Elevated Insulin Sensitivity in Low‐protein Offspring Rats Is Prevented by a High‐fat Diet and Is Associated With Visceral Fat

This study tests the hypothesis that a high‐fat postnatal diet increases fat mass and reduces improved insulin sensitivity (IS) found in the low‐protein model of maternal undernutrition. Offspring from Wistar dams fed either a 20% (control (CON)) or 8% (low protein (LP)) protein diet during gestation and lactation were randomly assigned to a control (con) or cafeteria (caf) diet at weaning (21 days) until 3 months of age at which point IS was measured (hyperinsulinemic–euglycemic clamp). Fat mass, growth, energy intake (EI) and expenditure (EE), fuel utilization, insulin secretion, and leptin and adiponectin levels were measured to identify a possible role in any changes in IS. IS was increased in LP‐con in comparison to CON‐con animals. Cafeteria feeding prevented this increase in LP animals but had no effect in CON animals (insulin‐stimulated glucose infusion rates (GIRs; mg/min/kg); CON‐con: 13.9 ± 1.0, CON caf: 12.1 ± 2.1, LP‐con: 25.4 ± 2.0, LP‐caf: 13.7 ± 3.7, P < 0.05). CON‐caf animals had similar percent epididymal white adipose tissue (%EWAT; CON‐con: 1.71 ± 0.09 vs. CON‐caf: 1.66 ± 0.08) and adiponectin (µg/ml: CON‐con: 4.61 ± 0.34 vs. CON‐caf: 3.67 ± 0.18) except hyperinsulinemia and relative hyperleptinemia in comparison to CON‐con. Differently, LP‐caf animals had increased %EWAT (LP‐con: 1.11 ± 0.06 vs. LP‐caf: 1.44 ± 0.08, P < 0.05) and adiponectin (µg/ml: LP‐con: 5.38 ± 0.39 vs. LP‐caf: 3.75 ± 0.35, P < 0.05) but did not show cafeteria‐induced hyperinsulinemia or relative hyperleptinemia. An increased propensity to store visceral fat in LP animals may prevent the elevated IS in LP offspring.     

Estradiol‐Induced Anorexia Is Independent of Leptin and Melanin‐Concentrating Hormone

Objective: Treatment of male rodents with estradiol (E₂) is associated with anorexia and weight loss by poorly understood mechanisms. We examined the role of the orexigenic hypothalamic peptide melanin‐concentrating hormone (MCH) and the appetite‐inhibiting, fat‐derived hormone leptin in mediating E₂‐induced anorexia. Research Methods and Procedures: We studied the effect of E₂ treatment (implantation of either E₂ pellet or matching placebo) in male C57Bl/6J mice, as well as in a lean mouse model (MCH knockout mice) and an obese model (leptin‐deficient ob/ob mice). We also studied the effect of E₂ treatment in the context of high‐fat diet. Results: We confirmed E₂ dose‐dependent anorexia in male wild type mice fed a normal chow diet. E₂ treatment was associated with a significant decrease in body fat, serum leptin levels, and arcuate hypothalamic proopiomelanocortin expression. E₂‐implanted mice also showed increased hypothalamic neuropeptide Y and MCH expression. As MCH has been implicated in E₂‐induced hypophagia, we performed E₂ pellet implantation in MCH knockout mice and observed hypophagia and weight loss, indicating that MCH is not an essential mediator of E₂‐induced anorexia. E₂‐implanted ob/ob mice also had hypophagia and weight loss, indicating that leptin is not essential for E₂‐induced anorexia. High‐fat diet significantly exacerbated the effect of E₂ treatment, leading to a 99.6% decrease in food intake at 48 hours and a 30% loss of body weight within 1 week. Discussion: The anorectic effects of E₂ were independent of MCH and leptin. Our results suggested that E₂ may have effects on nutrient preferences.     

Is the adhesive material secreted by sea urchin tube feet species‐specific?

