Sulforaphane Against the Metabolic Consequences of a High-Glycemic-Index Diet: Protective and Therapeutic Mechanisms Associated with Obesity and Insulin Resistance

<b>Objective:</b> This study investigated the effects of different doses and timing of sulforaphane (SFN) supplementation on reducing obesity induced by a high-glycemic-index diet (HGID) and on correcting poor glycemic control and dyslipidemia in C57BL/6 mice. <b>Method:</b> For 15 weeks, mice were administered a control diet (control), HGID, HGID + oral 5 mg/kg/day SFN (HGID + LSFN), or HGID + 20 mg/kg/day SFN (HGID + HSFN), and following 15 weeks of HGID, mice were treated with 5 mg/kg/day SFN (PO-HGID + LSFN) or 20 mg/kg/day SFN (PO-HGID + HSFN) for 5 weeks. <b>Results:</b> SFN reduced body weight gain and serum glucose. The lowest levels of HbA1c were observed in the control and HGID + LSFN groups. Mice in the HGID group exhibited impaired glucose clearance and were less sensitive to insulin compared to the control. A remarkable improvement in glucose and insulin tolerance was observed in both PO-HGID + SFN and HGID + SFN groups. Lipid profile parameters and serum insulin levels were found to be lower in the control and HGID + SFN groups compared to the HGID group. SFN increased serum adiponectin levels when administered concurrently with HGID. IRS1 and IRS2 levels were highest in the control and HGID + LSFN groups, and high-dose SFN supplementation suppressed IRS1 independently of timing. Exposure to HGID downregulated the expression of PGC-1α and sirtuins. SIRT1 and SIRT3 gene expressions showed a significant increase at both doses, whereas SIRT2 gene expression increased significantly only at 5 mg/kg/day SFN. FASN expression was upregulated in all HGID-fed groups with or without SFN intervention. <b>Conclusions:</b> SFN may reverse the adverse effects of HGID in a time- and dose-dependent manner by regulating postprandial insulin, inhibiting gluconeogenesis, and enhancing fatty acid oxidation through the activation of sirtuins and PGC-1α.