cDNA Cloning and mRNA analysis of PGC-1 in epitrochlearis muscle in swimming-exercised rats

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1), a cold-inducible coactivator of nuclear receptors, stimulates mitochondrial biogenesis and respiration in muscle cells. In the present study, we first cloned a rat PGC-1 gene from a brown adipose tissue cDNA library which encodes a predicted 796-amino-acid protein and exhibits respectively 98% and 95% identity with the mouse and human homologues. Next, we examined the effect of swimming exercise training on the level of expression of the PGC-1 gene in rat epitrochlearis (Epi) muscle. PGC-1 mRNA level in Epi muscle in rats that swam 2 h a day for 3 and 7 days increased dramatically by 154% and 163%, respectively, compared to the non-exercised control group. PGC-1 mRNA up-regulation was not observed in an immersion group treated at 35 degrees C during the training program but without swimming exercise. These results demonstrate that expression of the PGC-1 gene in Epi muscle is induced not only by cold exposure but also by prolonged low-intensity physical exercise.

Increased energy expenditure, decreased adiposity, and tissue-specific insulin sensitivity in protein-tyrosine phosphatase 1B-deficient mice

Protein-tyrosine phosphatase 1B (PTP-1B) is a major protein-tyrosine phosphatase that has been implicated in the regulation of insulin action, as well as in other signal transduction pathways. To investigate the role of PTP-1B in vivo, we generated homozygotic PTP-1B-null mice by targeted gene disruption. PTP-1B-deficient mice have remarkably low adiposity and are protected from diet-induced obesity. Decreased adiposity is due to a marked reduction in fat cell mass without a decrease in adipocyte number. Leanness in PTP-1B-deficient mice is accompanied by increased basal metabolic rate and total energy expenditure, without marked alteration of uncoupling protein mRNA expression. In addition, insulin-stimulated whole-body glucose disposal is enhanced significantly in PTP-1B-deficient animals, as shown by hyperinsulinemic-euglycemic clamp studies. Remarkably, increased insulin sensitivity in PTP-1B-deficient mice is tissue specific, as insulin-stimulated glucose uptake is elevated in skeletal muscle, whereas adipose tissue is unaffected. Our results identify PTP-1B as a major regulator of energy balance, insulin sensitivity, and body fat stores in vivo.

Direct coupling of transcription and mRNA processing through the thermogenic coactivator PGC-1

Transcription and mRNA processing are coupled events in vivo, but the mechanisms that coordinate these processes are largely unknown. PGC-1 is a transcriptional coactivator that plays a major role in the regulation of adaptive thermogenesis. PGC-1 also has certain motifs characteristic of splicing factors. We demonstrate here that mutations in the serine- and arginine-rich domain and RNA recognition motif of PGC-1 interfere with the ability of PGC-1 to induce mRNAs of target genes. These mutations also disrupt the ability of PGC-1 to co-localize and associate with RNA processing factors. PGC-1 can alter the processing of an mRNA, but only when it is loaded onto the promoter of the gene. These data demonstrate the coordinated regulation of RNA transcription and processing through PGC-1.

Impact of endotoxin on UCP homolog mRNA abundance, thermoregulation, and mitochondrial proton leak kinetics

Linking tissue uncoupling protein (UCP) homolog abundance with functional metabolic outcomes and with expression of putative genetic regulators promises to better clarify UCP homolog physiological function. A murine endotoxemia model characterized by marked alterations in thermoregulation was employed to examine the association between heat production, UCP homolog expression, and mitochondrial proton leak ("uncoupling"). After intraperitoneal lipopolysaccharide (LPS, approximately 6 mg/kg) injection, colonic temperature (T(c)) in adult female C57BL6/J mice dropped to a nadir of approximately 30 degrees C by 8 h, preceded by a four- to fivefold drop in liver UCP2 and UCP5/brain mitochondrial carrier protein 1 mRNA levels, with no change in their hindlimb skeletal muscle (SKM) expression. SKM UCP3 mRNA rose fivefold during development of hypothermia and was correlated with an LPS-induced increase in plasma free fatty acid concentration. UCP2 and UCP5 transcripts recovered about three- to sixfold in both tissues starting at 6-8 h, preceding a recovery of T(c) between 16 and 24 h. SKM UCP3 followed an opposite pattern. Such results are not consistent with an important influence of UCP3 in driving heat production but do not preclude a role for UCP2 or UCP5 in this process. The transcription coactivator PGC-1 displayed a transient LPS-evoked rise (threefold) or drop (two- to fivefold) in SKM and liver expression, respectively. No differences between control and LPS-treated mouse liver or SKM in vitro mitochondrial proton leak were evident at time points corresponding to large differences in UCP homolog expression.

Subacute toxicity of alpha-ergocryptine in Sprague-Dawley rats. 2: metabolic and hormonal changes

The present study describes the metabolic changes observed in a dietary subacute toxicity experiment with the ergot alkaloid alpha-ergocryptine in Sprague-Dawley rats. The observed effects on metabolic and hormonal parameters were described separately from the general toxicological effects, in view of the important role of dopamine agonists in metabolism (e.g. ergot alkaloids in fescue toxicosis). The rats were fed 0, 4, 20, 100 or 500 mg ergocryptine/kg diet for 28-32 days (equal to 0, 0.36, 1.7, 8.9 and 60 mg ergocryptine/kg body weight/day for females and 0, 0.34, 1.4, 6.6 and 44 mg ergocryptine/kg body weight/day for males). Total cholesterol and high-density lipoprotein (HDL)-cholesterol were decreased dose dependently in females but the ratio HDL-cholesterol/total cholesterol was only decreased at 20 mg/kg body weight. Triglycerides and glucose concentrations were decreased in the highest dose groups of both sexes. Serum urea concentrations were increased in the 20, 100 and 500 mg/kg dose groups. Insulin, glucagon and liver glycogen were increased in the highest dose group at the end of the study, when the animals were allowed to eat prior to blood sampling and necropsy. Prolactin, T4 and FT4 were decreased in the 20, 100 and 500 mg/kg dose groups of both sexes. Follicle-stimulating hormone (FSH) was decreased in the 20, 100 and 500 mg/kg female dose groups and luteinizing hormone (LH) was increased in the 20, 100 and 500 mg/kg male dose groups. It is postulated that the observed effects on food intake, metabolism (lipid and carbohydrate) and hormonal parameters are due to an interaction of ergocryptine with central dopaminergic activities, which comprise a major functional component of a central regulatory system for metabolism.

Expression of leptin receptors and induction of IL-1beta transcript in glial cells

To examine the role of leptin in the immune function of the brain, we examined the effect of leptin on interleukin-1beta (IL-1beta) expression in mouse primary cultured glial cells. The expression of leptin receptor isoforms Ob-Ra and Ob-Rb mRNA was detected by RT-PCR analysis of total RNA from primary cultured glial cells. Protein of leptin receptor was also expressed in mouse primary cultured glial cells as evaluated by Western blotting analysis. Leptin increased the expression of IL-1beta mRNA evaluated by RT-PCR. The expression of IL-1beta transcript peaked 2 to 6 h after leptin application. These results indicate that leptin could induce IL-1beta transcript in the brain and that one of the target cells of the leptin-induced IL-1beta transcript may be a glial cell.

