Genetic basis of type 2 diabetes mellitus: implications for therapy

Epigenetic Changes Induced by High Glucose in Human Pancreatic Beta Cells

Epigenetic changes in pancreatic beta cells caused by sustained high blood glucose levels, as seen in prediabetic conditions, may contribute to the etiology of diabetes. To delineate a direct cause and effect relationship between high glucose and epigenetic changes, we cultured human pancreatic beta cells derived from induced pluripotent stem cells and treated them with either high or low glucose, for 14 days. We then used the Arraystar 4x180K HG19 RefSeq Promoter Array to perform whole-genome DNA methylation analysis. A total of 478 gene promoters, out of a total of 23,148 present on the array (2.06%), showed substantial differences in methylation (p < 0.01). Out of these, 285 were hypomethylated, and 193 were hypermethylated in experimental vs. control. Ingenuity Pathway Analysis revealed that the main pathways and networks that were differentially methylated include those involved in many systems, including those related to development, cellular growth, and proliferation. Genes implicated in the etiology of diabetes, including networks involving glucose metabolism, insulin secretion and regulation, and cell cycle regulation, were notably altered. Influence of upstream regulators such as MRTFA, AREG, and NOTCH3 was predicted based on the altered methylation of their downstream targets. The study validated that high glucose levels can directly cause many epigenetic changes in pancreatic beta cells, suggesting that this indeed may be a mechanism involved in the etiology of diabetes.

PET imaging detection of macrophages with a formyl peptide receptor antagonist

Macrophages are a major inflammatory cell type involved in the development and progression of many important chronic inflammatory diseases. We previously found that apolipoprotein E-deficient (Apoe(-/-)) mice with the C57BL/6 (B6) background develop type 2 diabetes mellitus (T2DM) and accelerated atherosclerosis when fed a Western diet and that there are increased macrophage infiltrations in pancreatic islets and aorta. The formyl peptide receptor 1 (FPR1) is abundantly expressed on the surface of macrophages. The purpose of this study was to evaluate the applicability of cinnamoyl-F-(D)L-F-(D)L-F (cFLFLF), a natural FPR1 antagonist, to detection of macrophages in the pancreatic islets and aorta. (64)Cu labeled cFLFLF and (18)F-fluorodeoxyglucose (FDG) were administered to mice with or without T2DM. Diabetic mice showed an increased (18)FDG uptake in the subcutaneous fat compared with control mice, but pancreatic uptake was minimal for either group. In contrast, diabetic mice exhibited visually noticeable more cFLFLF-(64)Cu retention in pancreas and liver than control mice. The heart and pancreas isolated from diabetic mice contained more macrophages and showed stronger PET signals than those of control mice. Flow cytometry analysis revealed the presence of macrophages but not neutrophils in pancreatic islets. Real-time PCR analysis revealed much higher FPR1 expression in pancreatic islets of diabetic over control mice. Autoradiography and immunohistochemical analysis confirmed abundant FPR1 expression in atherosclerotic lesions. Thus, (64)Cu-labeled cFLFLF peptide is a more effective PET agent for detecting macrophages compared to FDG.

VALIDATION OF THEIN VITROINCUBATION OF EXTENSOR DIGITORUM LONGUS MUSCLE FROM MICE WITH A MATHEMATICAL MODEL

In vitro incubation of tissues; in particular, skeletal muscles from rodents, is a widely-used experimental method in diabetes research. This experimental method has previously been validated, both experimentally and theoretically. However, much of the method's experimental data remains unclear, including the high-rate of lactate production and the lack of an observable increase in glycogen content, within a given time. The predominant hypothesis explaining the high-rate of lactate production is that this phenomenon is dependent on a mechanism in glycolysis that works as a safety valve, producing lactate when glucose uptake is super-physiological. Another hypothesis is that existing anoxia forces more ATP to be produced from glycolysis, leading to an increased lactate concentration. The lack of an observable increase in glycogen content is assumed to be dependent on limitations in sensitivity of the measuring method used. We derived a mathematical model to investigate which of these hypotheses is most likely to be correct. Using our model, data analysis indicates that the in vitro incubated muscle specimens, most likely are sensing the presence of existing anoxia, rather than an overflow in glycolysis. The anoxic milieu causes the high lactate production. The model also predicts an increased glycogenolysis. After mathematical analyses, an estimation of the glycogen concentration could be made with a reduced model. In conclusion, central anoxia is likely to cause spatial differences in glycogen concentrations throughout the entire muscle. Thus, data regarding total glycogen levels in the incubated muscle do not accurately represent the entire organ. The presented model allows for an estimation of total glycogen, despite spatial differences present in the muscle specimen.

