Effect of low-dose baclofen administration on plasma insulin-like growth factor-I in persons with spinal cord injury

Predictors of muscle hypertrophy responsiveness to electrically evoked resistance training after spinal cord injury

The purpose of the study was to identify potential predictors of muscle hypertrophy responsiveness following neuromuscular electrical stimulation resistance training (NMES-RT) in persons with chronic spinal cord injury (SCI). Data for twenty individuals with motor complete SCI who completed twice weekly NMES-RT lasting 12-16 weeks as part of their participation in one of two separate clinical trials were pooled and retrospectively analyzed. Magnetic resonance imaging (MRI) was used to measure muscle cross-sectional area (CSA) of the whole thigh and knee extensor muscle before and after NMES-RT. Muscle biopsies and fasting biomarkers were also measured. Following the completion of the respective NMES-RT trials, participants were classified into either high-responders (n = 8; muscle CSA > 20%) or low-responders (n = 12; muscle CSA < 20%) based on whole thigh muscle CSA hypertrophy. Whole thigh muscle and knee extensors CSAs were significantly greater (P < 0.0001) in high-responders (29 ± 7% and 47 ± 15%, respectively) compared to low-responders (12 ± 3% and 19 ± 6%, respectively). There were no differences in total caloric intake or macronutrient intake between groups. Extensor spasticity was lower in the high-responders compared to the low-responders as was the dosage of baclofen. Prior to the intervention, the high-responders had greater body mass compared to the low-responders with SCI (87.8 ± 13.7 vs. 70.4 ± 15.8 kg; P = 0.012), body mass index (BMI: 27.6 ± 2.7 vs. 22.9 ± 6.0 kg/m2; P = 0.04), as well as greater percentage in whole body and regional fat mass (P < 0.05). Furthermore, high-responders had a 69% greater increase (P = 0.086) in total Akt protein expression than low-responders. High-responders also exhibited reduced circulating IGF-1 with a concomitant increase in IGFBP-3. Exploratory analyses revealed upregulation of mRNAs for muscle hypertrophy markers [IRS-1, Akt, mTOR] and downregulation of protein degradation markers [myostatin, MurF-1, and PDK4] in the high-responders compared to low-responders. The findings indicate that body composition, spasticity, baclofen usage, and multiple signaling pathways (anabolic and catabolic) are involved in the differential muscle hypertrophy response to NMES-RT in persons with chronic SCI.

Insulin-like growth factor 1 promotes neurological functional recovery after spinal cord injury through inhibition of autophagy via the PI3K/Akt/mTOR signaling pathway

Spinal cord injury (SCI) is a serious trauma; however, the mechanisms underlying the role of insulin-like growth factor 1 (IGF-1) in autophagy following SCI remain to be elucidated. The present study aimed to investigate the therapeutic effect of IGF-1 on SCI and to determine whether IGF-1 regulates autophagy via the PI3K/Akt/mTOR signaling pathway. SH-SY5Y neuroblastoma cells were assigned to the H₂O₂, IGF-1 and control groups to investigate subsequent neuron injury in vitro. An MTT assay was performed to evaluate cell survival. In addition, Sprague-Dawley rats were randomly assigned to SCI, SCI + IGF-1 and sham groups, and Basso-Beatlie-Bresnahan scores were assessed to determine rat neurological function. Western blotting was used to analyze the autophagy level and the activation of the PI3K/Akt/mTOR signaling pathway. Cell survival was increased significantly in the IGF-1 group compared with the control group in vitro (P<0.05). Furthermore, neurological function was improved in the SCI + IGF-1 group compared with the control group in vivo (P<0.05). The western blotting results further demonstrated that LC3II/LC3I expression was increased in the IGF-1 group compared with the sham group in vivo and compared with the control group in vitro (both P<0.05). In the SCI + IGF-1 group, the expression levels of PI3K, phosphorylated (p)-Akt and p-mTOR were higher compared with those in the sham and SCI groups in vivo (P<0.05). Moreover, in the IGF-1 group, the expression levels of p-Akt and p-mTOR were higher compared with the control and the H₂O₂ groups in vitro (P<0.05). Collectively, the results of the present study suggested that IGF-1 promoted functional recovery in rats following SCI through neuroprotective effects. Furthermore, the underlying mechanism may involve activation of the PI3K/Akt/mTOR signaling pathway, followed by inhibition of autophagy. However, further investigation into the association between IGF-1-regulated autophagy and the activation of different subtypes of PI3K is required.

