX3CR1) with obesity

The inflammatory component in obesity is now well established. The CX3CR1 gene encodes the fractalkine (CX3CL1) receptor and has two coding single-nucleotide polymorphisms, V249I and T280M, linked to a lower risk of other inflammatory diseases such as coronary artery disease (CAD) and asthma. To determine whether CX3CR1 is associated with obesity, we genotyped the V249I and T280M polymorphisms of the CX3CR1 gene in subjects with a BMI ≥30 kg/m² and nonobese controls with a BMI <30 kg/m². Binary logistic regression analyses revealed that the 280MM genotype was associated with obesity (P = 0.022). A gender-specific one-way ANOVA was also conducted to investigate mean BMI and waist circumference differences between genotypes of each polymorphism. For both polymorphisms independently, women carrying two copies of the minor allele had significant higher mean waist circumference than those carrying only one copy of the minor allele (MM > TM, P = 0.031; II > VI, P = 0.013) or those who were homozygous for the major allele (MM > TT, P = 0.005; II > VV, P = 0.006). We also observed significant higher mean waist circumference in men carrying one copy of the minor allele when compared to those who were homozygous for the major allele for the T280M polymorphism (TM > TT, P = 0.029). This study suggests that CX3CR1, a biomarker of obesity in this sample, constitutes a potential target for further investigation of the role of inflammation in the expression of obesity-related phenotypes.

Association of lifestyle factors, polymorphisms in adiponectin, perilipin and hormone sensitive lipase, and clinical markers in Japanese males

According to recent genome-wide association studies, a number of single nucleotide polymorphisms is reported to be associated with diseases or several clinical markers. Among them, adiponectin (ADIPOQ) and perilipin (PLIN) polymorphisms are major factors of obesity. However, the association between lifestyle factor, these polymorphisms and obesity-related clinical markers in Japanese is not well researched. Therefore, the aim of present study is to investigate the association between lifestyle factor, polymorphisms of lipid metabolic genes, and clinical markers in 148 middle-aged Japanese males. The study revealed that ADIPOQ 45 T>G and ADIPOQ 276 G>T genotypes were significantly associated with triglyceride, total cholesterol, hemoglobin A1c (HbA1c) in blood and body mass index (BMI). PLIN4 11482 G>A and hormone sensitive lipase (LIPE)-60 C>G genotypes were respectively associated with BMI and serum triglyceride. Not only genetic factors but also lifestyle factors influence several clinical markers. The BMI of subjects who like sweets and have the GG allele in ADIPOQ 276 G>T was higher than that of subjects who don't like sweets. The habit of eating fruits and fish affected low-density lipoprotein-cholesterol of the GT allele and HbA1c of the TT allele in ADIPOQ 276 G>T. Those findings indicate improvement and conservation of lifestyle depending on genetic predisposition in ADIPOQ, PLIN and LIPE should be encouraged.

A genome-wide linkage scan identifies multiple quantitative trait loci for HDL-cholesterol levels in families with premature CAD and MI

Plasma HDL cholesterol levels (HDL-C) are an independent predictor of coronary artery disease (CAD). We have completed a genome-wide linkage scan for HDL-C in a US cohort consisting of 388 multiplex families with premature CAD (GeneQuest). The heritability of HDL-C in GeneQuest was 0.37 with gender and age as covariates (P = 5.1 x 10(-4)). Two major quantitative trait loci (QTL) for log-transformed HDL-C adjusted for age and gender were identified onto chromosomes 7p22 and 15q25 with maximum multipoint logarithm of odds (LOD) scores of 3.76 and 6.69, respectively. Fine mapping decreased the 7p22 LOD score to a nonsignificant level of 3.09 and split the 15q25 QTL into two loci, one minor QTL on 15q22 (LOD = 2.73) that spanned the LIPC gene, and the other at 15q25 (LOD = 5.63). A family-based quantitative transmission disequilibrium test (QTDT) revealed significant association between variant rs1800588 in LIPC and HDL-C in the GeneQuest population (P = 0.0067), which may account for the minor QTL on 15q22. The 15q25 QTL is the most significant locus identified for HDL-C to date, and these results provide a framework for the ultimate identification of the underlying HDL-C variant and gene on chromosomes 15q25, which will provide insights into novel regulatory mechanisms of HDL-C metabolism.

