👤 Pavel Hamet

Whether apolipoproteins (apolipoprotein A1, apolipoprotein B, apolipoprotein B/apolipoprotein A1 [ApoB/ApoA1] ratio) or very-low-density lipoprotein (VLDL) cholesterol are better risk predictors than established lipid risk markers, and whether there are sex differences, is uncertain, both in general populations and in patients with diabetes. The aim of this study was to assess the association between established risk markers, apolipoproteins and the risk of macro- and microvascular disease and death in a large study of women and men with diabetes and to assess the potential sex differences in the associations. Established lipid risk markers were studied in 11 140 individuals with type 2 diabetes from the Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified-Release Controlled Evaluation (ADVANCE) trial, and apolipoproteins (A1, B, ApoB/ApoA1 ratio) and VLDL cholesterol from nuclear magnetic resonance (NMR) lipid analyses in biobanked samples from 3586 individuals included in the ADVANCE case-cohort study (ADVANCE CC). Primary outcomes were major macro- and microvascular events and death. Cox proportional hazards models adjusted for confounders were used to quantify the associations (hazard ratio [HR] and 95% confidence intervals [CIs]) between established lipid risk markers and apolipoproteins with study outcomes. To address potential effect modification by sex, we investigated the association between the lipid risk markers and outcomes in subgroup analyses by sex. There was a lower risk of macrovascular complications for high-density lipoprotein (HDL) cholesterol (HR [95%CI] 0.88 [0.82-0.95]), a higher risk for total cholesterol (1.10 [1.04-1.17]), low-density lipoprotein (LDL) cholesterol (1.15 [1.08-1.22]), non-HDL cholesterol (1.13 [1.07-1.20]) and the total cholesterol/HDL ratio (1.20 [1.14-1.27]) but no significant associations with triglycerides from ADVANCE. There was a higher risk of macrovascular complications for the ApoB/ApoA1 ratio (1.13 [1.03-1.24]) from the ADVANCE CC. Only the ApoB/ApoA1 ratio (1.19 [1.06-1.34]), but none of the established lipid risk markers, was associated with a higher risk of microvascular complications. There were no statistically significant sex differences for any of the established lipid risk markers or apolipoproteins with any outcome. Using C-statistics and net reclassification improvement (NRI) did not detect significant improvement in predicting all outcomes by adding lipids or apolipoproteins to the models with confounding factors only. All established lipid risk markers, except triglycerides, were predictors of macrovascular complications, but not microvascular complications, in patients with type 2 diabetes. The ApoB/ApoA1 ratio was associated with major macro- and microvascular complications, but there was no evidence that apolipoproteins are better than established lipid risk markers in predicting cardiovascular complications in patients with type 2 diabetes. Show less

Links between substance use habits, obesity, stress and the related cardiovascular outcomes can be, in part, because of loci with pleiotropic effects. To investigate this hypothesis, we performed genome-wide mapping in 119 multigenerational families from a population in the Saguenay-Lac-St-Jean region with a known founder effect using 58,000 single-nucleotide polymorphisms and 437 microsatellite markers to identify genetic components of the following factors: habitual alcohol, tobacco and coffee use; response to mental and physical stress; obesity-related traits; and heart rate (HR) and blood pressure (BP) measures. Habitual alcohol and/or tobacco users had attenuated HR responses to mental stress compared with non-users, whereas hypertensive individuals had stronger HR and systolic BP responses to mental stress and a higher obesity index than normotensives. Genetic mappings uncovered numerous shared genes among substance use, stress response, obesity and hemodynamic traits, including CAMK4, CNTN4, DLG2, FHIT, GRID2, ITPR2, NOVA1 and PRKCE, forming network of interacting proteins, sharing synaptic function and display higher and patterned expression profiles in brain-related tissues; moreover, pathway analysis of shared genes pointed to long-term potentiation. Subgroup genetic mappings uncovered additional shared synaptic genes, including CAMK4, CNTN5 and DNM3 (hypertension-specific); CNTN4, DNM3, FHIT and ITPR1 (sex-specific), having protein interactions with genes driven from general analysis. In summary, consistent with the observed phenotypic correlations, we found substantial overlap among genomic determinants of these traits in synapse, which supports the notion that the neural synapse may be a shared interface behind substance use, stress, obesity, HR, BP as well as the observed sex- and hypertension-specific genetic differences. Show less

