Preclinical studies suggest that activating branched-chain amino acid (BCAA) catabolism may improve chronic kidney disease (CKD). In this prospective clinical study, we sought to examine the association between urinary BCAA excretion and risk of CKD progression in patients with type 2 diabetes. Baseline urinary BCAAs were measured by mass spectrometry in 1,868 outpatients with type 2 diabetes. The study outcome was a composite of end-stage kidney disease (estimated glomerular filtration rate <15 mL/min/1.73 m2, dialysis, or death resulting from renal causes) or doubling of serum creatinine. During a median of 7.2 years of follow-up, 203 renal events were identified. One SD increment in urinary valine, leucine, and isoleucine concentration was associated with 1.29- (95% CI 1.11-1.51), 1.31- (1.11-1.55) and 1.29-fold (1.09-1.53) increased risk, respectively, of the composite renal outcome after adjustment for clinical risk factors. Mediation analysis showed that urinary MCP-1 mediated 57%, 47%, and 58% of the effects of valine, leucine, and isoleucine on the renal outcome, respectively. High levels of urinary BCAAs were also independently associated with an increased risk of CKD progression in the Chronic Renal Insufficiency Cohort in the U.S. Our data suggest that dysregulation of BCAA metabolism in the kidneys may be involved in intrarenal inflammation and drive CKD progression.

The hypothalamus monitors blood glucose levels and regulates glucose production in the liver. In response to hypoglycemia, glucose-inhibited (GI) neurons trigger counterregulatory responses (CRRs), which stimulate the release of glucagon, epinephrine, and cortisol to elevate blood glucose. Recurrent hypoglycemia (RH), however, reduces the effectiveness of these CRRs. This study examined the role of hypothalamic prostaglandins in glucose recovery during acute hypoglycemia and RH. Imaging mass spectrometry and liquid chromatography/mass spectrometry showed phospholipid and prostaglandin levels in the hypothalamus of C57BL mice were changed after insulin or 2-deoxy-glucose administration. Ibuprofen, a nonsteroidal anti-inflammatory drug, was infused into the ventromedial hypothalamus (VMH) to analyze its effect on glucose production during hypoglycemia, revealing that prostaglandin inhibition decreased glucagon secretion. Additionally, RH-treated mice decreased glucagon release and glucose production during hypoglycemia. Inhibiting prostaglandin production via shRNA against cytosolic phospholipase A2 (cPLA2) in the hypothalamus restored CRRs diminished by RH via increasing glucagon sensitivity. These findings suggest that hypothalamic prostaglandins play a critical role in glucose recovery from acute hypoglycemia by activating VMH neurons and are also crucial for the attenuation of CRRs during RH.

Atherosclerotic cardiovascular disease (ASCVD) risk begins increasing years before the clinical onset of type 2 diabetes, driven in part by ectopic lipid accumulation. Many individuals predisposed to diabetes often gain weight rapidly and have limited capacity to expand subcutaneous fat, leading to central fat storage and ectopic lipid deposition-especially in the liver. Hepatic fat contributes to metabolic dysfunction and elevated triglyceride-rich lipoproteins (TRLs), which are atherogenic. Alongside higher blood pressure, these factors accelerate atherosclerosis even before hyperglycemia is evident. Although traditional cardiovascular risk factors like LDL cholesterol (LDL-C) and smoking have declined, rising obesity-particularly among younger individuals-is shifting ASCVD risk more toward pathways linked to ectopic lipid accumulation and prolonged exposure to diabetes-related metabolic disturbances. Ethnic variation plays a significant role in modifying this risk. South Asians, for example, develop type 2 diabetes at lower BMIs and tend to have higher hepatic fat and TRL levels than White individuals, contributing to their increased ASCVD burden. Conversely, people of African ancestry often have lower hepatic fat and TRL levels at similar BMIs, correlating with lower ASCVD risk despite elevated diabetes risk. Risk profiles in other ethnic groups remain understudied. These findings highlight the need for early obesity prevention and ethnically tailored strategies for ASCVD risk assessment and management. Without targeted interventions, rising global rates of obesity and type 2 diabetes, especially in low- and middle-income countries, will increase ectopic lipid accumulation, TRLs, and blood pressure, ultimately accelerating ASCVD progression and reversing prior gains made in cardiovascular prevention.

