Increased plasma cholesteryl ester transfer activity in obese children

Impaired HDL-associated enzymes and proteins in children and adolescents with weight disorders and their association with novel cardiometabolic indexes

BACKGROUND AND AIMS

Overweight/obesity (OW/OB) is associated with modifications in lipoprotein (Lp)-associated enzymes and proteins, such as cholesteryl ester transfer protein (CETP), Lp-associated phospholipase A2 (LpPLA2) and paraoxonase (PON)1. No evidence is available regarding underweight (UW). The following indexes have been proposed to better assess atherogenic risk related to weight alterations: triglycerides-glucose index (TyG), visceral adiposity index (VAI) and height-corrected lipid accumulation product (HLAP).

AIM

To analyze the presence of alterations in Lp-associated enzymes and proteins in children and adolescents with UW and OW/OB and their relation to novel cardiometabolic indexes.

METHODS AND RESULTS

Thirty male children and adolescents with UW, 66 with normal weight (NW) and 30 with OW/OB were included. Anthropometric parameters, glucose, Lp profile and the activities of CETP, LpPLA2 and PON1 were evaluated. Body mass index (BMI)-z, TyG, VAI and HLAP were calculated. UW and NW showed lower CETP activity than OW/OB (Mean ± SD) (218 ± 38vs.224 ± 26vs.237 ± 26%/mL.h; p < 0.05). UW and OW/OB showed lower PON1 activity than NW (318 ± 170vs.409 ± 200vs.310 ± 184 nmol/mL.min; p < 0.05). TyG was higher in OW/OB than UW (p < 0.01), whilst both HLAP (p < 0.05) and VAI (p < 0.01) followed a linear trend across weight categories. After adjusting for age and BMI-z, TyG was an independent predictor of CETP (r2 = 0.25, β = -0.22, p < 0.01) and LpPLA2 (r2 = 0.21,β = -0.21,p < 0.05), while VAI (r2 = 0.21,β = -0.32,p < 0.01) and HLAP (r2 = 0.20,β = -0.31,p < 0.01) of CETP.

CONCLUSIONS

Both UW and OW/OB showed impaired antioxidant PON1 activity. Moreover, TyG, VAI and HLAP were all capable of predicting alterations in crucial modulators of Lp metabolism and vascular inflammation in children and adolescents with varying degrees of alterations in body weight.

Vascular inflammation and impaired reverse cholesterol transport and lipid metabolism in obese children and adolescents

BACKGROUND AND AIMS

Childhood obesity is associated to complications such as insulin resistance and dyslipidemia. High density lipoproteins (HDL) constitute the only lipoprotein fraction with ateroprotective properties. The aim of the present study was to analyze inflammatory markers, carbohydrate metabolism, lipid profile and HDL functionality in obese children and adolescents compared to healthy controls.

METHODS AND RESULTS

Twenty obese children and adolescents (Body mass index z score >3.0) (9-15 years old) and 20 age and sex similar controls were included in the study. Triglyceride (TG), total cholesterol (TC), HDL-C, LDL-C, apolipoproteins (apo) A-I and B, glucose and insulin levels were quantified. Lipid indexes and HOMA-IR were calculated. Cholesterol efflux (CEC), lipoprotein associated phospholipase A₂ (Lp-PLA₂), lecithin-cholesterol acyl transferase (LCAT) and cholesteryl ester transfer protein, plus paraoxonase and arylesterase (ARE) activities were evaluated. Obese children and adolescents showed significantly higher TG [69 (45-95) vs 96 (76-121); p < 0.05], non-HDL-C [99 ± 34 vs 128 ± 26; p < 0.01], TC/HDL-C [2.8 ± 0.6 vs 4.7 ± 1.5; p < 0.01], TG/HDL-C [1.1 (1.0-1.8) vs 2,2 (1.4-3.2); p < 0.01], and HOMA-IR [1.5 (1.1-1.9) vs. 2.6 (2.0-4.5); p < 0.01] values, plus Lp-PLA₂ activity [8.3 ± 1.9 vs 7.1 ± 1.7 umol/ml.h; p < 0,05] in addition to lower HDL-C [57 ± 10 vs 39 ± 9; p < 0.01], apo A-I [143 ± 25 vs 125 ± 19; p < 0.05], and CEC [6.4 (5.1-6.8) vs. 7.8 (5.7-9.5); p < 0.01] plus LCAT [12.6 ± 3.3 vs 18.7 ± 2.6; p < 0.05] and ARE [96 ± 19 vs. 110 ± 19; p < 0.05] activities. Lp-PLA₂ activity correlated with LDL-C (r = 0.72,p < 0.01), non-HDL-C (r = 0.76,p < 0.01), and apo B (r = 0.60,p < 0.01). LCAT activity correlated with triglycerides (r = -0.78,p < 0.01), HDL-C (r = 0.64,p < 0.01), and apo A-I (r = 0.62, p < 0.05). ARE activity correlated with HDL-C (r = 0.32,p < 0.05) and apoA-I (r = 0.43,p < 0.01). CEC was negatively associated with BMI z-score (r = -0.36,p < 0.05), and triglycerides (r = -0.28,p < 0.05), and positively with LCAT activity (r = 0.65,p < 0.05). In multivariate analysis, BMI z-score was the only parameter significantly associated to CEC (r2 = 0.43, beta = -0.38, p < 0.05).

