BRIEF COMMUNICATION

Relationship Between Serum Leptin Levels and Alcohol Consumption in a Controlled Feeding and Alcohol Ingestion Study

Mark J. Roth, David J. Baer, Paul S. Albert, Thomas W. Castonguay, Joanne F. Dorgan, Sanford M. Dawsey, Ellen D. Brown, Terry J. Hartman, William S. Campbell, Carol A. Giffen, Joseph T. Judd, Philip R. Taylor

Affiliations of authors: Cancer Prevention Studies Branch, Center for Cancer Research (MJR, SMD, WSC, PRT), and the Biometric Research Branch, Division of Cancer Treatment and Diagnosis (PSA), National Cancer Institute, National Institutes of Health, Rockville, MD; Beltsville Human Nutrition Research Center, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, MD (DJB, EDB, JTJ); Department of Nutrition and Food Science, University of Maryland, College Park (TWC); Fox Chase Cancer Center, Philadelphia, PA (JFD); Department of Nutrition, Pennsylvania State University, University Park (TJH); Information Management Services, Inc., Silver Spring, MD (CAG).

Correspondence to: Mark J. Roth, MD, Cancer Prevention Studies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 6116 Executive Blvd., Ste. 705, MSC 8314, Bethesda, MD 20892-8314 (e-mail: mr166i{at}nih.gov)

ABSTRACT

We examined serum leptin levels in a controlled feeding and alcohol ingestion study to elucidate potential mechanisms by which alcohol may affect cancer and immunologically related health risks. A total of 53 healthy, nonsmoking postmenopausal women completed a random-order, three-period crossover design study in which each woman received zero (0 g of alcohol), one (15 g of alcohol), or two (30 g alcohol) drinks per day. After accounting for differences in body mass index, women who consumed 15 or 30 g of alcohol per day had 7.3% (95% confidence interval [CI] = 3.0% to 15.1%) and 8.9% (95% CI = 1.6% to 16.7%) higher serum leptin levels, respectively (Ptrend = .018), than women who consumed 0 g of alcohol per day. Younger women (i.e., 49–54 years) demonstrated a statistically significantly larger association of alcohol consumption level with the increase in serum leptin levels than older women (i.e., 55–79 years) (24.4%, 95% CI = 9.3% to 42.0% versus 3.7%, 95% CI = -4.1% to 12.1% increase in serum leptin levels for 30 g of alcohol per day relative to 0 g of alcohol per day for the lowest age quartile compared with the three highest age quartiles combined; P = .022). These results indicate that moderate alcohol consumption (15–30 g of alcohol per day) increases serum leptin levels in postmenopausal women and may predispose moderate drinkers to the morbidities associated with chronic elevations of this hormone including cancer.


Leptin is a hormone produced by the adipocyte ob gene on chromosome 7q31–32 (1). It is involved in energy balance and may play a role in carcinogenesis (27), secondary to a growth factor-like effect on a variety of tissues, including those of the breast and colon (3,712). There is also evidence to support a role for leptin in the immune response such that decreased leptin levels are associated with increased susceptibility to infectious disease and increased leptin levels are associated with autoimmune disorders (1315). Increased serum leptin concentration has also been positively correlated with increased serum insulin concentration (1620). Interestingly, we (21) have found reduced serum insulin concentrations in postmenopausal women who consumed moderate (15–30 g of alcohol per day) amounts of alcohol in the Women’s Alcohol Study, a controlled feeding and alcohol ingestion study. Thus, we set out to examine serum leptin levels in the participants from the Women’s Alcohol Study (22) to elucidate potential mechanisms by which alcohol consumption may affect cancer and immunologically related health risks.

A detailed description of the Women’s Alcohol Study design and methods has been previously reported (22). The study was approved by the National Cancer Institute (Bethesda, MD) and The Johns Hopkins University School of Hygiene and Public Health (Baltimore, MD). Before entering the study, all participants gave written informed consent. A total of 65 healthy, nonsmoking postmenopausal women who were aged 49 years or older were enrolled, 53 of whom completed the study. At baseline, these woman had a mean (standard deviation) age of 59.7 (7.4) years, a mean body mass index (BMI) of 27.8 (6.0) kg/m2, no major health problems, and at least one intact ovary.

