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    Co-designing a community-based intervention for prediabetes among Tongan youths in New Zealand : a thesis presented in partial fulfilment of the requirements of Doctor of Philosophy in Public Health at Massey University, Wellington Campus, New Zealand
    (Massey University, 2023) Pulu, Veisinia
    The Tongan population is the second largest Pacific ethnic group in New Zealand, and they have a high rate of prediabetes, characterised by high obesity, hypertension, sedentary behaviours, and unhealthy diets. Addressing this condition through a Tongan community centred based programme, the progression of type 2 diabetes and future health complications can be prevented. Aim: The overall objective of this study was to investigate the Tongan youths and adults’ understanding of prediabetes by mobilising them into collective actions to lead healthier lives. Methods: There were three phases of this study. Phase one explored the perception and understanding of prediabetes and its impact on health and well-being among 8 youth and 11 adults. Phase two applied the Bratteteig co-design methodology to co-develop and implement a community-based intervention called Polokalama mo’ui lelei to address the main characteristics of prediabetes (diet, physical activity, weight management and enhanced knowledge about prediabetes). Phase three involved two online focus groups (youth group=4, adult group = 3) to evaluate the effectiveness of the Polokalama mo’ui lelei. Findings: Phase one findings highlighted that the Tongan youth and adults have limited knowledge of prediabetes which was attributed to the lack of understanding and access to health promotion services. This was compounded by generational health information that had been conceptualized within families, further enhancing their limited understanding. Phase two of the co-designed program showed improvements in weight management measurements; however, the number of participants was too small (n=10) to infer meaningful findings. Phase three findings highlighted key barriers for accessing the program, such as household income, education and motivation factors, and socio-cultural and economic factors. Conclusion: Education and knowledge about prediabetes was viewed as a major issue for the Tongan community members when they had learnt about it. The co-design approach in phase two was demonstrably a socially relevant approach to undertake with the Tongan community, but the method used was not a culturally relevant approach. As a result, a major development from this study was the establishment of the Fengaueaki Fakataha model, a new Tongan model of health. This model provides Tongan cultural insights and protocols which help explain the findings, and it could be used as a guide for conducting future research when working with Tongan communities.
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    Stopping the progression towards type 2 diabetes mellitus : investigating the hypoglycaemic (glucose-lowering) potential of antioxidant-rich plant extracts : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nutritional Science, Massey University, Albany, New Zealand
    (Massey University, 2021) Lim, Wen Xin Janice
    Background: Prediabetes is a condition where the blood glucose levels are high but not high enough to be classified as having type 2 diabetes mellitus (T2DM). It is also considered a high risk for developing T2DM. There is increasing evidence that demonstrates antioxidant-rich plant extracts exhibiting hypoglycaemic effects in humans. Therefore the extracts may improve glycaemic control in individuals with prediabetes and help prevent or delay the progression of prediabetes towards T2DM. Overall Aim: To examine the acute hypoglycaemic potential of four antioxidant-rich plant extracts, namely the New Zealand pine bark, grape seed, rooibos tea and olive leaf extracts in humans. Methods/Design: The hypoglycaemic effects of the New Zealand pine bark was examined in healthy participants (n=25) in an acute, placebo-controlled, single-blind, crossover, dose-response (50 and 400 mg), exploratory study (Pine Bark study). Blood samples were collected via finger pricking using disposable lancet to measure glucose levels at -20, 0, 15, 30, 45, 60, 90 and 120 min during an oral glucose tolerance test (OGTT) with 75 g of glucose. The hypoglycaemic effects of grape seed, rooibos tea and olive leaf extracts matched for antioxidant capacity were examined in an acute, placebo-controlled, crossover study (GLARE study) in participants with prediabetes (n=19). Blood samples were collected via cannulating the antecubital fossa region of the arm at -10, 0, 15, 30, 45, 60, 90 and 120 min during the OGTT with 75 g of glucose. Outcome glycaemic