Variation in the perilipin gene (PLIN) affects glucose and lipid metabolism in non-Hispanic white women with and without polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in women. It is characterized by chronic anovulation, hyperandrogenism, obesity and a predisposition to type 2 diabetes mellitus (T2DM). Since obesity plays an important role in the etiology of PCOS, we sought to determine if variants in the perilipin gene (PLIN), a gene previously implicated in the development of obesity, were also associated with PCOS. We typed six single nucleotide polymorphisms (haplotype tagging and/or previously associated with obesity or related metabolic traits) in PLIN in 305 unrelated non-Hispanic white women (185 with PCOS and 120 without PCOS). None of the variants was associated with PCOS (P<0.05). However, the variant rs1052700*A was associated with increased risk for glucose intolerance (impaired glucose tolerance or T2DM) in both non-PCOS (OR=1.75 [1.02-3.01], P=0.044) and PCOS subjects (OR=1.67 [1.08-2.59], P=0.022). It was also associated with increased LDL (P=0.007) and total cholesterol levels (P=0.042). These results suggest that genetic variation in PLIN may affect glucose and lipid metabolism in women both with and without PCOS.

Endurance exercise training effects on body fatness, VO2max, HDL-C subfractions, and glucose tolerance are influenced by a PLIN haplotype in older Caucasians

Perilipins are lipid droplet-coating proteins that regulate intracellular lipolysis in adipocytes. A haplotype of two perilipin gene (PLIN) single nucleotide polymorphisms, 13041A>G and 14995A>T, has been previously associated with obesity risk. Furthermore, the available data indicate that this association may be modified by sex. We hypothesized that this haplotype would associate with body fatness, aerobic fitness, and a number of cardiovascular (CV) risk factor phenotypes before and after a 6-mo endurance exercise training program in sedentary older Caucasians. The major haplotype group (13041A/14995A; n = 57) had significantly lower body mass index (BMI) and body fatness compared with noncarriers of the AA haplotype (n = 44) before the training intervention. Training improved body composition in both groups, but fatness remained higher in noncarriers than AA carriers after training. This fat retention in noncarriers blunted their maximal oxygen uptake (Vo(2 max)) adaptation to training. Female noncarriers had substantially higher concentrations of several conventionally and NMR-measured HDL-C subfractions than male noncarriers before and after training, but only minimal differences were found between the sexes in the AA haplotype group. Haplotype group differences in baseline and after-training responses to an oral glucose tolerance test (OGTT) also differed by sex, as noncarrier men had the highest baseline area under the insulin curve (insulin AUC), but were the only group to significantly improve insulin AUC with training. The insulin sensitivity index and plasma glucose responses to the OGTT were more favorable in AA carriers than noncarriers before and after training. Overall, our findings suggest that PLIN variation explains some of the interindividual differences in the response of obesity and CV phenotypes to exercise training. Furthermore, these data contribute to the growing understanding of PLIN as a candidate gene for human obesity and the cardiometabolic consequences of excess adiposity.

Perilipin gene 1237 T > C polymorphism is not associated with obesity risk in northern Chinese Han adults

OBJECTIVE

To identify the association between PLIN 1237 polymorphism and obesity in Chinese Han adults.

METHODS

A total of 994 adults (157 obese subjects, 322 overweight subjects, and 515 normal controls) were recruited from two rural communities. PLIN 1237 polymorphism was genotyped by polymerase chain reaction-restriction-fragment-length-polymorphism (PCR-RFLP). Association between PLIN polymorphisms and obesity status was estimated by ordinal logistic regression.

RESULTS

The three genotypes of PLIN 1237 were detected with a percentage of 54.3%, 37.1%, and 8.6% in TT, TC, and CC genotypes, respectively. For the PLIN 1237 polymorphism locus, the frequency of alleles T and C was 0.73 and 0.27, respectively. The PLIN 1237 polymorphisms were in Hardy-Weinberg equilibrium. PLIN 1237 polymorphism was not associated with obesity. The odds ratio for overweight or obesity for the CC+TC genotype was 0.8 (0.4, 1.4) in women (P = 0.4) and 0.6 (0.3, 1.3) in men (P = 0.2) after adjustment for age, education, household income and alcohol consumption, smoking, and physical activity.

CONCLUSION

Chinese Han adults have a lower frequency of variant-allele C in PLIN 1237. PLIN 1237 T > C polymorphism is not significantly associated with obesity in northern Chinese adults.

