High plasma leptin levels are associated with impaired diastolic function in patients with coronary artery disease

BACKGROUND AND AIMS

Obese subjects have elevated leptin levels, which have been associated with increased risk of cardiovascular events. Because leptin has direct cellular effects on various tissues, we tested the hypothesis that leptin levels are associated with cardiac structure or function in patients with coronary artery disease (CAD).

METHODS AND RESULTS

The study population consisted of 1 601 CAD patients, of whom 42% had type 2 diabetes mellitus. Plasma leptin was measured in fasted state and an echocardiography performed. Leptin levels were not related to LV dimensions or LV ejection fraction (NS for all), but higher leptin levels were associated with elevated E/E' (9.43 vs. 11.94 in the lowest and the highest leptin quartile, respectively; p=0.018 for trend). Correspondingly, a decreasing trend was observed in E/A (1.15 vs. 1.06; p=0.037). These associations were independent of obesity and other relevant confounding variables.

CONCLUSION

We conclude that elevated plasma leptin levels are associated with impaired left ventricular diastolic function in patients with CAD independently of obesity and other confounding variables. Leptin may be one of the mechanistic links explaining the development of congestive heart failure in obese subjects.

Serum 25-hydroxyvitamin D is associated with major cardiovascular risk factors and cardiac structure and function in patients with coronary artery disease

BACKGROUND AND AIMS

Vitamin D deficiency has been associated with increased risk for cardiovascular (CV) disease, but the possible effects of Vitamin D on cardiac structure and function are not well characterized.

METHODS AND RESULTS

The correlation between 25-hydroxyvitamin D levels and metabolic and cardiac echocardiographic parameters was studied in ARTEMIS study population including 831diabetic and 659 non-diabetic patients with stable coronary artery disease (CAD). Low levels of Vitamin D were associated with high BMI (p < 0.001), high total and LDL cholesterol and triglyceride levels (p < 0.001 for all) in both diabetics and non-diabetics. Among non-diabetic patients, low Vitamin D was also associated independently with elevated systolic and diastolic blood pressure (p < 0.005). Low Vitamin D levels were independently associated with reduced left ventricular (LV) ejection fraction (p < 0.005) and increased left atrial diameter (p < 0.03) measured by cardiac ultrasound by 2-dimensional echo. In the non-diabetic group, low Vitamin D levels were associated with impaired LV filling (high E/E') (p < 0.03) and low E/A mitral flow pattern measured by Doppler echocardiography (p < 0.05). Among diabetics, low Vitamin D levels were also related to increased LV end-systolic diameter (p < 0.05) and right ventricular diameter (p < 0.005). The association between LV diastolic filling (E/E') and Vitamin D levels was significant (p < 0.01) after adjustment for the commonly recognized risk factors of diastolic dysfunction in linear regression analysis.

CONCLUSIONS

Low Vitamin D is associated with several major cardiovascular risk factors and cardiac structural changes including impaired systolic and diastolic function, which together may explain the association of low Vitamin D to worse cardiovascular outcome.

High plasma ghrelin protects from coronary heart disease and Leu72Leu polymorphism of ghrelin gene from cancer in healthy adults during the 19 years follow-up study

The aim of our investigation was to find out if ghrelin concentrations or polymorphisms predict the future risk for cardiovascular diseases and cancer in a population-based cohort initiated in 1991 (491 hypertensive and 513 control subjects). Total mortality and hospital events were followed up for 19 years. Fasting total ghrelin concentrations were determined and Arg51Gln, Leu72Met and -501 A > C polymorphisms identified. Cox regression analysis was performed. The mean value in the control cohort was 674 pg/ml whereas in the hypertensive cohort it was 661 pg/ml. The associations found suggest that in the controls the highest ghrelin quartile protected from CHD (coronary heart disease). The results were significant without or with adjustments for age, sex, smoking, systolic blood pressure and LDL cholesterol, BMI, type 2 diabetes or QUICK index. C/C variant of the promoter associated with the prevention of IHD (ischemic heart disease) in the hypertensive group (p<0.05). The controls with the Leu72Leu genotype had less cancer (p<0.05). In conclusion, high plasma ghrelin concentration was related to protection from CHD and Leu72Leu genotype to prevention of cancer in healthy adults during the 19 years follow-up. C/C promoter protects from IHD in the hypertensive subjects.

Serum ghrelin and the prediction of the development of impaired glucose regulation and Type 2 diabetes in middle-aged subjects

BACKGROUND

Ghrelin is a peptide hormone which has been shown to associate with obesity, hypertension and Type 2 diabetes (T2DM) in cross-sectional studies.

AIM

To study whether total ghrelin levels have predictive value for the incidence of impaired glucose regulation (IGR) or T2DM.

SUBJECTS AND METHODS

The subjects of this prospective follow-up study (no.=201) belonged to a population-based cohort collected in Northern Finland. Oral glucose tolerance tests (OGTT) and measurements of fasting serum total ghrelin, lipids, blood pressure and body mass index were performed at the beginning and at the end of the study. The mean follow-up time was 5.1 yr. The subjects had normal glucose tolerance (NGT) at the beginning of the study.

RESULTS

T2DM developed in 6 (3%), impaired fasting glucose (IFG) in 6 (3%) and impaired glucose tolerance (IGT) in 35 (17.4%) subjects. The baseline ghrelin concentrations did not differ between the two studied groups: median fasting serum total ghrelin concentration was 733 pg/ml (25th-75th percentiles: 571-961 pg/ml) among those who maintained NGT, and 661 pg/ml (25th-75th percentiles: 527- 878 pg/ml) among those who developed IGR (IFG and/or IGT) or T2DM (p=0.421). The baseline ghrelin concentrations did not explain the changes in the 0-h or 2-h blood glucose concentrations in regression models.

CONCLUSIONS

Our findings suggest that fasting serum total ghrelin levels measured at one time point might not have predictive value for the development of abnormalities in glucose tolerance.

Gastric bypass and glucose metabolism

Roux-en-Y gastric bypass leads to a marked improvement of glucose control. The mechanisms are only partly known. Gastrointestinal hormones may play a role. Of these, glucagon-like peptide 1 and peptide YY have been most consistently associated with the beneficial effects of gastric bypass on glucose metabolism and weight. In this paper, a short review of the topic is presented and a suggestion of the improvement of glucose metabolism is made based on the current published work.

Plasma adiponectin concentration is associated with ambulatory daytime systolic blood pressure but not with the dipping status

The objective of this study was to analyse the relationship between the ambulatory blood pressure (ABP) measurement and plasma adiponectin levels in a population-based cohort. Non-hypertensive, non-diabetics from the Oulu Project Elucidating Risk of Atherosclerosis cohort aged 40-60 years with ABP measurement available in 226 men and 236 women were analysed. ABP was recorded using the fully automatic SpaceLabs 90207 oscillometric unit. Plasma adiponectin concentrations were assayed using the enzyme-linked immunosorbent assay method. Without adjustment the highest plasma adiponectin tertile was associated with the lowest ABP and office BP measurements (P from 0.025 to P<0.001, respectively). Only the association of plasma adiponectin concentration with systolic ABP was independent of other conventional risk factors (age, body mass index (BMI), waist, gender, insulin sensitivity index, smoking and alcohol consumption) for hypertension (P=0.017). No association was observed between systolic dipping pattern and adiponectin level. The plasma high adiponectin concentration is independently associated with low daytime systolic ABP value. The mechanisms may include effects on endothelial function and the sympathetic nervous system.