Role of leptin in reproduction

Leptin is a 16-kDa adipocyte-secreted protein the serum levels of which reflect mainly the amount of energy stores but are also influenced by short-term energy imbalance as well as several cytokines and hormones. Leptin, by binding to specific receptors, alters the expression of several hypothalamic neuropeptides that regulate neuroendocrine function as well as energy intake and expenditure. More specifically, accumulating evidence suggests that this hormone may serve to signal to the brain information on the critical amount of fat stores that are necessary for LHRH secretion and activation of the hypothalamic-pituitary-gonadal axis. Rising leptin levels have been associated with initiation of puberty in animals and humans and normal leptin levels are needed for maintenance of menstrual cycles and normal reproductive function. Moreover, circadian and ultradian variations of leptin levels are associated with minute to minute variations of LH and estradiol in normal women. Falling leptin levels in response to starvation result in decreased estradiol levels and amenorrhea in subjects with anorexia nervosa or strenuously exercising athletes. In addition, leptin has a potentially important role during pregnancy and in the physiology of the neonate. Finally, recent evidence suggests that leptin may influence ovarian steroidogenesis directly, but the exact role of intraovarian leptin action in the physiology and pathophysiology of the human reproductive system needs to be further elucidated.

Secretory granules of endocrine and chief cells of human stomach mucosa contain leptin

BACKGROUND

Leptin plays an important role in the control of food intake and body weight homeostasis. In humans, leptin is produced by adipocytes, placental cells and secretory cells of the mammary epithelium. Recently, it has been reported that stomach glands produce leptin in rats.

OBJECTIVE

To test the expression of leptin protein in human stomach and localize, by immunocytochemistry, the specific cell type producing leptin.

DESIGN

Endoscopic stomach biopsies of six patients were used to investigate leptin production in the fundic epithelium using reverse transcription polymerase chain reaction (RT-PCR) of RNA. Leptin protein was detected by immunoblot analysis and localized by immunohistochemistry and ultrastructural immunocytochemistry (immunogold method).

RESULTS

Human gastric epithelium expresses leptin mRNA and leptin protein. The cells in the lower half of the stomach glands were immunoreactive for leptin. Ultrastructural immunocytochemistry showed leptin immunoreactivity in the pepsinogen granules of chief cells, but the granules of a specific endocrine cell type in the basal portion of the glands were also positive.

CONCLUSIONS

Our results suggest that gastric leptin could function in the short-term system to control feeding behaviour and is probably secreted in the stomach lumen by chief cells and into the stomach circulation by a special type of endocrine cell.

G(i-1)/G(i-2)-dependent signaling by single-transmembrane natriuretic peptide clearance receptor

Single-transmembrane natriuretic peptide clearance receptor (NPR-C), which is devoid of a cytoplasmic guanylyl cyclase domain, interacts with pertussis toxin (PTx)-sensitive G proteins to activate endothelial nitric oxide synthase (eNOS) expressed in gastrointestinal smooth muscle cells. We examined the ability of NPR-C to activate other effector enzymes in eNOS-deficient tenia coli smooth muscle cells; these cells expressed NPR-C and NPR-B but not NPR-A. Atrial natriuretic peptide (ANP), the selective NPR-C ligand cANP-(4-23), and vasoactive intestinal peptide (VIP) inhibited (125)I-ANP and (125)I-VIP binding to muscle membranes in a pattern indicating high-affinity binding to NPR-C. Interaction of VIP with NPR-C was confirmed by its ability to inhibit (125)I-ANP binding to membranes of NPR-C-transfected COS-1 cells. In tenia muscle cells, all ligands selectively activated G(i-1) and G(i-2); VIP also activated G(s) via VIP(2) receptors. All ligands stimulated phosphoinositide hydrolysis, which was inhibited by ANP-(1-11), PTx, and antibodies to phospholipase C-beta3 (PLC-beta3) and Gbeta. cANP-(4-23) contracted tenia muscle cells; contraction was blocked by U-73122 and PTx and by antibodies to PLC-beta3 and Gbeta in intact and permeabilized muscle cells, respectively. VIP and ANP contracted muscle cells only after inhibition of cAMP- and cGMP-dependent protein kinases. ANP and cANP-(4-23) inhibited forskolin-stimulated cAMP in a PTx-sensitive fashion. We conclude that NPR-C is coupled to activation of PLC-beta3 via betagamma-subunits of G(i-1) and G(i-2) and to inhibition of adenylyl cyclase via alpha-subunits.

Partial saturation and regional variation in the blood-to-brain transport of leptin in normal weight mice

Impaired blood-brain barrier transport of leptin into the arcuate nucleus has been suggested to underlie obesity in humans and outbred aging mice. Here, we used a brain perfusion method in mice to measure transport rates and kinetic parameters for leptin at vascular concentrations between 0.15 and 130 ng/ml. Transport into whole brain was partially saturated at all concentrations, not only those seen in obesity. Leptin entered all regions of the brain, not only the hypothalamus, with entry and saturation rates differing among the brain regions. The value of the Michaelis-Menten constant of the transporter approximates normal serum levels and the maximum velocity value varies significantly among brain regions. These results suggest an important role for low serum levels signaling starvation status to the brain and show that the levels of leptin seen in obesity greatly saturate the transporter. Differences in regional uptake and saturation provide a mechanism by which leptin can control events mediated at the arcuate nucleus and other regions of the central nervous system with different regional thresholds for optimal function.

Leptina: o diálogo entre adipócitos e neurônios

A descoberta da leptina trouxe consigo um interesse renovado sobre o estudo do controle homeostático da energia. Sabe-se agora que o tecido adiposo branco é o maior sítio de produção da leptina. Uma vez na circulação sangüínea ela se liga a receptores específicos no cérebro, levando ao sistema nervoso central um sinal de saciedade que reflete a quantidade existente de energia em forma de gordura no organismo. Agindo por intermédio de receptores que fazem uso da via JAK/SAT de transdução do sinal intracelular, a leptina modifica a expressão e a atividade de inúmeros peptídeos hipotalâmicos que regulam o apetite e o gasto de energia. Além disso, a leptina sinaliza o estado nutricional do organismo a outros sistemas fisiológicos, modulando a função de várias glândulas alvo. Mais recentemente, a leptina recombinante foi administrada com sucesso numa paciente obesa com deficiência do hormônio devido a uma mutação do gene ob. Por outro lado, os efeitos da leptina recombinante no único estudo em pacientes com obesidade e concentrações elevadas de leptina foram menos impressionantes. Nesta revisão, discutiremos a complexidade das ações da leptina com ênfase no seu papel integrativo de sinalizadora do estado nutricional para o organismo.

