Evaluation of taurine and carnitine concentrations in whole blood, plasma, skeletal muscle and cardiac muscle in dogs.

Little is known about how plasma and whole blood taurine and plasma carnitine correlate to concentrations in skeletal and cardiac muscle and the effects of diet in dogs. The purpose of this study was to evaluate the correlation among plasma, skeletal and cardiac muscle carnitine and taurine and whole blood taurine and determine the effect of diet. The study protocol was approved by the Pet Food Solutions Institutional Animal Care and Use Committee. Thirty-three mixed-breed hounds and 32 beagles were evaluated at Day 0 then removed from their baseline diet and randomized to a test diet: high animal protein, grain-inclusive (HA-GI), low animal protein, grain-free (LA-GF), low animal protein, grain-inclusive (LA-GI), or high animal protein, grain-free (HA-GF). Blood was drawn every 30 days and endomyocardial (mixed breeds only) and skeletal muscle biopsies were collected at Days 0 and 180. The correlations between plasma and whole blood taurine, or plasma carnitine and skeletal and cardiac muscle concentrations were weak (p < 0.01-0.05). Mixed-breed hounds had increased (p = 0.029) whole blood taurine compared to beagles. Plasma taurine was lower with diet HA-GF, (p = 0.009) however, all diets had increased taurine from Day 0 and were, on average within the laboratory reference range. Dogs fed the HA-GI diet had increased cardiac muscle carnitine esters (p = 0.014). Increased carnitine esters were also appreciated in cardiac muscle in all diets from Day 0 to 180 (p = 0.0001). On Day 180 mixed-breed hounds had increased skeletal total carnitine (p < 0.001) compared to all time points and breeds. This study observed no correlation between plasma, whole blood, skeletal and cardiac muscle taurine concentrations but noted some effects between time, breed and diet.

The impact of protein source and grain inclusion on digestibility, fecal metabolites, and fecal microbiome in adult canines.

This study was conducted to determine the effect of animal protein inclusion rate and grain-free or grain-inclusive diets on macronutrient digestibility, fecal characteristics, metabolites, and microbiota in mixed-breed hounds and Beagles. Four experimental extruded kibble diets were made with varying amounts of animal protein and carbohydrates: 1) high animal protein, grain-inclusive (HA-GI), 2) low animal protein, grain-free (LA-GF), 3) low animal protein, grain-inclusive (LA-GI), and 4) high animal protein, grain-free (HA-GF). Thirty-two Beagles and 33 mixed-breed hounds were assigned to 1 of the 4 treatment groups in a completely randomized design that lasted 180 d. All diets were similar in chemical composition and well-digested by the animals. In general, for fecal metabolites, mixed-breed hounds had a greater concentration of total short-chain fatty acid (SCFA) and ammonia and lower indole concentration than Beagles (P < 0.05). In mixed-breed hounds, LA-GF had a greater (P < 0.05) total SCFA concentration than HA-GI and LA-GI; however, this was not observed in Beagles. There were greater concentrations of ammonia, phenol, and indole in HA-GI than in LA-GF (P < 0.05). Breed-affected fecal primary bile acid (BA) concentration, as mixed-breed hounds had a greater concentration of cholic acid (CA) than Beagles (P < 0.05). Mixed-breed hounds fed LA-GF resulted in greater CA concentrations than HA-GI and LA-GI (P < 0.05). Dogs who consumed LA-GF had lower fecal secondary BA content than the other groups (P < 0.05). The distribution of the fecal microbiota community differed in LA-GF compared with the other groups, with lower α-diversity. However, dogs fed LA-GF had the largest difference in composition with greater Selenomonadaceae, Veillonellaceae, Lactobacillaceae, Streptococcus, Ligilactobacillus, Megamonas, Collinsella aerofaciens, and Bifidobacterium sp. than the other groups. A significant breed effect was noted on nutrient digestibility, fecal metabolites, and microbiota. A treatment effect was observed in LA-GF as it resulted in greater fecal SCFA, lower protein fermentative end products, greater fecal primary BAs, lower fecal secondary BA concentrations, and shifts in fecal microbiota.

A recent topic of debate in pet food is whether grain or pulse ingredients and varying amounts of animal-based protein compared to plant proteins are better for pets' health. Thus, the need to examine ingredients used in pet food is important. This study aimed to evaluate macronutrient digestibility, fecal characteristics, fecal metabolites, and fecal microbiota in both mixed-breed hounds and Beagles when fed extruded diets containing different inclusion rates of animal protein and plant-based ingredients. Four experimental diets were studied 1) high animal protein, grain-inclusive (HA-GI), 2) low animal protein, grain-free (LA-GF), 3) low animal protein, grain-inclusive (LA-GI), and 4) high animal protein, grain-free (HA-GF). We found that all four diets were well-digested by the animals and all dogs remained healthy throughout the study. In addition, LA-GF produced a decrease in alpha diversity, yet was greater in the abundance of Megamonas, which are known to produce short-chain fatty acids. The other diets did not differ significantly. Apparent total tract nutrient digestibility, fecal characteristics, metabolites, and microbiota were affected by breed and dietary treatments. While some have postulated that pulse-rich diets could perhaps be a cause of nutrition-associated dilated cardiomyopathy in canines due to a potentially negative effect on digestibility, our results showed all diets were highly digestible.

