Serum concentration of adypocytokines in prepubertal vegetarian and omnivorous children

Stężenie adipocytokin w surowicy krwi dzieci stosujących dietę wegetariańską i tradycyjną

Jadwiga Ambroszkiewicz1, Witold Klemarczyk2, Joanna Gajewska1, Magdalena Chełchowska 1, Grażyna Rawicka2, Mariusz Ołtarzewski1, Teresa Laskowska-Klita1
11Screening Test Department
Chief of Department: dr n. biol. M. Ołtarzewski
2Department of Nutrition
Chief of Department: dr hab. n. med. H. Weker
Institute of Mother and Child in Warsaw
Director: S. Janus

Abstract
The aim of our study was to investigate associations between serum adipocytokines status and anthropometric parameters as well as total energy and macronutrient intake in vegetarian, normalweight omnivorous and obese omnivorous children.
Material and methods: We examined 90 healthy prepubertal children aged 4-10 years who had been referred to the Department of Nutrition at the Institute of Mother and Child in Warsaw for dietary consultation. Patients with endocrine disorders or genetic syndromes, as well as those who were taking medications that could affect growth, pubertal development or nutritional status were excluded. Children were divided into groups: vegetarians (n=30), normal-weight omnivores (n=30) and obese omnivores (n=30). Anthropometric measurement (weight, height) was performed in all children and body mass index (BMI) was calculated. A whole body dual-energy X-ray absorptiometry (DXA) scan was performed to determine fat mass, the percentage of body fat and lean body mass using a Lunar Prodigy (GE, USA). Dietary constituents were assessed by questionnaire (nutrient intake from a 3-day period: 2 weekdays and 1 weekend day) and calculated using the nutritional computer program Dietetyk2®. Serum total cholesterol, high-density and low-density lipoproteins, and triglycerides concentrations were assessed by standard enzymatic methods. Serum levels of leptin, soluble leptin receptor and adiponectin were determined by immunoenzymatic assays.
Results: There were no significant differences in body weight, height, BMI and lean mass values between vegetarians and normal-weight children on traditional mixed diet. Children on vegetarian diet had lower fat mass (p<0.05) and fat mass/lean mass ratio (p<0.05) than normal-weight omnivores. However, omnivorous children with simple obesity had significantly higher body weight, height, BMI, fat and lean mass in comparison to vegetarian as well to normal-weight omnivorous children. The fat mass/lean mass ratio in obese children was about 2.5-fold higher than in normalweight subjects on traditional diet. Total energy and percentage of energy from macronutrients in diets of all children were within the recommended daily intake. Children on vegetarian diet was related with lower fat and higher carbohydrates intake in comparison to their omnivorous peers. Vegetarian children had significantly lower mean total cholesterol (151.5±18.0 mg/dL), low-density lipoprotein (81.0±13.6 mg/dL) and triglycerides (61.6±20.5 mg/dL) than omnivores, especially the obese ones (165.0±22.3 mg/dL, 94.7±19.2 mg/dL, 82.4±32.3 mg/dL, respectively). These differences were statistically significant (p<0.05). Serum concentration of leptin was significantly lower in vegetarian children (3.0±2.1 ng/ml) compared with omnivores (6.8±3.4 ng/ml in normalweight versus 37.8±12.7 ng/ml in obese) (p<0.0001). However, serum soluble leptin receptor as well as adiponectin were at higher levels in vegetarians than in omnivores (p<0.001 and p<0.05, respectively). We observed that serum leptin levels positively and soluble leptin receptor negatively correlated with body mass index and fat mass in prepubertal children. Moreover, leptin levels negatively correlated with its soluble receptor and with adiponectin.
Conclusions: In children different kinds of diet might modify not only body mass and lipid pro le but also serum concentration of adipocytokines. Determination of leptin and its soluble receptor, as well as adiponectin levels may be clinically useful in the medical and nutritional care of obese as well as vegetarian prepubertal children.

