Geranylgeranyl reductase from Sulfolobus acidocaldarius was shown to catalyze the reduction of geranylgeranyl groups in the precursors of archaeal membrane lipids, generally reducing all four double bonds. However, when geranylgeranyl diphosphate was subjected to the reductase reaction, only three of the four double bonds were reduced. Mass spectrometry and acid hydrolysis indicated that the allylic double bond was preserved in the partially reduced product derived from geranylgeranyl diphosphate. Thus, the reaction product was shown to be phytyl diphosphate, which is a substrate for archaeal prenyltransferases, unlike the completely reduced compound phytanyl diphosphate.

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Complete saturation of the geranylgeranyl groups of biosynthetic intermediates of archaeal membrane lipids is an important reaction that confers chemical stability on the lipids of archaea, which generally inhabit extreme conditions. An enzyme encoded by the AF0464 gene of a hyperthermophilic archaeon, Archaeoglobus fulgidus, which is a distant homologue of plant geranylgeranyl reductases and an A. fulgidus menaquinone‐specific prenyl reductase[Hemmi H, Yoshihiro T, Shibuya K, Nakayama T, & Nishino T (2005) J Bacteriol187, 1937–1944], was recombinantly expressed and purified, and its geranylgeranyl reductase activity was examined. The radio HPLC analysis indicated that the flavoenzyme, which binds FAD noncovalently, showed activity towards lipid‐biosynthetic intermediates containing one or two geranylgeranyl groups under anaerobic conditions. It showed a preference for 2,3‐di‐O‐geranylgeranylglyceryl phosphate over 3‐O‐geranylgeranylglyceryl phosphate and geranylgeranyl diphosphate in vitro, and did not reduce the prenyl group of respiratory quinones in Escherichia coli cells. The substrate specificity strongly suggests that the enzyme is involved in the biosynthesis of archaeal membrane lipids. GC‐MS analysis of the reaction product from 2,3‐di‐O‐geranylgeranylglyceryl phosphate proved that the substrate was converted to archaetidic acid (2,3‐di‐O‐phytanylglyceryl phosphate). The archaeal enzyme required sodium dithionite as the electron donor for activity in vitro, similarly to the menaquinone‐specific prenyl reductase from the same anaerobic archaeon. On the other hand, in the presence of NADPH (the preferred electron donor for plant homologues), the enzyme reaction did not proceed.

Background Ovarian endometrioma is a common gynecological disease that is often treated with surgery or hormonal treatment. Ovarian cystectomy, a surgical procedure for ovarian endometrioma, can result in impaired ovarian reserve. Methods We conducted a randomized controlled trial to evaluate the efficacy of hormonal treatment [gonadotropin-releasing hormone agonist (GnRHa) or dienogest (DNG)] for preserving ovarian reserve after cystectomy for ovarian endometrioma. The primary endpoint was the level of serum Anti-Müllerian hormone (AMH) as a marker of ovarian reserve. Results Before and after laparoscopic surgery, 22 patients in the GnRHa group and 27 patients in the DNG group were administered hormonal treatment for a total of 4 months. After 1-year follow-up, >60% of the patients in the DNG group retained over 70% of their pretreatment AMH levels, whereas no patient in the GnRHa group retained their AMH levels after cystectomy (P < 0.01). Interleukin-6 (IL-6) is a key cytokine involved in inflammation. Compared with the GnRHa group, patients in the DNG group had lower IL-6 levels at the end of treatment. Conclusions Our data revealed that DNG is more effective than GnRHa in preserving ovarian reserve after cystectomy of ovarian endometrioma. This is achieved through the reduction of the inflammatory response during the perioperative period and other endometriosis-related inflammatory reactions. Trial registration The registration number of this trial is UMIN-CTR, UMIN000018569, registered 6 August 2015, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000021492, and Japan Registry of Clinical Trials, jRCTs041180140, registered 29 March 2019, https://jrct.niph.go.jp/en-latest-detail/jRCTs041180140. This randomized controlled trial was conducted in accordance with the CONSORT guidelines.

Background Endometriosis is a complex syndrome characterized by an estrogen-dependent chronic inflammatory process that affects 10% of women of reproductive age. Ovarian endometriosis (OE) is the most common lesion in endometriosis and may cause infertility, in addition to dysmenorrhea. Hormonal treatments, which are the conventional treatment methods for endometriosis, suppress ovulation and hence are not compatible with fertility. The inflammasome is a complex that includes Nod-like receptor (NLR) family proteins, which sense pathogen-associated molecular patterns and homeostasis-altering molecular processes. It has been reported that the nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain-containing (NLRP) 3 inflammasome, which contributes to the activation of interleukin-1 beta (IL-1β), might be related to the progression of endometriosis. Therefore, the aim of the present study was to evaluate non-hormonal therapies for OE, such as inhibitors of the NLRP3 inflammasome. Methods The expression of NLRP3 was measured in the eutopic endometrium (EM) of patients with and without endometriosis and OE samples, as well as stromal cells derived from the endometrium of patients with and without endometriosis and OE samples (endometrial stromal cells with endometriosis [ESCs] and cyst-derived stromal cells [CSCs]). The effects of an NLRP3 inhibitor (MCC950) on ESCs and CSCs survival and IL-1β production were evaluated. We then administered MCC950 to a murine model of OE to evaluate its effects on OE lesions and ovarian function. Results NLRP3 gene and protein expression levels were higher in OE and CSCs than in EM and ESCs, respectively. MCC950 treatment significantly reduced the survival of CSCs, but not that of ESCs. Moreover, MCC950 treatment reduced the co-localization of NLRP3 and IL-1β in CSCs, as well as IL-1β concentrations in CSCs supernatants. In the murine model, MCC950 treatment reduced OE lesion size compared to phosphate-buffered saline treatment (89 ± 15 vs. 49 ± 9.3 mm3 per ovary; P < 0.05). In the MCC950-treated group, IL-1β and Ki67 levels in the OE-associated epithelia were reduced along with the oxidative stress markers of granulosa cells. Conclusions These results indicated that NLRP3/IL-1β is involved in the pathogenesis of endometriosis and that NLRP3 inhibitors may be useful for suppressing OE and improving the function of ovaries with endometriosis.