Each participant rotated through three 8-week treatment periods and, in random order, consumed 0, 15 (equivalent to one drink), or 30 g (equivalent to two drinks) of alcohol per day. Participants were not told the amount of alcohol they were consuming (i.e., 0, 15, or 30 g of alcohol per day). Alcohol was supplied to each participantas 95% ethanol (Everclear; Pharmco Products, Brookfield, CN) in orange juice (12 ounces) 1–2 hours before bedtime. This time of day was chosen because it was after the time that most participants would have completed any activities requiring substantial manual dexterity as part of their controlled diet. Each controlled feeding period was preceded by a 2- to 5-week washout period during which time the participant consumed no alcohol. During the controlled feeding periods, all food and beverages including alcoholic beverages were prepared and supplied by the staff of the Beltsville Human Nutrition Research Center’s Human Study Facility (Beltsville, MD). Study participants were weighed each weekday by study investigators at the Beltsville facility, and energy intake was adjusted to maintain a constant body mass. Blood for hormone analysis was collected after an overnight fast on three separate days during the last week of each controlled feeding period, and an equal volume of serum from each day’s blood draw in each controlled feeding period was pooled for analysis. Circulating serum leptin concentration was measured in duplicate by radioimmunoassay using a commercially available kit (Human Leptin RIA Kit; Linco Research, St. Charles, MO) and quantified using a Cobra Quantum Gamma Counter (Packard Instruments, Downers Grove, IL). Standard reference materials were run as assay controls with each experiment. Insulin sensitivity was estimated with an MFFM index, according to the equation MFFM = exp [2.63 -0.28ln(insulin) - 0.31ln(TAG)] (21,23), where glucose disposal rate (M) corrected for fat-free mass (FFM) is equal to a weighted combination of log-transformed fasting insulin and triglyceride (TAG) concentration.

Serum leptin concentrations were transformed to the natural log before statistical analyses so that treatment effects could be evaluated as relative changes and so that error terms would be approximately normally distributed. Linear mixed models (24), with a single random intercept reflecting a participant effect, were used to estimate changes in serum leptin levels at 15 and 30 g of alcohol per day relative to 0 g of alcohol per day (i.e., placebo). Models were fit by treating the alcohol consumption level as two indicator variables and as a continuous (for dose-response analysis) variable. Paired t tests were used to test for differences in serum leptin levels between alcohol consumption levels without adjustments. Adjustments for BMI were performed by including it as a fixed effect in the linear mixed model. Carryover effects were analyzed by testing for an alcohol by treatment-order interaction in the linear mixed model. Effect modification by age, BMI, insulin sensitivity, and initial baseline serum leptin levels were also examined in the same manner. Effect modification for age was first examined by treating age and alcohol consumption level as continuous factors. Age quartiles were determined by categorizing the data at the 25th, 50th, and 75th percentiles. After determining whether there was an effect modification for age, we dichotomized the age quartiles into the first quartile and the three highest quartiles combined, based on the higher association of alcohol consumption level with the increase in serum leptin levels in the first quartile (younger women; 49–54 years) compared with the three highest quartiles (older women; 55–79 years). Statistical tests for treatment effects, carryover effects, and effect modification were performed with conditional t and F tests (24). Correlation between changes in serum leptin concentration and changes in insulin sensitivity was estimated using Pearson’s correlation coefficient. All statistical tests were two-sided.

The geometric mean concentration of serum leptin in women who consumed 0, 15, and 30 g of alcohol per day were 15.3 ng/mL (95% confidence interval [CI] = 12.4 to 18.7 ng/mL), 16.2 ng/mL (95% CI = 13.2 to 19.8 ng/mL), and 16.4 ng/mL (95% CI = 13.7 to 19.8 ng/mL), respectively. After adjusting for BMI, women who consumed 15 or 30 g of alcohol per day had 7.3% (95% CI = 3.0% to 15.1%) and 8.9% (95% CI = 1.6% to 16.7%) higher serum leptin levels, respectively, than women who consumed 0 g of alcohol per day; a trend test for the dose-response effect of alcohol on serum leptin levels was statistically significant (Ptrend = .018).

