Institute for Adult Diseases Asahi Life Foundation

The liver plays an important role in the control of glucose homeostasis. When insulin levels are low, such as in the fasting state, gluconeogenesis and glycogenolysis are stimulated to maintain the blood glucose levels. Conversely, in the presence of increased insulin levels, such as after a meal, synthesis of glycogen and lipid occurs to maintain the blood glucose levels within normal range. Insulin receptor signaling regulates glycogenesis, gluconeogenesis and lipogenesis through downstream pathways such as the insulin receptor substrate (IRS)-phosphoinositide 3 (PI3) kinase-Akt pathway. IRS-1 and IRS-2 are abundantly expressed in the liver and are thought to be responsible for transmitting the insulin signal from the insulin receptor to the intracellular effectors involved in the regulation of glucose and lipid homeostasis. Impaired insulin receptor signaling can cause hepatic insulin resistance and lead to type 2 diabetes. In the present study, we focus on a concept called "selective insulin resistance," which has received increasing attention recently: the frequent coexistence of hyperglycemia and hepatic steatosis in people with type 2 diabetes and obesity suggests that it is possible for the insulin signaling regulating gluconeogenesis to be impaired even while that regulating lipogenesis is preserved, suggestive of selective insulin resistance. In this review, we review the progress in research on the insulin actions and insulin signaling in the liver.

IntroductionThe presence of metabolic abnormalities in patients with type 2 diabetes (T2D) increases the risk of cardiovascular disease and other comorbidities. This analysis compared the effects of tirzepatide (5, 10, and 15 mg) and dulaglutide 0.75 mg on the prevalence of metabolic abnormalities in Japanese patients with T2D.MethodsThis was a post hoc analysis of SURPASS J-mono, a multicenter, randomized, double-blind, active-controlled, parallel-group, phase 3 trial that compared the efficacy and safety of tirzepatide monotherapy (5, 10, and 15 mg) to dulaglutide 0.75 mg in Japanese patients with T2D. Thresholds for abnormalities were based on the Japanese criteria for metabolic syndrome. Proportions of participants meeting a composite endpoint (visceral fat accumulation measured by waist circumference plus two or more of dyslipidemia, hypertension, or hyperglycemia) or individual component thresholds were calculated at baseline and week 52 for the overall population and for baseline body mass index (BMI) subgroups (< 25, 25 to < 30, and ≥ 30 kg/m2).ResultsOf 636 randomized participants, 431 (67.8%) met the composite endpoint at baseline, with similar findings observed across treatment arms. At week 52, the proportion of participants on treatment that met the composite endpoint was 31.7%, 23.0%, and 14.2% in the tirzepatide 5-, 10-, and 15-mg arms, respectively, and 56.5% in the dulaglutide arm (p < 0.001). A higher proportion met the composite endpoint at baseline in the BMI 25 to < 30 and ≥ 30 kg/m2 subgroups (73.2–79.3%) compared with the < 25 kg/m2 subgroup (45.3%), with reductions observed across all BMI subgroups treated with tirzepatide. The proportion of participants with individual metabolic abnormalities showed similar trends to those observed for the composite endpoint. Tirzepatide was consistently superior to dulaglutide across all assessments.ConclusionsTirzepatide reduced the prevalence of multiple metabolic abnormalities, indicating tirzepatide may have metabolic benefit in Japanese patients with T2D.Trial RegistrationClinicalTrials.gov, NCT03861052.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13300-024-01534-5.

The aim of this study was to clarify the characteristics of individuals with prediabetes who developed type 2 diabetes despite undergoing interventions, and to evaluate the performance of urinary myo-inositol (UMI) as a noninvasive indicator for the risk of developing diabetes. A total of 51 individuals with prediabetes who underwent a 75-g oral glucose tolerance test, ΔUMI (the difference in the UMI : creatinine ratio between before and 120 min after 75-g glucose loading), fasting plasma glucose, insulin, hemoglobin A1c, noninvasive testing (age, body mass index, blood pressure) and general blood tests were measured at baseline, and underwent dietary/exercise guidance for 8 years were studied. A total of 31 participants developed diabetes in 8 years. At baseline, the group that developed diabetes was characterized by high ΔUMI, hemoglobin A1c, fasting plasma glucose and low high-density lipoprotein cholesterol, and insulinogenic index (I.I.). I.I and ΔUMI showed a higher correlation than fasting plasma glucose and hemoglobin A1c. Regarding diabetes onset within 8 years, Cox regression analysis of diabetes onset showed the baseline ΔUMI is an independent predictor, adjusted for the result of not only noninvasive markers, but also that of noninvasive and general blood markers. The log-rank test showed that all glycemic indicators were significantly associated with diabetes onset. Participants who developed type 2 diabetes from prediabetes despite undergoing interventions were characterized by high glycemic control markers and low I.I. As noninvasive measurement of ΔUMI is associated with I.I. and diabetes onset, it could be a useful indicator for identifying individuals with a high risk of diabetes onset.

