Menopause is associated with decreased postprandial ghrelin, whereas a history of anorexia nervosa is associated with increased total ghrelin

Appetite-related Gut Hormone Responses to Feeding Across the Life Course

Appetite-related hormones are secreted from the gut, signaling the presence of nutrients. Such signaling allows for cross-talk between the gut and the appetite-control regions of the brain, influencing appetite and food intake. As nutritional requirements change throughout the life course, it is perhaps unsurprising that appetite and eating behavior are not constant. Changes in appetite-related gut hormones may underpin these alterations in appetite and eating. In this article, we review evidence of how the release of appetite-related gut hormones changes throughout the life course and how this impacts appetite and eating behaviour. We focus on hormones for which there is the strongest evidence of impact on appetite, food intake, and body weight: the anorexigenic glucagon like peptide-1, peptide tyrosine tyrosine, and cholecystokinin, and the orexigenic ghrelin. We consider hormone concentrations, particularly in response to feeding, from the very early days of life, through childhood and adolescence, where responses may reflect energy requirements to support growth and development. We discuss the period of adulthood and midlife, with a particular focus on sex differences and the effect of menstruation, pregnancy, and menopause, as well as the potential influence of appetite-related gut hormones on body composition and weight status. We then discuss recent advancements in our understanding of how unfavorable changes in appetite-related gut hormone responses to feeding in later life may contribute to undernutrition and a detrimental aging trajectory. Finally, we briefly highlight priorities for future research.

How gut hormones shape reward: A systematic review of the role of ghrelin and GLP-1 in human fMRI

The gastrointestinal hormones ghrelin and glucagon-like peptide-1 (GLP-1) have opposite secretion patterns, as well as opposite effects on metabolism and food intake. Beyond their role in energy homeostasis, gastrointestinal hormones have also been suggested to modulate the reward system. However, the potential of ghrelin and GLP-1 to modulate reward responses in humans has not been systematically reviewed before. To evaluate the convergence of published results, we first conduct a multi-level kernel density meta-analysis of studies reporting a positive association of ghrelin (N_comb = 353, 18 contrasts) and a negative association of GLP-1 (N_comb = 258, 12 contrasts) and reward responses measured using task functional magnetic resonance imaging (fMRI). Second, we complement the meta-analysis using a systematic literature review, focusing on distinct reward phases and applications in clinical populations that may account for variability across studies. In line with preclinical research, we find that ghrelin increases reward responses across studies in key nodes of the motivational circuit, such as the nucleus accumbens, pallidum, putamen, substantia nigra, ventral tegmental area, and the dorsal mid insula. In contrast, for GLP-1, we did not find sufficient convergence in support of reduced reward responses. Instead, our systematic review identifies potential differences of GLP-1 on anticipatory versus consummatory reward responses. Based on a systematic synthesis of available findings, we conclude that there is considerable support for the neuromodulatory potential of gut-based circulating peptides on reward responses. To unlock their potential for clinical applications, it may be useful for future studies to move beyond anticipated rewards to cover other reward facets.

Dysfunctional Eating Behaviour and Leptin in Middle-Aged Women: Role of Menopause and a History of Anorexia Nervosa

BACKGROUND

Weight gain is common as women approach mid-life. Reduced levels of leptin, an anorexigenic hormone, may facilitate this. Studies in middle-aged women with obesity have shown that dysfunctional eating behaviour, such as restrained eating, is linked to lower leptin. Furthermore, states of low oestradiol signalling, as are found in post-menopause or anorexia nervosa, have been found to impact leptin levels. The aim of this study was to investigate, for the first time, how different aspects of dysfunctional eating, menopausal status, and a history of anorexia nervosa relate to leptin levels in normal-weight middle-aged women.

METHODS

A total of N = 57 women were recruited. Thirty-one were post-menopausal, and 27 had a history of anorexia nervosa. Dysfunctional eating behaviour was measured by the Three-Factor Eating Questionnaire, which contains three subscales: susceptibility/responsiveness to hunger, restraint, and disinhibition. Body composition was assessed by bioelectrical impedance analysis. A fasting blood sample was obtained to determine leptin.

RESULTS

Controlling for age, body mass index, and fat mass, susceptibility/responsiveness to hunger was positively associated with leptin (β = 0.267, p = 0.031), whereas restrained eating (β = - 0.183, p = 0.079) and a history of anorexia nervosa (β = - 0.221, p = 0.059) were, by trend, negatively associated with leptin. Neither disinhibited eating nor menopausal status was related to leptin.

CONCLUSIONS

Leptin may decline as a response to repeated states of a negative energy balance. A possible implication is that mid-life weight management should avoid extreme changes in eating behaviour and instead focus on the macronutrient composition of diet and physical activity. Further, longitudinal enquiries are warranted to investigate these relationships.

A Systematic Review and Meta-Analysis Finds Increased Blood Levels of All Forms of Ghrelin in Both Restricting and Binge-Eating/Purging Subtypes of Anorexia Nervosa

Anorexia nervosa (AN) is a severe psychiatric condition associated with high mortality and chronicity. The hunt for state, trait, subtyping, and prognostic biomarkers is ongoing and the orexigenic hormone ghrelin and its different forms, acyl ghrelin and desacyl ghrelin, have been proposed to be increased in AN, especially in the restrictive subtype. A systematic literature search was performed using established databases up to 30 November 2020. Forty-nine studies met inclusion criteria for cross-sectional and longitudinal meta-analyses on total ghrelin, acyl ghrelin, and desacyl ghrelin. All forms of ghrelin were increased in the acute stage of anorexia nervosa during fasting compared to healthy controls. Previous notions on differences in ghrelin levels between AN subtypes were not supported by current data. In addition, a significant decrease in total ghrelin was observed pre-treatment to follow-up. However, total ghrelin levels at follow-up were still marginally elevated compared to healthy controls, whereas for acyl ghrelin, no overall effect of treatment was observed. Due to heterogeneity in follow-up designs and only few data on long-term recovered patients, longitudinal results should be interpreted with caution. While the first steps towards a biomarker in acute AN have been completed, the value of ghrelin as a potential indicator of treatment success or recovery status or its use in subtype differentiation are yet to be established.