Endocrine Abstracts

Acute hypoxia and exercise improve insulin sensitivity S_I^2* in individuals with type 2 diabetes

R Mackenzie¹, P Watt² & P Castle³

¹Department of Human and Biosciences, New Cavendish Street, London, UK; ²University of Brighton, Brighton, UK; ³University of Bedfordshire, Bedfordshire, UK.

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Exercise is known to stimulate insulin-dependent and -independent glucose transport activity. The majority of research has concluded that hypoxia also increases glucose transport but via insulin-independent mechanisms. The aim of the current study was to determine the effects of acute hypoxia with and without exercise on insulin sensitivity (S_I²) and glucose effectiveness (S_G^2*), measured by an intravenous glucose tolerance test (IVGTT), in individuals with type 2 diabetes (T2D).

Six individuals (age, 57.7 (1.6) year; BMI, 29.2 (3.1); HbA1c, 8.0 (1.0)%) with T2D were recruited for this study.

Following an overnight fast, subjects completed 60 min of the following: 1) normoxic rest (Nor Rest); 2) hypoxic (O₂~14.9%) rest (Hy Rest); 3) normoxic exercise (Nor Ex); 4) hypoxic (O₂~14.9%) exercise (Hy Ex). Exercise trials were set at 90% of the individual’s lactate threshold. Following each condition, an labelled IVGTT was administered to provide estimations of S_I² and S_G^2*. Values are presented as means (±S.E.M.). Statistical significance was set at P<0.05.

S_G^2* was not different between conditions (Table 1; P=0.321). Two-compartmental minimal model analysis showed S_I^2* to be higher following Hy Rest when comparisons were made with Nor Rest (Table 1; P=0.047). S_I^2* was also higher following Hy Ex compared to Nor Ex (P=0.048).

Table 1 S_I^2* and S_G^2* following normoxic and hypoxic conditions.

	Nor Rest	Hy Rest	Nor Ex	Hy Ex
SI2*×10−4 · min−1 (μU/ml)	1.39 (0.08)	2.25 (0.50)*	3.24 (0.51)*	4.37 (0.48)*
SG2*· min−1	0.0177 (0.001)	0.0171 (0.001)	0.0181 (0.001)	0.0189 (0.001)
*Significant difference from Nor Rest (P<0.05).

Insulin sensitivity, but not glucose effectiveness, is improved following an acute bout of moderate hypoxia in individuals with T2D. The increase in insulin sensitivity appears to be additive when Hy is combined with exercise. Our results suggest a potential therapeutic role for Hy in improving glucose tolerance in individuals with T2D, although exercise provides a greater stimulus.

Note: This abstract appears as P162A in the print version.

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Endocrine Abstracts (2009) 19 P162.1