几种海洋硬骨鱼类快、慢肌的化学组分差异分析

引用本文

王焕, 柳淑芳. 几种海洋硬骨鱼类快、慢肌的化学组分差异分析[J]. 渔业科学进展, 2025, 46(1): 59-70. DOI: 10.19663/j.issn2095-9869.20231120002.

WANG Huan, LIU Shufang. Comparative Study of the Chemical Composition Disparities Between Fast-twitch and Slow-twitch Muscles in Marine Teleost Fishes[J]. Progress in Fishery Sciences, 2025, 46(1): 59-70. DOI: 10.19663/j.issn2095-9869.20231120002.

基金项目

国家自然科学基金(32102768; 42076132)和中国水产科学研究院黄海水产研究所基本科研业务费(20603022023020)共同资助

作者简介

王焕，Email: wanghuan@ysfri.ac.cn

通讯作者

柳淑芳，研究员，Email: liusf@ysfri.ac.cn

文章历史

收稿日期：2023-11-20
收修改稿日期：2024-02-20

Contents Abstract Full text Figures/Tables PDF

几种海洋硬骨鱼类快、慢肌的化学组分差异分析

王焕 ¹, 柳淑芳 ^1,2

1. 海水养殖生物育种与可持续产出全国重点实验室中国水产科学研究院黄海水产研究所山东青岛 266071;
2. 青岛海洋科技中心海洋渔业科学与食物产出过程功能实验室山东青岛 266237

收稿日期：2023-11-20；收修改稿日期：2024-02-20

基金项目：国家自然科学基金(32102768; 42076132)和中国水产科学研究院黄海水产研究所基本科研业务费(20603022023020)共同资助

作者简介：王焕，Email: wanghuan@ysfri.ac.cn.

通讯作者：柳淑芳，研究员，Email: liusf@ysfri.ac.cn.

摘要：硬骨鱼类的骨骼肌根据收缩特征主要分为快肌和慢肌，分别支撑爆发性和持续性游泳。为认识这2种骨骼肌的化学组分特征，解析快、慢肌功能差异的物质基础，本研究整合3类不同游泳习性鱼类：黄带拟鲹(Pseudocaranx dentex)、梭鱼(Liza haematocheila)和金枪鱼类，通过自测结合文献资料，比较了快、慢肌在蛋白质、氨基酸、脂肪、脂肪酸及矿物元素等化学组分特征方面的差异。结果显示，快肌的粗蛋白及12种氨基酸含量更为丰富，其中尤以组氨酸含量差异最大(快肌为慢肌的1.22~3.83倍)；快、慢肌的主要氨基酸组成相似，必需氨基酸含量均占氨基酸总量的40%左右，谷氨酸和天冬氨酸是含量最丰富的2种氨基酸类型，赖氨酸和亮氨酸是含量最高的2种必需氨基酸；慢肌的粗脂肪及每种脂肪酸的含量均显著高于快肌；在脂肪酸组成方面，慢肌中饱和脂肪酸(saturated fatty acid, SFA)的比例较快肌高，而快肌中的多不饱和脂肪酸(polyunsaturated fatty acid, PUFA)比例则比慢肌高；慢肌含有更为丰富的微量元素铁(Fe)和锌(Zn)。结果表明，海洋硬骨鱼类的快肌和慢肌在蛋白质、氨基酸、脂肪、脂肪酸及矿物元素组成方面存在较大的差异，这些差异为其分别支撑爆发性游泳运动和持续性游泳运动提供了一定的物质基础。

关键词：海洋硬骨鱼类快肌慢肌化学成分特征

Comparative Study of the Chemical Composition Disparities Between Fast-twitch and Slow-twitch Muscles in Marine Teleost Fishes

WANG Huan ¹, LIU Shufang ^1,2

1. State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, China;
2. Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao Marine Science and Technology Center, Qingdao 266237, China

Corresponding author: LIU Shufang, Email: liusf@ysfri.ac.cn.

