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Hepatic lipid homeostasis depends on intracellular pathways that respire fatty acid in peroxisomes and mitochondria, and on systemic pathways that secrete fatty acid into the bloodstream, either free or condensed in very-low-density lipoprotein (VLDL) triglycerides. These systemic and intracellular pathways are interdependent, but it is unclear whether and how they integrate into a single cellular circuit. Here, we report that mouse liver wrappER, a distinct endoplasmic reticulum (ER) compartment with apparent fatty acid- and VLDL-secretion functions, connects peroxisomes and mitochondria. Correlative light electron microscopy, quantitative serial section electron tomography and three-dimensional organelle reconstruction analysis show that the number of peroxisome-wrappER-mitochondria complexes changes throughout fasting-to-feeding transitions and doubles when VLDL synthesis stops following acute genetic ablation of Mttp in the liver. Quantitative proteomic analysis of peroxisome-wrappER-mitochondria complex-enriched fractions indicates that the loss of Mttp upregulates global fatty acid β-oxidation, thereby integrating the dynamics of this three-organelle association into hepatic fatty acid flux responses. Therefore, liver lipid homeostasis occurs through the convergence of systemic and intracellular fatty acid-elimination pathways in the peroxisome-wrappER-mitochondria complex.

Summary The endoplasmic reticulum (ER) plays a central role in lipid homeostasis, but the role of individual ER subdomains in lipid biology has not been elucidated. WrappER is a curved wrapping type of rough-ER that establishes extensive contacts with almost every mitochondria of the hepatocyte in the mouse liver. Here, we describe a protocol for isolation of fractions enriched in wrappER-associated mitochondria from the mouse liver. We also provide techniques for assessing its quality by electron microscopy and biochemical/proteomic analysis. For complete information on the use and execution of this protocol, please refer to Anastasia et al. (2021)., Graphical abstract, Highlights • Protocol for isolating fractions enriched in wrappER-associated mitochondria (WAM) • Companion protocol for isolating a control ER-enriched fraction • Procedure to validate WAM- and ER-enriched fractions by electron microscopy analysis • Procedure to validate WAM- and ER-enriched fractions by immunoblot analysis, The endoplasmic reticulum (ER) plays a central role in lipid homeostasis, but the role of individual ER subdomains in lipid biology has not been elucidated. WrappER is a curved wrapping type of rough-ER that establishes extensive contacts with almost every mitochondria of the hepatocyte in the mouse liver. Here, we describe a protocol for isolation of fractions enriched in wrappER-associated mitochondria from the mouse liver. We also provide techniques for assessing its quality by electron microscopy and biochemical/proteomic analysis.

Summary Contacts between organelles create microdomains that play major roles in regulating key intracellular activities and signaling pathways, but whether they also regulate systemic functions remains unknown. Here, we report the ultrastructural organization and dynamics of the inter-organellar contact established by sheets of curved rough endoplasmic reticulum closely wrapped around the mitochondria (wrappER). To elucidate the in vivo function of this contact, mouse liver fractions enriched in wrappER-associated mitochondria are analyzed by transcriptomics, proteomics, and lipidomics. The biochemical signature of the wrappER points to a role in the biogenesis of very-low-density lipoproteins (VLDL). Altering wrappER-mitochondria contacts curtails VLDL secretion and increases hepatic fatty acids, lipid droplets, and neutral lipid content. Conversely, acute liver-specific ablation of Mttp, the most upstream regulator of VLDL biogenesis, recapitulates this hepatic dyslipidemia phenotype and promotes remodeling of the wrappER-mitochondria contact. The discovery that liver wrappER-mitochondria contacts participate in VLDL biology suggests an involvement of inter-organelle contacts in systemic lipid homeostasis.

Summary The mitochondrial contact site and cristae organizing system (MICOS) and Optic atrophy 1 (OPA1) control cristae shape, thus affecting mitochondrial function and apoptosis. Whether and how they physically and functionally interact is unclear. Here, we provide evidence that OPA1 is epistatic to MICOS in the regulation of cristae shape. Proteomic analysis identifies multiple MICOS components in native OPA1-containing high molecular weight complexes disrupted during cristae remodeling. MIC60, a core MICOS protein, physically interacts with OPA1, and together, they control cristae junction number and stability, OPA1 being epistatic to MIC60. OPA1 defines cristae width and junction diameter independently of MIC60. Our combination of proteomics, biochemistry, genetics, and electron tomography provides a unifying model for mammalian cristae biogenesis by OPA1 and MICOS., Graphical Abstract, Highlights • Complexes containing OPA1 and MIC60 are targeted during cristae remodeling • OPA1 lies upstream of MIC60 in regulating cristae junction number and stability • OPA1 is the sole regulator of cristae junction width, Mitochondrial ultrastructure dictates mitochondrial function and cell viability. Glytsou et al. find that Optic Atrophy 1 (OPA1) and the MICOS component MIC60 interact in cristae shape regulation and place OPA1 epistatic to MIC60 in cristae biogenesis and remodeling, providing a unifying molecular model of cristae morphology control.

Latar Belakang: Gingivitis pada saat kehamilan disebabkan oleh peningkatan konsentrasi hormon estrogen dan progesteron. Keadaan ini ditandai dengan papila interdental yang memerah, bengkak, mudah berdarah disertai rasa sakit menyebabkan gingiva menjadi sensitif khususnya terhadap toksin maupun iritan seperti plak dan kalkulus yang mengakibatkan gingiva mengalami peradangan. Tujuan: Untuk melihat hubungan antara tingkat kebersihan dengan tingkat keparahan gingivitis terhadap wanita hamil. Metode: Sebanyak 32 wanita hamil di RSUD DR. RM. Djoelham Binjai dibagi menjadi 2 kelompok, yaitu 16 orang trimester kedua dan 16 orang trimester ketiga dilakukan pemeriksaan status OHI-S dan gingivitis dengan menggunakan indeks OHI-S dan indeks gingivitis. Hasil: Berdasarkan hasil penelitian terdapat hasil yang signifikan (p