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Human IL6 enhances leptin action in mice
M Sadagurski1, L Norquay, J Farhang
1Howard Hughes Medical Institute, Division of Endocrinology, Children's Hospital Boston, Harvard Medical School, Karp Family Research Laboratories, Rm 4210, 300 Longwood Avenue, Boston, MA 02115, USA.
Aims/Hypothesis:
Interleukin-6 is an inflammatory cytokine with pleiotropic effects upon nutrient homeostasis. Many reports show that circulating IL6 correlates with obesity and contributes to insulin resistance; however, IL6 can promote energy expenditure that improves glucose homeostasis.
Methods:
We investigated nutrient homeostasis in C57BL/6J mice with sustained circulating human IL6 (hIL6) secreted predominantly from brain and lung (hIL6(tg) mice).
Results:
The hIL6(tg) mice displayed no features of systemic inflammation and were more insulin-sensitive than wild-type mice. On a high-fat diet, hIL6(tg) mice were lean, had low leptin concentrations, consumed less food and expended more energy than wild-type mice. Like ob/ob mice, the ob/ob (IL6) mice (generated by intercrossing ob/ob and hIL6(tg) mice) were obese and glucose-intolerant. However, low-dose leptin injections increased physical activity and reduced both body weight and food intake in ob/ob (IL6) mice, but was ineffective in ob/ob mice. Leptin increased hypothalamic signal transducer and activator of transcription-3 phosphorylation in ob/ob (IL6) mice, whereas ob/ob mice barely responded.
Conclusions/Interpretation:
Human IL6 enhanced central leptin action in mice, promoting nutrient homeostasis and preventing diet-induced obesity.