Effects of Use and Disuse on Non-paralyzed and Paralyzed Skeletal Muscles

Skeletal muscle is an integral part of the somatic nervous system and plays a primary role in the performance of physical activities. Because physical activity is vital to countering the effects of aging and age related diseases and is a key component in the maintenance of healthy body composition it is important to understand the effects of use and disuse on skeletal muscle. While voluntary muscle activity provides optimal benefits to muscle and the maintenance of healthy body composition, neuromuscular electrical stimulation may be a viable alternative activity for individuals with paralysis. Body composition with a healthy muscle to fat ratio has been associated with healthy blood lipid and glucose profiles that may decrease the risk of cardiovascular and metabolic diseases.

Effects of spinal cord injury on body composition and metabolic profile - part I

Several body composition and metabolic-associated disorders such as glucose intolerance, insulin resistance, and lipid abnormalities occur prematurely after spinal cord injury (SCI) and at a higher prevalence compared to able-bodied populations. Within a few weeks to months of the injury, there is a significant decrease in total lean mass, particularly lower extremity muscle mass and an accompanying increase in fat mass. The infiltration of fat in intramuscular and visceral sites is associated with abnormal metabolic profiles. The current review will summarize the major changes in body composition and metabolic profiles that can lead to comorbidities such as type 2 diabetes mellitus and cardiovascular diseases after SCI. It is crucial for healthcare specialists to be aware of the magnitude of these changes. Such awareness may lead to earlier recognition and treatment of metabolic abnormalities that may reduce the co-morbidities seen over the lifetime of persons living with SCI.

Spinal Cord Injury survey to determine pressure ulcer vulnerability in the outpatient population

Pressure ulcers are one of the most common causes of morbidity, mortality and rehospitalization for those living with Spinal Cord Injury (SCI). Literature examining risk and recurrence of pressure ulcers (PrUs) has primarily focused on the nursing home elderly who do not have SCI. More than 200 factors that increase PrU risk have been identified. Yet unlike the elderly who incur pressure ulcers in nursing homes or when hospitalized, most persons with SCI develop their pressure ulcers as outpatients, while residing in the community. The Veterans Health Administration (VHA) provides medical care for a large number of persons with chronic SCI. Included in the VHA SCI model of chronic disease management is the provision of an annual Comprehensive Preventive Health Evaluation, a tool that has potential to identify individuals at high risk for PrUs. This research was motivated by the clinical observation that some individuals appear to be protected from developing PrUs despite apparently 'risky' behaviors while others develop PrUs despite vigilant use of the currently known preventative measures. There is limited literature regarding protective factors and specific risk factors that reduce PrU occurrence in the community dwelling person with chronic SCI have not been delineated. The purpose of this study is to examine the preliminary hypothesis that there are biological and/or psychosocial factors that increase or reduce vulnerability to PrUs among persons with SCI. A limited number of refined hypotheses will be generated for testing in a prospective fashion. A retrospective cross-sectional survey of 119 randomly selected Veterans with SCI undergoing the Comprehensive Health Prevention Evaluation during the year 2009 was performed. Factors that differed between patients with 0, 1 or ⩾2 PrUs were identified and stratified, with an emphasis on modifiable risk factors. Three hypotheses generated from this study warrant further investigation: (1) cumulative smoking history increases the risk of PrUs independent of co-morbidities, (2) being moderately overweight, BMI>25, with or without spasticity, is a modifiable factor that may be protective and (3) increased use of a caregiver does not reduce PrU risk. Prospective studies that focus on these hypotheses will lead to evidence-based risk assessment tools and customized interventions to prevent PrUs in persons with SCI in the outpatient setting.

