Beneficial effects of omega-3 fatty acids on the consequences of a fructose diet are not mediated by PPAR delta or PGC1 alpha.

PURPOSE: To study, in high-fructose-fed rats, the effect of a dietary enrichment in omega-3 polyunsaturated fatty acids (n-3 PUFA) on the expression of genes involved in lipid metabolism and cardiovascular function. METHODS: Twenty-eight male "Wistar Han" rats received for 8 weeks, either a standard chow food or an isocaloric 67% fructose diet enriched or not in alpha-linolenic acid (ALA) or in docosahexaenoic (DHA) and eicosapentaenoic acids (EPA) mix (DHA/EPA). After sacrifice, blood was withdrawn for biochemical analyses; heart, periepididymal adipose tissue and liver were collected and analyzed for the expression of 22 genes by real-time PCR. RESULTS: Fructose intake resulted in an increase in liver weight and triglyceride content, plasma triglyceride and cholesterol concentrations, although no difference in glucose and insulin. In the liver, lipogenesis was promoted as illustrated by an increase in stearoyl-CoA desaturase and fatty acid synthase (Fasn) together with a decrease in PPAR gamma, delta and PPAR gamma coactivator 1 alpha (PGC1 alpha) expression. In the heart, Fasn and PPAR delta expression were increased. The addition of ALA or DHA/EPA into the diet resulted in a protection against fructose effects except for the decreased expression of PPARs in the liver that was not counterbalanced by n-3 PUFA suggesting that n-3 PUFA and fructose act independently on the expression of PPARs and PGC1 alpha. CONCLUSIONS: In liver, but not in heart, the fructose-enriched diet induces an early tissue-specific reduction in PPAR gamma and delta expression, which is insensitive to n-3 PUFA intake and dissociated from lipogenesis.

High dietary saturated fat intake accentuates obesity risk associated with the fat mass and obesity-associated gene in adults.

Fat mass and obesity-associated (FTO) is the strongest genetic determinant of obesity identified to date. Dietary fat is a key environmental factor that may interact with genotype to affect risk of obesity and metabolic syndrome (MetS). This study investigated associations among FTO rs9939609, obesity measures, and MetS phenotypes in adults and determined potential modulation by dietary fat intake at baseline and after a 7.5-y follow-up when MetS cases and controls were selected. FTO rs9939609 genotype, biochemical, dietary, and lifestyle measurements were determined in the LIPGENE-SU.VI.MAX study (n = 1754). FTO rs9939609 A allele carriers had a higher risk of being overweight or obese [OR = 1.66 (95% CI: 1.07, 2.57); P = 0.02] and of having a larger abdominal circumference [OR = 1.42 (95% CI: 1.01, 1.99); P = 0.04] compared with the TT homozygotes. These associations were independent of physical activity and energy intake and were maintained over the follow-up period, particularly in the MetS individuals. High dietary SFA intake (≥ 15.5% energy) and a low dietary PUFA:SFA intake ratio (<0.38) further accentuated the risk of having a BMI ≥ 25 kg/m(2) and being abdominally obese. Non-risk allele carriers appeared to be unresponsive to dietary SFA intake or to the dietary PUFA:SFA intake ratio with respect to obesity measures. In conclusion, FTO rs9939609 was associated with obesity measures, especially in those with the MetS, which was further exacerbated by high dietary SFA intake at baseline and 7.5 y later. These data indicate important novel modulation of genetic risk by dietary fat exposure in individuals with increased cardiometabolic risk.

Gene-nutrient interactions with dietary fat modulate the association between genetic variation of the ACSL1 gene and metabolic syndrome.

Long-chain acyl CoA synthetase 1 (ACSL1) plays an important role in fatty acid metabolism and triacylglycerol (TAG) synthesis. Disturbance of these pathways may result in dyslipidemia and insulin resistance, hallmarks of the metabolic syndrome (MetS). Dietary fat is a key environmental factor that may interact with genetic determinants of lipid metabolism to affect MetS risk. We investigated the relationship between ACSL1 polymorphisms (rs4862417, rs6552828, rs13120078, rs9997745, and rs12503643) and MetS risk and determined potential interactions with dietary fat in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n = 1,754). GG homozygotes for rs9997745 had increased MetS risk {odds ratio (OR) 1.90 [confidence interval (CI) 1.15, 3.13]; P = 0.01}, displayed elevated fasting glucose (P = 0.001) and insulin concentrations (P = 0.002) and increased insulin resistance (P = 0.03) relative to the A allele carriers. MetS risk was modulated by dietary fat, whereby the risk conferred by GG homozygosity was abolished among individuals consuming either a low-fat (<35% energy) or a high-PUFA diet (>5.5% energy). In conclusion, ACSL1 rs9997745 influences MetS risk, most likely via disturbances in fatty acid metabolism, which was modulated by dietary fat consumption, particularly PUFA intake, suggesting novel gene-nutrient interactions.

