Pathogenesis of A⁻β⁺ ketosis-prone diabetes

Clinical metabolomics in type 2 diabetes mellitus: from pathogenesis to biomarkers

As a multidimensional metabolic disorder, the disability and death rate of type 2 diabetes mellitus (T2DM) has increased over time. T2DM covers a wide range of pathological manifestations ranging from hyperglycemia to multi-organ failure, and it has the potential to evolve into acute complications, including ketosis and chronic complications such as peripheral neuropathy, retinopathy, and nephropathy. T2DM mainly occurs in microvascular and large vessels and thus it is restricted for the clinician to diagnose and prescribe. However, the pathological mechanism and clinical diagnosis are inadequate. High-throughput metabolomics, characterized by non-invasive diagnostic techniques to identify potential biomarkers and distinct stages of T2DM, has been increasingly recognized as a vigorous tool with latent capacity for clinical translation. The pathological stratification of T2DM can significantly reduce disability and mortality rates. By tracing the metabolome and associated pathways from impaired fasting blood glucose or impaired glucose tolerance to severe organ failure, the chief contributions of large, independent population-based cohorts are summarized herein. These results facilitate understanding the pathophysiology and mechanism and supports research in accurate diagnosis, risk prediction, curative effect, distinct stages, and prognosis judgment of T2DM.

A Rare Case of Ketosis-Prone Type 2 Diabetes With a Unique Human Leukocyte Antigen (HLA) Profile: Genetic and Metabolic Insights

This report describes the case of a 21-year-old man with ketosis-prone type 2 diabetes (KPD), highlighting the genetic and metabolic factors influencing disease progression. The patient presented with diabetic ketoacidosis and demonstrated rapid insulin secretory recovery, allowing early discontinuation of insulin. Genetic analysis revealed human leukocyte antigen (HLA)-DRB1*15:01 and DRB1*09:01 haplotypes, suggesting a role of immune factors typically associated with type 1 diabetes in the pathogenesis of KPD. Metabolic factors, evidenced by prolonged ketone clearance, further underscore the complexity of KPD. These findings contribute to a growing understanding of KPD as a unique subtype of diabetes, reinforcing the importance of personalized, genetically informed management approaches for optimal care.

Random C-Peptide and Islet Antibodies at Onset Predict β Cell Function Trajectory and Insulin Dependence in Pediatric Diabetes

OBJECTIVE

Identification of prognostic biomarkers in pediatric diabetes is important for precision medicine. We assessed whether C-peptide and islet autoantibodies are useful to predict the natural history of children with new-onset diabetes.

METHODS

We prospectively studied 72 children with new-onset diabetes (median follow-up: 8 months) by applying the Aβ classification system ("A+": islet autoantibody positive, "β+": random serum C-peptide ≥1.3 ng/mL at diagnosis). Beta-cell function was assessed longitudinally with 2 hours postprandial/stimulated urinary C-peptide-to-creatinine ratio (UCPCR) 3-12 weeks (V1) and 6 to 12 months after diagnosis (V2). We obtained a type 1 diabetes genetic risk score for each participant, and compared characteristics at baseline, and clinical outcomes at V2.

RESULTS

The cohort was 50% male. Racial distribution was 76.4% White, 20.8% Black, and 2.8% Asian or other races. A total of 46.5% participants were Hispanic. Median age (Q1-Q3) was 12.4 (8.3-14.5) years. The Aβ subgroup frequencies were 46 A+β-(63.9%), 1 A-β-(1.4%), 4 A+β+(5.6%), and 21 A-β+(29.2%). Baseline serum C-peptide correlated with UCPCR at both V1 (r = 0.36, P = .002) and V2 (r = 0.47, P < .001). There were significant subgroup differences in age, race, frequency of diabetic ketoacidosis, and type 1 diabetes genetic risk score (P < .01). At V2, the 2 β-subgroups had lower UCPCR and higher hemoglobin A1c compared with the 2 β+ subgroups (P < .001 and P = .02, respectively). Thirty-eight percent of A-β+ but none of the other subgroups were insulin-independent at V2 (P < .001).

CONCLUSION

C-peptide and islet autoimmunity at diagnosis define distinct phenotypes and predict beta-cell function and insulin dependence 6 to 12 months later in racially/ethnically diverse children with new-onset diabetes.

Atypical Diabetes: What Have We Learned and What Does the Future Hold?

As our understanding of the pathophysiology of diabetes evolves, we increasingly recognize that many patients may have a form of diabetes that does not neatly fit with a diagnosis of either type 1 or type 2 diabetes. The discovery and description of these forms of "atypical diabetes" have led to major contributions to our collective understanding of the basic biology that drives insulin secretion, insulin resistance, and islet autoimmunity. These discoveries now pave the way to a better classification of diabetes based on distinct endotypes. In this review, we highlight the key biological and clinical insights that can be gained from studying known forms of atypical diabetes. Additionally, we provide a framework for identification of patients with atypical diabetes based on their clinical, metabolic, and molecular features. Helpful clinical and genetic resources for evaluating patients suspected of having atypical diabetes are provided. Therefore, appreciating the various endotypes associated with atypical diabetes will enhance diagnostic accuracy and facilitate targeted treatment decisions.

High Prevalence of A-β+ Ketosis-Prone Diabetes in Children with Type 2 Diabetes and Diabetic Ketoacidosis at Diagnosis: Evidence from the Rare and Atypical Diabetes Network (RADIANT)

Background

A-β+ ketosis-prone diabetes (KPD) in adults is characterized by presentation with diabetic ketoacidosis (DKA), negative islet autoantibodies, and preserved β-cell function in persons with a phenotype of obesity-associated type 2 diabetes (T2D). The prevalence of KPD has not been evaluated in children. We investigated children with DKA at "T2D" onset and determined the prevalence and characteristics of pediatric A-β+ KPD within this cohort.

Methods

We reviewed the records of 716 children with T2D at a large academic hospital and compared clinical characteristics of those with and without DKA at onset. In the latter group, we identified patients with A-β+ KPD using criteria of the Rare and Atypical Diabetes Network (RADIANT) and defined its prevalence and characteristics.

Results

Mean age at diagnosis was 13.7 ± 2.4 years: 63% female; 59% Hispanic, 29% African American, 9% non-Hispanic White, and 3% other. Fifty-six (7.8%) presented with DKA at diagnosis and lacked islet autoantibodies. Children presenting with DKA were older and had lower C-peptide and higher glucose concentrations than those without DKA. Twenty-five children with DKA (45%) met RADIANT A-β+ KPD criteria. They were predominantly male (64%), African American or Hispanic (96%), with substantial C-peptide (1.3 ± 0.7 ng/mL) at presentation with DKA and excellent long-term glycemic control (HbA1c 6.6% ± 1.9% at follow-up (median 1.3 years postdiagnosis)).

Conclusions

In children with a clinical phenotype of T2D and DKA at diagnosis, approximately half meet criteria for A-β+ KPD. They manifest the key characteristics of obesity, preserved β-cell function, male predominance, and potential to discontinue insulin therapy, similar to adults with A-β+ KPD.

Plasma amino acid signatures define types of pediatric diabetes

BACKGROUND & AIMS

Metabolic biomarkers with pathophysiological relevance is lacking in pediatric diabetes. We aimed to identify novel metabolic biomarkers in pediatric type 1 (T1D) and type 2 diabetes (T2D). We hypothesized that (1) targeted plasma metabolomics, focused on plasma amino acid concentrations, could identify distinctively altered patterns in children with T1D or T2D, and (2) there are specific changes in concentrations of metabolites related to branch chain amino acids (BCAA) and arginine metabolism in children with T2D.

METHODS

In a pilot study, we enrolled children with T1D (n = 15) and T2D (n = 13), and healthy controls (n = 15). Fasting plasma amino acid concentrations were measured by ultra-performance liquid chromatography, and compared between the groups after adjustment for confounding factors.

RESULTS

The mean age (SD) of participants was 16.4 (0.9) years. There were no group differences in age, gender, race/ethnicity, or 24-h protein intake. Mean BMI percentile was higher in the T2D than the T1D group or controls (p < 0.001). The T2D group had lower arginine, citrulline, glutamine, glycine, phenylalanine, methionine, threonine, asparagine and symmetric dimethylarginine (SDMA) but higher aspartate than controls, after adjusting for BMI percentiles (all p < 0.05). Children with T2D also had lower glycine but higher ornithine, proline, leucine, isoleucine, valine, total BCAA, lysine and tyrosine than those with T1D after adjusting for confounding factors (all p < 0.05). Children with T1D had lower phenylalanine, methionine, threonine, glutamine, tyrosine, asymmetric dimethylarginine (ADMA) and SDMA than controls (all p < 0.05).

CONCLUSIONS

Children with T2D and T1D have distinct fasting plasma amino acid signatures that suggest varying pathogenic mechanisms and could serve as biomarkers for these conditions.

