Simultaneous creatine and phosphocreatine mapping of skeletal muscle by CEST MRI at 3T.

PURPOSE: To confirm that CrCEST in muscle exhibits a slow-exchanging process, and to obtain high-resolution amide, creatine (Cr), and phosphocreatine (PCr) maps of skeletal muscle using a POlynomial and Lorentzian Line-shape Fitting (PLOF) CEST at 3T. METHODS: We used dynamic changes in PCr/CrCEST of mouse hindlimb before and after euthanasia to assign the Cr and PCr CEST peaks in the Z-spectrum at 3T and to obtain the optimum saturation parameters. Segmented 3D EPI was employed to obtain multi-slice amide, PCr, and Cr CEST maps of human skeletal muscle. Subsequently, the PCrCEST maps were calibrated using the PCr concentrations determined by 31 P MRS. RESULTS: A comparison of the Z-spectra in mouse hindlimb before and after euthanasia indicated that CrCEST is a slow-exchanging process in muscle (<150.7 s-1 ). This allowed us to simultaneously extract PCr/CrCEST signals at 3T using the PLOF method. We determined optimal B1 values ranging from 0.3 to 0.6 µT for CrCEST in muscle and 0.3-1.2 µT for PCrCEST. For the study on human calf muscle, we determined an optimum saturation time of 2 s for both PCr/CrCEST (B1 = 0.6 µT). The PCr/CrCEST using 3D EPI were found to be comparable to those obtained using turbo spin echo (TSE). (3D EPI/TSE PCr: (2.6 ± 0.3) %/(2.3 ± 0.1) %; Cr: (1.3 ± 0.1) %/(1.4 ± 0.07) %). CONCLUSIONS: Our study showed that in vivo CrCEST is a slow-exchanging process. Hence, amide, Cr, and PCr CEST in the skeletal muscle can be mapped simultaneously at 3T by PLOF CEST.

A rapid method for phosphocreatine-weighted imaging in muscle using double saturation power-chemical exchange saturation transfer.

Monitoring the variation in phosphocreatine (PCr) levels following exercise provides valuable insights into muscle function. Chemical exchange saturation transfer (CEST) has emerged as a sensitive method with which to measure PCr levels in muscle, surpassing conventional MR spectroscopy. However, existing approaches for quantifying PCr CEST signals rely on time-consuming fitting methods that require the acquisition of the entire or a section of the CEST Z-spectrum. Additionally, traditional fitting methods often necessitate clear CEST peaks, which may be challenging to obtain at low magnetic fields. This paper evaluated the application of a new model-free method using double saturation power (DSP), termed DSP-CEST, to estimate the PCr CEST signal in muscle. The DSP-CEST method requires the acquisition of only two or a few CEST signals at the PCr frequency offset with two different saturation powers, enabling rapid dynamic imaging. Additionally, the DSP-CEST approach inherently eliminates confounding signals, offering enhanced robustness compared with fitting methods. Furthermore, DSP-CEST does not demand clear CEST peaks, making it suitable for low-field applications. We evaluated the capability of DSP-CEST to enhance the specificity of PCr CEST imaging through simulations and experiments on muscle tissue phantoms at 4.7 T. Furthermore, we applied DSP-CEST to animal leg muscle both before and after euthanasia and observed successful reduction of confounding signals. The DSP-CEST signal still has contaminations from a residual magnetization transfer (MT) effect and an aromatic nuclear Overhauser enhancement effect, and thus only provides a PCr-weighted imaging. The residual MT effect can be reduced by a subtraction of DSP-CEST signals at 2.6 and 5 ppm. Results show that the residual MT-corrected DSP-CEST signal at 2.6 ppm has significant variation in postmortem tissues. By contrast, both the CEST signal at 2.6 ppm and a conventional Lorentzian difference analysis of CEST signal at 2.6 ppm demonstrate no significant variation in postmortem tissues.

Insights into mitochondrial creatine kinase: examining preventive role of creatine supplement in doxorubicin-induced cardiotoxicity.