Low-dose baclofen therapy raised plasma insulin-like growth factor-1 concentrations, but not into the normal range in a predictable and sustained manner in men with chronic spinal cord injury

OBJECTIVE

To evaluate, whether once-daily oral baclofen administration increases and/or sustains plasma insulin-like growth factor-1 (IGF-1) concentration in 11 men with chronic spinal cord injury (SCI) and IGF-1 deficiency (i.e. <250 ng/ml).

DESIGN

Prospective, open-label, dose titration study. Baclofen was administered at 20 mg/day for 8 weeks; then increased to 40 mg/day for another 8 weeks. Plasma IGF-1 and self-reported side effects were measured at baseline and every other week for the duration of the study.

RESULTS

The subjects were 43 ± 12 years old, had duration of injury of 20 ± 12 years; eight subjects had a complete motor injury, and eight had paraplegia. Nine of 11 subjects completed the 20 mg/day treatment and 5 subjects completed the 40 mg/day treatment. Plasma IGF-1 levels improved with each baclofen dose; however, only one subject increased from baseline and remained above the targeted physiological range of 250 ng/ml throughout treatment. A significant increase in IGF-1concentration was observed between baseline and week 2 (154 ± 63 vs. 217 ± 69 ng/ml; P < 0.05), weeks 8 and 10 (188 ± 95 vs. 228 ± 93 ng/ml; P < 0.05), and weeks 8 and 16 (188 ± 95 vs. 259 ± 92 ng/ml; P < 0.05). No serious side effects were observed at 20 mg/day; the 40 mg/day dose was less well tolerated.

CONCLUSION

Baclofen was not effective at sustaining plasma IGF-1 concentrations in the physiological range in men with chronic SCI.

Effects of GABAB receptor agonists and antagonists on glycemia regulation in mice

γ-Aminobutyric acid (GABA) inhibits insulin secretion through GABA(B) receptors in pancreatic β-cells. We investigated whether GABA(B) receptors participated in the regulation of glucose homeostasis in vivo. BALB/c mice acutely pre-injected with the GABA(B) receptor agonist baclofen (7.5mg/kg, i.p.) presented glucose intolerance and diminished insulin secretion during a glucose tolerance test (GTT, 2g/kg body weight, i.p.). The GABA(B) receptor antagonist 2-hydroxysaclofen (15 mg/kg, i.p.) improved the GTT and reversed the baclofen effect. Also a slight increase in insulin secretion was observed with 2-hydroxysaclofen. In incubated islets 1.10(-5)M baclofen inhibited 20mM glucose-induced insulin secretion and this effect was reversed by coincubation with 1.10(-5)M 2-hydroxysaclofen. In chronically-treated animals (18 days) both the receptor agonist (5mg/kg/day i.p.) and the receptor antagonist (10mg/kg/day i.p.) induced impaired GTTs; the receptor antagonist, but not the agonist, also induced a decrease in insulin secretion. No alterations in insulin tolerance tests, body weight and food intake were observed with the treatments. In addition glucagon, insulin-like growth factor I, prolactin, corticosterone and growth hormone, other hormones involved in glucose metabolism regulation, were not affected by chronic baclofen or 2-hydroxysaclofen. In islets obtained from chronically injected animals with baclofen, 2-hydroxysaclofen or saline (as above), GABA(B2) mRNA expression was not altered. Results demonstrate that GABA(B) receptors are involved in the regulation of glucose homeostasis in vivo. Treatment with receptor agonists or antagonists, given acutely or chronically, altered glucose homeostasis and insulin secretion alerting to the need to evaluate glucose metabolism during the clinical use of these drugs.

