Diabetic cardiomyopathy (DbCM) is characterized by metabolic remodeling and energetic stress independent of coronary artery disease. Increased reliance on fatty acid and ketone body metabolism has been observed in DbCM, but the regulatory mechanisms linking altered substrate use to myocardial dysfunction remain poorly understood. In particular, lysine β-hydroxybutyrate (Kbhb), a ketone body-derived, posttranslational modification, has emerged as a potentially critical regulator but has not been fully investigated. We conducted a comprehensive multiomics study integrating metabolomics, transcriptomics, proteomics, and Kbhb-specific proteomics on myocardial tissues in a well-established mouse model of DbCM. Kbhb-modified proteins were systematically mapped and quantified, followed by motif, subcellular localization, and protein-protein interaction analyses. DbCM cardiac tissue exhibited coordinated upregulations of fatty acid β-oxidation, ketone metabolism, and tricarboxylic acid cycle activity at the transcriptomic, proteomic, and metabolomic levels. Kbhb profiling revealed extensive mitochondrial protein modification, with Atp5f1a-K239 identified as a key modification site strongly correlated with β-hydroxybutyrate and isocitric acid concentrations. This study identifies Kbhb as a potential metabolic-epigenetic modifier linking ketone body availability to the regulation of mitochondrial proteins in DbCM. Our findings provide novel insights into metabolic-epigenetic cross talk and identify potential therapeutic targets for interventions to restore mitochondrial function in alleviating diabetic heart disease.

Glucokinase (GK) deficiency can drive maturity-onset diabetes of the young (GCK-MODY) in heterozygotes and permanent neonatal diabetes in homozygotes. We describe a hypomorphic Gck allele that results in aberrant splicing in islets and liver lowering GK activity by ∼85%. Whereas heterozygous mutant mice are mildly hyperglycemic, homozygotes have frank diabetes but survive to adulthood. Dorzagliatin potentiates the effects of glucagon-like receptor-1 receptor activation sex dependently in heterozygous Gck mice and in obese hyperglycemic db/db mice. Combined use of these drugs may be useful in some forms of GCK-MODY and in obesity-related type 2 diabetes.

Neonatal transfer of immature dendritic cell-enriched Flt3L splenocytes significantly reduces the incidence of type 1 diabetes in female NOD mice. Early time points are associated with accumulation of anergic T cells. In adult mice, there is a reduction in CD4 T helper 1 cells and reduced proliferation and perforin of CD8 T cells. Our work demonstrates how targeting the neonatal window of tolerance alters autoimmunity outcome.

Activated neutrophils kill retinal endothelial cells (ECs) in early diabetic retinopathy, but how neutrophils become activated in diabetes is not well understood. We found that lysyl oxidase (LOX), whose matrix-localized form activates retinal ECs, can also directly activate neutrophils in its soluble form. LOX-induced release of neutrophil elastase and superoxide is mediated by actin remodeling and membrane aggregation of azurophilic granules. The dual ability of LOX to activate neutrophils (in its soluble form) and retinal ECs (in its matrix-localized form) implicates it as a key proinflammatory target for early diabetic retinopathy.

Endoplasmic reticulum stress response mediator activating transcription factor 6 (ATF6α) increases pancreatic β-cell proliferation in a glucose-dependent manner, but the mechanism remains unknown. ATF6α activation upregulated mRNA and protein expression of E2F1, a key G1/S phase transition regulator; however, E2F1 activity only increased in high glucose. Glucose dependence of E2F1 activity was mediated by cyclin-dependent kinase 4/6 phosphorylation of retinoblastoma (Rb) protein, derepressing E2F1 in high glucose. Generalized endoplasmic reticulum stressor thapsigargin increased E2F1 abundance in an ATF6-dependent manner. ATF6α increased E2F1 expression in human β-cells and increased human β-cell proliferation when cyclin-dependent kinase 6 (CDK6) was coexpressed.

Pericyte dysfunction is an early event in type 1 diabetes in humans, but how it affects islet microvascular homeostasis in vivo is unknown. We sought to determine whether vascular integrity and blood flow regulation in islets were impaired in a model of partial β-cell loss and inflammation. Islet capillaries lost functional pericyte coverage shortly after low-dose streptozotocin, compromising vascular stability and local control of blood flow. Strategies that preserve vascular niches in islets could be of important therapeutic potential.

