This Article Abstract Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Brown, D. R. Articles by Breslow, M. J. Search for Related Content PubMed PubMed Citation Articles by Brown, D. R. Articles by Breslow, M. J.

Weight Loss Is Not Associated with Hyperleptinemia in Humans with Pancreatic Cancer

Department of Anesthesiology and Critical Care, Mayo Clinic (D.R.B.), Rochester, Minnesota 55905; Department of Anesthesiology, Johns Hopkins University School of Medicine (D.E.B.), Baltimore, Maryland 21287; and ICUSA, Inc. (M.J.B.), Baltimore, Maryland 21224

Address all correspondence and requests for reprints to: Daniel R. Brown, M.D., Ph.D., Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905. E-mail: brown.daniel{at}mayo.edu

	Abstract

Top Abstract Introduction Materials and Methods Results Discussion References

 
Pathological weight loss is a feature of many diseases and contributes to mortality and morbidity. Although cytokines have been implicated in some models of pathological weight loss, little is known about cellular mechanisms responsible for cachexia in patients with cancer. Leptin is a fat cell product that acts centrally to reduce appetite and decrease metabolism. Leptin synthesis is stimulated by cytokines, and circulating levels of cytokines are elevated in some cancer patients. We hypothesized that cytokine-induced hyperleptinemia contributes to pathological weight loss in patients with pancreatic cancer. To evaluate this hypothesis, fasting serum leptin concentrations were measured in 64 patients undergoing surgery for pancreatic cancer. Preoperative interviews were used to assess body weight and appetite history. Thirty of 64 pancreatic cancer patients had cachexia (weight loss of >10% over the 6 months before surgery). Self-reported loss of appetite was associated with the presence of cachexia. Leptin concentrations, when corrected for body mass index, were lower than levels reported in healthy humans. Six patients had leptin levels more than 2 times those predicted by body mass index. There was no association between patients with increased leptin concentration and weight loss or anorexia. We conclude that a reduced appetite contributes to weight loss in patients with pancreatic cancer. High plasma leptin levels, however, do not appear to contribute to cachexia in these patients.

	Introduction

Top Abstract Introduction Materials and Methods Results Discussion References

 
PATHOLOGICAL WEIGHT loss is a feature of many diseases and, when present, contributes to morbidity and mortality. Weight loss occurs when energy expenditure exceeds energy consumption. The physiology of pathological weight loss in cancer patients is not completely understood, but is probably multifactorial (1). Decreased caloric intake and increased metabolic rate have been shown to be present in some cancer patients with pathological weight loss; however, the specific mechanisms by which these changes occur remain to be elucidated. Although pain, side-effects of therapy, and depression can affect appetite and energy expenditure, humoral mechanisms may also play a role. Cytokines, in particular, have been implicated in some models of cancer cachexia (1, 2).

Leptin is an adipocyte product that is thought to represent the afferent signal in a feedback mechanism regulating fat mass (3, 4). After release by adipocytes, leptin modulates food intake and energy balance (5, 6) through its actions at specific receptors in the hypothalamus (7). Downstream effects after activation of central leptin receptors include inhibition of hypothalamic biosynthesis and release of neuropeptide Y, a hormone that stimulates appetite and food intake and reduces energy expenditure (8). Mice that lack the ability to produce (ob) or respond to (db) leptin are characterized by obesity and energy-conserving behavior (4, 9). Leptin repletion in ob mice produces weight loss and resumption of energy-consuming behavior (6). Weight loss may also occur with exogenous administration of leptin in normal, and even lean, animals (10) and humans (11). By what mechanism(s) leptin secretion is regulated remains to be elucidated, although leptin expression has been shown to be dramatically altered by cytokines.

Tumor necrosis factor- (TNF), interleukin-6 (IL-6), and IL-1 increase ob gene expression and leptin secretion (12, 13, 14). These same cytokines have been suggested to play a role in cancer cachexia as well, although this association is less clear. TNF administration causes cachexia in humans and animals, although it does not appear to be elevated in animal cancer models or human cancer patients. It has been postulated that TNF acts as a paracrine/autocrine mediator rather than being the circulating messenger in cachexia (1). In contrast, increasing levels of IL-6 have been shown to correlate with the development of cachexia in the murine colon-26 adenocarcinoma model (15). Furthermore, elevated levels of IL-6 have been reported in cancer patients (16, 17), although this is not a universal finding. Again, it is possible that systemic IL-6 concentrations need not be elevated, as IL-6 may act as a paracrine/autocrine mediator. Supporting this is work showing increased peripheral blood mononuclear cell IL-6 production in pancreatic cancer patients despite normal serum IL-6 concentrations (2). Less information is available regarding IL-1 and cachexia, although IL-1 modulates IL-6 production and may thereby play a role in cancer cachexia (18).

