Active ghrelin levels across time and associations with leptin and anthropometrics in healthy ache Amerindian women of Paraguay.код для вставкиСкачать
AMERICAN JOURNAL OF HUMAN BIOLOGY 20:352–354 (2008) Short Report Active Ghrelin Levels Across Time and Associations with Leptin and Anthropometrics in Healthy Ache Amerindian Women of Paraguay RICHARD G. BRIBIESCAS,1* JAIME BETANCOURT,2 ANGÉLICA M. TORRES,1 AND MEREDITH REICHES3 Reproductive Ecology Laboratory, Department of Anthropology, Yale University, New Haven, Connecticut 06520-8277 2 Rutgers University, New Brunswick, New Jersey 08901 3 Department of Anthropology, Harvard University, Cambridge, Massachusetts 02138 1 ABSTRACT Active (acylated) ghrelin is a peptide hormone secreted primarily by the stomach, positively associated with fasting, orexigenic, and promotes growth hormone secretion. It is therefore important to energy intake management. The objective of this pilot research was to (1) compare active ghrelin with previous measurements of leptin and anthropometrics; (2) assess the consistency of active ghrelin across time in this population; (3) extend our understanding of potential population variation in active ghrelin. Two serum samples separated by 10 days at the same time between meals were collected from healthy Ache women (n ¼ 12, mean age 32.2 6 14.0 SD) to determine consistency over time, associations with leptin, and anthropmetric values. Mean active ghrelin was 72.9 6 23.0 pg/ml, highly correlated (r2 ¼ 0.95, P < 0.0001) between collections, and showed no paired mean differences (P < 0.18). There was no signiﬁcant correlation with leptin, age, or anthropometric measures. Active ghrelin appears to be consistent over time in this population, perhaps reﬂecting regimented meal schedules and less interpopulation variation compared to leptin. Am. J. Hum. Biol. 20:352–354, 2008. ' 2007 Wiley-Liss, Inc. Active (acylated) ghrelin is a peptide hormone secreted primarily by the stomach and serves as an orexigenic signal to the hypothalamus and is a useful biomarker of hunger and satiation (Kojima and Kangawa, 2005). Active ghrelin differs from its alternate form, total ghrelin in that active maintains a N-octanoyl group at the Ser3 position that is believed to be necessary for bioactivity. Related metabolic hormones such as leptin exhibit a broad range of variation across populations, with values generally lower in non-western populations after controlling for adiposity (Bribiescas, 2001). Despite the possibility of signiﬁcant nonpathological population variation in metabolic hormones, only a limited number of investigations have explored population variation in total ghrelin proﬁles (Shukla et al., 2005) and to our knowledge, none have investigated population variation in the active n-octanoylated active form. This pilot investigation addresses two preliminary questions that are meant to guide future ﬁeld investigations. First, are active ghrelin levels associated with leptin and anthropometric measures assessed in a previous investigation (Bribiescas, 2001)? Second, it would be useful to establish the consistency of active ghrelin in samples taken under similar conditions but separated by a signiﬁcant amount of time to determine the efﬁcacy of active ghrelin in investigations that may wish to incorporate a biomarker of hunger in human ecology research. Ache meal regimens in this community are believed to be somewhat regimented. Therefore, active ghrelin values measured at the same time of day, between meals, should be similar within individuals. MATERIALS AND METHODS Ache females were recruited from the community of Puerto Barra, a protestant mission located in the province of Alto Parana in eastern Paraguay as part of a larger investigation of the effects of ecological conditions on endocrine function. This community consists of about forty C 2007 V Wiley-Liss, Inc. households subsisting mostly on manual and mechanical agriculture with limited hunting in the surrounding forest. Descriptions of Ache ecology and demography have been described elsewhere (Hill and Hurtado, 1996). Subjects were recruited in exchange for a communal gift. Because active ghrelin can degrade rapidly (Hosoda et al., 2004), a brief synopsis of collection, storage, and handling methods is presented. Blood samples were collected using standard phlebotomy in SST vacuum tubes with a clotting activator (Vacutainer no. 6514, BectonDickinson, Franklin Lakes, NJ). No anticoagulants were used. Samples were frozen immediately after serum separation and collection, and stored at 208C. Some partial thawing may have occurred during shipment on blue ice but visual inspection upon arrival at the Yale Reproductive Ecology Laboratory conﬁrmed no complete thaw. One conﬁrmed thaw cycle occurred during leptin assessment with remaining serum kept at 808C until the measurement of active ghrelin. According to Hosoda et al. (2004), one freeze thaw cycle results in (100 6 4.0)% active ghrelin recovery and (89.8 6 2.7)% with two freeze thaw cycles using an assay without acidiﬁcation (the assay method used in this study as directed by the manufacturer). Since this investigation