Investigating the Incretin Effect in Cystic Fibrosis

Completed

Conditions: Cystic Fibrosis

Interventions: Drug: Oral Glucose Tolerance test (75g 2-hour)
Drug: Modified Oral Glucose Tolerance Test (50g 4-hours)
Drug: Matched isoglycemic clamp
Drug: Hyperglycemic clamp with concurrent GLP-1 infusion
Drug: Hyperglycemic Clamp with concurrent GIP infusion
Drug: Hyperglycemic clamp with placebo infusion
Other: Liquid Meal Test (Carbohydrate-rich)
Other: Liquid Meal Test (Fat-rich)
Other: Liquid Meal Test (Mixed)
Device: Continuous Glucose Monitoring

Registration Number: NCT01975259

Lead Sponsor: Liverpool Heart and Chest Hospital NHS Foundation Trust

Brief Summary: Most Cystic fibrosis (CF) patients now commonly live well into adulthood, this means they are progressively accumulating damage to the insulin-secreting cells inside their pancreas. This explains why most adult patients have some degree of abnormal sugar regulation \& rates of diabetes rise significantly with age. CF related diabetes is categorically different from other types of diabetes \& its development is serious as it heralds a faster decline in lung function \& a reduced life expectancy.

The hallmark of abnormal sugar handling in CF is high glucose levels after meals as the damaged pancreas responds abnormally slowly. Over 70% of the initial response of a healthy pancreas is induced, not by glucose alone, but by hormones released from the bowel known as incretins. We want to establish whether incretins are important in blood sugar handling in CF as specific drugs that enhance their effect are now available.

The study hypothesis is that the incretin system will function normally in patients with Cystic Fibrosis. To show this we will measure how much insulin secretion is dependant on incretin hormones in CF patients by comparing levels after a sugary drink test and then an intravenous glucose drip test (run at a rate that mimics the blood sugar levels obtained during the first test to make it a fair comparison ) - as incretins will only be produced in the first test when the sugar passes through the bowel any extra insulin produced will be due to these hormones. To detect resistance to the incretin hormones we will separately measure responses to direct infusions of the hormones themselves. We will explore which components of meals cause incretin hormone release from the bowel wall by measuring blood levels after different types of meals are consumed. Finally we will measure levels of the enzyme that breaks down the incretin hormones (DPP-4) to know if they are deactivated more quickly in people with CF. By describing the incretin system in CF we will considerably improve our understanding of this important condition as well as potentially highlighting new ways to treat it.

Detailed Description: Not available

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 50

Inclusion Criteria

Cystic fibrosis as diagnosed by EITHER Cystic fibrosis transmembrane conductance regulator (CFTR) mutation on genotyping OR Positive sweat test (Chloride ≥60mmol/L after pilocarpine iontophoresis) AND Clinical features in keeping with a diagnosis of Cystic Fibrosis
Clinically stable for at least 4 weeks without inpatient or outpatient treatment for an infective exacerbation - including antibiotics (other than long-term prophylactic therapy) or steroids

Exclusion Criteria

Active Pregnancy or <12 months Post-partum
Clinically unstable patients
Patients on long-term steroids
Patients with known gastroparesis or previous surgery to the gastrointestinal tract (including vagotomy)
History of organ transplant or planned organ transplant awaited
Non-CF related diabetes (e.g. Type 1 or 2 Diabetes Mellitus)
Active malignancy
Clinically significant derangements in haematological or biochemical indices
Clinical symptoms of malabsorption (frequent bowel motions/passing of undigested foodstuffs or steatorrhoea)
Known difficult venous access
Use of bile acid sequestrants in the previous 4 weeks

Study Type: OBSERVATIONAL

Study Design: Not specified

Arm && Interventions

Primary Outcome Measures

Name	Time	Method
Area Under Curve (AUC) of Insulin & C-peptide secretion during a matched isoglycemic clamp	4 hours	Differences in Insulin \& C-peptide secretion will be measured over a 4-hour period following an oral glucose tolerance test and then separately over the same period during a matched isoglycemic glucose infusion (which will recreate the glucose values obtained during the oral glucose tolerance test). The difference in these values can be wholly attributed to the effect of incretin hormones.
Volume of intravenous glucose required to maintain a hyperglycemic clamp at 180-216mg/dL	3 hours	A hyperglycemic clamp uses an intravenous glucose infusion to fix blood sugar at a certain level. We will use such a technique to fix blood sugar levels at 180-216mg/dL (10-12 mmol/l) for one hour then infuse either an incretin hormone (GLP-1/GIP) or placebo (sodium chloride) for a further two hours. The excess volume of intravenous glucose required during the last two hours of the test (compared to the first) will allow us to calculate what if any effect the incretin hormones have on the pancreas in patients with Cystic Fibrosis