In the above-cited article, the variant p.Asp1603Tyr was mistakenly given as p.Ala1603Tyr in the abstract, on p. 429 (second column, fourth row), and in the legend to Fig. 1. In addition, typographical errors in Table 1 were present for the clinical characteristics of female patients for FPL pedigrees FPL143.6, FPL340.3, and FPL 414.3. The authors apologize for the errors and confirm that correction of the errors does not affect the conclusions of the article. The online version of the article (https://doi.org/10.2337/db24-0624) has been updated with the correct text.

Hyperglycemia (HG) is a well-established risk factor for secondary osteoporosis, primarily due to suppressed osteoblast activity. While gut microbiota (GM) dysbiosis has been implicated in various diseases, its role in HG-induced osteoporosis remains poorly understood. Here, we demonstrate that HG mice develop low-turnover osteoporosis accompanied by reduced GM diversity. Fecal microbiota transplantation (FMT) from HG mice (GMHG-FMT) induced osteoporosis in recipient mice, independent of blood glucose levels. A depletion of Bifidobacterium pseudolongum was associated with bone loss, whereas supplementation with either microbiota of normoglycemic mice or B. pseudolongum alleviated osteoporosis in HG mice. Both HG and GMHG-FMT recipient mice exhibited elevated serum interleukin-17A (IL-17A) levels, and anti-IL-17A antibody treatment mitigated osteoporosis in the GMHG-FMT model. Furthermore, decanoic acid levels were elevated in the feces of HG mice and the serum of GMHG-FMT recipients. Decanoic acid promoted the differentiation of naive CD4+ T cells into T helper17 cells, leading to increased IL-17A production. These findings reveal a microbiome dysbiosis-driven decanoic acid/IL-17A axis in HG-induced osteoporosis and highlight the therapeutic potential of microbiome-associated targets.

Maternal obesity is a known risk factor for metabolic dysfunction in offspring; however, its effect on metabolism during pregnancy in female offspring remains unclear. This study investigated how maternal obesity, induced by high-fat (HF) feeding in C57BL/6J mice, affects the metabolic adaptation to pregnancy in female offspring. Dams were fed an HF diet (60% fat) or chow for 3 months before and during pregnancy. Offspring of HF diet-fed dams (OF-HFD) exhibited reduced fetal growth, followed by rapid postnatal catch-up and increased adult adiposity, compared with offspring of chow-fed dams (OF-CD), despite having similar baseline glucose and insulin levels. During pregnancy, OF-HFD exhibited diminished increases in maternal body fat, blood triglycerides, and insulin concentrations, accompanied by glucose intolerance. In cultured islets, glucose-stimulated insulin secretion was markedly reduced in pregnant OF-HFD, despite unchanged β-cell mass or proliferation. Hepatic triglyceride secretion was decreased, whereas liver insulin signaling was enhanced, suggesting alterations in lipid and glucose metabolism. Feeding OF-HFD an HF diet before and during pregnancy further impaired fetal growth. These findings indicate that maternal obesity impairs the metabolic adaptation to pregnancy in female offspring, characterized by insulin insufficiency and disrupted lipid homeostasis. This may initiate a transgenerational cycle of metabolic dysfunction, potentially increasing the risk of gestational diabetes in subsequent generations. Our findings underscore the need for more research to explore these mechanisms in humans and develop strategies to reduce the long-term effects of maternal obesity.

Hybrid insulin peptides (HIPs) have been identified as targets of autoreactive T cells in type 1 diabetes, although their causal role in disease pathogenesis has remained unclear. We demonstrated that a single leucine-to-isoleucine substitution in insulin C-peptide significantly disrupts cathepsin D-mediated HIP formation in NOD mouse islets. NOD mice engineered with this precise modification (NOD INS2I/I) showed significantly reduced HIP content, decreased T-cell reactivity, and significantly delayed diabetes onset (43% disease-free at 1 year vs. 10% in controls). These findings establish a mechanistic link between HIP formation and disease progression, revealing cathepsin D-mediated transpeptidation as a potential therapeutic target for intervention in at-risk individuals.