ACC2 gene polymorphisms, metabolic syndrome, and gene-nutrient interactions with dietary fat.

Acetyl-CoA carboxylase ß (ACC2) plays a key role in fatty acid synthesis and oxidation pathways. Disturbance of these pathways is associated with impaired insulin responsiveness and metabolic syndrome (MetS). Gene-nutrient interactions may affect MetS risk. This study determined the relationship between ACC2 polymorphisms (rs2075263, rs2268387, rs2284685, rs2284689, rs2300453, rs3742023, rs3742026, rs4766587, and rs6606697) and MetS risk, and whether dietary fatty acids modulate this in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n = 1754). Minor A allele carriers of rs4766587 had increased MetS risk (OR 1.29 [CI 1.08, 1.58], P = 0.0064) compared with the GG homozygotes, which may in part be explained by their increased body mass index (BMI), abdominal obesity, and impaired insulin sensitivity (P < 0.05). MetS risk was modulated by dietary fat intake (P = 0.04 for gene-nutrient interaction), where risk conferred by the A allele was exacerbated among individuals with a high-fat intake (>35% energy) (OR 1.62 [CI 1.05, 2.50], P = 0.027), particularly a high intake (>5.5% energy) of n-6 polyunsaturated fat (PUFA) (OR 1.82 [CI 1.14, 2.94], P = 0.01; P = 0.05 for gene-nutrient interaction). Saturated and monounsaturated fat intake did not modulate MetS risk. Importantly, we replicated some of these findings in an independent cohort. In conclusion, the ACC2 rs4766587 polymorphism influences MetS risk, which was modulated by dietary fat, suggesting novel gene-nutrient interactions.

Leptin receptor polymorphisms interact with polyunsaturated fatty acids to augment risk of insulin resistance and metabolic syndrome in adults.

The leptin receptor (LEPR) is associated with insulin resistance, a key feature of metabolic syndrome (MetS). Gene-fatty acid interactions may affect MetS risk. The objective was to investigate the relationship among LEPR polymorphisms, insulin resistance, and MetS risk and whether plasma fatty acids, a biomarker of dietary fatty acids, modulate this. LEPR polymorphisms (rs10493380, rs1137100, rs1137101, rs12067936, rs1805096, rs2025805, rs3790419, rs3790433, rs6673324, and rs8179183), biochemical measurements, and plasma fatty acid profiles were determined in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n = 1754). LEPR rs3790433 GG homozygotes had increased MetS risk compared with the minor A allele carriers [odds ratio (OR) = 1.65; 95% CI: 1.05-2.57; P = 0.028], which may be accounted for by their increased risk of elevated insulin concentrations (OR 2.40; 95% CI: 1.28-4.50; P = 0.006) and insulin resistance (OR = 2.15; 95% CI: 1.18-3.90; P = 0.012). Low (less than median) plasma (n-3) and high (n-6) PUFA status exacerbated the genetic risk conferred by GG homozygosity to hyperinsulinemia (OR 2.92-2.94) and insulin resistance (OR 3.40-3.47). Interestingly, these associations were abolished against a high (n-3) or low (n-6) PUFA background. Importantly, we replicated some of these findings in an independent cohort. Homozygosity for the LEPR rs3790433 G allele was associated with insulin resistance, which may predispose to increased MetS risk. Novel gene-nutrient interactions between LEPR rs3790433 and PUFA suggest that these genetic influences were more evident in individuals with low plasma (n-3) or high plasma (n-6) PUFA.

Dietary saturated fat modulates the association between STAT3 polymorphisms and abdominal obesity in adults.

