Author Correction: Linkage and association of novel DRD2 variants to the comorbidity of type 2 diabetes and depression.

Correction to: Eur Rev Med Pharmacol Sci 2022; 26 (22): 8370-8375-DOI: 10.26355/eurrev_202211_30372-PMID: 36459020-published online on November 20, 2022. • In Amin, Wu, Postolache, and Gragnoli (2022), the originally published Figure 1 inadvertently included an error in the markers. The authors have submitted a corrected version, which is shown here. There are amendments to this paper. The Publisher apologizes for any inconvenience this may cause. https://www.europeanreview.org/article/30372.

Novel linkage and association of TCF7L2 variants with PCOS in Italian families.

OBJECTIVE: Transcription factor 7-like 2 (TCF7L2) gene variants confer risk for type 2 diabetes and metabolic traits. We investigated the role of TCF7L2-variants in polycystic ovarian syndrome (PCOS), which is a common endocrine metabolic disorder affecting women of reproductive age. We tested whether TCF7L2 variants are in linkage to and/or in linkage disequilibrium [(LD), namely linkage and association)] with PCOS. PATIENTS AND METHODS: Within 212 families from the Italian peninsular population, we analyzed 78 variants using Pseudomarker software for linkage to and LD with PCOS under the dominant model with complete penetrance (D1). In a secondary analysis, we tested the variants under the recessive models with complete penetrance (R1), dominant with incomplete penetrance (D2), and recessive with incomplete penetrance (R2). We tested through in silico analysis the risk variants to detect any potential functional effects. RESULTS: We identified a total of 14 variants in the TCF7L2 gene significantly linked to and/or in LD with the risk of PCOS (p < 0.05) across different models. CONCLUSIONS: This study is the first to report TCF7L2 linkage and linkage disequilibrium in Italian families with PCOS.

Melatonin receptor 1A (MTNR1A) gene linkage and association to type 2 diabetes in Italian families.

OBJECTIVE: Melatonin regulates the mammalian circadian rhythm and plays metabolic functions such as glucose homeostasis. Both melatonin receptors (MTNR1A and MTNR1B, encoded by the MTNR1A and MTNR1B genes, respectively) are expressed in pancreatic beta cells and mediate the glucometabolic roles of melatonin as well as insulin secretion. The MTNR1B gene is a well-known genetic risk factor in type 2 diabetes (T2D); however, little is known about the involvement of the MTNR1A gene in here T2D. We aimed to investigate whether MTNR1A is linked to and/or associated with familial T2D. SUBJECTS AND METHODS: We genotyped 14 single nucleotide polymorphisms within the MTNR1A gene in 212 peninsular Italian families with T2D. We performed parametric linkage and linkage disequilibrium analyses to investigate the role of MTNR1A variants in conferring T2D risk. We considered variants statistically significant if conferring linkage or linkage disequilibrium with p < 0.05. RESULTS: We found 3 novel variants (rs62350392, rs2119883, and rs13147179) significantly linked to and/or associated with T2D in multigenerational Italian families. CONCLUSIONS: This is the first study to report MTNR1A as a novel risk gene in T2D. Functional studies are needed to confirm these results.

Novel implication of the prolactin (PRL) gene in the comorbidity of type 2 diabetes and depression.

OBJECTIVE: The prolactin (PRL) system plays important behavioral, social, and metabolic roles, such as mediating social bonding and insulin secretion. Inherited dysfunction of the PRL pathway-related genes is associated with psychopathology and insulin resistance. We have previously suggested that the PRL system might be implicated in the comorbidity of psychiatric (depression) and type 2 diabetes (T2D) owing to the pleiotropy of PRL pathway-related genes. To our knowledge, no PRL variants have so far been reported in patients with either major depressive disorder (MDD) and/or T2D. PATIENTS AND METHODS: In this study, we analyzed 6 variants within the PRL gene and tested them for the presence of parametric linkage and/or linkage disequilibrium (LD, i.e., linkage and association) with familial MDD, T2D, and their comorbidity. RESULTS: We found, for the first time, that the PRL gene and its novel risk variants are linked to and in LD (i.e., linkage and association) with familial MDD, T2D, and MDD-T2D comorbidity. CONCLUSIONS: PRL might play a key role in mental-metabolic comorbidity and can be considered a novel gene in MDD and T2D.

