Differences in cortical and pituitary activity in response to hypoglycaemia and cognitive testing in healthy men with different basal activity of the renin-angiotensin system.
BACKGROUND
High renin-angiotensin system (RAS) activity has been associated with a high risk of severe hypoglycaemia in patients with type 1 diabetes and with cognitive deterioration during experimental hypoglycaemia in healthy subjects. The aim of this study was to describe possible differences in cerebral activity during hypoglycaemia and cognitive testing in two groups of healthy men with different basal RAS activity.


METHODS
Ten healthy men with high RAS activity and 10 with low activity underwent six oxygen-15-labelled water positron emission tomography scans: twice during normoglycaemia, twice during insulin-induced hypoglycaemia and twice during post-hypoglycaemia. During the scans, the subjects performed a computer-based reaction time test.


RESULTS
Occipital areas were consistently more activated in the low RAS group than in the high RAS group throughout all three conditions. During normoglycaemia, the frontal region was more activated in the low RAS group than in the high RAS group. During hypoglycaemia, the high RAS group was more activated in the pituitary gland than the low RAS group.


CONCLUSIONS
Basal RAS activity influenced cerebral activity. Low RAS was associated with more pronounced cortical activation in all glycaemic conditions. High RAS was associated with pituitary activation during hypoglycaemia and post-hypoglycaemia, and this was associated with a greater growth hormone response.
Bie-Olsen
Lise G
LG
Endocrinology Section, Department of Cardiology and Endocrinology, Hillerød Hospital, Hillerød, Denmark. ligri@noh.regionh.dk
Pedersen-Bjergaard
Ulrik
U
Kjaer
Troels W
TW
Lonsdale
Markus N
MN
Law
Ian
I
Thorsteinsson
Birger
B
D000328:Adult; D003071:Cognition / Q000502:physiology*; D003072:Cognition Disorders / Q000175:diagnosis; D006801:Humans; D007003:Hypoglycemia / Q000139:chemically induced / Q000523:psychology*; D007328:Insulin / Q000009:adverse effects; D008297:Male; D009778:Occipital Lobe / Q000502:physiology*; D010296:Parietal Lobe / Q000502:physiology; D010902:Pituitary Gland / Q000502:physiology*; D049268:Positron-Emission Tomography; D011930:Reaction Time; D012084:Renin-Angiotensin System / Q000502:physiology*
D007328:Insulin