GnRH binding was characterized in the African catfish ovary by use of an analog of salmon GnRH (sGnRH- ; [D-Arg6, Trp7, Leu8, Pro9-NEt]-GnRH) as a labeled ligand. Binding of sGnRH-A to catfish ovarian membrane preparation was found to be saturable, displaceable, reversible, and dependent on time, temperature, and tissue concentration. Optimal binding was achieved after 70 min of incubation at room temperature (approximately 22 degrees C) at pH 7.6. Addition of unlabeled sGnRH-A displaced the bound 125I-sGnRH-A in a dose-related manner. Hill plot as well as Scatchard analysis indicated the presence of one class of high-affinity binding sites with a equilibrium dissociation constant (Kd) of 0.27 +/- 0.036 nM. Bound 125I-sGnRH-A was also found to be displaceable by catfish GnRH (cfGnRH; [His5, Leu7, Asn8]-GnRH), chicken GnRH-II (cGnRH-II; [His5, Trp7, Tyr8]-GnRH), and salmon GnRH (sGnRH; [Trp7, Leu8]-GnRH); all the peptides were found to bind with lower affinities than sGnRH-A to the catfish ovarian GnRH binding sites. Further experiments using ovarian extracts indicated the presence of compounds with GnRH-like activity in the ovary of African catfish. The crude ovarian extract was found to stimulate pituitary gonadotropin release from goldfish pituitary, as well as displacing 125I-sGnRH-A binding in the catfish ovary. HPLC analysis of the catfish ovarian extract revealed the presence of two fractions that bind specifically to the catfish ovary and release gonadotropin from cultured goldfish pituitary. These fractions include an early eluting peak that does not correspond with the retention time of known GnRH forms in addition to a fraction that co-elutes with the mammalian GnRH. Overall, the study provided characterization of GnRH binding sites in the catfish ovary, and evidence for the presence of compounds with GnRH-like activity in the catfish ovary.

Purpose Obese subjects with nonalcoholic fatty liver disease (NAFLD) are more prone to develop additional metabolic disturbances such as systemic insulin resistance (IR) and type 2 diabetes. NAFLD is defined by hepatic steatosis, lobular inflammation, ballooning and stage of fibrosis, but it is unclear if and which components could contribute to IR. Objective To assess which histological components of NAFLD associate with IR in subjects with obesity, and if so, to what extent. Methods This cross-sectional study included 78 obese subjects (mean age 46 ± 11 years; BMI 42.2 ± 4.7 kg/m2). Glucose levels were analysed by hexokinase method and insulin levels with electrochemiluminescence. Homeostasis model assessment-estimated insulin resistance (HOMA-IR) was calculated. Liver biopsies were evaluated for histological components of NAFLD. Results A positive association between overall NAFLD Activity Score and HOMA-IR was found (r s = 0.259, P = 0.022). As per individual components, lobular inflammation and fibrosis stage were positively associated with HOMA-IR, glucose and insulin levels (P < 0.05), and HOMA-IR was higher in patients with more inflammatory foci or higher stage of fibrosis. These findings were independent of age, BMI, triglyceride levels, diabetes status and sex (all P < 0.043). In a combined model, lobular inflammation, but not fibrosis, remained associated with HOMA-IR. Conclusion In this group of obese subjects, a major contributing histological component of NAFLD to the relation between NAFLD severity and IR seems to be the grade of hepatic lobular inflammation. Although no causal relationship was assessed, preventing or mitigating this inflammatory response in obesity might be of importance in controlling obesity-related metabolic disturbances.