A new method to study changes in microvascular blood volume in muscle and adipose tissue: real-time imaging in humans and rat

Abstract

We employed and evaluated a new application of contrast-enhanced ultrasound for real-time imaging of changes in microvascular blood volume (MBV) in tissues in females, males, and rat. Continuous real-time imaging was performed using contrast-enhanced ultrasound to quantify infused gas-filled microbubbles in the microcirculation. It was necessary to infuse microbubbles for a minimum of 5-7 min to obtain steady-state bubble concentration, a prerequisite for making comparisons between different physiological states. Insulin clamped at a submaximal concentration (∼75 μU/ml) increased MBV by 27 and 39% in females and males, respectively, and by 30% in female subcutaneous adipose tissue. There was no difference in the ability of insulin to increase muscle MBV in females and males, and microvascular perfusion rate was not increased significantly by insulin. However, perfusion rate of the microvascular space was higher in females compared with males. In rats, insulin clamped at a maximal concentration increased muscle MBV by 60%. Large increases in microvascular volume and perfusion rate were detected during electrical stimulation of muscle in rats and immediately after exercise in humans. We have demonstrated that real-time imaging of changes in MBV is possible in human and rat muscle and in subcutaneous adipose tissue and that the method is sensitive enough to pick up relatively small changes in MBV when performed with due consideration of steady-state microbubble concentration. Because of real-time imaging, the method has wide applications for determining MBV in different organs during various physiological or pathophysiological conditions.

Acute cocoa flavanol supplementation improves muscle macro- and microvascular but not anabolic responses to amino acids in older men

“…In agreement with our previous work and the work of Sjoberg et al, we found that with an infusion of 1.2ml·min -1 of Definity microbubbles a plateau signal was achieved at approximately 6 min Sjøberg et al 2011). Based on this an infusion time of 9 min was used before the measurements of MBV were obtained.…”

“…Here we have again shown that age-related decrements in LBF are associated with impairments in muscle MBV responses to feeding, findings that are consistent with reports of decrements in fed-state forearm MBF (inferred from indirect measurements) (Skilton et al 2005) and also the absence of increased muscle MBF in older people fed EAA and sucrose (Timmerman et al 2012). Whereas it is well established that acute bouts of exercise enhance microvascular perfusion in both human (Vincent et al 2006) and rodent muscle (Sjøberg et al 2011), the effects of an acute neutraceutical intervention (in this case cocoa flavanols) on muscle MBF in response to nutrition, have until now remained poorly defined. Here, we have shown that 350 mg cocoa flavanols improved nutrient-dependent increases in both LBF and muscle MBF in older men.…”

“…At 110 min (BASAL) and 240 min (110 min after the start of nutrition (FED)), measurements of MBV in the m. vastus lateralis were made using contrast enhanced ultrasound (CEUS), as previously described (Sjøberg et al 2011). In brief, a linear array transducer (L9-3 MHz;…”

A vascular mechanism for high-sodium-induced insulin resistance in rats

“…Importantly, this microvascular action is independent of the ability of insulin to increase net muscle flow [12], can occur as early as 15 min following insulin infusion [19] and is partly NO-dependent [16]. It should also be noted that insulin regulates blood flow to other tissues in the body, including the heart [38], skin [39], kidney [40] and adipose [41]; however, compared with skeletal muscle these tissues contribute significantly less to postprandial glucose disposal.…”

Cellular, molecular and physiological effects of post-resistance exercise cold water immersion: Implications for subsequent perofrmance

“…Contrast-enhanced ultrasound is an adapted method displaying promise for quantifying cutaneous microvascular blood flow (Sjoberg et al, 2011). To date however, this method has not been utilised following cold water immersion, having only been adopted following ice application (Selkow et al, 2012).…”