CONCLUSION

The obese group showed alterations in carbohydrate and lipid metabolism, which were associated to the presence of vascular specific inflammation and impairment of HDL atheroprotective capacity. These children and adolescents would present qualitative alterations in their lipoproteins which would determine higher risk of suffering premature cardiovascular disease.

Interaction between CETP polymorphism and dietary insulin index and load in relation to cardiovascular risk factors in diabetic adults

Gene-diet interactions may play an important role in the inter individual diversity observed in on cardiovascular disease (CVD) risk factors. Therefore, in the current study, we examined the interaction of CETP TaqB1 polymorphism with dietary insulin index and load (DII and DIL), in altering on CVD risk factors among type 2 diabetes mellitus (T2DM). In this cross-sectional study, blood samples were collected from 220 type 2 diabetic patients (134 females and 86 male) with a mean age of 52.24 years in Tehran, Iran. DIL and DII were obtained via validated food-frequency questionnaire (FFQ). Taq1B polymorphism was genotyped by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Biochemical markers including total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglyceride (TG), superoxide dismutase (SOD), C-reactive protein (CRP), total antioxidant capacity (TAC), pentraxin-3 (PTX3), isoprostaneF2α (PGF2α). interleukin 18 (IL18), leptin and ghrelin were measured by standard protocol. Patients with B1B1 genotype had lower lipid profiles include LDL/HDL (P < 0.001) and TG (P = 0.04) when they consumed diets higher on the DIL and DII index. Moreover, carriers of B2B2 genotype who were in the last tertile of DIL had higher antioxidant and inflammatory markers include SOD (P = 0.01), PGF2α (P = 0.04) and CRP (P = 0.02). Further, a significant interaction between CETP TaqB1 and DII was shown in terms of WC (P = 0.01), where the highest WC were observed in B2B2 genotype carriers following a DII score. However, the highest inflammatory and antioxidant markers include CRP (P = 0.04), TAC (P = 0.01), SOD (P = 0.02), and PGF2α (P = 0.02) were observed in B2B2 genotype carriers when they consumed diets higher on the DII index. Based on the current study, it could be proposed that CETP polymorphism may be associated with CVD risk factors in T2DM patients with high following insulin indices, including DII and DIL. It seems that CETP Taq1B polymorphism can invert the result produced by insulin. This conclusion illustrates that the CETP Taq1B B1 allele could counteract the CVD risk induced by high DII and DIL.

HDL cholesterol efflux capacity and cholesteryl ester transfer are associated with body mass, but are not changed by diet-induced weight loss: A randomized trial in abdominally obese men

BACKGROUND AND AIMS

Obesity is associated with a lower HDL-mediated cholesterol efflux from macrophages and a higher CETP (cholesteryl ester transfer protein) activity, but effects of weight loss are not clear. In addition, associations with visceral and subcutaneous adipose tissue are not known. We therefore investigated effects of diet-induced weight loss on HDL-mediated cholesterol efflux and cholesterol ester (CE) transfer in abdominally obese men. Differences between normal-weight and abdominally obese men were also examined.

METHODS

Twenty-five apparently healthy, normal-weight men (waist circumference: <94 cm) and 52 abdominally obese men (waist circumference: 102-110 cm) were included. Abdominally obese subjects were randomly allocated to a dietary weight-loss intervention group or a no-weight loss control group. Individuals from the intervention group followed a very-low-calorie diet for 6 weeks to obtain a waist circumference below 102 cm, followed by a 2-week weight-stable period. Cholesterol efflux was measured in BODIPY-labeled murine J774 macrophages. CE transfer was measured by quantifying the transfer of CE from radiolabeled exogenous HDL to apoB-containing lipoproteins.

RESULTS

Cholesterol efflux capacity was 9 percentage point (pp) lower in abdominally obese than in normal-weight men (p≤0.001), while CE transfer was 5 pp higher (p≤0.01). Diet-induced weight-loss of 10.3 kg did not change cholesterol efflux and CE transfer. In addition, stepwise regression analysis did not suggest that the different fat depots are differently related to efflux capacity and CE transfer.

CONCLUSIONS

After a 2-week weight-stable period, dietary weight loss of 10 kg did not improve ABCA1-mediated cholesterol efflux and CE transfer in abdominally obese men.

Slim Body Weight Is Highly Associated With Enhanced Lipoprotein Functionality, Higher HDL-C, and Large HDL Particle Size in Young Women

There has been no information about the correlations between body weight distribution and lipoprotein metabolism in terms of high-density lipoproteins-cholesterol (HDL-C) and cholesteryl ester transfer protein (CETP). In this study, we analyzed the quantity and quality of HDL correlations in young women (21.5 ± 1.2-years-old) with a slim (n = 21, 46.2 ± 3.8 kg) or plump (n = 30, 54.6 ± 4.4 kg) body weight. Body weight was inversely correlated with the percentage of HDL-C in total cholesterol (TC). The plump group showed 40% higher body fat (26 ± 3 %) and 86% more visceral fat mass (VFM, 1.3 ± 0.3 kg) than the slim group, which showed 18 ± 2% body fat and 0.7 ± 0.2 kg of VFM. Additionally, the plump group showed 20% higher TC, 58% higher triglyceride (TG), and 12% lower HDL-C levels in serum. The slim group showed 34% higher apoA-I but 15% lower CETP content in serum compared to the plump group. The slim group showed a 13% increase in particle size and 1.9-fold increase in particle number with enhanced cholesterol efflux activity. Although the plump group was within a normal body mass index (BMI) range, its lipid profile and lipoprotein properties were distinctly different from those of the slim group in terms of CETP mass and activity, HDL functionality, and HDL particle size.

