# Effects of High-Monounsaturated-Fatty-Acid (MUFA) Diet and Melatonin Supplementation on Lipid Metabolism in Female Rats

## TL;DR

This study found that melatonin and a high-MUFA diet altered gene expression related to lipid metabolism in female rats, but without clear health benefits.

## Contribution

The study reveals distinct molecular responses to melatonin and high-MUFA diets in lipid metabolism without physiological improvements.

## Key findings

- Melatonin and high-MUFA diet upregulated genes like PPARα and ACO in the liver.
- High-MUFA diet increased HSL expression in adipose tissue.
- Combined treatment altered FNDC5 and PGC-1α expression without affecting serum irisin.

## Abstract

This study explored whether melatonin supplementation and a high-monounsaturated-fatty-acid (MUFA) diet were associated with changes in lipid metabolism-related gene expression in female rats. After eight weeks, no significant changes were observed in body weight or blood lipid profiles. However, the combination of melatonin and the high-MUFA diet enhanced the expression of hepatic genes involved in fat oxidation, including peroxisome proliferator-activated receptor α (PPARα) and acyl-CoA oxidase (ACO), and the high-MUFA diet increased hormone-sensitive lipase (HSL) expression in adipose tissue. Interestingly, this combined treatment also upregulated fibronectin type III domain-containing protein 5 (FNDC5) while downregulating peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α). These findings indicate that melatonin and dietary fatty acid composition are associated with distinct molecular responses related to lipid metabolism; however, these responses did not translate into clear physiological benefits, highlighting the need for longer-term studies to clarify their biological significance.

Background: This study investigated the effects of melatonin (50 mg/kg/day) and a high-monounsaturated-fatty-acid (MUFA) diet (60% MUFAs; PUFA/SFA ratio = 5), alone or combined, on lipid metabolism-related gene expression in female Sprague–Dawley rats. Methods: Thirty-two eight-week-old rats were randomized into four groups: control (C), melatonin (M), experimental oil diet (E), and combined melatonin plus experimental oil diet (ME). Treatments lasted eight weeks, with melatonin given orally at 17:00–19:00 daily. Results: In the ME group, hepatic expression of peroxisome proliferator-activated receptor α (PPARα) and acyl-CoA oxidase (ACO) mRNA was markedly upregulated, while the E group showed significantly higher expression of hormone-sensitive lipase (HSL) in white adipose tissue. Additionally, ME rats exhibited increased fibronectin type III domain-containing protein 5 (FNDC5) mRNA with reduced peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), but serum irisin remained unchanged. Conclusions: Melatonin and a high-MUFA diet induced modest and non-uniform changes in lipid metabolism-related gene expression. However, these transcriptional responses were not accompanied by measurable physiological or metabolic outcomes, indicating that the observed effects represent early molecular adaptations rather than functional metabolic modulation.