*Article* **The Role of GPR120 Receptor in Essential Fatty Acids Metabolism in Schizophrenia**

**Joanna Rog 1,\*, Anna Bła ˙zewicz 2, Dariusz Juchnowicz 3, Agnieszka Ludwiczuk 4, Ewa Stelmach 5, Małgorzata Kozioł 6, Michal Karakula 7, Przemysław Nizi ´nski <sup>2</sup> and Hanna Karakula-Juchnowicz 1,8**


Received: 12 June 2020; Accepted: 21 July 2020; Published: 24 July 2020

**Abstract:** A growing body of evidence confirms abnormal fatty acid (FAs) metabolism in the pathophysiology of schizophrenia. Omega-3 polyunsaturated fatty acids (PUFAs) are endogenous ligands of the G protein-coupled receptors, which have anti-inflammatory properties and are a therapeutic target in many diseases. No clinical studies are concerned with the role of the GPR120 signaling pathway in schizophrenia. The aim of the study was to determine the differences in PUFA nutritional status and metabolism between patients with schizophrenia (SZ group) and healthy individuals (HC group). The study included 80 participants (40 in the SZ group, 40 in the HC group). There were no differences in serum GPR120 and PUFA concentrations and PUFA intake between the examined groups. In the HC group, there was a relationship between FAs in serum and GPR120 concentration (*p* < 0.05): α-linolenic acid (ALA) (*R* = −0.46), docosahexaenoic acid (DHA) (*R* = −0.54), omega-3 PUFAs (*R*=−0.41), arachidonic acid (AA) (*R*=−0.44). In the SZ group, FA serum concentration was not related to GPR120 (*p* > 0.05). In the HC group, ALA and DHA serum concentrations were independently associated with GPR120 (*p* < 0.05) in the model adjusted for eicosapentaenoic acid (EPA) and accounted for 38.59% of GPR120 variability (*p* < 0.05). Our results indicate different metabolisms of FAs in schizophrenia. It is possible that the diminished anti-inflammatory response could be a component connecting GPR120 insensitivity with schizophrenia.

**Keywords:** G protein-coupled receptors; GPR120; FFAR4; schizophrenia; polyunsaturated fatty acids; long-chain fatty acids; omega-3; nutritional psychiatry
