The present disclosure relates to alpha-1-microglobulin (A1M) for use in the treatment of a mitochondria-related disease such as respiratory chain disorders, Alpers disease, Barth syndrome, Fridreich&rsquos ataxia, KSS, Leigh 5 Disease or Syndrome, LHON, MELAS, MERRF, MIRAS and NARP, or damage or dysfunction of retina or ocular diseases associated with mitochondrial defect(s) or dysfunction(s).