Spinal-bulbar muscular atrophy (SBMA), is an X-linked motor neuron disease caused by a CAG-repeat expansion in the first exon of the androgen receptor gene (AR) on chromosome X. In SBMA, non-neural clinical phenotype includes disorders of glucose and lipid metabolism. We investigated the prevalence of metabolic syndrome (MS), insulin resistance (IR) and non alcoholic fatty liver disease (NAFLD) in a group of SBMA patients. Forty-seven consecutive patients genetically diagnosed with SBMA underwent biochemical analyses. In 24 patients abdominal sonography examination was performed. Twenty-three (49%) patients had fasting glucose above reference values and 31 (66%) patients had a homeostatic model assessment (HOMA-IR) ≥ 2.6. High levels of total cholesterol were found in 24 (51%) patients, of LDL-cholesterol in 18 (38%) and of triglycerides in 18 (38%). HDL-cholesterol was decreased in 36 (77%) patients. Twenty-four (55%) subjects had 3 or more criteria of MS. A positive correlation (r = 0.52; p < 0.01) was observed between HOMA-IR and AR-CAG repeat length. AST and ALT were above the reference values respectively in 29 (62%) and 18 (38%) patients. At ultrasound examination increased liver echogenicity was found in 22 patients (92 %). In one patient liver cirrhosis was diagnosed. Liver/kidney ratio of grey-scale intensity, a semi-quantitative parameter of severity of steatosis, strongly correlated with BMI (r = 0.68; p < 0.005). Our study shows a high prevalence of IR, MS and NAFLD in SBMA patients, conditions that increase the cardiovascular risk and can lead to serious liver damage, warranting pharmacological and non-pharmacological treatment.
Keywords: insulin resistance; metabolic syndrome; muscular atrophy; non alcoholic fatty liver disease; spinal-bulbar muscular atrophy.