Signal transducer and activator of transcription 3 (STAT3) plays a key role in body weight regulation and glucose homeostasis, 2 important determinants of metabolic syndrome (MetS). Dietary fat is a key environmental factor that may interact with genotype to affect MetS risk. In this study, we investigated the relationship between STAT3 polymorphisms and MetS phenotypes and determined potential interactions with dietary fatty acids. STAT3 polymorphisms (rs8069645, rs744166, rs2306580, rs2293152, and rs10530050), biochemical measurements, and dietary fat composition were determined in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n = 1754). STAT3 polymorphisms were not associated with MetS risk. However, minor G allele carriers for rs8069645, rs744166, and rs1053005 and major GG homozygotes for rs2293152 had increased risk of abdominal obesity compared with noncarriers [odds ratio (OR) = 2.22, P = 0.0005; OR = 2.08, P = 0.0017; OR = 2.00, P = 0.0033; and OR = 1.95, P = 0.028, respectively]. The number of risk alleles additively increased obesity risk (P = 0.0003). Dietary SFA intake exacerbated these effects; among all participants with the highest SFA intake (> or =15.5% of energy), individuals carrying >2 risk alleles had further increased risk of obesity (OR = 3.30; 95% CI = 1.50-7.28; P = 0.0079) compared with those carrying < or =1 risk allele. Interaction analysis confirmed this gene-nutrient interaction whereby increasing SFA intake was predictive of increased waist circumference (P = 0.038). In conclusion, STAT3 gene polymorphisms influenced the risk of abdominal obesity, which is modulated by dietary SFA intake, suggesting novel gene-nutrient interactions.

I-FABP expression alters the intracellular distribution of the BODIPY C16 fatty acid analog.

To investigate the structure-function relationships of intestinal fatty acid-binding protein (I-FABP) in cellular fatty acid (FA) trafficking, we compared the distribution of a fluorescent FA analog (BODIPY FL C16) in Cos-1 cells transiently transfected with the wild type protein (wt I-FABP) to that of a variant deleted of the alpha helical domain (HL I-FABP). In vector-only cells, BODIPY fluorescence was distributed throughout the cytoplasm. In the absence of added FA, wt I-FABP was found largely in the perinuclear region with some cytoplasmic staining as well. Addition of BODIPY FL C16 to transfected cells showed that the fluorescent FA was essentially completely colocalized with the protein in the cytoplasmic and perinuclear regions as well as in cytoplasmic clusters that are not observed in the absence of wt I-FABP. For HL I-FABP, the distribution of the protein in the absence of FA was diffusely cytoplasmic, in marked contrast to the wt protein. Addition of BODIPY led to less extensive colocalization than that observed for wt I-FABP. In particular, no localization to the perinuclear region was found. Organelle colocalization studies showed that both proteins colocalized with mitochondria and endoplasmic reticulum/golgi markers, but little with a lysosomal marker. The perinuclear localization for wt I-FABP and BODIPY did not show colocalization with any of the markers tested. Taken together, these results indicate that I-FABP binds FA in vivo and that the helical domain may be important for targeting I-FABP to a perinuclear domain but not, perhaps, to the endoplasmic reticulum, golgi apparatus or mitochondria.

Human fasting plasma concentrations of vitamin E and carotenoids, and their association with genetic variants in apo C-III, cholesteryl ester transfer protein, hepatic lipase, intestinal fatty acid binding protein and microsomal triacylglycerol transfer protein.

Plasma concentrations of vitamin E and carotenoids are governed by several factors, including genetic factors. Single nucleotide polymorphisms (SNP) in some genes involved in lipid metabolism have recently been associated with fasting plasma concentrations of these fat-soluble micronutrients. To further investigate the role of genetic factors that modulate the plasma concentrations of these micronutrients, we assessed whether SNP in five candidate genes (apo C-III, CETP, hepatic lipase, I-FABP and MTP) were associated with the plasma concentrations of these micronutrients. Fasting plasma vitamin E and carotenoid concentrations were measured in 129 French Caucasian subjects (forty-eight males and eighty-one females). Candidate SNP were genotyped by PCR amplification followed by restriction fragment length polymorphisms. Plasma gamma-tocopherol, alpha-carotene and beta-carotene concentrations were significantly different (P < 0.05) in subjects who carried different SNP variants in hepatic lipase. Plasma alpha-tocopherol concentrations were significantly different in subjects who had different SNP variants in apo C-III and cholesteryl ester transfer protein (CETP). Plasma lycopene concentrations were significantly different (P < 0.05) in women who had different SNP variants in intestinal fatty acid binding protein (I-FABP). Finally, there was no effect of SNP variants in microsomal TAG transfer protein upon the plasma concentrations of these micronutrients. Most of the observed differences remained significant after the plasma micronutrients were adjusted for plasma TAG and cholesterol. These results suggest that apo C-III, CETP and hepatic lipase play a role in determining the plasma concentrations of tocopherols while hepatic lipase and I-FABP may modulate plasma concentrations of carotenoids.

