Laser-Doppler flowmetry reveals rapid perfusion changes in adipose tissue of lean and obese females

Effects of exergaming on the microcirculation of adolescents with overweight or obesity-a clinical trial efficacy

To assess the effect of exergaming on the microcirculation function of adolescents with overweight or obesity, this non-randomized clinical trial efficacy was conducted with 61 adolescents aged between 10 and 16 years. The intervention group (n = 31) performed exergaming three times per week for 8 weeks. Both groups received guidelines for a healthy diet and staying physically active. Microcirculation was assessed using a laser Doppler flowmetry (LDF) at baseline and after intervention. Primary outcomes derived from LDF assessment included resting flow, maximum flow, maximum/resting flow ratio, area under hyperemia, and post-occlusive reactive hyperemia (PORH). Secondary outcomes were body mass index and systemic blood pressure. Unpaired Student's t test compared intergroup analyses, and paired Student's t test compared intragroup analyses. The significance was set at 5%. Statistical analysis intergroup and intragroup was done by fitting a two-way mixed effects model. Microcirculation was similar between groups. Maximum flow (109.0 ± 38.3 versus 124.6 ± 43.0, P = 0.022), area under hyperemia (1614 ± 472 versus. 1755 ± 461, P = 0.023), and PORH (2.18 ± 0.49 versus 2.01 ± 0.52, P = 0.031) were statistically different after intervention. Body mass index decreased in intervention (24.5 ± 3.8-24.1 ± 4.0 kg/m², P = 0.002) and control (25.2 ± 3.2-25.1 ± 3.3 kg/m², P = 0.031) groups. Systolic blood pressure decreased significantly in the intervention group (110 ± 10-106 ± 9 mm Hg; P = 0.041) but not diastolic blood pressure (66.0 ± 7-68.8 ± 8 mm Hg; P = 0.089). Exergaming for 8 weeks led to improvements in the microcirculation function in adolescents with overweighed or obesity. Clinical trials: NTC03532659.

Measurement of human abdominal and femoral intravascular adipose tissue blood flow using percutaneous Doppler ultrasound

Adipose tissue blood flow (ATBF) is an important determinant of adipose tissue (AT) function. ¹³³Xenon wash-out technique is considered the gold-standard for human ATBF measurements. However, decreasing ¹³³Xenon clinical use and costly production and preservation, make alternative (non-invasive) methods necessary. Here, we explored percutaneous Doppler ultrasound as a proxy method to quantify intravascular subcutaneous abdominal and femoral ATBF in humans (n= 17). Both fasting ATBF and the postprandial increase in ATBF were significantly higher in abdominal compared to femoral AT. Although anatomical variations in vein location and depot thickness may impact feasibility, we demonstrate that Doppler ultrasound detects the expected depot-differences and postprandial increase in ATBF in healthy individuals. This method warrants further investigation in other populations and metabolic conditions.

Effects of preadipocytes derived from mice fed with high fat diet on the angiogenic potential of endothelial cells

BACKGROUND AND AIMS

Obesity promotes a persistent inflammatory process in the adipose tissue, activating the endothelium and leading to vascular dysfunction. Preadipocytes can interact with endothelial cells in a paracrine way stimulating angiogenesis. However, the potential of preadipocytes from adipose tissue of high fat diet (HFD) fed animal to stimulate angiogenesis has not been evaluated yet. The aim of this study was to investigate the effects of such diet on the angiogenic potential of preadipocytes in a mice model.

METHODS AND RESULTS

We have evaluated body weight gain, fasting glucose levels and insulin resistance, mRNA expression in preadipocytes and endothelial cells after co-culture with preadipocytes, in vivo vascular function and in vitro endothelial cell migration and tubulogenesis. High fat diet promoted an increase in body weight, glycemic index and insulin resistance in mice. Preadipocytes mRNA expression of factors involved in angiogenesis was higher in these animals. In endothelial tEnd cells mRNA expression of factors involved in vessel growth were higher after co-culture with preadipocytes derived from mice fed with HFD. Although no significant differences were observed in in vivo vasodilatation response between control and HFD groups, endothelial tEnd cells showed an increase in migration and tubulogenesis when cultivated with conditioned media from preadipocytes derived from mice fed with HFD.

