Lin Jibin, Li Xueshan, Lu Kangle, Song Kai, Wang Ling, Dai Weiwei, Mohamed Mohsen, Zhang Chunxiao
State Key Laboratory for Mariculture Breeding, Fisheries College of Jimei University, Xiamen, PR China; Xiamen Key Laboratory for Feed Quality Testing and Safety Evaluation, Fisheries College, Jimei University, Xiamen, PR China.
Department of Biological Sciences, Xi'an Jiaotong-Liverpool University, Suzhou, PR China.
J Nutr. 2025 Jan;155(1):132-152. doi: 10.1016/j.tjnut.2024.10.044. Epub 2024 Nov 2.
Low phosphorus (LP) diets perturb hepatic energy metabolism homeostasis in fish. However, the specific mechanisms in LP-induced hepatic energy metabolism disorders remain to be fully elucidated.
This study sought to elucidate the underlying mechanisms of mitochondria involved in LP-induced energy metabolism disorders.
Spotted seabass were fed diets with 0.72% (S-AP, control) or 0.36% (S-LP) available phosphorus for 10 wk. Drp1 was knocked down or protein kinase (PK) A was activated using 8Br-cAMP (5 μM, a PKA activator) in spotted seabass hepatocytes under LP medium. Zebrafish were fed Z-LP diets (0.30% available phosphorus) containing Mdivi-1 (5 mg/kg, a Drp1 inhibitor) or 8Br-cAMP (0.5 mg/kg) for 6 wk. Biochemical and molecular parameters, along with transmission electron microscopy and immunofluorescence, were used to assess hepatic glycolipid metabolism, mitochondrial function, and morphology.
Spotted seabass fed S-LP diets showed reduced ATP (52%) and cAMP (52%) concentrations, along with reduced Drp1 (s582) (38%) and PKA (61%) phosphorylation concentrations in the liver compared with those fed S-AP diets (P < 0.05). Drp1 knockdown elevated ATP concentrations (1.99-fold), decreased mitochondrial DRP1 protein amounts (45%), and increased mitochondrial aspect ratio (1.82-fold) in LP-treated hepatocytes (P < 0.05). Furthermore, 8Br-cAMP-treated hepatocytes exhibited higher PKA phosphorylation (2.85-fold), ATP concentrations (1.60-fold), and mitochondrial aspect ratio (2.00-fold), along with decreased mitochondrial DRP1 protein concentrations (29%) under LP medium (P < 0.05). However, mutating s582 to alanine mimic Drp1 dephosphorylation decreased ATP concentrations (63%) and mitochondrial aspect ratio (53%) in 8Br-cAMP-treated hepatocytes (P < 0.05). In addition, zebrafish fed Z-LP diets containing Mdivi-1 or 8Br-cAMP had higher ATP concentrations (3.44-fold or 1.98-fold) than those fed Z-LP diets (P < 0.05).
These findings provide a potential mechanistic elucidation for LP-induced energy metabolism disorders through the cAMP/PKA/Drp1-mediated mitochondrial fission signaling pathway.
低磷（LP）饮食会扰乱鱼类肝脏能量代谢的稳态。然而，LP诱导肝脏能量代谢紊乱的具体机制仍有待充分阐明。
本研究旨在阐明线粒体参与LP诱导的能量代谢紊乱的潜在机制。
用含0.72%（S-AP，对照）或0.36%（S-LP）有效磷的饲料喂养花鲈10周。在LP培养基条件下，使用8Br-cAMP（5 μM，一种PKA激活剂）敲低花鲈肝细胞中的动力相关蛋白1（Drp1）或激活蛋白激酶（PK）A。用含Mdivi-1（5 mg/kg，一种Drp1抑制剂）或8Br-cAMP（0.5 mg/kg）的Z-LP饲料（0.30%有效磷）喂养斑马鱼6周。采用生化和分子参数，以及透射电子显微镜和免疫荧光技术，评估肝脏糖脂代谢、线粒体功能和形态。
与喂食S-AP饲料的花鲈相比，喂食S-LP饲料的花鲈肝脏中的ATP（52%）和cAMP（52%）浓度降低，同时肝脏中Drp1（s582）（38%）和PKA（61%）的磷酸化浓度降低（P < 0.05）。在LP处理的肝细胞中，敲低Drp1可提高ATP浓度（1.99倍），降低线粒体DRP1蛋白量（45%），增加线粒体纵横比（1.82倍）（P < 0.05）。此外，在LP培养基条件下，用8Br-cAMP处理的肝细胞表现出更高的PKA磷酸化水平（2.85倍）、ATP浓度（1.60倍）和线粒体纵横比（2.00倍），同时线粒体DRP1蛋白浓度降低（29%）（P < 0.05）。然而，将s582突变为丙氨酸模拟Drp1去磷酸化会降低8Br-cAMP处理的肝细胞中的ATP浓度（63%）和线粒体纵横比（53%）（P < 0.05）。此外，喂食含Mdivi-1或8Br-cAMP的Z-LP饲料的斑马鱼的ATP浓度比喂食Z-LP饲料的斑马鱼更高（分别为3.44倍或1.98倍）（P < 0.05）。
这些发现为LP通过cAMP/PKA/Drp1介导的线粒体分裂信号通路诱导能量代谢紊乱提供了一种潜在的机制解释。
