Genetic variation at the perilipin locus is associated with changes in serum free fatty acids and abdominal fat following mild weight loss

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.

Quantile-specific heritability of 8-isoprostane and the modulating effects of smoking, alcohol, cardiovascular disease and diabetes on 8-isoprostane-gene interactions

BACKGROUND

Urinary 8-isoprostane provides a significantly heritable measure of oxidative stress. Prior reports suggest that genetic variants may modulate oxidative stress due to smoking, other environmental factors, and disease. Alternatively, these apparent modulations may reflect a dependence of genetic effects on 8-isoprostane concentrations.

METHOD

To test whether genetic effects on 8-isoprostane concentrations are quantile-dependent, quantile-specific offspring-parent (β_OP) and full-sib regression slopes (β_FS) were estimated by applying quantile regression to the age- and sex-adjusted creatinine-standardized urinary 8-isoprostane concentrations of Framingham Heart Study families. Quantile-specific heritabilities were calculated as h² = 2β_OP/(1+r_spouse) and h² = {(1+8r_spouseβ_FS)^0.5-1}/(2r_spouse)).

RESULTS

Spouse 8-isoprostane concentrations were weakly concordant (r_spouse = 0.06). 8-isoprostane heritability (h²±SE) increased significantly with increasing percentiles of its distribution (P_{linear trend} = 0.0009, P_{quadratic trend} = 0.0007, P_{cubic trend} = 0.003) when estimated from β_OP, and when estimated from β_FS (P_{linear trend} = 0.005, P_{quadratic trend} = 0.09, P_{cubic trend} = 0.06). Compared to the 10th percentile, β_OP-estimated h² was over 22-fold greater at the 90th percentile (P_difference = 9.2 × 10^-5), and 5.3-fold greater when estimated from β_FS (P_difference = 0.004). Significantly higher 8-isoprostane heritability in smokers than nonsmokers (0.352 ± 0.147 vs. 0.061 ± 0.036, P_difference = 0.01), and heavier than lighter drinkers (0.449 ± 0.216 vs. 0.078 ± 0.037, P_difference = 0.01) were eliminated when corrected for the higher 8-isoprostane concentrations of the smokers and heavier drinkers.

CONCLUSION

Heritability of oxidative stress as measured by 8-isoprostane is quantile-dependent, which may contribute to the larger reported effects on oxidative stress by UCP2 -866G > A, IL6 -572C > G and LTA 252A > G polymorphisms in smokers than nonsmokers, by the UCP2 -866G > A polymorphism in coronary heart disease patients, by the ESRRG rs1890552 A > G polymorphism in type 2 diabetics, by the CYBA 242C > T polymorphism after exercise training, by the PLIN 11482G > A/14995A > T haplotype before weight loss, and by the CYBA -930A > G and GSTP1 I105V haplotypes in patients with pulmonary edema.

The importance of gene-environment interactions in human obesity

The worldwide obesity epidemic has been mainly attributed to lifestyle changes. However, who becomes obese in an obesity-prone environment is largely determined by genetic factors. In the last 20 years, important progress has been made in the elucidation of the genetic architecture of obesity. In parallel with successful gene identifications, the number of gene-environment interaction (GEI) studies has grown rapidly. This paper reviews the growing body of evidence supporting gene-environment interactions in the field of obesity. Heritability, monogenic and polygenic obesity studies provide converging evidence that obesity-predisposing genes interact with a variety of environmental, lifestyle and treatment exposures. However, some skepticism remains regarding the validity of these studies based on several issues, which include statistical modelling, confounding, low replication rate, underpowered analyses, biological assumptions and measurement precision. What follows in this review includes (1) an introduction to the study of GEI, (2) the evidence of GEI in the field of obesity, (3) an outline of the biological mechanisms that may explain these interaction effects, (4) methodological challenges associated with GEI studies and potential solutions, and (5) future directions of GEI research. Thus far, this growing body of evidence has provided a deeper understanding of GEI influencing obesity and may have tremendous applications in the emerging field of personalized medicine and individualized lifestyle recommendations.