Leptin and lipid metabolism in chronic kidney failure

OBJECTIVE

In the general population, leptin has been associated with atherosclerosis and has been shown to interfere with lipoprotein profiles. Patients with chronic renal failure are at increased risk of cardiovascular disease and display alterations in both lipoprotein and leptin levels. The aim of this study was to investigate the relationship between leptin and the lipoprotein profile in non-dialyzed patients with chronic kidney disease (CKD).

MATERIAL AND METHODS

Leptin and lipid and lipoprotein concentrations were studied in 73 CKD patients and in 68 healthy controls in a cross-sectional case-control design.

RESULTS

The mean leptin levels were increased in the CKD patients (24.0 (SD 37.1) ng/mL) compared to those in controls (9.0 (SD 8.5) ng/mL) (p = 0.008). Also, the ratio between leptin levels and body mass index (leptin/BMI) was increased in CKD patients (mean 0.80 (SD 1.03)) compared to that in controls (0.31 (SD 0.24)) (p = 0.001). In linear regression analysis, leptin independently predicted total cholesterol and triglycerides in CKD patients (p = 0.010 and p = 0.001, respectively) and ratio between total and HDL cholesterol (Chol/HDL) in controls (p = 0.024). Furthermore, in CKD patients, the leptin/BMI predicted the variation in total cholesterol and triglycerides (p = 0.010 and p = 0.002, respectively).

CONCLUSIONS

Leptin concentrations and leptin/BMI were elevated in CKD patients compared to those in controls. Leptin levels in both study groups, and leptin/BMI in the CKD group, were associated with atherogenic lipid profiles, which may contribute to the elevated cardiovascular risk that has been linked to hyperleptinaemia.

Early atherosclerosis and IgG2 to bacteria are associated with FcgammaRIIa genotype in non-smokers

BACKGROUND

Involvement of low density lipoprotein (LDL) immune complexes (ICs) in atherogenesis has been proposed. Human FcgammaRIIa receptor (CD32) plays a crucial role in the phagocytosis of IgG(2) ICs and a functional point mutation 131His/Arg diminishes IgG(2) binding to the receptor.

STUDY DESIGN

We examined FcgammaRIIa-131His/Arg polymorphism, IgG(2) antibody titres to oxidized low-density lipoprotein (OxLDL) and Streptococcus pneumoniae cell wall polysaccharide (CWPS) and subclinical atherosclerosis in a large cohort of Finnish subjects (n = 1041).

RESULTS

Non-smoking subjects with homozygous 131His/His genotype had more premature atherosclerosis (P = 0.004) and higher IgG(2) to bacterial CWPS (P = 0.002) compared with other genotypes. Smoking subjects had significantly higher intima-media thickness (IMT) than that of non-smokers (P < 0.001) and genotype-dependent associations were indistinct. There was no association between FcgammaRIIa genotype and antibody titres to OxLDL.

CONCLUSIONS

Our data demonstrate that FcgammaRIIa 131His/Arg polymorphism is associated with subclinical atherosclerosis in non-smoking subjects. Furthermore, FcgammaRIIa genotype is associated with IgG(2) titres to bacterial CWPS, but not to OxLDL. These data propose possible involvement of FcgammaRIIa receptor in atherogenesis.

ApoE phenotype is associated with inflammatory markers in middle-aged subjects

OBJECTIVES

Apolipoprotein (apo) E phenotype has been associated with inflammation markers. The determinants of these associations and the relationship between novel inflammation marker, resistin, and apoE phenotype are studied here.

METHODS AND RESULTS

Middle-aged subjects of the population- based cohort (n = 526) of the OPERA- study were studied. Intima-media thickness (IMT) was measured with carotid ultrasound. The results suggest that, apoE phenotype was a significant independent predictive factor for resistin (p < 0.01) and hsCRP (p < 0.01) levels. The association of ApoE phenotype with hsCRP was seen among the subjects with the normal renal function (p = 0.005). ApoE4 was associated (p < 0.01) with the lowest hsCRP in the lowest IMT quartile while it's relation with the highest resistin levels was evident in the highest IMT quartile.

CONCLUSIONS

ApoE phenotype is an independent determinant of plasma resistin and hsCRP levels. The extent of atherosclerosis and renal function seem to modify the effects of apoE phenotype on inflammatory parameters.

The effect of a short-term hypocaloric diet on liver gene expression and metabolic risk factors in obese women

BACKGROUND AND AIMS

Most gene expression studies examining the effect of obesity and weight loss have been performed using adipose tissue. However, the liver also plays a central role in maintaining energy balance. We wanted to study the effects of a hypocaloric diet on overall hepatic gene expression and metabolic risk factors.

METHODS AND RESULTS

The study subjects were middle-aged, obese women. The diet intervention subjects (n=12) were on a hypocaloric, low-fat diet for 8 weeks with a daily energy intake of 5.0 MJ (1200 kcal), while the control subjects (n=19) maintained their weight. Liver biopsies were taken at the end of the diet period during a gallbladder operation. Hepatic gene expression was analyzed using microarrays by comparing the gene expression profiles from four subjects per group. A global decrease in gene expression was observed with 142 down-regulated genes and only one up-regulated gene in the diet intervention group. The diet resulted in a mean weight loss of 5% of body weight. Triglyceride and fasting insulin concentrations decreased significantly after the diet.

CONCLUSIONS

The global decrease in hepatic gene expression was unexpected but the results are interesting, since they included several genes not previously linked to weight reduction. However, since the comparison was made only after the weight reduction, other factors in addition to weight loss may also have been involved in the differences in gene expression between the groups. The decrease in triglyceride and fasting plasma insulin concentrations is in accordance with results from previous weight-loss studies.

Adiponectin concentration and insulin indicators following overfeeding in identical twins

Low adiponectin levels have been associated with high body mass index, low insulin sensitivity, and diabetes.

OBJECTIVE

To assess the relationships between changes in serum adiponectin concentration and adiposity, glucose, and insulin in response to long-term overfeeding in identical twins and to calculate the twin resemblance in serum adiponectin concentrations.

SUBJECTS AND DESIGN

Twenty-four sedentary young men [mean (+/-SD) age, 21+/-2 yr] who constituted 12 pairs of healthy identical twins were studied for metabolic and adiponectin changes in response to overfeeding.

INTERVENTION

Subjects were overfed by 84,000 kcal over a 100-day period.

OUTCOME MEASURES

The overfeeding study provides an opportunity to examine the relationships between adiponectin and changes in body weight, adiposity, plasma glucose and insulin.