primarily reports within subject variation (day 1 to day 10) in which all samples were treated identically, collection, storage, and handling methods are not believed to have resulted in signiﬁcant degradation. Subjects had eaten their morning meal before 8 am and had not eaten since. Samples were collected between 11 and 12 pm, prior to their midday meal resulting in a 3–4 h *Correspondence to: Richard G. Bribiescas, Department of Anthropology, Yale University, New Haven, CT 06520-8277, USA. E-mail: firstname.lastname@example.org Received 23 April 2007; Accepted 24 April 2007 DOI 10.1002/ajhb.20699 Published online 26 December 2007 in Wiley InterScience (www.interscience. wiley.com). ACTIVE GHRELIN AMONG ACHE AMERINDIAN WOMEN OF PARAGUAY 353 TABLE I. Summary of means and day 1 active ghrelin associations with day 10 values, leptin, age, and anthropometrics Variable Mean 6 SD r2a Active ghrelin day 1 (pg/ml) (n ¼ 12) Active ghrelin day 10 (n ¼ 11)b Leptin (pg/ml) Fat (%) Weight (kg) Height (cm) BMI Age 76.0 6 18.2 72.9 6 23.0 5.6 6 3.2 33.3 6 4.4 55.2 6 7.4 147.6 6 5.4 25.2 6 1.9 32.2 6 14.0 0.95 (0.0001) 0.12 (0.27) 0.16 (0.20) 0.13 (0.26) 0.08 (0.37) 0.11 (0.29) 0.51 (0.83) b a The values within parentheses indicate the P values. One assay value was unreadable thereby yielding 11 comparison pairs for regression analysis. b fast. Other investigations have shown that similar periods of short in-between meal fasting is sufﬁcient to elevate ghrelin levels (Leidy and Williams, 2006). The 10-day separation between sample collection was conducted for experimental and logistical reasons. This allowed for en masse, communal sample collection and a more thorough control of diurnal variation and snacking. It also evoked a sufﬁcient amount of time in which each sample collection could be viewed as physiologically independent. That is, active ghrelin values during the second collection were not likely to be inﬂuenced by levels during the initial collection. This protocol was approved by the Yale University Committee for the Protection of Human Subjects. Active ghrelin was assessed using an iodine 125-based radioimmunoassay kit speciﬁc for the octanoylated active form (GHRA-88HK, Linco Research, St. Louis, MO). All samples were run in a single assay and quality controls were within the manufacturer speciﬁcations. Anthropometric assessments were conducted using previously validated and described methods (Bribiescas, 2001). Associations between Ache active ghrelin, leptin, fat %, weight, height, age, and body mass index (BMI) were analyzed using linear regression. Intraindividual comparisons of active ghrelin were performed using linear regression and paired t tests. Results were calculated using Prism 4.0 statistical software for the Macintosh (GraphPad Software, San Diego, CA). a was set at 0.05. RESULTS A summary of ghrelin and other variables is reported in Table 1. Active ghrelin measurements separated by 10 days were highly correlated, suggesting that active ghrelin exhibits limited variation within subjects (Fig. 1). No signiﬁcant intraindividual differences were noted between the 2 weeks (paired t test 1.45, P < 0.18). Correlations between active ghrelin, leptin, and anthropometric measurements were not signiﬁcant. DISCUSSION The hypothesis that active ghrelin should be consistent across time was supported. However, the tight association between active ghrelin values across the two sampling periods was especially noteworthy. While it was assumed that values should be somewhat similar, more variation was expected since random snacking and drinking yerba mate (a common South American tea) between the subjects’ morning and midday meal could not be totally controlled. This implies that either Ache eating habits within this community are very regimented or that active ghrelin Fig. 1. Active ghrelin levels in Ache women from samples collected 10 days apart (r2 ¼ 0.95, P < 0.0001). within this population exhibits a narrow range of variation. Total ghrelin measurements taken every 20 min in healthy well-fed European individuals during a 24-h fast suggests modest circadian variation with small rises around the common time period of meals (Natalucci et al., 2005). However, caution is warranted in extrapolating these results to other populations, since Salbe et al. (2004) reported that Pima Amerindians of Arizona exhibited ghrelin levels that were twice as high compared to nonPimas even after controlling for caloric intake, energy expenditure, and anthropometrics. Future investigations among the Ache would aim to measure active ghrelin before and after an overnight fast. Progress has been made in developing noninvasive strategies of assessing ghrelin but more work is necessary (Aydin et al., 2005). The lack of association between active ghrelin and anthropometrics was dissimilar from other investigations (Monti et al., 2006), perhaps resulting from less anthropometric variation among the Ache. Because of sample volume limitations, it was not possible to assess male ghrelin although Ache male leptin suggests that population variation in metabolic hormones extend to men also (Bribiescas and Hickey, 