Abstract: Skeletal muscle contraction, which generates movement by pulling on the internal skeleton, is a distinctive mode of movement in vertebrates. Renowned for its flexibility, diversity, and efficiency, this mode of movement is significant for the individual survival and reproductive success of animals. Being the most ancient vertebrates, fish inhabit aquatic environments, where their skeletal muscles serve as structural and locomotor organs and as a crucial source of high-quality protein for human consumption. Based on the contraction characteristics, the skeletal muscles in teleost fishes are primarily categorized into fast-twitch and slow-twitch muscles, which play distinct roles, supporting burst swimming and prolonged endurance swimming, respectively. Preliminary analyses have been conducted on the structural, metabolic, and functional differences between the fast-twitch and slow-twitch muscles in fish at histological, enzymatic activity, and molecular regulatory levels. Proteins, amino acids, fat, fatty acids, and minerals constitute the material basis for the swimming function of fish skeletal muscles, providing a more intuitive and accurate reflection of the distinct physiological characteristics of fast-twitch and slow-twitch muscles. However, reported research on the comparative analysis of the material constituents comprising fast-twitch and slow-twitch muscles is scarce. To comprehend the chemical composition characteristics and elucidate the material basis for the functional differences between fast-twitch and slow-twitch muscles, this study used biochemical analysis to determine the chemical components of the two muscle types in Pseudocaranx dentex and Liza haematocheila. We integrated data from the literature on tuna, including Thunnus tonggol, T. albacares, Auxis rochei, A. thazard, Euthynnus affinis, and Katsuwonus pelamisi. These fishes have different swimming habits, which can provide a more comprehensive perspective on the differences between fast-twitch and slow-twitch muscles. First, the fast-twitch muscles exhibited a substantial enrichment in protein and 12 types of amino acids, particularly histidine. Notably, histidine is pivotal as a proton-buffering substance and for maintaining pH stability. The relative content difference of histidine was pronounced, ranging from 1.22 to 3.83 times higher in fast-twitch muscles than in slow-twitch muscles. Regarding the amino acid compositions, fast-twitch and slow-twitch muscles displayed similarities, with essential amino acids constituting approximately 40% of the total amino acid content. Glutamate and aspartate were the predominant amino acids, playing essential roles in eliminating ammonia during exercise and serving as crucial energy substrates for muscle function. Lysine and leucine, the two essential amino acids with the highest content, were instrumental in ketone body formation, glucose metabolism, and fat metabolism, and provided an essential energy supply. Further analysis of the fat content and fatty acid composition revealed intriguing differences. Slow-twitch muscles exhibited significantly higher levels of fat and each fatty acid than their fast-twitch counterparts. The aerobic oxidation metabolism of fatty acids was characterized by a prolonged energy supply duration and substantial ATP generation. This unique metabolic profile suggests that slow-twitch muscles rely on fatty acids as their primary energy substrate during swimming for extended periods. Examining the fatty acid composition in detail, the proportion of saturated fatty acids (SFA) was higher in slow-twitch muscles, whereas fast-twitch muscles had a higher proportion of polyunsaturated fatty acids (PUFA). This divergence could be attributed to the specific requirements of each muscle type. Slow-twitch muscles, engaged in long-distance movements, necessitate more SFA and monounsaturated fatty acids (MUFA) for oxidative energy supply. Conversely, fast-twitch muscles, responsible for burst swimming, require more PUFA to maintain the structural integrity and functionality of cell membranes. The main fatty acid composition types of SFA, PUFA, and MUFA in the fast-twitch and slow-twitch muscles are the same. C16:0, C18:0, and C14:0 were the main SFA types. C18:1 and C16:1 were the main MUFA types. C22:6n3 and C20:5n3 were the main PUFA types. Finally, the mineral element analysis revealed that slow-twitch muscles possess higher iron and zinc concentrations, which are critical in oxygen transportation and catalyzation of oxidation processes. The potassium, magnesium, and calcium contents showed no significant correlation with muscle types. Potassium was identified as the most abundant constant element, magnesium exhibited minimal content fluctuation across diverse species, and calcium was the most abundant metallic element. In summary, our comprehensive investigation into the chemical composition of fast-twitch and slow-twitch muscles in marine teleost fishes uncovered significant distinctions in proteins, amino acids, fats, fatty acids, and mineral elements. These differences form the foundation for executing diverse swimming functions, shedding light on the intricate interplay between muscle composition and swimming performance in teleost fishes.

Key words: Marine teleost fish Fast-twitch muscle Slow-twitch muscle Chemical composition characteristics

骨骼肌是鱼体最主要的可食用部位，可达活体体重的40%~60% (Kiessling et al, 2006)，也是完成各种形式运动的主要动力来源，无论是对个体的生存还是种群的延续都至关重要。根据收缩特点及行使功能的差异，鱼类骨骼肌主要分为快肌和慢肌2种类型。快肌具有收缩速度快、力量大的特点，但抗疲劳能力弱，主要参与爆发性的游泳运动，如捕食、逃跑等(成嘉等, 2010; 石军等, 2013)。慢肌虽收缩速度较慢、力量相对较小，但持续时间长、不易疲劳，可为长距离持续性游动(如巡航、洄游等)提供保障(Syme, 2005)。

