The effects of corn on microRNA expression within horses
Date
2021
Authors
Carver, Clarissa, author
Hess, Tanja, advisor
Bruemmer, Jason E., committee member
Coleman, Stephen, committee member
Landolt, Gabriele, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Nutrition has been shown to play a major role in the health of horses in all life stages and levels of work. In recent years the prevalence of equine obesity has increased as more horses are kept in stalls with lower workloads, while receiving high energy and calorically dense feeds like grain, many of which contain corn, in addition to forage. The increase in equine obesity has been accompanied by more cases of metabolic diseases developing, often linked to poor nutrition and diets high in non-structural carbohydrates (NSC). Although more cases of metabolic disorders are emerging there currently are no good biomarkers to diagnose these diseases or identify horses on diets providing them with poor nutrition. Diets high in NSCs have been linked to insulin resistance and laminitis within horses, two of the main components of Equine Metabolic Syndrome (EMS), however nutrigenomic studies looking at the interaction of diets high in NSCs on gene expression, specifically through the regulation of endogenous microRNAs (miRNA) are rare. Recent research on mice and human models has demonstrated the large impact diet has on levels of miRNAs within the body and mRNA targets for these miRNAs resulting in the regulation of gene expression, in addition to identifying miRNAs in circulation that can be used as biomarkers for obesity, type 2 diabetes, and metabolic syndrome. Research has also demonstrated the ability of diet-derived exogenous miRNAs to be absorbed from the digestive tract, appear within circulation, and be taken up by various tissues throughout the body. Diet-derived miRNAs specifically from plants have been detected in tissue and circulating within the blood suggesting the possibility of cross-species gene regulation, but the exact role these miRNAs play physiologically is still unknown. miRNAs are small non-coding molecules that affect post-transcriptional gene regulation and RNA silencing by translational repression or degradation. Previous research revealed that some plant miRNAs could be identified in equine serum exosomes and tissues but was not able to identify a corn specific miRNA within any equine samples. We first hypothesized that diet-derived corn miRNAs can be detected in equine serum and muscle after corn supplementation. For this study twelve mares were blocked by weight and BCS and assigned to one of two treatments (n=6/group): 1) control, (basal diet: 20 lbs./head/d of chopped mixed alfalfa-grass hay and ad libitum mixed grass hay), 2) basal diet supplemented with 1 lb./d steam flaked corn. Muscle biopsies of the Gluteus medius and serum samples were collected from all horses on d0 and d28. Samples were analyzed using real-time RT-qPCR for 3 plant miRNAs. Our results revealed the presence of plant miRNAs in equine total serum and skeletal muscle. Our results also revealed the level of plant miRNAs, including the corn specific miRNA, within circulation vary after ingestion, suggesting plant miRNAs are capable of being taken up by equine tissues. These results are important for understanding how physiological processes may be impacted by diet-derived plant miRNAs. Moreover, these results suggest plant miRNAs could potentially serve a therapeutic role in helping to regulate endogenous gene expression in addition to the nutrients being provided by ingestion. The large impact diet can have on equine health and the association between diets high in NSC and insulin resistance, caused us to be interested in the effects a diet supplemented with corn would have on endogenous miRNAs within the horse. We hypothesized that supplementing horses with corn would alter the endogenous miRNA profiles within both serum and skeletal muscle. For this objective, we utilized the same serum and muscle samples collected for the feed trial horses as the plant miRNAs. Samples were analyzed using real-time RT-qPCR for 277 endogenous equine miRNAs. Our results showed 13 differentially expressed (P<.05) miRNAs in equine serum after 28 days of corn supplementation. Six of these miRNAs (eca-mir16, -4863p, -4865p, -126-3p, -296, and -192), were linked to obesity and/or metabolic disease. Within skeletal muscle, our results showed three miRNAs differentially expressed (P<.05) and three miRNAs with a trend toward differential expression (.05<P<.1) after 28 days of corn supplementation. The differently expressed (P<.05) miRNAs in muscle (eca-mir1515p, eca-mir106b, and eca-mir133a) were all associated with obesity or muscle insulin response, while two of the miRNAs with a trend towards differential expression (.05<P<.1), ecamir-10b and eca-mir129a5p, were associated with diabetes/hyperglycemia and glucose metabolism respectively. This data indicates that diet does influence levels of endogenous miRNAs. The results of our study indicate that diet-derived plant miRNAs can appear in circulation, be taken up into tissues, and hold the potential to regulate endogenous genes. This study also provides more information on how a diet high in NSCs, like diets containing corn, alters levels of endogenous miRNAs within serum and tissue and helps to better understand the relationship between diet, health, and disease within horses.
Description
Rights Access
Subject
equine
microRNA
nutrition
horses
corn
miRNA