![]() |
|
|
Diagnostic Systems Laboratories, Incorporated, Webster, TX 77598 and * Beth Israel Deaconess Medical Center, Department of Endocrinology Diabetes and Metabolism, RN 325, Boston, MA 02215
2To whom correspondence should be addressed. E-mail: cmantzor{at}bidmc.harvard.edu.
| ABSTRACT |
|---|
|
|
|---|
KEY WORDS: obesity energy homeostasis leptin ghrelin insulin adiponectin resistin peptide YY3-36
In the early 1950s, it was first postulated that food intake is closely linked to the amount of stored energy (fat mass) in the body. During the 1970s and 80s, gut peptide cholecystokinin, bombesin, gastrin-releasing peptide, neuromedin B (1) and glucagon (2) were identified as "immediate" satiety signals released from the gastrointestinal tract in response to the presence of food. During the 1990s, leptin was recognized as a longer-term adiposity signal, secreted in proportion to body fat stores. Moreover, in addition to modulating immediate peripheral satiety signals, insulin and leptin were shown to directly target the central nervous system and inhibit food intake (3). The currently accepted model of energy homeostasis proposes that peripheral signals become integrated with other regulators of food intake, such as the presence of food, habits or social behavior. Similarly, meal termination may be governed by extrinsic factors and intrinsic factors, the latter including signals generated in the organism in response to the consumption of food.
| Leptin. |
|---|
|
|
|---|
Initial studies investigating the physiologic role of leptin in mice demonstrated that leptin was directly involved in the regulation of satiety, energy balance and feeding behavior. Ob/ob mice, which do not produce functional leptin, become enormously obese when feeding regimens allow ad libitum consumption; they reach four times normal body weight compared with controls. The administration of leptin can reverse this weight gain in this and other mouse models of obesity, indicating that leptin plays an important role in the regulation of food intake.
Rare genetic mutations resulting in leptin or leptin receptor deficiencies in humans also support the notion that leptin plays an important role in satiety. Leptin-deficient children exhibit ravenous feeding behavior and develop extreme obesity. Administration of exogenous leptin to these children results in a remarkable decrease in their energy intake and a dramatic loss of fat mass while maintaining lean body mass (9,10). Although these studies demonstrate that leptin can be a most effective pharmaceutical preparation for treating obesity in leptin-deficient states, the administration of exogenous leptin fails to reduce adiposity significantly in most cases of human obesity that are characterized by increased adipocyte leptin content and high circulating leptin levels, reflecting a state of leptin resistance. The mechanisms underlying leptin resistance in obese humans may include defective transport of leptin into the brain, and/or reduced hypothalamic leptin signaling, which is in part due to up-regulation of specific inhibitors of leptin signaling. The pathogenesis of leptin resistance is currently under intense investigation, and it is expected that elucidation of the mechanisms underlying leptin resistance may lead to the development of new therapeutic options for the treatment of obesity.
Weight-loss programs are well known to be ineffective long term, with most individuals regaining any weight lost within a short period of time, and it has been proposed that the corresponding decline in serum leptin levels due to the loss in fat mass may contribute to the inability of these subjects to maintain their weight loss. Exogenous leptin administration to replace leptin levels to preweight-loss levels prevented the regaining of weight and promoted loss of fat mass while preserving fat-free mass (11) in a small group of subjects participating in a weight loss program, but these findings have to be replicated by larger studies.
In this context, it was shown recently that decreasing leptin levels in response to food deprivation are responsible for the starvation-induced suppression of the hypothalamic-pituitary-gonadal axis (12), as well as the malfunction of several other neuroendocrine axes. Thus, it seems that leptin may act as the critical link between adipose tissue and not only hypothalamic centers regulating energy homeostasis but also the reproductive system, indicating whether adequate energy reserves are present for normal reproductive function (13).
| Insulin. |
|---|
|
|
|---|
| Adiponectin. |
|---|
|
|
|---|
Adiponectin acts as an insulin-sensitizing hormone whose blood concentrations are reduced in obesity and type 2 diabetes. Administration of recombinant adiponectin to rodents increases glucose uptake and fat oxidation in muscle, reduces fatty acid uptake and hepatic glucose production in liver, and improves whole-body insulin resistance (17). In rhesus monkeys, the decrease in plasma adiponectin levels parallels the development of insulin resistance and type 2 diabetes (18). Moreover, thiazolidinediones, drugs that enhance insulin sensitivity, increase plasma adiponectin and mRNA levels in mice (19). In support of these findings, adiponectin was shown to be negatively correlated with body weight, body fat mass and insulin levels in humans.