For many years, brown adipose tissue (BAT) was primarily regarded as a "heat organ" for rodents. Over the past 15 years, however, research in this field has shifted significantly toward understanding of the role of BAT in metabolic health, including systemic glucose homeostasis, lipid metabolism, insulin sensitivity, and protection against cardiometabolic disease. In this award lecture, I highlight key contributions from our laboratory and others that transformed brown fat research, including molecular insights into brown and beige adipocyte biogenesis and the discovery of UCP1-independent pathways through which brown and beige fat influence metabolic health beyond thermogenesis.

TAS2R38 is a bitter taste receptor that influences bitter taste perception and diet and is also found in intestinal L cells that store and secrete glucagon-like peptide 1 (GLP-1). Preclinical studies have linked TAS2R38 activation to postprandial GLP-1 secretion, fueling interest in TAS2R38 as a therapeutic target for glucose regulation; however, evidence in humans remains limited. To further establish TAS2R38 actions in glucose homeostasis, we analyzed data from ∼220,000 European adults without type 2 diabetes in the UK Biobank to test whether functional variants conferring TAS2R38 sensitivity were associated with blood glucose. We found that individuals with two copies of a haplotype increasing receptor sensitivity (PAV) had significantly lower 0-2-h (i.e., postprandial) glucose than those with two copies of a nonfunctional haplotype (AVI), following a dose-response relationship per PAV haplotype. These associations were replicated in published genome-wide association studies of 2-h glucose, persisted after adjustment for diet and lifestyle behaviors related to bitter taste perception, and were not seen for variants in other bitter taste receptors without putative roles in glucose metabolism (TAS2R14 and TAS2R19). Collectively, these findings provide evidence in humans consistent with direct TAS2R38 actions in postprandial glycemia, supporting TAS2R38 as a novel therapeutic target for glucose regulation.

Diabetic kidney disease (DKD) progression involves intricate interactions among senescence, oxidative stress, inflammation, and fibrosis. This study systematically investigates the regulatory role and molecular mechanisms of NUAK1 in DKD pathogenesis. Bioinformatics analysis of Gene Expression Omnibus data sets identified NUAK1 as a differentially expressed gene, validated in human kidney proximal tubule epithelial (HK-2) cells, high-fat diet and streptozotocin-induced DKD mice, d-galactose-induced senescent mice, and human peripheral blood mononuclear cells. Functional studies demonstrated that NUAK1 inhibition via siRNA knockdown, pharmacological inhibitors, or kidney tubule-targeted adeno-associated virus serotype carrying shRNA against NUAK1 delivery attenuated reactive oxygen species-tumor protein 53 (ROS/P53) axis-mediated renal tubular senescence, oxidative stress, inflammation, and fibrosis in vitro and in vivo. Mechanistically, chromatin immunoprecipitation quantitative PCR revealed that transcription factor ETS1 directly binds to the NUAK1 promoter, driving its transcriptional activation in DKD. Furthermore, molecular docking and dynamics simulations identified Asiatic acid (AA) as a potent NUAK1 inhibitor, with a stable binding affinity. AA suppressed NUAK1 expression and downstream pathological processes, ameliorating renal injury in DKD models. These findings elucidate the role and regulatory mechanisms of NUAK1 in modulating ROS/P53 axis-driven tubular senescence and oxidative stress, providing a theoretical basis for structure optimization in drug development targeting NUAK1.

Early postprandial glucagon concentrations are higher in type 1 diabetes (T1D) than in individuals with no diabetes (ND). To determine the cause, we infused stable [13C9, 15N1]glucagon before, during, and after a mixed meal in 16 ND and 16 T1D individuals to measure glucagon turnover. In a subcohort of 9 ND and 12 T1D individuals, we estimated [13C9, 15N1]glucagon kinetics during steady state. A linear, single-compartment model described [13C9, 15N1]glucagon kinetics and allowed precise estimation of the volume of distribution (VD) and clearance rate (CL). Model parameters were similar between groups, with the VD of [13C9, 15N1]glucagon at 42.1 ± 3.3 mL/kg, implying that [13C9, 15N1]glucagon distributes in a single compartment and with VD approximating the plasma volume and CL at 10.6 ± 0.9 mL/kg/min. Higher early (0-120 min after meal ingestion) postprandial glucagon concentrations (1,907.9 ± 373.4 vs. -93.6 ± 240.5 pg/mL · 120 min P < 0.001) observed in T1D was due to higher rates of glucagon appearance (3.39 ± 2.8 vs. -3.95 ± 2.0 ng/kg · 120 min, P < 0.04) and disappearance (2.13 ± 2.6 vs. -5.28 ± 2.1 ng/kg · 120 min, P < 0.04) compared with ND. We have determined postprandial glucagon turnover in humans and have demonstrated that changes in postprandial glucagon concentrations in T1D are due to increased rates of glucagon turnover during the early postprandial period.

