Central to many human health issues is the reduction in tissue oxygen levels (e.g., stroke, cardiac or pulmonary dysfunction, ischemic events and trauma). Organisms, including humans, have evolved various mechanisms to respond to O2 deprivation; such adaptations include physiological, metabolic and molecular changes. Despite the response and rescue efforts within the organism the lack of O2 can damage tissues and ultimately cause death. The metabolic abnormalities associated with type 2 diabetes (T2D) (hyperglycemia, increased free fatty acids, insulin resistance) contribute to microvascular and macrovascular dysfunctions, which in-turn lead to reduced O2 availability and severe health issues (organ dysfunction, tissue damage, blindness and amputations). Given the prevalence of T2D, this is of major human health concern. Studies indicate that vascular dysfunction can lead to an ischemic event (e.g., myocardial, cerebral, limb ischemia) resulting in morbidity and mortality; individuals with T2D have worse recovery when challenged with an ischemic event. Furthermore, human and mammalian studies indicate that altered ceramide lipids in individuals with T2D are key mediators of insulin resistance and linked to ischemic responses. Our overarching objective is to identify how a sugar-supplemented diet independently or in conjunction with altered cellular ceramide species compromises O2 deprivation responses. We propose to use the genetic model system C. elegans to identify the molecular consequences a glucose diet and altered cellular ceramide species has on O2 deprivation sensitivity. Our recent studies reveal that a sugar- supplemented diet induces O2 deprivation sensitivity in wild-type animals, compared to animals fed a standard diet. Additionally, a mutation in a gene that codes for ceramide synthase (hyl-2(tm2031)) increased the sensitivity to O2 deprivation in glucose-fed animals. A transcriptomic approach (RNA-sequencing) was taken to determine the molecular changes induced by a glucose diet and ceramide misregulation. The RNA-sequencing analysis of wild-type and hyl-2(tm2031) animals fed a normal and glucose diet indicates that many cellular processes are likely to be impacted. We are using bioinformatics, cellular and genetic analysis to identify which of the altered cellular processes are relevant to O2 deprivation responses. We hypothesize that a glucose diet and altered cellular ceramide species induce mitochondrial dysfunction and change signaling pathways which compromise O2 deprivation survival. We will test this hypothesis with the following specific aims:
Aim 1 : Identify altered gee expression and signaling pathways in O2 deprivation sensitive animals;
Aim 2 : Identify gene expression changes that compromise O2 deprivation survival;
Aim 3 : Identify genetic suppressors of O2 deprivation sensitivity. Given the conservation in genes and signaling pathways between metazoans, accomplishing these objectives will translate to a greater understanding of molecular changes that occur in individuals with T2D challenged with an ischemic event.
Studies suggest that hyperglycemia will worsen the outcome of an ischemic event for various tissues including the central nervous system. Our overarching objective is to understand how a sugar diet impacts tissues and compromises O2 deprivation survival using the C. elegans model system. Ultimately, this study will contribute toward our broader understanding of the molecular consequences of a high-sugar diet.
| Ladage, Mary L; King, Skylar D; Burks, David J et al. (2016) Glucose or Altered Ceramide Biosynthesis Mediate Oxygen Deprivation Sensitivity Through Novel Pathways Revealed by Transcriptome Analysis in Caenorhabditis elegans. G3 (Bethesda) 6:3149-3160 |