Modulation of estrogen receptor-alpha transcriptional activity by the coactivator PGC-1

A transcriptional coactivator of the peroxisome proliferator-activated receptor-gamma (PPARgamma), PPARgamma-coactivator-1(PGC-1) interacts in a constitutive manner with the hinge domain of PPARgamma and enhances its transcriptional activity. In this study we demonstrate that PGC-1 is a coactivator of estrogen receptor-alpha (ERalpha)-dependent transcriptional activity. However the mechanism by which PGC-1 interacts with ERalpha is different from that of PPARgamma. Specifically, it was determined that the carboxyl terminus of PGC-1 interacts in a ligand-independent manner with the ERalpha hinge domain. In addition, an LXXLL motif within the amino terminus of PGC-1 was shown to interact in an agonist-dependent manner with the AF2 domain within the carboxyl terminus of ERalpha. The ability of PGC-1 to associate with and potentiate the transcriptional activity of an ERalpha-AF2 mutant that is unable to interact with the p160 class of coactivators suggests that this coactivator may have a unique role in estrogen signaling. It is concluded from these studies that PGC-1 is a bona fide ERalpha coactivator, which may serve as a convergence point between PPARgamma and ERalpha signaling.

Norepinephrine induces vascular endothelial growth factor gene expression in brown adipocytes through a beta -adrenoreceptor/cAMP/protein kinase A pathway involving Src but independently of Erk1/2

To identify the signaling pathway that mediates the adrenergic stimulation of the expression of the gene for vascular endothelial growth factor (VEGF) during physiologically induced angiogenesis, we examined mouse brown adipocytes in primary culture. The endogenous adrenergic neurotransmitter norepinephrine (NE) induced VEGF expression 3-fold, in a dose- and time-dependent manner (EC(50) approximately 90 nm). Also, the hypoxia-mimicking agent cobalt, as well as serum and phorbol ester, induced VEGF expression, but the effect of NE was additive to each of these factors, implying that a separate signaling mechanism for the NE-mediated induction was activated. The NE effect was abolished by propranolol and mimicked by isoprenaline or BRL-37344 and was thus mediated via beta-adrenoreceptors. The NE-induced VEGF expression was fully cAMP mediated, an effect which was inhibited by H-89 and thus was dependent on protein kinase A activity. Involvement of other adrenergic signaling pathways (alpha(1)-adrenoreceptors, Ca(2+), protein kinase C, alpha(2)-adrenoreceptors, and pertussis toxin-sensitive G(i)-proteins) was excluded. The specific inhibitor of Src tyrosine kinases, PP2, markedly reduced the stimulation by NE, which demonstrates that a cAMP-dependent Src-mediated pathway is positively connected to VEGF expression. However, inhibition of Erk1/2 MAP kinases by PD98059 was without effect. NE did not prolong VEGF mRNA half-life and its effect was thus transcriptional, and was independent of protein synthesis. These results demonstrate that adrenergic stimulation, through beta-adrenoreceptor/cAMP/protein kinase A signaling, recruits a pathway that branches off from the NE-activated Src-Erk1/2 cascade to enhance transcription of the VEGF gene.

Effects of long-term treatment with human pure follicle-stimulating hormone on semen parameters and sperm-cell ultrastructure in idiopathic oligoteratoasthenozoospermia

Ten subfertile men affected by idiopathic oligoteratoasthenozoospermia and exhibiting normal serum hormone levels received a long-term treatment with human pure follicle-stimulating hormone (hp-FSH) (150 IU, intramuscularly, three times per week for 6 months). Semen parameters and ultrastructural features of spermatozoa were evaluated before and after therapy. The results showed an increase in sperm cell concentration and, more interestingly, motility. Electron microscopic examination revealed an improved fine architectural pattern, mainly involving acrosome, head and chromatin and middle-piece, in accordance with the positive changes of functional data. No significant changes of hp-FSH treatment on serum hormone levels were observed, since the latter were found to be substantially unchanged after 6 months of therapy. The present data suggest: (i) the benefit of hp-FSH administration in idiopathic oligoteratoasthenozoospermia, when hormone parameters support a substantial integrity of spermatogenetic microenvironment and (ii) an optimal effect after long-term (6 months) therapy.

Towards a molecular understanding of adaptive thermogenesis

Obesity results when energy intake exceeds energy expenditure. Naturally occurring genetic mutations, as well as ablative lesions, have shown that the brain regulates both aspects of energy balance and that abnormalities in energy expenditure contribute to the development of obesity. Energy can be expended by performing work or producing heat (thermogenesis). Adaptive thermogenesis, or the regulated production of heat, is influenced by environmental temperature and diet. Mitochondria, the organelles that convert food to carbon dioxide, water and ATP, are fundamental in mediating effects on energy dissipation. Recently, there have been significant advances in understanding the molecular regulation of energy expenditure in mitochondria and the mechanisms of transcriptional control of mitochondrial genes. Here we explore these developments in relation to classical physiological views of adaptive thermogenesis.

New features of mitochondrial DNA replication system in yeast and man

In this review, we sum up the research carried out over two decades on mitochondrial DNA (mtDNA) replication, primarily by comparing this system in Saccharomyces cerevisiae and Homo sapiens. Brief incursions into systems of other organisms have also been achieved when they provide new information.S. cerevisiae and H. sapiens mitochondrial DNA (mtDNA) have been thought for a long time to share closely related architecture and replication mechanisms. However, recent studies suggest that mitochondrial genome of S. cerevisiae may be formed, at least partially, from linear multimeric molecules, while human mtDNA is circular. Although several proteins involved in the replication of these two genomes are very similar, divergences are also now increasingly evident. As an example, the recently cloned human mitochondrial DNA polymerase beta-subunit has no counterpart in yeast. Yet, yeast Abf2p and human mtTFA are probably not as closely functionally related as thought previously. Some mtDNA metabolism factors, like DNA ligases, were until recently largely uncharacterized, and have been found to be derived from alternative nuclear products. Many factors involved in the metabolism of mitochondrial DNA are linked through genetic or biochemical interconnections. These links are presented on a map. Finally, we discuss recent studies suggesting that the yeast mtDNA replication system diverges from that observed in man, and may involve recombination, possibly coupled to alternative replication mechanisms like rolling circle replication.

