Maternal insulin sensitivity is associated with oral glucose-induced changes in fetal brain activity

Aims/hypothesis

Fetal programming plays an important role in the pathogenesis of type 2 diabetes. The aim of the present study was to investigate whether maternal metabolic changes during OGTT influence fetal brain activity.

Methods

Thirteen healthy pregnant women underwent an OGTT (75 g). Insulin sensitivity was determined by glucose and insulin measurements at 0, 60 and 120 min. At each time point, fetal auditory evoked fields were recorded with a fetal magnetoencephalographic device and response latencies were determined.

Results

Maternal insulin increased from a fasting level of 67?±?25 pmol/l (mean ± SD) to 918?±?492 pmol/l 60 min after glucose ingestion and glucose levels increased from 4.4?±?0.3 to 7.4?±?1.1 mmol/l. Over the same time period, fetal response latencies decreased from 297?±?99 to 235?±?84 ms (p?=?0.01) and then remained stable until 120 min (235?±?84 vs 251?±?91 ms, p?=?0.39). There was a negative correlation between maternal insulin sensitivity and fetal response latencies 60 min after glucose ingestion (r?=?0.68, p?=?0.02). After a median split of the group based on maternal insulin sensitivity, fetuses of insulin-resistant mothers showed a slower response to auditory stimuli (283?±?79 ms) than those of insulin-sensitive mothers (178?±?46 ms, p?=?0.03).

Conclusions/interpretation

Lower maternal insulin sensitivity is associated with slower fetal brain responses. These findings provide the first evidence of a direct effect of maternal metabolism on fetal brain activity and suggest that central insulin resistance may be programmed during fetal development.     

Breast-feeding and maternal risk of type 2 diabetes: a prospective study and meta-analysis

Aims/hypothesis

We aimed to examine the association between breast-feeding and maternal risk of type 2 diabetes and to investigate whether this association is mediated by anthropometric and biochemical factors.

Methods

A case–cohort study nested within the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam Study between 1994 and 2005 including 1,262 childbearing women (1,059 in a random sub-cohort and 203 incident cases) mainly aged between 35 and 64 years at baseline was applied. Self-reported lifetime duration of breast-feeding was assessed by questionnaire. Blood samples were used for biomarker measurement (HDL-cholesterol, triacylglycerols, C-reactive protein, fetuin-A, γ-glutamyltransferase, adiponectin). A systematic literature search and meta-analysis was conducted of prospective cohort studies investigating breast-feeding and risk of type 2 diabetes.

Results

The HR for each additional 6 months of breast-feeding was 0.73 (95% CI 0.56, 0.94) in EPIC-Potsdam. Meta-analysis of three previous prospective studies and the current study revealed an inverse association between breast-feeding duration and risk of diabetes (pooled HR for lifetime breast-feeding duration of 6–11 months compared with no breast-feeding 0.89; 95% CI 0.82, 0.97). Adjustment for BMI and waist circumference attenuated the association (HR per six additional months in EPIC-Potsdam 0.80; 95% CI 0.61, 1.04). Further controlling for potentially mediating biomarkers largely explained this association (HR 0.89; 95% CI 0.68, 1.16).

Conclusions/interpretation

Longer duration of breast-feeding may be related to a lower risk of diabetes. This potentially protective effect seems to be reflected by a more favourable metabolic profile; however, the role of body weight as a mediator or confounder remains uncertain.     