Key words: leptin, soluble leptin receptor, adiponectin, anthropometric parameters, vegetarian diet, children

Streszczenie
Cel: Celem pracy była ocena zależności pomiędzy stężeniem adipocytokin a parametrami antropometrycznymi oraz podażą energii i makroskładników w diecie wegetarian oraz dzieci żywionych tradycyjnie (z prawidłową masą ciała, jak też otyłych).
Materiał i metody: Badaniami objęto 90 dzieci w wieku przedpokwitaniowym, pozostających pod opieką Instytutu Matki i Dziecka w Warszawie. Z badań zostali wykluczeni pacjenci z zaburzeniami hormonalnymi oraz chorobami genetycznymi mogącymi mieć wpływ na wzrost, rozwój i metabolizm kostny. Dzieci podzielono na trzy grupy: dzieci na diecie wegetariańskiej (n=30), dzieci z prawidłową masą ciała na diecie tradycyjnej (n=30) oraz dzieci otyłe na diecie tradycyjnej (n=30). U wszystkich dzieci wykonano pomiary antropometryczne (masa i wysokość ciała) oraz obliczono wskaźnik masy ciała (BMI). Badania densytometryczne całego ciała (DXA) z uwzględnieniem masy tłuszczowej, procentu tkanki tłuszczowej oraz beztłuszczowej masy ciała przeprowadzono z zastosowaniem aparatu Lunar Prodigy (GE, USA). Sposób żywienia oceniono na podstawie dzienniczka żywieniowego (jadłospisy z 3 kolejnych dni, w tym 1 świątecznego) obliczając wartość odżywczą średnich całodziennych racji pokarmowych z wykorzystaniem programu komputerowego Dietetyk2®. Dokonano pomiaru stężenia cholesterolu całkowitego oraz lipoprotein o niskiej i wysokiej gęstości, a także triacylogliceroli w surowicy krwi przy użyciu standardowych metod enzymatycznych. Stężenia leptyny, rozpuszczalnego receptora leptyny oraz adiponektyny oznaczono z użyciem metod immunoenzymatycznych.
Wyniki: Nie zaobserwowano istotnych różnic dotyczących masy i wysokości ciała, BMI oraz beztłuszczowej masy pomiędzy wegetarianami i dziećmi z prawidłową masą ciała na diecie tradycyjnej. Dzieci na diecie wegetariańskiej miały istotnie niższą masę tłuszczową (p<0,05) oraz stosunek masy tłuszczowej do beztłuszczowej (p<0,05) w porównaniu z dziećmi na diecie tradycyjnej z prawidłową masą ciała. Natomiast dzieci z otyłością prostą miały istotnie wyższą masę i wysokość ciała, BMI, masę tłuszczową oraz beztłuszczową w porównaniu do grupy wegetarian, jak też do dzieci z prawidłową masą ciała żywionych tradycyjnie. Stosunek masy tłuszczowej do beztłuszczowej u dzieci otyłych był około 2,5-krotnie wyższy niż u rówieśników z prawidłową masą ciała. Podaż energii oraz procentowy udział energii z makroskładników w dietach wszystkich dzieci był zgodny z zaleceniami. W dietach wegetarian stwierdzono niższy udział energii pochodzącej z tłuszczów, a wyższy z węglowodanów w porównaniu do rówieśników żywionych tradycyjnie. Dzieci na diecie wegetariańskiej miały niższe stężenia cholesterolu całkowitego (151,5±18,0 mg/dL), lipoprotein o niskiej gęstości (81,0±13,6 mg/dL) oraz triacylogliceroli (61,6±20,5 mg/dL) niż dzieci na diecie tradycyjnej, szczególnie w grupie otyłych (odpowiednio: 165.0±22,3 mg/dL, 94,7±19,2 mg/dL, 82,4±32,3 mg/dL). Były to różnice istotne statystycznie p<0,05. Stężenie leptyny w surowicy krwi było istotnie niższe (p<0,0001) u dzieci na diecie wegetariańskiej (3,0±2,1 ng/ml) w porównaniu do dzieci z prawidłową masą ciała żywionych tradycyjnie (6,8±3,4 ng/ml) i otyłych (37,8±12,7 ng/ml). U dzieci na diecie wegetariańskiej stwierdzono istotnie wyższe stężenie rozpuszczalnego receptora leptyny (p<0,001) i adiponektyny (p<0,05) niż u rówieśników stosujących dietę tradycyjną. We wszystkich badanych grupach dzieci zaobserwowano pozytywną korelację pomiędzy stężeniem leptyny i negatywną pomiędzy rozpuszczalnym receptorem leptyny a indeksem masy ciała i masą tłuszczową. Ponadto, stężenie leptyny ujemnie korelowało ze stężeniem jej receptora oraz z poziomem adiponektyny.
Wnioski: Rodzaj stosowanej diety może wpływać nie tylko na masę ciała i profil lipidowy, ale również na stężenie adipocytokin w surowicy krwi dzieci w wieku przedpokwitaniowym. Oznaczanie leptyny, rozpuszczalnego receptora leptyny oraz adiponektyny może być użyteczne w postępowaniu medyczno-żywieniowym u dzieci z otyłością prostą, jak też u dzieci na diecie wegetariańskiej.

