Association of hepatic steatosis with subclinical cardiac dysfunction in asymptomatic people with type 2 diabetes

Introduction

Non-alcoholic fatty liver disease is highly prevalent among people with type 2 diabetes (T2D) and is an emerging risk factor for heart failure with preserved ejection fraction (HFpEF). Whether excess liver adiposity is simply a marker of the coexisting adverse cardiometabolic risk profile or independently contributes to the development of HFpEF is unclear.

Purpose

To assess the association between liver fat fraction and subclinical cardiac dysfunction in adults with T2D.

Methods

Prospective cross-sectional study. Two-hundred and thirty-eight adults with T2D (mean age 63±7 years, 62% males, HbA1c 7.2±1.5%, diabetes duration 10±8 years) with no signs, symptoms, or evidence of cardiovascular disease and 40 age-, sex-, and ethnicity-matched non-diabetic controls (mean age 61±8 years, 63% males, HbA1c 5.2±1.2%) underwent comprehensive phenotyping with echocardiography and multiparametric cardiac MRI including adenosine stress and rest perfusion. Volumetric liver fat fraction (VLFF) was measured using a histologically validated, proprietary MRI technique blinded to all participant details. Inter-study reproducibility was assessed in participants (n=28) who underwent a repeat MRI within two weeks. Linear regression analysis was performed to assess any independent associations between VLFF and identified markers of subclinical cardiac dysfunction in subjects with T2D.

Results

People with T2D had evidence of concentric left ventricular (LV) remodelling (higher LV mass/volume), extracellular matrix expansion (higher ECV fraction), both systolic and diastolic dysfunction (lower global longitudinal systolic strain and E/A ratio, respectively), and coronary microvascular dysfunction (lower myocardial perfusion reserve) (Table 1). VLFF demonstrated excellent inter-study reproducibility with an intra-class correlation coefficient (ICC) of 0.988 (0.974–0.994). T2Ds had higher VLFF compared to controls [7.5 (3.8–13.7)% vs 2.9 (1.7–4.7)%, p<0.001]. In multivariable regression analysis adjusting for age, sex, ethnicity, body mass index, ambulatory systolic blood pressure, HbA1c, and low-density lipoprotein, VLFF (β=−0.161, p=0.027) was independently associated with E/A, but not other imaging measures of subclinical cardiac dysfunction.

Conclusion

Liver fat fraction is elevated in people with T2D and is independently associated with early LV diastolic dysfunction. These results add to the growing evidence that ectopic fat plays an important role in the pathogenesis of HFpEF and may be a potential target for intervention.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): National Institute for Health Research (NIHR) United Kingdom through a Research Professorship award (RP-2017-08-ST2-007).British Heart Foundation through a Clinical Research Training Fellowship (FS/16/47/32190).

Brain iron accumulation affects myelin-related molecular systems implicated in a rare neurogenetic disease family with neuropsychiatric features

The 'neurodegeneration with brain iron accumulation' (NBIA) disease family entails movement or cognitive impairment, often with psychiatric features. To understand how iron loading affects the brain, we studied mice with disruption of two iron regulatory genes, hemochromatosis (Hfe) and transferrin receptor 2 (Tfr2). Inductively coupled plasma atomic emission spectroscopy demonstrated increased iron in the Hfe^-/- × Tfr2^mut brain (P=0.002, n ≥5/group), primarily localized by Perls' staining to myelinated structures. Western immunoblotting showed increases of the iron storage protein ferritin light polypeptide and microarray and real-time reverse transcription-PCR revealed decreased transcript levels (P<0.04, n ≥5/group) for five other NBIA genes, phospholipase A2 group VI, fatty acid 2-hydroxylase, ceruloplasmin, chromosome 19 open reading frame 12 and ATPase type 13A2. Apart from the ferroxidase ceruloplasmin, all are involved in myelin homeostasis; 16 other myelin-related genes also showed reduced expression (P<0.05), although gross myelin structure and integrity appear unaffected (P>0.05). Overlap (P<0.0001) of differentially expressed genes in Hfe^-/- × Tfr2^mut brain with human gene co-expression networks suggests iron loading influences expression of NBIA-related and myelin-related genes co-expressed in normal human basal ganglia. There was overlap (P<0.0001) of genes differentially expressed in Hfe^-/- × Tfr2^mut brain and post-mortem NBIA basal ganglia. Hfe^-/- × Tfr2^mut mice were hyperactive (P<0.0112) without apparent cognitive impairment by IntelliCage testing (P>0.05). These results implicate myelin-related systems involved in NBIA neuropathogenesis in early responses to iron loading. This may contribute to behavioral symptoms in NBIA and hemochromatosis and is relevant to patients with abnormal iron status and psychiatric disorders involving myelin abnormalities or resistant to conventional treatments.