Review of canine dilated cardiomyopathy in the wake of diet-associated concerns.

Dilated cardiomyopathy (DCM) has been in the literature and news because of the recent opinion-based journal articles and public releases by regulatory agencies. DCM is commonly associated with a genetic predisposition in certain dog breeds and can also occur secondary to other diseases and nutritional deficiencies. Recent communications in veterinary journals have discussed a potential relationship between grain-free and/or novel protein diets to DCM, citing a subjective increase in DCM in dog breeds that are not known to have a genetic predisposition for the disease. This literature review describes clinical presentations of DCM, common sequelae, treatment and preventative measures, histopathologic features, and a discussion of the varied etiological origins of the disease. In addition, current literature limitations are addressed, in order to ascertain multiple variables leading to the development of DCM. Future studies are needed to evaluate one variable at a time and to minimize confounding variables and speculation. Furthermore, to prevent sampling bias with the current FDA reports, the veterinary community should be asked to provide information for all cases of DCM in dogs. This should include cases during the same time period, regardless of the practitioner's proposed etiology, due to no definitive association between diets with specific characteristics, such as, but not limited to, grain-free diets and those containing legumes, novel protein diets, and those produced by small manufacturers to DCM in dogs. In summary, in order to determine if certain ingredients, categories of diets, or manufacturing processes are related to an increased risk of DCM, further studies investigating these variables are necessary.

Lipid Intake Enhances Muscle Growth But Does Not Influence Glucose Kinetics in 3-Week-Old Low-Birth-Weight Neonatal Pigs.

BACKGROUND: Low-birth-weight (LBWT) neonates grow at a slower rate than their normal-birth-weight (NBWT) counterparts and may develop hypoglycemia postnatally. OBJECTIVE: We investigated whether dietary lipid supplementation would enhance growth and improve glucose production in LBWT neonatal pigs. METHODS: Twelve 3-d-old NBWT (1.606 kg) crossbred pigs were matched to 12 LBWT (1.260 kg) same-sex littermates. At 6 d of age, 6 pigs in each group were fed a low-energy (LE) or a high-energy (HE) isonitrogenous formula containing 5.2% and 7.3% fat, respectively. Body composition was assessed using dual-energy X-ray absorptiometry; plasma glucose and glycerol kinetics were assessed using stable isotope tracers. After killing, weights of skeletal muscles and visceral organs were measured. Data were analyzed by ANOVA for a 2 × 2 factorial design; temporal effects were investigated using repeated-measures analysis. RESULTS: Lipid supplementation did not affect body weight of LBWT or NBWT pigs. However, liver and longissimus dorsi weights as a percentage of body weight were greater for pigs fed an HE diet than for those fed an LE diet (4.3% compared with 3.4% and 1.5% compared with 1.2%, respectively) but remained less for LBWT than for NBWT pigs (3.8% compared with 3.9% and 1.3% compared with 1.5%, respectively) (P < 0.05). In addition, hepatic fat content increased (7.9 compared with 2.6 g) in pigs fed the HE compared with those fed the LE formula (P < 0.05). Lipid supplementation did not influence plasma glucose concentration which remained lower in the LBWT than in the NBWT group (4.1 compared with 4.5 mmol/L) (P < 0.05). CONCLUSIONS: Our data suggest that lipid supplementation modestly improved growth of skeletal muscle and the liver but did not affect glucose homeostasis in all groups, and glucose concentration remained lower in LBWT than in NBWT pigs. These data suggest that the previously reported hyperglycemic effect of lipid supplementation may depend on the route of administration or age of the neonatal pig.

Decreased abundance of eIF4F subunits predisposes low birth weight neonatal pigs to reduced muscle hypertrophy.