Etomoxir-induced PPARalpha-modulated enzymes protect during acute renal failure

Regulation of fatty acid beta-oxidation (FAO) represents an important mechanism for a sustained balance of energy production/utilization in kidney tissue. To examine the role of stimulated FAO during ischemia, Etomoxir (Eto), clofibrate, and WY-14,643 compounds were given 5 days prior to the induction of ischemia/reperfusion (I/R) injury. Compared with rats administered vehicle, Eto-, clofibrate-, and WY-treated rats had lower blood urea nitrogen and serum creatinines following I/R injury. Histological analysis confirmed a significant amelioration of acute tubular necrosis. I/R injury led to a threefold reduction of mRNA and protein levels of acyl CoA oxidase (AOX) and cytochrome P4A1, as well as twofold inhibition of their enzymatic activities. Eto treatment prevented the reduction of mRNA and protein levels and the inhibition of the enzymatic activities of these two peroxisome proliferator-activated receptor-alpha (PPARalpha) target genes during I/R injury. PPARalpha null mice subjected to I/R injury demonstrated significantly enhanced cortical necrosis and worse kidney function compared with wild-type controls. These results suggest that upregulation of PPARalpha-modulated FAO genes has an important role in the observed cytoprotection during I/R injury.

Antiretoviral Therapy and the Lipodystrophy Syndrome, Part 2: Concepts in Aetiopathogenesis

Clinical research has indicated that the use of nucleoside reverse transcriptase inhibitor (NRTI) and HIV protease inhibitor (PI) therapy is associated with a risk of long-term toxicity syndromes, and that the aetiopathogenesis of these adverse effects is independent of the antiretroviral effects of these drugs. In relation to the lipodystrophy syndrome, it appears that the most powerful determinant of subcutaneous fat wasting is an interaction between these two drug classes. In this review, possible mechanisms underlying the contributions of both PI and NRTI drugs are reviewed, with an emphasis on their effects on adipose tissue. On this basis, an ‘adipocentric’, or minimal model of the syndrome is developed, in which divergent effects at the adipocyte of NRTIs (mitochondrial toxicity) and PIs (insulin resistance and impaired adipocyte maturation) interact to produce a phenotype that is consistent with clinical observations.

Differential regulation of leptin transport by the choroid plexus and blood-brain barrier and high affinity transport systems for entry into hypothalamus and across the blood-cerebrospinal fluid barrier

Leptin is a circulating hormone that controls food intake and energy homeostasis. Little is known about leptin entry into the central nervous system (CNS). The blood-cerebrospinal fluid (CSF) barrier at the choroid plexus and the blood-brain barrier (BBB) at the cerebral endothelium are two major controlling sites for entry of circulating proteins into the brain. In the present study, we characterized leptin transport across the blood-CSF barrier and the BBB by using a brain perfusion model in lean rats. Rapid, high-affinity transport systems mediated leptin uptake by the hypothalamus (KM = 0.2 ng/ml) and across the blood-CSF barrier (KM = 1.1 ng/ml). High affinity in vivo binding of leptin was also detected in the choroid plexus (KD = 2.6 ng/ml). In contrast, low affinity carriers for leptin (KM = 88 to 345 ng/ml) were found at the BBB in the CNS regions outside the hypothalamus (e.g. cerebral cortex, caudate nucleus, hippocampus). Our findings suggest a key role of high affinity leptin transporters in the hypothalamus and choroid plexus in regulating leptin entry into the CNS and CSF under physiological conditions. Low affinity transporters at the BBB outside the hypothalamus could potentially contribute to overall neuropharmacological effects of exogenous leptin.

Control of food intake via leptin receptors in the hypothalamus

Food intake is regulated via neural circuits located in the hypothalamus. During the past decade our knowledge on the specific mediators and neuronal networks that regulate food intake and body weight has increased dramatically. An important contribution to the understanding of hypothalamic control of food intake has been the characterization of the ob gene product (leptin) via positional cloning. Absence of circulating, functionally active, leptin hormone results in massive obesity as seen in ob/ob mice. Leptin inhibits food intake and increases energy expenditure via an interaction with specific leptin receptors located in the hypothalamus. Leptin receptors, of which there are several splice variants (Ob-Ra through Ob-Re), belong to the superfamily of cytokine receptors, which use the JAK-STAT pathway of signal transduction. Obese db/db mice, which have a mutation in the db locus, are unable to perform JAK-STAT signal transduction due to absence of functionally active (long form; Ob-Rb) leptin receptors. Ob-Rb is primarily expressed in the hypothalamus, with particularly high levels in the arcuate, paraventricular, and dorsomedial nuclei and in the lateral hypothalamic area. The abundance of leptin receptors in the ventromedial and lateral hypothalamus supports early observations that these two regions are intimately associated with the regulation of food intake. Leptin receptors have been identified in neuropeptide Y (NPY)/lagouti-related peptide (AgRP)- and proopiomelanocortin (POMC)/cocaine- and amphetamine-regulated transcript (CART)-containing neurons of the ventromedial and ventrolateral arcuate nucleus, respectively, and in melanin-concentrating hormone (MCH)- and hypocretin/orexin-containing neurons of the lateral hypothalamus, suggesting that the above-mentioned messengers are mediators of leptin's action in the hypothalamus. Indeed, functional studies show that NPY, AgRP, POMC-derived peptides, CART, MCH, and hypocretins/orexins all are important regulators of food intake. Leptin is essential for normal body weight balance, but the exact mechanisms by which leptin activates hypothalamic neuronal circuitries is known to a limited extent. In order to find pharmaceutical approaches to treat obesity, further studies will be needed to reveal the exact mechanisms by which leptin lowers body weight and which role leptin and leptin receptors have in the pathogenesis of human obesity.

A tissue-specific coactivator of steroid receptors, identified in a functional genetic screen

Steroid receptors mediate responses to lipophilic hormones in a tissue- and ligand-specific manner. To identify nonreceptor proteins that confer specificity or regulate steroid signaling, we screened a human cDNA library in a steroid-responsive yeast strain. One of the identified cDNAs, isolated in the screen as ligand effect modulator 6, showed no homology to yeast or Caenorhabditis elegans proteins but high similarity to the recently described mouse coactivator PGC-1 and was accordingly termed hPGC-1. The hPGC-1 DNA encodes a nuclear protein that is expressed in a tissue-specific manner and carries novel motifs for transcriptional regulators. The expression of hPGC-1 in mammalian cells enhanced potently the transcriptional response to several steroids in a receptor-specific manner. hPGC-1-mediated enhancement required the receptor hormone-binding domain and was dependent on agonist ligands. Functional analysis of hPGC-1 revealed two domains that interact with steroid receptors in a hormone-dependent manner, a potent transcriptional activation function, and a putative dimerization domain. Our findings suggest a regulatory function for hPGC-1 as a tissue-specific coactivator for a subset of nuclear receptors.