measures were analysed in both clinical studies (Pine Bark study and GLARE study). An in vitro mechanistic study investigating the potential inhibitory action of all four plant extracts (grape seed, rooibos tea, olive leaf and New Zealand pine bark) on digestive enzyme α-amylase and the dipeptidyl peptidase-4 (DPP4) enzyme were carried out using appropriate enzymatic assays of inhibition. Results: Prior to secondary analysis in the Pine Bark study, a significant reduction in the primary outcome mean glucose incremental area under the curve (iAUC) was only observed for the 400 mg dose of pine bark (21.3% reduction, p=0.016) compared to control. After stratification in the monophasic glucose curve shape group (n=12), 50 and 400 mg of pine bark significantly reduced the mean glucose iAUC compared to control (28.1% reduction, p=0.034 and 29.5% reduction, p=0.012), respectively. In contrast, mean glucose iAUC was not significantly different in the complex glucose curve shape group (n=13). In the monophasic group, 400 mg dose further improved glycaemic indices by reducing mean percentage increment of postprandial glucose (%PG) (33.9% reduction, p=0.010), mean glucose peak (11.2% reduction, p=0.025), and mean 2h postprandial glucose (2hPG) (8.9% reduction, p=0.027) compared to control. Within the complex group, there were no other significant changes except for reductions in mean %PG after 50 mg and 400 mg dose (33.8% reduction, p=0.012 and 41.4% reduction, p=0.025) compared to control, respectively. There were no significant differences between treatments in both subgroups (p>0.05). In the GLARE study, there were no overall significant changes in glucose and insulin responses between the extracts and control, or amongst the plant extracts (p>0.05). After secondary analysis, the less healthy subgroup (n=9), grape seed consumption showed significant reduction in mean glucose iAUC (21.9% reduction, p=0.016), mean 2hPG (14.7% reduction, p=0.034) and mean 2h postprandial insulin (2hPI) (22.4% reduction, p=0.029), whilst there was significant improvement in mean overall insulin sensitivity (ISIoverall) (15.0% increase, p=0.028) and mean glucose metabolic clearance rate (MCR) (16.7% increase, p=0.016) compared to control. Rooibos tea extract was shown to improve β-cell function measured by the mean oral disposition index (DI) (32.4% increase, p=0.031) in the less healthy subgroup compared to control. This was coupled with a non-significant improvement in insulin sensitivity measured by mean insulin-secretion-sensitivity-index-2 (ISSI-2) (18.3% increase, p=0.074). Olive leaf exhibited improved mean insulin sensitivity indices of insulinogenic index (IGI₃₀) (27.8% increase, p=0.078), Stumvoll first phase insulin sensitivity (ISIfirst) (17.8% increase, p=0.075) and Stumvoll second phase insulin sensitivity (ISIsecond) (15.6% increase, p=0.062) in the less healthy subgroup compared to control, although significance was not reached. Olive leaf extract was also consistently shown to elevate insulin levels in the study, with a higher mean 2hPI in the healthier subgroup (49.5% increase, p=0.030) and an elevated mean insulin iAUC in the less healthy (16.7% increase, p=0.040) subgroups. There were no significant changes in glucose and insulin responses in the healthier subgroup (n=10) compared to control nor between treatments in both subgroups (p>0.05). The mechanistic study demonstrated that the New Zealand pine bark extract exhibited the greatest inhibitory effects against digestive enzyme α-amylase (IC₅₀ 3.98 ± 0.11 mg/mL) and DPP4 enzyme (IC₅₀ 2.51 ± 0.04 mg/mL) compared to the other extracts (p<0.001). Both grape seed and rooibos tea extracts showed good inhibition of both enzymes tested. Rooibos tea was able to inhibit DPP4 enzyme to a greater extent than grape seed (p=0.018). In contrast, olive leaf extract showed minimal inhibition on α-amylase and no inhibition action against DPP4 enzyme. Conclusions: All four plant extracts (New Zealand pine bark, grape seed, rooibos tea and olive leaf) have shown acute hypoglycaemic potential in the Pine Bark study and the GLARE study by improving various indices of glucose and insulin responses in humans. The inhibitory action of the New Zealand pine bark, grape seed and rooibos tea extracts on DPP4 enzyme might have contributed to the hypoglycaemic effects observed in the clinical studies conducted. Whereas for olive leaf extract other underlying mechanisms on glycaemia remain to be elucidated. Our acute studies have indicated the need to investigate the chronic impact of these plant extracts in longer-term studies. Future studies in the prediabetes cohort should also look to target different metabolic profiles of varying degrees of dysglycaemia, as this may provide more meaningful results.
