Skeletal muscle Miro1 accumulation drives insulin resistance in type 2 diabetes, reversible by exercise

Imbalanced mitochondrial dynamics in skeletal muscle are increasingly recognized as a key contributor to type 2 diabetes (T2D) onset and progression, yet the precise mechanisms remain incompletely understood. Current therapeutic strategies often focus on glucose control but may not fully address underlying cellular dysfunctions like mitochondrial health. This study investigates Mitochondrial Rho GTPase 1 (Miro1), an outer mitochondrial membrane enzyme, as a potential regulator of skeletal muscle insulin action and glucose homeostasis, aiming to bridge this mechanistic gap.

Researchers conducted a multi-pronged study, beginning with a cross-sectional clinical assessment of Miro1 levels in skeletal muscle from patients with obesity and T2D. This was followed by replication in mouse models of T2D. A randomized controlled trial (NCT02977442) then evaluated the impact of exercise training on skeletal muscle Miro1 accumulation and insulin sensitivity in T2D patients. Further mechanistic insights were gained by performing muscle-specific Miro1 deletion in both mice and cellular models, assessing oxidative capacity and insulin sensitivity.

Miro1 was found to accumulate significantly in the skeletal muscle of patients with obesity and T2D, a finding consistently replicated in mouse models of the disease. This accumulation was mechanistically linked to an inadequate insulin-mediated interaction between AKT and Miro1 at the outer mitochondrial membrane. In the randomized controlled trial, exercise training successfully relieved skeletal muscle Miro1 accumulation in T2D patients. Simultaneously, this intervention led to improved insulin sensitivity in these patients. > Muscle-specific Miro1 deletion in mice and cells directly improved both oxidative capacity and insulin sensitivity, strongly supporting a causal role for Miro1 in T2D pathophysiology.