5 Diabetes, hyperinsulinemia, and the hypoxic ventilatory response Dejour test A representative tracing of the modified Dejours test is given in Figure 5.3 on page 109, illustrating the effects of a brief period of hyperoxia. The reduction in minute ventilation during and following hyperoxia (i.e. hyperoxic inhibition, a measure of reduced carotid body discharge), showed notable differences in T2DM individuals between fasting and hyperinsulinemic conditions, respectively -1.13 ±0.42 and -1.88 ±0.49 (p = 0.039). The same effect was not observed in HC, respectively -1.41 ±0.59 and -1.62 ±0.49 (p > 0.05). Figure 5.3: Hyperoxic inhibiton of minute ventilation (Modified Dejour test). Representative tracing (A) and absolute hyperoxic-induced decrease in minute ventilation for NIDDM and HC during fasting and hyperinsulinemia (B). Inhibition increased in the NIDDM group during hypersinsulinemia. Heart rate variability Distinct patterns emerged based on the intervention (baseline, HEC, and hypoxia) and diagnosis (T2DM or HC). In the baseline condition, T2DM patients had higher sympathetic activity compared to HC (SNS indices of 7.2 ±5.7 and 4.0 ± 5.1, respectively). Parasympathetic activity was lower for T2DM compared to HC (-3.2 ±4.7 and 9.4 ±7.4, respectively). During hyperinsulinemia, the SNS index increased in T2DM (9.7 ± 5.4), but not in HC (0.2 ± 6.4). During hypoxia, both groups showed increased sympathetic responses, with a slight rise in T2DM’s sympathetic index (12.6 ± 4.0). In HC, hyperinsulinemia reduced sympathetic activity (SNS index: 0.3 ±6.3) and slightly reduced 109
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