CONCLUSION

Hypoxic and growth factors produced by preadipocytes derived from mice fed with HFD have higher capacity than preadipocytes derived from mice fed with standard diet to stimulate the angiogenic potential of endothelial cells, contributing to vascular disorders in obesity.

Diffuse optical monitoring of peripheral tissues during uncontrolled internal hemorrhage in a porcine model

Reliable, continuous and noninvasive blood flow and hemoglobin monitoring in trauma patients remains a critical, but generally unachieved goal. Two optical sensing methods - diffuse correlation spectroscopy (DCS) and diffuse reflectance spectroscopy (DRS) - are used to monitor and detect internal hemorrhage. Specifically, we investigate if cutaneous perfusion measurements acquired using DCS and DRS in peripheral (thighs and ear-lobe) tissues could detect severe hemorrhagic shock in a porcine model. Four animals underwent high-grade hepato-portal injury in a closed abdomen, to induce uncontrolled hemorrhage and were subsequently allowed to bleed for 10 minutes before fluid resuscitation. DRS and DCS measurements of cutaneous blood flow were acquired using fiber optical probes placed on the thigh and earlobe of the animals and were obtained repeatedly starting from 1 to 5 minutes pre-injury, up to several minutes post shock. Clear changes were observed in measured optical spectra across all animals at both sites. DCS-derived cutaneous blood flow decreased sharply during hemorrhage, while DRS-derived vascular saturation and hemoglobin paralleled cardiac output. All derived optical parameters had the steepest changes during the rapid initial hemorrhage unambiguously. This suggests that a combined DCS and DRS based device might provide an easy-to-use, non-invasive, internal-hemorrhage detection system that can be used across a wide array of clinical settings.

Regulation of human subcutaneous adipose tissue blood flow

Subcutaneous adipose tissue represents about 85% of all body fat. Its major metabolic role is the regulated storage and mobilization of lipid energy. It stores lipid in the form of triacylglycerol (TG), which is mobilized, as required for use by other tissues, in the form of non-esterified fatty acids (NEFA). Neither TG nor NEFA are soluble to any extent in water, and their transport to and out of the tissue requires specialized transport mechanisms and adequate blood flow. Subcutaneous adipose tissue blood flow (ATBF) is therefore tightly linked to the tissue's metabolic functioning. ATBF is relatively high (in the fasting state, similar to that of resting skeletal muscle, when expressed per 100 g tissue) and changes markedly in different physiological states. Those most studied are after ingestion of a meal, when there is normally a marked rise in ATBF, and exercise, when ATBF also increases. Pharmacological studies have helped to define the physiological regulation of ATBF. Adrenergic influences predominate in most situations, but nevertheless the regulation of ATBF is complex and depends on the interplay of many different systems. ATBF is downregulated in obesity (when expressed per 100 g tissue), and its responsiveness to meal intake is reduced. However, there is little evidence that this leads to adipose tissue hypoxia in human obesity, and we suggest that, like the downregulation of catecholamine-stimulated lipolysis seen in obesity, the reduction in ATBF represents an adaptation to the increased fat mass. Most information on ATBF has been obtained from studying the subcutaneous abdominal fat depot, but more limited information on lower-body fat depots suggests some similarities, but also some differences: in particular, marked alpha-adrenergic tone, which can reduce the femoral ATBF response to adrenergic stimuli.

Subcutaneous adipose tissue metabolism and pharmacology: a new investigative technique

According to the Fick principle, any metabolic or hormonal exchange through a given tissue depends on the product of blood flow by arteriovenous difference. Because adipose tissue plays dual storage and endocrine roles, regulation of adipose tissue blood flow (ATBF) is of pivotal importance. Monitoring ATBF in humans can be achieved through different methodologies, such as the 133Xe washout technique, considered to be the “gold standard”, as well as microdialysis and other methods that are not well validated as of yet. This report describes a new method, called “adipose tissue microinfusion” or “ATM”, which simultaneously quantifies ATBF by combining the 133Xe washout technique together with variations of ATBF induced by local infusion of vasoactive agents. The most appropriate site for ATM investigation is the subcutaneous adipose tissue of the anterior abdominal wall. This innovative method conveniently enables the direct comparison of the effects on ATBF of any vasoactive compound, drug, or hormone against a contralateral saline control. The ATM method improves the accuracy and feasibility of physiological and pharmacological studies on the regulation of ATBF in vivo in humans.

