T2D-nephropathy linkage within 12q24 locus

A Drosophila model of diabetic neuropathy reveals a role of proteasome activity in the glia

Diabetic peripheral neuropathy (DPN) is the most common chronic, progressive complication of diabetes mellitus. The main symptom is sensory loss; the molecular mechanisms are not fully understood. We found that Drosophila fed a high-sugar diet, which induces diabetes-like phenotypes, exhibit impairment of noxious heat avoidance. The impairment of heat avoidance was associated with shrinkage of the leg neurons expressing the Drosophila transient receptor potential channel Painless. Using a candidate genetic screening approach, we identified proteasome modulator 9 as one of the modulators of impairment of heat avoidance. We further showed that proteasome inhibition in the glia reversed the impairment of noxious heat avoidance, and heat-shock proteins and endolysosomal trafficking in the glia mediated the effect of proteasome inhibition. Our results establish Drosophila as a useful system for exploring molecular mechanisms of diet-induced peripheral neuropathy and propose that the glial proteasome is one of the candidate therapeutic targets for DPN.

Ubiquitin-proteasome system in diabetic retinopathy

Diabetic retinopathy (DR) is the most common complication of diabetes, being the most prevalent reason for blindness among the working-age population in the developed world. Despite constant improvement of understanding of the pathogenesis of DR, identification of novel biomarkers of DR is needed for improvement of patient risk stratification and development of novel prevention and therapeutic approaches. The ubiquitin-proteasome system (UPS) is the primary protein quality control system responsible for recognizing and degrading of damaged proteins. This review aims to summarize literature data on modifications of UPS in diabetes and DR. First, we briefly review the structure and functions of UPS in physiological conditions. We then describe how UPS is involved in the development and progression of diabetes and touch upon the association of UPS genetic factors with diabetes and its complications. Further, we focused on the effect of diabetes-induced hyperglycemia, oxidative stress and hypoxia on UPS functioning, with examples of studies on DR. In other sections, we discussed the association of several other mechanisms of DR (endoplasmic reticulum stress, neurodegeneration etc) with UPS modifications. Finally, UPS-affecting drugs and remedies are reviewed. This review highlights UPS as a promising target for the development of therapies for DR prevention and treatment and identifies gaps in existing knowledge and possible future study directions.

Novel Genetic Actors of Diabetes-Associated Microvascular Complications: Retinopathy, Kidney Disease and Neuropathy

Both type 1 and type 2 diabetes mellitus can lead to the common microvascular complications of diabetic retinopathy, kidney disease, and neuropathy. Diabetic patients do not universally develop these complications. Long duration of diabetes and poor glycemic control explain a lot of the variability in the development of microvascular complications, but not all. Genetic factors account for some of the remaining variability because of the heritability and familial clustering of these complications. There have been a large number of investigations, including linkage studies, candidate gene studies, and genome-wide association studies, all of which have sought to identify the specific variants that increase susceptibility. For retinopathy, several genome-wide association studies have been performed in small or midsize samples, but no reproducible loci across the studies have been identified. For diabetic kidney disease, genome-wide association studies in larger samples have been performed, and loci for this complication are beginning to emerge. However, validation of the existing discoveries, and further novel discoveries in larger samples is ongoing. The amount of genetic research into diabetic neuropathy has been very limited, and much is dedicated to the understanding of genetic risk factors only. Collaborations that pool samples and aim to detect phenotype classifications more precisely are promising avenues for a better explanation of the genetics of diabetic microvascular complications.

