Ratiometric Measurements of Adiponectin by Mass Spectrometry in Bottlenose Dolphins (Tursiops truncatus) with Iron Overload Reveal an Association with Insulin Resistance and Glucagon

Abstract

High molecular weight (HMW) adiponectin levels are reduced in humans with type 2 diabetes and insulin resistance. Similar to humans with insulin resistance, managed bottlenose dolphins (Tursiops truncatus) diagnosed with hemochromatosis (iron overload) have higher levels of 2 h post-prandial plasma insulin than healthy controls. A parallel reaction monitoring assay for dolphin serum adiponectin was developed based on tryptic peptides identified by mass spectrometry. Using identified post-translational modifications, a differential measurement was constructed. Total and unmodified adiponectin levels were measured in sera from dolphins with (n = 4) and without (n = 5) iron overload. This measurement yielded total adiponectin levels as well as site specific percent unmodified adiponectin that may inversely correlate with HMW adiponectin. Differences in insulin levels between iron overload cases and controls were observed 2 h post-prandial, but not during the fasting state. Thus, post-prandial as well as fasting serum adiponectin levels were measured to determine whether adiponectin and insulin would follow similar patterns. There was no difference in total adiponectin or percent unmodified adiponectin from case or control fasting animals. There was no difference in post-prandial total adiponectin levels between case and control dolphins (mean ± SD) at 763 ± 298 and 727 ± 291 pmol/ml, respectively (p = 0.91); however, percent unmodified adiponectin was significantly higher in post-prandial cases compared to controls (30.0 ± 6.3 versus 17.0 ± 6.6%, respectively; p = 0.016). Interestingly, both total and percent unmodified adiponectin were correlated with glucagon levels in controls (r = 0.999, p < 0.001), but not in cases, which is possibly a reflection of insulin resistance. Although total adiponectin levels were not significantly different, the elevated percent unmodified adiponectin follows a trend similar to HMW adiponectin reported for humans with metabolic disorders.

Blood-Based Indicators of Insulin Resistance and Metabolic Syndrome in Bottlenose Dolphins (Tursiops truncatus)

“…The above variables were measured photometrically on the Roche Diagnostics Modular Analytics P Module clinical chemistry analyzer (Roche Diagnostics, Indianapolis, IN, USA) at the Animal Health Diagnostic Center at Cornell University. Adiponectin was measured using parallel reaction monitoring (PRM) as described previously (23). …”

Proteomic analysis of cerebrospinal fluid in California sea lions (Zalophus californianus) with domoic acid toxicosis identifies proteins associated with neurodegeneration

“…Typically a database of confirmed protein sequences (e.g., UniProt Swiss‐Prot), or translated coding sequences (CDS) are utilized. Even low coverage genome sequencing can be used to search marine mammal data with success . Currently, there is no California sea lion genome, and only 86 protein sequences are in the UniProt Knowledge Base.…”

“…Peptide identifications of four proteins were validated using stable isotope standard (SIS) peptides synthesized by New England Peptide (Gardner, MA, USA) with isotopically labeled (‘^’; 13 C and 15 N) c‐terminus amino acids: QELENLER^ (dickkopf‐3), TGAQELLR^ (gelsolin), NAPTPQEFR^ (NCAM1), and IISVELPDDAR^ (reelin). Concentration was determined by amino acid analysis and collision energy was optimized as previously described . An aliquot of CSF (60 μL) was digested the same as described above except that a ratio of 1:10 trypsin:protein was used.…”

Dolphins and Diabetes: Applying One Health for Breakthrough Discoveries

“…Dr. Benjamin Neely et al dive deeper to assess the potential risk of insulin resistance in dolphins with lower levels of high-weight adiponectin ( 5 , 16 ). Previous studies in mice and humans have demonstrated the insulin-sensitizing effect of adiponectin and its decreasing beneficial impact in the face of iron overload.…”

“…Previous studies in mice and humans have demonstrated the insulin-sensitizing effect of adiponectin and its decreasing beneficial impact in the face of iron overload. Dr. Neeley et al’s discovery of disrupted associations between adiponectin and glucagon in dolphins with high insulin and iron overload, paired with high sequence similarity of dolphin and human adiponectin, continue to support increasing high-weight adiponectin as a potential therapeutic target for people and other animals with these diseases ( 16 ). Dr. Kirsten Eberle et al use their newly developed, dolphin-specific immunoassays to characterize inflammation present in a 46-year old dolphin with metabolic syndrome and iron overload compared to a dolphin without these diseases ( 17 ).…”