| Resistin. |
|---|
|
|
|---|
In 2001 Steppan and colleagues (22) reported that resistin secretion is decreased by the antidiabetic drug rosaglitazone and is increased in diet-induced and genetic mouse models of obesity. Moreover, administration of anti-resistin antibody improves blood sugar and insulin action in obese mice, and administration of recombinant resistin impairs glucose tolerance and insulin action in normal mice. These observations have not been confirmed by other investigators, however; thus, the role of resistin in mice remains controversial. Studies in humans to fully elucidate the role of resistin are still required, but initial observational and interventional studies have failed to support a role for circulating resistin in regulating insulin resistance in humans (23).
| Ghrelin. |
|---|
|
|
|---|
Although ghrelin has potent growth hormone-releasing properties comparable to those of growth hormone-releasing hormone (24), it also has powerful effects that are independent of growth hormone (25). Administration of ghrelin peripherally or centrally into the cerebral ventricles induces weight gain in rodents (26); in humans, ghrelin levels peak before each meal and then fall to lower levels immediately upon food consumption.
In humans, circulating ghrelin levels are decreased in acute states of positive energy balance and in chronic obesity, but elevated during fasting and in anorexia nervosa. These data further support the hypothesis that the secretion of ghrelin not only has effects opposite to leptin, but is also regulated antipodal to leptin. Whether increased ghrelin levels in anorexia nervosa reflect a pathophysiologic state of ghrelin resistance analogous to that of leptin resistance in obesity remains to be elucidated. In addition, the development of a ghrelin antagonist, or the development of a mechanism to inhibit ghrelin release to control appetite, may be an important pharmaceutical development for the management of obesity.
Finally, recent evidence suggests that ghrelin may play a role in reproductive function, a scenario that is analogous to the elucidation of a role of leptin in the control of reproductive function (13).
| Peptide YY3-36. |
|---|
|
|
|---|
| The Link between the Periphery and the Brain: Metabolic Circuitry in the Hypothalamus. |
|---|
|
|
|---|
|
-melanocyte-stimulating hormone (
-MSH). The latter hormone operates mainly through the melanocortin type 4 receptor (and to a lesser extent, through the melanocortin type 3 receptor) to inhibit appetite (31).
Leptin and insulin alike trigger the appetite-inhibitory circuit through up-regulation of
-MSH and inhibit the appetite-stimulatory neuron by suppressing NPY and AgRP mRNA expression in the hypothalamus, whereas ghrelin has largely the opposite effect.
In studies in animals, peptide YY3-36 released from the intestinal tract after the ingestion of food, inhibits the hypothalamic NPY- and AgRP-expressing neurons, thereby disinhibiting adjacent proopiomelanocortin-expressing neurons and decreasing food intake.
Ghrelin and leptin receptors were also demonstrated in brainstem nuclei, and direct injection of leptin into the dorsal vagal complex reduces food intake and body weight in rats (32). Thus, although it has been established that the hypothalamus is central to the control of energy balance, accumulating evidence suggests that neural circuits originating in the caudal brainstem are also involved (33), and this area represents the focus of intense research efforts at this time.
| Concluding Remarks. |
|---|
|
|
|---|
| FOOTNOTES |
|---|
3 Abbreviations used: AgRP, agouti-related peptide;
-MSH,
-melanocyte-stimulating hormone; NPY, neuropeptide Y; PVN, paraventricular nucleus. ![]()
| LITERATURE CITED |
|---|
|
|
|---|
1. Gibbs, J., Fauser, D. J., Rowe, E. A., Rolls, B. J., Rolls, E. T. & Maddison, S. P. (1979) Bombesin suppresses feeding in rats. Nature (Lond.) 282:208-210.[Medline]
2. Geary, N. (1990) Pancreatic glucagon signals postprandial satiety. Neurosci. Biobehav. Rev. 14:323-338.[Medline]
3. Flier, J. S. & Maratos-Flier, E. (1998) Obesity and the hypothalamus: novel peptides for new pathways. Cell 92:437-440.[Medline]
4. Zhang, Y., Proenca, R., Maffei, M., Barone, M., Leopold, L. & Friedman, J. M. (1994) Positional cloning of the mouse obese gene and its human homologue. Nature (Lond.) 372:425-432.[Medline]
5. Tartaglia, L. A., Dembski, M., Weng, X., Deng, N., Culpepper, J., Devos, R., Richards, G. J., Campfield, L. A., Clark, F. T. & Deeds, J. (1995) Identification and expression cloning of a leptin receptor, OB-R. Cell 83:1263-1271.[Medline]
6. Liu, C., Liu, X. J., Barry, G., Ling, N., Maki, R. A. & De Souza, E. B. (1997) Expression and characterization of a putative high affinity human soluble leptin receptor. Endocrinology 138:3548-3554.
