Katie Wynne

Subcutaneous Ghrelin Enhances Acute Food Intake in Malnourished Patients Who Receive Maintenance Peritoneal Dialysis: A Randomized, Placebo-Controlled Trial

Anorexia and malnutrition confer significant morbidity and mortality to patients with end-stage kidney disease but are resistant to therapy. The aim of this study was to determine whether subcutaneous administration of ghrelin, an appetite-stimulating gut hormone, could enhance food intake in patients who are receiving maintenance peritoneal dialysis and have evidence of malnutrition. The principal outcome measure was energy intake during a measured study meal. Secondary outcome measures were BP and heart rate and 3-d food intake after intervention. Nine peritoneal dialysis patients with mild to moderate malnutrition (mean serum albumin 28.6 +/- 5.0 g/L, total cholesterol 4.4 +/- 0.6 mmol/L, subjective global assessment score of 5.7 +/- 1.7) were given subcutaneous ghrelin (3.6 nmol/kg) and saline placebo in a randomized, double-blind, crossover protocol. Administration of subcutaneous ghrelin significantly increased the group mean absolute energy intake, compared with placebo, during the study meal (690 +/- 190 versus 440 +/- 250 kcal; P = 0.0062). When expressed as proportional energy increase for each individual, ghrelin administration resulted in immediate doubling of energy intake (204 +/- 120 versus 100%; P = 0.0319). Administration of ghrelin maintained a nonsignificant increase in energy intake over 24 h after intervention (2009 +/- 669 versus 1579 +/- 330 kcal) and was not followed by subsequent underswing (1790 +/- 370 versus 1670 +/- 530 and 1880 +/- 390 versus 1830 +/- 530 kcal on days 2 and 3, respectively). Ghrelin administration resulted in a significant fall in mean arterial BP (P = 0.0030 by ANOVA). There were no significant adverse events during the study. Subcutaneous ghrelin administration enhances short-term food intake in dialysis patients with mild to moderate malnutrition.

PYY3-36 and oxyntomodulin can be additive in their effect on food intake in overweight and obese humans.

OBJECTIVE Peptide YY3–36 (PYY3–36), a Y2 receptor agonist, and oxyntomodulin, a glucagon-like peptide 1 (GLP-1) receptor agonist, are cosecreted by intestinal L-cells after each meal. Separately each hormone acts as an endogenous satiety signal and reduces appetite in humans when infused intravenously. The aim of the current study was to investigate whether the anorectic effects of PYY3–36 and oxyntomodulin can be additive. RESEARCH DESIGN AND METHODS Twelve overweight or obese human volunteers underwent a randomized, double-blinded, placebo-controlled study. An ad libitum test meal was used to measure energy intake during intravenous infusions of either PYY3–36 or oxyntomodulin or combined PYY3–36/oxyntomodulin. RESULTS Energy intake during coadministration of PYY3–36 and oxyntomodulin was reduced by 42.7% in comparison with the saline control and was significantly lower than that during infusions of either hormone alone. CONCLUSIONS The anorectic effects of PYY3–36 and oxyntomodulin can be additive in overweight and obese humans. Coadministration of Y2 receptor agonists and GLP-1 receptor agonists may be a useful treatment strategy for obesity.

The role of oxyntomodulin and peptide tyrosine–tyrosine (PYY) in appetite control

Oxyntomodulin and peptide tyrosine–tyrosine (PYY) are released from intestinal enteroendocrine cells in response to a meal. These circulating hormones are considered to be satiety signals, as they have been found to decrease food intake, body weight and adiposity in rodents. Their effect on energy homeostasis is mediated by the hypothalamus and brainstem, and several studies have demonstrated alterations in neuropeptide signaling within the arcuate nucleus. The weight loss that has been observed in animal models after repeated administration of oxyntomodulin and PYY has led to interest in developing these peptides as antiobesity therapies in humans. Indeed, preliminary studies have found that oxyntomodulin or PYY administration reduces food intake and body weight effectively in overweight human volunteers. This research suggests that modulation of these gut hormones could prove to be effective long-term therapies in the quest to combat the obesity epidemic.