These observations prompted speculation that elevated leptin levels may contribute to the pathological weight loss of cancer cachexia (12). A study of lung cancer patients with pathological weight loss found no increase in leptin levels, and the researchers speculated that a disturbance in hypothalamic responses to leptin may contribute to negative energy balance in these patients (19). As multiple different mechanisms probably contribute to pathological weight loss in cancer and may differ between cancers of different cell types, we investigated the relationship among plasma leptin concentrations, weight loss, and appetite in patients with pancreatic cancer.

	Materials and Methods

Top Abstract Introduction Materials and Methods Results Discussion References

 
After institutional review board approval, informed consent was obtained from 64 patients who underwent surgery for resection of pancreatic cancer. Exclusion criteria were 1) age less than 18 yr, 2) pregnancy, 3) metastatic disease to the brain (which could affect appetite), 4) intentional weight loss before surgery, 5) primary or metastatic tumor size greater than 2 cm in any dimension, 6) transfusion within 72 h of surgery, 7) total parental nutrition, and 8) pancreatic insufficiency as evidenced by pancrease therapy.

Preoperatively, patients were interviewed about body weight and appetite during the 6 months before surgery. Baseline weight was defined as the patient’s weight 6 months before surgery. A calibrated balance beam scale determined body weight with patients wearing standard clothes and no shoes. Height was directly measured. Cachexia was defined as an unintentional 10% decrease in body weight occurring during the 6 months before surgery. Patients were asked whether their appetite over the past 6 months was increased, decreased, or unchanged.

All patients had their surgery performed as the first case of the day having fasted after midnight according to standard preoperative orders. Blood samples for plasma leptin determinations were obtained between 0800–0900 h. Samples were collected in ethylenediamine tetraacetate vacuum tubes, placed on ice, and immediately centrifuged at 5 C. Serum was frozen at -80 C, and leptin assays were performed in batches. Leptin levels were determined in duplicate with a commercial double antibody RIA using rabbit antihuman leptin, ¹²⁵I-labeled human leptin as tracer, and human leptin standards (Linco Research, Inc., St. Louis, MO). The lower level of detection is 0.5 ng/mL. The intra- and interassay coefficients of variation were less than 10%. Reported leptin concentrations are the mean of two determinations of the same sample.

Statistics

Demographic data are reported as mean ± SD. ² analysis was performed to evaluate relationships between changes in body weight and appetite. Linear regression analysis was used to evaluate the relationships between plasma leptin and weight loss. Leptin concentrations were corrected for body mass index (BMI) using published population data for men and women (20). Corrected leptin concentrations greater than 2 times those predicted were considered elevated. ² analysis was performed to evaluate whether hyperleptinemic patients had an increased incidence of cachexia or appetite loss. P < 0.05 was considered significant.

	Results

Top Abstract Introduction Materials and Methods Results Discussion References

 
A total of 64 patients were studied between July 1996 and August 1997. Characteristics of patients are presented in Table 1. Thirty-nine patients were male. Overall, slightly less than half of the patients were cachectic, a similar proportion of patients reported decreased appetite. There was a significant association between patients with weight loss and decreased appetite (P < 0.025).

View larger version (16K): [in this window] [in a new window]   Figure 1. Relationship between leptin and BMI in male (A) and female (B) pancreatic cancer patients. The solid line is the reported normal relationship in healthy subjects (20 ). Squares, Patients with islet cell tumors; circles, patients with histiocytoma.

View larger version (14K): [in this window] [in a new window]   Figure 2. Fasting plasma leptin concentration and change from baseline weight in male (A) and female (A) pancreatic cancer patients. Baseline weight is defined as weight 6 months before study. Squares, Patients with islet cell tumors; circles, patients with histiocytoma.

	Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

 
The purpose of this study was to determine whether cachexia in pancreatic cancer patients was associated with inappropriately elevated fasting plasma leptin concentrations. Elevated leptin concentrations could contribute to pathological weight loss in these patients by decreasing food intake and/or by preventing energy conservation, thereby exacerbating negative caloric balance. However, we found that, with few exceptions, plasma leptin concentrations were not elevated in these patients. Moreover, there was no apparent relationship between plasma leptin concentrations and appetite or weight loss. These data suggest that leptin is not a contributor to weight loss in patients with pancreatic cancer.

Although our data suggest that hyperleptinemia is not associated with pancreatic cancer, the interpretation is limited by the lack of a simultaneously studied control group with similar body composition. Unfortunately, patients in the present study were not available for preoperative determination of body composition. We used a previously reported leptin to BMI relationship (20) as the control to which our patients were compared. This previously reported relationship encompasses the range of BMIs in our population, the assay was performed with the same type of commercial assay, and our intra- and interassay coefficients of variation were within acceptable limits. Of note, several patients underwent surgery in which no cancer was found, and none of the leptin concentrations in these patients was more than twice or less than half of that expected based on BMI, suggesting that our leptin assay and comparison group were appropriate.

Another limitation of the current study is the use of self-evaluated changes in weight and appetite. It is possible that reported appetite changes might be weighted to very recent changes in appetite. However, we were most interested in recent appetite and its relationship with recent changes in body weight, as we assumed that were leptin to be playing a role in cachexia, its influence would parallel changes in appetite and/or body weight. In an effort to provide the most accurate history of weight and appetite, all interviews were performed preoperatively, and family and friends (when available) were used to confirm the accuracy of responses.

Although we did observe lower than expected leptin concentrations in many patients, there was no correlation with weight loss or decreased appetite. We speculate that low leptin concentrations in these patients may be due to altered body composition. Prior studies have shown that fat mass is decreased in patients with cancer (19). Leptin levels are highly correlated with the amount of body fat (20). Thus, lower than expected leptin levels may reflect reduced body fat mass in these cachectic patients. Simons et al. reported even more pronounced alterations in leptin concentrations in patients with lung cancer; levels were undetectable in 15 of 21 patients (19). It is interesting to note that Simons’ work was performed in The Netherlands, and it is possible that cultural differences in eating patterns and body habitus may have contributed to lower leptin concentrations in the patients with lung cancer. Alternatively, different tumor types may account for the differing results in these two studies.

Several of the pancreatic cancer patients had markedly elevated leptin levels. Although these patients did not report excessive weight loss or decreased appetite, the numbers were small, and it is unknown how long these patients were hyperleptinemic. It is interesting to speculate whether these individuals would have gone on to develop weight loss if the tumors were not removed. Alternatively, hypercortisolism, which may be associated with neoplasms and is associated with elevated leptin concentrations, may have contributed to hyperleptinemia in this group. No plasma cortisol levels were determined in these patients.

Despite our data suggesting that hyperleptinemia is not associated with pancreatic cancer cachexia, this does not preclude a role for leptin in this form of pathological weight loss. We did not perform a rigorous evaluation of leptin secretion over time. It is possible that there are pulsatile and/or circadian differences in leptin secretion that contribute to cachexia. Furthermore, abnormalities in the leptin pathway distal to the adipocyte (increased central sensitivity, altered neuropeptide Y synthesis/sensitivity) (21) could contribute to weight loss in cancer patients. Finally, leptin may act as a paracrine or autocrine pathway for other factors. A cachexia factor has been isolated in the urine of cachectic cancer patients as well as in murine models of cancer cachexia (22). The relationship between this factor and leptin remains unknown. The mechanism by which this or other cytokines may cause cachexia remains to be defined, although activation of the ATP-ubiquitin-proteasome pathway, which results in protein breakdown, has been shown in several models of cancer cachexia (23, 24).

Cachexia in cancer patients is a difficult subject to study, as there are many factors that determine net caloric balance. Tumor burden, direct gastrointestinal tract effects of the tumor, mood depression, and side-effects of treatment, such as chemotherapy-associated nausea, may also contribute to pathological weight loss. In the present population, tumors were uniformly small, as patients with pancreatic cancer are surgical candidates at our institution only early in their disease course. Although it is possible that tumors in the head of the pancreas may block pancreatic enzyme secretion and thereby influence nutrient absorption, we attempted to correct for this by excluding patients who were receiving pancrease therapy. No attempt was made to evaluate whether depression contributed to the loss of appetite. None of the patients studied had received chemotherapy.

