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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Prospectively registered

Titles & IDs
Public title
Effects of protein on gut motility and hormones, and appetite and energy intake in healthy older individuals
Scientific title
Effects of intraduodenal protein load, on energy intake, appetite, antropyloroduodenal motility, amino acids, hormones and glucose in healthy older individuals
Secondary ID [1] 281081 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Ageing 287231 0
Condition category
Condition code
Diet and Nutrition 287554 287554 0 0
Other diet and nutrition disorders
Oral and Gastrointestinal 287555 287555 0 0
Normal oral and gastrointestinal development and function

Study type
Description of intervention(s) / exposure
A single 60 minute intraduodenal infusion at 4mL/min of
i) 0 kcal/min (saline control)
ii) 0.5 kcal/min (Whey Protein Hydrolysate)
iii) 1.5 kcal/min (Whey Protein Hydrolysate)
iv) 3 kcal/min (Whey Protein Hydrolysate)
in 16 older subjects

Appetite sensation questionnaires in the form of a Visual Analogue Scale (VAS), blood samples.

A standard buffet meal will be provided at the end of the 60 minute infusion from which the volunteer has 30 minutes to eat until comfortably full. The buffet meal consists of 300ml orange juice, 600ml water, 375ml iced coffee, 4 slices white bread, 4 slices brown bread, 100g deli leg ham, 100g virginian chicken, 4 slices cheese, 100g tomato, 100g cucumber, 100g lettuce, 2 portions mayonnaise, 2 portions margarine, 1 medium apple, 1 medium banana, 200g chocolate custard, 150g fruit salad, 200g strawberry yoghurt, and a 14g milky way bar.

Each volunteer will receive one of each infusion solution over 4 study days. Each study visit will be seperated by no less than 3 days.

Each study visit will last approximately 3-6 hours.
Intervention code [1] 285535 0
Comparator / control treatment
Volunteers will act as their own control via administration of a single 0kcal/min intraduodenal infusion of saline solution, delivered at a rate of 4mL/min for 60 minutes, to enable comparison to nutrient containing infusions.
Control group

Primary outcome [1] 287806 0
Antropyloroduodenal motility (antropyloroduodenal pressures; number of antral, duodenal and isolated pyloric pressure waves; basal pyloric pressure) assessed by Manometry.
Timepoint [1] 287806 0
Intubation occurs on subject arrival.

At t= -15 until 0, a baseline of the antropyloroduodenal (APD) motility is recorded.

Infusion starts at t=0 until t=60 minutes. APD motility is assessed continuously for the duration of the infusion (t=0-60 minutes).

Subject is extubated at t=60 minutes.
Primary outcome [2] 287807 0
Plasma concentrations of gut hormones (cholecyctokinin (CKK), glucagon-like peptide-1 (GLP-1), peptide YY (PYY), gastric inhibitory polypeptide (GIP), ghrelin, glucagon and insulin), glucose and amino acids.
Timepoint [2] 287807 0
Blood samples are taken at t= 0, 15, 30, 45 and 60 minutes.
Primary outcome [3] 287808 0
Macronutrient and total energy intake of a standard buffet meal are quantified using Foodworks software.
Timepoint [3] 287808 0
Buffet meal will be presented at the end of the infusion and after extubation (t=60). The subject will be allowed to freely consume food for 30 minutes until comfortably full (until t=90).
Secondary outcome [1] 298865 0
Appetite sensations using a Visual Analogue Scale (VAS) (nausea, hunger, fullness, desire to eat, thirst).
Timepoint [1] 298865 0
VAS questionnaires are given at t= 0, 15, 30, 45, 60 and 90 minutes.
Secondary outcome [2] 298866 0
Blood pressure and heart rate are determined using an automatic sphygmomanometer.
Timepoint [2] 298866 0
Blood pressure and heart rate are measured at t= 0, 15, 30, 45, 60 and 90 minutes.

Key inclusion criteria
Body Mass Index (BMI): 20-30 kg/m2

Weight stable (<5% fluctuation in body weight in previous 3 months).
Minimum age
65 Years
Maximum age
No limit
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Significant gastrointestinal symptoms, disease, or surgery.

Current gallbladder or pancreatic disease; diabetes mellitus; epilepsy; cardiovasculr or respiratory diseases; any other illnesses as assessed by the investigator (including chronic illnesses not explicitly listed above).

Impaired cognitive function.


Use of prescribed or non-prescribed medications (including vitamins and herbal supplements) which may effect gastrointestinal function or appetite.

Lactose intolerant or other food allergies; intolerance or allergy to paracetomol.

Individuals with low ferritin levels or who have donated blood in the 12 weeks prior to taking part in the study.

Current intake of >2 standard drinks on >5 days per week.

Current smokers of cigarettes/cigars/marijuana.

Current intake of any illicit substance.

Experience claustrophobia in confined spaces.

Unable to tolerate nasogastrointestinal tube, or to comprehend study protocol.

