Quantitative assessment of muscle mass and gene expression analysis in dogs with glucocorticoid-induced muscle atrophy

Detection of renal tubular transporter proteins in canine urinary extracellular vesicles using liquid chromatography-tandem mass spectrometry

Urinary extracellular vesicles (UEVs) are membranous particles that carry renal tubular transporter proteins. Here, we evaluate whether selected renal tubular transporter proteins can be detected in UEVs isolated from small volume (1-5 mL) canine urine samples of healthy dogs and canine patients with elevated circulating parathyroid hormone (PTH)/PTH-related peptide (PTHrp) concentrations, hypercortisolism, and primary hypoadrenocorticism using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The total creatinine content of each urine sample was calculated from urine volume and creatinine concentration. UEVs were isolated by size exclusion chromatography prior to quantification by nanoparticle tracking analysis and proteomic analysis by LC-MS/MS. Group comparisons were made using non-parametric statistics. Aquaporin-2 (AQP2) and the renal sodium/phosphate co-transporter (NPT2A) were detected in UEVs isolated from small volume samples of almost all healthy dogs but were not detected in most dogs with elevated circulating PTH/PTH related peptide (PTHrp) concentrations, hypercortisolism and primary hypoadrenocorticism. Total creatinine content of the urine sample was strongly positively correlated with the number of UEVs (rs = .84, P < .001); thus, total creatinine was used as a surrogate marker of UEV number. In healthy dogs, AQP2 and NPT2A were both detected in samples containing at least 1.7 × 109 UEVs or 24 μmol creatinine, however in non-healthy dogs, AQP2 and NPT2A were not detected in most samples containing up to 6.3 × 109 UEVs or 32 μmol creatinine.

Muscle ultrasound to identify prednisone-induced muscle damage in adults with nephrotic syndrome

Steroid myopathy is a non-inflammatory toxic myopathy that primarily affects the proximal muscles of the lower limbs. Due to its non-specific symptoms, it is often overshadowed by patients' underlying conditions. Prolonged or high-dosage use of glucocorticoids leads to a gradual decline in muscle mass. There are no tools available to identify the course of steroid myopathy before the patient displays substantial clinical symptoms. In this study, we investigated individuals with nephrotic syndrome receiving prednisone who underwent muscle ultrasound to obtain cross-sectional and longitudinal pictures of three major proximal muscles in the lower limbs: the vastus lateralis, tibialis anterior, and medial gastrocnemius muscles. Our findings revealed that grip strength was impaired in the prednisolone group, creatine kinase levels were reduced within the normal range; echo intensity of the vastus lateralis and medial gastrocnemius muscles was enhanced, the pennation angle was reduced, and the tibialis anterior muscle exhibited increased echo intensity and decreased thickness. The total dose of prednisone and the total duration of treatment impacted the degree of muscle damage. Our findings indicate that muscle ultrasound effectively monitors muscle structure changes in steroid myopathy. Combining clinical symptoms, serum creatine kinase levels, and grip strength improves the accuracy of muscle injury evaluation.

Glucocorticoid-Induced Myopathy: Typology, Pathogenesis, Diagnosis, and Treatment

Glucocorticoid-induced myopathy is a non-inflammatory toxic myopathy typified by proximal muscle weakness, muscle atrophy, fatigue, and easy fatigability. These vague symptoms coupled with underlying disorders may mask the signs of glucocorticoid-induced myopathy, leading to an underestimation of the disease's impact. This review briefly summarizes the classification, pathogenesis, and treatment options for glucocorticoid-induced muscle wasting. Additionally, we discuss current diagnostic measures in clinical research and routine care used for diagnosing and monitoring glucocorticoid-induced myopathy, which includes gait speed tests, muscle strength tests, hematologic tests, bioelectrical impedance analysis (BIA), dual-energy X-ray absorptiometry (DXA), computed tomography (CT), magnetic resonance imaging (MRI), electromyography, quantitative muscle ultrasound, histological examination, and genetic analysis. Continuous monitoring of patients receiving glucocorticoid therapy plays an important role in enabling early detection of glucocorticoid-induced myopathy, allowing physicians to modify treatment plans before significant clinical weakness arises.

Evaluation of muscle mass and intramuscular fatty infiltration in dogs with hypercortisolism and their association with prognosis

BACKGROUND

Muscle atrophy and intramuscular fatty infiltration, as well as their association with prognosis, have not been quantified in dogs with spontaneous hypercortisolism (HC).

OBJECTIVE

To quantitatively evaluate muscle atrophy and IM fatty infiltration in dogs with HC and determine their prognostic impact.

ANIMALS

Fifty-three dogs with HC and 66 control dogs without HC.

METHODS

Retrospective cohort study. Medical records and computed tomography images obtained between 2014 and 2021 were evaluated. Kaplan-Meier curves and log-rank tests were used to analyze the effect of muscle atrophy and IM fatty infiltration on the prognosis of dogs with HC.

RESULTS

Dogs with HC showed lower visually measured cross-sectional area (VCSA) and cross-sectional area based on attenuation (HCSA) than control dogs (median [interquartile range {IQR}]: 50.3 mm2/mm [36.2-67.8] vs 66.7 mm2/mm [48.0-85.9]; P < .001; 30.4 mm2/mm [13.7-57.2] vs 54.8 mm2/mm [39.7-71.5]; P < .001, respectively). Dogs with HC had lower epaxial muscle attenuation (L3HU) than control dogs (median [IQR]: 21.2 Hounsfield [HU] [12.4-28.2] vs 33.2 HU [22.6-43.6]; P < .001). Dogs with HC with lower HCSA or L3HU had shorter survival (median [IQR]: 670 days [222-673] vs 949 days [788-1074], P < .01; 523 days [132-670] vs 949 days [756-1074], P < .01, respectively) but not lower VCSA (median [IQR]: 673 days [132-788] vs 949 days [523 to not applicable]; P = .30).

CONCLUSION AND CLINICAL IMPORTANCE

Hypercortisolism in dogs causes muscle atrophy and IM fatty infiltration and is associated with poor prognosis.