Bone and muscle loss after spinal cord injury: organ interactions

Spinal cord injury (SCI) results in paralysis and marked loss of skeletal muscle and bone below the level of injury. Modest muscle activity prevents atrophy, whereas much larger--and as yet poorly defined--bone loading seems necessary to prevent bone loss. Once established, bone loss may be irreversible. SCI is associated with reductions in growth hormone, IGF-1, and testosterone, deficiencies likely to exacerbate further loss of muscle and bone. Reduced muscle mass and inactivity are assumed to be contributors to the high prevalence of insulin resistance and diabetes in this population. Alterations in muscle gene expression after SCI share common features with other muscle loss states, but even so, show distinct profiles, possibly reflecting influences of neuromuscular activity due to spasticity. Changes in bone cells and markers after SCI have similarities with other conditions of unloading, although after SCI these changes are much more dramatic, perhaps reflecting the much greater magnitude of unloading. Adiposity and marrow fat are increased after SCI with intriguing, though poorly understood, implications for the function of skeletal muscle and bone cells.

Relationship of spasticity to soft tissue body composition and the metabolic profile in persons with chronic motor complete spinal cord injury

BACKGROUND/OBJECTIVE

To determine the effects of spasticity on anthropometrics, body composition (fat mass [FM] and fat-free mass [FFM]), and metabolic profile (energy expenditure, plasma glucose, insulin concentration, and lipid panel) in individuals with motor complete spinal cord injury (SCI).

METHODS

Ten individuals with chronic motor complete SCI (age, 33 +/- 7 years; BMI, 24 +/- 4 kg/m2; level of injury, C6-T11; American Spinal Injury Association A and B) underwent waist and abdominal circumferences to measure trunk adiposity. After the first visit, the participants were admitted to the general clinical research center for body composition (FFM and FM) assessment using dual energy x-ray absorptiometry. After overnight fasting, resting metabolic rate (RMR) and metabolic profile (plasma glucose, insulin, and lipid profile) were measured. Spasticity of the hip, knee, and ankle flexors and extensors was measured at 6 time points over 24 hours using the Modified Ashworth Scale.

RESULTS

Knee extensor spasticity was negatively correlated to abdominal circumferences (r = -0.66, P = 0.038). After accounting for leg or total FFM, spasticity was negatively related to abdominal circumference (r = -0.67, P = 0.03). Knee extensor spasticity was associated with greater total %FFM (r = 0.64; P = 0.048), lower % FM (r = -0.66; P = 0.03), and lower FM to FFM ratio. Increased FFM (kg) was associated with higher RMR (r = 0.89; P = 0.0001). Finally, spasticity may indirectly influence glucose homeostasis and lipid profile by maintaining FFM (r = -0.5 to -0.8, P < 0.001).

CONCLUSION

Significant relationships were noted between spasticity and variables of body composition and metabolic profile in persons with chronic motor complete SCI, suggesting that spasticity may play a role in the defense against deterioration in these variables years after injury. The exact mechanism is yet to be determined.

Oral baclofen administration in persons with chronic spinal cord injury does not prevent the protective effects of spasticity on body composition and glucose homeostasis

STUDY DESIGN

Correlation study.

OBJECTIVES

To determine the effects of oral baclofen on body composition (fat mass (FM), fat-free mass (FFM)), extra- and intracellular fluid compartments and glucose homeostasis (plasma glucose and plasma insulin concentrations) in individuals with spinal cord injury (SCI) after controlling for spasticity.

SETTINGS

Laboratory settings at the University of Michigan, MI, USA.

METHODS

Fifteen individuals with chronic motor complete SCI (32+/-8 years old, 25+/-5 kg/m(2), C6-T11, American Spinal Injury Association A and B) underwent multifrequency bioelectrical impedance analysis to measure body composition and body fluid compartments. Spasticity of the hip, knee and ankle flexors and extensors was measured using a modified Ashworth Scale and the dose of daily oral baclofen was recorded. After overnight fasting, plasma glucose and insulin sensitivity were measured in response to an oral glucose tolerance test.

