Age-Related Alteration in Serum Adiponectin in Rats and Its Association with Insulin Resistance Markers

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Introduction: Adiponectin is one of the most important adipose derived hormone that conflicting data are available about serum changes of adiponectin at different ages.The present study was done to determine the age related changes in serum adiponectin and its association with insulin resistance (IR) indices in aging in male rats. Methods: In this study, serum samples were obtained from male rats at different ages, including 2, 5, 10, 18, 52 and 72 weeks age (n=10 in each age group). Oral glucose tolerance and glucose stimulated insulin secretion tests were measured using determination of glucose concentrations at 15, 30, 45 and 60 min after oral ingestion of glucose (1 mg/kg body weight) for each animal. Serum adiponectin and insulin levels were determined using species specific ELISA kits. HOMA-IR was calculated based on glucose and insulin concentrations. Data were analyzed using SPSS version 16 software (SPSS Inc., Chicago, IL) also using one way analysis of variance and LSD posthoc tests. Results: Our results showed an age dependent decrease in serum adiponectin concentration, and 72-week old rats had the lowest level of adiponectin compared with those in other ages (p<0.05). IR indices, including fasting glucose, insulin, HOMA-IR and response to oral glucose ingestion was increased in an age dependent manner and 72-week old rats showed the highest levels of the IR indices. Conclusion: Regarding the role of adiponectin in glucose homeostasis and insulin sensitization, it seems that reduction of serum adiponectin with age progression may be an important mechanism of insulin resistance in aging.