Słowa kluczowe: leptyna, rozpuszczalny receptor leptyny, adiponektyna, parametry antropometryczne, dieta wegetariańska, dzieci

INTRODUCTION
In recent years, adipose tissue has been recognized as an endocrine organ which produces many biologically active substances. The secretory products of mature adipocytes, proteins called adipocytokines, play a significant role in the regulation of important systemic processes (endocrine function) as well as local metabolic functions (autocrine and paracrine). Leptin and adiponectin are essential for the regulation of body weight by inhibiting food intake and stimulating energy expenditure (1, 2, 3).
Leptin, a product of the ob gene, is localized in humans on chromosome 7q31. This protein consisting of 167 amino acids is formed by four α-helices and two short β-strands that contain an intrachain disulfide bond responsible for its biological activity. Leptin is largely synthesized in white adipose tissue, however, its small amounts are also secreted from secondary sources (muscle, blood, bone, placenta and pancreatic beta cells). Leptin interacts directly with the leptin receptor (OBR), which belongs to the large cytokine receptor family. In humans there are four known isoforms of leptin receptor with different Cterminal cytoplasmatic domains. All these forms have identical extracellular ligand binding domains but differ in the intracellular carboxy terminal region. The OBR isoforms were divided into three classes: long (OBRb), short (OBRa), and soluble (sOBR).
Soluble leptin receptor represents the main leptinbinding activity in human blood. sOBR modulates leptin levels by binding free leptin in the circulation, and preventing hormone degradation and clearance (1, 2, 4, 5).
Adiponectin is a biologically active 244-amino acids protein of a molecular weight 28kDa, coded by ACDC gene. It is expressed by mature adipocytes, with increasing secretion during the process of adipocyte differentiation. Higher adiponectin expression was observed in subcutaneous than in visceral fat. Structurally, adiponectin belongs to the collagen superfamily. Its monomeric subunits (3 kDa), built of a Cterminal globular domain oligomerize to trimers that further associate through disulphide bonds with the collagenous domain to form polymeric complexes of higher structure, including hexameres (approximately 180 kDa). These higher order complexes are the predominant forms in human serum and being biologically active play multivalent functions including regulation of insulin resistance, glucose, and lipid homeostasis (6, 7, 8).
In healthy humans serum adipocytokines change markedly during growth. Generally, there are no gender differences in leptin in prepubertal children, but during puberty girls have higher serum leptin levels than boys.
Adult females have a significantly higher serum leptin concentration and lower levels of soluble leptin receptor compared to males. Adiponectin levels correlate negatively to age, being higher in children than in adults. Its concentrations decrease most substantially during puberty and are lower in male adults compared to females (4, 9, 10).
Clinical studies have shown that leptin levels are increased in obese subjects and markedly lowered by fasting or dieting, however, they are rapidly recovered during refeeding (11, 12, 13, 14). On the other hand, concentrations of soluble leptin receptor and adiponectin increase in lean subjects or with weight reduction. Their lower expressions were observed in obese subjects (5, 13).
The identification of body composition and dietary factors that could be associated with circulating adipocytokines could be of clinical importance. It is known that leptin correlates positively and adiponectin negatively to the amount of fat mass and percentage of body fat (14).
The literature data regarding adipocytokines are mostly related to adults and apply to diabetic, anorexic or obese patients. However, studies binding relations between diet and body composition parameters and levels of adipocytokines with the kind of diet in childhood are still scarce. To our knowledge, there are no reports concerning serum leptin, its soluble receptor and adiponectin levels in subjects consuming vegetarian diets.
Recently, vegetarian diets are seen as an alternative to the traditional model of nutrition and are growing in popularity in developed countries, including Poland. The official position of the American Dietetic Association points out that wellplanned vegetarian diets are healthy, nutritionally adequate and appropriate for individuals at all stages of life, including infants, children, adolescents, adults and elderly (15). Researchers suggest that vegetarianism can be a healthy dietary option which offers a number of nutritional benefits and is associated with reduced risk of certain chronic diseases, including diabetes, coronary heart disease, and some cancers (16, 17, 18, 19, 20). Moreover, vegetarians consume a diet high in fruit and vegetables and low in energy density, which put them at decreased risk for obesity. On the other hand, individuals choosing to follow vegetarian restrictive diets might experience mineral and vitamins deficiencies and notice that using fortified foods or supplements can be helpful in meeting dietary recommendations (21, 22). This is especially important in childhood and adolescence, when growth and development are most intensive (23, 24).
The aim of our study was to investigate associations between serum adipocytokines status and anthropometric parameters as well as total energy and macronutrient intake in vegetarian, normalweight omnivorous and obese omnivorous children.

