Characterization of transcript enrichment and detection bias in single-nucleus RNA-seq for mapping of distinct human adipocyte lineages.

Single-cell RNA sequencing (scRNA-seq) enables molecular characterization of complex biological tissues at high resolution. The requirement of single-cell extraction, however, makes it challenging for profiling tissues such as adipose tissue, for which collection of intact single adipocytes is complicated by their fragile nature. For such tissues, single-nucleus extraction is often much more efficient and therefore single-nucleus RNA sequencing (snRNA-seq) presents an alternative to scRNA-seq. However, nuclear transcripts represent only a fraction of the transcriptome in a single cell, with snRNA-seq marked with inherent transcript enrichment and detection biases. Therefore, snRNA-seq may be inadequate for mapping important transcriptional signatures in adipose tissue. In this study, we compare the transcriptomic landscape of single nuclei isolated from preadipocytes and mature adipocytes across human white and brown adipocyte lineages, with whole-cell transcriptome. We show that snRNA-seq is capable of identifying the broad cell types present in scRNA-seq at all states of adipogenesis. However, we also explore how and why the nuclear transcriptome is biased and limited, as well as how it can be advantageous. We robustly characterize the enrichment of nuclear-localized transcripts and adipogenic regulatory lncRNAs in snRNA-seq, while also providing a detailed understanding for the preferential detection of long genes upon using this technique. To remove such technical detection biases, we propose a normalization strategy for a more accurate comparison of nuclear and cellular data. Finally, we show successful integration of scRNA-seq and snRNA-seq data sets with existing bioinformatic tools. Overall, our results illustrate the applicability of snRNA-seq for the characterization of cellular diversity in the adipose tissue.

Long-Term Outcomes of Medical Management vs Bariatric Surgery in Type 2 Diabetes.

Importance: Randomized clinical trials of bariatric surgery have been limited in size, type of surgical procedure, and follow-up duration. Objective: To determine long-term glycemic control and safety of bariatric surgery compared with medical/lifestyle management of type 2 diabetes. Design, Setting, and Participants: ARMMS-T2D (Alliance of Randomized Trials of Medicine vs Metabolic Surgery in Type 2 Diabetes) is a pooled analysis from 4 US single-center randomized trials conducted between May 2007 and August 2013, with observational follow-up through July 2022. Intervention: Participants were originally randomized to undergo either medical/lifestyle management or 1 of the following 3 bariatric surgical procedures: Roux-en-Y gastric bypass, sleeve gastrectomy, or adjustable gastric banding. Main Outcome and Measures: The primary outcome was change in hemoglobin A1c (HbA1c) from baseline to 7 years for all participants. Data are reported for up to 12 years. Results: A total of 262 of 305 eligible participants (86%) enrolled in long-term follow-up for this pooled analysis. The mean (SD) age of participants was 49.9 (8.3) years, mean (SD) body mass index was 36.4 (3.5), 68.3% were women, 31% were Black, and 67.2% were White. During follow-up, 25% of participants randomized to undergo medical/lifestyle management underwent bariatric surgery. The median follow-up was 11 years. At 7 years, HbA1c decreased by 0.2% (95% CI, -0.5% to 0.2%), from a baseline of 8.2%, in the medical/lifestyle group and by 1.6% (95% CI, -1.8% to -1.3%), from a baseline of 8.7%, in the bariatric surgery group. The between-group difference was -1.4% (95% CI, -1.8% to -1.0%; P < .001) at 7 years and -1.1% (95% CI, -1.7% to -0.5%; P = .002) at 12 years. Fewer antidiabetes medications were used in the bariatric surgery group. Diabetes remission was greater after bariatric surgery (6.2% in the medical/lifestyle group vs 18.2% in the bariatric surgery group; P = .02) at 7 years and at 12 years (0.0% in the medical/lifestyle group vs 12.7% in the bariatric surgery group; P < .001). There were 4 deaths (2.2%), 2 in each group, and no differences in major cardiovascular adverse events. Anemia, fractures, and gastrointestinal adverse events were more common after bariatric surgery. Conclusion and Relevance: After 7 to 12 years of follow-up, individuals originally randomized to undergo bariatric surgery compared with medical/lifestyle intervention had superior glycemic control with less diabetes medication use and higher rates of diabetes remission. Trial Registration: ClinicalTrials.gov Identifier: NCT02328599.

