Novel phenotypes of prediabetes?

Intra-pancreatic fat is associated with high circulating glucagon and GLP-1 concentrations following whey protein ingestion in overweight women with impaired fasting glucose: A randomised controlled trial

AIM

Intra-pancreatic fat deposition (IPFD) while hypothesised to impair beta-cell function, its impact on alpha-cells remains unclear. We evaluated the association between IPFD and markers of pancreatic cells function using whey protein.

METHODS

Twenty overweight women with impaired fasting glucose (IFG) and low or high IPFD (<4.66% vs ≥4.66%) consumed 3 beverage treatments: 0 g (water control), 12.5 g (low-dose) and 50.0 g (high-dose) whey protein, after an overnight fast, in randomised order. Blood glucose, insulin, C-peptide, glucagon, gastric-inhibitory polypeptide (GIP), glucagon-like peptide-1 (GLP-1) and amylin were analysed postprandially over 4 h. Incremental area-under-the-curve (iAUC), incremental maximum concentration (iCmax), and time to maximum concentration (Tmax) for these were compared between IPFD groups using repeated measures linear mixed models, also controlled for age (pcov).

RESULTS

iAUC and iCmax glucose and insulin while similar between the two IPFD groups, high IPFD and ageing contributed to higher postprandial glucagon (iAUC: p = 0.012; pcov = 0.004; iCmax: p = 0.069; pcov = 0.021) and GLP-1 (iAUC: p = 0.006; pcov = 0.064; iCmax: p = 0.011; pcov = 0.122) concentrations.

CONCLUSION

In our cohort, there was no evidence that IPFD impaired protein-induced insulin secretion. Conversely, IPFD may be associated with increased protein-induced glucagon secretion, a novel observation which warrants further investigation into its relevance in the pathogenesis of dysglycaemia and type-2 diabetes.

[Prediabetes as a therapeutic challenge in internal medicine]

The term prediabetes describes a fasting blood glucose level that is elevated but not yet in the diabetic range, a blood glucose level that is elevated after 120 min in a standard 75‑g oral glucose tolerance test, or both. The American Diabetes Association definition also includes glycated hemoglobin A (HbA1c). The incidence of prediabetes is rapidly increasing. Progression from normal glucose tolerance to diabetes is a continuous process. Insulin resistance and insulin secretory dysfunction, the simultaneous presence of which characterizes manifest diabetes, are already present in the prediabetic stage. Prediabetes is associated with an increased risk of diabetes; however, by no means all people with prediabetes go on to develop diabetes. Nevertheless, the identification of an increased risk of diabetes is still relevant insofar as it requires the adoption of diabetes prevention measures. Structured lifestyle intervention has been shown to be the most effective strategy for treating prediabetes. To increase its efficiency, it should, as far as possible, be made exclusively available to those people on whom it is most likely to confer a benefit. This would make it necessary to stratify people with prediabetes according to their risk profile. In a population of people at increased risk of diabetes (Tübingen Diabetes Family Study), a cluster analysis was performed, resulting in six clusters/subgroups. Within these, three high-risk subgroups were identified: Two of these risk groups show predominant insulin secretory dysfunction or predominant insulin resistance and high diabetes and cardiovascular risk. The third group shows a high risk of nephropathy and high mortality, but a comparatively lower diabetes risk. In general, prediabetes cannot yet be treated in a targeted pathophysiologically oriented manner. The new classification of prediabetes-based on pathophysiology-is now opening up new avenues for diabetes prevention. Current and future studies should confirm the assumption that the effectiveness of established, or not yet established, preventive measures depends on the respective subgroup.

Prediabetes blunts DPP4 genetic control of postprandial glycaemia and insulin secretion

AIMS/HYPOTHESIS

Imbalances in glucose metabolism are hallmarks of clinically silent prediabetes (defined as impaired fasting glucose and/or impaired glucose tolerance) representing dysmetabolism trajectories leading to type 2 diabetes. CD26/dipeptidyl peptidase 4 (DPP4) is a clinically proven molecular target of diabetes-controlling drugs but the DPP4 gene control of dysglycaemia is not proven.

METHODS

We dissected the genetic control of post-OGTT and insulin release responses by the DPP4 gene in a Portuguese population-based cohort of mainly European ancestry that comprised individuals with normoglycaemia and prediabetes, and in mouse experimental models of Dpp4 deficiency and hyperenergetic diet.

RESULTS

In individuals with normoglycaemia, DPP4 single-nucleotide variants governed glycaemic excursions (rs4664446, p=1.63x10^-7) and C-peptide release responses (rs2300757, p=6.86x10^-5) upon OGTT. Association with blood glucose levels was stronger at 30 min OGTT, but a higher association with the genetic control of insulin secretion was detected in later phases of the post-OGTT response, suggesting that the DPP4 gene directly senses glucose challenges. Accordingly, in mice fed a normal chow diet but not a high-fat diet, we found that, under OGTT, expression of Dpp4 is strongly downregulated at 30 min in the mouse liver. Strikingly, no genetic association was found in prediabetic individuals, indicating that post-OGTT control by DPP4 is abrogated in prediabetes. Furthermore, Dpp4 KO mice provided concordant evidence that Dpp4 modulates post-OGTT C-peptide release in normoglycaemic but not dysmetabolic states.

