10.6 μm laser moxibustion can improve oxidative stress and abnormal energy metabolism in liver of hypothyroidism rats through Nrf2/HO-1 and Nrf2/PGC-1α/TFAM pathways

Hypothyroidism (HypoT) is a systemic hypometabolic disorder characterized by thyroid hormone deficiency and is closely associated with oxidative stress (OS). The hypothalamic-pituitary-thyroid (HPT) axis plays a key role in regulating thyroid hormone secretion and the Nrf2 signaling pathway in alleviating OS. The aim of this study is to investigate whether 10.6 μm laser moxibustion can affect the activation of Nrf2 signaling pathway by HPT axis, reduce OS and thus alleviate liver damage in HypoT model. The far-infrared wavelength peak of 10.6 μm laser moxibustion is close to the infrared radiation spectrum of traditional moxibustion. It functions similarly to moxibustion without causing pain, infection, or irritating smoke. Twenty-four Sprague-Dawley (SD) rats were randomly divided into Con group, HypoT group, LM(laser moxibustion) group, and SLM(sham laser moxibustion) group (n = 6). HypoT was induced in 18 rats by intragastric administration of methimazole (10 mg/kg). Rats in the LM group and SLM group were irradiated at Guanyuan (CV4) and Mingmen (GV4) acupoints for 15 min, once every other day for 14 consecutive days, totaling 7 treatments. Rats in the Con group and HypoT group underwent the same handling and fixation procedures without additional intervention. Rectal temperature, body weight, and acupoint temperature were monitored throughout the study. Serum levels of T4, T3, TSH, TRH, cAMP, and cGMP were detected by enzyme-linked immunosorbent assay (ELISA). liver tissue microstructure was examined by hematoxylin and eosin staining (H&E). The content of adenosine ATP and the activities of CAT, SOD, Na+-K+-ATPase, and GSH-Px in hepatocyte mitochondria were determined by colorimetric method and MDA by ELISA. Western blotting was used to detect the protein expression levels of NRF2, HO-1, PGC-1α, and TFAM in liver. These results indicate that 10.6 μm laser moxibustion may regulate the NRF2 signaling axis through the HPT axis, reduce liver OS and improve the related symptoms of HypoT rats.