Estimation of LDL Particle Size Using Lipid Indices: A Population-Based Study of 1578 Schoolchildren

BACKGROUND

Low-density lipoprotein (LDL) is atherogenic and LDL particles are reduced in diameter in the presence of insulin resistance, forming small, dense LDL. This study was conducted to assess the relationship between commonly used lipid indices and LDL particle size and furthermore to clarify the best surrogate lipid markers that could conveniently be used to estimate LDL particle size in children.

METHODS

We determined LDL particle diameter by gradient gel electrophoresis in 1578 children aged 10-12 years. At the fasting state, the relationships between measured LDL particle size and lipid variables [total cholesterol (TC), triglycerides (TG), LDL-cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), atherogenic index [(TC-HDL-C)/HDL-C, TG/HDL-C, LDL-C/HDL-C, and LDL-C/apolipoprotein B (Apo B) and non-HDL-C (TC-HDL-C)] were analyzed.

RESULTS

The LDL particle diameter was 26.64 (mean) ± 0.48 (SD) nm in boys (n = 820) and 26.66 ± 0.49 nm in girls (n = 758); there was not a statistically significant difference. There were statistically significant correlations between LDL particle size and TG or HDL-C concentrations (r = 0.28∼0.37), but the correlations with LDL-C and ApoB were very weak. The combined lipid measures, such as atherogenic index, TC/HDL-C, TG/HDL-C, and LDL-C/HDL-C showed moderate correlations (r = 0.33∼0.38) with LDL particle size; however, the correlation of non-HDL-C with LDL particle size was weak (r = 0.18∼0.19). Simple HDL-C measure appeared to be of comparable value to combined lipid measures.

CONCLUSIONS

Our data indicate that various lipid indices are not superior to HDL-C levels alone as a clinical tool for estimating LDL particle size. Non-HDL-C was less valuable in this aspect.

A novel microdeletion affecting the CETP gene raises HDL-associated cholesterol levels

We describe a novel, inherited 16q13 microdeletion that removes cholesteryl ester transfer protein (CETP) and several nearby genes. The proband was originally referred for severe childhood-onset obesity and moderate developmental delay, but his fasting lipid profile revealed relatively high levels of high density lipoprotein cholesterol (HDL-C) and relatively low levels of low density lipoprotein cholesterol (LDL-C) for age, despite his obesity. Testing of first-degree relatives identified two other microdeletion carriers. Functional assays in affected individuals showed decreased CETP mRNA expression and enzymatic activity. This microdeletion may or may not be pathogenic for obesity and developmental delay, but based on the lipid profile, the functional studies, and the phenotype of other patients with loss-of-function mutations of CETP, we believe this microdeletion to be antipathogenic for cardiovascular disease.

Study to assess whether waist circumference and changes in serum glucose and lipid profile are independent variables for the CETP gene

AIMS

To observe the relationship among genes, obesity and the changes in serum glucose and lipid profile to assess whether obesity-related disease results from genes and/or obesity.

METHODS

Correlations among serum glucose, lipids, waist circumference (WC), and Taq1B, I405V, and D442G polymorphisms of the cholesteryl ester transfer protein (CETP) gene were assessed. Logistic regression analysis was used to screen independent variables among obesity-related anthropometric indexes and serum biochemical indicators for genes.

RESULTS

The waist circumference density index (WCDI) may be attributed to changes in serum biochemical indicators and among WCDI, BMI and serum biochemical indicators, however, only WCDI was an independent variable for the G allele. Differences were observed in anthropometric indexes and serum biochemical indicators between subjects with the G allele and those without (p<0.05).

CONCLUSION

Abdominal obesity and changes in serum glucose and lipid profile are affected by a group of genes, including CETP. Correlation of the CETP gene with waist circumference may be independent compared with serum glucose and lipid profile.

TAQIB and I405V polymorphisms of CETP are moderately associated with obesity risk in the Chinese adult population

Associations between the TAQIB and I405V polymorphisms and obesity risk were studied for a single locus as well as in combination. A total of 934 obese subjects and 924 normal controls were included in the study. TAQIB was associated with high-density lipoprotein (HDL) levels (P < 0.001), while I405V was associated with levels of low-density lipoprotein (P = 0.03) and total cholesterol (P = 0.007). Less common alleles of TAQIB and I405V were associated with decreased obesity risk and further drops in odds ratio (OR) were observed in carriers with rare homozygous alleles on both loci (OR = 0.659, P = 0.02). The TAQIB B2 allele was associated with reductions in both hip circumference (P = 0.034) and triceps skinfold thickness (TST) (P = 0.045), although this effect was completely abolished after controlling for HDL levels. The 405V variant was associated with reductions in hip circumference (P = 0.031), body fat composition (P = 0.039) and TST (P = 0.036); these effects were weakened (P < 0.1) after controlling for HDL levels. In conclusion, less common alleles of TAQIB and I405V appear to be modestly associated with obesity risk in an adult Chinese population. Adjustments for HDL levels completely (TAQIB) or partially (I405V) abolished the observed association.