CONCLUSIONS/INTERPRETATION

These results showed the DPP4 gene as a strong determinant of post-OGTT levels via glucose-sensing mechanisms that are abrogated in prediabetes. We propose that impairments in DPP4 control of post-OGTT insulin responses are part of molecular mechanisms underlying early metabolic disturbances associated with type 2 diabetes.

Fatty Pancreas-Centered Metabolic Basis of Pancreatic Adenocarcinoma: From Obesity, Diabetes and Pancreatitis to Oncogenesis

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest types of cancer, and it is currently the third most common cause of cancer death in the U.S.A. Progress in the fight against PDAC has been hampered by an inability to detect it early in the overwhelming majority of patients, and also by the reduced oxygen levels and nutrient perfusion caused by new matrix formation through the activation of stromal cells in the context of desmoplasia. One harbinger of PDAC is excess intrapancreatic fat deposition, namely, fatty pancreas, which specifically affects the tumor macro- and microenvironment in the organ. Over half of PDAC patients have diabetes mellitus (DM) at the time of diagnosis, and fatty pancreas is associated with subsequent DM development. Moreover, there is a strong association between fatty pancreas and fatty liver through obesity, and a higher intrapancreatic fat percentage has been noted in acute pancreatitis patients with DM than in those without DM. All these findings suggest that the link between fatty pancreas and PDAC might occur through metabolic alterations, either DM-related or non-DM-related. Based on clinical, in vivo and in vitro evidence, the current review highlights the etiologies of fatty pancreas (including fatty infiltration and replacement) and the fatty pancreas-associated metabolic alterations involved in oncogenesis to provide crucial targets to prevent, detect, and/or effectively treat PDAC.

Lipid-Induced Adaptations of the Pancreatic Beta-Cell to Glucotoxic Conditions Sustain Insulin Secretion

Over the last decades, lipotoxicity and glucotoxicity emerged as established mechanisms participating in the pathophysiology of obesity-related type 2 diabetes in general, and in the loss of β-cell function in particular. However, these terms hold various potential biological processes, and it is not clear what precisely they refer to and to what extent they might be clinically relevant. In this review, we discuss the basis and the last advances of research regarding the role of free fatty acids, their metabolic intracellular pathways, and receptor-mediated signaling related to glucose-stimulated insulin secretion, as well as lipid-induced β-cell dysfunction. We also describe the role of chronically elevated glucose, namely, glucotoxicity, which promotes failure and dedifferentiation of the β cell. Glucolipotoxicity combines deleterious effects of exposures to both high glucose and free fatty acids, supposedly provoking synergistic defects on the β cell. Nevertheless, recent studies have highlighted the glycerolipid/free fatty acid cycle as a protective pathway mediating active storage and recruitment of lipids. Finally, we discuss the putative correspondence of the loss of functional β cells in type 2 diabetes with a natural, although accelerated, aging process.

A Narrative Review on the Role of AMPK on De Novo Lipogenesis in Non-Alcoholic Fatty Liver Disease: Evidence from Human Studies

5′AMP-activated protein kinase (AMPK) is known as metabolic sensor in mammalian cells that becomes activated by an increasing adenosine monophosphate (AMP)/adenosine triphosphate (ATP) ratio. The heterotrimeric AMPK protein comprises three subunits, each of which has multiple phosphorylation sites, playing an important role in the regulation of essential molecular pathways. By phosphorylation of downstream proteins and modulation of gene transcription AMPK functions as a master switch of energy homeostasis in tissues with high metabolic turnover, such as the liver, skeletal muscle, and adipose tissue. Regulation of AMPK under conditions of chronic caloric oversupply emerged as substantial research target to get deeper insight into the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Evidence supporting the role of AMPK in NAFLD is mainly derived from preclinical cell culture and animal studies. Dysbalanced de novo lipogenesis has been identified as one of the key processes in NAFLD pathogenesis. Thus, the scope of this review is to provide an integrative overview of evidence, in particular from clinical studies and human samples, on the role of AMPK in the regulation of primarily de novo lipogenesis in human NAFLD.

Phenotyping the Prediabetic Population-A Closer Look at Intermediate Glucose Status and Cardiovascular Disease

Even though the new thresholds for defining prediabetes have been around for more than ten years, there is still controversy surrounding the precise characterization of this intermediate glucose metabolism status. The risk of developing diabetes and macro and microvascular disease linked to prediabetes is well known. Still, the prediabetic population is far from being homogenous, and phenotyping it into less heterogeneous groups might prove useful for long-term risk assessment, follow-up, and primary prevention. Unfortunately, the current definition of prediabetes is quite rigid and disregards the underlying pathophysiologic mechanisms and their potential metabolic progression towards overt disease. In addition, prediabetes is commonly associated with a cluster of risk factors that worsen the prognosis. These risk factors all revolve around a common denominator: inflammation. This review focuses on identifying the population that needs to be screened for prediabetes and the already declared prediabetic patients who are at a higher risk of cardiovascular disease and require closer monitoring.