Binding of a pure 125I-monoiodoleptin analog to mouse tissues: a developmental study

The preparation of a pure 125I-labeled monoiododerivative of mouse leptin is described. This radiolabeled analog has been used to characterize and localize central and peripheral leptin binding sites (Ob-R) of the mouse at different stages of its development. The affinity values found in membrane homogenates of various mouse tissues are similar and range between 0.1 and 0.3 nM, indicating that all the Ob-R isoforms have a similar affinity. Leptin binding sites are highly expressed at the membrane level in lung, intestine, kidney, liver, and skin and to a lesser degree in stomach, heart, and spleen. Brain, thymus, and pancreas homogenates are devoid of any specific binding. The distribution of mouse Ob-R has also been explored by autoradiography and dipping techniques on whole mouse sections. In lung, leptin binding sites are located at the pulmonary parenchyma and at the bronchiolar epithelial level. Binding sites are expressed all along the digestive tract from the tongue to the rectum (esophagus, stomach, intestine, colon, and rectum). In muscular visceral structures (stomach, intestine, and bladder) the binding is mainly present in the lamina propria. During development, leptin receptors are early expressed in the liver, kidney, and bone. In the lung, the Ob-R level increased gradually from birth to adulthood where the expression is maximal. By contrast, leptin receptors located in the medulla of the kidney remain remarkably constant all along the development. A broad signal is present in cartilage and bone particularly in vertebrae, limb, and ribs. Interestingly, leptin receptors are barely detectable in the mouse brain except in the choroid plexus and leptomeninges, whereas in the rat brain leptin binding sites are located in the thalamus, the piriform cortex, the cerebellum (at the granular and molecular cell layer), and the pineal gland.

Uncoupling protein homologs: emerging views of physiological function

The widespread occurrence of excess weight and related diseases demands that efforts be made to understand energy expenditure from the gene to the whole animal. For some time, it has been understood that mitochondrial oxidation of fuels generates an electrochemical gradient via outward pumping of protons by the electron transport chain. ATP production via F(1)F(0) ATP synthase is then facilitated by the inward flux of protons down the gradient. There is a growing appreciation that a significant portion of the metabolic rate of endotherms is attributable to counteracting "proton leak" (uncoupling), wherein a flux of protons down the electrochemical gradient generates heat independently of ATP production. Proton leak is especially apparent in thermogenic brown adipose tissue, which expresses a tissue-specific uncoupling protein (UCP1). The recent discovery of widely expressed putative UCP1 homologs [UCP2, UCP3, UCP4, UCP5/brain mitochondrial carrier protein-1 (BMCP1)] raised the possibility that innate proton leak and metabolic rate are regulated by UCP1-like proteins. On the basis of current published data, one may not exclude the possibility that UCP homologs influence metabolic rate.

Cholecystokinin and leptin act synergistically to reduce body weight

Leptin, the product of the obese gene, reduces food intake and body weight in rats and mice, whereas administration of the gut-peptide CCK reduces meal size but not body weight. In the current experiments, we report that repeated daily combination of intracerebroventricular leptin and intraperitoneal CCK results in significantly greater loss of body weight than does leptin alone. However, leptin plus CCK treatment does not synergistically reduce the size of individual 30-min sucrose meals during this period, and the effect of leptin-CCK combination on daily chow intake, while significant, is small compared with the robust effects on body weight loss. This synergistic effect on body weight loss depends on a peripheral action of CCK and a central action of leptin. These data suggest a previously unsuspected role for CCK in body weight regulation that may not depend entirely on reduction of feeding behavior and suggest a strategy for enhancing the effects of leptin in leptin-resistant obese individuals.

The SRC family of nuclear receptor coactivators

Nuclear hormone receptors are ligand-dependent transcription factors that regulate genes critical to such biological processes as development, reproduction, and homeostasis. Interestingly, these receptors can function as molecular switches, alternating between states of transcriptional repression and activation, depending on the absence or presence of cognate hormone, respectively. In the absence of hormone, several nuclear receptors actively repress transcription of target genes via interactions with the nuclear receptor corepressors SMRT and NCoR. Upon binding of hormone, these corepressors dissociate away from the DNA-bound receptor, which subsequently recruits a nuclear receptor coactivator (NCoA) complex. Prominent among these coactivators is the SRC (steroid receptor coactivator) family, which consists of SRC-1, TIF2/GRIP1, and RAC3/ACTR/pCIP/AIB-1. These cofactors interact with nuclear receptors in a ligand-dependent manner and enhance transcriptional activation by the receptor via histone acetylation/methylation and recruitment of additional cofactors such as CBP/p300. This review focuses on the mechanism of action of SRC coactivators in terms of interactions with receptors and activation of transcription. Specifically, the roles of the highly conserved LXXLL motifs in mediating SRC function will be detailed. Additionally, potential diversity among SRC family members, as well as several recently cloned SRC-associated cofactors, will be discussed.

Light and ultrastructural immunocytochemical study of somatotropic cells (GH cells) in ovine adenohypophysis: lactation and weaning influences

The influence of lactation period and weaning on the distribution, number, and structure of somatotropic cells (GH cells) in ewes was studied using immunocytochemical procedures for light and electron microscopy, as well as morphometric and stereological techniques. The adenohypophyseal gland of 12 ewes of the Segureña breed in different stages of milk production and weaning was studied, while three ewes in anoestrus served as controls. The size of secretory granules was heterogeneous in all stages, suggesting that this characteristic is not related to functional activity. During lactation and weaning the size of GH cells decreased, while the number of 'synthesis cells' increased. The rough endoplasmic reticulum and Golgi complex appeared more developed and small secretory granules showed lower gold particle labelling. These data suggest that GH cells are more active during lactation, particularly during late lactation.

The coactivator PGC-1 cooperates with peroxisome proliferator-activated receptor alpha in transcriptional control of nuclear genes encoding mitochondrial fatty acid oxidation enzymes

Peroxisome proliferator-activated receptor alpha (PPARalpha) plays a key role in the transcriptional control of genes encoding mitochondrial fatty acid beta-oxidation (FAO) enzymes. In this study we sought to determine whether the recently identified PPAR gamma coactivator 1 (PGC-1) is capable of coactivating PPARalpha in the transcriptional control of genes encoding FAO enzymes. Mammalian cell cotransfection experiments demonstrated that PGC-1 enhanced PPARalpha-mediated transcriptional activation of reporter plasmids containing PPARalpha target elements. PGC-1 also enhanced the transactivation activity of a PPARalpha-Gal4 DNA binding domain fusion protein. Retroviral vector-mediated expression studies performed in 3T3-L1 cells demonstrated that PPARalpha and PGC-1 cooperatively induced the expression of PPARalpha target genes and increased cellular palmitate oxidation rates. Glutathione S-transferase "pulldown" studies revealed that in contrast to the previously reported ligand-independent interaction with PPARgamma, PGC-1 binds PPARalpha in a ligand-influenced manner. Protein-protein interaction studies and mammalian cell hybrid experiments demonstrated that the PGC-1-PPARalpha interaction involves an LXXLL domain in PGC-1 and the PPARalpha AF2 region, consistent with the observed ligand influence. Last, the PGC-1 transactivation domain was mapped to within the NH(2)-terminal 120 amino acids of the PGC-1 molecule, a region distinct from the PPARalpha interacting domains. These results identify PGC-1 as a coactivator of PPARalpha in the transcriptional control of mitochondrial FAO capacity, define separable PPARalpha interaction and transactivation domains within the PGC-1 molecule, and demonstrate that certain features of the PPARalpha-PGC-1 interaction are distinct from that of PPARgamma-PGC-1.

