Hesperetin Ameliorates High-Fat Diet-Induced Skeletal Muscle Dysfunction by Regulating Mitochondrial Cristae Morphology Through the Sestrin2/AMPK/OPA1 Signalling Pathway

Background: Long-term consumption of a high-fat diet (HFD) may cause insulin resistance (IR), leading to physiological dysfunction in skeletal muscle. IR is closely associated with mitochondrial dysfunction, and naturally occurring flavonoids may help improve mitochondrial function. Methods: Eight-week-old male C57BL/6J mice (n = 10/group) were fed either a 10 kcal% fat chow diet (CON) or a 60 kcal% fat HFD for 12 weeks. HFD-fed mice received daily gavage with hesperetin (50 or 100 mg/kg body weight (BW), ≥98% purity) or vehicle. BW and food intake were recorded weekly. After 10 weeks, strength and exercise performance, intraperitoneal glucose tolerance test/intraperitoneal insulin tolerance test (IPGTT/IPITT), serum lipids, mitochondrial ultrastructure (transmission electron microscopy (TEM)), adenosine triphosphate (ATP) content, molecular docking and dynamics, and Western blotting were assessed. Results: The findings suggested that hesperetin improved exercise capacity (p < 0.05 and p < 0.01) and reduced body fat content and distribution (all p < 0.01). Hesperetin also improved mitochondrial function, as primarily evidenced by increased ATP content in the skeletal muscle of HFD-fed mice (HFD vs high-fat diet with a low dose of hesperetin (HFD-LH), p = 0.004; HFD vs high-fat diet with a high dose of hesperetin (HFD-HH), p < 0.01), reduced mitochondrial cristae damage in skeletal muscle (p < 0.05 and p < 0.01), and upregulated the expression of mitochondrial function-related proteins in complexes I to V, with effects varying by muscle type and dosage (p < 0.05 and p < 0.01). Additionally, hesperetin upregulated the expression of Sestrin2 (gastrocnemius: HFD vs HFD-LH, p = 0.047; HFD vs HFD-HH, p = 0.01; soleus: HFD vs HFD-LH, p = 0.016; HFD vs HFD-HH, p < 0.01) and Optic atrophy 1 (OPA1) (gastrocnemius: all p < 0.01; soleus: HFD vs HFD-LH, p = 0.017; HFD vs HFD-HH, p < 0.01), and incresaed Adenosine 5’-monophosphate (AMP)-activated protein kinase (AMPK) phosphorylation (gastrocnemius: HFD vs HFD-LH, p = 0.031; HFD vs HFD-HH, p = 0.001; soleus: HFD vs HFD-LH, p = 0.01; HFD vs HFD-HH, p = 0.002). Conclusions: We speculate that hesperetin may help preserve mitochondrial structure and function. This effect, which could contribute to reduced skeletal muscle dysfunction, may be linked to the Sestrin2/AMPK/OPA1 signalling pathway.