T2D and Depression Risk Gene Proteasome Modulator 9 is Linked to Insomnia

Insomnia increases type-2 diabetes (T2D) risk. The 12q24 locus is linked to T2D, depression, bipolar disorder and anxiety. At the 12q24 locus, the Proteasome-Modulator 9 (PSMD9) single nucleotide polymorphisms (SNPs) rs74421874 [intervening sequence (IVS) 3+nt460-G>A], rs3825172 (IVS3+nt437-C>T) and rs14259 (E197G-A>G) are linked to: T2D, depression, anxiety, maturity-onset-diabetes-of the young 3/MODY3, obesity, waist circumference, hypertension, hypercholesterolemia, T2D-macrovascular disease, T2D-microvascular disease, T2D-neuropathy, T2D-carpal-tunnel syndrome, T2D-nephropathy, T2D-retinopathy and non-diabetic retinopathy. PSMD9 SNP rs1043307/rs14259 (E197G-A>G) plays a role in anti-depressant therapy response, depression and schizophrenia. We aimed at determining PSMD9 rs74421874/rs3825172/rs14259 SNPs potential linkage to primary insomnia and sleep hours in T2D families. We recruited 200 Italian T2D families phenotyping them for primary insomnia and sleep hours per night. PSMD9-T2D-risk SNPs rs74421874/rs3825172 and rs1043307/rs14259 were tested for linkage with insomnia and sleep hours. Non-parametric-linkage analysis, linkage-disequilibrium-model analysis, single-SNP analysis, cluster-based-parametric analysis, quantitative-trait and variant-component analysis were performed using Merlin software. To validate data, 1000 replicates were executed for the significant non-parametric data. PSMD9 rs74421874 (IVS3+nt460-G>A), rs3825172 (IVS3+nt437-C>T) and rs1043307/rs14259 (E197G-A>G) SNPs are linked to insomnia in our Italian families.

Proteasome modulator 9 gene SNPs, responsible for anti-depressant response, are in linkage with generalized anxiety disorder

Proteasome modulator 9 (PSMD9) gene single nucleotide polymorphism (SNP) rs1043307/rs2514259 (E197G) is associated with significant clinical response to the anti-depressant desipramine. PSMD9 SNP rs74421874 [intervening sequence (IVS) 3 + nt460 G>A], rs3825172 (IVS3 + nt437 C>T) and rs1043307/rs2514259 (E197G A>G) are all linked to type 2 diabetes (T2D), maturity-onset-diabetes-of the young 3 (MODY3), obesity and waist circumference, hypertension, hypercholesterolemia, T2D-macrovascular and T2D-microvascular disease, T2D-neuropathy, T2D-carpal tunnel syndrome, T2D-nephropathy, T2D-retinopathy, non-diabetic retinopathy and depression. PSMD9 rs149556654 rare SNP (N166S A>G) and the variant S143G A>G also contribute to T2D. PSMD9 is located in the chromosome 12q24 locus, which per se is in linkage with depression, bipolar disorder and anxiety. In the present study, we wanted to determine whether PSMD9 is linked to general anxiety disorder in Italian T2D families. Two-hundred Italian T2D families were phenotyped for generalized anxiety disorder, using the diagnostic criteria of DSM-IV. When the diagnosis was unavailable or unclear, the trait was reported as unknown. The 200 Italians families were tested for the PSMD9 T2D risk SNPs rs74421874 (IVS3 + nt460 G>A), rs3825172 (IVS3 +nt437 T>C) and for the T2D risk and anti-depressant response SNP rs1043307/rs2514259 (E197G A>G) for evidence of linkage with generalized anxiety disorder. Non-parametric linkage analysis was executed via Merlin software. One-thousand simulation tests were performed to exclude results due to random chance. In our study, the PSMD9 gene SNPs rs74421874, rs3825172, and rs1043307/rs2514259 result in linkage to generalized anxiety disorder. This is the first report describing PSMD9 gene SNPs in linkage to generalized anxiety disorder in T2D families.

Overweight condition and waist circumference and a candidate gene within the 12q24 locus

Aims

Obesity and obesity-associated phenotypes are linked to the chromosome12q24 locus, the non-insulin-dependent-diabetes 2 (NIDDM2) locus. The gene of proteasome modulator 9 (PSMD9) lies in the NIDDM2 region and is linked to type 2 diabetes (T2D), microvascular and macrovascular complications of T2D.

We aimed at studying whether the PSMD9 T2D risk single nucleotide polymorphisms (SNPs) IVS3+nt460, IVS3+nt437, and 197G are linked to obesity, overweight status and waist circumference in Italian T2D families.

Methods and results

We screened 200 Italians T2D siblings/families for PSMD9 variants. Using Merlin software, we performed non-parametric linkage analysis to test for linkage with obesity and overweight condition and variance component analysis to test for linkage with waist circumference in our T2D siblings/families dataset.

Our study shows that the PSMD9 SNPs IVS3+nt460, IVS3+nt437, and 197G are in linkage with overweight condition and waist circumference in Italians. The statistical power tests performed via simulations on real data confirm that the results are not due to random chance.

