The question of the reasons for the extreme variation in morbidity among the gene carriers of acute porphyria and the great diversity of the precipitating factors are approached by the aid of a model of interacting genomic circuits. It is based on the current paradigm of the acute porphyric attack as a result of a toxic proximal overload of the enzyme-
deficient heme-biosynthetic patway. Porphyrogenic influx of precursors is seen as a consequence of uncontrolled induction of its gate-keeping enzyme, ubiquitous 5-aminolevulinate synthase (ALAS1), due to attenuated post-translational control of the enzyme combined with activated gene transcription. Focus is directed on the genomic
control of the master-regulator of ALAS1-transcription, the nuclear receptor pair constitutively active receptor (CAR) and pregnane xenobiotic receptor (PXR). On activation by their ligands, i.e. lipophilic drugs, solvents, alcohols, hormonal steroids and biocides, these DNA-binding proteins transform xenobiotic or steroid stimuli to coordinated
activations of gene transcription-programs for ALAS1 and apo-cytochromes P450 (apo-CYPs), thus effecting the formation of xenobiotic-metabolizing cytochrome P450 enzymes. The potency of the CAR/PXR-transduction axis is enhanced by co-activators generated in
at least four other genomic circuits, each triggered by different external and internal stimuli clinically experienced to be porphyroge
nic, and each controlled by co-activating and co-repressing modulators. The expressions of the genes for CAR and PXR are thus augmented by binding glucocorticoid receptor (GR) activated by a steroid hormone, e.g, cortisol generated in fasting, infection or different forms of stress. The promotor regions of ALAS1 and apoCYPs contain binding sites for at least three co-activating transcription factors enhancing CAR/PXR transduction: i.e. the ligand-independent growth hormone (GH)-pulse controlled hepatocyte nuclear factor 4 (HNF4), the insulin-responsive forkhead box class O-(FOXO) protein pathway activated in stress and infection, and the proliferator-activated receptor gamma co-activator 1 al
pha (PGC-1alpha) circuit responding to glucagon liberated in fasting. Many interactions and cross-talk take place within the tangle of genomic circuits that control ALAS1-transcription, which may explain the extreme inter- and intra-individual variability in morbidity in acute porphyria. Reasons for gender-differences are found in sex-dependent control of HPA- and GH-activity as well as in direct, or GR-mediated effects on CAR/PCR activation. Constitutional differences in individual porphyric morbidity may be discussed along lines of mutations or duplications of genes for co-activating or co-repressing nuclear proteins active at different levels within the circuits.
Heroin addiction markedly affects the nutritional and metabolic status and frequently leads to malnutrition. The aim of our study was to compare circulating concentration of adipose tissue-derived hormones leptin, adiponectin and resistin in 12 patients with heroin addiction before and after one-year methadone maintenance treatment with the group of 20 age- and body mass index-matched healthy subjects. Basal serum leptin and adiponectin levels in heroin addicts were significantly decreased (3.4±
0.4 vs. 4.5±0.6 ng/ml and 18.9±3.3 vs. 33.9±3.1 ng/μl, respectively; p<0.05) while serum resistin concentrations were increased compared to healthy subjects (10.1±1.2 vs. 4.6±0.3 ng/ml; p<0.05). Moreover, positive correlation of serum leptin levels with body mass index was lost in the addicts in contrast to control group. One year of methadone maintenance treatment normalized serum leptin, but not serum adiponectin and resistin concentrations. In conclusion, circulating concentrations of leptin, adiponectin and resistin are markedly altered in patients with chronic heroin addiction. These alterations appear to be relatively independent of nutritional status and insulin sensitivity.
It is now generally accepted that adipose tissue acts as an endocrine organ producing a number of substances with an important role in the regulation of food intake, energy expenditure and a series of metabolic processes. Adiponectin is a recently discovered protein produced exclusively by adipocytes. A number of studies have shown that obesity, insulin resistance and atherosclerosis are accompanied by decreased adiponectin levels and that adiponectin replacement under experimental settings is able to diminish both insulin resistance and atherosclerosis. The aim of this review is to summarize the current knowledge about the physiology and pathophysiology of adiponectin and to discuss its potential in the treatment of insulin resistance and atherosclerosis.