Genome-wide linkage and association study identifies novel genes and pathways implicated in polycystic ovarian syndrome.

OBJECTIVE: Polycystic ovarian syndrome (PCOS) is a complex heterogeneous condition that affects women of reproductive age, conferring increased cardiovascular morbidity and mortality. The syndrome is characterized by oligomenorrhea, hyperandrogenism, and/or polycystic ovaries and is often associated with obesity and type 2 diabetes. Individuals are predisposed to PCOS by environmental factors and risk variants in genes mostly involved in ovarian steroidogenesis and/or insulin resistance. Genetic risk factors have been identified by both familial and genome-wide (GW) association studies. However, most genetic components are still unknown and missing heritability needs to be elucidated. To learn more about the genetic determinants of PCOS, we performed a GW study in genetically highly homogeneous peninsular families. PATIENTS AND METHODS: We conducted the first GW-linkage and linkage disequilibrium (i.e., linkage + association) study in Italian families with PCOS. RESULTS: We identified several novel risk variants, genes, and pathways potentially implicated in the pathogenesis of PCOS. Specifically, we detected 79 novel variants with significant GW-linkage and/or -association with PCOS across 4 inheritance models (p < 0.00005), of which 50 variants were within 45 novel PCOS-risk genes. CONCLUSIONS: This is the first GW-linkage and linkage disequilibrium study performed in peninsular Italian families and reporting novel genes in PCOS.

Oxytocin receptor (OXTR) is a risk gene for polycystic ovarian syndrome.

OBJECTIVE: Oxytocin (OXT) controls appetite, promotes diet-induced energy expenditure, and may protect against obesity. Furthermore, the oxytocin system controls ovarian follicle luteinization and steroidogenesis as well as adrenal steroidogenesis, which if impaired might lead to anovulation and hyperandrogenism, signs found in women with polycystic ovarian syndrome (PCOS). PCOS is a common complex endocrine disorder of reproductive-age women, and it often presents with impaired glucose metabolism, insulin resistance (IR), and type 2 diabetes (T2D). The oxytocin receptor gene (OXTR) may confer a risk for PCOS, conceivably through dysregulation of metabolism, ovarian follicle maturation, and ovarian and adrenal steroidogenesis. Therefore, we aimed to investigate whether OXTR variants confer risk for PCOS. SUBJECTS AND METHODS: In 212 Italian subjects with T2D and PCOS, we have analyzed 22 single nucleotide polymorphisms (SNPs) within the OXTR gene for linkage to and/or linkage disequilibrium (LD, i.e., association) with PCOS. We tested whether the significant risk variants were independent or part of an LD block. RESULTS: We found 5 independent variants significantly linked to/in LD with PCOS within the peninsular families. CONCLUSIONS: This is the first study to report OXTR as a novel risk gene in PCOS. Functional and replication studies are needed to confirm these results.

Novel TCF7L2 familial linkage and association with Type 2 diabetes, depression, and their comorbidity.