Continuous glucose monitoring in patients with post-bariatric hypoglycaemia reduces hypoglycaemia and glycaemic variability.

AIM: To determine whether continuous glucose monitoring (CGM) can reduce hypoglycaemia in patients with post-bariatric hypoglycaemia (PBH). MATERIALS AND METHODS: In an open-label, nonrandomized, pre-post design with sequential assignment, CGM data were collected in 22 individuals with PBH in two sequential phases: (i) masked (no access to sensor glucose or alarms); and (ii) unmasked (access to sensor glucose and alarms for low or rapidly declining sensor glucose). Twelve participants wore the Dexcom G4 device for a total of 28 days, while 10 wore the Dexcom G6 device for a total of 20 days. RESULTS: Participants with PBH spent a lower percentage of time in hypoglycaemia over 24 hours with unmasked versus masked CGM (<3.3 mM/L, or <60 mg/dL: median [median absolute deviation {MAD}] 0.7 [0.8]% vs. 1.4 [1.7]%, P = 0.03; <3.9 mM/L, or <70 mg/dL: median [MAD] 2.9 [2.5]% vs. 4.7 [4.8]%; P = 0.04), with similar trends overnight. Sensor glucose data from the unmasked phase showed a greater percentage of time spent between 3.9 and 10 mM/L (70-180 mg/dL) (median [MAD] 94.8 [3.9]% vs. 90.8 [5.2]%; P = 0.004) and lower glycaemic variability over 24 hours (median [MAD] mean amplitude of glycaemic excursion 4.1 [0.98] vs. 4.4 [0.99] mM/L; P = 0.04). During the day, participants also spent a greater percentage of time in normoglycaemia with unmasked CGM (median [MAD] 94.2 [4.8]% vs. 90.9 [6.2]%; P = 0.005), largely due to a reduction in hyperglycaemia (>10 mM/L, or 180 mg/dL: median [MAD] 1.9 [2.2]% vs. 3.9 [3.6]%; P = 0.02). CONCLUSIONS: Real-time CGM data and alarms are associated with reductions in low sensor glucose, elevated sensor glucose, and glycaemic variability. This suggests CGM allows patients to detect hyperglycaemic peaks and imminent hypoglycaemia, allowing dietary modification and self-treatment to reduce hypoglycaemia. The use of CGM devices may improve safety in PBH, particularly for patients with hypoglycaemia unawareness.

Concept of the "Universal Slope": Toward Substantially Shorter Decentralized Insulin Immunoassays.

Decentralized sensing of analytes in remote locations is today a reality. However, the number of measurable analytes remains limited, mainly due to the requirement for time-consuming successive standard additions calibration used to address matrix effects and resulting in greatly delayed results, along with more complex and costly operation. This is particularly challenging in commonly used immunoassays of key biomarkers that typically require from 60 to 90 min for quantitation based on two standard additions, hence hindering their implementation for rapid and routine diagnostic applications, such as decentralized point-of-care (POC) insulin testing. In this work we have developed and demonstrated the theoretical framework for establishing a universal slope for direct calibration-free POC insulin immunoassays in serum samples using an electrochemical biosensor (developed originally for extended calibration by standard additions). The universal slope is presented as an averaged slope constant, relying on 68 standard additions-based insulin determinations in human sera. This new quantitative analysis approach offers reliable sample measurement without successive standard additions, leading to a dramatically simplified and faster assay (30 min vs 90 min when using 2 standard additions) and greatly reduced costs, without compromising the analytical performance while significantly reducing the analyses costs. The substantial improvements associated with the new universal slope concept have been demonstrated successfully for calibration-free measurements of serum insulin in 30 samples from individuals with type 1 diabetes using meticulous statistical analysis, supporting the prospects of applying this immunoassay protocol to routine decentralized POC insulin testing.

Microneedle Aptamer-Based Sensors for Continuous, Real-Time Therapeutic Drug Monitoring.

