however , orexigenic ( acylated and desacylated ghrelin and preptin ) and anorexigenic ( nesfatin-1 and leptin ) peptide hormones of the endocrine system may play a critical role in the development of obesity by regulating the energy balance and affecting the  eating center  and  satiety center  in the paraventricular nucleus , arcuate nucleus , and nucleus of the solitary tract . of the orexigenic peptides ,
ghrelin was discovered in 1999 by kojima et al .   in the x / a cells of the fundus and pylorus areas of the rat stomach and p / d1 cells of the stomach in humans .
ghrelin , which contains 28 amino acids , is called acylated ghrelin when it has a fatty acid attached to the n terminus of the third serine ( octanoic acid ) , and is called desacylated ghrelin when it has no fatty acid attached [ 2 , 3 ] . both forms of ghrelin
the effect of desacylated ghrelin on food intake in mice is weaker than acylated ghrelin .
behavioral studies led to controversial results regarding desacylated ghrelin , and albeit several studies suggest that it is anorexigenic peptide counteracting some of ags actions .
ghrelin levels in humans decrease with obesity and calorie intake and increase with hunger and in anorexia nervosa patients .
preptin is a 34-amino acid peptide hormone cosecreted from the  cells of pancreas along with insulin , amylin , and pancreastatin [ 7 , 8 ] .
its precursor is pro - igf - ii , which also produces insulin - like growth factor ii ( igf - ii ) .
igf - ii is involved in the regulation of cell growth , differentiation , and metabolism .
there is a strong correlation between obesity and hyperinsulinemia and insulin resistance , and these get stronger with increasing body weight .
nesfatin-1 , a recently found anorexigenic peptide , is derived from the 82-amino acid protein called nucleobindin-2 ( nucb2 ) , known as a satiety molecule in the hypothalamus [ 11 , 12 ] .
the middle segment of nesfatin-1 ( residues 24 to 53 ) is biologically active , and its injection reduces food intake , whereas the n-23 and the c-29 amino acid terminal segments are inactive .
nesfatin-1 is a new anorexigenic factor and energy stabilizer [ 13 , reviewed ] . shown to reduce food intake , nesfatin-1 has an inhibitory effect on food intake and thus alleviates obesity in a dose- and time - dependent manner upon intracerebroventricular and intraperitoneal injection , as well as after intranasal administration .
it is also known that there is a slightly positive but inconsistent correlation of nesfatin-1 with bmi in humans , since variables as sex and stress seem to confound this relationship [ 13 , reviewed ] .  
serum leptin levels correlate with body mass index ( bmi ) , serving as the key regulator of body weight through its neuroendocrine functioning .
leptin is bound in low - weight ( thin ) individuals but is free in obese individuals , its rhythmic release being affected by the time of eating , with lowest level in the morning and peaking at night .
leptin levels are also affected by sex , being higher in women than in men . since it is involved in the hunger and satiety centers of the brain , it functions primarily as a metabolic signal associated with the sufficiency  rather than a surplus  of energy .
its signal when reaching the hypothalamus brings the indication that fat reserves are full and thus inhibit expression of orexigenic peptides , neuropeptide y in particular , while increasing the expression of anorexigenic peptides , thereby decreasing food intake and increasing energy consumption [ 19 , 20 ] . in the light of these data ,
this study investigated cross - sectional in five bmi groups from underweight to morbidly obese subjects the serum levels of several peptides involved in the regulation of hunger and satiety : ghrelin in its acylated and desacylated form , nesfatin-1 , leptin , and the physiologic amplifier of glucose - mediated insulin secretion preptin.it was found that leptin , preptin , and acylated ghrelin ( ag ) levels increased with higher bmi , whereas desacylated ghrelin ( dag ) decreased and nesfatin-1 showed no clear relationship with bmi .
the study was carried out in the internal medicine department and biochemistry department of firat university , school of medicine .
after the approval of the ethics board had been obtained , the patients were informed about the study and written consents obtained . registered individuals ranging from 18 to 70 in age study
were allocated to one of 5 groups depending on their bmis . in order to assess subjective appetite sensations , visual analogue scale ( vas ) was applied .
classification of groups by their bmis was as follows : group i ( bmi < 18.5  kg / mlow - weight ) ; group ii ( bmi 18.524.9  kg / mnormal - weight ) ; group iii ( bmi : 2529.9  kg / moverweight ) ; group iv : ( bmi 3039.9  kg / mobese ) ; group v : ( bmi > 40  kg / mmorbidly obese ) .