We did not find a statistically significant association between treatment order and alcohol level, suggesting that there is little evidence of a carryover effect in serum leptin levels in this crossover study (data not shown). The association of alcohol level with increasing serum leptin levels did not vary by BMI or baseline serum leptin level. However, after adjusting for BMI, we found a statistically significant association between age and alcohol consumption level with the increase in serum leptin level, such that younger women had a statistically significantly larger association of alcohol consumption level with the increase in serum leptin levels than older women (P = .016, treating age and alcohol as continuous factors). Further analysis demonstrated that women in the lowest age quartile had a statistically significantly larger association of alcohol consumption level with the increase in serum leptin levels (24.4% [95% CI = 9.3% to 42.0%] increase on 30 g of alcohol per day relative to 0 g of alcohol per day) than women in the highest three age quartiles combined (3.7%, 95% CI = -4.1% to 12.1%) (P = .022, conditional t test, treating age as a dichotomous factor and alcohol as a continuous factor; Table 1).


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Table 1. Geometric mean and 95% confidence intervals (CIs) for serum leptin levels (ng/mL) by alcohol level and age without body mass index adjustment*

 
The increase in serum leptin levels with moderate alcohol consumption is similar in magnitude to the increase in insulin sensitivity index, which represents a weighted combination of logtransformed fasting insulin and triglyceride concentration (21,23). It isinteresting that we found a statistically significant negative association between changes in serum leptin concentration and changes in insulin sensitivity (both from 0 to 30 g of alcohol; r = -.31, P = .024) (Fig. 1), suggesting that, although overall moderate (15–30 g of alcohol per day) alcohol consumption independently increases serum leptin levels and improves insulin sensitivity, a large increase in one of these factors is associated with a decrease in the other. This association highlights how alcohol may modify the activation of leptin and insulin co-ligands along the insulin-signaling cascade, including insulin receptor substrate-1-associated phosphatidylinositol 3-kinase, signal transducer and activator of transcription-3 and -1, and mitogen-activated protein kinase (2527).



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Fig. 1. Change in insulin sensitivity versus change in serum leptin concentration with a 0–30 g of alcohol per day change in alcohol consumption. The log-transformed ratio for the change in serum leptin concentration between 0 and 30 g of alcohol per day is inversely associated with the log-transformed ratio for the change in serum insulin sensitivity [a weighted combination of log-transformed fasting insulin and triglyceride concentrations (21,23)] between 0 and 30 g of alcohol per day (r = -.31, Pearson correlation coefficient; P = .024). This correlation coefficient is similar in magnitude to the association of the log-transformed ratio for the change in serum leptin concentration between 0 and 15 g of alcohol per day and the log-transformed ratio for the change in insulin sensitivity from 0 to 15 g of alcohol per day (r =-.29, P = .035).

 
Our ability to highlight the association between alcohol level and serum leptin levels was enhanced by the design of this study, which included maintenance of each participant’s BMI and controlling for caloric and food composition intake for more than 6 months. To the best of our knowledge, this study represents the first controlled study of serum leptin levels and chronic alcohol ingestion. Our results are similar to previous reports (18) that found alcohol to be positively associated with increased serum leptin levels but are contrary to other studies (17,28) that found serum leptin concentrations to be inversely associated with alcohol consumption. However, these earlier studies were limited because 1) they had a cross-sectional design and relied on self-reported questionnaire data to ascertain alcohol consumption (17,18) and 2) they assessed serum leptin levels in response to acute alcohol ingestion (28). Furthermore, although this study was not designed to specifically look at race, we did not observe any differences in serum leptin concentrations between African American and Caucasian women, as reported by Ruhl and Everhart (29) and Nicklas et al. (30).