Nutrigenetics: links between genetic background and response to Mediterranean-type diets.

OBJECTIVE: It has been substantiated that the onset of most major diseases (CVD, diabetes, obesity, cancers, etc.) is modulated by the interaction between genetic traits (susceptibility) and environmental factors, especially diet. We aim to report more specific observations relating the effects of Mediterranean-type diets on cardiovascular risk factors and the genetic background of subjects. RESULTS AND CONCLUSIONS: In the first part, general concepts about nutrigenetics are briefly presented. Human genome has, overall, only marginally changed since its origin but it is thought that minor changes (polymorphisms) of common genes that occurred during evolution are now widespread in human populations, and can alter metabolic pathways and response to diets. In the second part, we report the data obtained during the Medi-RIVAGE intervention study performed in the South-East of France. Data obtained in 169 subjects at moderate cardiovascular risk after a 3-month dietary intervention indicate that some of the twenty-three single nucleotide polymorphisms (SNP) studied exhibit interactions with diets regarding changes of particular parameters after 3-month regimens. Detailed examples are presented, such as interactions between SNP in genes coding for microsomial transfer protein (MTTP) or intestinal fatty acid binding protein (FABP2) and triglyceride, LDL-cholesterol or Framigham score lowering in responses to Mediterranean-type diets. The data provided add further evidence of the interaction between particular SNP and metabolic responses to diets. Finally, improvement in dietary recommendations by taking into account known genetic variability has been discussed.

Sex-specific association of fatty acid binding protein 2 and microsomal triacylglycerol transfer protein variants with response to dietary lipid changes in the 3-mo Medi-RIVAGE primary intervention study.

BACKGROUND: The dietary guidelines targeted at reducing cardiovascular risk lead to largely heterogeneous responses in which genetic determinants are largely involved. OBJECTIVES: We evaluated the effect of fatty acid binding protein 2 (FABP2) Ala54Thr and microsomal triacylglycerol transfer protein (MTTP) -493G/T allelic variations on plasma lipid markers, at baseline and on the response to the 3-mo Medi-RIVAGE primary prevention study. DESIGN: Subjects with moderate cardiovascular disease risk (n = 169) were advised to reduce total and saturated dietary fats and to increase intake of monounsaturated and polyunsaturated fats. They were genotyped for FABP2 Ala54Thr and MTTP -493G/T allelic variations, and plasma was processed for cardiovascular risk marker analyses. RESULTS: At baseline, men and women homozygous for Thr54 presented a significant opposite profile for plasma oleic acid (18:1), triacylglycerol-rich lipoprotein (TRL) cholesterol, and TRL phospholipids. In addition, all Thr/Thr men presented higher 18:1 values than did women. For the MTTP -493G/T polymorphism, although all TT subjects presented high apolipoprotein B-48, a genotype x sex interaction was present for palmitic acid, linolenic acid, eicosatrienoic acid, and insulin. The prudent diet clearly improved plasma lipid markers. FABP2 genotype did not interact much with the amplitude of the response. However, for MTTP polymorphism, men homozygous for the T allele displayed a significantly more pronounced response than did men carrying the G allele, which is particularly evident by their larger decrease in the Framingham score. CONCLUSIONS: These 2 polymorphic loci are thus differently associated with the baseline lipid markers as well as with the response to nutritional recommendations, but both presented a marked sex-specific profile, with the response to diet being particularly efficient in men homozygous for the MTTP -493T allele.

Human plasma levels of vitamin E and carotenoids are associated with genetic polymorphisms in genes involved in lipid metabolism.

