Association of serum bilirubin and non-alcoholic fatty liver disease: A feasible therapeutic avenue?

A high-fat eucaloric diet induces reprometabolic syndrome of obesity in normal weight women

We examined the effects of 1 month of a eucaloric, high-fat (48% of calories) diet (HFD) on gonadotropin secretion in normal-weight women to interrogate the role of free fatty acids and insulin in mediating the relative hypogonadotropic hypogonadism of obesity. Eighteen eumenorrheic women (body mass index [BMI] 18-25 kg/m2) were studied in the early follicular phase of the menstrual cycle before and after exposure to an HFD with frequent blood sampling for luteinizing hormone (LH) and follicle-stimulating hormone (FSH), followed by an assessment of pituitary sensitivity to gonadotropin-releasing hormone (GnRH). Mass spectrometry-based plasma metabolomic analysis was also performed. Paired testing and time-series analysis were performed as appropriate. Mean endogenous LH (unstimulated) was significantly decreased after the HFD (4.3 ± 1.0 vs. 3.8 ± 1.0, P < 0.01); mean unstimulated FSH was not changed. Both LH (10.1 ± 1.0 vs. 7.2 ± 1.0, P < 0.01) and FSH (9.5 ± 1.0 vs. 8.8 ± 1.0, P < 0.01) responses to 75 ng/kg of GnRH were reduced after the HFD. Mean LH pulse amplitude and LH interpulse interval were unaffected by the dietary exposure. Eucaloric HFD exposure did not cause weight change. Plasma metabolomics confirmed adherence with elevation of fasting free fatty acids (especially long-chain mono-, poly-, and highly unsaturated fatty acids) by the last day of the HFD. One-month exposure to an HFD successfully induced key reproductive and metabolic features of reprometabolic syndrome in normal-weight women. These data suggest that dietary factors may underlie the gonadotrope compromise seen in obesity-related subfertility and therapeutic dietary interventions, independent of weight loss, may be possible.

The Protective Role of the Heme Catabolic Pathway in Hepatic Disorders

Significance: As the central metabolic organ, the liver is exposed to a variety of potentially cytotoxic, proinflammatory, profibrotic, and carcinogenic stimuli. To protect the organism from these deleterious effects, the liver has evolved a number of defense systems, which include antioxidant substrates and enzymes, anti-inflammatory tools, enzymatic biotransformation systems, and metabolic pathways. Recent Advances: One of the pivotal systems that evolved during phylogenesis was the heme catabolic pathway. Comprising the important enzymes heme oxygenase and biliverdin reductase, this complex pathway has a number of key functions including enzymatic activities, but also cell signaling, and DNA transcription. It further generates two important bile pigments, biliverdin and bilirubin, as well as the gaseous molecule carbon monoxide. These heme degradation products have potent antioxidant, immunosuppressive, and cytoprotective effects. Recent data suggest that the pathway participates in the regulation of metabolic and hormonal processes implicated in the pathogenesis of hepatic and other diseases. Critical Issues: This review discusses the impact of the heme catabolic pathway on major liver diseases, with particular focus on the involvement of cellular targeting and signaling in the pathogenesis of these conditions. Future Directions: To utilize the biological consequences of the heme catabolic pathway, several unique therapeutic strategies have been developed. Research indicates that pharmaceutical, nutraceutical, and lifestyle modifications positively affect the pathway, delivering potentially long-term clinical benefits. However, further well-designed studies are needed to confirm the clinical benefits of these approaches. Antioxid. Redox Signal. 35, 734-752.