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E.M. Corrêa1, L. Medina2, J. Barros-Monteiro3, N.O. Valle1, R. Sales1, A. Magalães1, F.C.A. Souza4, T.B. Carvalho1, J.R. Lemos1, E.F. Lira5, E.S. Lima6, D.M.L. Galeno1, L. Morales7, C. Ortiz8, R.P. Carvalho1


1. Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas; 2. Departamento de Química, Instituto de Ciências Exatas Universidade Federal do Amazonas , Av. Gen. Rodrigo Octávio Jordão Ramos, 3000 – Coroado, Manaus– AM – Brazil; 3. Biochemistry Department at Ponce School of Medicine and Health Sciences Ponce, Puerto Rico; 4. Instituto Nacional de Pesquisas da Amazônia – Coordenação Sociedade Saúde Ambiente- Laboratório de Alimentos; 5. Fundação de Hematologia e Hemoterapia do Estado do Amazonas (FEMOAM)- Nucleo de Estatística – Av. Constatino Nery; 6. Faculdade de Ciências Farmacêuticas, Universidade Federal do Amazonas, Rua Alexandre Amorin, 330 – Aparecida, Manaus-AM/Brazil,CEP: 69010-300; 7. Public Health Program; 8. Physiology and Pharmacology Department at Ponce School of Medicine and Health Sciences Ponce, Puerto Rico

Corresponding Author: Rosany Piccolotto Carvalho, Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade Federal do Amazonas , Av. Gen. Rodrigo Octávio Jordão Ramos, 3000 – Coroado, Manaus – AM – Brazil.- Doutora – Docente, Tel.: + 55 92 99874139, Fax: + 55 92 33054038, E-mail address: prosany@hotmail.com/prosany@ufam.edu.br



Background: Diabetes mellitus (DM) is a major risk factor for coronary artery disease, renal failure, retinopathy, and neuropathy. Over the last years, there has been an increasing demand in folk medicine for natural sources that could help in the treatment of chronic diseases, including diabetes. The rind of passion fruit (Passiflora edulis f. Flavicarpa) is traditionally used as a functional food due to its high concentration of soluble and insoluble fiber. Objective: The aim of this study was to determine the effect of high-fiber diet albedo of passion fruit on the metabolic and biochemical profile in diabetic rats induced by alloxan (2%). Design: The passion fruit mesocarp fiber was dried in an oven with circulating air at 60°C and pulverized. We used 32 adult male rats, divided into 4 groups: Wistar group 1 control (GC), Wistar group 2, 15% fiber (GF15), Wistar group 3, 30% fiber (GF30), Wistar group 4, fiber disolved in water (GFH2O). The ratio of passion fruit was prepared according to the AIN 93M guidelines, varying only the source of dietary fiber. The corresponding diet for each group was offered to the animals for 60 days. Results: There was a statically significant decrease in plasma glucose for GFH2O, GF15%, and GF30% groups with 27.0%, 37.4%, and 40.2%, respectively. Conclusion: The use of mesocarp fiber of passion fruit at concentrations of 15% and 30% are an important dietary supplement for the treatment of DM due to its potential hypoglycemic effect, and its ability to reduce triglycerides and VLDL- cholesterol levels with a principal reduction of insulin and leptin.


Key words: Diabetes, passion fruit fiber.



Diabetes Mellitus (DM) is defined as a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both (1). DM is a chronic disease and a serious public health problem due to its high frequency among the

population, complications, morbidity, high financial costs, and social aspects involved in the treatment of the disease and the significant deterioration produced in quality of life of the patients (2).