Vitamin E and carotenoids are fat-soluble micronutrients carried by plasma lipoproteins. Their plasma concentrations are governed by several factors, some of which are genetic, but data on these genetic factors remain scarce. We hypothesized that genes involved in lipid metabolism, i.e. the genes implicated in intestinal uptake, intracellular trafficking, and the lipoprotein distribution of lipids, play a role in the plasma concentrations of these micronutrients. To verify this hypothesis, we assessed whether the plasma status of vitamin E and carotenoids is related to genes involved in lipid metabolism. Fasting plasma vitamin E (alpha- and gamma-tocopherol) and carotenoid (alpha- and beta-carotene, lutein, lycopene, beta-cryptoxanthin, and zeaxanthin) concentrations were measured in 48 males and 80 females. The following genes were genotyped [single nucleotide polymorphisms (SNP)]: apolipoprotein (apo) A-IV, apo B, apo E, lipoprotein lipase, and scavenger-receptor class B type I (SR-BI). Plasma alpha-tocopherol concentrations were different (P < 0.05) in subjects bearing different SNP in apo A-IV, apo E, and SR-BI. Plasma gamma-tocopherol concentrations were different (P < 0.05) in subjects bearing different SNP in apo A-IV and SR-BI. Alpha-carotene concentrations were different (P < 0.05) in subjects bearing different SNP in SR-BI. Beta-carotene concentrations were different (P < 0.05) in subjects bearing different SNP in apo B and SR-BI. Lycopene concentrations were different (P < 0.05) in subjects bearing different SNP in apo A-IV and apo B. Beta-cryptoxanthin concentrations were different (P < 0.05) in subjects bearing different SNP in SR-BI. Plasma lutein and zeaxanthin concentrations did not differ in subjects bearing different SNP. Most of the differences remained significant after the plasma micronutrients were adjusted for plasma triglycerides and cholesterol. These results suggest that genes involved in lipid metabolism influence the plasma concentrations of these fat-soluble micronutrients.

Isolation and molecular characterization of LVP1 lipolysis activating peptide from scorpion Buthus occitanus tunetanus.

LVP1, a novel protein inducing lipolytic response in adipose cells, was purified from scorpion Buthus occitanus tunetanus venom. It represented 1% of crude venom proteins, with pHi approximately 6 and molecular mass of 16170 Da. In contrast to well-characterized scorpion toxins, reduction and alkylation of LVP1 revealed an heterodimeric structure. Isolated alpha and beta chains of LVP1 have a respective molecular mass of 8877 and 8807 Da as determined by mass spectrometry. The N-terminal and some internal peptide sequences of LVP1alpha and beta were determined by Edman degradation. The full amino acid sequences of both chains were deduced from nucleotide sequences of the corresponding cDNAs prepared based on peptide sequences and the 3' and 5' RACE methodologies. LVP1alpha and beta cDNAs encode a signal peptide of 22 residues and a mature peptide of 69 and 73 residues, respectively. Each mature peptide contains seven cysteines, which are compatible with an interchain disulfide bridge. The cDNA deduced protein structures share a high similarity with those of some Na+ channel scorpion toxins. LVP1 was not toxic to mice after intracerebro-ventricular injection. LVP1 stimulated lipolysis on freshly dissociated rat adipocytes in a dose-dependent manner with EC50 of approximately 1+0.5 microg/ml. LVP1 subunits did not display any lipolytic activity. As previously described for venom, beta adrenergic receptor (beta AR) antagonists interfere with LVP1 activity. Furthermore, it is shown that LVP1 competes with [3H]-CGP 12177 (beta1/beta2 antagonist) for binding to adipocyte plasma membrane with an IC50 of about 10(-7) M. These results demonstrate the existence of a new type of scorpion venom nontoxic peptides that are structurally related to Na+ channel toxins but can exert a distinct biological activity on adipocyte lipolysis through a beta-type adrenoreceptor pathway.

Dietary fiber intake and risk factors for cardiovascular disease in French adults.

BACKGROUND: Increased consumption of dietary fiber is widely recommended to maintain or improve health, but knowledge of the relation between dietary fiber sources and cardiovascular disease risk factors is limited. OBJECTIVE: We examined the relation between the source or type of dietary fiber intake and cardiovascular disease risk factors in a cohort of adult men and women. DESIGN: In a cross-sectional study, quintiles of fiber intake were determined from dietary records, separately for 2532 men and 3429 women. Age- and multivariate-controlled logistic models investigated the odds ratios of abnormal markers for quintiles 2-5 of fiber intake compared with the lowest quintile. RESULTS: The highest total dietary fiber and nonsoluble dietary fiber intakes were associated with a significantly (P < 0.05) lower risk of overweight and elevated waist-to-hip ratio, blood pressure, plasma apolipoprotein (apo) B, apo B:apo A-I, cholesterol, triacylglycerols, and homocysteine. Soluble dietary fiber was less effective. Fiber from cereals was associated with a lower body mass index, blood pressure, and homocysteine concentration; fiber from vegetables with a lower blood pressure and homocysteine concentration; and fiber from fruit with a lower waist-to-hip ratio and blood pressure. Fiber from dried fruit or nuts and seeds was associated with a lower body mass index, waist-to-hip ratio, and fasting apo B and glucose concentrations. Fiber from pulses had no specific effect. CONCLUSION: Dietary fiber intake is inversely correlated with several cardiovascular disease risk factors in both sexes, which supports its protective role against cardiovascular disease and recommendations for its increased consumption.

