Factors affecting resting heart rate in free-living healthy humans

Resting heart rate (RHR) is a potential cardiac disease prevention target because it is strongly associated with cardiac morbidity and mortality, yet community-based monitoring of RHR remains in its infancy. Recently, smartwatches have become available enabling measurement with non-intrusive devices of relationships between RHR and other factors outside the laboratory. We carried out cross-sectional observational retrospective analysis of anonymised smartwatch data obtained by participants in their everyday lives between 2016 and 2021 in a single centre community-based study, using convenience sampling. Between participants, overall RHR means strongly or moderately inversely correlated with means of stand hour (SH), calculated VO(2) max, walking and running distance (WRD), steps and flights climbed (FC). Within participants, in quarterly averages, RHR inversely correlated moderately with frequency of standing (stand hours, SH). RHR also inversely correlated moderately with heart rate variability (HRV), consistent with the known impact of increasing parasympathetic dominance on RHR. These within participant correlations suggest that RHR might be modifiable by changes in SH and HRV within individuals. Indeed, analysing paired daily data, relationships between these three categories were dose dependent. 15 SH versus 5 SH associated with a reduction of 10 beats per minute in mean RHR and increase in mean HRV of 14 ms, respectively. We conclude that within individuals, RHR inversely correlates with frequency of standing and HRV, with paired daily measurements indicating effects are mediated that day. RHR also inversely correlates with fitness and activity measures between participants. Our findings provide initial community-based observational evidence supporting further prospective interventional investigation of frequency of standing or HRV modifiers, alongside more familiar interventions, for cardiac disease prevention

Identification and analysis of phosphodiesterase isoenzymes

The second messenger cAMP is involved in the mediation of a wide range of signals in response to a wide range of external stimuli, including processes as varied as neurotransmission, metabolism and embryonic development. Each of the components of the cAMP signalling system are encoded by families of genes. In the case of cAMP phosphodiesterases, the enzymes that hydrolyse cAMP, this variety produces proteins with different targeting, expression and kinetic characteristics. A full understanding of the differing functions of these isoenzymes may in the longer term allow drugs to be designed which allow specific interventions in human pathologies. To realise such an approach, it is important that each isoenzyme be identified and characterised. This thesis concentrates on the characterisation of four of these isoenzymes, namely PDE1B, PDE3B, PDE4A1 and PDE4A10. In chapter three of this thesis, I use immunoblotting of cell fractions to examine the particulate association of transiently expressed full-length PDE3B. I show solubilisation of full-length PDE3B for the first time. In addition to this I determine the solubility of two deletion mutants which delete a putative membrane association domain. I demonstrate that a mutant with a deleted putative membrane association domain is still particulate, which strongly suggests that PDE3B possesses additional membrane association determinants. I also present data which suggests that PDE3B can be stimulated by protein kinase B. In chapter four I examine a PKC-mediated induction of PDE1 in Chinese hamster ovary cells. There was no sequence information for Chinese hamster PDEs. This compelled me to design molecular probes to phylogenetically stable pieces of PDE1. Sequencing of amplification products of these probes reveal that PDE1B is the induced PDE1 form in Chinese hamster ovary cells. Selective isoforms of PKC appear to mediate this stimulation. Chapters five and six of this thesis are devoted to furthering knowledge of the number and primary structure of PDEs. In chapter five I identify mammalian homologues for the rat PDE RD1. Thus, RD1 becomes only the second PDE4A which has been identified in human and rat. The putative membrane association sequences of RD1 are perfectly conserved across a range of mammalian species, supporting the notion that the sequences may have a conserved functional role. Serendipitously, this work exposes a rodent-lineage specific deletion of apparently ancient PDE4A sequence. This finding, which may be associated with functional alterations, may be a first step in the production of single state PDE inhibitors, since it suggests a possible target for such inhibitors. The deletion may also be of considerable interest to molecular taxonomists as a phylogenetic marker with the potential to solve previously intractable controversies over rodent phylogeny. In chapter six of this thesis I identify, clone and express a novel human PDE4A splice variant, PDE4A10. I then make a survey of endogenous expression of this PDE in native brain and cell lines by RT-PCR. Furthermore, I identify almost the full open reading frame of the rat homologue of this splice variant. This PDE is therefore the third PDE4A which has been identified in both rat and human. The work in chapter six also makes a wider contribution, by describing a novel method for producing precise overlaps in clones of DNA made by a modification of shotgun cloning. Shotgun cloning was already the easiest way to fragment a large piece of DNA into smaller ones. The innovation to shotgun cloning that I describe makes it easier and extends its utility. The overlaps of DNA fragments that result will allow the shotgun fragments to be ordered as they appeared in the original DNA sequence and if the ordered fragments are sized, this will produce a restriction map for the contig. This approach is considerably faster than existing methods for producing DNA contigs and restriction maps. If it is taken up, the ease and speed of this new technique should significantly hasten sequencing projects such as the Human Genome Project

