title: Perivascular fatty tissue at the brachial artery is linked to insulin resistance but not to local endothelial dysfunction.
abstract: OBJECTIVE
  Different ectopic fat depots, such as visceral or hepatic fat, are known to affect whole body insulin sensitivity. It has recently been hypothesised that differences in perivascular adipose tissue (PVAT) mass around resistance vessels may also contribute to insulin resistance, possibly via direct vascular effects leading to reduced capillary cross-sectional area in the muscle, which in turn affects muscular blood flow and glucose uptake. Based on this, the aim of the present study was to test whether PVAT around conduit arteries (i.e. the brachial artery) influences NO bioavailability, expressed as flow-mediated dilation (FMD), or insulin sensitivity in humans in vivo.
  
  
  METHODS
  Insulin sensitivity was measured by OGTT in all 95 participants (59 women, 36 men; median age 47 years, range 19-66 years) and by the gold standard, a euglycaemic-hyperinsulinaemic clamp, in a randomly selected subgroup of 33 participants. Quantification of the different fat compartments, including PVAT around the brachial artery, was achieved by high-resolution magnetic resonance imaging (1.5 T). Blood flow and FMD were measured at the brachial artery using high-resolution (13 MHz) ultrasound, after 5 min of forearm occlusion.
  
  
  RESULTS
  PVAT was negatively correlated with insulin sensitivity and the post-ischaemic increase in blood flow. The association between PVAT and insulin sensitivity (r = -0.54, beta = -0.37, p = 0.009) was independent of age, sex, visceral adipose tissue, liver fat, BMI and further cardiovascular risk factors. No correlation could be detected between PVAT and local endothelial function. However, we observed an independent association between PVAT and post-ischaemic increase in blood flow (r = -0.241; beta = -1.69; p = 0.02).
  
  
  CONCLUSIONS
  PVAT seems to play an independent role in the pathogenesis of insulin resistance. This may be due to direct vascular effects influencing muscular blood flow.
authors: Department of Endocrinology, University of Tübingen, Otfried-Müller Strasse 10, 72076, Tübingen, Germany.
authors: K
authors: K
authors: Rittig
authors: K
authors: K
authors: Staib
authors: J
authors: J
authors: Machann
authors: M
authors: M
authors: Böttcher
authors: A
authors: A
authors: Peter
authors: F
authors: F
authors: Schick
authors: C
authors: C
authors: Claussen
authors: N
authors: N
authors: Stefan
authors: A
authors: A
authors: Fritsche
authors: H-U
authors: HU
authors: Häring
authors: B
authors: B
authors: Balletshofer
mesh_terms: D000273:Adipose Tissue / Q000502:physiology* / Q000503:physiopathology; D000328:Adult; D000368:Aged; D001132:Arm; D001783:Blood Flow Velocity; D001786:Blood Glucose / Q000378:metabolism; D001916:Brachial Artery / Q000033:anatomy & histology / Q000502:physiology / Q000503:physiopathology*; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology; D005260:Female; D015309:Glucose Clamp Technique; D005951:Glucose Tolerance Test; D006801:Humans; D006946:Hyperinsulinism / Q000503:physiopathology*; D007511:Ischemia / Q000503:physiopathology; D008099:Liver / Q000033:anatomy & histology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D014664:Vasodilation
chemical_list: D001786:Blood Glucose