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Encyclopedia > Leptin
Leptin (obesity homolog, mouse)
PDB rendering based on 1ax8.
Available structures: 1ax8
Identifiers
Symbol(s) LEP; OB; OBS
External IDs OMIM: 164160 MGI: 104663 Homologene: 193
RNA expression pattern

Image File history File links Size of this preview: 766 × 599 pixelsFull resolution‎ (928 × 726 pixels, file size: 268 KB, MIME type: image/png) File historyClick on a date/time to view the file as it appeared at that time. ... The Protein Data Bank (PDB) is a repository for 3-D structural data of proteins and nucleic acids. ... Look up Hugo in Wiktionary, the free dictionary. ... The Mouse Genome Informatics (MGI) website is run by The Jackson Laboratory. ... HomoloGene[1], a tool of the National Center for Biotechnology Information (NCBI)[2], is a system for automated detection of homologs (similarity attributable to descent from a common ancestor) among the annotated genes of several completely sequenced eukaryotic genomes. ... The Gene Ontology, or GO, project can be broadly split into two parts. ... Image File history File links No higher resolution available. ...


More reference expression data

Orthologs
Human Mouse
Entrez 3952 16846
Ensembl ENSG00000174697 ENSMUSG00000059201
Uniprot P41159 Q544U0
Refseq NM_000230 (mRNA)
NP_000221 (protein)
NM_008493 (mRNA)
NP_032519 (protein)
Location Chr 7: 127.67 - 127.68 Mb Chr 6: 29.01 - 29.02 Mb
Pubmed search [1] [2]
leptin receptor
Identifiers
Symbol LEPR
Entrez 3953
HUGO 6554
OMIM 601007
RefSeq NM_002303
UniProt P48357
Other data
Locus Chr. 1 p31

Leptin (from the Greek word leptos, meaning thin) is a 16 kDa protein hormone that plays a key role in regulating energy intake and energy expenditure, including the regulation (decrease) of appetite and (increase) of metabolism. The Entrez logo The Entrez Global Query Cross-Database Search System allows access to databases at the National Center for Biotechnology Information (NCBI) website. ... Ensembl is a bioinformatics research project aiming to develop a software system which produces and maintains automatic annotation on selected eukaryotic genomes. It is run in a collaboration between the Wellcome Trust Sanger Institute and the European Bioinformatics Institute, an outstation of the European Molecular Biology Laboratory. ... UniProt is the universal protein database, a central repository of protein data created by combining Swiss-Prot, TrEMBL and PIR. This makes it the worlds most comprehensive resource on protein information. ... Medline is a comprehensive literature database of life sciences and biomedical information. ... Orthologs Human Mouse Entrez Ensembl na Uniprot na Refseq Location na Pubmed search Leptin receptor, also known as LEPR, is a human gene. ... Orthologs Human Mouse Entrez Ensembl na Uniprot na Refseq Location na Pubmed search Leptin receptor, also known as LEPR, is a human gene. ... The Entrez logo The Entrez Global Query Cross-Database Search System allows access to databases at the National Center for Biotechnology Information (NCBI) website. ... Look up Hugo in Wiktionary, the free dictionary. ... The Mendelian Inheritance in Man project is a database that catalogues all the known diseases with a genetic component, and - when possible - links them to the relevant genes in the human genome. ... National Center for Biotechnology Information logo The National Center for Biotechnology Information (NCBI) is part of the United States National Library of Medicine (NLM), a branch of the National Institutes of Health. ... Swiss-Prot is a curated biological database of protein sequences created in 1986 by Amos Bairoch during his PhD and developed by the Swiss Institute of Bioinformatics and the European Bioinformatics Institute. ... Short and long arms Chromosome. ... Chromosome 1 is, by convention, the designation for the largest human chromosome. ... The unified atomic mass unit (u), or dalton (Da), is a small unit of mass used to express atomic and molecular masses. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... For other uses, see Hormone (disambiguation). ... The appetite is the desire to eat food, felt as hunger. ... Structure of the coenzyme adenosine triphosphate, a central intermediate in energy metabolism. ...


