Forskning ved Københavns Universitet - Københavns Universitet


Seaweed Bioactivity: Effects on Glucose Liberation

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

  • Nazikussabah Binti Zaharudin
Hyperglycaemia (high blood sugar levels) is one of the risk factor of type 2 diabetes (T2D)
when it is sustained over a longer period of time. Various factors that can lead to high blood
glucose levels include glucose absorption by the small intestine and the production of glucose by
liver cells. Maintenance of normal plasma glucose concentration is essential for the human health.
Diet and exercise play important role to control blood sugar level. Limiting intake of high
Glycaemic Index (GI) foods as part of a balanced diet is known to be important. In addition, having
the right food intake such ad functional foods that affect the blood sugar increase, e.g by containing
inhibitors of α-amylase and/or α-glucosidase, may also help lowering the average blood sugar
levels. Thus, such foods may in theory help to lower blood glucose postprandially and could
potentially help delay the development of T2D in subjects with impaired glucose tolerance who
regularly consume starchy foods.
The present study involved the investigation of crude extracts of dried edible seaweeds in
inhibiting the carbohydrate digestive enzymes, α-amylase and α-glucosidase. Bioactive
compounds from selected edible seaweeds that inhibit α-amylase and α-glucosidase were
identified. The edible seaweeds that were showing high potential for inhibiting the enzymes were
selected to investigate their effect on the postprandial blood glucose and insulin levels following
a starch load in a human meal study.
In vitro studies and a human study were performed as part of this thesis. In Paper 1 and
Paper 2, the inhibition of α-amylase and α-glucosidase activity in vitro by edible red, green and
brown seaweeds were investigated. Aqueous and alcoholic extracts of dried edible seaweeds were
tested to investigate the inhibition kinetics on these enzyme activities. The most potent edible
seaweed extracts were showing mixed-type inhibition (lowering both Km and Vmax) and were
selected for bioactive compound identification. The brown seaweeds, Laminaria digitata and
Undaria pinnatifida, were found to be the most potent inhibitors of α-amylase and α-glucosidase
activities. Polyphenols, alginates and fucoxanthin found in the selected seaweeds are among the
bioactive compounds that contributed to inhibition of the enzyme activities.
In Paper 3, the same two edible seaweeds were tested in a human study. The primary
endpoint was the ability of the edible seaweeds to reduce human postprandial blood glucose and
insulin concentrations following a starch load in a human meal study. There was no significant
effect in plasma glucose but both brown seaweeds lowered postprandial insulin response following
consumption of Laminaria digitata or Undaria pinnatifida compared to the control meal.
In conclusion, two brown seaweeds, Laminaria digitata and Undaria pinnatifida, inhibited
α-amylase and α-glucosidase activities due to their content of several bioactive components with
a potential use for future functional foods. Their effects on the postprandial insulin response and
the in vitro findings regarding the phenolics, alginate and fucoxanthin in these seaweeds may
further support that brown seaweeds, particularly Undaria pinatifida, might be used as a potential
functional food to help control postprandial hyperinsulinaemia.
ForlagDepartment of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen
Antal sider155
ISBN (Trykt)978-87-7209-091-7
StatusUdgivet - 2017

Bibliografisk note

CURIS 2017 NEXS 366

ID: 187080708