MATERIAL AND METHODS
We examined 90 healthy prepubertal children aged 410 years who had been referred to the Department of Nutrition at the Institute of Mother and Child (Warsaw) for dietary consultation. Patients with endocrine disorders or genetic syndromes, as well as those who were taking medications that could affect growth, pubertal development or nutritional status were excluded. The whole group of investigated children was ethnically homogeneous and in good general health. Among them 30 children (18 girls, 12 boys, median age 7 years) were vegetarians. They came from vegetarian families and were on this kind of diet from birth. In our group there were 15 lacto-ovovegetarians (did not consume meat, poultry, fish, but ate eggs and dairy products), 2 lacto-vegetarians (excluded eggs, but ate milk products), 9 ovo-vegetarians (excluded milk products, but ate eggs) and 4 vegans (excluded all foods of animal origin).
The group consisting of 60 children (31 girls, 29 boys, median age 8 years) were omnivores. This group was further divided in two subgroups: normal-weight children (n=30, 15 girls, 15 boys, median age 8 years) and obese children (n=30, 18 girls, 12 boys, median age 8 years). Children were considered as normal-weight (z-score BMI <-1+1>) and as obese (z-score BMI >2). In the over-weight group, only children with simple obesity without endocrine disorders or genetic obesity syndrome were included.
Anthropometric measurements (weight, height) were performed on all children and body mass index (BMI) was calculated. A whole body dual-energy X-ray absorptiometry (DXA) scan was performed to determine fat mass (FM), the percentage of body fat and lean body mass (LM) using a Lunar Prodigy densitometer (GE, USA). Dietary constituents were assessed by questionnaire (nutrient intake from a 3-day period: 2 weekdays and 1 weekend day) and calculated using the nutritional computer programme Dietetyk2®.
Venous blood samples were taken in the morning from fasting patients. Serum was prepared by centrifugation (1000 g for 15 min at 4°C) and concentrations of total cholesterol (TC), HDL-cholesterol (HDL-C), LDLcholesterol (LDL-C) and triglycerides (TG) were measured by standard enzymatic methods using commercially available kits from Roche (Switzerland). The remaining serum samples were frozen and collected for the analysis of leptin and its receptor and adiponectin, which were measured immunoenzymatically using ELISA kits (DRG Instruments, GmbH, Germany). Concentration of leptin was determined by Leptin (Sandwich) ELISA assay, the sensitivity of this method was 1 ng/ml; intraassay coefficient of variation (CV) were 5.95% at 3.15 ng/ml and 6.91% at 24.62 ng/ml and inter-assay CVs were 11.55% at 2.71 ng/ml and 8.66% at 26.15 ng/ml. Soluble leptin receptor was measured by Leptin Receptor (human) ELISA assay with detection limit 0.04 ng/ml; the intra-assay precision was 7.23% at 17.35 ng/ml and 7.10% at 30.82 ng/ml; inter-assays CVs are 9.81% at 12.24 and 6.21% at 30.92 ng/ml. The level of adiponectin was evaluated by Adiponectin (human) ELISA assay, the sensitivity of which was 0.78 ng/ml; intra-assay CVs were below 7.4% and inter-assay CVs were between 6.2-8.4%.
The protocol study was carried out in accordance with the Helsinki Convention and was approved by the Ethics Committee of the Institute of Mother and Child. Informed consent was obtained from the parents of all the examined children.
The Statistica (version 8.0) computer software was used for statistical analysis. Differences between vegetarian and omnivores in their anthropometric parameters, nutrient intake and biochemical measurements were determined using the Student`s t-test. Correlation analysis was performed using Pearson`s correlation coefficients. Values presented in the text are means ± SD. The differences were regarded as statistically significant at p<0.05.

RESULTS
Anthropometry and body composition
The results of anthropometric measurements of the studied children are presented in table I. There were no significant differences in body weight, height, BMI and lean mass values between vegetarians and normal-weight children on traditional mixed diet. Children on vegetarian diet had lower fat mass (p<0.05) and FM/LM ratio (p<0.05) than normal-weight omnivores. However, omnivorous children with simple obesity had significantly higher body weight, height, BMI, fat and lean mass in comparison to vegetarian as well to normal-weight omnivorous children. The FM/LM ratio in obese children was about 2.5-fold higher than in normal-weight subjects on traditional diet and above 3-fold higher than in vegetarians.

