Loss of CtBP2 may be a mechanistic link between metabolic derangements and progressive impairment of pancreatic β cell function

The adaptive increase in insulin secretion in early stages of obesity serves as a safeguard mechanism to maintain glucose homeostasis that cannot be sustained, and the eventual decompensation of β cells is a key event in the pathogenesis of diabetes. Here we describe a crucial system orchestrated by a transcriptional cofactor CtBP2. In cultured β cells, insulin gene expression is coactivated by CtBP2. Global genomic mapping of CtBP2 binding sites identifies a key interaction between CtBP2 and NEUROD1 through which CtBP2 decompacts chromatin in the insulin gene promoter. CtBP2 expression is diminished in pancreatic islets in multiple mouse models of obesity, as well as human obesity. Pancreatic β cell-specific CtBP2-deficient mice manifest glucose intolerance with impaired insulin secretion. Our transcriptome analysis highlights an essential role of CtBP2 in the maintenance of β cell integrity. This system provides clues to the molecular basis in obesity and may be targetable to develop therapeutic approaches.

Obesity-induced metabolic imbalance allosterically modulates CtBP2 to inhibit PPAR-alpha transcriptional activity

Maintenance of metabolic homeostasis is secured by metabolite-sensing systems, which can be overwhelmed by constant macronutrient surplus in obesity. Not only the uptake processes but also the consumption of energy substrates determine the cellular metabolic burden. We herein describe a novel transcriptional system in this context comprised of peroxisome proliferator-activated receptor alpha (PPARα), a master regulator for fatty acid oxidation, and C-terminal binding protein 2 (CtBP2), a metabolite-sensing transcriptional co-repressor. CtBP2 interacts with PPARα to repress its activity, and the interaction is enhanced upon binding to malonyl-CoA, a metabolic intermediate increased in tissues in obesity and reported to suppress fatty acid oxidation through inhibition of carnitine palmitoyltransferase 1 (CPT1). In line with our preceding observations that CtBP2 adopts a monomeric configuration upon binding to acyl-CoAs, we determined that mutations in CtBP2 that shift the conformational equilibrium toward monomers increase the interaction between CtBP2 and PPARα. In contrast, metabolic manipulations that reduce malonyl-CoA decreased the formation of the CtBP2/PPARα complex. Consistent with these in vitro findings, we found that the CtBP2/PPARα interaction is accelerated in obese livers while genetic deletion of CtBP2 in the liver causes derepression of PPARα target genes. These findings support our model where CtBP2 exists primarily as a monomer in the metabolic milieu of obesity to repress PPARα, representing a liability in metabolic diseases that can be exploited to develop therapeutic approaches.

A case of NASH with genetic predisposition successfully treated with an SGLT2 inhibitor: a possible involvement of mitochondrial dysfunction

Summary

In this study, we herein describe a 47-year-old Japanese woman who manifested inheritable non-alcoholic steatohepatitis (NASH) and severe dyslipidemia. Interestingly, her NASH progression was ameliorated by treatment with a sodium-glucose co-transporter 2 (SGLT2) inhibitor. This inheritability prompted us to comprehensively decode her genomic information using whole-exome sequencing. We found the well-established I148M mutation in PNPLA3 as well as mutations in LGALS3 and PEMT for her NASH. Mutations in GCKR may contribute to both NASH and dyslipidemia. We further mined gene mutations potentially responsible for her manifestations that led to the identification of a novel M188fs mutation in MUL1 that may be causally associated with her mitochondrial dysfunction. Our case may provide some clues to better understand this spectrum of disease as well as the rationale for selecting medications.

Learning points

While the PNPLA3 I148M mutation is well-established, accumulation of other mutations may accelerate susceptibility to non-alcoholic steatohepatitis (NASH). NASH and dyslipidemia may be intertwined biochemically and genetically through several key genes. SGLT2 inhibitors emerge as promising treatment for NASH albeit with interindividual variation in efficacy. Genetic background may explain the mechanisms behind the variation. A novel dysfunctional mutation in MUL1 may lead to metabolic inflexibilities through impaired mitochondrial dynamics and function.

