高强度间歇运动通过调控Nrf2/ARE和NF-κB信号通路调节高脂饮食诱导肥胖大鼠的氧化应激和炎症反应

为了揭示高强度间歇运动对肥胖大鼠的氧化应激和炎症反应的调节作用及机制,本研究将60只大鼠随机分为对照组、肥胖组、中强度持续运动组(MICE)和高强度间歇运动组(HIIE)。对照组大鼠采用标准饲料喂养,其他组大鼠采用高脂饲料喂养以建立肥胖大鼠模型。MICE组大鼠进行中强度持续运动,HIIE组大鼠进行高强度间歇运动,共运动4周。采用苏木精-伊红(HE)染色检测大鼠骨骼肌形态。采用TUNEL法检测骨骼肌细胞凋亡。通过商用试剂盒检测活性氧(ROS)水平。通过RT-PCR或Western blotting检测大鼠骨骼肌组织中Nrf2、SOD、GSH-PX、CAT、p65、p-p65、IκB、p-IκB、TNF-α、IL-1β和IL-6的表达。研究显示,与肥胖组比较,MICE组和HIIE组大鼠骨骼肌组织中的ROS水平均显著降低,HIIE组大鼠骨骼肌组织中的ROS水平显著低于MICE组。MICE组和HIIE组大鼠的骨骼肌形态基本正常,仅少量肌纤维排列异常。与肥胖组比较,MICE组和HIIE组大鼠骨骼肌细胞凋亡率均显著降低,HIIE组大鼠骨骼肌细胞凋亡率显著低于MICE组。与肥胖组比较,MICE组和HIIE组大鼠骨骼肌组织中Nrf2、SOD、GSH-PX和CAT的蛋白水平均显著升高,HIIE组均显著高于MICE组。与肥胖组比较,MICE组和HIIE组大鼠骨骼肌组织中p-p65、p-IκB、TNF-α、IL-1β和IL-6的蛋白水平均显著降低,HIIE组均显著低于MICE组。总之,HIIE运动可通过抑制NF-κB信号通路来抑制肥胖引起的慢性炎症。HIIE运动可通过激活Nrf2/ARE信号通路来提高机体抗氧化能力并减弱氧化应激损伤。     

MCT在精子发生中的表达规律及调控机制的研究进展

单羧酸转运蛋白(monocarboxylate transporters,MCTs)是哺乳动物细胞膜上一类重要的跨膜转运蛋白,主要负责乳酸盐、丙酮酸盐、酮体等单羧酸类化合物的跨膜转运。MCT基因在睾丸生精上皮细胞发育、分化过程中具有不同程度表达,并通过多种途径调节精子发生过程。开展对MCT基因在精子发生过程的作用研究有助于人们从能量代谢角度进一步阐明生精细胞发育和精子发生的调控机制。本研究着重从MCT在精子发生过程中的表达定位、功能及调节机制进行综述。     

单羧酸转运蛋白基因SNP 与肝细胞肝癌预后的关联研究

目的:探讨单羧酸转运蛋白基因(monocarboxylate transporter,MCT)单核苷酸多态性(single nucleotide polymorphism,SNPs)与肝细胞肝癌(hepatocellular carcinoma,HCC)根治术患者预后的关系。方法:运用Sequenom i PLEX分型技术对830例原发性HCC患者MCT家族(MCT1、MCT2和MCT4)基因上的8个功能性SNP位点进行基因分型,并分析这些SNP与HCC患者预后的相关性。结果:MCT1基因rs1049434位点和MCT2基因rs995343位点基因型与HCC患者总体生存期及无复发生存期均显著相关(P0.05)。携带MCT1 AT基因型或TT基因型的患者死亡及复发风险均显著低于携带AA基因型的患者(HR=0.72;P=0.042或HR=0.64;P=0.002);携带MCT2 CT基因型或TT基因型的患者死亡及复发风险均显著高于携带CC基因型的患者(HR=1.64;P=0.018或HR=1.52;P=0.026)。而且,MCT1基因rs1049434位点和MCT2基因rs995343位点对HCC预后存在显著的累积效应,携带2个危险基因型的患者死亡及复发风险分别是没有危险基因型患者的2.16倍和2.54倍。此外,携带2个危险基因型的HCC患者在术后行TACE辅助治疗后死亡及复发风险均显著降低(P0.05)。结论:MCT1和MCT2基因上的功能性SNP位点有可能作为HCC根治术后预后评估和TACE辅助治疗反应预测的独立标志物。     