Perilipin overexpression in mice protects against diet-induced obesity

Perilipin A is the most abundant phosphoprotein on adipocyte lipid droplets and is essential for lipid storage and lipolysis. Perilipin null mice exhibit diminished adipose tissue, elevated basal lipolysis, reduced catecholamine-stimulated lipolysis, and increased insulin resistance. To understand the physiological consequences of increased perilipin expression in vivo, we generated transgenic mice that overexpressed either human or mouse perilipin using the adipocyte-specific aP2 promoter/enhancer. Phenotypes of female transgenic and wild-type mice were characterized on chow and high-fat diets (HFDs). When challenged with an HFD, transgenic mice exhibited lower body weight, fat mass, and adipocyte size than wild-type mice. Expression of oxidative genes was increased and lipogenic genes decreased in brown adipose tissue of transgenic mice. Basal and catecholamine-stimulated lipolysis was decreased and glucose tolerance significantly improved in transgenic mice fed a HFD. Perilipin overexpression in adipose tissue protects against HFD-induced adipocyte hypertrophy, obesity, and glucose intolerance. Alterations in brown adipose tissue metabolism may mediate the effects of perilipin overexpression on body fat, although the mechanisms by which perilipin overexpression alters brown adipose tissue metabolism remain to be determined. Our findings demonstrate a novel role for perilipin expression in adipose tissue metabolism and regulation of obesity and its metabolic complications.

Hepatic gene expression in morbidly obese women: implications for disease susceptibility

The objective of this study was to determine the molecular bases of disordered hepatic function and disease susceptibility in obesity. We compared global gene expression in liver biopsies from morbidly obese (MO) women undergoing gastric bypass (GBP) surgery with that of women undergoing ventral hernia repair who had experienced massive weight loss (MWL) following prior GBP. Metabolic and hormonal profiles were examined in MO vs. MWL groups. Additionally, we analyzed individual profiles of hepatic gene expression in liver biopsy specimens obtained from MO and MWL subjects. All patients underwent preoperative metabolic profiling. RNAs were extracted from wedge biopsies of livers from MO and MWL subjects, and analysis of mRNA expression was carried out using Affymetrix HG-U133A microarray gene chips. Genes exhibiting greater than twofold differential expression between MO and MWL subjects were organized according to gene ontology and hierarchical clustering, and expression of key genes exhibiting differential regulation was quantified by real-time-polymerase chain reaction (RT-PCR). We discovered 154 genes to be differentially expressed in livers of MWL and MO subjects. A total of 28 candidate disease susceptibility genes were identified that encoded proteins regulating lipid and energy homeostasis (PLIN, ENO3, ELOVL2, APOF, LEPR, IGFBP1, DDIT4), signal transduction (MAP2K6, SOCS-2), postinflammatory tissue repair (HLA-DQB1, SPP1, P4HA1, LUM), bile acid transport (SULT2A, ABCB11), and metabolism of xenobiotics (GSTT2, CYP1A1). Using gene expression profiling, we have identified novel candidate disease susceptibility genes whose expression is altered in livers of MO subjects. The significance of altered expression of these genes to obesity-related disease is discussed.

Possible role for ENPP1 polymorphism in obesity but not for INSIG2 and PLIN variants

Previous studies have suggested that ENPP1, INSIG2, and PLIN may be linked with a higher risk for obesity or with increased phenotypic measures of obesity. We selected polymorphisms in these candidate genes based on their prior associations with obesity risk or obesity parameters. K121Q (rs1044498) in ENPP1, rs7566605 in INSIG2, and rs894160 in PLIN were genotyped by Taqman assays in a Belgian sample of 1,078 obese subjects (body mass index (BMI) > 30 kg/m(2)) and 323 lean controls (18.5 < BMI < 25 kg/m(2)). BMI, waist circumference, and waist-to-hip ratio (WHR) were assessed by standard methods while a computerized tomography-scan was used to measure visceral (VFA), subcutaneous (SFA), and total (TFA) abdominal fat areas. Presence of the rare allele was not significantly different between cases and controls for the three variants that were tested, while only WHR was associated with ENPP1 in obese subjects. Our data thus indicate that K121Q, rs7566605, and rs894160 are not major contributing factors for obesity.

Relationship between perilipin gene polymorphisms and body weight and body composition during weight loss and weight maintenance

BACKGROUND

Genetic variation in the perilipin (PLIN) gene may play a role in the etiology and treatment of obesity.

OBJECTIVE

To examine different polymorphisms in the PLIN gene in relation to body-weight regulation.

METHODS

118 subjects followed a 6 wk VLCD, followed by 1 year weight maintenance. Body-weight (BW), body composition, leptin concentration, and polymorphisms of the PLIN gene: PLIN1:rs2289487, PLIN4:rs894160, PLIN6:rs1052700, PLIN5:rs2304795 and PLIN7:rs 2304796 were determined.