OBJECTIVE: Alterations in the activity of the transcription factor 7-like 2 (TCF7L2) generate defects previously associated with neuropsychiatric disorders. We investigated the role of the TCF7L2 gene in major depressive disorder (MDD), type 2 diabetes (T2D), and MDD-T2D comorbidity. We tested whether TCF7L2 is in linkage to and/or in linkage disequilibrium (LD, namely association) with MDD, T2D, and MDD-T2D. PATIENTS AND METHODS: In 212 families with T2D and MDD in the Italian population, we analyzed 80 microarray-based SNPs using Pseudomarker software for linkage to and LD with T2D and MDD under the recessive model with complete penetrance (R1). In a secondary analysis, we tested the variants under the dominant models with complete penetrance (D1), recessive with incomplete penetrance (R2), and recessive with incomplete penetrance (R2). RESULTS: We found several novel linkage signals and genetic associations. In addition, we found two new transcription-factor (TF) binding sites created by two risk variants found: the MDD-risk variant rs12255179 creates a new TF-binding site for the CCAAT/enhancer-binding protein α (C/EBPα), and the T2D-risk variant rs61872794 creates a new TF-binding site for the organic cation-uptake transporter (OCT1). Both new binding sites are related to insulin metabolism. CONCLUSIONS: These results highlight the cross-interactivity between T2D and MDD. Further replication is needed in diverse ethnic groups.

The mineralocorticoid receptor gene (NR3C2) is linked to and associated with polycystic ovarian syndrome in Italian families.

OBJECTIVE: Polycystic ovarian syndrome (PCOS) is a complex heterogeneous disorder characterized by hyperandrogenism, irregular menses, and subfertility and often accompanied by other related comorbid disorders such as insulin resistance, obesity, and type 2 diabetes. Several genetic risk factors predispose to PCOS, but most are still unknown. Up to 30% of women with PCOS may have hyperaldosteronism. Blood pressure and the ratio of blood levels of aldosterone to renin are higher in women with PCOS compared to healthy controls, even if still in the normal range; and the aldosterone antagonist spironolactone has been used as therapy for PCOS, mainly due to its antiandrogenic activity. Thus, we aimed to investigate the potential pathogenetic role of the mineralocorticoid receptor gene (NR3C2) as the encoded NR3C2 product binds aldosterone and plays a role in folliculogenesis, fat metabolism, and insulin resistance. SUBJECTS AND METHODS: Within 212 Italian families with T2D and phenotyped for PCOS, we analyzed 91 single nucleotide polymorphisms in the NR3C2 gene. We tested the NR3C2 variants for linkage and linkage disequilibrium to the PCOS phenotype by using parametric analysis. RESULTS: We found 18 novel risk variants significantly linked to and/or associated with the risk of PCOS. CONCLUSIONS: We are the first to report NR3C2 as a risk gene in PCOS. However, our findings need to be replicated in other ethnic groups in order to reach more solid conclusions.

Linkage and association of novel DRD2 variants to the comorbidity of type 2 diabetes and depression.

OBJECTIVE: The dopamine receptor 2 (DRD2) binds dopamine in both central tissues (e.g., basal ganglia, pituitary gland) and peripheral tissues (e.g., adrenal gland, kidneys, intestine) and mediates dopamine actions in cognition, emotional processing, and prolactin-secretion inhibition and stimulation, and in DRD2-/- knockout mice insulin secretion is impaired. Variants in or around the DRD2 gene have been implicated in major depressive disorder (MDD), schizophrenia, obesity, and type 2 diabetes (T2D) but not in comorbid MDD-T2D patients; DRD2 agonists (e.g., bromocriptine) are approved treatments in T2D. This study aimed to detect whether the DRD2 gene plays a role in T2D, MDD, and T2D-MDD comorbidity in Italian families. SUBJECTS AND METHODS: In 212 Italian families with T2D and MDD, we investigated the presence of linkage and linkage disequilibrium of variants in the DRD2 gene with T2D and/or MDD. A test was considered statistically significant if p was <0.05. RESULTS: We found 3 novel variants (rs6276, rs35608204, and rs1800499) significantly linked to and/or associated with the risk of T2D and 1 novel variant (rs112646785) significantly linked and associated to the comorbidity of T2D and MDD. CONCLUSIONS: This is the first study to link and associate DRD2 variants with the comorbidity of T2D and MDD.

PSMD9 is linked to T2D age of onset, years of isolated and combined insulin therapy, irregular menses, and hot flashes.