目前，不同类型骨骼肌游泳运动功能性的差异已被证实与其结构特征、代谢方式、分子表达等多个方面的异质性有关。例如，研究发现，快肌纤维的直径和Z线密度普遍大于慢肌纤维，而慢肌纤维的Z线更宽，神经连接更为紧密，线粒体体积更大、嵴的数量更多(Nakajima, 1969; Patterson et al, 1972; George et al, 1978; 朱琼等, 2011; Wu et al, 2018; 曾祥辉等, 2023)。有研究也指出，与有氧代谢相关的己糖激酶、苹果酸脱氢酶、琥珀酸脱氢酶和细胞色素氧化酶在慢肌中的活性较高，而与无氧代谢相关的乳酸脱氢酶活性则在快肌中较高(Johnston, 1977; Ciciliot et al, 2013)，这意味着慢肌可能以有氧代谢供能为主，而快肌主要进行无氧代谢供能。随后，研究鉴定到多个参与代谢过程、收缩过程及发育过程的基因在mRNA和蛋白层面都呈现出快、慢肌的差异性表达特征(Gao et al, 2017; Wang et al, 2022a、b)，这些基因可能是参与调控快慢肌表型及功能差异性的关键因子。可以发现，上述研究多集中在组织学、酶活性及分子调控等层面对鱼类快、慢肌结构、代谢和功能的差异性进行解析，对于构成骨骼肌的物质组分的比较研究却鲜见报道。

黄带拟鲹(Pseudocaranx dentex)隶属于鲈形目(Perciformes)、鲹科(Carangidae)、拟鲹属(Pseudocaranx)，是一种大洋暖水性长距离洄游型鱼类，其游泳速度较快，需进行持续不断的游泳运动。梭鱼(Liza haematocheila)隶属于鲈形目(Perciformes)、鲻科(Mugilidae)、梭属(Liza)，是一种近岸内湾短距离洄游型鱼类，持续性游泳运动时间较短。金枪鱼类是鲈形目(Perciformes)、鲭科(Scombridae)、金枪鱼属(Thunnus)、鲔属(Euthynnus)、舵鲣属(Auxis)、鲣属(Katsuwonus)和狐鲣属(Sarda)鱼类的统称，以其优异的游泳速度和长距离游泳能力而著称，最大游泳速度可达到54 km/h，是海洋中顶尖的远洋游泳者之一(Shadwick et al, 2013)。与黄带拟鲹和梭鱼的慢肌主要分布在体表侧线下方浅层不同，金枪鱼类的慢肌主要分布在躯体深处的脊椎附近，且持续活跃的代谢不断产生热量，保持体温略高于周围水温，这使其成为罕见的恒温性硬骨鱼类(Shadwick et al, 2013)。为充分认识2种主要骨骼肌类型的化学组分特征，解析快慢肌功能差异的物质基础，本研究选用上述3类具有不同游泳习性的海洋硬骨鱼类作为研究对象，通过自测结合文献资料的方式，定量分析并比较了快、慢肌的蛋白质、氨基酸、脂肪、脂肪酸和矿物质的组成差异，旨在通过对多种海洋硬骨鱼类数据资料的整合，充分了解、归纳快、慢肌的化学组分特征差异，解析骨骼肌游泳运动功能差异性的物质基础，为系统研究硬骨鱼类骨骼肌运动生理学提供基础资料。

1 材料与方法 1.1 实验材料来源

黄带拟鲹样品采自辽宁省大连天正实业有限公司陆基工厂化养殖车间，随机采集体质健康、体型相近的2龄个体6尾，平均体质量为(812.72±52.73) g，平均体长为(32.13±1.76) cm。梭鱼样品购自山东青岛小港码头，为山东青岛近海野生个体6尾，平均体质量为(572.92±41.22) g，平均体长为(34.58±2.92) cm。实验材料用纱布拭净体表水分后，去除鳞片和皮肤，取背部快肌和侧线下方慢肌用于后续比较分析。

用于常规营养成分、氨基酸和脂肪酸分析的青干金枪鱼(Thunnus tonggol)、圆鲣(Auxis rochei)和鲣(Katsuwonus pelamis)捕自南海海域(苏阳等, 2015)，用于矿物元素含量分析的黄鳍金枪鱼(Thunnus albacares)、圆鲣、扁鲣、巴鲣(Euthynnus affinis)和鲣来自斯里兰卡尼甘布市的Pitipana渔港(Karunarathna et al, 2009)。

