Differential contribution of alpha and beta cell dysfunction to impaired fasting glucose and impaired glucose tolerance.

AIMS/HYPOTHESIS: People with isolated impaired fasting glucose (IFG) have normal beta cell function. We hypothesised that an increased glucose threshold for beta cell secretion explains IFG. METHODS: We used graded glucose infusion to examine the relationship of insulin secretion rate (ISR) and glucagon secretion rate (GSR) with rising glucose. We studied 39 non-diabetic individuals (53 ± 2 years, BMI 30 ± 1 kg/m2), categorised by fasting glucose and glucose tolerance status. After an overnight fast, a variable insulin infusion was used to maintain glucose at ~4.44 mmol/l (07:00 to 08:30 hours). At 09:00 hours, graded glucose infusion commenced at 1 mg kg-1 min-1 and doubled every 60 min until 13:00 hours. GSR and ISR were calculated by nonparametric deconvolution from concentrations of glucagon and C-peptide, respectively. RESULTS: The relationship of ISR with glucose was linear and the threshold for insulin secretion in isolated IFG did not differ from that in people with normal fasting glucose and normal glucose tolerance. GSR exhibited a single-exponential relationship with glucose that could be characterised by G50, the change in glucose necessary to suppress GSR by 50%. G50 was increased in IFG compared with normal fasting glucose regardless of the presence of impaired or normal glucose tolerance. CONCLUSIONS/INTERPRETATION: These data show that, in non-diabetic humans, alpha cell dysfunction contributes to the pathogenesis of IFG independently of defects in insulin secretion. We also describe a new index that quantifies the suppression of glucagon secretion by glucose.

Effects of acute changes in fasting glucose and free fatty acid concentrations on indices of ß-cell function and glucose metabolism in subjects without diabetes.

Elevated fasting free fatty acids (FFAs) and fasting glucose are additively associated with impaired glucose tolerance (IGT) and decreased ß-cell function [quantified as disposition index (DI)]. We sought to examine how changes in fasting FFA and glucose alter islet function. We studied 10 subjects with normal fasting glucose (NFG) and normal glucose tolerance (NGT) on two occasions. On one occasion, Intralipid and glucose were infused overnight to mimic conditions present in IFG/IGT. In addition, we studied seven subjects with IFG/IGT on two occasions. On one occasion, insulin was infused to lower overnight FFA and glucose concentrations to those observed in people with NFG/NGT. The following morning, a labeled mixed meal was used to measure postprandial glucose metabolism and ß-cell function. Elevation of overnight fasting FFA and glucose in NFG/NGT did not alter peak or integrated glucose concentrations (2.0 ± 0.1 vs. 2.0 ± 0.1 Mol per 5 h, Saline vs. Intralipid/glucose, P = 0.55). Although overall ß-cell function quantified by the Disposition Index was unchanged, the dynamic component of ß-cell responsivity (ϕd) was decreased by Intralipid and glucose infusion (9 ± 1 vs. 16 ± 3 10-9, P = 0.02). In people with IFG/IGT, insulin did not alter postprandial glucose concentrations or indices of ß-cell function. Endogenous glucose production and glucose disappearance were also unchanged in both groups. We conclude that acute, overnight changes in FFA, and glucose concentrations do not alter islet function or glucose metabolism in prediabetes.NEW & NOTEWORTHY This experiment studied the effect of changes in overnight concentrations of free fatty acids (FFAs) and glucose on ß-cell function and glucose metabolism. In response to elevation of these metabolites, the dynamic component of the ß-cell response to glucose was impaired. This suggests that in health overnight hyperglycemia and FFA elevation can deplete preformed insulin granules in the ß-cell.

Implementation of genomic medicine for rare disease in a tertiary healthcare system: Mayo Clinic Program for Rare and Undiagnosed Diseases (PRaUD).