Tengdan Capsule Prevents Hypertensive Kidney Damage in SHR by Inhibiting Periostin-Mediated Renal Fibrosis

BACKGROUND: Hypertension-induced renal damage is a serious and complex condition that has not been effectively treated by conventional blood pressure-lowering drugs. Tengdan capsule (TDC) is a China FDA-approved compound herbal medicine for treating hypertension; however, its chemical basis and pharmacological efficacy have not been fully investigated in a preclinical setting.

METHODS: High-performance liquid chromatography (HPLC) was used to identify and quantify the major chemical components of TDC extracted from ultrapure water. Adult spontaneously hypertensive rats (SHR) and age/sex-matched Wistar Kyoto normotensive rats (WKY) were both treated with TDC, losartan, or saline for one month, and their blood pressure (BP) was monitored at the same time by tail-cuff BP system. Biochemical indexes such as urine creatinine (CRE) and blood urea nitrogen (BUN) were determined. Kidney tissue sections were examined with (H&E), and Masson staining to evaluate the pathological effect of TDC on SHR’s kidneys. After TDC treatment, the differentially expressed proteins in the kidneys of SHR were identified by the TMT-based quantitative proteomics analysis, which may provide the targets and possible mechanisms of TDC action. In addition, Western blot analysis, RT-qPCR, and ELISA assays were carried out to further verify the proteomics findings. Finally, two different models involving in vitro renal injuries were established using human kidney HEK293 cells; and the molecular mechanism of TDC kidney protection was demonstrated.

RESULTS: Seven chemical compounds, namely Notoginsenoside R1, Ginsenoside RG1, Ginsenoside Re, Ginsenoside Rb1, Sodium Danshensu, Protocatechualdehyde, and Salvianolic acid B, were identified and quantified from the water-soluble extracts of TDC by HPLC. In vivo study using rats showed that TDC effectively reduced BP, BUN, and CRE levels and attenuated renal fibrosis in SHR, and ameliorated damage to the kidneys. Proteomics and subsequent bioinformatics analyses indicated that periostin-mediated inflammatory response and TGFβ/Smad signaling pathway proteins were closely related to the therapeutic effect of TDC in rat kidneys. Western blot analysis and RT-qPCR showed that TDC markedly downregulated the mRNA and protein expression of periostin in renal tissues compared to the untreated SHR. In addition, TGF-β and COL1A1 mRNA levels also decreased in SHR renal tissues following TDC treatment. In vitro studies showed that low to medium doses of TDC down-regulated the expression of periostin in the injury model of HEK293 cell. In addition, medium to high doses of TDC significantly inhibited collagen deposition in TGFβ1-induced HEK293 cell fibrosis.

CONCLUSIONS: Major components from the compound herbal medicine Tengdan Capsule are identified and quantified. TDC effectively lowers blood pressure and protects against renal damage caused by hypertension in SHR. Mechanistically, TDC blocks periostin by regulating the TGF-β/Smad signaling pathway in the kidney, both in vivo and in vitro. Preventing periostin-mediated renal fibrosis and inflammation might be a promising strategy for treating a hypertensive renal injury.

The Diabetes Syndrome - A Collection of Conditions with Common, Interrelated Pathophysiologic Mechanisms

The four basic pathophysiologic mechanisms which damage the β-cell within diabetes (ie, genetic and epigenetic changes, inflammation, an abnormal environment, and insulin resistance [IR]) also contribute to cell and tissue damage and elevate the risk of developing all typical diabetes-related complications. Genetic susceptibility to damage from abnormal external and internal environmental factors has been described including inflammation and IR. All these mechanisms can promote epigenetic changes, and in total, these pathophysiologic mechanisms interact and react with each other to cause damage to cells and tissues ultimately leading to disease. Importantly, these pathophysiologic mechanisms also serve to link other common conditions including cancer, dementia, psoriasis, atherosclerotic cardiovascular disease (ASCVD), nonalcoholic fatty liver disease (NAFLD), and nonalcoholic steatohepatitis (NASH). The “Diabetes Syndrome”, an overarching group of interrelated conditions linked by these overlapping mechanisms, can be viewed as a conceptual framework that can facilitate understanding of the inter-relationships of superficially disparate conditions. Recognizing the association of the conditions within the Diabetes Syndrome due to common pathophysiologies has the potential to provide both benefit to the patient (eg, prevention, early detection, precision medicine) and to the advancement of medicine (eg, driving education, research, and dynamic decision-based medical practice).

Intranasal insulin administration decreases cerebral blood flow in cortico-limbic regions: A neuropharmacological imaging study in normal and overweight males

AIM

To assess and compare the effects of 160 IU intranasal insulin (IN-INS) administration on regional cerebral blood flow (rCBF) in healthy male individuals with normal weight and overweight phenotypes.

METHODS

Thirty young male participants (mean age 25.9 years) were recruited and stratified into two cohorts based on body mass index: normal weight (18.5-24.9 kg/m² ) and overweight (25.0-29.9 kg/m² ). On separate mornings participants received 160 IU of IN-INS using an intranasal protocol and intranasal placebo as part of a double-blind crossover design. Thirty minutes following administration rCBF data were collected using a magnetic resonance imaging method called pseudocontinuous arterial spin labelling. Blood samples were collected to assess insulin sensitivity and changes over time in peripheral glucose, insulin and C-peptide.

