The improvement in corneal nerve regeneration was seen in the increase of the corneal nerve fibre length (CNFL), corneal nerve fibre density (CNFD), and corneal nerve branch density (CNBD) – all of which will decrease in size in type I diabetes patients due to diabetic sensorimotor polyneuropathy (DSP).
DSP affects about 50 per cent of diabetic patients and develops due to chronic hyperglycaemic exposure. Early-stage DSP is associated with the loss of small sensory nerve fibres in the cornea.
In type I diabetes patients, the change in CNFL is estimated to be a loss of 0.8 per cent per year.
At the moment, intensive glycaemic control is the only established method for slowing the progression of DSP in patients with type I diabetes.
However, a group of researchers from Australia and New Zealand pointed out that omega-3 polyunsaturated fatty acids (PUFAs) supplementation or intake from daily diet could be a promising intervention.
Writing in Diabetes, the researchers from Australia and New Zealand said this could be because of the anti-inflammatory and neuroprotective properties of lipid metabolites, resolvins, and protectins.
They conducted a trial involving 43 type I diabetes patients.
The patients were randomised to receive either an omega-3 supplement consisting of 1,080 mg of EPA and 720 mg of DHA or the placebo, which consists of 600mg of olive oil for 180 days.
The intervention product used was Caruso’s Natural Health Triple Strength fish oil concentrate capsules.
The study was conducted between July 2017 and September 2019.
Corneal nerve regeneration improvements
By the end of this study, the intervention group saw significant improvement in their corneal nerve regeneration as compared to the placebo group, with an increase in their CNFL, CNBD, and CNFD values.
In contrast, the placebo group recorded a drop in all three parameters.
For example, CNFL in the intervention group increased from 11.49mm/mm2 at baseline to 13.55 mm/mm2 at day 180.
However, CNFL in the placebo group dropped from 12.38mm/mm2 at baseline to 11.41mm/mm2 at day 180.
At day 180, the estimated increase in CNFL in the intervention group, compared to the placebo, was 2.70 mm/mm2.
On the other hand, the estimated increase in CNFD and CNBD in the intervention group was 4.98 nerves/mm2 and 11.23 branches/mm2 respectively when compared to the placebo.
However, there was not much differences between the two groups in terms of habitual visual acuity, intraocular pressure, blood chemistry parameters or diabetic retinopathy grading.
The researchers said the findings were consistent with results from a previous rodent study, where oral omega-3 supplementation could reverse CNFL loss and corneal sensitivity impairment.
Another study showed that supplementation of 1,500 mg of omega-3 daily for three months had significantly increased corneal nerve density when compared to the placebo group.
The improvement in corneal nerve regeneration was also accompanied by a higher omega-3 index in the intervention group.
Omega-3 index in the intervention group increased from 4.9 per cent at baseline to 8.2 per cent at day 180.
As for the placebo group, the participants’ omega-3 index was similar during the start (4.6 per cent) and the end of the study (4.8 per cent).
Investigating the neuroprotective effect of oral omega-3 fatty acid supplementation in type I diabetes (Nproofs1): a randomised, placebo-controlled trial
Authors: Laura E Downie, et al