7. Moschos, S., Chan, J. L. & Mantzoros, C. S. (2002) Leptin and reproduction: a review. Fertil. Steril. 77:433-444.[Medline]
8. Friedman, J. M. & Halaas, J. L. (1998) Leptin and the regulation of body weight in mammals. Nature (Lond.) 395:763-770.[Medline]
9. Farooqi, I. S., Jebb, S. A., Langmack, G., Lawrence, E., Cheetham, C. H., Prentice, A. M., Hughes, I. A., McCamish, M. A. & ORahilly, S. (1999) Effects of recombinant leptin therapy in a child with congenital leptin deficiency. N. Engl. J. Med. 341:879-884.
10. Farooqi, I. S., Matarese, G., Lord, G. M., Keogh, J. M., Lawrence, E., Agwu, C., Sanna, V., Jebb, S. A., Perna, F., Fontana, S., Lechler, R. I., DePaoli, A. M. & ORahilly, S. (2002) Beneficial effects of leptin on obesity, T cell hyporesponsiveness, and neuroendocrine/metabolic dysfunction of human congenital leptin deficiency. J. Clin. Investig. 110:1093-1103.[Medline]
11. Rosenbaum, M., Murphy, E. M., Heymsfield, S. B., Matthews, D. E. & Leibel, R. L. (2002) Low dose leptin administration reverses effects of sustained weight-reduction on energy expenditure and circulating concentrations of thyroid hormones. J. Clin. Endocrinol. Metab. 87:2391-2394.
12. Chan, J. L., Heist, K., DePaoli, A. M., Veldhuis, J. D. & Mantzoros, C. S. (2003) The role of falling leptin levels in the neuroendocrine and metabolic adaptation to short-term starvation in healthy men. J. Clin. Investig. 111:1409-1421.[Medline]
13. Henson, M. C. Castracane, V. D. eds. Leptin and Reproduction 2003 Kluwer Academic Publishers New York, NY. .
14. Bagdade, J. D., Bierman, E. L. & Porte, D., Jr (1967) The significance of basal insulin levels in the evaluation of the insulin response to glucose in diabetic and nondiabetic subjects. J. Clin. Investig. 46:1549-1557.
15. Baskin, D. G., Wilcox, B. J., Figlewicz, D. P. & Dorsa, D. M. (1988) Insulin and insulin-like growth factors in the CNS. Trends Neurosci. 11:107-111.[Medline]
16. Chavez, M., Seeley, R. J. & Woods, S. C. (1995) A comparison between effects of intraventricular insulin and intraperitoneal lithium chloride on three measures sensitive to emetic agents. Behav. Neurosci. 109:547-550.[Medline]
17. Heilbronn, L. K., Smith, S. R. & Ravussin, E. (2003) The insulin-sensitizing role of the fat derived hormone adiponectin. Curr. Pharm. Design 9:1411-1418.[Medline]
18. Hotta, K., Funahashi, T., Bodkin, N. L., Ortmeyer, H. K., Arita, Y., Hansen, B. C. & Matsuzawa, Y. (2001) Circulating concentrations of the adipocyte protein adiponectin are decreased in parallel with reduced insulin sensitivity during the progression to type 2 diabetes in rhesus monkeys. Diabetes 50:1126-1133.
19. Diez, J. J. & Iglesias, P. (2003) The role of the novel adipocyte-derived hormone adiponectin in human disease. Eur. J. Endocrinol. 148:293-300.[Abstract]
20. Kim, K. H., Lee, K., Moon, Y. S. & Sul, H. S. (2001) A cysteine-rich adipose tissue-specific secretory factor inhibits adipocyte differentiation. J. Biol. Chem. 276:11252-11256.
