Correlation of insulin resistance and motor function in spinal and bulbar muscular atrophy
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This study aimed to evaluate various metabolic parameters in patients with spinal and bulbar muscular atrophy (SBMA), to investigate the association between those indices and disease severity, and to explore the underlying molecular pathogenesis. We compared the degree of obesity, metabolic parameters, and blood pressure in 55 genetically confirmed SBMA patients against those in 483 age- and sex-matched healthy control. In SBMA patients, we investigated the correlation between these factors and motor functional indices. SBMA patients had lower body mass index, blood glucose, and Hemoglobin A1c, but higher blood pressure, homeostasis model assessment of insulin resistance (HOMA-IR, a marker of insulin resistance), total cholesterol, and adiponectin levels than the control subjects. There were no differences in visceral fat areas, high-density lipoprotein-cholesterol (HDL-C), or triglyceride levels in two groups. Revised amyotrophic lateral sclerosis functional rating scale (ALSFRS-R) correlated positively with HDL-C, but negatively with HOMA-IR. Through stepwise multiple regression analysis, we identified HOMA-IR as a significant metabolic determinant of ALSFRS-R. In biochemical analysis, we found that decreased expressions of insulin receptors, insulin receptor substrate-1 and insulin receptor-β, in autopsied muscles and fibroblasts of SBMA patients. This study demonstrates that SBMA patients have insulin resistance, which is associated with the disease severity. The expressions of insulin receptors are attenuated in the skeletal muscle of SBMA, providing a possible pathomechanism of metabolic alterations. These findings suggested that insulin resistance is a metabolic index reflecting disease severity and pathogenesis as well as a potential therapeutic target for SBMA.
KeywordsSpinal and bulbar muscular atrophy SBMA Insulin resistance Insulin receptor
Compliance with ethical standards
This work was supported by the Grant-in-Aids (KAKENHI) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (Nos. 26293206, 26670440, 2667043, 15K15337, and 16K15480) and a Grant from the Japan Agency for Medical Research and Development (AMED) (No. 15ek0109025).
Conflicts of interest
Drs. Nakatsuji, Araki, Hashizume, Hijikata, Yamada, Inagaki, Suzuki, Banno, Suga, Ohyama, Nakagawa, and Shimomura report no disclosures.
Dr. Okada is supported by KAKENHI Grants from MEXT/JSPS, Japan (Nos. 25640038, 25110730, 15H04278, and 15H01568), a Grant from the Japan Agency for Medical Research and Development (AMED) (No. 15ek0109025, 15ek0109048, and 15ek0109165), and Grants from the Ministry of Welfare, Health, and Labor of Japan.
Dr. Kishida is supported in part by a Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area) “Molecular Basis and Disorders of Control of Appetite and Fat Accumulation” (No. 22126008).
Dr. Funahashi is supported in part by a Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area) “Molecular Basis and Disorders of Control of Appetite and Fat Accumulation” (No. 22126008). He is a member of the “Department of Metabolism and Atherosclerosis”, a sponsored course endowed by Kowa Co. Ltd. The company has a scientific officer who oversees the program.
Dr. Okano is a founder scientist of SanBio Co. Ltd and K Pharma Co. Ltd. He is supported by the Program for Intractable Disease Research Utilizing Disease-specific iPS Cells funded by the Japan Science and Technology Agency (JST)/Japan Agency for Medical Research and Development (AMED).
Dr. Katsuno is supported by KAKENHI Grants from MEXT/JSPS, Japan (Nos. 26293206, 26670440, 2667043, 15K15337, and 16K15480) and a Grant from the Japan Agency for Medical Research and Development (AMED) (No. 15ek0109025 and 15ek0109165).
Dr. Sobue serves as a scientific advisory board member for the Kanae Science Foundation for the Promotion of Medical Science, Naito Science Foundation; an advisory board member of Brain; and an editorial board member of Degenerative Neurological and Neuromuscular Disease, the Journal of Neurology, and Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration. He is supported by KAKENHI Grants from MEXT/JSPS, Japan (Nos. 26117001); Grants from the Japan Science and Technology Agency; Grants from the Japan Agency for Medical Research and Development (AMED) (Nos. 15ek0109025, 15ek0109048, and 15ek0109165); and Grants from the Ministry of Welfare, Health, and Labor of Japan.
This study was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.
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