Conclusions

In summary, the linkage strategy using a homogeneous family/subject dataset can identify a gene contributing to a complex trait. PMSD9 may be at least one of the genes responsible for the linkage to obesity and obesity-associated phenotypes at the locus 12q24 in other populations.

Proteasome modulator 9 is linked to microvascular pathology of T2D

The locus 12q24 is linked to type 2 diabetes (T2D) and to changes in retinal vascular caliber in Caucasians. Proteasome Modulator 9 gene (PSMD9) lies in the 12q24 locus and is implicated in diabetes onset and in degradation of intracellular proteins in antigenic peptides in the immune response to antigen presentation by MHC class I cells. Within PSMD9, we reported a linkage to T2D and to MODY3 in Italian families. We recently demonstrated a linkage of the PSMD9 T2D risk SNPs with T2D-nephropathy, T2D-neuropathy, retinopathy, hypercholesterolemia, and macrovascular pathology. We aimed at studying the presence of the linkage signal of the PSMD9 T2D risk SNPs IVS3 + nt460, IVS3 + nt437, E197G to microvascular pathology associated to T2D in Italian siblings/families. We screened 200 T2D siblings/families for the PSMD9 above-mentioned variants and performed a parametric and non-parametric linkage study by Merlin software. Our results show significant LOD score in linkage with microvascular pathology for the PSMD9 SNPs studied using the non-parametric and parametric linkage analysis. The strongest signal is present under the recessive model. Our statistical power relies on the presence of T2D affected siblings, which represent an ideal dataset to identify linkage with a recessive disease model. Our simulation analysis confirms that the results are not due to random chance. In summary, the PSMD9 IVS3 + nt460, IVS3 + nt437, E197G SNPs are linked via the recessive model to microvascular pathology of T2D in Italians. A possible role of PSMD9 in microvascular pathology may be related to a causative pathogenetic role in inflammation as part of an autoimmune process.

Proteasome modulator 9 and carpal tunnel syndrome

Proteasome modulator 9 (PSMD9) is linked to type 2 diabetes (T2D). The author studied whether PSMD9 IVS3 + nt460 A > G, IVS3 + nt437 T > C and E197 are linked to carpal tunnel syndrome in T2D Italian families. Non-parametric linkage, linkage disequilibrium-based and independent SNPs-based linkage analyses were performed. The PSMD9 SNPs show linkage to carpal tunnel syndrome.

PSMD9 is linked to type 2 diabetes neuropathy

OBJECTIVE

Diabetic neuropathy, a long-term complication of type 2 diabetes (T2D), has a genetic inheritance component to its manifestation. We aimed at identifying whether the proteasome modulator 9 (PSMD9) gene responsible for linkage with T2D and maturity-onset diabetes of the young 3 in Italian families may play a role in the inheritance of diabetic neuropathy in T2D as well.

METHODS

We characterized the Italian families with T2D for presence and/or absence of diabetic neuropathy. The diabetic neuropathy is reported as unknown in all cases in which either the diagnosis was unclear or the data were not available for the subject studied. Thus, in our 200 Italian families, the data presence was less than 100%. We tested in the 200 Italians families for the presence of the linkage of the PSMD9 single nucleotide polymorphisms (SNPs) with diabetic neuropathy. The nonparametric as well as the parametric linkage analysis was performed by using the Merlin software; the LOD score and correspondent P value were calculated. For the significance and/or trends toward significance linkage score, 1000 replicates were performed to determine the empirical P value.

RESULTS

We report the linkage study of the PSMD9 SNPs [intervening sequence IVS3+nt460A/G, IVS3+nt437C/T and E197G] in Italian families with T2D neuropathy.

CONCLUSION

In summary, the PSMD9 gene SNPs studied contribute to the genetic risk of diabetic neuropathy in our Italian data set, showing statistical significance for an additive model-based inheritance.

Proteasome modulator 9 SNPs are linked to hypertension in type 2 diabetes families

Background

Chromosome 12q24 was recently associated with hypertension. Proteasome Modulator 9 (PSMD9) lies in the 12q24 locus and is in linkage with MODY3, type 2 diabetes (T2D), microvascular and macrovascular pathology, carpal tunnel syndrome, and hypercholesterolemia in Italian families.

Aims

Our goal was to determine whether PSMD9 is linked to elevated blood pressure/hypertension in T2D families.

