A Single Supplement of a Standardised Bilberry Extract Modifies Glycaemic Response

Dietary strategies for alleviating health complications, such as premature vascular disease, associated with type 2 diabetes (T2D) and obesity are actively being pursued as alternatives to pharmaceutical interventions. The genus Vaccinium (e.g. blueberry, bilberry, cranberry) has been used traditionally as a source of folk remedies for established diabetic symptoms.

Berries from this genus are enriched in anthocyanins, polyphenols recognized for their ability to provide and activate cellular antioxidant protection and inhibit inflammatory gene expression, activities that may contribute to the efficacy of the Vaccinium genus as ameliorators for type 2 diabetes. Consumption of a freeze-dried blueberry beverage for an 8 week period for example decreased plasma concentrations of the cardiovascular risk factors oxidized LDL, malondialdehyde and hydroxynonenal. In another trial, bioactives from blueberries improved insulin sensitivity in obese insulin-resistant men and women. In both these studies the investigators reported no change in inflammatory markers following supplementation although bilberry juice was shown to modulate plasma markers of inflammation C-reactive protein and IL-6 in subjects with increased risk of cardiovascular disease. These beneficial responses from human studies are supported by data that demonstrate long-term beneficial effects of anthocyanins from mouse models of obesity and diabetes.

There are also a number of studies in vitro and in vivo that suggest that polyphenols influence carbohydrate digestion and absorption, resulting in improved postprandial glycaemia in the short term. Polyphenols inhibit intestinal alpha glucosidase activity and glucose transport in vitro. In association with this, polyphenols administered to rodents suppress the elevation of blood glucose concentration after oral administration of mono- and di-saccharides. In humans, several studies have examined the effect of polyphenols on the post-prandial glycaemic response. In one study a test meal of mixed berry purée with sucrose showed a lower plasma glucose concentration after 15-30 min compared with a control matched for sugars.

Overall, evidence suggests that consuming edible berries, particularly from the genus Vaccinium, that have high concentrations of anthocyanins could provide a supplementary intervention to improve glycaemia in subjects with T2D or impaired glucose tolerance. The object of this study was to investigate whether a single supplementation with a standardised (36% w/w anthocyanins) concentrated bilberry extract could alter glucose metabolism in overweight/obese volunteers with impaired glucose intolerance or T2D compared with a control capsule matched for sugars and to explore the possible mechanisms of action.

• Bilberry capsule first, then control cap (Dietary supplement): Male subjects aged >40 and <70 years, with type 2 diabetes controlling their diabetes by diet alone closely matched for adiposity as determined by waist circumference (n=8). Volunteers will be randomised double blinded into two groups (n=4 per group) and given a single capsule of either 0.47 grams of a bilberry extract (mirtoselect provided by Indena S.p.A (http://www.mirtoselect.info/) or a control capsule. Following a two week wash out period the volunteers will be asked to take a second single capsule of either of 0.47 grams of mirtoselect or a control capsule in a cross over study, the opposite of what they took the first time.
• Control capsule first then bilberry cap (Dietary supplement): Male subjects aged >40 and <70 years, with type 2 diabetes controlling their diabetes by diet alone closely matched for adiposity as determined by waist circumference (n=8). Volunteers will be randomised double blinded into two groups (n=4 per group) and given a single capsule of either 0.47 grams of a bilberry extract (mirtoselect provided by Indena S.p.A (http://www.mirtoselect.info/) or a control capsule. Following a two week wash out period the volunteers will be asked to take a second single capsule of either of 0.47 grams of mirtoselect or a control capsule in a cross over study, the opposite of what they took the first time.