Currently, studies on new hypoglycemic drugs have been performed using especially medicinal plants. Of the several medicinal plants used for the treatment of diabetes only some have been scientifically validated and recommended by the World Health Organization (WHO) (3). Córdova and colleagues (2005) reported the functional properties of passion fruit peel, especially those related to the content and type of fiber (4). Several studies have reported that the genus Passiflora has been used as an aid in the treatment (or control) of diabetes, mainly due to the presence of soluble fibers such as pectin (5, 6). The WHO recommends a diet fiber consumption of 25 – 35 g/day, 35% of which shall consist of 65% soluble and insoluble fiber. According to Pereira (2002), soluble fibers tend to delay gastric emptying and the passage of food through the intestines (7). Therefore, promoting lower glucose absorption, increased insulin

sensitivity, reduction in plasma cholesterol and blood pressure, and also helping in weight control. These actions are due to the property of soluble fibers to bind water molecules and forming a gel-like substance. This reduces the absorption of fat and sugars and promotes lubrication of the stomach and intestinal wall, thus contributing to the proper functioning of the intestinal transit (3). As for the insoluble fiber, it has been found to accelerate intestinal transit, increasing fecal bulk and slowing the hydrolysis of glucose (3). Thus, a high fiber diet tends to lower the risk of obesity and cardiovascular and gastrointestinal diseases (3). There is no doubt of the great benefits of dietary fiber as a constituent of food.

The action of pectin as a hypocholesterolemic agent in animals has also been demonstrated (2, 8). Moreover, pectin showed a hypoglycemic and plasma insulin secretion-inducing effects in rodents (9, 10). These characteristics and functional properties make the passion fruit peel a potential ingredient for the development of new products such as foodstuffs, mainly due to the considerable amount of pectin in the fruit mesocarp (11, 12).

Due to the high prevalence of diabetes, especially in developed countries, this disease is considered the seventh leading cause of death in the world. It is essential to search for new sources of efficient alternatives to treat this disease. In this context, the present study evaluated the effect of passion fruit mesocarp fibers on plasma levels of glucose, insulin, leptin, triglycerides, total cholesterol and its fractions in rats with alloxan induced diabetes type I.


Materials and methods

Raw materials and vegetable diet preparation

The fiber of passion fruit dehydrated albedo was developed by the Biotechnology Program PPGBiotec of the Federal University of Amazonas (UFAM), and incubated by the company “Divine Fruit” in the industrial district of Manaus. The fruits were purchased from producers in the municipality of Manaus-Am and selected by the stage of maturity and firm shells. Albedo (the white part of the peel) was removed from the flavelo (yellow part of the rind) and the pulp. The albedo was subjected to the process of inactivation using the bleaching method, steam heated to a temperature of 90⁰C for 5 minutes and dehydrated in an oven with circulating air at 60⁰C for 4 hours. The dried albedo was pulverized in Hammer Mill and sieved to obtain desired particle size. The formulation of rodent Labina was produced according to the AIN 93M which is in agreement with the data from Reeves et al. (1993), varying only the source of dietary fiber (13).

Biological assays and animal experimentation

We used 32 adult male rats (Rattus norvegicus) of the Wistar strain, with 1 month of age. The animals were obtained from the animal house of the Universidade Federal do Amazonas (UFAM) and kept in individual plastic cages, under the light-dark cycle of 12 hours with free access to food (Labina Rat Chow®) or feed on the passion fruit and water free (ad libtum) except for 12 hours before the experiments, which were performed with fasted animals under appropriate conditions of light and temperature. This project is under the approval of the Ethics Committee on Animal Experiments (EAEC-UFAM) under protocol No. 069/2010, strictly following the international standards for laboratory animal care.

The animals were divided into four groups (n = 8): Group 1 – Control (CG): diabetic rats fed commercial feed; Group 2 – 15% Fiber (GF15): diabetic rats fed with a diet prepared with 15% of passion fruit mesocarp fiber; Group 3 – Fiber 30% (GF30): diabetic rats fed with a diet prepared with 30% of passion fruit mesocarp fiber; and Group 4 – Fiber dissolved in water (GFH2O): diabetic rats fed with commercial feed dissolving passion fruit mesocarp fiber in water.

