Associations between high-metabolic rate organ masses and fasting hunger: A study using whole-body magnetic resonance imaging in healthy males

IMPROVE 2022 International Meeting on Pathway-Related Obesity: Vision of Excellence

Nearly 90 clinicians and researchers from around the world attended the first IMPROVE 2022 International Meeting on Pathway-Related Obesity. Delegates attended in person or online from across Europe, Argentina and Israel to hear the latest scientific and clinical developments in hyperphagia and severe, early-onset obesity, and set out a vision of excellence for the future for improving the diagnosis, treatment, and care of patients with melanocortin-4 receptor (MC4R) pathway-related obesity. The meeting co-chair Peter Kühnen, Charité Universitätsmedizin Berlin, Germany, indicated that change was needed with the rapidly increasing prevalence of obesity and the associated complications to improve the understanding of the underlying mechanisms and acknowledge that monogenic forms of obesity can play an important role, providing insights that can be applied to a wider group of patients with obesity. World-leading experts presented the latest research and led discussions on the underlying science of obesity, diagnosis (including clinical and genetic approaches such as the role of defective MC4R signalling), and emerging clinical data and research with targeted pharmacological approaches. The aim of the meeting was to agree on the questions that needed to be addressed in future research and to ensure that optimised diagnostic work-up was used with new genetic testing tools becoming available. This should aid the planning of new evidence-based treatment strategies for the future, as explained by co-chair Martin Wabitsch, Ulm University Medical Center, Germany.

Cdo1-Camkk2-AMPK axis confers the protective effects of exercise against NAFLD in mice

Exercise is an effective non-pharmacological strategy for ameliorating nonalcoholic fatty liver disease (NAFLD), but the underlying mechanism needs further investigation. Cysteine dioxygenase type 1 (Cdo1) is a key enzyme for cysteine catabolism that is enriched in liver, whose role in NAFLD remains poorly understood. Here, we show that exercise induces the expression of hepatic Cdo1 via the cAMP/PKA/CREB signaling pathway. Hepatocyte-specific knockout of Cdo1 (Cdo1LKO) decreases basal metabolic rate of the mice and impairs the effect of exercise against NAFLD, whereas hepatocyte-specific overexpression of Cdo1 (Cdo1LTG) increases basal metabolic rate of the mice and synergizes with exercise to ameliorate NAFLD. Mechanistically, Cdo1 tethers Camkk2 to AMPK by interacting with both of them, thereby activating AMPK signaling. This promotes fatty acid oxidation and mitochondrial biogenesis in hepatocytes to attenuate hepatosteatosis. Therefore, by promoting hepatic Camkk2-AMPK signaling pathway, Cdo1 acts as an important downstream effector of exercise to combat against NAFLD.

The importance of fat-free mass and constituent tissue-organs in the control of human appetite

PURPOSE OF REVIEW

Traditional models of human appetite focus on the contribution of adipose tissue and the gastrointestinal tract, both of which exert mainly inhibitory influences. The purpose of this review is to consider the biological factors that influence the drive to eat.

RECENT FINDINGS

Fat-free mass is positively associated with objectively measured meal size and daily energy intake. These findings have been replicated in multiple populations across the life-course in laboratory and free-living studies. Studies have shown that the effect of fat-free mass is statistically mediated by resting metabolic rate, suggesting that energy expenditure per se may influence energy intake. A recent MRI study has reported that fasting hunger was associated with high metabolic rate organ (heart, liver, brain, kidneys) and skeletal muscle mass. Integrating measures of body composition at the tissue-organ level and markers of their metabolic function with appetitive measures could provide novel insight into the mechanisms that influence appetite.

SUMMARY

These recent findings suggest that fat-free mass and resting metabolic rate are determinants of energy intake. Consideration of fat-free mass and energy expenditure as physiological sources of appetitive signals helps reconcile the mechanisms underpinning the inhibition of eating with those that drive eating.