Insights into the functional aspects of poly(ADP-ribose) polymerase-1 (PARP-1) in mitochondrial homeostasis in Dictyostelium discoideum.

BACKGROUND INFORMATION: Poly(ADP-ribose) Polymerase-1 (PARP-1) is predominantly a nuclear protein and involved in various cellular processes like DNA repair, cell death, development, chromatin modulation etc. PARP-1 utilizes NAD+ and adds negatively charged PAR moieties on the target proteins. Over-activation of PARP-1 has been shown to cause energy crisis mediated cell death in which mitochondrial homeostasis is also affected. Moreover, the presence of mitochondrial NAD+ pools highlights the role of PARP-1 in mitochondria. The aim of present study is to understand the physiological role of PARP-1 in regulating mitochondrial functioning by varying the levels of PARP-1 in Dictyostelium discoideum. Intra-mitochondrial PARylation was analyzed by indirect immunofluorescence. Further, the effect of altered levels of PARP-1 i.e. overexpression, downregulation, knockout and its chemical inhibition was studied on mitochondrial respiration, reactive oxygen species (ROS) levels, ATP production, mitochondrial fission-fusion, mitochondrial morphology and mitochondrial DNA (mtDNA) content of D. discoideum. RESULTS: Our results show intra-mitochondrial PARylation under oxidative stress. Altered levels of PARP-1 caused impairment in the mitochondrial respiratory capacity, leading to elevated ROS levels and reduced ATP production. Moreover, PARP-1 affects the mitochondrial morphology and mtDNA content, alters the mitochondrial fission-fusion processes in lieu of preventing cell death under physiological conditions. CONCLUSION: The current study highlights the physiological role of PARP-1 in mitochondrial respiration, its morphology, fission-fusion processes and mtDNA maintenance in D. discoideum. SIGNIFICANCE: This study would provide new clues on the PARP-1's crucial role in mitochondrial homeostasis, exploring the therapeutic potential of PARP-1 in various mitochondrial diseases.

ß-cell replenishment: Possible curative approaches for diabetes mellitus.

AIMS: Diabetes mellitus (DM) is a disorder of heterogeneous etiology marked by persistent hyperglycemia. Exogenous insulin is the only treatment for type 1 diabetes (T1D). Islet transplantation is a potential long cure for T1D but is disapproved due to the possibility of immune rejection in the later stage. The approaches used for treating type 2 diabetes (T2D) include diet restrictions, weight management and pharmacological interventions. These procedures have not been able to boost the quality of life for diabetic patients owing to the complexity of the disorder. DATA SYNTHESIS: Hence, research has embarked on permanent ways of managing, or even curing the disease. One of the possible approaches to restore the pancreas with new glucose-responsive ß-cells is by their regeneration. Regeneration of ß-cells include islet neogenesis, dedifferentiation, and trans-differentiation of the already differentiated cells. CONCLUSIONS: This review briefly describes the islet development, functions of ß-cells, mechanism and factors involved in ß-cell death. It further elaborates on the potential of the existing and possible therapeutic modalities involved in the in-vivo replenishment of ß-cells with a focus on exercise, diet, hormones, small molecules, and phytochemicals.

Genetic variants of resistin and its plasma levels: Association with obesity and dyslipidemia related to type 2 diabetes susceptibility.

Resistin, an adipokine, is involved in obesity and Type 2 Diabetes (T2D). The current study evaluates the association between RETN polymorphisms (-638 G/A, -420C/G & -358 G/A) and the risk towards T2D. Controls and T2D patients were enrolled from Gujarat, India. Polymorphisms of RETN were genotyped by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism. For the genotype-phenotype correlation analysis Fasting Blood Glucose (FBG), Body Mass Index (BMI) and plasma lipid profile were used. Plasma levels of resistin were assayed by ELISA. Our study suggests an association of RETN -420C/G polymorphism with T2D risk. The CC genotype of RETN -420C/G polymorphism was found to be associated with FBG, BMI, and total cholesterol. Plasma resistin levels were found to be significantly increased in diabetic patients as compared to controls. Our findings suggest -420C/G polymorphism of RETN as an important factor which could pose a powerful risk towards T2D susceptibility.

Repurposing Pitavastatin and L-Glutamine: Replenishing ß-Cells in Hyperlipidemic Type 2 Diabetes Mouse Model.

Type 2 diabetes (T2D) is associated with obesity and declining ß-cells. L-glutamine has been implicated in the amelioration of T2D by virtue of its incretin secretagogue property while, there are mixed reports on pitavastatin's adiponectin potentiating ability. We aimed to investigate the effect of pitavastatin (P), L-glutamine (LG), and combination (P + LG) on glycemic control and ß-cell regeneration in a high-fat diet (HFD) + streptozotocin (STZ)-induced T2D mouse model. C57BL6/J mice treated with HFD + STZ were divided into four groups: diabetes control (HFD + STZ), P, LG, and P + LG, while the control group (NCD) was fed with the normal-chow diet. Significant amelioration was observed in the combination therapy as compared to monotherapies in respect of (i) insulin resistance, glucose intolerance, lipid profile, adiponectin levels, and mitochondrial complexes I, II, and III activities, (ii) reduced phosphoenolpyruvate carboxykinase, glucose 6-phophatase, glycogen phosphorylase, and GLUT2 transcript levels with increased glycogen content in the liver, (iii) restoration of insulin receptor 1ß, pAkt/Akt, and AdipoR1 protein levels in skeletal muscle, and (iv) significant increase in islet number due to ß-cell regeneration and reduced ß-cell death. L-glutamine and pitavastatin in combination can ameliorate T2D by inducing ß-cell regeneration and regulating glucose homeostasis.