Vertebrate mitochondrial DNA-a circle of surprises

Evidence for the existence of a vertebrate mitochondrial genome first arose over 30 years ago. Application of emerging techniques of molecular biology established the structure of vertebrate mitochondrial DNA (mtDNA) as a small closed-circular species. The ability to purify these mtDNAs to a high degree facilitated studies on the overall replication and expression pattern of the genome. With the acquisition of the genomic sequences of human and mouse mtDNAs, it was possible to infer the genetic organization and some of the genes contained therein, as well as providing a basis for developing strategies to assign important regulatory elements involved in mtDNA replication and transcription. This, in turn, presented the opportunity to identify nucleus-encoded proteins that target to mtDNA and, in doing so, determine the replication and expression modes of the genome. Vertebrate cells, in general, need mtDNA due to the requirements for maintaining a functional oxidative phosphorylation pathway. Depression of mtDNA content or mutations in mtDNA can result in metabolic dysfunction severe enough, in some cases, to result in human lethality. The emergence of mouse models for human mitochondrial diseases should provide the experimental context to understand the full role of mtDNA in different cells, tissues, and organs; the control of organelle biogenesis; and the development of therapeutic strategies for treatment of mitochondrial disorders.

Basement membrane proteins and apolipoprotein E in growth hormone secreting adenomas and their correlation to amyloid: an immunoelectron microscopic study

Having previously demonstrated the association of basement membrane components (BMC), as well as apolipoprotein E and amyloid in growth hormone (GH)-producing pituitary adenomas, the aim of this study was to further analyze this relationship at the ultrastructural level. Ultrathin sections from four amyloidotic sparsely granulated monohormonal GH-producing adenomas previously investigated light microscopically were selected. Immunoelectron microscopy was performed, using a single labeling postembedding on-grid Protein-A gold method with antisera directed against laminin, fibronectin and apolipoprotein E. In all four adenomas, anti-laminin, anti-fibronectin, and anti-apolipoprotein E reacted with amyloid fibrils. No BMC were demonstrated between amyloid deposits, making it likely that synthesis and deposition of BMC may be secondary to the deposition of amyloid. The intimate spatial relationship between BMC as well as apolipoprotein E and amyloid fibrils may indicate morphological evidence of a particular arrangement of amyloid components in GH-secreting adenoma amyloid and a pathophysiological link.

Regulation of energy metabolism in human cells in aging and diabetes: FoF(1), mtDNA, UCP, and ROS

Recent advances in bioenergetics consist of discoveries related to rotational coupling in ATP synthase (FoF(1)), uncoupling proteins (UCP), reactive oxygen species (ROS) and mitochondrial DNA (mtDNA). As shown in cloned sheep, mammalian genomes are composed of both nuclear DNA (nDNA) and maternal mtDNA. Oxidative phosphorylation (oxphos) varies greatly depending on cellular activities, and is regulated by both gene expression and the electrochemical potential difference of H(+) (Delta muH(+)). The expression of both mtDNA (by mtTFA) and nDNA for oxphos and UCP (by NRFs, etc.) is coordinated by a factor called PGC-1. The Delta muH(+) rotates an axis in FoF(1) that is regulated by inhibitors and ATP-sensitive K(+)-channels. We cultured human rho(o) cells (cells without mtDNA) in synthetic media and elucidated relationships among mtDNA, nDNA, Delta muH(+), UCPs, ROS, and apoptosis. These cells lack oxphos-dependent ROS formation and survive under conditions of high O(2). Cells cultured in the absence of ROS scavengers have proliferated for 40 years. UCPs lower Delta muH(+) and prevent ROS formation and resulting apoptosis. These results were applied to diabetology and gerontology. The pancreatic rho(o) cells did not secrete insulin, and mtDNA mutations caused diabetes, owing to the deficient Delta muH(+). Insulin resistance was closely related to UCPs and other energy regulators. The resulting high-glucose environment caused glycation of proteins and ROS-mediated apoptosis in vascular cells involved in diabetic complications. Telomeres, oxphos, and ROS are determinants in cellular aging. Cell division and ROS shortened telomeres and accelerated aging. In aged cells, Delta muH(+) was reduced by the slow respiration, and this change induced apoptosis. Cybrids made from aged cytoplasts and rho(o) cells showed that both decreased expression of nDNA, and somatic mutations of mtDNA are involved in the slowing of respiration in aged cells.

Brain uncoupling protein 2: uncoupled neuronal mitochondria predict thermal synapses in homeostatic centers

Distinct brain peptidergic circuits govern peripheral energy homeostasis and related behavior. Here we report that mitochondrial uncoupling protein 2 (UCP2) is expressed discretely in neurons involved in homeostatic regulation. UCP2 protein was associated with the mitochondria of neurons, predominantly in axons and axon terminals. UCP2-producing neurons were found to be the targets of peripheral hormones, including leptin and gonadal steroids, and the presence of UCP2 protein in axonal processes predicted increased local brain mitochondrial uncoupling activity and heat production. In the hypothalamus, perikarya producing corticotropin-releasing factor, vasopressin, oxytocin, and neuropeptide Y also expressed UCP2. Furthermore, axon terminals containing UCP2 innervated diverse hypothalamic neuronal populations. These cells included those producing orexin, melanin-concentrating hormone, and luteinizing hormone-releasing hormone. When c-fos-expressing cells were analyzed in the basal brain after either fasting or cold exposure, it was found that all activated neurons received a robust UCP2 input on their perikarya and proximal dendrites. Thus, our data suggest the novel concept that heat produced by axonal UCP2 modulates neurotransmission in homeostatic centers, thereby coordinating the activity of those brain circuits that regulate daily energy balance and related autonomic and endocrine processes.

Cryoglobulinemia

Cryoglobulinemia may be found in a spectrum of disorders spanning clear-cut-B-cell neoplastic states, in which cryoprecipitation manifests as ischemic or occlusive vasculopathy, to a variety of immune complex diseases, in which vasculitis or glomerulonephritis may occur. Symptomatic cryoglobulinemia is many diseases, driven by and driving antibody-antigen responses, hepatic dysfunction, lymphoproliferation, and immune complexes. Distinguishing features that cause only some cryoglobulins to be symptomatic, elucidating the pathogenic mechanisms of HCV in cryoglobulin formation, and devising better therapies and more systematic evaluation of existing therapies are among the challenges for the future. Prognostication and classification will continue to rely on Brouet's classification (types I, II, and III), but additional features will probably include the presence or absence of HCV, HCV factors (genotype, titer), coexisting infections, B-cell clone burden, host factors, and immune system interactions (B- and T-cell idiotype networks, cytokines). Although antiviral therapy is a reasonable option for HCV-associated cryoglobulinemia, not all patients are HCV-positive, and only 60% to 80% of HCV-positive patients respond to IFN. In addition, not all patients tolerate IFN, and in those who do, the response is often short-lived once the treatment is discontinued. Only creative strategies, systematically studied, will provide long-awaited solutions.

