White adipose tissue is not just a storage organ. It is now recognised as anendocrine organ. It secretes many substances known as adipokines, which arethought to link obesity with type 2 diabetes (T2D). One of the most importantadipokines is adiponectin. It is a peptide hormone consisting of 244 aminoacids with molecular weight of 30 KD. It circulates in plasma in highconcentrations (3-30 4g/ml). Adiponectin polymerises to form many biggerforms. Those are low molecular weight (LMW); middle molecular weight(MMW) and high molecular weight (HMW). The HMW adiponectin is the activeform of the hormone.The concentrations of most adipokines are increased in obese people.Adiponectin is unusual in that its concentration is lower in obese people.Consequently its concentration is decreased in some related metabolicdisorders. Its concentrations decrease in cardiovascular diseases, diabetes,dyslipidemia and insulin resistances. It is well known that exercise increasesinsulin sensitivity, also adiponectin was reported to regulate insulin. Theeffect of exercise on the adiponectin concentrations in plasma iscontroversial, but the extent to which the exercise regulates the interstitialadiponectin concentrations is not fully examined. The main site of adipokinessecretion is adipose tissue. Therefore the study of these substances at thesite of their production has a special interest. Recently, microdialysistechniques have been extended to become important in the measurement ofsubstances in the extracellular fluid of many tissues such as subcutaneousadipose tissue. In particular, it has been used for measurement of adipokines.This thesis includes three studies. The first study was aimed at examining theeffect of one hour of moderate exercise at 50% of maximum oxygenconsumption v on adiponectin concentration in dialysate samples taken fromsubcutaneous abdominal adipose tissues (SCAAT). 15 healthy young femalevolunteers, age 22.8 ± 3.0 years (mean ± SD) participated in this experimentdivided into two groups depending on their body mass index (BMI), a leangroup BMI 22.2 ± 1.6 kg/m2 (mean ± SD) and an overweight group BMI 27.7 ±1.9 kg/m2 (mean ± SD). The samples were collected using CMA 66M. Alzwayi iiimicrodialysis catheters with membrane cut off 100 KD. Fitness assessmentwas done for all volunteers about one week before the main trials. The maintrials were done on two consecutive days, a rest day and an exercise day.Each day lasted for 4 to 6 hours. On the first day the microdialysis catheterwere inserted in abdominal subcutaneous tissue 4 cm lateral to the umbilicuson the left side. Dialysate samples were collected every 30 - 45 minutes. Onthe exercise day volunteers exercised for one hour at 50% 2.V O max. Allsamples were analysed for adiponectin concentrations using Mercodia ELISAtechnique.The principle findings of this study were that CMA 66 microdialysis cathetersworked effectively for two consecutive days for fluid recovery. Adiponectinconcentrations were very low and varied, in same volunteer from time totime, and between volunteers. However, the statistical analysis showed nosignificant difference in adiponectin concentrations between lean andoverweight groups. Adiponectin concentrations in the first two samples onthe first day of the insertion were significantly higher than the first twosamples on the second day of the insertion. Finally, adiponectinconcentrations in dialysate samples recovered by 100 KD microdialysiscatheters were very low. Therefore, the effect of the exercise was not clear.The second study aimed to compare the adiponectin concentrations in plasmaand dialysate samples. Six healthy male volunteers age 32.8 ± 13.1 years andBMI 25.9 ± 3.3 kg/m2 (mean ± SD), were recruited for this study. Theexperiment was run for two consecutive days using the same microdialysiscatheters CMA 66. Dialysate samples were collected as before. 2 ml of bloodsamples were collected using a cannula inserted into the anticubital vein.Samples were taken every hour for a period of five hours each day. Theplasma and dialysate samples were analysed for adiponectin using theMercodia kits. Adiponectin concentrations in plasma samples were 256 and1791 times higher than the adiponectin concentrations in dialysate samples.The conclusion of the two studies was that the CMA 66 microdialysis catheterwith cut off 100 KD membranes only recovers a small part of the totaladiponectin present.M. Alzwayi ivTherefore a third study was designed to use plasma samples. The aim of thestudy was to investigate the effect of acute exercise at 50% 2.V O max on HMWadiponectin, total adiponectin, interleukin (IL)-6, tumour necrosis factoralpha (TNF-α), insulin and glucose concentrations directly after the exercise,one hour after and 48 hours. 13 young healthy female volunteers age 24.3 ±2.7 years and BMI 21.9 ± 2.2 kg/m2 (mean ± SD) contributed in this study. Thevolunteers were invited for five visits. Their fitness was measured on the firstvisit. Then they came for two main trials rest day and exercise day, whichthey were randomly assigned. The main trails lasted for two hours. Threeblood samples were collected each day using same cannulated system in thesecond study. The volunteers followed 48 hours after each trial, one bloodsample were collected each day. The 8 plasma samples were analysed for:total adiponectin and insulin concentrations via Mercodia ELISA kits, HMWadiponectin, IL-6 and TNF-α concentration via R&D systems and glucoseconcentration using the glucose oxidase colorimetric method.The results showed no statistical difference in total or HMW adiponectin,TNF-α and glucose concentrations under the effect of moderate exercise at50% 2.V O max either directly or 48 (p value > 0.05). IL-6 concentrationsincreased about two fold one hour after the exercise above the resting level(P value < 0.05). IL-6 concentrations return to the basal level 48 hour latter.Insulin concentrations show a decrease one hour after the exercise finished.The number of volunteers was small and the change was close to significance.A one way ANOVA returned a P value of < 0.05, but a two way ANOVA withrepeated measures returned a P value of > 0.05.In conclusion, the acute exercise at 50% 2.V O max changes IL-6 concentrationsbut it has no effect on adiponectin concentrations in dialysate or plasmasamples. Low adiponectin concentration is related to obesity, insulinresistance and T2D. Therefore, increase in adiponectin concentrationprobably lies in weight loss and the exercise may play role, even if it haslittle direct action on adiponectin concentration.
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An investigation of the effect of short bouts ofexercise on adiponectin concentrations in young healthy females
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