Adipose tissue is central to regulation of energy homeostasis. Adaptive thermogenesis, which relies on mitochondrial oxidative phosphorylation (Ox-Phos), dissipates energy to counteract obesity. On the other hand, chronic inflammation in adipose tissue is linked to type 2 diabetes and obesity. Here, we show that nuclear factor I-A (NFIA), a transcriptional regulator of brown and beige adipocytes, improves glucose homeostasis by upregulation of Ox-Phos and reciprocal downregulation of inflammation. Mice with transgenic expression of NFIA in adipocytes exhibited improved glucose tolerance and limited weight gain. NFIA up-regulates Ox-Phos and brown-fat-specific genes by enhancer activation that involves facilitated genomic binding of PPARγ. In contrast, NFIA in adipocytes, but not in macrophages, down-regulates proinflammatory cytokine genes to ameliorate adipose tissue inflammation. NFIA binds to regulatory region of the Ccl2 gene, which encodes proinflammatory cytokine MCP-1 (monocyte chemoattractant protein-1), to down-regulate its transcription. CCL2 expression was negatively correlated with NFIA expression in human adipose tissue. These results reveal the beneficial effect of NFIA on glucose and body weight homeostasis and also highlight previously unappreciated role of NFIA in suppressing adipose tissue inflammation.

The molecular subtypes of pancreatic cancer (PC), either classical/progenitor-like or basal/squamous-like, are currently a major topic of research because of their direct association with clinical outcomes. Some transcription factors (TFs) have been reported to be associated with these subtypes. However, the mechanisms by which these molecular signatures of PCs are established remain unknown. Epigenetic regulatory processes, supported by dynamic changes in the chromatin structure, are essential for transcriptional profiles. Previously, we reported the importance of open chromatin profiles in the biological features and transcriptional status of PCs. Here, we aimed to analyze the relationships between three-dimensional (3D) genome structures and the molecular subtypes of human PCs using Hi-C analysis. We observed a correlation of the specific elements of 3D genome modules, including compartments, topologically associating domains, and enhancer-promoter loops, with the expression of related genes. We focused on HNF1B, a TF that is implicated in the progenitor subtype. Forced expression of HNF1B in squamous-type PC organoids induced the upregulation and downregulation of genes associated with progenitor and squamous subtypes, respectively. Long-range genomic interactions induced by HNF1B were accompanied by compartment modulation and H3K27ac redistribution. We also found that these HNF1B-induced changes in subtype-related gene expression required an intrinsically disordered region, suggesting a possible involvement of phase separation in compartment modulation. Thus, mapping of 3D structural changes induced by TFs, such as HNF1B, may become a useful resource for further understanding the molecular features of PCs.

C57BL/6J (B6J) and C57BL/6N (B6N) mice are the most frequently used substrains in C57BL/6 (B6) inbred mice, serving as physiological models for in vivo studies and as background strains to build transgenic mice. However, the differences in metabolic phenotypes between B6J and B6N mice are not coherent, and genotypic differences in metabolically important tissues have not been well studied. The phenotypic differences between B6J and B6N substrains have often been attributed to the role of the nicotinamide nucleotide transhydrogenase (Nnt) gene, whereby B6J has a spontaneous missense mutation of Nnt. Nevertheless, phenotypic differences between the two cannot be explained by Nnt mutations alone, especially in metabolic traits. Therefore, we aimed to investigate the genetic cause of the phenotypic differences between B6J and B6N mice. Determining consistent genetic differences across multiple tissues involved in metabolic traits such as subcutaneous and visceral white adipose tissues, brown adipose tissue, skeletal muscle, liver, hypothalamus, and hippocampus, may help explain phenotypic differences in metabolism between the two substrains. We report candidate genes along with comparative data on body weight, tissue weight, blood components involved in metabolism, and energy balance of B6J and B6N mice. Insulin degrading enzyme, adenylosuccinate synthase 2, and ectonucleotide triphosphate diphosphohydrolase 4 were highly expressed in B6J mice compared with those in B6N mice, and Nnt, WD repeat and FYVE domain containing 1, and dynein light chain Tctex-type 1 were less expressed in B6J mice compared with those in B6N mice in all seven tissues. Considering the extremely wide use of both substrains and their critical importance in generating transgenic and knock-out models, these findings guide future research across several interrelated fields.

