Pharmacokinetics, mass balance, and metabolism of [14C]vicagrel, a novel irreversible P2Y12 inhibitor in humans.

Vicagrel, a novel irreversible P2Y12 receptor inhibitor, is undergoing phase III trials for the treatment of acute coronary syndromes in China. In this study, we evaluated the pharmacokinetics, mass balance, and metabolism of vicagrel in six healthy male Chinese subjects after a single oral dose of 20 mg [14C]vicagrel (120 µCi). Vicagrel absorption was fast (Tmax = 0.625 h), and the mean t1/2 of vicagrel-related components was ~38.0 h in both plasma and blood. The blood-to-plasma radioactivity AUCinf ratio was 0.55, suggesting preferential distribution of drug-related material in plasma. At 168 h after oral administration, the mean cumulative excreted radioactivity was 96.71% of the dose, including 68.03% in urine and 28.67% in feces. A total of 22 metabolites were identified, and the parent vicagrel was not detected in plasma, urine, or feces. The most important metabolic spot of vicagrel was on the thiophene ring. In plasma pretreated with the derivatization reagent, M9-2, which is a methylated metabolite after thiophene ring opening, was the predominant drug-related component, accounting for 39.43% of the radioactivity in pooled AUC0-8 h plasma. M4, a mono-oxidation metabolite upon ring-opening, was the most abundant metabolite in urine, accounting for 16.25% of the dose, followed by M3-1, accounting for 12.59% of the dose. By comparison, M21 was the major metabolite in feces, accounting for 6.81% of the dose. Overall, renal elimination plays a crucial role in vicagrel disposition, and the thiophene ring is the predominant metabolic site.

Identification of a novel fusion gene, TRIM52-RACK1, in oral squamous cell carcinoma.

Gene fusion is caused by the linkage of previously separate genes or sequences. Recently, an increasing number of novel fusion genes have been identified and associated with tumor progression, and several of them have been suggested as promising targets for tumor therapy. However, there are hardly any studies reporting the association of fusion genes with the progression of oral squamous cell carcinoma (OSCC). In this study, we identified a total of 11 fused genes in OSCC cells. We further analyzed the structure of one fused gene, TRIM52-RACK1, and detected its function in tumor progression in vitro. We found that TRIM52-RACK1 was caused by a deletion of 181,257,187-181,247,386 at 5q35.3 and it promoted OSCC cell proliferation, migration, and invasion. Therefore, TRIM52-RACK1 can be a promising target for tumor therapy in OSCC.

Genetic boundaries delineate the potential human pathogen Salmonella bongori into discrete lineages: divergence and speciation.

BACKGROUND: Salmonella bongori infect mainly cold-blooded hosts, but infections by S. bongori in warm-blooded hosts have been reported. We hypothesized that S. bongori might have diverged into distinct phylogenetic lineages, with some being able to infect warm-blooded hosts. RESULTS: To inspect the divergence status of S. bongori, we first completely sequenced the parakeet isolate RKS3044 and compared it with other sequenced S. bongori strains. We found that RKS3044 contained a novel T6SS encoded in a pathogenicity island-like structure, in addition to a T6SS encoded in SPI-22, which is common to all S. bongori strains so far reported. This novel T6SS resembled the SPI-19 T6SS of the warm-blooded host infecting Salmonella Subgroup I lineages. Genomic sequence comparisons revealed different genomic sequence amelioration events among the S. bongori strains, including a unique CTAG tetranucleotide degeneration pattern in RKS3044, suggesting non-overlapping gene pools between RKS3044 and other S. bongori lineages/strains leading to their independent accumulation of genomic variations. We further proved the existence of a clear-cut genetic boundary between RKS3044 and the other S. bongori lineages/strains analyzed in this study. CONCLUSIONS: The warm-blooded host-infecting S. bongori strain RKS3044 has diverged with distinct genomic features from other S. bongori strains, including a novel T6SS encoded in a previously not reported pathogenicity island-like structure and a unique genomic sequence degeneration pattern. These findings alert cautions about the emergence of new pathogens originating from non-pathogenic ancestors by acquiring specific pathogenic traits.

Distinct evolutionary origins of common multi-drug resistance phenotypes in Salmonella typhimurium DT104: a convergent process for adaptation under stress.