insulin resistance was calculated using the homoeostasis model assessment of insulin resistance ( homa - ir ) index ( fasting insulin ( units per milliliter ) * fasting glucose ( millimolar)/22.5 ) .
bmi ( kg / m ) was calculated by using body weight ( kg ) and the height in square meters ( m ) .
none of the subjects had diabetes type 1 or 2 ( including the family history ) , moderate to severe hypertension ( resting blood pressure ( bp ) > 130/80>140/85  mmhg ) , acute infectious disease , and chronic medical illness .
pregnant women and subjects who had gastrointestinal disease were excluded and anyone using use drugs , tobacco products ( former and current ) , and alcoholic drinks .
those doing intense exercise regularly ( > 15 min of aerobics 3 times per week ) were also excluded .
none of the subjects had undergone gastrointestinal surgery . to conduct biochemical analyses , venous blood samples ( 8  ml )
the remaining 4  ml was put into tubes containing 500 kallikrein inhibitor unit ( kiu ) aprotinin and centrifuged at 4000  rpm ( 1792  g ) for 5  min .
serum samples from the centrifuging process were transferred to eppendorf tubes and stored at 20c until analyzed .
blood glucose , total cholesterol , low - density lipoprotein ( ldl ) , ldl - cholesterol , high - density lipoprotein ( hdl ) , hdl - cholesterol , very low - density lipoprotein ( vldl ) , vldl - cholesterol , triglyceride ( tg ) , urea , creatine , aspartate aminotransferase ( ast ) , and alanine aminotransferase ( alt ) were analyzed using the olympus au 600 autoanalyzer .
thyroid function ( serum triiodothyronine ( st3 ) , total serum thyroxin ( st4 ) , thyroid stimulating hormone ( tsh ) , adrenocorticotropic hormone ( acth ) , cortisol , insulin , and c - peptide ) was assessed using the immulite 200 device and hba1c shimadzu silver 20a prominence apparatus .
serum acylated ghrelin levels were analyzed using human acylated ghrelin elisa commercial kit ( cat .
no : a05106 spi - bio , human acylated ghrelin enzyme immunoassay kit , france ) , and desacylated ghrelin was measured using human unacylated ghrelin elisa commercial kit ( cat .
a05119 , spi - bio , human unacylated ghrelin immunoassay kit ) in an elx 800 elisa reader .
csb - e09772  h , cusabio biotech co. ltd . ) , serum nesfatin-1 with human / mouse / rat nesfatin enzyme immunoassay kit ( cat .
eia - nes-1 , raybiotech , inc . ) , and serum leptin with leptin ( sandwich ) elisa kit ( cat .
possible differences between the parametric data of groups used anova and post hoc tukey test , when necessary , while possible correlation among parameters used the pearson 's correlation analysis method . after adjusting age and bmi ,
pearson 's and spearman 's correlation coefficients with a bonferroni correction were calculated to examine the relationship between orexigenic and anorexigenic peptides and obesity .
the comparison of the groups in terms of their demographic characteristics showed a statistically significant difference between the mean age and bmi values of the groups ( p < 0.001 ) . the highest mean age among the groups was in group iii ( 55.2    12.8 ) and the lowest mean age in group i ( 28.8    16.2 ) .
the significantly lowest bmi occurred in group i ( 17.6    0.8 ) ; in the other groups bmis were in ascending order from group ii ( 21.7    1.6 ) , group iii ( 27.4    2.1 ) , group iv ( 34.9    2.46 ) , to group v ( 44.8    4.2 ) .
fasting glucose levels increase from underweight to overweight and then are lower when measured in different states of obesity
. additionally , insulin , homa - ir , total cholesterol , ldl , and triglycerides are higher in group ii , iii , or iv than those of morbidly obese subjects ( table 1 ) .
however , it is possible that comorbidities and medication may play a role in the fluctuations of these parameters .  
serum acylated ghrelin levels of the participants by bmi were 16.0  11.1 in group i , 16.07  5.8 in group ii , 16.8  4.1 in group iii , 19.6  3.6 in group iv , and 19.7  5.6  pg / ml in group v ( figure 1 ) . when the groups were compared individually with each other , serum acylated ghrelin levels followed an ascending order from group i to group v ; that is , they were the lowest in low - weight ( thin ) individuals and the highest in obese individuals ( figure 1 ) .