Sea urchin adoral tube feet are highly specialized organs that have evolved to provide efficient attachment to the substratum. They consist of a disk and a stem that together form a functional unit. Tube foot disk tenacity (adhesive force per unit area) and stem mechanical properties (e.g., stiffness) vary between species but are apparently not correlated with sea urchin taxa or habitats. Moreover, ultrastructural studies of sea urchin disk epidermis pointed out differences in the internal organization of the adhesive secretory granules among species. This prompted us to look for interspecific variability in the composition of echinoid adhesive secretions, which could explain the observed variability in adhesive granule ultrastructure and disk tenacity. Antisera raised against the footprint material of Sphaerechinus granularis (S. granularis) were first used to locate the origin of adhesive footprint constituents in tube feet by taking advantage of the polyclonal character of the generated antibodies. Immunohistochemical assays showed that the antibodies specifically labeled the adhesive secretory cells of the disk epidermis in the tube feet of S. granularis. The antibodies were then used on tube foot histological sections from seven other sea urchin species to shed some light on the variability of their adhesive substances by looking for antibody cross‐reactivity. Surprisingly, no labeling was observed in any of the species tested. These results indicate that unlike the adhesive secretions of asteroids, those of echinoids do not share common epitopes on their constituents and thus would be “species‐specific.” In sea urchins, variations in the composition of adhesive secretions could therefore explain interspecific differences in disk tenacity and in adhesive granule ultrastructure. J. Morphol., 2011. © 2011 Wiley Periodicals, Inc.     

F1FO ATP Synthase Is Expressed at the Surface of Embryonic Rat Heart‐Derived H9c2 Cells and Is Affected by Cardiac‐Like Differentiation

Taking advantage from the peculiar features of the embryonic rat heart‐derived myoblast cell line H9c2, the present study is the first to provide evidence for the expression of F₁F_O ATP synthase and of ATPase Inhibitory Factor 1 (IF₁) on the surface of cells of cardiac origin, together documenting that they were affected through cardiac‐like differentiation. Subunits of both the catalytic F₁ sector of the complex (ATP synthase‐β) and of the peripheral stalk, responsible for the correct F₁‐F_O assembly/coupling, (OSCP, b, F6) were detected by immunofluorescence, together with IF₁. The expression of ATP synthase‐β, ATP synthase‐b and F6 were similar for parental and differentiated H9c2, while the levels of OSCP increased noticeably in differentiated cells, where the results of in situ Proximity Ligation Assay were consistent with OSCP interaction within ecto‐F₁F_O complexes. An opposite trend was shown by IF₁ whose ectopic expression appeared greater in the parental H9c2. Here, evidence for the IF₁ interaction with ecto‐F₁F_O complexes was provided. Functional analyses corroborate both sets of data. i) An F₁F_O ATP synthase contribution to the exATP production by differentiated cells suggests an augmented expression of holo‐F₁F_O ATP synthase on plasma membrane, in line with the increase of OSCP expression and interaction considered as a requirement for favoring the F₁‐F_O coupling. ii) The absence of exATP generation by the enzyme, and the finding that exATP hydrolysis was largely oligomycin‐insensitive, are in line in parental cells with the deficit of OSCP and suggest the occurrence of sub‐assemblies together evoking more regulation by IF₁. J. Cell. Biochem. 9999: 1–13, 2015. © 2015 Wiley Periodicals, Inc. J. Cell. Biochem. 117: 470–482, 2016. © 2015 Wiley Periodicals, Inc.     

COX‐2‐mediated Inflammation in Fat Is Crucial for Obesity‐linked Insulin Resistance and Fatty Liver

The aim was to examine the role of cyclooxygenase (COX)‐2‐mediated inflammation in the development of obese linked insulin resistance and fatty liver. The rats were fed separately regular diet (CONT), high‐fat diet (HFD) ad libitum, or energy restrictedly for 12 weeks. Rats fed HFD ad libitum were further divided into three subgroups co‐treated with vehicle (HFa), or a selective COX‐2 inhibitor celecoxib (HFa‐Cel) or mesulid (HFa‐Mes). Euglycemic hyperinsulinemic clamp (EHC) experiment was performed at the end of study. Another set of rats with similar grouping was further divided into those with a 4, 8, or 12‐week intervention period for hepatic sampling. Body weight was increased significantly and similarly in HFa, HFa‐Cel, and HFa‐Mes. Time‐dependent increases in plasma insulin, glucose, 8‐isoprostanes, leptin levels, homeostasis model assessment of insulin resistance (HOMA‐IR) and hepatic triglyceride contents shown in HFa were significantly reversed in HFa‐Cel and HFa‐Mes. During EHC period, the reduction in stimulation of whole body glucose uptake, suppression of hepatic glucose production and metabolic clearance rate of insulin shown in HFa were significantly reversed in HFa‐Cel and HFa‐Mes. The enhanced COX‐2 and tumor necrosis factor‐α (TNF‐α) but attenuated PPAR‐γ and C/EBP‐α mRNA expressions in epididymal fat shown in HFa were significantly reversed in HFa‐Cel and HFa‐Mes. The increases in average cell size of adipocytes and CD68 positive cells shown in HFa were also significantly reversed in HFa‐Cel and HFa‐Mes. Our findings suggest that COX‐2 activation in fat inflammation is important in the development of insulin resistance and fatty liver in high fat induced obese rats.