Association of two CETP polymorphisms with HDL levels in the Chinese obese population

The association of two cholesterol ester transfer protein (CETP) polymorphisms, D442G and TAQIB (B1-->B2), with high-density lipoprotein (HDL) levels in 932 Chinese obese individuals (BMI >or= 27) was investigated in comparison with normal controls (BMI <or= 24). Independent association was demonstrated for TAQIB minor allele B2 and CETP442 minor allele G with elevated HDL levels. The CETP D442G polymorphism was associated with a much greater increase in HDL levels in subjects with BMI exceeding 27 kg/m(2) (+5.42 mg/dl, P = 0.0007) compared to normal controls (+1.97 mg/dl, P = 0.275), and the increase in HDL reached the highest level among subjects with BMI exceeding 30 kg/m(2) (+6.80 mg/dl, P = 0.016). TAQIB showed significant association with HDL levels only in normal BMI subgroup (P = 0.0017). TAQIB significantly interacted with serum triglyceride (TG) on modulating HDL levels (P = 0.027). The TAQIB-TG interaction effect remained marginally significant after controlling for BMI (P = 0.057). We conclude that D442G polymorphism is associated with more HDL elevation in obesity. TAQIB interacts with serum TG on modulating HDL levels, and the interaction is partly independent of BMI.

Effect of hypoalbuminemia on the increased serum cholesteryl ester transfer protein concentration in children with idiopathic nephrotic syndrome

OBJECTIVES

To examine the alteration of cholesteryl ester transfer protein (CETP) mass with the regression of albumin level in childhood nephrotic syndrome (NS) in order to clarify the effect of albumin on CETP in NS.

DESIGN AND METHODS

Serum concentrations of CETP, kidney parameters and lipid traits were determined in 110 children with idiopathic NS and 150 control subjects. Of the NS patients, 69 children with an active phase formed group 1, and 41 in remission formed group 2.

RESULTS

Group 1 presented severe hypoalbuminemia and hyperlipidemia, while group 2 exhibited marked recovery in both serum albumin level and lipid/lipoprotein profile. CETP concentration was significantly higher in group 1 (7.36+/-2.43 mg/L, compared with controls 3.38+/-1.83 mg/L, P<0.0001), and declined to within normal range in group 2 (2.91+/-1.77 mg/L). CETP concentration had a strong inverse correlation with serum albumin level (r=-0.688, P<0.0001) in NS patients. Furthermore, when multiple linear regression analysis was performed, in which albumin, proteinuria, lipid traits, and prednisone dose were treated as independent variables, albumin was the only variable showing a significant correlation with CETP in the NS patients (R(2)=0.587, beta=-0.475, P<0.0001).

CONCLUSIONS

The results demonstrate that the decreased serum albumin level might be a main determinant of the increased CETP concentration in pediatric NS.

Obesity induced during sexual maturation is linked to LDL-triacylglycerols in Yucatan miniature swine

The incidence of childhood obesity is rising dramatically throughout industrialised countries. To evaluate and study the impact of childhood obesity on lipoprotein metabolism, we developed a new animal model of premature obesity. Yucatan mini-pigs aged 4 months were studied over a 12-month period from childhood to adulthood. Animals were divided into two groups: the first group were overfed a Western misbalanced diet; the second group were normally fed a recommended human-type diet. Cholesterol and triacylglycerol concentrations in VLDL-, LDL- and HDL-lipoproteins were followed from baseline to adulthood by fast protein liquid chromatography. At 10 (the end of sexual maturation) and 16 months old (adulthood), liver, visceral and subcutaneous adipose tissues were sampled. Real-time RT-PCR was performed in order to compare apo AI, apo B, apo C-III, PPAR-α, insulin receptor and lipoprotein lipase gene expression between groups and ages. Differences between groups were observed only after sexual maturity. Adult overfed mini-pigs had a higher LDL-cholesterol:HDL-cholesterol ratio (P<0·05; 0·55 (SE 0·06) for overfedv. 0·42 (SE 0·04) for normally fed pigs at the tenth month of the study). In both groups, VLDL-triacylglycerol decreased (P<0·05). VLDL-triacylglycerol evolution in the overfed group was associated with an increase in LDL-triacylglycerol plasma concentrations (P<0·05) after sexual maturation. LDL-triacylglycerol concentration in overfed mini-pigs went from an average of 0·28 mmol/l before sexual maturation to reach an average concentration of 0·56 mmol/l afterwards. This phenomenon has never been observed in similar studies when obesity is induced in adult mini-pigs and may represent a specific hallmark of an obesity induced during sexual maturity.

Early decreases in plasma lipid transfer proteins during weight reduction

OBJECTIVE

To determine the effect of short-term weight loss in obese women on concentrations of plasma cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP), two new risk factors for cardiovascular disease.