1.2 测定方法 1.2.1 常规化学成分测定

准确称取10 g样品，采用常压干燥法(GB 5009.3-2016)测定水分含量；称取10 g样品，采用高温灼烧法(GB 5009.4-2016)测定灰分含量；称取5 g样品，采用凯氏定氮法(GB 5009.5-2016)测定粗蛋白质含量；称取5 g样品，采用索氏提取法(GB 5009.6-2016)测定粗脂肪含量。

1.2.2 氨基酸含量测定

依据GB 5009.124-2016，将5 g样品中的蛋白质用盐酸水解成游离氨基酸后，采用全自动氨基酸分析仪日立L-8800测定。

1.2.3 脂肪酸含量测定

脂肪酸的测定参考GB 5009.168-2016，5 g样品经KOH-甲醇溶液皂化，三氟化硼-甲醇溶液甲酯化后，采用正己烷萃取，安捷伦7890A气相色谱仪测定。

1.2.4 矿物元素含量测定

锌(Zn)的测定参考GB 5009.14-2017，镁(Mg)的测定参考GB 5009.241-2017，铁(Fe)的测定参考GB 5009.90-2016，钾(K)的测定参考GB 5009.91-2017，钙(Ca)的测定参考GB 5009.92-2016，分别称取1 g样品消解后，采用等离子体发射光谱法测定。

1.3 数据统计分析

采用SPSS 19.0独立样本t检验进行差异显著性分析，结果以平均值±标准差(Mean±SD)呈现，P < 0.05代表差异显著。

2 结果与分析 2.1 常规营养成分分析

5种海洋硬骨鱼类快、慢肌的常规营养成分数据见表 1。5种鱼类快肌的粗蛋白含量显著高于慢肌(P < 0.05)，慢肌的粗脂肪含量显著高于快肌(P < 0.05)，水分含量在快、慢肌中无显著性差异，黄带拟鲹和梭鱼快肌的灰分含量显著高于慢肌，金枪鱼类的趋势则相反。

表 1 5种海洋硬骨鱼类快、慢肌常规营养成分比较 Tab.1 Comparison of nutrients in the fast-twitch and slow-twitch muscles of five marine teleost fishes (w/%)

物种 Species	肌肉类型 Muscle types	水分 Moisture	粗蛋白(干基) Protein (dry basis)	粗脂肪(干基) Lipid (dry basis)	灰分 Ash	参考文献 Reference
黄带拟鲹 P. dentex	快肌 Fast-twitch muscle	72.93±0.13^a	85.64±0.28^a	5.91±0.15^b	1.26±0.14^a	本研究 This study
黄带拟鲹 P. dentex	慢肌 Slow-twitch muscle	72.90±0.15^a	46.86±0.06^b	34.01±0.05^a	0.96±0.01^b	本研究 This study
梭鱼 L. haematocheila	快肌 Fast-twitch muscle	78.85±0.13^a	85.09±0.26^a	2.71±0.15^b	1.16±0.09^a	本研究 This study
梭鱼 L. haematocheila	慢肌 Slow-twitch muscle	78.82±0.14^a	37.85±0.04^b	49.73±0.04^a	0.94±0.01^b	本研究 This study
青干金枪鱼 T. tonggol	快肌 Fast-twitch muscle	72.42±0.37^a	85.29±0.21^a	6.50±0.04^b	1.37±0.06^b	苏阳等, 2015
青干金枪鱼 T. tonggol	慢肌 Slow-twitch muscle	72.63±0.34^a	75.34±0.76^b	9.38±0.01^a	1.67±0.30^a	苏阳等, 2015
圆鲣 A. rochei	快肌 Fast-twitch muscle	73.11±0.52^a	87.72±0.19^a	2.00±0.01^b	1.22±0.06^b	苏阳等, 2015
圆鲣 A. rochei	慢肌 Slow-twitch muscle	72.83±0.33^a	81.07±0.31^b	7.38±0.01^a	1.47±0.05^a	苏阳等, 2015
鲣K. pelamis	快肌 Fast-twitch muscle	71.07±0.31^a	84.11±0.46^a	4.94±0.09^b	1.44±0.07^b	苏阳等, 2015
鲣K. pelamis	慢肌 Slow-twitch muscle	70.99±0.40^a	75.35±0.00^b	10.26±0.10^a	1.52±0.08^a	苏阳等, 2015
注：不同肩标小写字母表示同一物种快、慢肌的差异显著(P < 0.05)。下同。 Note: Data with different lowercase superscript letters were significantly different between fast-twitch muscle (P < 0.05). The same below.