Development and validation of a multivariable risk prediction model for identifying ketosis-prone type 2 diabetes

BACKGROUND

To develop and validate a multivariable risk prediction model for ketosis-prone type 2 diabetes mellitus (T2DM) based on clinical characteristics.

METHODS

A total of 964 participants newly diagnosed with T2DM were enrolled in the modeling and validation cohort. Baseline clinical data were collected and analyzed. Multivariable logistic regression analysis was performed to select independent risk factors, develop the prediction model, and construct the nomogram. The model's reliability and validity were checked using the receiver operating characteristic curve and the calibration curve.

RESULTS

A high morbidity of ketosis-prone T2DM was observed (20.2%), who presented as lower age and fasting C-peptide, and higher free fatty acids, glycated hemoglobin A1c and urinary protein. Based on these five independent influence factors, we developed a risk prediction model for ketosis-prone T2DM and constructed the nomogram. Areas under the curve of the modeling and validation cohorts were 0.806 (95% confidence interval [CI]: 0.760-0.851) and 0.856 (95% CI: 0.803-0.908). The calibration curves that were both internally and externally checked indicated that the projected results were reasonably close to the actual values.

CONCLUSIONS

Our study provided an effective clinical risk prediction model for ketosis-prone T2DM, which could help for precise classification and management.

The Rare and Atypical Diabetes Network (RADIANT) Study: Design and Early Results

OBJECTIVE

The Rare and Atypical Diabetes Network (RADIANT) will perform a study of individuals and, if deemed informative, a study of their family members with uncharacterized forms of diabetes.

RESEARCH DESIGN AND METHODS

The protocol includes genomic (whole-genome [WGS], RNA, and mitochondrial sequencing), phenotypic (vital signs, biometric measurements, questionnaires, and photography), metabolomics, and metabolic assessments.

RESULTS

Among 122 with WGS results of 878 enrolled individuals, a likely pathogenic variant in a known diabetes monogenic gene was found in 3 (2.5%), and six new monogenic variants have been identified in the SMAD5, PTPMT1, INS, NFKB1, IGF1R, and PAX6 genes. Frequent phenotypic clusters are lean type 2 diabetes, autoantibody-negative and insulin-deficient diabetes, lipodystrophic diabetes, and new forms of possible monogenic or oligogenic diabetes.

CONCLUSIONS

The analyses will lead to improved means of atypical diabetes identification. Genetic sequencing can identify new variants, and metabolomics and transcriptomics analysis can identify novel mechanisms and biomarkers for atypical disease.

Data Mining Framework for Discovering and Clustering Phenotypes of Atypical Diabetes

CONTEXT

Some individuals present with forms of diabetes that are "atypical" (AD), which do not conform to typical features of either type 1 diabetes (T1D) or type 2 diabetes (T2D). These forms of AD display a range of phenotypic characteristics that likely reflect different endotypes based on unique etiologies or pathogenic processes.

OBJECTIVE

To develop an analytical approach to identify and cluster phenotypes of AD.

METHODS

We developed Discover Atypical Diabetes (DiscoverAD), a data mining framework, to identify and cluster phenotypes of AD. DiscoverAD was trained against characteristics of manually classified patients with AD among 278 adults with diabetes within the Cameron County Hispanic Cohort (CCHC) (Study A). We then tested DiscoverAD in a separate population of 758 multiethnic children with T1D within the Texas Children's Hospital Registry for New-Onset Type 1 Diabetes (TCHRNO-1) (Study B).

RESULTS

We identified an AD frequency of 11.5% in the CCHC (Study A) and 5.3% in the pediatric TCHRNO-1 (Study B). Cluster analysis identified 4 distinct groups of AD in Study A: cluster 1, positive for the 65 kDa glutamate decarboxylase autoantibody (GAD65Ab), adult-onset, long disease duration, preserved beta-cell function, no insulin treatment; cluster 2, GAD65Ab negative, diagnosed at age ≤21 years; cluster 3, GAD65Ab negative, adult-onset, poor beta-cell function, lacking central obesity; cluster 4, diabetic ketoacidosis (DKA)-prone participants lacking a typical T1D phenotype. Applying DiscoverAD to the pediatric patients with T1D in Study B revealed 2 distinct groups of AD: cluster 1, autoantibody negative, poor beta-cell function, lower body mass index (BMI); cluster 2, autoantibody positive, higher BMI, higher incidence of DKA.

CONCLUSION

DiscoverAD can be adapted to different datasets to identify and define phenotypes of participants with AD based on available clinical variables.

Remission in Ketosis-Prone Diabetes

Heterogeneous forms of Ketosis-prone diabetes (KPD) are characterized by patients who present with diabetic ketoacidosis (DKA) but lack the typical features and biomarkers of autoimmune T1D. The A-β+ subgroup of KPD provides unique insight into the concept of "remission" since these patients have substantial preservation of beta-cell function permitting the discontinuation of insulin therapy, despite initial presentation with DKA. Measurements of C-peptide levels are essential to predict remission and guide potential insulin withdrawal. Further studies into predictors of remission and relapse can help us guide patients with A-β+ KPD toward remission and develop targeted treatments for this form of atypical diabetes.

Branched-chain α-keto acids and glutamate/glutamine: Biomarkers of insulin resistance in childhood obesity

OBJECTIVES

Insulin resistance (IR) in adolescents with obesity is associated with a sex-dependent metabolic 'signature' comprising the branched-chain amino acids (BCAAs), glutamate/glutamine, C3/C5 acylcarnitines and uric acid. Here, we compared the levels of branched-chain α-keto acids (BCKAs) and glutamate/glutamine, which are the byproducts of BCAA catabolism and uric acid among adolescents with obesity prior to and following a 6-month lifestyle-intervention program.

METHODS

Fasting plasma samples from 33 adolescents with obesity (16 males, 17 females, aged 12-18 year) were analysed by flow-injection tandem MS and LC-MS/MS. Multiple linear regression models were used to correlate changes in BCKAs, glutamate/glutamine and uric acid with changes in weight and insulin sensitivity as assessed by HOMA-IR, adiponectin and the ratio of triglyceride (TG) to HDL. In predictive models, BCKAs, glutamate/glutamine and uric acid at baseline were used as explanatory variables.

RESULTS

Baseline BCKAs, glutamate/glutamine and uric acid were higher in males than females despite comparable BMI-metrics. Following lifestyle-intervention, α-keto-β-methylvalerate (α-KMV, a metabolic by product of isoleucine) decreased in males but not in females. The ratio of BCKA/BCAA trended lower in males. In the cohort as a whole, BCKAs correlated positively with the ratio of TG to HDL at baseline and HOMA-IR at 6-month-follow-up. Glutamate/glutamine was positively associated with HOMA-IR at baseline and 6-month-follow-up. A reduction in BCKAs was associated with an increase in adiponectin, and those with higher BCKAs at baseline had higher adiponectin levels at 6-month-follow-up. Interestingly those adolescents with higher uric acid levels at baseline had greater reduction in weight.

CONCLUSIONS

BCKAs and glutamate/glutamine may serve as biomarkers of IR in adolescents with obesity, and uric acid might serve as a predictor of weight loss in response to lifestyle-intervention. Differential regulation of BCAA catabolism in adolescent males and females implicates critical roles for sex steroids in metabolic homeostasis.

Ketosis-prone diabetes mellitus: A phenotype that hospitalists need to understand

Diabetes has been classified mainly into types 1 and 2. Some type 2 diabetes patients, when developing ketosis, have been labeled as having atypical diabetes. Lately, syndromes of ketosis-prone diabetes, primarily in patients who we previously classified as type 2 diabetics, have emerged, and calls are being made to even reclassify diabetes. This mini-review will extensively deal with the historical, molecular, phenotypical, and clinical basis of why ketosis-prone diabetes is different than the traditional principles of type 1 and 2 diabetes and should be classified as such. Clinicians, especially those who are not diabetologists or endocrinologists, as well as hospitalists, intensivists, and primary care providers, will greatly benefit from this review.

A patient with ketosis-prone type 2 diabetes showing nearly normalized glucose tolerance after recovery from severe diabetic ketoacidosis

Unprovoked A-β+ ketosis-prone type 2 diabetes (KPD) is characterized by the sudden onset of diabetic ketosis/ketoacidosis (DK/DKA) without precipitating factors, negative anti-islet autoantibodies ("A- "), and preservation of β-cell function ("β+ ") after recovery from DKA using insulin therapy. However, there have been few reports on glucose tolerance after recovery. We present a case of KPD with nearly normalized glucose tolerance after recovery from severe DKA. A 41-year-old obese woman first presented with unprovoked severe DKA, i.e., ketonuria, plasma glucose 570 mg/dL, pH 7.18, and HCO₃ ^- 5.2 mmol/L, without anti-islet autoantibodies. She achieved insulin-free glycemic remission after recovery from DKA, leading to the diagnosis of KPD. Thereafter, 75 g oral glucose tolerance test showed impaired fasting glucose and time-in-range using intermittently scanned continuous glucose monitoring was 97% without medication. These findings suggest that, despite the initial severe DKA, some patients with KPD might achieve normalized glucose tolerance after recovery. The similar onset patterns of DKA necessitates appropriately distinguishing KPD from acute-onset type 1B (idiopathic) diabetes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13340-022-00599-6.

