Exercise-Induced Muscular and Hepatic Lipid Adaptations in Type 2 Diabetes Mellitus: A Systematic Review

Abstract

Introduction: Type 2 diabetes (T2D) is characte-rized by insulin resistance and ectopic lipid accumula-tion in muscle and liver. This dysfunction contribu-tes to metabolic impair-ment and increased car-diovascular risk. Physical exercise is considered a cornerstone therapy, al-though the specific effects of different exercise moda-lities on these lipid depots are not fully defined. Objective: To evaluate the impact of exercise on in-tramyocellular lipids (IMCL) and intrahepatic lipids (IHL) in adults with T2D and to identify the most effective protocols. Methods: A systematic review was conducted following PRISMA 2020 guidelines in PubMed, Scopus, Web of Science, and Cochrane (2000–2023). Randomized and quasi-experimental trials analyzing aerobic, HIIT, resistance, or combined training and assessing IMCL/IHL via MRI, ¹H-MRS, or biopsy were included. Risk of bias was evaluated with RoB 2/ROBINS-I, and certainty of evidence was rated using GRADE. Results: Twelve studies (≈296 participants, 49–59 years) were included. Aerobic exercise and HIIT reduced IHL by 30–45 %, even without weight loss. Combined training produ-ced similar reductions and additional improvements in strength and muscle profile. Changes in IMCL reflected a favorable reor-ganization toward an “ath-lete-like phenotype,” cha-racterized by small, in-tramyofibrillar lipid dro-plets coupled to mitochon-dria (↑ PLIN5), associated with greater metabolic flexibility. Conclusions: Exercise, particularly HIIT and com-bined programs, is effecti-ve in reducing IHL and optimizing IMCL profile in T2D. Prescription should be individualized and may be enhanced by dietary strategies.