RESULTS

Serum adiponectin concentration correlated positively with body weight (r= 0.41, p=0.05) at baseline but not with indicators of adiposity or with visceral fat. No relationship existed between baseline adiponectin concentration and body weight or adiposity gains with overfeeding. However, serum adiponectin decreased significantly by -2.35+/-0.48 microg/ml (p=0.001) in response to overfeeding. Baseline adiponectin levels correlated negatively with changes in plasma fasting glucose levels (r=-0.53, p=0.01) and homeostasis model assessment index (r=-0.41, p=0.05), independently of fat mass. The intrapair coefficient for twin resemblance (r=0.75, p=0.001) strongly suggests that baseline serum adiponectin concentration is a familial trait.

CONCLUSIONS

These data provide evidence that adiponectin concentration is a familial trait in normal-weight individuals, that it decreases when challenged by positive energy balance, and that its overfeeding-induced variations are correlated with glucose and insulin levels.

Rosiglitazone treatment increases plasma levels of adiponectin and decreases levels of resistin in overweight women with PCOS: a randomized placebo-controlled study

OBJECTIVE

Abdominal obesity, insulin resistance and compensatory hyperinsulinaemia play a central role in the pathogenesis of the polycystic ovary syndrome (PCOS). Abdominal adipose tissue is a source of adipokines, such as adiponectin and resistin, both of which may be involved in the development of insulin resistance and chronic inflammation in PCOS. Ghrelin, an important regulatory peptide of food intake, may also play a role in metabolic disturbances related to PCOS. The aim of this study was to examine the effects of 4 months of treatment with the insulin sensitizer rosiglitazone on plasma adiponectin, resistin and ghrelin levels in overweight women with PCOS.

DESIGN

A randomised placebo-controlled study.

METHODS

Thirty overweight/obese women with PCOS (body mass index>25 kg/m(2), mean age 29.1+/- 1.2 (S.E.M.) years) were randomly allocated to either rosiglitazone (Avandia, 4 mg twice a day) or placebo treatment. Plasma levels of adiponectin, resistin and ghrelin and their correlation to serum levels of insulin, C-peptide and steroid hormones, and insulin sensitivity (euglycaemic hyperinsulinaemic clamp) were assessed.

RESULTS

Adiponectin and ghrelin levels correlated significantly with most metabolic markers of insulin resistance and with serum levels of DHEA and 17-hydroxyprogesterone. Plasma levels of adiponectin increased from 9.26+/-0.90 (S.E.M.) to 22.22+/-3.66 microg/ml (P<0.001) and those of resistin decreased from 12.57+/-1.63 to 9.21+/-0.53 ng/ml (P=0.009) at 4 months of treatment, but plasma ghrelin levels did not change.

CONCLUSIONS

Rosiglitazone had beneficial effects on serum levels of adiponectin and resistin, suggesting that these adipocytokines may contribute to the improvement in insulin sensitivity observed during the treatment.

Leu7Pro polymorphism of PreproNPY associated with an increased risk for type II diabetes in middle-aged subjects

OBJECTIVES

Neuropeptide Y (NPY) plays a central in energy homeostasis and potentially in the development of obesity-related comorbidities, like type II diabetes. As the PreproNPY Leu7Pro polymorphism probably changes the intracellular processing of the synthesized preproNPY peptide, we assessed the hypothesis that PreproNPY Leu7Pro polymorphism is a risk factor for type II diabetes, impaired glucose tolerance and hypertension.

DESIGN

Blood pressure recordings and oral glucose tolerance test were performed in the hypertensive (n=515) and control cohorts (n=525) of our well-defined Oulu Project Elucidating Risk of Atherosclerosis (OPERA) study. The prevalence of type II diabetes was 9% (n=93). The genotypes, insulin and glucose metabolism indexes and plasma ghrelin of the subjects were determined.

RESULTS

Pro7 allele frequencies were 5.9, 5.3 and 11.3% in the total cohort, in subjects without and with type II diabetes, respectively. The PreproNPY Pro7 carrier status was a significant risk factor for type II diabetes, and the effect remained significant after adjustment for age, sex, waist circumference and study group (odds ratio=3.02, confidence interval: 1.67-5.44 and P<0.001). Pro7 carriers were more insulin resistant and showed lower ghrelin levels compared to non-carriers.

CONCLUSIONS

The PreproNPY Pro7 allele is associated with an increased risk for type II diabetes. The risk seems to be associated with a higher insulin resistance among Pro7 carriers whereas low ghrelin concentrations in Pro7 carriers are possibly a consequence of high insulin levels.

Plasma ghrelin concentrations are positively associated with carotid artery atherosclerosis in males

BACKGROUND

Ghrelin, a peptide hormone from stomach, stimulates food intake and decreases fat utilization. Ghrelin binds to growth hormone secretagogue receptor (GHSR). GHSR density has been shown to be upregulated in atherosclerotic lesions, but the relationship between ghrelin concentration and atherosclerosis has not yet been studied. We, therefore, characterized the association between ghrelin concentration and carotid artery intima-media thickness (IMT) in a population-based cohort of 1024 middle-aged (40-60 years) men and women.

METHODS

Intima-media thickness and the number of atherosclerotic plaques were determined ultrasonographically. Fasting plasma ghrelin concentrations were analysed using RIA-kit (PhoenixPeptide).

RESULTS

There was a positive association between mean IMT and ghrelin concentration in the analysis of males before and after adjustments for the traditional risk factors of atherosclerosis [age, systolic blood pressure, LDL cholesterol, body mass index (BMI), and smoking (ancova, P = 0.004 and P = 0.007, respectively)]. However, no such association was found in females (P = 0.985 and P = 0.915). There was no correlation between ghrelin and CRP concentrations or ghrelin and smoking.

CONCLUSION

Ghrelin concentrations and carotid artery atherosclerosis are positively associated in males even after adjustment for the commonly recognized risk factors of atherosclerosis. Experimental and prospective studies are warranted to elucidate the role of ghrelin in atherosclerosis.

Role of candidate genes in the lipid responses to intensified treatment in Type 2 diabetes

OBJECTIVE

To identify genetic factors related to individual differences in lipid responses to intensified treatment in Type 2 diabetes.

DESIGN AND METHODS

After evaluation and intensification of their treatment, 107 Type 2 diabetes patients with poor metabolic control were re-evaluated after mean follow-up time of 15.6 (0, 4) (SE) months. The genes coding major lipid regulatory proteins and their relations to plasma lipid and lipoprotein changes were studied.

RESULTS

During the follow-up, levels of glycohemoglobin A1 (GHBA1) decreased (-1.7%), plasma HDL cholesterol (+0.05 mmol/l) and lipoprotein (a) [Lp(a)] (+4.2 mg/dl) increased, while triglyceride (TG) levels decreased (-1.2mmol/l) despite mean weight gain of 2.1 kg (p from <0.01 to <0.001). Of the gene markers studied, the lipoprotein lipase (LPL) Pvull (p=0.005) independently affected changes in HDL-cholesterol and was associated with the frequency of coronary heart disease (CHD). Lp(a) changes were associated with apolipoprotein B (ApoB) Glu4154Lys polymorphism (p=0.004).

CONCLUSIONS

These results suggest that genetic variations at LPL and ApoB loci are among the factors contributing to the variability in response to lipid parameters to therapy in Type 2 diabetes. LPL Pvull rare allele homozygote status seems to be beneficial with more favorable lipid changes and protection against CHD.

