High Intensity Interval Training Improves Glycaemic Control and Pancreatic β Cell Function of Type 2 Diabetes Patients

Abstract

Physical activity improves the regulation of glucose homeostasis in both type 2 diabetes (T2D) patients and healthy individuals, but the effect on pancreatic β cell function is unknown. We investigated glycaemic control, pancreatic function and total fat mass before and after 8 weeks of low volume high intensity interval training (HIIT) on cycle ergometer in T2D patients and matched healthy control individuals. Study design/method: Elderly (56 yrs±2), non-active T2D patients (n = 10) and matched (52 yrs±2) healthy controls (CON) (n = 13) exercised 3 times (10×60 sec. HIIT) a week over an 8 week period on a cycle ergometer. Participants underwent a 2-hour oral glucose tolerance test (OGTT). On a separate day, resting blood pressure measurement was conducted followed by an incremental maximal oxygen uptake (VO2max) cycle ergometer test. Finally, a whole body dual X-ray absorptiometry (DXA) was performed. After 8 weeks of training, the same measurements were performed. Results: in the T2D-group, glycaemic control as determined by average fasting venous glucose concentration (p = 0.01), end point 2-hour OGTT (p = 0.04) and glycosylated haemoglobin (p = 0.04) were significantly reduced. Pancreatic homeostasis as determined by homeostatic model assessment of insulin resistance (HOMA-IR) and HOMA β cell function (HOMA-%β) were both significantly ameliorated (p = 0.03 and p = 0.03, respectively). Whole body insulin sensitivity as determined by the disposition index (DI) was significantly increased (p = 0.03). During OGTT, the glucose continuum was significantly reduced at -15 (p = 0.03), 30 (p = 0.03) and 120 min (p = 0.03) and at -10 (p = 0.003) and 0 min (p = 0.003) with an additional improvement (p = 0.03) of its 1st phase (30 min) area under curve (AUC). Significant abdominal fat mass losses were seen in both groups (T2D: p = 0.004 and CON: p = 0.02) corresponding to a percentage change of -17.84%±5.02 and -9.66%±3.07, respectively. Conclusion: these results demonstrate that HIIT improves overall glycaemic control and pancreatic β cell function in T2D patients. Additionally, both groups experienced abdominal fat mass losses. These findings demonstrate that HIIT is a health beneficial exercise strategy in T2D patients.

Trial registration: ClinicalTrials.gov NCT02333734 http://clinicaltrials.gov/ct2/show/NCT02333734.

Fig 1. Flow chart.

1 T2D patient was excluded due to impossible insertion of catheter, and the last T2D patient dropped out of the study immediately after the initiation of HIIT. 5 matched controls were excluded due low BMI.

Fig 2. Study overview of the experiment prior to and after the HIIT intervention.

On a separate day, a urine sample, oral glucose tolerance test (OGTT), weight and height measurements were conducted. On another day: resting blood pressure measurement in supine position and 12-lead electrocardiogram (ECG) prior and after measurement of maximal oxygen consumption on bicycle ergometer. On the last experimental day, a whole body dual energy X-ray absorptiometry (DXA) was performed. These measurements were followed by 8 weeks of HIIT. Finally, laboratory measurements were repeated.

Fig 3. The development of glycaemic control prior to and after the HIIT intervention.

In the CON-group, there were no statistical effects (p>0.05) observed on average fasting venous glucose concentration (A), HbA_1C (B) or postprandial glucose concentration 2 hours after OGTT (C). However, following 8 weeks of low volume HIIT, statistical significant reductions were detected on average fasting venous glucose concentration (A), HbA_1C (B) and postprandial glucose concentration 2 hours after OGTT (C) in the T2D-group (all denoted by †).

Fig 4. The development of HOMA-IR.

Following 8 weeks of HIIT, the HOMA-IR in the CON-group remained unchanged (p>0.05), whereas HOMA-IR was significantly reduced p = 0.035 in the T2D-group (as denoted by †).

Fig 5. The development of HOMA-%β.

Following 8 weeks of HIIT, the HOMA-%β in the CON-group remained unchanged (p>0.05), whereas HOMA-%β was significantly reduced p = 0.026 in the T2D-group (as denoted by †).

Fig 6. The development of ISI_composite (A), Insulin secretion (B) and DI (C).

Following 8 weeks of HIIT, ISI_composite, Insulin secretion and DI remained unchanged (p>0.05) in the CON-group. In the T2D-group, pancreatic β-cell function as determined by DI was significantly elevated (p = 0.03) (denoted by †). In both groups, neither ISI_composite nor insulin secretion was significantly reduced (p>0.05).

Fig 7. Insulin sensitivity (abscissa axis) and insulin secretion (y-axis) among controls (A) and among T2D diabetes patients (B).

Small dots represent values prior HIIT intervention, whereas big dots represent values after HIIT intervention. Each colour represents one individual.

Fig 8. Hyperbola fitting of insulinogenic index and composite insulin sensitivity index.

These differences between before and after HIIT can be seen from both the CON-group (A and B) and the T2D-group (C and D).

Fig 9. Plasma glucose levels and total AUC before and after the HIIT intervention in the CON- and T2D-group.

Following 8 weeks of HIIT, the plasma glucose levels were not significantly reduced (p>0.05 at all time points) in the CON-group (A). Total AUC in the CON-group were not significantly reduced (p>0.05) (A). In the T2D-group (B), plasma glucose concentrations were significantly lowered at time points -15 min (p = 0.03 as denoted by †), -10 min (p = 0.003 as denoted by ‡), 0 min (p = 0.003 as denoted by ‡), 30 min (p = 0.03 as denoted by †) and 120 min (p = 0.03 as denoted by †). AUC was not statistically changed (p = 0.0982) (B).

Fig 10. 1st phase AUC after 30 minutes of the plasma glucose concentration.

Following 8 weeks of HIIT, the CON-group had unaltered (p>0.05) 1st phase AUC of plasma glucose concentration, whereas the T2D-group had reduced p = 0.03 its 1st phase plasma glucose concentration (as indicated by †).

Fig 11. Plasma insulin levels before and after the HIIT intervention.

Following 8 weeks of HIIT, the fasting insulin levels were not significantly changed in the CON-group (A) and T2D-group (B) (p>0.05 at all time points). AUC in the CON-group (A) and T2D-group (B) were not significantly reduced (p>0.05).

Fig 12. Plasma glucagon levels before and after the HIIT intervention.

Following 8 weeks of HIIT, the fasting glucagon levels were not significantly changed in any group (p>0.05 at all time points). Additionally, AUC in the both groups was not significantly changed (p>0.05).

Fig 13. Percentage change in abdominal fat mass (A) and waist circumference (B) after 8 weeks HIIT intervention.

The CON-group lowered its abdominal fat mass significantly (p = 0.02 as denoted by †) by -9.66±3.07% and the T2D-group by -17.84±5.02% (p = 0.004 as denoted by ‡). Waist circumference changed significantly in both groups by -4.04±1.20% (p = 0.006 as denoted by ‡) in the CON-group and by -5.74±2.05% (p = 0.02 as denoted by †) in the T2D-group.