OBJECTIVE: PSMD9 is a ubiquitous protein present at high concentrations in eukaryotic cells. It contributes to the degradation of intracellular proteins in the immune system. It is part of the 26S proteasome complex, and its regulatory role on proteasomal activity as well as its effect on genetic transcription have been recognized. PSMD9 has been related with insulin secretion, and it regulates the ligand-dependent retinoid-target genes transcription. Importantly, PSMD9 rs74421874 (IVS3+nt460-G>A), rs3825172 (IVS3+nt437-C>T), and rs14259 SNPs have been previously linked to type 2 diabetes (T2D), maturity-onset diabetes of the young 3 (MODY3), overweight status and waist circumference, hypertension, hypercholesterolemia, cardiovascular disease, microvascular disease (retinopathy, neuropathy, and nephropathy), carpal tunnel syndrome, depression, anxiety, insomnia, and sleep hours. MATERIALS AND METHODS: In this study, we analyzed the above-mentioned PSMD9 rs74421874 (IVS3+nt460-G>A), rs3825172 (IVS3+nt437-C>T), and rs14259 SNPs for linkage to the T2D quantitative traits of T2D age of onset, duration in years of combined oral hypoglycemic agents and insulin therapy and only insulin therapy, stress, and the birth weight of the subjects' children; and with the T2D qualitative phenotypes of irregular menses, couple infertility, and menopausal hot flashes. RESULTS: We found that PSMD9 was linked to irregular menses of reproductive age, menopausal hot flashes, T2D age of onset, years of combined oral and insulin therapy and of insulin therapy; we also found that it shows only a tendency towards linkage to stress, birthweight, and couple infertility. CONCLUSIONS: This is the first time that this gene is implicated with irregular menses of reproductive age (a trait of polycystic ovarian syndrome), hot flashes, T2D onset age, and duration years of combined oral and insulin therapy and only insulin therapies.

Heavy metals as risk factors for human diseases - a Bayesian network approach.

Modern industrial agricultural processes expose human beings to multifactorial environmental pollution including heightened levels of heavy metals. The effects of acute heavy metal exposures at toxic levels are usually known; they are tested for and treated promptly. The effects of low/moderate-level chronic heavy metal exposures are less known as they may be subclinical, and pathogenic effects may only manifest clinically over time under the disguise of a diagnosable disease or miscellaneous symptoms attributed to aging. Consequently, the health impact of low-moderate heavy metal exposure is unlikely to be identified. Furthermore, established heavy metal safety levels often fail to recognize the potential toxic effects on humans. We report in this review what is known about the sub-chronic and chronic effects of exposure to heavy metals, particularly lead, mercury, cadmium, arsenic, and nickel, and we highlight their possible effects in the brain, cardiovascular and endocrine-metabolic systems, and on reproduction.

Dopamine-prolactin pathway potentially contributes to the schizophrenia and type 2 diabetes comorbidity.

Schizophrenia (SCZ) and type 2 diabetes (T2D) are clinically associated, and common knowledge attributes this association to side effects of antipsychotic treatment. However, even drug-naive patients with SCZ are at increased risk for T2D. Dopamine dysfunction has a central role in SCZ. It is well-known that dopamine constitutively inhibits prolactin (PRL) secretion via the dopamine receptor 2 (DR2D). If dopamine is increased or if dopamine receptors hyperfunction, PRL may be reduced. During the first SCZ episode, low PRL levels are associated with worse symptoms. PRL is essential in human and social bonding, as well as it is implicated in glucose homeostasis. Dopamine dysfunction, beyond contributing to SCZ symptoms, may lead to altered appetite and T2D. To our knowledge, there are no studies of the genetics of the SCZ-T2D comorbidity focusing jointly on the dopamine and PRL pathway in the attempt to capture molecular heterogeneity correlated to possible disease manifestation heterogeneity. In this dopamine-PRL pathway-focused-hypothesis-driven review on the association of SCZ with T2D, we report a specific revision of what it is known about PRL and dopamine in relation to what we theorize is one of the missing links between the two disorders. We suggest that new studies are necessary to establish the genetic role of PRL and dopamine pathway in SCZ-T2D comorbidity.