Muscle hypertrophy is limited in low birth weight (LBWT) neonates, suggesting a reduction in protein synthesis and increased protein degradation. Sixteen pairs of one-day-old normal birth weight (NBWT) and LBWT littermates (n = 16) were euthanized, and the longissimus dorsi (LD) was sampled for protein abundance and kinase phosphorylation profile measures. Eukaryotic initiation factor (eIF)4E and eIF4G abundance, and assembly of the active eIF4E-eIF4G complex, was less for LBWT than for NBWT pig muscles. Similarly, eIF3f abundance was reduced in the muscle of LBWT compared with NBWT pigs and was associated with diminished ribosomal protein S6 kinase 1 phosphorylation. This decrease was linked to a lower phosphorylation of programmed cell death protein 4 (PDCD4) in LBWT pig muscle. By contrast, PDCD4 abundance was greater in the muscle of the LBWT than NBWT group, suggesting lower release and availability of eIF4A from the PDCD4-eIF4A complex. Moreover, protein abundance of eIF4A was lower in LBWT muscle, which is expected to further impair the formation of eIF4F translation initiation complex. Microtubule-associated light chain 3 (LC3) II to total LC3 ratio was greater in LBWT LD lysates, yet P62 abundance was similar between the two groups, suggesting no difference in autophagy. Muscle atrophy F-box (atrogin-1) abundance was less in LBWT LD lysates, suggesting decreased degradation through the ubiquitin-proteasome system. In conclusion, limited eIF4F subunit abundance and downregulated translation initiation are plausible mechanisms for diminished muscle growth in LBWT compared with NBWT neonatal pigs.NEW & NOTEWORTHY We demonstrated that eukaryotic initiation factor (eIF)4E, eIF4G, and eIF4A abundance, and assembly of the active eIF4E-eIF4G complex, were reduced in low birth weight (LBWT) compared with normal birth weight pig muscle. In contrast, our data indicated that protein degradation signaling does not seem to affect protein turnover in LBWT pig muscle. Thus, downregulated translation initiation is likely the key contributor that predisposes LBWT neonatal pigs to slower postnatal muscle growth.

Downregulated Translation Initiation Signaling Predisposes Low-Birth-Weight Neonatal Pigs to Slower Rates of Muscle Protein Synthesis.

Low-birth-weight (LBWT) neonates experience restricted muscle growth in their perinatal life. Our aim was to investigate the mechanisms that contribute to slower skeletal muscle growth of LBWT neonatal pigs. Twenty-four 1-day old male LBWT (816 ± 55 g) and normal-birth-weight (NBWT; 1,642 ± 55 g) littermates (n = 12) were euthanized to collect blood and longissimus dorsi (LD) muscle subsamples. Plasma glucose, insulin, and insulin-like growth factor-I (IGF-I) were lower in LBWT compared with NBWT pigs. Muscle IGF-I mRNA expression were lower in LBWT than NBWT pigs. However, IGF-I receptor mRNA and protein abundance was greater in LD of LBWT pigs. Abundance of myostatin and its receptors, and abundance and phosphorylation of smad3 were lower in LBWT LD by comparison with NBWT LD. Abundance of eukaryotic initiation factor (eIF) 4E binding protein 1 and mitogen-activated protein kinase-interacting kinases was lower in muscle of LBWT pigs compared with NBWT siblings, while eIF4E abundance and phosphorylation did not differ between the two groups. Furthermore, phosphorylation of ribosomal protein S6 kinase 1 (S6K1) was less in LBWT muscle, possibly due to lower eIF3e abundance. In addition, abundance and phosphorylation of eIF4G was reduced in LBWT pigs by comparison with NBWT littermates, suggesting translation initiation complex formation is compromised in muscle of LBWT pigs. In conclusion, diminished S6K1 activation and translation initiation signaling are likely the major contributors to impaired muscle growth in LBWT neonatal pigs. The upregulated IGF-I R expression and downregulated myostatin signaling seem to be compensatory responses for the reduction in protein synthesis signaling.

Diminished satellite cell fusion and S6K1 expression in myotubes derived from skeletal muscle of low birth weight neonatal pigs.

Low birth weight (LBWT) is consistently associated with impaired postnatal muscle growth in mammals. Satellite cell (SC)-mediated myonuclear incorporation precedes protein accumulation in the early stages of postnatal muscle development and growth. The objective of this study was to investigate proliferation and differentiation of SCs and the regulation of protein synthesis signaling in response to insulin-like growth factor (IGF)-I stimulation in SC-derived myotubes of LBWT neonatal pigs. SCs isolated from Longissimus dorsi muscle of LBWT and NBWT pigs (3-d-old, n = 8) were cultured and induced to proliferate and differentiate to myotubes in vitro. On day 3 of differentiation, myotubes were fasted in serum-free media for 3 h and treated with human recombinant R3-insulin-like growth factor-I (rh IGF-I) at 0, 25, and 50 ng × mL-1 for 30 min. There was no difference in proliferation rates of SCs from LBWT and NBWT pigs. However, LBWT SC fusion was 15% lower (P ≤ 0.05) without a difference in MyoD or myogenin mRNA expression in comparison with NBWT pigs, suggesting SCs are not intrinsically different between the two groups. IGF-Ι stimulation at physiological concentrations activated downstream effectors of mTOR similarly in myotubes from LBWT and NBWT pigs. However, abundance of ribosomal protein S6 kinase 1(S6K1) was lower in myotubes of LBWT compared to their NBWT siblings (P ≤ 0.05). These results indicate that the modest reduction in SC fusion and S6K1 expression are not the major contributors to the impaired postnatal muscle growth of LBWT pigs.