Shape, membrane morphology, and morphodynamic response of metabolically active human mitochondria revealed by scanning ion conductance microscopy.

Mitochondrial network dynamics play a key role in enabling cells to adapt to environmental changes. Fusion and fission of mitochondria, as well as their contact with other organelles, are central processes. Consequently, the outer membrane, which separates the mitochondrion from the cytoplasm, has become a focus of investigation.

Effects of coding variants in the glucokinase regulatory protein gene on hepatic glucose and triglyceride metabolism suggest a gene regulatory function of glucokinase.

Background: Regulation of glucose metabolism after a meal is the major task of hepatic glucokinase (GCK). Inhibition and nuclear retention of glucokinase during fasting is achieved by glucokinase regulatory protein (GKRP). Compounds disrupting the GCK-GKRP interaction alter glucose but not triglyceride levels, whilst GKRP coding alleles lower glucose but elevate triglycerides.

The novel GCK variant p.Val455Leu associated with hyperinsulinism is susceptible to allosteric activation and is conducive to weight gain and the development of diabetes.

Aims/hypothesis: The mammalian enzyme glucokinase (GK), expressed predominantly in liver and pancreas, plays an essential role in carbohydrate metabolism. Monogenic GK disorders emphasise the role of GK in determining the blood glucose set point.

Methods: A family with congenital hyperinsulinism (CHI) was examined for GCK gene variants by Sanger sequencing.

The Role of Neurotropic B Vitamins in Nerve Regeneration.

Damage and regeneration naturally occur in the peripheral nervous system. The neurotropic B vitamins thiamine (B1), pyridoxine (B6), and cobalamin (B12) are key players, which maintain the neuronal viability in different ways. Firstly, they constantly protect nerves against damaging environmental influences.

Collagen Remodeling Plays a Pivotal Role in Endothelial Corneal Dystrophies.

Purpose: To elucidate the collagen structure in the Descemet membrane (DM) of the human cornea and to characterize its rearrangement in patients with endothelial corneal dystrophies.

Methods: Corneas from nine human donors and dystrophic DMs removed from 16 affected eyes of 13 patients by endothelial keratoplasty (DMEK) were investigated using a correlative RT-qPCR and label-free two-channel multiphoton microscopy (MPM) setup. Although collagen formation was visualized by second harmonic generation, the cellular structure was determined by autofluorescence.

MiD51 Is Important for Maintaining Mitochondrial Health in Pancreatic Islet and MIN6 Cells.

Mitochondrial dynamics are important for glucose-stimulated insulin secretion in pancreatic beta cells. The mitochondrial elongation factor MiD51 has been proposed to act as an anchor that recruits Drp1 from the cytosol to the outer mitochondrial membrane. Whether MiD51 promotes mitochondrial fusion by inactivation of Drp1 is a controversial issue.

Cytosolic and mitochondrial Ca concentrations in primary hepatocytes change with ageing and in consequence of an mtDNA mutation.

Mitochondrial Ca flux is crucial for the regulation of cell metabolism. Ca entry to the mitochondrial matrix is mediated by VDAC1 and MCU with its regulatory molecules. We investigated hepatocytes isolated from conplastic C57BL/6NTac-mt mice (mtNOD) that differ from C57BL/6NTac mice (controls) by a point mutation in mitochondrial-encoded subunit 3 of cytochrome c oxidase, resulting in functional and morphological mitochondrial adaptations.

6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase and small chemical activators affect enzyme activity of activating glucokinase mutants by distinct mechanisms.

Glucokinase (GK), a monomeric glucose-phosphorylating enzyme characterised by high structural flexibility, acts as a glucose sensor in pancreatic beta cells and liver. Pharmaceutical efforts to control the enzyme are hampered by an incomplete understanding of GK regulation. We investigated GK characteristics of wild-type and activating S64Y and G68V mutant proteins in the presence of various combinations of the synthetic activators RO-28-1675 and compound A, the endogenous activator fructose-2,6-bisphosphatase (FBPase-2), and the inhibitor mannoheptulose.

Mitochondrial complex IV mutation increases reactive oxygen species production and reduces lifespan in aged mice.

Aim: Mitochondrial DNA (mtDNA) mutations can negatively influence lifespan and organ function. More than 250 pathogenic mtDNA mutations are known, often involving neurological symptoms. Major neurodegenerative diseases share key etiopathogenetic components ie mtDNA mutations, mitochondrial dysfunction and oxidative stress.

An mtDNA mutation accelerates liver aging by interfering with the ROS response and mitochondrial life cycle.

Mitochondrial dysfunction affects liver metabolism, but it remains unclear whether this interferes with normal liver aging. We investigated several mitochondrial pathways in hepatocytes and liver tissue from a conplastic mouse strain compared with the control C57BL/6NTac strain over 18 months of life. The C57BL/6NTac-mtNODLtJ mice differed from C57BL/6NTac mice by a point mutation in mitochondrial-encoded subunit 3 of cytochrome c oxidase.

Polymorphism in Murine mtATP8 Gene Correlates with Decreased Reactive Oxygen Species in Aging Hematopoietic Cells.

Background: Mitochondrial DNA (mtDNA) encodes for the respiratory chain proteins. Genetic alterations in mtDNA have been described during aging and linked to impaired hematopoiesis.

Materials And Methods: We investigated two novel conplastic mouse strains harboring a mitochondrial nt7778 G/T polymorphism leading to an amino acid exchange in respiratory chain complex V.

Polymorphisms of the murine mitochondrial ND4, CYTB and COX3 genes impact hematopoiesis during aging.