Dietary intake
Nutrient intake from the 3-day dietary record kept by the parents of the children was calculated and is described in table II. Generally, all individuals had total energy and macronutrient intakes within the recommended daily intake for children (25). There were no significant differences in dietary energy, carbohydrates and fat intake between vegetarians and normal-weight omnivorous children. Omnivorous obese children had significantly higher protein (p<0.05) and dietary cholesterol (p<0.0001) intakes in their diets than vegetarians. However, vegetarian diet was characterized with a lower intake of fat (p<0.05) and higher carbohydrates (p<0.05) in comparison to omnivorous diet, especially to the group of obese children.

Biochemical measurements
Mean values of lipid parameters in all groups of children were within the reference range. However, vegetarian children had significantly lower mean total cholesterol, LDL-cholesterol and triglycerides than omnivores, especially obese children (tab. III). As for HDL-cholesterol level no difference was reported between the studied groups of children, but HDL-C/TC ratio was significantly higher in vegetarians than in omnivorous obese subjects (p<0.01).
Figure 1 presents serum levels of leptin and its receptor as well as adiponectin in the studied prepubertal children. Serum concentration of leptin was significantly lower in vegetarian children (3.0±2.1 ng/ml) compared with omnivores (6.8±3.4 ng/ml in normal-weight versus 37.8±12.7 ng/ml in obese) (p<0.0001). Mean leptin level in children on vegetarian diet was about 2-fold lower than in normal-weight and above 10-fold lower than in obese children on omnivorous diet. Adequately serum soluble leptin receptor (p<0.001) as well as adiponectin (p<0.05) were at higher levels in vegetarians than in omnivores. The leptin/sOB-R ratio was significantly lower (0.08) in vegetarians than in normal-weight omnivores (0.21) and in obese omnivores (1.98) (p<0.0001).
In examining, the association of adipokines and anthropometric parameters, serum leptin levels positively and soluble leptin receptor negatively correlated with BMI and fat mass in the studied group of children (tab. IV). We also found negative correlation between sOB-R and lean mass and between adiponectin and BMI in vegetarian and obese children. No statistically significant correlations between serum adiponectin concentrations and fat mass as well as lean body mass were observed. Apart from that, we found that leptin levels negatively correlated with soluble leptin receptor and with adiponectin.