表 1 5种海洋硬骨鱼类快、慢肌常规营养成分比较 Tab.1 Comparison of nutrients in the fast-twitch and slow-twitch muscles of five marine teleost fishes (w/%)

2.2 氨基酸成分分析

5种海洋硬骨鱼类快、慢肌的氨基酸含量见表 2。常见氨基酸类型均被检出，说明鱼类快、慢肌在氨基酸种类方面均构成完整且全面。5种鱼类快肌氨基酸总量都高于慢肌，这与快肌更为丰富的蛋白质含量一致，其中，黄带拟鲹和梭鱼的快、慢肌氨基酸含量差异比其他3种鱼类更为剧烈。共有12种氨基酸在5种鱼类快肌中的含量普遍高于慢肌，其中，组氨酸是快、慢肌含量差异最大的氨基酸类型(快肌约为慢肌的1.22~3.83倍)，这说明海洋硬骨鱼类快肌可能普遍具有更为丰富的组氨酸。

表 2 5种海洋硬骨鱼类快、慢肌氨基酸含量(干重，g/100 g) Tab.2 Contents of amino acids in the fast-twitch and slow-twitch muscles of five marine teleost fishes (dry weight, g/100 g)

分析并比较氨基酸组成特点，如图 1所示，快、慢肌均以谷氨酸含量最高，其次为天冬氨酸，二者含量占氨基酸总量的23%以上。必需氨基酸含量占快、慢肌氨基酸总量的40%左右，其中，赖氨酸和亮氨酸是2种最主要的必需氨基酸类型，占必需氨基酸总量的42%以上。

图 1 5种海洋硬骨鱼类快、慢肌氨基酸含量占比 Fig.1 Proportion of amino acids in the fast-twitch and slow-twitch muscles of five marine teleost fishes EAA: Essential amino acid; HEAA: Half-essential amino acid; NEAA: Non-essential amino acid.

2.3 脂肪酸成分分析

5种海洋硬骨鱼类快、慢肌的脂肪酸含量见表 3。在黄带拟鲹和梭鱼的快、慢肌中共检测到20种脂肪酸，包含6种饱和脂肪酸(saturated fatty acid, SFA)、7种单不饱和脂肪酸(monounsaturated fatty acid, MUFA)和7种多不饱和脂肪酸(polyunsaturated fatty acid, PUFA)。此外，在青干金枪鱼、圆鲣和鲣还检测到了C12:0、C13:0、C17:0、C21:0、C23:0、C24:0、C22:4和C22:5，这种检出种类的差异可能是由于采用的实验方法及仪器的灵敏度不同。综合5种鱼类的数据可以发现，慢肌脂肪酸总量以及每种脂肪酸含量均高于快肌，这与慢肌更为丰富的粗脂肪含量相吻合。青干金枪鱼、圆鲣和鲣的快、慢肌脂肪酸含量差异虽不如黄带拟鲹和梭鱼剧烈，但趋势相一致。梭鱼的EPA含量显著高于DHA，而其他4种鱼类则相反。

表 3 5种海洋硬骨鱼类快、慢肌脂肪酸含量分析(干重，g/100 g) Tab.3 Contents of fatty acids in the fast-twitch and slow-twitch muscles of five marine teleost fishes (dry weight, g/100 g)

本研究中，5种海洋硬骨鱼类快肌的PUFA含量占比为23.28%~42.00%，MUFA含量占比为16.95%~31.54%，SFA含量占比为30.24%~57.31%；慢肌的PUFA含量占比为21.68%~33.46%，MUFA含量占比为13.16%~42.82%，SFA含量占比为33.04%~62.47% (图 2)，可以发现，慢肌中的SFA占比明显高于快肌，PUFA占比则恰恰相反。进一步分析各类脂肪酸的组成特点，发现快肌和慢肌均是以C16:0、C18:0和C14:0为主要SFA组成类型，含量占比达到80%以上；C18:1和C16:1为主要MUFA组成类型，含量占比在快、慢肌中均达到82%以上；C22:6n3和C20:5n3为主要PUFA组成类型，含量占比在快肌中达到74%以上，在慢肌中也达到了至少67%；C20:3n3几乎是快、慢肌中含量最低的脂肪酸，这与亚历山大丝鲹(Alectis alexandrinus)、小银绿鳍鱼(Aspitrigla cuculus)等多种海水鱼类的脂肪酸组成特点相似(Özogul et al, 2009)。

图 2 5种海洋硬骨鱼类快、慢肌脂肪酸含量占比 Fig.2 Proportion of fatty acids in the fast-twitch and slow-twitch muscles of five marine teleost fishes PUFA: Polyunsaturated fatty acid; MUFA: Monounsaturated fatty acid; SFA: Saturated fatty acid.

