engleski

Can Bears be Fatty? Preliminary Study of Adipokines in Brown Bears

Adipose tissue is an important endocrine organ. It is dynamic tissue with the potential to produce a broad spectrum of biological modifiers. Adipokines are key regulators of energy metabolism, cardiovascular health, and immune function, and their production and function may be influenced by nutrition and reproductive status, with some species-specific considerations. Dysregulation of adipokines appears to contribute to the development of a number of complications associated with obesity. These connections have mostly been explored in humans and rodent models. Similar mechanistic studies are in early stages in dogs, cats, and horses, while there are no known studies in brown bears or other wild animals. Adiponectin has anti-inflammatory and anti-atherogenic properties. Resistin appears to control feeding as well as activating de novo hepatic lipogenesis and peripheral lipid metabolism. Therefore, higher resistin levels may be a marker of systemic inflammation. Myostatin functions as a potent inhibitor of skeletal muscle growth. Moreover, myostatin regulates metabolism and its inhibition can significantly attenuate the progression of obesity and diabetes. In this preliminary study we measured serum levels of adiponectin, resistin, and myostatin in sera of 18 wild and captive brown bears from Croatia. Serum was separated from blood cells by centrifugation and stored at –20 °C until analysis. Assay of serum adiponectin, resistin and myostatin was determined using canine ELISA kits obtained from Biotang Inc., Source International, Camarillo, California, USA, following the manufacturer instructions. The optical density was measured with a microplate reader at 450 nm (Biorad). The standard curve, prepared from 5 standard dilutions in duplicate was used for calculating the concentration of analyte in the samples, expressed in ng/mL. Mean value of adiponectin concentration measured in 15 sera samples was 142.16 ng/mL ± 4.33 (1 SE) with a range from 119.30 ng/mL to 172.40 ng/mL. Median value was 145 ng/mL, ten percentiles was at 122.47 ng/mL and ninety percentiles at 162.79 ng/mL. Resistin in sera was present in mean concentration of 26.64 ng/mL ± 1.61 (1 SE, n = 15) with a range from 11.90 ng/mL to 38.65 ng/mL. Median value was 27.3 ng/mL, ten percentiles was at 21.44 ng/mL while ninety percentiles was at 32 ng/mL. Mean value of myostatin concentration was 903.93 ± 20.95 ng/mL (1 SE, n = 15) with a range from 795.35 ng/mL to 1098.45 ng/mL. Median value was 898.1 ng/mL, ten percentiles was at 805.63 ng/mL while ninety percentiles was at 991.6 ng/ml. Since no previous studies on adipokines in brown bears were conducted the listed means and ranges (10–90 percentiles) represent reference values of the adiponectin, resistin, and myostatin concentration in the serum of brown bears in Croatia. Future research objective is to investigate if in obese bears comparing to “normal” bears different values in adipokines serum concentration are present. The bears from our initial sample could not be clearly separated in those 2 groups and we were not able to point out the differences in obtained serum values. If difference will not be significant the protective mechanisms maintaining adipokines level should be put under the lens.

adiponectin; resistin; myostatin; brown bear

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