Physiologically relevant in vitro methodology to determine true digestibility of carbohydrates and to predict the glycaemic response

Transcription

1 Physiologically relevant in vitro methodology to determine true digestibility of carbohydrates and to predict the glycaemic response TNO Quality of Life, Zeist, The Netherlands TIM-Carbo Robert Havenaar DVM, PhD 57th Starch Convention Detmold, Germany, April 25-28, 2006

2 Aim: development of fast and reliable in vitro methodology for CH digestion and prediction of GR / GI Preconditions: simulating the physiological conditions in the gastrointestinal tract of humans Based on experience: dynamic GI tract model: TIM system Dedicated system: digestion of CH bioaccessibility of monosaccharides prediction of plasma levels (GR, GI)

3 PRECONDITIONS: Successive dynamic conditions in the GI tract gastric acid, salivary and gastric enzymes peristalsis gastric emptying secretion of digestive enzymes, bile peristalsis, intestinal transit absorption of digested products and water dense active microflora, microbial enzymes

4 BASED ON EXPERIENCE: TIM-1 system. stomach and small intestine body temperature peristaltic movements gastrointestinal ph curves gastrointestinal transit times secretion of gastric acid and salivary and gastric enzymes secretion of bile, pancreatic juice absorption of digested products and water continuous process control and data collection modular set-up, high flexibility

5 Peristaltic movements

6 Gastrointestinal transit

7 Gastrointestinal model: computer display

8 Validation and applications of the TIM system nutritional studies digestibility of foods and food ingredients availability for absorption of nutrients some examples on CH novel / functional foods safety assessment studies microbial digestive ecology pharmaceutical / pharmacological studies

9 Carbohydrates in TIM-1: total absorption of glucose 60 Glucose (% of intake) h 1-2 h 2-3 h 3-5 h 0 cooked starch prod #1 prod #2 prod #3 glucose capsule

10 'Glycemic' response after intake of pasta meal TIM system versus human diabetics 16 Glucose (mg/ml) dialysate TIM system plasma diabetics plasma glucose (mmol/l) Time (min)

11 100 Bioaccessibility of energy from carbohydrates intake of 50 g of high energy bar versus 50 g of cheese sandwich 80 Energy (kj) High Energy bar Cheese sandwich Time (min)

12 Water binding capacity of dietary fibres (development of clinical food) 16 water binding (ml/g intest. content) prod A prod B prod C prod D prod E

13 TIM systems: types, numbers and sites patented in NL (1993), USA (1996) and EU (1998) human models: infants, adults, elderly; - healthy conditions - some disease conditions dog model (FIDO; PhD thesis) pig model pre-ruminant calf model at TNO (NL) 6x TIM-1 6x TIM-2 > 1993 in Europe 9x TIM-1 4x TIM-2 > 1996 / 2006 in USA 4x TIM-1 > 2003 / 2006 in Canada 1x TIM-1 3x TIM-2 > 2004

14 TIM-1 system simulation of the physiology of proximal GI tract highly reproducible results suitable for various types of meals, additives, supplements absorption systems: water soluble and fat soluble nutrients high correlation in vitro versus in vivo BUT Not rapid enough for fast screening of food ingredients / products Development and validation of a rapid system: Tiny-TIM

15 Tiny-TIM: prototype of a dedicated screening tool Advantages Relatively simplified system: less labour intensive lower operating costs more units operating simultaneously K A L M Maintaining: E H dynamic conditions sampling in time F B C K G I and high predictive quality?? Validation

16 Tiny-TIM Four Tiny-TIM units: higher throughput; lower costs ph electrode water 37 C level sensor stomach pyloric sphincter small intestine secretion of bicarbonate, bile, pancreatin secretion HCl, pepsine semi-permeable membrane (as part of small intestine) dialysis liquid water 37 C ph electrode pre-filter

17 Validation: bioaccessibility of amino acids from proteins Validation versus body weight gain of chickens bioaccessibility of AA (mg) poultry egg egg poultry fish fish egg R = 0,987 egg body weight gain (g)

18 Validation: bioaccessibility of essential amino acids from proteins Tiny-TIM versus body weight gain of chickens (%) AA absorption (mg) * * ** ** lysine R = methionine R = BWG (% in comp. to ovalbumin) * methionine limitation ** tryptophane limitation

19 Bioaccessibility of glucose from (modified) starches Glucose units (% of intake) Time (min) Soluble starch Product X Product Y Product Z

20 Tiny-TIM: TIM: rapid and cost effective research tool predictive for digestibility of proteins and bioaccessibility of (eesential) amino acids predictive for carbohydrate digestion and bioaccessibility of monosaccharides BUT Not yet prediction of plasma glucose levels / glycaemic response / GI

21 Tiny-TIM data show similarities with in vivo data Glucose response of maltodextrin in Tiny-TIM and healthy humans Glucose in TIM (g/l) insulin response distribution, clearance Tiny-TIM In vivo kinetic modelling Glucose in blood (mmol/l) Time (min)

22 Further development: prediction of plasma glucose levels TIM-Carbo Carbo Tiny-TIM system + In-Silico modelling digestibility of CH glucose Mari et al.2002, Diabetes

23 New developments: combination with biological models for functionality testing human intestinal cell lines: intestinal / mucosal transport production of gut hormones liver cells: liver metabolism dendritic cells: immune endpoint

24 Conclusions about the TIM-Carbo system - simulates GI conditions of target species and age e.g. infants, adults, elderly; dogs, pigs - true ileal digestibility of carbohydrates - bio-accessibility of monosaccharides (and CH energy) - highly reproducible results - high predictive quality - no ethical constrains; no need for ethical approval - very cost-effective - rapid: results within 2-3 days (time saving: 3-4 weeks) - developments: in-silico modelling; gut hormones