BACKGROUND: In the United States, rare disease (RD) is defined as a condition that affects fewer than 200,000 individuals. Collectively, RD affects an estimated 30 million Americans. A significant portion of RD has an underlying genetic cause; however, this may go undiagnosed. To better serve these patients, the Mayo Clinic Program for Rare and Undiagnosed Diseases (PRaUD) was created under the auspices of the Center for Individualized Medicine (CIM) aiming to integrate genomics into subspecialty practice including targeted genetic testing, research, and education. METHODS: Patients were identified by subspecialty healthcare providers from 11 clinical divisions/departments. Targeted multi-gene panels or custom exome/genome-based panels were utilized. To support the goals of PRaUD, a new clinical service model, the Genetic Testing and Counseling (GTAC) unit, was established to improve access and increase efficiency for genetic test facilitation. The GTAC unit includes genetic counselors, genetic counseling assistants, genetic nurses, and a medical geneticist. Patients receive abbreviated point-of-care genetic counseling and testing through a partnership with subspecialty providers. RESULTS: Implementation of PRaUD began in 2018 and GTAC unit launched in 2020 to support program expansion. Currently, 29 RD clinical indications are included in 11 specialty divisions/departments with over 142 referring providers. To date, 1152 patients have been evaluated with an overall solved or likely solved rate of 17.5% and as high as 66.7% depending on the phenotype. Noteworthy, 42.7% of the solved or likely solved patients underwent changes in medical management and outcome based on genetic test results. CONCLUSION: Implementation of PRaUD and GTAC have enabled subspecialty practices advance expertise in RD where genetic counselors have not historically been embedded in practice. Democratizing access to genetic testing and counseling can broaden the reach of patients with RD and increase the diagnostic yield of such indications leading to better medical management as well as expanding research opportunities.

Biology of Activating Transcription Factor 4 (ATF4) and Its Role in Skeletal Muscle Atrophy.

Activating transcription factor 4 (ATF4) is a multifunctional transcription regulatory protein in the basic leucine zipper superfamily. ATF4 can be expressed in most if not all mammalian cell types, and it can participate in a variety of cellular responses to specific environmental stresses, intracellular derangements, or growth factors. Because ATF4 is involved in a wide range of biological processes, its roles in human health and disease are not yet fully understood. Much of our current knowledge about ATF4 comes from investigations in cultured cell models, where ATF4 was originally characterized and where further investigations continue to provide new insights. ATF4 is also an increasingly prominent topic of in vivo investigations in fully differentiated mammalian cell types, where our current understanding of ATF4 is less complete. Here, we review some important high-level concepts and questions concerning the basic biology of ATF4. We then discuss current knowledge and emerging questions about the in vivo role of ATF4 in one fully differentiated cell type, mammalian skeletal muscle fibers.

American Association of Clinical Endocrinology Clinical Practice Guideline: Developing a Diabetes Mellitus Comprehensive Care Plan-2022 Update.

OBJECTIVE: The objective of this clinical practice guideline is to provide updated and new evidence-based recommendations for the comprehensive care of persons with diabetes mellitus to clinicians, diabetes-care teams, other health care professionals and stakeholders, and individuals with diabetes and their caregivers. METHODS: The American Association of Clinical Endocrinology selected a task force of medical experts and staff who updated and assessed clinical questions and recommendations from the prior 2015 version of this guideline and conducted literature searches for relevant scientific papers published from January 1, 2015, through May 15, 2022. Selected studies from results of literature searches composed the evidence base to update 2015 recommendations as well as to develop new recommendations based on review of clinical evidence, current practice, expertise, and consensus, according to established American Association of Clinical Endocrinology protocol for guideline development. RESULTS: This guideline includes 170 updated and new evidence-based clinical practice recommendations for the comprehensive care of persons with diabetes. Recommendations are divided into four sections: (1) screening, diagnosis, glycemic targets, and glycemic monitoring; (2) comorbidities and complications, including obesity and management with lifestyle, nutrition, and bariatric surgery, hypertension, dyslipidemia, retinopathy, neuropathy, diabetic kidney disease, and cardiovascular disease; (3) management of prediabetes, type 2 diabetes with antihyperglycemic pharmacotherapy and glycemic targets, type 1 diabetes with insulin therapy, hypoglycemia, hospitalized persons, and women with diabetes in pregnancy; (4) education and new topics regarding diabetes and infertility, nutritional supplements, secondary diabetes, social determinants of health, and virtual care, as well as updated recommendations on cancer risk, nonpharmacologic components of pediatric care plans, depression, education and team approach, occupational risk, role of sleep medicine, and vaccinations in persons with diabetes. CONCLUSIONS: This updated clinical practice guideline provides evidence-based recommendations to assist with person-centered, team-based clinical decision-making to improve the care of persons with diabetes mellitus.