Doxorubicin (Dox) is an effective and commonly used anticancer drug; however, it leads to several side effects including cardiotoxicity which contributes to poor quality of life for cancer patients. Creatine (Cr) is a promising intervention to alleviate Dox-induced cardiotoxicity. This study aimed to examine the effects of Cr beforeDox on cardiac mitochondrial creatine kinase (MtCK). Male rats were randomly assigned to one of two 4-week Cr feeding interventions (standard Cr diet or Cr loading diet) or a control diet (Con, n = 20). Rats in the standard Cr diet (Cr1, n = 20) were fed 2% Cr for 4-weeks. Rats in the Cr loading diet (Cr2, n = 20) were fed 4% Cr for 1-week followed by 2% Cr for 3-weeks. After 4-weeks, rats received either a bolus injection of 15 mg/kg Dox or a placebo saline injection (Sal). Five days post-injections left ventricle (LV) was excised and analyzed for MtCK expression using Western blot and ELISA. A significant drug effect was observed for LV mass (p < 0.05), post hoc testing revealed LV mass of Con + Dox and Cr2 + Dox was significantly lower than Con + Sal (p < 0.05). A significant drug effect was observed for MtCK (p = 0.03) through Western blot. A significant drug effect (p = 0.03) and interaction (p = 0.02) was observed for MtCK using ELISA. Post hoc testing revealed that Cr2 + Dox had significantly higher MtCK than Cr1 + Sal and Cr2 + Sal. Data suggest that a reduction in LV mass and MtCK may contribute to Dox-induced cardiotoxicity, and Cr supplementation may play a potential role in mitigating cardiotoxicity by preserving mitochondrial CK.

Aspects of human uterine creatine metabolism during the menstrual cycle and at term pregnancy†.

Creatine metabolism likely contributes to energy homeostasis in the human uterus, but whether this organ synthesizes creatine and whether creatine metabolism is adjusted throughout the menstrual cycle and with pregnancy are largely unknown. This study determined endometrial protein expression of creatine-synthesizing enzymes arginine:glycine amidinotransferase (AGAT) and guanidinoacetate methyltransferase (GAMT), creatine kinase (CKBB), and the creatine transporter (SLC6A8) throughout the menstrual cycle in fertile and primary infertile women. It also characterized creatine metabolism at term pregnancy, measuring aspects of creatine metabolism in myometrial and decidual tissue. In endometrial samples, AGAT, GAMT, SLC6A8, and CKBB were expressed in glandular and luminal epithelial cells. Except for SLC6A8, the other proteins were also located in stromal cells. Irrespective of fertility, AGAT, GAMT, and SLC6A8 high-intensity immunohistochemical staining was greatest in the early secretory phase of the menstrual cycle. During the proliferative phase, staining for SLC6A8 protein was greater (P = 0.01) in the primary infertile compared with the fertile group. Both layers of the term pregnant uterus contained creatine, phosphocreatine, guanidinoacetic acid, arginine, glycine, and methionine; detectable gene and protein expression of AGAT, GAMT, CKBB, and ubiquitous mitochondrial CK (uMt-CK); and gene expression of SLC6A8. The proteins AGAT, GAMT, CKBB, and SLC6A8 were uniformly distributed in the myometrium and localized to the decidual glands. In conclusion, endometrial tissue has the capacity to produce creatine and its capacity is highest around the time of fertilization and implantation. Both layers of the term pregnant uterus also contained all the enzymatic machinery and substrates of creatine metabolism.

Chemical exchange saturation transfer imaging of creatine, phosphocreatine, and protein arginine residue in tissues.

Chemical exchange saturation transfer (CEST) MRI has become a promising technique to assay target proteins and metabolites through their exchangeable protons, noninvasively. The ubiquity of creatine (Cr) and phosphocreatine (PCr) due to their pivotal roles in energy homeostasis through the creatine phosphate pathway has made them prime targets for CEST in the diagnosis and monitoring of disease pathologies, particularly in tissues heavily dependent on the maintenance of rich energy reserves. Guanidinium CEST from protein arginine residues (i.e. arginine CEST) can also provide information about the protein profile in tissue. However, numerous obfuscating factors stand as obstacles to the specificity of arginine, Cr, and PCr imaging through CEST, such as semisolid magnetization transfer, fast chemical exchanges such as primary amines, and the effects of nuclear Overhauser enhancement from aromatic and amide protons. In this review, the specific exchange properties of protein arginine residues, Cr, and PCr, along with their validation, are discussed, including the considerations necessary to target and tune their signal effects through CEST imaging. Additionally, strategies that have been employed to enhance the specificity of these exchanges in CEST imaging are described, along with how they have opened up possible applications of protein arginine residues, Cr and PCr CEST imaging in the study and diagnosis of pathology. A clear understanding of the capabilities and caveats of using CEST to image these vital metabolites and mitigation strategies is crucial to expanding the possibilities of this promising technology.