The Medi-RIVAGE study: reduction of cardiovascular disease risk factors after a 3-mo intervention with a Mediterranean-type diet or a low-fat diet.

BACKGROUND: Epidemiologic studies link Mediterranean-type diets to a low incidence of cardiovascular disease; however, few dietary intervention studies have been undertaken, especially in primary prevention. OBJECTIVES: In the Mediterranean Diet, Cardiovascular Risks and Gene Polymorphisms (Medi-RIVAGE) study, the effects of a Mediterranean-type diet (Med group) or a low-fat diet (low-fat group) on risk factors were evaluated in 212 volunteers (men and women) with moderate risk factors for cardiovascular disease. DESIGN: After the 3-mo dietary intervention, changes in many risk factors were evaluated. Dietary questionnaires and plasma nutritional markers were used to test compliance. RESULTS: Although the dietary goals were only partially reached, changes in dietary habits were observed in both groups (n = 169): protein, carbohydrate, and fiber intakes increased and fat quality (decreased saturated fat and increased monounsaturated or polyunsaturated fat) improved. BMI, total and triacylglycerol-rich lipoprotein (TRL) cholesterol, triacylglycerols, TRL triacylglycerols, apolipoproteins A-I and B, insulinemia, glycemia, and the homeostasis model assessment score were significantly lower after 3 mo. The reductions in total cholesterol, triacylglycerols, and insulinemia remained significant after adjustment for BMI. There was a trend for a diet-by-time interaction for LDL cholesterol (P = 0.09). Our data predicted a 9% reduction in cardiovascular disease risk with the low-fat diet and a 15% reduction with this particular Mediterranean diet. CONCLUSION: After a 3-mo intervention, both diets significantly reduced cardiovascular disease risk factors to an overall comparable extent.

Expression of the 1,25-(OH)2 vitamin D3 receptor gene during the differentiation of mouse Ob17 preadipocytes and cross talk with the thyroid hormone receptor signalling pathway.

1,25-(OH)2-Vitamin D3 (1,25-D3) and the thyroid hormone tri-iodothyronine (T3) were previously shown to behave as adipogenic agents in murine Ob17 preadipocytes. Moreover, these agents interfere with each other's action during adipocyte differentiation. T3 receptor (TR) expression and a downmodulation of T3 binding sites (TR sites) by 1,25-D3 were also reported. A cross talk at the T3 and 1,25-D3 receptor (VDR) level was suggested. We report here that Ob17 cells contain VDR receptor sites in markedly modulated number. This includes a sharp decrease during differentiation that was largely counteracted by 1,25-D3 added to preadipocytes in physiological, adipogenic concentrations. In parallel, the VDR mRNA level did not change significantly, neither did a variant produced by alternative splicing in the penultimate exon and defined for the first time in the mouse. The differentiation- and 1,25-D3-related modulations of VDR sites are likely to be, at least for the most part, the result of variations in abundance of the VDR protein, and may thus mainly involve post-translational events. In contrast, the addition of T3 to the preadipocytes amplified the differentiation-related decrease in VDR sites, even in the presence of 1,25-D3. T3 significantly decreased the levels of VDR transcripts and thus mainly exerts a pretranslational action. With regard to the reciprocal downmodulation of the TR sites (identified as almost exclusively of the TRalpha type) by physiological concentrations of 1,25-D3, a post-translational action and a sequestration of the TR sites had previously been suggested and are further studied here. Analyses of receptor properties after co-incubations of recombinant VDRs and TRs did not favour direct VDR-TR interaction as a main cause of TR site sequestration. Interestingly, when taken together, the data on downregulation of VDRs and TRs by the alternate ligands define a potential step in the cross talk exerted between 1,25-D3 and T3 for their adipogenic action. In addition, the present results also show for the first time that 1,25-D3 acts as a strong trigger of a transient expression of TRbeta1 subtype at an early preadipocyte step, an effect that had previously been assigned to T3. This last interesting event introduces further incentive for deciphering the T3/1,25-D3 cross talk in preadipocyte differentiation.

Effects of antiretroviral drug combinations on the differentiation of adipocytes.

