The Impact of Nutrient Restriction and Metformin Treatment on Genome Structure and Function in Hutchinson-Gilford Progeria Syndrome (HGPS) Fibroblasts
Date
2022-02-23
Authors
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Publisher
ORCID
Type
Thesis
Degree Level
Doctoral
Abstract
Hutchinson-Gilford Progeria Syndrome (HGPS) is a rare disease in which children age at an accelerated rate. Patients suffering from HGPS have a shortened lifespan and succumb to cardiac events at ~14 years of age. At the cellular level, HGPS patient fibroblasts exhibit numerous hallmarks of the disease, including irregular nuclear morphology, hindered DNA damage repair pathways, global loss of gene repression, and mislocalization of chromosomes within the nuclear volume. Combined, these defects increase the rates at which HGPS fibroblasts become old (senescent). These defects are attributed to accumulation of the mutant protein, progerin, resulting from of a single point mutation in the laminA/C gene. Previously, inhibition of the mammalian target of rapamycin (mTOR) pathway via rapamycin induced progerin degradation and improved cellular phenotypes of HGPS; however, this compound has potentially severe side effects. Therefore, other methods of inhibiting mTOR, such as restriction of amino acids, or treatment with the antidiabetic drug metformin, could decrease progerin levels and restore normal genome organization and function in HGPS patient cells.
Using HGPS primary fibroblasts grown in cell culture, this data demonstrates that restriction of amino acids (specifically arginine and leucine) or treatment with the nutrient restriction mimetic metformin decrease progerin levels across patient cell lines. Furthermore, these HGPS fibroblasts also exhibited improved nuclear morphology, increased rates of DNA damage repair and re-localization of chromosome territories. These same conditions also significantly increased survival time of HGPS fibroblasts and non-diseased fibroblasts in culture. Importantly, no changes in nuclear morphology or decreases in cell viability were observed in non-diseased primary fibroblasts. On examining HGPS fibroblasts at 5 weeks of arginine and leucine restriction or metformin treatment, molecular pathways associated with HGPS disease progression (including (class A/1 (rhodopsin-like receptors) viral protein interaction with cytokine and cytokine receptor, and transforming growth factor (TGF)- signalling) were down-regulated. Analyses also identified pathways, such as PLK1 signalling events, that may be associated with the health and lifespan extending properties of these treatments independent of ameliorating HGPS phenotypes. These findings indicate that amino acid restriction or treatments with nutrient restriction mimetics such as metformin, could supply potential therapeutic options for HGPS patients.
Description
Keywords
Hutchinson-Gilford Progeria Syndrome, Amino Acid Restriction, Leucine, Arginine, Transcriptome, Genome Function, Genome Organization, Metformin
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Biochemistry
Program
Biochemistry