ABSTRACT Ingestion of different foods containing identical amounts of starch can result in very d... more ABSTRACT Ingestion of different foods containing identical amounts of starch can result in very different postprandial rises in blood glucose and insulin concentrations. Limitation of the early rises in blood glucose and insulin levels seems to be beneficial to human health in the long term. Many studies of starch digestion in vitro are made to understand the molecular basis for differences in digestion rates in vivo to enable prediction of likely rates of digestion of particular starchy foods. Michaelis-Menten kinetics of starch digestibility provides estimates of available (digestible) substrate as starch samples are hydrothermally treated. Combined with studies of starch structure using calorimetry and FTIR spectroscopy, key features influencing rates of amylolysis were identified. Measurement of product formation during prolonged incubations of starch with α-amylase produces digestibility curves. Use of logarithm of slope (LOS) plots to analyse the curves by 1 st order kinetics gave values for digestibility rate constants and the total digestible starch, C ∞ . An important conclusion is that contrary to many reports in the literature, cooked starches do not contain distinct fractions of rapidly and slowly digested material. These kinetic approaches have also been used in studies of plant-encapsulated starch to understand how cell walls influence access of amylase to starch. This work was funded by the BBSRC, UK (DRINC BB/H004866/1).
Neuropathic pain can arise from a wide variety injury to peripheral, including metabolic disorder... more Neuropathic pain can arise from a wide variety injury to peripheral, including metabolic disorders, traumatic injury, inflammation, and neurotoxicity, and is characterized by spontaneous pain, hyperalgesia and allodynia which can persist long after the initial injury is resolved. TRPV1 is a Ca2+ permeable non-selective channel expressed in sensory neurons. Moreover, activation of TRPV1 during oxidative stress has been linked to cell death. Selenium has been considered a potent antioxidant that detoxifies a variety of reactive oxygen species in many neurological diseases. In addtion recently we observed modulator role of selenium on TRP channels in dorsal root ganglin (DRG) neuron of rtas. In order to better characterize the actions of selenium in the peripheral pain, we tested the effects of selenium on apoptosis, oxidative stress and calcium entry through TRPV1 channel in the DRG neuron of streptozotcin (STZ)induced diabetic rats. Sixty rats were randomly divided into four groups. ...
Oat mixed-linkage β-glucan has been shown to lower fasting blood cholesterol concentrations due n... more Oat mixed-linkage β-glucan has been shown to lower fasting blood cholesterol concentrations due notably to an increase in digesta viscosity in the proximal gut. To exert its action, the polysaccharide has to be released from the food matrix and hydrated. The dissolution kinetics of β-glucan from three oat materials, varying in their structure, composition and degree of processing, was investigated by incubating the oats at 37°C over multiple time points (up to 72h). The samples were analysed for β-glucan content, weight-average molecular weight and rheological behaviour. Regardless of the materials studied and the processing applied, the solubilisation of β-glucan was not complete. Mechanical and hydrothermal processing led to differences in the viscosity flow curves of the recovered solutions, with the presence of particulates having a marked effect. This study revealed that the structure and processing methods applied to oat materials resulted in varied and complex rheological pro...
Within plant tissues of different particle sizes, the extent of gelatinisation revealed by DSC wa... more Within plant tissues of different particle sizes, the extent of gelatinisation revealed by DSC was related to the in vitro digestion of encapsulated starch granules.
LOS plots of first-order digestibility data enable the rapid identification of nutritionally-impo... more LOS plots of first-order digestibility data enable the rapid identification of nutritionally-important starch fractions, and allow the final extent (C∞) of starch amylolysis to be accurately predicted.
Factors affecting the α-amylase-catalysed hydrolysis kinetics of starch are incompletely understo... more Factors affecting the α-amylase-catalysed hydrolysis kinetics of starch are incompletely understood, but are of importance to postprandial metabolism and many industrial processes (e.g. bioethanol production). Also, reports on the role of surface area and amorphous content in influencing amylolysis are conflicting. Binding kinetics of pancreatic α-amylase with native starch granules at 0°C were compared with information on starch characteristics. Dissociation constants (Kd), obtained for amylase binding to starches of different particle sizes by solution-depletion assay, varied from 0.16 to 2.05mg/mL. Kd was strongly dependent on specific surface area of the starch granules. Binding rates of amylase (4nM concentration) to the starch were calculated from the time-dependency of amylase depletion and ranged from 1.95 to 22.04×10−3s−1. The rates were strongly dependent on the degree of order of α-glucan chains of starch, as measured by DSC and FTIR–ATR. Thus, α-amylase binds most readily to exposed/available amorphous α-glucan chains.