The ability to continuously monitor the concentration of specific molecules in the body is a long-sought goal of biomedical research. For this purpose, interstitial fluid (ISF) was proposed as the ideal target biofluid because its composition can rapidly equilibrate with that of systemic blood, allowing the assessment of molecular concentrations that reflect full-body physiology. In the past, continuous monitoring in ISF was enabled by microneedle sensor arrays. Yet, benchmark microneedle sensors can only detect molecules that undergo redox reactions, which limits the ability to sense metabolites, biomarkers, and therapeutics that are not redox-active. To overcome this barrier, here, we expand the scope of these devices by demonstrating the first use of microneedle-supported electrochemical, aptamer-based (E-AB) sensors. This platform achieves molecular recognition based on affinity interactions, vastly expanding the scope of molecules that can be sensed. We report the fabrication of microneedle E-AB sensor arrays and a method to regenerate them for multiple uses. In addition, we demonstrate continuous molecular measurements using these sensors in flow systems in vitro using single and multiplexed microneedle array configurations. Translation of the platform to in vivo measurements is possible as we demonstrate with a first E-AB measurement in the ISF of a rodent. The encouraging results reported in this work should serve as the basis for future translation of microneedle E-AB sensor arrays to biomedical research in preclinical animal models.

It Is Not Just Fat: Dissecting the Heterogeneity of Adipose Tissue Function.

PURPOSE OF REVIEW: The purpose of the current review is to summarize findings from the most recent and impactful studies which investigated human and mouse adipose tissue transcriptomes at a single-cell level. We provide perspective about the potential importance of data derived from these single-cell technologies in improving our understanding of the adipose organ and metabolic disease and likely future directions of this approach. RECENT FINDINGS: The majority of single-cell or single-nuclei studies of the adipose organ so far have focused on investigating the stromal-vascular fraction (SVF) of mouse subcutaneous and intraabdominal white and interscapular brown fat depots. Few studies have also evaluated the impact of additional factors as drivers of adipose phenotypes, such as high-fat diet-induced obesity, adolescence, aging, and cold exposure. Recent studies have also investigated human cell lines and human fat biopsies across a range of body mass index (BMI) and in response to insulin resistance or T2D. These studies have identified numerous previously unexplored subpopulations of adipocyte progenitors, immune cells, and mature adipocytes in both mice and men. Single-cell and single-nuclei technologies have brought an explosion of data that have advanced our understanding of the adipose organ in health and disease. However, we are still at the dawn of achieving a complete and comprehensive map of the mouse and human adipose organ. Multi-modal single-cell approaches to identify both anatomic localization of specific cellular populations and epigenetic mechanisms responsible for observed transcriptomic patterns are underway and will likely provide an even deeper understanding of the adipose organ in response to health and disease.

Growth Hormone and Counterregulation in the Pathogenesis of Diabetes.

PURPOSE OF REVIEW: Canonical growth hormone (GH)-dependent signaling is essential for growth and counterregulatory responses to hypoglycemia, but also may contribute to glucose homeostasis (even in the absence of hypoglycemia) via its impact on metabolism of carbohydrates, lipids and proteins, body composition, and cardiovascular risk profile. The aim of this review is to summarize recent data implicating GH action in metabolic control, including both IGF-1-dependent and -independent pathways, and its potential role as target for T2D therapy. RECENT FINDINGS: Experimental blockade of the GHR can modulate glucose metabolism. Moreover, the soluble form of the GH receptor (GHR, or GHBP) was recently identified as a mediator of improvement in glycemic control in patients with T2D randomized to bariatric surgery vs. medical therapy. Reductions in GHR were accompanied by increases in plasma GH, but unchanged levels of both total and free IGF-1. Likewise, hepatic GHR expression is reduced following both RYGB and VSG in rodents. Emerging data indicate that GH signaling is important for regulation of long-term glucose metabolism in T2D. Future studies will be required to dissect tissue-specific GH signaling and sensitivity and their contributions to systemic glucose metabolism.

Pramlintide for post-bariatric hypoglycaemia.

AIMS: The aim of this study was to examine the hypothesis that pramlintide would reduce hypoglycaemia by slowing gastric emptying and reducing postprandial glucagon secretion, thus limiting postprandial glycaemic excursions and insulin secretion, and thus to determine the efficacy of pramlintide on frequency and severity of hypoglycaemia in post-bariatric hypoglycaemia (PBH). MATERIALS AND METHODS: Participants with PBH following gastric bypass were recruited from outpatient clinics at the Joslin Diabetes Center, Boston, Massachusetts for an open-label study of pramlintide efficacy over 8 weeks. Twenty-three participants were assessed for eligibility, 20 participants had at least one pramlintide dose, and 14 completed the study. A mixed-meal tolerance test (MMTT) was performed at baseline and after 8 weeks of subcutaneous pramlintide with a sequential dose increase to a maximum of 120 micrograms (mean 69 ± 32 mcg) three times daily. The primary endpoint was change in glucose excursions during the MMTT. Secondary measures included MMTT insulin response, satiety and dumping score, percentage time with sensor glucose (SG) <3.9 mM, and number of days with minimum SG <3 mM, during masked continuous glucose monitoring. RESULTS: There were no differences in MMTT glucose, glucagon or insulin between baseline and post treatment. We observed no significant change in satiety or dumping scores. The overall frequency of low SG values did not change, although there was substantial inter-individual variability. CONCLUSIONS: In PBH, pramlintide does not modulate glycaemic or insulin responses, satiety, or dumping scores during an MMTT and does not impact glycaemic excursions or decrease low SG levels in the outpatient setting.