Insulin secretion and action and the response of endogenous glucose production to a lack of glucagon suppression in nondiabetic subjects.

Type 2 diabetes is a disease characterized by impaired insulin secretion and defective glucagon suppression in the postprandial period. We examined the effect of impaired glucagon suppression on glucose concentrations and endogenous glucose production (EGP) at different degrees of insulin secretory impairment. The contribution of anthropometric characteristics, peripheral, and hepatic insulin action to this variability was also examined. To do so, we studied 54 nondiabetic subjects on two occasions in which endogenous hormone secretion was inhibited by somatostatin, with glucagon infused at a rate of 0.65 ng/kg/min, at 0 min to prevent a fall in glucagon (nonsuppressed day) or at 120 min to create a transient fall in glucagon (suppressed day). Subjects received glucose (labeled with [3-3H]-glucose) infused to mimic the systemic appearance of 50-g oral glucose. Insulin was infused to mimic a prandial insulin response in 18 subjects, another 18 received 80% of the dose, and the remaining 18 received 60%. EGP was measured using the tracer-dilution technique. Decreased prandial insulin resulted in greater % increase in peak glucose but not in integrated glucose concentrations attributable to nonsuppressed glucagon. The % change in integrated EGP was unaffected by insulin dose. Multivariate regression analysis, adjusted for age, sex, weight, and insulin dose, did not show a relationship between the EGP response to impaired suppression of glucagon and insulin action as measured at the time of screening by oral glucose tolerance. A similar analysis for hepatic insulin action also did not show a relationship with the EGP response. These data indicate that the effect of impaired glucagon suppression on EGP is independent of anthropometric characteristics and insulin action.NEW & NOTEWORTHY In prediabetes, anthropometric characteristics as well as insulin action do not alter the hepatic response to glucagon. The postprandial suppression or lack of suppression of glucagon secretion is an important factor governing postprandial glucose tolerance independent of insulin secretion.

Assessment of individual and standardized glucagon kinetics in healthy humans.

Impaired glucose tolerance arises out of impaired postprandial insulin secretion and delayed suppression of glucagon. These defects occur early and independently in the pathogenesis of prediabetes. Quantification of the contribution of α-cell dysfunction to glucose tolerance has been lacking because knowledge of glucagon kinetics in humans is limited. Therefore, in a series of experiments examining the interaction of glucagon suppression with insulin secretion we studied 51 nondiabetic subjects (age = 54 ± 13 yr, BMI = 28 ± 4 kg/m2). Glucose was infused to mimic the systemic appearance of an oral challenge. Somatostatin was used to inhibit endogenous hormone secretion. 120 min after the start of the experiment, glucagon was infused at 0.65 ng/kg/min. The rise in glucagon concentrations was used to estimate its kinetic parameters [volume of distribution (Vd), half-life (t1/2), and clearance rate (CL)]. A single-exponential model provided the best fit for the data, and individualized kinetic parameters were estimated: Vd = 8.2 ± 2.7 L, t1/2 = 4 ± 1.1 min, CL = 1.4 ± 0.33 L/min. Stepwise linear regression was used to correlate Vd with BMI and sex (R2adj = 0.44), whereas CL similarly correlated with lean body mass or BSA (both R2 = 0.28). This enabled the development of a population-based model using anthropometric characteristics to predict Vd and CL. These data demonstrate that it is feasible to derive glucagon kinetic parameters from anthropometric characteristics, thereby enabling quantitation of the rate of glucagon appearance in the systemic circulation in large populations.NEW & NOTEWORTHY State-of-the-art measurement of insulin secretion in humans is accomplished by deconvolution of peripheral C-peptide concentrations using population-derived parameters of C-peptide kinetics. In contrast, knowledge of the kinetic parameters of glucagon in humans is lacking so that measurement of glucagon secretion to date is largely qualitative. This series of experiments enabled measurement of glucagon kinetics in 51 subjects, and subsequently, stepwise linear regression was used to correlate these parameters with anthropometric characteristics. This enabled the development of a population-based model using anthropometric characteristics to predict the volume of distribution and the rate of clearance. This is a necessary first step in the development of a model to quantitate of glucagon secretion and action (and its contribution to glucose tolerance) in large populations.

