Diabetologia ( IF 8.4 ) Pub Date : 2021-06-16 , DOI: 10.1007/s00125-021-05481-9 Rasmus J O Sjögren 1 , David Rizo-Roca 1 , Alexander V Chibalin 1 , Elin Chorell 2 , Regula Furrer 3 , Shintaro Katayama 4 , Jun Harada 5 , Håkan K R Karlsson 1 , Christoph Handschin 3 , Thomas Moritz 6 , Anna Krook 7 , Erik Näslund 8 , Juleen R Zierath 1, 7
|
Aims/hypothesis
Increased levels of branched-chain amino acids (BCAAs) are associated with type 2 diabetes pathogenesis. However, most metabolomic studies are limited to an analysis of plasma metabolites under fasting conditions, rather than the dynamic shift in response to a metabolic challenge. Moreover, metabolomic profiles of peripheral tissues involved in glucose homeostasis are scarce and the transcriptomic regulation of genes involved in BCAA catabolism is partially unknown. This study aimed to identify differences in circulating and skeletal muscle BCAA levels in response to an OGTT in individuals with normal glucose tolerance (NGT) or type 2 diabetes. Additionally, transcription factors involved in the regulation of the BCAA gene set were identified.
Methods
Plasma and vastus lateralis muscle biopsies were obtained from individuals with NGT or type 2 diabetes before and after an OGTT. Plasma and quadriceps muscles were harvested from skeletal muscle-specific Ppargc1a knockout and transgenic mice. BCAA-related metabolites and genes were assessed by LC-MS/MS and quantitative RT-PCR, respectively. Small interfering RNA and adenovirus-mediated overexpression techniques were used in primary human skeletal muscle cells to study the role of PPARGC1A and ESRRA in the expression of the BCAA gene set. Radiolabelled leucine was used to analyse the impact of oestrogen-related receptor α (ERRα) knockdown on leucine oxidation.
Results
Impairments in BCAA catabolism in people with type 2 diabetes under fasting conditions were exacerbated after a glucose load. Branched-chain keto acids were reduced 37–56% after an OGTT in the NGT group, whereas no changes were detected in individuals with type 2 diabetes. These changes were concomitant with a stronger correlation with glucose homeostasis biomarkers and downregulated expression of branched-chain amino acid transaminase 2, branched-chain keto acid dehydrogenase complex subunits and 69% of downstream BCAA-related genes in skeletal muscle. In primary human myotubes overexpressing peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α, encoded by PPARGC1A), 61% of the analysed BCAA genes were upregulated, while 67% were downregulated in the quadriceps of skeletal muscle-specific Ppargc1a knockout mice. ESRRA (encoding ERRα) silencing completely abrogated the PGC-1α-induced upregulation of BCAA-related genes in primary human myotubes.
Conclusions/interpretation
Metabolic inflexibility in type 2 diabetes impacts BCAA homeostasis and attenuates the decrease in circulating and skeletal muscle BCAA-related metabolites after a glucose challenge. Transcriptional regulation of BCAA genes in primary human myotubes via PGC-1α is ERRα-dependent.
Graphical abstract
中文翻译：
支链氨基酸代谢在人类原代肌管中受 ERRα 调节，并在 2 型糖尿病中受到葡萄糖负荷的进一步损害
目标/假设
支链氨基酸 (BCAA) 水平升高与 2 型糖尿病发病机制相关。然而，大多数代谢组学研究仅限于禁食条件下血浆代谢物的分析，而不是响应代谢挑战的动态变化。此外，参与葡萄糖稳态的外周组织的代谢组学特征很少，并且参与支链氨基酸分解代谢的基因的转录组调控部分未知。本研究旨在确定正常糖耐量 (NGT) 或 2 型糖尿病个体对 OGTT 的反应中循环和骨骼肌 BCAA 水平的差异。此外，还鉴定了参与 BCAA 基因组调节的转录因子。
方法
在 OGTT 前后对 NGT 或 2 型糖尿病患者进行血浆和股外侧肌活检。从骨骼肌特异性Ppargc1a敲除小鼠和转基因小鼠中收获血浆和股四头肌。分别通过 LC-MS/MS 和定量 RT-PCR 评估 BCAA 相关代谢物和基因。在原代人骨骼肌细胞中使用小干扰RNA和腺病毒介导的过表达技术来研究PPARGC1A和ESRRA在BCAA基因组表达中的作用。使用放射性标记的亮氨酸来分析雌激素相关受体 α (ERRα) 敲低对亮氨酸氧化的影响。
结果
2 型糖尿病患者在空腹条件下支链氨基酸分解代谢的受损在葡萄糖负荷后会加剧。 NGT 组进行 OGTT 后，支链酮酸减少了 37-56%，而 2 型糖尿病患者则没有检测到任何变化。这些变化伴随着与葡萄糖稳态生物标志物更强的相关性，以及骨骼肌中支链氨基酸转氨酶 2、支链酮酸脱氢酶复合体亚基和 69% 下游 BCAA 相关基因的表达下调。在过表达过氧化物酶体增殖物激活受体 γ 共激活因子-1α（PGC-1α，由PPARGC1A编码）的原代人肌管中，所分析的 61% BCAA 基因上调，而在骨骼肌特异性Ppargc1a敲除小鼠的股四头肌中，67% 下调。 ESRRA （编码 ERRα）沉默完全消除了 PGC-1α 诱导的人原代肌管中 BCAA 相关基因的上调。
结论/解释
2 型糖尿病的代谢不灵活会影响 BCAA 稳态，并减弱葡萄糖激发后循环和骨骼肌 BCAA 相关代谢物的减少。通过 PGC-1α 对人类原代肌管中 BCAA 基因的转录调节是 ERRα 依赖性的。
京公网安备 11010802027423号