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

Chapter 4 was published under a Creative Commons Attribution 4.0 license (CC BY 4.0) as: Lim, W X J, Chepulis, L, von Hurst, P, Gammon, C S, & Page, R A. (2020). An acute, placebo-controlled, single-blind, crossover, dose-response, exploratory study to assess the effects of New Zealand pine bark extract (Enzogenol ®) on glycaemic responses in healthy participants. Nutrients,12(2):497. https://doi.org/10.3390/nu12020497Background: 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

Application of linear moments and uncertainty analysis to extreme rainfall events in Sabah

Linear moments (LM) has been applied in extreme rainfall study for several countries, including China, United States of America, and Peninsular Malaysia. In this study, the LM procedures were applied to extreme rainfall data corresponding to locations provided in Malaysia Urban Stromwater Manual (MSMA) to derive new design rainfalls. Different record lengths were considered to assess the changes in design rainfall, and Monte Carlo simulations were carried out to compute confidence interval of the derived design rainfalls. Based on the Goodness-of-Fit (GoF) test results, the Generalized Extreme Value (GEV) probability distribution was chosen to derive the design rainfalls. The updated design rainfalls at all four locations showed significant reduction at design rainfalls of 50-year ARI and above. The difference of the design rainfalls from shorter record lengths with respect to the full record length and the confidence intervals do not necessarily reduce with a longer record. In hypothetical cases where 100-yr ARI rainfall was added, the increase in design rainfalls did not exceed the upper bound of the confidence intervals. The derived confidence intervals hence allow for better risk assessment, and should be considered in the design of critical structures, i.e. dams

A STUDY OF MUSCLE FATIGUE FOR PROLONGED STANDING USING SURFACE ELECTROMYOGRAM: A CASE STUDY

The purpose of this study is to use surface Electromyogram (sEMG) for the investigation of muscle activities in the lower limbs of human subjects during prolonged standing. It has been suggested that prolonged standing leads to muscle fatigue. This is a single-subject investigation that involves a healthy female subject, performing 8 similar quiet standing trials for one hour on separate days. sEMG methods were used to record myoelectric activity from the Tibialis Anterior (TA), Peroneus Longus (PE) and Gastrocnemius muscles (GA). In the preliminary analysis, a progressive decrease in the median frequency curve has been observed in all muscle groups investigated and the trend was statistically significant (p < 0.05). The results of this study confirmed that muscle fatigue sets in during prolonged standing

Digestible indispensable amino acid score (DIAAS): 10 years on

The objective of the review is to revisit the findings of the 2011 Food and Agriculture Organization of the United Nations (FAO) Expert Consultation on Dietary Protein Quality Evaluation in Human Nutrition, and to report on progress on uptake of the findings. It is evident that since 2011 there has been a concerted research effort to enhance an understanding of the protein quality of foods. The validity of the growing pig ileal protein digestibility assay has been confirmed and numerous studies reported using the growing pig as a model to give true ileal amino acid digestibility values for foods as consumed by humans. This has allowed for the determination of digestible indispensable amino acid scores (DIAAS) for a range of foods. A new non-invasive true ileal amino acid digestibility assay in humans which can be applied in different physiological states, called the dual-isotope assay, has been developed and applied to determine the DIAAS values of foods. It is concluded that DIAAS is currently the most accurate score for routinely assessing the protein quality rating of single source proteins. In the future, the accuracy of DIAAS can be enhanced by improved information on: the ideal dietary amino acid balance including the ideal dispensable to indispensable amino acid ratio; dietary indispensable amino acid requirements; effects of processing on ileal amino acid digestibility and lysine bioavailability. There is a need to develop rapid, inexpensive in vitro digestibility assays. Conceptual issues relating DIAAS to food regulatory claims, and to holistic indices of food nutritional and health status are discussed. The first recommendation of the 2011 Consultation regarding treating each indispensable amino acid as an individual nutrient has received little attention. Consideration should be given to providing food label information on the digestible contents of specific indispensable amino acids

Frontal, Sensorimotor, and Posterior Parietal Regions Are Involved in Dual-Task Walking After Stroke

Background: Walking within the community requires the ability to walk while simultaneously completing other tasks. After a stroke, completing an additional task while walking is significantly impaired, and it is unclear how the functional activity of the brain may impact this. Methods: Twenty individual in the chronic stage post-stroke participated in this study. Functional near-infrared spectroscopy (fNIRS) was used to measure prefrontal, pre-motor, sensorimotor, and posterior parietal cortices during walking and walking while completing secondary verbal tasks of varying difficulty. Changes in brain activity during these tasks were measured and relationships were accessed between brain activation changes and cognitive or motor abilities. Results: Significantly larger activations were found for prefrontal, pre-motor, and posterior parietal cortices during dual-task walking. Increasing dual-task walking challenge did not result in an increase in brain activation in these regions. Higher general cognition related to lower increases in activation during the easier dual-task. With the harder dual-task, a trend was also found for higher activation and less motor impairment. Conclusions: This is the first study to show that executive function, motor preparation/planning, and sensorimotor integration areas are all important for dual-task walking post-stroke. A lack of further brain activation increase with increasing challenge suggests a point at which a trade-off between brain activation and performance occurs. Further research is needed to determine if training would result in further increases in brain activity or improved performance