L-Asparaginase-Induced Continuous Hyperglycemia With Type 1 Diabetes-Related Antibodies and HLA Genotypes: A Case Study

A 19-year-old male presented with fatigue and dyspnea on exertion. He was diagnosed with acute T-cell lymphoblastic leukemia. After following the Group for Research on Adult Acute Lymphoblastic Leukemia (GRAALL) 2003 protocol that incorporates L-asparaginase (L-Asp) treatment, blood glucose levels became elevated for more than one year and insulin secretion was depleted. Anti-glutamic acid decarboxylase (GAD) and anti-islet antigen 2 (IA-2) antibody levels were both positive, which is rare. The patient’s HLA genotype was sensitive for type 1 diabetes. L-Asp can cause transient hyperglycemia as a side effect. However, cases with the anti-GAD antibody have not been reported in L-Asp-induced diabetes. In summary, L-Asp-induced continuous hyperglycemia might be associated with a type 1 diabetes-related HLA genotype through elevations of anti-GAD and anti-IA-2 antibodies.

A case of early-onset diabetes with impaired insulin secretion carrying a PAX6 gene Gln135* mutation

Summary

A paired homeodomain transcription factor, PAX6 (paired-box 6), is essential for the development and differentiation of pancreatic endocrine cells as well as ocular cells. Despite the impairment of insulin secretion observed in PAX6-deficient mice, evidence implicating causal association between PAX6 gene mutations and monogenic forms of human diabetes is limited. We herein describe a 33-year-old Japanese woman with congenital aniridia who was referred to our hospital because of her uncontrolled diabetes with elevated hemoglobin A1c (13.1%) and blood glucose (32.5 mmol/L) levels. Our biochemical analysis revealed that her insulin secretory capacity was modestly impaired as represented by decreased 24-h urinary C-peptide levels (38.0 μg/day), primarily explaining her diabetes. Intriguingly, there was a trend toward a reduction in her serum glucagon levels as well. Based on the well-recognized association of PAX6 gene mutations with congenital aniridia, we screened the whole PAX6 coding sequence, leading to an identification of a heterozygous Gln135* mutation. We tested our idea that this mutation may at least in part explain the impaired insulin secretion observed in this patient. In cultured pancreatic β-cells, exogenous expression of the PAX6 Gln135* mutant produced a truncated protein that lacked the transcriptional activity to induce insulin gene expression. Our observation together with preceding reports support the recent attempt to include PAX6 in the growing list of genes causally responsible for monogenic diabetes. In addition, since most cases of congenital aniridia carry PAX6 mutations, we may need to pay more attention to blood glucose levels in these patients.

Learning points

PAX6 Gln135* mutation may be causally associated not only with congenital aniridia but also with diabetes. Blood glucose levels may deserve more attention in cases of congenital aniridia with PAX6 mutations. Our case supports the recent attempt to include PAX6 in the list of MODY genes, and Gln135* may be pathogenic.

Exploratory analysis using machine learning of predictive factors for falls in type 2 diabetes

We aimed to investigate the status of falls and to identify important risk factors for falls in persons with type 2 diabetes (T2D) including the non-elderly. Participants were 316 persons with T2D who were assessed for medical history, laboratory data and physical capabilities during hospitalization and given a questionnaire on falls one year after discharge. Two different statistical models, logistic regression and random forest classifier, were used to identify the important predictors of falls. The response rate to the survey was 72%; of the 226 respondents, there were 129 males and 97 females (median age 62 years). The fall rate during the first year after discharge was 19%. Logistic regression revealed that knee extension strength, fasting C-peptide (F-CPR) level and dorsiflexion strength were independent predictors of falls. The random forest classifier placed grip strength, F-CPR, knee extension strength, dorsiflexion strength and proliferative diabetic retinopathy among the 5 most important variables for falls. Lower extremity muscle weakness, elevated F-CPR levels and reduced grip strength were shown to be important risk factors for falls in T2D. Analysis by random forest can identify new risk factors for falls in addition to logistic regression.

