The modulation of pancreatic lipase activity by alginates

Abstract

Alginates are comprised of mannuronic (M) and guluronic acid (G) and have been shown to inhibit enzyme activity. Pancreatic lipase is important in dietary triacylglycerol breakdown; reducing pancreatic lipase activity would reduce triacylglycerol breakdown resulting in lower amounts being absorbed by the body. Lipase activity in the presence of biopolymers was assessed by enzymatic assay using natural and synthetic substrates. Alginate inhibited pancreatic lipase by a maximum of 72.2% (±4.1) with synthetic substrate (DGGR) and 58.0% (±9.7) with natural substrate. High-G alginates from Laminaria hyperborea seaweed inhibited pancreatic lipase to a significantly higher degree than High-M alginates from Lessonia nigrescens, showing that inhibition was related to alginate structure. High-G alginates are effective inhibitors of pancreatic lipase and are used in the food industry at low levels. They could be included at higher levels in foods without altering organoleptic qualities, potentially reduce the uptake of dietary triacylglycerol aiding in weight management.

Keywords: Alginate; Inhibition; Lipase; Obesity; Weight management.

Copyright © 2013 Elsevier Ltd. All rights reserved.

Figures

Supplementary Fig. 1

Correlation of the specific viscosity of alginate against lipase inhibition in the reaction mixture. The specific viscosity of each reaction mixture for the lipase activity assay containing 3.43 mg/ml was measures with a Contraves low shear 30. The error bars are the standard error of the mean of three replicated. The line of best fit is to indicate the direction of correlation, if any. A correlation analysis indicated a Sprearman r value of −0.27.

Fig. 1

Lipase activity using the DGGR assay measured in absorbance over time. ■ – Lipase control (lipase plus substrate), ▾ – alginate SF200 at 3.43 mg/ml (as an example) and ▴ – inhibition control 0.025 mg/ml orlistat. The error bars show the standard error of the mean of 3 replicates. All enzyme inhibition is calculated with data from 12 min as the reaction is still close to a linear phase.

Fig. 2

(A) Inhibition of lipase caused by Laminaria hyperborea and Lessonia nigrescens alginates (DGGR substrate). Four alginates of differing molecular weight are shown for Laminaria hyperborea and Lessonia nigrescens as their respective source. Inhibition of lipase shown in this figure is for 3.43 mg/ml of alginate. The alginates from Laminaria hyperborea species are (from left to right) LFR5/60, SF120, SF/LF, and SF200, full characteristics can be found in Table 1. The Lessonia nigrescens seaweed alginates are (from left to right) LF10L, LF120L, SF60 and H120L, again full details can also be found in Table 1. Error bars shown are the standard error of the mean of six replicates. Laminaria hyperborea alginates inhibit lipase to significantly higher degree than Lessonia nigrescens alginates (p = 0.0015). Bars annotated with letter 'a' are significantly different to those with letter 'b'. (B) Concentration dependent inhibition of lipase by the four alginates from Laminaria genus of seaweeds (DGGR substrate). □ – 0.21 mg/ml, ▨ – 0.86 mg/ml and ■ – 3.43 mg/ml. The error bars are the standard error of the mean of six replicates.

Fig. 3

The absorbance change (at 405 nm) over time as a measure of lipase activity (olive oil substrate). ▴ – Lipase control (lipase plus substrate), ▾ – alginate SF200 at 3.43 mg/ml (as an example) and ■ – inhibition control 0.025 mg/ml orlistat. The error bars show the standard error of the mean of three replicates. All enzyme inhibition was calculated with data from 12 min.

Fig. 4

(A) Comparison of lipase inhibition, using olive oil as a substrate, by alginates extracted from Laminaria and Lessonia seaweeds. Four alginates of increasing molecular weight from left to right are shown for both Laminaria and Lessonia as their respective source. Inhibition of lipase shown in this figure is caused by 3.43 mg/ml of alginate. There was a statistical difference between the two species of seaweed with p values of less than 0.001. Error bars shown are the standard error of the mean of three replicates. Bars annotated with letter 'a' are significantly different to those with letter 'b'. (B) Concentration dependent inhibition of lipase by the four alginates from Laminaria hyperborea genus of seaweeds (olive oil substrate). □ – 0.21 mg/ml, ▨ – 0.86 mg/ml and ■ – 3.43 mg/ml. The error bars are the standard error of the mean of three replicates. The molecular weight of the biopolymers increases from left to right (LFR5/60 to SF200).