ARMC5 mutations in macronodular adrenal hyperplasia with Cushing's syndrome

BACKGROUND

Corticotropin-independent macronodular adrenal hyperplasia may be an incidental finding or it may be identified during evaluation for Cushing's syndrome. Reports of familial cases and the involvement of both adrenal glands suggest a genetic origin of this condition.

METHODS

We genotyped blood and tumor DNA obtained from 33 patients with corticotropin-independent macronodular adrenal hyperplasia (12 men and 21 women who were 30 to 73 years of age), using single-nucleotide polymorphism arrays, microsatellite markers, and whole-genome and Sanger sequencing. The effects of armadillo repeat containing 5 (ARMC5) inactivation and overexpression were tested in cell-culture models.

RESULTS

The most frequent somatic chromosome alteration was loss of heterozygosity at 16p (in 8 of 33 patients for whom data were available [24%]). The most frequent mutation identified by means of whole-genome sequencing was in ARMC5, located at 16p11.2. ARMC5 mutations were detected in tumors obtained from 18 of 33 patients (55%). In all cases, both alleles of ARMC5 carried mutations: one germline and the other somatic. In 4 patients with a germline ARMC5 mutation, different nodules from the affected adrenals harbored different secondary ARMC5 alterations. Transcriptome-based classification of corticotropin-independent macronodular adrenal hyperplasia indicated that ARMC5 mutations influenced gene expression, since all cases with mutations clustered together. ARMC5 inactivation decreased steroidogenesis in vitro, and its overexpression altered cell survival.

CONCLUSIONS

Some cases of corticotropin-independent macronodular adrenal hyperplasia appear to be genetic, most often with inactivating mutations of ARMC5, a putative tumor-suppressor gene. Genetic testing for this condition, which often has a long and insidious prediagnostic course, might result in earlier identification and better management. (Funded by Agence Nationale de la Recherche and others.).

Low HDL-cholesterol: a strong predictor of glycemic response to glitazone treatment in patients with type 2 diabetes

We performed a study in 102 people with type 2 diabetes aiming to determine "easy-to-use" predictive factors for glycemic response to glitazones. We found that low baseline HDL-cholesterol (<40 mg/L [1.04 mmol/L] in males, <50 mg/L [1.30 mmol/L] in females) was a strong independent predictor of glycemic response to glitazones (OR=2.67 [2.02-3.52], p=0.0004).

Specific phenotype associated with diabetes mellitus secondary to chronic hepatitis C infection

AIM

A link between chronic hepatitis C virus (HCV) infection, Type 2 diabetes mellitus and insulin resistance has been suggested by several studies. However, HCV infection appears to be associated with insulin resistance but not with the metabolic syndrome. The aim of this study was to determine whether chronic HCV infection had an impact on the clinical characteristics of Type 2 diabetes.

METHODS

We studied retrospectively a group of patients with diabetes mellitus associated with HCV infection (HCV-DM) and compared them with patients with conventional Type 2 diabetes (DM).

RESULTS

The HCV-DM patients had a lower body mass index (P = 0.001) and systolic blood pressure (P = 0.04) compared with patients with DM diabetes. Ten patients (27.0%) in the HCV-DM group and 35 (47.3%) in the DM group had microalbuminuria (P = 0.04). DM patients had significantly higher serum creatinine levels than HCV-DM patients [87 (72-108) vs. 77 (64-86) micromol/l, P = 0.02; median (interquartile range)] but creatinine clearance (Cockroft Gault calculation) was similar. One HCV-DM patient (2.7%) and 44 DM patients (59.4%) were treated with hypolipidaemic therapy (P = 0.0001). Even although nearly two-thirds of the overall DM group were prescribed cholesterol-lowering drugs, DM patients had significantly higher total cholesterol, high-density lipoprotein cholesterol and triglyceride levels than HCV-DM patients.

CONCLUSION

Our study provides further evidence that HCV-DM patients have specific clinical characteristics in comparison with classical DM patients. These data suggest an association between HCV virus infection and the development of insulin resistance or diabetes mellitus without the typical features of the metabolic syndrome.

Cell surface expression of LDL receptor in chronic hepatitis C: correlation with viral load

The LDL receptor (LDL-R) has been proposed as the viral receptor for Hepatitis C virus (HCV). This hypothesis has been based exclusively on in vitro studies. In human mononuclear cells, LDL-R gene expression has been demonstrated to be parallel and be coordinately regulated to gene expression in the human liver. The purpose of the current study was to determine the mononuclear cell surface expression of the LDL receptor in patients with HCV chronic infection according to viral load. Sixty-eight consecutive untreated chronic hepatitis C patients were studied to determine the mononuclear cell surface expression of the LDL-R. LDL-Rs were quantified at the surface of mononuclear cells in fresh blood samples taken after fasting using flow cytometry. LDL-R expression was significantly associated with LDL-cholesterol (r = -0.25; P = 0.03) and HCV-viral load (r = 0.37, P = 0.002). In multivariate analysis, the LDL-R expression was significantly associated with HCV viral load, whereas genotype, age, body mass index, and fibrosis were not. In conclusion, our data provided by a human study, suggest that the LDL-R may be one of the receptors implicated in HCV replication.