Effects of rice bran oil on plasma lipid concentrations, lipoprotein composition, and glucose dynamics in mares1

Value of measuring markers of lipid metabolism in horses during an oral glucose test

BACKGROUND

Characterizing the lipid response to an oral glucose test (OGT) might improve our understanding of Equine Metabolic Syndrome.

HYPOTHESIS/OBJECTIVES

To describe the effects of an OGT on lipid metabolism and determine the value of measuring triglyceride and nonesterified fatty acid (NEFA) concentrations in hyperinsulinemic (HI) and insulin-resistant (IR) horses.

ANIMALS

Twenty horses including 7 HI-IR horses, 4 HI-non-IR horses, and 9 non-HI-non-IR horses (control).

METHODS

Cross-sectional design. Horses underwent an OGT, with blood samples collected at 0, 60, 90, and 120 minutes. Insulin, glucose, triglyceride, and NEFA concentrations were measured and compared over time and between groups, with P < .05 considered significant.

RESULTS

In all horses, the OGT had a significant effect on triglyceride concentrations (median [interquartile range]: .35 [.30-.50] mmol/L at 0 minute vs .25 [.21-.37] mmol/L at 120 minutes, P = .005) and on NEFA concentrations (.1 [.1-.2] mEq/L at 0 minute vs .05 [.05-.1] mEq/L at 120 minutes, P = .0009). However, horses with HI and IR had higher triglyceride areas under the curve (AUC, 79.46 ± 46.59 vs 33.32 ± 6.75 mmol/L*min, P = .01) as well as NEFA AUC (9.1 ± 2.9 vs 6.0 ± 6.8 mEq/L*min, P = .03) than control horses. No significant difference was detected between control and HI non-IR horses.

CONCLUSIONS AND CLINICAL IMPORTANCE

Determining triglyceride and NEFA concentrations might help assess tissue insulin resistance during an OGT.

Rice bran in old horse’s nutrition and their influence on condition, blood biochemical parameters, total feces bacteria and methanogen population

This study aimed to verify whether the inclusion of 0.5 kg full-fat rice bran per day in the diet of geriatric horses will improve their condition, increase the population of methanogens in the cecum, and thus affect the biochemical blood parameters. The experiment assumed 2 research periods: 6 healthy, non-working horses over 20 years of age (480 ± 20 kg of body weight) were fed only hay (±8.86 kg/day/head) in the first period and hay (±8.00 kg/day/head) and rice bran (0.5 kg/day/head) in the second one. Each of these periods lasted 4 months. The Body Condition Scoring (BCS) assessment was performed at the beginning and end of the experiment. Blood and feces samples were collected on the first and last day of each period. After feeding with the addition of rice bran, BCS increased by 1.17 units on a 9-point scale. The experiment showed an increase in the total number of bacteria and methanogens inhabiting the cecum of horses. This can lead to better digestion of carbohydrates, absorption of nutrients, and, consequently, increased body weight. No differences occurred in the hematology and serum biochemistry indices of horses fed a diet including rice bran, except for the amount of serum globulin and the albumin to globulin ratio. Rice bran affected essential serum fatty acid profile (increased PUFA and decreased MUFA) which confirmed the possibility to use diet as a serum fatty acids profile modulator.

Comparison of insulin sensitivity between healthy neonatal foals and horses using minimal model analysis