A novel therapeutic combination of sitagliptin and melatonin regenerates pancreatic ß-cells in mouse and human islets.

Autoimmune-led challenge resulting in ß-cell loss is responsible for the development of type 1 diabetes (T1D). Melatonin, a pineal hormone or sitagliptin, a dipeptidyl peptidase IV (DPP-IV) inhibitor, has increased ß-cell mass in various diabetic models and has immunoregulatory property. Both ß-cell regenerative capacity and melatonin secretion decrease with ageing. Thus, we aimed to investigate the therapeutic potential of melatonin combined with sitagliptin on ß-cell regeneration under glucotoxic stress, in the streptozotocin-induced young and old diabetic mouse models, and euglycemic humanized islet transplant mouse model. Our results suggest that combination therapy of sitagliptin and melatonin show an additive effect in inducing mouse ß-cell regeneration under glucotoxic stress, and in the human islet transplant mouse model. Further, in the young diabetic mouse model, the monotherapies induce ß-cell transdifferentiation and reduce ß-cell apoptosis whereas, in the old diabetic mouse model, melatonin and sitagliptin induce ß-cell proliferation and ß-cell transdifferentiation, and it also reduces ß-cell apoptosis. Further, in both the models, combination therapy reduces fasting blood glucose levels, increases plasma insulin levels and glucose tolerance and promotes ß-cell proliferation, ß-cell transdifferentiation, and reduces ß-cell apoptosis. It can be concluded that combination therapy is superior to monotherapies in ameliorating diabetic manifestations, and it can be used as a future therapy for ß-cell regeneration in diabetes patients.

Calorie restriction potentiates the therapeutic potential of GABA in managing type 2 diabetes in a mouse model.

Dysfunctional adipocytes/ß-cells advance type 2 diabetes (T2D). Calorie restriction (CR) improves insulin sensitivity and fasting blood glucose (FBG) levels, while γ-aminobutyric acid (GABA) exerts regenerative effects. The impact of therapies was assessed by a high-fat diet (HFD) + streptozotocin (STZ) induced T2D mouse model. The mice were fed a CR diet (30% reduction of HFD) and treated with GABA (2.5 mg/kg i.p) for 5 weeks. Standard protocols were used to assess metabolic parameters. The mRNA expression was monitored by SYBR Green-qPCR in the targeted tissues. Oxygen consumption rate in the mitochondrial complexes was evaluated by oxytherm clark-type oxygen electrode. Pancreatic ß-cell regeneration and apoptosis were analysed by immunohistochemistry. CR + GABA combination therapy showed improved metabolic parameters compared to the monotherapies. We have observed improved transcript levels of G6Pase, PEPCK, Glycogen Phosphorylase, GLUT2 and GCK in liver; ACC and ATGL in adipose tissue. Also increased SIRT-1, PGC-1α and TFAM expression; up-regulated mitochondrial complexes I-III activities were observed. We have seen increased BrdU/Insulin and PDX1/Ngn3/Insulin co-positive cells in CR + GABA treated group with a reduction in apoptotic marker (TUNEL/Insulin co-positive cells). Our results indicate that CR in combination with GABA ameliorates T2D in HFD + STZ treated mice by GABA induced ß-cell regeneration, and CR mediated insulin sensitivity.

Intron specific polymorphic site of vaspin gene along with vaspin circulatory levels can influence pathophysiology of type 2 diabetes.

Vaspin, an insulin-sensitizing adipokine, has been associated with type 2 diabetes (T2D). The present study aimed to investigate the distribution of genotypes and high-risk alleles of vaspin genetic variants (rs77060950 G/T and rs2236242 A/T), in Gujarat subpopulation (India). Genomic DNA isolated from PBMCs was used to genotype vaspin polymorphisms by PCR-RFLP and ARMS-PCR from 502 controls and 478 patients. RNA isolated from visceral adipose tissue (VAT) of 22 controls and 20 patients was used to assess vaspin transcript levels by qPCR while the vaspin titre of the subjects was assayed using ELISA. Phenotypic characteristics of Fasting Blood Glucose (FBG), BMI and plasma lipid profile were estimated and analyzed for the genotype-phenotype correlation. We identified a significant association of rs2236242 A/T with T2D as the TT genotype conferred a 3.087-fold increased risk. The TT genotype showed association with increased FBG, BMI and Triglycerides levels. Increased GA, GT and TA haplotype frequencies, decreased VAT transcript and vaspin protein levels in T2D patients was observed, which were further negatively correlated with FBG and BMI. In conclusion, rs2274907 A/T polymorphism is strongly associated with reduced vaspin transcript and protein levels, and related metabolic alterations that may play a role in the advancement of T2D.