The mechanisms responsible for the ectopic adrenal expression of glucose-dependent insulinotropic peptide (GIP) receptor (GIPR) in GIP-dependent Cushing's syndrome (CS) are unknown. Chronic adrenal stimulation by ACTH in Cushing's disease or GIP in GIP-dependent ACTH-independent macronodular adrenal hyperplasia both lead to the induction of genes implicated in adrenal proliferation and steroidogenesis. The objective of the study was to identify genes differentially expressed specifically in GIP-dependent CS that could be implicated in the ectopic expression of GIPR. We used the Affymetrix U133 plus 2.0 microarray oligochips to compare the whole genome expression profile of adrenal tissues from five cases of GIP-dependent bilateral ACTH-independent macronodular adrenal hyperplasia with CS, one case of GIP-dependent unilateral adenoma with CS, five cases of ACTH-dependent hyperplasias, and a pool of adrenals from 62 normal individuals. After data normalization and statistical filtering, 723 genes with differential expression were identified, including 461 genes or sequences with a known functional implication, classified in eight dominant functional classes. Specific findings include repression of perilipin, the overexpression of 13 G protein-coupled receptors, and the potential involvement of Rho-GTPases. We also isolated 94 probe sets potentially linked to the formation of GIP-dependent nodules adjacent to the diffuse hyperplasia. These included probe sets related to the linker histone H1 and repression of RXRa and CCND2. The expression profiles for eight genes were confirmed by real-time RT-PCR. This study identified an extensive series of potentially novel target candidate genes that could be implicated in the molecular mechanisms of ectopic expression of the GIPR as well as in the multistep progression of GIP-dependent CS. Show less

The molecular mechanisms responsible for glucose-dependent insulinotrophic peptide receptor or gastric inhibitory polypeptide receptor (GIPR) ectopic expression and function in GIP-dependent Cushing's syndrome (CS) are still unknown. GIPR presumably acts, like the ACTH receptor (ACTHR), through the Gs protein/cyclic AMP/protein kinase A (PKA) pathway to stimulate steroidogenesis. We studied the expression of several genes involved in this pathway in the adrenal tissues of patients with GIP-dependent CS. RNA was extracted from adrenal tissues from nine patients with GIP-dependent CS [seven ACTH-independent bilateral macronodular adrenal hyperplasia (AIMAH), two adenomas], two control whole adult adrenals, two fasciculata cell-enriched preparations from normal adrenals, seven patients with Cushing's disease (CD) and two normal pancreas. Multiplex reverse transcriptase polymerase chain reaction (RT-PCR) evaluated the expression of GIPR, ACTHR, SF-1, Nur77, DAX-1, CYP11A, 3beta-HSD, CYP21, CREB and CREM genes. GIPR mRNA was overexpressed in all GIP-dependent cases. In normal adrenals and in the adrenal tissues from patients with CD, minimal amounts of GIPR mRNA were detected. ACTHR mRNA expression was observed in all GIP-dependent adrenal tissues. The expression of steroidogenic enzymes and some specific and ubiquitous transcription factors (TFs) involved in the ACTHR cascade was significantly reduced. Our results indicate that the expression of ACTHR and other genes located downstream in the ACTHR cascade, including steroidogenic enzymes genes and some transcription factors, are relatively suppressed in GIP-dependent CS. Although the expression of aberrant receptors plays an important role in steroidogenesis and initiation of cell proliferation, additional genetic events might occur, altering the activity of the ACTHR pathway. Show less

The best characterized effect of glucose-dependent insulinotropic polypeptide (GIP) is its stimulatory effect on insulin secretion by pancreatic beta-cells. Recently, it was demonstrated that some cases of primary adrenal Cushing's syndrome were secondary to the ectopic expression of non-mutated GIP receptor (GIP-R) in bilateral adrenal hyperplasias or unilateral adrenal adenomas, resulting in food-dependent steroidogenesis. Using a human multiple-expression tissue array, GIP-R was found to be expressed in a large number of human adult and fetal tissues, but not in the adrenal gland. The analysis of the promoter region of human (h) GIP-R gene revealed six consensus sequences important in regulating the reporter gene activity and capable of binding to Sp1 and Sp3 transcription factors. Data obtained by gene array and semi-quantitative RT-PCR showed an increase in the expression of Sp3 and CRSP9 (co-regulator of Sp1 transcription factor, subunit 9) in the adrenal adenomas or bilateral macronodular hyperplasias of patients with GIP-dependent Cushing's syndrome; they were, however, also increased in some patients with non-GIP-dependent cortisol-secreting adenomas or with ACTH-dependent Cushing's disease. This study represents the first step in our understanding of the mechanisms involved in the regulation of the expression of the hGIP-R gene. Show less