The equine neonate is considered to have impaired glucose tolerance due to delayed maturation of the pancreatic endocrine system. Few studies have investigated insulin sensitivity in newborn foals using dynamic testing methods. The objective of this study was to assess insulin sensitivity by comparing the insulin-modified frequently sampled intravenous glucose tolerance test (I-FSIGTT) between neonatal foals and adult horses. This study was performed on healthy neonatal foals (n = 12), 24 to 60 hours of age, and horses (n = 8), 3 to 14 years of age using dextrose (300 mg/kg IV) and insulin (0.02 IU/kg IV). Insulin sensitivity (SI), acute insulin response to glucose (AIRg), glucose effectiveness (Sg), and disposition index (DI) were calculated using minimal model analysis. Proxy measurements were calculated using fasting insulin and glucose concentrations. Nonparametric statistical methods were used for analysis and reported as median and interquartile range (IQR). SI was significantly higher in foals (18.3 L·min^-1· μIU^-1 [13.4–28.4]) compared to horses (0.9 L·min^-1· μIU^-1 [0.5–1.1]); (p < 0.0001). DI was higher in foals (12 × 10³ [8 × 10³−14 × 10³]) compared to horses (4 × 10² [2 × 10²−7 × 10²]); (p < 0.0001). AIRg and Sg were not different between foals and horses. The modified insulin to glucose ratio (MIRG) was lower in foals (1.72 μIU_insulin²/10·L·mg_glucose [1.43–2.68]) compared to horses (3.91 μIU _insulin²/10·L·mg_glucose [2.57–7.89]); (p = 0.009). The homeostasis model assessment of beta cell function (HOMA-BC%) was higher in horses (78.4% [43–116]) compared to foals (23.2% [17.8–42.2]); (p = 0.0096). Our results suggest that healthy neonatal foals are insulin sensitive in the first days of life, which contradicts current literature regarding the equine neonate. Newborn foals may be more insulin sensitive immediately after birth as an evolutionary adaptation to conserve energy during the transition to extrauterine life.

The Safety and Efficacy in Horses of Certain Nutraceuticals that Claim to Have Health Benefits

Equine nutraceuticals are promoted as useful therapies to help optimize health and athletic performance, often without the benefit of independent research to support product efficacy and safety. This review focuses on 4 main categories of equine supplements that are frequently used as nutraceuticals: (i) supplements to support metabolic health, (ii) gastric support products, (iii) common ingredients that are included in supplements designed to support hoof health, and (iv) supplements to support joint health.

Novel lipoprotein density profiling in laminitic, obese, and healthy horses

Lipoproteins are water-miscible macromolecules enabling the transport of lipids in blood. In humans, altered proportions of lipoproteins are used to detect and classify metabolic diseases. Obesity and obesity-related comorbidities are common in horses. The pathophysiology of obesity is poorly understood and likely multifactorial. Development of new diagnostic tests to identify horses at risk of developing obesity to implement preventative measures is critical; however, a necessary first step to accomplish this goal is to improve our understanding of the pathophysiology of disease. Thus, the objective of this study was to characterize and compare lipoprotein profiles of horses with normal and excess body conditions, with and without laminitis using a novel method of continuous lipoprotein density profiling (CLPDP). Comparisons were made between 4 groups of horses: (1) laminitic, obese horses (n = 66); (2) laminitic, nonobese horses (n = 35); (3) nonlaminitic, obese horses (n = 41); and (4) nonlaminitic, nonobese horses (n = 95). Lipoprotein profiling, including evaluation of triglyceride-rich lipoprotein (TRL), low-density lipoproteins (LDLs), and high-density lipoproteins (HDLs) was performed using CLPDP, and all 4 groups were compared. A significant difference was observed among groups for the subfractions TRL, LDL1, LDL2, HDL2b, HDL2a, HDL3a, HDL3b, HDL3c, and total HDL. This is the first known description of CLPDP to characterize equine lipid profiles and holds promise as a useful method for lipid characterization of horses.

Investigation of nutriactive phytochemical - gamma-oryzanol in experimental animal models

Gamma-oryzanol (GO) is an abundant dietary antioxidant that is considered to have beneficial effects in cardiovascular disease, cancer and diabetes. Other potential properties of GO include inhibition of gastric acid secretion and decreased post-exercise muscle fatigue. GO is a unique mixture of triterpene alcohol and sterol ferulates present in rice bran oil, a byproduct of rice processing. GO has been studied by many researchers over the last three decades. In particular, the utility of GO supplementation has been documented in numerous animal models. A large variety of species was examined, and various experimental methodologies and targets were applied. The aim of this study was to summarize the body of research on GO supplementation in animals and to examine possible mechanisms of GO action. Furthermore, while the safety of GO supplementation in animals has been well documented, studies demonstrating pharmacokinetics, pharmacodynamics and efficiency are less clear. The observed differences in these findings are also discussed.