RESEARCH METHODS AND PROCEDURES

Plasma CETP and PLTP mass concentrations were measured in 38 obese, non-diabetic women before and after a moderate, 4% weight loss that was obtained by a 1250 kcal/d diet for 4 weeks. Anthropometric and biological parameters were measured before and after weight loss.

RESULTS

Plasma CETP concentration decreased substantially after weight loss (2.76 +/- 0.79 before and 2.31 +/- 0.69 mg/L after; p = 0.000), and the same was true for plasma PLTP concentration (9.01 +/- 2.44 mg/L before vs. 8.34 +/- 2.57 after; p = 0.043). The HDL profile shifted toward the small-sized range, with significant decreases in the relative abundance of HDL(2b) and HDL(2a) at the expense of HDL(3b) after weight loss. A significant, positive correlation between CETP and PLTP mass concentrations is reported for the first time in obese patients (r = 0.43, p = 0.004), and weight reduction was accompanied by early, concomitant, and parallel decreases in plasma CETP and PLTP levels (r = 0.47, p = 0.003). The significant relationship between CETP and PLTP levels was lost after the dietary intervention (r = 0.27; p = 0.11).

DISCUSSION

CETP and PLTP correlate positively and significantly in obese patients. The hypocaloric dietary manipulation constitutes a relevant intervention to reduce rapidly and simultaneously plasma levels of CETP and PLTP. The impact of reduced PLTP activity on HDL size appeared to be more prominent than the impact of concomitant reduction in CETP activity.

Effect of the cholesteryl ester transfer protein genotypes on plasma lipid and lipoprotein levels in Vietnamese children

Cholesteryl ester transfer protein (CETP) is understood to play a regulatory role in HDL cholesterol (HDLC) metabolism. In this study, the effect of CETP genotypes on plasma lipid and lipoprotein levels in 348 Vietnamese girls (aged 7-9) with different nutritional conditions was analyzed. The two mutations, intron 14 G(+1)-to-A (I14A) and Asp 442 to Gly within exon 15 (D442G), and the TaqIB polymorphism in the CETP gene were identified by an Invader assay. The D442G mutation was present with a frequency of 0.034, while the I14A mutation was absent. HDLC levels were significantly higher in carriers of the D442G mutation than in noncarriers, regardless of the nutritional status. Low-density lipoprotein (LDL) cholesterol and triglyceride levels were not significantly lower in carriers of D442G mutation. The frequency of the TaqIB2 allele was 0.34, which was lower than that observed in other Asian populations. TaqIB2B2 carriers also had significantly higher HDLC levels, but this association was weaker than that of the D442G mutation. Overall, genetic variations at the CETP gene locus may account for a significant proportion of HDLC variation in Vietnamese children.

Childhood obesity and insulin resistance in a Yucatan mini-piglet model: putative roles of IGF-1 and muscle PPARs in adipose tissue activity and development

OBJECTIVE

To explore metabolic and cellular modifications induced during childhood obesity, in a novel animal model of obese mini-piglets.

DESIGN

A total of 10 four-month old Yucatan mini-pigs were followed from prepuberty to adulthood. Animals were divided into two groups. The first one had been overfed (OF) a western-type diet and the second one had been normally fed a control recommended human-type diet (NF).

MEASUREMENTS

Plasma insulin-like growth factor 1 (IGF-1), insulin, leptin, nonesterified fatty acids, triglycerides (TGs) and glucose were determined at sexual maturity and at young adulthood. Quantitative gene expressions of peroxysome-proliferator-activated receptors (PPARs), glucose transporter 4, insulin receptor, IGF-1, leptin and interleukin-6 (IL-6) in skeletal muscle, adipose tissue and liver were also measured at both stages. Adult insulin sensitivity was measured via euglycaemic-hyperinsulinaemic clamps.

RESULTS

Increased body weight in adult OF pigs was associated with increased body size and low insulin sensitivity. Sexually mature OF pigs had higher IGF-1 plasma concentrations than their lean littermates (P < 0.05). In the OF group, TGs and glucose were both decreased (P < 0.05). Muscle PPARgamma and alpha in OF pubescent pigs as compared to NF pigs were 11 times higher and 20 times lower, respectively (P < 0.01).

CONCLUSION

Obesity and insulin resistance induced by overfeeding mini-pigs during development and puberty were not associated with the cluster of metabolic modifications frequently observed in their adult littermates. Increased IGF-1 concentrations and modifications of skeletal muscle PPAR (alpha and gamma) expressions may help the young obese pig to partially regulate its glycaemia and triglyceridaemia through an increase of fat mass, which maintains its high insulin sensitivity.

