Corrigendum: Non-invasive methods to assess muscle function in dogs: a scoping review.

[This corrects the article DOI: 10.3389/fvets.2023.1116854.].

Muscle function assessment of the hindlimbs in healthy dogs using acoustic myography.

INTRODUCTION: Impaired muscle function is a frequent consequence of musculoskeletal disorders in dogs. Musculoskeletal disorders, especially stifle joint diseases, are common in dogs and assessment of muscle function in dogs is clinically relevant. Acoustic myography (AMG) is a non-invasive method to assess muscle activity. Quantifying muscle function in normal dogs could help identify clinically relevant changes in dogs with orthopaedic disease and allow targeted interventions to improve recovery in these. The objectives of the study were to characterize hindlimb muscle function in healthy dogs using AMG and to investigate the repeatability and reproducibility of AMG in dogs. METHODS: Healthy dogs (15-40 kg) without musculoskeletal disorders were recruited and screened for eligibility to participate in the study. The muscle activity in four hindlimb muscles related to the stifle was assessed using AMG. The degree of symmetry between the hindlimbs in these dogs was investigated and the reliability of AMG was evaluated. RESULTS AND CONCLUSIONS: The study population comprised 21 dogs. Reference intervals and symmetry indices for AMG scores of the hindlimb muscles were identified, with highest variability for the E-scores. For all AMG-scores, same-day variation was lower than between days variation, and both were lowest for S- and T-scores. Further investigation is needed to establish if AMG can enable discrimination between dogs with altered muscle function and healthy dogs.

Non-invasive methods to assess muscle function in dogs: A scoping review.

Skeletal muscle function can be affected by multiple disorders in dogs of which cranial cruciate ligament rupture or disease (CCLD) is one of the most common. Despite the significance of this condition only sparse research exists regarding assessment of muscle function in dogs. This scoping review aimed to identify the non-invasive methods for canine muscle function assessments that have been reported in the literature in the past 10 years. A systematic literature search was conducted 1st March 2022 across six databases. After screening, 139 studies were considered eligible for inclusion. Among the included studies, 18 different muscle function assessment categories were identified, and the most frequently reported disease state was CCLD. We included an attempt to elucidate the clinical applicability of the 18 reported methods, as experts were asked to subjectively assess the methods for their clinical relevance as well as their practical applicability in dogs with CCLD.

The impact of water depth and speed on muscle fiber activation of healthy dogs walking in a water treadmill.

BACKGROUND: Water treadmills are frequently used in the rehabilitation of dogs, for example with the purpose of re-building muscular strength after surgery. However, little is known about how different water depths and velocities affect the muscular workload during aquatic locomotion. This study used acoustic myography to assess hind limb muscle fiber activation in 25 healthy large-breed dogs walking in a water treadmill. Acoustic myography sensors were attached to the skin over the vastus lateralis of the quadriceps and the biceps femoris muscles. The dogs walked at two velocities (30 and 50 m/min) and four water depths: bottom of the pads, hock, stifle and mid-femur. Acoustic myograph signals were analyzed for changes in three muscle function parameters: efficiency/coordination (E-score) and spatial (S-score) and temporal (T-score) summation. RESULTS: Differences between E, S, and T were statistically significant compared across different speeds (30, 50) and water levels (0, 1, 2, 3) using a one-way ANOVA with multiple comparisons (Tukey; Geisser-Greenhouse correction) as well as a two-tailed one sample t-test. At 50 m/min in water at the mid-femur, the biceps femoris was less efficient (P < 0.001) and recruited more fibers (P = 0.01) at a higher firing rate (P = 0.03) compared to working in shallower water, while the vastus lateralis was also less efficient (P < 0.01), but spatial and temporal summation did not change significantly. At 30 m/min, biceps efficiency was reduced (P < 0.01) when water was at the mid-femur compared to the bottom of the pads level. Walking in stifle- or hock-deep water did not show increased muscle activation for either muscle compared to walking in water at the bottom of the pads. CONCLUSION: More muscle activation was required to walk in water at a depth at the level of the mid-femur compared to shallower water, and this exercise was more demanding for the biceps femoris, a muscle engaged in propulsion, than for vastus lateralis. These findings may help practitioners towards making more precise rehabilitation protocols.

Kinetic gait analysis in healthy dogs and dogs with osteoarthritis: An evaluation of precision and overlap performance of a pressure-sensitive walkway and the use of symmetry indices.

