Effects of Ferric Citrate Supplementation on Brain Omega-3 Polyunsaturated Fatty Acids Metabolism

Background: Obesity is associated with decreased omega-3 polyunsaturated fatty acids (n-3 PUFAs) and increased tissue iron overload. Both iron and n-3 PUFAs are essential nutrients for the brain. We and others found that chronic inflammation impaired iron metabolism and iron dysregulation further disrupt hepatic n-3 PUFAs transportation. Currently, the effects of iron on brain n-3 PUFAs utilization remains unclear.
Aim: This aim was to investigate the effects of iron supplementation on brain n-3 PUFAs metabolism in high-fat diet (HFD) induced obese rats.
Methods: Sprague-Dawley (SD) rats were divided into 5 groups, including a control group feds with a standard diet and obese rats received 50% HFD without or with iron supplemented (0.25g, 1g, 2g ferric iron/kg diet) for 13 weeks. Lipidomics were used to identify hippocampus fatty acid (FA) profiles. Expression of hipocampal n-3 PUFAs converting enzymes, PUFAs transporter-related enzymes, Land’s cycle-related enzymes, iron utilization in hippocampus was detected by western blotting. Behavior tests were used to evaluate the effects of dietary feeding on cognitive function of the rats.
Result: At week 13, obese rats fed with 1g or 2g ferric iron/kg diet had decreased hippocampal n-3 and n-6 PUFAs and n-3 PUFAs converting enzymes, ∆5 and ∆6 desaturases, and elongase 2 compared to lean rats (all p < 0.05). Western blot analysis revealed that obese rats received ≥1g/kg diet ferric iron decreased hippocampal PUFAs transporters [major facilitator superfamily domain-containing protein 2A (MFSD2A) and fatty acid transport protein 1 (FATP1) and impaired Land’s cycle remodeling pathways [Acyl-CoA Synthetase Long-Chain Family Member 1 (ACSL1), Acyl-CoA Synthetase Long-Chain Family Member 6 (ACSL6), Lysophosphatidylcholine Acyltransferase 3 (LPCAT3), Lysophosphatidylcholine Acyltransferase 4 (LPCAT4)] (all p < 0.05). High dose iron supplementation (≥1g /kg diet ferric iron) also impaired hippocampal iron metabolism, indicated by increased transferrin receptor protein 1 (TFR1), ferritin heavy chain 1 (FTH1), and hepcidin levels, but decreased levels of divalent metal transporter 1 (DMT1) and ferroportin 1 (FPN1) (all p < 0.05). Behavioral measurements showed that the HFD alone significantly decreased total distance in the open field test (OFT), the discrimination index in the novel object recognition test (NORT), and long-term spatial memory in the Morris Water Maze (MWM), however, ferric citrate improved these effects (all p < 0.05). Spearman correlation analysis showed distinct relationships between hippocampal iron biomarkers, PUFAs levels, and markers of PUFAs transportation and recycled (all p < 0.05). MWM and OFT were negatively correlated with hippocampal MFSD2A, ACSL6, and LPCAT4 (all p < 0.05). Hippocampal iron and PUFAs did not correlated with behavior test.
Conclusion: High-dose ferric citrate supplementation impaired hippocampal iron and n-3 PUFAs signaling pathways but had no effect on cognitive function.

Keywords: Obesity, iron supplementation, brain omega-3 PUFAs, brain iron overload, land cycle, cognitive function
Background: Obesity is associated with decreased omega-3 polyunsaturated fatty acids (n-3 PUFAs) and increased tissue iron overload. Both iron and n-3 PUFAs are essential nutrients for the brain. We and others found that chronic inflammation impaired iron metabolism and iron dysregulation further disrupt hepatic n-3 PUFAs transportation. Currently, the effects of iron on brain n-3 PUFAs utilization remains unclear.
Aim: This aim was to investigate the effects of iron supplementation on brain n-3 PUFAs metabolism in high-fat diet (HFD) induced obese rats.
Methods: Sprague-Dawley (SD) rats were divided into 5 groups, including a control group feds with a standard diet and obese rats received 50% HFD without or with iron supplemented (0.25g, 1g, 2g ferric iron/kg diet) for 13 weeks. Lipidomics were used to identify hippocampus fatty acid (FA) profiles. Expression of hipocampal n-3 PUFAs converting enzymes, PUFAs transporter-related enzymes, Land’s cycle-related enzymes, iron utilization in hippocampus was detected by western blotting. Behavior tests were used to evaluate the effects of dietary feeding on cognitive function of the rats.
Result: At week 13, obese rats fed with 1g or 2g ferric iron/kg diet had decreased hippocampal n-3 and n-6 PUFAs and n-3 PUFAs converting enzymes, ∆5 and ∆6 desaturases, and elongase 2 compared to lean rats (all p < 0.05). Western blot analysis revealed that obese rats received ≥1g/kg diet ferric iron decreased hippocampal PUFAs transporters [major facilitator superfamily domain-containing protein 2A (MFSD2A) and fatty acid transport protein 1 (FATP1) and impaired Land’s cycle remodeling pathways [Acyl-CoA Synthetase Long-Chain Family Member 1 (ACSL1), Acyl-CoA Synthetase Long-Chain Family Member 6 (ACSL6), Lysophosphatidylcholine Acyltransferase 3 (LPCAT3), Lysophosphatidylcholine Acyltransferase 4 (LPCAT4)] (all p < 0.05). High dose iron supplementation (≥1g /kg diet ferric iron) also impaired hippocampal iron metabolism, indicated by increased transferrin receptor protein 1 (TFR1), ferritin heavy chain 1 (FTH1), and hepcidin levels, but decreased levels of divalent metal transporter 1 (DMT1) and ferroportin 1 (FPN1) (all p < 0.05). Behavioral measurements showed that the HFD alone significantly decreased total distance in the open field test (OFT), the discrimination index in the novel object recognition test (NORT), and long-term spatial memory in the Morris Water Maze (MWM), however, ferric citrate improved these effects (all p < 0.05). Spearman correlation analysis showed distinct relationships between hippocampal iron biomarkers, PUFAs levels, and markers of PUFAs transportation and recycled (all p < 0.05). MWM and OFT were negatively correlated with hippocampal MFSD2A, ACSL6, and LPCAT4 (all p < 0.05). Hippocampal iron and PUFAs did not correlated with behavior test.
Conclusion: High-dose ferric citrate supplementation impaired hippocampal iron and n-3 PUFAs signaling pathways but had no effect on cognitive function.

Keywords: Obesity, iron supplementation, brain omega-3 PUFAs, brain iron overload, land cycle, cognitive function