Type 2 diabetes is affected by genetics and environmental factors. We aimed to assess the effect of an in-utero diabetic environment independently of the genetic background for type 2 diabetes.

We measured insulin sensitivity and insulin secretion in response to oral and intravenous glucose in 15 non-diabetic adult offspring of mothers with type 1 diabetes (exposed participants) and 16 offspring of type 1 diabetic fathers (controls). No participants had type 1 diabetes-associated autoantibodies. We also measured pancreatic polypeptide, a marker of parasympathetic drive to the pancreas.

There was no difference between the groups with respect to percent body fat and insulin sensitivity. Five of the 15 exposed participants, but none of the controls had impaired glucose tolerance (p=0·02). Early insulin secretion after an oral glucose tolerance test was lower in exposed participants than in controls: 8·6 IU/mmol (SD 5·4) in exposed participants with impaired glucose tolerance, 14·2 IU/mmol (6·5) in those with normal glucose tolerance and 17·7 IU/mmol (10·9) in controls (p=0·04). Mean insulin secretion rate during glucose infusion study was 4·7 pmol/kg per min (3·6) in people with impaired glucose tolerance, 5·5 pmol/kg per min (4·5) in exposed participants with normal glucose tolerance and 7·5 pmol/kg per min (6·1) in controls (p <0·0001). The area under the curve of pancreatic polypeptide 120 min after oral glucose ingestion was 1007 (429) in people with impaired glucose tolerance, 2829 (1701) in those with normal glucose tolerance, and 3224 (1352) in controls (p=0·04).

Exposure to a diabetic environment in utero is associated with increased occurence of impaired glucose tolerance and a defective insulin secretory response in adult offspring, independent of genetic predisposition to type 2 diabetes. This insulin secretory defect could be related to low parasympathetic tone. Epidemiological studies are needed to confirm our observations before therapeutic strategies can be devised.