Pharmacogenomics in type II diabetes mellitus management: Steps toward personalized medicine

Advances in genotype technology in the last decade have put the pharmacogenomics revolution at the forefront of future medicine in clinical practice. Discovery of novel gene variations in drug transporters, drug targets, effector proteins and metabolizing enzymes in the form of single-nucleotide polymorphisms (SNPs) continue to provide insight into the biological phenomena that govern drug efficacy and toxicity. To date, novel gene discoveries extracted from genome-wide association scans and candidate gene studies in at least four antidiabetic drug classes have helped illuminate possible causes of interindividual variability in response. Inadequate protocol guidelines for pharmacogenomics studies often leads to poorly designed studies, making it hard to formulate a definitive conclusion regarding the clinical relevance of the information at hand. These issues, along with the ethical, social, political, legislative, technological, and economic challenges associated with pharmacogenomics have only delayed its entry to mainstream clinical practice. On the other hand, these issues are being actively pursued and rapid progress is being made in each area which assures the possibility of gaining widespread acceptance in clinical practice.

The role of genealogy and clinical family histories in documenting possible inheritance patterns for diabetes mellitus in the pre-insulin era: part 1. The clinical case of Josephine Imperato

Establishing the role of heredity in type 2 diabetes mellitus (type 2 DM) is challenging. While type 2 DM frequently displays a pattern of familial aggregation, many other risk factors are responsible for the clinical expression of the disease. This paper reviews a number of the early twentieth-century studies of inheritance patterns for type 2 DM and presents in detail the history of Josephine Foniciello Imperato (Maria Giuseppa Foniciello) who died from the disease in New York City at the age of 52 years on 14 November 1921, ten months before commercial insulin became available.

Personalizing nutrigenomics research through community based participatory research and omics technologies

Personal and public health information are often obtained from studies of large population groups. Risk factors for nutrients, toxins, genetic variation, and more recently, nutrient-gene interactions are statistical estimates of the percentage reduction in disease in the population if the risk were to be avoided or the gene variant were not present. Because individuals differ in genetic makeup, lifestyle, and dietary patterns than those individuals in the study population, these risk factors are valuable guidelines, but may not apply to individuals. Intervention studies are likewise limited by small sample sizes, short time frames to assess physiological changes, and variable experimental designs that often preclude comparative or consensus analyses. A fundamental challenge for nutrigenomics will be to develop a means to sort individuals into metabolic groups, and eventually, develop risk factors for individuals. To reach the goal of personalizing medicine and nutrition, new experimental strategies are needed for human study designs. A promising approach for more complete analyses of the interaction of genetic makeups and environment relies on community-based participatory research (CBPR) methodologies. CBPR's central focus is developing a partnership among researchers and individuals in a community that allows for more in depth lifestyle analyses but also translational research that simultaneously helps improve the health of individuals and communities. The USDA-ARS Delta Nutrition Intervention Research program exemplifies CBPR providing a foundation for expanded personalized nutrition and medicine research for communities and individuals.

Do Different Vascular Risk Factors Affect All Arteries Equally?

Established vascular risk factors (ie, smoking, hypertension, diabetes mellitus, and dyslipidemia) play an important role in the development of vascular disease. Emerging evidence suggests that some of these risk factors may have a more intense effect on specific arterial beds, a finding that holds implications for a prognostic role for certain types of vascular disease.

Prevalence of common disease-associated variants in Asian Indians

Background

Asian Indians display a high prevalence of diseases linked to changes in diet and environment that have arisen as their lifestyle has become more westernized. Using 1200 genome-wide polymorphisms in 432 individuals from 15 Indian language groups, we have recently shown that: (i) Indians constitute a distinct population-genetic cluster, and (ii) despite the geographic and linguistic diversity of the groups they exhibit a relatively low level of genetic heterogeneity.

Results

We investigated the prevalence of common polymorphisms that have been associated with diseases, such as atherosclerosis (ALOX5), hypertension (CYP3A5, AGT, GNB3), diabetes (CAPN10, TCF7L2, PTPN22), prostate cancer (DG8S737, rs1447295), Hirschsprung disease (RET), and age-related macular degeneration (CFH, LOC387715). In addition, we examined polymorphisms associated with skin pigmentation (SLC24A5) and with the ability to taste phenylthiocarbamide (TAS2R38). All polymorphisms were studied in a cohort of 576 India-born Asian Indians sampled in the United States. This sample consisted of individuals whose mother tongue is one of 14 of the 22 "official" languages recognized in India as well as individuals whose mother tongue is Parsi, a cultural group that has resided in India for over 1000 years. Analysis of the data revealed that allele frequency differences between the different Indian language groups were small, and interestingly the variant alleles of ALOX5 g.8322G>A and g.50778G>A, and PTPN22 g.36677C>T were present only in a subset of the Indian language groups. Furthermore, a latitudinal cline was identified both for the allele frequencies of the SNPs associated with hypertension (CYP3A5, AGT, GNB3), as well as for those associated with the ability to taste phenylthiocarbamide (TAS2R38).

