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Background Due to the emergence of COVID-19, many countries have started mass immunization programs. To date, no cases of optic neuritis following COVID-19 vaccination have been reported in the literature. Case presentation Objective: Here, we report 2 cases of unilateral optic neuritis after vaccination against COVID-19 using the Sinopharm vaccine (Sinopharm Group Co. Ltd, China). Design The clinical history, examination, and test findings of two individuals with unilateral optic neuritis associated with the timing of COVID-19 vaccination were described and further analyzed. Setting Two patients developed optic neuritis after receiving the COVID-19 vaccine. One patient developed optic neuritis 6 weeks after the first dose and 3 weeks after the second dose. The other patient developed optic neuritis 3 weeks after the first dose. Participants: Two female patients, aged 21 and 39 years. Result The patients were successfully treated with intravenous methylprednisolone pulse therapy. Both patients had typical manifestations of optic neuritis and their visual acuity recovered fully after treatment. The second of these patients was positive for anti-myelin oligodendrocyte glycoprotein antibodies (MOG). Conclusion Optic neuritis is a potential adverse effect after vaccination against the coronavirus disease (COVID-19). Supplementary Information The online version contains supplementary material available at 10.1007/s10633-022-09880-0.

It is widely reported how betaine addition regulates lipid metabolism but how betaine affects cholesterol metabolism is still unknown. This study aimed to investigate the role of betaine in hepatic cholesterol metabolism of Sprague-Dawley rats. Rats were randomly allocated to four groups and fed with a basal diet or a high-fat diet with or without 1% betaine. The experiment lasted 28 days. The results showed that dietary betaine supplementation reduced the feed intake of rats with final weight unchanged. Serum low-density-lipoprotein cholesterol was increased with the high-fat diet. The high-fat diet promoted cholesterol synthesis and excretion by enhancing the HMG-CoA reductase and ABCG5/G8, respectively, which lead to a balance of hepatic cholesterol. Rats in betaine groups showed a higher level of hepatic total cholesterol. Dietary betaine addition enhanced cholesterol synthesis as well as conversion of bile acid from cholesterol by increasing the levels of HMGCR and CYP7A1. The high-fat diet decreased the level of bile salt export pump, while dietary betaine addition inhibited this decrease and promoted bile acid efflux and increased total bile acid levels in the intestine. In summary, dietary betaine addition promoted hepatic cholesterol metabolism, including cholesterol synthesis, conversion of bile acids, and bile acid export.

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