Antimicrobial resistance makes pathogenic bacteria hard to control, but little is known about the general processes of resistance gain or loss. Here, we compared distinct S. typhimurium DT104 strains resistant to zero, two, five, or more of the tested antimicrobials. We found that common resistance phenotypes could be encoded by distinct genes, on SGI-1 or plasmid. We also demonstrated close clonality among all the tested non-resistant and differently resistant DT104 strains, demonstrating dynamic acquisition or loss (by total deletion or gradual decaying of multi-drug resistance gene clusters) of the genetic traits. These findings reflect convergent processes to make the bacteria resistant to multiple antimicrobials by acquiring the needed traits from stochastically available origins. When the antimicrobial stress is absent, the resistance genes may be dropped off quickly, so the bacteria can save the cost for maintaining unneeded genes. Therefore, this work reiterates the importance of strictly controlled use of antimicrobials.

Dorzagliatin (HMS5552), a novel dual-acting glucokinase activator, improves glycaemic control and pancreatic ß-cell function in patients with type 2 diabetes: A 28-day treatment study using biomarker-guided patient selection.

AIMS: To investigate the pharmacokinetics and pharmacodynamics of a dual-acting glucokinase activator, dorzagliatin, and its safety, tolerability and effect on pancreatic ß-cell function in Chinese patients with type 2 diabetes (T2D). MATERIALS AND METHODS: A total of 24 T2D patients were selected, utilizing a set of predefined clinical biomarkers, and were randomized to receive dorzagliatin 75 mg twice or once daily (BID, QD respectively) for 28 days. Changes in HbA1c and glycaemic parameters from baseline to Day 28 were assessed. In addition, changes in ß-cell function from baseline to Day 32 were evaluated. RESULTS: Significant reductions in HbA1c were observed in both regimens on Day 28 (-0.79%, 75 mg BID; -1.22%, 75 mg QD). Similar trends were found in the following parameters, including reductions from baseline in fasting plasma glucose by 1.20 mmol/L and 1.51 mmol/L, in 2-hour postprandial glucose by 2.48 mmol/L and 5.03 mmol/L, and in glucose AUC0-24 by 18.59% and 20.98%, for the BID and QD groups, respectively. Both regimens resulted in improvement in ß-cell function as measured by steady state HOMA 2 parameter, %B, which increased by 36.31% and 40.59%, and by dynamic state parameter, ΔC30 /ΔG30 , which increased by 24.66% and 167.67%, for the BID and QD groups, respectively. Dorzagliatin was well tolerated in both regimens, with good pharmacokinetic profiles. CONCLUSIONS: Dorzagliatin treatment for 28 days in Chinese T2D patients, selected according to predefined biomarkers, resulted in significant improvement in ß-cell function and glycaemic control. The safety and pharmacokinetic profile of dorzagliatin supports a subsequent Phase II trial design and continued clinical development.

Serum atrial natriuretic peptide (ANP) as an objective indicator for the diagnosis of neurogenic shock: animal experiment and human case report.

In forensic medicine, the diagnosis of death due to neurogenic shock is considered to be an aporia, as lacking objective indicators and presenting atypical symptoms in autopsy. Medico-legal disputes and complaints occasionally result from this ambiguity. To explore potential objective indicators of neurogenic shock, we set up a model of neurogenic shock by applying an external mechanical force on the carotid sinus baroreceptor in rabbits. The serum atrial natriuretic peptide (ANP) level was measured by radioimmunoassay in the control group (n = 8), survival group (n = 15) and death group (n = 5) both before and after the insult. The serum ANP level showed a significant increase after the insult in the death group compared with the serum obtained before the insult (P = 0.006), while the serum ANP level after the insult in the survival group and control group was not statistically significant compared with the serum obtained before the insult (P = 0.332 and P = 0.492, respectively). To verify the repeatability of the model and the postmortem behavior of serum ANP, five healthy adult rabbits underwent the same procedure as the experimental group. The mortality rate was consistent with the former experiment (20 %). There were no significant changes in serum ANP level in vitro and in vivo (within 48 and 24 h, respectively). But there was a significant decrease in serum ANP level at 48 h postmortem in vivo (P = 0.001). A female patient who expired due to neurogenic shock during a hysteroscopy was reported. Neither fatal primary disease nor evidence for mechanical injuries or intoxication was found according to the autopsy. The serum ANP level was assayed as a supplementary indicator and was found to be three-fold higher than the normal maximum limit. Combined with the animal experiment, this case highlights that serum ANP has the potential to be an objective indicator for the diagnosis of death due to neurogenic shock.