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.

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.

A systematic review and meta-analysis on the effects of exercise training versus hypocaloric diet: distinct effects on body weight and visceral adipose tissue

Exercise training ('exercise') and hypocaloric diet ('diet') are frequently prescribed for weight loss in obesity. Whilst body weight changes are commonly used to evaluate lifestyle interventions, visceral adiposity (VAT) is a more relevant and stronger predictor for morbidity and mortality. A meta-analysis was performed to assess the effects of exercise or diet on VAT (quantified by radiographic imaging). Relevant databases were searched through May 2014. One hundred seventeen studies (n = 4,815) were included. We found that both exercise and diet cause VAT loss (P < 0.0001). When comparing diet versus training, diet caused a larger weight loss (P = 0.04). In contrast, a trend was observed towards a larger VAT decrease in exercise (P = 0.08). Changes in weight and VAT showed a strong correlation after diet (R(2)  = 0.737, P < 0.001), and a modest correlation after exercise (R(2)  = 0.451, P < 0.001). In the absence of weight loss, exercise is related to 6.1% decrease in VAT, whilst diet showed virtually no change (1.1%). In conclusion, both exercise and diet reduce VAT. Despite a larger effect of diet on total body weight loss, exercise tends to have superior effects in reducing VAT. Finally, total body weight loss does not necessarily reflect changes in VAT and may represent a poor marker when evaluating benefits of lifestyle-interventions.

The role of genes involved in lipolysis on weight loss program in overweight and obese individuals

The ability of obese people to reduce weight in the same treatment varied. Genetic make up as well as the behavioral changes are important for the successfulness of the program. One of the most proposed genetic variations that have been reported in many intervention studies was genes that control lipolysis process. This review summarizes studies that were done showing the influence of genetic polymorphisms in lipolysis pathway and weight loss in a weight loss treatment program. Some studies had shown that certain enzymes involved in this process were related to successfulness of weight loss program. Single Nucleotide Polymorphism (SNP) in PLIN (11482G>A) and ADRB3 (Trp64Arg) are the most studied polymorphisms that have effect on weight loss intervention. However, those studies were not conclusive because of limited number of subjects used and controversies in the results. Thus, replication and confirmation on the role of those genes in weight loss are important due to their potential to be used as predictors of the results of the program.

Future Perspectives of Personalized Weight Loss Interventions Based on Nutrigenetic, Epigenetic, and Metagenomic Data

As obesity has become a major global public health challenge, a large number of studies have analyzed different strategies aimed at inducing a negative energy balance and, consequently, body weight loss. However, most existing weight loss programs are generally unsuccessful, so several interventions have been carried out to identify physiologic and behavioral factors concerning this variability in order to implement more personalized treatment. Nowadays, an individualized approach is being proposed through so-called personalized nutrition, whereby not only the phenotype but also the genotype is used for customized nutrition treatment. Regarding body weight regulation, ∼70 polymorphisms have been identified in or near genes related to energy expenditure, appetite, adipogenesis, insulin resistance, and lipid metabolism. Although personalized nutrition refers mainly to genetic makeup, recent advances in the investigation of the epigenome and the microbiome open the door to implement more personalized recommendations for body weight management. In this context, recent studies have demonstrated the existence of several epigenetic markers that may modify gene expression and could be involved in the outcome of weight loss interventions. Moreover, different studies have shown that dietary interventions could affect the composition of gut microbiota and have an impact on body weight. The integration of nutrigenetic, epigenetic, and metagenomic data may lead to the design of more personalized dietary treatments to prevent chronic diseases and to optimize the individual's response to dietary interventions.

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.

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 polymorphism interacts with saturated fat and carbohydrates to modulate insulin resistance

BACKGROUND AND AIMS

Macronutrient intakes and genetic variants have been shown to interact to alter insulin resistance, but replications of gene-nutrient interactions across independent populations are rare, despite their critical importance in establishing credibility. We aimed to investigate a previously demonstrated saturated fat and carbohydrate interaction for insulin resistance for perilipin (PLIN1), a regulator of adipocyte metabolism.

