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S Stan

Publications and source records attributed to S Stan.

13 recordsLinked to original sources
PubMed2006

Dietary fat and fat types as early determinants of childhood obesity: a reappraisal.

BACKGROUND: The growing prevalence of childhood overweight and obesity has renewed interest in determining the influence of the maternal and infant diet on the risk of developing excess fat mass later in life. APPROACH: Review of available human and animal data reporting the effects of dietary fat and fat types early in life on adipose development. RESULTS: Rodent studies tend to show that maternal high-fat feeding during pregnancy and lactation results in increased adiposity of the offspring. Nevertheless, today there is a lack of population-based studies investigating this potential detrimental effect of maternal high-fat intake. Most epidemiological studies, performed so far, do not find any association between the level of dietary fat intake of infants and children and body weight and/or fatness. Regarding fat types exposure to high levels of dietary n-6 fatty acids during gestation and post-natal life, has been shown to promote obesity in mice. Nevertheless, other rodent studies do not demonstrate such an effect. CONCLUSION: There is no evidence supporting a restriction of fat intake during the first two post-natal years but the potential detrimental effects of maternal high-fat intake during gestation should be further investigated. The role of dietary fat types as early determinants of childhood obesity has so far been poorly studied. Robust evidence to support the adipogenic effects of n-6 fatty acids enriched-diets is currently lacking but this hypothesis is of importance and should be further evaluated in different animal models as well as in longitudinal human studies.

Adiposity↗
PubMed2001

Effect of human recombinant leptin on lipid handling by fully differentiated Caco-2 cells.

It has been established that leptin displays a number of effects on peripheral tissues. We have investigated the effect of the hormone on lipid synthesis, apolipoprotein biogenesis and lipoprotein secretion in Caco-2 cells. Immunocytochemistry revealed the presence of leptin receptors (Ob-Rb) on the basolateral membrane. Incubation of cells with 200 nM leptin resulted in a decreased export of triglycerides in the basolateral medium without affecting monoglyceride, diglyceride and cholesterol ester lipid classes. It also significantly reduced the output of de novo-synthesized apolipoprotein (Apo)B-100 and ApoB-48 as well as that of newly formed chylomicrons and of low-density lipoproteins. It also enhanced that of ApoA-I, ApoA-IV and ApoE. Our results support the hypothesis that leptin can affect energy balance at the gut level by reducing lipid release into the circulation.

Apolipoproteins↗
PubMed2001

The polymorphism at codon 54 of the FABP2 gene increases fat absorption in human intestinal explants.

Based on titration microcalorimetry and Caco-2 cell line transfection studies, it has been suggested that the A54T of the FABP2 gene plays a significant role in the assimilation of dietary fatty acids. However, reports were divergent with regard to the in vivo interaction between this polymorphism and postprandial lipemia. We therefore determined the influence of this intestinal fatty acid-binding protein polymorphism on intestinal fat transport using the human jejunal organ culture model, thus avoiding the interference of various circulating factors capable of metabolizing in vivo postprandial lipids. Analysis of DNA samples from 32 fetal intestines revealed 22 homozygotes for the wild-type Ala-54/Ala-54 genotype (0.83) and 10 heterozygotes for the polymorphic Thr-54/Ala-54 genotype (0.17). The Thr-encoding allele was associated with increased secretion of newly esterified triglycerides, augmented de novo apolipoprotein B synthesis, and elevated chylomicron output. On the other hand, no alterations were found in very low density lipoprotein and high density lipoprotein production, apolipoprotein A-I biogenesis, or microsomal triglyceride transfer protein mass and activity. Similarly, the alanine to threonine substitution at residue 54 did not result in changes in brush border hydrolytic activities (sucrase, glucoamylase, lactase, and alkaline phosphatase) or in glucose uptake or oxidation. Our data clearly document that the A54T polymorphism of FABP2 specifically influences small intestinal lipid absorption without modifying glucose uptake or metabolism. It is proposed that, in the absence of confounding factors such as environmental and genetic variables, the FABP2 polymorphism has an important effect on postprandial lipids in vivo, potentially influencing plasma levels of lipids and atherogenesis.