Induction of Diabetes Mellitus

DM was induced by administration of an aqueous solution of alloxan monohydrate (Sigma-Aldrich, St. Louis, USA) diluted to 2% in a solution of 0.05 M sodium citrate, pH 4.5 after 24 h of fasting (13), injected intraperitoneally at a dose of 42 mg/kg. Rats were considered diabetic if they had blood glucose levels greater than or equal to 120 mg/dL (14, 15).

Food consumption

Animals were housed in individual cages and fed the experimental diets ad libitum. Food intake was recorded daily and calculated based on the remains checked the following day.

Body Mass Index

Animals were weighed at the beginning and at the end of the experiment to monitor the clinical course.

Biochemical profile

Blood glucose levels were determined at the beginning and at the end of the experiment, using the ACCU- CHEK® device, using the blood taken from the tail tip of the animals. The other biochemical parameters including: triglycerides, total plasma cholesterol, plasma HDL-Cholesterol, LDL and VLDL plasma-cholesterol, total protein, plasma leptin, and insulin levels were determined using appropriate kits. The determination of plasma levels of LDL and VLDL were obtained from the Friedewald equation

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[16]. = TG VLDL / LDL cholesterol = total cholesterol – (VLDL + HDL)


Statistical Analysis

Data analysis was performed using Systat 12.0, employing the Steam and Leaf test to check for “outliers”. These values were removed from the analysis. All data were tested for normality using the Shapiro-Wilk test. Since the data was not normally distributed, we applied the nonparametric Kruskal-Wallis test assuming a reliability of 95% (p <0.05). ANOVA was used to compare the difference between groups.



In the experiment conducted in a period of sixty days, there was no statistically significant difference between the treated groups, in relation to food intake and body mass gain, when compared with the control group (p> 0.05) (Table 1). These results are in agreement with Janebro et al. (2008) , where healthy and diabetic rats treated with the passion fruit peel fiber also showed no statistically significant differences in relation to food intake and body mass gain (Table 1) (2).

Table 1 Food intake and body mass gain on Winstar rats with different diets

Table 1: Food intake and body mass gain on Winstar rats with different diets

*a: Difference in relation to control group, median ± stantard error (p>0.05)


In Table 2, the evaluation of total cholesterol, HDL- cholesterol, and LDL-cholesterol levels did not showed statistically significant differences between the experimental groups when compared to the control group. A hypoglycemic response occurred in the GFH2O, GF15%, and GF30% groups with a 27%, 37.4%, and 40.2% reduction, respectively. There was no change in total protein concentration for groups GFH2O (15.2% increase), GF15% (30.4% decrease) and GF30% (25.3% decrease). There was a reduction in triglyceride levels for GFH2O, GF15%, and GF30% groups of 26.8%, 61.7%, and 74.4%, respectively. HDL-cholesterol levels showed a 11% and 7.6% decrease in the GFH2O and GF15% groups, while the GF30% showed an increase of 19.1%. VLDL-cholesterol levels were reduced in GFH2O, GF15%, and GF30% groups by 26.9%, 61.9%, and 74.4%, respectively. Insulin levels were also decreased in GFH2O, GF15%, and GF30% groups by 36.8%, 89.5%, and 73.7%, respectively. The same effect was seen for leptin levels for GFH2O,

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GF15%, and GF30% groups with 38.2%, 94.1%, and 91.2% reduction, respectively (p <0.05).

It is important to establish that there was significant change (p <0.05) between the levels of glucose, total protein, triglycerides, and VLDL-cholesterol between the groups GF15% and GF30%%, with lower percentages in relation with the GC and GFH2O groups. In addition to these findings, it can be seen that the levels of triglycerides and VLDL-cholesterol were also lower in the GF30% group when compared to the GF15% group (Table 2).

Table 2 Comparison of biochemical parameters (mean ± SE) between the groups

Table 2: Comparison of biochemical parameters (mean ± SE) between the groups

*Different letters indicate statistical differences between the parameters evaluated by using ANYWAY ANOVA and Tukey post-test (p <0.05).