Thermotropic liquid crystals from biomacromolecules

Complexation of biomacromolecules (e.g., nucleic acids, proteins, or viruses) with surfactants containing flexible alkyl tails, followed by dehydration, is shown to be a simple generic method for the production of thermotropic liquid crystals. The anhydrous smectic phases that result exhibit biomacromolecular sublayers intercalated between aliphatic hydrocarbon sublayers at or near room temperature. Both this and low transition temperatures to other phases enable the study and application of thermotropic liquid crystal phase behavior without thermal degradation of the biomolecular components.Liquid crystals (LCs) play an important role in biology because their essential characteristic, the combination of order and mobility, is a basic requirement for self-organization and structure formation in living systems (1–3). Thus, it is not surprising that the study of LCs emerged as a scientific discipline in part from biology and from the study of myelin figures, lipids, and cell membranes (4). These and the LC phases formed from many other biomolecules, including nucleic acids (5, 6), proteins (7, 8), and viruses (9, 10), are classified as lyotropic, the general term applied to LC structures formed in water and stabilized by the distinctly biological theme of amphiphilic partitioning of hydrophilic and hydrophobic molecular components into separate domains. However, the principal thrust and achievement of the study of LCs has been in the science and application of thermotropic materials, structures, and phases in which molecules that are only weakly amphiphilic exhibit LC ordering by virtue of their steric molecular shape, flexibility, and/or weak intermolecular interactions [e.g., van der Waals and dipolar forces (11)]. These characteristics enable thermotropic LCs (TLCs) to adopt a wide variety of exotic phases and to exhibit dramatic and useful responses to external forces, including, for example, the electro-optic effects that have led to LC displays and the portable computing revolution. This general distinction between lyotropic LCs and TLCs suggests there may be interesting possibilities in the development of biomolecular or bioinspired LC systems in which the importance of amphiphilicity is reduced and the LC phases obtained are more thermotropic in nature. Such biological TLC materials are very appealing for several reasons. Most biomacromolecules were extensively characterized in aqueous environments, but in TLC phases, their solvent-free properties and functions could be investigated in a state in which no or only traces of water are present. Water exhibits a high dielectric constant and has the ability to form hydrogen bonds, greatly influencing the structure and functions of biomacromolecules or compromising electronic properties such as charge transport (12–15). Indeed, anhydrous TLC systems containing glycolipids (16–19), ferritin (20), and polylysine have been reported (21–23). However, a general approach to fabricating TLCs based on nucleic acids, polypeptides, proteins, and protein assemblies of large molecular weights such as virus particles remains elusive.Here we propose that the combination of biomaterials with suitably chosen surfactants, followed by dehydration, can be effectively applied as a simple generic scheme for producing biomacromolecular-based TLCs. We demonstrate that biological TLCs can be made from a remarkable range of biomolecules and bio-inspired molecules, including nucleic acids, polypeptides, fusion proteins, and viruses. TLC materials typically combine rigid or semirigid anisometric units, which introduce orientational anisotropy, with flexible alkyl chains, which suppress crystallization (24). In the present experiments, negatively charged biomolecules and bio-inspired molecules act as rigid parts, and cationic surfactants make up the flexible units to produce TLC phases with remarkably low LC-isotropic clearing temperatures, which is another TLC signature. Electrostatic interactions couple these rigid and flexible components into hybrid assemblies, which then order into lamellar phases of alternating rigid and flexible layers (Fig. 1) stabilized by the tendency in TLCs for rigid and flexible to spatially segregate (25).Open in a separate windowFig. 1.Proposed structures of TLCs formed by the biological building blocks complexed with surfactants, showing sketches of various lamellar phases and the corresponding phase transition temperatures (°C). The lamellar bilayer structures are made of, alternately, a sublayer of the biomacromolecules and an interdigitated sublayer of the surfactants, where the negatively charged parts of the biomolecules (e.g., phosphate groups of ssDNA and ssRNA, glutamate residues of supercharged ELPs, and N-terminal glutamate and aspartate residues of pVIII protein in phages) electrostatically interact with the cationic head groups of the surfactants. For the ssDNA–DOAB and ssRNA–DOAB smectic TLCs, the oligonucleotides are randomly orientated in the DNA (RNA) sublayers. For the ELP–DDAB complexes, in addition to the bilayer smectic phase, a modulated smectic (Sm_mod) phase is observed at lower temperature. For the phage–DOAB–DDAB lamellar structures, rodlike virus particles are embedded in a sublayer between interdigitated surfactants with additional in-plane orientational order.     

Metformin and phenformin deplete tricarboxylic acid cycle and glycolytic intermediates during cell transformation and NTPs in cancer stem cells

