HNF4α isoforms regulate the circadian balance between carbohydrate and lipid metabolism in the liver

Hepatocyte Nuclear Factor 4α (HNF4α), a master regulator of hepatocyte differentiation, is regulated by two promoters (P1 and P2) which drive the expression of different isoforms. P1-HNF4α is the major isoform in the adult liver while P2-HNF4α is thought to be expressed only in fetal liver and liver cancer. Here, we show that P2-HNF4α is indeed expressed in the normal adult liver at Zeitgeber time (ZT)9 and ZT21. Using exon swap mice that express only P2-HNF4α we show that this isoform orchestrates a distinct transcriptome and metabolome via unique chromatin and protein-protein interactions, including with different clock proteins at different times of the day leading to subtle differences in circadian gene regulation. Furthermore, deletion of the Clock gene alters the circadian oscillation of P2- (but not P1-)HNF4α RNA, revealing a complex feedback loop between the HNF4α isoforms and the hepatic clock. Finally, we demonstrate that while P1-HNF4α drives gluconeogenesis, P2-HNF4α drives ketogenesis and is required for elevated levels of ketone bodies in female mice. Taken together, we propose that the highly conserved two-promoter structure of the Hnf4a gene is an evolutionarily conserved mechanism to maintain the balance between gluconeogenesis and ketogenesis in the liver in a circadian fashion.

Glucocorticoids in myocarditis therapy after COVID-19

 

The aim of the study - to evaluate the efficacy of glucocorticoids (GC) in patients with acute myocarditis (AM) after COVID-19 infection.

Material and methods

We included 60 pts with severe AM and heart failure (HF) with reduced (<40%) left ventricular (LV) ejection fraction (EF) who had COVID-19 infection 1–2 months before the enrollment. According to the results of cardiac magnetic resonance (CMR) included pts had ≥2 Lake Louise criteria for myocarditis. All pts on the background of HF therapy (β-blockers, ACE-inhibitors, MRA antagonists, diuretics) were prescribed GC: 0.25 mg/kg per day methylprednisolone for 3 months, followed by a gradual dose reduction of 1–2 mg per week until complete discontinuation after 6 months. Evaluation before the start of GC therapy and after 6 months included CMR, 2D- and speckle-tracking echocardiography.

Results

After 6 months according to the results of CMR the number of LV segments with inflammatory lesions decreased to (3,58±0,42) from (6,32±0,77) segments in average (p=0,001). This was followed by improvement of LV systolic function: increase of LV EF in average to (43,5±2,6) from (32,2±2,4) % (p=0,003), longitudinal global systolic strain (LGSS) absolute value to (11,3±1,1) from (7,9±0,5) % (p=0,012) and circumferential global systolic strain (CGSS) to (12,1±1,0) from (8,9±0,6) % (p=0,023). Also we observed LV volume reduction: decrease of LV end-diastolic (from 118,9±8,6 to 95,3±7,2 ml/m2, p=0,033) and LV end-systolic (from 80,1±5,1 to 59,1±4,4 ml/m2, p=0,027) volume indexes. Wherein in 24 of 60 pts (41,6%) on the background of significant decrease in the number of LV segments with inflammatory lesions (to 1,34±0,21 from 6,12±0,73 segments, p=0,0001) after 6 months we observed the recovery of LV EF ≥50%, followed by an improvement of LGSS and CGSS on 42,1 and 39,4% respectively (p=0,001). According to multivariate regression analysis, predictors of LV EF recovery (≥50%) after 6 months of GC treatment were established: presence of inflammatory lesions in ≤5,0 LV segments, values of LGSS and CGSS ≥9.0% and ≥9.5% respectively before the start of GC.

Conclusions

The use of GC in pts with severe AM after COVID-19 was followed by the decrease of LV segments number affected by inflammation, improvement of LV systolic function and reduction of LV volume indexes. In 41,6% of pts GC therapy was associated with LV EF recovery after 6 months and predictors of its effectiveness were found: presence of inflammatory lesions in ≤5,0 LV segments, values of LGSS and CGSS ≥9.0% and ≥9.5% respectively before the start of GC.

Funding Acknowledgement

Type of funding sources: None.

SUN-023 HNF4a Isoforms Regulate the Circadian Balance between Carbohydrate and Fatty Acid Metabolism in the Liver

Nuclear receptor genes often contain alternative promoters but the physiological relevance of the different promoters or the proteins they generate is largely unknown. Hepatocyte Nuclear Factor 4α (HNF4α), master regulator of hepatocyte differentiation and the most abundant nuclear receptor in the liver, is regulated by two promoters (P1 and P2). P1-HNF4α, a tumor suppressor, is the major isoform in the adult liver while P2-HNF4α is expressed in fetal liver and liver cancer: a role for P2-HNF4α in normal adult liver has not been identified. Here we show for the first time that P2-HNF4α is expressed at ZT9 and ZT21 in the normal adult liver and use P2-HNF4α-expressing exon swap mice and ‘omics approaches to demonstrate that P2-HNF4α orchestrates a distinct transcriptome and metabolome via unique chromatin and protein-protein interactions. Cytochrome P450 and sex-specific gene expression is impacted as well as carbohydrate and fatty acid metabolism. The exon swap mice exhibit subtle differences in circadian gene regulation and disruption of the clock increases expression of P2-HNF4α. They also exhibit notable differences in carbohydrate versus fatty acid metabolism with P1-HNF4α driving gluconeogenesis and P2-HNF4α driving ketogenesis. Our results also show that P2-HNF4α is required for the elevated levels of ketone bodies in female mice. Taken together, we propose that the highly conserved two-promoter structure in the Hnfa gene is designed, at least in part, to respond to the availability of food resources and maintain the balance between gluconeogenesis and ketogenesis in a circadian and sex-specific fashion. (Funding: NIH NIDDK, West Cost Metabolomics Center, NIEHS T32, USDA NIFA, CCFA, Superfund Research Program)

Preattentive voice discrimination by the human brain as indexed by the mismatch negativity

The goal of the present study was to determine whether the mismatch negativity (MMN), a component of the auditory event-related potential (ERPs) indexing perceptual difference between any two sounds, could be used as an objective measure of speaker discriminability and similarity/dissimilarity. ERPs were recorded in response to natural speech sounds from subjects watching a silent video. The stimuli consisted of a sequence of repetitive 'standard' sounds (the vowel /e/ pronounced by a female voice), which was infrequently interspersed with 'deviant' stimuli; the same /e/vowel pronounced by different speakers (one male and three females). Voice intensity and duration were matched between all the voices used. A separate behavioural discrimination task measured the perceptual distance of each deviant voice from the standard voice through pair-wise dissimilarity ratings. The MMN was elicited by all deviant voices. Furthermore, the dissimilarity ratings on the behavioural task paralleled the preattentive discrimination as indexed by the MMN amplitude. These results suggest that the MMN could be used as an objective measure of voice similarity/dissimilarity, and thus could serve objective speaker recognition.