Drugs targeting β-cells have provided new options in the management of T2DM; however, their role in β-cell regeneration remains elusive. The recent emergence of cell-based therapies such as autologous bone marrow-derived mesenchymal stem cells (ABM-MSCs) and mononuclear cells (ABM-MNCs) seems to offer a pragmatic approach to augment β-cell function/mass. This study aims to examine the efficacy and safety of ABM-MSC and ABM-MNC transplantation in T2DM and explores alterations in glucose-insulin homeostasis by metabolic studies. Thirty patients of T2DM with duration of disease ≥5 years, receiving triple oral antidiabetic drugs along with insulin (≥0.4 IU/Kg/day) with HbA1c ≤7.5%(≤58.0 mmol/mol), were randomized to receive ABM-MSCs or ABM-MNCs through targeted approach and a sham procedure (n = 10 each). The primary endpoint was a reduction in insulin requirement by ≥50% from baseline, while maintaining HbA1c <7.0% (<53.0 mmol/mol) during 1-year follow-up. Six of 10 (60%) patients in both the ABM-MSC and ABM-MNC groups, but none in the control group, achieved the primary endpoint. At 12 months, there was a significant reduction in insulin requirement in ABM-MSC (P < 0.05) and ABM-MNC groups (P < 0.05), but not in controls (P = 0.447). There was a significant increase in second-phase C-peptide response during hyperglycemic clamp in the ABM-MNC (P < 0.05) group, whereas a significant improvement in insulin sensitivity index (P < 0.05) accompanied with an increase in insulin receptor substrate-1 gene expression was observed in the ABM-MSC group. In conclusion, both ABM-MSCs and ABM-MNCs result in sustained reduction in insulin doses in T2DM. Improvement in insulin sensitivity with MSCs and increase in C-peptide response with MNCs provide newer insights in cell-based therapies.

Background and aimHyperglycemia-mediated oxidative stress impedes cell-reparative process like autophagy, which has been implicated in impairment of β-cell function in type 2 diabetes mellitus (T2DM). However, the role of mitophagy (selective mitochondrial autophagy) in progression of hyperglycemia remains elusive. This study aimed to assess the impact of increasing severity of hyperglycemia on mitochondrial stress and mitophagy.Design and methodsA case–control study included healthy controls, subjects with prediabetes, newly diagnosed T2DM (NDT2DM) and advanced duration of T2DM (ADT2DM) (n = 20 each). Mitochondrial stress indices, transcriptional and translational expression of mitophagy markers (PINK1, PARKIN, MFN2, NIX, LC3-II, and LAMP-2) and transmission electron microscopic (TEM) studies were performed in peripheral blood mononuclear cells.ResultsWith mild hyperglycemia in subjects with prediabetes, to moderate to severe hyperglycemia in NDT2DM and ADT2DM, a progressive rise in mitochondrial oxidative stress was observed. Prediabetic subjects exhibited significantly increased expression of mitophagy-related markers and showed a positive association with HOMA-β, whereas, patients with NDT2DM and ADT2DM demonstrated decreased expression, with a greater decline in ADT2DM subjects. TEM studies revealed significantly reduced number of distorted mitochondria in prediabetics, as compared to the T2DM patients. In addition, receiver operating characteristic analysis showed HbA1C > 7% (53 mmol/mol) was associated with attenuated mitophagy.ConclusionIncreasing hyperglycemia is associated with progressive rise in oxidative stress and altered mitochondrial morphology. Sustenance of mitophagy at HbA1C < 7% (53 mmol/mol) strengthens the rationale of achieving HbA1C below this cutoff for good glycemic control. An “adaptive” increase in mitophagy may delay progression to T2DM by preserving the β-cell function in subjects with prediabetes.

