Chemical-physical properties of lipoproteins in anorexia nervosa

BACKGROUND

Anorexia nervosa (AN), a psychosomatic disorder, has serious negative effects on multiple organs and systems of the human body. Anorexia nervosa usually runs a chronic course and is associated with significant morbidity and mortality. In order to elucidate the role played by lipids in AN, in the present study we compared the plasma lipid profile and the chemical-physical properties of lipoproteins obtained from subjects affected by AN.

MATERIALS AND METHODS

The study was performed on lipoproteins of AN subjects and of age-matched healthy subjects used as controls. We tested the susceptibility to oxidative stress in vitro, the fatty acid content, the fluidity using 2-dimethylamino-(6-lauroyl)-naphthalene (Laurdan) and 1,6-difenil-1,3,5-esatriene (DPH) probes.

RESULTS

Present results indicate that AN patients present a deep alteration of the composition and of chemical-physical properties in circulating lipoproteins, even in the absence of significant modifications to clinical metabolic parameters. A significantly decreased body mass index (BMI) was found in AN patients in comparison with controls. Anorexia nervosa patients showed a significant modification of phospholipids to protein ratio and a significantly increased percentage of unsaturated fatty acids compared with control subjects as well as a decreased fluidity, a significantly increased percentage of liquid-crystalline phase in VLDL, and a significantly reduced susceptibility to oxidative stress, more pronounced in LDL.

CONCLUSIONS

These results confirm the hypothesis that anorexia is accompanied by changes of lipid metabolism in the central nervous system (CNS).

Comparison of circulating and local adipose tissue renin-angiotensin system in normotensive and hypertensive obese subjects

The renin-angiotensin-aldosterone system (RAAS) plays a well-recognized role in the regulation of BP and in salt and water balance. Since hypertension affects a considerable proportion of obese patients, circulating RAAS has been studied in obese subjects with and without hypertension, albeit with conflicting results. Furthermore, attention has recently focused on the expression of the components of the Renin-angiotensin system (RAS) in some organs, including adipose tissue where it seems to be involved in the regulation of growth and differentiation. The aim of our study was to investigate circulating RAAS and adipose tissue RAS in obese patients with and without hypertension and in matched controls. PRA, and plasma and urinary aldosterone levels were measured in 35 obese, 30 hypertensive obese patients and in 20 controls. In addition, the expression of angiotensinogen (AGT) and angiotensin II type 1 receptor (AT1) genes was studied in sc adipose tissue from 8 obese, 6 hypertensive obese and 6 healthy subjects. As previously demonstrated in other studies, there were no significant differences in the levels of circulating RAAS components in the 3 groups. As regards local RAS, interestingly, we found that AT1 gene was significantly more expressed in sc adipose tissue from obese patients with hypertension than in those without hypertension and controls. By contrast, AGT levels were similar in the 3 groups. Our data do not support the hypothesis of an involvement of circulating RAAS in the development of obesity-related hypertension. On the other hand, local RAS seems to be differently regulated in sc adipose tissue from obese patients with hypertension with respect to normotensive obese patients and controls.

Contribution of weight cycling to serum leptin in human obesity

OBJECTIVE

To investigate to what extent serum leptin concentrations in obese humans are influenced by a history of weight cycling.

DESIGN

Cross-sectional study on serum leptin concentrations and body composition in a cohort of obese subjects in whom a retrospective recall of weight and diet history was made.

SUBJECTS

One hundred and twenty-eight obese patients (89 females and 39 males), aged 18-61 y, body mass index (BMI) 31.2-63.4 kg/m(2).

MEASUREMENTS

Serum leptin; various fatness and fat distribution parameters (by anthropometry and bioelectrical impedance analysis); history of overweight at puberty; number, magnitude and timing of previous diet episodes and of consequent weight regain by interview.

RESULTS

By univariate analysis, serum leptin concentrations were significantly correlated with weight, waist-hip ratio, percentage body fat, maximal percentage weight loss in a single diet episode, cumulative percentage weight loss in all diet episodes, cumulative weight regained in all diet episodes, but not with the number of diet episodes. All correlations related to anthropometric and body composition parameters were stronger for men, compared to women, although the male subgroup was smaller. On the contrary, there was a strong positive correlation between weight cycling parameters and serum leptin in women but not in men. Leptin concentrations were significantly higher in patients who were overweight at puberty than in those who were not overweight at puberty. After correction for percentage body fat, presence of overweight at puberty did not correlate any longer with leptin concentrations in either gender. In women, cumulative percentage weight loss in all diet episodes contributed an additional 5% to the variance of serum leptin in the overall model.