There is significant evidence that acute stress, a challenge to an organism's homeostasis, has dramatic effects on metabolic control. Acute stress impairs blood glucose control in people with both type 1 and type 2 diabetes. In addition, growing evidence suggests that metabolic responses to stress in people without diabetes may be a crucial determinant of health. Acute dysregulation of blood glucose in the hospital setting, including both hyper- and hypoglycemia, predicts short- and long-term morbidity and mortality in patients with critical illnesses. Animal studies indicate that exposure to physiological and psychological stressors activates a highly conserved network of neural circuits that ultimately coordinate the functions of multiple organs to increase blood glucose. In this article, we provide an overview of the neural populations and circuits that increase blood glucose in response to acute stress, including our research funded by the American Diabetes Association Pathway to Stop Diabetes program, highlighting the impacts on clinical outcomes and opportunities for the development of therapies for diabetes. This article is part of a series of perspectives that report on research funded by the American Diabetes Association Pathway to Stop Diabetes program.

Gestational diabetes mellitus (GDM) causes hyperglycemia during pregnancy and adverse maternal and neonatal outcomes. Bulk placental gene expression has been reported largely unchanged. RNA sequencing of Norwegian and Chinese GDM placentas reveals hundreds of differential splicing events enriched for metabolic- and diabetes-related pathways. Motif enrichment and cross-linking and immunoprecipitation sequencing integration identify serine/arginine splicing factor 10 as a key regulator of GDM-associated missplicing. Silencing serine/arginine splicing factor 10 in placental models recapitulates the GDM-associated missplicing program.

Preclinical studies show that dietary or central administration of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) can reduce food intake, enhance energy expenditure, and attenuate hypothalamic inflammation (HI), whereas saturated fatty acids (SFAs) promote weight gain, HI, and neuronal injury. However, whether hypothalamic exposure to different fatty acids similarly influences HI and body weight in humans remains unclear. In this longitudinal study, we compared cerebrospinal fluid (CSF) free fatty acid (FFA) profiles between 19 normal-weight control participants and 44 individuals with obesity, both at baseline and 1 year after bariatric surgery (BS). We also examined associations between CSF FFA composition, MRI-based markers of HI (i.e., increased hypothalamic mean diffusivity [MD] and volume), and postoperative weight loss. At baseline, individuals with obesity had similar CSF concentrations of total FFA, SFA, and MUFA compared with control participants but significantly lower PUFA levels, mainly due to reduced docosahexaenoic acid (DHA) levels. BS did not substantially alter CSF FFA profiles. Lower baseline CSF DHA levels were associated with higher hypothalamic MD and independently predicted less weight loss at 1 year. Postoperative increases in CSF DHA levels correlated with reductions in hypothalamic MD. These findings suggest brain DHA level may influence hypothalamic microstructure and contribute to body weight regulation in human obesity.

We sought to investigate whether baseline insulin secretion (ϕtotal), quantified using the oral minimal model assessing β-cell function, could identify a subgroup of responders to abatacept (a cytotoxic T lymphocyte-associated protein 4 immunoglobulin that inhibits T-cell costimulation) among those with stage 1 type 1 diabetes (T1D). Abatacept preserved ϕtotal during and up to 1 year after treatment cessation; high baseline secretors treated with abatacept gained ∼16 months of progression-free survival and had a 54% lower hazard of progression versus those receiving placebo, whereas no benefit was observed in low secretors. This is the first evidence of an immune intervention delaying disease progression in those with stage 1 T1D. Continued treatment may result in a greater delay in progression.

Polygenic scores strongly predict type 1 diabetes risk, but most scores were developed in European-ancestry populations. In this study, we leveraged recent multiancestry genome-wide association studies to create a Type 1 Diabetes Multi-Ancestry Polygenic Score (T1D MAPS). We trained the score in the Mass General Brigham (MGB) Biobank (372 individuals with type 1 diabetes) and tested the score in the All of Us program (86 individuals with type 1 diabetes). We evaluated the area under the receiver operating characteristic curve (AUC), and we compared the AUC to two published single-ancestry scores for European (EUR) and African (AFR) populations: T1D Genetic Risk Score 2 (GRS2EUR) and T1D GRSAFR. We also developed an updated score (T1D MAPS2) that combines T1D GRS2EUR and T1D MAPS. Among individuals with non-European ancestry, the AUC of T1D MAPS was 0.90, significantly higher than T1D GRS2EUR (0.82) and T1D GRSAFR (0.82). Among individuals with European ancestry, the AUC of T1D MAPS was slightly lower than T1D GRS2EUR (0.89 vs. 0.91). However, T1D MAPS2 performed equivalently to T1D GRS2EUR in European ancestry (0.91 vs. 0.91) and performed better in non-European ancestry (0.90 vs. 0.82). Overall, these findings advance the accuracy of type 1 diabetes genetic risk prediction across diverse populations.