The effects of leptin were observed by studying mutant obese mice that arose at random within a mouse colony at the Jackson Laboratory in 1950. These mice were massively obese and hyperphagic. Leptin itself was discovered in 1994 by Jeffrey M. Friedman and colleagues at the Rockefeller University through the study of those mutant mice. The Ob(Lep) gene (Ob for obese and Lep for leptin) is located on chromosome 7 in humans. Leptin is produced by adipose tissue and interacts with six types of receptor (LepRa–LepRf). LepRb is the only receptor isoform that contains active intracellular signaling domains. This receptor is present in a number of hypothalamic nuclei, where it exerts its effects. Importantly, leptin binds to the ventral medial nucleus of the hypothalamus, known as the "appetite center." Binding of leptin to this nucleus signals to the brain that the body has had enough to eat—a sensation of satiety. A very small group of humans possess homozygous mutations for the leptin gene which lead to a constant demand for food, resulting in severe obesity. This condition can be successfully treated by the administration of recombinant human leptin.[1] This article is about biological mutants. ... Obesity is a condition in which the natural energy reserve, stored in the fatty tissue of humans and other mammals, is increased to a point where it is associated with certain health conditions or increased mortality. ... Mice may refer to: An abbreviation of Meetings, Incentives, Conferencing, Exhibitions. ... The Jackson Laboratory was founded in Bar Harbor, Maine in 1929 by C. C. Little. ... Jeffrey Friedman, MD, PhD, is a molecular geneticist at New York Citys Rockefeller University. ... Founders Hall Rockefeller University is a private university focusing primarily on graduate and postgraduate education research in the biomedical fields, located between 63rd and 68th Streets along York Avenue, on the Upper East Side of Manhattan island in New York City, New York. ... Chromosome 7 is one of the 23 pairs of chromosomes in humans. ... Adipose tissue is one of the main types of connective tissue. ... The hypothalamus links the nervous system to the endocrine system via the pituitary gland (hypophysis). ... The hypothalamus links the nervous system to the endocrine system via the pituitary gland (hypophysis). ... The appetite is the desire to eat food, felt as hunger. ...


Thus, circulating leptin levels give the brain a reading of energy storage for the purposes of regulating appetite and metabolism. Leptin works by inhibiting the activity of neurons that contain neuropeptide Y (NPY) and agouti-related peptide (AgRP), and by increasing the activity of neurons expressing α-melanocyte-stimulating hormone (α-MSH). The NPY neurons are a key element in the regulation of appetite; small doses of NPY injected into the brains of experimental animals stimulates feeding, while selective destruction of the NPY neurons in mice causes them to become anorexic. Conversely, α-MSH is an important mediator of satiety, and differences in the gene for the receptor at which α-MSH acts in the brain are linked to obesity in humans. The appetite is the desire to eat food, felt as hunger. ... Structure of the coenzyme adenosine triphosphate, a central intermediate in energy metabolism. ... Neurons (also called nerve cells) are the primary cells of the nervous system. ... Neuropeptide Y (NPY) is a 36 amino acid peptide neurotransmitter found in the brain and autonomic nervous system. ... This page is a candidate for speedy deletion because: nonsense If you disagree with its speedy deletion, please explain why on its talk page or at Wikipedia:Speedy deletions. ... Neurons (also called nerve cells) are the primary cells of the nervous system. ... Melanocyte-stimulating hormone (MSH) is a peptide hormone produced by cells in the intermediate lobe of the pituitary gland. ... Anorexia (deriving from the Greek α(ν)- (a(n)-, a prefix that denotes absence) + όρεξη (orexe) = appetite) is the decreased sensation of appetite. ... For other uses, see Gene (disambiguation). ...


Leptin is also regulated (downward) by melatonin during the night.[2] Melatonin, 5-methoxy-N-acetyltryptamine, is a hormone found in all living creatures from algae[1] to humans, at levels that vary in a diurnal cycle. ...

Contents

Leptin as adiposity signal

To date, only leptin and insulin fulfill the criteria of an adiposity signal: Not to be confused with inulin. ...

  • It circulates at levels proportional to body fat.
  • It enters the central nervous system (CNS) in proportion to its plasma concentration.
  • Its receptors are found in brain neurons involved in regulating energy intake and expenditure.

Adipose tissue is one of the main types of connective tissue. ... A diagram showing the CNS: 1. ... Blood plasma is the liquid component of blood, in which the blood cells are suspended. ...