Absorption↗
PubMed2001

Circulating lipoproteins and hepatic sterol metabolism in Psammomys obesus prone to obesity, hyperglycemia and hyperinsulinemia.

The liver plays a central role in lipoprotein metabolism and cholesterol homeostasis. As the physiopathology of lipid disorders in non-insulin-dependent diabetes mellitus (NIDDM) is multifactorial and still imperfectly known, we evaluated its onset on plasma lipid transport and hepatic cholesterol metabolism in Psammomys obesus. This sand rat lapses into hyperinsulinemia and hyperglycemia when transferred from its native food to laboratory rodent diets. Marked hypertriglyceridemia and hypercholesterolemia developed in hyperinsulinemic (Group B) and hyperglycemic/ hyperinsulinemic (Group C), compared with normal P. obesus (Group A). Group B showed significantly (P<0.05) higher plasma VLDL-cholesterol (41.9%) and LDL-cholesterol (47.3%) concentrations, whereas Group C was characterized by an even more marked increase in VLDL-cholesterol (176%, P<0.001) compared with Group A. Lipoprotein composition was also altered, displaying impaired lipid and apolipoprotein moiety distribution in IDL, LDL, HDL(2) and HDL(3) lipoprotein fractions of Groups B and C. The activity of hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-limiting enzyme in cholesterol biosynthesis, was consistently lower in Group B (P<63.4%, P<0.001) and C (43.9%, P<0.005). In contrast, the direct measurement of microsomal acyl-CoA:cholesterol acyltransferase (ACAT), controlling the acylation of cholesterol, showed an increase averaging 53% in Group B (P<0.01) and 61% in Group C (P<0.005). Similarly, elevated activity (171.1%, P<0.05 and 291.4%, P<0.001, respectively) was related to cholesterol 7alpha-hydroxylase, the rate-limiting enzyme in bile acid biosynthesis. These alterations were accompanied with abundant deposition of triglycerides and cholesterol in the liver. Changes in circulating lipids and liver parameters were related to glucose and insulin levels, indicating the implication of insulin resistance and diabetes. Therefore, our findings demonstrate various disturbances in plasma lipid profile and lipoprotein composition, as well as in liver cholesterol metabolism during the sequential development of insulin resistance and diabetes in P. obesus rats. Furthermore, the current data point to an undoubtedly important role of the liver in the pathogenesis of metabolic disorders in the progression of nutritionally-induced insulin resistance and diabetes in P. obesus. Finally, current research shows that more marked plasma and hepatic lipid perturbations occur in insulin resistance than in diabetes, which may culminate in the development of atherosclerosis.

Animals↗
PubMed2001

Immunolocalization, ontogeny, and regulation of microsomal triglyceride transfer protein in human fetal intestine.

To examine the multiple stages of lipoprotein packaging during development, we studied localization, ontogeny, and regulation of microsomal transfer protein (MTP), a crucial protein for lipid transport. With the use of immunofluorescence, MTP was identified in villus and crypt epithelial cells in different regions of human fetal intestine, including colon. Staining was detected as early as the 13th wk of gestation in all gut segments and was almost entirely confined to the columnar epithelial cells of the jejunum and colon. Unlike immunofluorescence, which provides qualitative but not quantitative information on MTP signal, enzymatic assays revealed a decreasing gradient from proximal small intestine to distal, as confirmed by immunoblot. Activity of MTP in small intestinal explants cultured for different incubation periods (0, 4, 8, and 24 h) peaked at 4 h but remained insensitive to different concentrations of oleic acid. Also, a trend toward increasing MTP activity was observed at 20-22 wk of gestation. Finally, in strong contrast to jejunal efficiency, colonic explants displayed impaired lipid production, apolipoprotein biogenesis, and lipoprotein assembly, in association with poor expression of MTP. These findings provide the first evidence that human fetal gut is able to express MTP and emphasize the distinct regional distribution, regulation by oleic acid, and ontogeny of MTP.

Adult↗
PubMed2001

Deep vein thrombosis in patients admitted for exacerbation of chronic obstructive pulmonary disease.