ABSTRACTAims/IntroductionAging of society is accelerating in many countries. The purpose of this study was to describe the clinical features and sulfonylurea usage among diabetes outpatients aged ≥90 years (nonagenarians).Materials and MethodsThis study was a retrospective observational study. The study population consisted of 69 nonagenarian diabetes outpatients and 857 diabetes outpatients aged <90 years. Patients were classified into four groups: group 1, <65 years; group 2, 65–74 years; group 3, 75–89 years; and group 4, ≥90 years. The presence of hypoglycemic episodes was defined as having self‐reported symptoms, or self‐monitored or clinically measured blood glucose level <70 mg/dL.ResultsThe median glycated hemoglobin (HbA1c) in group 1 and group 4 was 7.0% and 7.2%, respectively (P = 0.506). The proportion of sulfonylurea treatment in group 4 was 45.5%, which is significantly higher compared with the other three groups (20.0–27.8%, P < 0.001). In group 4, there was no difference between patients with or without sulfonylurea in age, sex, body mass index, HbA1c and number of antihyperglycemic agents. Five out of 25 nonagenarian sulfonylurea‐treated patients had hypoglycemic episodes within the last 2 years, their HbA1c were all 7.0 ≤ HbA1c < 8.0, and sulfonylurea or insulin was tapered in all cases after confirming hypoglycemia. Tapering dosage was attempted in all 25 sulfonylurea‐treated nonagenarian patients, but 15 needed to continue sulfonylurea for glycemic control, and 10 continued sulfonylurea with unknown reasons from their medical records.ConclusionsAlthough tapering the dosage of sulfonylurea was attempted in nonagenarian patients, sulfonylurea was widely continued for glycemic control. Reverse clinical inertia may exist in some sulfonylurea‐treated nonagenarian patients.

Enhanced de novo lipogenesis mediated by sterol regulatory element–binding proteins (SREBPs) is thought to be involved in nonalcoholic steatohepatitis (NASH) pathogenesis. In this study, we assessed the impact of SREBP inhibition on NASH and liver cancer development in murine models. Unexpectedly, SREBP inhibition via deletion of the SREBP cleavage–activating protein (SCAP) in the liver exacerbated liver injury, fibrosis, and carcinogenesis despite markedly reduced hepatic steatosis. These phenotypes were ameliorated by restoring SREBP function. Transcriptome and lipidome analyses revealed that SCAP/SREBP pathway inhibition altered the fatty acid (FA) composition of phosphatidylcholines due to both impaired FA synthesis and disorganized FA incorporation into phosphatidylcholine via lysophosphatidylcholine acyltransferase 3 (LPCAT3) downregulation, which led to endoplasmic reticulum (ER) stress and hepatocyte injury. Supplementation with phosphatidylcholines significantly improved liver injury and ER stress induced by SCAP deletion. The activity of the SCAP/SREBP/LPCAT3 axis was found to be inversely associated with liver fibrosis severity in human NASH. SREBP inhibition also cooperated with impaired autophagy to trigger liver injury. Thus, excessively strong and broad lipogenesis inhibition was counterproductive for NASH therapy; this will have important clinical implications in NASH treatment.

