Bariatric surgery restores visual cortical plasticity in nondiabetic subjects with obesity

Abstract

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Effect of fasting on short‐term visual plasticity in adult humans

“…Coherently, we found that raising fasting GLP‐1 levels through direct infusion did not modify the plasticity levels, which remained undistinguishable from those recorded under fasting—although variability in the supraphysiological concentrations of active GLP‐1 achieved upon GLP‐1 infusion did associate with inter‐individual variability in short‐term plasticity (Figure 4b), providing a possible explanation for the lack of correlation between plasticity effects in the GLP‐1 infusion condition and the other two conditions (Figure 3d). The GLP‐1 levels reached upon infusion in the present study were in the same order of magnitude as in Daniele et al (2021). However, in this case, the GLP‐1 increase was only produced acutely during the short‐term monocular deprivation.…”

“…By measuring the ocular dominance shift that follows 2‐h monocular deprivation, we found that short‐term ocular dominance plasticity was reduced after overnight fasting compared to after a standardised meal. This modulation of ocular dominance suggests that hormonal and/or metabolic factors can exert an acute modulation of homeostatic plasticity, which is sufficiently rapid to manifest itself over the 2 hours of our protocol—similar to the acute effects of other non‐visual factors, such as physical exercise (Lunghi & Sale, 2015; Lunghi, Sframeli, et al, 2019; but see Finn et al, 2019; Virathone et al, 2021) and pharmacologic manipulations (Sheynin et al, 2019), and in stark contrast with the chronic effects of obesity and bariatric surgery (Daniele et al, 2021; Lunghi, Daniele, et al, 2019).…”

“…Both insulin and GLP‐1 have well‐documented effects in the central nervous system (Alvarez et al, 2005; Schulingkamp et al, 2000). The increase in the circulating levels of GLP‐1 has been suggested to contribute to the increase of ocular dominance plasticity following bariatric surgery (Daniele et al, 2021). Nonetheless, in the non‐obese individuals enrolled in the present study, we found no correlation between plasticity effects and any of these key players in glucose homeostasis.…”

“…Recent evidence suggests that shorter deprivation durations may be sufficient to induce a plasticity effect (Min et al, 2018). However, we chose to maintain the 2‐h deprivation schedule because it has been used in previous studies on obesity and bariatric surgery (Daniele et al, 2021; Lunghi, Daniele, et al, 2019), allowing direct comparison. As in those studies, the eye patch was made of a translucent plastic material that allowed light to reach the retina (attenuation 15%) but completely prevented pattern vision (Figure 1a).…”

“…Metabolic abnormalities and obesity are associated with impaired cognitive performance and learning ability (Tanaka et al, 2020). We recently showed that, in obese individuals, this impairment extends to an aspect of sensory processing: short‐term ocular dominance plasticity (Daniele et al, 2021; Lunghi, Daniele, et al, 2019). This is measured in adult humans, by transiently applying a translucent patch over one eye, that is, monocular deprivation.…”