The fiber of passion fruit peel has been the subject of great speculation. In 2007, Ramos and colleagues demonstrated a significant reduction in fasting blood glucose levels and triglycerides upon supplementation with yellow passion fruit peel during the first four weeks of the study (17). As shown in Table 2, the plasma insulin levels of groups ingesting feed-based fibers (GF15% and GF30%) were significantly lower than GC and GFH2O groups. Plasma levels of leptin alone showed a significant reduction when compared to the control group.

The data presented in Table 2 shows that intake of mesocarp fiber of passion fruit (Passiflora edulis) in proportions of 15% and 30% led to a decrease in plasma glucose when compared to the group of Type 1 diabetic rats treated with commercial feed after sixty days of experimental diets. These results are in agreement with previous studies that show that feeding passion fruit peel flour to normal and diabetic rats can effectively control diabetes, as it is a byproduct rich in pectin (2). It was also reported by other study that feeding hamsters with fiber flour of Passiflora edulis; whose constitution resembles the passion fruit peel, resulted in decreased levels of triglycerides, cholesterol and liver lipids (9). Other studies have assessed the importance of including food products that promote improvement in glucose tolerance and reduction in total cholesterol and plasma triglyceride levels in diets of diabetic patients (18, 19).

A preclinical study using passion fruit husk fiber in the diet of normal and diabetic rats showed a reduction in blood glucose after four weeks of feeding. This effect was due to the action of soluble fiber on glucose absorption in the gastrointestinal tract and increased insulin secretion (10, 20). The use of the extract from Passiflora mollissima showed a hypoglycemic effect in diabetic rats treated for eight days, causing a reduction of almost 50% in blood glucose concentration. Another study stated that a long term diet supplemented with fiber (without addition of carbohydrate), improved glucose homeostasis (3).

Ramos et al. (2007) observed by means of a pilot clinical study that treatment with passion fruit peel flour (P. edulis fo. Flavicarpa) resulted in decreased cholesterol levels in women between 30 and 60 years of age who had hypercholesterolemia (cholesterol ≥ 200 mg / dL) (17). Ramos (2004) showed that the dry extract of passion fruit bark exerts a positive effect on glycemic control in the treatment of diabetes type II, due to the presence of totally degradable fibers in the body which help to decrease the levels of blood glucose and cholesterol (21). This suggests that the use of dry extract of passion fruit peel can be used as adjuvant therapies. This effect is attributed to the property of insoluble fiber and other soluble constituents of albedo yellow passion fruit (Passiflora edulis) to reduce total cholesterol and fractions, plasma level of triglycerides, and glucose (3). Since fibers are substances of plant origin which are not digested and absorbed by the body they can resist the action of human digestive enzymes; therefore, reaching the colon intact and being partially or totally hydrolyzed and fermented by the colonic bacterial flora in the large intestine (22). According to Zeraik et al. (2010), due to the high content of pectin in the passion fruit peel it can also induce plasma insulin and leptin secretion, in addition to its hypoglycemic and hypocholesterolemic effects (23). This finding confirms the results of this study in which we observed a reduction of these parameters in GF15% and GF30% groups, when compared with the control and GFH2O groups probably generated by hypoglycemic factors in these rats.

Thus, the hypoglycemic action of the passion fruit peel (Passiflora edulis f. Flavicarpa) can also be attributed to the presence of pectin, a fraction of soluble fiber which is able to absorb water and form a viscous gel that can delay gastric emptying and bowel traffic. The fiber content found in wet passion fruit peel corresponds to 1.58 (g/100g) of soluble fiber (4, 24).



Our results showed that the mesocarp fiber of passion fruit (Passiflora edulis), at concentrations of 15% and 30%, could be an important dietary supplement for the treatment of diabetes due to its hypoglycemic potential. Mesocarp fiber of passion fruit also promotes the reduction of triglycerides, VLDL -cholesterol, insulin, and leptin levels. However, more specific studies of the biochemical mechanisms involved in the observed effects are needed. In addition, a more detailed analysis of the benefits of fiber toxicity and the passion fruit peel should be performed, to assess any risk in the human population.