Quantitative Assessment of Peripheral Oxidative Metabolism With a New Dynamic 1 H MRI Technique: A Pilot Study in People With and Without Diabetes Mellitus.

BACKGROUND: Type 2 diabetes mellitus (T2DM) is linked to impaired mitochondrial function. Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) is a gadolinium-contrast-free 1 H method to assess mitochondrial function by measuring low-concentration metabolites. A CEST MRI-based technique may serve as a non-invasive proxy for assessing mitochondrial health. HYPOTHESIS: A 1 H CEST MRI technique may detect significant differences in in vivo skeletal muscle phosphocreatine (SMPCr) kinetics between healthy volunteers and T2DM patients undergoing standardized isometric exercise. STUDY TYPE: Cross-sectional study. SUBJECTS: Seven subjects without T2DM (T2DM-) and seven age, sex, and BMI-matched subjects with T2DM (T2DM+). FIELD STRENGTH/SEQUENCE: Single-shot rapid acquisition with refocusing echoes (RARE) and single-shot gradient-echo sequences, 3 T. ASSESSMENT: Subjects underwent a rest-exercise-recovery imaging protocol to dynamically acquire SMPCr maps in calf musculature. Medial gastrocnemius (MG) and soleus SMPCr concentrations were plotted over time, and SMPCr recovery time, τ $$ \tau $$ , was determined. Mitochondrial function index was calculated as the ratio of resting SMPCr to τ $$ \tau $$ . Participants underwent a second exercise protocol for imaging of skeletal muscle blood flow (SMBF), and its association with SMPCr was assessed. STATISTICAL TESTS: Unpaired t-tests and Pearson correlation coefficient. A P value <0.05 was considered statistically significant. RESULTS: SMPCr concentrations in MG and soleus displayed expected declines during exercise and returns to baseline during recovery. τ $$ \tau $$ was significantly longer in the T2DM+ cohort (MG 83.5 ± 25.8 vs. 54.0 ± 21.1, soleus 90.5 ± 18.9 vs. 51.2 ± 14.5). The mitochondrial function index in the soleus was significantly lower in the T2DM+ cohort (0.33 ± 0.08 vs. 0.66 ± 0.19). SMBF was moderately correlated with the SMPCr in T2DM-; this correlation was not significant in T2DM+ (r = -0.23, P = 0.269). CONCLUSION: The CEST MRI method is feasible for quantifying SMPCr in peripheral muscle tissue. T2DM+ individuals had significantly lower oxidative capacities than T2DM- individuals. In T2DM, skeletal muscle metabolism appeared to be decoupled from perfusion. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 1.

Effect of recovery time on [Formula: see text]-ON kinetics in humans at the onset of moderate-intensity cycling exercise.

PURPOSE: τ of the primary phase of [Formula: see text] kinetics during square-wave, moderate-intensity exercise mirrors that of PCr splitting (τPCr). Pre-exercise [PCr] and the absolute variations of PCr (∆[PCr]) occurring during transient have been suggested to control τPCr and, in turn, to modulate [Formula: see text] kinetics. In addition, [Formula: see text] kinetics may be slower when exercise initiates from a raised metabolic level, i.e., from a less-favorable energetic state. We verified the hypothesis that: (i) pre-exercise [PCr], (ii) pre-exercise metabolic rate, or (iii) ∆[PCr] may affect the kinetics of muscular oxidative metabolism and, therefore, τ. METHODS: To this aim, seven active males (23.0 yy ± 2.3; 1.76 m ± 0.06, [Formula: see text]: 3.32 L min-1 ± 0.67) performed three repetitions of series consisting of six 6-min step exercise transitions of identical workload interspersed with different times of recovery: 30, 60, 90, 120, 300 s. RESULTS: Mono-exponential fitting was applied to breath-by-breath [Formula: see text], so that τ was determined. τ decays as a first-order exponential function of the time of recovery (τ = 109.5 × e(-t/14.0) + 18.9 r2 = 0.32) and linearly decreased as a function of the estimated pre-exercise [PCr] (τ = - 1.07 [PCr] + 44.9, r2 = 0.513, P < 0.01); it was unaffected by the estimated ∆[PCr]. CONCLUSIONS: Our results in vivo do not confirm the positive linear relationship between τ and pre-exercise [PCr] and ∆[PCr]. Instead, [Formula: see text] kinetics seems to be influenced by the pre-exercise metabolic rate and the altered intramuscular energetic state.

