Diet Induced Obesity Alters Muscle Spindle Afferent Function in Adult Male Mice

Balance impairment and chronic low level systemic inflammation have both been associated with obesity. As inflammatory factors have been shown to alter the activity of Group Ia/II muscle spindle afferents (Delliaux et al., 2009), we hypothesized that obesity would lead to a reduced response to stretch and less sensitivity to vibrations in muscle spindle afferents. Five-week-old male C57Bl/6 mice were fed either a high fat diet (HFD; 60% kcal from fat, Research Diets) or a control diet (10% kcal from fat) for 10 weeks. Mice fed a HFD were significantly heavier after 10 weeks than controls (HFD = 37.6g ± 3.52[SD]; control = 28.1g ± 2.60[SD]; p < 0.05). The extensor digitorum longus muscle and innervating sciatic nerve were dissected and placed into an in vitro bath. Muscle spindle afferent activity was recorded during ramp and hold stretches of three physiological stretch lengths and during 10-100Hz frequency vibrations. Muscle spindle afferent firing frequencies increased linearly in both HFD (n = 14) and ...