Impaired mitochondrial autophagy (mitophagy) and NLRP3 inflammasome activation have been incriminated in the pathogenesis of T2DM. Metformin besides being an insulin sensitizer also induces autophagy; however, its effect on mitophagy and NLRP3 activation in patients with T2DM still remains elusive. Forty‐five drug‐naïve T2DM patients with HbA1C 7%‐9% (53‐75 mmol/mol) were randomly assigned to receive either metformin, voglibose, or placebo for 3 months, and were also recommended for lifestyle intervention programme (n = 15 each). Mitochondrial oxidative stress (MOS) parameters, qPCR and immunoblotting of mitophagy‐related markers (PINK1, PARKIN, MFN2, NIX, LC3‐II, LAMP2), p‐AMPKα (T172), and NLRP3 proteins, as well as transmission electron microscopy (TEM) for assessing mitochondrial morphology were performed in the mononuclear cells of study patients. Both metformin and voglibose showed a similar efficacy towards the reduction in HbA1c and MOS indices. However, multivariate ANCOVA divulged that mRNA and protein expression of mitophagy markers, NLRP3 and p‐AMPKα (T172), were significantly increased only with metformin therapy. Moreover, PINK1 expression displayed a significant positive association with HOMA‐β indices, and TEM studies further confirmed reduced distortions in mitochondrial morphology in the metformin group only. Our observations underscore that metformin upregulates mitophagy and subsequently ameliorates the altered mitochondrial morphology and function, independent of its glucose‐lowering effect. Further, restoration of normal mitochondrial phenotype may improve cellular function, including β‐cells, which may prevent further worsening of hyperglycaemia in patients with T2DM.

Increased oxidative stress in patients with type 2 diabetes mellitus (T2DM) results in abnormalities in cell repair processes, such as mitophagy, which compromises mitochondrial function and contributes to insulin resistance and β cell failure. Metformin, widely recommended in the management of T2DM, exerts its pleiotropic effects via 5ʹ‐AMP–activated protein kinase (AMPK); however, its effect on mitophagy remains elusive. Recent evidence demonstrates that peripheral blood mononuclear cells (PBMCs) express insulin receptors and the human organic cation transporter protein, and they are extensively being used as a surrogate for examining mitochondrial function in T2DM. Metformin treatment increased the formation of acidic vesicles and mitophagosomes, upregulated mitophagy markers, and enhanced mitophagic flux, as indicated by increased LC3‐II expression and reduced p62 protein levels. In addition, pretreatment with compound C (an AMPK inhibitor) significantly decreased the expression of mitophagy markers in metformin‐treated cells, indicating that metformin induces mitophagy via the AMPK pathway. In conclusion, metformin‐induced mitophagy may improve cellular function, including in β cells, by restoring normal mitochondrial phenotype, which may prove beneficial in patients with T2DM and other mitochondrial‐related diseases. Moreover, PBMCs may be used as a novel diagnostic biomarker for identifying mitochondrial disorders.

BackgroundInsulin resistance and insulin deficiency are the cardinal defects in the pathogenesis of type 2 diabetes mellitus (T2DM). Despite the plethora of anti-diabetic medications, drugs specifically targeting the β-cells are still desired. Stem cell therapy has emerged as a novel therapeutics strategy to target β-cells; however, their mechanism of action has not been well defined. This study aims to examine the efficacy and safety of autologous bone marrow-derived mononuclear cells (ABM-MNCs) transplantation in T2DM, and explores the mechanistic insights into stem cells action through metabolic studies.MethodsSeven T2DM patients with the duration of disease ≥5 years, receiving triple oral anti-diabetic drugs along with insulin (≥0.4 IU per kg per day) and HbA1c ≤ 7.5% (≤58.0 mmol/mol) were enrolled for ABM-MNCs administration through a targeted approach. The primary end-point was a reduction in insulin requirement by ≥50% from baseline, while maintaining HbA1c < 7.0% (<53.0 mmol/mol) with improvement in insulin secretion, and/or insulin sensitivity after ABM-MNCs transplantation.ResultsSix out of 7 (90%) patients achieved the primary end-point. At 6 months, there was a significant reduction in insulin requirement by 51% as compared to baseline (p < 0.003). This was accompanied by a significant increase in the 2nd phase C-peptide response during hyperglycemic clamp (p = 0.018), whereas there were no significant alterations in insulin sensitivity and glucose disposal rate during hyperinsulinemic–euglycemic clamp relative to the baseline. Other measures of β-cell indices like HOMA-β, and stimulated C-peptide response to glucagon and mixed meal tolerance test were non-contributory.ConclusionABM-MNCs transplantation results in significant reduction in insulin doses and improvement in C-peptide response in patients with T2DM. Metabolic studies may be more useful than conventional indices to predict β-cell function in patients with advanced duration of T2DM. Trial registration -Clinicaltrials.gov NCT01759823Electronic supplementary materialThe online version of this article (doi:10.1186/s13098-017-0248-7) contains supplementary material, which is available to authorized users.