Methods

We characterized the Italian T2D families' members for presence and/or absence of elevated blood pressure (≥ 130/80) and/or hypertension. The phenotypes were described as unknown in all cases in which the diagnosis was either unclear or the data were not available for the subject studied. We tested in the 200 Italians families for the presence of the linkage of the PSMD9 T2D risk single nucleotide polymorphisms (SNPs) IVS3+nt460 A > G, IVS3+nt437 T > C and E197G A > G with elevated blood pressure/hypertension. The non-parametric linkage analysis was performed for this qualitative phenotype by using the Merlin software; the Lod score and correspondent P-value were calculated. Parametric linkage analysis was also performed. For the significant linkage score, 1000 replicates were run to calculate the empirical P-value.

Results

The PSMD9 gene SNPs studied are in linkage with elevated blood pressure/hypertension in our Italian families.

Conclusions

We conclude that the PSMD9 gene and/or any variant in linkage disequilibrium with the SNPs studied contribute to the linkage to hypertension within our family dataset. This is the first report of PSMD9 linkage to hypertension within the 12q24 locus.

Hypercholesterolemia and a candidate gene within the 12q24 locus

Background

The 12q24 locus entails at least one gene responsible for hypercholesterolemia. Within the 12q24 locus lies the gene of proteasome modulator 9 (PSMD9). PSMD9 is in linkage with type 2 diabetes (T2D), T2D-nephropathy and macrovascular pathology in Italian families and PSMD9 rare mutations contribute to T2D.

Aims

In the present study, we aimed at determining whether the PSMD9 T2D risk single nucleotide polymorphisms (SNPs) IVS3 + nt460 A > G, IVS3 + nt437 T > C and E197G A > G are linked to hypercholesterolemia in 200 T2D Italian families.

Methods

We characterized 200 Italian families for presence and/or absence of hypercholesterolemia characterized by LDL levels ≥ 100 mg/dl in drug-naïve patients and/or presence of a diagnosis of hypercholesterolemia in a patient treated with statin medication. The phenotypes were described as unknown in all cases in which the diagnosis was either unclear or the data were missing. We tested in the 200 Italians families for evidence of linkage of the PSMD9 SNPs with hypercholesterolemia. The non-parametric linkage analysis was performed for the qualitative phenotype by using the Merlin software; the Lod score and correspondent P-value were calculated. For the significant linkage score, 1000 replicates were performed to calculate the empirical P-value.

Results

The PSMD9 gene SNPs studied show linkage to hypercholesterolemia. The results are not due to random chance.

Conclusions

PSMD9 should be tested in all populations reporting linkage to hypercholesterolemia within the chromosome 12q24 locus. The impact of this gene on hypercholesterolemia and contribution to cardio- and cerebrovascular events may be high.

Proteasome modulator 9 and macrovascular pathology of T2D

Aims

Coronary artery disease (CAD) and stroke share a major linkage at the chromosome 12q24 locus. The same chromosome region entails at least a major risk gene for type 2 diabetes (T2D) within NIDDM2, the non-insulin-dependent-diabetes 2 locus. The gene of Proteasome Modulator 9 (PSMD9) lies in the NIDDM2 region and is implicated in diabetes in mice. PSMD9 mutations rarely cause T2D and common variants are linked to both late-onset T2D and maturity-onset-diabetes of the young (MODY3). In this study, we aimed at determining whether PSMD9 is linked to macrovascular pathology of T2D.

Methods and Results

In our 200 T2D families from Italy, we characterized the clinical phenotype of macrovascular pathology by defining the subjects for presence or absence of CAD, stroke and/or transitory ischemic attacks (TIA), plaques of the large arterial vessels (macro-vasculopathy) and arterial angioplasty performance. We then screened 200 T2D siblings/families for PSMD9 +nt460A/G, +nt437C/T and exon E197G A/G single nucleotide polymorphisms (SNPs) and performed a non-parametric linkage study to test for linkage for coronary artery disease, stroke/TIA, macro-vasculopathy and macrovascular pathology of T2D. We performed 1,000 replicates to test the power of our significant results. Our results show a consistent significant LOD score in linkage with all the above-mentioned phenotypes. Our 1000 simulation analyses, performed for each single test, confirm that the results are not due to random chance.

Conclusions

In summary, the PSMD9 IVS3+nt460A/G, +nt437C/T and exon E197G A/G SNPs are linked to CAD, stroke/TIA and macrovascular pathology of T2D in Italians.