Ghrelin concentrations reflect body mass index rather than feeding status in obese girls

Reward-related brain activity and behavior are associated with peripheral ghrelin levels in obesity

BACKGROUND/OBJECTIVES

While excessive food consumption represents a key factor in the development of obesity, the underlying mechanisms are still unclear. Ghrelin, a gut-brain hormone involved in the regulation of appetite, is impaired in obesity. In addition to its role in eating behavior, this hormone was shown to affect brain regions controlling reward, including the striatum and prefrontal cortex, and there is strong evidence of impaired reward processing in obesity. The present study investigated the possibility that disrupted reward-related brain activity in obesity relates to ghrelin deficiency.

SUBJECTS/METHODS

Fifteen severely obese subjects (BMI > 35 kg/m²) and fifteen healthy non-obese control subjects (BMI < 30 kg/m²) were recruited. A guessing-task paradigm, previously shown to activate the ventral striatum, was used to assess reward-related brain neural activity by functional magnetic resonance imaging (fMRI). Fasting blood samples were collected for the measurement of circulating ghrelin.

RESULTS

Significant activations in the ventral striatum, ventromedial prefrontal cortex and extrastriate visual cortex were elicited by the fMRI task in both obese and control subjects. In addition, greater reward-related activations were present in the dorsolateral prefrontal cortex, and precuneus/posterior cingulate of obese subjects compared to controls. Obese subjects exhibited longer choice times after repeated reward and lower circulating ghrelin levels than lean controls. Reduced ghrelin levels significantly predicted slower post-reward choices and reward-related hyperactivity in dorsolateral prefrontal cortices in obese subjects.

CONCLUSION

This study provides evidence of association between circulating ghrelin and reward-related brain activity in obesity and encourages further exploration of the role of ghrelin system in altered eating behavior in obesity.

Hormones and cytokines in childhood obesity

OBJECTIVE

Obesity is a growing worldwide health problem affecting both adults and children. Effective prevention and treatment modalities can be achieved by understanding the pathogenesis of obesity better. This review addresses some of the issues related to the hormones and cytokines taking part in the pathogenesis of obesity, energy balance and inflammation.

DESIGN

We reviewed current literature on this broad subject especially concentrating on the functions of the hormones and cytokines taking part in the pathogenesis of the childhood obesity. Using the key words obesity, children, hormones, cytokines publications and cross references were evaluated from PubMed database between 1957 and 2009.

RESULTS

In children, leptin and ghrelin are two hormones which have major influence on energy balance. Leptin is responsible from long term regulation of energy balance and ghrelin functions as an appetite stimulatory signal. In contrast to ghrelin, obestatin acts as an anorexigenic hormone by suppressing food intake. Adipokines secreted from adipose tissue are the key regulators of inflammation in obesity. Increased TNF-alpha and IL-6 levels but decreased levels of adiponectin and IL-10 are associated with increased inflammation, tissue injury and complications of obesity.

CONCLUSIONS

Development, pathogenesis and complications of childhood obesity consist of complex mechanisms including numerous cytokines and hormones. New treatment modalities depend on understanding these complex mechanisms.

Ghrelin levels in children with constitutional delay of growth and puberty

OBJECTIVE

In this study, we aimed to show the role of ghrelin in growth delay in children with constitutional delay of growth and puberty (CDGP).

METHODS

Thirty male children with CDGP constituted the study group and fifteen healthy children with normal growth of similar ages-the control group. In both groups, fasting and postprandial plasma ghrelin levels, serum insulin-like growth factor-1 (IGF-1) and IGF-binding protein-3 (IGFBP-3) levels were determined.

RESULTS

There were no differences in fasting and postprandial ghrelin levels (824.23±523.46 pg/mL and 447.26±259.92 pg/mL, respectively) in children with CDGP compared to the levels in the control group (687.38±481.43 pg/mL and 365.59±260.43 pg/mL, respectively; p>0.05). Differences in fasting and postprandial ghrelin levels were also similar in the two groups (394.44±369.10 pg/mL and 346.55±338.67 pg/mL, respectively; p>0.05). Serum IGF-1 levels were significantly depressed in children with CDGP compared to those in the control group (239.5±83.95 ng/mL and 339.20±63.08 ng/mL, respectively; p<0.05).

CONCLUSION

Decreased appetite and feeding problems in children with CDGP were not related to depressed ghrelin levels. In addition, ghrelin levels did not increase to compensate for the decreased appetite and feeding problems in CDGP.

Molecular characterization of the ghrelin and ghrelin receptor genes and effects on fat deposition in chicken and duck

Ghrelin (GHRL) and its receptor (GHSR) are involved in various bioactivities. In this study, the complete cDNA and 5′ flanking region of the duck GHRL (dGHRL) gene and a 3717 bp fragment of the duck GHSR (dGHSR) gene were obtained. A total of 19, 8, 43, and 48 SNPs identified in 2751, 1358, 3671, and 3567 bp of the chicken GHRL (cGHRL), chicken GHSR (cGHSR), dGHRL, and dGHSR genes, respectively. Both cGHRL and dGHRL were expressed predominantly in the proventriculus, whereas the highest mRNA levels of cGHSR and dGHSR were detected in the breast muscle and pituitary. Association analysis showed that C-2047G, A-2355C, and A-2220C of the cGHRL gene were significantly associated with abdominal fat weight (AFW; P = .01), crude protein content of leg muscle (CPCLM; P = .02), and CPCLM (P = .0009), respectively. C-1459T of the cGHSR gene was also significantly associated with CPCLM (P = .0004). C-729T of dGHRL and A3427T of dGHSR were both significantly associated with subcutaneous fat thickness (SFT; P = .04). It was indicated by this study that the GHRL and GHSR genes were related to fat deposition in both chicken and duck.