Daily Endocrinology Research Analysis
Three impactful studies span clinical and mechanistic endocrinology. A large prospective cohort links tighter CGM time-in-tight-range (70–140 mg/dL) with lower all-cause and cardiovascular mortality in type 2 diabetes, independent of HbA1c. Mechanistic papers reveal that APOBEC-1 cofactors and hnRNPs govern APOBEC3 mutagenesis in HBV, and that glutamatergic transmission from arcuate to preoptic kisspeptin neurons is required for the estrogen-induced LH surge.
Summary
Three impactful studies span clinical and mechanistic endocrinology. A large prospective cohort links tighter CGM time-in-tight-range (70–140 mg/dL) with lower all-cause and cardiovascular mortality in type 2 diabetes, independent of HbA1c. Mechanistic papers reveal that APOBEC-1 cofactors and hnRNPs govern APOBEC3 mutagenesis in HBV, and that glutamatergic transmission from arcuate to preoptic kisspeptin neurons is required for the estrogen-induced LH surge.
Research Themes
- CGM-derived glycemic metrics (time-in-tight-range) and long-term mortality
- Cellular regulation of APOBEC3 mutagenesis by APOBEC-1 cofactors/hnRNPs in viral and cancer contexts
- Neuroendocrine glutamatergic control of ovulatory LH surge via kisspeptin neuronal circuits
Selected Articles
1. APOBEC-1 cofactors regulate APOBEC3-induced mutations in hepatitis B virus.
Using HBV replication as a model, the authors show that APOBEC-1 cofactors and associated hnRNPs physically associate with APOBEC3 proteins to enhance their mutational activity. Disrupting A3–hnRNP interactions via mutagenesis or siRNA knockdown markedly reduces A3 activity, and A1 cofactors increase A3C access to HBV (−)DNA, generating kataegis-like hypermutation.
Impact: Reveals a regulatory mechanism governing APOBEC3 mutagenesis, bridging antiviral innate immunity and cancer mutagenesis. Identifies potential cellular targets to modulate A3 activity therapeutically.
Clinical Implications: Targeting APOBEC-1 cofactors/hnRNP interactions may offer strategies to limit APOBEC-driven tumor mutagenesis or to enhance antiviral restriction. It also informs biomarker development for A3 activity in HBV infection and possibly cancers.
Key Findings
- APOBEC-1 cofactors and hnRNPs strongly interact with APOBEC3 proteins and enhance A3 mutational activity in HBV replication systems.
- siRNA knockdown of cofactors reduces A3 activity, while mutagenesis disrupting A3–hnRNP interactions nearly abolishes mutagenesis.
- A1 cofactors increase A3C accessibility to HBV (−)DNA and promote kataegis-like hypermutation genome-wide.
Methodological Strengths
- Multipronged mechanistic approach combining protein interaction, siRNA knockdown, and mutagenesis to establish causality
- Genome-wide HBV mutation profiling demonstrating kataegis-like patterns with cofactor modulation
Limitations
- Findings are based on cellular replication models; in vivo physiological relevance remains to be confirmed
- Focuses primarily on HBV and selected APOBEC3 family members; generalizability across viruses and tissues is uncertain
Future Directions: Validate cofactor-dependent A3 regulation in vivo, map interaction interfaces structurally, and develop small molecules to modulate A3–hnRNP interactions in antiviral or anticancer settings.
UNLABELLED: APOBEC3 proteins (A3s) play an important role in host innate immunity against viruses and DNA mutations in cancer. A3s-induced mutations in both viral and human DNA genomes vary significantly from non-lethal mutations in viruses to localized hypermutations, such as kataegis in cancer. How A3s are regulated remains largely unknown. Since A3s exist in complexes and belong to the same family as APOBEC-1 (A1), which requires cofactors to be functional, we investigated the role of A1 cofactors and other A3 potentially associated hnRNPs on A3 mutational activity using hepatitis B virus (HBV) cellular replication as a model. We found that A1-associated cofactors and other hnRNPs were involved in A3 mutational act
2. Glutamatergic Input From Arcuate Nucleus Kiss1 Neurons to Preoptic Kiss1 Neurons Is Required for LH Surge in Female Mice.
Estradiol upregulates Vglut2 and excitatory conductances in arcuate Kiss1 neurons, boosting glutamate release. Optogenetic activation of these neurons excites preoptic Kiss1 neurons via ionotropic and metabotropic glutamate receptors, and CRISPR deletion of Vglut2 in arcuate Kiss1 neurons abolishes the estrogen-induced LH surge and reduces corpora lutea.
Impact: Defines a glutamatergic microcircuit essential for the LH surge, reshaping understanding of neuroendocrine control of ovulation. Provides mechanistic targets for disorders of ovulation.
Clinical Implications: Identifies glutamatergic signaling between kisspeptin populations as a potential therapeutic target for anovulation and infertility. May inform strategies modulating excitatory inputs in hypothalamic circuits.
Key Findings
- Estradiol increases Vglut2 expression and excitability in arcuate Kiss1 neurons, enhancing glutamate release.
- Optogenetic stimulation of arcuate Kiss1 neurons excites preoptic Kiss1 neurons via ionotropic and metabotropic glutamate receptors.
- CRISPR mutagenesis of Vglut2 in arcuate Kiss1 neurons abolishes the estrogen-induced LH surge and reduces corpora lutea formation.
