大口黑鲈sirtuin家族基因鉴定、特征分析及其对高淀粉饲料的急性响应

Identification, characterization and acute response to high starch diet of sirtuin family genes in Micropterus salmoides

  • 摘要:
    目的 鉴定大口黑鲈sirtuin家族成员,解析其基因与蛋白结构,及短期高淀粉负荷下的响应特征。
    方法 参考基因组(GCF_014851395.1)HMM/BLASTP筛选与CDD验证后获得候选基因,基于生物信息学分析sirtuin家族基因的理化特性与进化关系。分别饲喂8%和20%淀粉水平饲料,于0~24 h测大口黑鲈血糖、肝脏丙酮酸、NAD+和NADH含量及sirtuin表达。
    结果 共鉴定到7个sirtuin基因分布于7条scaffold,均含Motif4、NAD+和Zn2+结合位点,但CDS长度、外显子和内含子数目及蛋白pI、稳定性等差异显著,系统发育分4支,与鳜、尼罗罗非鱼序列近缘。sirt1~sirt7均在脑中高表达,而在肌肉中表达水平最低。摄食后2~12 h,20%淀粉组血糖水平显著高于8%淀粉组,6 h达到最大值,同时肝脏丙酮酸和NADH含量升高、NAD+含量下降。相比8%淀粉组,20%淀粉组sirt1于2 h表达上调并持续至12 h,而sirt3和sirt4表达相继在8~24 h升高,其余成员无显著时序变化。
    结论 本研究在大口黑鲈基因组中鉴定到7个非簇散列、结构具有多样性的sirtuin基因,其蛋白具有不同的理化差异和共同保守的NAD+/Zn2+结合位点。短期高淀粉负荷下,sirt1、sirt3和sirt4的时序表达与NAD+和NADH动态变化耦合,表明其可能参与调控糖脂代谢,其中sirt1响应最早,可作为鱼类营养精准调控的首选靶点。

     

    Abstract: The tolerance threshold for Micropterus salmoides regarding starch is below 10%, and above 20% will result in persistent hyperglycemia and the accumulation of glucose and lipids in hepatocytes. Studies on mammals have revealed the regulatory role of SIRT family genes in glucose and lipid metabolism. However, the structure, protein characteristics of the SIRT genes in M. salmoides and their response mechanisms to acute carbohydrate stress remain unclear, which hinders the in-depth analysis of this gene family and its application in targeted intervention studies. This study aimed to systematically identify the sirtuin family members in M. salmoides, characterize their gene structure and protein properties, and examine their response to acute high starch stress. Candidate genes were obtained based on the reference genome (GCF_014851395.1) HMM/BLASTP screening and CDD verification, and their physicochemical properties and evolutionary relationship were analyzed by bioinformatics. Two experimental treatment groups were established. Following a 24-hour fast, the fish were administered feed with 8% and 20% starch levels, respectively. Serum glucose level, liver pyruvate, NAD+ and NADH contents, and relative expression level of sirtuin were measured from 0 to 24 h. Seven non-clustered sirtuin genes were found across seven scaffolds. The CDS length, the quantity of exons and introns, and the protein's isoelectric point and stability exhibited substantial differences. All of them included Motif4, NAD+, and Zn2+ binding sites. The phylogenetic tree of SIRTs proteins was divided into four branches, closely associated with the sequences of Siniperca chuatsi and Oreochromis niloticus. sirt1-sirt7 were all highly expressed in the brain, and the expression level in muscle were generally the lowest. 24 hours post-feeding, the serum glucose levels in the 20% starch group was significantly elevated compared to the 8% starch group from 2 to 12 hours, peaking at 6 hours. Simultaneously, the concentration of pyruvate rose, the concentration of NAD+ diminished, and the concentration of NADH markedly increased at 6 hours. In comparison to the 8% starch group, the 20% starch group exhibited up-regulation of sirt1 at 2 hours, persisting until 12 hours, while sirt3 and sirt4 showed sequential increases between 8 and 24 hours; while the other members showed no significant temporal changes. In summary, this study identified 7 non-clustered and structurally diverse sirtuin genes in the genome of the M. salmoides, characterized by distinct physicochemical properties and conserved NAD+/Zn2+ catalytic domains. Under short-term high-starch nutritional stress, the temporal expression of sirt1, sirt3 and sirt4 was coupled with the changes in NAD+ and NADH contents, suggesting that they may be involved in regulating glycolipid metabolism. Among them, sirt1 responded earliest and could be used as the preferred target for precise nutritional regulation of fish. This study provides a theoretical basis for the subsequent verification of the function of the sirtuin family genes and the screening of the targets of precise nutritional regulation in fish.

     

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