2.4 矿物元素含量分析

7种海洋硬骨鱼类快、慢肌中K、Mg、Ca、Fe和Zn的含量如表 4所示。7种鱼类慢肌的Fe含量都显著高于快肌(P < 0.05)；慢肌含有更为丰富Zn (尽管圆鲣和鲣的快、慢肌差异不显著，但趋势一致)；K、Mg和Ca的含量与肌肉类型不存在相关性，其快、慢肌分布模式呈现物种特异性。此外，还发现无论在快肌还是慢肌中，K都是含量最为丰富的常量元素，这与其他海洋硬骨鱼类的结果相一致(Martínez-Valverde et al, 2000)；Mg是不同物种间含量波动最小的常量元素(47.600~82.255 mg/100 g)；Ca是含量最高的金属矿物元素。

表 4 7种海洋硬骨鱼类快、慢肌矿物元素含量分析(湿基, mg/100 g) Tab.4 Mineral elements composition in the fast-twitch and slow-twitch muscles of seven marine teleost fishes (wet weight, mg/100 g)

物种 Species	肌肉类型 Muscle types	钾K	镁Mg	钙Ca	铁Fe*	锌Zn*	参考文献 Reference
黄带拟鲹 P. dentex	快肌 Fast-twitch muscle	1710.48±56.63^a	97.72±1.25^a	46.85±3.60^a	0.82±0.12^b	1.41±0.10^b	本研究 This study
黄带拟鲹 P. dentex	慢肌 Slow-twitch muscle	935.24±68.54^b	66.79±0.76^b	41.93±0.51^b	11.70±0.42^a	2.19±0.15^a	本研究 This study
梭鱼 L. haematocheila	快肌 Fast-twitch muscle	1059.04±25.95^a	82.57±1.19^a	30.15±0.36^a	0.80±0.19^b	1.31±0.06^b	本研究 This study
梭鱼 L. haematocheila	慢肌 Slow-twitch muscle	677.86±35.54^b	52.36±0.64^b	11.17±0.24^b	10.62±0.28^a	1.92±0.14^a	本研究 This study
黄鳍金枪鱼 T. albacares	快肌 Fast-twitch muscle	170.59±87.96^b	68.95±31.16^a	11.29±9.98^a	1.06±0.14^b	0.68±0.08^b	Karunarathna et al, 2009
黄鳍金枪鱼 T. albacares	慢肌 Slow-twitch muscle	311.08±59.02^a	67.40±31.16^a	6.84±9.98^a	5.59±0.58^a	1.05±0.16^a	Karunarathna et al, 2009
圆鲣 A. rochei	快肌 Fast-twitch muscle	227.06±40.94^a	69.58±6.12^a	11.48±8.18^a	1.32±0.04^b	0.87±0.27^a	Karunarathna et al, 2009
圆鲣 A. rochei	慢肌 Slow-twitch muscle	221.71±30.50^a	71.63±14.51^a	21.97±32.79^a	5.02±1.75^a	1.18±0.37^a	Karunarathna et al, 2009
扁鲣 A. thazard	快肌 Fast-twitch muscle	178.17±57.12^b	61.97±20.90^a	11.13±8.52^a	1.45±0.29^b	0.65±0.07^b	Karunarathna et al, 2009
扁鲣 A. thazard	慢肌 Slow-twitch muscle	294.81±37.39^a	33.23±4.85^b	15.63±9.46^a	6.26±2.94^a	0.94±0.16^a	Karunarathna et al, 2009
巴鲣 E. affinis	快肌 Fast-twitch muscle	304.73±16.29^a	56.37±12.85^a	10.41±8.89^a	2.99±0.29^b	0.73±0.07^b	Karunarathna et al, 2009
巴鲣 E. affinis	慢肌 Slow-twitch muscle	179.24±28.52^b	54.89±8.36^a	14.30±9.27^a	5.97±2.94^a	1.21±0.16^a	Karunarathna et al, 2009
鲣 K. pelamis	快肌 Fast-twitch muscle	256.69±75.72^a	70.70±7.63^a	12.79±3.38^a	1.52±0.31^b	0.84±0.16^a	Karunarathna et al, 2009
鲣 K. pelamis	慢肌 Slow-twitch muscle	253.89±97.69^a	57.57±12.96^b	27.81±18.59^a	6.15±2.44^a	0.96±0.12^a	Karunarathna et al, 2009
注：为微量元素。 Note: represent minor elements.