Methodological Strengths
- Integration of single-cell qPCR, whole-cell electrophysiology, optogenetics, and CRISPR mutagenesis to establish circuit-level causality
- Physiological readouts (LH surge, corpora lutea) link circuit manipulation to reproductive outcomes
Limitations
- Findings in mice may not directly translate to humans; species differences need consideration
- Focus on female estrous stage; broader endocrine states and neuromodulators require evaluation
Future Directions: Test whether modulating glutamatergic inputs rescues ovulatory defects in disease models and explore pharmacologic modulation of VGLUT2-dependent signaling in reproductive disorders.
Hypothalamic kisspeptin (Kiss1) neurons are vital for maintaining fertility in the mammal. In the female rodent, Kiss1 neurons populate the anteroventral periventricular/periventricular nuclei (Kiss1AVPV/PeN) and the arcuate nucleus (Kiss1ARH). Kiss1ARH neurons (also known as KNDy neurons since they coexpress neurokinin B and dynorphin) are considered the "pulse-generator" neurons that presynaptically excite gonadotropin-releasing hormone (GnRH) axons in the median eminence, whereas the Kiss1AVPV/PeN neurons are the "surge-generator" neurons that depolarize preoptic GnRH neurons directly to drive ovulation. Traditionally, it is believed that Kiss1ARH neurons are relatively quiet during the late follicular, preovulatory stage of the reproductive cycle due to the 17β-estradiol (E2)-mediated downregulation of the expression of the KNDy peptides. However, based on our single-cell, quantitative polymerase chain reaction and whole-cell electrophysiological recordings, we found that the messenger RNA (mRNA) expression of vesicular glutamate transporter 2 (Vglut2) mRNA and excitatory cation channels in Kiss1ARH neurons were significantly upregulated by E2, which increased the excitability and glutamate release from these "pulse-generator" neurons. Presently, we demonstrate that optogenetic stimulation of Kiss1ARH neurons releases glutamate to excite Kiss1AVPV/PeN neurons via activation of both ionotropic and metabotropic glutamate receptors. CRISPR mutagenesis of Vglut2 in Kiss1ARH neurons abolished glutamatergic neurotransmission, which significantly reduced the overall glutamatergic input to Kiss1AVPV/PeN neurons. The mutagenesis of Vglut2 in Kiss1ARH neurons abrogated the E2-induced luteinizing hormone surge and reduced the formation of corpus lutea, indicative of a reduced ovulatory drive in these Vglut2-mutated Kiss1ARH mice. Therefore, Kiss1ARH neurons appear to play a critical role in augmenting the GnRH surge through glutamatergic neurotransmission to Kiss1AVPV/PeN neurons.
3. Impact of time in tight range on all-cause and cardiovascular mortality in type 2 diabetes: A prospective cohort study.
In 6061 adults with type 2 diabetes followed for a median of 10.9 years, lower baseline CGM time-in-tight-range (70–140 mg/dL) was linearly associated with higher all-cause and cardiovascular mortality. Each 10% decrement in TITR conferred a 4% higher risk of both outcomes, independent of HbA1c, with effects persisting among those with HbA1c <7%.
Impact: Shifts focus from HbA1c to physiologic-range glycemic stability as a predictor of hard outcomes, informing CGM-based quality metrics and treatment goals in type 2 diabetes.
Clinical Implications: Incorporate TITR (70–140 mg/dL) into routine risk stratification and therapeutic titration, testing interventions to increase TITR even in patients with target HbA1c.
Key Findings
- Lower baseline CGM time-in-tight-range is linearly associated with higher all-cause and cardiovascular mortality over 10.9 years.
- Each 10% decrease in TITR increases all-cause and cardiovascular mortality risk by 4%, independent of HbA1c.
- Associations persist in subgroups with HbA1c <7.0% and fasting glucose <7.0 mmol/L.
Methodological Strengths
- Large prospective cohort with long follow-up and adjudicated mortality outcomes
- Robust multivariable Cox models and restricted cubic spline analyses adjusting for HbA1c and covariates
Limitations
- Single-center cohort; generalizability may be limited
- TITR measured at baseline only; temporal changes not captured
Future Directions: Randomized trials to test whether TITR-targeted interventions reduce mortality; repeated CGM measures to assess dynamic TITR and causality.
AIMS: Currently, there is a lack of evidence regarding time in tight range (TITR) and long-term adverse outcomes. We aimed to investigate the association between TITR and the risk of all-cause and cardiovascular mortality among patients with type 2 diabetes. MATERIALS AND METHODS: A total of 6061 patients with type 2 diabetes were prospectively recruited in a single centre. TITR was measured with continuous glucose monitoring (CGM) at baseline and was defined as the percentage of time in the target glucose range of 3.9-7.8 mmol/L (70-140 mg/dL) during a 24-h period. Cox proportion hazard regression models were used to examine the association between TITR and the risk of all-cause and cardiovascular mortality. RESULTS: During a median follow-up period of 10.9 years, 1898 (31.3%) death events were confirmed, with 689 (11.4%) due to cardiovascular mortality. The restricted cubic spline revealed significant linear relationships between lower TITR and higher risks of all-cause and cardiovascular mortality (p for linearity <0.01). In the fully adjusted model including glycated haemoglobin A1c, each 10% decrease in TITR was associated with 4% (95% confidence interval, 1.01-1.06) increased risk of all-cause mortality and 4% (95% confidence interval, 1.00-1.08) increased risk of cardiovascular mortality. Subgroup analyses showed that the linear relationship between TITR and all-cause mortality risk was sustained in patients with haemoglobin A1c <7.0% and patients with fasting plasma glucose <7.0 mmol/L. CONCLUSIONS: Lower TITR is associated with an increased risk of all-cause and cardiovascular mortality in patients with type 2 diabetes, indicating that tight glycaemic control within the physiological range may be crucial for reducing long-term mortality risk, especially in those with seemingly well-controlled diabetes.