Metabolic syndrome is characterised by insulin resistance and is a risk factor for type 2 diabetes. The exact cause of metabolic syndrome is unknown, but research suggests that a low quality diet high in refined carbohydrates and added sugars is a probably contributory factor. One of the physiological changes that is associated with the metabolic syndrome is an increase in abdominal adiposity. As adiposity progresses, inflammation and oxidative stress occur and cytokine production from adipocytes is modified. These findings have altered the perception of adipose tissue from that of a storage organ for triglycerides to a metabolically active endocrine organ that can has considerable influence of the milieu of the body. One of the cytokines released from adipocytes is adiponectin, a protein associated with lipid and glucose metabolism. Evidence suggests that normal concentrations of between 3 to 30µg/mL fall with increasing obesity, suggesting metabolic dysfunction.
For example, a cross-sectional study1 involving 789 subjects with type 2 diabetes was conducted in order to investigate the associations between adiponectin, dietary intake and metabolic syndrome. Serum adiponectin levels were negatively associated with body mass index, waist circumference, body fat percentage, serum insulin and serum triglycerides. There was a positive association between adiponectin and high density lipoprotein levels. Of the subjects with adiponectin levels below 4µg/mL, 57.4% were men and 32.4% were women. The dietary associations were weak, as would be expected, but there was an inverse correlation with body mass index and protein and calcium intakes, as has been reported previously. Both insulin concentrations and insulin resistance were negatively associated with calcium. Those groups with the lowest concentrations of adiponectin had the highest prevalence of metabolic syndrome, something that was true for both sexes.
These findings support other research that has reported low circulating adiponectin concentrations in obese subjects with increased abdominal adiposity. They also add further evidence to support a role for calcium deficiency in the development of weight gain. Adiponectin is the most abundant adipokine in the body, but it is unclear just why levels fall as adiposity increases. The cause and effect of this relationship are not understood and further research is needed to find the mechanisms by which adipokine concentrations are modified. Other research has demonstrated that men and women in the lowest quartile for adiponectin concentration have a 4.4 and 7.5-fold increase in the risk of having metabolic syndrome, respectively, when compared to those in the highest quartile. Adiponectin levels have been shown to be associated with Mediterranean dietary patterns, suggesting that diet quality may influence circulating adiponectin concentrations.
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