Defining Activity Thresholds Triggering a ‘Stand Hour’ for Apple Watch Users:A Cross-Sectional Study

Background:Sedentary behavior (SB) is one of the largest contributing factors increasing the risk of developing noncommunicable diseases, including cardiovascular disease and type 2 diabetes. Guidelines from the World Health Organization for physical activity suggest the substitution of SB with light physical activity. The Apple Watch contains a health metric known as the stand hour (SH). The SH is intended to record standing with movement for at least 1 minute per hour; however, the activity measured during the determination of the SH is unclear.Objective:In this cross-sectional study, we analyzed the algorithm used to determine time spent standing per hour. To do this, we investigated activity measurements also recorded on Apple Watches that influence the recording of an SH. We also aimed to estimate the values of any significant SH predictors in the recording of a SH.Methods:The cross-sectional study used anonymized data obtained in August 2022 from 20 healthy individuals gathered via convenience sampling. Apple Watch data were extracted from the Apple Health app through the use of a third-party app. Appropriate statistical models were fitted to analyze SH predictors.Results:Our findings show that active energy (AE) and step count (SC) measurements influence the recording of an SH. Comparing when an SH is recorded with when an SH is not recorded, we found a significant difference in the mean and median AE and SC. Above a threshold of 97.5 steps or 100 kJ of energy, it became much more likely that an SH would be recorded when each predictor was analyzed as a separate entity.Conclusions:The findings of this study reveal the pivotal role of AE and SC measurements in the algorithm underlying the SH recording; however, our findings also suggest that a recording of an SH is influenced by more than one factor. Irrespective of the internal validity of the SH metric, it is representative of light physical activity and might, therefore, have use in encouraging individuals through various means, for example, notifications, to reduce their levels of SB

Defining Activity Thresholds Triggering a ‘Stand Hour’ for Apple Watch Users:A Cross-Sectional Study

Background:Sedentary behavior (SB) is one of the largest contributing factors increasing the risk of developing noncommunicable diseases, including cardiovascular disease and type 2 diabetes. Guidelines from the World Health Organization for physical activity suggest the substitution of SB with light physical activity. The Apple Watch contains a health metric known as the stand hour (SH). The SH is intended to record standing with movement for at least 1 minute per hour; however, the activity measured during the determination of the SH is unclear.Objective:In this cross-sectional study, we analyzed the algorithm used to determine time spent standing per hour. To do this, we investigated activity measurements also recorded on Apple Watches that influence the recording of an SH. We also aimed to estimate the values of any significant SH predictors in the recording of a SH.Methods:The cross-sectional study used anonymized data obtained in August 2022 from 20 healthy individuals gathered via convenience sampling. Apple Watch data were extracted from the Apple Health app through the use of a third-party app. Appropriate statistical models were fitted to analyze SH predictors.Results:Our findings show that active energy (AE) and step count (SC) measurements influence the recording of an SH. Comparing when an SH is recorded with when an SH is not recorded, we found a significant difference in the mean and median AE and SC. Above a threshold of 97.5 steps or 100 kJ of energy, it became much more likely that an SH would be recorded when each predictor was analyzed as a separate entity.Conclusions:The findings of this study reveal the pivotal role of AE and SC measurements in the algorithm underlying the SH recording; however, our findings also suggest that a recording of an SH is influenced by more than one factor. Irrespective of the internal validity of the SH metric, it is representative of light physical activity and might, therefore, have use in encouraging individuals through various means, for example, notifications, to reduce their levels of SB