Proteasome modulator 9 and depression in type 2 diabetes.

BACKGROUND: The chromosome 12q24 locus is linked to bipolar disorder, depression, and type 2 diabetes (T2D). PSMD9 lies in the 12q24 locus and is linked to MODY3, T2D, T2D-nephropathy, T2D-neuropathy, retinopathy, macrovascular pathology, hypertension, and hypercholesterolemia in Italian families. Interestingly, PSMD9 gene common variants contribute to the therapeutic response to anti-depressant treatment. Further, PSMD9 is implicated in a model of prediction to susceptibility to depression. AIMS: Our goal was to determine whether PSMD9 is linked to depression in 200 T2D Italian families. METHODS: We characterized the Italian families' members for presence and/or absence of depression using the diagnostic criteria of DSM-IV. The phenotype was described as unknown in all cases in which the diagnosis was unclear or data were not available. We tested in the 200 Italians families for evidence of linkage of the PSMD9 single nucleotide polymorphisms (SNPs) IVS3+nt460 A > G, IVS3+nt437 T > C and E197G A > G with the depression phenotype. The non-parametric linkage analysis was performed by using the Merlin software. To rule out results due to random chance, 1000 replicates were executed. RESULTS: The PSMD9 gene SNPs studied and/or any gene variants in linkage disequilibrium with them are linked to depression in our Italian families. CONCLUSIONS: This is the first report of PSMD9 linkage to depression. This finding highlights the pleiotropic effects of PSMD9.

Meta-analysis of the IPF1 D76N polymorphism in a worldwide type 2 diabetes population.

AIM: Mutations in the IPF1 gene cause MODY4; IPF1 D76N is a polymorphism, which inhibits the insulin promoter and decreases insulin-secretion. We planned to estimate the odds ratio (OR) between D76N genotype and type 2 diabetes (T2D) in Italian, European and worldwide cohorts. METHODS: We recruited 90 unrelated late-onset T2D subjects and 50 unrelated control subjects from Italy. We screened the subjects for IPF1 mutations. We sequenced the control subjects' DNA to determine D76N presence/absence and tested for association in the Italian dataset. We estimated the OR for a T2D cohort of D76N carriers by performing a meta-analysis of published data from multiple populations. We performed the association by pooling ORs and we tested for heterogeneity between the different population samples. We analyzed separately total, late-onset and early-onset T2D subjects using both European and worldwide data. The statistical power for each data set was defined. RESULTS: In the Italian cohort, we identified one late-onset T2D subject and his affected sibling as D76N carriers and one late-onset T2D subject as a carrier of a silent mutation (P244P). Our meta-analysis shows only a trend toward association in the early-onset European population. Given the observed rarity of the putative susceptibility genotype, power to detect a significant association between D76N and T2D for OR < 1.59 was less than 0.8 in all samples. CONCLUSION: So far, this is the largest association study regarding the effect of D76N IPF1 on T2D. We conclude that D76N IPF1 is not contributing to T2D in early-onset or late-onset cohorts in the currently present worldwide dataset.

PSMD9 gene variants within NIDDM2 may rarely contribute to type 2 diabetes.

Multiple genome-wide scans in different populations have linked the chromosome 12q24 region, known as NIDDM2 (non-insulin-dependent-diabetes, locus 2), to type 2 diabetes. Within NIDDM2 we examined the PSMD9 (proteasome modulator 9/Bridge-1) gene that encodes a PDZ-domain transcriptional coactivator of insulin production. Our goal was to identify a potential contribution of the PSMD9 gene to type 2 diabetes in Italians. We directly sequenced the entire gene PSMD9 in Italian type 2 diabetes patients (n = 237) and controls subjects (n = 215) and performed an association study with the identified gene variants. We found five single nucleotide polymorphisms (SNPs), A17V, IVS1+nt29, IVS3+nt460, IVS3+nt437, and E197G, which are not associated with disease in our case-control study. Furthermore, we identified two PSMD9 gene variants in type 2 diabetes patients, which produced nonconservative amino acid substitutions S143G and N166S within the PDZ domain and two other gene variants. Three out of four of these variants are absent from the control subjects screened. We propose that the three PSMD9 gene variants (S143G, N166S and G > A at IVS3+nt102), absent in control subjects, contribute rarely to late-onset type 2 diabetes in Italians. In fact, the frequency rate of such variants in unrelated cases equals 0.016. We may not exclude that PSMD9 gene variants may contribute, either commonly or rarely, to an increased risk of type 2 diabetes in other populations.