Optical fiber probe spectroscopy for laparoscopic monitoring of tissue oxygenation during esophagectomies

Anastomotic complication is a major morbidity associated with esophagectomy. Gastric ischemia after conduit creation contributes to anastomotic complications, but a reliable method to assess oxygenation in the gastric conduit is lacking. We hypothesize that fiber optic spectroscopy can reliably assess conduit oxygenation, and that intraoperative gastric ischemia will correlate with the development of anastomotic complications. A simple optical fiber probe spectrometer is designed for nondestructive laparoscopic measurement of blood content and hemoglobin oxygen saturation in the stomach tissue microvasculature during human esophagectomies. In 22 patients, the probe measured the light transport in stomach tissue between two fibers spaced 3-mm apart (500- to 650-nm wavelength range). The stomach tissue site of measurement becomes the site of a gastroesophageal anastamosis following excision of the cancerous esophagus and surgical ligation of two of the three gastric arteries that provide blood perfusion to the anastamosis. Measurements are made at each of five steps throughout the surgery. The resting baseline saturation is 0.51±0.15 and decreases to 0.35±0.20 with ligation. Seven patients develop anastomotic complications, and a decreased saturation at either of the last two steps (completion of conduit and completion of anastamosis) is predictive of complication with a sensitivity of 0.71 when the specificity equaled 0.71.

Determination of body fat distribution by dual-energy X-ray absorptiometry and attenuation of visceral fat vasoconstriction by enalapril

Use of dual-energy X-ray absorptiometry (DEXA) data to calculate the percent of body fat in the visceral (%VF) and subcutaneous (%SF) compartments and the mechanism of visceral fat vasoconstriction when intestinal mucosal afferent nerves are stimulated has not been reported. The aim of this study was to compare visceral fat weight determined by DEXA and direct weighing and determine whether enalapril attenuates visceral fat vasoconstriction induced by stimulation of intestinal mucosal afferent nerves. We performed two studies. Study 1: In euthanized mice, DEXA scans were obtained before and after visceral fat dissection. The dissected fat weight was determined by DEXA (VF) and by direct weighing. Study 2: In anesthetized rat preparations, visceral (mesenteric) fat blood flow was monitored by laser Doppler flowmetry (LDF). After baseline, vehicle or 3 mg/kg enalapril (angiotensin-converting enzyme inhibitor) was administered intravenously, followed by 2 ml/kg of 640 microm capsaicin intraduodenally. In study 1, there was agreement between visceral fat weight determined by the DEXA (y) and direct weighing (x): y = 0.98x, r = 0.99, n = 10. In study 2, LDF signals showed an instantaneous decline when capsaicin was administered into the duodenal lumen. After enalapril treatment, the reductions were significantly attenuated compared with those after vehicle treatment. DEXA results combined with visceral fat dissection permit determination of body fat distribution. The instantaneous decline in visceral fat blood flow suggests that the reduction is a neural- rather than a hormone-mediated event, and attenuation by enalapril suggests angiotensin II plays a role.

Human adipose tissue blood flow and micromanipulation of human subcutaneous blood flow

Regulation of blood flow in tissues such as skeletal muscle, liver, and adipose tissue is needed to meet the changing local metabolic and physiological demands under varying conditions. In healthy individuals, adipose tissue blood flow (ATBF) is remarkably responsive to meal ingestion, but changes in ATBF in response to other physiological stimuli, such as stress and physical exercise, have also been noted. The ATBF response to nutrient intake may be of particular importance in the regulation of metabolism by facilitating transport of nutrients as well as signaling between adipose tissue and other metabolically active tissues. A reduction in both fasting and postprandial ATBF has been observed in obesity; this impairment is associated with insulin resistance. A better understanding of the physiological basis for (nutritional) regulation of ATBF may therefore give insight to the relationship between disturbances in ATBF and the metabolic disturbances observed in response to insulin resistance. In this chapter, we describe some different approaches to quantify human ATBF, with a particular emphasis on the 133xenon wash-out technique and a method by which regulatory properties of subcutaneous ATBF can be studied by pharmacological micromanipulation (microinfusion).