RESULTS

Insulin sensitivity did not significantly differ between groups. Compared with placebo, IN-INS administration reduced rCBF in parts of the hippocampus, insula, putamen, parahippocampal gyrus and fusiform gyrus in the overweight group. No effect was seen in the normal weight group. Insula rCBF was greater in the overweight group versus normal weight only under placebo conditions. Peripheral glucose and insulin levels were not affected by IN-INS. C-peptide levels in the normal weight group decreased significantly over time following IN-INS administration but not placebo.

CONCLUSION

Insulin-induced changes within key regions of the brain involved in gustation, memory and reward were observed in overweight healthy male individuals. Following placebo administration, differences in gustatory rCBF were observed between overweight and normal weight healthy individuals.

BMP7 overexpression in adipose tissue induces white adipogenesis and improves insulin sensitivity in ob/ob mice

BACKGROUND/OBJECTIVES

During obesity, hypertrophic enlargement of white adipose tissue (WAT) promotes ectopic lipid deposition and development of insulin resistance. In contrast, WAT hyperplasia is associated with preservation of insulin sensitivity. The complex network of factors that regulates white adipogenesis is not fully understood. Bone morphogenic protein 7 (BMP7) can induce brown adipogenesis, but its role on white adipogenesis remains to be elucidated. Here, we assessed BMP7-mediated effects on white adipogenesis in ob/ob mice.

METHODS

BMP7 was overexpressed in either WAT or liver of ob/ob mice using adeno-associated viral (AAV) vectors. Analysis of gene expression, histological and morphometric alterations, and metabolites and hormones concentrations were carried out.

RESULTS

Overexpression of BMP7 in adipocytes of subcutaneous and visceral WAT increased fat mass, the proportion of small-size adipocytes and the expression of adipogenic and mature adipocyte genes, suggesting induction of adipogenesis irrespective of fat depot. These changes were associated with reduced hepatic steatosis and improved insulin sensitivity. In contrast, liver-specific overproduction of BMP7 did not promote WAT hyperplasia despite BMP7 circulating levels were similar to those achieved after genetic engineering of WAT.

CONCLUSIONS

This study unravels a new autocrine/paracrine role of BMP7 on white adipogenesis and highlights that BMP7 may modulate WAT plasticity and increase insulin sensitivity.

Brain insulin sensitivity is linked to adiposity and body fat distribution

Brain insulin action regulates eating behavior and energy fluxes throughout the body. However, numerous people are brain insulin resistant. How brain insulin responsiveness affects long-term weight and body fat composition in humans is still unknown. Here we show that high brain insulin sensitivity before lifestyle intervention associates with a more pronounced reduction in total and visceral fat during the program. High brain insulin sensitivity is also associated with less regain of fat mass during a nine year follow-up. Cross-sectionally, strong insulin responsiveness of the hypothalamus associates with less visceral fat, while subcutaneous fat is unrelated. Our results demonstrate that high brain insulin sensitivity is linked to weight loss during lifestyle intervention and associates with a favorable body fat distribution. Since visceral fat is strongly linked to diabetes, cardiovascular risk and cancer, these findings have implications beyond metabolic diseases and indicate the necessity of strategies to resolve brain insulin resistance.

Brain insulin action regulates eating behavior and whole-body energy fluxes, however the impact of brain insulin resistance on long-term weight and body fat composition is unknown. Here, the authors show that high brain insulin sensitivity is linked to weight loss during lifestyle intervention and associates with a favorable body fat distribution.

When does diabetes start? Early detection and intervention in type2 diabetes mellitus

Type 2 diabetes mellitus (DM2) is a progressive disease whose pathophysiological changes occur several years before its detection. An approach based on the pathophysiological development of DM2 and its complications emphasises the importance of early and intensive intervention, not only to prevent beta-cell dysfunction but also to act on the potential associated cardiovascular risk factors before reaching the blood glucose thresholds currently set for diagnosing DM2. In the field of recently diagnosed DM2, the VERIFY study has shown that early treatment combined with metformin-vildagliptin provides relevant improvements in long-term glycaemic control and can positively affect the disease's progression.

Association of Visceral Adiposity Surrogates with Impaired Fasting Glucose in Nonobese Individuals