RESULTS

BW loss during VLCD was 7.0+/-3.1 kg (p<0.05), and BW regain was 3.7+/-1.4 kg (p<0.05), including changes in body mass index (BMI), waist-circumference, body-composition and leptin concentrations (p<0.05). Linkage disequilibria were observed between PLIN1 and PLIN4: D' >0.9, r2=0.72; PLIN5 and PLIN7: D' >0.9, r2=0.85. In men, body weight, BMI, waist circumference, body fat, leptin concentrations were significantly lower for the haplotype of PLIN1 (C-alleles) and PLIN4 (A-alleles). In women weight loss and loss of fat mass were larger for the haplotype of PLIN1 (C-alleles) and PLIN4 (A-alleles). For PLIN6 genotypes body weight and body fat were lower for homozygotes of the minor allele (T/T) in the men; in the women leptin concentrations were lower. The haplotype of PLIN5 and PLIN7 consisting of A/G and G/G of PLIN5 and A/A of PLIN7 showed a reduction in FM: 5.9+/-0.6 kg vs 3.1+/-0.4 kg, % body fat: 5.5+/-0.6% vs 2.2+/-0.2%, and leptin: 20.5+/-10.8 ng/ml vs 12.9+/-6.7 ng/ml over time in the women (p<0.05).

CONCLUSION

Since the haplotype of the minor alleles PLIN1-4, PLIN5-7 and PLIN6, was related to body-weight regulation at a lower level of body-weight in the men as well in the women we conclude that the PLIN1-4, 6, and 5-7 locus appears as a genetic influencer of obesity risk in humans.

PAT proteins, an ancient family of lipid droplet proteins that regulate cellular lipid stores

The PAT family of lipid droplet proteins includes 5 members in mammals: perilipin, adipose differentiation-related protein (ADRP), tail-interacting protein of 47 kDa (TIP47), S3-12, and OXPAT. Members of this family are also present in evolutionarily distant organisms, including insects, slime molds and fungi. All PAT proteins share sequence similarity and the ability to bind intracellular lipid droplets, either constitutively or in response to metabolic stimuli, such as increased lipid flux into or out of lipid droplets. Positioned at the lipid droplet surface, PAT proteins manage access of other proteins (lipases) to the lipid esters within the lipid droplet core and can interact with cellular machinery important for lipid droplet biogenesis. Genetic variations in the gene for the best-characterized of the mammalian PAT proteins, perilipin, have been associated with metabolic phenotypes, including type 2 diabetes mellitus and obesity. In this review, we discuss how the PAT proteins regulate cellular lipid metabolism both in mammals and in model organisms.

Metabolic syndrome pathophysiology: the role of adipose tissue

The metabolic syndrome comprises a set of metabolic and physiological risk factors associated with elevated cardiovascular disease risk. The expression of each one of its major factors (hypertriglyceridemia, low high-density lipoprotein cholesterol levels, hypertension, abdominal obesity, and insulin resistance) has been found to be the result of complex interactions between genetic and environmental factors. Moreover, one of them, obesity, may play a major role in triggering the metabolic syndrome by interacting with genetic variants at candidate genes for dyslipidemia, hypertension, and insulin resistance. In support of this hypothesis, several studies at several candidate genes, mainly adipokines and perilipin, have already demonstrated the significance of these interactions; however, the information and its solidity are still very limited and in many cases, replication studies are still lacking in the literature. Therefore, more studies with better epidemiological design and standardized adiposity measures are needed to estimate the contribution of body weight and fat distribution to the genetic predisposition to the metabolic syndrome, the most common CVD risk factor in industrialized societies.

Nutrigenetics and personalised nutrition: how far have we progressed and are we likely to get there?

Nutrigenetics and personalised nutrition are components of the concept that in the future genotyping will be used as a means of defining dietary recommendations to suit the individual. Over the last two decades there has been an explosion of research in this area, with often conflicting findings reported in the literature. Reviews of the literature in the area of apoE genotype and cardiovascular health, apoA5 genotype and postprandial lipaemia and perilipin and adiposity are used to demonstrate the complexities of genotype–phenotype associations and the aetiology of apparent between-study inconsistencies in the significance and size of effects. Furthermore, genetic research currently often takes a very reductionist approach, examining the interactions between individual genotypes and individual disease biomarkers and how they are modified by isolated dietary components or foods. Each individual possesses potentially hundreds of ‘at-risk’ gene variants and consumes a highly-complex diet. In order for nutrigenetics to become a useful public health tool, there is a great need to use mathematical and bioinformatic tools to develop strategies to examine the combined impact of multiple gene variants on a range of health outcomes and establish how these associations can be modified using combined dietary strategies.

Effects of perilipin (PLIN) gene variation on metabolic syndrome risk and weight loss in obese children and adolescents

CONTEXT

Genetic polymorphisms at the perilipin (PLIN) locus have been investigated for their potential utility as markers for obesity and metabolic syndrome (MS). We examined in obese children and adolescents (OCA) aged 7-14 yr the association of single-nucleotide polymorphisms (SNP) at the PLIN locus with anthropometric, metabolic traits, and weight loss after 20-wk multidisciplinary behavioral and nutritional treatment without medication.