serum desacylated ghrelin levels ( figure 2 ) were 692  345 in group i , 628.4  344.2 
pg / ml in group ii , 522.0  249.5 in group iii , 356.8  219.4 in group iv , and 257.7  16.1  pg / ml in group v. comparison of groups with each other showed that serum desacylated ghrelin levels decreased with increasing bmi .
the highest desacylated ghrelin levels were in low - weight ( thin ) individuals and the lowest in morbidly obese individuals .
in normal - weight individuals , the levels were significantly lower than in obese and morbidly obese individuals ( p < 0.01 , p < 0.001 , resp . ) ( figure 2 ) .
serum preptin levels were the lowest in the normal - weight individuals of group ii .
they were 137  168 in group i , 91  85 in group ii , 151  193 in group iii , 255  153 in group iv , and 262  166  pg / ml in group v. preptin levels in low - weight and overweight individuals were slightly higher than in normal - weight individuals .
obese and morbidly obese groups had significantly higher preptin levels than low - weight and overweight individuals ( p < 0.001 ) ( figure 3 ) . serum nesfatin-1 levels ( figure 4 ) were 5.2  0.9 in group i , 5.6  0.9 in group ii , 5.8  1.7 in group iii , 4.2  2.1 in group iv , and 4.4  0.9  ng / ml in group v. comparing each group with the others , levels followed the following ascending order : group iv < group v < group i < group ii < group iii .
comparison of group ii with groups iv and v showed that group ii had significantly higher serum nesfatin-1 levels than the other 2 groups ( p < 0.01 , p < 0.05 , resp . ) . similarly , comparing nesfatin-1 levels of group iii with those in groups
iv and v , significantly elevated levels were present in group iii ( p < 0.001 , p < 0.01 , resp . ) ( figure 4 ) .
serum leptin levels were the lowest in low - weight individuals : 4.3  4.4 in group i , 6.0  3.94 in group ii , 14.9  4.92 in group iii , 23.9  9.0 in group iv , and 24.6  11.3  pg / ml in group v. leptin levels were higher in the individuals who had high bmis .
overweight individuals had statistically significantly higher leptin levels than low- and normal - weight individuals ( p < 0.001 , p < 0.01 ) .
leptin levels in the obese group were higher than those in low - weight , normal - weight and overweight individuals , the differences being statistically significant ( p < 0.001 , p < 0.001 , p < 0.01 ; figure 5 ) .
correlations found between acylated and desacylated ghrelin , preptin , nesfatin-1 , and leptin levels and bmi are given in table 2 .
based on age , there were also correlations in groups ii and iv ( table 2 ) .
obesity , which is becoming increasingly widespread around the world , is estimated to have a prevalence of 8.2% . when obesity was accepted as a bmi 30  kg / m , us studies between 1982 and 1984 , and between 1988 and 1998 ,
showed that obesity increased from 16.5 to 25% in females and from 12 to 20% in males .
these rather high figures are similar to those in almost all developed and developing countries of the world .
a study was conducted in turkey in 1996 as the first of its kind ; the prevalence of obesity was 18.6% , a figure that rose to 21.9% in 2002 [ 23 , 24 ] .
thus , the prevalence of obesity in turkey was not different from that in the developed countries of the western world , and it reached markedly high levels particularly in females , among whom the prevalence of obesity was as high as 30% .
obesity has a greater effect on alt than on ast . in line with the results of our study concerning the relation between alt and obesity
, we found that 16% of the individuals who had a bmi of 30  kg / m or above had higher alt levels , consistent with bruckert et al .   and
serum lipid levels also rose with increasing bmi from group i to group iv , being statistically significant in all groups .
obesity develops when the chronic mismatch between energy intake and consumption produces a surplus of energy , which is stored as excess fat in the form of tg in the adipose tissue . in a normal human being
, the rate of feeding is reduced to prevent excessive storage once fat and carbohydrate reserves exceed the optimal level .
previous studies showed that plasma ghrelin levels were higher in cachexia and lower in obesity [ 29 , 30 ] .
reported reduced serum ghrelin levels in the gastrointestinal system tissues and serum of rats , which were obese due to diet .
we think that the decrease in desacylated ghrelin levels in our study resulted from elevated glucose levels in obesity .
desacylated ghrelin levels are known to decrease with increasing glucose and increase with decreasing glucose .
however , surprisingly , active acylated ghrelin levels in our analysis were elevated in line with increased bmi , although the increase was not statistically significant .
phoenix pharmaceuticals belmont , ca company ghrelin kits measure total ghrelin , not specifically acylated ghrelin . increased acylated ghrelin concentrations observed in obesity might represent a physiological adaptation to the regulation of energy balance associated with obesity .