New Evidence for the Mechanism of Action of a Type-2 Diabetes Drug Using a Magnetic Bead-Based Automated Biosensing Platform

The mechanism of action (MOA) of the first line type-2 diabetes drug metformin remains unclear despite its widespread usage. However, recent evidence suggests that the mitochondrial copper (Cu)-binding action of metformin may contribute toward the drug’s MOA. Here, we present a novel biosensing platform for investigating the MOA of metformin using a magnetic microbead-based agglutination assay which has allowed us to demonstrate for the first time the interaction between Cu and metformin at clinically relevant low micromolar concentrations of the drug, thus suggesting a potential pathway of metformin’s blood-glucose lowering action. In this assay, cysteine-functionalized magnetic beadswere agglutinated in the presence of Cu due to cysteine’s Cu-chelation property. Addition of clinically relevant doses of metformin resulted in disaggregation of Cu-bridged bead-clusters, whereas the effect of adding a closely related but blood-glucose neutral drug propanediimidamide (PDI) showed completely different responses to the clusters. The entire assay was integrated in an automated microfluidics platform with an advanced optical imaging unit by which we investigated these aggregation–disaggregation phenomena in a reliable, automated, and user-friendly fashion with total assay time of 17 min requiring a sample (metformin/PDI) volume of 30 μL. The marked difference of Cu-binding action between the blood-glucose lowering drug metformin and its inactive analogue PDI thus suggests that metformin’s distinctive Cu-binding properties may be required for its effect on glucose homeostasis. The novel automated platform demonstrating this novel investigation thus holds the potential to be utilized for investigating significant and sensitive molecular interactions via magnetic bead-based agglutination assay

Molecular mechanism of action of metformin: old or new insights?

Metformin is the first-line drug treatment for type 2 diabetes. Globally, over 100 million patients are prescribed this drug annually. Metformin was discovered before the era of target-based drug discovery and its molecular mechanism of action remains an area of vigorous diabetes research. An improvement in our understanding of metformin's molecular targets is likely to enable target-based identification of second-generation drugs with similar properties, a development that has been impossible up to now. The notion that 5' AMP-activated protein kinase (AMPK) mediates the anti-hyperglycaemic action of metformin has recently been challenged by genetic loss-of-function studies, thrusting the AMPK-independent effects of the drug into the spotlight for the first time in more than a decade. Key AMPK-independent effects of the drug include the mitochondrial actions that have been known for many years and which are still thought to be the primary site of action of metformin. Coupled with recent evidence of AMPK-independent effects on the counter-regulatory hormone glucagon, new paradigms of AMPK-independent drug action are beginning to take shape. In this review we summarise the recent research developments on the molecular action of metformi

Level 9 CPD Module Educating for Food Sector Sustainability

Module Descriptor for lecturer professional development in Educating for Food Sustainability. In response to SDG 4.7, which requires learners acquire knowledge and skills for sustainability, this module addresses a gap identified by the National Strategy on Education for Sustainable Development in the ‘preparedness of lecturers to facilitate the type of participatory learning’ associated with balancing social and economic well-being with Earth’s ability to replenish its natural resources. For food-sector educators committed to embedding sustainability in their academic practice, this module aims to develop a community of practice, comprising faculty, students, industry and community that can support authentic and transformative living-lab experiences for a sustainable future of our food systems. Deploying inquiry-based, evidence-based and action-learning approaches, this module focuses on addressing future-of-food issues within a holistic framework informed by the 4 Cs of culture, campus, curriculum and community as a means for transforming food-sector higher education