Alliance of Randomized Trials of Medicine vs Metabolic Surgery in Type 2 Diabetes (ARMMS-T2D): Study rationale, design, and methods.

AIMS: Long-term data from randomized clinical trials comparing metabolic (bariatric) surgery versus a medical/lifestyle intervention for treatment of patients with obesity/overweight and type 2 diabetes (T2D) are lacking. The Alliance of Randomized Trials of Medicine vs Metabolic Surgery in Type 2 Diabetes (ARMMS-T2D) is a consortium of four randomized trials designed to compare long-term efficacy and safety of surgery versus medical/lifestyle therapy on diabetes control and clinical outcomes. MATERIALS AND METHODS: Patients with T2D and body mass index (BMI) of 27-45 kg/m2 who were previously randomized to metabolic surgery (Roux-en-Y gastric bypass, adjustable gastric band, or sleeve gastrectomy) versus medical/lifestyle intervention in the STAMPEDE, SLIMM-T2D, TRIABETES, or CROSSROADS trials have been enrolled in ARMMS-T2D for observational follow-up. The primary outcome is change in glycated haemoglobin after a minimum 7 years of follow-up, with additional analyses to determine rates of diabetes remission and relapse, as well as cardiovascular and renal endpoints. RESULTS: In total, 302 patients (192 surgical, 110 medical/lifestyle) previously randomized in the four parent studies were eligible for participation in the ARMMS-T2D observational study. Participant demographics were 71% white, 27% African-American and 68% female. At baseline: age, 50 ± 8 years; BMI, 36.5 ± 3.5 kg/m2 ; duration of diabetes, 8.8 ± 5.6 years; glycated haemoglobin, 8.6% ± 1.6%; and fasting glucose, 168 ± 64 mg/dl. More than 35% of patients had a BMI <35 kg/m2 . CONCLUSIONS: ARMMS-T2D will provide the largest body of long-term, level 1 evidence to inform clinical decision-making regarding the comparative durability, efficacy and safety of metabolic surgery relative to a medical/lifestyle intervention among patients with T2D, including those with milder class I obesity or mere overweight.

Skeletal muscle expression of adipose-specific phospholipase in peripheral artery disease.

Flow-limiting atherosclerotic lesions of arteries supplying the limbs are a cause of symptoms in patients with peripheral artery disease (PAD). Musculoskeletal metabolic factors also contribute to the pathophysiology of claudication, which is manifest as leg discomfort that impairs walking capacity. Accordingly, we conducted a case-control study to determine whether skeletal muscle metabolic gene expression is altered in PAD. Calf skeletal muscle gene expression of patients with PAD and healthy subjects was analyzed using microarrays. The top-ranking gene differentially expressed between PAD and controls (FDR < 0.001) was PLA2G16, which encodes adipose-specific phospholipase A2 (AdPLA) and is implicated in the maintenance of insulin sensitivity and regulation of lipid metabolism. Differential expression was confirmed by qRT-PCR; PLA2G16 was downregulated by 68% in patients with PAD (p < 0.001). Expression of Pla2g16 was then measured in control (db/+) and diabetic (db/db) mice that underwent unilateral femoral artery ligation. There was significantly reduced expression of Pla2g16 in the ischemic leg of both control and diabetic mice (by 51%), with significantly greater magnitude of reduction in the diabetic mice (by 79%). We conclude that AdPLA is downregulated in humans with PAD and in mice with hindlimb ischemia. Reduced AdPLA may contribute to impaired walking capacity in patients with PAD via its effects on skeletal muscle metabolism. Further studies are needed to fully characterize the role of AdPLA in PAD and to investigate its potential as a therapeutic target for alleviating symptoms of claudication.

Paternal Nongenetic Intergenerational Transmission of Metabolic Disease Risk.

