Doses of testosterone might prevent a key brain abnormality associated with Alzheimer鈥檚 disease, say US researchers. Their work in rats suggests that older women as well as men should be given testosterone to help prevent or treat the disease, they say.
Sozos Papasozomenos and Alikunju Shanavas at the University of Texas-Houston Medical School first induced a process called tau hyperphosphorylation in female rats. In people, this chemical over-reaction can create so-called tau tangles 鈥� bundles of tau protein. These bundles, along with plaques of beta amyloid protein, are a key characteristic of the brains of patients with Alzheimer鈥檚 disease.
Papasozomenos and Shanavas found that safe doses of testosterone prevented tau hyperphosphrylation in the rats by blocking the action of an enzyme involved in the process. Oestrogen in combination with testosterone 鈥� but not oestrogen alone 鈥� had the same effect.
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鈥淭he hyperphosphorylation of tau was completely abolished,鈥� Papasozomenos says.
Risk factors
As many men age, their testosterone levels gradually fall. And previous research has shown that men with lower than normal testosterone levels have higher levels of beta amyloid protein in their blood.
Other data suggests that post-menopausal women given hormone replacement therapy 鈥� containing oestrogen 鈥� have a much lower risk of developing Alzheimer鈥檚 disease.
The exact interplay of sex hormones and Alzheimer鈥檚 risk factors remains unclear. But the new work suggests that maintaining normal levels of testosterone in ageing men, and adding testosterone to oestrogen supplements for postmenopausal women, could help reduce their risk of developing the disease, say the Texas researchers.
Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.032646799)