Ghrelin and the metabolic balance

Several studies have provided evidence that ghrelin is involved in the regulation of metabolic balance. Recent data provide evidence that when studying the effects of ghrelin on energy balance, differential influences of the acylated and non-acylated forms of the peptide must be considered. Although the correlation between the two forms is good, they may be different hormones with opposite actions with non-acylated ghrelin being able to antagonize some of the effects of the acylated form. Future studies will reveal which of the two forms of ghrelin, the acylated or non-acylated forms, dominates and determines the net influence on energy balance.

Resistin polymorphisms are associated with cerebrovascular disease in Finnish Type 2 diabetic patients

AIMS

Resistin is a hormone secreted by adipocytes and it is also expressed in monocytes. Resistin has been found to increase insulin resistance, a key feature in Type 2 diabetes. The aim of this study was to investigate whether resistin polymorphisms are associated with Type 2 diabetes and its clinical characteristics.

METHODS

We studied the allele and genotype frequencies of the single-nucleotide polymorphisms (SNPs)-420 (C>G), +157 (T>C) and +299 (G>A) in the resistin gene in 258 Finnish Type 2 diabetics and 494 controls.

RESULTS

These three markers were in significant linkage disequilibrium with each other. No significant (P<0.05) differences in the allele or genotype frequencies were observed between the study groups. Subjects with Type 2 diabetes showed a significant association between cerebrovascular disease and the SNPs-420 (P=0.004) and +299 (P=0.007), the G-G and A-A genotypes, respectively, had the highest frequencies. SNPs-420 (P=0.000) and +299 (P=0.002) in men and SNP+157 in men (P=0.005) and in women (P=0.019) showed significant association with higher mean blood glucose. The rare allele homozygotes also had the highest mean blood glucose values. We also observed associations between at least one of the SNPs and fasting blood glucose, glycosylated haemoglobin A1 (GHbA1), low-density lipoprotein (LDL) cholesterol and systolic and diastolic blood pressure. After correction for multiple comparisons, the association between the promoter variant SNP-420 and cerebrovascular disease in both genders and the associations between mean blood glucose and SNP-420 and SNP+299 in men remained significant.

CONCLUSIONS

The results suggest that resistin may play a role in atherogenesis probably through increasing insulin resistance.

The negative association between plasma ghrelin and IGF-I is modified by obesity, insulin resistance and type 2 diabetes

AIMS/HYPOTHESIS

Ghrelin is a natural growth hormone-releasing peptide thought to be involved in the regulation of energy metabolism. The recent studies concerning the association between ghrelin and insulin-like growth factor-I (IGF-I) concentrations have shown either negative correlation or no correlation at all. The aims of this study were to clarify the association between ghrelin and IGF-I concentrations in a large cohort and to characterize whether obesity, insulin resistance and type 2 diabetes affect this association.

METHODS

We analysed fasting plasma ghrelin and IGF-I concentrations of 1,004 middle-aged subjects of the population-based OPERA study. Insulin resistance was estimated using QUICKI.

RESULTS

IGF-I concentrations were negatively associated with ghrelin concentrations in the analysis of all subjects before (beta=-0.32, p<0.001) and after adjustments for BMI, insulin levels, sex and age (beta=-0.40, p<0.001). The association was particularly strong in males and in the higher BMI tertiles. The degree of association varied in relation to the glycaemic status: no insulin resistance: r(2)=6.5% (p<0.001), insulin resistance without type 2 diabetes: r(2)=21.0% (p<0.001), type 2 diabetes: r(2)=25.4 (p<0.001). IGF-I levels explained larger proportion (r(2)=9.8%) of the variation in ghrelin concentrations compared to fasting insulin concentration (r(2)=3.0%) and BMI (r(2)=1.5%).

CONCLUSIONS/INTERPRETATION

There is a negative and independent association between ghrelin and IGF-I concentrations in middle-aged subjects. The interaction between IGF-I and ghrelin is modified by obesity, IR and type 2 diabetes. Further studies are warranted to elucidate the role of ghrelin in the development of these states.

Two variants in the resistin gene and the response to long-term overfeeding

OBJECTIVE AND SUBJECTS

To investigate the role of resistin gene variants on the adiposity and metabolic changes observed in response to a 100-day overfeeding protocol conducted with 12 pairs of monozygotic twins.

MEASUREMENTS

Body-fat measurements included hydrodensitometry and abdominal fat from computed tomography. Plasma glucose and insulin during fasting and in response to an oral glucose tolerance test (OGTT) were assayed. A 4.2 MJ test meal was consumed, after which calorimetric measurements were performed for 240 min.

RESULTS

Respiratory quotient (RQ) decreased (P=0.001) more in AA/AG than in GG subjects of the IVS2+181G>A polymorphism after the caloric surplus and the significance persisted when correction for multiple testing was performed. Total abdominal (P=0.027) and visceral (P=0.004) fat increased more in TC than in TT subjects of the IVS2+39C>T polymorphism. In response to overfeeding, glucose area under the curve during the OGTT showed a slight decrease (P=0.031) in the TC while it increased in TT subjects. OGTT insulin area tended to increase less (P=0.055) in TC than in TT subjects. After overfeeding, fasting insulin was lower in TC than in TT subjects (P=0.010). In addition, TC subjects experienced more decrease in RQ than TT subjects (P=0.034).

CONCLUSION

The IVS2+181G>A variant was associated with the changes in RQ in response to overfeeding. The IVS2+39C>T polymorphism was associated with overfeeding-induced changes in abdominal visceral fat, OGTT glucose area and RQ. The results suggest that sequence variation in the resistin gene is involved in the adaptation to chronic positive energy balance.

Tyrosine phosphatase 1B and leptin receptor genes and their interaction in type 2 diabetes

OBJECTIVES

The association between three tyrosine phosphatase 1B (PTP1B) gene polymorphisms and type 2 diabetes was examined by comparing the prevalence rates of these polymorphisms in type 2 diabetic patients and healthy control subjects. Furthermore, the association of the polymorphisms and PTP1B and leptin receptor (LepR) gene-gene interactions with complications of type 2 diabetes were examined in type 2 diabetic patients.

SUBJECTS AND METHODS

A total of 257 Finnish patients with type 2 diabetes and 285 nondiabetic subjects were screened. Single nucleotide polymorphisms were determined using polymerase chain reaction and restriction enzymes. The diagnosis of coronary heart disease was based on clinical and ECG criteria. The prevalences of cerebrovascular and peripheral vascular diseases were assessed on the basis of clinical criteria. Laboratory analyses were carried out in the hospital laboratory.

RESULTS

We did not find any differences in the genotype distributions or allele frequencies of IVS6 + G82A and Pro387Leu polymorphisms between the type 2 diabetics and controls. There were differences in the genotype frequencies of the Pro303Pro (C981T)-polymorphism between the two studied groups (P = 0,018); there were eight T981T subjects in the control population but none amongst the type 2 diabetics. However, there were no differences in the allele frequencies. In addition, significant associations between the IVS6 + G82A polymorphism and body mass index (BMI), albuminuria, glycohaemoglobin A1 (GHBA1) and hypertension in type 2 diabetic patients (P = 0,026-0,031) were observed. Pro387Leu and Pro303Pro did not associate with risk factors or diabetic complications. We also found a gene-gene interaction effect between PTP1B and the LepR gene with the genotype combination IVS6 + A82A and Arg223Arg having the highest BMI compared with the other genotype combinations (P = 0.0043 for trend). The interaction between these two polymorphisms explained 3% of the variation in BMI in diabetic patients when the other covariates were taken into account.