Adipose tissue macrophage populations and inflammation are associated with systemic inflammation and insulin resistance in obesity.

Obesity is accompanied by numerous systemic and tissue-specific derangements, including systemic inflammation, insulin resistance, and mitochondrial abnormalities in skeletal muscle. Despite growing recognition that adipose tissue dysfunction plays a role in obesity-related disorders, the relationship between adipose tissue inflammation and other pathological features of obesity is not well-understood. We assessed macrophage populations and measured the expression of inflammatory cytokines in abdominal adipose tissue biopsies in 39 nondiabetic adults across a range of body mass indexes (BMI 20.5-45.8 kg/m2). Skeletal muscle biopsies were used to evaluate mitochondrial respiratory capacity, ATP production capacity, coupling, and reactive oxygen species production. Insulin sensitivity (SI) and ß cell responsivity were determined from test meal postprandial glucose, insulin, c-peptide, and triglyceride kinetics. We examined the relationships between adipose tissue inflammatory markers, systemic inflammatory markers, SI, and skeletal muscle mitochondrial physiology. BMI was associated with increased adipose tissue and systemic inflammation, reduced SI, and reduced skeletal muscle mitochondrial oxidative capacity. Adipose-resident macrophage numbers were positively associated with circulating inflammatory markers, including tumor necrosis factor-α (TNFα) and C-reactive protein (CRP). Local adipose tissue inflammation and circulating concentrations of TNFα and CRP were negatively associated with SI, and circulating concentrations of TNFα and CRP were also negatively associated with skeletal muscle oxidative capacity. These results demonstrate that obese humans exhibit increased adipose tissue inflammation concurrently with increased systemic inflammation, reduced insulin sensitivity, and reduced muscle oxidative capacity and suggest that adipose tissue and systemic inflammation may drive obesity-associated metabolic derangements.NEW AND NOTEWORTHY Adipose inflammation is proposed to be at the nexus of the systemic inflammation and metabolic derangements associated with obesity. The present study provides evidence to support adipose inflammation as a central feature of the pathophysiology of obesity. Adipose inflammation is associated with systemic and peripheral metabolic derangements, including increased systemic inflammation, reduced insulin sensitivity, and reduced skeletal muscle mitochondrial respiration.

Limitations of the fasting proinsulin to insulin ratio as a measure of ß-cell health in people with and without impaired glucose tolerance.

BACKGROUND: The fasting proinsulin to insulin ratio is elevated in people with type 2 diabetes and has been suggested as a marker of ß-cell health. However, its utility in discriminating between individuals with varying degrees of ß-cell dysfunction is unclear. Proinsulin has a very different half-life to insulin and unlike insulin does not undergo hepatic extraction prior to reaching the systemic circulation. Given these limitations, we sought to examine the relationship between fasting and postprandial concentrations of ß-cell polypeptides (proinsulin, insulin and C-peptide) in people with normal and impaired glucose tolerance in differing metabolic environments. DESIGN: Subjects were studied on two occasions in random order while undergoing an oral challenge. During one study day, free fatty acids were elevated (to induce insulin resistance) by infusion of Intralipid with heparin. Proinsulin to insulin and proinsulin to C-peptide ratios were calculated for the 0-, 30-, 60- and 240-minute time points. Insulin action (Si) and ß-cell responsivity (Φ) indices were calculated using the oral minimal model. RESULTS: The fasting proinsulin to c-peptide or fasting proinsulin to insulin ratios did not differ between groups and did not predict subsequent ß-cell responsivity to glucose during the glycerol or Intralipid study days in either group. CONCLUSIONS: Among nondiabetic individuals, the fasting proinsulin to insulin ratio is not a useful marker of ß-cell function.

Burden and management of type 2 diabetes in rural United States.

