The Effect Of Different Feeding Patterns In The Early Life On Ghrelin And Leptin In Adult Rats

Obesity is a disease with nutrition and metabolism disorder as excessive energy intake and less energy consumption.In the past three decades,the incidence of obesity and related chronic diseases are increasing with rapid economic development and lifestyle changes. A number of clinical and animal studies have been confirmed that early life of nutrition is closely related to health status and obesity in adult . Over-nutrition during lactation increases the risk of obesity and insulin resistance. The studies on a variety of hormone and nutrients related to feeding central which involved the food intake are so much ,However, the exact mechanism is unclear. At previous study,we observed the effects of postnatal over-feeding and different diet intervention in postweaning on growth and development as well as Ghrelin and leptin.In this study,Our aim is to clarify the molecular mechanism of early overfeeding lead to adult obesity and insulin resistance ,it might provide practical molecular target and critical time for the prevention of adult diseases during childhood.Part one: The effect of neonatal overfeeding on ghrelin and leptin in adult ratsObjective: To elevate the effects of neonatal overfeeding on the ghrelin expression in gastric and serum ghrelin,leptin,Insulin, and explore the pathophysiology of over-feeding and metabolic syndrome.Methods: Male Sprague-Dawley neonate rats pup litters were adjusted to litter sizes of 10 (normal feeding, NF) or 3 (over feeding, OF) in postnatal day 3 and then given standard diet after weaning. Serum insulin was assayed by specific RIA, leptin and ghrelin were assayed by ELISA. Ghrelin mRNA and protein levels in gastric were quantified by real-time PCR and immunohistochemical.Results: (1)There was no significant difference in food intake between two groups. (2) Compared with NF group ,OF rats kept higher body weight from postnatal 1 weeks to 16 weeks (p=0.033), and presented impaired glucose tolerance and insulin resistance in postnatal 16 weeks (p<0.05). (3) Both groups the ghrelin mRNA expression in gastric increased with age and peaked at 8 weeks (p<0.05). The positive cell area of ghrelin immunohistochemistry was similar to mRNA expression in the gastric. There were no differences in Ghrelin-IP,hypothalamus ghrelin mRNA expression and serum ghrelin between two groups at each time point (p>0.05). (4)Serum Leptin levels increased during puberty in both groups and were significantly higher in OF than that in the NF from 4 weeks (F=7.94, p=0.018). Leptin was negatively correlated with ghrelin in all rats(r=-0.397,p=0.008)..Conclusions: Neonatal overfeeding in rats induced obesity and insulin resistance in adult. Neonatal overfeeding had no effect on ghrelin expression and secretion, but increased serum leptin level during offspring.Part two: The effect of different postweaning diet on ghrelin and leptin in adult ratsObjective: To observe the effect of the high-fat diet andω-3 polyunsaturated fatty acid diet after weaning on Ghrelin and Leptin and Insulin. Methods: The pup litters in male Sprague-Dawley nepnate rats were adjusted to litter sizes of 10 (normal feeding, NF) or 3 (over feeding, OF) in postnatal day 3. After weaning, NF groups were given standard diet (NF+Con)and high-fat diet after weaning (NF+HF). OF groups given standard diet( OF+Con), high-fat diet( OF+Con) (OF+HF) andω-3 polyunsaturated fatty acid diet (OF+ω-3) . Serum insulin was assayed by specific RIA, leptin and ghrelin were assayed by ELISA. Ghrelin mRNA and protein levels in gastric were quantified by real-time PCR and immunohistochemical.Results: (1)Food intake in NF + HF group increased only in 4 and 8 weeks, while the food intake in OF + HF group was higher than OF + Con group in all time points (F = 7.259, p = 0.043). (2) The body weight in NF + HF group was significantly higher than that of NF + Con group from 8 week (t =2.483, p = 0.029). The body weight in OF + HF group was higher than that of OF + Con from 6 week(t =3.767, p = 0.002),and body weight in OF +ω-3 was significantly lower than the OF + Con group and similar to NF+Con in the 16 week (t =2.387, p = 0.024). Regardless of feeding status during lactation, blood glucose levels in high-fat diet were significantly higher than the normal diet group in the 16 week , while the blood glucose concentration in OF +ω-3 was significantly lower than other groups (F=15.539, p=0.000). (3) Regardless of feeding status during lactation, Ghrelin mRNA expression in gastric was high in fat diet groups (t=3.46,p=0.013;t =8.486, p = 0.000). While there were no change in Ghrelin-IP and the serum Ghrelin at the same time in16 week.(4) In the 16 week serum leptin in OF + HF group was significantly higher than that of in OF + Con group(t=3.531,p=0.005);, serum leptin (t=-3.028,p=0.014)and insulin ( t=2.729,p=0.018) levels in NF + HF group were significantly higher than that of NF + Con group inthe 16 week. Leptin was negatively correlated with ghrelin in all rats.(6 weeks,r=-0.38,p=0.008;16 weeks, r=-0.482,p=0.026). Conclusion: The findings suggeste that high fat diet induce obesity and metabolic disorders, and OF+HF group is more sensitive compare with NF+HF group. Increased ghrelin mRNA expression and leptin resistance appear in high fat diet. Theω-3 PUFAs can prevent obesity, impaired glucose tolerance, leptin, insulin resistance in rats.