The control of muscle glucose uptake (MGU) is distributed across delivery, transport, and phosphorylation of glucose. These steps have been defined as control points of MGU in vivo due to the application of isotopic tracer techniques to transgenic mouse models. Using these techniques in a classic study published in Diabetes, Fueger et al. demonstrated that overexpression in skeletal muscle of hexokinase II (HKII), the enzyme responsible for intracellular glucose phosphorylation, enhanced MGU in insulin-sensitive but not in insulin-resistant mice. Conversely, HKII overexpression enhanced MGU in insulin-resistant mice in response to exercise. Since exercise reduces barriers of glucose delivery and transport, this suggested that these two processes contribute to the dysregulation of MGU in insulin-resistant states. These fundamental findings have spurred subsequent studies highlighting the contribution of glucose delivery and transport to the regulation of MGU in health and disease.

Low birth weight (LBW) is a risk factor for type 2 diabetes (T2D). We hypothesized that 4 weeks of carbohydrate overfeeding (COF) with +25% energy would unmask key T2D perturbations among 22 nonobese LBW men, including five with screen-detected metabolic dysfunction-associated steatotic liver disease (MASLD), compared with 21 healthy control participants with normal birth weight (NBW). Body weight, lean and fat mass, and hepatic fat content increased to the same extent in both groups during COF, whereas fasting glucose and insulin resistance increased significantly more in LBW compared with NBW participants. The differential COF responses were most pronounced in LBW participants without MASLD, including increased resting energy expenditure. Plasma adiponectin was lower, whereas fibroblast growth factor 21 levels increased more during COF in LBW participants. Subcutaneous adipose tissue (SAT) density was lower in LBW participants and decreased during COF in both groups. Serum alanine, phosphatidylcholines, and triglycerides increased significantly more in LBW participants during COF. Multiomics analysis of SAT RNA sequencing, serum lipidomics, and metabolomics uncovered impaired peroxisome proliferator-activated receptor signaling as well as aberrant collagen and extracellular matrix regulation in LBW participants. The results document differential and MASLD-independent metabolic perturbations in LBW participants during COF.

Adipocyte size is linked to insulin resistance and the risk of developing type 2 diabetes. We aimed to generate a surrogate method to estimate adipocyte size by measuring adipose tissue gene expression using quantitative real-time PCR (qRT-PCR), which could be used alongside systemic measures of insulin sensitivity to predict type 2 diabetes risk. We examined the relationship of 40,591 genes with abdominal subcutaneous adipocyte size in 132 adults and validated the findings in additional cohorts with available transcriptomic and adipocyte size data. qRT-PCR analysis of gene expression in abdominal adipose tissue biopsies was used to develop a standardized adipocyte size estimate. This estimate was compared alongside systemic and adipose insulin sensitivity measures, including adipocyte lipogenesis, hyperinsulinemic-euglycemic clamp, adipose insulin resistance, and HOMA. Transcriptome-wide analyses found that UCHL1 gene expression strongly correlated with adipocyte size, independent of other genes and additional cofactors, such as insulin resistance (β-coefficient 0.32; P = 0.002). Using qRT-PCR, UCHL1 expression accurately estimated adipocyte size across a wide range of adipocyte volumes with high precision (receiver operating characteristic area under the curve 0.94) and showed strong correlations with all insulin sensitivity measures (adjusted r2 = 0.2-0.6; P < 0.0001). We scaled the measurement of UCHL1 expression to 25-mg adipose biopsies and provided a standard operating procedure for routinely estimating adipocyte size. In summary, we provide a simple, accurate, and accessible surrogate measure to estimate an individual's adipocyte size, which may be useful in clinical insulin resistance studies.

Diabetes currently affects ∼37 million adults in the U.S. and 537 million people worldwide, with type 2 diabetes (T2D) accounting for 90%-95% of the diabetes burden. The transition from normal glucose regulation (NGR) to T2D is via an intermediate stage of prediabetes, characterized by impaired fasting glucose (IFG) and impaired glucose tolerance (IGT). Prediabetes affects ∼98 million adults in the U.S.; worldwide, more than 541 million adults have IGT and 319 million adults have IFG. Prediabetes is associated with increased risks of developing vascular and neuropathic complications, besides the risk of progression to T2D. Discussed herein are the demographic, anthropometric, biobehavioral, biochemical, and molecular factors associated with the transition from NGR to prediabetes. The natural history of prediabetes predicts time-dependent progression to T2D, as sustained recovery from prediabetes is uncommon without intervention. Lifestyle modification and certain medications interrupt the progression to T2D and may restore NGR. The landmark intervention trials are discussed, with an interpretive focus on their limitations and the need for novel approaches for durable reversal of prediabetes.

