In vivo absolute quantification of carnosine in the vastus lateralis muscle with 1H MRS using a surface coil and water as internal reference

OBJECTIVE

To standardize a method for ¹H MRS intramuscular absolute quantification of carnosine in the thigh, using a surface coil and water as internal reference.

MATERIALS AND METHODS

Carnosine spectra were acquired in phantoms (5, 10, and 15 mM) as well as in the right gastrocnemius medialis (GM) and right vastus lateralis (VLM) muscles of young team sports athletes, using volume (VC) and surface (SC) coils on a 3 T scanner, with the same receiver gain. Water spectra were used as internal reference for the absolute quantification of carnosine.

RESULTS

Phantom's experiments showed a maximum error of 7%, highlighting the validity of the measurements in the study setup. The carnosine concentrations (mmol/kg ww, mean ± SD) measured in the GM were 6.8 ± 2.2 with the VC (C_carVC) and 10.2 ± 3.0 with the SC (C_carSC) (P = 0.013; n = 9). Therefore, a correction was applied to these measurements (C_carVC = 0.6582*C_carSC), to make coils performance comparable (6.8 ± 2.2 for VC and 6.7 ± 2.0 for SC, P = 0.97). After that, only the SC was used to quantify carnosine in the VLM, where a concentration of 5.4 ± 1.5 (n = 30) was found, with significant differences between men (6.2 ± 1.3; n = 15) and women (4.6 ± 1.2; n = 15). The error in quantitation was 5.3-5.5% with both coils.

CONCLUSION

The method using the SC and water as internal reference can be used to quantify carnosine in voluminous muscles and regions of the body in humans, where the VC is not suitable, such as the VLM.

Musclin Is Related to Insulin Resistance and Body Composition, but Not to Body Mass Index or Cardiorespiratory Capacity in Adults

BACKGROUND

We studied whether musclin function in humans is related to glycemic control, body composition, and cardiorespiratory capacity.

METHODS

A cross-sectional study was performed in sedentary adults with or without metabolic syndrome (MS). Serum musclin was measured by enzyme-linked immunosorbent assay. Insulin resistance (IR) was evaluated by the homeostatic model assessment (HOMA-IR). Body composition was determined by dual-energy X-ray absorptiometry and muscle composition by measuring carnosine in the thigh, a surrogate of fiber types, through proton magnetic resonance spectroscopy. Cardiorespiratory capacity was assessed through direct ergospirometry.

RESULTS

The control (n=29) and MS (n=61) groups were comparable in age (51.5±6.5 years old vs. 50.7±6.1 years old), sex (72.4% vs. 70.5% women), total lean mass (58.5%±7.4% vs. 57.3%±6.8%), and peak oxygen consumption (VO2peak) (31.0±5.8 mL O2./kg.min vs. 29.2±6.3 mL O2/kg.min). Individuals with MS had higher body mass index (BMI) (30.6±4.0 kg/m2 vs. 27.4± 3.6 kg/m2), HOMA-IR (3.5 [95% confidence interval, CI, 2.9 to 4.6] vs. 1.7 [95% CI, 1.1 to 2.0]), and musclin (206.7 pg/mL [95% CI, 122.7 to 387.8] vs. 111.1 pg/mL [95% CI, 63.2 to 218.5]) values than controls (P˂0.05). Musclin showed a significant relationship with HOMA-IR (β=0.23; 95% CI, 0.12 to 0.33; P˂0.01), but not with VO2peak, in multiple linear regression models adjusted for age, sex, fat mass, lean mass, and physical activity. Musclin was significantly associated with insulin, glycemia, visceral fat, and regional muscle mass, but not with BMI, VCO2peak, maximum heart rate, maximum time of work, or carnosine.

CONCLUSION

In humans, musclin positively correlates with insulinemia, IR, and a body composition profile with high visceral adiposity and lean mass, but low body fat percentage. Musclin is not related to BMI or cardiorespiratory capacity.