Mammalian target of rapamycin complex 1 (mTORC1) signaling is essential to β-cell mass, function, and adaptive immunity; however, its specific downstream mediators in type 1 diabetes (T1D) remain poorly defined. We investigated eukaryotic translation initiation factor 4E-binding protein 2 (4E-BP2), a major translational regulator downstream of mTORC1, by using global 4E-BP2-knockout mice on the NOD background. Loss of 4E-BP2 protected male NOD mice from T1D through preservation of β-cell mass and function, coupled with attenuation of autoimmune responses. These findings identify 4E-BP2 as a novel immunometabolic node, highlighting its potential as a therapeutic target for T1D prevention and treatment.

Obstructive sleep apnea (OSA) is a common condition strongly linked to increased cardiovascular risk and poor glycemic control. Little is known about OSA, cardiovascular risk, and glycemia in maturity-onset diabetes of the young (MODY), an inherited form of diabetes, which is different than both type 1 and type 2 diabetes. We assessed OSA, resting heart rate (RHR), an important prognostic marker of cardiovascular disease, and glycemic variability among the most common subtypes of MODY, glucokinase (GCK)-MODY, and transcription factor (TF)-related MODY (HNF1A, HNF4A, and HNF1B). Adults with GCK-MODY (n = 63) and TF-related MODY (n = 60) and control subjects without diabetes (n = 65) were screened for OSA by home sleep test. Glycemic variability (continuous glucose monitoring) and RHR (wearable sleep-activity tracker) were concomitantly assessed for 2 weeks at home. Data from 188 subjects (2,853 recorded days) were analyzed. Subjects with TF-related MODY, compared with those with GCK-MODY or control subjects, had more OSA (48.3%, 27.0%, and 30.8%, respectively; P = 0.033), higher RHR (72.8 ± 10.8, 65.2 ± 7.9, and 67.3 ± 7.7 bpm, respectively; P < 0.001), and higher glycemic variability (coefficient of variation of glucose 31.6 ± 6.0%, 17.3 ± 4.5%, and 17.5 ± 4.0%, respectively; P < 0.001). Greater severity of OSA and higher RHR were associated with higher glycemic variability. These findings may have important clinical implications for cardiovascular risk assessment in MODY.

In type 1 diabetes, CD8+ T cells destroy pancreatic β-cells. Since most β-cells avoid direct T-cell contact, we asked whether bystander effects drive their dysfunction and loss. We asked whether CD8+ T cells can damage β-cells indirectly via bystander inflammation. By developing and using a chimeric pseudoislet model, we show that β-cell killing requires direct CD8+ T-cell contact, contact-free β-cells are impacted by inflammation, that these effects are reproduced using conditioned medium from activated CD8+ T cells, and that insulin secretion is preserved with reduced storage and impaired protein translation. Our model provides a platform to dissect type 1 diabetes pathogenesis and test therapies to preserve β cells.

miRNAs are key regulators of metabolic homeostasis, yet their role in obesity-associated dysfunction remains incompletely understood. Here, we identify miR-432 as a driver of systemic metabolic dysregulation. Serum miRNA profiling revealed a positive correlation between miR-432 expression and obesity/type 2 diabetes mellitus. Functionally, adipose-specific miR-432 exacerbated high-fat diet-induced obesity and insulin resistance. Similarly, hepatic-specific miR-432 aggravated hepatic steatosis and systemic glucose dysregulation, while skeletal muscle-specific miR-432 disrupted glucose homeostasis without affecting body composition. Mechanistically, miR-432 disrupted insulin sensitivity by inhibiting the PIK3R3/AKT pathway and perturbed lipid homeostasis by suppressing the PIK3R3/PPAR-α axis. Notably, obesity-induced miR-432 upregulation was predominantly localized in adipocytes and driven by the CDK5/PPAR-γ axis. Furthermore, adipocyte-derived exosomal miR-432 was identified as a mediator of systemic metabolic dysfunction, facilitating intertissue cross talk in obesity. Collectively, our data demonstrate that miR-432 exacerbates obesity-induced dysregulation of glucose and lipid metabolism.