White adipose tissue is not just a storage organ. It is now recognised as an endocrine organ. It secretes many substances known as adipokines, which are thought to link obesity with type 2 diabetes (T2D). One of the most important adipokines is adiponectin. It is a peptide hormone consisting of 244 amino acids with molecular weight of 30 KD. It circulates in plasma in high concentrations (3-30 4g/ml). Adiponectin polymerises to form many bigger forms. Those are low molecular weight (LMW); middle molecular weight (MMW) and high molecular weight (HMW). The HMW adiponectin is the active form 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 metabolic disorders. Its concentrations decrease in cardiovascular diseases, diabetes, dyslipidemia and insulin resistances. It is well known that exercise increases insulin sensitivity, also adiponectin was reported to regulate insulin. The effect of exercise on the adiponectin concentrations in plasma is controversial, but the extent to which the exercise regulates the interstitial adiponectin concentrations is not fully examined. The main site of adipokines secretion is adipose tissue. Therefore the study of these substances at the site of their production has a special interest. Recently, microdialysis techniques have been extended to become important in the measurement of substances in the extracellular fluid of many tissues such as subcutaneous adipose tissue. In particular, it has been used for measurement of adipokines. This thesis includes three studies. The first study was aimed at examining the effect of one hour of moderate exercise at 50% of maximum oxygen consumption v on adiponectin concentration in dialysate samples taken from subcutaneous abdominal adipose tissues (SCAAT). 15 healthy young female volunteers, age 22.8 ± 3.0 years (mean ± SD) participated in this experiment divided into two groups depending on their body mass index (BMI), a lean group 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 66 M. Alzwayi iii microdialysis catheters with membrane cut off 100 KD. Fitness assessment was done for all volunteers about one week before the main trials. The main trials 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 catheter were inserted in abdominal subcutaneous tissue 4 cm lateral to the umbilicus on the left side. Dialysate samples were collected every 30 - 45 minutes. On the exercise day volunteers exercised for one hour at 50% 2 . V O max. All samples were analysed for adiponectin concentrations using Mercodia ELISA technique. The principle findings of this study were that CMA 66 microdialysis catheters worked effectively for two consecutive days for fluid recovery. Adiponectin concentrations were very low and varied, in same volunteer from time to time, and between volunteers. However, the statistical analysis showed no significant difference in adiponectin concentrations between lean and overweight groups. Adiponectin concentrations in the first two samples on the first day of the insertion were significantly higher than the first two samples on the second day of the insertion. Finally, adiponectin concentrations in dialysate samples recovered by 100 KD microdialysis catheters were very low. Therefore, the effect of the exercise was not clear. The second study aimed to compare the adiponectin concentrations in plasma and dialysate samples. Six healthy male volunteers age 32.8 ± 13.1 years and BMI 25.9 ± 3.3 kg/m2 (mean ± SD), were recruited for this study. The experiment was run for two consecutive days using the same microdialysis catheters CMA 66. Dialysate samples were collected as before. 2 ml of blood samples were collected using a cannula inserted into the anticubital vein. Samples were taken every hour for a period of five hours each day. The plasma and dialysate samples were analysed for adiponectin using the Mercodia kits. Adiponectin concentrations in plasma samples were 256 and 1791 times higher than the adiponectin concentrations in dialysate samples. The conclusion of the two studies was that the CMA 66 microdialysis catheter with cut off 100 KD membranes only recovers a small part of the total adiponectin present. M. Alzwayi iv Therefore a third study was designed to use plasma samples. The aim of the study was to investigate the effect of acute exercise at 50% 2 . V O max on HMW adiponectin, total adiponectin, interleukin (IL)-6, tumour necrosis factor alpha (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. The volunteers were invited for five visits. Their fitness was measured on the first visit. Then they came for two main trials rest day and exercise day, which they were randomly assigned. The main trails lasted for two hours. Three blood samples were collected each day using same cannulated system in the second study. The volunteers followed 48 hours after each trial, one blood sample were collected each day. The 8 plasma samples were analysed for: total adiponectin and insulin concentrations via Mercodia ELISA kits, HMW adiponectin, IL-6 and TNF-α concentration via R&D systems and glucose concentration 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 at 50% 2 . V O max either directly or 48 (p value > 0.05). IL-6 concentrations increased 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 with repeated measures returned a P value of > 0.05. In conclusion, the acute exercise at 50% 2 . V O max changes IL-6 concentrations but it has no effect on adiponectin concentrations in dialysate or plasma samples. Low adiponectin concentration is related to obesity, insulin resistance and T2D. Therefore, increase in adiponectin concentration probably lies in weight loss and the exercise may play role, even if it has little direct action on adiponectin concentration.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:578594 |
| Date | January 2013 |
| Creators | Alzwayi, Mabroukah M. A. |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/4552/ |
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