Pharmacological modulation of cholesteryl ester transfer protein, a new therapeutic target in atherogenic dyslipidemia

In mediating the transfer of cholesteryl esters (CE) from antiatherogenic high density lipoprotein (HDL) to proatherogenic apolipoprotein (apo)-B-containing lipoprotein particles (including very low density lipoprotein [VLDL], VLDL remnants, intermediate density lipoprotein [IDL], and low density lipoprotein [LDL]), the CE transfer protein (CETP) plays a critical role not only in the reverse cholesterol transport (RCT) pathway but also in the intravascular remodeling and recycling of HDL particles. Dyslipidemic states associated with premature atherosclerotic disease and high cardiovascular risk are characterized by a disequilibrium due to an excess of circulating concentrations of atherogenic lipoproteins relative to those of atheroprotective HDL, thereby favoring arterial cholesterol deposition and enhanced atherogenesis. In such states, CETP activity is elevated and contributes significantly to the cholesterol burden in atherogenic apoB-containing lipoproteins. In reducing the numbers of acceptor particles for HDL-derived CE, both statins (VLDL, VLDL remnants, IDL, and LDL) and fibrates (primarily VLDL and VLDL remnants) act to attenuate potentially proatherogenic CETP activity in dyslipidemic states; simultaneously, CE are preferentially retained in HDL and thereby contribute to elevation in HDL-cholesterol content. Mutations in the CETP gene associated with CETP deficiency are characterized by high HDL-cholesterol levels (>60 mg/dL) and reduced cardiovascular risk. Such findings are consistent with studies of pharmacologically mediated inhibition of CETP in the rabbit, which argue strongly in favor of CETP inhibition as a valid therapeutic approach to delay atherogenesis. Consequently, new organic inhibitors of CETP are under development and present a potent tool for elevation of HDL in dyslipidemias involving low HDL levels and premature coronary artery disease, such as the dyslipidemia of type II diabetes and the metabolic syndrome. The results of clinical trials to evaluate the impact of CETP inhibition on premature atherosclerosis are eagerly awaited.

Decrease in serum adiponectin level due to obesity and visceral fat accumulation in children

OBJECTIVE

To determine whether serum adiponectin is decreased in obesity and is restored toward normal level after treatment in children.

RESEARCH METHODS AND PROCEDURES

Subjects were 53 Japanese obese children, 33 boys and 20 girls (6 to 14 years old), and 30 age-matched nonobese controls for measuring adiponectin (16 boys and 14 girls). Blood was drawn after an overnight fast, and the obese children were subjected to anthropometric measurements including waist and hip circumferences and skinfold thicknesses. Paired samples were obtained from 21 obese children who underwent psychoeducational therapy. Visceral adipose tissue area was measured by computed tomography. Adiponectin was assayed by an enzyme-linked immunosorbent assay.

RESULTS

The serum levels of alanine aminotransferase, uric acid, triglyceride, total cholesterol, low-density lipoprotein-cholesterol, total cholesterol/high-density lipoprotein-cholesterol, apo B, apo B/apo A(1), and insulin in obese children were higher than the reference values. Serum adiponectin level was lower in the obese children than in the controls (6.4 +/- 0.6 vs. 10.2 +/- 0.8 mg/L, means +/- SEM, p < 0.001). In 21 obese children whose percent overweight declined during therapy, the adiponectin level increased (p = 0.002). The adiponectin level was correlated inversely with visceral adipose tissue area in obese children (r = -0.531, p < 0.001). The inverse correlations of adiponectin with alanine aminotransferase, uric acid, and insulin were significant after being adjusted for percentage overweight, percentage body fat, or sex.

DISCUSSION

Serum adiponectin level is decreased in obese children depending on the accumulation of visceral fat and is restored toward normal level by slimming.

Increased serum cholesteryl ester transfer protein in obese children

OBJECTIVE

To determine whether serum cholesteryl ester transfer protein (CETP), which is one of the physiologically active gene products secreted from adipose tissue, is increased and associated with atherogenic lipoprotein profile in obese children.

RESEARCH METHODS AND PROCEDURES

Subjects were 42 consecutive outpatient Japanese obese children, 29 boys and 13 girls, ranging in age from 5 to 14 years, and 25 age-matched non-obese children, 13 boys and 12 girls, as the control group for measuring CETP mass. Blood was drawn after an overnight fast and, at the same time, and anthropometric measurements including height, body weight, waist girth, hip girth, and triceps and subscapular skinfold thicknesses were taken. Paired samples were obtained from 15 obese children who underwent psychoeducational therapy. Serum CETP mass was assayed by an enzyme-linked immunosorbent assay.

RESULTS

The serum levels of triglyceride, total cholesterol (TC), low-density lipoprotein cholesterol, TC/high-density lipoprotein cholesterol (HDLC), apolipoproteins (apo) B, apo B/apo A(1), and insulin in obese children were significantly higher than the respective reference values. Serum CETP level was approximately 2-fold higher (98.7 +/- 3.6 vs. 50.9 +/- 4.0 nM, means +/- SEM, p < 0.001) in the obese children than in the controls. In 15 obese children, whose percentage of overweight declined during therapy, CETP levels decreased significantly. CETP level was correlated with HDLC, TC/HDLC, and insulin, and with percentage of overweight when the data of the obese and non-obese children were combined.

DISCUSSION

CETP is increased and associated with the atherogenic lipoprotein profile in obese children.

Threshold values of visceral fat measures and their anthropometric alternatives for metabolic derangement in Japanese obese boys

OBJECTIVE

To determine whether the direct measure of visceral adipose tissue (VAT) by computed tomography (CT) is a superior diagnostic criterion to the anthropometric surrogates and more classical criteria of obesity.

DESIGN

Cross-sectional, clinical study. Obese boys were classified according to the occurrence of abnormal values in either serum triglyceride, alanine aminotransferase or insulin level. A threshold value of each criterion for such metabolic derangement was calculated, using the analysis of receiver operating characteristic (ROC) curve.