Clinical Significance of Insulin Peptide-specific Interferon-γ-related Immune Responses in Ketosis-prone Type 2 Diabetes

CONTEXT

Unprovoked A-β+ ketosis-prone type 2 diabetes (KPD) is characterized by the sudden onset of diabetic ketosis/ketoacidosis (DK/DKA) without precipitating factors, negative anti-islet autoantibodies ("A-"), and preservation of β-cell function ("β+") after recovery from DKA. Although this phenotype often appears with acute hyperglycemia and DK/DKA just like acute-onset type 1 diabetes (AT1D), the involvement of anti-islet immune responses remains unknown.

OBJECTIVE

We sought to clarify the immunological role of insulin-associated molecules in unprovoked A-β+ KPD.

METHODS

In this cross-sectional study, blood samples from 75 participants (42 with AT1D and 33 with KPD) were evaluated for interferon (IFN)-γ-secreting peripheral blood mononuclear cells (PBMCs) reactive to 4 insulin B-chain amino acid 9-23-related peptides (B:9-23rPep) using an enzyme-linked immunospot (ELISpot) assay.

RESULTS

Overall, 36.4% (12/33) of KPD participants showed positive IFN-γ ELISpot assay results; the positivity rate in KPD was similar to that in AT1D (38.1%; 16/42) and statistically significantly higher than the previously reported rate in type 2 diabetes (8%; 2/25; P < .0167). Moreover, B:9-23rPep-specific IFN-γ-producing PBMC frequency was negatively correlated with age and ad lib serum C-peptide levels in all KPD participants and positively correlated with glycated hemoglobin A1c level in KPD participants with positive IFN-γ ELISpot results.

CONCLUSION

These findings suggest the involvement of B:9-23rPep-specific IFN-γ-related immunoreactivity in the pathophysiology of some unprovoked A-β+ KPD. Moreover, increased immunoreactivity may reflect transiently decreased β-cell function and increased disease activity at the onset of DK/DKA, thereby playing a key role in DK/DKA development in this KPD phenotype.

Characterizing progressive beta-cell recovery after new-onset DKA in COVID-19 provoked A-β+ KPD (ketosis-prone diabetes): A prospective study from Eastern India

BACKGROUND

Recent literature suggests a bi-directional relationship between COVID-19 infection and diabetes mellitus, with an increasing number of previously normoglycemic adults with COVID-19 being admitted with new-onset diabetic ketoacidosis (DKA). However, the possibility of COVID-19 being a potential trigger for A-β + ketosis-prone diabetes (KPD) in these patients needs elucidation. Our study aimed at analyzing such a cohort of patients and determining their natural course of β-cell recovery on serial follow-up.

METHODS

After initial screening, n = 42 previously non-diabetic patients with new-onset DKA and RT-PCR positive COVID-19, were included in our ten-month follow-up study. Of these, n = 22 were negative (suspected A-β + KPD) and n = 20 were positive (Type 1A DM) for autoantibodies (GAD/IA-2/ZnT8). Subsequently, n = 19 suspected KPD and n = 18 Type 1A DM patients were followed-up over ten months with serial assessments of clinical, biochemical and β-cell secretion. Amongst the former, n = 15 (79%) patients achieved insulin independence, while n = 4 (21%) continued to require insulin at ten-months follow-up.

RESULTS

On comparison, the suspected KPD patients showed significantly greater BMI, age, Hba1c, IL-6 and worse DKA parameters at presentation. Serial C-peptide estimations demonstrated significant β-cell recovery in KPD group, with complete recovery seen in the 15 patients who became insulin independent on follow-up. Younger age, lower BMI, initial severity of DKA and inflammation (IL-6 levels), along-with reduced 25-hydroxy-Vitamin-D levels were associated with poorer recovery of β-cell secretion at ten-month follow-up amongst the KPD patients, CONCLUSIONS: This is the first prospective study to demonstrate progressive recovery of β-cell secretion in new-onset A-β + KPD provoked by COVID-19 infection in Indian adults, with a distinctly different profile from Type 1A DM. Given their significant potential for β-cell recovery, meticulous follow-up involving C-peptide estimations can help guide treatment and avoid injudicious use of insulin.

Spectrum of Phenotypes and Causes of Type 2 Diabetes in Children

Several factors, including genetics, family history, diet, physical activity, obesity, and insulin resistance in puberty, appear to increase the risk of type 2 diabetes in youth. Youth-onset type 2 diabetes is often thought of as a single entity but rather exists as a spectrum of disease with differences in presentation, metabolic characteristics, clinical progression, and complication rates. We review what is currently known regarding the risks associated with developing type 2 diabetes in youth. Additionally, we focus on the spectrum of phenotypes of pediatric type 2 diabetes, discuss the pathogenic underpinnings and potential therapeutic relevance of this heterogeneity, and compare youth-onset type 2 diabetes with type 1 diabetes and adult-onset type 2 diabetes. Finally, we highlight knowledge gaps in prediction and prevention of youth-onset type 2 diabetes.

Toward an Improved Classification of Type 2 Diabetes: Lessons From Research into the Heterogeneity of a Complex Disease

CONTEXT

Accumulating evidence indicates that type 2 diabetes (T2D) is phenotypically heterogeneous. Defining and classifying variant forms of T2D are priorities to better understand its pathophysiology and usher clinical practice into an era of "precision diabetes."

EVIDENCE ACQUISITION AND METHODS

We reviewed literature related to heterogeneity of T2D over the past 5 decades and identified a range of phenotypic variants of T2D. Their descriptions expose inadequacies in current classification systems. We attempt to link phenotypically diverse forms to pathophysiology, explore investigative methods that have characterized "atypical" forms of T2D on an etiological basis, and review conceptual frameworks for an improved taxonomy. Finally, we propose future directions to achieve the goal of an etiological classification of T2D.

EVIDENCE SYNTHESIS

Differences among ethnic and racial groups were early observations of phenotypic heterogeneity. Investigations that uncover complex interactions of pathophysiologic pathways leading to T2D are supported by epidemiological and clinical differences between the sexes and between adult and youth-onset T2D. Approaches to an etiological classification are illustrated by investigations of atypical forms of T2D, such as monogenic diabetes and syndromes of ketosis-prone diabetes. Conceptual frameworks that accommodate heterogeneity in T2D include an overlap between known diabetes types, a "palette" model integrated with a "threshold hypothesis," and a spectrum model of atypical diabetes.

CONCLUSION

The heterogeneity of T2D demands an improved, etiological classification scheme. Excellent phenotypic descriptions of emerging syndromes in different populations, continued clinical and molecular investigations of atypical forms of diabetes, and useful conceptual models can be utilized to achieve this important goal.

Pancreatic Differentiation of Stem Cells Reveals Pathogenesis of a Syndrome of Ketosis-Prone Diabetes

Genetic analysis of an adult patient with an unusual course of ketosis-prone diabetes (KPD) and lacking islet autoantibodies demonstrated a nucleotide variant in the 5'-untranslated region (UTR) of PDX1, a β-cell development gene. When differentiated to the pancreatic lineage, his induced pluripotent stem cells stalled at the definitive endoderm (DE) stage. Metabolomics analysis of the cells revealed that this was associated with leucine hypersensitivity during transition from the DE to the pancreatic progenitor (PP) stage, and RNA sequencing showed that defects in leucine-sensitive mTOR pathways contribute to the differentiation deficiency. CRISPR/Cas9 manipulation of the PDX1 variant demonstrated that it is necessary and sufficient to confer leucine sensitivity and the differentiation block, likely due to disruption of binding of the transcriptional regulator NFY to the PDX1 5'-UTR, leading to decreased PDX1 expression at the early PP stage. Thus, the combination of an underlying defect in leucine catabolism characteristic of KPD with a functionally relevant heterozygous variant in a critical β-cell gene that confers increased leucine sensitivity and inhibits endocrine cell differentiation resulted in the phenotype of late-onset β-cell failure in this patient. We define the molecular pathogenesis of a diabetes syndrome and demonstrate the power of multiomics analysis of patient-specific stem cells for clinical discovery.