Mechanism of action

It is unknown whether leptin can cross the blood-brain barrier to access receptor neurons, because the blood-brain barrier is somewhat absent in the area of the median eminence, close to where the NPY neurons of the arcuate nucleus are. If it does cross the blood-brain barrier, it is unknown whether this occurs via an active or passive process. It is generally thought that leptin might enter the brain at the choroid plexus, where there is intense expression of a form of leptin receptor molecule that might act as a transport mechanism. The blood-brain barrier (BBB) is a membranic structure that acts primarily to protect the brain from chemicals in the blood, while still allowing essential metabolic function. ... Median Eminence The median eminence is part of the inferior boundary for the hypothalamus. ... In neuroanatomy, a nucleus is a central nervous system structure that is composed mainly of gray matter, and which acts as a hub or transit point for electrical signals in a single neural subsystem. ... The choroid plexus is the area on the ventricles of the brain where cerebrospinal fluid (CSF) is produced by modified ependymal cells. ...


Once leptin has bound to the Ob-Rb receptor, it activates the molecule stat3, which is phosphorylated and travels to the nucleus, it is presumed, to effect changes in gene expression. One of the main effects on gene expression is the down-regulation of the expression of endocannabinoids, responsible—among their many other functions—for increasing appetite. There are other intracellular pathways activated by leptin, but less is known about how they function in this system. In response to leptin, receptor neurons have been shown to remodel themselves, changing the number and types of synapses that fire onto them. 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... Cannabinoids are a group of chemicals which activate the bodys cannabinoid receptors. ...


Although leptin is a circulating signal that reduces appetite, in general, obese people have an unusually high circulating concentration of leptin.[3] These people are said to be resistant to the effects of leptin, in much the same way that people with type 2 diabetes are resistant to the effects of insulin. Thus, obesity develops when people take in more energy than they use over a prolonged period of time, and this excess food intake is not driven by hunger signals, occurring in spite of the anti-appetite signals from circulating leptin. The high sustained concentrations of leptin from the enlarged fat stores result in the cells that respond to leptin becoming desensitized. See diabetes mellitus for further general information on diabetes. ... Insulin resistance is the condition in which normal amounts of insulin are inadequate to produce a normal insulin response from fat, muscle and liver cells. ... Not to be confused with inulin. ... For other uses, see FAT. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. ...


In mice, leptin is also required for male and female fertility. In mammals generally, and in humans in particular, puberty in females is linked to a critical level of body fat. When fat levels fall below this threshold (as in anorexia), the ovarian cycle stops and females stop menstruating. Fertility is the natural capability of giving life. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary...


Leptin is also strongly linked with angiogenesis, increasing VEGF levels. Angiogenesis is the physiological process involving the growth of new blood vessels from pre-existing vessels. ... Vascular endothelial growth factor (VEGF) is an important signaling protein involved in both vasculogenesis (the de novo formation of the embryonic circulatory system) and angiogenesis (the growth of blood vessels from pre-existing vasculature). ...


Leptin and reproduction

The body's fat cells, under normal conditions, are responsible for the constant production and release of leptin. This can also be produced by the placenta.[4] Leptin levels rise during pregnancy and fall at parturition (childbirth). Leptin is also expressed in fetal membranes and uterine tissue. Uterine muscle contractions are inhibited by leptin.[5] The placenta is a sack of fat present in placental vertebrates, such as some mammals and sharks during gestation (pregnancy). ...


Recent discoveries

Professor Cappuccio of the University of Warwick has recently discovered that short sleep duration may lead to obesity, through an increase of appetite via hormonal changes. Lack of sleep produces ghrelin which, among other effects, stimulates appetite and creates less leptin which, amongst its many other effects, suppresses appetite. The University of Warwick is a British campus university located on the outskirts of Coventry, West Midlands, England. ... Ghrelin is a hormone produced by P/D1 cells lining the acer of the human stomach that stimulate appetite. ...


