Tea Tree Oil Mediates Antioxidant Factors Relish and Nrf2-Autophagy Axis Regulating the Lipid Metabolism of Macrobrachium rosenbergii

Abstract

Both oxidative stress and autophagy refer to regulating fat metabolism, and the former affects autophagy, but the role and mechanism of the antioxidant–autophagy axis in regulating lipid metabolism remains unclear. As an antioxidant, tea tree oil (TTO) has little research on the regulatory mechanism of lipid metabolism in crustaceans. This study investigated whether TTO could alter hepatopancreatic lipid metabolism by affecting the antioxidant–autophagy axis. Feed Macrobrachium rosenbergii with three different levels of TTO diets for 8 weeks: CT (0 mg/kg TTO), 100TTO (100 mg/kg TTO), and 1000TTO (1000 mg/kg TTO). The results showed that 100TTO treatment reduced the hemolymph lipids level and hepatopancreatic lipid deposition compared to CT. In contrast, 1000TTO treatment increased hepatopancreatic lipid deposition, damaging both morphology and function in the hepatopancreas. The 100TTO treatment promoted lipolysis and reduced liposynthesis at the transcriptional level compared to the CT group. Meanwhile, it improved the hepatopancreas antioxidant capacity and maintained mitochondrial structural and ROS homeostasis. In addition, it simultaneously activated the expression of transcription factors Keap1-Nrf2 and Imd-Relish. By contrast, the 1000TTO group significantly enhanced the ROS level, which considerably activated the Keap1-Nrf2 signaling expression but had no significant effects on the expression of Imd-Relish. The 100TTO group supplementation significantly enhanced lipid droplet breakdown and autophagy-related genes and protein expression. On the contrary, the 1000TTO group significantly inhibited the expression of genes and proteins related to autophagy. Pearson analysis revealed that Nrf2 has a positive correlation to lipid anabolism-related genes (Fasn, Srebp1, Pparγ) and autophagy regulators (mtor, akt, p62), and were negatively correlated with lipolysis-related genes (Cpt1, Hsl, Ampkα) and autophagy markers (Ulk1, Lc3). Relish was positively correlated with Atgl, Cpt1, Ampkα, Ulk1, and Lc3, and negatively correlated with Pparγ and p62. Moreover, Keap1 and Imd were negatively correlated with p62 and mtor, respectively. In sum, 100 mg/kg TTO enhanced antioxidant activity and increased autophagy intensity through the Relish-Imd pathway to enhance lipid droplet breakdown, while 1000 mg/kg TTO overexpressed Nrf2, thus inhibiting autophagy and ultimately causing excessive lipid deposition and peroxidation. Our study gives a fresh perspective for deciphering the bidirectional regulation mechanism of lipid metabolism by different doses of TTO based on the antioxidant–autophagy axis.

Effects of adding tea tree oil on growth performance, immune function, and intestinal function of broilers

“…Tea tree oil contains a variety of active ingredients, mainly 4-terpineol, 1,8-eudesmanol, and α-pinoresinol ( Bekhof et al, 2023 ). Tea tree oil has been shown to possess several beneficial properties, including anti-inflammatory ( Hart et al, 2000 ), antiviral ( Romeo et al, 2022 ), antitumor ( Clark et al, 2021 ), and antioxidant ( Liu et al, 2022a ) activities. This has drawn significant attention to its potential use as a replacement for antibiotics.…”

