Date of Award

10-1-2021

Publication Type

Thesis

Degree Name

M.H.K.

Department

Kinesiology

Keywords

Ceramide, Ceramide-1-phosphate, Diabetic myopathy, Skeletal muscle, Sphingolipid, Type 1 diabetes mellitus

Supervisor

M. Krause

Supervisor

A. Bain

Rights

info:eu-repo/semantics/embargoedAccess

Abstract

Type 1 Diabetes Mellitus (T1DM) is an autoimmune disease that destroys the pancreatic β-cells. Poor skeletal muscle regeneration and atrophy are associated with T1DM, termed diabetic myopathy, which includes an accumulation of muscle lipids. Sphingolipids are a class of lipids that display powerful cellular effects and are implicated in roles in skeletal muscle regeneration and diabetic myopathy. However, sphingolipids have yet to be quantified in regenerating skeletal muscle of animal models of T1DM. This project aimed to examine the sphingolipid profile of wild type (WT) and Ins2Akita+/- (Akita) mice following cardiotoxin(CTX)-induced injury. 22 WT and 20 Akita mice received an injection of CTX in their quadriceps, gastrocnemius-plantaris-soleus complex, and tibialis anterior (TA) muscles. Muscle samples were collected at 1, 3, 5, and 7 days post-injury. TAs of WT and Akita mice were cryosectioned and stained with BODIPY 493/503 to visualize lipids. Total lipids were elevated in the injured Akita mice (p=0.044). Liquid Chromatography-Mass Spectrometry was used to assess sphingolipid content of injured and uninjured quadriceps of both WT and Akita mice. Analysis revealed that C22:0 (p=0.003) and C24:0 (p=0.003) ceramides and ceramide-1-phosphate (C1P; p<0.001), were elevated in the Akita mice, whereas C24:1 (p<0.001) ceramide content was reduced in the Akita mice. Finally, SDS-PAGE and Western blot analysis of the uninjured and injured GPS complexes in WT and Akita mice was done to quantify CerK protein expression. Analysis revealed no statistically significant differences at any time-point post-injury (p>0.05). This represents the first analysis of sphingolipids in regenerating skeletal muscle in a model of T1DM. Quantification of ceramides and C1P revealed significant differences between WT and Akita mice indicating a potential role in diabetic myopathy. Despite increased concentrations of some ceramides and C1P, there were no significant differences in CerK expression, suggesting that an alternative route of ceramide phosphorylation likely exists, however, no candidate mechanism has been identified. Future studies will be needed to examine the role of various sphingolipids in skeletal muscle regeneration and diabetic myopathy.

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