不同训练方式对大鼠骨骼肌纤维类型转化和CaMK II/MEF2传导途径的影响*

目的: 探讨间歇速度训练和耐力训练对大鼠骨骼肌纤维类型转化及钙调蛋白激酶/肌细胞增强因子2(CaMK II/MEF2)信号传导通路的影响。方法: 成年雄性SD大鼠(8周龄)18只,随机分成间歇速度训练组(IST),耐力训练组(ET),设空白组(C),每组6只,IST组采用75 m/min×1 min、20 m/min×1 min的交替训练6次,跑台坡度15,持续时间12 min/d;ET组采用速度30 m/ min、跑台坡度7、持续时间90 min/d的耐力训练。干预8周后,分别取小鼠右侧胫骨前肌、比目鱼肌,酶联免疫吸附法检测骨骼肌琥珀酸脱氢酶(SDH)、乳酸脱氢酶(LDH)活性,ATP酶染色法观察I、Ⅱ型肌纤维面密度、数密度变化情况,SDS-PAGE凝胶电泳技术观察骨骼肌MHC亚型百分比含量、骨骼肌mRNA表达谱测序分析及qRT-PCR技术检测CaN、CaMKII、MEF2水平。结果: 相比C组,ET组SDH活性显著上升,LDH活性降低(P＜0.05);IST组胫骨前肌中LDH活性值升高(P＜0.01)。ET组胫骨前肌MHCIIa%升高,MHCIIb%降低(P＜0.05),比目鱼肌MHCI% 和MHCIIa%升高,MHCIIb%均降低(P＜0.05)。相比IST组,ET组胫骨前肌MHCIIx%升高(P＜0.05)。相比C组,ET组胫骨前肌 I、II 型纤维纤维密度上升,IST组II型纤维纤维密度提高,IST组、ET组比目鱼肌I型纤维纤维密度上升(P＜0.05)。相比C组,ET组骨骼肌CaN、CaMKII、MEF2 mRNA表达水平增高,IST组CaN、CaMKII、MEF2 mRNA表达水平下降(P＜0.01)。Illumina高通量测序筛选骨骼肌纤维转化相关因子及关联分析,运动干预促使骨骼肌纤维转化相关因子表达变化富集于TGF-β/Smad3、CaN/MEF2、AdipoQ等信号通路,而耐力训练显著提高骨骼肌纤维转化、干细胞功能相关信号通路的富集。结论: 耐力训练促进向氧化型肌纤维转化(慢肌),而间歇速度训练向酵解型肌纤维转化(快肌),并伴随着CaMK II/MEF2传导途径中CaN、CaMKII、MEF2基因的高表达。     

针刺对大鼠运动性骨骼肌损伤内质网应激的干预作用及机制

目的: 观察针刺对大鼠运动性骨骼肌损伤内质网功能酶SERCA、PDI、内质网应激标志蛋白GRP78和PERK通路的影响,探讨针刺防治运动性骨骼肌损伤的内质网途径作用机制。方法: 8周龄雄性SD大鼠随机分为空白对照组(C组,n=6)、单纯运动组(E组,n=30)、针刺对照组(A组,n=30)和运动针刺组(EA组,n=30)。其中,E组和EA组通过一次离心运动建立运动性骨骼肌损伤模型,EA组在运动后即刻于大鼠小腿跟腱上0.5 cm施以针刺干预,A组在同期施以针刺干预。各组根据运动和针刺干预后不同取材时间点分为0 h/12 h/24 h/48 h/72 h亚组(n=6),在对应时相取比目鱼肌进行指标测试。透射电镜观察肌纤维超微机构;ELISA法测定Ca²⁺-ATP酶(SERCA)和蛋白二硫键异构酶(PDI)含量;Western blot检测内质网应激标志蛋白GRP78及p-PERK、p-eIF2α表达。结果: 与C组比较,A组指标各时相均无显著差异(P＞0.05),E组肌纤维超微结构出现不同损伤,SERCA含量0 h至48 h均显著降低(P＜0.05),PDI含量0 h显著升高(P＜0.05),GRP78表达0 h至72 h均显著升高(P＜ 0.05),p-PERK表达0 h至24 h显著升高(P＜0.05), p-eIF2α表达与p-PERK一致;与E组对应时相比较,EA组肌纤维超微结构明显改善,SERCA含量48 h和72 h显著升高(P＜0.05),PDI含量0 h至72 h均显著升高(P＜0.05),GRP78表达0 h至72 h均显著降低(P＜0.05),p-PERK和p-eIF2α表达12 h和24 h显著降低(P＜0.05)。结论: 针刺可有效改善一次大负荷离心运动后导致的运动性骨骼肌损伤并缓解内质网应激,其机制可能与上调蛋白二硫键异构酶PDI以及抑制内质网应激PERK通路有关。     