Publisher Correction: A genetic analysis identifies a haplotype at adiponectin locus: Association with obesity and type 2 diabetes.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A genetic analysis identifies a haplotype at adiponectin locus: Association with obesity and type 2 diabetes.

Adiponectin is a prime determinant of the status of insulin resistance. Association studies between adiponectin (ADIPOQ) gene single nucleotide polymorphisms (SNPs) and metabolic diseases have been reported earlier. However, results are ambiguous due to apparent contradictions. Hence, we investigated (1) the association between ADIPOQ SNPs: -11377C/G, +10211T/G, +45T/G and +276G/T for the risk towards type 2 diabetes (T2D) and, (2) genotype-phenotype association of these SNPs with various biochemical parameters in two cohorts. Genomic DNA of diabetic patients and controls from Gujarat and, Jammu and Kashmir (J&K) were genotyped using PCR-RFLP, TaqMan assay and MassArray. Transcript levels of ADIPOQ were assessed in visceral adipose tissue samples, and plasma adiponectin levels were estimated by qPCR and ELISA respectively. Results suggest: (i) reduced HMW adiponectin/total adiponectin ratio in Gujarat patients and its association with +10211T/G and +276G/T, and reduced ADIPOQ transcript levels in T2D, (ii) association of the above SNPs with increased FBG, BMI, TG, TC in Gujarat patients and (iii) increased GGTG haplotype in obese patients of Gujarat population and, (iv) association of -11377C/G with T2D in J&K population. Reduced HMW adiponectin, in the backdrop of obesity and ADIPOQ genetic variants might alter metabolic profile posing risk towards T2D.

Genetic variants of tumor necrosis factor-α and its levels: A correlation with dyslipidemia and type 2 diabetes susceptibility.

BACKGROUND & AIM: Tumor necrosis factor-α (TNF-α) and its genetic variants are implicated in the development of type 2 diabetes (T2D) as a result of systemic inflammation, dyslipidemia, and insulin resistance. The aim of the present study was to investigate i) single nucleotide polymorphisms (SNPs) of TNF-α and its association with altered TNF-α transcript levels and plasma concentrations ii) free fatty acid (FFA) concentrations as a marker for dyslipidemia and its association with TNF-α and iii) genotype-phenotype correlation analysis in T2D patients. METHODS: Plasma and PBMCs were separated from venous blood of 478 diabetic patients and 502 age-matched non-diabetic individuals. Genomic DNA was isolated from PBMCs and RNA was isolated from PBMCs and adipose tissue samples. PCR-RFLP was used for genotyping and qPCR to estimate TNF-α levels. TNF-α and FFA concentrations were estimated from plasma samples by ELISA. RESULTS: Our study suggests: i) involvement of TNF-α -857 C/T in T2D patients (p < 0.0001), ii) 2.072 and 6.7 fold elevation in TNF-α transcript levels in patients' PBMCs and adipose tissues respectively, increased plasma TNF-α (p = 0.0122) particularly in obese patients (p = 0.0405), increased plasma FFA (p = 0.0215) and, iii) association of TNF-α -238 G/A with body mass index (BMI) (p = 0.0270) and, -857 C/T with fasting blood glucose (FBG) (p = 0.0122) and triglycerides (TG) (p = 0.0015). Correlation analysis suggests that TNF-α concentrations are positively correlated with BMI (r = 0.3, p = 0.04) and negatively correlated with HDL (r = -0.39, p = 0.001) while the FFA concentrations are positively correlated with BMI (r = 0.35, p = 0.0004). CONCLUSION: It can be concluded that the genetic variant of TNF-α along with elevated TNF-α and FFA concentrations play a role in the development of dyslipidemia which could be a potent risk factor towards T2D in Gujarat population.

Association of melatonin &MTNR1B variants with type 2 diabetes in Gujarat population.

AIM/HYPOTHESIS: Melatonin is a circadian rhythm regulator and any imbalance in its levels can be related to various metabolic disorders. Melatonin and the genetic variants of Melatonin Receptor 1B (MTNR1B) are reported to be associated with Type 2 Diabetes (T2D) susceptibility. The aim of the present study was to investigate i) plasma melatonin levels ii) Single Nucleotide Polymorphisms (SNPs) of MTNR1B and iii) Genotype-phenotype correlation analysis in T2D patients. METHODS: Plasma and PBMCs were separated from venous blood of 478 diabetes patients and 502 controls. Genomic DNA was isolated from PBMCs. PCR-RFLP was used for genotyping. Melatonin was estimated from plasma samples by ELISA. RESULTS: Our study suggests: i) decreased plasma melatonin levels in T2D patients and, ii) association of MTNR1B rs10830963 GG genotype with increased Fasting Blood Glucose (FBG). CONCLUSION: It can be concluded that reduced titer of melatonin along with altered FBG due to MTNR1B genetic variant could act as a potent risk factor towards T2D in Gujarat population.