In summary, this controlled feeding study provides evidence for a statistically significant positive association between moderate alcohol consumption and increased serum leptin levels, which appear to be strongest in younger women. This study also illustrates the relationship between changes in serum leptin levels and insulin sensitivity, suggesting that additional research is needed to determine whether alcohol consumption can potentiate the effect of serum leptin on cancer risk and/or immune function.

REFERENCES

1 Isse N, Ogawa Y, Tamura N, Masuzaki H, Mori K, Okazaki T, et al. Structural organization and chromosomal assignment of the human obese gene. J Biol Chem 1995;270: 27728–33.[Abstract/Free Full Text]

2 Chang S, Hursting SD, Contois JH, Strom SS, Yamamura Y, Babaian RJ, et al. Leptin and prostate cancer. Prostate 2001;46: 62–7.[CrossRef][ISI][Medline]

3 Hardwick JC, Van Den Brink GR, Offerhaus GJ, Van Deventer SJ, Peppelenbosch MP. Leptin is a growth factor for colonic epithelial cells. Gastroenterology 2001;121: 79–90.[ISI][Medline]

4 Stattin P, Soderberg S, Hallmans G, Bylund A, Kaaks R, Stenman UH, et al. Leptin is associated with increased prostate cancer risk: a nested case-referent study. J Clin Endocrinol Metab 2001;86: 1341–5.[Abstract/Free Full Text]

5 Tessitore L, Vizio B, Jenkins O, De Stefano I, Ritossa C, Argiles JM, et al. Leptin expression in colorectal and breast cancer patients.Int J Mol Med 2000;5: 421–6.[ISI][Medline]

6 Petridou E, Papadiamantis Y, Markopoulos C, Spanos E, Dessypris N, Trichopoulos D. Leptin and insulin growth factor I in relation to breast cancer (Greece). Cancer Causes Control 2000;11: 383–8.[CrossRef][ISI][Medline]

7 Rose DP, Gilhooly EM, Nixon DW. Adverse effects of obesity on breast cancer prognosis, and the biological action of leptin (review).Int J Oncol 2002;21: 1285–92.[ISI][Medline]

8 Hu X, Juneja SC, Maihle NJ, Cleary MP. Leptin-a growth factor in normal and malignant breast cells and for normal mammary gland development. J Natl Cancer Inst 2002;94: 1704–11.[Abstract/Free Full Text]

9 O’Brien SN, Welter BH, Price TM. Presence of leptin in breast cell lines and breast tumors. Biochem Biophys Res Commun 1999;259: 695–8.[CrossRef][ISI][Medline]

10 Laud K, Gourdou I, Pessemesse L, Peyrat JP, Djiane J. Identification of leptin receptors in human breast cancer: functional activity in the T47-D breast cancer cell line. Mol Cell Endocrinol 2002;188: 219–26.[CrossRef][ISI][Medline]

11 Laud K, Gourdou I, Belair L, Keisler DH, Djiane J. Detection and regulation of leptin receptor mRNA in ovine mammary epithelial cells during pregnancy and lactation. FEBS Lett 1999;463: 194–8.[CrossRef][ISI][Medline]

12 Liu Z, Uesaka T, Watanabe H, Kato N. High fat diet enhances colonic cell proliferation and carcinogenesis in rats by elevating serum leptin. Int J Oncol 2001;19: 1009–14.[ISI][Medline]

13 Evereklioglu C, Bulbul M, Ozerol E, Er H, Ozbek E. Serum leptin concentration is increased in patients with Behcet’s syndrome and is correlated with disease activity. Br J Dermatol 2002;147: 331–6.[CrossRef][ISI][Medline]

14 Garcia-Gonzalez A, Gonzalez-Lopez L, Valera-Gonzalez IC, Cardona-Munoz EG, Salazar-Paramo M, Gonzalez-Ortiz M, et al. Serum leptin levels in women with systemic lupus erythematosus. Rheumatol Int 2002;22: 138–41.[CrossRef][ISI][Medline]

15 Matarese G, La Cava A, Sanna V, Lord GM, Lechler RI, Fontana S, et al. Balancing susceptibility to infection and autoimmunity: a role for leptin? Trends Immunol 2002;23: 182–7.