21. Holcomb, I. N., Kabakoff, R. C., Chan, B., Baker, T. W., Gurney, A., Henzel, W., Nelson, C., Lowman, H. B., Wright, B. D., Skelton, N. J., Frantz, G. D., Tumas, D. B., Peale, F. V., Jr, Shelton, D. L. & Hebert, C. C. (2000) FIZZ1, a novel cysteine-rich secreted protein associated with pulmonary inflammation, defines a new gene family. EMBO J. 19:4046-4055.[Medline]
22. Steppan, C. M., Bailey, S. T., Bhat, S., Brown, E. J., Banerjee, R. R., Wright, C. M., Patel, H. R., Ahima, R. S. & Lazar, M. A. (2001) The hormone resistin links obesity to diabetes. Nature (Lond.) 409:307-312.[Medline]
23. Lee, J. H., Chan, J. L., Yiannakouris, N., Kontogianni, M., Estrada, E., Seip, R., Orlova, C. & Mantzoros, C. S. () Circulating resistin levels are not associated with obesity or insulin resistance in humans and are not regulated by fasting or leptin administrationcross-sectional and interventional studies in normal, insulin-resistant and diabetic subjects. J. Clin. Endocinol. Metab. 88:4848-4856.
24. Kojima, M., Hosoda, H., Date, Y., Nakazato, M., Matsuo, H. & Kangawa, K. (1999) Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature (Lond.) 402:656-660.[Medline]
25. Nakazato, M., Murakami, N., Date, Y., Kojima, M., Matsuo, H., Kangawa, K. & Matsukura, S. (2001) A role for ghrelin in the central regulation of feeding. Nature (Lond.) 409:194-198.[Medline]
26. Wren, A. M., Small, C. J., Ward, H. L., Murphy, K. G., Dakin, C. L., Taheri, S., Kennedy, A. R., Roberts, G. H., Morgan, D. G., Ghatei, M. A. & Bloom, S. R. (2000) The novel hypothalamic peptide ghrelin stimulates food intake and growth hormone secretion. Endocrinology 141:4325-4328.
27. Tatemoto, K. & Mutt, V. (1980) Isolation of two novel candidate hormones using a chemical method for finding naturally occurring polypeptides. Nature (Lond.) 285:417-418.[Medline]
28. Batterham, R. L., Cowley, M. A., Small, C. J., Herzog, H., Cohen, M. A., Dakin, C. L., Wren, A. M., Brynes, A. E., Low, M. J., Ghatei, M. A., Cone, R. D. & Bloom, S. R. (2002) Gut hormone PYY(3-36) physiologically inhibits food intake. Nature (Lond.) 418:650-654.[Medline]
29. Batterham, R. L., Cohen, M. A., Ellis, S. M., Le Roux, C. W., Withers, D. J., Frost, G. S., Ghatei, M. A. & Bloom, S. R. (2003) Inhibition of food intake in obese subjects by peptide YY3-36. N. Engl. J. Med. 349:941-948.
30. Korner, J., Savontaus, E., Chua, S. C., Jr, Leibel, R. L. & Wardlaw, S. L. (2001) Leptin regulation of Agrp and Npy mRNA in the rat hypothalamus. J. Neuroendocrinol. 13:959-966.[Medline]
31. Korner, J. & Leibel, R. L. (2003) To eat or not to eathow the gut talks to the brain. N. Engl. J. Med. 349:926-928.
32. Grill, H. J., Schwartz, M. W., Kaplan, J. M., Foxhall, J. S., Breininger, J. & Baskin, D. G. (2002) Evidence that the caudal brainstem is a target for the inhibitory effect of leptin on food intake. Endocrinology 143:239-246.
33. Zigman, J. M. & Elmquist, J. K. (2003) Minireview: from anorexia to obesitythe yin and yang of body weight control. Endocrinology 144:3749-3756.
