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Have pancreatic sufficient patients also an increased risk of diabetes?
Will so much prevention in form of a healthy diet be really working or is the cause purely genetic and nothing can be done?
Thank you

It is first necessary to clarify that there are several types of diabetes. For more information click on the link [in French]:

Diabetes type 1 insulin-DEPENDENT Diabetes (IDD): it affects 10% of diabetics, usually occurs in children, adolescents or young adults, and is expressed by clear symptoms that allow the diagnosis very quickly: intense thirst, abundant urine and rapid weight loss indeed an acid-ketotic coma. This is an autoimmune disease, pancreatic beta cells are destroyed by autoantibodies. There is also little known about environmental factors and genetic predisposition factors (include history in one parent in 5% of cases). As the Body is secreting no more insulin the only treatment is to date insulin injection.

Type 2 diabetes, Diabetes insulin-RESISTANT: it represents 85% of diabetics, typically occurs in subjects over 40 years but now increasingly in adolescents and young adults. Contributing factors are primarily genetic (the risk of transmission to a child is 40% when one parent is type 2 diabetes and 70% when both parents are). Overweight, obesity and lack of physical activity are revealing the cause of the diabetes in genetically predisposed people. Evolving in a sneaky way, it passes unnoticed long (it takes an average of 5 to 10 years from onset of hyperglycemia and diagnosis) and is often diagnosed during a particular complication as a stroke. This shows the importance of prevention. Two factors are responsible for high blood sugar in type 2 diabetes, either the pancreas still makes insulin but not enough (insulinopenia) or insulin doesn’t work well (insulin resistance). Accordingly, it is treated with lifestyle changes then quickly antidiabetic oral treatments (or injection including insulin when deficiency becomes too great). Their effectiveness is optimal only if these treatments are associated with a balanced diet and regular physical activity +++.

Diabetes in cystic fibrosis is very special. It is part of the 5% of other forms of diabetes. The French Cystic Fibrosis Registry reported in 2014 data of 6356 patients: 1154 (18.2%) of them were treated diabetics, of them 222 (6.6%) were treated with insulin. As being a price of treatment progress, the frequency of diabetes increases with increasing patient's life span: among 3334 patients under 20 years, 192 (5.8%) were treated diabetes including 42 (1.3%) treated with insulin while among 3022 patients 20 years or older, 962 (31.8%) were treated diabetes including 180 (5.9%) treated with insulin. Diabetes in CF patients is secondary to a more or less extensive destruction of pancreatic beta and also alpha cells which respectively secrete insulin and glucagon. This destruction is secondary to pancreatic fibrosis that gradually develops around the cystic dilatation of the pancreas related to the closure of the pancreatic ducts by the viscous thickened mucus. It is further possible that the CFTR protein synthesized by the mutated gene impairs insulin secretion mechanism. We do not know by now whether other genetic factors may come into play.
It was generally accepted that pancreatic sufficient CF patients (15% of patients) were not at risk of developing diabetes. As a result of a generally milder form of the disease pancreatic ducts congestion and fibrosis are less important and don’t altered insulin secretion by the beta cells. However, more recent studies question this idea. A study published by an American pediatric team in 2015 in the Journal of Cystic Fibrosis (see reference) provides more specific elements for answer. It involved 146 CF pancreatic insufficient (PI) and 7 pancreatic sufficient (PS) patients. If the glucose tolerance tests were normal in 7 PS patients and abnormal in 2/3 of the PI, a semi-continuous record of blood glucose and insulin during the test showed abnormalities (decreased secretion insulin in terms of glucose) in all patients even if they were less important in pancreatic sufficient patients.

In conclusion, although these results deserve to be confirmed by studies on a larger number of patients, it appears that PS patients are also at risk of glucose intolerance and CF Related Diabetes even if much lower than in PI patients. The good practice guidlines, particularly with regard to lifestyle (diet and physical activity) and the annual control glucose tolerance after age 10 years, concern all the patients either PI or PS. Finally, the possible role of the mutated CFTR protein in the disruption of insulin secretion, if confirmed by future studies, gives hope to a possibility of new current and future therapeutic.

Hope this answer can help.
Best wishes
Gilles RAULT, MD, Roscoff CF Center