CtBP2 confers protection against oxidative stress through interactions with NRF1 and NRF2

While molecular oxygen is essential for aerobic organisms, its utilization is inseparably connected with generation of oxidative insults. To cope with the detrimental aspects, cells evolved antioxidative defense systems, and insufficient management of the oxidative insults underlies the pathogenesis of a wide range of diseases. A battery of genes for this antioxidative defense are regulated by the transcription factors nuclear factor-erythroid 2-like 1 and 2 (NRF1 and NRF2). While the regulatory steps for the activation of NRFs have been investigated with particular emphasis on nuclear translocation and proteosomal degradation, unknown redundancy may exist considering the indispensable nature of these defense systems. Here we unraveled that C-terminal binding protein 2 (CtBP2), a transcriptional cofactor with redox-sensing capability, is an obligate partner of NRFs. CtBP2 forms transcriptional complexes with NRF1 and NRF2 that is required to promote the expression of antioxidant genes in response to oxidative insults. Our findings illustrate a basis for understanding the transcriptional regulation of antioxidative defense systems that may be exploited therapeutically.

Relationships between Cognitive Function and Odor Identification, Balance Capability, and Muscle Strength in Middle-Aged Persons with and without Type 2 Diabetes

AIM

We investigated the relationship between cognitive function and olfactory and physical functions in middle-aged persons with and without type 2 diabetes (T2D) to examine the potential of olfactory and physical functions as biomarkers for early cognitive impairment.

METHODS

Enrolled were 70 T2D patients (age 40 to <65 y) and 81 age-matched control participants without diabetes. Cognitive function was assessed by the Montreal Cognitive Assessment (MoCA), Trail Making Test parts A and B (TMT-A/-B), Wisconsin Card Sorting Test (WCST), Quick Inventory of Depressive Symptomatology Self-Report (QIDS), and Starkstein Apathy Scale (SAS). Multiple linear regression analyses were performed.

RESULTS

Odor identification was an independent determinant shown in the results of the TMT-A in the entire participant group and was independently associated with the MoCA and TMT-B in the T2D group. Balance capability assessed with a stabilometer was independently associated with all cognitive function tests except for QISD and SAS in the entire participant group and the T2D group and was independently associated with TMT-A in the control group. Knee extension strength was independently associated with the SAS in the entire participant group and the T2D group.

CONCLUSIONS

Odor identification, balance capability, and knee extension strength were potential markers for cognitive decline in middle-aged persons with T2D.

Deciphering genetic signatures by whole exome sequencing in a case of co-prevalence of severe renal hypouricemia and diabetes with impaired insulin secretion

Background

Renal hypouricemia (RHUC) is a hereditary disorder where mutations in SLC22A12 gene and SLC2A9 gene cause RHUC type 1 (RHUC1) and RHUC type 2 (RHUC2), respectively. These genes regulate renal tubular reabsorption of urates while there exist other genes counterbalancing the net excretion of urates including ABCG2 and SLC17A1. Urate metabolism is tightly interconnected with glucose metabolism, and SLC2A9 gene may be involved in insulin secretion from pancreatic β-cells. On the other hand, a myriad of genes are responsible for the impaired insulin secretion independently of urate metabolism.