3 讨论

本研究发现，快肌和慢肌在主要氨基酸组成方面呈现出一致性，即谷氨酸和天冬氨酸是含量最高的2种氨基酸，赖氨酸和亮氨酸是2种最主要的必需氨基酸。对虹鳟(Oncorhynchus mykiss)的研究发现，通过谷氨酰胺合酶催化谷氨酸和氨转化为谷氨酰胺是消除运动时骨骼肌中大量产生的氨的主要策略(Todgham et al, 2001)。此外，谷氨酸还可在转氨基的作用下转化为丙氨酸，此过程产生大量的ATP可为运动供能。天冬氨酸是肌肉的重要能量底物，其氧化效率甚至显著高于葡萄糖，对于保证良好的运动能力至关重要(Li et al, 2009)。赖氨酸参与酮体生成、葡萄糖和脂肪代谢，与鱼体能量供应过程有关(Hoppel, 2003)。亮氨酸，作为雷帕霉素靶蛋白的激活剂，被认为是具有刺激肌肉蛋白质合成和抑制蛋白质水解的功能性氨基酸(Nakashima et al, 2007)。有研究发现，当鱼类进行力竭性训练(肌肉中ATP和糖原水平降低，乳酸水平升高)后，肌肉中亮氨酸含量显著下降，催化亮氨酸氧化的限速酶-支链酮酸脱氢酶活性显著升高，这表明亮氨酸氧化可能是运动后恢复过程中ATP和糖原再合成的重要燃料来源(Milligan, 1997)。在海洋硬骨鱼类快、慢肌中，这4种氨基酸构成了主要的氨基酸类型，说明它们对于快、慢肌行使正常的生理功能都发挥了至关重要的作用。

总体上，慢肌相较于快肌呈现高脂肪、低蛋白的特点，在羽鳃鲐(Rastrelliger kanagurta)(Mohan et al, 2008)和驼背大麻哈鱼(Oncorhynchus gorbuscha) (Ahmed et al, 2022)等鱼类中也有报道。慢肌中几乎所有类型的脂肪酸都呈现更为丰富的含量。脂肪酸是细胞的主要组成成分，也是机体最重要的能源物质之一。脂肪酸的有氧氧化具有持续时间长、产生ATP多的特点(Ozório, 2008)，前期研究发现，肉毒碱脂酰转移酶、脂肪酰辅酶A裂解酶、羟脂酰辅酶A脱氢酶、还原酶和硫解酶等一系列脂肪酸β氧化酶具有慢肌高表达的模式(Wang et al, 2022b)，较高的脂肪含量有助于为慢肌脂肪酸β氧化提供充足的底物。目前普遍认为，鱼类的骨骼肌会优先利用SFA作为游泳运动的主要燃料(Bell et al, 1986)，本研究发现，慢肌不仅脂肪和脂肪酸总量显著高于快肌，同时脂肪酸中SFA的占比也更高，较其他脂肪酸更易被氧化利用的C16:0、C18:0和C14:0构成了SFA的主要类型(Tocher, 2003)，这种脂肪酸构成特点为慢肌支撑持续性游泳运动提供了一定的物质基础。MUFA是另一类会被肌肉优先利用的脂肪酸(Weber et al, 2002)，研究发现，以C16:1和C18:1为底物时，催化鱼类组织脂肪酸氧化代谢的关键限速酶—肉碱棕榈酰转移的酶活性比其他脂肪酸为底物时更强(McKenzie et al, 1998)。此外，还发现MUFA会以非活性形式转移到工作肌群(Weber et al, 2002; Booth et al, 1999)。据此，我们推测，在鱼类的长距离游泳过程中，快肌的MUFA，尤其是C16:1和C18:1极有可能会被转移到慢肌中而为躲避敌害、捕获猎物、求偶和洄游等供能。

具有较高的矿物元素Fe和Zn含量是本研究发现的慢肌的另一个特点，在虹鳟(Carpenè et al, 1990)、沙丁鱼(Sardina pilchardus) (Carpenè et al, 1990)和胡子鲶(Clarias macrocephalus) (Chaijan et al, 2013)等鱼类中也有类似的趋势，说明这可能是海洋硬骨鱼类的普遍现象。研究表明，鱼体内约80.0%以上的Fe以血红素的形式存在，而血红素是肌红蛋白和血红蛋白等与氧气转运有关的蛋白质的关键组分(Hafzan et al, 2023)。Zn是代谢过程中多种金属催化酶的辅助因子，在呼吸链上电子传递等方面起着重要作(Adebayo et al, 2016)。前期有关黄带拟鲹的研究发现，几乎所有编码线粒体电子呼吸链的基因在mRNA和蛋白层面上都呈现慢肌高表达的趋势(Wang et al, 2022a、b)，这说明慢肌具有更强的氧化磷酸化的能力，较高的Fe和Zn含量可能为其有氧代谢提供了更多的氧气及更强的催化酶活性。