We identify threonine 302 as the critical O-GlcNAcylation site on NIMA-related kinase 7 (NEK7), which stabilizes NEK7 by inhibiting its proteasomal degradation, thereby enhancing NLRP3 inflammasome activation and podocyte pyroptosis in diabetic kidney disease (DKD). Chronic hyperglycemia activates the hexosamine biosynthetic pathway (HBP), driving pathological O-GlcNAcylation and significant upregulation of NEK7, O-GlcNAc transferase, and glutamine fructose-6-phosphate amidotransferase 1 in glomeruli from patients with DKD and experimental models. This study establishes the discovery of the pathogenic glucose/O-GlcNAc/NEK7/NLRP3 signaling axis, identifying a novel posttranslational mechanism driving podocyte loss in DKD progression. Pharmacological inhibition of the HBP with 6-diazo-5-oxo-l-norleucine normalizes O-GlcNAcylation, suppresses NEK7-driven pyroptosis, and mitigates renal injury, demonstrating the therapeutic potential of targeting threonine 302, NEK7, or the HBP for DKD management.

Optical activation or δ-cells stimulate somatostatin secretion. δ-Cell depolarization evokes β-cell action potential firing and insulin release. δ-Cell activation results in islet-wide synchronized β-cell cytoplasmic free Ca2+ concentration increases. δ-Cell inhibition aborts cytoplasmic free Ca2+ concentration oscillations in β-cell neighbors.

Prediction of kidney function decline is challenging in patients with type 2 diabetes mellitus (T2DM). Urinary Dickkopf-3 (uDKK3), a profibrotic tubular protein, is a promising biomarker for detecting tubular injury and predicting the progression of chronic kidney disease. This study assessed whether uDKK3 measurements improve risk prediction in patients with T2DM treated at the primary care level. Elevated uDKK3 levels were associated with kidney function decline, on top of established biomarkers (estimated glomerular filtration rate and albuminuria). uDKK3 also identified patients at increased risk for cardiovascular events. uDKK3 may help identify high-risk patients in primary care who could benefit from intensified treatment and/or referrals to specialists.

This study was undertaken to further investigate the ability of a monoclonal autoantibody to GAD65 from a patient with pre-type 1 diabetes to be deleterious to islet function. The study was designed to further characterize the effects, understand the mechanism mediating the effects, and demonstrate that the effects were operational in vivo. The effects of the GAD65 monoclonal antibody reduced ATP, γ-aminobutyric acid secretion, and insulin secretion with a similar time course and concentration dependency, which appeared to be mediated by effects on mitochondrial energetics and were similar in vivo in rats as in vitro. These findings raise the possibility that autoantibodies could play a pathogenic role in the development of type 1 diabetes.

The exact mechanism of postbariatric hypoglycemia (PBH) is unclear, but β-cell mass expansion is hypothesized to play a role. We used [68Ga]Ga-NODAGA-exendin-4 positron emission tomography/computed tomography (PET/CT) to determine β-cell mass in individuals with and without PBH after Roux-en-Y gastric bypass surgery. β-Cell mass did not differ between individuals with and without PBH. Pancreas volume was lower in individuals with PBH compared with those without PBH. Our data argue against β-cell mass expansion to explain PBH after Roux-en-Y gastric bypass. Further study is required to understand PBH.

Insulin-like growth factor-2 receptor (IGF2R), also known as cation-independent mannose-6-phosphate receptor, is localized in cytosolic vesicles and is unique in its ability to transport enzymes to the lysosome and to clear IGF2 from the cell surface by acting as a scavenger receptor. To evaluate the direct role of IGF2R in β-cell biology, we undertook complementary in vitro knockdown and in vivo knockout approaches. A β-cell line with a stable knockdown of IGF2R (IGF2RKD) exhibited decreased glucose-induced insulin secretion and enhanced cell proliferation. Tamoxifen-inducible β-cell-specific IGF2R knockout mice exhibited impaired glucose tolerance and blunted insulin secretion after high-fat-diet loading that was likely secondary to reduced β-cell mass due to attenuated proliferation. β-cells with IGF2RKD had fewer autophagosomes after starvation and reduced expression of p62, LC3B, and ULK1. Aged mice also had impaired autophagy in βIGF2R-deficient β-cells. Reduced IGF2R function and N6-methyladenosine (m6A) mRNA methylation were observed in islets from both mouse and human type 2 diabetes. Taken together, these data point to IGF2R as an important regulator of insulin secretion, cell proliferation, and autophagy in mammalian β-cells.