Editors' ChoiceMetabolism

Perceiving Your Appetite

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Science Translational Medicine  30 May 2012:
Vol. 4, Issue 136, pp. 136ec97
DOI: 10.1126/scitranslmed.3004354

Whether you feel hungry or full is regulated by the central nervous system (CNS), which monitors whole body energy balance and guides food-intake behavior. Cerebral insulin is a known appetite supressant; however, the mechanisms underlying this effect are still unclear. Jauch-Chara et al. now propose an inverse correlation between intranasal insulin administration–mediated brain energy induction and subsequent food intake.

Brain energy levels seem to correlate with food consumption in humans. For instance, cerebral energy content, as measured by molecules such as adenosine triphosphate (ATP) and phosphocreatine (PCr), is negatively associated with body mass in humans. Because intranasal insulin administration, which can elevate insulin levels in the cerebrospinal fluid, results in inhibition of food intake in normal fasting men, the authors hypothesized that intranasally administrated insulin increases cerebral energy content and thus suppresses appetite.

Cerebral energy content was analyzed in 15 normal-weight healthy men with an average age in their 20s by using 31P magnetic resonance spectroscopy. Intranasal insulin treatment after 8 hours of fasting considerably increased cerebral high-energy phosphate content, indicating that this treatment modulates the brain’s energy supply. In contrast, this insulin treatment correlated with a subsequent reduction in free-choice calorie consumption.

This finding suggests that insulin regulates appetite by controlling the brain’s energy levels, thus establishing a systemic metabolic homeostasis. In addition, the effect of intranasal insulin treatment on cerebral energy content and appetite gives further insight into potential cures for diseases related to body weight dysregulation. Although the impact of intranasal insulin administration on the hypothalamic appetite center is unclear, the fact that this relatively convenient administration affects cerebral energy content and appetite will be informative in the development of therapeutics that combat obesity.

K. Jauch-Chara et al., Intranasal insulin suppresses food intake via enhancement of brain energy levels in humans. Diabetes, 14 May 2012 (10.2337/db12-0025). [Abstract]

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