SUBJECTS

Seventy-five consecutive outpatient Japanese obese boys, ranging in age from 6 to 14 y, were studied.

MEASUREMENTS

Anthropometric indices measured were height, body weight, waist girth, hip girth, triceps and subscapular skinfold thicknesses. Classical criteria for obesity used were percentage overweight (POW), body mass index (BMI) and percentage body fat. Waist girth, sagittal diameter by CT and waist-hip ratio (WHR) were evaluated as anthropometric surrogates for VAT. The areas of total abdominal fat (TAF), VAT and subcutaneous adipose tissue (SAT) were measured by CT at the level of the umbilicus. Clinical blood biochemistry was analyzed in fasting blood samples of obese boys.

RESULTS

Thirty-three boys were classified into a no-complication group, and 42 into a complication group. TAF, VAT and SAT areas were closely associated with age, body size and degree of overweight and adiposity, while VAT/SAT was not. VAT area, sagittal diameter, TAF area and waist girth were closely correlated with alanine aminotransferase, insulin, TG and HDL-C. VAT/SAT, BMI, SAT area, WHR, percentage body fat and POW were less closely associated with these biochemical indices. The descending order of the values of area under the curve for the ROC curves were as follows: VAT>sagittal diameter>TAF>VAT/SAT>waist girth>BMI>WHR>percentage body fat>POW. Both VAT area and VAT/SAT gave >80% of sensitivity and specificity. Among the anthropometric indices studied, the sagittal diameter was the best surrogate of visceral fat measure. The sensitivity and specificity for the rest of the anthropometric indices were in an unsatisfactory range. The threshold values for VAT area, VAT/SAT and sagittal diameter were 58.0 cm(2), 0.276 and 19.2 cm, respectively.

CONCLUSION

The threshold values for VAT area, VAT/SAT and sagittal diameter for detecting biochemical complication in Japanese obese boys were lower than the respective values reported in adults. These values can be used for classifying the obese boys into two types: those with medical problem and those without.

Subcutaneous and visceral adipose tissue: their relation to the metabolic syndrome

Methods for assessment, e.g., anthropometric indicators and imaging techniques, of several phenotypes of human obesity, with special reference to abdominal fat content, have been evaluated. The correlation of fat distribution with age, gender, total body fat, energy balance, adipose tissue lipoprotein lipase and lipolytic activity, adipose tissue receptors, and genetic characteristics are discussed. Several secreted or expressed factors in the adipocyte are evaluated in the context of fat tissue localization. The body fat distribution and the metabolic profile in nonobese and obese individuals is discussed relative to lipolysis, antilypolysis and lipogenesis, insulin sensitivity, and glucose, lipid, and protein metabolism. Finally, the endocrine regulation of abdominal visceral fat in comparison with the adipose tissue localized in other areas is presented.

Critical value for the index of body fat distribution based on waist and hip circumferences and stature in obese girls

OBJECTIVE

To determine the critical value for the standard deviation score (SDS) of waist-hip ratio (WHR)/height (Ht), as an age-adjusted measure of body fat distribution, in relation to occurrence of biochemical complications in obese girls.

DESIGN

Cross-sectional, clinical study. The (WHR/Ht)-SDS was calculated as described previously. Obese girls were classified into two groups according to the occurrence of abnormal values in either serum triglyceride, alanine aminotransferase or insulin level. The criteria for obesity were subjected to the receiver operating characteristic (ROC) analysis.

SUBJECTS

One-hundred and twenty-four outpatient Japanese obese girls, ranging in age from 9 to 15 y.

MEASUREMENTS

Height, body weight, waist girth and hip girth as anthropometric measures. Percentage overweight, waist girth, WHR and (WHR/Ht)-SDS as criteria for obesity. Clinical laboratory analysis for fasting blood samples of obese children.

RESULTS

Fifty-nine girls were classified into the no complication group, and 65 girls into the complication group. Those with complications were older, more obese, and their waist girth and WHR were larger, than the girls without complications. The (WHR/Ht)-SDS was >2-fold higher and lipoprotein profile was more atherogenic in the complication group than in the no complication group. Among the four criteria of obesity, (WHR/Ht)-SDS gave the ROC curve skewed furthest into the top left corner of the diagram. Both sensitivity and specificity for (WHR/Ht)-SDS were >80% at the critical value of 2.00. The sensitivity for waist girth was as high as that for specificity for the rest of the criteria were <80%.

CONCLUSION

Only (WHR/Ht)-SDS showed high enough sensitivity and specificity to predict metabolic derangement in the present obese girls. (WHR/Ht)-SDS can serve as the diagnostic criterion that classifies obesity in Japanese adolescent girls into two types.