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Volunteers are asked to visit the clinic for a screening visit. A series of screening questionnaires are answered by the volunteer, and a blood sample is taken for determination of ferritin levels. Eligibility is determined based on the inclusion/exclusion criteria. A signed informed consent form is obtained and study dates are established. Eligible volunteers are assigned a subject number and randomised into a treatment for each study visit using a randomisation table created on an excel spreadsheet. Randomisation involves contacting the holder of the randomisation table (study assistant) to inform them of the subjects details and study dates. The unblinded study assistant is therefore responsible for allocating a random treatment to the subject and preparing the solution for infusion on each study day.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
The randomisation table was created using Microsoft Office Excel.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?

Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)

Funding & Sponsors
Funding source category [1] 285864 0
Government body
Name [1] 285864 0
National Health and Medical Research Council Grant
Address [1] 285864 0
Level 1 16 Marcus Clarke Street
Canberra ACT 2601
Country [1] 285864 0
Primary sponsor type
Dr Stijn Soenen
Level 6 Eleanor Harrald Building,
Frome Road,
Adelaide, SA 5000
Secondary sponsor category [1] 284687 0
Name [1] 284687 0
University of Adelaide
Address [1] 284687 0
North Terrace
Adelaide, SA 5005
Country [1] 284687 0
Secondary sponsor category [2] 284688 0
Name [2] 284688 0
Royal Adelaide Hospital
Address [2] 284688 0
North Terrace
Adelaide, SA 5005
Country [2] 284688 0

Ethics approval
Ethics application status
Ethics committee name [1] 287893 0
Royal Adelaide Hospital Research Ethics Committee
Ethics committee address [1] 287893 0
Level 3, Hanson Institute, North Terrace
Adelaide, South Australia, 5000
Ethics committee country [1] 287893 0
Date submitted for ethics approval [1] 287893 0
Approval date [1] 287893 0
Ethics approval number [1] 287893 0

Brief summary
Ageing is associated with a physiological reduction of appetite and energy intake, which has been called the “anorexia of ageing”. Dietary supplementation with liquid protein preparations is now used frequently to increase energy and protein intake in older adults in both institutionalized and community-dwelling populations. Although the latter would appear a logical approach, evidence for success of increased energy intake in older individuals is limited. There is consensus that nutrient stimuli in the gastrointestinal (GI) tract, especially in the small intestine, play a major role in the regulation of appetite and energy intake via modulation of GI motility and hormone release. Increasing our knowledge of how protein affects GI motility and hormone release is of increasing relevance in older individuals. Urgent investigation is warranted to determine the optimal load of protein that can be incorporated into their diet to assist in sparing muscle mass without reducing their appetite.

The study aims to characterise in healthy older individuals, the effect of different intraduodenal protein loads on energy intake, appetite, antropyloroduodenal motility, plasma concentrations of amino acids, gut hormones and glucose, and to determine the relationship between the suppression of appetite and energy intake by protein with ‘small intestinal’ mechanisms.
Trial website
Trial related presentations / publications
Soenen S, Giezenaar C, Horowitz M, Ryan AT, Chapman I, Luscombe-Marsh ND. Energy-intake suppression of intraduodenally infused protein in older and young people. 46th Australian Association of Gerontology (AAG) National Conference, Sydney, Australia, December 2013 (accepted).

Soenen S, Giezenaar C, Horowitz M, Ryan AT, Chapman I, Luscombe-Marsh ND. Effects of intraduodenally infused protein on suppression of energy intake in older and young individuals. 9th Congress of the European Union Geriatric Medicine Society (EUGMS), Venice, Italy, October 2013 (accepted).
Public notes

Principal investigator
Name 34610 0
Dr Stijn Soenen
Address 34610 0
Discipline of Medicine, University of Adelaide
attn.: Dr Stijn Soenen
Level 6, Eleanor Harrald Building,
Frome Road,
Adelaide, SA 5000
Country 34610 0
Phone 34610 0
+61 8 8313 3638
Fax 34610 0
Email 34610 0
Contact person for public queries
Name 17857 0
Dr Stijn Soenen
Address 17857 0
Discipline of Medicine, University of Adelaide
attn.: Dr Stijn Soenen
Level 6, Eleanor Harrald Building,
Frome Road,
Adelaide, SA 5000
Country 17857 0
Phone 17857 0
+61 8 8313 3638
Fax 17857 0
+61 8 8223 3870
Email 17857 0
Contact person for scientific queries
Name 8785 0
Dr Stijn Soenen
Address 8785 0
Discipline of Medicine, University of Adelaide
attn.: Dr Stijn Soenen
Level 6, Eleanor Harrald Building,
Frome Road,
Adelaide, SA 5000
Country 8785 0
Phone 8785 0
+61 8 8313 3638
Fax 8785 0
+61 8 8223 3870
Email 8785 0

No information has been provided regarding IPD availability
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary