Effect of Increasing Age on Brain Dysfunction in Cirrhosis

Abstract

Patients with cirrhosis are growing older, which could have an impact on brain dysfunction beyond hepatic encephalopathy. Our aim was to study the effect of concomitant aging and cirrhosis on brain inflammation and degeneration using human and animal experiments. For the human study, age-matched patients with cirrhosis and controls between 65 and 85 years underwent cognitive testing, quality of life (QOL) assessment, and brain magnetic resonance (MR) spectroscopy and resting state functional MR imaging (rs-fMRI) analysis. Data were compared between groups. For the animal study, young (10-12 weeks) and old (1.5 years) C57BL/6 mice were given either CCl₄ gavage to develop cirrhosis or a vehicle control and were followed for 12 weeks. Cortical messenger RNA (mRNA) expression of inflammatory mediators (interleukin [IL]-6, IL-1β, transforming growth factor β [TGF-β], and monocyte chemoattractant protein 1), sirtuin-1, and gamma-aminobutyric acid (GABA)-ergic synaptic plasticity (neuroligin-2 [NLG2], discs large homolog 4 [DLG4], GABA receptor, subunit gamma 1/subunit B1 [GABRG1/B1]) were analyzed and compared between younger/older control and cirrhotic mice. The human study included 46 subjects (23/group). Patients with cirrhosis had worse QOL and cognition. On MR spectroscopy, patients with cirrhosis had worse changes related to ammonia and lower N-acetyl aspartate, whereas rs-fMRI analysis revealed that these patients demonstrated functional connectivity changes in the frontoparietal cortical region compared to controls. Results of the animal study showed that older mice required lower CCl₄ to reach cirrhosis. Older mice, especially with cirrhosis, demonstrated higher cortical inflammatory mRNA expression of IL-6, IL-1β, and TGF-β; higher glial and microglial activation; and lower sirtuin-1 expression compared to younger mice. Older mice also had lower expression of DLG4, an excitatory synaptic organizer, and higher NLG2 and GABRG1/B1 receptor expression, indicating a predominantly inhibitory synaptic organization. Conclusion: Aging modulates brain changes in cirrhosis; this can affect QOL, cognition, and brain connectivity. Cortical inflammation, microglial activation, and altered GABA-ergic synaptic plasticity could be contributory.

Figure 1

MR spectroscopic results. Creatine ratios of the three metabolites in patients with cirrhosis (red bars) and patients without cirrhosis (blue bars) are shown as mean ± SDs. P values of comparisons are displayed, with * indicating significant difference. (A) Glutamate + glutamine, (B) myo‐inositol, and (C) choline. There was a significantly higher glutamate + glutamine and lower myo‐inositol and choline in patients with cirrhosis compared to patients without cirrhosis (controls) at all sites except PGM glutamate + glutamine. Abbreviations: ACC, anterior cingulate cortex; Cirr, cirrhosis; NoCirr, without cirrhosis; PGM, posterior gray matter; RPWM, right parietal white matter.

Figure 2

Resting state network analysis. Significant differences in visual and attentional RSNs in control compared to patients with cirrhosis are shown. On the left, we show group‐level RSNs corresponding to visual and attentional networks. Blue areas on the right correspond to areas of the brain that have greater functional connectivity to visual RSN (top) and attentional RSN (bottom) in controls compared to elderly patients with cirrhosis. None of the RSNs were higher in patients with cirrhosis compared to controls. Scale is Z‐transformed independent component coefficients.

Figure 3

Cortical inflammation and glial/microglial activation. Comparisons among the four mouse groups. All data are presented as median and 95% confidence interval (CI). * indicates significant differences by the Mann‐Whitney test between cirrhotic and noncirrhotic mice in the same age group; # indicates significant differences by the Mann‐Whitney test between cirrhotic mice in different age groups. Abbreviations: OCirr, old cirrhosis; OCtrl, old control; YCirr, young cirrhosis; YCtrl, young control.

Figure 4

ELISA and western blot changes. Comparisons among the four mouse groups. Data presented in the graphs are median and 95% CI. *P < 0.05, **P < 0.01, ***P < 0.001 indicate significant differences by the Mann‐Whitney or Kruskal‐Wallis test. Abbreviations: Cirr, cirrhosis; Ctrl, control; S1RT1, sirtuin‐1.

Figure 5

Cortical synaptic plasticity and GABA receptor expression. Comparisons among the four mouse groups. All data are presented as median and 95% CI. * indicates significant differences by the Mann‐Whitney test between cirrhotic and noncirrhotic mice in the same age group; # indicates significant differences by the Mann‐Whitney test between cirrhotic mice in different age groups. Abbreviations: OCirr, old cirrhosis; OCtrl, old control; YCirr, young cirrhosis; YCtrl, young control.