UV Exposure and Metabolic Function: Distinct Effects on Appetite, Adiposity, and Cardiometabolic Health

Written by Aliyah Zendklina Amerta W.S (012111133070) and supervised by Annette d’Arqom, dr., M.Sc., PhD

Prodi S1 Kedokteran FK UNAIR

    The collected studies highlight the distinct effects of UV exposure on metabolic functions. In mice, long-term UV exposure increased appetite without causing weight gain due to norepinephrine's dual role in enhancing appetite and stimulating subcutaneous white adipose tissue (WAT) to brown. The browning process converts energy-storing white adipocytes into energy-burning brown adipocytes, balancing the increased caloric intake. UV exposure significantly lowered blood leptin levels in mice, reducing hunger, as well as showing decreased adipose tissue size and weight in high-fat diet mice.

    In humans, vitamin D, absorbed through sun exposure, helps modulate fat cells and lowers the risk of metabolic diseases such as type-2 diabetes, NAFLD (Non-Alcoholic Fatty Liver Disease) and cardiometabolic disorders. Next, there are distinct sex-based differences in response to UVB radiation. In males, UVB exposure increases food-seeking behavior through the action of ghrelin, mediated by p53 in skin adipocytes. Estrogen inhibits p53's transcriptional activity, preventing the same response in females. Ghrelin plasma levels peak in the summer, correlating with increased food-seeking behavior in males.

    A systematic review (Gorman et al., 2019) on UVR and metabolic dysfunction further supports these findings, indicating that UVR exposure can reduce risk factors for diabetes, adiposity, and cardiometabolic dysfunction in overweight mice. However, the review also notes limitations such as small sample sizes, short intervention durations, and variability in study designs, complicating result interpretation. Despite these limitations, the evidence suggests that controlled UV exposure can induce beneficial metabolic changes without increasing physical activity. 

    Overall, UV radiation has multiple influences on metabolism, adiposity and cardiometabolic dysfunction, which affect obesity and weight management. This occurs because UV exposure affects various components that affect weight gain such as leptin and ghrelin (appetite hormones), vitamin D (which influences adipose tissue), glucose sensitivity and other factors addressed in the meta-analysis.

References:

Quan, Q.-L. et al. (2024) ‘UV irradiation increases appetite and prevents body weight gain through the upregulation of norepinephrine in mice’, Journal of Investigative Dermatology [Preprint]. doi:10.1016/j.jid.2024.03.012.

Gorman, S., de Courten, B., & Lucas, R. (2019). Systematic review of the effects of ultraviolet radiation \ on markers of metabolic dysfunction. Clinical Biochemist Reviews, 40(3), 147–162. https://doi.org/10.33176/aacb-19-00026

Fleury, N., Sian Geldenhuys, & Gorman, S. (2016). Sun Exposure and Its Effects on Human Health: Mechanisms through Which Sun Exposure Could Reduce the Risk of Developing Obesity and Cardiometabolic Dysfunction. International Journal of Environmental Research and Public Health/International Journal of Environmental Research and Public Health, 13(10), 999–999. https://doi.org/10.3390/ijerph13100999

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