相较于慢肌，快肌普遍具有高组氨酸含量这一特点。组氨酸除参与合成蛋白质外，还是肌肽、鹅肌肽、鲸肌肽和高肌肽等功能性二肽(histidine-related compounds, HRC)的主要成分。研究发现，组氨酸及HRCs在生理环境中既可作为质子供体，又可作为质子受体，具有质子传递的作用(Rebek, 1990)。Abe (2000)以乳酸脱氢酶的活力来代表无氧运动能力，发现由于无氧运动能力的不同，不同物种和不同肌肉类型的质子缓冲能力存在显著差异，即无氧运动能力更强的物种和肌肉类型，其质子缓冲能力也更强。同时，质子缓冲能力、HRCs含量以及支撑无氧运动能力的快肌纤维占比存在高度的正相关性(Abe, 2000)。Suyama等(1986)将黄鳍金枪鱼肌肉中的HRCs去除后，快肌几乎完全丧失了缓冲能力，而慢肌的缓冲能力却并未受到显著影响。在本研究中，我们在5种海洋硬骨鱼类中均检测到组氨酸在快肌中的含量显著高于慢肌的趋势，表明组氨酸相关物质是海洋硬骨鱼类快肌适应高速运动和长时间缺氧条件下，维持肌细胞pH稳定的主要缓冲物质。在快肌收缩时，组氨酸相关物质缓冲肌肉进行糖酵解而积累的H⁺，对保证肌肉收缩，供给肌肉运动能量和糖酵解不断进行发挥重要作用。

青干金枪鱼、圆鲣、鲣等金枪鱼类快、慢肌的脂肪酸含量虽有差异，但不似黄带拟鲹和梭鱼剧烈。根据文献资料报道，通过测定和比较柠檬酸合酶、肉碱棕榈酰转移酶和己糖激酶等表征有氧氧化能力的酶活性，发现金枪鱼类快、慢肌的有氧氧化能力虽有显著差异但远没有其他鱼类剧烈(Moyes et al, 1992; Dickson, 1995; Ciezarek et al, 2020)。脂肪酸作为有氧氧化的主要燃料，其含量的差异可能也在一定程度上反映了快、慢肌有氧氧化能力的差异性，因此，金枪鱼类的快、慢肌脂肪酸含量差异没有黄带拟鲹和梭鱼显著。进一步分析，未发现快、慢肌在蛋白质、氨基酸、脂肪、脂肪酸及矿物元素组成方面与不同游泳习性之间存在直接关联，这说明不同游泳习性鱼类在爆发性游泳运动或持续性游泳运动能力方面的差异性可能是通过其他组分的差异来调控的，比如慢肌总质量(Greek-Walker et al, 1975)、酶活性(Teulier et al, 2019)等，而非单位肌肉质量下的蛋白质、氨基酸、脂肪、脂肪酸及矿物元素含量。

4 结论

通过对黄带拟鲹和梭鱼快、慢肌的基本成分、氨基酸、脂肪酸与矿物质含量测定，结合青干金枪鱼、黄鳍金枪鱼、圆鲣、鲣等金枪鱼类的报道数据，得到以下结论：

(1) 快肌中蛋白质及12种氨基酸含量均显著高于慢肌，其中尤以组氨酸的相对含量最高(1.22~3.83倍)。

(2) 海洋硬骨鱼类快、慢肌的氨基酸组成相似，谷氨酸和天冬氨酸是含量最丰富的2种氨基酸，必需氨基酸含量均占氨基酸总量的40%左右，赖氨酸和亮氨酸是含量最高的2种必需氨基酸。

(3) 慢肌的脂肪含量及每种脂肪酸含量均显著高于快肌。

(4) 在脂肪酸组成方面，慢肌中SFA的比例较快肌高，而快肌中的PUFA比例则比慢肌高，快、慢肌均是以C16:0、C18:0和C14:0为主要SFA组成类型；C18:1和C16:1为主要MUFA组成类型；C22:6n3和C20:5n3为主要PUFA组成类型。

(5) 慢肌含有更为丰富的微量元素Fe和Zn。

(6) 海洋硬骨鱼类的快慢肌的化学组成差异为其行使不同运动功能提供了物质基础。

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