Oxidative Stress in Aquatic Organisms

“…Taxonomically, these papers cover freshwater fish ( Carassius auratus [ 4 ], Monopterus albus [ 5 ], Ictalurus punctatus [ 6 ], Megalobrama amblycephala [ 7 ], Micropterus salmoides [ 8 ], Lateolabrax maculatus [ 9 , 10 , 11 , 12 ], Carassius gibelio [ 13 , 14 ], Aplodinotus grunniens [ 15 ], Pangasianodon hypophthalmus [ 16 ], Danio rerio [ 17 ], and hybrid grouper [ 18 ]), marine fish ( Scophthalus maximus [ 19 ]), crustaceans ( Macrobrachium rosenbergii [ 20 , 21 , 22 ], Litopenaeus vannamei [ 23 , 24 , 25 ], Penaeus monodon [ 26 ], Scylla paramamosain [ 27 ], and Eriocheir sinensis [ 28 ]), and molluscs ( Crassostrea hongkongensis [ 29 ], Trachinotus ovatus [ 30 ], and Pacific abalone [ 31 ]). Meanwhile, these papers reveal several endogenous and exogenous factors that induce oxidative stress, such as environmental factors (water hardness [ 4 ], chronic hyperthermia [ 6 ], acute hypoxic stress [ 10 ], acute ammonia nitrogen [ 12 ], hypothermia [ 15 ], low salinity [ 23 ], and ammonia-N-stress [ 26 ]), nutritional factors (high carbohydrate levels [ 5 ], oxidized lipids [ 7 ], high-fat diet [ 12 , 20 ], and lipopolysaccharide [ 29 ...…”

“…Meanwhile, these papers reveal several endogenous and exogenous factors that induce oxidative stress, such as environmental factors (water hardness [ 4 ], chronic hyperthermia [ 6 ], acute hypoxic stress [ 10 ], acute ammonia nitrogen [ 12 ], hypothermia [ 15 ], low salinity [ 23 ], and ammonia-N-stress [ 26 ]), nutritional factors (high carbohydrate levels [ 5 ], oxidized lipids [ 7 ], high-fat diet [ 12 , 20 ], and lipopolysaccharide [ 29 , 31 ]), essential or heavy metals (Zn [ 4 ], cadmium [ 13 , 27 ], Cu 2+ [ 28 ], and polyinosinic–polycytidylic acid sodium salt [ 31 ]), pathogenic bacteria or virus (aflatoxin B1 and cyprinid herpesvirus 2 [ 14 ], water bubble disease (WBD) [ 21 ], Vibrio harveyi [ 29 , 31 ], and Streptococcus agalactiae [ 30 ]), and feeding practices (stocking density [ 8 ], transport stress [ 11 ]). Therapeutically, some papers have also explored some medicines or immunostimulants to resist oxidative stress, such as herbal medicine (mulberry leaf flavonoids [ 5 ], emodin [ 7 ], berberine [ 17 ], Sophora flavescens root extract [ 19 ], and tea tree oil [ 22 ]), nutritional stimulants ( Atractylodes macrocephala polysaccharide [ 9 ], taurine alleviates [ 13 ], histamine [ 16 , 18 ], vitamin E [ 20 ], β-Glucan [ 23 ], krill oil [ 24 ], and zinc [ 25 ]), antibiotics (florfenicol and ofloxacin [ 21 ]), and feeding admin...…”

“…To uncover the relationship between oxidative stress inducers and response mechanisms, tissue or cell morphology, antioxidant and immunity enzymes and related gene expression, metabolic homeostasis, and cell fate related autophagy and apoptosis, as well as mortality, have been extensively studied in these papers. Mechanically, some key molecular signaling processes were studied, such as Nrf2 signaling [ 7 , 9 , 22 , 27 ], Notch signaling [ 7 ], PPAR signaling [ 8 ], MAPK signaling [ 10 ], NF-κB signaling [ 15 , 20 , 30 ], Relish-Imd signaling [ 22 ], TLR2-MyD88-NF-κB [ 28 ], and epigenetic regulator m6A methylation [ 17 ]. Additionally, the regulation of gut microbiota on oxidative stress resistance was also investigated in some papers [ 5 , 10 , 11 , 14 , 24 , 25 ].…”

“…Zhao et al [ 21 ] demonstrated how antibiotic florfenicol and ofloxacin prevent Citrobacter freundii -induced water bubble disease (WBD) in giant freshwater prawns, M. rosenbergii , evidenced by improved antioxidant capacity, immune-related gene expression, and the anti-lipopolysaccharide factor in hepatopancreas. Liu et al [ 22 ] reported that 100 mg/kg tea tree oil (TTO) could alter the hepatopancreatic lipid metabolism by affecting the antioxidant–autophagy axis in M. rosenbergii . The relish-Imd pathway functions significantly in the regulation.…”