OBJECTIVE: Preadipocyte cell lines present a cell model with which to understand the physiopathological mechanisms underlying lipodystrophy syndrome, a common complication observed in patients treated with highly active antiretroviral therapy (HAART) that, in general, is associated with the use of protease inhibitors (PI) and nucleoside reverse transcriptase inhibitors (NRTI). The aim of this study was to evaluate the effects of NRTI and of PI and NRTI combinations in this cell model. METHODS: The differentiation of 3T3-F442A cells was studied by monitoring the expression of specific genes in the presence of therapeutic concentrations of antiretroviral drugs. Messenger RNA (mRNA) was quantified by two reverse transcription-PCR-based methods. RESULTS: In the presence of 2 microM saquinavir, 30 microM ritonavir or 1 microM zidovudine preadipocytes delayed their differentiation, whereas the use of 10 microM nelfinavir led to cell death. Indinavir (10 microM) promoted lipoprotein lipase expression whereas 1 microM lamivudine or 1 microM stavudine enhanced slightly the expression of the malic enzyme gene. However, the combination of indinavir, lamivudine and stavudine led to a large increase in both lipoprotein lipase and malic enzyme mRNA transcription whereas the combination of indinavir, lamivudine and zidovudine led to a 2.5-fold increase in the expression of the lipogenic malic enzyme gene. Similar potentiating effects of NRTI and PI were observed on the expression of the fatty acid synthase gene. CONCLUSIONS: Our data suggest that, like PI (although to a lesser extent) NRTI interfere with the differentiation process of adipocytes. In addition, we demonstrate that the effects produced by combinations of NRTI and PI are different from those elicited by each drug separately. This point may be particularly relevant in understanding the physiopathological mechanisms underlying the lipodystrophic syndrome.

The postprandial chylomicron triacylglycerol response to dietary fat in healthy male adults is significantly explained by a combination of single nucleotide polymorphisms in genes involved in triacylglycerol metabolism.

CONTEXT: The postprandial chylomicron (CM) triacylglycerol (TG) response to dietary fat, which is positively associated with atherosclerosis and cardiovascular disease risk, displays a high interindividual variability. This is assumed to be due, at least partly, to polymorphisms in genes involved in lipid metabolism. Existing studies have focused on single nucleotide polymorphisms (SNPs), resulting in only a low explained variability. OBJECTIVE: We aimed to identify a combination of SNPs associated with the postprandial CM TG response. PARTICIPANTS AND METHODS: Thirty-three healthy male volunteers were subjected to 4 standardized fat tolerance test meals (to correct for intraindividual variability) and genotyped using whole-genome microarrays. The plasma CM TG concentration was measured at regular interval times after each meal. The association of SNPs in or near candidate genes (126 genes representing 6225 SNPs) with the postprandial CM TG concentration (0-8 h areas under the curve averaged for the 4 test meals) was assessed by partial least squares regression, a multivariate statistical approach. RESULTS: Data obtained allowed us to generate a validated significant model (P = 1.3 × 10(-7)) that included 42 SNPs in 23 genes (ABCA1, APOA1, APOA5, APOB, BET1, CD36, COBLL1, ELOVL5, FRMD5, GPAM, INSIG2, IRS1, LDLR, LIPC, LPL, LYPLAL1, MC4R, NAT2, PARK2, SLC27A5, SLC27A6, TCF7L2, and ZNF664) and explained 88% of the variance. In 39 of these SNPs, univariate analysis showed that subjects with different genotypes exhibited significantly different (q < .05) postprandial CM TG responses. CONCLUSIONS: Using a multivariate approach, we report a combination of SNPs that explains a significant part of the variability in the postprandial CM TG response.

Dietary fat, abdominal obesity and smoking modulate the relationship between plasma complement component 3 concentrations and metabolic syndrome risk.

