LEPR gene polymorphisms: associations with overweight, fat mass and response to diet in women.

BACKGROUND: In humans, a mutation of the leptin receptor gene (LEPR) leads to a rare obese syndrome of mendelian inheritance. However, obesity in humans results from interactions between genes and environment, mainly nutritional factors. Variations at the LEPR locus could be involved in the regulation of body weight. DESIGN: Genetic variations at the LEPR locus were screened in a selection of 30 French overweight subjects by Single Strand Conformation Polymorphism (SSCP) analysis, then an association study between genotypes and obesity phenotypes was performed in 179 French overweight patients recruited from the Nutrition Department of Bichat Hospital in Paris who were prescribed a low calorie diet and in 387 unrelated volunteers (98 overweight, 289 normal weight) drawn from the Stanislas Family Study in Nancy. RESULTS: Two new genetic variants were found: T + 70-->C (exon 1) and Asp (A) 96 Asp (G) (exon 4). In Nancy, the T + 70-->C polymorphism was associated with fat mass adjusted for BMI in women (P = 0.025). The genotype and allele frequencies of the Ser (T) 343 Ser (C) polymorphism (exon 9) were significantly different between normal and overweight women, with the T allele being more frequent in the overweight group (T frequency in Nancy, 0.82; in Nancy + Paris, 0.79) than in the normal weight group (0.69; P = 0.017 vs. Nancy overweight, P = 0.003 vs. Nancy + Paris overweight). In women from Nancy, fat mass adjusted for BMI was significantly associated with this polymorphism (P = 0.01). The overweight women carrying the C allele of this polymorphism lost more weight in response to low calorie diet than the non carriers (P = 0.006). CONCLUSIONS: In women, genetic variations at the LEPR gene level are associated with overweight and fat mass in a cross sectional study and with response to low calorie diet in an intervention study. These results indicate that variations at the leptin receptor locus are associated with common obesity phenotypes and are a part of the polygenic influences on the response to nutritional environment.

Association of the G-2548A polymorphism in the 5' region of the LEP gene with overweight.

Mutations in the translated part of the leptin gene (LEP) have been found in only two families. Nevertheless DNA polymorphisms in the LEP region are linked to extreme obesity. We previously found in the 5' region of LEP a polymorphism, G-2548A, associated with a differerce in BMI reduction following a low calorie diet in overweight women. Recently, this polymorphism was associated with extreme obesity in women. In this work, we genotyped a new sample from the general population including 314 normal weight (BMI < 27 kg/m2) and 109 overweight subjects (BMI > or = 27 kg/m2). The genotype and allele frequencies were significantly different between groups, with the G-2548 allele being more frequent in the overweight subjects (p < 0.01). In men, carriers of this allele had lower leptin concentrations adjusted for fat mass (p = 0.05). Our results indicate that variations at the leptin locus are associated with common obesity phenotypes, and not only with extreme obesity or the rare mendelian obesity syndromes.

Correlation between increased cortisol:DHEA ratio and malnutrition in HIV-positive men.

Malnutrition in HIV-infected patients is characterized by a loss of both fat-free mass (FFM) and fat mass (FM). Glucocorticoids and androgens change during the course of the infection and may play a key role in the protein balance. The serum concentrations of cortisol, adrenal (DHEA and DHEA sulfate) and gonadal androgens (androstenedione, testosterone, and dihydrotestosterone) of HIV-positive men were measured and compared with several parameters of body composition as a function of body weight loss (BWL). The patients were assigned to one of five groups according to their BWL: group I (controls, n = 10) < 5%, group II (n = 7) 5-10%, group III (n = 8) 10.1-16%, group IV (n = 9) 16.1-24%, and group V (n = 4) > 24.1%. Correlation analysis showed significant positive or negative relationships between several markers of malnutrition and adrenal androgens and the cortisol:DHEA ratio, but not with cortisol. BWL was negatively correlated with DHEA (r = -0.69, P < 0.0001), DHEA sulfate (r = -0.58, P < 0.0001) and testosterone (r = -0.34, P < 0.03), but positively with the cortisol:DHEA ratio (r = 0.61, P < 0.0001). In contrast, BCM was positively correlated with DHEA (r = 0.34, P < 0.04) and DHEA sulfate (r = 0.36, P < 0.03) and negatively with the cortisol:DHEA ratio (r = -0.58, P < 0.0001). The cortisol:DHEA ratio was also negatively correlated with BMI (body mass index) (r = -0.56, P < 0.01), fat-free mass (r = -0.48, P < 0.004), fat mass (r = -0.39, P < 0.02), and BCM:weight ratio (r = -0.47, P < 0.005) and positively with the extracellular:intracellular water ratio (r = 0.54, P < 0.001). These data indicate that the steroid hormone environment of patients, particularly their cortisol:DHEA ratio, is linked to the malnutrition associated with HIV infection. The decreased DHEA and increased cortisol in patients with the advanced stages of disease could be associated with increased protein catabolism.

