Hyperinsulinemia and overweight in obese Zucker rats effectively suppressed by exercise training with hypoxia recovery

Abstract

It is currently unknown whether hypoxia training can effectively suppress overweight and hyperinsulinemia in genetically obese animals. In this study, both lean and obese Zucker rats were randomly assigned into the following groups: control (CON, n=7), exercise training (EX, n=7), hypoxia (HYP, n=7) and exercise training with hypoxia recovery (EX+HYP, n=7). During a 6-week training period, rats performed swimming exercise progressively from 30 to 180 min·day⁻¹, and recovered under hypoxia (14% oxygen for 8 h·day⁻¹). Obese Zucker rats exhibited substantially greater fasting insulin levels, and exaggerated glucose and insulin responses following an oral glucose challenge compared with lean rats. At the beginning of week 6, body weight, fasting glucose, fasting insulin, area under curve of glucose (GAUC) and insulin (IAUC) in the EX+HYP group were significantly lower than CON group among the obese rats. Meanwhile, only GAUC was significantly lower in the EX group compared to the CON group. At the end of week 6, capillaries to fibre ratio (C/F), capillary density (CD) and type IIa fibre proportion of the plantaris muscle in the EX group were significantly greater than the CON group (P<0.05), but no additive effect of hypoxia on exercise training was observed. Our data demonstrate that exercise training with prolonged hypoxia recovery offers better metabolic benefits than exercise training alone for the obese Zucker rats. This advantage was closely associated with effective weight reduction.

Keywords:

• Muscle fibre transformation
• capillary density
• insulin resistance
• AMPK
• PGC-1α

Acknowledgements

This study was supported by grants from National Science Council (NSC 95-2413-H-154-007), China Medical University (CMU98-S-14), and Taiwan Department of Health Clinical Trial and Research Center of Excellence (DOH 100-TD-B-111-004).

Declaration of interest: We report no conflict of interest.

Additional information

Notes on contributors

Chia-Hua Kuo

These authors equally contributed to this work