This FOODplus seminar was held by Drs Natalie Luscombe-Marsh and Tanya Little, both post-doctoral researchers from the School of Medicine. Natalie and Tanya both have an interest in understanding how the gut senses different macronutrients, and the differential effect of different macromolecules from the diet on gut function and satiety. We learnt that fat has a more significant and prolonged appetite-suppressing effect than carbohydrate, and that this effect is also influenced by fat type; that is, properties of different fats, like chain length and degree of saturation, can alter how they affect gastrointestinal function and the release of gut peptides. Natalie’s work focused more on the gastrointestinal sensing of protein, and Natalie presented preliminary results from a trial that is currently underway which aims to better understand the impact of protein on gut function and satiety. There is no doubt that understanding more about how different foods and different food components influence satiety is important when we are trying to determine the potential health benefits of different foods. The methods that were presented by Natalie and Tanya have enormous potential for helping us to understand how the novel food products developed within FOODPlus might influence how long feelings of fullness are maintained after a meal and the release of gut peptides which are critical for the regulation of appetite.

1. The Waite Research Institute
FOODplus Research Centre
Scientific Seminar Series – 2010
#3a
Dr Tanya Little
Life Impact | The University of Adelaide

2. Dr Tanya Little
University of Adelaide Discipline of Medicine
NHMRC Centre of Clinical Research Excellence (CCRE) in
Nutritional Physiology, Interventions and Outcomes

3.  Gastrointestinal (GI) sensing of dietary fat
 Which factors determine the GI responses to
dietary fat?
 Oral detection of dietary fat
 Relationships between:
▪ dietary fat intake and body weight
▪ oral and GI sensitivity

4.  There is a strong positive relationship
between the intake of dietary fat with total
energy intake and body weight
(Golay and Bobbioni, Int J Obes Relat Metab Disord, 1997)
 Obese individuals have an increased
preference for high-fat foods
(Mela and Sacchetti, AJCN, 1991)

5. 5000
4000
*
*
3000
2000
1000
0
Control Fat Glucose
* P<0.01 vs. control and glucose
(Chapman et al. , AJCN , 1999)

6.  We examine downstream effects of fat
sensing identified in cell line and animal
studies. For example, changes in:
 GI motility
 plasma concentrations of GI peptides
 food intake
 Expression of fat sensing receptors in small
intestinal biopsies

7. isolated pyloric
 proximal gastric
pressure waves
relaxation
(IPPWs)
pyloric tone
small  antral pressure
intestinal waves
fat
 duodenal
pressure waves slowing of
gastric emptying
(Seimon et al., AJCN, 2010)

8. small
inhibits energy intestinal fat
intake
CCK, PYY, GL
P-1
ghrelin
slows gastric
emptying
(Seimon et al., AJCN, 2010)

9. triacyl- monoacyl-
glyceride glyceride
↓ Food intake
↓ food intake
+
lipase inhibition
(Orlistat) FFAs ↑ CCK, GLP-1,
↑ CCK, GLP-
PYY
1, PYY
↓ gastric ↓ ghrelin
↓ ghrelin
emptying Pancreatic and
pancreatic and
gallbladder
gallbladder
secretion
secretion

10. 9 CCK IPPWs
8 90
7 A 70
6
pmol/l
5 50
P
4 30
3 10
2 D
1 * -10
mmHg
0 Fat Fat+orlistat
0 15 30 45 60 75 90 105 120
Time (min)
Energy intake
6400 *
5600 Fat
4800
Fat+Orlistat
(kJ) 4000 * P<0.05 vs. Fat
kJ
3200
2400
1600
800
0
(Feinle et al., Am J Physiol Gastrointest Liver Physiol, 2003)

11. IPPWs CCK
40 * 6
30
4
Number
pmol/l
20
*
2
10
0 0
-15 0 30 60 90 120 0 30 60 90 120
Time (min) Time (min)
Control
LE-0.26 µm * P < 0.05, LE-0.26 vs. control
LE-30 µm
LE-170 µm (Seimon et al., AJCN, 2009)

12. 40
Control
LE-0.26 µm
LE-30 µm
Score (mm)
20 LE-170 µm
0
*
-20
0 30 60 90 120
Time (min)
* P < 0.05, LE-0.26 vs. control
(Seimon et al., AJCN, 2009)

13. 45
Effectiveness in slowing
35
gastric emptying
25
15
5
-5
0 2 4 6 8 10 12 14 16 18
Number of carbon atoms in chain
(Hunt & Knox, J Physiol, 1968)

14. Pylorus Energy intake
120 # 6000
100
80 4000
Total *
60
No.
40 2000
20
0 0
Control C10 C12 Control C10 C12
# vs control: P < 0.05
* vs control/C10: P < 0.05
(Feltrin et al., Am J Physiol Regul Integr Comp Physiol, 2004)

15. CCK GLP-1
16 30
12 * 20 *
pmol/l
8 #
10
4
0 0
0 15 30 45 60 75 90 0 15 30 45 60 75 90
Time (min) Time (min)
Control * vs. control/C10: P < 0.05
# vs. control P < 0.01
C10
C12
(Feltrin et al., Am J Physiol Regul Integr Comp Physiol, 2004)

16. PYY Ghrelin
50 500
450
40
* 400
pmol/l
30 350
300
20
250
*
10 200
0 15 30 45 60 75 90 0 15 30 45 60 75 90
Time (min) Time (min)
Control
* vs. control/C10: P < 0.05
C10
C12
(Feltrin et al., Peptides, 2006)

