Chromosome 7p linkage and association study for diabetes related traits and type 2 diabetes in an African-American population enriched for nephropathy

Stress and the CRH System, Norepinephrine, Depression, and Type 2 Diabetes

Major depressive disorder (MDD) increases the risk of type 2 diabetes (T2D) by 60% in untreated patients, and hypercortisolism is common in MDD as well as in some patients with T2D. Patients with MDD, despite hypercortisolism, show inappropriately normal levels of corticotropin-releasing hormone (CRH) and plasma adrenocorticotropin (ACTH) in the cerebrospinal fluid, which might implicate impaired negative feedback. Also, a positive feedback loop of the CRH-norepinephrine (NE)-CRH system may be involved in the hypercortisolism of MDD and T2D. Dysfunctional CRH receptor 1 (CRHR1) and CRH receptor 2 (CRHR2), both of which are involved in glucose regulation, may explain hypercortisolism in MDD and T2D, at least in a subgroup of patients. CRHR1 increases glucose-stimulated insulin secretion. Dysfunctional CRHR1 variants can cause hypercortisolism, leading to serotonin dysfunction and depression, which can contribute to hyperglycemia, insulin resistance, and increased visceral fat, all of which are characteristics of T2D. CRHR2 is implicated in glucose homeostasis through the regulation of insulin secretion and gastrointestinal functions, and it stimulates insulin sensitivity at the muscular level. A few studies show a correlation of the CRHR2 gene with depressive disorders. Based on our own research, we have found a linkage and association (i.e., linkage disequilibrium [LD]) of the genes CRHR1 and CRHR2 with MDD and T2D in families with T2D. The correlation of CRHR1 and CRHR2 with MDD appears stronger than that with T2D, and per our hypothesis, MDD may precede the onset of T2D. According to the findings of our analysis, CRHR1 and CRHR2 variants could modify the response to prolonged chronic stress and contribute to high levels of cortisol, increasing the risk of developing MDD, T2D, and the comorbidity MDD-T2D. We report here the potential links of the CRH system, NE, and their roles in MDD and T2D.

Comorbidity of Novel CRHR2 Gene Variants in Type 2 Diabetes and Depression

The corticotropin-releasing hormone receptor 2 (CRHR2) gene encodes CRHR2, contributing to the hypothalamic–pituitary–adrenal stress response and to hyperglycemia and insulin resistance. CRHR2−/− mice are hypersensitive to stress, and the CRHR2 locus has been linked to type 2 diabetes and depression. While CRHR2 variants confer risk for mood disorders, MDD, and type 2 diabetes, they have not been investigated in familial T2D and MDD. In 212 Italian families with type 2 diabetes and depression, we tested 17 CRHR2 single nucleotide polymorphisms (SNPs), using two-point parametric-linkage and linkage-disequilibrium (i.e., association) analysis (models: dominant-complete-penetrance-D1, dominant-incomplete-penetrance-D2, recessive-complete-penetrance-R1, recessive-incomplete-penetrance-R2). We detected novel linkage/linkage-disequilibrium/association to/with depression (3 SNPs/D1, 2 SNPs/D2, 3 SNPs/R1, 3 SNPs/R2) and type 2 diabetes (3 SNPs/D1, 2 SNPs/D2, 2 SNPs/R1, 1 SNP/R2). All detected risk variants are novel. Two depression-risk variants within one linkage-disequilibrium block replicate each other. Two independent novel SNPs were comorbid while the most significant conferred either depression- or type 2 diabetes-risk. Although the families were primarily ascertained for type 2 diabetes, depression-risk variants showed higher significance than type 2 diabetes-risk variants, implying CRHR2 has a stronger role in depression-risk than type 2 diabetes-risk. In silico analysis predicted variants’ dysfunction. CRHR2 is for the first time linked to/in linkage-disequilibrium/association with depression-type 2 diabetes comorbidity and may underlie the shared genetic pathogenesis via pleiotropy.

Genetic Signatures of Glucose Homeostasis: Synergistic Interplay With Long-Term Exposure to Cigarette Smoking in Development of Primary Colorectal Cancer Among African American Women

INTRODUCTION

Insulin resistance (IR)/glucose intolerance is a critical biologic mechanism for the development of colorectal cancer (CRC) in postmenopausal women. Whereas IR and excessive adiposity are more prevalent in African American (AA) women than in White women, AA women are underrepresented in genome-wide studies for systemic regulation of IR and the association with CRC risk.

METHODS

With 780 genome-wide IR single-nucleotide polymorphisms (SNPs) among 4,692 AA women, we tested for a causal inference between genetically elevated IR and CRC risk. Furthermore, by incorporating CRC-associated lifestyle factors, we established a prediction model on the basis of gene-environment interactions to generate risk profiles for CRC with the most influential genetic and lifestyle factors.