OBJECTIVE: Chronic inflammation plays a role in the pathogenesis of metabolic syndrome (MetS) and cardiovascular disease (CVD). Complement component 3 (C3) is a novel cardiometabolic risk factor. Whether dietary fat intake modulates MetS risk conferred by elevated C3 concentrations is unknown. Our objective is to investigate the relationship between C3 concentrations and risk of the MetS and its phenotypes, and to further examine whether dietary fat intake modulates these relationships. METHODS: Biochemical, dietary and lifestyle measurements were determined in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n=1754). RESULTS: Elevated C3 concentrations (>median) were associated with increased risk of impaired insulin sensitivity [OR 1.78, CI 1.34-2.36, P<0.0001], insulin resistance [OR 1.73, CI 1.31-2.89, P=0.0001], abdominal obesity [OR 2.15, CI 1.43-3.24, P=0.0002] and low HDL cholesterol [OR 1.40, CI 1.05-1.86, P=0.02] compared to low C3 concentrations. Increased MetS risk conferred by elevated C3 concentrations [OR 3.11, 95% CI 2.52-3.82, P<0.0001] was further accentuated among high dietary fat consumers [OR 4.80, 95% CI 2.77-8.33, P<0.0001] (particularly of saturated [OR 4.05, 95% CI 2.33-7.05, P<0.0001] and monounsaturated fat [OR 4.48, 95% CI 2.62-7.56, P<0.0001]), and smokers [OR 3.83, 95% CI 2.12-6.94, P<0.0001], however this effect was abolished in abdominally lean individuals [OR 1.46, 95% CI 0.69-3.14, P=0.33]. CONCLUSIONS: Dietary fat (intake and composition), abdominal obesity and smoking modulate the relationship between elevated plasma C3 concentrations and MetS risk.

Dietary saturated fat, gender and genetic variation at the TCF7L2 locus predict the development of metabolic syndrome.

Transcription factor 7-like 2 (TCF7L2) is the strongest genetic determinant of type 2 diabetes (T2DM) and insulin-related phenotypes to date. Dietary fat is a key environmental factor which may interact with genotype to affect risk of metabolic syndrome (MetS) and T2DM. This study investigated the relationship between the TCF7L2 rs7903146 polymorphism, insulin sensitivity/resistance and MetS in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n=1754) and determined potential interactions with dietary fat intake. Female minor T allele carriers of rs7903146 had increased MetS risk (odds ratio [OR] 1.66, confidence interval [CI] 1.02-2.70, P=.04) and displayed elevated insulin concentrations (P=.005), impaired insulin sensitivity (P=.011), increased abdominal obesity (P=.008) and body mass index (P=.001) and higher blood pressure (P<.05) compared to the CC homozygotes. Metabolic syndrome risk was also modulated by dietary saturated fat (SFA) intake (P=.035 for interaction). High dietary SFA intake (≥15.5% energy) exacerbated MetS risk (OR 2.35, 95% CI 1.29-4.27, P=.005) and was associated with further impaired insulin sensitivity in the T allele carriers relative to the CC homozygotes (P=.025) and particularly to the T allele carriers with the lowest SFA intake (P=.008). No significant genotype effect on MetS risk or insulin sensitivity was evident among low-SFA consumers. In conclusion, the TCF7L2 rs7903146 polymorphism influences MetS risk, which is augmented by both gender and dietary SFA intake, suggesting novel gene-diet-gender interactions.

Cholesterol absorption status and fasting plasma cholesterol are modulated by the microsomal triacylglycerol transfer protein -493 G/T polymorphism and the usual diet in women.

An important inter-individual variability in cholesterol absorption has been reported. It could result from polymorphisms in genes coding for proteins involved in the absorption process and in interaction with dietary intakes. To assess whether the extent of cholesterol absorption or synthesis is modified in adult women according to the -493 G/T polymorphism in the microsomal triglyceride transfer protein gene (MTP) and/or the habitual diet. Cholestanol and sitosterol, as well as desmosterol and lathosterol, surrogate markers of cholesterol absorption or synthesis, respectively, were analyzed in the fasting plasma of 69 middle-aged women under a Western-type diet (WD) and after 3 months on a low-saturated fat, low-cholesterol/Mediterranean-type diet (LFLCD). Genotypes for MTP -493G/T polymorphism were determined. Under an usual WD, subjects homozygous for the MTP -493 T allele exhibited higher (P < 0.05) fasting serum concentrations of cholestanol (199.0 ± 30.0 vs. 133 ± 7.4 × 10(2 )mmol/mol cholesterol) and lathosterol (188.7 ± 21.8 vs. 147.6 ± 9.1 × 10(2) mmol/mol cholesterol), as well as total cholesterol (7.32 ± 0.22 vs. 6.63 ± 0.12 mmol/l) compared to G carrier subjects. After 3 months on a LFLCD, level of absorption markers decreased in TT subjects with no change in synthesis ones, leading to values comparable to those measured in G carriers. The lowering of plasma total and LDL cholesterol due to dietary change was 2.4- and 2.3-fold greater in TT women than in G carriers. The polymorphism -493G/T in MTP modulates the level of cholesterol absorption but not synthesis in women under a WD, an effect abolished under a prudent LFLCD.