DESIGN

A total of 234 OCA [body mass index (BMI = 30.4 +/- 4.4 kg/m(2); BMI Z-score = 2.31 +/- 0.4) were evaluated at baseline and after intervention. We genotyped four SNPs (PLIN1 6209T-->C, PLIN4 11482G-->A, PLIN5 13041A-->G, and PLIN6 14995A-->T).

RESULTS

Allele frequencies were similar to other populations, PLIN1 and PLIN4 were in linkage disequilibrium (D' = 0.999; P < 0.001). At baseline, no anthropometric differences were observed, but minor allele A at PLIN4 was associated with higher triglycerides (111 +/- 49 vs. 94 +/- 42 mg/dl; P = 0.003), lower high-density lipoprotein cholesterol (40 +/- 9 vs. 44 +/- 10 mg/dl; P = 0.003) and higher homeostasis model assessment for insulin resistance (4.0 +/- 2.3 vs. 3.5 +/- 2.1; P = 0.015). Minor allele A at PLIN4 was associated with MS risk (age and sex adjusted) hazard ratio 2.4 (95% confidence interval = 1.1-4.9) for genotype GA and 3.5 (95% confidence interval = 1.2-9.9) for AA. After intervention, subjects carrying minor allele T at PLIN6 had increased weight loss (3.3 +/- 3.7 vs. 1.9 +/- 3.4 kg; P = 0.002) and increased loss of the BMI Z-score (0.23 +/- 0.18 vs. 0.18 +/- 0.15; P = 0.003). Due to group size, risk of by-chance findings cannot be excluded.

CONCLUSION

The minor A allele at PLIN4 was associated with higher risk of MS at baseline, whereas the PLIN6 SNP was associated with better weight loss, suggesting that these polymorphisms may predict outcome strategies based on multidisciplinary treatment for OCA.

Gene-environment interactions and susceptibility to metabolic syndrome and other chronic diseases

There is an intrinsic complexity in the pathogenesis of common diseases. The concept of gene-environment interaction is receiving support from emerging evidence coming primarily from studies involving diet and cardiovascular disease (CVD) and its various risk factors. The accumulating evidence shows that common variants at candidate genes for lipid metabolism, inflammation, and obesity are associated with altered plasma levels of classic and new biomarkers of metabolic syndrome and CVD risk. Major contributors to this knowledge have been a series of large population studies containing phenotype-rich databases and dietary information to which genetic data have been added. Although this approach has provided strong evidence supporting the concept of gene-diet interactions modulating CVD risk factors, the strength of the individual effect is very small, and the replication among studies is rather disappointing. Current population studies are starting to incorporate experimental and analytical approaches that could provide more solid and comprehensive results. However, other limitations, such as the size of the populations required to examine higher-level interactions, are still major obstacles to translating this knowledge into practical public health applications. Nevertheless, data from numerous molecular and genetic epidemiological studies provide tantalizing evidence suggesting that gene-environment interactions, i.e., the modulation by a genetic polymorphism of a dietary component effect on a specific phenotype (e.g., cholesterol levels and obesity), can interact in ways that increase the risk for developing chronic disease, including susceptibility to developing the metabolic syndrome. Once further experience is gained from patients and/or individuals at high risk, more personalized genetic-based approaches may be applied toward the primary prevention and treatment of CVDs and other complex inflammatory diseases.

Perilipin polymorphism interacts with dietary carbohydrates to modulate anthropometric traits in hispanics of Caribbean origin

Perilipin (PLIN) is the major protein surrounding lipid droplets in adipocytes and regulates adipocyte metabolism by modulating the interaction between lipases and triacylglycerol stores. Associations between PLIN gene polymorphisms and obesity risk have been described, but interactions with dietary macronutrients require further attention. We examined whether dietary macronutrients (e.g. carbohydrates and fats) modulated the associations of the common PLIN 11482G > A (rs894160) single nucleotide polymorphism with obesity. We studied a population-based sample of Caribbean-origin Hispanics (n = 920, aged 45-74 y) living in the Boston area. Obesity measures (waist and hip circumference, BMI) did not differ between GG subjects and carriers of the A allele (GA and AA). In multivariate linear regression models, we found a significant interaction between complex carbohydrate intake as a continuous variable and PLIN 11482 G > A genotype for waist circumference (P = 0.002). By dichotomizing complex carbohydrate intake, we found significantly different effects across PLIN 11482G > A genotypes. When complex carbohydrate intake was <144 g/d, waist circumference was larger in PLIN 11482G > A carriers (P = 0.024). Conversely, when complex carbohydrate intake was >/=144 g/d, waist and hip circumferences were less in PLIN 11482G > A carriers (P < 0.05). These interactions were not found for simple sugars or total carbohydrates. We identified a significant gene-diet interaction associated with obesity at the PLIN locus. In subjects with higher complex carbohydrate intake, the minor allele was protective against obesity, whereas in subjects with lower carbohydrate intake, the minor allele was associated with increased obesity. These interactions may be relevant to dietary management of obesity.