Physiological roles of the leptin endocrine system: differences between mice and humans

Leptin is a 16-kDa cytokine secreted in humans primarily but not exclusively by adipose tissues. Its concentration in blood is usually proportional to body fat mass, but is higher in women than in men not only because of a different distribution of and greater fat mass in women, but also because testosterone reduces its level in men. Leptin features in different ways during the life span. It is synthesized in the ovary, transported in the oocyte, and made by both fetus and placenta, particularly during the last month of gestation. It is made by the lactating mammary gland and ingested by the newborn infant in its milk. The prime importance of leptin is realized at puberty when it is necessary for progression to a normal adult reproductive status in females. Fasting and chronic undernutrition result in a lower level of leptin in the blood. Lack of leptin results in hunger, ensuring that the individual eat to survive, and also inhibition of reproduction, until such time as food and fat stores are adequate to supply energy for pregnancy and lactation. Thus, leptin is important for survival of the individual and survival of the species. Although an extremely rare genetic absence of leptin induces hyperphagia and obesity in humans, as it does in mice, there appears to be little role for leptin in humans in ensuring that fat stores are not in excess of adequate, that is, in preventing obesity. The mouse differs from humans in many respects, in particular in the far more drastic ways it conserves energy when it very rapidly adapts to lack of food. These include not only suppression of reproduction but also lowering of its body temperature (torpor), suppressing its thyroid function, suppressing its growth, and increasing secretion of stress hormones (from the adrenal). This review concentrates on roles of leptin in human physiology and pathophysiology but also discusses why some observations on actions of leptin in mice are not applicable to humans.

Activation of PPARgamma coactivator-1 through transcription factor docking

Transcriptional coactivators have been viewed as constitutively active components, using transcription factors mainly to localize their functions. Here, it is shown that PPARgamma coactivator-1 (PGC-1) promotes transcription through the assembly of a complex that includes the histone acetyltransferases steroid receptor coactivator-1 (SRC-1) and CREB binding protein (CBP)/p300. PGC-1 has a low inherent transcriptional activity when it is not bound to a transcription factor. The docking of PGC-1 to peroxisome proliferator-activated receptor gamma (PPARgamma) stimulates an apparent conformational change in PGC-1 that permits binding of SRC-1 and CBP/p300, resulting in a large increase in transcriptional activity. Thus, transcription factor docking switches on the activity of a coactivator protein.

Effects of leptin on fasting-induced inhibition of neuronal nitric oxide synthase mRNA in the paraventricular and supraoptic nuclei of rats

Fasting induced a reduction in neuronal nitric oxide synthase (nNOS) mRNA in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of rats. The effect of intracerebroventricular (i.c.v.) administration of leptin on the nNOS mRNA level in the PVN and SON of fasting rats was studied by in situ hybridization histochemistry. Leptin (10 microg/kg b.wt) or vehicle was administered i.c.v. at 1700 h on two successive days fasting for 2 days. Fasting for 2 days with i.c.v. administration of vehicle induced a significant reduction of nNOS mRNA in the PVN and SON. Central administration of leptin prevented the fasting-induced reduction of nNOS mRNA in the PVN and SON. Administration of leptin also prevented the fasting-induced reductions of thyrotropin-releasing hormone (TRH) and corticotropin-releasing hormone (CRH) mRNAs in the parvocellular division of the PVN. These results suggest that leptin is associated with fasting-induced reduction of nNOS mRNA in the PVN and SON as well as TRH and CRH mRNAs in the PVN.

Noninvasive (13)C-octanoic acid breath test shows delayed gastric emptying in patients with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive loss of motor neurons. However, ALS has been recognized to also involve non-motor systems. Subclinical involvement of the autonomic system in ALS has been described. The recently developed (13)C-octanoic acid breath test allows the noninvasive measurement of gastric emptying. With this new technique we investigated 18 patients with ALS and 14 healthy volunteers. None of the patients had diabetes mellitus or other disorders known to cause autonomic dysfunction. The participants received a solid standard test meal labeled with (13)C-octanoic acid. Breath samples were taken at 15-min intervals for 5 h and were analyzed for (13)CO(2) by isotope selective nondispersive infrared spectrometry. Gastric emptying peak time (t(peak)) and emptying half time (t(1/2)) were determined. All healthy volunteers displayed normal gastric emptying with a mean emptying t(1/2) of 138 +/- 34 (range 68-172) min. Gastric emptying was delayed (t(1/2) > 160 min) in 15 of 18 patients with ALS. Emptying t(1/2) in ALS patients was 218 +/- 48 (range 126-278) min (p < 0.001). These results are compatible with autonomic involvement in patients with ALS, causing delayed gastric emptying of solids and encouraging the theory that ALS is a multisystem disease rather than a disease of the motor neurons only.

Insulin but not IGF-I is required for the maintenance of the adipose phenotype in the adipogenic cell line 1246

The mouse adipogenic cell line 1246 which possesses both insulin and insulin-like growth factor I (IGF-I) receptors was used to investigate the role of IGF-I and insulin on the proliferation of adipocyte precursors and their differentiation into mature adipocytes. Results indicate that both insulin and IGF-I stimulate the proliferation of the 1246 adipocyte precursors with IGF-I being slightly more potent than insulin. Dose-response studies indicated that both polypeptides acted at physiological concentrations corresponding to binding to their own receptors. In contrast, comparison of insulin and IGF-I capacity to stimulate terminal adipose differentiation indicated that only insulin was active when added at physiological concentrations. IGF-I could not stimulate adipocyte differentiation except at supraphysiological concentrations (100 ng/ml and above) permitting its binding to the insulin receptors on 1246 cells. Time course study of expression of early and late markers of adipose differentiation indicated that the induction of markers such as adipose differentiation-related protein (ADRP), lipoprotein lipase (LPL) and fatty acid binding protein (FAB) took place even in the absence of insulin. However, the level of early and late differentiation markers decreased to a level below the one found in undifferentiated cells when cells had been maintained in the absence of insulin after differentiation had been initiated. These data indicate that although insulin is not necessary for the early onset of the adipose differentiation program, it is stringently required for the maintenance of the adipocyte phenotype and cannot be substituted by IGF-I.

Adaptive thermogenesis: orchestrating mitochondrial biogenesis

The biogenesis of mitochondria requires products of the nuclear and mitochondrial genomes. Recent studies of adaptive thermogenesis have shown how mitochondrial proliferation and respiratory activity in brown fat and skeletal muscle are directed by the transcriptional coactivator PGC-1.

