Insulin resistance is associated with lower acetylcholine-induced microvascular reactivity in nondiabetic women.
BACKGROUND
The association between insulin resistance and microvascular dysfunction is well established in obese individuals with type 2 diabetes. It is unclear whether this relationship is dependent on obesity and body fat in insulin-resistant persons. This study investigated acetylcholine (ACh)-induced microvascular reactivity in apparently healthy women (n=37, 20-45 years), with and without insulin resistance.


METHODS
Body fat mass (dual X-ray absorptiometry), waist circumference (WC), blood pressure, fasting glucose, insulin, and free fatty acid concentrations were measured. Insulin resistance was estimated using homeostasis model assessment of insulin resistance (HOMA-IR), and subjects were divided into insulin-resistant (IR, n=16) and insulin-sensitive (IS, n=21) groups. ACh-induced forearm microvascular reactivity was measured by laser Doppler imagery using iontophoresis of ACh and compared between groups adjusting for WC and skin resistance (SR).


RESULTS
The IR group had a higher body mass index (BMI) (30.7 ± 6.4 vs. 22.9 ± 7.3 kg/m(2), P < 0.01), fat mass (34.7 ± 11.9 vs. 19.7 ± 9.6 kg, P < 0.01), WC (89.9 ± 13.6 vs. 74.4 ± 9.7 cm, P < 0.01), and a lower SR (0.24 ± 0.08 vs. 0.32 ± 0.08 Ω, P < 0.05) than the IS group. Microvascular reactivity, expressed as percentage increase in perfusion from baseline, was significantly lower in IR subjects after adjusting for differences in WC and SR (420.9 ± 166.5 vs. 511.6 ± 214.8%, P < 0.05). There were associations between microvascular reactivity and SR (r=-0.34, P < 0.05) and systolic blood pressure (r=-0.36, P < 0.05), but not BMI, body fat mass, WC, or HOMA-IR.


CONCLUSIONS
ACh-induced microvascular reactivity was different between IR and IS apparently healthy, nondiabetic women once differences in WC and SR were accounted for.
1 UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, Faculty of Health Sciences, University of Cape Town , Cape Town, South Africa .
Paula R
PR
Pienaar
Lisa K
LK
Micklesfield
Naomi S
NS
Levitt
Kim
K
Gooding
Angela C
AC
Shore
Julia H
JH
Goedecke
Jason M R
JM
Gill
Estelle V
EV
Lambert
D000109:Acetylcholine / Q000008:administration & dosage / Q000494:pharmacology*; D000293:Adolescent; D000328:Adult; D050218:Body Fat Distribution; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology; D004730:Endothelium, Vascular / Q000502:physiology; D005260:Female; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D007478:Iontophoresis; D008833:Microcirculation / Q000187:drug effects*; D011795:Surveys and Questionnaires; D014665:Vasodilator Agents / Q000494:pharmacology*; D055105:Waist Circumference; D055815:Young Adult
D014665:Vasodilator Agents; D000109:Acetylcholine