Phase-dependent Brain Activation of the Frontal and Parietal Regions During Walking After Stroke - An fNIRS Study

Background: Recovery of walking post-stroke is highly variable. Accurately measuring and documenting functional brain activation characteristics during walking can help guide rehabilitation. Previous work in this area has been limited to investigations of frontal brain regions and have not utilized recent technological and analytical advances for more accurate measurements. There were three aims for this study: to characterize the hemodynamic profile during walking post-stroke, to investigate regional changes in brain activation during different phases of walking, and to related brain changes to clinical measures. Methods: Functional near-infrared spectroscopy (fNIRS) along the pre-frontal, premotor, sensorimotor, and posterior parietal cortices was used on twenty individuals greater than six months post-stroke. Individual fNIRS optodes were digitized and used to estimate channel locations on each participant and short separation channels were used to control for extracerebral hemodynamic changes. Participants walked at their comfortable pace several times along a hallway while brain activation was recorded. Exploratory cluster analysis was conducted to determine if there was a link between brain activation and clinical measures. Results: Sustained activation was observed in the pre-frontal cortex with the ipsilesional hemisphere showing greater activation compared to the contralesional side. Sensorimotor cortex was active during the early, acceleration stage of walking only. Posterior parietal cortex showed changes in activation during the later, steady-state stage of walking. Faster gait speeds also related to increased activation in contralesional sensorimotor and posterior parietal cortices. Exploratory analysis clustered participants into two distinct groups based on their brain activation profiles and generally showed that individuals with greater activation tended to have better physical outcomes. Conclusions: These findings can guide future research for obtaining adequate power and determining factors that can be used as effect modifiers to reduce inter-subject variability. Overall, this is the first study to report specific oxygenated and deoxygenated hemoglobin changes in frontal to parietal regions during walking in the stroke population. Our results shed light on the importance of measuring brain activation across the cortex and show the importance of pre-frontal, sensorimotor, and posterior parietal cortices in walking after a stroke

Histopathological analysis of vascular malformations

OBJECTIVE: To propose and develop a histopathological criteria to help diagnose vascular malformations. METHODS: All patients who underwent surgical resection and had a confirmed histopathological diagnosis of vascular malformations from 01 March 2018-26 February 2020 were included. A criteria based on 10 parameters was developed to help diagnose vascular malformations. Discrepancies between clinical and histopathological diagnosis were evaluated. RESULTS: A total of 18 cases were identified. There was a discrepancy between the clinical diagnosis and the initially reported histopathological diagnosis in 16 cases (88.9%). This was reduced to 7 (38.9%) and 6 cases (33.3%) with first and second time revised histopathological analysis using proposed criteria. CONCLUSIONS: The discrepancy between clinical and histopathological diagnoses of vascular malformations has highlighted the requirement of an agreed criteria for histopathologists to help formulate their diagnosis. The proposed criteria may be used as a guide in addressing this and guide treatment and improve clinical practice

Early follow-up quality of life and mental health of patients with congenital vascular malformations cared for in a multi-disciplinary specialist centre

OBJECTIVE: The study aimed to evaluate the early follow-up quality of life (QoL), pain and mental health of patients with congenital vascular malformation (CVM) from a variety of treatment options. METHODS: All patients with CVM who received care and had follow-up between February 1st 2018 and January 31st 2020 were included. The health-related QoL, pain, and mental health were assessed with RAND Health Care 36-Item Short Form Survey (SF-36), visual analogue score for pain (VAS-P) and Hospital Anxiety and Depression Scale (HADS). Paired t-test was used for all analyses. p < .05 were considered significant. RESULTS: In total, 110 patients with a mean age of 36.9 years were included in this study. In all patients following care, significant improvement was found in the bodily pain domain of SF-36 and VAS-P (both p = .01). This was largely driven by high-flow vascular malformation patients who responded better to embolo-sclerotherapy, which revealed significant improvement in the bodily pain domain of SF-36 (p = .002) and VAS-P (p = .02). Patients who received supportive treatment only reported significant improvement in mental health (p = .004) and social functioning (p = .03) domains of SF-36. Meanwhile, patients treated with embolo-sclerotherapy reported significant improvement only in VAS-P (p = .02). CONCLUSIONS: This study concluded that the effects of care on early follow-up QoL, pain and mental health of patients with CVM were heterogenous. Future research should therefore, include larger sample size and longer term follow-up to understand the various factors that affect the QoL and mental health of these patients, as well as the holistic approaches to manage them

Respiratory Infections during SARS Outbreak, Hong Kong, 2003

The effect of community hygienic measures during the outbreak of severe acute respiratory syndrome in Hong Kong was studied by comparing the proportion of positive specimens of various respiratory viruses in 2003 with those from 1998 to 2002. Community hygienic measures significantly reduced the incidence of various respiratory viral infections