Differential efficiency in exogenous DNA acquisition among closely related Salmonella strains: implications in bacterial speciation.

BACKGROUND: Acquisition of exogenous genetic material is a key event in bacterial speciation. It seems reasonable to assume that recombination of the incoming DNA into genome would be more efficient with higher levels of relatedness between the DNA donor and recipient. If so, bacterial speciation would be a smooth process, leading to a continuous spectrum of genomic divergence of bacteria, which, however, is not the case as shown by recent findings. The goal of this study was todetermine if DNA transfer efficiency is correlated with the levels of sequence identity. RESULTS: To compare the relative efficiency of exogenous DNA acquisition among closely related bacteria, we carried out phage-mediated transduction and plasmid-mediated transformation in representative Salmonella strains with different levels of relatedness. We found that the efficiency was remarkably variable even among genetically almost identical bacteria. Although there was a general tendency that more closely related DNA donor-recipient pairs had higher transduction efficiency, transformation efficiency exhibited over a thousand times difference among the closely related Salmonella strains. CONCLUSION: DNA acquisition efficiency is greatly variable among bacteria that have as high as over 99% identical genetic background, suggesting that bacterial speciation involves highly complex processes affected not only by whether beneficial exogenous DNA may exist in the environment but also the "readiness" of the bacteria to accept it.

Results of a phase III clinical trial with an HBsAg-HBIG immunogenic complex therapeutic vaccine for chronic hepatitis B patients: experiences and findings.

BACKGROUND & AIMS: Even though various experimental therapeutic approaches for chronic hepatitis B infection have been reported, few of them have been verified by clinical trials. We have developed an antigen-antibody (HBsAg-HBIG) immunogenic complex therapeutic vaccine candidate with alum as adjuvant (YIC), aimed at breaking immune tolerance to HBV by modulating viral antigen processing and presentation. A double-blind, placebo-controlled, phase II B clinical trial of YIC has been reported previously, and herein we present the results of the phase III clinical trial of 450 patients. METHODS: Twelve doses of either YIC or alum alone as placebo were administered randomly to 450 CHB patients and they were followed for 24weeks after the completion of immunization. The primary end point was HBeAg seroconversion, and the secondary end points were decrease in viral load, improvement of liver function, and histology. RESULTS: In contrast to the previous phase II B trial using six doses of YIC and alum as placebo, six more injections of YIC or alum resulted in a decrease of the HBeAg seroconversion rate from 21.8% to 14.0% in the YIC group, but an increase from 9% to 21.9% in the alum group. Decrease in serum HBV DNA and normalization of liver function were similar in both groups (p>0.05). CONCLUSIONS: Overstimulation with YIC did not increase but decreased its efficacy due to immune fatigue in hosts. An appropriate immunization protocol should be explored and is crucial for therapeutic vaccination. Multiple injections of alum alone could have stimulated potent inflammatory and innate immune responses contributing to its therapeutic efficacy, and needs further investigation.

Genomic comparison of Salmonella typhimurium DT104 with non-DT104 strains.

DT104 emerged as a new branch of Salmonella typhimurium with resistance to multiple antimicrobials. To reveal some general genomic features of DT104 for clues of evolutionary events possibly associated with the emergence of this relatively new type of this pathogen, we mapped 11 independent DT104 strains and compared them with non-DT104 S. typhimurium strains. We found that all 11 DT104 strains contained three insertions absent in non-DT104 strains, i.e., the previously reported ST104, ST104B and ST64B. However, SGI-1, a genomic island known to be responsible for DT104 multidrug resistance, was not present in all DT104 strains examined in this study: one DT104 strain did not contain SGI-1 but carried a 144 kb plasmid, suggesting possible evolutionary relationships between the two DNA elements in the development of antimicrobial resistance.

Double-bundle reconstruction results in superior clinical outcome than single-bundle reconstruction.