高强度间歇运动对脑梗死后大鼠的脑保护作用及HDAC6表达的影响

为了考察高强度间歇运动(HIIE)对脑梗死后大鼠的脑保护作用及组蛋白去乙酰化酶6 (HDAC6)表达的影响。本研究将60只SD大鼠随机分为3组,假手术组、大脑中动脉闭塞模型组和HIIE组,每组20只。HIIE组大鼠在建模48 h后进行4周的高强度间歇运动,其他组大鼠不进行运动。通过神经损伤评分来评价大鼠神经功能,TTC染色检测梗死面积,TUNEL染色测定脑组织的细胞凋亡,RT-PCR和Western blotting检测大鼠海马组织中HDAC6、TNF-α、IL-1β和IL-6的m RNA和蛋白表达。研究发现,高强度间歇运动后,HIIE组的神经损伤评分显著低于模型组(p<0.05)。TTC染色显示,HIIE组的梗死面积比例显著低于模型组(p<0.05)。TUNEL染色显示,HIIE组的海马神经细胞凋亡数显著低于模型组(p<0.05)。RT-PCR和Western blotting结果显示,HIIE组的HDAC6、TNF-α、IL-1β和IL-6 m RNA和蛋白表达水平均显著低于模型组(p<0.05)。本研究表明,高强度间歇运动可显著改善脑梗死大鼠的神经功能,降低脑梗死面积,抑制海马神经细胞凋亡。高强度间歇运动的神经保护作用机制可能与抑制HDAC6有关。     

大蒜素通过抑制OPN表达和NF‑κB通路活化对大鼠肾结石形成的作用研究

大蒜素可改善草酸诱导的肾小管上皮细胞损伤,以肾结石大鼠为研究对象,探讨大蒜素对肾结石大鼠的作用及其可能的机制。采用1%乙二醇+2%氯化铵混合液灌胃造模（空白组除外）,分别灌胃大蒜素7.5 mg·kg^-1（低剂量大蒜素组）、15 mg·kg^-1（高剂量大蒜素组）、胃枸橼酸氢钾钠颗粒0.6 g·kg^-1（阳性对照组）,其余组灌胃0.9%氯化钠溶液（空白组）,检测各组大鼠与肾结石疾病相关的指标。与空白组相比,模型组大鼠肾指数、肌酐（creatinine,Cr）、血清尿素氮（blood urea nitrogen,BUN）水平和天冬氨酸转氨酶（aspartate aminotransferase,AST）、谷丙转氨酶（alanine aminotransferase,ALT）活性及24 h尿量、尿液中草酸、钙和磷含量显著升高（P<0.05）,草酸钙结晶评分显著升高（P<0.05）,镁含量显著降低（P<0.05）,骨桥蛋白（osteopontin,OPN）表达显著升高（P<0.05）,核因子κB（nuclear factor-κB,NF-κB）通路活化;与模型组相比,低剂量大蒜素组、高剂量大蒜素组和阳性对照组大鼠肾指数、Cr、BUN水平和AST、ALT活性、24 h尿量、尿液中草酸、钙和磷含量显著降低（P<0.05）,草酸钙结晶评分显著降低（P<0.05）,镁含量显著升高（P<0.05）,OPN表达显著降低（P<0.05）,NF?κB通路被抑制。结果表明,大蒜素通过改善大鼠肾功能指标、抑制骨桥蛋白表达和NF?κB通路活化进而抑制肾结石形成。     