CONCLUSION

The positive correlation between weight cycling and leptin concentration in obesity is mainly accounted for the higher percentage body fat in obese weight cyclers, although in women weight cycling per se independently contributes to the variance of serum leptin.

Adipose tissue as an endocrine organ? A review of some recent data

Recent clinical and experimental data have radically modified the concept of adipose tissue as one solely devoted to energy storage and release. Adipose tissue is a target organ for glucocorticoids. Several studies of the function of the hypothalamic-pituitary-adrenal axis in obese subjects have failed to reach conclusive results. An innovative finding is that adipose tissue produces cortisol from its inactive precursor, cortisone. Identification of leptin, a hormone synthesised by adipose tissue, has ushered in the modern view that it is a true endocrine organ. Leptin is produced by subcutaneous and to a lesser extent by visceral adipose tissue. It has a central role in body weight and especially fat stores regulation, but is also involved in several complex functions, including the physiological processes associated with puberty. Angiotensinogen (AGT), another hormone synthesised in abundance by adipose tissue, is produced in larger amounts by visceral than subcutaneous fat. In addition, in man and animals adipose tissue appears to possess the whole renin-angiotensin system (RAS), suggesting that angiotensin II, the final effector of the system, is locally produced. The function of adipose RAS is not well known; besides participating, together with other hormones and substances, in adipocyte differentiation and fat tissue growth, it could be involved in the pathogenesis of the complications of obesity. All these findings have opened interesting prospects and are expected to yield further stimulating insights into the physiopathology of the adipose organ.

Gene expression of angiotensinogen in adipose tissue of obese patients

Recently, the genes of components of the renin-angiotensin system (RAS), namely angiotensinogen (AGT), angiotensin converting enzyme and angiotensin II receptor have been described in adipose tissue. In animal models the angiotensinogen in adipose tissue has been implicated in the pathogenesis of metabolic alterations and hypertension associated with obesity. The aim of our study was to evaluate the AGT gene expression both in visceral and subcutaneous adipose tissue in obese patients and lean subjects. AGT mRNA levels were measured by reverse transcriptase polymerase chain reaction (RT-PCR) using specific primers. AGT mRNA was expressed at variable levels in obese patients. It was significantly greater in visceral than in subcutaneous adipose tissue. Positive and significant correlation was found between the expression of AGT in visceral adipose tissue and BMI. These data suggest that angiotensinogen may be determinant of fat distribution and may be involved in the plurimetabolic syndrome of central obesity.

Physicochemical and functional modifications induced by obesity on human erythrocyte membranes

BACKGROUND

Na+,K(+)-ATPase activity was evaluated in relation to membrane composition and molecular organization in erythrocyte membranes from obese patients by the amphyphylic molecule 6-dodecanoyl-2-dimethylamino-naphthalene (Laurdan). Its possible relationship with fat distribution and hyperinsulinaemia was also investigated.

DESIGN

Subjects were 10 obese men (OM), 12 women with subcutaneous obesity (FSO), 10 women with abdominal obesity (FAO) and 41 healthy lean subjects, 26 women (FC) and 15 men (MC). An oral glucose tolerance test was administered to all subjects to evaluate insulin secretion and glucose tolerance.

RESULTS

Na+,K(+)-ATPase activity was increased in all obese patients. Values were higher in FSO and FAO than in FC (with FAO greater than FSO) and in OM than in MC. The erythrocyte membrane cholesterol-to-phospholipid ratio was increased in obese patients and was significantly different in FSO patients compared with FC. The erythrocyte membrane protein-to-phospholipid ratio was also increased in all obese subjects, reaching statistical significance only in FSO vs. FC. The liquid crystalline phase, as tested by Laurdan generalized polarization (GP), was decreased in obese patients, indicating the presence of greater molecular environmental order; all patients groups showed lower GP values than control subjects, but only FAO reached statistical significance compared with FC. There was no evident correlation between membrane Na+,K(+)-ATPase activity and insulin levels, nor did membrane composition and properties show any evident relationship with insulin levels.

CONCLUSION

Both increased Na+,K(+)-ATPase activity and altered fluidity and lipid composition were observed in the erythrocyte membrane of all obese patients. These findings are in line with previous observations by our group and indicate that the changes in Na+,K(+)-ATPase activity observed in obese patients could be related to changes in plasma membrane organization and composition.

[Scrofula in an elderly woman. A clinical case]

The case is described of an elderly woman with scrofula. The peculiarity of this case consisted in the comparative rarity of primary tubercular lymphadenopathy (a pathology that in the past used to be common in poor socioeconomic conditions) even considering the present renewed diffusion of tuberculosis; especially as this elderly patient had no previous history of tubercular infection.