Brain transcriptome perturbations in the transferrin receptor 2 mutant mouse support the case for brain changes in iron loading disorders, including effects relating to long-term depression and long-term potentiation

Iron abnormalities within the brain are associated with several rare but severe neurodegenerative conditions. There is growing evidence that more common systemic iron loading disorders such as hemochromatosis can also have important effects on the brain. To identify features that are common across different forms of hemochromatosis, we used microarray and real-time reverse transcription polymerase chain reaction (RT-PCR) to assess brain transcriptome profiles of transferrin receptor 2 mutant mice (Tfr2(mut)), a model of a rare type of hereditary hemochromatosis, relative to wildtype control mice. The results were compared with our previous findings in dietary iron-supplemented wildtype mice and Hfe(-/-) mice, a model of a common type of hereditary hemochromatosis. For transcripts showing significant changes relative to controls across all three models, there was perfect (100%) directional concordance (i.e. transcripts were increased in all models or decreased in all models). Comparison of the two models of hereditary hemochromatosis, which showed more pronounced changes than the dietary iron-supplemented mice, revealed numerous common molecular effects. Pathway analyses highlighted changes for genes relating to long-term depression (6.8-fold enrichment, p=5.4×10(-7)) and, to a lesser extent, long-term potentiation (3.7-fold enrichment, p=0.01), with generalized reductions in transcription of key genes from these pathways, which are involved in modulating synaptic strength and efficacy and are essential for memory and learning. The agreement across the models suggests the findings are robust and strengthens previous evidence that iron loading disorders affect the brain. Perturbations of brain phenomena such as long-term depression and long-term potentiation might partly explain neurologic symptoms reported for some hemochromatosis patients.

Quantitative MR imaging R2 relaxometry in elderly participants reporting memory loss

BACKGROUND AND PURPOSE

In Alzheimer disease (AD), elevated brain iron concentrations in gray matter suggest a disruption in iron homeostasis, while demyelination processes in white matter increase the water content. Our aim was to assess whether the transverse proton relaxation rate, or R2, an MR imaging parameter affected by changes in brain iron concentration and water content, was different in elderly participants with mild to severe levels of cognitive impairment compared with healthy controls.

METHODS

Twelve elderly participants reporting memory problems and 11 healthy volunteers underwent single-spin-echo MR imaging in a 1.5T scanner, with subsequent neuropsychological testing. R2 data were collected from 14 brain regions in cortical and subcortical gray and white matter. Those with memory complaints were separated into 2 further subgroups: MC1 (no objective cognitive impairment) and MC2 (mild to severe objective cognitive impairment).

RESULTS

Mean brain R2 values from the 11 controls correlated strongly (r = 0.94, P < .0001) with reference brain iron concentrations for healthy adults. R2 values in the MC1 and MC2 subgroups were significantly higher in the right temporal cortex and significantly lower in the left internal capsule, compared with healthy controls. R2 values in the MC2 subgroup were significantly lower in the left temporal and frontal white matter, compared with healthy controls.

CONCLUSIONS

R2 differences between both subgroups and the healthy controls suggest iron has increased in the temporal cortex, and myelin has been lost from several white matter regions in those with memory complaints, consistent with incipient AD pathogenesis and biochemical data.

A further family with congenital renal proximal tubular dysgenesis

A new syndrome of oligohydramnios, Potter's syndrome, and anuric renal failure leading to stillbirth or neonatal death from respiratory failure has recently been described. Histologically, there is renal tubular dysgenesis, especially of the proximal tubules, and apparent glomerular crowding. To date, five families have been reported, in four of which there have been affected sibs and in two parental consanguinity. The disorder is, therefore, thought to be inherited in an autosomal recessive manner.

Abdominal actinomycosis. Complication of laparoscopy? Case report

A 26 year old woman who had had an intrauterine contraceptive device had an abdominal mass due to actinomycosis excised three months after routine laparoscopy. The aetiology and possible association with laparoscopy is discussed.