RESUTLS

In the pooled Mendelian randomization analysis, the genetically elevated IR was associated with 9 times increased risk of CRC, but with lack of analytic power. By addressing the variation of individual SNPs in CRC in the prediction model, we detected 4 fasting glucose-specific SNPs in GCK, PCSK1, and MTNR1B and 4 lifestyles, including smoking, aging, prolonged lifetime exposure to endogenous estrogen, and high fat intake, as the most predictive markers of CRC risk. Our joint test for those risk genotypes and lifestyles with smoking revealed the synergistically increased CRC risk, more substantially in women with longer-term exposure to cigarette smoking.

DISCUSSION

Our findings may improve CRC prediction ability among medically underrepresented AA women and highlight genetically informed preventive interventions (e.g., smoking cessation; CRC screening to longer-term smokers) for those women at high risk with risk genotypes and behavioral patterns.

Exome sequencing reveals novel rare variants in Iranian familial multiple sclerosis: The importance of POLD2 in the disease pathogenesis

The prevalence of familial multiple sclerosis (FMS) is increasing worldwide which endorses the heritability of the disease. Given that many genome variations are ethnicity-specific and consanguineous marriage could affect genetic diseases, hereditary disease gene analysis among FMS patients from Iran, a country with high rates of parental consanguinity, could be highly effective in finding mutations underlying disease pathogenesis. To examine rare genetic mutations, we selected three Iranian FMS cases with ≥3 MS patients in more than one generation and performed whole exome sequencing. We identified a homozygous rare missense variant in POLD2 (p. Arg141Cys; rs372336011). Molecular dynamics analysis showed reduced polar dehydration energy and conformational changes in POLD2 mutant. Further, we found a heterozygote rare missense variant in NBFP1 (p. Gly487Asp; rs778806175). Our study revealed the possible role of novel rare variants in FMS. Molecular dynamic simulation provided the initial evidence of the structural changes behind POLD2 mutant.

The impact of PNPLA3 and JAZF1 on hepatocellular carcinoma in non-viral hepatitis patients with type 2 diabetes mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is an established independent risk factor for hepatocellular carcinoma (HCC). T2DM is associated with non-alcoholic steatohepatitis (NASH), which is a major cause of non-HBV and non-HCV-related HCC; nevertheless, it has been difficult to identify those patients with T2DM who have a high risk of developing HCC. The aim of this study was to identify genetic determinants that predispose T2DM patients to HCC by genotyping T2DM susceptibility loci and PNPLA3.

METHODS

We recruited 389 patients with T2DM who satisfied the following three criteria: negative for HBs-Ag and anti-HCV Ab, alcohol intake <60 g/day, and history of T2DM >10 years. These patients were divided into two groups: T2DM patients with HCC (DM-HCC, n = 59) or those without HCC (DM-non-HCC, n = 330). We genotyped 51 single-nucleotide polymorphisms (SNPs) previously reported as T2DM or NASH susceptibility loci (PNPLA3) compared between the DM-HCC and DM-non-HCC groups with regard to allele frequencies at each SNP.

RESULTS

The SNP rs738409 located in PNPLA3 was the greatest risk factor associated with HCC. The frequency of the PNPLA3 G allele was significantly higher among DM-HCC individuals than DM-non-HCC individuals (OR 2.53, p = 1.05 × 10(-5)). Among individuals homozygous for the PNPLA3 G allele (n = 115), the frequency of the JAZF1 rs864745 G allele was significantly higher among DM-HCC individuals than DM-non-HCC individuals (OR 3.44, p = 0.0002).

CONCLUSIONS

PNPLA3 and JAZF1 were associated with non-HBV and non-HCV-related HCC development among Japanese patients with T2DM.

Renal Disease Risk Factors Among Risk Groups Comprised of African American Women With Type 2 Diabetes: A Secondary Analysis

PURPOSE

The purpose of this study was to explore and describe the prevalence of renal disease risk factors and the categorization of renal disease risk groups among African American women with type 2 diabetes mellitus (T2DM) who participated in a self-management and coping skills training intervention. We also explored and described the change in renal disease risk factors within and between risk groups, determining if participation in a culturally relevant coping skills training intervention decreased renal disease risk.

METHODS

This study was a secondary analysis of data from a longitudinal intervention study and included all 109 African American women with T2DM from the primary intervention study. This study examined the prevalence of 4 renal disease risk factors among the women at baseline via descriptive statistics, used cluster analysis to divide the women into risk groups and categorize the risk groups, and also measured the change in risk factors over time among risk groups via mixed modeling.

RESULTS

A majority of the women had a hemoglobin A1C ≥7% (62.39%) and were obese (75.93%). The high-risk cluster displayed clinically significant declines in mean systolic blood pressure, triglycerides, and A1C in both the control and intervention groups, and the intervention was more effective in reducing triglycerides and A1C levels among high-risk participants than low-risk. Overall, the control, high-risk group exhibited the largest declines in systolic blood pressure, triglycerides, and A1C.

CONCLUSIONS

This study displays the importance of acknowledging African American women with type 2 diabetes mellitus (T2DM) at high risk for renal disease in health care settings, which is often overlooked, and realizing that renal disease risk reduction is obtainable.

