Department of Health and Human Performance, High Point University, High Point, NC, USA.
Department of Chemistry, High Point University, High Point, NC, USA.
Biochimie. 2024 Apr;219:155-164. doi: 10.1016/j.biochi.2023.11.009. Epub 2023 Nov 25.
Type 2 diabetes is characterized by elevated circulating blood metabolites such as glucose, insulin, and branched chain amino acids (BCAA), which often coincide with reduced mitochondrial function. 4-Phenylbutyrate (PBA), an ammonia scavenger, has been shown to activate BCAA metabolism, resolve endoplasmic reticulum (ER) stress, and rescue BCAA-mediated insulin resistance. To determine the effect of PBA on the altered metabolic phenotype featured in type 2 diabetes, the present study investigated the effect of PBA on various metabolic parameters including mitochondrial metabolism and mitochondrial biogenesis. C2C12 myotubes were treated with PBA at 0.5 mM (representing physiologically attainable blood concentrations) or 10 mM (representing physiologically unattainable/proof-of-concept levels) for up to 24 h. Mitochondrial and glycolytic metabolism were assessed via oxygen consumption and extracellular acidification rate, respectively. Mitochondrial content, lipid content, and ER stress were measured by fluorescent staining. Metabolic gene expression was measured by qRT-PCR. Both doses of PBA increased expression of indicators of mitochondrial biogenesis, though only PBA at 0.5 mM increased mitochondrial function and content while 10 mM PBA reduced mitochondrial function and content. PBA at 0.5 mM also rescued reduced mitochondrial function during insulin resistance, though PBA also caused a reduced insulin stimulated pAkt expression during insulin resistance. PBA treatment also increased extracellular BCAA accumulation during insulin resistance despite unchanged pBCKDH expression. Taken together, PBA may increase mitochondrial biogenesis, content, and function in a dose-dependent fashion which may have implications for prevention or treatment of metabolic disease such as insulin resistance.
2 型糖尿病的特征是循环血液代谢物（如葡萄糖、胰岛素和支链氨基酸（BCAA））升高，这通常与线粒体功能降低同时发生。4-苯丁酸（PBA），一种氨清除剂，已被证明可以激活 BCAA 代谢、解决内质网（ER）应激，并挽救 BCAA 介导的胰岛素抵抗。为了确定 PBA 对 2 型糖尿病中改变的代谢表型的影响，本研究调查了 PBA 对各种代谢参数的影响，包括线粒体代谢和线粒体生物发生。用 0.5 mM（代表生理上可达到的血液浓度）或 10 mM（代表生理上不可达到/概念验证水平）的 PBA 处理 C2C12 肌管长达 24 小时。通过耗氧量和细胞外酸化率分别评估线粒体和糖酵解代谢。通过荧光染色测量线粒体含量、脂质含量和 ER 应激。通过 qRT-PCR 测量代谢基因表达。两种剂量的 PBA 均增加了线粒体生物发生指标的表达，尽管只有 0.5 mM 的 PBA 增加了线粒体功能和含量，而 10 mM 的 PBA 降低了线粒体功能和含量。0.5 mM 的 PBA 还在胰岛素抵抗期间挽救了线粒体功能的降低，尽管 PBA 在胰岛素抵抗期间也导致胰岛素刺激的 pAkt 表达降低。尽管 pBCKDH 表达不变，但 PBA 处理在胰岛素抵抗期间也增加了细胞外 BCAA 的积累。总之，PBA 可能以剂量依赖的方式增加线粒体生物发生、含量和功能，这可能对预防或治疗代谢疾病（如胰岛素抵抗）具有重要意义。