2006). Ghrelin may also vary in association with menstrual cycles. Menstrual phases were not known in this study but the consistency of values within individuals makes menstrual cycle timing an unlikely source of variation. Interestingly, ghrelin values are elevated in exercising amenorrheic women (De Souza et al., 2004) but only marginally associated with daily energetic expenditure in healthy women (St-Pierre et al., 2004). This is noteworthy in light of the fact that Ache women are also very physically active in conducting their daily chores and energetically demanding tasks. Post hoc comparisons with mean values from other active ghrelin measurements reported in the literature (Nakai et al., 2003) suggest no signiﬁcant differences compared to healthy control subjects (P < 0.33) but were signiﬁcantly lower than anorectic patients (P < 0.03), implying that active ghrelin levels among the Ache do not exhibit similar population differences as observed with leptin (Bribiescas, 2001, 2005; Bribiescas and Hickey, American Journal of Human Biology 354 R.G. BRIBIESCAS ET AL. 2006). However, formal comparisons with proper controls are needed. This preliminary investigation suggests that the relationship between active ghrelin, leptin, and anthropometrics is not strong. Active ghrelin also appears to be less variable compared to leptin and may be a universal cue of feeding and satiety among populations. To our knowledge, this is the ﬁrst report of active ghrelin in a developing population. It would be useful to continue exploring the utility of ghrelin as an independent biomarker of hunger in developing populations as well as the development less invasive methods of assessment. ACKNOWLEDGMENTS The authors wish to thank the Ache community of Puerto Barra, especially Angel Tatunambiangi, Carmen Bywangi, Bjarne, and Rosalba Fostervold for their cooperation as well as Richard Lawler for his aid in the ﬁeld. The authors also extend our sincere gratitude to Dr. Liza Cariaga-Lo, Dean of the Yale University Ofﬁce for Diversity and Equal Opportunity for her support to JB. This research was supported by a Yale University Junior Faculty Fellowship (RGB) and a Summer Undergraduate Research Fellowship (JB). LITERATURE CITED Aydin S, Halifeoglu I, Ozercan IH, Erman F, Kilic N, Ilhan N, Ozkan Y, Akpolat N, Sert L, Caylak E. 2005. A comparison of leptin and ghrelin levels in plasma and saliva of young healthy subjects. Peptides 26:647– 652. Bribiescas RG. 2001. Serum leptin levels and anthropometric correlates in Ache Amerindians of eastern Paraguay. Am J Phys Anthropol 115:297– 303. American Journal of Human Biology Bribiescas RG. 2005. Serum leptin levels in Ache Amerindian females with normal adiposity are not signiﬁcantly different from American anorexia nervosa patients. Am J Hum Biol 17:207–210. Bribiescas RG, Hickey MS. 2006. Population variation and differences in serum leptin independent of adiposity: a comparison of Ache Amerindian men of Paraguay and lean American male distance runners. Nutr Metab (Lond) 3:34. De Souza MJ, Leidy HJ, O’Donnell E, Lasley B, Williams NI. 2004. Fasting ghrelin levels in physically active women: relationship with menstrual disturbances and metabolic hormones. J Clin Endocrinol Metab 89: 3536–3542. Hill K, Hurtado AM. 1996. Ache life history: the ecology and demography of a foraging people, Vol. 19. New York: Aldine de Gruyter. 561 p. Hosoda H, Doi K, Nagaya N, Okumura H, Nakagawa E, Enomoto M, Ono F, Kangawa K. 2004. Optimum collection and storage conditions for ghrelin measurements: octanoyl modiﬁcation of ghrelin is rapidly hydrolyzed to desacyl ghrelin in blood samples. Clin Chem 50:1077–1080. Kojima M, Kangawa K. 2005. Ghrelin: structure and function. Physiol Rev 85:495–522. Leidy HJ, Williams NI. 2006. Meal energy content is related to features of meal-related ghrelin proﬁles across a typical day of eating in non-obese premenopausal women. Horm Metab Res 38:317–322. Monti V, Carlson JJ, Hunt SC, Adams TD. 2006. Relationship of ghrelin and leptin hormones with body mass index and waist circumference in a random sample of adults. J Am Diet Assoc 106:822–828. quiz 829-830. Nakai Y, Hosoda H, Nin K, Ooya C, Hayashi H, Akamizu T, Kangawa K. 2003. Plasma levels of active form of ghrelin during oral glucose tolerance test in patients with anorexia nervosa. Eur J Endocrinol 149:R1– R3. Natalucci G, Riedl S, Gleiss A, Zidek T, Frisch H. 2005. Spontaneous 24-h ghrelin secretion pattern in fasting subjects: maintenance of a mealrelated pattern. Eur J Endocrinol 152:845–850. Salbe AD, Tschop MH, DelParigi A, Venti CA, Tataranni PA. 2004. Negative relationship between fasting plasma ghrelin concentrations and ad libitum food intake. J Clin Endocrinol Metab 89:2951–2956. Shukla V, Singh SN, Vats P, Singh VK, Singh SB, Banerjee PK. 2005. Ghrelin and leptin levels of sojourners and acclimatized lowlanders at high altitude. Nutr Neurosci 8:161–165. St-Pierre DH, Karelis AD, Cianﬂone K, Conus F, Mignault D, RabasaLhoret R, St-Onge M, Tremblay-Lebeau A, Poehlman ET. 2004. Relationship between ghrelin and energy expenditure in healthy young women. J Clin Endocrinol Metab 89:5993–5997.