Background: Nonobese individuals with disproportionate body fat distribution are also vulnerable to dysglycemia. This study aimed to evaluate the association between three visceral adiposity surrogates and impaired fasting glucose (IFG) in nonobese Chinese individuals. Methods: A total of 70,200 nonobese adults without diabetes were included in this analysis. Two diagnostic criteria (IFG-ADA and IFG-WHO) were used to define IFG. The values of the visceral adiposity index, lipid accumulation product index (LAP), and cardiometabolic index (CMI) were calculated. Multivariable logistic analysis was used to evaluate the association between these surrogates and IFG. Results: Among the three indicators, only LAP and CMI were positively correlated with fasting plasma glucose (all P < 0.001). After fully adjusting for confounders, only LAP and CMI exhibited significant associations with IFG. For women, the odds ratios (ORs) for IFG-ADA in the highest quartile of the LAP and CMI were 1.967 (95% confidence interval [CI]: 1.645-2.353) and 1.594 (95% CI: 1.383-1.836), respectively; and were 2.025 (95% CI: 1.597-2.567) and 2.017 (95% CI: 1.647-2.470), respectively, for IFG-WHO (all P < 0.001). For men, the ORs for IFG-ADA of the LAP and CMI were 1.503 (95% CI: 1.233-1.833) and 2.045 (95% CI: 1.752-2.388), respectively; and were 1.534 (95% CI: 1.174-2.005) and 2.541 (95% CI: 2.025-3.188), respectively, for IFG-WHO (all P < 0.001). Conclusions: The LAP and CMI, cost-effective and simple visceral adiposity surrogates, are strongly associated with IFG in nonobese Chinese individuals. These surrogates might be potential targets to monitor for the recognition and management of excess visceral adiposity in nonobese individuals with prediabetes.

Porcine models for studying complications and organ crosstalk in diabetes mellitus

The worldwide prevalence of diabetes mellitus and obesity is rapidly increasing not only in adults but also in children and adolescents. Diabetes is associated with macrovascular complications increasing the risk for cardiovascular disease and stroke, as well as microvascular complications leading to diabetic nephropathy, retinopathy and neuropathy. Animal models are essential for studying disease mechanisms and for developing and testing diagnostic procedures and therapeutic strategies. Rodent models are most widely used but have limitations in translational research. Porcine models have the potential to bridge the gap between basic studies and clinical trials in human patients. This article provides an overview of concepts for the development of porcine models for diabetes and obesity research, with a focus on genetically engineered models. Diabetes-associated ocular, cardiovascular and renal alterations observed in diabetic pig models are summarized and their similarities with complications in diabetic patients are discussed. Systematic multi-organ biobanking of porcine models of diabetes and obesity and molecular profiling of representative tissue samples on different levels, e.g., on the transcriptome, proteome, or metabolome level, is proposed as a strategy for discovering tissue-specific pathomechanisms and their molecular key drivers using systems biology tools. This is exemplified by a recent study providing multi-omics insights into functional changes of the liver in a transgenic pig model for insulin-deficient diabetes mellitus. Collectively, these approaches will provide a better understanding of organ crosstalk in diabetes mellitus and eventually reveal new molecular targets for the prevention, early diagnosis and treatment of diabetes mellitus and its associated complications.

Reduced serum concentrations of vitamin B12 and folate and elevated thyroid-stimulating hormone and homocysteine levels in first-trimester pregnant Saudi women with high A1C concentrations

Better understanding of the risk factors for diabetes can lead to proper prevention of this devastating metabolic abnormality. It is hypothesized that diabetes pathogenesis is linked to complex metabolic abnormalities involving homocysteine (HCY) pathways and affecting B₁₂, folate, and thyroid-stimulating hormone (TSH) concentrations. This study was conducted to determine the associations between serum concentrations of vitamin B₁₂, folate, TSH, and HCY in pregnant women with normal glycemic control, diabetes, or prediabetes. This cross-sectional study included 1159 healthy first-trimester pregnant women who were randomly selected from antenatal clinics in 2 hospitals and 21 health care centers across Al-Madinah, Saudi Arabia. Data collected included clinical history and blood sample analyses for serum folate, vitamin B₁₂, TSH, HCY, and glycated hemoglobin (A1C). Participants were classified with normal A1C (<5.7%), prediabetes (≥5.7 and <6.5%), or undiagnosed type 2 diabetes (≥6.5%). Results revealed that 79.5% of the participants had normal A1C levels, whereas 19.3% and 1.21% had A1C levels in prediabetic and diabetic ranges, respectively. Serum concentrations of vitamin B₁₂ and folate were lower in prediabetes subjects than in participants with normal A1C concentrations, whereas serum concentrations of TSH and HCY were significantly higher. There was a strong negative correlation among the concentrations of A1C, vitamin B_12, and folate, whereas positive correlations among A1C, TSH, and HCY were reported. Regression analysis identified TSH as having the strongest impact on A1C concentrations. These complex metabolic changes that occur at the prediabetic stage that involve TSH, HCY, folate, and vitamin B₁₂ might direct research on diabetes prevention.

Duodenal adipose tissue is associated with obesity in baboons (Papio sp): a novel site of ectopic fat deposition in non-human primates

AIMS

Ectopic fat is a recognized contributor to insulin resistance and metabolic dysfunction, while the role of fat deposition inside intestinal wall tissue remains understudied. We undertook this study to directly quantify and localize intramural fat deposition in duodenal tissue and determine its association with adiposity.

METHODS

Duodenal tissues were collected from aged (21.2 ± 1.3 years, 19.5 ± 3.1 kg, n = 39) female baboons (Papio sp.). Fasted blood was collected for metabolic profiling and abdominal circumference (AC) measurements were taken. Primary tissue samples were collected at the major duodenal papilla at necropsy: one full cross section was processed for hematoxylin and eosin staining and evaluated; a second full cross section was processed for direct chemical lipid analysis on which percentage duodenal fat content was calculated.