DISCUSSION
Our studied group of children on vegetarian diet was in good health with no noticeable problems and was under regular medical and nutritional care. Generally, children grew normally, all individuals had total energy and macronutrient intakes within the recommended daily intake for children (25, 26). There were no significant differences in body weight, height, BMI and lean mass values between vegetarians and their normal-weight counterparts on traditional mixed diet. Several studies showed that vegetarian diets contribute to a better lipid profile and bring benefits in atherosclerosis protection (27, 28, 29). These studies have been carried out mainly on adults, few of them included children. Our results point towards the association between vegetarian diet (with lower fat and cholesterol intakes) and lower serum total cholesterol, low-density lipoprotein and triglycerides levels in prepubertal children. Moreover, as for HDL-C level there were no differences between the two groups of children, but HDL-C/TC ratio was significantly higher in vegetarians versus omnivores, especially in the obese subjects.
Our previous studies showed that vegetarian children had lower serum leptin concentration than their omnivorous peers (29, 30). To our knowledge there are no data regarding soluble leptin receptor and adiponectin levels in subjects on vegetarian diets. In our present study mean serum leptin concentration in prepubertal children on vegetarian diet was about 2-fold lower than in normal-weight and above 10-fold lower than in obese children on omnivorous diet. However, serum soluble leptin receptor was at a higher level in vegetarians than in omnivores. Its mean value in vegetarian children was higher by 75% than in normal-weight and above 2-fold higher than in obese omnivorous children. Moreover, the leptin/sOB-R ratio was significantly lower in vegetarians than in normal-weight as well as in obese omnivores (0.08; 0.21; 1.98, respectively). Additionally, we showed that serum leptin levels positively and soluble leptin receptor negatively correlated with body mass index and with fat mass in all the studied groups of children.
Similarly, Ogawa et al. (9) observed that serum sOB-R level was negatively correlated with leptin and with serum triglycerides levels and positively correlated with HDLcholesterol and serum adiponectin levels in healthy adult subjects. According to the authors these relations were independent of age, sex, and BMI. Moreover, they showed that the leptin/sOB-R ratio correlated positively with BMI, the percentage of body fat and negatively with HDL, adiponectin and sOB-R levels. In the group of obese children, positive correlation between leptin and the percentage of fat mass and negative with the concentration of soluble leptin receptor were found. It is widely acknowledged that leptin is highly correlated with the amount of adipose tissue and that is why obese individuals have higher serum leptin levels and reduced concentrations of soluble leptin receptor. It concerns adults as well as children (11, 14, 31, 32). Soluble leptin receptor represents the main leptin-binding compound in plasma resulting in a fraction of bound and a fraction of free leptin in plasma. In obesity, due to the abundant food intake, high leptin levels are probably caused by high leptin release by adipocytes. However, concentrations of sOB-R are decreased compared to normal-weight subjects, resulting in an increased fraction of free leptin. Reduction of body weight through diet significantly decreases the concentration of circulating leptin and increases the level of soluble leptin receptor. This is connected with an increase in the fraction of bound leptin (13). These mechanisms are not clear, but studies on mice suggest that leptin suppresses the expression of its own receptor (4, 12). Thus, sOB-R might act as a modulating factor of leptin action and play an important role in leptin resistance.
Although leptin is responsible for signaling satiety to the hypothalamus, its concentration is paradoxically raised in obesity. Therefore, hyperleptinemia was interpreted as leptin resistance. In children, leptin resistance may be a more salient indicator of risk for greater adipose growth than in adults.
As far as our results are concerned, adiponectin was at higher levels in vegetarians than in omnivores. Moreover, the leptin/adiponectin ratio was significantly lower (0.22) in vegetarians than in normal-weight omnivores (0.59) and in obese omnivores (3.43). Adiponectin is an adipocytokine which is down-regulated in obesity. The mechanism of this negative regulation remains unclear. Probably, the increasing mass of white adipose tissue in obesity reduces adiponectin protein synthesis by feedback inhibition. Furthermore, adiponectin secretion in vitro is lower in visceral than in subcutaneous adipocytes in children, indicating the influence of body fat distribution (7, 8). Additionaly, leptin and adiponectin are adipocytokines which increase tissue sensitivity to insulin. Both stimulate the oxidation of fatty acids thus decreasing the amount of accumulated triglycerides. Both acting at the level of the central nervous system decrease food intake and increase energy expenditure. Moreover, these hormones regulate long term energy homeostasis (33).
It is interesting whether dietary patterns alter serum adipocytokines concentrations independently of energy intake. Limited studies in this field have revealed conflicting results (34, 35, 36). Some authors found no association between dietary intake of macronutrients and leptin levels and hypothesized that fat mass rather than the dietary origin of the energy is a critical determinant of serum leptin concentration. Other researchers suggest that different dietary and lifestyle interventions may modify the predictive value of serum leptin. Larson et al. (37) reported that higher carbohydrate dietary intake and a high glycemic index diet caused decrease in leptin concentrations. According to Yannakoulia et al. (38) energy provided by carbohydrates was positively related to sOB-R, and negatively to leptin levels and to the leptin/sOB-R ratio. The authors obtained opposite results for the percentage of energy intake derived from dietary fat, where an increase in dietary fat corresponds to a decrease in sOB-R concentration and to an increase in the ratio leptin/sOB-R).
These studies were carried out in adults, but there were no data related to children. We presented for the first time the concentrations of adipocytokines, including adiponectin, in prepubertal children on vegetarian diet. In our present study vegetarian children had higher dietary intake of carbohydrates and lower dietary fat intakes than omnivores. They had low serum leptin but high soluble leptin receptor as well as adiponectin levels. However, obese children with higher concentration of leptin and lower levels of leptin soluble receptor and adiponectin, consumed more fat and fewer carbohydrates.

CONCLUSIONS
1. Different kinds of diet can modify not only the body mass and lipid profile but also the serum concentration of adipocytokines.
2. Determination of leptin and its receptor, as well as adiponectin may be clinically useful in the medical and nutritional care of obese as well as vegetarian prepubertal children.
3. Further studies are needed to assess the potential long-term effects of the diet pattern on serum adipocytokines levels.