PURPOSE OF REVIEW: Paternal metabolic disease before conception and during spermatogenesis can adversely impact the metabolic health of offspring in later life. Here, we review the current understanding of sperm epigenetic markers as contributors to intergenerational transmission of disease risk in both human and animal studies, and review potential intervention strategies. RECENT FINDINGS: Epidemiological studies suggest an increased risk of adverse outcomes in the offspring of fathers with obesity, diabetes, advanced age, smoking, and ancestral exposures. Potential molecular mechanisms contributing to intergenerational disease risk include genetics (DNA sequence) as well as epigenetic factors in the sperm, such as DNA methylation, chromatin and histone modification, and coding and noncoding RNAs. Potential strategies to interrupt intergenerational transmission of disease risk include increased physical activity, weight loss, bariatric surgery, cold exposure, and improved glycemic control prior to conception. Many studies suggest environmental factors experienced by fathers can program disease risk in the next generation via sperm cell-mediated transmission. Better understanding the mechanisms through which paternal metabolism influences sperm cells will help to design better intervention strategies. Future research will focus on the molecular signals that mediate the impact of paternal factors on sperm epigenetic signals and also how these affect offspring embryonic development and disease risk during adult life.

Myotubes derived from human-induced pluripotent stem cells mirror in vivo insulin resistance.

Induced pluripotent stem cells (iPS cells) represent a unique tool for the study of the pathophysiology of human disease, because these cells can be differentiated into multiple cell types in vitro and used to generate patient- and tissue-specific disease models. Given the critical role for skeletal muscle insulin resistance in whole-body glucose metabolism and type 2 diabetes, we have created a novel cellular model of human muscle insulin resistance by differentiating iPS cells from individuals with mutations in the insulin receptor (IR-Mut) into functional myotubes and characterizing their response to insulin in comparison with controls. Morphologically, IR-Mut cells differentiated normally, but had delayed expression of some muscle differentiation-related genes. Most importantly, whereas control iPS-derived myotubes exhibited in vitro responses similar to primary differentiated human myoblasts, IR-Mut myotubes demonstrated severe impairment in insulin signaling and insulin-stimulated 2-deoxyglucose uptake and glycogen synthesis. Transcriptional regulation was also perturbed in IR-Mut myotubes with reduced insulin-stimulated expression of metabolic and early growth response genes. Thus, iPS-derived myotubes from individuals with genetically determined insulin resistance demonstrate many of the defects observed in vivo in insulin-resistant skeletal muscle and provide a new model to analyze the molecular impact of muscle insulin resistance.

Insulin Resistance and Mitochondrial Dysfunction.

Insulin resistance precedes and predicts the onset of type 2 diabetes (T2D) in susceptible humans, underscoring its important role in the complex pathogenesis of this disease. Insulin resistance contributes to multiple tissue defects characteristic of T2D, including reduced insulin-stimulated glucose uptake in insulin-sensitive tissues, increased hepatic glucose production, increased lipolysis in adipose tissue, and altered insulin secretion. Studies of individuals with insulin resistance, both with established T2D and high-risk individuals, have consistently demonstrated a diverse array of defects in mitochondrial function (i.e., bioenergetics, biogenesis and dynamics). However, it remains uncertain whether mitochondrial dysfunction is primary (critical initiating defect) or secondary to the subtle derangements in glucose metabolism, insulin resistance, and defective insulin secretion present early in the course of disease development. In this chapter, we will present the evidence linking mitochondrial dysfunction and insulin resistance, and review the potential for mitochondrial targets as a therapeutic approach for T2D.

What Have Metabolomics Approaches Taught Us About Type 2 Diabetes?

Type 2 diabetes (T2D) is increasing worldwide, making identification of biomarkers for detection, staging, and effective prevention strategies an especially critical scientific and medical goal. Fortunately, advances in metabolomics techniques, together with improvements in bioinformatics and mathematical modeling approaches, have provided the scientific community with new tools to describe the T2D metabolome. The metabolomics signatures associated with T2D and obesity include increased levels of lactate, glycolytic intermediates, branched-chain and aromatic amino acids, and long-chain fatty acids. Conversely, tricarboxylic acid cycle intermediates, betaine, and other metabolites decrease. Future studies will be required to fully integrate these and other findings into our understanding of diabetes pathophysiology and to identify biomarkers of disease risk, stage, and responsiveness to specific treatments.