RESULTS

Oral baclofen dose was positively related to body mass index, but not to extensor or flexor spasticity. The dose of baclofen seemed to be correlated to extensor spasticity after considering spasticity per FFM. The increased dose of oral baclofen was positively associated with increased FFM, extra- and intracellular fluid compartments and total body water, but not with FM. Oral baclofen dose was negatively associated with the homeostatic model assessment index.

CONCLUSION

Administration of oral baclofen did not attenuate the protective effects of spasticity on body composition and metabolic profile after SCI. The possibility that oral baclofen could exert an independent protective effect needs to be further investigated.

The effects of passive exercise therapy initiated prior to or after the development of hyperreflexia following spinal transection

Hyperreflexia develops after spinal cord injury (SCI) in the human and in the spinal cord transected animal, and can be measured by the loss of low frequency-dependent depression of the H-reflex. Previous studies demonstrated normalization of low frequency-dependent depression of the H-reflex using passive exercise when initiated prior to the development of hyperreflexia. We examined the effects of passive exercise prior to compared to after the development of hyperreflexia in the transected rat. Adult female rats underwent complete transection (Tx) at T10. Frequency-dependence of the H-reflex was tested following passive exercise for 30 days, initiated prior to hyperreflexia in one group compared to initiation after hyperreflexia became established, and compared to intact and untreated Tx groups. An additional Tx group completed 60 days of exercise initiated after hyperreflexia was established. Lumbar enlargement tissue was harvested for western blot to compare Connexin-36 protein levels in control vs Tx animals vs Tx animals that were passively exercised. No differences in whole tissue were evident, although regional differences may still be present in Connexin-36 levels. Statistically significant decreases in low frequency-dependent depression of the H-reflex were observed following 30 days of exercise initiated prior to the onset of hyperreflexia, and also after 60 days of exercise when initiated after hyperreflexia had been established, compared with Tx only animals. We concluded that modulation of spinal circuitry by passive exercise took place when initiated before and after the onset of hyperreflexia, but different durations of exercise were required.

Provocative stimulation of growth hormone: a monozygotic twin study discordant for spinal cord injury

BACKGROUND/OBJECTIVE

A blunted growth hormone (GH) response to provocative testing and/or low levels of plasma insulin-like growth factor-I (IGF-I) have been reported in persons with spinal cord injury (SCI). A reduction in activity of the GH-IGF-I axis may have deleterious effects on body composition and function. Provocative testing for GH stimulation was performed to determine the response in monozygotic twins that were discordant for SCI.

METHODS

GH stimulation testing was performed by the administration of intravenous arginine.

RESULTS

Nine SCI twins with paraplegia, a mean age of 39 +/- 9 years, and duration of injury of 14 +/- 9 years were studied. The twins with SCI had a significantly lower body mass index than non-SCI twins (22.5 +/- 4.0 vs 25.1 +/- 4.2 kg/m2; P < 0.05); percent fat mass was greater in the twins with SCI (30 +/- 11% vs 22 +/- 10%; P < 0.05). Baseline serum GH was correlated with percent fat only in the SCI twins. The response to GH provocative stimulation was less in the twins with SCI: peak GH response was 5.8 +/- 6.6 vs 13.0 +/- 7.3 ng/mL (P < 0.05), and sum GH response was 15.7 +/- 15.6 vs 30.2 +/- 17.3 ng/mL (P = 0.06). Although baseline serum GH was correlated with stimulated response in the SCI twins, this relationship was not found in the non-SCI twins. Adiposity was positively related to the provocative serum GH response in twins with SCI rather than negatively related, as noted in the non-SCI twins.

CONCLUSIONS

This study confirms and extends prior work that reported a reduction in stimulated GH release in persons with SCI, which was related to baseline values.