Abstract
Excessive glucocorticoids (GC) may lead to the aggravation of several basic diseases including myopia, due to plasma hormone imbalances associated with the hypothalamic–pituitary–adrenal axis (HPAA). Electroacupuncture (EA) is an effective therapeutic method to treat many diseases, although it remains unclear whether EA at acupoints on the foot or back would be effective in treating eye diseases. It was recently found that visual cortex activity for responses to visual stimuli with spatial frequency and resting-state functional connectivity (FC) between the supramarginal gyrus and rostrolateral prefrontal cortex was significantly reduced in patients with high myopia. The present study aims to investigate the role of the alternation of resting-state FC among the bilateral visual cortex and hypothalamus in exerting anti-myopia effects of EA in GC-enhanced lens-induced myopic (LIM) guinea pigs such that the mechanisms of EA to treat GC-enhanced myopia at Shenshu (BL23) acupoints can be probed. To confirm the effects of EA, ocular parameters including axial length and GC-associated physiological parameters such as animal appearance, behavior, bodyweight, and levels of four HPAA-associated plasma hormones [free triiodothyronine (FT3), free thyroxine (FT4), estradiol (E2), and testosterone (T)] were also collected. Increased resting-state FC between the left and right visual cortex was detected in GC-enhanced lens-induced myopic guinea pigs with EA at BL23 acupoints (LIM+GC+EA) guinea pigs compared to GC-enhanced lens-induced myopic guinea pigs with EA at sham acupoints (LIM+GC+Sham) guinea pigs, as well as suppressed myopia and recovery of symptoms initially caused by overdose of GC. Recovered symptoms included improved animal appearance, behavior, bodyweight, and HPAA-associated plasma hormone levels were observed after 4 weeks of EA treatment. In contrast, the LIM+GC+Sham group showed decreased FC with elongation of axial length for myopization as compared to the control group and LIM group and exhibited a deterioration in physiological parameters including reduced body weight and balance disruption in the four measured HPAA-associated plasma hormones. Our findings suggest that EA could effectively treat GC-enhanced myopia by increasing resting-state FC between the left and right visual cortices, which may be pivotal to further understanding the application and mechanisms of EA in treating GC-enhanced myopia.
Highlights
High myopia is a major public health concern, often accompanied by several severe comorbidities, including retinal detachment, cataracts, and glaucoma due to the elongation of axial length (Rudnicka et al, 2016; Morgan et al, 2018)
After 4 weeks of EA treatment, the LIM+GC+EA group showed significantly increased body weight compared to the LIM+GC+Sham group, suggesting the GC-induced symptoms were ameliorated by EA (Figures 2A,B)
Results from the analyses showed a positive association between functional connectivity (FC) of the visual cortex and bodyweight, FT3 and T, whereas a negative association was found between FC of the visual cortex and E2 or axial length (Figure 5)
Summary
High myopia is a major public health concern, often accompanied by several severe comorbidities, including retinal detachment, cataracts, and glaucoma due to the elongation of axial length (Rudnicka et al, 2016; Morgan et al, 2018). Excessive myopic axial length elongation and increased risk of irreversible visual impairment have been found in experimental lens-induced myopia after intraperitoneal injection of the glucocorticoids (GC) (Ding et al, 2018). Previous studies reported that visual cortex activity for responses to visual stimuli with spatial frequency, and resting-state FC between the supramarginal gyrus and the rostrolateral prefrontal cortex, was significantly reduced in highmyopia patients (Zhai et al, 2016; Mirzajani et al, 2017). The role of resting-state FC between the left and right visual cortex on the treatment of high myopia has not yet been explored
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