Gastric inhibitory polypeptide (GIP)-dependent Cushing's syndrome (CS) results from the ectopic expression of non-mutated GIP receptor (hGIPR) in the adrenal cortex. We evaluated whether mutations or polymorphisms in the regulatory region of the GIPR gene could lead to this aberrant expression. We studied 9.0kb upstream and 1.3kb downstream of the GIPR gene putative promoter (pProm) by sequencing leukocyte DNA from controls and from adrenal tissues of GIP- and non-GIP-dependent CS patients. The putative proximal promoter region (800 bp) and the first exon and intron of the hGIPR gene were sequenced on adrenal DNA from nine GIP-dependent CS, as well as on leukocyte DNA of nine normal controls. Three variations found in this region were found in all patients and controls; at position -4/-5, an insertion of a T was seen in four out of nine patients and in five out of nine controls. Transient transfection studies conducted in rat GC and mouse Y1 cells showed that the TT allele confers loss of 40% in the promoter activity. The analysis of the 8-kb distal pProm region revealed eight distal single nucleotide polymorphisms (SNPs) without probable association with the disease, since frequencies in patients and controls were very similar. In conclusion, mutations or SNPs in the regulatory region of the GIPR gene are unlikely to underlie GIP-dependent CS. Show less

Gastric inhibitory polypeptide (GIP)-dependent Cushing's syndrome has been reported to occur either in unilateral adrenal adenoma or in bilateral macronodular adrenal hyperplasia. A 33-yr-old woman with Cushing's syndrome was found to have two 2.5- to 3-cm nodules in the right adrenal on computed tomography scan; the left adrenal appeared normal except for the presence of a small 0.8 x 0.6-cm nodule. Uptake of iodocholesterol was limited to the right adrenal. Plasma morning cortisol was 279 nmol/L fasting and 991 nmol/L postprandially, and ACTH remained suppressed. Plasma cortisol increased after oral glucose (202%) or a lipid-rich meal (183%), but not after a protein-rich meal (95%) or iv glucose (93%); the response to oral glucose was blunted by pretreatment with 100 microg octreotide, sc. Plasma cortisol and GIP levels were positively correlated (r = 0.95; P = 0.0001); cortisol was stimulated by the administration of human GIP iv (225%), but not by GLP-1, insulin, TRH, GnRH, glucagon, arginine vasopressin, upright posture, or cisapride orally. A right adrenalectomy was performed; GIP receptor messenger ribonucleic acid was overexpressed in both adrenal nodules and in the adjacent cortex. Histopathology revealed diffuse macronodular adrenal hyperplasia without internodular atrophy. Three months after surgery, fasting plasma ACTH and cortisol were suppressed, but cortisol increased 3.6-fold after oral glucose, whereas ACTH remained suppressed; this was inhibited by octreotide pretreatment, suggesting that cortisol secretion by the left adrenal is also GIP dependent. We conclude that GIP-dependent nodular hyperplasia can progress in an asynchronous manner and that GIPR overexpression is an early event in this syndrome. Show less

Abnormal responsiveness of adrenocortical cells to gastric inhibitory polypeptide (GIP) in food-dependent Cushing's syndrome suggested that adrenal expression of ectopic, overexpressed, or mutated GIP receptor (GIPR) underlies this syndrome. The expression of GIPR was studied by RT-PCR in human adrenal tissues from two patients with GIP-dependent Cushing's syndrome (adenoma, bilateral hyperplasia), five fetal or adult controls, one patient with Cushing's disease, and four patients with non-food-dependent cortisol-secreting adenomas or bilateral hyperplasias and compared to that in normal pancreas. Hybridization of the RT-PCR-amplified ribonucleic acids with the human GIPR complementary DNA showed an overexpression of GIPR in the adrenals of the two GIP-dependent Cushing's syndrome patients compared to that in normal adrenal tissues (2-3 orders of magnitude) or pancreas (10-fold); no signal could be seen in adrenal adenomas or macronodular hyperplasia from cases of non-food-dependent Cushing's syndrome. No mutation of the GIPR was identified by sequencing the full-length receptor in GIP-dependent adrenal tissue. New alternative spliced isoforms of the GIPR were found, but are identical in GIP-dependent and normal adrenal tissues. Incubation of adrenal cells with GIP stimulates cortisol secretion in GIP-dependent, but not in normal fetal, adult, or non-food-dependent Cushing's syndrome, adrenals. We conclude that the GIPR overexpression and its coupling to steroidogenesis underlie GIP-dependent Cushing's syndrome. Show less