Secondary Outcome Measures

Name	Time	Method
AUC incretin hormone levels (GLP-1/GIP)	4 hours	Incretin hormone levels (GLP-1/GIP) will be measured in response to an oral glucose tolerance test, an intravenous isoglycemic glucose infusion as well as in response to standardised meals of different composition (fat-rich, carbohydrate rich \& mixed).
Serum DPP-4 levels	0 mins	We will measure serum DPP-4 levels on 2 separate occasions in both CF and control groups to establish if there are any differences in how rapidly the incretin hormones are deactivated between the groups

Trial Locations

Locations (1): Liverpool Heart and Chest Hospital
🇬🇧
Liverpool, United Kingdom

Investigating the Incretin Effect in Cystic Fibrosis

Recruitment & Eligibility

Study & Design

Trial Locations

Instant Trial Alerts

Instant Trial Alerts

Group	Intervention	Description
Controls	Modified Oral Glucose Tolerance Test (50g 4-hours)	Adult Non-CF subjects matched for age and body mass index with normal glucose tolerance. Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich)
Cystic Fibrosis	Oral Glucose Tolerance test (75g 2-hour)	Adult patients with confirmed cystic fibrosis who are clinically stable. Interventions: Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich) Continuous Glucose Monitoring
Controls	Oral Glucose Tolerance test (75g 2-hour)	Adult Non-CF subjects matched for age and body mass index with normal glucose tolerance. Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich)
Cystic Fibrosis	Modified Oral Glucose Tolerance Test (50g 4-hours)	Adult patients with confirmed cystic fibrosis who are clinically stable. Interventions: Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich) Continuous Glucose Monitoring
Cystic Fibrosis	Liquid Meal Test (Carbohydrate-rich)	Adult patients with confirmed cystic fibrosis who are clinically stable. Interventions: Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich) Continuous Glucose Monitoring
Cystic Fibrosis	Liquid Meal Test (Mixed)	Adult patients with confirmed cystic fibrosis who are clinically stable. Interventions: Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich) Continuous Glucose Monitoring
Cystic Fibrosis	Matched isoglycemic clamp	Adult patients with confirmed cystic fibrosis who are clinically stable. Interventions: Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich) Continuous Glucose Monitoring
Controls	Liquid Meal Test (Carbohydrate-rich)	Adult Non-CF subjects matched for age and body mass index with normal glucose tolerance. Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich)
Controls	Liquid Meal Test (Fat-rich)	Adult Non-CF subjects matched for age and body mass index with normal glucose tolerance. Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich)
Cystic Fibrosis	Hyperglycemic clamp with concurrent GLP-1 infusion	Adult patients with confirmed cystic fibrosis who are clinically stable. Interventions: Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich) Continuous Glucose Monitoring
Cystic Fibrosis	Hyperglycemic Clamp with concurrent GIP infusion	Adult patients with confirmed cystic fibrosis who are clinically stable. Interventions: Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich) Continuous Glucose Monitoring
Cystic Fibrosis	Hyperglycemic clamp with placebo infusion	Adult patients with confirmed cystic fibrosis who are clinically stable. Interventions: Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich) Continuous Glucose Monitoring
Controls	Matched isoglycemic clamp	Adult Non-CF subjects matched for age and body mass index with normal glucose tolerance. Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich)
Controls	Hyperglycemic Clamp with concurrent GIP infusion	Adult Non-CF subjects matched for age and body mass index with normal glucose tolerance. Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich)
Controls	Liquid Meal Test (Mixed)	Adult Non-CF subjects matched for age and body mass index with normal glucose tolerance. Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich)
Cystic Fibrosis	Liquid Meal Test (Fat-rich)	Adult patients with confirmed cystic fibrosis who are clinically stable. Interventions: Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich) Continuous Glucose Monitoring
Controls	Hyperglycemic clamp with concurrent GLP-1 infusion	Adult Non-CF subjects matched for age and body mass index with normal glucose tolerance. Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich)
Cystic Fibrosis	Continuous Glucose Monitoring	Adult patients with confirmed cystic fibrosis who are clinically stable. Interventions: Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich) Continuous Glucose Monitoring
Controls	Hyperglycemic clamp with placebo infusion	Adult Non-CF subjects matched for age and body mass index with normal glucose tolerance. Oral Glucose Tolerance test (75g 2-hour) Modified Oral Glucose Tolerance Test (50g 4-hours) Matched isoglycemic clamp Hyperglycemic clamp with concurrent GLP-1 infusion Hyperglycemic Clamp with concurrent GIP infusion Hyperglycemic clamp with placebo infusion Liquid Meal Test (Carbohydrate-rich)