Leptin and the adipocyte endocrine system

Trans fatty acids: effects on metabolic syndrome, heart disease and diabetes

The major dietary sources of trans fatty acids (TFAs) in most countries are partially hydrogenated vegetable oils. TFA consumption is a modifiable dietary risk factor for metabolic syndrome, diabetes mellitus, and coronary heart disease. Here, we review the available data on various effects of TFAs, including metabolic and signaling pathways that mediate these effects, affected tissues, and relationships with clinical end points. TFA consumption causes metabolic dysfunction: it adversely affects circulating lipid levels, triggers systemic inflammation, induces endothelial dysfunction, and, according to some studies, increases visceral adiposity, body weight, and insulin resistance. Dietary TFAs influence the function of multiple cell types, including hepatocytes, adipocytes, macrophages and endothelial cells. Among dietary fats and nutrients, TFAs seem to have a unique cardiometabolic imprint that is linked to insulin-resistance and metabolic-syndrome pathways. Consistent with these adverse physiological effects, consumption of even small amounts of TFAs (2% of total energy intake) is consistently associated with a markedly increased incidence of coronary heart disease. Relationships between TFA consumption and diabetes mellitus have been less consistent, possibly owing to differences in study designs. Nevertheless, the documented adverse effects of TFAs underscore their potential to cause harm and the importance of policy measures to minimize consumption of industrially produced TFAs.

Deleterious effects of high-fat diet on perinatal and postweaning periods in adult rat offspring

BACKGROUND & AIMS

Pre- and postnatal environmental changes can reset the developmental path during intrauterine development leading to obesity and cardiovascular and metabolic disorders later in life. The effects of high-fat diets on body mass, fat mass, the plasma level of glucose, insulin and leptin, as well as the insulin/glucose ratio and cardiovascular parameters in adult rat offspring were studied.

METHODS

Pregnant Wistar rats in a standard chow group (SC) or high-fat chow group (HFC), at weaning their SC and HFC offspring were randomly divided into two postnatal groups: fed on SC or HFC. With euthanasia at 6-month-old, three-way ANOVA there were three-factor interactions among gender, perinatal diet and postweaning diet to body mass (BM), BP, left ventricle (LV) thickness, carbohydrate metabolism, plasma corticosterone concentrations and leptin/fat mass/adipocyte size pattern.

RESULTS

HFC/SC and SC/HFC offspring of both genders had high BM and BP, which were increased in HFC/HFC offspring. There was hyperinsulinism, hyperleptinemia, as well as high insulin/glucose ratio and high plasma corticosterone concentrations mainly in HFC/HFC offspring with adipocytes and LV hypertrophy.

CONCLUSIONS

Postweaning HFC was deleterious to the health of adult offspring from dams fed HFC during pregnancy and then during the first half of lactation period. HFC administrated in both periods shows supplementary effects, elevating BP with consequent LV hypertrophy, altering carbohydrate metabolism, plasma corticosterone concentrations and disturbing leptin/fat mass/adipocyte size pattern.

Beneficial effects of physical exercise on hypertension and cardiovascular adverse remodeling of diet-induced obese rats

BACKGROUND AND AIMS

Obesity is present among all age groups and in all socioeconomic groups. This study on obese rats aims to quantify the beneficial effects of physical exercise on blood pressure (BP), the heart, the elasticity and resistance of arteries.

METHODS AND RESULTS

Obese male Wistar rats, (obesity due to a high fat diet with 30% fat), and non-obese rats, were assigned to four groups (n=5): sedentary obese; exercise-practice obese; sedentary control; and exercise-practice control (motor treadmill for 13 weeks). Their organs were studied through light microscopy and stereology. The diet-induced obesity caused mild hypertension with adverse cardiovascular changes. Physical exercise diminished the alterations associated with BP elevation and obesity. The pressure-lowering effect observed in obese rats submitted to physical exercise improved the myocardial vascularization and the aortic and the carotid wall structure by reducing the thickness and normalizing both the elastic lamellae and the smooth muscle cells. The adaptive response of the gluteus superficialis muscle to physical exercise also improved the peripheral resistance arteries of obese rats.

CONCLUSION

Current research supports the notion of physical exercise as a potential non-pharmacological antihypertensive treatment for diet-induced obesity hypertension.

Ageing and plasma adiponectin concentration in apparently healthy males and females

OBJECTIVE

It is well known that ageing is associated with several hormonal alterations. However, the consequence of ageing on the endocrine function of adipose tissue is not fully elucidated. Adiponectin is a new anti-inflammatory protein secreted exclusively by adipocytes and plays a protective role against insulin resistance and atherosclerosis. Therefore, the aim of present study was to estimate plasma adiponectin concentration in apparently healthy elderly subjects.

SUBJECTS

Fifty-eight women and 67 men aged 20-93 years were included in this study. Subjects were divided into three groups: younger than 50 years, between 50 and 70 years and older than 70 years of age.

MEASUREMENTS

Plasma adiponectin concentration was estimated by an enzyme-linked immunosorbant assay in blood samples withdrawn in the morning after overnight fasting. In males plasma testosterone and dehydroepiandrostendione sulphate concentrations were assessed by a radioimmunoassay method.

