Characterizing and identifying of miRNAs involved in berberine modulating glucose metabolism of Megalobrama amblycephala.

The present study, as one part of a larger project that aimed to investigate the effects of dietary berberine (BBR) on fish growth and glucose regulation, mainly focused on whether miRNAs involve in BBR's modulation of glucose metabolism in fish. Blunt snout bream Megalobrama amblycephala (average weight of 20.36 ± 1.44 g) were exposed to the control diet (NCD, 30% carbohydrate), the high-carbohydrate diet (HCD, 43% carbohydrate) and the berberine diet (HCB, HCD supplemented with 50 mg/kg BBR). After 10 weeks' feeding trial, intraperitoneal injection of glucose was conducted, and then, the plasma and liver were sampled at 0 h, 1 h, 2 h, 6 h, and 12 h. The results showed the plasma glucose levels in all groups rose sharply and peaked at 1 h after glucose injection. Unlike the NCD and HCB groups, the plasma glucose in the HCD group did not decrease after 1 h, while remained high level until at 2 h. The NCD group significantly increased liver glycogen content at times 0-2 h compared to the other two groups and then liver glycogen decreased sharply until at times 6-12 h. To investigate the role of BBR that may cause the changes in plasma glucose and liver glycogen, miRNA high-throughput sequencing was performed on three groups of liver tissues at 2 h time point. Eventually, 20 and 12 differentially expressed miRNAs (DEMs) were obtained in HCD vs NCD and HCB vs HCD, respectively. Through function analyzing, we found that HCD may affect liver metabolism under glucose loading through the NF-κB pathway; and miRNAs regulated by BBR mainly play roles in adipocyte lipolysis, niacin and nicotinamide metabolism, and amino acid transmembrane transport. In the functional exploration of newly discovered novel:Chr12_18892, we found its target gene, adenylate cyclase 3 (adcy3), was widely involved in lipid decomposition, amino acid metabolism, and other pathways. Furthermore, a targeting relationship of novel:Chr12_18892 and adcy3 was confirmed by double luciferase assay. Thus, BBR may promote novel:Chr12_18892 to regulate the expression of adcy3 and participate in glucose metabolism.

Excessive linoleic acid induces muscle oxidative stress through 5-lipoxygenase-dependent peroxidation.

Oxidative stress in muscles is closely related to the occurrence of insulin resistance, muscle weakness and atrophy, age-related sarcopenia, and cancer. Aldehydes, a primary oxidation intermediate of polyunsaturated fatty acids, have been proven to be an important trigger for oxidative stress. However, the potential role of linoleic acid (LA) as a donor for volatile aldehydes to trigger oxidative stress has not been reported. Here, we reported that excessive dietary LA caused muscle redox imbalance and volatile aldehydes containing hexanal, 2-hexenal, and nonanal were the main metabolites leading to oxidative stress. Importantly, we identified 5-lipoxygenase (5-LOX) as a key enzyme mediating LA peroxidation in crustaceans for the first time. The inhibition of 5-LOX significantly suppressed the content of aldehydes produced by excessive LA. Mechanistically, the activation of the cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) pathway facilitated the translocation of 5-LOX from the nucleus to the cytoplasm, where 5-LOX oxidized LA, leading to oxidative stress through the generation of aldehydes. This study suggests that 5-LOX is a potential target to prevent the production of harmful aldehydes.

New insights into methylmercury induced behavioral and energy-related gene transcriptional responses in European glass eel (Anguilla anguilla).

The effect of methylmercury (MeHg) was investigated in glass eel migration behavior and metabolism. To migrate up estuary, glass eels synchronize their swimming activity to the flood tide and remain on or in the substratum during ebb tide. Following seven days of exposure to MeHg (100 ng L-1), glass eels migration behavior was expressed by their swimming synchronization to the water current reversal every 6.2 h (mimicking the alternation of flood and ebb tides) and their swimming activity level. In relation to their behavior, we then analyzed the energy-related gene expression levels in individual head, viscera and muscle. Results showed that MeHg decreased the number of glass eels synchronized to the change in water current direction and their swimming activity level. This last effect was more pronounced in non-synchronized fish than in synchronized ones, supporting the idea that non-synchronized glass eels could be more vulnerable to stress. As regard the expression of energy-related genes, no significant difference was observed between control and MeHg-exposed fish. In contrast, when the swimming activity levels were plotted against transcriptional responses, positive correlations were evidenced in viscera and especially in the head of exposed glass eels but not in control. Finally, it is noteworthy that non-synchronized glass eels displayed lower expression level of metabolism genes than their synchronized counterpart, but only in the head. Altogether, these results support the interest of focusing on the head to investigate the facultative migration behavior in glass eels and the effect of environmental stressors on this rhythmic behavior.