In conclusion, in this group of pancreatic cancer patients, elevated fasting plasma leptin concentrations were not associated with cachexia or changes in appetite. The leptin axis may still contribute to pathological weight loss in other states or by other mechanisms. Cachexia remains a significant clinical problem that deserves further investigation to determine its pathophysiology and possible therapeutic interventions.

	Footnotes

 
¹ Foundation for Anesthesia Education and Research/Marion Roussel, Inc., Research Fellow.

Received November 5, 1999.

Revised June 5, 2000.

Revised August 28, 2000.

Accepted September 14, 2000.

	References

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Tisdale MJ. 1997 Cancer cachexia: metabolic alterations and clinical manifestations. Nutrition. 13:1–7.[CrossRef][Medline]
2. Falconer JS, Fearon KC, Plester CE, Ross JA, Carter DC. 1994 Cytokines, the acute-phase response, and resting energy expenditure in cachectic patients with pancreatic cancer. Ann Surg. 219:325–331.[Medline]
3. Zhang Y, Proenca R, Maffei M, Barone M, Leopold L, Friedman JM. 1994 Positional cloning of the mouse obese gene and its human homologue. Nature. 372:425–432.[CrossRef][Medline]
4. Auwerx J, Staels B. 1998 Leptin. Lancet. 351:737–742.[CrossRef][Medline]
5. Campfield LA, Smith FJ, Guisez Y, Devos R, Burn P. 1995 Recombinant mouse OB protein: evidence for a peripheral signal linking adiposity and central neural networks. Science. 269:546–549.[Abstract/Free Full Text]
6. Pelleymounter MA, Cullen MJ, Baker MB, Hecht R, Winters D, Boone T, Collins F. 1995 Effects of the obese gene production body weight regulation in ob/ob mice. Science. 269:540–543.[Abstract/Free Full Text]
7. Malik KF, Young III WS. 1996 Localization of binding sites in the central nervous system for leptin (OB protein) in normal, obese (ob/ob), and diabetic (db/db) C57BL/6J mice. Endocrinology. 137:1497–1500.[Abstract]
8. Stephens TW, Basinski M, Bristow PK, et al. 1995 The role of neuropeptide Y in the antiobesity action of the obese gene product. Nature. 377:530–532.[CrossRef][Medline]
9. Spiegelman BM, Flier JS. 1996 Adipogenesis and obesity: rounding out the big picture. Cell. 87:377–389.[CrossRef][Medline]
10. LeBel C, Bourdeau A, Lau D, Hunt P. 1999 Biologic response to peripheral and central administration of recombinant human leptin in dogs. Obesity Res. 7:577–785.[Medline]
11. Heymsfield SB, Greenberg AS, Fujioka K, et al. 1999 Recombinant leptin and weight loss in obese and lean adults: a randomized, controlled, dose-escalation trial. JAMA. 282:1568–1575.[Abstract/Free Full Text]
12. Grunfeld C, Zhao C, Fuller J, Pollock A, Moser A, Friedman J, Feingold KR. 1996 Endotoxin and cytokines induce expression of leptin, the ob gene product, in hamsters. J Clin Invest. 97:2152–2157.[Medline]
13. Berkowitz DE, Brown DR, Lee KM, Emala C, Palmer D, An Y, Breslow M. 1998 Endotoxin-induced alteration in the expression of leptin and ß₃-adrenergic receptor in adipose tissue. Am J Physiol. 274:E992–E997.
14. Meisser A, Cameo P, Islami D, Campana A, Bischof P. 1999 Effects of interleukin-6 (IL-6) on cytotrophoblastic cells. Mol Hum Reprod. 5:1055–1058.[Abstract/Free Full Text]
15. Strassmann G, Fong M, Kenney JS, Jacob CO. 1992 Evidence for the involvement of interleukin 6 in experimental cancer cachexia. J Clin Invest. 89:1681–1684.
16. Fearon KC, McMillan DC, Preston T, Winstanley FP, Cruickshank AM, Shenkin A. 1991 Elevated circulating interleukin-6 is associated with an acute phase response, but reduced fixed hepatic protein synthesis in patients with cancer. Ann Surg. 213:26–31.[Medline]
17. Yanagawa H, Sone S, Takahashi Y, Haku T, Yano S, Shinohara T, Ogura T. 1995 Serum levels of interleukin 6 in patients with lung cancer. Br J Cancer. 71:1095–1098.[Medline]
18. Strassmann G, Masui Y, Chizzonite R, Fong M. 1993 Mechanisms of experimental cancer cachexia. Local involvement of IL-1 in colon-26 tumor. J Immunol. 150:2341–2345.[Abstract]
19. Simons JP, Schols A, Campfield LA, Wouters EFM, Saris WH. 1997 Plasma concentration of total leptin and human lung-cancer-associated cachexia. Clin Sci. 93:273–277.[Medline]
20. Kennedy A, Gettys TW, Watson P, Wallace P, Ganaway E, Pan Q, Garvey WT. 1997 The metabolic significance of leptin in humans: gender-based differences in relationship to adiposity, insulin sensitivity, and energy expenditure. J Clin Endocrinol Metab. 82:1293–1300.[Abstract/Free Full Text]
21. Schwartz MW, Seeley RJ. 1997 Neuroendocrine responses to starvation and weight loss. N Engl J Med. 336:1802–1811.[Free Full Text]
22. Todorov P, Cariuk P, McDevitt T, Coles B, Fearon K, Tisdale M. 1996 Characterization of a cancer cachectic factor. Nature. 379:739–742.[CrossRef][Medline]
23. Baracos VE, DeVito C, Hoyle DHR, Goldberg AL. 1995 Activation of the ATP-ubiquitin-proteasome pathway in skeletal muscle of cachectic rats bearing a hepatoma. Am J Physiol. 268:E996–E1006.
24. Temparis S, Asensi M, Taillandier D, et al. 1994 Increased ATP-ubiquitin-dependent proteolysis in skeletal muscles of tumor-bearing rats. Cancer Res. 54:5568–5573.[Abstract/Free Full Text]