MR Imaging of Muscle Trauma: Anatomy, Biomechanics, Pathophysiology, and Imaging Appearance

Muscle is an important component of the muscle-tendon-bone unit, driving skeletal motion through contractions that alter the length of the muscle. The muscle and myotendinous junction (MTJ) are most commonly injured in the young adult, as a result of indirect mechanisms such as overuse or stretching, direct impact (penetrating or nonpenetrating), or dysfunction of the supporting connective tissues. Magnetic resonance (MR) imaging is widely used for assessment of muscle injuries. This review illustrates the MR imaging appearance of a broad spectrum of acute, subacute, and chronic traumatic lesions of muscle, highlighting the pathophysiology, biomechanics, and anatomic considerations underlying these lesions. Concentric (shortening) contractions are more powerful, but it is eccentric (lengthening) contractions that produce the greatest muscle tension, leading to indirect injuries such as delayed-onset muscle soreness (DOMS) and muscle strain. Strain is the most commonly encountered muscle injury and is characteristically located at the MTJ, where maximal stress accumulates during eccentric exercise. The risk of strain varies among muscles based on their fiber composition, size, length, and architecture, with pennate muscles being at highest risk. Direct impact to muscle results in laceration or contusion, often accompanied by intramuscular interstitial hemorrhage and hematoma. Disorders related to the muscle's collagen framework include compartment syndrome, which is related to acute or episodic increases in pressure, and muscle herniation through anatomic defects in the overlying fascia. The healing response after muscle trauma can result in regeneration, degeneration with fibrosis and fatty replacement, or disordered tissue proliferation as seen in myositis ossificans. In athletes, accurate grading of the severity and precise location of injury is necessary to guide rehabilitation planning to prevent reinjury and ensure adequate healing. In elite athletes, MR imaging grading of muscle trauma plays an increasingly important role in recently developed comprehensive grading systems that are replacing the imprecise three-grade injury classification system currently used. ^©RSNA, 2017.

Intra- and interobserver agreement on the Oestern and Tscherne classification of soft tissue injury in periarticular lower-limb closed fractures

BACKGROUND

The soft tissues injury in periarticular fractures of the lower extremities determines the proper time to perform bone fixation.

OBJECTIVE

The aim of this study was to determine the intra and interobserver agreement in the Tscherne classification.

METHODS

This is a descriptive, prospective study for patients admitted to the Pablo Tobón Uribe Hospital (PTUH) with tibial plateau or tibial pilon fractures. We performed a standardize evaluation using video photography at the time of admission and 24, 48, and 72 h after admission. Fifteen five reviewers who had various levels of training produced a total of 1,200 observations. The intra- and interobserver agreement was assessed using a weighted kappa for multiple raters and more than two categories.

RESULTS

Twenty patients were admitted with tibial plateau and tibial pilon fractures. The intraobserver agreement for all 15 raters was kappa 0.81 (95% CI 0.79-0.83), and the interobserver agreement for all 15 raters was kappa 0.65 (95% CI 0.55-0.73). The interobserver agreement at 24 h was kappa 0.67 (95% CI 0.46-0.86).

CONCLUSIONS

Classifying the severity of soft tissue injury is critical in planning the surgical management of fractures of the lower extremities. Based on our results, we can reasonably argue that the Tscherne classification produced an adequate level of agreement and could be used to standardize and to guide the treatment, and to conduct research studies.

Intra- and interobserver agreement on the Oestern and Tscherne classification of soft tissue injury in periarticular lower-limb closed fractures

Background: The soft tissues injury in periarticular fractures of the lower extremities determines the proper time to perform bone fixation. Objetive: The aim of this study was to determine the intra and interobserver agreement in the Tscherne classification. Methods: This is a descriptive, prospective study for patients admitted to the Pablo Tobón Uribe Hospital (PTUH) with tibial plateau or tibial pilon fractures. We performed a standardize evaluation using video photography at the time of admission and 24, 48, and 72 h after admission. Fifteen five reviewers who had various levels of training produced a total of 1,200 observations. The intra- and interobserver agreement was assessed using a weighted kappa for multiple raters and more than two categories. Results: Twenty patients were admitted with tibial plateau and tibial pilon fractures. The intraobserver agreement for all 15 raters was kappa 0.81 (95% CI 0.79-0.83), and the interobserver agreement for all 15 raters was kappa 0.65 (95% CI 0.55-0.73). The interobserver agreement at 24 h was kappa 0.67 (95% CI 0.46-0.86). Conclusions:Classifying the severity of soft tissue injury is critical in planning the surgical management of fractures of the lower extremities. Based on our results, we can reasonably argue that the Tscherne classification produced an adequate level of agreement and could be used to standardize and to guide the treatment, and to conduct research studies. Level of Evidence: Level IV, Case Series