PURPOSE: To compare the short- and long-term clinical outcomes of the double-bundle (DB) anterior cruciate ligament (ACL) reconstruction with those of single-bundle (SB) ACL reconstruction. METHODS: An electronic search of the database PubMed (1966-September 2011), EMBASE (1984-September 2011), and Cochrane Controlled Trials Register (CENTRAL; 3rd Quarter, 2011) was undertaken to identify relevant studies. Main clinical outcomes were knee stability measurements including KT-1000 arthrometer measurement, Pivot shift test, and Lachman test, and clinical outcome measurements including International Knee Documentation Committee (IKDC), Lysholm knee score, Tegner activity score, and complications. RESULTS: Eighteen studies were finally included in this meta-analysis, which were all classified as high risk of bias according to the Collaboration's recommended tool. It is seen that compared to SB ACL reconstruction, DB ACL reconstruction results in a KT-1000 arthrometer outcome 0.63 and 1.00 mm closer to the normal knee in a short- and long-term follow-up, respectively. Our results also reveal that DB-treated patients have a significantly higher negative rate of the pivot shift test (p < 0.00001 and = 0.006 in a short- and long-term follow-up, respectively) and Lachman test (n.s. and p < 0.0001 in a short- and long-term follow-up, respectively) compared to SB-treated patients. As for the clinical outcome measurements, a significant difference is found between SB versus DB ACL reconstruction regarding the IKDC (p = 0.006 and < 0.0001 in a short- and long-term follow-up, respectively) and complications (p = 0.03), while there is no significant difference between the two groups regarding Lysholm knee score (n.s.) and Tegner activity score (n.s.). CONCLUSION: Overall, double-bundle ACL reconstruction yields better clinical outcomes when compared to single-bundle ACL reconstruction. LEVELS OF EVIDENCE: II.

The type VI secretion system gene cluster of Salmonella typhimurium: required for full virulence in mice.

Type VI secretion system (T6SS) has increasingly been believed to participate in the infection process for many bacterial pathogens, but its role in the virulence of Salmonella typhimurium remains unclear. To look into this, we deleted the T6SS cluster from the genome of S. typhimurium 14028s and analyzed the phenotype of the resulting T6SS knockout mutant (T6SSKO mutant) in vitro and in vivo. We found that the T6SSKO mutant exhibited reduced capability in colonizing the spleen and liver in an in vivo colonization competition model in BALB/c mice infected by the oral route. Additionally, infection via intraperitoneal administration also showed that the T6SSKO mutant was less capable of colonizing the mouse spleen and liver than the wild-type strain. We did not detect significant differences between the T6SSKO and wild-type strains in epithelial cell invasion tests. However, in the macrophage RAW264.7 cell line, the T6SSKO mutant survived and proliferated significantly more poorly than the wild-type strain. These findings indicate that T6SS gene cluster is required for full virulence of S. typhimurium 14028s in BALB/c mice, possibly due to its roles in bacterial survival and proliferation in macrophages.

Complete genome sequence of Salmonella enterica serovar pullorum RKS5078.

Salmonella enterica serovar Pullorum is a chicken-adapted pathogen, causing pullorum disease. Its strict host adaptation has been suspected to result in gene decay. To validate this hypothesis and identify the decayed genes, we sequenced the complete genome of S. Pullorum RKS5078. We found 263 pseudogenes in this strain and conducted functional analyses of the decayed genes.

Sudapyridine (WX-081), a Novel Compound against Mycobacterium tuberculosis.

Bedaquiline (BDQ) was historically listed by the World Health Organization (WHO) in 2018 as the preferred option for rifampin-resistant tuberculosis (RR-TB) and multidrug-resistant tuberculosis (MDR-TB). However, when there is no other effective regimen, the side effects and weaknesses of BDQ limit its use of MDR-TB. There is a black box warning in the package insert of BDQ to warn patients and health care professionals that this drug may increase the risk of unexplained mortality and QT prolongation, which may lead to abnormal and potentially fatal cardiac rhythm. In addition, the phenomenon of elevated liver enzymes in clinical trials of BDQ is a potential sign of hepatotoxicity. Therefore, it is still a medical need to develop new compounds with better safety profiles, patient compliance, affordability, and the ability to retain the efficacy of BDQ. After extensive lead generation and optimization, a new analog, sudapyridine (WX-081), was selected as a potential new antituberculosis candidate to move into clinical trials. Here, we evaluated WX-081's overall preclinical profile, including efficacy, pharmacokinetics, and toxicology. The in vitro activity of WX-081 against drug-sensitive and drug-resistant tuberculosis was comparable to that of BDQ, and there was comparable efficacy between WX-081 and BDQ in both acute and chronic mouse tuberculosis models using low-dose aerosol infection. Moreover, WX-081 improved pharmacokinetic parameters and, more importantly, had no adverse effects on blood pressure, heart rate, or qualitative ECG parameters from nonclinical toxicology studies. WX-081 is under investigation in a phase 2 study in patients. IMPORTANCE This study is aimed at chemotherapy for multidrug-resistant tuberculosis (MDR-TB), mainly to develop new anti-TB drugs to kill Mycobacterium tuberculosis, a microorganism with strong drug resistance. In this study, the structure of a potent antituberculosis compound, bedaquiline (BDQ), was optimized to generate a new compound, sudapyridine (WX-081). This experiment showed that its efficacy was similar to that of BDQ, its cardiotoxicity was lower, and it had good kinetic characteristics. This compound will certainly achieve significant results in the control and treatment of tuberculosis in the future.