ABSTRACTAims/IntroductionThe purpose of this retrospective observational cohort study was to compare outpatient diabetes care and glycated hemoglobin (HbA1c) level during the coronavirus disease 2019 pandemic in 2020 with 2019, and to compare the glucose‐lowering effect of telemedicine and clinic visits during the state of emergency in Japan declared from 7 April to 25 May (inter‐period) 2020.Materials and MethodsA total of 13 weeks before and after the inter‐period were designated as the pre‐period and post‐period, respectively. The number of study participants who had clinic visits during the pre‐period and the post‐period were 3,333 in 2020 and 3,608 in 2019. Propensity score matching was carried out to compare the effect of telemedicine and clinic visits on diabetes control in 2020 among diabetes patients with insufficient glucose control (HbA1c ≥7%). The primary outcome was post‐period HbA1c.ResultsThe major difference between 2020 and 2019 was the use of telemedicine in 2020. After adjustment for age, sex, diabetes type, pre‐period HbA1c and pre‐period body mass index, glycemic control evaluated by HbA1c was significantly worse in the post‐period of 2020 than 2019. In the propensity score‐matched 618 pairs, the clinic visit group had significantly better post‐period HbA1c than the telemedicine group (7.5% vs 7.4%, P = 0.023).ConclusionsGlycemic control was slightly, but significantly, worse in 2020 than 2019. Although telemedicine significantly improved glycemic control during the coronavirus disease 2019 pandemic in 2020, clinic visits improved HbA1c significantly more. The substitution of telemedicine for clinic visits appears to be a viable option under emergency conditions, but clinic visits might be a better option when possible.

The effects of tirzepatide, a dual glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonist, as an addition to insulin glargine for treatment of type 2 diabetes have not been described. To assess the efficacy and safety of tirzepatide added to insulin glargine in patients with type 2 diabetes with inadequate glycemic control. Randomized phase 3 clinical trial conducted at 45 medical research centers and hospitals in 8 countries (enrollment from August 30, 2019, to March 20, 2020; follow-up completed January 13, 2021) in 475 adults with type 2 diabetes and inadequate glycemic control while treated with once-daily insulin glargine with or without metformin. Patients were randomized in a 1:1:1:1 ratio to receive once-weekly subcutaneous injections of 5-mg (n = 116), 10-mg (n = 119), or 15-mg (n = 120) tirzepatide or volume-matched placebo (n = 120) over 40 weeks. Tirzepatide was initiated at 2.5 mg/week and escalated by 2.5 mg every 4 weeks until the assigned dose was achieved. The primary end point was mean change from baseline in glycated hemoglobin A1c (HbA1c) at week 40. The 5 key secondary end points included mean change in body weight and percentage of patients achieving prespecified HbA1c levels. Among 475 randomized participants (211 [44%] women; mean [SD] age, 60.6 [9.9] years; mean [SD] HbA1c, 8.31% [0.85%]), 451 (94.9%) completed the trial. Treatment was prematurely discontinued by 10% of participants in the 5-mg tirzepatide group, 12% in the 10-mg tirzepatide group, 18% in the 15-mg tirzepatide group, and 3% in the placebo group. At week 40, mean HbA1c change from baseline was -2.40% with 10-mg tirzepatide and -2.34% with 15-mg tirzepatide vs -0.86% with placebo (10 mg: difference vs placebo, -1.53% [97.5% CI, -1.80% to -1.27%]; 15 mg: difference vs placebo, -1.47% [97.5% CI, -1.75% to -1.20%]; P < .001 for both). Mean HbA1c change from baseline was -2.11% with 5-mg tirzepatide (difference vs placebo, -1.24% [95% CI, -1.48% to -1.01%]; P < .001]). Mean body weight change from baseline was -5.4 kg with 5-mg tirzepatide, -7.5 kg with 10-mg tirzepatide, -8.8 kg with 15-mg tirzepatide and 1.6 kg with placebo (5 mg: difference, -7.1 kg [95% CI, -8.7 to -5.4]; 10 mg: difference, -9.1 kg [95% CI, -10.7 to -7.5]; 15 mg: difference, -10.5 kg [95% CI, -12.1 to -8.8]; P < .001 for all). Higher percentages of patients treated with tirzepatide vs those treated with placebo had HbA1c less than 7% (85%-90% vs 34%; P < .001 for all). The most common treatment-emergent adverse events in the tirzepatide groups vs placebo group were diarrhea (12%-21% vs 10%) and nausea (13%-18% vs 3%). Among patients with type 2 diabetes and inadequate glycemic control despite treatment with insulin glargine, the addition of subcutaneous tirzepatide, compared with placebo, to titrated insulin glargine resulted in statistically significant improvements in glycemic control after 40 weeks. ClinicalTrials.gov Identifier: NCT04039503.