NEUROG3 variants and type 2 diabetes in Italians.

AIM: Type 2 diabetes (T2D) is a complex polygenic disorder. Genetic predisposition may vary in different ethnic groups. A potential candidate gene for T2D is Neurogenin 3 (Ngn3, NEUROG3), which lies on chromosome 10 in a region with several potential linkage signals to T2D in various population studies. The goal of this study was to establish whether NEUROG3 gene variants are contributing to T2D in an Italian T2D cohort. METHODS: We genotyped AFMa210xh1 macrosatellite marker in 202 Italian T2D families/sib-pairs. We performed two-point linkage analysis in the late- and early-onset dataset. For the case control study, we selected families with a positive logarithm of odds (LOD) score. Then, we screened NEUROG3 in the selected 61 single unrelated T2D patients and 101 Italian controls and performed association studies. RESULTS: Several variants were identified: a new 152ntC/G, and 44-45delCA, Gly167Arg, Ser 199Phe single nucleotide polymorphisms (SNPs) and 2 new 5'UTR variations (-nt498G/T and nt367C/T) and a new Gly167fsinsCAE Arg167X234 mutation. The variants 44-45delCA/ Ser199Phe and Gly167Arg/Ser199Phe show significant linkage disequilibrium. The haplotype CCCAGT/A/C shows association to T2D in our cohort, while the allele 167Arg, the haplotypes CCCAGT/A and A/C and the diplotype LL/GA/TC show a trend towards association to disease. The 5'UTR and frameshift variants are absent in the controls. Nonparametric linkage analysis within NEUROG3 variants in 9 early-onset T2D families shows a nonparametric LOD score=2.49 (P=0.006). CONCLUSIONS: The biological impact of NEUROG3 might be due to the presence of either CCCAGT at 44-45nt, 167Arg, 199Ser or by a haplotype combination of these 3 or 2 of them.

Early-onset Type II diabetes mellitus in Italian families due to mutations in the genes encoding hepatic nuclear factor 1 alpha and glucokinase.

AIMS/HYPOTHESIS: Maturity-onset-diabetes of the young (MODY) is caused by mutations in at least five different genes. Our aim was to determine the prevalence of the most common MODY genes in Italian families with early-onset Type II (non-insulin-dependent) diabetes mellitus. METHODS: We screened 28 Italian early-onset Type II diabetic families (diagnosis < 35 years) for mutations in the hepatic nuclear factor-4 alpha, (MODY1), glucokinase (MODY2) and hepatic nuclear factor-1 alpha (MODY3). Both strands of exons, flanking introns and minimal promoter regions of the above-mentioned genes were amplified using polymerase chain reaction and were sequenced directly. RESULTS: We identified four different mutations, three of which are not described, (W113X, G42P43fsCC --> A, H514R) and four new polymorphisms (G184G, T513T, IVS3-nt47delG, IVS1- nt53C --> G) in the hepatic nuclear factor-1 alpha gene, two new potential mutations (G44S, IVS4nt + 7C --> T) and three new polymorphisms (promoter-nt84C --> G, IVS9 + nt8C --> T, IVS9 + nt49G --> A) in the glucokinase gene, and a new polymorphism (IVS1c-nt11T --> G) in the hepatic nuclear factor-4 alpha gene. CONCLUSION/INTERPRETATION: Mutations in the hepatic nuclear factor-1 alpha and glucokinase are associated with Type II diabetes in 14 % and 7 % of Italian families, respectively. Our findings provide an impetus for screening Italian MODY and early-non Type II diabetic families for mutations in the above mentioned genes to identify relatives at risk who could benefit from primary prevention care. [

Identification of seven novel nucleotide variants in the hepatocyte nuclear factor-1alpha (TCF1) promoter region in MODY patients.