collectively , these data suggest why acylated ghrelin increased with bmi , which needs to be further investigated .
the decrease in serum desacylated ghrelin levels in obese and morbid obese individuals was statistically significant compared to lower level in normal - weight participants .
leptin and insulin have been shown to be peripheral regulators of ghrelin secretion , and a reciprocal relationship exists between plasma ghrelin and leptin or insulin levels . increased leptin
might cause a decrement of desacylated ghrelin beside acylated ghrelin as reported here . in this study indeed , desacylated ghrelin levels are decreased in human obesity , whereas leptin levels are increased , and the effects of desacylated ghrelin on energy homeostasis are opposite to those of leptin and acylated ghrelin . also , it was first time shown that serum preptin concentrations increased with increasing bmi
. however , we could not find any report to compare the effects of preptin levels and appetite and bmi in obese individuals .
yang et al . , reported that the circulating level of preptin was 398  13  ng / l in normal - weight individuals , with levels in males being lower than in females .
their study showed a positive correlation between plasma preptin level and diastolic blood pressure , tg , total cholesterol , hba1c , and homa - ir index .
our preptin levels rose with increasing bmi , as in yang et al . , but the increase was not statistically significant .
.   found that nesfatin-1 was a depot - specific adipokine produced preferably by the adipose tissue in obese individuals and individuals with arranged dietary deprivation .
nesfatin-1 levels were statistically higher in mice fed on a high - fat diet ( p < 0.05 ) and correlated positively with human bmi ( p < 0.01 ) .
they fell in food - deprived individuals compared to the control group ( p < 0.01 ) .
prepared especially sensitive elisa to measure nesfatin-1 level after oral glucose tolerance test ( ogtt ) and food tests following overnight fasting .
there were 43 nonobese males ( age : 24.5  0.3 ; bmi : 21.2  0.3  kg / m ) and 9 males with a high bmi ( age : 32  3.7 ; bmi : 37.3  3.8 
kg / m ) , all of whom were given 75  g ogtt and a food test before their fasting nesfatin-1 concentrations were quantified .
the concentrations showed a significant negative correlation with bmi , body fat percentage , body fat weight , and blood glucose ( p < 0.05 ) .
however , fasting plasma nesfatin-1 levels were significantly lower in the individuals with a high bmi than those with a normal bmi
. nesfatin-1 decreased with increasing body weight and functioned as a new anorexigenic factor and energy stabilizer .
reduction in the blood nesfatin-1 level with rising bmi might be related to impaired insulin sensitivity and glucose homeostasis . in our groups ,
compared plasma ghrelin and leptin responses to exogenous and endogenous stimuli in intact rats and other that had been starved for 16  h to inhibit the increase in ghrelin secretion due to hunger .
high insulin levels led to higher leptin levels .   additionally , high and low ambient temperatures , stress , or insulin supplementation affected plasma ghrelin .
bell - anderson and bryson   successfully used leptin in the treatment of leptin - deficient obese patients and consequently determined that leptin levels were associated with bmi .
preptin and leptin levels , however , rise with increasing bmi . also , acylated ghrelin rose in obesity and nesfatin-1 showed no clear relationship to bmi .
 this study examines the levels of acylated and desacylated ghrelin , preptin , leptin , and nesfatin-1 peptide changes related to the body mass index ( bmi ) . 
 the subjects were allocated to 5 groups depending on their bmis as follows : group i ( bmi < 18.5  kg / m2 ) ; group ii ( bmi 18.524.9  kg / m2 ) ; group iii ( bmi 2529.9  kg / m2 ) ; group iv ( bmi 3039.9  kg / m2 ) ; group v ( bmi > 40  kg / m2 ) . serum acylated and desacylated ghrelin , preptin , and leptin levels were measured by the enzyme - linked immunosorbent assay ( elisa ) and nesfatin-1 was measured by the enzyme immunoassay ( eia ) . 
 desacylated ghrelin levels showed a gradual and statistically significant drop from group i to group v , while preptin and leptin levels exhibited a gradual and significant increase from group i to group iv . 
 serum nesfatin-1 levels gradually , but not significantly , increased from group i to group iii and showed a significant decrease in groups iv and v. in conclusion , leptin , preptin , and acylated ghrelin ( ag ) levels increased with higher bmi , whereas desacylated ghrelin ( dag ) decreased and nesfatin-1 showed no clear relationship to bmi . 
1. Introduction
2. Material and Method
3. Results
4. Discussion
5. Conclusion