RESULTS

Plasma adiponectin concentration only tended to be higher in all elderly subjects (above 70 years) than in the group of all subjects aged between 50 and 70 and the group younger than 50 years of age (12.8 +/- 5.7; 9.9 +/- 5.7 and 10.7 +/- 5.4 microg/ml, respectively). Plasma adiponectin concentration was of similar magnitude in female subjects of these three groups (11.2 +/- 5.7; 11.2 +/- 6.8 and 11.7 +/- 4.9 microg/ml, respectively). In contrast, males over 70 years old are characterized by significantly higher plasma adiponectin (14.0 +/- 5.4 microg/ml) concentration than males between 50 and 70 years of age (8.9 +/- 4.7 microg/ml, P < 0.01) and males younger than 50 years of age (9.6 +/- 5.7 microg/ml, P < 0.05). In the entire studied group a significant but weak, positive correlation was found between plasma adiponectin concentration and age (tau = 0.12; P = 0.04). Additionally, significant correlation was found between plasma adiponectin concentration and age in males when analysed separately (tau = 0.28; P = 0.0007). Such correlation was not significant in females (tau = -0.06; P = 0.5).

CONCLUSIONS

Plasma adiponectin concentration in females did not change significantly with age. In contrast to females, elderly males over 70 years of age are characterized by significantly higher plasma adiponectin concentration than younger ones.

Correlates of adiponectin and the leptin/adiponectin ratio in obese and non-obese children

Adiponectin is an adipocyte secreted protein that has been reported to increase fatty acid oxidation and improve insulin sensitivity. Our aim was to study the relationship between adiponectin and leptin, body fat, insulin and lipoproteins in obese compared to non-obese children matched for age and gender. Adiponectin serum concentrations were significantly lower in the obese compared to the non-obese children (9.1+/-3.7 vs 17.1+/-12.3 microg/ml, p <0.05), in contrast to serum leptin concentrations which were greater in the obese compared to the non-obese subjects (31.8+/-11.1 vs 8.2+/-5.7 ng/ml, p <0.001). When considered as a single group to assess adiponectin concentrations over a spectrum of body size, adiponectin values correlated inversely with body weight (r = -0.33, p <0.05) and BMI (r = -0.35, p <0.05). Adiponectin values correlated directly with HDL-C (r = 0.47, p <0.005), but not with total cholesterol, IGF-I, or leptin binding activity. Since leptin and adiponectin change inversely in relation to BMI, the leptin/adiponectin (L/A) ratio was determined as a potential index relating adiposity to the development of complications of obesity. The L/A ratio was eight-fold greater in the obese compared to the non-obese children, and correlated more strongly with BMI (r = 0.779, p <0.0001) and with HDL-C (r = -0.53, p <0.001), than did adiponectin alone. The L/A ratio also correlated significantly with triceps skinfold thickness (TSF) (r = 0.77, p <0.001) and percent body fat (r = 0.79, p <0.0001) in non-obese children. These data suggest that adiponectin concentrations are already differentially regulated in childhood obesity. The index of increased leptin concentration corrected by reduced adiponectin values (L/A ratio) merits investigation as a marker for morbidities associated with childhood obesity.

Comparison of renal morphology in the Streptozotocin and the SHR/N-cp models of diabetes

The Streptozotocin (STZ) model of diabetes is commonly used for studies of diabetic nephropathy although the histological lesions of the kidney are mild and do not resemble those seen in diabetic patients. The SHR/N-cp rat model of type II diabetes spontaneously develops pronounced abnormalities in renal histology. In the present study, we compared renal morphology in the STZ rat and the diabetic SHR/N-cp rat. Sprague-Dawley rats received STZ, developed diabetes after 2 days and were treated with insulin. In the SHR/N-cp rat, obesity is inherited as an autosomal recessive trait. The progeny are either lean (used as controls) or obese and diabetic. After 6 months of observation, STZ and SHR/N-cp rats were killed. The renal damage was evaluated by assessing damage indices and by using stereological techniques. In addition, immunohistochemistry and electron microscopy were performed. The glomerular and tubulointerstitial changes were much more pronounced in the diabetic SHR/N-cp compared to the STZ model. In parallel glomerular PCNA+cells were significantly more frequent and expression of TGF-beta and PDGF by immunohistochemistry in glomeruli and in the tubulointerstitial space was more pronounced in SHR/N-cp compared to STZ rats. The glomeruli of SHR/N-cp contained less and larger podocytes as well as smaller mesangial cells embedded in more mesangial matrix compared to STZ. Similarly, less, but larger endothelial cells were found in SHR/N-cp than in STZ rats. The mean glomerular volume was similarly increased in the two models. Albumin excretion was only modestly increased in STZ diabetes, but pronounced in the SHR/N-cp rat. Although the STZ model of diabetes exhibits numerous biochemical sequelae of hyperglycemia, the morphological lesions are unimpressive. In contrast, the diabetic SHR/N-cp exhibits marked structural lesions, particularly podocyte damage and mesangial expansion that promise to make it a more suitable model for investigation of diabetic glomerulosclerosis.