RESULTS

Duodenal fat content obtained by direct tissue quantification showed considerable variability (11.95 ± 6.93%) and was correlated with AC (r = 0.60, p < 0.001), weight (r = 0.38, p = 0.02), leptin (r = 0.63, p < 0.001), adiponectin (r = - 0.32, p < 0.05), and triglyceride (r = 0.41, p = 0.01). The relationship between duodenal fat content and leptin remained after adjusting for body weight and abdominal circumference. Intramural adipocytes were found in duodenal sections from all animals and were localized to the submucosa. Consistent with the variation in tissue fat content, the submucosal adipocytes were non-uniformly distributed in clusters of varying size. Duodenal adipocytes were larger in obese vs. lean animals (106.9 vs. 66.7 µm², p = 0.02).

CONCLUSIONS

Fat accumulation inside the duodenal wall is strongly associated with adiposity and adiposity related circulating biomarkers in baboons. Duodenal tissue fat represents a novel and potentially metabolically active site of ectopic fat deposition.

Genetic variation in TCF7L2 rs7903146 and history of GDM negatively and independently impact on diabetes-associated metabolic traits

AIMS

Gestational diabetes (GDM) is recognized as a major risk factor for the development of type 2 diabetes (T2DM) later in life. Risk allele carriers at TCF7L2 rs7903146 have increased susceptibility for both GDM and T2DM. We hypothesized that carrying TCF7L2 risk alleles would further aggravate the negative impact of a positive history for GDM on metabolic traits related to T2DM later in life.

METHODS

210 women with a confirmed history of gestational diabetes and 810 controls without evidence for GDM underwent standardized 75 g oral glucose tolerance tests (OGTT). Liver fat was quantified in a subset of subjects (n = 444) using magnetic resonance spectroscopy.

RESULTS

504 women were homozygous or heterozygous risk allele carriers. The risk allele carriers had a higher risk for GDM (p = 0.0076, OR 1.52, 95% CI 1.11-2.06). Multivariable regression analysis demonstrated that both a history of GDM, or carrying a TCF7L2 risk allele resulted in lower insulin secretion, impaired proinsulin processing and higher fasting and 2-hour glucose levels. Liver fat content was not associated with either a history of GDM or a TCF7L2 risk genotype. There was no significant interaction (all p > 0.05) between history of GDM and TCF7L2 risk alleles on all diabetes-associated metabolic traits tested.

CONCLUSION

The TCF7L2 rs7903146 polymorphism is a risk factor for gestational diabetes. However, the additional presence of TCF7L2 rs7903146 risk alleles does not further aggravate the negative impact of a history of gestational diabetes on metabolic traits related to T2DM.

Mapping novel genetic loci associated with female liver weight variations using Collaborative Cross mice

BACKGROUND

Liver weight is a complex trait, controlled by polygenic factors and differs within populations. Dissecting the genetic architecture underlying these variations will facilitate the search for key role candidate genes involved directly in the hepatomegaly process and indirectly involved in related diseases etiology.

METHODS

Liver weight of 506 mice generated from 39 different Collaborative Cross (CC) lines with both sexes at age 20 weeks old was determined using an electronic balance. Genomic DNA of the CC lines was genotyped with high-density single nucleotide polymorphic markers.

RESULTS

Statistical analysis revealed a significant (P < 0.05) variation of liver weight between the CC lines, with broad sense heritability (H 2) of 0.32 and genetic coefficient of variation (CVG) of 0.28. Subsequently, quantitative trait locus (QTL) mapping was performed, and results showed a significant QTL only for females on chromosome 8 at genomic interval 88.61-93.38 Mb (4.77 Mb). Three suggestive QTL were mapped at chromosomes 4, 12 and 13. The four QTL were designated as LWL1-LWL4 referring to liver weight loci 1-4 on chromosomes 8, 4, 12 and 13, respectively.

CONCLUSION

To our knowledge, this report presents, for the first time, the utilization of the CC for mapping QTL associated with baseline liver weight in mice. Our findings demonstrate that liver weight is a complex trait controlled by multiple genetic factors that differ significantly between sexes.

Prevention and Treatment of Type 2 Diabetes: A Pathophysiological-Based Approach

Prediabetes affects approximately 40% of American adults. Randomized trials report that a proportion of individuals with prediabetes develop diabetes despite caloric restriction, physical activity, and/or when treated with metformin, the first-line medication for patients with type 2 diabetes mellitus (T2DM). Currently, there are no valid predictors of the effectiveness of these measures in determining who will and who will not progress to the T2DM state. Few studies have examined the clinical and phenotypic predictors of better and worse glycemic response to lifestyle interventions and metformin in prediabetes and diabetes. Further studies incorporating 'omic' approaches to discover novel markers of phenotypes and treatment effectiveness may pave the way to personalizing the treatment of prediabetes and diabetes.