Development of a method to separate lipoprotein-bound and lipoprotein-depleted tissue factor pathway inhibitor. Measurement of free tissue factor pathway inhibitor activity.

The aim of this study was to develop a method to separate lipoprotein-bound from lipoprotein-free tissue factor pathway inhibitor (TFPI) and to measure the TFPI chromogenic activity and antigen in both fractions. This was performed by ultracentrifugation of plasma, after increasing its density to 1.21 g/ml with potassium bromide. Blood was taken from nine volunteers before and after an injection of low-molecular-weight heparin. The ultracentrifugation procedure was adequate, since the mean cholesterol recovery was 91% and only 2% of the cholesterol remained in the lipoprotein-depleted fraction. No free TFPI protein was found in the lipoprotein-rich fraction. Moreover, the amount of free TFPI in the lipoprotein-depleted fraction was close to that found in plasma. Using this method, we confirmed that heparin does not induce an increase in bound TFPI and that the moderate increase in total TFPI antigen in plasma is entirely caused by the enhancement of free TFPI. We then applied the TFPI chromogenic assay to the lipoprotein-depleted fraction to assess the activity of free TFPI. The activity was 0.11+/-0.03 and 0.36+/-0.08 U/ml before and after heparin, respectively (a 3.6-fold increase) while the activity of bound TFPI did not increase at all. We suggest that this method may be an alternative to gel filtration for measuring free TFPI activity, and might be of value in the search for TFPI abnormalities in patients with thrombosis.

Serum cortisol and DHEA concentrations during HIV infection.

The progression of HIV infection is accompanied by severe immunodepression and cachexia, particularly during advanced stages. The immune depression is due largely to a dramatic drop in the number of CD4 cells. The loss of body weight is mainly due to a reduced fat-free mass with no change in adipose tissue. We determined the serum concentrations of cortisol and DHEA and their correlations with absolute CD4 cell counts and changes in body weight of HIV-positive men. The results of five retrospective and prospective studies indicate that the serum concentrations of cortisol and DHEA in HIV-infected patients were different from those of HIV-negative controls. Serum cortisol was elevated at all stages of infection (+20 to +50%, p < .05 to p < .001) particularly in AIDS patients (stage IV C). In contrast, the serum DHEA concentrations were closely correlated with the stage of HIV-infection, being higher in the early stages (stages II and III or > 500 CD4) than in advanced stages (IV C or < 500 CD4)-in the latter being below those of HIV-negative men-or in controls (+40 to 100%, p < .01 to p < .001). There was a negative linear correlation between the CD4 cell counts and cortisol (r = -0.4, p < .02) and a positive linear correlation with DHEA (r = +0.36, p < .01). There was no significant correlation between delta body weight and serum cortisol. In contrast, there was a negative correlation between serum DHEA and delta body weight (%) (r = -0.69, p < .0001) and a positive correlation with the cortisol/DHEA ratio (r = +0.61, p < .0001). There is thus a link between the circulating concentrations of adrenal steroids and the progression of immunosuppression and cachexia during HIV-infection. This raises the question of whether there is a cause-and-effect relationship between clinical progression and circulating steroid concentrations. Further investigations into the relationship between the ratio cortisol/DHEA and the immune response and cachexia should indicate the contributions of these steroids to the etiology of HIV infection and lead to the development of new therapeutic strategies.