白藜芦醇通过糖代谢重编程抑制DEN诱导大鼠肝细胞癌前阶段的恶性增殖

白藜芦醇(resveratrol,RES)可抑制肝癌细胞的生长与增殖。但其在癌前阶段的作用尚不十分清楚。本文研究白藜芦醇对二乙基亚硝胺(diethylinitrosamine, DEN)诱导大鼠肝癌前阶段的作用及机制。SD大鼠分为正常对照组、RES处理组、DEN处理组和RES-DEN处理组。研究结果表明,DEN处理大鼠8周时,肝细胞的总增殖细胞核抗原(proliferating cell nuclear antigen,PCNA)升高至2倍(P<0.05),核内PCNA蛋白表达水平升高至3倍(P<0.001),而RES-DEN处理组大鼠肝细胞总PCNA(P<0.05)和核内PCNA蛋白表达水平(P<0.001)降低。结果提示,RES可显著抑制肝细胞恶性增生。通过非靶向代谢物组学及代谢通路富集分析,结果表明,RES-DEN处理大鼠的肝细胞中,虽然磷酸戊糖途径向糖酵解途径的转变增强,但相较于DEN组大鼠,糖酵解水平并未出现显著提高,提示磷酸烯醇式丙酮酸-丙酮酸-乳酸这条代谢途径被抑制。进一步验证发现,这条代谢途径上的关键酶M2型丙酮酸激酶(M2-type pyruvate kinase,PKM2)和乳酸脱氢酶(lactate dehydrogenase,LDHA)蛋白质表达水平被抑制(P<0.05)。RES可通过调节糖代谢重编程,在肝癌的癌前阶段抑制DEN诱导的大鼠肝细胞的过度增殖,为RES预防肝癌提供了实验依据。     

不同运动方式对2型糖尿病大鼠骨骼肌Rab5蛋白及糖代谢的影响*

目的: 探讨持续运动和间歇负重运动对2型糖尿病(T2DM)骨骼肌组织细胞形态、骨骼肌Rab5 mRNA及蛋白表达、骨骼肌糖代谢的影响。方法: SD大鼠选取8只为空白对照组(CR),其他采用高脂高糖饲料喂养6周后,腹腔注射STZ(35 mg/kg)构建T2DM模型。选取24只T2DM分3组(n=8),分别为:T2DM模型组(DRM)、持续运动组(DCRE)、间歇负重运动组(DWRE)。持续运动方案:为前1～2 周准备活动15 m/min(10 min)、运动20 m/min(40 min)、整理活动15 m/min(10 min),后3～8周为 18 m/min(10 min)、25 m/min(40 min)、15 m/min(10 min);间歇负重运动方案:采用负荷重量为15%(1～2周)、30%(3～4周)、45%(5～8周),运动均为15 m/min(5 min),共12组,组间休息3 min。8周后,通过HE观察骨骼肌病理形态变化,qRT-PCR检测骨骼肌Rab5、葡萄糖转运酶4(GLUT4)的mRNA表达,免疫荧光组化技术及Western blot检测骨骼肌Rab5的蛋白表达,ELISA检测血浆Rab5和糖化血红蛋白(GHb)浓度。结果: 相比CR,DRM存在骨骼肌病理损伤,骨骼肌Rab5mRNA及蛋白表达、GLUT4 mRNA表达均降低(P＜0.01),血浆Rab5和GHb均显著升高(P＜0.01);与DRM比较, DCRE、DWRE骨骼肌病理损伤均显著减轻,骨骼肌Rab5 mRNA及蛋白表达、GLUT4 mRNA表达均升高(P＜0.05,P＜0.01),血浆Rab5和GHb降低(P＜0.01);DCRE与DWRE组间均无统计学差异(P＞0.05)。结论: 2种运动方式均能改善2型糖尿病大鼠骨骼肌病理损伤,并可通过提高骨骼肌Rab5基因和蛋白表达从而增强 GLUT4转运能力,缓解骨骼肌糖代谢稳态失衡,但2种运动方式对骨骼肌Rab5蛋白和糖代谢的影响无明显差异性。     