Acknowledgements: Research was supported by the RCMI program G12MD007579 (JBM) and the MBRS-RISE program funded by RISE grant R25GM082406 from the National Institutes of Health (CO) at Ponce School of Medicine and Health Sciences.

Conflict of interest: The authors declare no conflict of interest.



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16. Friedewald WT, Levy RI, Fredrickson DS: Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem 1972, 18(6):499-502.

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18. Rodriguez M, Hasegawa M, Gonzalez-Mujica F, Motta N, Castillo A, Castillo J, Zea E, Mora K, Sousa L, Gonzalez A et al: Antidiabetic and antiradical activities of plants from Venezuelan Amazon. Rev Bras Farmacogn 2008, 18(3):331-338.

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B. Phillips, S. Ali, M. Chopra


IBBS, School of Pharmacy and Biomedical Science University of Portsmouth, Portsmouth PO1 2DT

Corresponding Author: Dr Mridula Chopra, School of Pharmacy and Biomedical Sciences, St Michael’s Building, White Swan Road, University of Portsmouth, Portsmouth PO1 2DT. United Kingdom, Tel: 02392842796; Fax:02392843565; Email: Mridula.Chopra@port.ac.uk



Objectives: Benefits of physical activity on maintenance of blood glucose within an acceptable range are well documented. This study explores the possible beneficial effect

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of animated conversation and mental activities on blood glucose levels following dietary carbohydrate loading. Design and Participants: Blood glucose changes were examined in 18 non-diabetic individuals following the consumption of two doughnuts providing ~48g of carbohydrate. The participants acted as their own controls and were studied twice. On the first occasion they maintained quiet/passive behaviour, on the second they conversed and participated in structured mental activities e.g. reading and solving puzzles. Measurements: Using the Freestyle Freedom Lite glucose metre, baseline, then post-fasting blood glucose concentrations were evaluated every 30 minutes over a 2 hour period after the consumption of doughnuts. Results: ANOVA repeated measures analysis of the results showed that time (P


Key words: Diabetes, glucose, quiet, animated conversation, mental activities.

Abbreviations: ISO: Organization for Standardization; IBBS: Institute of Biomedical and Biomolecular Research.



Maintaining blood glucose homeostasis within a healthy range is important for health. Several factors can influence the glycaemic response of an individual following a carbohydrate loading. These include the glycaemic index of foods, co-ingestion of other macronutrients such as protein and fibre as well as engaging in physical activity (1-3). The effect of physical activity on glycaemic response is well known and a variety of activities can be just as valuable as performing one type of exercise (4). Although regular moderate aerobic exercise, alongside lifestyle interventions are beneficial for health, a lack of time means that many people do not fully comply with the guidelines and recommendations. There may also be times when exercise is not convenient or feasible due to a number of factors e.g. disability, illness, weather, work commitments or time constraints. Lack and inability to engage in physical activity can also be an issue for the elderly. In such situations alternative activities which are likely to increase glucose usage may be an option.

The effect of a relatively non-physical activity such as verbal communication on glycaemic response, following a carbohydrate load has not been examined before. Benefits of engaging in social activities and solitary reading are well documented for their physical and psychological benefits (5-7). The present study was set out to examine whether simple activities such as animated conversation combined with mental activities such as reading and/or solving puzzles could influence blood glucose changes following a carbohydrate load. The glycaemic response of participants was determined using a finger prick blood sample analysed by a glucose metre.

The accuracy and precision of glucose metres are known to vary and in some studies not all metres have been found to meet the minimum accuracy criteria of the WHO’s Organization for Standardization ISO 15197-2003 (8-10). The ISO standard for quality of capillary blood sample analysis with a glucose metre states that at glucose concentrations of



Ethical approval for this study was obtained from the Biosciences Research Ethics Committee of the University. The research was conducted in compliance with the declaration of Helsinki, as adopted at the 18th World Medical Association (WMA) General Assembly, Helsinki, Finland, 1964 and last amended at the 59th World Medical Association General Assembly, Seoul 2008.