Metabolomics Profiling of Patients With A-β+ Ketosis-Prone Diabetes During Diabetic Ketoacidosis

When stable and near-normoglycemic, patients with "A-β+" ketosis-prone diabetes (KPD) manifest accelerated leucine catabolism and blunted ketone oxidation, which may underlie their proclivity to develop diabetic ketoacidosis (DKA). To understand metabolic derangements in A-β+ KPD patients during DKA, we compared serum metabolomics profiles of adults during acute hyperglycemic crises, without (n = 21) or with (n = 74) DKA, and healthy control subjects (n = 17). Based on 65 kDa GAD islet autoantibody status, C-peptide, and clinical features, 53 DKA patients were categorized as having KPD and 21 type 1 diabetes (T1D); 21 nonketotic patients were categorized as having type 2 diabetes (T2D). Patients with KPD and patients with T1D had higher counterregulatory hormones and lower insulin-to-glucagon ratio than patients with T2D and control subjects. Compared with patients withT2D and control subjects, patients with KPD and patients with T1D had lower free carnitine and higher long-chain acylcarnitines and acetylcarnitine (C2) but lower palmitoylcarnitine (C16)-to-C2 ratio; a positive relationship between C16 and C2 but negative relationship between carnitine and β-hydroxybutyrate (BOHB); higher branched-chain amino acids (BCAAs) and their ketoacids but lower ketoisocaproate (KIC)-to-Leu, ketomethylvalerate (KMV)-to-Ile, ketoisovalerate (KIV)-to-Val, isovalerylcarnitine-to-KIC+KMV, propionylcarnitine-to-KIV+KMV, KIC+KMV-to-C2, and KIC-to-BOHB ratios; and lower glutamate and 3-methylhistidine. These data suggest that during DKA, patients with KPD resemble patients with T1D in having impaired BCAA catabolism and accelerated fatty acid flux to ketones-a reversal of their distinctive BCAA metabolic defect when stable. The natural history of A-β+ KPD is marked by chronic but varying dysregulation of BCAA metabolism.

The first series of cases of ketosis-prone type 2 diabetes (flatbush diabetes) in Brazilian adults

Ketosis-prone type 2 diabetes (KPD) is an emerging form of diabetes mellitus characterized by unprovoked ketoacidosis, absence of autoimmunity and beta-cell dysfunction. The KPD may improve after initial glycemic compensation and evolve to exogenous insulin independence, most cases were observed in populations with African or Hispanic backgrounds. We reviewed the literature on KPD and, to date, only one case of KPD has been described in Brazil's multi-ethnic population. A group of adult Brazilian KPD patients without autoimmunity and insulinopenia was identified for this study. We report a retrospective study of four KPD cases (3 males) evaluated in southeast Brazil, the patients were overweight or obese, age between the third and fifth decades of life, had a family history of type 2 diabetes, hyperglycemia (809.5 ± 344.2 mg/dL), acidosis (pH 7.21 ± 0.07; normal range (nr): 7.35-7.45 and bicarbonate 9.1 ± 6.2; nr: 22-26 mEq/mL), ketonuria (142.5 ± 114.4 mg/dL; nr: absence), absence of glutamic acid decarboxylase antibodies (GAD-65), and beta-cell function reserve (C-peptide 1.19 ± 0.53 ng/mL - nr: 1.1-4.4 ng/mL) on diagnosis. After glycemic compensation, there was increase of C-peptide (2.21 ± 0.41) indicating the recovery of beta-cell function and the time to insulin independence was 7.7 ± 3.5 months. They evolved after the period of glucotoxicity with insulin withdrawal and could be treated with oral antidiabetic therapy. This is the first case series of KPD described in Brazil being characterized by ketoacidosis at diagnosis, absence of autoimmunity, recovery of beta-cell function and insulin independence.

Defining and Classifying New Subgroups of Diabetes

An etiologically based classification of diabetes is needed to account for the heterogeneity of type 1 and type 2 diabetes (T1D and T2D) and emerging forms of diabetes worldwide. It may be productive for both classification and clinical discovery to consider variant forms of diabetes as a spectrum. Maturity onset diabetes of youth and neonatal diabetes serve as models for etiologically defined, rare forms of diabetes in the spectrum. Ketosis-prone diabetes is a model for more complex forms, amenable to phenotypic dissection. Bioinformatic approaches such as clustering analyses of large datasets and multi-omics investigations of rare and atypical phenotypes are promising avenues to explore and define new subgroups of diabetes.

Atypical diabetes: a diagnostic challenge

In medical school, we learned how to classify diabetes according to different clinical characteristics. However, at the dawn of the precision medicine era, it is clear that today's clinical reality does not always align well with textbook teachings. The terms juvenile versus elderly-onset diabetes, as well as insulin-dependent versus non-insulin-dependent diabetes, have become obsolete. Contrary to what is often taught severe ketoacidosis may occur in type 2 diabetes. Patients may also suffer from two or more forms of diabetes simultaneously or consecutively. Five authentic cases of diabetes with uncommon characteristics that pose diagnostic challenges are presented here.

Management of ketosis-prone type 2 diabetes mellitus

Diabetic ketoacidosis (DKA) has largely been considered unique to type 1 diabetes because of the absolute lack of insulin production secondary to beta-cell dysfunction. However, a relatively new diabetes subtype known as ketosis-prone type 2 diabetes mellitus (DM) may also elicit diabetic ketoacidosis. Ketosis-prone type 2 DM shares a similar pathophysiology as type 2 DM, but presents initially with signs and symptoms consistent with type 1 DM. Patients with ketosis-prone type 2 DM often present with elevated glucose levels of 500-700 mg/dl, elevated ketone levels, and elevations in hemoglobin A1C. Unlike DKA seen in type 1 DM, they do not exhibit autoantibodies to beta cells. The similarity with type 1 DM exists in their impaired insulin secretion, which, when combined with extreme insulin resistance, will lead to ketoacidosis. Despite the initial clinical presentation that resembles type 1 DM, patients may not require lifelong insulin and achieve appropriate glycemic control with oral agents. Nurse practitioners must recognize the clinical picture of ketosis-prone type 2 DM and use a multifaceted approach, encouraging dietary changes, increased physical activity, and medication adherence to build the self-management skills of the patient and ultimately decrease the long-term disease burden.

Risk Factors of Ketosis in Obese Ketosis-Prone Diabetic Patients: A Case-Control Study

INTRODUCTION

Different types of ketosis-prone obese diabetic patients are seen in the clinic. At present, the mechanism responsible for ketosis onset in these patients remains unclear, and we do not know how these patients should be optimally treated to prevent recurrent ketosis. Therefore, this study aims to investigate risk factors of ketosis in obese ketosis-prone diabetic (OB-KPD) patients.

METHODS

In an observational case-control study, primary OB-KPD patients [body mass index (BMI) ≥ 28 kg/m²] were selected as the study group (OB-KPD group), and primary obese type 2 diabetes patients served as the control group (OB-T2DM group). Clinical diagnostic assessments of fasting plasma glucose (FPG), glycated hemoglobin (HbA1c), blood lipid, area under curve of serum C-peptide (AUC_C-P) after steamed bread meal, insulin sensitivity index (ISI), β-hydroxybutyric acid (β-HB) and free fatty acid (FFA) vlaues of the subjects were collected. Subjects in the OB-KPD group were followed up for 1 year to determine the likelihood of insulin therapy cessation and whether ketosis recurred by assessing clinical chemistry parameters at 1-year follow-up.

RESULTS

Seventy-five subjects were screened, of which 15 were not included in the study for several identified clinical reasons. On enrollment, the OB-KPD group displayed significantly higher FPG, HbA1c and FFA levels than the OB-T2DM group (p < 0.01), while AUC_C-P and ISI values were significantly lower than in the OB-T2DM group (p < 0.01 and p = 0.03). Statistical analysis showed that increases in β-HB in the OB-KPD group were associated with increased blood glucose and FFA and decreased AUC_C-P and ISI values. Furthermore, decreases in AUC_C-P were closely associated with increased blood glucose values.

CONCLUSION

The occurrence of ketosis in ketosis-prone obese diabetic patients may be related to glucose and lipid metabolism disorders, increased insulin resistance and decreased β-cell secretory functions.

TRIAL REGISTRATION

This work was registered at the Chinese Clinical Trial Registry with trial registration identifier no. ChiCTR1900025909.

Ketosis-Prone Type 2 Diabetes: A Case Series

Ketosis-prone type 2 diabetes ("Flatbush diabetes") carries features of both classical type 1 and type 2 diabetes and is highly prevalent in African populations. The disease, which is highly ketosis-prone, but neither chronically insulinopenic nor autoimmune, is discussed regarding pathogenesis, diagnosis and treatment from a patient case perspective.

