Genetic polymorphisms 415 (T>C) (RS9658635) and +87 (C>T) (RS7610) and serum level of chromogranin A in subjects with metabolic syndrome in the Fars ethnic group

The aim of study was to assess genetic polymorphisms and serum level of chromogranin A (CgA) and its association with metabolic syndrome (MetS) components in the Fars ethnic group. Two hundred and forty-six people from Fars ethnic group participated in the study. The ATP III criteria were used to determine MetS components. The serum CgA level was measured by ELISA and the detection of the two regions were performed by TETRA ARMs-PCR and RFLPPCR methods. In results, the CC, CT, and TT genotypes of +87 C>T were 65%, 31.7%, and 3.2%, and were 74.8%, 25.2%, and 0% in subjects with and without MetS, respectively. The C and T alleles of +87 C>T were 81%, 19% and 79%, 21% in both groups, respectively. The TT, CT, and CC genotypes of -415 T>C were 76.4%, 21.1%, 2.4% and were 58.5%, 40.6% and 0.8% in subjects with and without MetS, respectively. The T and C alleles were 87% and 13% and 79% and 21% in both groups, respectively. There was correlation between serum level of fasting blood sugar (FBS) and CgA in subjects with MetS. We conclude that the increased CgA level in the subjects with MetS has a positive significant relationship with serum level of FBS. The most differences in CgA gene polymorphism were seen in -415 T>C genotype than that of +87C>T genotype when compared two groups. It may mean that subjects with MetS in the Fars ethnic group are more sensitive and greater risk for the development of MetS in the genotype of -415 T>C.

The importance of acclimatisation and habituation to experimental conditions when investigating the anorectic effects of gastrointestinal hormones in the rat

OBJECTIVE

Peptide YY3-36 (PYY(3-36)), glucagon-like peptide-1 (GLP-1), oxyntomodulin and cholecystokinin (CCK) are gastrointestinal-derived hormones that are released postprandially in proportion to the amount of calories ingested. All significantly reduce food intake following peripheral administration to rodents. We have investigated the effect of handling, exposure to a novel environment or to environmental enrichment on the anorectic effect of these gut hormones.

RESULTS

Results suggest that the transfer of a rat into a novel environment (cage change) inhibits the anorectic response to peripherally administered PYY(3-36) and oxyntomodulin (1 h food intake reduction (% saline control): PYY/home cage 82.3 +/- 5.9%, P < 0.05; PYY/clean cage 103.4 +/- 9.7%; oxyntomodulin/home cage 71.6 +/- 12.1%, P < 0.05; oxyntomodulin/clean cage 103.0 +/- 8.5%) and attenuates the anorectic response to GLP-1 and CCK (1 h food intake reduction (% saline control): GLP-1/home cage 68.8 +/- 6.4%, P < 0.01; GLP-1/clean cage 80.0 +/- 9.3%; CCK/home cage 49.8 +/- 6.2%, P < 0.001; CCK/clean cage 69.4 +/- 10.6%, P < 0.05). We have also observed that exposure to a novel environment does not alter anorectic effect of peripherally administered melanocortin 3/4 receptor agonist, melanotan II (MTII) (1 h food intake reduction (% saline control): MTII/home cage 32.0 +/- 6.3%, P < 0.001; MTII/clean cage 24.8 +/- 4.2%, P < 0.001). The attenuation in food intake observed following exposure to a novel environment can be attributed, in part, to a significant reduction in the food intake of the saline treated animals. In a further study, the anorectic effect of peripherally administered PYY(3-36) is attenuated in unhandled rats (88 +/- 4.2% saline control, P = ns) or rats exposed to environmental enrichment (103.3 +/- 9.7% saline control, P = ns), but not in animals that were handled extensively prior to the study (80.1 +/- 7.3% saline control, P < 0.05).

CONCLUSION

These studies highlight the importance of handling, acclimatisation and habituation of rodents to experimental conditions prior to investigating the ability of gut hormones to alter food intake.

