The effect of long-term oral L-carnitine administration on insulin sensitivity, glucose disposal, plasma concentrations of leptin and acylcarnitines, and urinary acylcarnitine excretion in warmblood horses

Adiposity in mares induces insulin dysregulation and mitochondrial dysfunction which can be mitigated by nutritional intervention

Obesity is a complex disease associated with augmented risk of metabolic disorder development and cellular dysfunction in various species. The goal of the present study was to investigate the impacts of obesity on the metabolic health of old mares as well as test the ability of diet supplementation with either a complex blend of nutrients designed to improve equine metabolism and gastrointestinal health or L-carnitine alone to mitigate negative effects of obesity. Mares (n = 19, 17.9 ± 3.7 years) were placed into one of three group: normal-weight (NW, n = 6), obese (OB, n = 7) or obese fed a complex diet supplement for 12 weeks (OBD, n = 6). After 12 weeks and completion of sample collections, OB mares received L-carnitine alone for an additional 6 weeks. Obesity in mares was significantly associated with insulin dysregulation, reduced muscle mitochondrial function, and decreased skeletal muscle oxidative capacity with greater ROS production when compared to NW. Obese mares fed the complex diet supplement had better insulin sensivity, greater cell lipid metabolism, and higher muscle oxidative capacity with reduced ROS production than OB. L-carnitine supplementation alone did not significantly alter insulin signaling, but improved lipid metabolism and muscle oxidative capacity with reduced ROS. In conclusion, obesity is associated with insulin dysregulation and altered skeletal muscle metabolism in older mares. However, dietary interventions are an effective strategy to improve metabolic status and skeletal muscle mitochondrial function in older mares.

Interactions of CDKAL1 rs7747752 polymorphism and serum levels of L-carnitine and choline are related to increased risk of gestational diabetes mellitus

BACKGROUND

Interactions between genetic, metabolic, and environmental factors lead to gestational diabetes mellitus (GDM). We aimed to examine interactive effects of cyclin-dependent kinase 5 regulatory subunit-associated protein1-like 1(CDKAL1) rs7747752 polymorphism with low serum levels of L-carnitine, choline, and betaine for GDM.

METHODS

A nested case-control study of 207 GDM women and their one-to-one, age-matched controls was organized from a prospective cohort of pregnant women in Tianjin, China. Conditional logistic regressions were used to test associations between CDKAL1 rs7747752 and serum levels of L-carnitine, choline, and betaine, and the risk of GDM. Additive interactions were performed to examine interactive effects of rs7747752 and low serum levels of L-carnitine, choline, and betaine on the risk of GDM.

RESULTS

The CDKAL1 rs7747752 G > C was associated with GDM in additive, dominant, and recessive model (P <0.05). The rs7747752 CC genotype enhanced the OR of L-carnitine ≤ vs. > 150 nmol/mL for GDM from 6.14 (2.61-14.4) to 19.6 (5.65-68.1) and the OR of choline ≤ vs. > 110 nmol/mL from 2.37 (1.07-5.28) to 12.1 (3.22-45.6), with significant additive interactions. Similarly, CG genotype also enhanced the OR of L-carnitine ≤ vs. > 150 nmol/mL for GDM from 4.70 (2.01-11.0) to 11.4 (3.98-32.9), with a significant additive interaction. However, the additive interaction between rs7747752 and betaine ≤ 200 nmol/mL on the risk of GDM was not significant.

CONCLUSIONS

The CC or CG genotype carriers in rs7747752 of CDKAL1 who have a low serum level of L-carnitine or choline are at a particular high risk of GDM. Randomized controlled trials are warranted to test the effect of supplement of L-carnitine or choline on the risk of GDM in the high-risk group.

Dynamic Change of Free Serum L-carnitine Concentration in Relation to Age, Sex, and Exercise in Anglo-Arabian Thoroughbred Horses

The physiological role of L-carnitine in equine species is worthy of investigation; however, the systemic content of free L-carnitine and its dynamic change in growing foals as well as in exercising horses are still poorly investigated. In this study, the influence of age and exercise on free serum L-carnitine levels was evaluated in equine species. Ten foals were monitored from 6 up to 18 months of age (group 1), whereas 60 horses were divided in six groups in accordance with their age: group 2, 2-year-old; group 3, 3-year-old; group 4, 4-year-old; group 5, 5-year-old; group 6, 6-year-old; group 7, 7-year-old. To assess the age and sex effect on free serum L-carnitine values, blood samples were collected from foals and horses. Adult horses (groups 2-7) were subjected to a simulate 1,660-m race, and blood samples were collected before the simulate race (T_PRE), within 10 minutes (T_POST10) from the end of race, and after 30 minutes (T_POST30) from the end of race. The amino acid levels were influenced by age (P < .0001) in foals and horses. Decreased levels of amino acid were observed at T_POST10 with respect to T_PRE and T_POST30. (P < .001). The findings suggest that the biosynthetic pathway of L-carnitine is organizing and adapting to the metabolic needs of skeletal and cardiac muscle tissue in the course of growth. L-carnitine could play a role for the provision of energy to the exercising muscles. Further studies are needed to evaluate possible beneficial effects of L-carnitine during growing phase and on parameters of equine physical performance.

Acylcarnitine ester utilization by the hindlimb of warmblood horses at rest and following low intensity exercise and carnitine supplementation

BACKGROUND

Acylcarnitines play an important role in fuel metabolism in skeletal muscle.

OBJECTIVE

To assess acylcarnitine ester utilization by the hindlimb of horses at rest and following low intensity exercise and carnitine supplementation.

ANIMALS AND METHODS

Acylcarnitine ester uptake by the hindlimb was investigated using the arteriovenous difference technique. Blood from six warmblood mares (mean age 12 ± 3 (SD) years and weighing 538 ± 39 kg) was collected simultaneously from the transverse facial artery and from the caudal vena cava. Food was withheld for 12 hours prior to exercise. Exercise comprised a standardized treadmill protocol consisting of 5 minutes of walk, 20 minutes of trot and thereafter another 5 minutes of walk. At the end of the first exercise day, three horses were given carnitine supplementation (100 mg/kg bodyweight), whereas the other horses received saline. The next day the exercise was repeated and blood samples collected similarly. Free carnitine and acylcarnitines were analyzed as their butyl ester derivatives in heparinized plasma by electrospray tandem mass spectrometry. Statistical analysis was performed using a general linear mixed model.

RESULTS

C3-carnitine, C6-carnitine and C14:1-carnitine showed the largest average extraction by the hindlimb at rest and C3-carnitine, C5:1-carnitine and C16-carnitine immediately after low-intensity exercise. Carnitine supplementation significantly increased free carnitine, C5-carnitine and C8-carnitine extraction.

CONCLUSION

Carnitine supplementation altered the extraction of acylcarnitines by the hindlimb in horses exercising at low intensity.

CLINICAL IMPORTANCE

Findings might aid in optimizing performance and myopathy prevention of the equine athlete.