达格列净对2型糖尿病大鼠肾脏葡萄糖转运蛋白2及葡萄糖转运蛋白4基因表达的影响*

目的:探讨达格列净对2型糖尿病大鼠肾脏葡萄糖转运蛋白2(GLUT2)和葡萄糖转运蛋白4(GLUT4)基因表达的影响。方法:使用高脂饲料和一次性注射40 mg/kg链脲佐菌素(STZ)建立2型糖尿病大鼠模型,造模大鼠以空腹血糖(FBG)含量≥16.7 mmol/L时视为造模成功。造模成功后随机分为模型组(B组,生理盐水)、达格列净低剂量组(C组,0.75 mg/kg)、达格列净中剂量组(D组,1.5 mg/kg)、达格列净高剂量组(E组,3.0 mg/kg),每组6只;另选取6只健康的SD大鼠作为正常对照组(A组,生理盐水)。各组均为灌胃给药,每天1次,连续7周。灌胃给药7周后测定大鼠的体重以及血清FBG、糖化血红蛋白(HbA1c)、血尿素氮(BUN)、血肌酐(Scr)的变化;采用酶联免疫吸附测定血清及肾组织丙二醛(MDA)、超氧化物歧化酶(SOD)和谷胱甘肽过氧化物酶(GSH-Px);采用HE观察肾脏病理学变化;采用Western blot检测肾脏组织中GLUT2、GLUT4蛋白表达;RT-qPCR检测肾脏组织中GLUT2、GLUT4 mRNA相对表达量。结果: 与A组比较,各组大鼠的体重及SOD、GSH-PX水平明显降低(P＜ 0.05),FBG、HbA1c、BUN、Scr、MDA水平明显升高(P＜0.05),肾脏病理损伤严重,肾组织GLUT2、GLUT4 mRNA相对表达量和蛋白表达均明显降低(P均＜0.05)。与B组比较,C组、D组和E组大鼠的体重、SOD、GSH-PX水平和肾组织GLUT2、GLUT4 mRNA相对表达量明显升高(P＜0.05),FBG、HbA1c、BUN、Scr、MDA水平明显降低(P＜ 0.05);D组和E组肾脏病理损伤明显减轻,肾组织GLUT2、GLUT4蛋白表达均明显升高(P均＜0.05)。结论:达格列净可缓解2型糖尿病模型大鼠的病情,并上调肾脏GLUT2及GLUT4基因的表达。     

Monocarboxylate transporters in the central nervous system: distribution, regulation and function

Monocarboxylate transporters (MCTs) are proton-linked membrane carriers involved in the transport of monocarboxylates such as lactate, pyruvate, as well as ketone bodies. They belong to a larger family of transporters composed of 14 members in mammals based on sequence homologies. MCTs are found in various tissues including the brain where three isoforms, MCT1, MCT2 and MCT4, have been described. Each of these isoforms exhibits a distinct regional and cellular distribution in rodent brain. At the cellular level, MCT1 is expressed by endothelial cells of microvessels, by ependymocytes as well as by astrocytes. MCT4 expression appears to be specific for astrocytes. By contrast, the predominant neuronal monocarboxylate transporter is MCT2. Interestingly, part of MCT2 immunoreactivity is located at postsynaptic sites, suggesting a particular role of monocarboxylates and their transporters in synaptic transmission. In addition to variation in expression during development and upon nutritional modifications, new data indicate that MCT expression is regulated at the translational level by neurotransmitters. Understanding how transport of monocarboxylates is regulated could be of particular importance not only for neuroenergetics but also for areas such as functional brain imaging, regulation of food intake and glucose homeostasis, or for central nervous system disorders such as ischaemia and neurodegenerative diseases.     

Subacute ruminal acidosis suppressed the expression of MCT1 in rumen of cows

Subacute ruminal acidosis (SARA) is characterized by the depression of ruminal pH and an increase in the concentrations of short-chain fatty acids (SCFAs) and lipopolysaccharide (LPS) in the rumen of cows. The onset of SARA was linked to the accumulation of SCFAs. However, the mechanism of SCFAs transport is unknown. The proton-linked monocarboxylate transporter (MCT1) plays a vital role in the transportation of SCFAs. The goal of this study was to elucidate the distribution of MCT1 along the gastrointestinal tract of calves and adult cows; the expression change of MCT1 in SARA cows and the effect of ruminal pH, SCFAs, and LPS on MCT1 expression in rumen epithelial cells in vitro. The results indicated the presence of MCT1 along the gastrointestinal tract of calves and adult cows, most abundantly expressed in the rumen. Importantly, the expression of MCT1 was decreased in the rumen epithelium of SARA cows, and the expression of MCT1 was restored in the SARA treatment group. In vitro, LPS, low rumen fluid pH, high concentrations of SCFAs (90 mM acetate, 40 mM propionate, and 30 mM butyrate), and high concentrations of acetate, propionate, and butyrate, respectively, inhibited the expression of MCT1 in rumen epithelial cells. Taken together, these results indicated that LPS, low ruminal pH, and high concentrations of SCFAs decreased the expression of MCT1, further aggravating the accumulation of SCFAs in the rumen by decreasing the absorption of SCFAs.     