A case of a death caused by an atrial-oesophageal-thoracic fistula after radiofrequency ablation of atrial fibrillation.

The report is about a 49-year-old man with rheumatic heart disease and atrial fibrillation. He underwent mitral valve replacement, tricuspid valvuloplasty, and atrial fibrillation radiofrequency ablation in the hospital. He vomited blood on the 2nd postoperative day, and the bleeding gradually worsened thereafter. He had to have repeated drainage of large amounts of blood from his right thoracic cavity and digestive tract. He died suddenly after undergoing an oesophageal endoscopy on the 24th postoperative day. The autopsy revealed an atrial-oesophageal-thoracic fistula. By excluding the possibility of the fistula being caused by complications from nasoenteric feeding, tracheal intubation, and a foreign body ingestion, we determined that the atrial-oesophageal-thoracic fistula was a complication after radiofrequency ablation according to the finding of coagulation necrosis of the myocardial cells at the left atrium fistula. In addition, we also performed an elemental analysis on the radiofrequency ablation area and other cardiac tissues by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and found five metal elements, Cr, Cu, Zn, Mn, and Ti, which specifically existed in the radiofrequency ablation area. This finding has the potential to serve as new evidence for radiofrequency ablation and is a worthy direction of research.

Semi-mechanistic population pharmacokinetics analysis reveals distinct CYP2C19 dependency in the bioactivation of vicagrel and clopidogrel to active metabolite M15-2.

AIMS: Vicagrel is a novel antiplatelet drug used to mitigate clopidogrel resistance due to CYP2C19 polymorphism. This study aimed to develop a semi-mechanistic population pharmacokinetic (PopPK) model to characterize the pharmacokinetic (PK) profile of M15-2, the active metabolite of vicagrel and clopidogrel, and to evaluate the influence of CYP2C19 polymorphisms and other covariates in healthy subjects and patients with acute coronary syndrome (ACS) after oral administration. METHODS: The analysis utilized data from 213 subjects, including 178 healthy subjects and 35 patients, from five clinical trials. PopPK modeling and simulation were used to estimate PopPK parameters and evaluate the impact of covariates. RESULTS: The M15-2 PK profiles were well characterized by a model incorporating transit compartments, two-compartment parent models and two-compartment M15-2 models for both vicagrel and clopidogrel. The parameter estimates indicated the dose fraction of vicagrel that formed M15-2 was approximately 20-fold that of clopidogrel. Covariate analysis identified a significant effect of CYP2C19 on M15-2 apparent clearance (CL/F) and apparent volume of distribution (V3/F) for clopidogrel but only CL/F for vicagrel. The analysis suggested that the nonlinear PK of M15-2 for clopidogrel was due the first-step bioactivation of clopidogrel to 2-oxoclopidogrel. CONCLUSION: The model illustrated the bioactivation of vicagrel is more efficient and less dependent on CYP2C19 than that of clopidogrel. M15-2 is formed in a linear process from vicagrel, versus a nonlinear and less predictable process from clopidogrel. Advantages in both PK and pharmacogenetics suggest that vicagrel may reduce the complexity of currently recommended CYP2C19-based dosage adjustment for clopidogrel.

[Brown adipose tissue in human and its potential physiological significance].

Brown adipose tissue (BAT) plays an important role in nonshiverthing thermogenesis, thermoregulation and body mass regulation in small mammals. However, in human, the presence of brown adipose tissue was thought to be relevant only in infants, with negligible physiologic relevance in adult. Recently, using 18F-fluorodeoxyglucose (18F-FDG) positron-emission tomographic and computed tomographic (PET-CT) scans showed that adults retain metabolically active BAT depots that can be induced in response to cold and sympathetic nervous system activation. These findings highlight BAT as a potential relevant target for pharmacological and gene expression manipulation to combat human obesity. We reviewed the recent research progresses of BAT in human and its potential functional significance.