Metformin, a first-line diabetes drug linked to cancer prevention in retrospective clinical analyses, inhibits cellular transformation and selectively kills breast cancer stem cells (CSCs). Although a few metabolic effects of metformin and the related biguanide phenformin have been investigated in established cancer cell lines, the global metabolic impact of biguanides during the process of neoplastic transformation and in CSCs is unknown. Here, we use LC/MS/MS metabolomics (>200 metabolites) to assess metabolic changes induced by metformin and phenformin in an Src-inducible model of cellular transformation and in mammosphere-derived breast CSCs. Although phenformin is the more potent biguanide in both systems, the metabolic profiles of these drugs are remarkably similar, although not identical. During the process of cellular transformation, biguanide treatment prevents the boost in glycolytic intermediates at a specific stage of the pathway and coordinately decreases tricarboxylic acid (TCA) cycle intermediates. In contrast, in breast CSCs, biguanides have a modest effect on glycolytic and TCA cycle intermediates, but they strongly deplete nucleotide triphosphates and may impede nucleotide synthesis. These metabolic profiles are consistent with the idea that biguanides inhibit mitochondrial complex 1, but they indicate that their metabolic effects differ depending on the stage of cellular transformation.Altered metabolism is a hallmark of malignantly transformed cells. Cancer risk is linked to metabolic syndrome, a disease state that includes obesity, type 2 diabetes, high cholesterol, and atherosclerosis. Retrospective studies of type 2 diabetes patients treated with metformin, the most widely prescribed antidiabetic drug, show a strong correlation between drug intake and reduced tumor incidence or reduced cancer-related deaths (1–4).In the breast lineage, metformin inhibits growth of cancer cell lines (5–7), blocks transformation in a Src-inducible cell system (8, 9), and selectively inhibits the growth of cancer stem cells (CSCs) (8). As a consequence of its selective effects on CSCs, combinatorial therapy of metformin and standard chemotherapeutic drugs (doxorubicin, paclitaxel, and cisplatin) increases tumor regression and prolongs remission in mouse xenografts (8, 10). In addition, metformin can decrease the chemotherapeutic dose for prolonging tumor remission in xenografts involving multiple cancer types (10).Phenformin, a related biguanide and formerly used diabetes drug, acts as an anticancer agent in tumors including lung, lymphoma, and breast cancer with a greater potency than metformin. Phenformin mediates antineoplastic effects at a lower concentration than metformin in cell lines, a PTEN-deficient mouse model, breast cancer xenografts, and drug-induced mitochondrial impairment (11–14). The chemical similarities of these biguanides, as well as their similar effects in diabetes and cancer, have led to the untested assumption that phenformin is essentially a stronger version of metformin.In a Src-inducible model of cellular transformation and CSC formation, multiple lines of evidence suggest that metformin inhibits a signal transduction pathway that results in an inflammatory response (15). In the context of atherosclerosis, metformin inhibits NF-κB activation and the inflammatory response via a pathway involving AMP kinase (AMPK) and the tumor suppressor PTEN (16, 17). As metformin alters energy metabolism in diabetics, we speculated that metformin might block a metabolic stress response that stimulates the inflammatory pathway (15). However, very little is known about the metabolic changes that inhibit the inflammatory pathway.Previous studies on metformin-induced metabolic effects in cancer have focused on single metabolic alterations or pathways in already established cancer cell lines. Metformin leads to activation of AMPK, which plays a key role in insulin signaling and energy sensing (18). Metformin can reduce protein synthesis via mTOR inhibition (19). In addition, metformin may directly impair mitochondrial respiration through complex I inhibition and has been described to boost glycolysis as a compensation mechanism (14, 20). In this regard, lactic acidosis can be a side effect of metformin and phenformin treatment of diabetic patients, presumably because inhibition of complex I prevents NADH oxidation, thereby leading to a requirement for cytosolic NADH to be oxidized by the conversion of pyruvate to lactate. There is some knowledge about the metabolic effects of metformin (21, 22), but very little is known about the specific metabolic alterations linking biguanides to inhibition of neoplastic transformation.Here, we perform a metabolomic analysis on the effects of metformin and phenformin in a Src-inducible model of transformation and in CSCs. This inducible model permits an analysis of the transition from nontransformed to transformed cells in an isogenic cell system and hence differs from analyses of already established cancer cell lines. We studied CSCs to address why this population, which is resistant to standard chemotherapeutics and hypothesized to be a major reason for tumor recurrence, is selectively inhibited by metformin. Our results indicate the metabolic effects of metformin and phenformin are remarkably similar to each other, with only a few differences. Both biguanides dramatically decrease tricarboxylic acid (TCA) cycle intermediates in the early stages of transformation, and they inhibit the boost in select glycolytic intermediates that normally occurs with transformation along with increases in glycerol 3-phosphate and lactate, which are metabolites branching from glycolysis. Unexpectedly, in CSCs, biguanides have only marginal effects on glycolytic and TCA cycle metabolites, but they severely decrease nucleotide triphosphates. These detailed metabolic analyses provide independent support for the idea that metformin inhibits mitochondrial complex 1 (14, 20), and they indicate that the metabolic effects of biguanides depend on the stage of the cellular transformation.     

Evaluating glucose-lowering treatment in older people with diabetes: Lessons from the IMPERIUM trial

Understanding the benefits and risks of treatments to be used by older individuals (≥65 years old) is critical for informed therapeutic decisions. Glucose-lowering therapy for older patients with diabetes should be tailored to suit their clinical condition, comorbidities and impaired functional status, including varying degrees of frailty. However, despite the rapidly growing population of older adults with diabetes, there are few dedicated clinical trials evaluating glucose-lowering treatment in older people. Conducting clinical trials in the older population poses multiple significant challenges. Despite the general agreement that individualizing treatment goals and avoiding hypoglycaemia is paramount for the therapy of older people with diabetes, there are conflicting perspectives on specific glycaemic targets that should be adopted and on use of specific drugs and treatment strategies. Assessment of functional status, frailty and comorbidities is not routinely performed in diabetes trials, contributing to insufficient characterization of older study participants. Moreover, significant operational barriers and problems make successful enrolment and completion of such studies difficult. In this review paper, we summarize the current guidelines and literature on conducting such trials, as well as the learnings from our own clinical trial (IMPERIUM) that assessed different glucose-lowering strategies in older people with type 2 diabetes. We discuss the importance of strategies to improve study design, enrolment and attrition. Apart from summarizing some practical advice to facilitate the successful conduct of studies, we highlight key gaps and needs that warrant further research.