Muscular carnosine is a marker for cardiorespiratory fitness and cardiometabolic risk factors in men with type 1 diabetes

Purpose Muscle is an essential organ for glucose metabolism and can be influenced by metabolic disorders and physical activity. Elevated muscle carnosine levels have been associated with insulin resistance and cardiometabolic risk factors. Little is known about muscle carnosine in type 1 diabetes (T1D) and how it is influenced by physical activity. The aim of this study was to characterize muscle carnosine in vivo by proton magnetic resonance spectroscopy ( 1 H MRS) and evaluate the relationship with physical activity, clinical characteristics and lipoprotein subfractions. Methods 16 men with T1D (10 athletes/6 sedentary) and 14 controls without diabetes (9/5) were included. Body composition by DXA, cardiorespiratory capacity ( V O 2 peak) and serum lipoprotein profile by proton nuclear magnetic resonance ( 1 H NMR) were obtained. Muscle carnosine scaled to water (carnosine W ) and to creatine (carnosine CR ), creatine and intramyocellular lipids (IMCL) were quantified in vivo using 1 H MRS in a 3T MR scanner in soleus muscle. Results Subjects with T1D presented higher carnosine CR levels compared to controls. T1D patients with a lower V O 2 peak presented higher carnosine CR levels compared to sedentary controls, but both T1D and control groups presented similar levels of carnosine CR at high V O 2 peak levels. Carnosine W followed the same trend. Integrated correlation networks in T1D demonstrated that carnosine W and carnosine CR were associated with cardiometabolic risk factors including total and abdominal fat, pro-atherogenic lipoproteins (very low-density lipoprotein subfractions), low V O 2 peak, and IMCL. Conclusions Elevated muscle carnosine levels in persons with T1D and their effect on atherogenic lipoproteins can be modulated by physical activity.