REFERENCES
1. Koerner A., Kratzsch J., Kiess W.: Adipocytokines: leptin – the classical, resistin – the controversical, adiponectin – the promising, and more to come. Best Pract. Res. Clin. Endocrinol. Metab., 2005, 19(4), 525-546.
2. Venner A., Lyon M.E., Doyle-Baker P.K.: Leptin: A potential biomarker for childhood obesity? Clin. Biochem., 2006, 39, 1047-1056.
3. Sledzinska M., Liberek A., Kaminska B.: Hormony tkanki tłuszczowej a otyłość u dzieci i młodzieży. Med. Wieku Rozwoj. 2009, XIII, 4, 244-251.
4. Mann D.R., Johnson A.O.K., Gimpel T., Castracane D.: Changes in circulating leptin, leptin receptor, and gonadal hormones from infancy until advanced age in humans. J. Clin. Endocrinol. Metab., 2003, 88(7), 3339-3345.
5. Cinaz P., Bideci A., Camundan M.O., Guven A., Gonen S.: Leptin and soluble leptin receptor levels in obese children in fasting and satiety states. J. Pediatr. Endocrinol. Metab., 2005, 18(3), 303-307.
6. Kovacova Z., Vitkova M., Kovacikova M., Klimcakova E., Bajzova M., Hnevkovska Z., Rossmeislova L., Stich V., Langin D., Polak J.: Secretion of adiponectin multimeric complexes from adipose tissue explants is not modified by very low caloric diet. Eur. J. Endocrinol., 2009, 160, 585-592.
7. Araki S., Dobashi K., Kubo K., Asayama K., Shirahata A.: High molecular weight, rather than total, adiponectin levels better reflect metabolic abnormalities associated with childhood obesity. J. Clin. Endocrinol. Metab., 2006, 91, 5113-5116.
8. Reinehr T., Roth C., Menke T., Andler W.: Adiponectin before and after weight loss in obese children. J. Clin. Endocrinol. Metab., 2004, 89(8), 3790-3794.
9. Ogawa T., Hirose H., Yamamoto Y., Nishikai K., Miyashita K., Nakamura H., Saito I., Saruta T.: Relationships between serum soluble leptin receptor level and serum leptin and adiponectin levels, insulin resistance index, lipid profile, and leptin receptor gene polymorphisms in the Japanese population. Metabolism, 2004, 53(7), 879-885.
10. Kratzsch J., Lammert A., Bottner A., Seidel B., Mueller G., Thierry J., Hebebrand J., Kiess W.: Circulating soluble leptin receptor and free leptin index during childhood, puberty and adolescence. J. Clin. Endocrinol. Metab., 2002, 87, 4587-4594.
11. Fleisch A.F., Agarwal N., Roberts M.D., Han J.C., Theim K.R., Vexler A., Troendle J., Yanovski S.Z., Yanovski J.A.: Influence of serum leptin on weight and body fat growth in children at high risk for adult obesity. J. Clin. Endocrinol. Metab., 2007, 92(3), 948-954.
12. Sandhofer A., Laimer M., Ebenbichler C.F., Kaser S., Paulweber B., Patsch J.R.: Soluble leptin receptor and soluble receptorbound fraction of leptin in the metabolic syndrome. Obes. Res., 2003, 11, 760-768.
13. Van Dielen F.M.H., van Veer C., Buurman W.A., Greve J.W.M.: Leptin and soluble leptin receptor levels in obese and weight-losing individuals. J. Clin. Endocrinol. Metab., 2002, 87, 1708-1716.
14. Reinehr T., Kratzsch J., Kiess W., Andler W.: Circulating soluble leptin receptor, leptin, and insulin resistance before and after weight loss in obese children. Int. J. Obes., 2005, 29, 1230-1235.
15. Craig W.J., Mangels A.R.: Position of the American Dietetic Association: Vegetarian diets. J. Am. Diet. Assoc., 2009, 109, 1266-1282.
16. Rajaram S., Sabate J.: Health benefits of vegetarian diet. Nutrition, 2000, 16, 531-533.
17. Key T.J., Appleby P.N., Rosell M.S.: Health effects of vegetarian and vegan diets. Proc. Nutr. Soc., 2006, 65, 35-41.
18. Leitzmann C.: Vegetarian diets: what are the advantages? Forum Nutr., 2005, 57, 147-156.
19. Siani V., Mohamed E.I., Maiolo C., Di Daniele N., Ratin A., Leonardi A., De Lorenzo A.: Body composition analysis for healthy Italian vegetarians. Acta Diabetol., 2003, 40(Suppl 1), 297-298.