Myocardial protection with phosphocreatine in high-risk cardiac surgery patients: a randomized trial.

BACKGROUND: This study was conducted to test the hypothesis that phosphocreatine (PCr), administered intravenously and as cardioplegia adjuvant in patients undergoing cardiac surgery with prolonged aortic cross clamping and cardiopulmonary bypass (CPB) time, would decrease troponin I concentration after surgery. METHODS: In this randomized, double-blind, placebo-controlled pilot study we included 120 patients undergoing double/triple valve repair/replacement under cardiopulmonary bypass in the cardiac surgery department of a tertiary hospital. The treatment group received: intravenous administration of 2 g of PCr after anesthesia induction; 2.5 g of PCr in every 1 L of cardioplegic solution (concentration = 10 mmol/L); intravenous administration of 2 g of PCr immediately after heart recovery following aorta declamping; 4 g of PCr at intensive care unit admission. The control group received an equivolume dose of normosaline. RESULTS: The primary endpoint was peak concentration of troponin I after surgery. Secondary endpoints included peak concentration of serum creatinine, need for, and dosage of inotropic support, number of defibrillations after aortic declamping, incidence of arrhythmias, duration of Intensive Care Unit (ICU) stay, length of hospitalization. There was no difference in peak troponin I concentration after surgery (PCr, 10,508 pg/ml [IQR 6,838-19,034]; placebo, 11,328 pg/ml [IQR 7.660-22.894]; p = 0.24). There were also no differences in median peak serum creatinine (PCr, 100 µmol/L [IQR 85.0-117.0]; placebo, 99.5 µmol/L [IQR 90.0-117.0]; p = 0.87), the number of patients on vasopressor/inotropic agents (PCr, 49 [88%]; placebo, 57 [91%]; p = 0.60), the inotropic score on postoperative day 1 (PCr, 4.0 (0-7); placebo, 4.0 (0-10); p = 0.47), mean SOFA score on postoperative day 1 (PCr, 5.25 ± 2.33; placebo, 5,45 ± 2,65; p = 0.83), need for defibrillation after declamping of aorta (PCr, 22 [39%]; placebo, 25 [40%]; p = 0.9),, duration of ICU stay and length of hospitalization as well as 30-day mortality (PCr, 0 (0%); placebo,1 (4.3%); p = 0.4). CONCLUSION: PCr administration to patients undergoing double/triple valve surgery under cardiopulmonary bypass is safe but is not associated with a decrease in troponin I concentration. Phosphocreatine had no beneficial effect on clinical outcomes after surgery. TRIAL REGISTRATION: The study is registered at ClinicalTrials.gov with the Identifier: NCT02757443. First posted (published): 02/05/2016.

Phosphocreatine addition to extender enhances the quality and antioxidant capacity of cryopreserved boar sperm.

Boar sperm are less resistant to drastic changes in the external environment during cryopreservation, mainly because their plasma membranes are rich in unsaturated fatty acids but lack cholesterol and are thus susceptible to lipid peroxidation caused by the attack of reactive oxygen species. This study evaluated the effect of adding phosphocreatine to cryopreservation extenders on boar sperm quality and antioxidant capacity. Different concentrations (0, 5.0, 7.5, 10.0 and 12.5 mmol/L) of phosphocreatine were added to the cryopreservation extender. After thawing, sperm were analysed for morphological parameters, kinetic parameters, acrosome integrity, membrane integrity, mitochondrial activity, DNA integrity and antioxidant enzyme activity. The results showed that 10.0 mmol/L phosphocreatine samples enhanced the boar sperm motility, viability, average path velocity, straight-line velocity, curvilinear velocity and beat cross frequency after cryopreservation and reduced the malformation rate compared to the control group (p < .05). The acrosome integrity, membrane integrity, mitochondrial activity and DNA integrity of boar sperm were higher than those of the control group after adding 10.0 mmol/L phosphocreatine to the cryopreservation extender (p < .05). Extenders containing 10.0 mmol/L phosphocreatine maintained high total antioxidant capacity; elevated the activities of catalase, glutathione peroxidase and superoxide dismutase; reduced malondialdehyde and H2 O2 content (p < .05). Therefore, adding phosphocreatine to the extender is potentially beneficial for boar sperm cryopreservation at an optimal 10.0 mmol/L concentration.

Protection of Exogenous Phosphocreatine for Myocardium in Percutaneous Coronary Intervention Related to Inflammation.

