A hypothalamus-liver-skeletal muscle axis controlled by JNK1 and FGF21 mediates olanzapine-induced insulin resistance in an intraperitoneal treatment in male mice

BackgroundOlanzapine (OLA), a widely prescribed second-generation antipsychotic, is associated with adverse metabolic effects. We recently showed that oral OLA treatment in male mice induces weight gain and hepatic steatosis, whereas intraperitoneal (i.p.) administration leads to weight loss due to higher hypothalamic OLA levels and activation of brown adipose tissue. Since clinical studies report insulin resistance in individuals treated with OLA, here we investigated the impact of OLA i.p. treatment on insulin sensitivity, focusing on the liver- skeletal muscle axis. Material and MethodsWild-type male mice were treated with OLA (10 mg/kg, i.p.) for 8 weeks or received a single intrahypothalamic injection (15 nmol). Glucose homeostasis parameters were assessed. Mechanistic studies were performed in vagotomized mice, mice lacking JNK in either the hypothalamus or liver, mice overexpressing hepatic FGF21, and PTP1B-deficient mice (PTP1B-KO). ResultsOLA i.p. treatment induced systemic insulin resistance, pyruvate intolerance, and reduced insulin signaling in both liver and skeletal muscle. These effects were accompanied by increased hepatic JNK phosphorylation and IRS1 serine phosphorylation. A single intrahypothalamic OLA injection similarly impaired peripheral insulin action and activated hepatic JNK. Deletion of hypothalamic or hepatic JNK1, as well as vagotomy, prevented these defects. OLA reduced hepatic Fgf21 expression, an effect reversed by hypothalamic JNK1 deletion or vagotomy. Hepatic FGF21 overexpression prevented OLA-induced insulin resistance in skeletal muscle but not in liver. PTP1B-KO mice were protected from all metabolic impairments. ConclusionAlthough OLA i.p. treatment prevents weight gain, it decreases peripheral insulin sensitivity through a hypothalamus-liver axis driven by hypothalamic JNK1, which activates hepatic JNK via the vagus nerve, suppresses hepatic FGF21 and ultimately impairs insulin signaling in skeletal muscle. Importantly, the protection conferred by PTP1B deficiency against OLA-induced insulin resistance strongly suggests that targeting PTP1B might prevent metabolic comorbidities in patients under OLA treatment in a personalized manner.