Augmented gut hormone response to feeding in older adults exhibiting low appetite

Age-related changes in gut hormones may play a role in anorexia of ageing. The aim of this study was to determine concentrations of ghrelin, PYY, and GLP-1 in older adults exhibiting an anorexia of ageing phenotype. Thirteen older adults with healthy appetite (OA-HA; 8f, 75 ± 7 years, 26.0 ± 3.2 kg m^-2), fifteen older adults with low appetite (OA-LA; 10f, 72 ± 7 years, 23.6 ± 3.1 kg m^-2), and twelve young adults (YA; 6f, 22 ± 2 years, 24.4 ± 2.0 kg m^-2) completed the study. Healthy appetite and low appetite were determined based on BMI, habitual energy intake, self-reported appetite, and laboratory-assessed ad libitum lunch intake. Participants provided a fasted measure of subjective appetite and blood sample (0 min) before consuming a standardised breakfast (450 kcal). Appetite was measured and blood samples were drawn throughout a 240-min rest period. At 240 min, an ad libitum lunch meal was consumed. Relative intake at lunch (expressed as percentage of estimated total energy requirement) was lower for OA-LA (19.8 ± 7.7%) than YA (41.5 ± 9.2%, p < 0.001) and OA-HA (37.3 ± 10.0%, p < 0.001). Ghrelin suppression was greater for OA-LA (net AUC, -78719 ± 74788 pg mL^-1·240min^-1) than both YA (-23899 ± 27733 pg mL^-1·240min^-1, p = 0.016) and OA-HA (-21144 ± 31161 pg mL^-1·240min^-1, p = 0.009). There were trends for higher GLP-1 concentrations in OA-LA compared with YA at 90 min (8.85 ± 10.4 pM vs. 1.88 ± 4.63 pM, p = 0.073) and 180 min (5.00 ± 4.71 pM vs. 1.07 ± 2.83 pM, p = 0.065). There was a trend for a greater PYY response for OA-LA compared with OA-HA (net AUC p = 0.062). "Anorexigenic response score" - a composite score of gut hormone responses to feeding - showed greater anorexigenic response in OA-LA, compared with YA and OA-HA. No differences were seen in subjective appetite. These observations suggest augmented anorexigenic responses of gut hormones to feeding may be causal mechanisms of anorexia of ageing.