SYNDROMES OF KETOSIS-PRONE DIABETES

Ketosis-prone diabetes (KPD) is a heterogeneous condition characterized by patients who present with diabetic ketoacidosis but lack the phenotype of autoimmune type 1 diabetes. Here I review progress in our understanding of KPD and its place in the expanding universe of "atypical diabetes." I focus on investigations of our collaborative research group at Baylor College of Medicine and the University of Washington using a longitudinally followed, heterogeneous, multiethnic cohort of KPD patients. We have identified clinically and pathophysiologically distinct KPD subgroups, separable by the presence or absence of islet autoimmunity and the presence or absence of beta cell functional reserve. The resulting "Aß" classification of KPD accurately predicts long-term glycemic control and insulin dependence. I describe key characteristics of the KPD subgroups, their natural histories, and our investigations into their immunologic, genetic, and metabolic etiologies. These studies serve as a paradigm for the investigation of atypical forms of diabetes.

Evaluation and management of ketosis-prone diabetes

INTRODUCTION

Patients presenting with diabetic ketoacidosis (DKA) who lack the classic phenotype of autoimmune type 1 diabetes have become increasingly identified in recent decades. This has led to the recognition of heterogeneous syndromes of 'ketosis-prone diabetes' (KPD). Evaluation and optimal management of KPD differs from that of 'typical' type 1 or type 2 diabetes. Awareness of these differences and a systematic approach to diagnosis and treatment can improve glycemic control and prevent both acute and chronic complications of diabetes.

AREAS COVERED

This article reviews the Aß classification scheme ('A' for autoantibody status and 'ß' for beta cell functional reserve) which accurately delineates subgroups of KPD, and addresses the relevance of defining these subgroups for clinical outcomes and long-term insulin dependence. Subsequently, the detailed evaluation and management of KPD patients after their index DKA episode is described.

EXPERT COMMENTARY

Among patients presenting with DKA, it is important to diagnose specific subgroups of KPD and not assume that they represent exclusively patients with autoimmune type 1 diabetes. The Aß classification is an accurate aid to diagnosis, and permits optimal management of the subgroups (e.g., insulin treatment for the ß- subgroups; follow-up testing and a range of treatment options for the ß+ subgroups).

Alterations in branched-chain amino acid kinetics in nonobese but insulin-resistant Asian men

Background

Branched-chain amino acids (BCAAs) are elevated in the insulin-resistant (IR) state. The reasons for this increase remain unclear, but it may be related to abnormalities in BCAA metabolism and free fatty acid (FFA) metabolism.

Objective

In this study, we quantified BCAA and FFA kinetics of IR and insulin-sensitive (IS) nonobese Asian men with the use of stable-isotope tracers. We hypothesized that in addition to greater substrate flux, the BCAA oxidative pathway is also impaired to account for the higher plasma BCAA concentration in the IR state.

Design

We recruited 12 IR and 14 IS nonobese and healthy Asian men. Oral-glucose-tolerance tests (OGTTs) were performed to quantify insulin sensitivity, and subjects underwent 2 stable-isotope infusion studies. [U-13C6]Leucine was infused to measure leucine flux and oxidation as indexes of BCAA metabolism, whereas [U-13C16]palmitate was infused to measure palmitate flux and oxidation to represent FFA metabolism, The 2H2O dilution method was used to estimate body composition.

Results

IR subjects had greater adiposity and significantly higher fasting and post-OGTT glucose and insulin concentrations compared with the IS group. However, none of the subjects were diabetic. Despite similar dietary protein intake, IR subjects had a significantly higher plasma BCAA concentration and greater leucine flux. Leucine oxidation was also greater in the IR group, but the relation between leucine oxidation and flux was significantly weaker in the IR group than in the IS group (r = 0.530 compared with 0.695, P < 0.0388 for differences between slope). FFA oxidation was, however, unaffected despite higher FFA flux in the IR group.

Conclusion

The higher plasma BCAA concentration in healthy nonobese individuals with IR is associated with a weaker relation between BCAA oxidation and BCAA flux and this occurs in the presence of accelerated FFA flux and oxidation.

Heterogeneous clinical features of ketosis-prone type 2 diabetes mellitus patients: gender, age, loss of weight and HbA1c

BACKGROUND

The aim of this study was to observe the clinical features of type 2 diabetes mellitus (T2DM) patients with ketosis as the initial symptom, and investigate its differences from clinical features of non-ketotic T2DM patients.

METHODS

A total of 385 T2DM patients treated in our hospital from 2014 to 2017 were selected and divided into ketosis-prone T2DM group and non-ketotic T2DM group. Ketosis-prone T2DM patients refer to DM patients with the urine ketone body++ or above or the blood ketone body ≥1.0 mmol/L when treated. Fasting venous blood was collected from all patients in the early morning at 2 d after admission to detect the liver function, renal function, blood glucose, triglyceride, total cholesterol, glycosylated hemoglobin and fasting C-peptide, glutamic acid decarboxylase antibody (GAD-Ab) and islet cell antibody (ICA) were also detected, and the 24 h urine specimen was retained to detect the 24 h urine microalbumin excretion rate.

RESULTS

The proportion of male in ketosis-prone T2DM group was significantly higher than that in non-ketotic T2DM group (P<0.01). Patients in ketosis-prone T2DM group was younger than those in non-ketotic T2DM group (P<0.05). The number of days from initial symptom to treatment in ketosis-prone T2DM group was smaller than that in non-ketotic T2DM group (P<0.05). The fasting C-peptide level in ketosis-prone T2DM group was significantly lower than that in non-ketotic T2DM group (P<0.05). The degree of weight loss and level of glycosylated hemoglobin in ketosis-prone T2DM group were significantly higher than those in non-ketotic T2DM group (P<0.05).

CONCLUSIONS

Ketosis-prone T2DM patients are characterized by lower age at onset, higher proportion of male, shorter duration of disease, poorer islet function, higher blood glucose and more significant weight loss than non-ketotic T2DM patients.

Ketosis-Prone Diabetes (Flatbush Diabetes): an Emerging Worldwide Clinically Important Entity

PURPOSE OF REVIEW

Ketosis-prone diabetes or Flatbush diabetes has been widely recognized as a clinical entity since 1984. Most of the early clinical studies focused on African American or Afro-Caribbean individuals. It is now being recognized as an important clinical entity in sub-Saharan Africans, Asian and Indian populations, and Hispanic populations. Major questions remain as to its pathogenesis and whether it is a unique type of diabetes or a subset of more severe type 2 diabetes with greater loss of insulin action in target tissues. This review summarizes the main clinical and mechanistic studies to improve the understanding of ketosis-prone (Flatbush) diabetes.

RECENT FINDINGS

Little data are available on the magnitude of KPD in the different susceptible populations. It is relatively common in black populations. KPD is defined as a syndrome in which diabetes commences with ketoacidosis in individuals who are GAD and anti-islet cell antibody negative and have no known precipitating causes. The patients present during middle age, are overweight or mildly obese, and in many reports are more likely to be male. After intensive initial insulin therapy, many patients become insulin independent and can be well controlled on diet alone or diet plus oral medications. The clinical course of KPD is like that of patients with type 2 diabetes rather than that of type 1 diabetes. Little differences are found in the clinical characteristics and clinical outcomes between patients presenting with KPD and those presenting with severe hyperglycemia with no ketoacidosis. The mechanisms responsible for the development of ketosis-prone diabetes as well its remission remain unknown.

Metabolomics and Lipidomics Study of Mouse Models of Type 1 Diabetes Highlights Divergent Metabolism in Purine and Tryptophan Metabolism Prior to Disease Onset

With the increase in incidence of type 1 diabetes (T1DM), there is an urgent need to understand the early molecular and metabolic alterations that accompany the autoimmune disease. This is not least because in murine models early intervention can prevent the development of disease. We have applied a liquid chromatography (LC-) and gas chromatography (GC-) mass spectrometry (MS) metabolomics and lipidomics analysis of blood plasma and pancreas tissue to follow the progression of disease in three models related to autoimmune diabetes: the nonobese diabetic (NOD) mouse, susceptible to the development of autoimmune diabetes, and the NOD-E (transgenic NOD mice that express the I-E heterodimer of the major histocompatibility complex II) and NOD-severe combined immunodeficiency (SCID) mouse strains, two models protected from the development of diabetes. All three analyses highlighted the metabolic differences between the NOD-SCID mouse and the other two strains, regardless of diabetic status indicating that NOD-SCID mice are poor controls for metabolic changes in NOD mice. By comparing NOD and NOD-E mice, we show the development of T1DM in NOD mice is associated with changes in lipid, purine, and tryptophan metabolism, including an increase in kynurenic acid and a decrease in lysophospholipids, metabolites previously associated with inflammation.

Arginine Metabolism Is Altered in Adults with A-β + Ketosis-Prone Diabetes

Background

A-β + ketosis-prone diabetes (KPD) is a subset of type 2 diabetes in which patients have severe but reversible β cell dysfunction of unknown etiology. Plasma metabolomic analysis indicates that abnormal arginine metabolism may be involved.

Objective

The objective of this study was to determine the relation between gut microbiome and arginine metabolism and the relation between arginine availability and β cell function in KPD patients compared with control participants.

