Implications of genetic variations, differential gene expression, and allele-specific expression on metformin response in drug-naïve type 2 diabetes

PURPOSE

Metformin is widely used to treat type 2 diabetes mellitus (T2DM) individuals. Clinically, inter-individual variability of metformin response is of significant concern and is under interrogation. In this study, a targeted exome and whole transcriptome analysis were performed to identify predictive biomarkers of metformin response in drug-naïve T2DM individuals.

METHODS

The study followed a prospective study design. Drug-naïve T2DM individuals (n = 192) and controls (n = 223) were enrolled. T2DM individuals were administered with metformin monotherapy and defined as responders and non-responders based on their glycated haemoglobin change over three months. 146 T2DM individuals were used for the final analysis and remaining samples were lost during the follow-up. Target exome sequencing and RNA-seq was performed to analyze genetic and transcriptome profile. The selected SNPs were validated by genotyping and allele specific gene expression using the TaqMan assay. The gene prioritization, enrichment analysis, drug-gene interactions, disease-gene association, and correlation analysis were performed using various tools and databases.

RESULTS

rs1050152 and rs272893 in SLC22A4 were associated with improved response to metformin. The copy number loss was observed in PPARGC1A in the non-responders. The expression analysis highlighted potential differentially expressed targets for predicting metformin response (n = 35) and T2DM (n = 14). The expression of GDF15, TWISTNB, and RPL36A genes showed a maximum correlation with the change in HbA1c levels. The disease-gene association analysis highlighted MAGI2 rs113805659 to be linked with T2DM.

CONCLUSION

The results provide evidence for the genetic variations, perturbed transcriptome, allele-specific gene expression, and pathways associated with metformin drug response in T2DM.

EUGLYCEMIC DIABETIC KETOACIDOSIS (EDKA) IN A PATIENT RECEIVING DAPAGLIFLOZIN

SGLT-2 inhibitors have gained importance in recent years because of their cardio-protective and reno-protective properties in diabetes. SGLT-2 inhibitors, when introduced in diabetic patients, may cause euglycemic diabetic ketoacidosis. A 55-year-old woman presented with low-grade fever, vomiting, and lethargy. She was started on dapagliflozin two years back. On workup, she was diagnosed with euglycemic diabetic ketoacidosis (EDKA) and was managed accordingly. She improved clinically while her dapagliflozin was stopped. With a literature search, we have identified 15 case reports of EDKA with dapagliflozin since 2015. There are no standard guidelines regarding the monitoring of patients for this rare but potentially morbid complication. Moreover, the exact mechanism for this is unknown. Various precipitating factors are linked with SGLT-2 inhibitors in promoting EDKA. We recommend that customary plans should comprise educating the patient about this rare complication before commencing medication, close follow-up with serial electrolyte monitoring, and discontinuing medications in the state of infection, dehydration and recent surgery and serious illness requiring hospitalization.

Diabetes in Bolivia

OBJECTIVE

To measure the prevalence of diabetes mellitus (DM), hypertension, obesity, and related risk factors in major cities in Bolivia.

METHODS

A population-based survey was conducted in four Bolivian cities: La Paz, El Alto, Santa Cruz, and Cochabamba. The total sample size was chosen to be 2,948 persons. The overall response rate was 86%, with the rate varying somewhat among the four cities. DM was diagnosed through an oral glucose tolerance test (OGTT) 2 hours after an overload of 75 grams of glucose, using World Health Organization criteria.

RESULTS

The overall prevalence of DM in the four urban areas combined was 7.2% (95% confidence interval (CI): 6.2%-8.3%) and of impaired glucose tolerance (IGT) was 7.8%. A total of 73.1% (95% CI: 65.0%-81.0%) of those previously diagnosed with DM and 73.7% (95% CI: 61.0%-86.4%) of newly diagnosed cases were overweight, according to measurements of body mass index. Hypertension was found in 36.5% (95% CI: 27.6%-45.5%) of known diabetics and in 36.6% (95% CI: 23.0%-50.1%) of newly diagnosed cases, compared to only 15.9% (95% CI: 14.3%-17.5%) among people without DM. The disease was most common among older persons and those with little education.

CONCLUSIONS

Diabetes is a genuine public health problem in Bolivia. Further, the high prevalence of IGT that was found suggests that diabetes prevalence will increase in the near future in the country unless prevention strategies are implemented.

The determination of histamine in the Drosophila head

Histamine is a neurotransmitter at arthropod photoreceptors. Even though the fruit fly, Drosophila melanogaster, is a widely used model in neuroscience research, the histamine content of its nervous system has not so far been reported. We have developed a high performance liquid chromatography (HPLC) method with pre-column o-phtaldialdehyde-mercaptoethanol (OPA-ME) derivatization and electrochemical detection, to determine this amine in Drosophila. The histamine content of the fly's head averages about 2.0 ng per head. In heads of the mutant hdc(JK910), a presumed null for the gene encoding the enzyme that synthesizes histamine, histamine was not detected in measurable amounts. In heads of the mutant sine oculis, which lacks compound eyes, only 28% of this amine was found compared with wild type flies, so histamine is mainly present in the compound eye photoreceptors. Also observed in histamine-deficient mutants was a decrease in the peak which contains a substance having the same retention time as carcinine (beta-alanyl-histamine). Our method was not able to detect compounds previously reported as histamine metabolites in insects. In spite of this, the method we have developed enables the fast and accurate measurement of histamine in the heads of Drosophila, suitable for screening mutants.

Prolonged inhibition of human myometrial contractility by intermittent isoproterenol

Regular, spontaneous contractions of human myometrial strips obtained at the time of elective cesarean section were recorded in a tissue bath in five experiments. Administration of the beta-adrenergic agonist isoproterenol (1 mumol/L) resulted in the rapid onset of myometrial relaxation. In the continuous presence of the beta-agonist, myometrial contractions of amplitude equal to or greater than that of baseline resumed after 10 to 40 minutes (mean +/- SEM = 29.7 +/- 7.3), indicating the development of desensitization of the tissue to the tocolytic effects of isoproterenol. In contrast, intermittent exposure of the myometrial strips to isoproterenol prevented the onset of desensitization and resulted in prolonged inhibition of myometrial contractions. These findings suggest that modification of the present regimen of administration of beta-adrenergic agonists from continuous to intermittent infusion may improve the success of these agents in the prevention of preterm births.