Muscle contraction increases lactate transport while reducing sarcolemmal MCT4, but not MCT1

Rates of lactate uptake into giant sarcolemmal vesicles were determined in vesicles collected from rat muscles at rest and immediately after 10 min of intense muscle contraction. This contraction period reduced muscle glycogen rapidly by 37-82% in all muscles examined (P < 0.05) except the soleus muscle (no change P > 0.05). At an external lactate concentration of 1 mM lactate, uptake into giant sarcolemmal vesicles was not altered (P > 0.05), whereas at an external lactate concentration of 20 mM, the rate of lactate uptake was increased by 64% (P < 0.05). Concomitantly, the plasma membrane content of monocarboxylate transporter (MCT)1 was reduced slightly (-10%, P < 0.05), and the plasma membrane content of MCT4 was reduced further (-25%, P < 0.05). In additional studies, the 10-min contraction period increased the plasma membrane GLUT4 (P < 0.05) while again reducing MCT4 (-20%, P < 0.05) but not MCT1 (P > 0.05). These studies have shown that intense muscle contraction can increase the initial rates of lactate uptake, but only when the external lactate concentrations are high (20 mM). We speculate that muscle contraction increases the intrinsic activity of the plasma membrane MCTs, because the increase in lactate uptake occurred while plasma membrane MCT4 was decreased and plasma membrane MCT1 was reduced only minimally, or not at all.     

Lactate uptake contributes to the NAD(P)H biphasic response and tissue oxygen response during synaptic stimulation in area CA1 of rat hippocampal slices

Synaptic train stimulation (10 Hz × 25 s) in hippocampal slices results in a biphasic response of NAD(P)H fluorescence indicating a transient oxidation followed by a prolonged reduction. The response is accompanied by a transient tissue PO₂ decrease indicating enhanced oxygen utilization. The activation of mitochondrial metabolism and/or glycolysis may contribute to the secondary NAD(P)H peak. We investigated whether extracellular lactate uptake via monocarboxylate transporters (MCTs) contributes to the generation of the NAD(P)H response during neuronal activation. We measured the effect of lactate uptake inhibition [using the MCT inhibitor α-cyano-4-hydroxycinnamate (4-CIN)] on the NAD(P)H biphasic response, tissue PO₂ response, and field excitatory post-synaptic potential in hippocampal slices during synaptic stimulation in area CA1 (stratum radiatum). The application of 4-CIN (150–250 μmol/L) significantly decreased the reduction phase of the NAD(P)H response. When slices were supplemented with 20 mmol/L lactate in 150–250 μmol/L 4-CIN, the secondary NAD(P)H peak was restored; whereas 20 mmol/L pyruvate supplementation did not produce a recovery. Similarly, the tissue PO₂ response was decreased by MCT inhibition; 20 mmol/L lactate restored this response to control levels at all 4-CIN concentrations. These results indicate that lactate uptake via MCTs contributes significantly to energy metabolism in brain tissue and to the generation of the delayed NAD(P)H peak after synaptic stimulation.     

CD147 regulates the expression of MCT1 and lactate export in multiple myeloma cells

Increased use of the glycolytic pathway, even in the presence of oxygen, has recently been recognized as a key characteristic of malignant cells. However, the glycolytic phenotype results in increased lactic acid production and, in order to prevent cellular acidosis, tumor cells must increase proton efflux via upregulation of pH regulators such as proton-pumps, sodium-proton exchangers, and/or monocarboxylate transporters (MCT) (e.g., MCT1, MCT4). Interestingly, expression of MCT1 and MCT4 has been previously shown to be dependent upon expression of the transmembrane glycoprotein CD147. Recently, we demonstrated that primary patient multiple myeloma (MM) cells and human MM cell lines (HMCLs) overexpress CD147. Therefore, the goal of the current study was to specifically determine if MCT1 and MCT4 were also overexpressed in MM cells. RT-PCR analysis demonstrated both primary patient MM cells and HMCLs overexpress MCT1 and MCT4 mRNA. Notably, primary MM cells or HMCLs were found to express variable levels of MCT1 and/or MCT4 at the protein level despite CD147 expression. In those HMCLs positive for MCT1 and/or MCT4 protein expression, MCT1 and/or MCT4 were found to be associated with CD147. Specific siRNA-mediated downregulation of MCT1 but not MCT4 resulted in decreased HMCL proliferation, decreased lactate export, and increased cellular media pH. However, western blot analysis revealed that downregulation of MCT1 also downregulated CD147 and vice versa despite no effect on mRNA levels. Taken together, these data demonstrate the association between MCT1 and CD147 proteins in MM cells and importance of their association for lactate export and proliferation in MM cells.     