Methods

Kinetics of arginine and related metabolites were measured with stable isotope tracers, and insulin secretory responses to arginine and glucose were determined under euglycemic and hyperglycemic conditions in 6 KPD patients and 6 age-, gender-, and body mass index-matched control participants. Glucose potentiation of arginine-induced insulin secretion was performed in a different set of 6 KPD and 3 control participants.

Results

Arginine availability was higher in KPD patients during euglycemia [53.5 ± 4.3 (mean ± SEM) compared with 40.3 ± 2.4 μmol · kg lean body mass (LBM)-1 · h-1, P = 0.03] but declined more in response to hyperglycemia (Δ 10.15 ± 2.6 compared with Δ 3.20 ± 1.3 μmol · kg LBM-1 · h-1, P = 0.041). During hyperglycemia, ornithine flux was not different between groups but after an arginine bolus, plasma ornithine AUC trended higher in KPD patients (3360 ± 294 compared with 2584 ± 259 min · μmol · L-1, P = 0.08). In both euglycemia and hyperglycemia, the first-phase insulin responses to glucose stimulation were lower in KPD patients (euglycemic insulin AUC 282 ± 108 compared with 926 ± 257 min · μU · mL-1, P = 0.02; hyperglycemic insulin AUC 358 ± 79 compared with 866 ± 292 min · μU · mL-1, P = 0.05), but exogenous arginine restored first-phase insulin secretion in KPD patients to the level of control participants.

Conclusion

Compared with control participants, KPD patients have increased arginine availability in the euglycemic state, indicating a higher requirement. This is compromised during hyperglycemia, with an inadequate supply of arginine to sustain metabolic functions such as insulin secretion. Exogenous arginine administration restores a normal insulin secretory response.

Higher cardiometabolic risk in idiopathic versus autoimmune type 1 diabetes: a retrospective analysis

BACKGROUND

Idiopathic type 1 diabetes mellitus (IDM) is characterized by an onset with insulinopenia and ketoacidosis with negative β-cell autoimmunity markers and lack of association with HLA. The aim of the study is to compare the clinical and metabolic parameters, the macro and microvascular complications, the adipose tissue dysfunction and the insulin secretion and sensitivity indexes in patients with IDM and autoimmune type 1 diabetes mellitus (ADM) at clinical onset.

METHODS

Thirty patients with IDM and 30 with ADM, matched for age and gender, were retrospectively analyzed. BMI, waist circumference, lipids, glycemia, HbA1c, insulin requirement, glutamic oxaloacetic and glutamic pyruvic transaminases (GOT and GPT), glucagon stimulated c-peptide (GSC-pep) test levels, M value during hyperinsulinemic euglycemic clamp and Visceral Adiposity Index (VAI) were obtained from our database.

RESULTS

Patients with IDM showed a significantly higher BMI (p 0.012), WC (p 0.07), VAI (p 0.004), LDL-cholesterol (p 0.027), GOT (p 0.005), GPT (p 0.001), M value (p 0.006) and GSC-pep peak (p 0.036), with concomitant lower HDL-cholesterol (p < 0.001), than patients with ADM. In addition, patients with IDM showed a more marked familial history for diabetes (p 0.005) and a higher percentage of hepatic steatosis (p 0.001), visceral obesity (p 0.032) and hypercholesterolemia (p 0.007) compared to patients with ADM.

CONCLUSIONS

Patients with IDM show many metabolic complications at onset, such as visceral obesity, hepatic steatosis and hypercholesterolemia and a higher cardiometabolic risk, than patients with ADM, similarly to patients with type 2 diabetes at onset.

Clinical heterogeneity of type 1 diabetes (T1D) found in Asia

Diabetes mellitus among young patients in Asia is caused by a complex set of factors. Although type 1 diabetes (T1D) remains the most common form of diabetes in children, the recent unabated increase in obesity has resulted in the emergence of type 2 diabetes (T2D) as a new type of diabetes among adolescents and young adults. In addition to the typical autoimmune type 1 diabetes (T1aD) and T2D patients, there is a variable incidence of cases of non-autoimmune types of T1D associated with insulin deficiency (T1bD). Additional forms have been described, including fulminant T1D (FT1D). Although most diagnoses of T1D are classified as T1aD, fulminant T1D exists as a hyper-acute subtype of T1D that affects older children, without associated autoimmunity. Patient with this rare aetiology of diabetes showed a complete loss of β-cell secretory capacity without evidence of recovery, necessitating long-term treatment with insulin. In addition, latent autoimmune diabetes in adults is a form of autoimmune-mediated diabetes, usually diagnosed during the insulin-dependent stage that follows a non-insulin requiring phase, which can be diagnosed earlier based on anti-islet autoantibody positivity. Some reports discuss T1bD. Others are elaborating on the presence of "atypical T1b diabetes," such as Flatbush diabetes. The prevalence of diabetes mellitus in young adults continues to rise in Asian populations as T2D increases. With improved characterization of patients with diabetes, the range of diabetic subgroups will become even more diverse in the future. Distinguishing T1D, T2D, and other forms of diabetes in young patients is challenging in Asian populations, as the correct diagnosis is clinically important and has implications for prognosis and management. Despite aetiological heterogeneity in the usual clinical setting, early diagnosis and classification of patients with diabetes relying on clinical grounds as well as measuring islet autoantibodies and fasting plasma C-peptide could provide a possible viable method to minimize complications.

DIABETIC KETOACIDOSIS: A COMMON DEBUT OF DIABETES AMONG AFRICAN AMERICANS WITH TYPE 2 DIABETES

OBJECTIVE

More than half of African Americans (AA) with a new diagnosis of diabetic ketoacidosis have clinical and metabolic features of type 2 diabetes during follow-up. This particular presentation of diabetes has been termed as ketosis-prone type 2 diabetes (KPDM) or atypical diabetes.

METHODS

We review the epidemiology, diagnosis, pathophysiology, and acute and long-term management of AA with KPDM and compare these similarities to patients with type 2 diabetes.

RESULTS

In contrast to the long-term insulin requirement of auto-immune type 1 diabetes, patients with KPDM are able to discontinue insulin after a few months of therapy and maintain acceptable glycemic control for many years on either diet or oral agents. Patients with KPDM have significant impairment of both insulin secretion and insulin action at presentation; however, at the time of near-normoglycemia remission, insulin secretion and action improve to levels similar to hyperglycemic patients with ketosis-resistant type 2 diabetes. In the long term, however, patients with KPDM have a decline in β-cell function similar to patients with type 2 diabetes. Recent studies indicate that treatment with metformin and dipeptidyl peptidase-4 inhibitors can prolong the period of near-normoglycemia remission for several years compared to placebo therapy.

CONCLUSION

KPDM is a unique but common presentation of newly diagnosed African Americans with type 2 diabetes.

ABBREVIATIONS

A(+/-) = auto-antibody positive/negative AA = African Americans DKA = diabetic ketoacidosis FFA = free fatty acids G6PD = glucose-6-phosphate dehydrogenase GAD-65 = 65-kDA glutamic acid decarboxylase HBA1c = glycated hemoglobin A1c HHV8 = human herpes virus 8 HLA = human leukocyte antigen KPDM = ketosis-prone type 2 diabetes.

Metabolomic Fingerprinting in the Comprehensive Study of Liver Changes Associated with Onion Supplementation in Hypercholesterolemic Wistar Rats

The consumption of functional ingredients has been suggested to be a complementary tool for the prevention and management of liver disease. In this light, processed onion can be considered as a source of multiple bioactive compounds with hepatoprotective properties. The liver fingerprint of male Wistar rats (n = 24) fed with three experimental diets (control (C), high-cholesterol (HC), and high-cholesterol enriched with onion (HCO) diets) was obtained through a non-targeted, multiplatform metabolomics approach to produce broad metabolite coverage. LC-MS, CE-MS and GC-MS results were subjected to univariate and multivariate analyses, providing a list of significant metabolites. All data were merged in order to figure out the most relevant metabolites that were modified by the onion ingredient. Several relevant metabolic changes and related metabolic pathways were found to be impacted by both HC and HCO diet. The model highlighted several metabolites (such as hydroxybutyryl carnitine and palmitoyl carnitine) modified by the HCO diet. These findings could suggest potential impairments in the energy−lipid metabolism, perturbations in the tricarboxylic acid cycle (TCA) cycle and β-oxidation modulated by the onion supplementation in the core of hepatic dysfunction. Metabolomics shows to be a valuable tool to evaluate the effects of complementary dietetic approaches directed to hepatic damage amelioration or non-alcoholic fatty liver disease (NAFLD) prevention.