Next to a biomarker for body fat, serum leptin levels also reflect individual energy balance. Several studies have shown that fasting or following a very low calorie diet (VLCD) lowers leptin levels.[6] It might be that on short term leptin is an indicator of energy balance. In line with evolution this system is more sensitive to starvation than to overfeeding,[7] i.e. leptin levels do not rise extensively after overfeeding. It might be that the dynamics of leptin due to an acute change in energy balance are related to appetite and eventually in food intake. Although this is a new hypothesis, there is already some data that supports it.[8][9] Biomarker is an occasionally used synonym for biosignature, which is a term used in astrobiology to indicate a measurable phenomenon that indicates the presence of life. ... Fasting is primarily the act of willingly abstaining from some or all food, drink, or both, for a period of time. ... Very low calorie diet (VLCD) is a diet with very or extremely low calorie consumption per day. ...


There is gradual recognition that leptin action is more decentralized than previously assumed. In addition to its endocrine action at a distance (from adipose tissue to brain), leptin also acts as a paracrine mediator.[10] In fetal lung leptin is induced in the alveolar interstitial fibroblasts ("lipofibroblasts") by the action of PTHrP secreted by formative alveolar epithelium (endoderm) under moderate stretch. The leptin from the mesenchyme in turn acts back on the epithelium at the leptin receptor carried in the alveolar type II pneumocytes and induces surfactant expression which is one of the main functions of these type II pneumocytes.[11] In addition to white adipose tissue -the major source of leptin, it can also be produced by brown adipose tissue, placenta (syncytiotrophoblasts), ovaries, skeletal muscle, stomach (lower part of fundic glands), mammary epithelial cells, bone marrow, pituitary and liver.[10] Fetus at eight weeks A fetus (alternatively foetus or fœtus) is an embryo in later stages of development, from the third month of pregnancy until birth in humans. ... Parathyroid hormone-related protein (or PTHrP) is a protein occasionally secreted by cancer cells (breast cancer, certain types of lung cancer). ...


There is also evidence that leptin plays a role in hyperemesis gravidarum (severe morning sickness),[12] in polycystic ovary syndrome[13] and a 2007 research suggest that hypothalamic leptin is implicated in bone growth.[14] Hyperemesis gravidarum (from the Latin for extreme vomiting of the pregnant woman) is a severe form of morning sickness. ... Morning sickness, also called nausea, vomiting of pregnancy (emesis gravidarum or NVP), or pregnancy sickness, affects between 50 [1] and 95 percent of all pregnant women as well as some women who use hormonal contraception or hormone replacement therapy. ... Polycystic ovary syndrome (PCOS, also known clinically as Stein-Leventhal syndrome), is an endocrine disorder that affects approximately one in ten women. ...


Modulation of T cells activity in immune system

The important role of Leptin/Leptin receptors were shown in this experiment with mice. It modulates the immune response to atherosclerosis, which is a predisposing factor in patients with obesity. [15]


