Peptide YY is a gut hormone consisting of 36 amino acids which shares structural similarity to neuropeptide Y and pancreatic polypeptide. Peptide YY is released from the mucosa of the ileum of the small intestine and the colon where it acts to increase satiety, decrease food intake, decrease pancreatic secretion and decrease gastrointestinal gut motility. Peptide YY is realised in proportion to the energy content of the food ingested and therefore acts to limit energy intake once sufficient energy have been ingested. Evidence suggests that peptide YY is involved in short term appetite regulation and energy balance, but less is known about its role in the development of obesity. Some data suggests that the signal may become weaker in some individuals which then ultimately results in overeating and weight gain. However, evidence from animals and human studies are inconsistent.
Researchers1 have investigated the regulation of peptide YY in 69 healthy male subjects following 7 days of over feeding. Healthy subjects between the ages of 19 and 29 were categorised into normal-weight, overweight or obese and then overfed at 70% above normal calorie levels. The food consisted of 15% protein, 50% carbohydrate and 35% fat in order to replicate the typical North American diet ratios. At baseline the mean energy intake was 2969 kcal and during overfeeding this rose to 5471 kcal. On average subjects gained 2.4 kg of bodyweight or which 43.2% was body fat. In addition, following overfeeding there was also significant deterioration in insulin sensitivity, an increase in serum lipids and increased β-cell function. At baseline there was no differences in peptide YY concentrations between groups. During overfeeding there was a significant increase in peptide YY concentrations in all subjects but no significant difference between groups.
The gastrointestinal tract is the largest endocrine gland in the human body and its secretary activity is complex and not fully understood. A number of hormonal substances are secreted that aid in the regulation of appetite, satiety and energy balance. This study shows that peptide YY concentrations in plasma increase as a result of overfeeding but that this increase is not dependent on the adipose tissue size of the individual. Interestingly, those individuals with the lowest baseline peptide YY had the largest increase in HDL, LDL and total cholesterol in response to the overfeeding. Peptide YY was therefore negatively correlated with the increase in cholesterol measurements in response to feeding. Interestingly, evidence suggests that peptide YY is stimulated to a greater degree by the ingestion of protein. This may in part explain the findings that high protein diets are able to aid in weight loss and improve satiety.
RdB