Individuals with known diabetes, cardiovascular disease, gastrointestinal problems and bleeding disorders were excluded from participating. Individuals on any medication that was likely to influence glucose metabolism proper warm up before exercising and cool down afterward is essential to avoid injury and achieve peak performance i.e. Baclofen, Corticosteroids, L-dopa, and Tolazamide were also excluded from the study.

Metre comparison

Four hand held glucose metres were compared for their blood glucose measurements with the laboratory values of glucose. Metres that were used included:- Freestyle Freedom Lite (Abbott Diabetes Care, UK), Contour XT (Bayer Diabetes Care, UK), Accu-Chek Aviva (Roche Diagnostics Ltd, Accu-Chek UK) and One Touch Ultra 2 (LifeScan UK and Ireland). The reference laboratory value for glucose was obtained using Randox GLUC-PAP kit.

Thirty-two participants (13 male:19 female), age range 22-65 years were asked to provide 5 mL of venous blood as well as finger prick blood samples for glucose analysis. Participants were asked to wash their hands with warm water and their finger prick blood samples were obtained using One touch ultra soft lancets. Fingers were gently

squeezed to obtain the blood sample. The first drop of blood was wiped clean and the subsequent drops were used to determine the blood glucose values by four metres. Venous blood samples were obtained in fluoride oxalate tubes, plasma samples were obtained after centrifugation at 3000 rpm for 10 minutes and glucose concentrations were measured using Randox GLUC-PAP kit.

Doughnut Study

Twenty participants (8 male:12 female) gave their consent for participation and those with fasting blood glucose >6.0mmol/L (1 male, 1 female) were excluded from the study. Eighteen participants (7 male:11 female) age range 22-64 years (mean age ~ 40 ± 13), BMI 24.8 ± 3.3 kg/m2 (range 21-30) completed the study. Participants were advised to eat their evening meal at the same time of the day before each intervention and to maintain a similar exercise regime. After the evening meal, subjects were asked to fast overnight and to provide a fasting finger-prick blood sample the following morning. Prior to blood sampling, participants were asked to wash their hands with warm water and samples were obtained from the side of the fingers of the left hand. The first drop of blood was wiped off and subsequent drops were analysed using the Freestyle Freedom Lite metre. Duplicate measurements were performed at each time point.

Participants were asked to consume two doughnuts (sugar glazed, Morrisons, UK) providing ~48g of carbohydrate, then finger-prick blood samples were obtained at 30 minute intervals over a 2 hour period. Time intervals were determined using a timer after the last bite had been swallowed (note: participants were advised to maintain a similar chewing frequency for both interventions and it ranged from 12-16 chews/bite). The participants were then asked to either a) sit quietly for 2 hours or b) engage in non-physical activities such as animated conversation and/or problem solving or reading. Most volunteers however spent more time talking than on reading or problem solving. Overall, only about 25% of the time (20-30 minutes) was spent on reading and problem solving, the rest of the time was spent engaged in conversation. Each participant acted as their own control. Most participants completed both interventions within a week except for four participants, who had a gap of 2-3 weeks between the two interventions.

Data was compared using IBM SPSS for windows software (PASW18) with significance of difference set at P



Metre accuracy and precision

Except for one touch ultra 2 metre which showed a precision of ~9% on six replicate measurements, all remaining three meters showed a precision of

i.e ≥5.6 mmol/l, only Accu Chek metre showed glucose concentrations significantly higher than the reference values (P P

Doughnut intervention

Blood glucose concentrations increased and peaked at 60 minutes in both interventions. Repeated measures ANOVA showed a significant effect of time (P=0.000) and activity (P=0.006) and a significant interaction between time and activity (P=0.04). Figure 1 shows that except for the baseline measurement, there is a clear difference in blood glucose levels when participants observed quiet/passive behaviour compared to when they were interactive. Figure 2 shows the change in blood glucose concentrations after correction for the baseline level. The change in blood glucose concentration was ~30-38% lower in the ‘active’ subjects, even at the first measurement at 30 minutes (Figure 2). Repeated measures ANOVA showed a significant effect of time at P value of 0.002 and activity at P=0.01, however interaction between time and activity was not significant when analysis was run on the differences.