CONCLUSIONS

We conclude that the PTP1B IVS6 + G82A polymorphism was associated with BMI, albuminuria, GHBA1 and hypertension in type 2 diabetic patients. The 981T/T-genotype of the Pro303Pro- polymorphism might have some protective role against the development of type 2 diabetes. The interaction effects between the PTP1B IVS6 + A82A and LepR Arg223Arg genotypes influenced BMI, explaining 3% of its variation. A synergistic effect of PTP1B and LepR variants on the leptin signalling may be involved.

Role of candidate genes in the responses to long-term overfeeding: review of findings

An overfeeding experiment conducted with 12 pairs of young male identical twins revealed that genetic factors were likely to play an important role in the response to caloric affluence. Significant intrapair resemblance was observed for the overfeeding-induced changes in body weight, fat mass, abdominal fat, fasting insulin, fasting cholesterol and triglycerides. In an attempt to define the molecular basis of these genotype-energy balance interaction effects, a panel of candidate genes has been investigated. Among the most significant findings, an adipsin polymorphism was associated with increases in body weight, total fat mass and subcutaneous fat in response to overfeeding. In addition, the beta2 adrenergic receptor gene Gln27Glu polymorphism showed a strong association with the gains in body weight and subcutaneous fat. Only a few markers were related to abdominal fat changes and, among them, the adipsin Hinc II polymorphism was associated with both computed tomography (CT)-measured abdominal visceral and total fat. The changes in insulin parameters brought about by long-term overfeeding were influenced most consistently by leptin receptor (LEPR) Gln223Arg and insulin-like growth factor-II Apa I polymorphisms. The LEPR Gln223Arg variant was also associated with the changes in plasma total triglycerides and high-density lipoprotein cholesterol concentrations. Further research with larger sample sizes should make it possible to identify the specific contributions of DNA sequence variations at multiple candidate gene loci in the complex response to chronic positive energy balance.

Peripheral regulation of food intake: new insights

Appetite is controlled by a complicated system with hunger and satiety signals interacting in complex pathways both peripherally and centrally. Insulin, leptin and ghrelin are key hormonal regulators of food intake. Ghrelin enhances appetite while leptin is a satiety signal. A novel peripheral regulator of food intake, peptide YY(3-36), is released from the gastrointestinal tract postprandially. In this review old and new peripheral signals and their interaction in the control of food intake are briefly discussed.

Preproghrelin Leu72Met polymorphism in patients with type 2 diabetes mellitus

OBJECTIVES

The association between the Leu72Met polymorphism of the preproghrelin gene and diabetic complications was examined in patients with type 2 diabetes mellitus.

SUBJECTS AND METHODS

A total of 258 patients with type 2 diabetes mellitus and 522 control subjects were screened. Genotypes were determined by polymerase chain reaction technique. The diagnosis of coronary heart disease was based on clinical and ECG criteria. Laboratory analyses were carried out in the hospital laboratory.

RESULTS

No differences in the genotype distributions and allele frequencies of the preproghrelin Leu72Met polymorphism were found between type 2 diabetes mellitus patients and controls. The polymorphism was not associated with macro- or micro-angiopathy or hypertension. However, Leu72Met polymorphism was associated with serum creatinine (P = 0.006) and lipoprotein(a) [Lp(a)] levels (P = 0.006) with Leu72Leu subjects showing the highest values. This association was observed only amongst diabetic group.

CONCLUSIONS

The Leu72Met polymorphism of the preproghrelin gene was not related to cardiovascular disease in type 2 diabetes mellitus patients. Leu72Met polymorphism was, however, associated with serum creatinine and Lp(a) levels in diabetic patients. The mechanism might be associated with a possible change in ghrelin product and its somatotropic effect.

Genetic variation at the adipsin locus and response to long-term overfeeding

OBJECTIVES

The role of adipsin and adipsin Hinc II polymorphisms on the metabolic and body composition changes in response to overfeeding was studied.

SUBJECTS

A total of 12 pairs of male monozygotic twins ate a 4.2 MJ/day energy surplus, 6 days a week, during a period of 100 days.

RESULTS

The preoverfeeding plasma adipsin concentration correlated positively with the change in CT-measured abdominal total and subcutaneous (P<0.05) fat. The changes in abdominal total fat and abdominal subcutaneous fat correlated negatively with changes in plasma adipsin concentrations (P<0.005). Overfeeding induced greater increases in body weight, fat mass, abdominal total and subcutaneous fat (P<0.05) in 6.1 kb noncarriers (n=10) than in 6.1 kb carriers (n=14) of the adipsin Hinc II polymorphism. The 6.1 kb noncarriers had a greater increase in plasma leptin levels (P<0.01). Also the total (P<0.01) and very-low-density lipoprotein (VLDL)-triglycerides (P<0.05), apolipoprotein B (P<0.05) and VLDL-cholesterol (P<0.05) levels increased more in the 6.1 kb noncarriers than in the 6.1 kb carriers.

CONCLUSIONS

Adipsin plasma level could be a predictor of the changes in abdominal subcutaneous fat during times of increased energy intake. However, a greater increase in the abdominal subcutaneous fat was related to a lower increase in the plasma adipsin level. The adipsin Hinc II 6.1 kb allele noncarriers gained more abdominal subcutaneous fat and had a greater increase in plasma levels of leptin- and triglyceride-rich lipoproteins when exposed to a long-term positive energy balance. These findings provide new information on the role of adipsin on individual differences in response to chronically elevated food intake.

Ghrelin Arg51Gln mutation is a risk factor for Type 2 diabetes and hypertension in a random sample of middle-aged subjects

AIMS/HYPOTHESIS

Experimental studies have suggested that ghrelin, a novel gastrointestinal peptide hormone, could play a role in glucose homeostasis. In addition, ghrelin has been associated with beneficial haemodynamic effects in experimental settings. Since the Arg51Gln mutation changes the carboxyterminal amino acid of the mature hormone and is associated with low ghrelin concentrations, we assessed the hypothesis that Arg51Gln mutation is a risk factor for Type 2 diabetes, impaired glucose tolerance, and hypertension.

METHODS

Blood pressure recordings and oral glucose tolerance test were carried out in the hypertensive ( n=519) and control cohorts ( n=526) of our well-defined OPERA study. The genotypes and plasma IGF-I and IGFBP-1 concentrations of 1031 subjects were analysed.

RESULTS

The ghrelin 51Gln allele was a risk factor for Type 2 diabetes, and the effect remained significant after adjustment for age, BMI, and study group (OR=2.53, CI: 1.11-5.75, p=0.027). In addition, the 51Gln allele was a risk factor for hypertension (OR=2.63, CI: 1.37-5.08, p=0.003). 51Gln carriers had lower concentrations of IGF-I and higher concentrations of IGFBP-1 compared to non-carriers.