Characterization of rice bran wax policosanol and its nanoemulsion formulation

Policosanol, a mixture of long-chain alcohols found in animal and plant waxes, has several biological effects; however, it has a bioavailability of less than 10%. Therefore, there is a need to improve its bioavailability, and one of the ways of doing this is by nanoemulsion formulation. Different droplet size distributions are usually achieved when emulsions are formed, which solely depends on the preparation method used. Mostly, emulsions are intended for better delivery with maintenance of the characteristics and properties of the leading components. In this study, policosanol was extracted from rice bran wax, its composition was determined by gas chromatography mass spectrophotometry, nanoemulsion was made, and the physical stability characteristics were determined. The results showed that policosanol nanoemulsion has a nanosize particle distribution below 100 nm (92.56–94.52 nm), with optimum charge distribution (−55.8 to −45.12 mV), pH (6.79–6.92) and refractive index (1.50); these were monitored and found to be stable for 8 weeks. The stability of policosanol nanoemulsion confers the potential to withstand long storage times.

Phospholipid composition of plasma and erythrocyte membranes in animal species by 31P NMR

The aim of this study was to provide basal values of phospholipid (PL) composition in different animal species by 31P NMR analysis using detergents. This fast and accurate method allowed a quantitative analysis of PLs without any previous separation. Plasma and erythrocyte membrane PLs were investigated in mammals (pig, cow, horse). Moreover, for the first time, the composition of plasma PLs in avian (chicken and ostrich) was performed by 31P NMR. Significant qualitative and quantitative interspecies differences in plasma PL levels were found. Phosphatidilcholine (PC) and sphingomyelin (SPH) levels were significantly higher (P < 0.001) in chicken plasma than all the other species tested. In erythrocytes, cow PC and phosphatidylcholine diarachidoyl were significantly lower (P < 0.001) than for pigs and horses, whereas pig PC presented intermediate values among cows and horses. Inorganic phosphate and 2,3-diphosphoglycerate levels were also significantly different between the species under investigation. The [SPH/total PLs] molar ratios in erythrocytes confirmed interspecies differences in phospholipid composition while the PC/SPH molar ratios could be related to a distinct erythrocyte flexibility and aggregability. Diet and nutrition may contribute primarily to the interspecies differences in plasma PL amounts detected. Significant differences between chicken plasma PC and SPH levels and those of the other animal species could be ascribed to a fat metabolism specific to egg production.

Endocrinopathic laminitis: reducing the risk through diet and exercise

Certain individual animals appear predisposed to recurrent pasture-associated laminitis, but the exact mechanisms underlying their predisposition remain a fundamental question in laminitis research. The risk of endocrinopathic laminitis can be reduced if steps are taken to improve insulin sensitivity and reduce inflammation using strategies based on exercise and diet. Exercise has been shown to reduce insulin resistance and suppress inflammation, and dietary manipulation can significantly affect insulin sensitivity.

Physical characteristics, blood hormone concentrations, and plasma lipid concentrations in obese horses with insulin resistance

OBJECTIVE

To compare obese horses with insulin resistance (IR) with nonobese horses and determine whether blood resting glucose, insulin, leptin, and lipid concentrations differed between groups and were correlated with combined glucose-insulin test (CGIT) results.

ANIMALS

7 obese adult horses with IR (OB-IR group) and 5 nonobese mares.

PROCEDURES

Physical measurements were taken, and blood samples were collected after horses had acclimated to the hospital for 3 days. Response to insulin was assessed by use of the CGIT, and maintenance of plasma glucose concentrations greater than the preinjection value for > or = 45 minutes was used to define IR. Area under the curve values for glucose (AUC(g)) and insulin (AUC(i)) concentrations were calculated.

RESULTS

Morgan, Paso Fino, Quarter Horse, and Tennessee Walking Horse breeds were represented in the OB-IR group. Mean neck circumference and BCS differed significantly between groups and were positively correlated with AUC values. Resting insulin and leptin concentrations were 6 and 14 times as high, respectively, in the OB-IR group, compared with the nonobese group, and were significantly correlated with AUC(g) and AUC(i). Plasma nonesterified fatty acid, very low-density lipoprotein, and high-density lipoprotein-cholesterol (HDL-C) concentrations were significantly higher (86%, 104%, and 29%, respectively) in OB-IR horses, and HDL-C concentrations were positively correlated with AUC values.

CONCLUSIONS AND CLINICAL RELEVANCE

Measurements of neck circumference and resting insulin and leptin concentrations can be used to screen obese horses for IR. Dyslipidemia is associated with IR in obese horses.