Impact of type 2 diabetes mellitus on sympathetic neural mechanisms in hypertension.
BACKGROUND
Essential hypertension (EHT) is a major cardiovascular risk factor, and the additional presence of type 2 diabetes mellitus (DM2) increases this risk. However, although the sympathetic nerve hyperactivity of EHT is known to play a role in cardiovascular risk, the level of sympathetic nerve activity is known neither in DM2 nor in hypertensive type 2 diabetic patients (EHT+DM2). Therefore, we planned to quantify the vasoconstrictor sympathetic nerve activity in patients with EHT+DM2 and with DM2 relative to that in matched groups with EHT and normal blood pressure (NT).


RESULTS
In 68 closely matched subjects with EHT+DM2 (n=17), DM2 (n=17), EHT (n=17), and NT (n=17), we measured resting muscle sympathetic nerve activity as the mean frequency of multiunit bursts (MSNA) and of single units (s-MSNA) with defined vasoconstrictor properties. The s-MSNA in EHT+DM2 (97+/-3.8 impulses/100 beats) was greater (at least P<0.001) than in EHT (69+/-3.4 impulses/100 beats) and DM2 (78+/-4.1 impulses/100 beats), and all these were significantly greater (at least P<0.01) than in NT (53+/-3.3 impulses/100 beats) despite similar age and body mass index. The MSNA followed a similar trend. In addition, the level of insulin was also raised in EHT+DM2 (20.4+/-3.6 microU/mL) and DM2 (18.1+/-3.1 microU/mL; at least P<0.05) compared with HT or NT.


CONCLUSIONS
Patients with EHT+DM2, EHT, or DM2 had central sympathetic hyperactivity, although plasma insulin levels were raised only in EHT+DM2 and DM2. The combination of EHT and DM2 resulted in the greatest sympathetic hyperactivity and level of plasma insulin, and this hyperactivity could constitute a mechanism for the increased risks of this condition.
Huggett
Robert J
RJ
Department of Cardiology, St James's University Hospital, Beckett St, Leeds LS9 7TF, United Kingdom. roberthuggett@hotmail.com
Scott
Eleanor M
EM
Gilbey
Stephen G
SG
Stoker
John B
JB
Mackintosh
Alan F
AF
Mary
David A S G
DA
D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009132:Muscles / Q000294:innervation; D013564:Sympathetic Nervous System / Q000503:physiopathology*