OBJECTIVES: Although injury of myocardium after percutaneous coronary intervention (PCI) has been reported, the mechanism and effect of exogenous phosphocreatine (PCr) supplementation on the injury are yet to be elucidated. Biomarkers, such as interleukin-6 (IL-6) and variations in white blood cells for inflammation, and serum cardiac troponin I (cTnI) for myocardial injury are examined. METHODS: A total of 105 patients undergoing PCI were included and randomly divided into two groups: control (treated with routine hydration therapy) and PCr (treated with additional intravenous infusion of exogenous PCr). The serum levels of biomarkers were detected at administration and 4, 12, 24, and 48 h after PCI, with natural logarithmic (loge) transformation of data when modeling assumptions were not fulfilled. RESULTS: The level of loge-transformed IL-6 increased in both groups, especially at 12 and 24 h after the operation, and that of PCr group was less than the control group at 48 h. The content of loge-transformed cTnI was significantly increased in both groups, while that of the PCr group was markedly lower than the control group at all time points after PCI. Moreover, the ratio of neutrophils was elevated at all time points after PCI, while that of the PCr group was lower at 48 h, and the variations in the ratio of lymphocytes showed opposite results. CONCLUSIONS: Exogenous phosphocreatine reduces stent implantation, triggers inflammation manifested as decreased serum levels of IL-6 and the aggregation of neutrophils, and protects the myocardium of the patients undergoing PCI. These findings provided the potential mechanism and treatment for myocardial injury associated with PCI.

Protection of pancreatic ß-cell by phosphocreatine through mitochondrial improvement via the regulation of dual AKT/IRS-1/GSK-3ß and STAT3/Cyp-D signaling pathways.

Diabetes mellitus (DM) is a metabolic syndrome, caused by insufficient insulin secretion or insulin resistance (IR). DM enhances oxidative stress and induces mitochondrial function in different kinds of cell types, including pancreatic ß-cells. Our previous study has showed phosphocreatine (PCr) can advance the mitochondrial function through enhancing the oxidative phosphorylation and electron transport ability in mitochondria damaged by methylglyoxal (MG). Our aim was to explore the potential role of PCr as a molecule to protect mitochondria from diabetes-induced pancreatic ß-cell injury with insulin secretion deficiency or IR through dual AKT/IRS-1/GSK-3ß and STAT3/Cyclophilin D (Cyp-D) signaling pathways. MG-induced INS-1 cell viability, apoptosis, mitochondrial division and fusion, the morphology, and function of mitochondria were suppressed. Flow cytometry was used to detect the production of intracellular reactive oxygen species (ROS) and the changes of intracellular calcium, and the respiratory function was measured by oxygraph-2k. The expressions of AKT, IRS-1, GSK-3ß, STAT3, and Cyp-D were detected using Western blot. The result showed that the oxidative stress-related kinases were significantly restored to the normal level after the pretreatment with PCr. Moreover, PCr pretreatment significantly inhibited cell apoptosis, decreased intracellular calcium, and ROS production, and inhibited mitochondrial division and fusion, and increased ATP synthesis damaged by MG in INS-1 cells. In addition, pretreatment with PCr suppressed Cytochrome C, p-STAT3, and Cyp-D expressions, while increased p-AKT, p-IRS-1, p-GSK-3ß, caspase-3, and caspase-9 expressions. In conclusion, PCr has protective effect on INS-1 cells in vitro and in vivo, relying on AKT mediated STAT3/ Cyp-D pathway to inhibit oxidative stress and restore mitochondrial function, signifying that PCr might become an emerging candidate for the cure of diabetic pancreatic cancer ß-cell damage.

Short-Term Creatine Supplementation and Repeated Sprint Ability-A Systematic Review and Meta-Analysis.

The aim of this study was to conduct a systematic review and meta-analysis of the effects of short-term creatine supplementation on repeated sprint ability. Fourteen studies met the inclusion criteria of adopting double-blind randomized placebo-controlled designs in which participants (age: 18-60 years) completed a repeated sprint test (number of sprints: 4 < n ≤ 20; sprint duration: ≤10 s; recovery duration: ≤90 s) before and after supplementing with creatine or placebo for 3-7 days in a dose of ∼20 g/day. No exclusion restrictions were placed on the mode of exercise. Meta-analyses were completed using random-effects models, with effects on measures of peak power output, mean power output, and fatigue (performance decline) during each repeated sprint test presented as standardized mean difference (δ), and with effects on body mass and posttest blood lactate concentration presented as raw mean difference (D). Relative to placebo, creatine resulted in a significant increase in body mass (D = 0.79 kg; p < .00001) and mean power output (δ = 0.61; p = .002). However, there was no effect of creatine on measures of peak power (δ = 0.41; p = .10), fatigue (δ = 0.08; p = .61), or posttest blood lactate concentration (D = 0.22 L/min; p = .60). In conclusion, creatine supplementation may increase mean power output during repeated sprint tests, although the absence of corresponding effects on peak power and fatigue means that more research, with measurements of intramuscular creatine content, is necessary to confirm.