Insulin does not regulate the promoter of cholesteryl ester transfer protein (CETP) in HIRc/pCETP-CAT cells

Cholesteryl ester transfer protein (CETP) is a plasma enzyme involved in cholesterol metabolism. As a potential target in the treatment of atherosclerosis, a number of studies have focused how this enzyme is regulated. It has been postulated that insulin may regulate CETP gene expression, and these effects may be mediated through CCAAT/enhancer binding protein alpha (C/EBPalpha). The present study examines the effects of insulin on the activity of the CETP promoter in rat fibroblasts expressing the human insulin receptor (HIRc). HIRc cells were stably transfected with a chimeric construct containing 3.2 kb of the CETP promoter attached to the bacterial chloramphenicol acyltransferase gene (pCETP-CAT) without significantly affecting the expression of the insulin receptor. CAT activity was 8-fold higher in cultured HIRc/pCETP-CAT in the presence of 100 mg/dL LDL cholesterol, than those cultured without cholesterol (p < 0.05). However, culturing these cells in the presence of 100 nM insulin did not result in any change in CAT activity when compared to control cells. In HIRc/pCETP-CAT cells transiently transfected with a construct that constitutively expressed C/EBPalpha protein, a 3-fold increase in CAT activity was observed when compared to cells transiently transfected with non-specific DNA (p < 0.05). However, no observable effect on the CETP promoter was observed in the presence of insulin. Thus, in HIRc/pCETP-CAT cells, we were unable to substantiate the hypothesis that insulin regulates CETP gene transcription. These results suggest that the effects of insulin on CETP expression regulation may be downstream of transcription.

Differential expression of cholesteryl ester transfer protein in the liver and plasma of fasted and fed transgenic mice

Because cholesteryl ester transfer protein (CETP) is considered a potential target in the treatment of atherosclerosis, several reports have focused on the regulation of this enzyme, and there is evidence that insulin may be a regulatory factor. The present study examines the differential expression of the human CETP gene between physiologic conditions that are accompanied by low (fasted) and high (fed) insulin levels. CETP expression was examined in plasma and tissues of transgenic mice expressing the human CETP minigene after 12 hours of fasting (n = 20) or ad libitum feeding (n = 20) with normal mouse chow. Plasma cholesteryl ester transfer activity (CETA) was 20% higher in fed than in fasted mice, reflecting higher levels of CETP (P < 0.05). This observation was accompanied by higher liver mRNA in fed mice (100%, P < 0.05), as determined by ribonuclease protection assays, as well as by higher CETA (23%, P < 0.05) and CETP mass (29%, P < 0.05) in the particulate fraction of liver homogenates. These parameters of liver CETP expression correlated well with each other, as well as with plasma CETA. CETP in the liver particulate fraction was found as a doublet (approximately 70 and 65 kDa), which resolved to a single band (approximately 60 kDa) upon deglycosylation. No differences in CETP expression were observed in pooled adipose tissue samples from fed and fasted mice. Insulin and glucose were not related to any plasma or tissue parameter of CETP expression. In summary, the concerted, differential expression of CETP in the liver of fed and fasted transgenic mice appears to contribute to higher plasma CETP levels in fed mice, but the precise role of insulin and glucose in regulating CETP expression under fasted and fed conditions needs to be defined.

Combined effects of probucol and benzafibrate on lipoprotein metabolism and liver cholesteryl ester transfer protein mRNA in cholesterol-fed rabbits

Probucol decreases and bezafibrate increases plasma high density lipoprotein-cholesterol (HDL-C) levels in humans. This study was performed to determine whether the HDL-C-lowering effects of probucol could be reversed by treatment with bezafibrate in hypercholesterolemic rabbits. Forty-nine normolipidemic Japanese White rabbits were divided into 5 groups [group 1: normal chow; group 2: 0.2% cholesterol (Ch) diet; group 3: 0.2% Ch and 1% probucol diet; group 4: 0.2% Ch and 1% bezafibrate diet; group 5: 0.2% Ch and 1% probucol plus 1% bezafibrate diet] and treated for 8 weeks. Plasma lipids, cholesteryl ester transfer protein (CETP) activity in the lipoprotein-deficient plasma fraction, CETP mRNA in liver tissue and plasma drug concentrations were investigated. Serum total cholesterol (TC) increased after the rabbits in groups 2, 3, 4 and 5 were fed Ch, but overall, no significant differences were observed in serum TC and triglyceride (TG) among these groups. Serum HDL-C levels increased (p<0.01) in the bezafibrate-treated group, but a significant (p<0.05) reduction in HDL-C was observed in both the Ch + probucol (group 3) and Ch + probucol plus bezafibrate (group 5) groups; no significant difference was observed between groups 3 and 5. Significant correlation (p<0.01) was found between serum low density lipoprotein cholesterol (LDL-C) levels and plasma probucol concentrations in groups 3 and 5, but no correlation was found between plasma concentrations of probucol/bezafibrate and serum HDL-C levels. CETP activity in the lipoprotein-deficient plasma fraction increased in the Ch-, Ch + probucol-, and Ch + probucol and bezafibrate-fed groups (groups 2, 3 and 5, respectively), whereas a significant reduction in this activity was observed in the Ch + bezafibrate-fed group (group 4). An analysis of covariance showed that the CETP activity responded more sensitively to drug treatment than did the serum HDL-C level. CETP mRNA in liver tissue was assessed by Northern blotting at 8 weeks, but no changes were observed among the 5 groups. Probucol decreased and bezafibrate increased serum HDL-C levels, through CETP activity without affecting liver CETP mRNA levels, and the decrease in HDL-C levels produced by probucol could not be reversed by bezafibrate.