It is that the bene®t of conventional
antihypertensive treatment with betablockers
will be offset amongst diabetic patients, because
some negative effects on metabolic parameters such
as insulin sensitivity and blood glucose have been
reported for these agents in some studies.moreover,
betablocking agents are often
referred to as less nephroprotective when compared
with other antihypertensive agents like ACEI. In
addition, there is still a fear of an increased risk of
severe hypoglycaemia in diabetic patients treated
with betablockers.

source:http://www.blackwell-synergy.com/doi/pdf/10.1046/j.1365-2796.2001.00829.x?cookieSet=1