Insulin resistance (IR) and hepatic steatosis are increasingly prevalent conditions, significantly contributing to type 2 diabetes mellitus (T2DM) and metabolic syndrome (MetS). The pathogenesis of IR involves ectopic lipid accumulation, increased liver glucose production, and decreased glucose uptake in insulin-sensitive tissues. Non-alcoholic fatty liver disease (NAFLD), encompassing simple steatosis and non-alcoholic steatohepatitis (NASH), is a common liver disorder often associated with IR. While the "multiple hit" model now supersedes the "two hit" hypothesis in explaining NAFLD pathogenesis, dietary fiber has emerged as a crucial protective factor. This study focuses on basil seeds (*Ocimum basilicum* L.), a widely used plant with largely unexplored health-promoting properties. The researchers hypothesized that a fiber-rich fraction from partially defatted basil seeds could mitigate IR and hepatic steatosis in a mouse model.

Extensive research links dietary fiber intake to improved metabolic health, including body weight management, lipid regulation, and enhanced insulin sensitivity. However, the search continues for novel fiber sources with diverse characteristics suitable for functional foods. Previous studies have demonstrated the amelioration of adiposity and IR in mice fed high-fat diets through dietary fiber supplementation. The positive effects on serum triglycerides, total cholesterol, and LDL cholesterol have also been documented with the use of fermentable dietary fibers and artichoke fiber. The role of alpha-linolenic acid (ALA), a polyunsaturated fatty acid, in reducing triglyceride and cholesterol levels is also well-established. Furthermore, the importance of gut microbiota-derived short-chain fatty acids (SCFAs) in regulating energy homeostasis and mitigating inflammation is increasingly recognized. However, research into basil seed by-products and their impact on IR and hepatic steatosis remains limited.

Basil seeds were obtained and processed to isolate a fiber-rich fraction (BSF). The nutritional composition, including protein, fat, and dietary fiber content, was analyzed using standard methods (AACC, AOAC). Fatty acid profiles were determined using gas-liquid chromatography (GC). Male C57BL/6J mice were randomly assigned to four groups: control diet (CD), high-fat diet (HFD), HFD + BSF, and HFD + oat flour (OAF, control). After 14 weeks (with BSF/OAF supplementation for the last 4 weeks), metabolic parameters (glycemia, insulinemia, HOMA-IR, lipids), liver histology (steatosis score, fat content, TG, cholesterol, transaminases), oxidative stress markers (TBARS, isoprostanes, protein carbonyls), inflammatory markers (TNF-α, IL-6, IL-1β), antioxidant defenses (GSH, GSSG, GSH/GSSG ratio), and fatty acid profiles in liver, adipose tissue, erythrocytes, brain, and stool were assessed using various techniques (ELISA, colorimetric assays, GC). Gene expression levels of key enzymes related to lipid metabolism and inflammation (PPAR-α, CPT1α, SREBP-1c, FAS, NFκB-1, TNF-α, IL-1β, IL-6) were analyzed using real-time PCR. SCFAs in stool were also quantified by GC. Statistical analysis included one-way ANOVA and non-parametric methods (Kruskal Wallis, Dunn's test).

The HFD induced IR, hepatic steatosis, inflammation, oxidative stress, and reduced SCFA production. BSF supplementation significantly attenuated these effects. Specifically, BSF supplementation led to: * Reduced plasma glucose, insulin, and HOMA-IR. * Decreased triglycerides, total cholesterol, and LDL cholesterol. * Reduced liver steatosis, as evidenced by histology, hepatic fat content, and TG/cholesterol levels. * Lower levels of liver damage markers (AST, ALT). * Reduced hepatic TBARS, isoprostanes, and protein carbonyls (markers of oxidative stress). * Decreased levels of inflammatory cytokines (TNF-α, IL-6, IL-1β). * Increased levels of n-3 PUFAs (ALA, EPA, DHA) in liver, adipocytes, and erythrocytes. * Increased total SCFAs in stool, primarily acetic, propionic, and butyric acids. * Increased stool moisture. * Down-regulation of PPAR-α mRNA expression and upregulation of CPT1α mRNA expression in liver. * Attenuation of hepatic SREBP-1c and FAS mRNA expression (involved in de novo lipogenesis).

The study's findings demonstrate that BSF effectively mitigates HFD-induced IR and hepatic steatosis in mice. The improvements in metabolic parameters, reduced inflammation and oxidative stress, and altered fatty acid profiles strongly support the potential therapeutic use of BSF. The increased SCFA production suggests a beneficial effect on gut microbiota composition and function. The mechanisms involved are likely multifaceted, including improved lipid metabolism via PPAR-α activation and inhibition of lipogenic enzymes, reduced inflammation, enhanced antioxidant defenses, and modulation of gut microbiota. The rich fiber content in BSF plays a crucial role in these improvements, through mechanisms like increased satiety, reduced nutrient absorption, and altered bile acid metabolism. The high ALA content in BSF, and its conversion to DHA, likely contributes to the observed anti-inflammatory and protective effects. These results extend previous research highlighting the benefits of dietary fiber and n-3 PUFAs in metabolic disorders.

This study shows that the fiber-rich fraction from partially defatted basil seeds (BSF) effectively combats HFD-induced IR and hepatic steatosis in mice. The multifaceted protective effects highlight the potential of BSF as a therapeutic agent. Future research should investigate the specific bioactive components of BSF responsible for these effects and its efficacy in human populations.

The study used a mouse model, which may not fully translate to human physiology. The long-term effects of BSF supplementation remain unknown. The study did not investigate the specific changes in gut microbiota composition.