During aging, mitochondrial DNA (mtDNA) can accumulate mutations leading to increasing levels of reactive oxygen species (ROS). Increased ROS were described to activate formerly quiescent hematopoietic stem cells (HSC). Mutations in mtDNA were shown to enhance the risk for myelodysplastic syndrome and leukemia.

Early detection of diabetic neuropathy by investigating CNFL and IENFD in thy1-YFP mice.

Small fiber neuropathy is one of the most common and painful long-term complications of diabetes mellitus. Examination of the sub-basal corneal nerve plexus is a promising surrogate marker of diabetic neuropathy. To investigate the efficacy, reliability and reproducibility of in vivo corneal confocal microscopy (IVCCM), we used thy1-YFP mice, which express yellow fluorescence protein (YFP) in nerve fibers.

Precise expression of Fis1 is important for glucose responsiveness of beta cells.

Mitochondrial network functionality is vital for glucose-stimulated insulin secretion in pancreatic beta cells. Altered mitochondrial dynamics in pancreatic beta cells are thought to trigger the development of type 2 diabetes mellitus. Fission protein 1 (Fis1) might be a key player in this process.

Drp1 guarding of the mitochondrial network is important for glucose-stimulated insulin secretion in pancreatic beta cells.

Mitochondria form a tubular network in mammalian cells, and the mitochondrial life cycle is determined by fission, fusion and autophagy. Dynamin-related protein 1 (Drp1) has a pivotal role in these processes because it alone is able to constrict mitochondria. However, the regulation and function of Drp1 have been shown to vary between cell types.

Mitochondrial network regulation and its potential interference with inflammatory signals in pancreatic beta cells.

Mitochondria fulfil multiple tasks in nutrient metabolism, energy production, redox homeostasis and stress response, and are essential for pancreatic beta cell function. The dynamism and health of the mitochondrial network is regulated by fission- and fusion-triggering factors and by a quality control system that removes dysfunctional organelles. Alongside the role of mitochondria in regulating apoptotic cell death mediated primarily via production of reactive oxygen species and release of cytochrome c, there is evidence of other links between mitochondria and inflammation that have implications for cell viability.

In vivo nonlinear imaging of corneal structures with special focus on BALB/c and streptozotocin-diabetic Thy1-YFP mice.

Two-photon microscopy (TPM) allows high contrast imaging at a subcellular resolution scale. In this work, the microscopy technique was applied to visualize corneal structures in two mouse models (BALB/c and B6.Cg-Tg(Thy1-YFP)16Jrs/J) in vivo.

Age-Related Changes in Murine Corneal Nerves.

Purpose: The aim of this study is to determine age-related morphological changes in the corneal subbasal nerve plexus (SNP) in two inbred mouse strains.

Materials And Methods: The corneal SNP was investigated by in vivo confocal laser scanning microscopy (CLSM) in 0.5-, 1-, 1.

Characterization of two MODY2 mutations with different susceptibility to activation.

Glucokinase plays a key role in glucose sensing in pancreatic beta cells and in liver metabolism. Heterozygous inactivating glucokinase mutations cause the autosomal dominantly inherited MODY2 subtype of maturity-onset diabetes of the young. The goal of this study was to elucidate the pathogenicity of the recently described glucokinase mutants L304P and L315H, located in an alpha-helix and connecting region, respectively, at the outer region of the large domain of glucokinase.

Reduced adolescent-age spatial learning ability associated with elevated juvenile-age superoxide levels in complex I mouse mutants.

Large-scale, heteroplasmic and generally pathogenic mtDNA defects (as induced by defective mitochondrial DNA polymerase, clonal mutations or DNA deletions) are known to negatively impact on life span and can result in apoptosis and tissue loss in, e.g., skeletal muscle or reduce learning abilities.

Diabetic foot syndrome and corneal subbasal nerve plexus changes in congolese patients with type 2 diabetes.

Background: To study the severity of diabetic neuropathy, diabetic retinopathy and grades of diabetic foot syndrome for correlations with corneal subbasal nerve plexus (SBP) changes in Congolese patients with type 2 diabetes.

Methodology/principal Findings: Twenty-eight type 2 diabetes patients with diabetes-related foot ulceration were recruited in a diabetic care unit in Kinshasa, Democratic Republic of Congo. Corneal SBP was investigated by confocal laser-scanning microscopy to analyse nerve fibre density (NFD) [µm/ µm²], number of branches [n] and number of connectivity points [n].

Systems biology approaches in aging research.

Aging is a systemic process which progressively manifests itself at multiple levels of structural and functional organization from molecular reactions and cell-cell interactions in tissues to the physiology of an entire organ. There is ever increasing data on biomedical relevant network interactions for the aging process at different scales of time and space. To connect the aging process at different structural, temporal and spatial scales, extensive systems biological approaches need to be deployed.

Inheritance of rare functional GCKR variants and their contribution to triglyceride levels in families.

Significant resources have been invested in sequencing studies to investigate the role of rare variants in complex disease etiology. However, the diagnostic interpretation of individual rare variants remains a major challenge, and may require accurate variant functional classification and the collection of large numbers of variant carriers. Utilizing sequence data from 458 individuals with hypertriglyceridemia and 333 controls with normal plasma triglyceride levels, we investigated these issues using GCKR, encoding glucokinase regulatory protein.

Inbred mouse strains reveal biomarkers that are pro-longevity, antilongevity or role switching.

Traditionally, biomarkers of aging are classified as either pro-longevity or antilongevity. Using longitudinal data sets from the large-scale inbred mouse strain study at the Jackson Laboratory Nathan Shock Center, we describe a protocol to identify two kinds of biomarkers: those with prognostic implication for lifespan and those with longitudinal evidence. Our protocol also identifies biomarkers for which, at first sight, there is conflicting evidence.