20. Craig W.J.: Health effects of vegan diets. Am. J. Clin. Nutr., 2009, 89, 1627S-1633S.
21. Robinson-O`Brien R., Perry C.L., Wall M.M., Story M., Neumark-Sztainer D.: Adolescent and young adult vegetarianism: Better dietary intake and weight outcomes but increased risk of disordered eating behaviors. J. Am. Diet. Assoc., 2009, 109, 648-655.
22. Smith A.M.: Veganism and osteoporosis: a review of the current literature. Int. J. Nurs. Pract., 2006, 12, 302-306.
23. Thane C.W., Bates C.J.: Dietary intakes and nutrient status of vegetarian preschool children from a British national survey. J. Hum. Nutr. Diet., 2000, 13, 149-162.
24. Dunham L., Kollar L.M.: Vegetarian eating for children and adolescents. J. Pediatr. Health Care, 2006, 20, 27-34.
25. Jarosz M., Bułhak-Jachymczyk B.: Normy żywienia człowieka. PZWL, Warszawa, 2008, 433-445.
26. Palczewska I., Niedzwiecka A.: Wskaźniki rozwoju somatycznego dzieci i młodzieży warszawskiej. Med. Wieku Rozwoj., 2001, 2, Suppl I, 17-118.
27. Krajcovicova-Kudlackova M., Simoncic R., Bederova A., Ondreicka R., Klvanova J.: Selected parameters of lipid metabolism in young vegetarians. Ann. Nutr. Metab., 1994, 38, 331-335.
28. Yen C.E., Yen C.H., Huang M.C, Cheng CH, Huang Y.C.: Dietary intake and nutritional status of vegetarian and omnivorous preschool children and their parents in Taiwan. Nutr. Res., 2008, 28, 430-436.
29. Laskowska-Klita T., Ambroszkiewicz J., Klemarczyk W.: Serum leptin concentration and some lipid parameters in vegetarian children, Pol.Merk.Lek., 2004, 16(94), 340-343.
30. Ambroszkiewicz J., Laskowska-Klita T., Klemarczyk W.: Low serum lepton concentration in vegetarian prepubertal children, Rocz. Akad. Med. Białymst., 2004, 49, 103-105.
31. Gajewska J., Weker H., Ambroszkiewicz J., Chełchowska M., Dylag H., Ołtarzewski M., Laskowska-Klita T.: Can leptin and soluble leptin receptor concentrations be used in assessing the efficacy of weight reduction programme in prepubertal obese children? Preliminary report. Med. Wieku Rozwoj., 2009, 4, 237-243.
32. Laskowska-Klita T., Ambroszkiewicz J., Weker H., Szymborska M., Klemarczyk W.: Serum leptin level in prepubertal children with simple obesity. Part II. Med. Wieku Rozwoj., 2002, 6, 213-220.
33. Gnacinska M., Małgorzewicz S., Stojek M., Łysiak-Szydłowska W., Sworczak K.: Role of adipokines in complications related to obesity. A review. Adv. Med. Sci., 2009, 54(2), 150-157.
34. Hakanen M., Ronnemaa T., Talvia S., Rask-Nissila L., Koulu M., Viikari J., Bergendahl M., Simell O.: Serum leptin concentration poorly reflects growth and energy and nutrient intake in young children. Pediatrics, 2004, 113, 1273-1275.
35. Fung T.T., Rimm E.B., Spiegelman D., Rifai N., Tofler G.H., Willett W.C., Hu F.B.: Association between dietary patterns and serum biomarkers of obesity and cardiovascular disease risk. Am. J. Clin. Nutr., 2001, 73(1), 61-67.
36. Agus M.S.D., Swain J.F., Larson C.L., Eckert E.A., Ludwig D.S.: Dietary composition and physiologic adaptations to energy restriction. Am. J. Clin. Nutr., 2000, 71, 901-907.
37. Larsson H., Elmstahl S., Berglund G., Ahren B.: Evidence of leptin regulation of food intake in humans. J. Clin. Endocrinol. Metab., 1998, 83, 4382-4385.
38. Yannakoulia M., Yiannakouris N., Bluher S., Metalas A.L., Klimis-Zacas D., Mantzoros C.S.: Body fat mass and macronutrient intake in relation to circulating soluble leptin receptor, free leptin index, adiponectin, and resistin concentrations in healthy humans. J. Clin. Endocrinol. Metab., 2003, 88(4), 1730-1736.


Adres do korespondencji / Address for correspondence:
Jadwiga Ambroszkiewicz
Screening Department
Institute of Mother and Child
ul. Kasprzaka 17a, 01-211 Warsaw
tel. (48 22) 32-77-260
bioklin.imid@imid.med.pl