Leptin and adiponectin, two adipocytokines, may work together in regulating energy homeostasis and insulin action. Leptin gene expression has been investigated in term placental tissue complicated by gestational diabetes mellitus (GDM), but never in conjunction with all isoforms of the leptin receptor (LEPR A-D), or with adiponectin receptors (ADIPOR1 and 2). In this study we examined the association between changes in expression of these genes in placental tissue and GDM risk. We assessed placental gene expression of leptin, LEPR A-D and ADIPOR1 and 2 by real time PCR using mRNA from maternal and fetal biopsies. Tissues were collected from uncomplicated pregnancies (n=28) and those complicated by GDM (n=19). Gene expression was normalized to three endogenous housekeeping genes. Relative gene expression values were reported as fold change between groups. Adiponectin gene expression was out of the sensitive range of our assay. There were increases in leptin mRNA expression in GDM cases compared with controls for maternal-side (p=0.06), and fetal-side (p=0.09) placental biopsies. No significant changes were seen in GDM cases compared with controls in LEPR A-D or ADIPOR1 and 2. mRNA derived from maternal-side tissue was positively correlated with tissue from the fetal side for all genes studied (all p<0.01). Finally, we noted that absence or presence of GDM was a major factor in leptin mRNA expression after adjusting for maternal age, mode of delivery, parity and smoking status. In conclusion, increases in leptin mRNA expression in term placenta, but not that of its receptors, are associated with the diagnosis of GDM. Changes seen in the ligand, but not the receptor, of the leptin pathway in GDM-complicated pregnancies may also apply to the adiponectin pathway, as the ADIPOR1 and 2 mRNAs do not change with GDM diagnosis.
We examined the effect of leptin on the insulin resistance in skeletal muscles by measuring glucose transport. Male Wistar rats were fed rat chow or high-fat diets for 30 days. Before sacrifice, rats fed high-fat diet were subcutaneously injected with leptin (1 mg/kg b.w.) for 3 days. The glucose transport in epitrochlearis and soleus muscles did not differ in the experimental groups under basal conditions, however these values decreased significantly in the rats fed high-fat diet under insulin stimulation (p<0.01). Leptin treatment recovered the decreased glucose transport in epitrochlearis (p<0.05) and soleus muscles (p=0.08). Triglyceride concentrations in soleus muscles were increased significantly in the rats fed high-fat diet as compared to rats fed chow diet (p<0.01), and were decreased significantly by leptin treatment (p<0.01). The glucose transport was measured under basal conditions and after 60 μU/ml of insulin treatment with or without 50 ng/ml of leptin. Leptin had no direct stimulatory effect on glucose transport under both basal and insulin-stimulated conditions in vitro. These results demonstrate that leptin injection to rats fed high-fat diet recovered impaired insulin responsiveness of skeletal muscles and muscle triglyceride concentrations. However, there was no direct stimulatory effect of leptin on insulin sensitivity of skeletal muscles in vitro.
We investigated the effects of different weight loss protocols on leptin levels in obese females with the aim of addressing the leptin resistance which has been found to be an aggravating factor in obesity. Twenty-four obese females enrolled to one of three 12-week weight loss protocols: orlistat-induced weight loss (OWL, n=8), exercise-induced weight loss (EWL, n=8) and orlistat plus exercise-induced weight loss (OEWL, n=8). Serum leptin levels were measured in duplicate by radioimmunoassay. There were significant reductions (P<0.01) in body weight and fat mass after the 12 week period in all groups: -11.4±0.5 kg and -9.8
±0.5 kg (OEWL), -8.3±0.8 kg and -5.7±0.9 kg (OWL), -8.9±1.2 kg and -7.4±1.2 kg (EWL), respectively. Serum leptin levels were also decreased markedly in all groups: -59.2 %(OEWL1), -37.8 % (OWL) and -48.6 % (EWL) (P<0.01 all). In addition, there were marked decreases in leptin levels for each kilogram of fat mass after the 12 week period: -48.2
±7.2 % (OEWL), -27.8±4.8 % (OWL) and -39.3±4.3% (EWL) (P<0.01 all). Decreases in serum leptin levels expressed per kilogram of fat mass were significantly higher in the OEWL group compared to the OWL group (P=0.03). Consequently, an exercise training program in adjunct to
pharmacotherapy provides higher weight reduction and fat mass loss in obesity treatment. It also seems to have further beneficial effects on leptin re
sistance, as indicated by decreases in leptin levels expressed per kilogram of fat mass.