Monogenic Diabetes: What It Teaches Us on the Common Forms of Type 1 and Type 2 Diabetes

To date, more than 30 genes have been linked to monogenic diabetes. Candidate gene and genome-wide association studies have identified > 50 susceptibility loci for common type 1 diabetes (T1D) and approximately 100 susceptibility loci for type 2 diabetes (T2D). About 1-5% of all cases of diabetes result from single-gene mutations and are called monogenic diabetes. Here, we review the pathophysiological basis of the role of monogenic diabetes genes that have also been found to be associated with common T1D and/or T2D. Variants of approximately one-third of monogenic diabetes genes are associated with T2D, but not T1D. Two of the T2D-associated monogenic diabetes genes-potassium inward-rectifying channel, subfamily J, member 11 (KCNJ11), which controls glucose-stimulated insulin secretion in the β-cell; and peroxisome proliferator-activated receptor γ (PPARG), which impacts multiple tissue targets in relation to inflammation and insulin sensitivity-have been developed as major antidiabetic drug targets. Another monogenic diabetes gene, the preproinsulin gene (INS), is unique in that INS mutations can cause hyperinsulinemia, hyperproinsulinemia, neonatal diabetes mellitus, one type of maturity-onset diabetes of the young (MODY10), and autoantibody-negative T1D. Dominant heterozygous INS mutations are the second most common cause of permanent neonatal diabetes. Moreover, INS gene variants are strongly associated with common T1D (type 1a), but inconsistently with T2D. Variants of the monogenic diabetes gene Gli-similar 3 (GLIS3) are associated with both T1D and T2D. GLIS3 is a key transcription factor in insulin production and β-cell differentiation during embryonic development, which perturbation forms the basis of monogenic diabetes as well as its association with T1D. GLIS3 is also required for compensatory β-cell proliferation in adults; impairment of this function predisposes to T2D. Thus, monogenic forms of diabetes are invaluable "human models" that have contributed to our understanding of the pathophysiological basis of common T1D and T2D.

THE CLINICAL AND METABOLIC CHARACTERISTICS OF YOUNG-ONSET KETOSIS-PRONE TYPE 2 DIABETES IN CHINA

OBJECTIVE

To investigate the prevalence and clinical characteristics of ketosis-prone type 2 diabetes (KPD) in Chinese patients with young-onset diabetes.

METHODS

A total of 238 young diabetic patients were recruited from our inpatient department from January 1, 2012, to December 28, 2014. KPD was defined as diabetes without precipitating illness and with the presence of ketosis or diabetic ketoacidosis in the absence of autoantibodies at the time of diagnosis. We reviewed the clinical characteristics and disease progression of this group of patients.

RESULTS

Eighteen patients fulfilled the criteria for KPD, and the prevalence of patients with KPD was 7.6%. The mean (SD) age of the KPD group at the time of diagnosis of diabetes was 27.6 (4.85) years, and these patients were predominantly male (male to female ratio, 8:1) and had a high proportion of obesity and new-onset diabetes and a strong family history of diabetes. β-Cell function in the KPD group was intermediate between type 1 and type 2 diabetes. Patients with KPD had the highest levels of glycated hemoglobin, triglycerides, total cholesterol, and free fatty acids and the lowest levels of high-density lipoprotein. After 3 to 12 months of follow-up, 17 of 18 patients with KPD (94.4%) were able to discontinue insulin therapy, and 11 patients (61.1%) were managed with diet or exercise alone.

CONCLUSION

KPD patients accounted for 7.6% of the diabetic patients requiring admission to a large urban hospital in China, with an age of onset of diabetes of ≤35 years. These patients are more likely to be male, have abnormal lipid metabolism, and have more reversible β-cell dysfunction.

Factors associated with early relapse to insulin dependence in unprovoked A-β+ ketosis-prone diabetes

OBJECTIVE

Unprovoked "A-β+" Ketosis-Prone Diabetes (KPD), a unique diabetic syndrome of adult-onset, obesity and proneness to ketoacidosis, is associated with rapid recovery of β cell function and insulin-independence. Whereas most patients experience prolonged remission, a subset relapses early to insulin dependence. We sought to define factors associated with early relapse.

METHODS

We utilized a prospective, longitudinal database to analyze 50 unprovoked A-β+ KPD patients with >2 measurements of β cell function and glycemia following baseline assessment.

RESULTS

19 patients (38%) relapsed to insulin dependence <1 year after the index DKA episode, while 31 (62%) remained insulin-independent for >1 year (median 4.2 years). Younger age at baseline (OR=0.947, P=0.033), and lower HOMA2-%β (OR=0.982, P=0.001), lower HOMA2-IR (OR=0.582, P=0.046) and higher HbA1c at 1 year (OR=1.71, P=0.002) were associated with early relapse. A multivariate model with these variables and the interaction of HOMA2-%β and HbA1c at 1 year provided a good fit (P<0.05).

CONCLUSIONS

Relapse to insulin dependence in unprovoked A-β+ KPD patients is associated with younger age and, after 1 year, lack of robust increase in β cell functional reserve, and suboptimal glycemic control. Measurements of these parameters 1 year after the index DKA episode can be used to assess the need for insulin therapy.

A systems view of type 2 diabetes-associated metabolic perturbations in saliva, blood and urine at different timescales of glycaemic control

AIMS/HYPOTHESIS

Metabolomics has opened new avenues for studying metabolic alterations in type 2 diabetes. While many urine and blood metabolites have been associated individually with diabetes, a complete systems view analysis of metabolic dysregulations across multiple biofluids and over varying timescales of glycaemic control is still lacking.

METHODS

Here we report a broad metabolomics study in a clinical setting, covering 2,178 metabolite measures in saliva, blood plasma and urine from 188 individuals with diabetes and 181 controls of Arab and Asian descent. Using multivariate linear regression we identified metabolites associated with diabetes and markers of acute, short-term and long-term glycaemic control.

RESULTS

Ninety-four metabolite associations with diabetes were identified at a Bonferroni level of significance (p < 2.3 × 10(-5)), 16 of which have never been reported. Sixty-five of these diabetes-associated metabolites were associated with at least one marker of glycaemic control in the diabetes group. Using Gaussian graphical modelling, we constructed a metabolic network that links diabetes-associated metabolites from three biofluids across three different timescales of glycaemic control.

CONCLUSIONS/INTERPRETATION

Our study reveals a complex network of biochemical dysregulation involving metabolites from different pathways of diabetes pathology, and provides a reference framework for future diabetes studies with metabolic endpoints.

Association of HLA class II markers with autoantibody-negative ketosis-prone atypical diabetes compared to type 2 diabetes in a population of sub-Saharan African patients

AIM

We investigated the association of HLA DRB1 and DQB1 alleles, haplotypes and genotypes with unprovoked antibody-negative ketosis-prone atypical diabetes (A(-) KPD) in comparison to type 2 diabetes (T2D).

METHODS

A(-) KPD and T2D sub-Saharan African patients aged 19-63 years were consecutively recruited. Patients positive for cytoplasmic islet cell, insulin, glutamic acid decarboxylase or islet antigen-2 autoantibodies were excluded. Odds ratios were obtained via logistic regression after considering alleles with a minimum frequency of 5% in the study population. Bonferroni correction was used in the case of multiple comparisons.

RESULTS

Among the 130 participants, 35 (27%) were women and 57 (44%) were A(-) KPD. DRB1 and DQB1 allele frequencies were similar for both A(-) KPD and T2D patients; they did not confer any substantial risk even after considering type 1 diabetes susceptibility and resistance alleles. We found no association between A(-) KPD and the derived DRB1*07-DQB1*02:02 (OR: 0.55 [95%CI: 0.17-1.85], P=0.336); DRB1*11-DQB1*03:01 (OR: 2.42 [95%CI: 0.79-7.42], P=0.123); DRB1*15-DQB1*06:02 (OR: 0.87 [95%CI: 0.39-1.95], P=0.731) and DRB1*03:01-DQB1*02:01 (OR: 1.48 [95%CI: 0.55-3.96], P=0.437) haplotypes. Overall, we did not find any evidence of susceptibility to ketosis associated with DRB1 and DQB1 genotypes (all P>0.05) in A(-) KPD compared to T2D. Similar results were obtained after adjusting the analysis for age and sex.

CONCLUSION

Factors other than DRB1 and DQB1 genotype could explain the propensity to ketosis in A(-) KPD. These results need to be confirmed in a larger population with the perspective of improving the classification and understanding of the pathophysiology of A(-) KPD.

Quantification and genotyping of lipoprotein lipase in patients with diabetic lipaemia

AIMS

To determine if diabetic lipaemia is caused by loss of function mutations in the lipoprotein lipase gene, LPL.

METHODS

We conducted a case-control study over 2 years in two tertiary care hospitals in South Australia. Six patients with a history of diabetic lipaemia and 12 control subjects, with previous diabetic ketoacidosis and peak triglyceride concentrations < 2.4 mmol/l were included. Participants were well at the time of study investigations.