An insulin resistance associated neural correlate of impulsivity in type 2 diabetes mellitus

Central insulin resistance (IR) influences striatal dopamine (DA) tone, an important determinant of behavioral self-regulation. We hypothesized that an association exists between the degree of peripheral IR and impulse control, mediated by the impact of IR on brain circuits controlling the speed of executing “go” and/or “stop” responses. We measured brain activation and associated performance on a stop signal task (SST) in obese adults with type 2 diabetes (age, 48.1 ± 6.9 yrs (mean ± SD); BMI, 36.5 ± 4.0 kg/m²; HOMA-IR, 7.2 ± 4.1; 12 male, 18 female). Increasing IR, but not BMI, was a predictor of shorter critical stop signal delay (cSSD), a measure of the time window during which a go response can be successfully countermanded (R² = 0.12). This decline was explained by an IR-associated increase in go speed (R² = 0.13) with little impact of IR or BMI on stop speed. Greater striatal fMRI activation contrast in stop error (SE) compared with stop success (SS) trials (CON_SE>SS) was a significant predictor of faster go speeds (R² = 0.33, p = 0.002), and was itself predicted by greater IR (CON_SE>SS vs HOMA-IR: R² = 0.10, p = 0.04). Furthermore, this impact of IR on striatal activation was a significant mediator of the faster go speeds and greater impulsivity observed with greater IR. These findings suggest a neural mechanism by which IR may increase impulsivity and degrade behavioral self-regulation.

Non-alcoholic fatty liver disease and impaired proinsulin conversion as newly identified predictors of the long-term non-response to a lifestyle intervention for diabetes prevention: results from the TULIP study

AIMS/HYPOTHESIS

Lifestyle intervention is effective to prevent type 2 diabetes. However, a considerable long-term non-response occurs to a standard lifestyle intervention. We investigated which risk phenotypes at baseline and their changes during the lifestyle intervention predict long-term glycaemic non-response to the intervention.

METHODS

Of 300 participants at high risk for type 2 diabetes who participated in a 24 month lifestyle intervention with diet modification and increased physical activity, 190 participants could be re-examined after 8.7 ± 1.6 years. All individuals underwent a five-point 75 g OGTT and measurements of body fat compartments and liver fat content with MRI and spectroscopy at baseline, 9 and 24 months during the lifestyle intervention, and at long-term follow-up. Fasting proinsulin to insulin conversion (PI/I ratio) and insulin sensitivity and secretion were calculated from the OGTT. Non-response to lifestyle intervention was defined as no decrease in glycaemia, i.e. no decrease in AUC for glucose at 0-120 min during OGTT (AUCglucose_0-120 min).

RESULTS

Before the lifestyle intervention, 56% of participants had normal glucose regulation and 44% individuals had impaired fasting glucose and/or impaired glucose tolerance. At long-term follow-up, 11% had developed diabetes. Multivariable regression analysis with adjustment for age, sex, BMI and change in BMI during the lifestyle intervention revealed that baseline insulin secretion and insulin sensitivity, as well as change in insulin sensitivity during the lifestyle intervention, predicted long-term glycaemic control after 9 years. In addition, increased hepatic lipid content as well as impaired fasting proinsulin conversion at baseline were newly detected phenotypes that independently predicted long-term glycaemic control.

CONCLUSIONS/INTERPRETATION

Increased hepatic lipid content and impaired proinsulin conversion are new predictors, independent of change in body weight, for non-response to lifestyle intervention in addition to the confirmed factors, impaired insulin secretion and insulin sensitivity.

Plasma proteomics reveals coagulation, inflammation, and metabolic shifts in H-type hypertension patients with and without acute ischemic stroke

Systematic profiling of a larger portion of circulating plasma proteome provide opportunities for unbiased discovery of novel markers to improve diagnostic, therapeutic, or predictive accuracy. This study aimed to identify differentially expressed proteins (DEPs) in plasma that could provide overall insight into the molecular changes of both H- type hypertension (HH) and HH-related acute ischemic stroke (AIS). This study used an iTRAQ-based LC-MS/MS proteomics approach to screen for plasma DEPs in HH patients with and without AIS, and controls. After excluding highly abundant plasma proteins, more than 600 proteins, and their relative levels, were identified. Of these, 26 DEPs, each showing > 1.2-fold change, were identified in HH and HH-related AIS patients compared with controls. Bioinformatics analysis revealed that these DEPs were enriched in 21 functional gene ontology items; “blood coagulation” was the most predominant pathway showing enrichment. Of these, eight DEPs were located in the hub position of networks involved with protein-protein interactions. AT-3, CRP, ApoB, and AHSG were further validated in each group by enzyme-linked immune sorbent assays. Comparing HH-related AIS with HH, the areas under the curve for AT-3, CRP, ApoB, and AHSG were 0.698, 0.892, 0.626, and 0.847, respectively. This proteomic profiling study provided enhanced pathophysiological understanding of the regulatory processes involved in coagulation, inflammation, and metabolism, and identified a panel of novel biomarkers for detecting HH-related AIS during its pre-stroke stage.

Increased hepatic fatty acid polyunsaturation precedes ectopic lipid deposition in the liver in adaptation to high-fat diets in mice

OBJECTIVE

We monitored hepatic lipid content (HLC) and fatty acid (FA) composition in the context of enhanced lipid handling induced by a metabolic high-fat diet (HFD) challenge and fasting.