References

  1. ^ OMIM - LEPTIN; LEP
  2. ^ Kus I, Sarsilmaz M, Colakoglu N, et al (2004). "Pinealectomy increases and exogenous melatonin decreases leptin production in rat anterior pituitary cells: an immunohistochemical study". Physiological research / Academia Scientiarum Bohemoslovaca 53 (4): 403–8. PMID 15311999. 
  3. ^ Considine RV, Sinha MK, Heiman ML, Kriauciunas A, Stephens TW, Nyce MR, Ohannesian JP, Marco CC, McKee LJ & Bauer TL (1996). "Serum Immunoreactive-Leptin Concentrations in Normal-Weight and Obese Humans". N Engl J Med 334 (5): 292-295. PMID 8532024. 
  4. ^ Zhao J, Townsend KL, Schulz LC, Kunz TH, Li C, Widmaier EP (2004). "Leptin receptor expression increases in placenta, but not hypothalamus, during gestation in Mus musculus and Myotis lucifugus". Placenta 25 (8-9): 712–22. PMID 15450389. 
  5. ^ Moynihan AT, Hehir MP, Glavey SV, Smith TJ, Morrison JJ (2006). "Inhibitory effect of leptin on human uterine contractility in vitro". Am. J. Obstet. Gynecol. 195 (2): 504-9. PMID 16647683. 
  6. ^ Studies include:
    • Dubuc G, Phinney S, Stern J, Havel P (1998). "Changes of serum leptin and endocrine and metabolic parameters after 7 days of energy restriction in men and women". Metab. Clin. Exp. 47 (4): 429-34. PMID 9550541. 
    • Pratley R, Nicolson M, Bogardus C, Ravussin E (1997). "Plasma leptin responses to fasting in Pima Indians". Am. J. Physiol. 273 (3 Pt 1): E644-9. PMID 9316457. 
    • Weigle D, Duell P, Connor W, Steiner R, Soules M, Kuijper J (1997). "Effect of fasting, refeeding, and dietary fat restriction on plasma leptin levels". J. Clin. Endocrinol. Metab. 82 (2): 561-5. PMID 9024254. 
  7. ^ Chin-Chance C, Polonsky K, Schoeller D (2000). "Twenty-four-hour leptin levels respond to cumulative short-term energy imbalance and predict subsequent intake". J. Clin. Endocrinol. Metab. 85 (8): 2685-91. PMID 10946866. 
  8. ^ Keim N, Stern J, Havel P (1998). "Relation between circulating leptin concentrations and appetite during a prolonged, moderate energy deficit in women". Am. J. Clin. Nutr. 68 (4): 794-801. PMID 9771856. 
  9. ^ Mars M, de Graaf C, de Groot C, van Rossum C, Kok F (2006). "Fasting leptin and appetite responses induced by a 4-day 65%-energy-restricted diet". International journal of obesity (Lond) 30 (1): 122-8. PMID 16158086. 
  10. ^ a b Margetic S, Gazzola C, Pegg GG, Hill RA (2002). "Leptin: a review of its peripheral actions and interactions". Int. J. Obes. Relat. Metab. Disord. 26 (11): 1407-33. PMID 12439643. 
  11. ^ John S. Torday, Virender K. Rehan (2006). "Up-regulation of fetal rat lung parathyroid hormone-related protein gene regulatory network down-regulates the Sonic Hedgehog/Wnt/betacatenin gene regulatory network". Pediatr. Res. 60 (4): 382-8. PMID 16940239.  — published online before print as DOI 10.1203/01.pdr.0000238326.42590.03
  12. ^ Aka N, Atalay S, Sayharman S, Kiliç D, Köse G, Küçüközkan T (2006). "Leptin and leptin receptor levels in pregnant women with hyperemesis gravidarum". The Australian & New Zealand journal of obstetrics & gynaecology 46 (4): 274-7. PMID 16866785. 
  13. ^ Cervero A, Domínguez F, Horcajadas JA, Quiñonero A, Pellicer A, Simón C (2006). "The role of the leptin in reproduction". Curr. Opin. Obstet. Gynecol. 18 (3): 297-303. PMID 16735830. 
  14. ^ Iwaniec UT, Boghossian S, Lapke PD, Turner RT, Kalra SP (2007). "Central leptin gene therapy corrects skeletal abnormalities in leptin-deficient ob/ob mice". Peptides. PMID 17346852. 
  15. ^ Taleb S, Herbin O, Ait-Oufella H, Verreth W, Gourdy P, Barateau V, Merval R, Esposito B, Clément K, Holvoet P, Tedgui A, Mallat Z. (2007). "Defective leptin/leptin receptor signaling improves regulatory T cell immune response and protects mice from atherosclerosis.". Arterioscler Thromb Vasc Biol. 27 (12): 2691-2698. PMID 17690315. 

