Expression data from hearts (left ventricle apex) of rats with and without metformin treatment

In a subacute study, male Wistar rats were treated daily by gavage with 800 mg/kg metformin for 1, 3, or 14 consecutive days, followed by necropsy 24h after the last application. The biguanide metformin is a widely used antidiabetic drug, which has received great interest in oncology research in recent years after an epidemiological study showed a link between metformin treatment and a reduced cancer risk in diabetic patients. Since mitochondrial metabolism has become a target for possible cancer therapeutic approaches, especially for tumors relying on oxidative metabolism, mitochondrial complex I inhibition is under discussion to be responsible for the anti-cancer effect of metformin. The known strong complex I inhibitor Rotenone has also shown anti-cancer activity, however is associated with toxic effects. Therefore, we compared metformin and phenformin, another biguanide withdrawn from the marked as antidiabetic due to safety reasons, with rotenone, to elucidate potential mechanisms rendering biguanides apparently less toxic than rotenone. In this context, various blood and tissue parameters as well as histopathology were measured and/or evaluated. Moreover, gene expression profiling was conducted in liver and heart due to the high metabolic activity and high energy demand. All investigations were based on an experimental design previously described for mechanistic investigations of the effects of rotenone. Our examinations regarding gene expression showed that 1630 transcripts were deregulated by rotenone, metformin and/or phenformin in liver, whereas 777 transcripts were deregulated in heart, indicating that the heart is less affected by these compounds. Overall, the mechanistic profile of phenformin appears to be similar to that of rotenone, yet at a quantitatively reduced level, whereas metformin displayed only transient similarities after one day of treatment. These differences are likely due to differential molecular properties of these compounds, especially concerning their effects on mitochondria: Metformin, in contrast to rotenone, requires a certain mitochondrial potential to allow accumulation in this organelle, thereby self-limiting its entry and thus ability to inhibit mitochondrial function, whereas rotenone and to some extent also phenformin can enter mitochondria freely. Thus, our more detailed molecular characterization of these compounds suggests that inhibition of mitochondrial functions can serve as target for an anti-cancer mode of action, yet should be self-limited or balanced to some extent to avoid exhaustion of all energy stores.本亚急性试验中，雄性Wistar大鼠每日灌胃给予800 mg/kg二甲双胍(metformin)，连续给药1天、3天或14天，末次给药24小时后进行剖检。双胍类药物二甲双胍是临床广泛应用的抗糖尿病药物，近年来因一项流行病学研究显示其治疗与糖尿病患者癌症风险降低存在关联，而在肿瘤学研究中受到广泛关注。由于线粒体代谢已成为潜在癌症治疗策略的靶点，尤其针对依赖氧化代谢的肿瘤，线粒体复合物I抑制被认为与二甲双胍的抗癌作用机制相关。已知强效复合物I抑制剂鱼藤酮(rotenone)同样展现出抗癌活性，但伴随毒性反应。因此，本研究将二甲双胍与另一种因安全性问题退市的双胍类抗糖尿病药物苯乙双胍(phenformin)，与鱼藤酮进行对比，以阐明为何双胍类药物的毒性显著低于鱼藤酮的潜在机制。本研究对多项血液与组织参数及组织病理学进行了检测与/或评估。此外，鉴于肝脏与心脏具有高代谢活性与高能量需求，本研究对这两种组织开展了基因表达谱分析。所有实验均基于此前用于鱼藤酮作用机制研究的实验设计方案。基因表达分析结果显示，经鱼藤酮、二甲双胍和/或苯乙双胍处理后，肝脏中有1630个转录本出现表达失调，而心脏中仅777个转录本失调，表明心脏受这些化合物的影响更小。总体而言，苯乙双胍的作用机制谱与鱼藤酮相似，但作用强度在定量上有所减弱；而二甲双胍仅在给药1天后展现出短暂的相似性。这些差异可能源于这些化合物的分子特性差异，尤其是其对线粒体的作用：与鱼藤酮不同，二甲双胍需要一定的线粒体膜电位才能在该细胞器中富集，从而自我限制其进入量，进而抑制线粒体功能的能力；而鱼藤酮以及一定程度上的苯乙双胍可自由进入线粒体。因此，我们对这些化合物的更详细分子表征表明，线粒体功能抑制可作为抗癌作用的靶点，但需在一定程度上实现自我限制或平衡，以避免耗尽所有能量储备。