Post-exercise intramuscular O2 supply is tightly coupled with a higher proximal-to-distal ATP synthesis rate in human tibialis anterior.

KEY POINTS: The post-exercise recovery of phosphocreatine, a measure of the oxidative capacity of muscles, as assessed by 31 P MR spectroscopy, shows a striking increase from distal to proximal along the human tibialis anterior muscle. To investigate why this muscle exhibits a greater oxidative capacity proximally, we tested whether the spatial variation in phosphocreatine recovery rate is related to oxygen supply, muscle fibre type or type of exercise. We revealed that oxygen supply also increases from distal to proximal along the tibialis anterior, and that it strongly correlated with phosphocreatine recovery. Carnosine level, a surrogate measure for muscle fibre type was not different between proximal and distal, and type of exercise did not affect the gradient in phosphocreatine recovery rate. Taken together, the findings of this study suggest that the post-exercise spatial gradients in oxygen supply and phosphocreatine recovery are driven by a higher intrinsic mitochondrial oxidative capacity proximally. ABSTRACT: Phosphorus magnetic resonance spectroscopy (31 P MRS) of human tibialis anterior (TA) revealed a strong proximo-distal gradient in the post-exercise phosphocreatine (PCr) recovery rate constant (kPCr ), a measure of muscle oxidative capacity. The aim of this study was to investigate whether this kPCr gradient is related to O2 supply, resting phosphorylation potential, muscle fibre type, or type of exercise. Fifteen male volunteers performed continuous isometric ankle dorsiflexion at 30% maximum force until exhaustion. At multiple locations along the TA, we measured the oxidative PCr resynthesis rate (VPCr = kPCr × PCr depletion) by 31 P MRS, the oxyhaemoglobin recovery rate constant (kO2Hb ) by near infrared spectroscopy, and muscle perfusion with MR intravoxel incoherent motion imaging. The kO2Hb , kPCr , VPCr and muscle perfusion depended on measurement location (P < 0.001, P < 0.001, P = 0.032 and P = 0.003, respectively), all being greater proximally. The kO2Hb and muscle perfusion correlated with kPCr (r = 0.956 and r = 0.852, respectively) and VPCr (r = 0.932 and r = 0.985, respectively), the latter reflecting metabolic O2 consumption. Resting phosphorylation potential (PCr/inorganic phosphate) was also higher proximally (P < 0.001). The surrogate for fibre type, carnosine content measured by 1 H MRS, did not differ between distal and proximal TA (P = 0.884). Performing intermittent exercise to avoid exercise ischaemia, still led to larger kPCr proximally than distally (P = 0.013). In conclusion, the spatial kPCr gradient is strongly associated with the spatial variation in O2 supply. It cannot be explained by exercise-induced ischaemia nor by fibre type. Our findings suggest it is driven by a higher proximal intrinsic mitochondrial oxidative capacity, apparently to support contractile performance of the TA.

Dysfunctional energy metabolisms in fibromyalgia compared with healthy subjects.

This study aimed to investigate the levels of creatine (Cr) metabolites in the anterior cingulate cortex (ACC), thalamus, and insula of patients with fibromyalgia (FM) using proton magnetic resonance spectroscopy (MRS). The levels of Cr and phosphocreatine (PCr) relative to total Cr (tCr), which includes Cr and PCr, in the ACC, thalamus, and insula were determined using MRS in 12 patients with FM and in 13 healthy controls. The FM group had lower levels of PCr/tCr in the ACC and right insula compared to healthy controls. There was a negative correlation between Cr/tCr in the ACC and total pain levels (McGill Pain Questionnaire-Total; r = -0.579, p = 0.049) and between Cr/tCr in the left insula and affective pain levels (McGill Pain Questionnaire-Affective; r = -0.638, p = 0.047) in patients with FM. In addition, there were negative correlations between stress levels (Stress Response Inventory) and Cr/tCr in the right (r = -0.780, p = 0.005) and left thalamus (r = -0.740, p = 0.006), as well as in the right insula (r = -0.631, p = 0.028) in patients with FM. There were negative correlations between symptom levels of post-traumatic stress disorder (PTSD; PTSD checklist) and Cr/tCr in the right (r = -0.783, p = 0.004) and left thalamus (r = -0.642, p = 0.024) of patients with FM. These findings are paramount to understanding the decisive pathologies related to brain energy metabolism in patients with FM.