Further reading

  • Torday JS, Sun H, Wang L, Torres E, Sunday ME, Rubin LP (Mar 2002). "Leptin mediates the parathyroid hormone-related protein paracrine stimulation of fetal lung maturation". Am. J. Physiol. Lung Cell Mol. Physiol. 282 (3): L405-10. PMID 11839533. 
  • Torday JS, Rehan VK (Jul 2002). "Stretch-stimulated surfactant synthesis is coordinated by the paracrine actions of PTHrP and leptin". Am. J. Physiol. Lung Cell Mol. Physiol. 283 (1): L130-5. PMID 12060569. 
  • Friedman JM, Halaas JL (1998). "Leptin and the regulation of body weight in mammals.". Nature 395 (6704): 763-70. doi:10.1038/27376. PMID 9796811. 
  • Prolo P, Wong ML, Licinio J (1999). "Leptin.". Int. J. Biochem. Cell Biol. 30 (12): 1285-90. PMID 9924798. 
  • Heshka JT, Jones PJ (2001). "A role for dietary fat in leptin receptor, OB-Rb, function.". Life Sci. 69 (9): 987-1003. PMID 11508653. 
  • Janeckova R (2002). "The role of leptin in human physiology and pathophysiology.". Physiological research / Academia Scientiarum Bohemoslovaca 50 (5): 443-59. PMID 11702849. 
  • Lee DW, Leinung MC, Rozhavskaya-Arena M, Grasso P (2002). "Leptin and the treatment of obesity: its current status.". Eur. J. Pharmacol. 440 (2-3): 129-39. PMID 12007531. 
  • Al-Daghri N, Bartlett WA, Jones AF, Kumar S (2002). "Role of leptin in glucose metabolism in type 2 diabetes.". Diabetes, obesity & metabolism 4 (3): 147-55. PMID 12047393. 
  • Sabath Silva EF (2002). "[Leptin]". Rev. Invest. Clin. 54 (2): 161-5. PMID 12053815. 
  • Thomas T, Burguera B (2003). "Is leptin the link between fat and bone mass?". J. Bone Miner. Res. 17 (9): 1563-9. PMID 12211425. 
  • Kraemer RR, Chu H, Castracane VD (2002). "Leptin and exercise.". Exp. Biol. Med. (Maywood) 227 (9): 701-8. PMID 12324651. 
  • Waelput W, Brouckaert P, Broekaert D, Tavernier J (2003). "A role for leptin in the systemic inflammatory response syndrome (SIRS) and in immune response.". Current drug targets. Inflammation and allergy 1 (3): 277-89. PMID 14561193. 
  • Stenvinkel P, Pecoits-Filho R, Lindholm B (2004). "Leptin, ghrelin, and proinflammatory cytokines: compounds with nutritional impact in chronic kidney disease?". Advances in renal replacement therapy 10 (4): 332-45. PMID 14681862. 
  • Cohen P, Ntambi JM, Friedman JM (2004). "Stearoyl-CoA desaturase-1 and the metabolic syndrome.". Curr. Drug Targets Immune Endocr. Metabol. Disord. 3 (4): 271-80. PMID 14683458. 
  • Sahu A (2004). "Leptin signaling in the hypothalamus: emphasis on energy homeostasis and leptin resistance.". Frontiers in neuroendocrinology 24 (4): 225-53. PMID 14726256. 
  • Elefteriou F, Karsenty G (2004). "[Bone mass regulation by leptin: a hypothalamic control of bone formation]". Pathol. Biol. 52 (3): 148-53. doi:10.1016/j.patbio.2003.05.006. PMID 15063934. 
  • Blüher S, Mantzoros CS (2004). "The role of leptin in regulating neuroendocrine function in humans.". J. Nutr. 134 (9): 2469S-2474S. PMID 15333744. 
  • Farooqi S, O'Rahilly S (2007). "Genetics of obesity in humans.". Endocr. Rev. 27 (7): 710-18. doi:10.1210/er.2006-0040. PMID 17122358. 

A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

External links


  Results from FactBites:
 
Genomics|HuGENet|Reviews|Leptin and obesity|PubMed ID: 15972940 (4811 words)
Leptin is an important regulator of the mass of adipose tissue and of body weight; it operates by inhibiting food intake and stimulating energy expenditure.
Leptin is also known to play a role in different parts of the body, such as the male and female reproductive organs, the mammary gland, bone mineral density, the immune system, the gut, the kidney, and the lung (1).
The inability of such elevated leptin levels to alter the obese state of these persons may be related to "leptin resistance," an inability of leptin to enter the cerebral spinal fluid to reach the hypothalamus regions that regulate appetite, or it may simply reflect the large amount of fat tissue in these persons (4).
Olympus MIC-D: Polarized Light Gallery - Leptin (378 words)
A protein hormone, leptin is manufactured in adipose tissue (fat cells) and acts on receptors in the hypothalamus of the brain.
The level of circulating leptin is directly proportional to the total amount of fat in the body and leptin helps maintain the homeostatic control of food intake.
Leptin also acts directly on the cells of the liver and skeletal muscle by stimulating the oxidation of fatty acids found in the mitochondria.
  More results at FactBites »

 
 

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