MATERIALS AND METHODS

Mice received a control diet (10% of kilocalories from fat, N = 14) or an HFD (45% or 60% of kilocalories from fat, N = 10 and N = 16, respectively) for 26 weeks. A subset of five mice receiving an HFD (60% of kilocalories from fat) were switched to the control diet for the final 7 weeks. At nine time points, magnetic resonance spectroscopy was performed in vivo at 14.1 T, interleaved with glucose tolerance tests.

RESULTS

Glucose intolerance promptly developed with the HFD, followed by a progressive increase of fasting insulin level, simultaneously with that of HLC. These metabolic defects were normalized by dietary reversal. HFD feeding immediately increased polyunsaturation of hepatic FA, before lipid accumulation. Fasting-induced changes in hepatic lipids (increased HLC and FA polyunsaturation, decreased FA monounsaturation) in control-diet-fed mice were not completely reproduced in HFD-fed mice, not even after dietary reversal.

CONCLUSION

A similar adaptation of hepatic lipids to both fasting and an HFD suggests common mechanisms of lipid trafficking from adipose tissue to the liver. Altered hepatic lipid handling with fasting indicates imperfect metabolic recovery from HFD exposure.

Dynamics of Glucose Metabolism After Kidney Transplantation

BACKGROUND/AIMS

Posttransplantation diabetes mellitus (PTDM) impacts patient and allograft survival after kidney transplantation. Prediabetes, which is an independent risk factor for PTDM, is modifiable also in a post-transplant setting. Understanding the risks and dynamics of impaired glucose metabolism after transplantation is a key component for targeted intervention.

METHODS

A retrospective chart analysis of all adult non-diabetic renal allograft recipients (n=251, 2007-2014) was performed. Longitudinal follow-up included fasting plasma glucose and HbA1c, as well as data on allograft function and immunosuppression at consecutive time points (months 3-6 to >5 years post transplantation).

RESULTS

Throughout follow-up, median prevalence of prediabetes and PTDM was 53.3 [52.4-55.7]% and 15.4 [15.0-16.5]%, respectively. Continuously high fluxes between states of glucose metabolism, with individual patients' state deteriorating or improving over time, resulted in a high number of incident patients even long after transplantation. The greatest number of patients shifted between normal glucose tolerance and prediabetes, followed by those between prediabetes and PTDM.

CONCLUSION

Prediabetes and PTDM are highly prevalent after kidney transplantation and incidences remain relevant throughout follow-up. Patient fluxes into and out of the prediabetic state show that glucose metabolism is highly dynamic after transplantation. This provides a continuous opportunity for intervention in an aim to reduce diabetes-associated complications.

Basal Glucose Can Be Controlled, but the Prandial Problem Persists-It's the Next Target!

Both basal and postprandial elevations contribute to the hyperglycemic exposure of diabetes, but current therapies are mainly effective in controlling the basal component. Inability to control postprandial hyperglycemia limits success in maintaining overall glycemic control beyond the first 5 to 10 years after diagnosis, and it is also related to the weight gain that is common during insulin therapy. The "prandial problem"-comprising abnormalities of glucose and other metabolites, weight gain, and risk of hypoglycemia-deserves more attention. Several approaches to prandial abnormalities have recently been studied, but the patient populations for which they are best suited and the best ways of using them remain incompletely defined. Encouragingly, several proof-of-concept studies suggest that short-acting glucagon-like peptide 1 agonists or the amylin agonist pramlintide can be very effective in controlling postprandial hyperglycemia in type 2 diabetes in specific settings. This article reviews these topics and proposes that a greater proportion of available resources be directed to basic and clinical research on the prandial problem.

4-Hydroxyalkenal-activated PPARδ mediates hormetic interactions in diabetes

Activated peroxisome proliferator-activated receptor-δ (PPARδ) induces the expression of genes encoding enzymes that metabolize fatty acids and carbohydrate. Attempts to identify cellular activators of PPARδ produced large lists of various fatty acids and their metabolic derivatives; however, there is no consensus on specific and selective binding interactions of natural ligands with PPARδ. Most models on binding interactions within the ligand binding domain (LBD) of PPARδ have been derived from analyses of PPARδ-LBD crystals formed with synthetic low molecular weight ligands. Nonetheless, crystals of the whole receptor with natural ligands or of its heterodimer with its cognate retinoid X receptor (RXR) are not yet available for analysis. We have found that 4-hydroxyalkenals, non-enzymatic peroxidation products of polyunsaturated fatty acids (PUFA), namely, 4-hydroxy-2E,6Z-dodecadienal (4-HDDE) and 4-hydroxy-2E-nonenal (4-HNE), activate PPARδ in vascular endothelial cells and insulin-secreting beta cells, respectively. In both cases activated PPARδ induced adaptive responses that allowed the cells to adjust to ambient stressful metabolic conditions. This review article addresses the interactions of 4-hydroxyalkenals with PPARδ and the resulting hormetic interactions in cells exposed to nutrient overload conditions.