A single dose of enterolactone activates estrogen signaling and regulates expression of circadian clock genes in mice.

Enterolactone (EL) is an enterolignan produced by gut microbiota from dietary plant lignans. Epidemiological and experimental studies suggest that EL and plant lignans may reduce the risk of breast and prostate cancer as well as cardiovascular disease. These effects are thought to at least in part involve modulation of estrogen receptor activity. Surprisingly little is known about the in vivo estrogenicity of EL. In the present study, we investigated the target tissues of EL, the genes affected by EL treatment, and the response kinetics. Following a single dose of EL, luciferase was significantly induced in reproductive and nonreproductive tissues of male and female 3xERE-luciferase mice, indicating estrogen-like activity. Microarray analysis revealed that EL regulated the expression of only 1% of 17ß-estradiol target genes in the uterus. The majority of these genes were traditional estrogen target genes, but also members of the circadian signaling pathway were affected. Kinetic analyses showed that EL undergoes rapid phase II metabolism and is efficiently excreted. In vivo imaging demonstrated that the estrogen response followed similar, fast kinetics. We conclude that EL activates estrogen signaling in both male and female mice and that the transient responses may be due to the fast metabolism of the compound. Lastly, EL may represent a link among diet, gut microbiota, and circadian signaling.

Ataxia with loss of Purkinje cells in a mouse model for Refsum disease.

Refsum disease is caused by a deficiency of phytanoyl-CoA hydroxylase (PHYH), the first enzyme of the peroxisomal alpha-oxidation system, resulting in the accumulation of the branched-chain fatty acid phytanic acid. The main clinical symptoms are polyneuropathy, cerebellar ataxia, and retinitis pigmentosa. To study the pathogenesis of Refsum disease, we generated and characterized a Phyh knockout mouse. We studied the pathological effects of phytanic acid accumulation in Phyh(-/-) mice fed a diet supplemented with phytol, the precursor of phytanic acid. Phytanic acid accumulation caused a reduction in body weight, hepatic steatosis, and testicular atrophy with loss of spermatogonia. Phenotype assessment using the SHIRPA protocol and subsequent automated gait analysis using the CatWalk system revealed unsteady gait with strongly reduced paw print area for both fore- and hindpaws and reduced base of support for the hindpaws. Histochemical analyses in the CNS showed astrocytosis and up-regulation of calcium-binding proteins. In addition, a loss of Purkinje cells in the cerebellum was observed. No demyelination was present in the CNS. Motor nerve conduction velocity measurements revealed a peripheral neuropathy. Our results show that, in the mouse, high phytanic acid levels cause a peripheral neuropathy and ataxia with loss of Purkinje cells. These findings provide important insights in the pathophysiology of Refsum disease.