Abstract
Background: The interactions of adipose tissue with the kidney are hypothesized to affect kidney function. Also, excessive peri-renal fat may increase the risk of cardiometabolic risk. However, the role(s) of peri-renal fat adipocytokine has never been evaluated.Objectives: To elucidate levels of adiponectin expression in peri-renal and subcutaneous adipose tissue and its determinants in human biopsied samples.Methods: A pair of subcutaneous and perirenal fat tissue samples were collected from 80 patients (men: 54; women: 26) who underwent urological operations. Subcutaneous adipose tissue (SAT) area, visceral adipose tissue (VAT) area and peri-renal adipose tissue (RAT) volume were quantified on abdominal computed tomography. Cytokine/adipocytokine expression was evaluated by real-time semi-quantitative polymerase chain reaction (qPCR). Probability was considered significant if P < 0.05.Results: Current study evaluated determinants of plasma adiponectin levels and expression levels of adiponectin in SAT and RAT in human samples. We found that: first, plasma adiponectin levels were correlated with VAT area but not with BMI, waist circumference, SAT area, and RAT volume; second, expression levels of adiponectin in SAT were correlated with BMI, waist circumference, and SAT area but not with VAT area and RAT volume; and third, expression levels of adiponectin in RAT were correlated with all adiposity indices including BMI, waist circumference, SAT area, VAT area, and RAT volume.Conclusion: This study evaluated levels of adiponectin expression in RAT and SAT and its determinants in patients who underwent urological operation. Levels of adiponectin mRNA in RAT were negatively correlated with remote fat mass in SAT and VAT and also with local fat mass in RAT, while level of adiponectin in SAT was not correlated with RAT volume. Further studies are warranted to evaluate roles of peri-renal fat mass accumulation and its pathophysiological machineries.
Highlights
Adiponectin is a circulating protein exclusively produced from adipocytes and shows unique insulin-sensitizing, antiinflammatory, and anti-apoptotic properties [1]
BMI, waist circumference, subcutaneous adipose tissue (SAT) area, and visceral adipose tissue (VAT) area were negatively correlated with SAT and RENAL ADIPOSE TISSUE (RAT) adiponectin, but not with plasma adiponectin
Multivariate regression analysis showed that VAT area, but not SAT area nor RAT volume, was a determinant for plasma adiponectin levels after corrected for known confounding factors such as age, gender, hyperlipidemia, hypertension, type 2 diabetes, and smoking (Table 2)
Summary
Adiponectin is a circulating protein exclusively produced from adipocytes and shows unique insulin-sensitizing, antiinflammatory, and anti-apoptotic properties [1]. It is known that protein production or gene expression of various adipocytokines is regulated in a depot-specific manner, e.g., subcutaneous adipose tissue (SAT) vs visceral adipose tissue (VAT) [9,10,11,12]. Central obesity and visceral fat obesity, which can be assumed by an increased VAT volume, have been shown to be associated with lower plasma levels of adiponectin [2,3,4]. One can assume that a decrease in protein production or gene expression of adiponectin in VAT could explain hypoadiponectinemia at least partially. Excessive peri-renal fat may increase the risk of cardiometabolic risk. The role(s) of peri-renal fat adipocytokine has never been evaluated
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