Abnormalities of the somatotrophic axis in the obese agouti mouse

OBJECTIVE

Abnormalities of the melanocortin system produce obesity and increased linear growth. While the obesity phenotype is well characterised, the mechanism responsible for increased linear growth is unclear. The somatotrophic axis was studied in the obese agouti (A(y)/a) mouse as a model of a perturbed melanocortin system.

DESIGN

Adult obese A(y)/a mice were compared to age- and sex-matched wild-type (WT) controls. Weight and body length (nose-anus) were recorded. Plasma growth hormone (GH), insulin-like growth factor-I (IGFI), insulin and leptin were measured using radioimmunoassay. Since ghrelin is a potent GH secretagogue, plasma ghrelin, stomach ghrelin peptide and stomach ghrelin mRNA expression were studied. Hypothalamic periventricular (PeVN) somatostatin neurones and arcuate (Arc) neuropeptide Y (NPY) neurones inhibit the growth axis, whereas Arc growth hormone-releasing hormone (GHRH) neurones are stimulatory. Therefore, specific hypothalamic expression of somatostatin, NPY and GHRH was measured using quantitative in situ hybridisation.

RESULTS

Obese A(y)/a mice were significantly heavier and longer than WT controls. Plasma IGFI concentrations were 30% greater in obese A(y)/a mice. Obese A(y) /a mice were hyperinsulinaemic and hyperleptinaemic, yet plasma ghrelin, and stomach ghrelin peptide and mRNA were significantly reduced. In obese A(y)/a mice, PeVN somatostatin and Arc NPY mRNA expression were reduced by 50% compared to WT controls, whereas Arc GHRH mRNA expression was unchanged.

CONCLUSION

Increased body length in adult obese A(y)/a mice may result from reduced Arc NPY and PeVN somatostatin mRNA expression, which in turn, may increase plasma IGFI concentrations and upregulate the somatotrophic axis.

Pre-obese and obese agouti mice are sensitive to the anorectic effects of peptide YY(3-36) but resistant to ghrelin

OBJECTIVE

The role of the melanocortin system in the feeding effects of peripheral peptide YY(3-36) (PYY(3-36)) and ghrelin was investigated using the agouti (A(y)/a) mouse as a model of abnormal melanocortin signalling. Furthermore, we examined whether the ectopic expression of agouti protein in A(y)/a mice results in complete MC4-R inhibition, by studying the effects of peripheral alpha-melanocyte-stimulating hormone (alpha-MSH) and leptin on food intake.

DESIGN

Adult A(y)/a mice were studied in the pre-obese state (7-8 weeks) and obese state (14-15 weeks). Animals received PYY(3-36) (0.02 micromol/kg), NDP-alpha-MSH (0.2 micromol/kg), leptin (2 micromol/kg) (all 24 h fasted state) and ghrelin (0.2 micromol/kg) (fed state) by intraperitoneal (i.p.) injection. Age-matched A(y)/a controls received i.p. saline. A separate cohort of wild-type (WT), age-matched controls received the same peptide dose or saline. Food intake was measured at 1, 2, 4, 8 and 24 h post-injection and compared in all four groups. Plasma leptin-, ghrelin- and PYY-like immunoreactivity (IR) were measured using radioimmunoassay (RIA).

RESULTS

At 2 h post-injection, PYY(3-36) reduced food intake in pre-obese and obese A(y)/a mice, whereas ghrelin had no effect. Plasma ghrelin levels were significantly reduced in pre-obese and obese A(y)/a mice compared to WT controls. Peripheral administration of NDP-alpha-MSH and leptin acutely suppressed feeding (0-2 h) in pre-obese and obese A(y)/a mice.

CONCLUSIONS

Responsiveness of pre-obese and obese A(y)/a mice to PYY(3-36) suggests that the melanocortin system may not be essential for the anorectic effects of this peptide. Melanocortinergic antagonism by agouti protein in A(y)/a mice may be sufficient to block the effects of endogenous, but not exogenous PYY(3-36), alpha-MSH and leptin. The mechanism underlying ghrelin resistance in A(y)/a mice may result from antagonism of hypothalamic melanocortin receptors-4 by agouti protein, supporting a role for the melanocortin system in mediating ghrelin's actions.