In the United States, rural areas have a higher burden of type 2 diabetes (T2DM) compared to urban areas. However, there is limited information on risk factors and interventions that improve the primary prevention and management of T2DM in rural areas. To synthesize current knowledge on T2DM in rural areas and to guide healthcare providers and policy makers, we reviewed five scientific databases and the grey literature over the last decade (2010-2020). We described classification systems for rurality and the T2DM burden based on rurality and region (West, South, Midwest, and Northeast). We highlighted risk factors for T2DM in rural compared to urban areas, and summarized interventions to screen and manage T2DM based on opportunistic screening, T2DM self-management, community-based initiatives, as well as interventions targeting comorbidities and T2DM. Several studies identified the co-existence of T2DM and depression/psychological symptoms, which could reduce adherence to non-pharmacologic and pharmacologic management of T2DM. We highlighted the role of technology in education and counselling of patients with geographic and financial barriers to accessing care, which is exacerbated by the SARS-CoV-2 coronavirus disease-19 pandemic. We identified knowledge gaps and next steps in improving T2DM care in rural areas. There is an urgent need for interventions tailored to rural areas given that rural Americans currently experience a disproportionate burden of T2DM and are encumbered by its associated morbidity, mortality, and loss in economic productivity.

Endoscopic management of dumping syndrome after Roux-en-Y gastric bypass: a large international series and proposed management strategy.

BACKGROUND AND AIMS: Roux-en-Y gastric bypass (RYGB) is refractory to lifestyle and pharmacotherapy measures, requiring reversal of the patient's bariatric surgery. Reversal can lead to weight regain and recrudescence of their comorbidities. Our aim was to report a multicenter experience on the endoscopic management of refractory dumping syndrome with endoscopic transoral outlet reduction (TORe). METHODS: A multicenter international series of consecutive patients who underwent TORe with a full-thickness endoscopic suturing device was analyzed for technical success, improvement in Sigstad scores, and weight trajectories after the procedure. Failure was defined as needing an enteral feeding tube, surgical reversal, or repeat TORe. RESULTS: One hundred fifteen patients across 2 large academic centers in Germany and the United States underwent TORe for dumping syndrome. Patient age was mean 8.9 ± 1.1 years from their initial RYGB with an average percent total body weight loss of 31% ± 10.6% at the time of endoscopy. Three months postprocedure, the Sigstad score improved from a mean of 17 ± 6.1 to 2.6 ± 1.9 (paired t test P = .0001) with only 2% of patients (n = 2) experiencing weight gain. Mean weight loss and percentage of total body weight loss 3 months post-TORe were 9.47 ± 3.6 kg and 9.47% ± 2.5%, respectively. Six patients (5%) failed initial endoscopic therapy, with 50% (n = 3) successfully treated with a repeat TORe. Three patients underwent surgical reversal, indicating an overall 97% endoscopic success rate. CONCLUSIONS: TORe as an adjunct to lifestyle and pharmacologic therapy for refractory dumping syndrome is safe and effective at improving dumping syndrome and reducing rates of surgical revision.

Malignant Insulinoma: A Rare Form of Neuroendocrine Tumor.

INTRODUCTION: Due to the rarity of malignant insulinoma, a lack of the literature describing factors affecting outcomes exists. Our aim was to review malignant insulinoma incidence, characteristics and survival trends. METHODS: We identified all patients with malignant insulinoma in the SEER registries from 1973 to 2015. Incidence, neoplasm characteristics and factors affecting cancer-specific survival (CSS) were described. RESULTS: A total of 121 patients were identified. The crude annual overall incidence was low (range 0.0-0.27 cases per million person years). The largest proportion had localized disease (40%), while 16% had regional disease, 39% distant metastatic disease, and stage was unreported in 5%. Most neoplasms were in the body/tail of the pancreas, followed by the head of the pancreas. Grade was reported in 40% of patients; only a single patient reported as having grade IV with the remainder all grades I/II. Surgical resection was performed in 64% of patients. Within surgical patients, the median primary neoplasm size was 1.8 cm. Regional lymph nodes were examined in 57.1% of surgical patients, while 34% of examined nodes were positive. The median CSS was 183 months. On multivariable analysis, surgical resection, male sex and absence of metastatic disease were associated with superior survival. CONCLUSION: While the greatest proportion of patients with malignant insulinoma present with localized disease, regional lymph node involvement was found in 34% of whose nodes were tested. Further studies are needed to assess the role of lymph node dissection in improving survival and preventing recurrence given the observed frequency of lymph node involvement.

Walking a fine line between ß-cell secretion and proliferation.

Of the many common genetic variants associated with type 2 diabetes, that in TCF7L2 remains the most studied because it has the greatest effect size. However, the mechanism by which this variant alters diabetes risk remains elusive. A new study adds another layer of complexity, suggesting that the effects of TCF7L2 are context-dependent, and highlights a novel interaction that might bias a ß-cell to a secretory or proliferative phenotype. This in turn might open up new avenues to the restoration of insulin secretion in people with type 2 diabetes.