Lipomatous hemangiopericytoma: a morphologically distinct soft tissue tumor

Hemangiopericytoma of soft tissue is a controversial pathologic entity. The relative nonspecificity of the characteristic branching capillary pattern and cytologic features of the constituent cells, in addition to the lack of a distinct immunohistochemical staining profile, has resulted in uncertainty and a lack of consensus regarding this subgroup of tumors. Notwithstanding the doubt surrounding this entity, a morphologically unique variant, designated lipomatous hemangiopericytoma, was reported in 1995. To our knowledge, there have been no further reports of these tumors since the original description. We describe a lipomatous hemangiopericytoma that arose within the thigh of a 41-year-old woman. The tumor presented as a slowly enlarging, minimally tender, pulsatile mass. The tumor was completely excised and was found to be composed of an admixture of typical hemangiopericytoma and predominantly mature adipose tissue. Unlike previous descriptions of this entity, the current example exhibited a full range of adipocyte differentiation, including many multivacuolated adipocytes of variable size with characteristic nuclear scalloping (lipoblast-like cells). The mitotic count was less than 2 per 10 high-power fields examined. The clinical course has been benign during the short follow-up period. We discuss the pathologic features, including the immunohistochemical staining profile and ultrastructural appearance of this distinctive tumor, and briefly discuss the relationship between hemangiopericytoma and solitary fibrous tumor of soft tissue, a neoplasm with many clinical and pathologic similarities.

Frequency and significance of the A-->G (-3826) polymorphism in the promoter of the gene for uncoupling protein-1 with regard to metabolic parameters and adipocyte transcription factor binding in a large population-based Caucasian cohort

BACKGROUND

The recently described A-->G (-3826) point mutation within the distal region of the UCP-1 promoter is possibly involved in the development of obesity, diabetes and related metabolic disorders. It was the aim of this study to examine the allelic frequency and the prevalence of the three UCP-1 genotypes in a broad caucasian cohort and to investigate the significance of this polymorphism for obesity and diabetes.

METHODS

1020 subjects were randomly chosen from 6450 participants in the Diabetomobile Study. The UCP-1 genotype was determined by genomic PCR and Bcl-I-RFLP analysis in 1020 subjects and tested for association with a variety of metabolic parameters. In addition, the influence of this mutation on adipocyte nuclear factor binding was investigated by electrophoretic mobility shift assays (EMSA).

RESULTS

The genotype frequencies in 1020 subjects were: AA genotype, 57.0%; AG genotype, 35.4%; GG genotype, 7.6%; with allelic frequencies of 0.75 for allele A and 0.25 for allele G. No significant differences between the genotypes and age, gender, BMI, leptin, glucose, fasting insulin, C-peptide, HbA1c, diabetes manifestation, total cholesterol, and HDL cholesterol were found. Analysis of the Trp64Arg polymorphism of the beta3-adrenergic receptor in a subgroup of 343 subjects revealed no additive effect to the UCP-1 polymorphism. An yet unknown adipocyte-specific factor of nuclear extracts from 3T3-L1 adipocytes during differentiation is able to bind specifically to the distal UCP-1 promoter region and this binding ability can not be abolished by the mutation.

CONCLUSIONS

We determined the genotype and allelic frequency of the UCP-1 promoter polymorphism in the largest known population-based study. The results from genotyping demonstrate clearly that this polymorphism does not play a major role in the pathogenesis obesity and diabetes. A yet unknown adipocyte derived and differentiation-dependent regulated transcription factor is able to bind to the distal UCP-1 promoter surrounding -3826 bp. This binding is not affected by presence of the mutation.

Pathological difference between retractile and cryptorchid testes

PURPOSE

We compared testicular biopsies from retractile and cryptorchid testes to determine the histological effect of testicular retraction and the necessity of treatment for retractile testes.

MATERIALS AND METHODS

A total of 61 testicular biopsies were performed during orchiopexy in 36 boys 1.3 to 9.8 years old (mean age 5.4) with retractile testes (unilateral in 11, bilateral in 50) and 115 testicular biopsies were done in 83 patients with cryptorchidism (unilateral in 51, bilateral in 64) 0.5 to 14.9 years old (mean age 3.7). Parameters for germ and Sertoli cells were determined in each group.

RESULTS

Mean average spermatogonial number (S/T value) and Sertoli cell index were statistically different between retractile and cryptorchid testes with values of 2.96+/-1.33 versus 0.61+/-0.87 and 26.81+/-6.75 versus 23.04+/-5.85, respectively. Average tubular degeneration phase V to VII ratio was 0.23+/-0.18 for retractile testes and 0.22+/-0.17 for cryptorchid testes which was not statistically different.

CONCLUSIONS

Similar tubular degeneration phase V to VII values between retractile and cryptorchid testes indicate histological change in retractile testes and suggest the need for hormonal or surgical therapy for those patients with retractile testes lacking spontaneous descent.

A novel promoter variant of the natriuretic peptide clearance receptor gene is associated with lower atrial natriuretic peptide and higher blood pressure in obese hypertensives

OBJECTIVE AND DESIGN

The clearance receptor for natriuretic peptides (NPRC), a candidate gene for essential hypertension, is highly expressed in adipose tissue, where is nutritionally regulated. The objectives of the present study were to sequence the human 5'-flanking regulatory region of NPRC, to identify allelic variants and their frequencies, and to study the genotype/phenotype correlation in hypertensive patients.

METHODS AND RESULTS

Using polymerase chain reaction (PCR) and direct automated sequencing, a biallelic (A/C) polymorphism was detected at position -55 in a conserved promoter element named P1. The novel C(-55) variant makes the promoter sequence identical to the mouse gene and introduces a second Hgal site in the amplified DNA, allowing the genotyping of a large number of subjects. In a random sample of 232 white Caucasians the C(-55) allele was more commonly found (81.7% of all alleles) with 155 CC (66.8%), 69 AC (29.7%) and only eight AA (3.5%) genotypes. Atrial natriuretic peptide (ANP) levels were determined in 84 patients with essential hypertension. In the presence of obesity (body mass index (BMI) > or = 30 kg/m2) the homozygous CC hypertensives (n = 21) had significantly lower plasma ANP (33.6 +/- 11.1 pg/ml) compared with the AC patients (n = 11; 46.8 +/- 15.9 pg/ml; P = 0.01), whereas systolic blood pressure (SBP) and mean blood pressure (MBP) had the opposite association (SBP 163.9 +/- 18.7 versus 150.9 +/- 12.9 and MBP 123.3 +/- 12 versus 114.5 +/- 5.9 mmHg; P< 0.05). The difference in ANP levels were also present when overweight patients (BMI > or = 27 kg/m2) were considered.

CONCLUSION

A common 'ancestral' C(-55) variant of the NPRC P1 promoter is associated with lower ANP levels and higher SBP and MBP in obese hypertensives. The C(-55) variant, in the presence of increased adiposity, might reduce plasma ANP through increased NPRC-mediated ANP clearance, contributing to higher blood pressure.