RESULTS

Only one patient with lipaemia had a loss of function mutation in LPL and no functional mutations in APOC2 or GPIHBP1 were identified. The mean lipoprotein lipase concentration was lower in patients with diabetic lipaemia than in control subjects (306 vs. 484 μg/l, P = 0.04). The mean fasting C-peptide concentration was higher in patients with diabetic lipaemia than in control subjects (771 vs. 50 pmol/l; P = 0.001).

CONCLUSIONS

Lipoprotein lipase deficiency in patients with a history of diabetic lipaemia was predominantly quantitative, rather than secondary to mutations in LPL, APOC2 or GPIHBP1. The majority of patients with severe hypertriglyceridaemia in diabetic ketoacidosis may have ketosis-prone Type 2, rather than Type 1, diabetes.

Inhibition of insulin receptor function by a human, allosteric monoclonal antibody: a potential new approach for the treatment of hyperinsulinemic hypoglycemia

Novel therapies are needed for the treatment of hypoglycemia resulting from both endogenous and exogenous hyperinsulinema. To provide a potential new treatment option, we identified XMetD, an allosteric monoclonal antibody to the insulin receptor (INSR) that was isolated from a human antibody phage display library. To selectively obtain antibodies directed at allosteric sites, panning of the phage display library was conducted using the insulin-INSR complex. Studies indicated that XMetD bound to the INSR with nanomolar affinity. Addition of insulin reduced the affinity of XMetD to the INSR by 3-fold, and XMetD reduced the affinity of the INSR for insulin 3-fold. In addition to inhibiting INSR binding, XMetD also inhibited insulin-induced INSR signaling by 20- to 100-fold. These signaling functions included INSR autophosphorylation, Akt activation and glucose transport. These data indicated that XMetD was an allosteric antagonist of the INSR because, in addition to inhibiting the INSR via modulation of binding affinity, it also inhibited the INSR via modulation of signaling efficacy. Intraperitoneal injection of XMetD at 10 mg/kg twice weekly into normal mice induced insulin resistance. When sustained-release insulin implants were placed into normal mice, they developed fasting hypoglycemia in the range of 50 mg/dl. This hypoglycemia was reversed by XMetD treatment. These studies demonstrate that allosteric monoclonal antibodies, such as XMetD, can antagonize INSR signaling both in vitro and in vivo. They also suggest that this class of allosteric monoclonal antibodies has the potential to treat hyperinsulinemic hypoglycemia resulting from conditions such as insulinoma, congenital hyperinsulinism and insulin overdose.

Selective allosteric antibodies to the insulin receptor for the treatment of hyperglycemic and hypoglycemic disorders

Many therapeutic monoclonal antibodies act as antagonists to receptors by targeting and blocking the natural ligand binding site (orthosteric site). In contrast, the use of antibodies to target receptors at allosteric sites (distinct from the orthosteric site) has not been extensively studied. This approach is especially important in metabolic diseases in which endogenous ligand levels are dysregulated. Herein, we review our investigations of 3 categories of human monoclonal antibodies that bind allosterically to the insulin receptor (INSR) and affect its activity: XMetA, XMetS and XMetD. XMetA directly activates the INSR either alone or in combination with insulin. XMetS, in contrast, does not directly activate the INSR but markedly enhances the receptor's ability to bind insulin and potentiate insulin signaling. Both XMetA and XMetS are effective in controlling hyperglycemia in mouse models of diabetes. A third allosteric antibody, XMetD, is an inhibitor of INSR signaling. This antibody reverses insulin-induced hypoglycemia in a mouse model of hyperinsulinemia. These studies indicate, therefore, that allosteric antibodies to INSR can modulate its signaling and correct conditions of glucose dysregulation. These studies also raise the possibility that the use of allosteric antibodies can be expanded to other receptors for the treatment of metabolic disorders.

Ketosis onset type 2 diabetes had better islet β-cell function and more serious insulin resistance

Diabetic ketosis had been identified as a characteristic of type 1 diabetes mellitus (T1DM), but now emerging evidence has identified that they were diagnosed as T2DM after long time follow up. This case control study was aimed at comparing the clinical characteristic, β-cell function, and insulin resistance of ketosis and nonketotic onset T2DM and providing evidence for treatment selection. 140 cases of newly diagnosed T2DM patients were divided into ketosis (62 cases) and nonketotic onset group (78 cases). After correction of hyperglycemia and ketosis with insulin therapy, plasma C-peptide concentrations were measured at 0, 0.5, 1, 2, and 3 hours after 75 g glucose oral administration. Area under the curve (AUC) of C-peptide was calculated. Homoeostasis model assessment was used to estimate basal β-cell function (HOMA-β) and insulin resistance (HOMA-IR). Our results showed that ketosis onset group had higher prevalence of nonalcoholic fatty liver disease (NAFLD) than nonketotic group (P = 0.04). Ketosis onset group had increased plasma C-peptide levels at 0 h, 0.5 h, and 3 h and higher AUC(0-0.5), AUC₀₋₁, AUC₀₋₃ (P < 0.05). Moreover, this group also had higher HOMA-β and HOMA-IR than nonketotic group (P < 0.05). From these data, we concluded that ketosis onset T2DM had better islet β-cell function and more serious insulin resistance than nonketotic onset T2DM.

Clinical and biological characteristics of diabetic patients under age 40 in Cameroon: relation to autoantibody status and comparison with Belgian patients

AIMS

We investigated the prevalence of diabetes autoantibodies (Abs) in Cameroonian patients and controls, assessed their contribution in disease classification and compared results with data from Belgium.

METHODS

Abs against GAD (GADA), IA-2 (IA-2A) and zinc transporter 8 (ZnT8A) were assessed in 302 recently diagnosed Cameroonian patients with diabetes and 184 control subjects without diabetes aged below 40 years.

RESULTS

Only 27 (9%) Cameroonian patients were younger than 15 years. Overall, 29% of patients presented at least one diabetes-associated antibody vs 9% in healthy controls (24% vs 7% for GADA (p<0.001), 10% vs 3% for IA-2A (p<0.006), 4% vs 2% for ZnT8A). Ab(+) patients had lower C-peptide levels (p<0.001), were more often insulin-treated (p<0.002) and were as frequently diagnosed with type 1 diabetes as Ab(-) patients. Only 43% of Ab(+) patients aged 15-39 years were clinically classified as having type 1 diabetes in Cameroon vs 96% in Belgium (p<0.001). Not one Ab(+) Cameroonian patient carried HLA-DQ2/DQ8 genotype vs 23% of Belgian Ab(+) patients (p<0.001). Younger age at diagnosis and antibody positivity were independent predictors of insulin therapy. Ab(+) Cameroonian patients were older (p<0.001), had higher BMI (p<0.001) and lower Ab titers than Belgian Ab(+) patients. In ketonuric patients, prevalence of autoantibodies was similar as in non-ketonuric patients.

CONCLUSIONS

In Cameroonian patients with diabetes aged under 40 years, antibody-positivity is not clearly related to disease phenotype, but may help predict the need for insulin treatment.

Islet-specific T-cell responses and proinflammatory monocytes define subtypes of autoantibody-negative ketosis-prone diabetes

OBJECTIVE

Ketosis-prone diabetes (KPD) is characterized by diabetic ketoacidosis (DKA) in patients lacking typical features of type 1 diabetes. A validated classification scheme for KPD includes two autoantibody-negative ("A-") phenotypic forms: "A-β-" (lean, early onset, lacking β-cell functional reserve) and "A-β+" (obese, late onset, with substantial β-cell functional reserve after the index episode of DKA). Recent longitudinal analysis of a large KPD cohort revealed that the A-β+ phenotype includes two distinct subtypes distinguished by the index DKA episode having a defined precipitant ("provoked," with progressive β-cell function loss over time) or no precipitant ("unprovoked," with sustained β-cell functional reserve). These three A- KPD subtypes are characterized by absence of humoral islet autoimmune markers, but a role for cellular islet autoimmunity is unknown.

RESEARCH DESIGN AND METHODS

Islet-specific T-cell responses and the percentage of proinflammatory (CD14+CD16+) blood monocytes were measured in A-β- (n = 7), provoked A-β+ (n = 15), and unprovoked A-β+ (n = 13) KPD patients. Genotyping was performed for type 1 diabetes-associated HLA class II alleles.

RESULTS

Provoked A-β+ and A-β- KPD patients manifested stronger islet-specific T-cell responses (P < 0.03) and higher percentages of proinflammatory CD14+CD16+ monocytes (P < 0.01) than unprovoked A-β+ KPD patients. A significant relationship between type 1 diabetes HLA class II protective alleles and negative T-cell responses was observed.

CONCLUSIONS

Provoked A-β+ KPD and A-β- KPD are associated with a high frequency of cellular islet autoimmunity and proinflammatory monocyte populations. In contrast, unprovoked A-β+ KPD lacks both humoral and cellular islet autoimmunity.