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    Development and evaluation of an ACT-based lifestyle education intervention for patients with pre-diabetes : a randomised controlled trial : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Psychology at Massey University, Palmerston North, New Zealand
    (Massey University, 2019) Malthus, Sarah
    Type 2 diabetes is a potentially debilitating health condition, and rising prevalence rates of both diabetes and pre-diabetes (the precursor to diabetes) globally and in New Zealand has made prevention an important research focus. Early research indicated dramatic reductions in modifiable diabetes risks factors through the provision of lifestyle education interventions for those with pre-diabetes. However, the time and resource intensive nature of these interventions presented challenges for their implementation, and studies employing briefer more pragmatic interventions produced less compelling results. Incorporating a psychological component into lifestyle education interventions has been highlighted as a possible avenue for enhancing outcomes. This thesis describes the development/adaptation of two intervention approaches for patients with pre-diabetes; lifestyle education alone and lifestyle education combined with Acceptance and Commitment Therapy (ACT). The goal of the ACT/Education approach was to connect participants’ lifestyle goals to personally meaningful values, and equip them with skills to deal with difficult emotions that can function as barriers to goal attainment. A randomised controlled design was used to compare the effectiveness of these approaches with the provision of standard medical care. Results indicated the presence of significant cumulative intervention effects over time for HbA1c, BMI, waist circumference, saturated fat intake, life satisfaction, anxiety, and pre-diabetes knowledge; and education alone was more effective than standard care for reducing total cholesterol and waist circumference. However, results indicated that incorporating an ACT approach was no more beneficial than education alone or standard care across any of the outcome measures. Limitations related to statistical power, participant characteristics and methodology makes definitive interpretations of these results difficult. Addressing these limitations in future research may produce more meaningful outcomes.
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    Living with acute coronary syndrome and prediabetes : an interpretive description of complex illness : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nursing at Massey University, Wellington, New Zealand
    (Massey University, 2013) Van Wissen, Kim
    The purpose of this research is to reveal the experience and interpretation people have of cardiovascular disease (CVD) and prediabetes as complex illness. CVD and diabetes are both increasing in prevalence in New Zealand and globally. Prediabetes is known to be precursory to type 2 diabetes; CVD and prediabetes are fast becoming an established comorbidity. As the prevalence of complex illness soars, the experience and interpretation people have of their condition requires deeper appreciation by nurses as members of a practice discipline. This doctoral research draws attention to the experiences as interpreted by participants and subsequently by the researcher, using interpretive description informed by Gadamer and Merleau-Ponty. Thirty three participants with CVD and prediabetes were recruited into this study. Open ended interviews were undertaken in hospital before discharge and then approximately 9 months later in the community. Interviews were transcribed, data managed by NVivo 9 software, data analysed using thematic analysis, and a thematic framework was developed to organise themes. The overarching theme is in/conspicuous detail indicating the visible and the invisible elements of complex illness. The two major themes, invisible disequilibrium and dialogue as caring, foreground further subthemes and embedded subthemes. The major theme invisible disequilibrium describes the experience of illness and is supported by three subthemes: losing equilibrium, becoming embattled and making sense of evolving illness. The second major theme dialogue as caring interprets the experiences participants had and is supported by subthemes: restorative dialogue, caring and constructing illness. Major findings indicate that complex illness is heterogeneous and participants were continually working with and making sense of the conspicuous and less conspicuous detail of ‘the whole’. Further findings include the proclivity of risk (choice) as a function of participants’ lifestyle such as diet type, activity levels, understanding of medications, plus how this risk may in the longer term cause disease and illness. A third major finding is that participants focussed on self-care as part of their construction of illness. This research provided insights into the experiences of people with CVD and prediabetes. It also showed that complex illness is the occurrence of an intricate meshing of personal circumstances, signs and symptoms that requires attending to needs as identified by the patient. This continues the debate concerning how illness affects the lives of individuals, potentially influencing future service planning.