This article has been cited by other articles:
![]() |
D. Moreau, S. Kalaboka, M. Choquet, and I. Annesi-Maesano Asthma, obesity, and eating behaviors according to the Diagnostic and Statistical Manual of Mental Disorders IV in a large population-based sample of adolescents Am. J. Clinical Nutrition, May 1, 2009; 89(5): 1292 - 1298. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. C Prince, S. J Brooks, D. Stahl, and J. Treasure Systematic review and meta-analysis of the baseline concentrations and physiologic responses of gut hormones to food in eating disorders Am. J. Clinical Nutrition, March 1, 2009; 89(3): 755 - 765. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. B. Landersdorfer, D. C. DuBois, R. R. Almon, and W. J. Jusko Mechanism-Based Modeling of Nutritional and Leptin Influences on Growth in Normal and Type 2 Diabetic Rats J. Pharmacol. Exp. Ther., February 1, 2009; 328(2): 644 - 651. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. C Choquette, S. Lemieux, A. Tremblay, Y. C Chagnon, C. Bouchard, M.-C. Vohl, and L. Perusse Evidence of a quantitative trait locus for energy and macronutrient intakes on chromosome 3q27.3: the Quebec Family Study Am. J. Clinical Nutrition, October 1, 2008; 88(4): 1142 - 1148. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. R. Bloom, F. P. Kuhajda, I. Laher, X. Pi-Sunyer, G. V. Ronnett, T. M.M. Tan, and D. S. Weigle The Obesity Epidemic: Pharmacological Challenges Mol. Interv., April 1, 2008; 8(2): 82 - 98. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. Shinmura, K. Tamaki, K. Saito, Y. Nakano, T. Tobe, and R. Bolli Cardioprotective Effects of Short-Term Caloric Restriction Are Mediated by Adiponectin via Activation of AMP-Activated Protein Kinase Circulation, December 11, 2007; 116(24): 2809 - 2817. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. E. Barlow and and the Expert Committee Expert Committee Recommendations Regarding the Prevention, Assessment, and Treatment of Child and Adolescent Overweight and Obesity: Summary Report Pediatrics, December 1, 2007; 120(Supplement_4): S164 - S192. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. Barb, C. J Williams, A. K Neuwirth, and C. S Mantzoros Adiponectin in relation to malignancies: a review of existing basic research and clinical evidence Am. J. Clinical Nutrition, September 1, 2007; 86(3): 858S - 866S. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. E. Relling and C. K. Reynolds Feeding Rumen-Inert Fats Differing in Their Degree of Saturation Decreases Intake and Increases Plasma Concentrations of Gut Peptides in Lactating Dairy Cows J Dairy Sci, March 1, 2007; 90(3): 1506 - 1515. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. M. Arafat, F. H. Perschel, B. Otto, M. O. Weickert, H. Rochlitz, C. Schofl, J. Spranger, M. Mohlig, and A. F. H. Pfeiffer Glucagon Suppression of Ghrelin Secretion Is Exerted at Hypothalamus-Pituitary Level J. Clin. Endocrinol. Metab., September 1, 2006; 91(9): 3528 - 3533. [Abstract] [Full Text] [PDF] |
||||
![]() |
The ESHRE Capri Workshop Group Nutrition and reproduction in women Hum. Reprod. Update, May 1, 2006; 12(3): 193 - 207. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. S. McIntyre and J. Z. Konarski Obesity and Psychiatric Disorders: Frequently Encountered Clinical Questions Focus, October 1, 2005; 3(4): 511 - 519. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. E. Gordon and K. H. McKeever Diurnal variation of ghrelin, leptin, and adiponectin in Standardbred mares J Anim Sci, October 1, 2005; 83(10): 2365 - 2371. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Talsania, Y. Anini, S. Siu, D. J. Drucker, and P. L. Brubaker Peripheral Exendin-4 and Peptide YY3-36 Synergistically Reduce Food Intake through Different Mechanisms in Mice Endocrinology, September 1, 2005; 146(9): 3748 - 3756. [Abstract] [Full Text] [PDF] |
||||
![]() |
Y. Tu, J. N. Thupari, E.-K. Kim, M. L. Pinn, T. H. Moran, G. V. Ronnett, and F. P. Kuhajda C75 Alters Central and Peripheral Gene Expression to Reduce Food Intake and Increase Energy Expenditure Endocrinology, January 1, 2005; 146(1): 486 - 493. [Abstract] [Full Text] [PDF] |
||||
![]() |
U. Meier and A. M. Gressner Endocrine Regulation of Energy Metabolism: Review of Pathobiochemical and Clinical Chemical Aspects of Leptin, Ghrelin, Adiponectin, and Resistin Clin. Chem., September 1, 2004; 50(9): 1511 - 1525. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. H. Schulpis, I. Papassotiriou, M. Vounatsou, G. A. Karikas, S. Tsakiris, and G. P. Chrousos Morning Preprandial Plasma Ghrelin and Catecholamine Concentrations in Patients with Phenylketonuria and Normal Controls: Evidence for Catecholamine-Mediated Ghrelin Regulation J. Clin. Endocrinol. Metab., August 1, 2004; 89(8): 3983 - 3987. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||