Figure 1 Comparison of the mean blood glucose concentrations (mmol/L) at 5 time points for each study period

Figure 1: Comparison of the mean blood glucose concentrations (mmol/L) at 5 time points for each study period

a. Blood glucose values in mmol/l were measured in duplicate using Freestyle Freedom Lite meter. Values shown are mean and standard error obtained for quiet and active intervention at 5 time points.


Table 1 Comparison of finger-prick blood glucose concentrations (mmol/L) from 4 different glucose metres with the laboratory reference method

Table 1: Comparison of finger-prick blood glucose concentrations (mmol/L) from 4 different glucose metres with the laboratory reference method

Median and interquartile range of glucose values obtained with four metres (One touch ultra2, Accu Chek Aviva, ContourXT and Freestyle Freedom Lite) were compared with the venous blood glucose concentrations determined by the laboratory reference method (Randox GLUC-PAP). Percent deviation from the reference values was calculated for each metre. Significance of difference from the laboratory reference method was calculated using Wilcoxon paired sample test. Within each row, (a). that values are not significantly different from the reference values and (b). a significant difference at P


Figure 2 Change in blood glucose concentrations (mmol/L) for each study period after correction for baseline glucose concentrations

Figure 2: Change in blood glucose concentrations (mmol/L) for each study period after correction for baseline glucose concentrations

b. Baseline glucose concentrations (mmol/l) were subtracted from glucose concentrations all time points and change in blood glucose levels is shown for 30, 60, 90 and 120 minutes for the quiet and active intervention.



In agreement with previously published reports (9) the Freestyle Freedom Lite glucose metre met the ISO standards most reliably, and although using a different principle of glucose analysis (glucose dehydrogenase) than the laboratory reference method (glucose oxidase) was found to be the most accurate in comparison (9,11).

However, all glucose metres gave slightly higher blood glucose concentrations than the laboratory reference method, especially at low concentrations. The Freestyle Freedom lite, ContourXT and Accu Check Aviva metres all use the glucose dehydrogenase method for blood glucose determination. The One Touch ultra2 glucose metre uses the glucose oxidase enzyme and gave results, which were less accurate. The methods differ in their specificity for glucose. Glucose oxidase with its cofactor flavin adenine dinucleotide (FAD) is very specific for glucose but interference can come from mannose. However it has been suggested that this interference only exists at very high mannose concentrations and is unlikely to be the case in real life (12). Medications containing non-glucose sugars (e.g. xylose and maltose) can interfere with the glucose dehydrogenase enzyme with its cofactor pyrroloquinoline quinine (13, 14). Therefore sugars other than glucose can cause potential errors in blood glucose measurements but were unlikely the case in the present investigation.

To our knowledge this is the first study that has shown that a non-physical activity such as animated conversation combined with reading and/or problem solving activity can lower the blood glucose concentration following a carbohydrate loading. Although there appear to be no studies on the effect of animated conversation on blood glucose levels, several studies have examined the effect of cognitive demand on blood glucose levels (15-18). One study found that the performance of cognitively demanding tasks was improved following a glucose drink, and the decline in blood glucose levels were dependent on the type of cognitive task, with liquid weed the reduction in blood glucose concentrations being greatest when the tasks were more demanding (18). Although the participants in the present study only spent 20-30 minutes on tasks that required focussed mental activity i.e. reading newspapers/ magazines or problem solving, they did spend the rest of the study in animated conversation which must also have required mental agility. We did find in our preliminary experiments (data not shown) that quiet conversation was not as effective at lowering the blood glucose concentrations as talking loudly, suggesting that just as the type of cognitive task influences the extent of blood glucose changes, the ‘type’ of talking will also influence blood glucose levels. Hence, not only physical exercise and mental activity as found by Scholey et al (18) but other activities such as animated conversation can also lower blood glucose concentrations. Perhaps such simple lifestyle interactions can be explored further for its benefits in patients with type 2 diabetes.