ABSTRACT Ingestion of different foods containing identical amounts of starch can result in very d... more ABSTRACT Ingestion of different foods containing identical amounts of starch can result in very different postprandial rises in blood glucose and insulin concentrations. Limitation of the early rises in blood glucose and insulin levels seems to be beneficial to human health in the long term. Many studies of starch digestion in vitro are made to understand the molecular basis for differences in digestion rates in vivo to enable prediction of likely rates of digestion of particular starchy foods. Michaelis-Menten kinetics of starch digestibility provides estimates of available (digestible) substrate as starch samples are hydrothermally treated. Combined with studies of starch structure using calorimetry and FTIR spectroscopy, key features influencing rates of amylolysis were identified. Measurement of product formation during prolonged incubations of starch with α-amylase produces digestibility curves. Use of logarithm of slope (LOS) plots to analyse the curves by 1 st order kinetics gave values for digestibility rate constants and the total digestible starch, C ∞ . An important conclusion is that contrary to many reports in the literature, cooked starches do not contain distinct fractions of rapidly and slowly digested material. These kinetic approaches have also been used in studies of plant-encapsulated starch to understand how cell walls influence access of amylase to starch. This work was funded by the BBSRC, UK (DRINC BB/H004866/1).
Neuropathic pain can arise from a wide variety injury to peripheral, including metabolic disorder... more Neuropathic pain can arise from a wide variety injury to peripheral, including metabolic disorders, traumatic injury, inflammation, and neurotoxicity, and is characterized by spontaneous pain, hyperalgesia and allodynia which can persist long after the initial injury is resolved. TRPV1 is a Ca2+ permeable non-selective channel expressed in sensory neurons. Moreover, activation of TRPV1 during oxidative stress has been linked to cell death. Selenium has been considered a potent antioxidant that detoxifies a variety of reactive oxygen species in many neurological diseases. In addtion recently we observed modulator role of selenium on TRP channels in dorsal root ganglin (DRG) neuron of rtas. In order to better characterize the actions of selenium in the peripheral pain, we tested the effects of selenium on apoptosis, oxidative stress and calcium entry through TRPV1 channel in the DRG neuron of streptozotcin (STZ)induced diabetic rats. Sixty rats were randomly divided into four groups. ...
Oat mixed-linkage β-glucan has been shown to lower fasting blood cholesterol concentrations due n... more Oat mixed-linkage β-glucan has been shown to lower fasting blood cholesterol concentrations due notably to an increase in digesta viscosity in the proximal gut. To exert its action, the polysaccharide has to be released from the food matrix and hydrated. The dissolution kinetics of β-glucan from three oat materials, varying in their structure, composition and degree of processing, was investigated by incubating the oats at 37°C over multiple time points (up to 72h). The samples were analysed for β-glucan content, weight-average molecular weight and rheological behaviour. Regardless of the materials studied and the processing applied, the solubilisation of β-glucan was not complete. Mechanical and hydrothermal processing led to differences in the viscosity flow curves of the recovered solutions, with the presence of particulates having a marked effect. This study revealed that the structure and processing methods applied to oat materials resulted in varied and complex rheological pro...
Within plant tissues of different particle sizes, the extent of gelatinisation revealed by DSC wa... more Within plant tissues of different particle sizes, the extent of gelatinisation revealed by DSC was related to the in vitro digestion of encapsulated starch granules.
LOS plots of first-order digestibility data enable the rapid identification of nutritionally-impo... more LOS plots of first-order digestibility data enable the rapid identification of nutritionally-important starch fractions, and allow the final extent (C∞) of starch amylolysis to be accurately predicted.
Factors affecting the α-amylase-catalysed hydrolysis kinetics of starch are incompletely understo... more Factors affecting the α-amylase-catalysed hydrolysis kinetics of starch are incompletely understood, but are of importance to postprandial metabolism and many industrial processes (e.g. bioethanol production). Also, reports on the role of surface area and amorphous content in influencing amylolysis are conflicting. Binding kinetics of pancreatic α-amylase with native starch granules at 0°C were compared with information on starch characteristics. Dissociation constants (Kd), obtained for amylase binding to starches of different particle sizes by solution-depletion assay, varied from 0.16 to 2.05mg/mL. Kd was strongly dependent on specific surface area of the starch granules. Binding rates of amylase (4nM concentration) to the starch were calculated from the time-dependency of amylase depletion and ranged from 1.95 to 22.04×10−3s−1. The rates were strongly dependent on the degree of order of α-glucan chains of starch, as measured by DSC and FTIR–ATR. Thus, α-amylase binds most readily to exposed/available amorphous α-glucan chains.
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Papers by Peter J Butterworth