Maturity onset diabetes of the young (MODY) is a heterogeneous subtype of type II diabetes mellitus. To date, five MODY genes have been identified. Mutations in the hepatocyte nuclear factor-1alpha (HNF-1alpha) gene are associated with MODY3. In the present work, we implemented the HNF-1alpha promoter region in the screening of MODY-suspect patients and identified seven variants not detected in control subjects. The family was available for the -119delG variant, and segregration between MODY and the variant is observed. Most of these variants are located in highly conserved regions and may alter HNF-1alpha expression through binding alteration of nuclear factors or other mechanisms. We demonstrate by functional studies that the transcriptional activity of the -283A>C and -218T>C variant promoters were 30% and 70% of the wild type activity, respectively. These data suggest that HNF-1alpha promoter variants could be diabetogenic mutations, and emphasize that the accurate HNF-1alpha expression is important for the maintenance of normal pancreatic beta cell function.

Maturity-onset diabetes of the young due to a mutation in the hepatocyte nuclear factor-4 alpha binding site in the promoter of the hepatocyte nuclear factor-1 alpha gene.

Recent studies have shown that mutations in the transcription factor hepatocyte nuclear factor (HNF)-1 alpha are the cause of one form of maturity-onset diabetes of the young (MODY3). These studies have identified mutations in the mRNA and protein coding regions of this gene that result in the synthesis of an abnormal mRNA or protein. Here, we report an Italian family in which an A-->C substitution at nucleotide-58 of the promoter region of the HNF-1 alpha gene cosegregates with MODY. This mutation is located in a highly conserved region of the promoter and disrupts the binding site for the transcription factor HNF-4 alpha, mutations in the gene encoding HNF-4 alpha being another cause of MODY (MODY1). This result demonstrates that decreased levels of HNF-1 alpha per se can cause MODY. Moreover, it indicates that both the promoter and coding regions of the HNF-1 alpha gene should be screened for mutations in subjects thought to have MODY because of mutations in this gene.

Hepatic function in a family with a nonsense mutation (R154X) in the hepatocyte nuclear factor-4alpha/MODY1 gene.

Maturity-onset diabetes of the young (MODY) is a genetically heterogeneous monogenic disorder characterized by autosomal dominant inheritance, onset usually before 25 yr of age, and abnormal pancreatic beta-cell function. Mutations in the hepatocyte nuclear factor(HNF)-4alpha/MODY1, glucokinase/MODY2, and HNF-1alpha/MODY3 genes can cause this form of diabetes. In contrast to the glucokinase and HNF-1alpha genes, mutations in the HNF-4alpha gene are a relatively uncommon cause of MODY, and our understanding of the MODY1 form of diabetes is based on studies of only a single family, the R-W pedigree. Here we report the identification of a second family with MODY1 and the first in which there has been a detailed characterization of hepatic function. The affected members of this family, Dresden-11, have inherited a nonsense mutation, R154X, in the HNF-4alpha gene, and are predicted to have reduced levels of this transcription factor in the tissues in which it is expressed, including pancreatic islets, liver, kidney, and intestine. Subjects with the R154X mutation exhibited a diminished insulin secretory response to oral glucose. HNF-4alpha plays a central role in tissue-specific regulation of gene expression in the liver, including the control of synthesis of proteins involved in cholesterol and lipoprotein metabolism and the coagulation cascade. Subjects with the R154X mutation, however, showed no abnormalities in lipid metabolism or coagulation except for a paradoxical 3.3-fold increase in serum lipoprotein(a) levels, nor was there any evidence of renal dysfunction in these subjects. The results suggest that MODY1 is primarily a disorder of beta-cell function.