Rice Bran Compound: Gamma-Oryzanol Improves Metabolic Syndrome and Oxi-Inflammation in Phasic Musculature of Rats with a Preserved Obese Phenotype

Rice bran (RB) is a byproduct of rice refinement that is usually discarded. RB derived from the Oryza sativa species contains gamma-oryzanol (GORY), a strong free radical scavenger with anti-inflammatory, anti-obesity, antidiabetic, and hypolipidemic properties. Due to its wide range of biological activities, GORY represents a promising intervention for diet induced-Metabolic Syndrome (DiMetS) and consequent phasic musculature oxi-inflammation. This study aimed to evaluate the therapeutic effects of gamma-oryzanol treatment on diet-induced metabolic syndrome and phasic musculature oxi-inflammation. Male Wistar rats were randomly assigned to four groups (n=6/group): Control (CTRL), CTRL supplemented with GORY (CTRL+GORY), DiMetS, feed with a high sugar-fat chow enriched with sucrose (80g/kg), fructose (180g/kg) and lard (154g/kg) plus 25% of sucrose in drinking water, and DiMetS supplemented with GORY (0.5% w/w) (DiMetS+GORY). After 30 weeks, the animals were fasted, anesthetized, and euthanized (1458/2024-CEUA). Metabolic syndrome indicators were measured through enzymatic-colorimetric methods and enzyme-linked immunosorbent assay (ELISA). The oxi-inflammation parameters were assessed in the extensor digitorum longus (EDL) muscle. Muscle samples were homogenized in cold PBS or KH₂PO4/KCL for the evaluations. Data were analyzed by Two-way Anova followed by Tukey´s post-hoc test (α=5%). Compared to the CTRL group, the DiMetS group presented higher caloric intake (p<0.001), body weight (p<0.001), adiposity index (p<0.001), fasting glucose (p<0.001), triglycerides (p<0.001), insulin resistance (p<0.001), and blood pressure (p<0.001). Regarding the EDL muscle, the DiMetS group showed increased lipid peroxidation (p<0.001) and protein carbonylation (p<0.001), impaired superoxide dismutase (SOD) activity (p=0.010), and higher levels of Interleukin-6 (p<0.006). Compared to the DiMetS group, the DiMetS+GORY group presented improved fasting glucose (p<0.001), triglycerides (p<0.001), insulin resistance (p<0.001), muscular protein carbonylation (p=0.009), SOD (p=0.019) and catalase activities (p<0.001), and IL-6 levels (p<0.001). Our diet effectively induced MetS and the oxi-inflammation in the EDL muscle, which is responsible for fast-twitch contractions and locomotion. Despite any changes in caloric intake, body weight, or adiposity index, GORY exerted hypoglycemic, hypolipidemic, and redox and inflammatory modulatory properties in fast-twitch musculature. These effects can be attributed to its structural similarity to cholesterol and to the four major compounds of GORY (24-Methylene cycloartenyl ferulate, Cycloartenyl ferulate, Campesteryl ferulate and β-sitosteryl ferulate), with 24-Methylene cycloartenyl ferulate being the component with the highest antioxidant activity. In conclusion, GORY treatment improved metabolic syndrome and the associated phasic muscle oxi-inflammation of rats with a preserved obese phenotype.

Acknowledgments: FAPESP (2023/06451-6).