Case presentation

We describe a 67 year-old Japanese man who manifested severe hypouricemia (0.7 mg/dl (3.8–7.0 mg/dl), 41.6 μmol/l (226–416 μmol/l)) and diabetes with impaired insulin secretion. His high urinary fractional excretion of urate (65.5%) and low urinary C-peptide excretion (25.7 μg/day) were compatible with the diagnosis of RHUC and impaired insulin secretion, respectively. Considering the fact that metabolic pathways regulating urates and glucose are closely interconnected, we attempted to delineate the genetic basis of the hypouricemia and the insulin secretion defect observed in this patient using whole exome sequencing. Intriguingly, we found homozygous Trp258* mutations in SLC22A12 gene causing RHUC1 while concurrent mutations reported to be associated with hyperuricemia were also discovered including ABCG2 (Gln141Lys) and SLC17A1 (Thr269Ile). SLC2A9, that also facilitates glucose transport, has been implicated to enhance insulin secretion, however, the non-synonymous mutations found in SLC2A9 gene of this patient were not dysfunctional variants. Therefore, we embarked on a search for causal mutations for his impaired insulin secretion, resulting in identification of multiple mutations in HNF1A gene (MODY3) as well as other genes that play roles in pancreatic β-cells. Among them, the Leu80fs in the homeobox gene NKX6.1 was an unreported mutation.

Conclusion

We found a case of RHUC1 carrying mutations in SLC22A12 gene accompanied with compensatory mutations associated with hyperuricemia, representing the first report showing coexistence of the mutations with opposed potential to regulate urate concentrations. On the other hand, independent gene mutations may be responsible for his impaired insulin secretion, which contains novel mutations in key genes in the pancreatic β-cell functions that deserve further scrutiny.

P767Survey of palliative sedation at the end-of-life in terminally ill heart failure patients - a five year experience in national cardiovascular center

Background

Palliative sedation is a therapeutic option when symptom relief is difficult to achieve at the end-of-life. However, little is known regarding palliative sedation in terminally ill heart failure (HF) patients.

Purpose

To survey the practice of palliative sedation in terminally ill HF patients at a tertiary referral cardiovascular center, and to investigate the efficacy and safety of sedative agents in HF patients.

Methods

We retrospectively reviewed consecutive patients who were referred to palliative care team at our institution between September 2013 and August 2018. Patients who were hospitalized for HF and died during hospitalization despite optimal medical therapy were selected and defined as terminally ill HF. We investigated the practice of palliative sedation in terminally ill HF patients and analysed the vital signs and sedation scale before starting sedative agents and about 1 hour afterward.

Results

Among 95 terminally ill HF patients, 37 were prescribed palliative sedation at the end-of-life (Picture). Of 37 patients (mean age: 70 years, median B-type natriuretic peptide: 1018 pg/ml, median creatinine: 3.0 mg/dl, intravenous inotrope: 81%), 25 were prescribed dexmedetomidine, and 12 were prescribed midazolam as first agent for sedation. Patient's backgrounds were comparable between the two groups. Richmond Agitation-Sedation Scale was significantly reduced (P<0.01), whereas blood pressure and heart rate were not altered after treatments in both groups. In midazolam group, significant decreases were noted regarding respiratory rate (P=0.01) and oxygen saturation (P=0.02); however, these parameters were not changed in dexmedetomidine group (Table).

Table 1. Vital signs and sedation scale Dexmedetomidine group (n=25) Midazolam group (n=12) Baseline After P value Baseline After P value Richmond Agitation-Sedation Scale 1 (0, 1) −1 (−2, 0) <0.01 1 (0, 1) −2 (−3, −1) <0.01 Vital signs   Systolic blood pressure (mmHg) 90±15 89±16 0.51 89±21 84±23 0.33   Diastolic blood pressure (mmHg) 52±13 54±11 0.34 60±14 56±23 0.48   Heart rate (beats per minute) 95±20 91±22 0.17 90±21 90±19 0.70   Respiratory rate (breaths per minute) 22±5 20±5 0.24 21±5 17±2 0.01   Oxygen saturation (%) 97±3 96±6 0.59 96±5 94±5 0.02

Picture. Study flowchart

Conclusions

Dexmedetomidine and midazolam were commonly used in real-word practice for HF patients at the end-of-life. Although impact on respiratory system differed by treatments, both agents could be prescribed effectively and safely in terminally ill HF patients.