CONCLUSION/INTERPRETATION

The ghrelin 51Gln allele could increase the risk for Type 2 diabetes and hypertension. The low IGF-I concentrations in 51Gln carriers suggest that the mechanism might be associated with low GH concentrations.

Interactions among the beta2- and beta3- adrenergic receptor genes and total body fat and abdominal fat level in the HERITAGE Family Study

OBJECTIVE AND SUBJECTS

Interactions between markers in the beta2- and beta3-adrenergic receptor (ADR) genes and total body fat and computerized tomography-measured abdominal fat phenotypes were studied in the HERITAGE Family Study cohort of Black (n=205; 81 males and 124 females) and White (n=415; 198 males and 217 females) subjects before and after an endurance training program.

RESULTS

In Black subjects, beta2- and beta3-ADR gene variants showed evidence of interactions on changes in total body fat mass and abdominal fat area (P<0.005 and =0.010, respectively). Black subjects who were carriers of both beta2-ADR Arg16 and beta3-ADR Arg64 alleles had a greater decrease in total fat mass as well as abdominal total and subcutaneous, but not visceral fat areas in response to endurance training than subjects with other genotype combinations (P from 0.011 to 0.047). After correction for multiple tests, the findings remained essentially unchanged for total body fat mass and abdominal fat area, but became nonsignificant for subcutaneous fat area. The changes in abdominal fat correlated positively with the changes in fat mass (P<0.0001). The interactions between beta2 and beta3-ADR gene markers accounted for a maximum of 3% of the variances in the response of total fat mass and abdominal fat area to endurance training in Black subjects but it was not significant in White subjects.

CONCLUSION

Interactions between sequence variants in the beta2-beta3-ADR gene contributed to the changes in fat mass and abdominal adiposity in response to endurance training in Black subjects.

Protein tyrosine phosphatase 1B: a new target for the treatment of obesity and associated co-morbidities

Impaired insulin action is important in the pathophysiology of multiple metabolic abnormalities such as obesity and type 2 diabetes. Protein tyrosine phosphatase 1B (PTP1B) is considered a negative regulator of insulin signalling. This is best evidenced by studies on knockout mice showing that lack of PTP1B is associated with increased insulin sensitivity as well as resistance to obesity and in vitro studies whilst studies in animals and humans have given contradictory results. However, several studies support the notion that insulin signalling can be enhanced by the inhibition of PTP1B providing an attractive target for therapy against type 2 diabetes and obesity. In addition, recent genetic studies support the association between PTP1B with insulin resistance. The development of PTP1B inhibitors has already begun although it has become clear that is not easy to find both a selective, safe and effective PTP1B inhibitor. The objective of this paper is to review the current evidence of PTP1B in the pathophysiology of obesity, type 2 diabetes and cancer as well as in the treatment of these disorders.

Lipoprotein lipase polymorphisms and responses to long-term overfeeding

OBJECTIVES

The role of the lipoprotein lipase (LPL) gene Hind III, S447X, Bam HI and Pvu II polymorphisms on body composition and lipid and lipoprotein changes in response to long-term overfeeding was studied.

SUBJECTS

Twelve pairs of male monozygotic twins ate a 4.2 MJ day-1 energy surplus, 6 days a week, during a period of 100 days.

RESULTS

Overfeeding induced a decrease in high-density lipoprotein 2 cholesterol (HDL2-C) and HDL2-C to HDL3-C ratio in the H2H2 (n = 12) subjects of the LPL Hind III polymorphism. In contrast, the H1H1/H1H2 (n = 12) subjects experienced increases both in the HDL2-C and HDL2-C to HDL3-C ratio (P = 0.009 and 0.007, respectively, for differences in percentage changes between H2H2 and H1H1/H1H2). In addition, the H2H2 genotype was associated with higher levels of very-low-density lipoprotein triglyceride (VLDL-TG) (P < 0.03) and VLDL-C (P < 0.05) before and after overfeeding and higher HDL-TG levels (P < 0.003) after overfeeding. Postheparin lipoprotein lipase (PH-LPL) activity tended to increase in H1H1/H1H2 and decrease in H2H2 subjects. The H2H2 subjects had lower total HDL-C than those with the genotype H1H1/H1H2 4 months and 5 years after overfeeding (P = 0.04 and 0.10, respectively). The plasma lipid differences were similar amongst subjects with the S447S (n = 4) genotype of the S447X and H2H2 genotype of the Hind III polymorphisms. Body composition changes in response to overfeeding were not different between the Hind III genotypes. LPL Pvu II and Hind III polymorphisms were associated weakly with body weight gain (P = 0.015-0.039) but strongly with adipose tissue LPL activity (P < 0.01) after the caloric surplus.

CONCLUSIONS

We conclude that the H2H2 subjects of the LPL gene Hind III polymorphism experience a decrease in the concentration of antiaterogenic lipoproteins when they are exposed to long-term positive energy balance. This may have been partly caused by a diminished catabolism of TG-rich particles in H2H2 subjects. LPL Pvu II and Bam HI polymorphisms were associated with body weight gain and adipose tissue LPL activity. Genetic variation at the LPL locus could thus be one of the factors responsible for the inter-individual differences observed in plasma lipid and lipoprotein responses to chronic positive energy balance. It must be kept in mind that the sample size for this study was small. Nonetheless, it provides useful information on the genes and pathways that should be further explored.

Insulin-like growth factor 2 (IGF2 ) and IGF-binding protein 1 (IGFBP1) gene variants are associated with overfeeding-induced metabolic changes

AIMS/HYPOTHESIS

The aim of this study was to investigate the role of insulin-like growth factor 1 (IGF1), IGF2, IGF binding protein 1 (IGFBP1) and IGFBP3 gene variants on the metabolic changes observed in response to a 100-day overfeeding protocol conducted with 12 pairs of monozygotic twins.

METHODS

Genotyping was done by PCR-RFLP and DNA sequencer methods. Body fat measurements included hydrodensitometry and abdominal fat from computed tomography. Plasma glucose and insulin during fasting and in response to an OGTT were assayed. Plasma lipids were measured enzymatically.

RESULTS

In response to caloric surplus, fasting plasma insulin (p < 0.05) and OGTT insulin (p = 0.004) but not glucose area, increased more among the subjects with IGF2 Apa I GG (n = 12) than those with AA + AG (n = 12). The changes were independent of changes in total fatness. The subjects with IGFBP1 Bgl II AA (n = 8) showed greater increases in abdominal visceral fat (p < 0.01), OGTT insulin area (p = 0.05) and total cholesterol (p < 0.03) with overfeeding than the subjects with AG + GG (n = 16). IGFBP3 Nde I and the IGF1 (CT)n markers were not associated with responsiveness to overfeeding.

CONCLUSION/INTERPRETATION

Insulin sensitivity decreased in the subjects with IGF2 Apa I GG and the subjects with IGFBP1 Bgl II AA showed an accumulation of abdominal visceral fat and the early symptoms of the metabolic syndrome after long-term caloric surplus. Genetic variation at the IGF2 and IGFBP1 loci could be among the factors responsible for the inter-individual differences observed in the response to long-term alterations in energy balance and should be further investigated in larger cohorts.

