Obesity and insulin resistance are associated with low-grade systemic inflammation, which is related to increased concentrations of plasma FFAs, glucose, or insulin. Prolonged fasting induces insulin resistance due to elevated plasma FFAs, but is not accompanied by hyperinsulinemia or hyperglycemia. This makes it possible to study effects of physiologically increased FFA concentrations on inflammatory markers, when insulin and glucose concentrations are not increased. In random order, 10 healthy young lean men (mean BMI: 22.8 kg/m2) were fasted or fed in energy balance for 60 h with a 2-week wash-out period. Subjects stayed in a respiration chamber during the 60-h periods. Blood samples were taken after 12, 36, and 60 h. Then, a hyperinsulinemic-euglycemic clamp was performed.Fasting decreased insulin sensitivity by 45% and increased FFA concentrations 5-fold. Fasting did not change concentrations of the inflammatory cytokines TNF-alpha, IL-1beta, IL-6 and IL-8, or of hs-CRP. Effects on vascular endothelial growth factor (VEGF) - which may positively relate to insulin resistance, and on chemerin and leptin - adipokines related to obesity, and obesity-related pathologies, were also studied. At t=60 h, VEGF concentrations were significantly increased during the fasted period (p<0.05). At the same time point, chemerin (p<0.01) and leptin (p<0.01) were significantly decreased after fasting. For leptin, this decrease was also significant after 36 h (p<0.01). Adiponectin levels remained unchanged. In healthy young lean men, fasting-induced increases in FFAs leading to insulin resistance do not cause changes in concentrations of the inflammatory cytokines. VEGF concentrations increased and those of chemerin decreased.
van Herpen, N. A., Sell, H., Eckel, J., Schrauwen, P., & Mensink, R. P. (2013). Prolonged fasting and the effects on biomarkers of inflammation and on adipokines in healthy lean men. Hormone and Metabolic Research, 45(5), 378-382. https://doi.org/10.1055/s-0032-1330015