Insulin growth factors may explain relationship between spasticity and skeletal muscle size in men with spinal cord injury

Abstract

Abstract-The major objectives of this cross-sectional study were to (1) measure insulin-like growth factor-1 (IGF-1) in individuals with complete spinal cord injury (SCI) and spasticity and (2) determine the relationships between IGF-1 and cross-sectional areas (CSAs) of thigh skeletal muscle groups. Eight individuals with motor complete SCI underwent magnetic resonance imaging to measure the CSA of the whole thigh, knee extensor, and knee flexor skeletal muscle groups and dual-emission X-ray absorptiometry to measure fat-free mass. After participants fasted for 12 h, we measured their IGF-1 levels and determined spasticity using the Modified Ashworth Scale (MAS). Spearman rho correlations were used to test for the relationships among the tested variables, and independent t-tests were used to determine the difference in plasma IGF-1. Plasma IGF-1 was 44% greater in those with MAS scores of 2 or higher (p < 0.05). Plasma IGF-1 was positively related to knee extensor skeletal muscle CSA (r = 0. 83, p < 0.01). IGF-1 was strongly related to knee extensor and flexor spasticity (r = 0.88, p < 0.004). The findings suggest that IGF-1 is greater in SCI individuals with increased spasticity, and this may explain the strong positive relationships that were noted between spasticity and skeletal muscle CSA.

Chronic activity-based therapy does not improve body composition, insulin-like growth factor-I, adiponectin, or myostatin in persons with spinal cord injury

“…49 However, IGF-1 was strongly correlated to muscle size in men with complete SCI. 50 In the present study, lower adiponectin concentration in overweight (9.9 ± 3.1 μg/ml) compared to normal weight premenopausal women (14.4 ± 4.7 μg/ml), with adiponectin inversely related to parameters including BMI, body weight, and truncal fat. In a cross-sectional study in men with SCI, 58 adiponectin ranged from 2.9 to 37.2 μg/ml and was inversely associated with waist circumference and trunk fat, although in another study, 59 it was similar between able-bodied individuals and those with SCI, with this discrepancy being explained by similar body weight and BMI between subjects as well as different assays performed (ELISA versus RIA) across studies.…”

Effects of spinal cord injury on body composition and metabolic profile – Part I

“…46 The positive relationship between spasticity and muscle size as well as lean mass has recently been explained by the effect of spasticity on the circulating plasma IGF-1. 47 Those with MAS greater than 2 have 44% higher plasma IGF-1 than those with lower MAS. 47 In summary, the above findings suggest that body composition adaptations after SCI occur at cellular, muscular, regional, and whole-body levels.…”

Severe spasticity in lower extremities is associated with reduced adiposity and lower fasting plasma glucose level in persons with spinal cord injury

“…[24][25][26] Spasticity may provoke muscular IGF-1 that compensates for the reduced growth hormone-IGF-1 axis after SCI. 7 Although MAS is the most commonly used tool for measuring spasticity in clinical practice and research, the reliability and validity of this scale remain unclear. 27,28 Moreover, the degree of spasticity can vary according to the patient's physical and emotional conditions, even within a single day.…”

“…In addition, mechanisms through which severe spasticity ameliorates the derangement of body compositions and glucose homeostasis could be investigated. For example, differences in the expression of glucose transport protein, GLUT4 proteins, 30 IGF-1 concentration 7,29 and muscle fiber type composition 22,23 have been suggested as related mechanisms.…”

“…2,3 By contrast, spasticity may have beneficial effects on paralyzed skeletal muscle, that is, defending against skeletal muscle atrophy. [4][5][6][7] Gorgey and Dudley 6 demonstrated that eight higher-level SCI persons showed larger thigh muscle cross-sectional areas as compared with five lower level (T12-L2) SCI persons with no or mild spasticity. Gorgey and Gater 7 also showed that knee extensor spasticity positively correlated with knee extensor and whole thigh skeletal muscle cross-sectional areas.…”