Interleukin-6 genotypes and serum levels in Chinese Hui population

Interleukin-6 (IL-6) is a key pro-inflammatory cytokine involved in different physiologic and pathophysiologic processes, and circulating levels of IL-6 differ greatly between individuals. The Chinese Hui is one of the largest ethnic minorities, little is known about the distribution of IL-6 genetic variations and their effects on serum levels in Hui population. The aim of the present study is to determine the prevalence of -174G/C (rs1800795), -597G/A (rs1800797), and -634C/G (rs1800796) polymorphisms in the IL-6 gene promoter region and their association with IL-6 serum levels in the Ningxia Hui population. A total of 96 Hui subjects, (57 men and 39 women; mean age 49.65 ± 19.73 years) unrelated nationality residents in Ningxia Hui Autonomous Region were enrolled. Genotyping of the three polymorphisms were performed by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) combined with gel electrophoresis and then confirmed by direct sequencing. The -174G/C (97.92% GG, 2.08% GC, and 0% CC) and -597G/A (98.96% GG, 1.04% GA, and 0% AA) polymorphisms were rare. The frequencies of -634C/G genotypes CC, CG, and GG were found to be 54.17%, 40.62%, and 5.21%, respectively in total studied subjects, the derived allele frequencies for the C and G alleles were 74.48% and 25.52%. Increased IL-6 levels were correlated with the IL-6 -634G allele carriers (CG+GG genotypes). The results suggest that IL-6 -174G/C and -597G/A are rare but -634C/G is common in the Ningxia Hui population, and the -634G allele is associated with circulating levels of IL-6.

Hypothesis of the neuroendocrine cortisol pathway gene role in the comorbidity of depression, type 2 diabetes, and metabolic syndrome

Depression, type 2 diabetes (T2D), and metabolic syndrome (MetS) are often comorbid. Depression per se increases the risk for T2D by 60%. This risk is not accounted for by the use of antidepressant therapy. Stress causes hyperactivation of the hypothalamic–pituitary–adrenal (HPA) axis, by triggering the hypothalamic corticotropin-releasing hormone (CRH) secretion, which stimulates the anterior pituitary to release the adrenocorticotropin hormone (ACTH), which causes the adrenal secretion of cortisol. Depression is associated with an increased level of cortisol, and CRH and ACTH at inappropriately “normal” levels, that is too high compared to their expected lower levels due to cortisol negative feedback. T2D and MetS are also associated with hypercortisolism. High levels of cortisol can impair mood as well as cause hyperglycemia and insulin resistance and other traits typical of T2D and MetS. We hypothesize that HPA axis hyperactivation may be due to variants in the genes of the CRH receptors (CRHR1, CRHR2), corticotropin receptors (or melanocortin receptors, MC1R-MC5R), glucocorticoid receptor (NR3C1), mineralocorticoid receptor (NR3C2), and of the FK506 binding protein 51 (FKBP5), and that these variants may be partially responsible for the clinical association of depression, T2D and MetS. In this review, we will focus on the correlation of stress, HPA axis hyperactivation, and the possible genetic role of the CRHR1, CRHR2, MCR1–5, NR3C1, and NR3C2 receptors and FKBP5 in the susceptibility to the comorbidity of depression, T2D, and MetS. New studies are needed to confirm the hypothesized role of these genes in the clinical association of depression, T2D, and MetS.

The G to A polymorphism at -597 of the interleukin-6 gene is extremely rare in southern Han Chinese

Interleukin-6 (IL-6) is a cytokine involved in different physiologic and pathophysiologic processes including essential hypertension (EH). Associations of the IL-6 promoter region polymorphisms with circulating level of IL-6 have been reported in various studies. We detected the IL-6-597G/A polymorphism in 246 EH patients and 194 healthy controls from Jiangsu area (south of China). Individuals all carried the GG wild genotype, no GA or AA genotypes were found. Our results suggest that IL-6-597G/A polymorphism is extremely rare and unlikely to be contributing significantly to disease susceptibility in southern Han Chinese.

Genetic contribution and associated pathophysiology in end-stage renal disease

End-stage renal disease (ESRD) or chronic kidney disease (CKD) is the terminal state of the kidney when its function has been permanently and irreversibly damaged. A wide variety of etiologies and pathological processes culminate in ESRD, and both environmental and genetic factors contribute to its development and progression. Various reports suggest that susceptibility to develop ESRD has a significant genetic component. These studies include familial aggregation studies, comparisons of incidence rates between different racial or ethnic populations, and segregation analysis. Genetic approaches have been used to identify genes that contribute to genetic susceptibility. Many studies have now been carried out assessing the contribution of specific “candidate genes”, which correlate with different functions that are involved in the renal pathogenesis. Independent studies for specific associated genes have frequently provided contradictory results. This may be due, in part, to the modest contribution to genetic susceptibility which these genes impart. With the availability of different genomewide association studies, chromosomal regions harboring novel, previously unrecognized, genes that may contribute to renal diseases have been recently reported. We have focused on different genetic studies conducted on ESRD and have discussed the strength and weaknesses of these studies. The nonmuscle myosin heavy chain 9 gene (MYH9) and renin–angiotensin system (RAS) have been discussed in detail.