Common variations in perilipin gene, central obesity, and risk of type 2 diabetes in US women

OBJECTIVE

The variations in perilipin gene (PLIN) were previously associated with obesity and insulin sensitivity. We examined whether PLIN variability was associated with diabetes risk and obesity status modified such associations.

METHODS AND PROCEDURES

We conducted a nested case-control study of 431 incident cases of type 2 diabetes and 791 healthy control women from the Nurses' Health Study. Obesity was defined by BMI or waist circumference (central obesity).

RESULTS

In the sample of all participants, PLIN variations were not significantly associated with the incidence of diabetes. The central obesity status (by National Cholesterol Education Program Adult Treatment Panel III definition of waist circumference>35 inches) significantly interacted with PLIN polymorphisms in relation to diabetes risk (P for interaction=0.027, 0.009, and 0.02 for rs2289487, rs8179043, and rs894160, respectively). In nonobese (central) women, carriers of rs2289487, rs8179043, and rs894160 had significantly greater risk of type 2 diabetes, adjusting for diabetes risk factors (odds ratio (OR)=1.52, 1.03-2.25; 1.54, 1.07-2.23; and 1.57, 1.09-2.27, respectively). Haplotypes possessing the three polymorphisms were also significantly associated with diabetes risk (global test, P=0.01). As compared with the most common haplotype 111, haplotype 222 and 211 (1 codes the common and 2 codes the minor alleles) were associated with 44% (OR=1.44, 95% confidence interval (CI) 1.09-1.91; P=0.01) and 70% (OR=1.70, 95% CI 1.04-2.77; P=0.03) greater risk, respectively. The PLIN variations were not significantly associated with the disease risk among women with central obesity.

DISCUSSION

Our data indicate that central obesity may modify the associations between PLIN variations and diabetes risk in women.

Gender, a significant factor in the cross talk between genes, environment, and health

BACKGROUND

Although men and women share most genetic information, they have significantly different disease susceptibilities that go well beyond the expected gender-specific diseases. Sex influences the risk of nearly all common diseases that affect both men and women, including atherosclerosis and diabetes and their preceding risk factors (eg, hyperlipidemia, insulin resistance, and obesity).

OBJECTIVE

The goal of this article was to examine the interplay between genes, gender, and disease susceptibility, and assess it in the context of the added complexity of environmental factors (ie, dietary habits, smoking, alcohol consumption) in the modulation of the balance between health and disease.

METHODS

Original and review articles published by the author were reexamined for evidence of gene-gender interactions.

RESULTS

Evidence from some key factors in lipid metabolism (apolipoprotein E [APOE])and obesity (perilipin [PLIN]) indicates that the interplay between genes, gender, and environmental factors modulates disease susceptibility. In the Framingham Heart Study, complex interactions have been shown between a promoter polymorphism at the apolipoprotein A1 gene, gender, and dietary poly-unsaturated fatty acid intake that modulate plasma concentrations of high-density lipoprotein cholesterol. Likewise, highly and clinically relevant interactions have been observed between the APOE gene common alleles APOE2 , APOE3, and APOE4 , gender, and smoking that determine cardiovascular disease risk. Most interesting is the gender-dependent association between common polymorphisms at the PLIN locus and obesity risk that has been replicated in several populations around the world.

CONCLUSIONS

These data support the idea that gender-specific differences in morbidity and mortality may be mediated in part by genetic factors and by their differential response to the environment. The new knowledge generated by a more careful and complete elucidation of the complex interactions predisposing to common diseases will result in an increased ability to provide successful personalized behavioral recommendations to prevent chronic disorders.