Patient pathway analysis of tuberculosis diagnostic delay: a multicentre retrospective cohort study in China.

OBJECTIVES: Delay in diagnosis of tuberculosis (TB) is an important but under-appreciated problem. Our study aimed to analyse the patient pathway and possible risk factors of long diagnostic delay (LDD). METHODS: We enrolled 400 new bacteriologically diagnosed patients with pulmonary TB from 20 hospitals across China. LDD was defined as an interval between the initial care visit and the confirmation of diagnosis exceeding 14 days. Its potential risk factors were investigated by multivariate logistic regression and multilevel logistic regression. Hospitals in China were classified by increasing size, from level 0 to level 3. TB laboratory equipment in hospitals was also evaluated. RESULTS: The median diagnostic delay was 20 days (IQR: 7-72 days), and 229 of 400 patients (57.3%, 95%CI 52.4-62.1) had LDD; 15% of participants were diagnosed at the initial care visit. Compared to level 0 facilities, choosing level 2 (OR 0.27, 95%CI 0.12-0.62, p 0.002) and level 3 facilities (OR 0.34, 95%CI 0.14-0.84, p 0.019) for the initial care visit was independently associated with shorter LDD. Equipping with smear, culture, and Xpert at initial care visit simultaneously also helped to avoid LDD (OR 0.28, 95%CI 0.09-0.82, p 0.020). The multilevel logistic regression yielded similar results. Availability of smear, culture, and Xpert was lower in level 0-1 facilities than in level 2-3 facilities (p < 0.001, respectively). CONCLUSIONS: Most patients failed to be diagnosed at the initial care visit. Patients who went to low-level facilities initially had a higher risk of LDD. Improvement of TB laboratory equipment, especially at low-level facilities, is urgently needed.

SPC-P1: a pathogenicity-associated prophage of Salmonella paratyphi C.

BACKGROUND: Salmonella paratyphi C is one of the few human-adapted pathogens along with S. typhi, S. paratyphi A and S. paratyphi B that cause typhoid, but it is not clear whether these bacteria cause the disease by the same or different pathogenic mechanisms. Notably, these typhoid agents have distinct sets of large genomic insertions, which may encode different pathogenicity factors. Previously we identified a novel prophage, SPC-P1, in S. paratyphi C RKS4594 and wondered whether it might be involved in pathogenicity of the bacteria. RESULTS: We analyzed the sequence of SPC-P1 and found that it is an inducible phage with an overall G+C content of 47.24%, similar to that of most Salmonella phages such as P22 and ST64T but significantly lower than the 52.16% average of the RKS4594 chromosome. Electron microscopy showed short-tailed phage particles very similar to the lambdoid phage CUS-3. To evaluate its roles in pathogenicity, we lysogenized S. paratyphi C strain CN13/87, which did not have this prophage, and infected mice with the lysogenized CN13/87. Compared to the phage-free wild type CN13/87, the lysogenized CN13/87 exhibited significantly increased virulence and caused multi-organ damages in mice at considerably lower infection doses. CONCLUSIONS: SPC-P1 contributes pathogenicity to S. paratyphi C in animal infection models, so it is possible that this prophage is involved in typhoid pathogenesis in humans. Genetic and functional analyses of SPC-P1 may facilitate the study of pathogenic evolution of the extant typhoid agents, providing particular help in elucidating the pathogenic determinants of the typhoid agents.

Physiological and biochemical basis of basal metabolic rates in Brandt's voles (Lasiopodomys brandtii) and Mongolian gerbils (Meriones unguiculatus).

Basal metabolic rate (BMR) has been shown to be a highly flexible phenotypic trait both between and within species, but the physiological, biochemical and molecular mechanisms are still unclear. Brandt's voles (Lasiopodomys brandtii) and Mongolian gerbils (Meriones unguiculatus) are two sympatric rodent species in Inner Mongolian grasslands of China. It has been shown that Brandt's voles have higher metabolic rate than Mongolian gerbils. In this study, we elucidated the inter-specific variation in BMR integratively from the molecular levels to whole organism. Our results showed that differences in organ mass were not good predictors for the observed variations in BMR, while variations in the activity of thyroid hormones and the metabolic biochemical markers of tissues, such as mitochondria density, cytochrome c oxidase activity and state 4 respiration, were strongly correlated with variations in BMR, and there was also a positive relationship between residuals of T(3)/T(4) and state 4 respiration, suggesting that thyroid hormones play an important role in the determination of BMR variations.