Glucocorticoid receptor suppresses gene expression of Rev-erbα (Nr1d1) through interaction with the CLOCK complex

Glucocorticoids have various medical uses but are accompanied by side effects. The glucocorticoid receptor (GR) has been reported to regulate the clock genes, but the underlying mechanisms are incompletely understood. In this study, we focused on the suppressive effect of the GR on the expression of Rev-erbα (Nr1d1), an important component of the clock regulatory circuits. Here we show that the GR suppresses Rev-erbα expression via the formation of a complex with CLOCK and BMAL1, which binds to the E-boxes in the Nr1d1 promoter. In this GR-CLOCK-BMAL1 complex, the GR does not directly bind to DNA, which is referred to as tethering. These findings provide new insights into the role of the GR in the control of circadian rhythm.

Malondialdehyde-modified LDL-related variables are associated with diabetic kidney disease in type 2 diabetes

BACKGROUND AND AIMS

Oxidized low-density lipoprotein (oxLDL) causes the development of atherosclerosis and kidney injury. Although circulating oxLDL levels were reportedly increased in type 2 diabetic patients with macroalbuminuria, it remains unclear whether albuminuria or the reduced glomerular filtration rate (GFR) is independently associated with the circulating oxLDL level. This study aimed to elucidate the association between the stage of diabetic nephropathy and serum malondialdehyde-modified LDL (MDA-LDL) and the ratio of MDA-LDL to LDL-cholesterol (MDA-LDL/LDL).

METHODS AND RESULTS

This retroactive cross-sectional study used data from 402 patients with type 2 diabetes. Patients undergoing hemodialysis were excluded. Serum MDA-LDL levels were significantly increased with increases in severity of albuminuria (103 ± 44 U/L, 109 ± 54 U/L, and 135 ± 72 U/L for normoalbuminuria, microalbuminuria, and macroalbuminuria, respectively; P for trend = 0.020) but not according to the estimated GFR (eGFR). An increased MDA-LDL/LDL ratio was significantly associated with both increased albuminuria (35 ± 13, 37 ± 14, and 40 ± 15 for normoalbuminuria, microalbuminuria, and macroalbuminuria, respectively; P for trend = 0.003) and reduced eGFR (34 ± 13, 36 ± 13, 38 ± 12, and 51 ± 28 for grade 1, 2, 3 and 4, respectively; P for trend = 0.002). Multiple linear regression analysis showed that neither the albumin excretion rate nor eGFR but ln-transformed triglycerides and LDL-C levels were independent determinants of both serum MDA-LDL levels and MDA-LDL/LDL ratios.

CONCLUSION

Serum MDA-LDL levels and MDA-LDL/LDL ratios were increased in those with dyslipidemia associated with diabetic kidney disease.

A Rare Coexistence of Pheochromocytoma and Parkinson's Disease With Diagnostic Challenges

We herein report a case of pheochromocytoma occurring in the course of Parkinson's disease. The coexistence of these two disease is extremely rare, with only four cases hitherto reported across the public databases. It is also noteworthy that biochemical tests, which are critical for the diagnosis of pheochromocytoma, are severely confounded by dopaminergic medications for Parkinson's disease, highlighting the importance of image-based modalities in this setting. We further attempted to gain insight into the potential molecular mechanisms, proposing that hypoxia-inducible factor signaling could make these two diseases mutually exclusive, while excessive reactive oxygen species could enable their coexistence.

A candidate functional SNP rs7074440 in TCF7L2 alters gene expression through C-FOS in hepatocytes

The SNP rs7903146 at the transcription factor 7-like 2 (TCF7L2) locus is established as the strongest known genetic marker for type 2 diabetes via genome-wide association studies. However, the functional SNPs regulating TCF7L2 expression remain unclear. Here, we show that the SNP rs7074440 is a candidate functional SNP highly linked with rs7903146. A reporter plasmid with rs7074440 normal allele sequence exhibited 15-fold higher luciferase activity compared with risk allele sequence in hepatocytes, demonstrating a strong enhancer activity at rs7074440. Additionally, we identified C-FOS as an activator binding to the rs7074440 enhancer using a TFEL genome-wide screen method. Consistently, knockdown of C-FOS significantly reduced TCF7L2 expression in hepatocytes. Collectively, a novel enhancer regulating TCF7L2 expression was revealed through searching for functional SNPs.