Lipid droplets in lipogenesis and lipolysis

Organisms store energy for later use during times of nutrient scarcity. Excess energy is stored as triacylglycerol in lipid droplets during lipogenesis. When energy is required, the stored triacylglycerol is hydrolyzed via activation of lipolytic pathways. The coordination of lipid storage and utilization is regulated by the perilipin family of lipid droplet coat proteins [perilipin, adipophilin/adipocyte differentiation-related protein (ADRP), S3-12, tail-interacting protein of 47 kilodaltons (TIP47), and myocardial lipid droplet protein (MLDP)/oxidative tissues-enriched PAT protein (OXPAT)/lipid storage droplet protein 5 (LSDP5)]. Lipid droplets are dynamic and heterogeneous in size, location, and protein content. The proteins that coat lipid droplets change during lipid droplet biogenesis and are dependent upon multiple factors, including tissue-specific expression and metabolic state (basal vs. lipogenic vs. lipolytic). New data suggest that proteins previously implicated in vesicle trafficking, including Rabs, soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs), and motor and cytoskeletal proteins, likely orchestrate the movement and fusion of lipid droplets. Thus, rather than inert cytoplasmic inclusions, lipid droplets are now appreciated as dynamic organelles that are critical for management of cellular lipid stores. That much remains to be discovered is suggested by the recent identification of a novel lipase [adipocyte triglyceride lipase (ATGL)] and lipase regulator [Comparative Gene Identification-58 (CGI-58)], which has led to reconsideration of the decades-old model of lipolysis. Future discovery likely will be driven by the exploitation of model organisms and by human genetic studies.

Postprandial triacylglycerol metabolism is modified by the presence of genetic variation at the perilipin (PLIN) locus in 2 white populations

BACKGROUND

Several perilipin (PLIN) polymorphic sites have been studied for their potential use as markers for obesity and the metabolic syndrome.

OBJECTIVE

We aimed to examine whether the presence of polymorphisms at the perilipin (PLIN) locus (PLIN1, 6209T-->C; PLIN4, 11482G-->A; PLIN5, 13041A-->G; and PLIN6, 14995A-->T) influence postprandial lipoprotein metabolism in 2 white populations.

DESIGN

Eighty-eight healthy Spanish men and 271 healthy US subjects (men and women) underwent an oral-fat-load test in 2 independent studies. Blood samples were taken in the fasting state and during the postprandial phase at regular intervals. Total cholesterol and triacylglycerol and triacylglycerol in triacylglycerol-rich lipoproteins (TRL, large and small) were measured.

RESULTS

Carriers of the minor C allele at the PLIN1 variant displayed lower postprandial concentrations of large-TRL triacylglycerol (Spanish subjects: P = 0.024; US subjects: P = 0.005) than did subjects carrying the T/T genotype. The same pattern was observed in the Spanish population at the PLIN4 locus (P = 0.015), and both SNPs were in strong linkage disequilibrium. In both populations, subjects carrying the minor C and A alleles at PLIN1 and PLIN4, respectively, had significantly lower postprandial concentrations of plasma triacylglycerol (P < 0.05) and lower concentrations of small-TRL triacylglycerol than did those who were homozygous for the major alleles at PLIN1 and PLIN4 (Spanish subjects: P = 0.020 and 0.008, respectively; US subjects: P = 0.021 and 0.035, respectively).

CONCLUSION

These 2 studies suggest that the presence of the minor C and A alleles at PLIN1 and PLIN4, respectively, are associated with a lower postprandial response that may result in lower atherogenic risk for these persons.

Obesity and carpal tunnel syndrome: is there a causal relationship?

OBJECTIVES

Obesity is defined as a risk factor for carpal tunnel syndrome (CTS). In this study, the presence or absence of recovery in median nerve conduction velocities after weight loss in obese patients was assessed in order to determine whether excess weight or other factors influence the higher prevalence of CTS in obese patients.

METHODS

Patients with body mass indexes (BMIs) >or=30 were included in the study. CTS symptoms, age, gender, height, body weight, and concomitant diseases were evaluated. Nerve conduction studies (NCS) were obtained on one upper extremity. All patients were included in dietetic programs. Three months later, NCS were repeated and compared with the first NCS.

RESULTS

BMIs were statistically significantly lower on the second visits 3 months later (p = 0.0001). No statistically significant difference was observed in the second NCS of electromyographically diagnosed cases with CTS (p > 0.05).

CONCLUSION

We expected a recovery in median nerve conduction velocities in patients with CTS after weight loss. In the literature, even in untreated cases with CTS, spontaneous improvements in second NCS have been reported. This finding suggests that factors other than excess body weight may be influential in the higher prevalence of CTS in obese patients. A more detailed, genetic-factor-targeted investigation may prove more beneficial to clarify this issue.