Quantifying the fractional concentrations and exchange rates of small-linewidth CEST agents using the QUCESOP method under multi-solute conditions in MRI signals.

PURPOSE: To develop a novel method for quantifying the fractional concentration (fb ) and the exchange rate (kb ) of a specific small-linewidth chemical exchange saturation transfer (CEST) solute in the presence of other unknown CEST solutes. THEORY AND METHODS: A simplified R1ρ model was proposed assuming a small linewidth of the specific solute and a linear approximation of the other solutes' contribution to R1ρ . Two modes of CEST data acquisition, using various saturation offsets and various saturation powers, were used. The fb and kb of the specific solute could be fitted using the proposed model. In MRI experiments, using either single-solute or multi-solute phantoms with various creatine concentrations and pHs, the fb and kb values of creatine were calculated for each phantom; the fb and kb values of phosphocreatine in rats' skeletal muscles were also evaluated. RESULTS: The fitted fb value of creatine from the phantoms were in excellent agreement. The fitted kb value of creatine from the phantoms coincides with that from the literature, as do the fb and kb values of phosphocreatine in skeletal muscles. CONCLUSION: The proposed approach enables us to quantify the fb and kb values of a specific small-linewidth solute in the presence of other unknown solutes.

Recovery kinetics of creatine in mild plantar flexion exercise using 3D creatine CEST imaging at 7 Tesla.

PURPOSE: Two-dimensional creatine CEST (2D-CrCEST), with a slice thickness of 10-20 mm and temporal resolution (τRes ) of about 30 seconds, has previously been shown to capture the creatine-recovery kinetics in healthy controls and in patients with abnormal creatine-kinase kinetics following the mild plantar flexion exercise. Since the distribution of disease burden may vary across the muscle length for many musculoskeletal disorders, there is a need to increase coverage in the slice-encoding direction. Here, we demonstrate the feasibility of 3D-CrCEST with τRes of about 30 seconds, and propose an improved voxel-wise B1+ -calibration approach for CrCEST. METHODS: The current 7T study with enrollment of 5 volunteers involved collecting the baseline CrCEST imaging for the first 2 minutes, followed by 2 minutes of plantar flexion exercise and then 8 minutes of postexercise CrCEST imaging, to detect the temporal evolution of creatine concentration following exercise. RESULTS: Very good repeatability of 3D-CrCEST findings for activated muscle groups on an intraday and interday basis was established, with coefficient of variance of creatine recovery constants (τCr ) being 7%-15.7%, 7.5%, and 5.8% for lateral gastrocnemius, medial gastrocnemius, and peroneus longus, respectively. We also established a good intraday and interday scan repeatability for 3D-CrCEST and also showed good correspondence between τCr measurements using 2D-CrCEST and 3D-CrCEST acquisitions. CONCLUSION: In this study, we demonstrated for the first time the feasibility and the repeatability of the 3D-CrCEST method in calf muscle with improved B1+ correction to measure creatine-recovery kinetics within a large 3D volume of calf muscle.

Chemical exchange rotation transfer imaging of phosphocreatine in muscle.

In chemical exchange saturation transfer (CEST) imaging, the signal at 2.6 ppm from the water resonance in muscle has been assigned to phosphocreatine (PCr). However, this signal has limited specificity for PCr since the signal is also sensitive to exchange with protein and macromolecular protons when using some conventional quantification methods, and will vary with changes in the water longitudinal relaxation rate. Correcting for these effects while maintaining reasonable acquisition times is challenging. As an alternative approach to overcome these problems, here we evaluate chemical exchange rotation transfer (CERT) imaging of PCr in muscle at 9.4 T. Specifically, the CERT metric, AREXdouble,cpw at 2.6 ppm, was measured in solutions containing the main muscle metabolites, in tissue homogenates with controlled PCr content, and in vivo in rat leg muscles. PCr dominates CERT metrics around 2.6 ppm (although with nontrivial confounding baseline contributions), indicating that CERT is well-suited to PCr specific imaging, and has the added benefit of requiring a relatively small number of acquisitions.

