15 BEDREST: Targeting bed rest-induced adipose tissue dysfunction with anti-inflammatory & antioxidant nutrients

卧床休息是一种有用的生理调节实验模型，类似于越来越久坐人群的加速衰老。作为ELIPS项目的一部分，欧洲航天局正在计划一项长期卧床休息研究，以确定营养抗炎和抗氧化对策（包括白藜芦醇、维生素E和C、番茄红素和表没食子儿茶素）的影响。我们假设，卧床休息将导致皮下脂肪组织（脂肪）的炎症和代谢紊乱，这与衰老和缺乏身体活动时皮下脂肪组织的许多变化相似，而计划的对策将抵消由卧床休息引起的变化。总的来说，近年来我们对脂肪组织的理解发生了巨大的变化，脂肪组织显然不仅仅是一个简单的能量储存。脂肪组织在多种生理系统中发挥着积极作用，从骨骼重塑到肌肉基质（燃料）利用。脂肪组织通过分泌原型“脂肪因子”（如脂联素）与其他组织交流，但脂肪组织也负责分泌许多其他蛋白质和介质，这些蛋白质和介质对其他远端组织（包括肌肉和骨骼）有影响。我们假设，脂肪组织对卧床休息的葡萄糖摄取增加会引发细胞和氧化应激，导致脂肪细胞分泌/表达一些分子，这些分子在一定程度上是为了启动免疫反应，但随后会加剧脂肪功能障碍。对照组和干预组在休息60 d前后分别进行脂肪组织活检（每组8 ~ 12例）。我们将在基因表达和蛋白质水平上确定整个脂肪组织的变化。由于我们不能假设卧床休息以及抗炎和抗氧化措施会对组成脂肪组织的异质细胞产生相同的效果，因此我们将把脂肪细胞与非脂肪细胞（例如免疫细胞）分开，并分别检查脂肪细胞和免疫细胞。我们将测定基础和胰岛素刺激条件下脂肪细胞的葡萄糖摄取。我们将检查驻留在脂肪内的特定免疫细胞（如巨噬细胞）数量的变化，以及这些细胞是否具有促炎表型或抗炎表型。我们将培养小块脂肪组织，以检查脂肪因子分泌的变化，以及所选脂肪因子的模式和数量是否受到卧床休息的影响。最后，我们将开展探索性工作，研究卧床休息时脂肪因子分泌的改变是否有可能影响骨和肌肉细胞模型。几乎所有上述工作都将在英国使用冷冻样本进行。重要的是，计划的对策有可能对脂肪组织功能产生积极影响，从最早的机制步骤（例如，白藜芦醇和表没食子儿茶素减少脂肪组织葡萄糖摄取）一直到与继发氧化应激和炎症相关的下游后果（例如，所有成分都已被证明针对脂肪组织中的氧化应激和/或炎症）。迄今为止，大多数这些机制只在啮齿动物脂肪组织中进行了研究，因此计划的干预是验证我们是否可以将这些令人兴奋的发现转化为人类的绝佳机会。脂肪组织功能障碍与衰老、糖尿病和心血管疾病的病因有关，缺乏身体活动是一个潜在的共同中介。在此背景下，本研究将(i)表征卧床休息引起的脂肪组织功能障碍，（ii）证明这些变化是否对其他组织（即肌肉和骨骼）有影响，（iii）确定抗炎和抗氧化对策是否成功针对人类脂肪组织功能障碍。

Bed rest is a useful experimental model of physiological deconditioning which is analogous to accelerated ageing in an increasingly sedentary population. As part of the ELIPS programme, the European Space Agency are planning a long-term bed rest study to determine the impact of a nutritional anti-inflammatory and antioxidant countermeasure (including resveratrol, vitamins E and C, lycopene and epigallocatechin). We hypothesise that bed rest will lead to inflammatory and metabolic disturbances in subcutaneous adipose tissue (fat) which mimic many of the changes in this tissue seen with ageing and physical inactivity - and that the planned countermeasures will offset the changes induced by bed rest.Collectively, our understanding of adipose tissue has changed enormously in recent years and adipose tissue is clearly much more than a simple energy store. Adipose tissue is an active player in diverse physiological systems ranging from bone remodelling through to muscle substrate (fuel) utilisation. Adipose tissue communicates with other tissues via the secretion of archetypal 'adipokines' (e.g., adiponectin) but adipose tissue is also responsible for the secretion of many other proteins and mediators which have implications for other distant tissues including muscle and bone. We hypothesise that increased glucose uptake by adipose tissue in response to bed rest will provoke cellular and oxidative stress - causing adipocytes to secrete/express molecules designed in part to initiate an immune response but which then exacerbates adipose dysfunction. We will take adipose tissue biopsies before and after 60-d bed rest in both control and intervention groups (n=8 to 12 in each group). We will determine changes in whole adipose tissue at both gene expression and protein levels. Since we cannot assume that bed rest and the anti-inflammatory and antioxidant countermeasures will elicit equal effects in the heterogeneous cells that comprise adipose tissue, we will separate adipocytes from non-adipocytes (e.g. immune cells) and examine adipocytes and immune cells separately. We will determine adipocyte glucose uptake in basal and insulin-stimulated conditions. We will examine changes in the number of specific immune cells that are resident within adipose (e.g. macrophages) and also whether these cells have a pro- or anti-inflammatory phenotype. We will culture small pieces of adipose tissue to examine changes in adipokine secretion - and whether the pattern and amount of selected adipokines is impacted upon by bed rest. Finally, we will undertake exploratory work to examine whether altered adipokine secretion with bed rest has the potential to impact upon bone and muscle cell models. Virtually all of the above work will be conducted in the UK using frozen samples.Importantly, the planned countermeasures have the potential to positively impact upon adipose tissue function from the earliest mechanistic step (e.g., resveratrol and epigallocatechin decrease adipose tissue glucose uptake) all the way through to downstream consequences related to secondary oxidative stress and inflammation (e.g., all of the ingredients have been shown to target either oxidative stress and/or inflammation in adipose tissue). To date, most of these mechanisms have only been examined in rodent adipose tissue and thus the planned intervention represents an excellent opportunity to verify whether we can translate these exciting findings into humans. Adipose tissue dysfunction has been implicated in the aetiology of ageing, diabetes, and cardiovascular disease - with physical inactivity being a potential common mediator. In this context, this research will (i) characterise bed rest-induced adipose tissue dysfunction, (ii) demonstrate whether these changes have implications for other tissues (i.e. muscle and bone) and (iii) determine whether the anti-inflammatory and antioxidant countermeasures successfully target adipose tissue dysfunction in humans.