In veterinary practice, a thorough gait examination is essential in the clinical workup of any orthopedic patient, including the large population of dogs with chronic pain as a result of osteoarthritis. The traditional visual gait examination is, however, a subjective discipline, and systems for kinetic gait analysis may potentially offer an objective alternative for gait assessment by the measurement of ground reaction forces. In order to avoid unnecessary testing of patients, a thorough, stepwise evaluation of the diagnostic performance of each system is recommended before clinical use for diagnostic purposes. The aim of the study was to evaluate the Tekscan pressure-sensitive walkway system by assessing precision (agreement between repetitive measurements in individual dogs) and overlap performance (the ability to distinguish dogs with lameness due to osteoarthritis from clinically healthy dogs). Direction of travel over the walkway was investigated as a possible bias. Symmetry indices are commonly used to assess lameness by comparing ground reaction forces across different combinations of limbs in each dog. However, SIs can be calculated in several different ways and specific recommendations for optimal use of individual indices are currently lacking. Therefore the present study also compared indices in order to recommend a specific index preferable for future studies of canine osteoarthritis. Forty-one clinically healthy dogs and 21 dogs with osteoarthritis were included in the study. High precision was demonstrated. The direction of travel over the walkway was excluded as a possible bias. A significant overlap was observed when comparing ground reaction forces measured in dogs with osteoarthritis compared to clinically healthy dogs. In some affected dogs, symmetry indices comparing contralateral limbs differed from clinically healthy dogs, but in general, the overlap performance was insufficient and, consequently, general use of this method for diagnostic purposes in dogs with osteoarthritis cannot be recommended.

Analytical performance of canine acylated and unacylated ghrelin enzyme-linked immunosorbent assays.

OBJECTIVES: Ghrelin is a major appetite-stimulating hormone. It circulates as acylated ghrelin (AG) and unacylated ghrelin (UAG), which could have different metabolic actions in obesity. Our objective was to study the analytical performance of two new canine AG and UAG ELISAs using blood samples from healthy, normal-weight dogs. Additionally, the effect of a protease inhibitor (PI) on short-term sample storage was analyzed. METHODS: The intra- and inter-assay precision for low, intermediate, and high AG and UAG concentrations, accuracy, limits of quantification (LQ), and detection limit (DL) of a blank sample were determined in ten healthy dogs. To study the effects of a PI on ghrelin concentrations, and AG and UAG concentrations were compared in five canine plasma samples stored for 1 month with (PI+), without (PI-), and with PI added at sample thawing (PI+th). RESULTS: The intra- and inter-assay coefficients of variation were 1.8%-5.7% and 2.9%-6.4% for the AG assay, and 0.8%-7.5% and 2.8%-13.4% for the UAG assay, respectively. Accuracy analyses showed nonsignificant deviation from linearity for the AG (R2  = .99; Runs test: P = .37) and UAG (R2  = .99; Runs test: P = .42) assays. For the AG assay, the upper LQ was >1261 pg/mL, the lower LQ was 6.2 pg/mL, and the DL was 0.3 pg/mL. For the UAG assay, the upper LQ was >1785 pg/mL, the lower LQ was 16.3 pg/mL, and the DL was 1.8 pg/mL. No differences in the AG (P = .54) and UAG (P = .95) concentrations were detected in the plasma samples subjected to PI+, PI-, and PI+th. CONCLUSION: The AG and UAG ELISA assays had acceptable precision, accuracy, lower LQ, and DLs, but upper LQ could not be established. An influence of the PI on short-term storage was not detectable. Long-term storage ± PI was not evaluated and should be investigated further.

Gut microbiota composition may relate to weight loss rate in obese pet dogs.

Obese dogs seem to have a different gut microbiome (GM) composition compared to lean dogs, and in humans, GM composition may negatively impact the ability to lose weight in some individuals. The purpose of this study was to investigate the interaction between exercise, weight-loss and the composition of GM in dogs. Eighteen obese pet dogs were recruited for a 12-week weight-loss intervention. All dogs were fed restrictively with a commercial high-protein/high-fibre dry diet, and eight of these dogs were enrolled in an exercise program in addition to the diet intervention. Faecal samples were collected and the dogs were weighed at week 0, week 6 and week 12. GM composition was determined using MiSeq-based tag-encoded 16S rRNA gene high-throughput amplicon sequencing, and concentrations of short chain fatty acids (SCFA) by gas-liquid chromatography. Total weight loss, food allowance and GM were not changed by exercise inclusion. However, Megamonas abundance negatively correlated with weight loss rate and Ruminococcaceae relative abundance was lower at 12 weeks in dogs with a faster weight loss rate (≥1% per week) compared with slower weight loss rate (<1% per week) independent of exercise. Acetic and propionic acid concentrations decreased in the dogs with a faster weight loss rate. Members of Megamonas and Ruminococcaceae produce acetic and propionic acids and we therefore interpret that having a GM that favour SCFA production may negatively affect weight loss rate in dogs. Weight loss rate in dogs may be related to the composition of the GM and its production of metabolites.

Integration of a physical training program in a weight loss plan for overweight pet dogs.

