Variations in Postprandial Ghrelin Status following Ingestion of High-Carbohydrate, High-Fat, and High-Protein Meals in Males

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Abstract
The purpose of this study was to investigate the response of postprandial acylated ghrelin to changes in macronutrient composition of meals in healthy adult males. A randomized crossover study was performed. Ten healthy adult males were recruited. All subjects received, on separate occasions, a high-carbohydrate (HC), a high-fat (HF), and a high-protein (HP) meal. Blood samples were collected before and 15, 30, 60, 120, and 180 min following the ingestion of each meal. Plasma acylated ghrelin as well as serum insulin, glucose, and triglycerides were measured. The levels of acylated ghrelin fell significantly following the three meals. The HC meal induced the most significant decrease in postprandial ghrelin secretion (-15.5 +/- 2.53 pg/ml) as compared with HF (-8.4 +/- 2.17 pg/ml) and HP (-10.0 +/- 1.79 pg/ml) meals (p < 0.05). However, at 180 min, the HP meal maintained significantly lower mean ghrelin levels (29.7 +/- 3.56 pg/ml) than both HC (58.4 +/- 5.75 pg/ml) and HF (45.7 +/- 5.89 pg/ml) meals and lower levels than baseline (43.4 +/- 5.34 pg/ml) (p <0.01). The postprandial insulin levels increased to significantly higher levels following the HC meal (+80.6 +/- 11.14 microU/ml) than following both HF (37.3 +/- 4.82 microU/ml) and HP (51.4 +/- 6.00 microU/ml) meals (p < 0.001). However, at 180 min, the mean insulin levels were found to be significantly higher following the HP meal (56.4 +/- 10.80 microU/ml) as compared with both HC (30.9 +/- 4.31 microU/ml) and HF (33.7 +/- 4.42 microU/ml) meals (p < 0.05). Acylated ghrelin was also found to be negatively correlated with circulating insulin levels, across all meals. These results indicate that the nutrient composition of meals affects the extent of suppression of postprandial ghrelin levels and that partial substitution of dietary protein for carbohydrate or fat may promote longer-term postprandial ghrelin suppression and satiety. Our results also support the possible role of insulin in meal-induced ghrelin suppression.