This article has been cited by other articles:

				E. R. Ropelle, J. R. Pauli, K. G. Zecchin, M. Ueno, C. T. de Souza, J. Morari, M. C. Faria, L. A. Velloso, M. J. A. Saad, and J. B. C. Carvalheira A Central Role for Neuronal Adenosine 5'-Monophosphate-Activated Protein Kinase in Cancer-Induced Anorexia Endocrinology, November 1, 2007; 148(11): 5220 - 5229. [Abstract] [Full Text] [PDF]

				S. Perboni and A. Inui Anorexia in cancer: role of feeding-regulatory peptides Phil Trans R Soc B, July 29, 2006; 361(1471): 1281 - 1289. [Abstract] [Full Text] [PDF]

				Q. Huang, X. Zhang, Z.-W. Jiang, B.-Z. Liu, N. Li, and J.-S. Li Hypoleptinemia in Gastric Cancer Patients: Relation to Body Fat Mass, Insulin, and Growth Hormone JPEN J Parenter Enteral Nutr, July 1, 2005; 29(4): 229 - 235. [Abstract] [Full Text] [PDF]

				D Basso, C Millino, E Greco, C Romualdi, P Fogar, A Valerio, M Bellin, C-F Zambon, F Navaglia, N Dussini, et al. Altered glucose metabolism and proteolysis in pancreatic cancer cell conditioned myoblasts: searching for a gene expression pattern with a microarray analysis of 5000 skeletal muscle genes Gut, August 1, 2004; 53(8): 1159 - 1166. [Abstract] [Full Text] [PDF]

				F. Santolaria, A. Perez-Cejas, M.-R. Aleman, E. Gonzalez-Reimers, A. Milena, M.-J. De La Vega, A. Martinez-Riera, and M.-A. Gomez-Rodriguez LOW SERUM LEPTIN LEVELS AND MALNUTRITION IN CHRONIC ALCOHOL MISUSERS HOSPITALIZED BY SOMATIC COMPLICATIONS Alcohol Alcohol., January 1, 2003; 38(1): 60 - 66. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Brown, D. R. Articles by Breslow, M. J. Search for Related Content PubMed PubMed Citation Articles by Brown, D. R. Articles by Breslow, M. J.