Effect of sodium-glucose cotransporter 2 (SGLT2) inhibition on weight loss is partly mediated by liver-brain-adipose neurocircuitry

Sodium-glucose cotransporter 2 (SGLT2) inhibitors have both anti-diabetic and anti-obesity effects. However, the precise mechanism of the anti-obesity effect remains unclear. We previously demonstrated that the glycogen depletion signal triggers lipolysis in adipose tissue via liver-brain-adipose neurocircuitry. In this study, therefore, we investigated whether the anti-obesity mechanism of SGLT2 inhibitor is mediated by this mechanism. Diet-induced obese mice were subjected to hepatic vagotomy (HVx) or sham operation and loaded with high fat diet containing 0.015% tofogliflozin (TOFO), a highly selective SGLT2 inhibitor, for 3 weeks. TOFO-treated mice showed a decrease in fat mass and the effect of TOFO was attenuated in HVx group. Although both HVx and sham mice showed a similar level of reduction in hepatic glycogen by TOFO treatment, HVx mice exhibited an attenuated response in protein phosphorylation by protein kinase A (PKA) in white adipose tissue compared with the sham group. As PKA pathway is known to act as an effector of the liver-brain-adipose axis and activate triglyceride lipases in adipocytes, these results indicated that SGLT2 inhibition triggered glycogen depletion signal and actuated liver-brain-adipose axis, resulting in PKA activation in adipocytes. Taken together, it was concluded that the effect of SGLT2 inhibition on weight loss is in part mediated via the liver-brain-adipose neurocircuitry.

EFFECT OF SEASONAL CHANGES ON TESTICULAR MORPHOLOGY AND THE EXPRESSION OF CIRCADIAN CLOCK GENES IN JAPANESE WOOD MICE (APODEMUS SPECIOSUS)

This study aimed to determine the seasonality of reproduction throughout the year in Japanese wood mice (Apodemus speciosus). The effect of seasonal changes on testicular morphology and the periodic expression of circadian clock genes in the hypothalamus and testes of male individuals was evaluated. We also examined the morphology of the testes and caudae epididymides of male mice. In addition, RT-PCR analysis was carried out with mRNA extracted from the hypothalamus and testes to evaluate the expression of the circadian clock genes Clock, Bmal1, Per1, and Cry1. The complete induction of testicular activity was detected from February to April and from August to October, with testes weight increasing with the completion of spermatogenesis (reproductive season). From May to early June and from November to early January, testicular weight declined, the seminiferous tubules reduced in size, spermatogenesis was arrested, and sperm were not produced (non-reproductive season). From mid- June to July and mid-January, the re-induction of testicular activity for spermatogenesis was observed in the seminiferous tubules (transitional season). Out of the four examined genes, Cry1 had the highest expression level in both the hypothalamus and testes throughout the year, followed by Bmal1, Per1, and Clock. The expression of Bmal1 was significantly lower in the hypothalamus and testes during the transitional season compared to the reproductive and non-reproductive seasons. Cry1 transcript levels were also significantly lower in the hypothalamus and testes during the transitional season compared to the reproductive season. In conclusion, the results indicating changes in testicular morphology revealed annual reproductive, non-reproductive, and transmission periods in Japanese wood mice. When an increase in testicular activity was observed indicating the onset of the reproductive season, the mean day length was approximately 11–13 h. The expression of the circadian clock genes Bmal1 and Cry1 in the hypothalamus and testes during the reproductive season was significantly higher than that of the same genes during the transitional season. Consequently, completion of spermatogenesis occurred in the seminiferous tubules of Japanese wood mice testes during the reproductive period.