The Effect of Creatine Supplementation on Markers of Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis of Human Intervention Trials.

This systematic review and meta-analysis examined the effects of creatine supplementation on recovery from exercise-induced muscle damage, and is reported according to the PRISMA guidelines. MEDLINE and SPORTDiscus were searched for articles from inception until April 2020. Inclusion criteria were adult participants (≥18 years); creatine provided before and/or after exercise versus a noncreatine comparator; measurement of muscle function recovery, muscle soreness, inflammation, myocellular protein efflux, oxidative stress; range of motion; randomized controlled trials in humans. Thirteen studies (totaling 278 participants; 235 males and 43 females; age range 20-60 years) were deemed eligible for analysis. Data extraction was performed independently by both authors. The Cochrane Collaboration Risk of Bias Tool was used to critically appraise the studies; forest plots were generated with random-effects model and standardized mean differences. Creatine supplementation did not alter muscle strength, muscle soreness, range of motion, or inflammation at each of the five follow-up times after exercise (<30 min, 24, 48, 72, and 96 hr; p > .05). Creatine attenuated creatine kinase activity at 48-hr postexercise (standardized mean difference: -1.06; 95% confidence interval [-1.97, -0.14]; p = .02) but at no other time points. High (I2; >75%) and significant (Chi2; p < .01) heterogeneity was identified for all outcome measures at various follow-up times. In conclusion, creatine supplementation does not accelerate recovery following exercise-induced muscle damage; however, well-controlled studies with higher sample sizes are warranted to verify these conclusions. Systematic review registration (PROSPERO CRD42020178735).

TNAP: A New Multitask Enzyme in Energy Metabolism.

Tissue-nonspecific alkaline phosphatase (TNAP) is mainly known for its necessary role in skeletal and dental mineralization, which relies on the hydrolysis of the mineralization inhibitor inorganic pyrophosphate (PPi). Mutations in the gene encoding TNAP leading to severe hypophosphatasia result in strongly reduced mineralization and perinatal death. Fortunately, the relatively recent development of a recombinant TNAP with a bone anchor has allowed to correct the bone defects and prolong the life of affected babies and children. Researches on TNAP must however not be slowed down, because accumulating evidence indicates that TNAP activation in individuals with metabolic syndrome (MetS) is associated with enhanced cardiovascular mortality, presumably in relation with cardiovascular calcification. On the other hand, TNAP appears to be necessary to prevent the development of steatohepatitis in mice, suggesting that TNAP plays protective roles. The aim of the present review is to highlight the known or suspected functions of TNAP in energy metabolism that may be associated with the development of MetS. The location of TNAP in liver and its function in bile excretion, lipopolysaccharide (LPS) detoxification and fatty acid transport will be presented. The expression and function of TNAP in adipocyte differentiation and thermogenesis will also be discussed. Given that TNAP is a tissue- and substrate-nonspecific phosphatase, we believe that it exerts several crucial pathophysiological functions that are just beginning to be discovered.

Creatine metabolism in the uterus: potential implications for reproductive biology.

Creatine is an amino acid derivative synthesized from arginine, glycine and methionine. It serves as the substrate for the creatine kinase system, which is vital for maintaining ATP levels in tissues with high and fluctuating energy demand. There exists evidence that the creatine kinase system operates in both the endometrial and myometrial layers of the uterus. While use and regulation of this system in the uterus are not well understood, it is likely to be important given uterine tissues undergo phases of increased energy demand during certain stages of the female reproductive cycle, pregnancy, and parturition. This review discusses known adaptations of creatine metabolism in the uterus during the reproductive cycle (both estrous and menstrual), pregnancy and parturition, highlighting possible links to fertility and the existing knowledge gaps. Specifically, we discuss the adaptations and regulation of uterine creatine metabolite levels, cell creatine transport, de novo creatine synthesis, and creatine kinase expression in the various layers and cell types of the uterus. Finally, we discuss the effects of dietary creatine on uterine metabolism. In summary, there is growing evidence that creatine metabolism is up-regulated in uterine tissues during phases where energy demand is increased. While it remains unclear how important these adaptations are in the maintenance of healthy uterine function, furthering our understanding of uterine creatine metabolism may uncover strategies to combat poor embryo implantation and failure to conceive, as well as enhancing uterine contractile performance during labor.