METHODS AND RESULTS

We investigated the previously shown interaction for PLIN1 11482G > A (rs894160) on insulin resistance in US men (n = 462) and women (n = 508) (mean ± SD, 49 ± 16 years). In multivariable linear regression models, we found an interaction (P < 0.05) between the ratio of saturated fat to carbohydrate intake as a continuous variable and PLIN1 11482G > A for HOMA-IR (homeostasis model assessment of insulin resistance) in women. For carriers of the minor allele but not for non-carriers, as the ratio of saturated fat to carbohydrate intake increased, predicted HOMA-IR increased (P = 0.002). By dichotomizing the ratio of saturated fat to carbohydrate intake into high and low, we found significant interaction terms for insulin and HOMA-IR (P < 0.05). When the ratio of saturated fat to carbohydrate was high, insulin and HOMA-IR were higher in minor allele carriers (P = 0.004 and P = 0.003, respectively), but did not differ when the ratio was low. Similar patterns or trends were observed when saturated fat and carbohydrate were dichotomized into high and low as individual macronutrients.

CONCLUSIONS

Replication of the previously reported interaction between macronutrient intakes and PLIN1 genotype for insulin resistance reinforces the potential usefulness of applying genotype information in the dietary management of insulin resistance.

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.

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.

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.

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.

Lipid metabolism predicts changes in body composition during energy restriction in overweight humans

Dietary weight loss regimens could be more effective by selectively targeting adipose while sparing lean mass (LM) if predictive information about individuals' lipid metabolic responses to an intervention were available. The objective of this study was to examine the relationships among changes in 4 anthropometric outcomes, weight, waist circumference (WC), percent body fat (BF), and percent LM, and comprehensive circulating lipid metabolites in response to energy reduction in overweight participants. This was a cohort study (n = 46) from a larger multi-center (n = 105) weight loss trial. We used stepwise regression to examine relationships among baseline plasma fatty acids of 7 lipid classes, biochemical metabolites, and diet to explain the variance of 4 anthropometric outcomes after intervention. No predictor variables explained the variance in the percent change in body weight. The circulating concentration of FFA 18:1(n-9) at baseline explained 31% of the variance in percent change of WC, with adjustment for energy intake at 12 wk. Circulating concentrations of phosphatidylcholine 18:0 and FFA 18:1(n-9) at baseline together explained 33% of the variance in percent LM change. The circulating concentration of phosphatidylcholine 18:0 at baseline explained 23% of the variance in the change in percent BF. This study determined relationships among comprehensive and quantitative measurements of complex lipid metabolites and metabolic outcomes as changes in body composition. Measurements of plasma circulating metabolites explained 20-30% of the variance in changes in body composition after a weight loss intervention. Thus, circulating lipids reflect lipid metabolism in relation to changes in body composition.

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.

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.

Effects of mild calorie restriction on reproduction, plasma parameters and hepatic gene expression in mice with altered GH/IGF-I axis

The somatotropic axis, the hypothalamic-pituitary-gonadal axis and the nutritional status are deeply interrelated in mammals. Calorie restriction (CR) prolongs lifespan, but usually at some cost to reproduction. Interestingly, many of the physiological characteristics of animals with interruption in the somatotropic axis are shared by CR animals. The level of CR in most studies is 30-60%. We tested if a milder (20%) CR would promote health benefits without inhibiting reproduction in four types of mice with altered somatotropic axis: Ames dwarfs, GHR-KO, and PEPCK-bGH and MT-bGH transgenics. Fertility was not altered by CR in any of the examined groups. Mild CR did not affect final body weights or relative reproductive organ weights; did not alter plasma levels of glucose, insulin, IGF-I, testosterone, progesterone or estradiol; and did not influence hepatic expression of genes related to longevity. Altered activity of the GH/IGF-I axis in the different mice models studied had a major impact on the parameters analyzed. This preliminary study encourages speculation that mild regimens of CR can produce health and longevity benefits without the "costs" of impaired reproductive potential.

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.