A novel insulin mimetic without a proliferative effect on vascular smooth muscle cells.
BACKGROUND
Insulin induces vascular smooth muscle cell (VSMC) proliferation, which is an important step in the atherosclerotic process. Recently, a nonpeptidyl fungal metabolite originally referred to as L-783,281, but also known as demethylasterriquinone B-1 (DMAQB-1), was found to have hypoglycemic activity in diabetic mice through interaction with the intracellular beta subunit of the insulin receptor. This study was designed to determine whether DMAQB-1 has an insulin-like proliferative effect on human infragenicular VSMCs.


METHODS
Human infragenicular VSMCs were isolated from diabetic patients undergoing amputations. DMAQB-1 cell culture dose response was measured in both serum-free media and media with 1% fetal bovine serum (FBS). A working concentration of DMAQB-1 that ranged from 0.5 to 500 nmol/L was studied in the presence of varying concentrations of glucose and insulin. The ability of DMAQB-1 to stimulate glucose transport at less than or equal to 100 nmol/L was determined by [(14)C]-2-deoxyglucose uptake. DNA synthesis was used as the marker for proliferative stimulus and detected by [(3)H]-thymidine uptake measured at 24 hours. Analysis of variance was used to compare the results among the groups; a P value less than.05 was considered significant. Polynomial regression was used to calculate the median lethal dose.


RESULTS
In normal glucose media (100 mg/dL), various concentrations of DMAQB-1 demonstrated a small but statistically significant decrease in DNA synthesis at 0.5 nmol/L in serum-free media and at 5 nmol/L in media supplemented with 1% FBS. The corresponding median lethal dose was 107 nmol/L in serum-free media and 650 nmol/L in media supplemented with 1% FBS. A DMAQB-1 concentration of 5 nmol/L induced glucose transport that was equivalent to an insulin concentration of 100 microU/mL. In serum-free, high glucose media (200 mg/dL), DMAQB-1 concentrations up to 500 nmol/L did not cause a statistically significant change in DNA synthesis. When serum-free, high glucose media was combined with mild (100 microU/mL) or moderate (250 microU/mL) concentrations of insulin, DMAQB-1 caused no statistically significant increase in DNA synthesis.


CONCLUSIONS
Nontoxic doses of DMAQB-1 can induce glucose transport equivalent to insulin in the physiologic range. However, DMAQB-1 does not have an insulin-like proliferative effect on human VSMCs in normal-glucose, high-glucose, or high-insulin environments.
Weber
M A
MA
Department of Surgery, Veterans Affairs Medical Center, George Washington University Medical Center, DC, USA.
Lidor
A
A
Arora
S
S
Salituro
G M
GM
Zhang
B B
BB
Sidawy
A N
AN
D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D003470:Culture Media; D004247:DNA / Q000096:biosynthesis; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D007150:Immunohistochemistry; D007211:Indoles / Q000008:administration & dosage / Q000494:pharmacology*; D007328:Insulin / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D012044:Regression Analysis; D013566:Sympathomimetics; D013997:Time Factors
D003470:Culture Media; D007004:Hypoglycemic Agents; D007211:Indoles; D007328:Insulin; C119066:L 783281; D013566:Sympathomimetics; D004247:DNA; D005947:Glucose