Obesity and polymorphisms in genes regulating human adipose tissue

Obesity is the result of an imbalance between food intake and energy expenditure resulting in the storing of energy as fat. Adipose tissue contains the largest store of energy in the body and plays important roles in regulating energy partitioning. Developments in genomics, in particular microarray-based expression profiling, have provided scientists with a number of new candidate genes whose expression in adipose tissue is regulated by obesity. Integrating expression profiles with genome-wide linkage and/or association analyses is a promising strategy to identify new genes underlying susceptibility to obesity. This article provides a comprehensive review of adipose-tissue-expressed genes implicated in predisposition to human obesity. The authors consider the following genes of particular interest: peroxisome proliferator-activated receptor gamma and, potentially, INSIG2 acting in adipogenesis; the adrenoreceptors beta 2 and 3, as well as hormone-sensitive lipase acting on lipolysis; uncoupling protein 2 acting in mitochondria energy expenditure; and among secreted molecules the cytokine tumor necrosis factor alpha and the hormone leptin. With the rapid development in genome research, we predict that additional alleles in genes regulating adipose tissue function will be established as risk factors for common obesity in the coming years. This has important implications for the prevention of obesity and may also offer new therapeutic targets.

Regulation of adipocyte lipolysis by degradation of the perilipin protein: nelfinavir enhances lysosome-mediated perilipin proteolysis

A decrease in the lipid droplet-associated protein perilipin may constitute a mechanism for enhanced adipocyte lipolysis under nonstimulated (basal) conditions, and increased basal lipolysis has been linked to whole body metabolic dysregulation. Here we investigated whether the lipolytic actions of the human immunodeficiency virus protease inhibitor, nelfinavir, are mediated by decreased perilipin protein content and studied the mechanisms by which it occurs. Time course analysis revealed that the decrease in perilipin protein content preceded the increase in lipolysis. A causative relationship was suggested by demonstrating that nelfinavir potently increased lipolysis in adipocytes derived from mouse embryonal fibroblasts expressing perilipin but not in mouse embryonal fibroblast adipocytes devoid of perilipin and that adenoviral mediated overexpression of perilipin in 3T3-L1 adipocytes blocked the lipolytic actions of nelfinavir. Nelfinavir did not alter mRNA content of perilipin but rather decreased perilipin proteins t((1/2)) from >70 to 12 h. Protein degradation of perilipin in both control and nelfinavir-treated adipocytes could be prevented by inhibiting lysosomal proteolysis using leupeptin or NH(4)Cl but not by the proteasome inhibitor MG-132. We propose that proteolysis of perilipin involving the lysosomal protein degradation machinery may constitute a novel mechanism for enhancing adipocyte lipolysis.

The role of perilipin in human obesity and insulin resistance

PURPOSE OF REVIEW

More than 1.1 billion people worldwide are overweight or obese. We know that obesity is determined by a combination of environmental and genetic factors. Although hundreds of obesity candidate genes have been identified through different metabolic pathways, the fundamental basis of obesity resides with excessive storage of triacylglycerides in adipose tissue.

RECENT FINDINGS

The mechanisms that control the storage and release of triacylglycerides in lipid droplets are complex and poorly understood; yet, they are likely to be crucial to the understanding of the regulation of body weight. In this regard, the family of perilipin, adipophilin and TIP47 proteins may play key roles in obesity. It has recently been shown that variants at the perilipin locus were associated with BMI and obesity risk in females from several population studies. Moreover, the reported interactions between perilipin and dietary factors may shed light on the complex relation between dietary intake and body weight changes observed on an individual basis.

SUMMARY

These findings support an important role for PLIN as a candidate gene for obesity risk in humans as well as a modulator of dietary response to therapies aimed to reduce body weight and decrease metabolic syndrome risk.

Metabolic syndrome pathophysiology: the role of adipose tissue

Several pathophysiological explanations for the metabolic syndrome have been proposed involving insulin resistance, chronic inflammation and ectopic fat accumulation following adipose tissue saturation. However, current concepts create several paradoxes, including limited cardiovascular risk reduction with intensive glucose control in diabetics, therapies that result in weight gain (PPAR agonists), and presence of some of the metabolic traits among some lipodystrophies. We propose the functional failure of an organ, in this case, the adipose tissue as a model to interpret its manifestations and to reconcile some of the apparent paradox. A cornerstone of this model is the failure of the adipose tissue to buffer postprandial lipids. In addition, homeostatic feedback loops guide physiological and pathological adipose tissue activities. Fat turnover is determined by a complex equilibrium in which insulin is a main factor but not the only one. Chronically inadequate energy balance may be a key factor, stressing the system. In this situation, an adipose tissue functional failure occurs resulting in changes in systemic energy delivery, impaired glucose consumption and activation of self-regulatory mechanisms that extend their influence to whole body homeostasis system. These include changes in adipokines secretion and vascular effects. The functional capacity of the adipose tissue varies among subjects explaining the incomplete overlapping among the metabolic syndrome and obesity. Variations at multiple gene loci will be partially responsible for these interindividual differences. Two of those candidate genes, the adiponectin (APM1) and the perilipin (PLIN) genes, are discussed in more detail.