Assessment of pulsatile insulin secretion derived from peripheral plasma C-peptide concentrations by nonparametric stochastic deconvolution.

The characteristics of pulsatile insulin secretion are important determinants of type 2 diabetes pathophysiology, but they are understudied due to the difficulties in measuring pulsatile insulin secretion noninvasively. Deconvolution of either peripheral C-peptide or insulin concentrations offers an appealing alternative to hepatic vein catheterization. However, to do so, there are a series of methodological challenges to overcome. C-peptide has a relatively long half-life and accumulates in the circulation. On the other hand, peripheral insulin concentrations reflect relatively fast clearance and hepatic extraction as it leaves the portal circulation to enter the systemic circulation. We propose a method based on nonparametric stochastic deconvolution of C-peptide concentrations, using individually determined C-peptide kinetics, to overcome these limitations. The use of C-peptide (instead of insulin) concentrations allows estimation of portal (and not post-hepatic) insulin pulses, whereas nonparametric stochastic deconvolution allows evaluation of pulsatile signals without any a priori assumptions of pulse shape and occurrence. The only assumption required is the degree of smoothness of the (unknown) secretion rate. We tested this method first on simulated data and then on 29 nondiabetic subjects studied during euglycemia and hyperglycemia and compared our estimates with the profiles obtained from hepatic vein insulin concentrations. This method produced satisfactory results both in the ability to fit the data and in providing reliable estimates of pulsatile secretion, in agreement with hepatic vein measurements. In conclusion, the proposed method enables reliable and noninvasive measurement of pulsatile insulin secretion. Future studies will be needed to validate this method in people with type 2 diabetes.

Coronary microvascular dysfunction is associated with poor glycemic control amongst female diabetics with chest pain and non-obstructive coronary artery disease.

BACKGROUND: Patients with type 2 diabetes mellitus are at an increased risk of adverse cardiovascular events compared to those without diabetes. The timing, relative to disease onset, and degree of glycemic control that reduces the risk of adverse cardiovascular events remains uncertain. Coronary microvascular dysfunction is prevalent in patients with type 2 diabetes mellitus and is linked to adverse cardiovascular events. We assessed the association between endothelial-dependent and endothelial-independent coronary microvascular dysfunction and glycemic control in patients presenting with chest pain and nonobstructive coronary disease at angiography. METHODS: Patients presenting with chest pain and found to have non-obstructive CAD (stenosis < 40%) at angiography underwent an invasive assessment of endothelial-independent and endothelial -dependent microvascular function. Endothelial-independent microvascular function was assessed by comparing the coronary flow velocity, measured using a Doppler guidewire, in response to intracoronary infusion of adenosine to calculate the coronary flow reserve ratio in response to adenosine (CFRAdn Ratio). A CFRAdn Ratio ≤ 2.5 was considered abnormal. Endothelial-dependent microvascular function was assessed by measuring the percent change in coronary blood flow in response to intracoronary infusions of acetylcholine (%ΔCBFAch), and microvascular endothelial dysfunction defined as a %ΔCBFAch of ≤ 50%. Patients were classified by normal versus abnormal CFRAdn Ratio and %ΔCBFAch. Measurements of HbA1c and fasting serum glucose were obtained prior to catheterization and compared between groups. RESULTS: Between 1993 and 2012, 1469 patients (mean age 50.4 years, 35% male) underwent coronary angiography and invasive testing for coronary microvascular dysfunction, of which 129 (8.8%) had type 2 diabetes. Fifty-one (39.5%) had an abnormal %ΔCBFAch and 49 (38.0%) had an abnormal CFRAdn Ratio. Conventional cardiovascular risk factors and cardiovascular or diabetic medication use did not vary significantly between groups. Females with an abnormal CFRAdn Ratio or abnormal %ΔCBFAch had a significantly higher HbA1c compared to patients with a normal CFRAdn Ratio or %ΔCBFAch respectively: HbA1c % (standard deviation) 7.4 (2.1) vs. 6.5 (1.1), p = 0.035 and 7.3 (1.9) vs. 6.4 (1.2), p = 0.022, respectively. Female patients with an abnormal CFRAdn Ratio had significantly higher fasting serum glucose concentrations compared to those with a normal CFRAdn Ratio: fasting serum glucose mg/dL (standard deviation) 144.4 (55.6) vs. 121.9 (28.1), p = 0.035. This was not observed in men. Amongst female diabetics, a higher HbA1c was significantly associated with any coronary microvascular dysfunction both in a univariate and multivariate analysis: odds ratio (95% confidence interval) 1.69 (1.01-2.86) p = 0.049; and a fasting serum glucose > 140 mg/dL was significantly associated with an abnormal CFRAdn Ratio, 4.28 (1.43-12.81). CONCLUSION: Poor glycemic control is associated with coronary microvascular dysfunction amongst female diabetics presenting with chest pain and non-obstructive CAD. These findings highlight the importance of sex specific risk stratification models and treatment strategies when managing cardiovascular risk amongst diabetics. Further studies are required to identify additional risk prevention tools and therapies targeting microvascular dysfunction as an integrated index of cardiovascular risk.

