Pleiotrophin deletion prevents high-fat diet-induced cognitive impairment, glial responses, and alterations of the perineuronal nets in the hippocampus

Obesity and metabolic disorders, such as metabolic syndrome (MetS) facilitate the development of neurodegenerative diseases and cognitive decline. Persistent neuroinflammation plays an important role in this process. Pleiotrophin (PTN) is a cytokine that regulates energy metabolism and high-fat diet (HFD)-induced neuroinflammation, suggesting that PTN could play an important role in the connection between obesity and brain alterations, including cognitive decline. To test this hypothesis, we used an HFD-induced obesity model in Ptn genetically deficient mice (Ptn^−/−). First, we confirmed that Ptn deletion prevents HFD-induced obesity. Our findings demonstrate that feeding wild-type (Ptn^+/+) mice with HFD for 6 months results in short- and long-term memory loss in the novel object recognition task. Surprisingly, we did not observe any sign of cognitive impairment in Ptn^−/− mice fed with HFD. In addition, we observed that HFD induced microglial responses, astrocyte depletion, and perineuronal nets (PNNs) alterations in Ptn^+/+ mice, while these effects of HFD were mostly prevented in Ptn^−/− mice. These results show a crucial role of PTN in metabolic responses and brain alterations induced by HFD and suggest the PTN signalling pathway as a promising therapeutic target for brain disorders associated with MetS.