Primary outcomes

• Plasma Glucose iAUC (Incremental Area Under the Curve; mM*Min) [Plasma was collected at -15, -10 and -5 (fasted) and at 15, 30, 45, 60, 90, 120, 150 and 300 min post capsule]: Volunteers were fasted (10-12 h) overnight before the OGTT. Venous blood samples were taken through an indwelling cannula inserted into a forearm vein at -15, -10 and -5 (fasted) and at 15, 30, 45, 60, 90, 120, 150 and 300 min after consuming 75 g of Polycal liquid (carbohydrate, 61·9%; polysaccharide, 49·2 %; sugars, 12·2%; glucose, 0·6%; maltose, 11·6%; http://www. nutricia.co.uk). Polycal was selected as the main carbohydrate as it is in the form of polysaccharides and this is closer to normal dietary consumption than glucose only.The volunteers consumed the appropriate capsule (0 min), glucose load and a further sample of water (70 ml) within 3 min. For those volunteers taking the control capsule, additional sugar (fructose and dextrose/glucose) was added double-blinded to the water to match the free sugar content of the Mirtoselect® capsules. Movement during the 300 min OGTT was kept to a minimum.
• Plasma Insulin iAUC (Incremental Area Under the Curve; ng/ml*Min) [Plasma was collected at -15, -10 and -5 (fasted) and at 15, 30, 45, 60, 90, 120, 150 and 300 min after the capsule]: Volunteers were fasted (10-12 h) overnight before the OGTT. Venous blood samples were taken through an indwelling cannula inserted into a forearm vein at -15, -10 and -5 (fasted) and at 15, 30, 45, 60, 90, 120, 150 and 300 min after consuming 75 g of Polycal liquid (carbohydrate, 61•9%; polysaccharide, 49•2 %; sugars, 12•2%; glucose, 0•6%; maltose, 11•6%; http://www. nutricia.co.uk). Polycal was selected as the main carbohydrate as it is in the form of polysaccharides and this is closer to normal dietary consumption than glucose only.The volunteers consumed the appropriate capsule (0 min), glucose load and a further sample of water (70 ml) within 3 min. For those volunteers taking the control capsule, additional sugar (fructose and dextrose/glucose) was added double-blinded to the water to match the free sugar content of the Mirtoselect® capsules. Movement during the 300 min OGTT was kept to a minimum.

Secondary outcomes

• Bioavailability in Plasma [Plasma will also be collected -15,-10, -5, 15, 30, 45, 60, 90, 120, 150, and 300 minutes and 24 hours post intervention]: To measure the amount of anthocyanins and phenolic-derived metabolites by liquid chromatography mass spectrometry (LC-MS) being absorbed from the gut and excreted following the single intervention.
• Bioavailability in Urine [Urine will also be collected (if possible) 0, 1, 3 and 5 hours, with all urine collected within the 24 hour time period post intervention]: To measure the amount of anthocyanins and phenolic-derived metabolites by liquid chromatography mass spectrometry (LC-MS) being absorbed from the gut and excreted following the single intervention.

Sex: Male, ages: 40 Years to 70 Years

Inclusion Criteria:

* Male subjects
* Aged >40 and <70
* Clinical diagnosis of Type 2 diabetes controlling their diabetes by diet alone
* All subjects must live in the Aberdeenshire area of Scotland

Exclusion Criteria:

* Medical exclusion criteria
* Clinical diagnosis of thromboembolic or coagulation disease
* Clinical diagnosis of unregulated thyroid disease
* Clinical diagnosis of kidney disease
* Clinical diagnosis of severe gastrointestinal disorders
* History of Alcohol or any other substance abuse

Participant flow

Outcome results

• Plasma Glucose iAUC (Incremental Area Under the Curve; mM*Min) (Primary), Mean, glucose iAUC (mM*min): Single Placebo Capsule 836 +/- 97; Single Blaeberry Capsule 693 +/- 103 (p 0.003)
• Plasma Insulin iAUC (Incremental Area Under the Curve; ng/ml*Min) (Primary), Mean, insulin iAUC (ng/ml*min): Single Control Capsule 358 +/- 131; Single Bilberry Capsule 294 +/- 113 (p 0.028)
• Bioavailability in Plasma (Secondary)
• Bioavailability in Urine (Secondary)

Adverse events

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• Lau FC, Bielinski DF, Joseph JA. Inhibitory effects of blueberry extract on the production of inflammatory mediators in lipopolysaccharide-activated BV2 microglia. J Neurosci Res. 2007 Apr;85(5):1010-7. doi: 10.1002/jnr.21205. PMID 17265471
• DeFuria J, Bennett G, Strissel KJ, Perfield JW 2nd, Milbury PE, Greenberg AS, Obin MS. Dietary blueberry attenuates whole-body insulin resistance in high fat-fed mice by reducing adipocyte death and its inflammatory sequelae. J Nutr. 2009 Aug;139(8):1510-6. doi: 10.3945/jn.109.105155. Epub 2009 Jun 10. PMID 19515743
• Results publication: Hoggard N, Cruickshank M, Moar KM, Bestwick C, Holst JJ, Russell W, Horgan G. A single supplement of a standardised bilberry (Vaccinium myrtillus L.) extract (36 % wet weight anthocyanins) modifies glycaemic response in individuals with type 2 diabetes controlled by diet and lifestyle. J Nutr Sci. 2013 Jul 24;2:e22. doi: 10.1017/jns.2013.16. eCollection 2013. PMID 25191571

• Nigel Hoggard, PhD, Principal investigator, University of Aberdeen Rowett Institute of Nutrition and Health