Plantar Ulcers and Neuropathic Arthropathies: Associated Diseases, Polyneuropathy Correlates, and Risk Covariates.

OBJECTIVE: To evaluate the associated diseases, polyneuropathy correlates, and risk covariates of neuropathic plantar ulcers (PUs) and neuropathic arthropathies (NAs). DESIGN: The authors conducted a retrospective, observational study over 3.5 years of 69 patients with neuropathy, NA, or PU seen in a wound clinic who also had a comprehensive neurologic evaluation and neurophysiologic testing. Comparisons were made to a population representative cohort of patients with diabetes mellitus (DM; n = 259). RESULTS: Of the 69 wound clinic patients, 32 had PUs, 14 had NAs, and 23 had both. Of the 61 adequately assessed patients, 37 (61%) had DM, 22 (36%) had no known associated disease, and 2 (3%) had hereditary sensory and autonomic neuropathy. Of the 37 patients with DM, 35 had distal polyneuropathy, and 2 did not. In 22 patients with chronic idiopathic axonal polyneuropathy, 20 had distal polyneuropathy. CONCLUSIONS: Although DM was the disease most commonly associated with PUs and NAs, chronic hyperglycemia may not have been the major underlying risk factor. The major risk covariates are sensation loss from polyneuropathy, old age, obesity, repetitive foot injury, and inadequate foot care or treatment. Physicians and other healthcare providers can help by identifying patients at risk and instituting measures such as adequate foot care to decrease these risks.

Obstacles to Translating Genotype-Phenotype Correlates in Metabolic Disease.

Type 2 diabetes mellitus is a polygenic disease with a variable phenotype. Many genetic associations have been described; however, understanding their underlying pathophysiological role in Type 2 diabetes mellitus is important for development of future therapeutic targets. Here, we review the physiological mechanisms of diabetes-associated variants that affect glycemia.

A novel triple-tracer approach to assess postprandial protein turnover.

Insulin and nutrients have profound effects on proteome homeostasis. Currently no reliable methods are available to measure postprandial protein turnover. A triple-tracer method was developed using phenylalanine stable isotope tracers to estimate appearance rates of ingested (Ra meal) and endogenous phenylalanine and the rate of phenylalanine disposal (Rd). This was compared with the "traditional" dual-tracer method, using one (1-CM)- and two (2-CM)-compartment models. For both methods, [13C6]phenylalanine was given orally, and [15N]phenylalanine was constantly infused; the triple-tracer method added [2H5]phenylalanine, infused at rates to mimic meal [13C6]phenylalanine appearance. Additionally, incorporation of meal-derived phenylalanine into specific proteins was measured after purification by two-dimensional electrophoresis. The triple-tracer approach reduced modeling errors, allowing improved reconstruction of Ra meal with a tracer-to-tracee ratio that was more constant and better estimated Rd. The 2-CM better described phenylalanine kinetics and Rd than 1-CM. Thus, the triple-tracer approach using 2-CM is superior for measuring non-steady-state postprandial protein turnover. This novel approach also allows measurement of postprandial synthesis rates of specific plasma proteins. We offer a valid non-steady-state model to measure postprandial protein turnover and synthesis of plasma proteins that can safely be applied in adults, children, and pregnant women.