The Impact of Aging on the Tongue Proteome

The tongue is a highly important, multifunctional, and complex organ in human physiology. It is critical for digestion, speech, immune surveillance, and sensory perception, playing a dynamic role in daily life. Abnormalities in the innervation and/or myofiber integrity of the tongue can have severe pathophysiological effects on swallowing, speaking, chewing and bodily balance. The age-related decrease in skeletal muscle mass and contractile strength, a recognized risk factor for sarcopenia and frailty, also impacts the tongue muscles. This report has examined the tongue proteome and evaluated changes in protein abundance associated with the aging phenotype. Interestingly, the proteomic cataloging of the contractile apparatus of tongue muscle identified myosin heavy chain isoform MyHC-13, which is the superfast type of myosin that is restricted to specialized skeletal muscles such as extraocular and laryngeal muscles. Proteomics revealed that tongue aging is associated with considerable changes in the protein expression pattern. Decreases were identified in membrane repair-associated annexin A isoforms, luminal calcium-binding proteins, contractile proteins, and cytoskeletal elements. Lower levels of fast myosin isoform MyHC-2B suggests potential age-associated fiber type shifting towards slower twitch properties. Elevated levels of the fibrosis marker collagen COL-VI, which increased deposition in aged tongue muscle was verified by immunofluorescence microscopy, agrees with the idea of a higher degree of susceptibility to reactive myofibrosis in sarcopenia of old age.