17. vagotomy
CCK1 receptor
antagonist
CCK ↓ Gastric ↓ Food Intake
emptying
Small intestinal
fat

18. 60 Medulla 60 Hypothalamus
%BOLD from baseline
%BOLD from baseline
50 50
40 40
30 30
20 20
10 10
0 0
Lipid + - + - Lipid + - + -
Dex - - + + Dex - - + +
(Lassman et al., Gastroenterology, 2010)

19. CCK Ghrelin
2100 ^ 270000
(pmol/l*180min)
(pg/ml*180min)
1575 202500
*
AUC
AUC
1050 135000
525 * 67500
0 0
Saline LCFA LCFA Saline LCFA LCFA
+ Dex + Dex
PYY
32000 *
(pg/ml*180min)
24000
AUC
16000
8000
0
^ P<0.05 ,LCFA+DEX vs. saline Saline LCFA LCFA
* P<0.05, LCFA vs. saline + Dex
(Degen et al. Am J Physiol Regul Integr Comp Physiol, 2007)

20. 10000 ^
Energy intake (kcal)
8000
*
6000
4000
2000
0
Saline C18 C18+Lox
Treatment
(Matzinger et al., Gut, 2000)

21. CD36 GPR120, GPR119, GPR40
free fatty acid (>C12) Gut peptides (CCK/GLP-1)
apo A-IV/chylomicron Gut peptide receptors (e.g. CCK/GLP-1)
lumen
OA
OEA
?
PPAR-ɑ ?
intestinal L-cell enterocyte
intestinal I-cell
vagal afferent
vagal afferent
(from Richard Young)

22. CD36 GPR119
mRNA copy number
mRNA copy number
1.0 R2 = 0.59 0.0003 R2 = 0.34
0.8 P = 0.02 P = NS
0.0002
0.6
0.4 0.0001
0.2
0.0 0.0000
20 25 30 35 40 20 25 30 35 40
BMI (kg/m2) BMI (kg/m2)
(Little et al., unpublished observations)

23.  FFAs are required for GI and appetite
responses to fat
 Only FFAs with a chain length ≥12 are
effective
 FFAs effects on GI function and energy
intake are dependent on the CCK1 receptor
 Expression of FA sensing receptors in the
human SI may be related to BMI

24.  Recent evidence of a sixth “taste” modality
responsive to oral free fatty acids (Chale-Rush et
al., Chem Senses, 2007 et al.; Chale-Rush et al., AJP , 2007)
 FA taste mechanisms analogous to those
involved in intestinal fat sensing, e.g.
CD36, GPR119, GPR120
 Animal studies have revealed a relationship
between oral sensing of dietary fat with fat
preference (Pittman et al., Chem Senses, 2008; Gilbertson et
al., Ann NY Acad Sci, 1998)

25. Energy intake Fat intake
10000 40 *
8000 * 30
6000
kJ
%
20
4000
2000 10
0 0
Hyper Hypo Hyper Hypo
Taste sensitivity Taste sensitivity
N = 54 (12 hyper sensitive, 42 hyposensitive
Mean BMI: 22.8 (0.8), range 16.8 – 29, kg/m2
* P < 0.05 vs. hypersensitive
(Stewart et al., Br J Nutr, 2010)

26. Fat taste threshold Energy intake Fat intake
12 14000 120 * *
Concentration C18:1 (mM)
* *
10 12000 100
10000
8 80
Weight (g)
8000
kJ
6 60
g
6000
4 40
4000
2 2000 20
0 0 0
Lean Obese
Lean Obese Lean Obese Lean Obese
(Seimon et al., unpublished observations)

27. Sensory detection threshold IPPWs
Detection threshold (mmol/L)
Total no. IPPWs/90 min
15 80 R = -0.615
P = 0.00
60
10
40
5
20
R = 0.669
P = 0.002
0 0
20 25 30 35 40 20 25 30 35 40
BMI (kg/m2) BMI (kg/m2)
N = 19 (10 lean, 9 obese)
(Seimon et al., unpublished observations)

28. Oral detection Habitual fat
threshold intake
IPPWs R = -0.515 R = -0.532
P = 0.029 P = 0.028
CCK R = -0.430 R = -0.538
P = 0.075 P = 0.015
PYY R = -0.478,
P = 0.045
(Seimon et al., unpublished observations)

29.  Individuals are able to sense or “taste”
FFAs in the oral cavity
 There is large inter-individual variation in
taste thresholds for oleic acid
 Individuals with lower sensitivity to oral fat
have :
 increased BMI
 increased energy and fat intakes
 impaired GI responses to intestinal fat infusion

30.  FFAs have potent effects on GI
function, which favour suppression of
energy intake
 Oral fat sensing appears important in
mediating dietary fat intake
 Individuals who are less sensitive to oral FFAs
have higher habitual fat, and energy, intakes
and BMI
 Individuals with decreased oral sensitivity
to FFAs also appear to have impaired GI
sensitivity

31.  Need to determine:
 whether the GI responses to fat can be restored
in obese individuals, e.g. by energy restriction
 relationships between intestinal expression of
fat sensing receptors with body weight, and
acute and chronic nutrient exposure

32.  Assoc Prof Christine Feinle-Bisset
 Radhika Seimon
 Dr Richard Young
 Assoc Prof Chris Rayner
 Lena Brandlhuber
Deakin University
 Jessica Stewart
 Dr Russell Keast