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Chronic lymphoedema is a disease caused by a congenital or acquired damage to the lymphatic system and characterized by complex chains of pathophysiologic events such as lymphatic fluid stasis, chronic inflammation, lymphatic vessels impairment, adipose tissue deposition and fibrosis. These events seem to maintain and reinforce themselves through a positive feedback loop: regardless of the initial cause of lymphatic stasis, the dysfunctional adipose tissue and its secretion products can worsen lymphatic vessels' function, aggravating lymph leakage and stagnation, which can promote further adipose tissue deposition and fibrosis, similar to what may happen in obesity. In addition to the current knowledge about the tight and ancestral interrelation between immunity system and metabolism, there is evidence for similarities between obesity-related and lymphatic damage-induced lymphoedema. Together, these observations indicate strong reciprocal relationship between lymphatics and adipose tissue and suggest a possible key role of the adipocyte in the pathophysiology of chronic lymphoedema's vicious circle.

BACKGROUND: Glucose-dependent insulinotropic polypeptide (GIP) appears to have impaired effect on subcutaneous abdominal adipose tissue metabolism in obese subjects. The aim of the present study was to examine whether weight loss may reverse the impaired effect of GIP on subcutaneous abdominal adipose tissue in obese subjects.METHODS: Five obese males participated in a 12-week weight loss program, which consisted of caloric restriction (800 Cal day(-)(1)) followed by 4 weeks of weight-maintenance diet. Before and after weight loss, subcutaneous adipose tissue lipid metabolism was studied by conducting regional measurements of arterio-venous plasma concentrations of metabolites and blood flow (adipose tissue blood flow, ATBF) across a segment of the abdominal adipose tissue in the fasting state and during GIP infusion (1.5 pmol kg(-)(1 )min(-)(1)) in combination with a hyperinsulinemic-hyperglycemic clamp.RESULTS: After weight loss (7.5±0.8 kg), glucose tolerance and insulin sensitivity increased significantly as expected. No significant differences were seen in basal ATBF before (1.3±0.4 ml min(-1) 100 g tissue(-1)) and after weight loss (2.1±0.4 ml min(-1) 100 g tissue)(-1); however, a tendency to increase was seen. After weight loss, GIP infusion increased ATBF significantly (3.2±0.1 ml min(-1) 100 g tissue(-1)) whereas there was no increase before weight loss. Triacylglycerol (TAG) uptake did not change after weight loss. Baseline free fatty acid (FFA) and glycerol output increased significantly after weight loss, P<0.001. During the clamp period, FFA and glycerol output declined significantly, P<0.05, with no differences before and after weight loss. Weight loss increased glucose uptake and decreased FFA/glycerol ratio during the clamp period, P<0.05.CONCLUSIONS: In obese subjects, weight loss, induced by calorie restriction, improves the blunted effect of GIP on subcutaneous abdominal adipose tissue metabolism.

The aim of this study was to investigate subcutaneous adipose tissue lymphatic drainage (ATLD) of macromolecules in lean and obese subjects and, furthermore, to evaluate whether ATLD may change in parallel with adipose tissue blood flow. Lean and obese male subjects were studied before and after an oral glucose load. Adipose-tissue blood flow was measured in the anterior subcutaneous abdominal adipose tissue by the (133)Xe-washout technique. ATLD was measured as the disappearance rate of (99m)Tc-labelled nanoaggregated human albumin, during fasting and after an oral glucose load. A significant increase in ATLD was seen after the glucose load in the lean subjects. In the obese subjects, ATLD remained constant throughout the study and was significantly lower compared to the lean subjects. These results indicate a reduced ability to remove macromolecules from the interstitial space through the lymphatic system in obese subjects. Furthermore, they suggest that postprandial changes in ATLD taking place in lean subjects are not observed in obese subjects. This may have a role in the development of obesity-related inflammation in hypertrophic adipose tissue.International Journal of Obesity advance online publication, 3 July 2012; doi:10.1038/ijo.2012.98.

The adipose tissue metabolism is dependent on its blood perfusion. During lipid mobilization e.g. during exercise and during lipid deposition e.g. postprandial, adipose tissue blood flow is increased. This increase in blood flow may involve capillary recruitment in the tissue. We investigated the basic and postprandial microvascular volume in adipose tissue using real-time contrast-enhanced ultrasound (CEU) imaging in healthy normal weight subjects. In nine subjects, CEU was performed in abdominal subcutaneous adipose tissue and in the underlying skeletal muscle after a bolus injection of ultrasound contrast agent to establish the reproducibility of the technique. In nine subjects, the effect of an oral glucose load on blood flow and microvascular volume was measured in abdominal subcutaneous adipose tissue and forearm skeletal muscle. ¹³³Xe washout and venous occlusion strain-gauge plethysmography was used to measure the adipose tissue and forearm blood flow, respectively. Ultrasound signal intensity of the first plateau phases was 27 ± dB in the abdominal subcutaneous adipose tissue and 18 ± 2 dB (P <0.05) in the underlying skeletal muscle. The reproducibility of the measurements was good with a 4% coefficient of variation in both tissues. Blood flow and the change in signal intensity as a measure of the microvascular volume increased significantly and simultaneously in abdominal subcutaneous adipose tissue after glucose intake. The forearm blood flow and muscle signal intensity remained constant. It is concluded that the microvascular volume and changes in volume in abdominal subcutaneous adipose tissue can be assessed using CEU with good reproducibility. Postprandial capillary recruitment takes place in abdominal subcutaneous adipose tissue.

GH administration results in increased lean body mass (LBM), decreased fat mass (FM) and increased energy expenditure (EE). GH therapy may therefore have potential benefits, especially in the elderly, who are known to have decreased function of the GH/IGF-I axis. Several studies have focused on effects of GH administration in the elderly in the last decade. However, very limited information is available regarding changes in body composition and EE upon GH discontinuation in the elderly. The present study therefore investigated the effects of 12 weeks of GH administration and subsequent discontinuation on body composition, resting oxygen uptake (VO2), resting heart rate (HR) and GH related serum markers in healthy elderly men.

In the present study, the effect of endurance training alone and endurance training combined with recombinant human growth hormone (rhGH) administration on subcutaneous abdominal adipose tissue lipolysis was investigated. Sixteen healthy women [age 75 +/- 2 yr (mean +/- SE)] underwent a 12-wk endurance training program on a cycle ergometer. rhGH was administered in a randomized, double-blinded, placebo-controlled design in addition to the training program. Subcutaneous abdominal adipose tissue lipolysis was estimated by means of microdialysis combined with measurements of subcutaneous abdominal adipose tissue blood flow (ATBF; (133)Xe washout). Whole body fat oxidation was estimated simultaneously by indirect calorimetry. Before and after completion of the training program, measurements were performed both at rest and during 60 min of continuous cycling at a workload corresponding to 60% of pretraining peak oxygen uptake. Endurance training alone did not affect subcutaneous abdominal adipose tissue lipolysis either at rest or during exercise, as reflected by identical levels of interstitial adipose tissue glycerol, subcutaneous abdominal ATBF, and plasma nonesterified fatty acids before and after completion of the training program. Similarly, no effect on subcutaneous abdominal adipose tissue lipolysis was observed when combining endurance training with rhGH administration. However, in both the placebo and the GH groups, fat oxidation was significantly increased during exercise performed at the same absolute workload after completion of the training program. We conclude that the changed lipid metabolism during exercise observed after endurance training alone or after endurance training combined with rhGH administration is not due to alterations in subcutaneous abdominal adipose tissue metabolism in elderly women.