Various groups have researched the effect of physical activity on glycaemic control and quality of life in patients with type 2 diabetes. Many have confirmed improvements with regular exercise. A low intensity exercise such as arm swinging, 30 minutes a day, 3 days/week in patients with type 2 diabetes was shown to improve their glycaemic control (19). Two studies explored the effects of a home based physical exercise program and concluded that such a program has the potential for improvements in the quality of life, glycaemic control and weight loss in these patients (20, 21). The latter study also included a questionnaire about the barriers to physical exercise and highlighted that pain after physical activity, a lack of motivation and a low perception of capabilities for activity prevented individuals from adhering to their regime (21). Perseverance to an exercise program therefore can be a barrier that may prevent participation in regular exercise (22). This can be especially an issue for older adults (23). Our study has highlighted another factor that can be explored for its benefit in maintaining blood glucose levels within a healthy range. If interactive behaviour such as talking or engaging in mental activity can help patients control their blood glucose levels, then this may be a regime that patients can follow when they are unable to engage in regular exercise due to personal and environmental constraints.

There are many variables that can influence the outcome of an experiment such as the present one, for example, it has been suggested that the degree of mastication can influence the glycaemic response of an individual (24, 25). Participants in this study were therefore asked to keep a note of their chewing frequency during the first study period and were asked to maintain the same rate in the second to minimise its influence. Diet and lifestyle preceding the intervention may also affect the results. Dekker et al (26) found that the daily intake of caffeine over a two week period by caffeine naïve young males showed alterations to glucose homeostasis with increased serum insulin and blood glucose concentrations in response to the 5 mg caffeine/kg body weight/day. Exercise has also been shown to influence insulin sensitivity as studied by O’Donovan et al (27) who reported that 24 weeks of exercise can reduce insulin resistance and that both moderate or high intensity exercise can result in an improvement in insulin sensitivity of cells. A detailed record of the diet and exercise regime of participants at least 2-3 days preceding the intervention should have been taken as regular exercise of three times per week (27) or a one off exercise on the previous day of intervention (28) have both been shown to affect the insulin sensitivity of cells. We advised all our participants to eat their evening meal at the same time before each intervention and also maintain a similar exercise regime; and except for four, all participants completed the two interventions within 6 days. It is therefore unlikely to influence the results of our investigations. However the participants were not asked to provide a record of their diet and lifestyle preceding the experiment. This is something that should be considered for the future studies.

In conclusion, our investigation has highlighted a simple lifestyle change that can significantly influence blood glucose levels. We have shown that it is important to assist those unable to take part in physical activities to interact with other people and to encourage them to undertake mental activities and that such small change could assist in the control of blood glucose concentrations.


Acknowledgements: Authors would like to thank all volunteers without whose contribution this research could not have been completed. Authors would also like to thank Mrs Blerta Jakaj and Mrs Sonali Chopra for their assistance with the doughnut intervention study. This work was funded by IBBS, University of Portsmouth.

Authorship: All authors took part in the doughnut intervention experiment. Glucose comparison of pin prick samples with the laboratory results was undertaken by Syed and Beverly. All authors confirm there is no conflict of interest. Ethical approval for this study was obtained from the Biosciences Research Ethics Committee of the University. The research was conducted in compliance with the declaration of Helsinki, as adopted at the 18th World Medical Association (WMA) General Assembly, Helsinki, Finland, 1964 and last amended at the 59th World Medical Association General Assembly, Seoul 2008.



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