Genetic variation at the uncoupling protein 1, 2 and 3 loci and the response to long-term overfeeding

OBJECTIVE

To evaluate the effects of uncoupling protein (UCP) 1, UCP2 and UCP3 gene variants on body composition and metabolic changes in response to chronic overfeeding and the recovery after the period of overfeeding.

SUBJECTS AND DESIGN

Twenty-four normal weight men (21+/-2 y), who constituted 12 pairs of identical twins, ate a 4.2 MJ/day energy surplus, 6 days a week, during a period of 100 days. The subjects were asked to return to the laboratory for testing at 4 months and for a final examination 5 y after completion of the overfeeding protocol.

METHODS

Resting metabolic rate (RMR) measurements were performed before and after overfeeding. A 4.2 MJ test meal was consumed, after which calorimetric measurements were continued for 240 min. Total body fat was assessed by hydrodensitometry and total subcutaneous fat by the sum of eight skinfolds. Polymorphisms were typed by PCR and PCR-RFLP-techniques. Thyroid stimulating hormone (TSH) concentrations after a thyrotropin releasing hormone (TRH) injection were measured by radioimmunoassay (RIA).

RESULTS

The changes in body weight and adiposity were not different between UCP1 Bcl I, UCP2 alanine to valine (A55V), UCP2 insertion/deletion (I/D) or UCP3 Rsa I genotypes. However, the recovery from overfeeding was worse among G-allele carriers of the UCP1 Bcl I, I allele non-carriers of the UCP2 I/D, AV heterozygote subjects of the UCP2 A55V and CC subjects of the UCP3 Rsa I polymorphisms. RMR was lower both before (P=0.01) and after (P=0.001) overfeeding in subjects with the CC genotype of the UCP3 Rsa I polymorphism. Moreover, after overfeeding, the UCP2 A55V heterozygote and UCP3 Rsa I CC homozygote subjects had significantly higher respiratory quotient (RQ) values at rest (P<0.01) and during the meal test (P from<0.01 to<0.05). Also mean plasma TSH concentrations 20, 30 and 45 min after the TRH injection increased more with overfeeding among UCP2 A55V (P<0.005) and UCP3 Rsa I CC (P=0.017) subjects.

CONCLUSIONS

These data suggest that UCP polymorphisms may play a role in the recovery from the overfeeding by regulating substrate oxidation in response to long-term caloric surplus. The association of the UCP2 A55V and UCP3 Rsa I CC genotypes with a greater increase in the TSH response to TRH load could reflect a compensatory mechanism counteracting the effects of overfeeding. A longer period of exposure to chronic positive energy balance conditions may be necessary before sequence variation in UCP2 and UCP3 makes an impact on thyroid metabolism to influence body mass and composition changes.

Genome-wide linkage scan to detect loci influencing levels of dehydroepiandrosterones in the HERITAGE Family Study

A genome-wide linkage scan was performed to identify genomic regions that influence levels of dehydroepiandrosterone (DHEA), DHEA sulfate (DHEAS), and DHEA fatty acid esters (DHEA-FA) at baseline and in response to 20 weeks of endurance exercise training in sedentary white and black participants in the HERITAGE Family Study. The baseline levels were log-transformed and adjusted for the effects of age and sex prior to genetic analysis. The training responses were adjusted for the effects of age, sex, and the baseline values. A total of 509 autosomal component polymorphic markers were used for the genome scan with an average spacing of 6.0 Mb. Multipoint variance components linkage analyses were performed in nuclear families containing 360 white and 106 black sibling pairs. We found 5 genomic regions with significant linkages for baseline DHEA-FA in whites, with log odd (LOD) scores over 3.6 (P < 2 x 10(-5)). They include (1) D1S468 (LOD 4.56, 2.533 Mb, 1p36.22); (2) D2S177 (LOD 5.65, 52.663 Mb, 2p16.3); (3) D4S2397 (LOD 3.98, 32.246 Mb, 4p15.2); (4) the paraoxonase loci (LOD 3.93 approximately 3.99, 101.544 approximately 102.933 Mb, 7q21.3), and D7S821 (LOD 3.88, 104.497 Mb, 7q22.1); and (5) D12S372 (LOD 4.66, 2.129 Mb, 12q13.33). In addition, we obtained evidence of suggestive linkages (2.2 < LOD < 3.6; 2 x 10(-5) < P < 7 x 10(-4)) on chromosomes 3p, 6q, and 8q for baseline DHEAS; on chromosomes 2q, 3p, 9q, 10p, 16q, and 17p for baseline DHEA-FA in whites; and on chromosomes 9q and 11p for baseline DHEA in blacks. This is the first genome-wide linkage scan searching for genomic regions influencing human DHEA levels. Several potential candidate genes are located in these genomic regions, which warrant further studies in HERITAGE and other cohorts.

Beta-2 adrenergic receptor variants are associated with subcutaneous fat accumulation in response to long-term overfeeding

OBJECTIVE

The effects of alpha-2A (A2A)-, beta-2 (B2)- and beta-3 (B3)-adrenergic receptor (ADR) gene polymorphisms on adiposity, fat distribution and plasma insulin and leptin changes in response to long-term overfeeding were explored.

METHODS

Twenty four men (mean (+/-s.d.) age 21+/-2 y) who constituted 12 pairs of identical twins ate a 4.2 MJ/day energy surplus, 6 days a week, for a period of 100 days. Total body fat was assessed by hydrodensitometry and total subcutaneous fat by the sum of eight skinfolds. Abdominal fat areas were measured by computerized tomography (CT). Plasma glucose and insulin during fasting and in response to an oral glucose tolerance test (OGTT) were assayed. The insulin and glucose areas were computed using the trapezoidal method. Plasma leptin was measured with an enzyme-linked immunosorbent assay. The ADR polymorphisms were identified by PCR or Southern blot technique.

RESULTS

The ADRB2 Gln27Gln genotype (n=10) was associated with a larger gain (percentage change) in weight (P<0.001) and total subcutaneous (P<0.005) fat than the Glu27Glu/Gln27Glu genotype (n=14). In addition, overfeeding induced greater increases in the insulin areas under the curve during the OGTT and the fasting plasma level of leptin (P<0.01 and <0.03, respectively) among Gln27Gln than in the Glu27Glu/Gln27Glu subjects. The body composition and metabolic changes among the ADRB2 BanI 3.7/3.4 kb subjects (n=10) were similar to those of Gln27Gln subjects. ADRA2A DraI (n=4) 6.3/6.3 kb subjects experienced a decrease (-8%) while 6.7/6.3 kb subjects (n=20) registered an increase (+10%; P=0.017) of OGTT glucose area after the 100-day caloric surplus. The four carriers of the ADRB3 variant (Trp64Arg) experienced the same magnitude of changes as the 20 homozygotes for the Trp allele. In general, comparisons based on the 24 subjects considered as unrelated men and the mean values for each of the 12 pairs yielded similar results.

CONCLUSION

The ADRB2 Gln27Gln subjects gained more weight and total subcutaneous fatness and also experienced a greater increase in insulin resistance than Glu27Glu/Gln27Glu subjects with exposure to long-term overfeeding. Similar differences were observed between carriers and non-carriers of the ADRB2 3.7/3.4 kb BanI variant. Genetic variation at the ADRB2 locus could thus be one of the factors responsible for the large inter-individual differences observed in the response to long-term alterations in energy balance and should be further investigated.