Cytokines play a critical and multifarious role in follicular maturation. Consequently, they may influence the pregnancy outcome in cycles of assisted reproduction. The aim of this study was to measure the levels of tumor necrosis factor-α(TNFα), vascular endothelial growth factor (VEGF) and leptin in serum and follicular fluids (FFs) from women undergoing controlled ovarian hyperstimulation (COH) for intracytoplasmic sperm injection cycles (ICSI). We tried to investigate their interrelationships and to evaluate them as predictive markers for the cycle’s outcome. Seventeen
women participated in this study. Male factor infertility was the only indication for ICSI cycles. For COH, the long agonist protocol with triptorelin and recombinant FSH was employed. Cytokines levels were evaluated by ELISA. Serum cytokine levels did not differ between pregnant and non-pregnant women. FF-VEGF levels were significantly
elevated in non-pregnant women (722.2±1093.2 pg/ml) as compared to pregnant women (290.3±259.8 pg/ml). Leptin concentrations were also significantly higher in FFs of non-pregnant women (682.6±625.1 ng/ml) than those of pregnant women (231.6±286.5 ng/ml). There were significant
positive correlations between FF-leptin and age, as well as between FF-leptin and FF-VEGF concentrations. It was concluded that elevated FF-leptin and VEGF levels are associated with failure of conception in IVF cycles and may serve as markers in clinical practice.
Tumor necrosis factor α (TNFα) and leptin concentrations were determined in the abdominal subcutaneous and visceral (omental) adipose tissue of patients undergoing elective open-abdominal surgery and compared with their body mass index. The concentration of leptin did not differ significantly between women and men, being high in subcutaneous fat tissue and low in visceral fat tissue. TNFα concentration in subcutaneous fat tissue was approximately the same in both genders, but it was significantly lower in visceral fat tissue of women and unchanged in visceral fat tissue of men. A significant correlation between BMI and leptin was found in the two fat tissue compartments of both genders, but the correlation between BMI and TNFα was found only in subcutaneous fat tissue of women.
Ghrelin is a new endogenous peptide, discovered in 1999 by Kojima et al., as the result of a search for an endogenous ligand for an orphan receptor of known structure and function. Ghrelin is composed of 28 amino acids and is produced mostly by cells of the stomach, hypothalamus, and hypophysis, but it has also been detected in other tissues. Its discovery is related to the development of a new hypothesis regarding the regulation of growth hormone secretion. It is an antagonist of somatostatin. Ghrelin activates the release of growth hormone from the somatotrophic cells of the hypophysis. It participates in the regulation of energy homeostasis, increases food intake, decreases energy output and exerts a lipogenetic effect. Its metabolic effects do not depend on the GH/IGF-I system, but are mediated by the NPY/Y1 and AGRP receptor system. Ghrelin influences the secretion and motility of the gastrointestinal tract, especially the stomach. The presence of ghrelin and its receptors has also been demonstrated in many other tissues. Its function in these tissues has not yet been studied, thus providing many possibilities for further research., M. Rosická, M. Kršek, Z. Jarkovská, J. Marek, V. Schreiber., and Obsahuje bibliografii
Few investigators have simultaneously evaluated leptin, soluble leptin receptor (SLR) and leptin gene polymorphisms in preeclampsia cases and controls.We examined these three biomolecular markers in 40 preeclampsia cases and 39 controls.Plasma leptin and SLR concentrations were determined using immunoassays. Genotype for the tetranucleotide
repeat (TTTC)n, polymorphism in the 3′-flanking region of the leptin gene was determined using PCR.Alleles of the polymorphism were characterized by size distributions [short repeats (class I); and long repeats (class II)].Logistic regression was used to calculate odds ratio
s (OR) and 95 % confidence intervals (CI).Leptin concentrations were
higher in our cases than in the controls (53.1±4.7 vs. 17.7±2.4 ng/ml,p<0.05).
SLR concentrations were slightly lower in our patients than in the controls (25.7±1.9 vs. 29.1±1.1 ng/ml, p>0.05). Elevated leptin (≥ 14.5 ng/ml) was associated with a 3.8-fold (CI 1.0-14.4) increased risk; whereas low SLR (< 28.5 ng/ml) was associated with a 6.3-fold (CI 1.7-23.2) increased risk of preeclampsia. The I/II genotype was associated with a 3.8-fold increased risk of preeclampsia (OR=3.8; 95 % CI 0.8-18.0); and the II/II genotype was not observed among our cases (0 % vs. 33 % p<0.001). Larger studies would be needed to confirm and further clarify the relations between functional variants in the leptin gene and preeclampsia risk.