16 Martini G, Valenti R, Giovani S, Campagna S, Franci B, Nuti R. Leptin and body composition in healthy postmenopausal women.Panminerva Med 2001;43: 149–54.[ISI][Medline]

17 Donahue RP, Zimmet P, Bean JA, Decourten M, DeCarlo Donahue RA, Collier G, et al. Cigarette smoking, alcohol use, and physical activity in relation to serum leptin levels in a multiethnic population: The Miami Community Health Study. Ann Epidemiol 1999;9: 108–13.[CrossRef][ISI][Medline]

18 Mantzoros CS, Liolios AD, Tritos NA, Kaklamani VG, Doulgerakis DE, Griveas I, et al. Circulating insulin concentrations, smoking, and alcohol intake are important independent predictors of leptin in young healthy men.Obes Res 1998;6: 179–86.[Abstract]

19 De Silva A, De Courten M, Zimmet P, Nicholson G, Kotowicz M, Pasco J, et al. Lifestyle factors fail to explain the variation in plasma leptin concentrations in women. Nutrition 1998;14: 653–7.[CrossRef][ISI][Medline]

20 Ahren B, Larsson H. Leptin-a regulator of islet function?: its plasma levels correlate with glucagon and insulin secretion in healthy women.Metabolism 1997;46: 1477–81.[ISI][Medline]

21 Davies MJ, Baer DJ, Judd JT, Brown ED, Campbell WS, Taylor PR. Effects of moderate alcohol intake on fasting insulin and glucose concentrations and insulin sensitivity in postmenopausal women: a randomized controlled trial. JAMA 2002;287: 2559–62.[Abstract/Free Full Text]

22 Dorgan JF, Baer DJ, Albert PS, Judd JT, Brown ED, Corle DK, et al. Serum hormones and the alcohol-breast cancer association in postmenopausal women. J Natl Cancer Inst 2001;93: 710–5.[Abstract/Free Full Text]

23 McAuley KA, Williams SM, Mann JI, Walker RJ, Lewis-Barned NJ, Temple LA, et al. Diagnosing insulin resistance in the general population. Diabetes Care 2001;24: 460–4.[Abstract/Free Full Text]

24 Pinheiro JC, Bates DM. Mixed-effects models in S and S-Plus. New York (NY): Springer-Verlag; 2000.

25 Harris RB, Mitchell TD, Hebert S. Leptin-induced changes in body composition in high fat-fed mice. Exp Biol Med (Maywood) 2003;228: 24–32.[Abstract/Free Full Text]

26 Kim YB, Uotani S, Pierroz DD, Flier JS, Kahn BB. In vivo administration of leptin activates signal transduction directly in insulin-sensitive tissues: overlapping but distinct pathways from insulin. Endocrinology 2000;141: 2328–39.[Abstract/Free Full Text]

27 Cohen B, Novick D, Rubinstein M. Modulation of insulin activities by leptin. Science 1996;274: 1185–8.[Abstract/Free Full Text]

28 Rojdmark S, Calissendorff J, Brismar K. Alcohol ingestion decreases both diurnal and nocturnal secretion of leptin in healthy individuals. Clin Endocrinol (Oxf) 2001;55: 639–47.[CrossRef][ISI][Medline]

29 Ruhl CE, Everhart JE. Leptin concentrations in the United States: relations with demographic and anthropometric measures. Am J Clin Nutr 2001;74: 295–301.[Abstract/Free Full Text]

30 Nicklas BJ, Toth MJ, Goldberg AP, Poehlman ET. Racial differences in plasma leptin concentrations in obese postmenopausal women. J Clin Endocrinol Metab 1997;82: 315–7.[Abstract/Free Full Text]

Manuscript received April 11, 2003; revised August 20, 2003; accepted September 3, 2003.


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