Conclusion

Although caution is warranted due to the fact that this US-sampled Indian cohort may not represent a random sample from India, our results will hopefully assist in the design of future studies that investigate the genetic causes of these diseases in India. Our results also support the inclusion of the Indian population in disease-related genetic studies, as it exhibits unique genotype as well as phenotype characteristics that may yield new insights into the underlying causes of common diseases that are not available in other populations.

Complexity of type 2 diabetes mellitus data sets emerging from nutrigenomic research: a case for dimensionality reduction?

Nutrigenomics promises personalized nutrition and an improvement in preventing, delaying, and reducing the symptoms of chronic diseases such as diabetes. Nutritional genomics is the study of how foods affect the expression of genetic information in an individual and how an individual's genetic makeup affects the metabolism and response to nutrients and other bioactive components in food. The path to those promises has significant challenges, from experimental designs that include analysis of genetic heterogeneity to the complexities of food and environmental factors. One of the more significant complications in developing the knowledge base and potential applications is how to analyze high-dimensional datasets of genetic, nutrient, metabolomic (clinical), and other variables influencing health and disease processes. Type 2 diabetes mellitus (T2DM) is used as an illustration of the challenges in studying complex phenotypes with nutrigenomics concepts and approaches.

Application of nutrigenomic concepts to Type 2 diabetes mellitus

The genetic makeup that individuals inherit from their ancestors is responsible for variation in responses to food and susceptibility to chronic diseases such as Type 2 diabetes mellitus (T2DM). Common variations in gene sequences, such as single nucleotide polymorphisms, produce differences in complex traits such as height or weight potential, food metabolism, food-gene interactions, and disease susceptibilities. Nutritional genomics, or nutrigenomics, is the study of how foods affect the expression of genetic information in an individual and how an individual's genetic makeup affects the metabolism and response to nutrients and other bioactive components in food. Since both diet and genes alter one's health and susceptibility to disease, identifying genes that are regulated by diet and that cause or contribute to chronic diseases could result in the development of diagnostic tools, individualized intervention, and eventually strategies for maintaining health. Translating this research through clinical studies promises contributions to the development of personalized medicine that includes nutritional as well as drug interventions. Reviewed here are the key nutrigenomic concepts that help explain aspects of the development and complexity of T2DM.

Association of selective HLA class II susceptibility-conferring and protective haplotypes with type 2 diabetes in patients from Bahrain and Lebanon

The association of HLA class II with type 2 diabetes (T2DM) was investigated in Bahraini and Lebanese subjects. DRB1*070101 (Lebanese and Bahraini) and DQB1*0201 (Lebanese) were susceptibility-conferring alleles, and unique susceptibility-conferring/protective haplotypes were found in both patient groups. Regression analysis confirmed that DRB1*070101-DQB1*0201 (Bahraini) and DRB1*110101-DQB1*0201 (Lebanese) were susceptibility-conferring haplotypes.

Genetic linkage of hyperglycemia, body weight and serum amyloid-P in an intercross between C57BL/6 and C3H apolipoprotein E-deficient mice

Dyslipidemia and hyperglycemia are integral components of the metabolic perturbations in type 2 diabetes. Apolipoprotein E-deficient (apoE(-/-)) mice develop severe hyperlipidemia and significant hyperglycemia when fed a western diet containing 21% fat (w/w), 0.15% cholesterol and 19.5% casein. Using an intercross between C57BL/6J (B6) and C3H/HeJ (C3H) apoE(-/-) mice, we performed quantitative trait locus (QTL) analysis to identify loci contributing to hyperglycemia and associated traits. Fasting plasma levels of glucose, insulin and serum amyloid-P (SAP) and body weight in 234 female F2 mice were measured after being fed the western diet for 12 weeks. QTL analysis revealed one significant QTL, named Bglu3 [95.8 cM, logarithm of odds ratio (OR)(LOD) 4.1], on chromosome 1 and a suggestive QTL on chromosome 9 (38 cM, LOD 2.3) that influenced plasma glucose levels. Bglu3 coincided with loci on distal chromosomal 1 that had a major influence on plasma SAP levels and body weight. Significant correlations between plasma glucose, SAP and body weight were observed in F2 mice. Thus, these results demonstrate genetic linkages of hyperglycemia and body weight with SAP, a marker of the acute-phase response, in hyperlipidemic apoE(-/-) mice and suggest a probability for the Sap gene to be a positional candidate of Bglu3.

Indol-1-yl acetic acids as peroxisome proliferator-activated receptor agonists: design, synthesis, structural biology, and molecular docking studies

A series of novel indole-based PPAR agonists is described leading to discovery of 10k, a highly potent PPAR pan-agonist. The structural biology and molecular docking studies revealed that the distances between the acidic group and the linker, when a ligand was complexed with PPARgamma protein, were important for the potent activity. The hydrophobic tail part of 10k makes intensive hydrophobic interaction with the PPARgamma protein resulting in potent activity.