INTRODUCTION: There is a lack of data on the prevalence of deep vein thrombosis and pulmonary embolism in patients admitted to hospital for exacerbation of chronic obstructive pulmonary disease. Studies have found that most pulmonary embolism originate from deep vein thrombosis in the lower limbs, thus the prevalence of deep vein thrombosis may give an accurate reflection of the prevalence of pulmonary embolism. The aim of our study was to determine the prevalence of deep vein thrombosis in these patients, using duplex ultrasound of the lower limbs as the screening tool. METHODS: Thirty-three male patients admitted to the general ward for exacerbation of chronic obstructive pulmonary disease were screened for presence of deep vein thrombosis of the lower limbs using duplex ultrasound scan. RESULT: No patient in this study was found to have deep vein thrombosis of the lower limbs. CONCLUSIONS: The prevalence of deep vein thrombosis in local patients admitted for exacerbation of chronic obstructive pulmonary disease is likely to be low. We do not recommend the use of duplex ultrasound to screen for deep vein thrombosis in this group of patients.

Aged↗
PubMed1999

Modulation of apo A-IV transcript levels and synthesis by n-3, n-6, and n-9 fatty acids in CACO-2 cells.

It has been postulated that apolipoprotein (apo) A-IV plays various significant roles in lipid transport and lipoprotein metabolism. Although it is controlled by fat feeding, so far little else is known about its regulation by specific fatty acids. In this study, we focused on the modulation of apo A-IV mRNA levels, mass, and biogenesis by mono- and polyunsaturated fatty acids (FA) in the human intestinal Caco-2 cell line. In confluent cells incubated with 1 mM oleic (n-9), linoleic (n-6), alpha-linolenic (n-3), or docosahexaenoic (n-3) acids for a long-term period, both apo A-IV protein levels and de novo synthesis were increased. The induction resulted from the up-regulation of apo A-IV mRNA transcripts. In contrast, an inhibitory effect was evident with short-term incubation. FA chain length and degree of unsaturation had little effect altering apo A-IV transcript and biogenesis. These data offer evidence that isolated fatty acids regulate gene expression and the production of apo A-IV in the enterocyte.

Apolipoproteins A↗
PubMed1989

[A new approach to the biomechanics of the normal and pathologic lumbar disk using the finite element method].

The model was created based on the L2-L3 intervertebral disc considering it to be symmetrical on a longitudinal axis and a mid-transverse plane and could be subjected to a longitudinal load of 400 N in compression. The analysis of this two-dimensional problem by using the finite element program S.A.M.C.E.F. utilizes a quadrangular isoparametric and axi-symmetric element. The results took into account the vertical deflection and radial displacement of the nodal points and also the deformation diagram and stress distribution (Von Mises comparison) of the three regions studied: nucleus pulposus, annulus fibrosus and the end plate. This model has been applied to three pathological states: fissuring of the annulus and nucleus herniation, simulation of an enucleation, and a fracture of the central area of end plate with Schmörl's nodule formation. In each case, a deformation and a stress distribution modified relatively to those observed in normal discs were obtained. For instance, in the case of herniation the maximum stress equals 3.700 N/mm2 in comparison with 1.350 N/mm2 found in normal cases. This simplified model is one of the first which reproduces some pathological states of intervertebral discs and facilitates the understanding of the biomechanics of these states.

Biomechanical Phenomena↗
PubMedDate not supplied

On the doublet formation in the flocculation process of the yeast cells.

The combination of single cells to form doublets is regarded as the rate-limiting step of flocculation and requires the presence of surface proteins in active form. The process of activation of the flocculation proteins of yeast cells is described in the frame of the autocrine interaction regime (Science 224 (1984) 1312). The influence of several effectors (the cell efficiency to use sugars, the calcium content in the external medium and the probability that free cells collide each other under thermal motion conditions) on the initial rate of flocculation and on the fraction of remaining free cells in the steady state is briefly discussed in the paper. The present model offers a useful tool for further quantitative investigations in this topic. Also, it indicates qualitatively a way in which the regulation of flocculation might be controlled at the level of the expression of cell-surface activation abilities.

Calcium↗