Non-Involvement of the Human Monocarboxylic Acid Transporter 1 (MCT1) in the Transport of Phenolic Acid

Phenolic acids such asp-coumaric acid and microbial metabolites of poorly absorbed polyphenols are absorbed by the monocarboxylic acid transporter (MCT)-mediated transport system which is identical to the fluorescein/H⁺ cotransport system. We focus here on the physiological impact of MCT-mediated absorption and distribution. We examined whether MCT1, the best-characterized isoform found in almost all tissues, is involved in this MCT-mediated transport system. The induction of MCT1 expression in Caco-2 cells by a treatment with sodium butyrate (NaBut) did not increase the fluorescein permeability. Moreover, the transfection of Caco-2 cells with an expression vector encoding MCT1 caused no increase in either the permeability or uptake of fluorescein. Furthermore, in the MCT1-expressing oocytes, no increase ofp-coumaric acid uptake was apparent, whereas the uptake of salicylic acid, a substrate of MCT1, nearly doubled. Our data therefore establish that MCT1 was not involved in the MCT-mediated transport of phenolic acids.     

T3 increases lactate transport and the expression of MCT4, but not MCT1, in rat skeletal muscle

Triiodothyronine (T3) regulates the expression of genes involved in muscle metabolism. Therefore, we examined the effects of a 7-day T3 treatment on the monocarboxylate transporters (MCT)1 and MCT4 in heart and in red (RG) and white gastrocnemius muscle (WG). We also examined rates of lactate transport into giant sarcolemmal vesicles and the plasmalemmal MCT1 and MCT4 in these vesicles. Ingestion of T3 markedly increased circulating serum T3 (P < 0.05) and reduced weight gain (P < 0.05). T3 upregulated MCT1 mRNA (RG +77, WG +49, heart +114%, P < 0.05) and MCT4 mRNA (RG +300, WG +40%). However, only MCT4 protein expression was increased (RG +43, WG +49%), not MCT1 protein expression. No changes in MCT1 protein were observed in any tissue. T3 treatment doubled the rate of lactate transport when vesicles were exposed to 1 mM lactate (P < 0.05). However, plasmalemmal MCT4 was only modestly increased (+13%, P < 0.05). We conclude that T3 1) regulates MCT4, but not MCT1, protein expression and 2) increases lactate transport rates. This latter effect is difficult to explain by the modest changes in plasmalemmal MCT4. We speculate that either the activity of sarcolemmal MCTs has been altered or else other MCTs in muscle may have been upregulated.     

单羧酸转运泵基因家族研究进展

单羧酸转运泵（monocarboxylate transporter,MCT）是哺乳动物细胞中的重要跨膜蛋白,涉及细胞的多种功能,包括胞内pH值调节及乳酸跨膜转运等.目前,已克隆出至少8个MCT亚型的cDNA,构成了哺乳动物细胞离子转运泵的一个新基因家族.各亚型具有底物和抑制剂的特异性以及组织学分布的差异性.因此,研究MCT的结构功能及调控机制,将可能为肿瘤等疾病诊治提供新的手段.     

Isoform-specific regulation of the lactate transporters MCT1 and MCT4 by contractile activity

We examined the isoform-specific regulation of monocarboxylate transporter (MCT)1 and MCT4 expression by contractile activity in red and white tibialis anterior muscles. After 1 and 3 wk of chronic muscle stimulation (24 h/day), MCT1 protein expression was increased in the red muscles (+78%, P < 0.05). In the white muscles, MCT1 was increased after 1 wk (+191%) and then was decreased after 3 wk. In the red muscle, MCT1 mRNA accumulation was increased only after 3 wk (+21%; P < 0.05). In the white muscle, MCT1 mRNA was increased after 1 wk (+30%; P < 0.05) and 3 wk (+15%; P < 0.05). MCT4 protein was not altered in either the red or white muscles after 1 or 3 wk. MCT4 mRNA was transiently lowered (approximately 15%) in both muscles in the 1st wk, but MCT4 mRNA levels were back to control levels after 3 wk. In conclusion, chronic contractile activity induces the expression of MCT1 but not MCT4. This increase in MCT1 alone was sufficient to increase lactate uptake from the circulation.