OBJECTIVE: To investigate whether a controlled physical training plan for overweight dogs during a weight loss program would improve cardiorespiratory fitness and better preserve lean body mass, compared with results for dogs undergoing a weight loss program based on caloric restriction alone. DESIGN: Prospective, nonrandomized clinical study. ANIMALS: 19 client-owned overweight or obese dogs. PROCEDURES: All dogs were fed the same calorie-restricted diet rationed to achieve a weight loss rate of 1% to 2%/wk for 12 weeks. The fitness-and-diet (FD) group participated in a training program that included underwater and land-based treadmill exercise 3 times/wk. The diet-only (DO) group had no change in exercise routines. Daily activity before and during the intervention was recorded by accelerometry. Before and after intervention, heart rate during exercise was recorded to assess cardiovascular fitness, and body composition was analyzed by dual-energy x-ray absorptiometry. Differences between groups were evaluated with t tests and multiple regression analysis. RESULTS: Mean weight loss was 13.9% and 12.9% for the FD and DO groups, respectively (n = 8 dogs/group that completed the study). Mean accelerometer counts during intervention were 13% higher than baseline counts for the FD group. Heart rate during exercise declined after intervention in both groups. Lean body mass was preserved in the FD group and lost in the DO group during intervention. CONCLUSIONS AND CLINICAL RELEVANCE: The controlled exercise plan used with a dietary weight loss program prevented loss of lean body mass in dogs. This finding supports inclusion of controlled physical training for obesity management in dogs.

Physical training and weight loss in dogs lead to transcriptional changes in genes involved in the glucose-transport pathway in muscle and adipose tissues.

Obesity is a worldwide problem in humans and domestic animals. Interventions, including a combination of dietary management and exercise, have proven to be effective for inducing weight loss in humans. In companion animals, the role of exercise in the management of obesity has received relatively little attention. The aim of the present study was to investigate changes in the transcriptome of key energy metabolism genes in muscle and adipose tissues in response to diet-induced weight loss alone, or combined with exercise in dogs. Overweight pet dogs were enrolled on a weight loss programme, based on calorie restriction and physical training (FD group, n = 5) or calorie restriction alone (DO group, n = 7). mRNA expression of 12 genes and six microRNAs were investigated using quantitative real-time PCR (qPCR). In the FD group, FOXO1 and RAC1 were expressed at lower levels in adipose tissue, whereas ESRRA and AKT2 were more highly expressed in muscle, when compared with the DO group. Comparing expression before and after the intervention, in the DO group, nine genes and three microRNAs showed significant altered expression in adipose tissue (PPARG, ADIPOQ and FOXO1; P < 0.001) and seven genes and two microRNAs were significantly downregulated (NRF2, RAC1, ESRRA, AKT2, PGC1a and mir-23; P < 0.001) in muscle. Thus, calorie restriction causes regulation of several metabolic genes in both tissues. The mild exercise, incorporated into this study design, was sufficient to elicit transcriptional changes in adipose and muscle tissues, suggesting a positive effect on glucose metabolism. The study findings support inclusion of exercise in management of canine obesity.

Evaluation of the oral (13)C-bicarbonate technique for measurements of energy expenditure in dogs before and after body weight reduction.

BACKGROUND: Overweight and obesity are the most common nutritional disorders in dogs and may lead to various secondary diseases and decreased lifespan. In obesity research, measurement of energy expenditure (EE) and determination of the energy requirements are essential. The objective with this study was to validate and evaluate the suitability of the oral (13)C-bicarbonate technique (o(13)CBT) for measuring EE in dog obesity studies. A further objective was to investigate the impact of body weight (BW) reduction and changes in body composition on the EE when measured under conditions corresponding to the basal metabolic rate (BMR). RESULTS: The EE in five privately owned, overweight dogs was measured simultaneously with the o(13)CBT and indirect calorimetry (IC) for comparison of the results. Two measurements per dog were performed under the same standardised conditions (i.e. fasted and resting state) at the start, and after completing a 12-week BW reduction program. Additionally, measurements of body composition by Dual-energy X-ray absorptiometry (DEXA) were conducted at the beginning and at the end of the BW reduction program. There were no differences in EE results obtained by the o(13)CBT and IC. Overweight and the BW reduction did not affect the estimates for the respiratory quotient (RQ) or the recovery factor for the (13)C-tracer (RF), both needed when using the o(13)CBT. The dogs lost 16% (SD ± 2.0) of their initial BW in reduced fat mass (P < 0.001), whereas fat free mass (FFM) remained unchanged. There was no effect of the BW reduction on the determined EE expressed in kJ/kg BW/d, or in kJ/kg BW(0.75)/d. However, EE was lower (P < 0.001) after the BW reduction program when expressed in relation to FFM (kJ/kg FFM/d). CONCLUSIONS: Results from the present study show that the o(13)CBT can be a used in obesity research to determine EE in fasted dogs and under resting conditions. Furthermore, the results suggest that the BMR does not change with reduced BW in overweight dogs as long as the FFM remains unchanged. This indicates that the BMR to maintain one gram of fat is equal to maintaining one gram of FFM in overweight dogs.