Genetic variation at the lipoprotein lipase locus and plasma lipoprotein and insulin levels in the Québec Family Study

The associations between the S447X, BamHI, HindIII and PvuII DNA variants of the lipoprotein lipase (LPL) gene and indicators of body fat, fat distribution and plasma lipids and insulin were studied in the Québec Family Study cohort. Strong linkage disequilibrium among all the markers was observed. For the S447X polymorphism, plasma very low density lipoprotein (VLDL)-cholesterol (chol) (P<0.001), total triglyceride (TG) (P=0.033) and VLDL-TG (P<0.001) levels were lower and high density lipoprotein (HDL)-chol level higher (P<0.001) in the subjects homozygous or heterozygous for X447 (X447+, n=160) compared to the homozygotes for the S447 allele (X447-, n=576). The BamHI, PvuII and HindIII polymorphisms were not associated with the plasma lipid values when all X447 allele carriers were removed. In addition, the HindIII polymorphism as well as the HindIII and S447X markers combination influenced the insulin area under the curve during an oral glucose tolerance test. We conclude that DNA sequence variation in the LPL gene contributes significantly to the variability in the levels of VLDL-chol, total- and VLDL-TG as well as HDL-chol. The effects of the other polymorphisms considered here are most likely mediated by their linkage disequilibrium with the S447X mutation. In addition, genetic variation at the LPL locus may, by an unknown mechanism, influence insulin metabolism but not body fat variability.

Interactions among the glucocorticoid receptor, lipoprotein lipase and adrenergic receptor genes and abdominal fat in the Québec Family Study

OBJECTIVE

To investigate whether interactions between glucocorticoid receptor (GRL), lipoprotein lipase (LPL) and adrenergic receptor (ADR) gene markers contribute to individual differences in indicators of adiposity and abdominal obesity, including visceral fat level.

DESIGN AND SUBJECTS

Cross-sectional study; 742 individuals from the phase 2 of the Québec Family Study cohort.

MEASUREMENTS

Total body fat assessed by hydrodensitometry and the sum of six skinfolds. Abdominal fat areas measured by computed tomography and adjusted for age, sex and total fat mass in all analyses. GRL Bcl I, alpha 2A-ADR Dra I and beta 2-ADR Ban I markers were typed by Southern blot, and other markers by polymerase chain reaction technique.

RESULTS

It is confirmed that the 4.5 kb allele of the GRL BclI polymorphism is associated with a higher amount of abdominal visceral fat (AVF) depot (P for trend<0.001) independent of the level of total body fat. Furthermore, the alpha 2-ADR Dra I variant is associated with lower cross-sectional areas of abdominal total (P=0.003) and subcutaneous (P=0.012) adipose tissue. Gene-gene interactions between GRL and alpha 2-ADR genes affecting overall adiposity (P=0.016) as well as between GRL and beta 2-ADR genes (P=0.049) having influence on total abdominal fat levels were observed. When the three genes were considered together in the same analysis, significant interactions having influence on overall adiposity (P=0.017), abdominal total (P=0.032) and visceral fat (P=0.002) were observed. About 1-2% of the total variation in total fatness and abdominal fat was explained by these gene-gene interactions.

CONCLUSION

There is an association between the GRL BclI polymorphism and increased AVF levels independent of the level of total body fat. The alpha 2-ADR DraI variant is associated with a lower cross-sectional area of abdominal total fat. Numerous interactions between GRL and ADR markers on overall adiposity and total abdominal fat as well as between GRL, LPL and ADR genes on overall adiposity, abdominal total and visceral fat suggest that the genetic architecture of body fat content and adipose tissue distribution is complex although some genes, like GRL, may have ubiquitous effects.

Mutations in the preproghrelin/ghrelin gene associated with obesity in humans

Ghrelin and preproghrelin sequences were determined in 96 unrelated female subjects with severe obesity (mean body mass index (BMI) 42.3 +/- 3.4 kg/m(2)) and in 96 non-obese female controls (mean BMI 23.0 +/- 1.4 (kg/m2) of the Swedish Obese Subjects cohort. A mutation at amino acid position 51 (Arg51Gln) of the preproghrelin sequence that corresponds to the last amino acid in mature ghrelin product was identified in six (all heterozygotes) obese subjects (6.3%) but not among controls (p < 0.05). The self-reported weight at 20, 30, and 40 years of age tended to be 7.5, 4.7 and 6.4 kg lower, respectively, among obese Gln allele carriers versus obese non-carriers. In addition, a mutation at codon 72 of the preproghrelin gene (Leu72Met) was detected in 15 obese (12 hetero- and 3 homozygotes) and 12 control (all heterozygotes) subjects. This mutation outside the coding region of the mature ghrelin product tended to be associated with lower age of self-reported onset of obesity (15.6 +/- 7.9 vs. 20.5 +/- 10.5 years; p = 0.09). In addition to these two mutations in coding regions, a G274A base change in a non-coding region between exons one and two was found only in two obese individuals. The Arg51Gln amino acid substitution may alter the cleavage site of endoproteases and the length of the mature ghrelin product. The functional significance of the Leu72Met mutation and a G274A base change remains to be determined. In conclusion, the data provide evidence that a low frequency sequence variation in the ghrelin gene could play a role in the etiology of obesity.

Glucocorticoid receptor Bcl I variant is associated with an increased atherogenic profile in response to long-term overfeeding

The effect of the glucocorticoid receptor (GRL) gene Bcl I polymorphism on body composition and metabolic changes in response to overfeeding was studied. Twenty-four men (mean age 21+/-2 years) who constituted 12 pairs of identical twins ate a 4.2 MJ/day energy surplus, 6 days a week, during a period of 100 days. The GRL Bcl I marker was identified by Southern Blot technique. Total body fat was assessed by hydrodensitometry and abdominal fat areas were measured by computed tomography. Fasting plasma glucose and insulin during an oral glucose tolerance test (OGTT) were assayed. The insulin and glucose areas were computed using the trapezoidal method. Triglyceride and cholesterol concentrations in plasma and lipoprotein fractions were determined enzymatically. The results showed that overfeeding induced a greater increase in body weight (p=0.002) in the 2.3/2.3 kb (n=12) than in the 4.5/2.3 kb (n=12) subjects. In addition, plasma levels of total (p=0.007) and low-density lipoprotein (LDL) cholesterol (p=0.003), as well as systolic blood pressure (p=0.036) increased more in the 2.3/2.3 kb than in the 4.5/2.3 kb subjects. The 2.3/2.3 kb genotype was also associated with a greater increase in abdominal visceral fat (p=0.040) compared to the 4.5/2.3 kb genotype. In conclusion, 2.3/2.3 kb subjects of the GRL Bcl I polymorphism experience greater increases in body weight, blood pressure and cholesterol levels as well as visceral fat than 4.5/2.3 kb subjects in response to overfeeding. These data suggest that overfeeding induces an atherogenic profile in subjects who are homozygotes for the 2.3 kb allele.