Acute hypoxia improves insulin sensitivity (SI2*) and β cell function in individuals with Type 2 Diabetes

Type 2 diabetes is a multifactorial metabolic disease characterized by defects in β-cells function, insulin sensitivity, glucose effectiveness and endogenous glucose production (1). It is widely accepted that insulin and exercise are potent stimuli for glucose transport (2). Acute exercise is known to promote glucose uptake in skeletal muscle via an intact contraction stimulated mechanism (3), while post-exercise improvements in glucose control are due to insulin-dependant mechanisms (2). Hypoxia is also known to promote glucose uptake in skeletal muscle using the contraction stimulated pathway. This has been shown to occur in vitro via an increase in β-cell function, however data in vivo is lacking. The aim of this study was to examine the effects of acute hypoxia with and without exercise on insulin sensitivity (SI2*), glucose effectiveness (SG2*) and β-cell function in individuals with type 2 diabetes. Following an overnight fast, six type 2 diabetics, afer giving informed written consent, completed 60 min of the following: 1) normoxic rest (Nor Rest); 2) hypoxic rest [Hy Rest; O2 = 14.6 (0.4)%]; 3) normoxic exercise (Nor Ex); 4) hypoxic exercise [Hy Ex; O2 = 14.6 (0.4)%]. Exercise trails were set at 90% of lactate threshold. Each condition was followed by a labelled intravenous glucose tolerance test (IVGTT) to provide estimations of SI2*, SG2* and β-cell function. Values are presented as means (SEM). Two-compartmental minimal model analysis showed SI2* to be higher following Hy Rest when comparisons were made with Nor Rest (P = 0.047). SI2* was also higher following Hy Ex [4.37 (0.48) x10-4 . min-1 (μU/ml)] compared to Nor Ex [3.24 (0.51) x10-4 . min-1 (μU/ml)] (P = 0.048). Acute insulin response to glucose (AIRg) was reduced following Hy Rest vs. Nor Rest (P = 0.014 - Table 1). This study demonstrated that 1) hypoxia has the ability to increase glucose disposal; 2) hypoxic-induced improvements in glucose tolerance in the 4 hr following exposure can be attributed to improvements in peripheral SI2*; 3) resting hypoxic exposure improves β-cell function and 4) exercise and hypoxia have an additive effect on SG2* in type 2 diabetics. These findings suggest a possible use for hypoxia both with and without exercise in the clinical treatment of type 2 diabetes.

A repeated measures experiment of school playing environment to increase physical activity and enhance self esteem in UK school children

School playtime provides daily opportunities for children to be active outdoors, but only makes small contributions to physical activity (PA) requirements. Natural environments facilitate unstructured PA and children report a preference for play in nature. Thus, play on the school field might encourage children to be more active during playtime. The primary aim of this study was to examine the impact of the school playing environment on children's PA. Descriptive data and fitness were assessed in 25 children aged 8–9 years from a single primary school. Over two consecutive weeks participants were allocated to either play on the school field or playground during playtime. The order of play in the two areas was randomised and counterbalanced. Moderate to vigorous PA (MVPA) was assessed during playtime on the last two days of each week using accelerometers. There was a significant interaction of environment and sex on MVPA during morning play (F(1,22) = 6.27; P<0.05; np2 = 0.222), but not during lunch (P>0.05; np2 = 0.060) or all of playtime combined (P>0.05; np2 = 0.140). During morning play boys were significantly more active than girls on the playground (t(23) = 1.32; P<0.01; n2 = 0.291), but not on the field (P>0.05; n2 = 0.071). For lunch (F(1,22) = 24,11; P<0.001; np2 = 0.523) and all of playtime combined (F(1,22) = 33.67; P<0.001; np2 = 0.616) there was a significant effect of environment. There was also a significant main effect of sex during lunch (F(1,22) = 11.56; P<0.01; np2 = 0.344) and all of playtime combined (F(1,22) = 12.37; P<0.01; np2 = 0.371). MVPA was higher on the field and boys were more active than girls. Play on the field leads to increases in MVPA, particularly in girls. The promising trend for the effect of the natural environment on MVPA indicates that interventions aimed at increasing MVPA should use the natural environment and that schools should encourage greater use of their natural areas to increase PA.