A 6-month, randomized, double-masked, placebo-controlled study evaluating the effects of the protein kinase C-beta inhibitor ruboxistaurin on skin microvascular blood flow and other measures of diabetic peripheral neuropathy.
OBJECTIVE
Diabetes leads to protein kinase C (PKC)-beta overactivation and microvascular dysfunction, possibly resulting in disordered skin microvascular blood flow (SkBF) and other changes observed in diabetic peripheral neuropathy (DPN) patients. We investigate the effects of the isoform-selective PKC-beta inhibitor ruboxistaurin mesylate on neurovascular function and other measures of DPN.


METHODS
Endothelium-dependent and C fiber-mediated SkBF, sensory symptoms, neurological deficits, nerve fiber morphometry, quantitative sensory and autonomic function testing, nerve conduction studies, quality of life (using the Norfolk Quality-of-Life Questionnaire for Diabetic Neuropathy [QOL-DN]), and adverse events were evaluated for 20 placebo- and 20 ruboxistaurin-treated (32 mg/day) DPN patients (aged > or =18 years; with type 1 or type 2 diabetes and A1C < or =11%) during a randomized, double-masked, single-site, 6-month study.


RESULTS
Endothelium-dependent (+78.2%, P < 0.03) and C fiber-mediated (+56.4%, P < 0.03) SkBF at the distal calf increased from baseline to end point. Significant improvements from baseline within the ruboxistaurin group were also observed for the Neuropathy Total Symptom Score-6 (NTSS-6) (3 months -48.3%, P = 0.01; end point -66.0%, P < 0.0006) and the Norfolk QOL-DN symptom subscore and total score (end point -41.2%, P = 0.01, and -41.0, P = 0.04, respectively). Between-group differences in baseline-to-end point change were observed for NTSS-6 total score (placebo -13.1%; ruboxistaurin -66.0%, P < 0.03) and the Norfolk QOL-DN symptom subscore (placebo -4.0%; ruboxistaurin -41.2%, P = 0.041). No significant ruboxistaurin effects were demonstrated for the remaining efficacy measures. Adverse events were consistent with those observed in previous ruboxistaurin studies.


CONCLUSIONS
In this cohort of DPN patients, ruboxistaurin enhanced SkBF at the distal calf, reduced sensory symptoms (NTSS-6), improved measures of Norfolk QOL-DN, and was well tolerated.
Casellini
Carolina M
CM
Strelitz Diabetes Institutes, Eastern Virginia Medical School, Norfolk, Virginia, USA.
Barlow
Patricia M
PM
Rice
Amanda L
AL
Casey
Melissa
M
Simmons
Kathryn
K
Pittenger
Gary
G
Bastyr
Edward J
EJ
Wolka
Anne M
AM
Vinik
Aaron I
AI
D000368:Aged; D001783:Blood Flow Velocity; D003922:Diabetes Mellitus, Type 1 / Q000150:complications; D003924:Diabetes Mellitus, Type 2 / Q000150:complications; D003929:Diabetic Neuropathies / Q000175:diagnosis / Q000188:drug therapy*; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007211:Indoles / Q000627:therapeutic use*; D008297:Male; D008301:Maleimides / Q000627:therapeutic use*; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology*; D008875:Middle Aged; D010919:Placebos; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D064546:Protein Kinase C beta; D044469:Racial Groups; D012039:Regional Blood Flow / Q000187:drug effects*; D012867:Skin / Q000098:blood supply*
D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D010919:Placebos; C099154:ruboxistaurin; D011493:Protein Kinase C; D064546:Protein Kinase C beta