Beneficial effects of l-arginine on reducing obesity: potential mechanisms and important implications for human health

Over the past 20 years, growing interest in the biochemistry, nutrition, and pharmacology of l-arginine has led to extensive studies to explore its nutritional and therapeutic roles in treating and preventing human metabolic disorders. Emerging evidence shows that dietary l-arginine supplementation reduces adiposity in genetically obese rats, diet-induced obese rats, finishing pigs, and obese human subjects with Type-2 diabetes mellitus. The mechanisms responsible for the beneficial effects of l-arginine are likely complex, but ultimately involve altering the balance of energy intake and expenditure in favor of fat loss or reduced growth of white adipose tissue. Recent studies indicate that l-arginine supplementation stimulates mitochondrial biogenesis and brown adipose tissue development possibly through the enhanced synthesis of cell-signaling molecules (e.g., nitric oxide, carbon monoxide, polyamines, cGMP, and cAMP) as well as the increased expression of genes that promote whole-body oxidation of energy substrates (e.g., glucose and fatty acids) Thus, l-arginine holds great promise as a safe and cost-effective nutrient to reduce adiposity, increase muscle mass, and improve the metabolic profile in animals and humans.     

Aryldiazenido derivatives: A new entry to the functionalization of Keggin polyoxometalates

A series of aryldiazenido polyoxomolybdates of the type (nBu₄N)₂[Mo₅O₁₃(OMe)₄(NNAr){Na(MeOH)}] (Ar = C₆F₅, 1; Ar = O₂N-o-C₆H₄, 2; Ar = O₂N-m-C₆H₄, 3; Ar = O₂N-p-C₆H₄, 4a; Ar = (O₂N)₂-o,p-C₆H₃, 5) have been obtained by controlled degradation of the parent compounds (nBu₄N)₃[Mo₆O₁₈(NNAr)] with NaOH in methanol. They have been characterized by elemental analysis and UV-Vis and IR spectroscopy. In addition, 4a has been characterized by ⁹⁵Mo NMR spectroscopy and the crystal structure of (nBu₄N)₂[Mo₅O₁₃(OMe)₄(NNC₆H₄-p-NO₂){Na(H₂O))]·H₂O (4b) has been determined by X-ray diffraction. The molecular structure of the anion of 4b features a lacunary Lindqvist-type anion [Mo₅O₁₃(OMe)₄(NNC₆H₄-p-NO₂)]³⁻ interacting with a sodium cation through the four terminal axial oxygen atoms. The 1:1 sodium complexes react with BaCl₂ and BiCl₃ to yield 2:1 complexes which have been isolated as (nBu₄N)₄[Ba{Mo₅O₁₃(OMe)₄(NNAr)}₂] (Ar = C₆F₅, 6; Ar = O₂N-p-C₆H₄, 7) and (nBu₄N)₃[Bi{Mo₅O₁₃(OMe)₄(NNAr)}₂] (Ar = C₆F₅, 8; Ar = O₂N-p-C₆H₄, 9). X-ray crystallography analysis of 9·Me₂CO has shown that the tetradentate [Mo₅O₁₃(OMe)₄(N₂C₆H₄-p-NO₂)]³⁻ anions provide a square-antiprismatic environment for Bi. In contrast, IR spectroscopy provides evidence for a square-prismatic environment of Ba in 6 and 7. In acetonitrile-methanol mixed solvent, [Mo₅O₁₃(OMe)₄(NNAr)]³⁻ and [PW₁₁O₃₉]⁷⁻, generated in situ by alkaline degradation of their respective parents, [Mo₆O₁₈(NNAr)]³⁻ and [PW₁₂O₄₀]³⁻, react together to give the Keggin-type diazenido compounds (nBu₄N)₄[PW₁₁O₃₉(MoNNAr)] (Ar = O₂N-o-C₆H₄, 10; Ar = O₂N-m-C₆H₄, 11; Ar = O₂N-p-C₆H₄, 12), which have been characterized by ³¹P and ¹⁸³W NMR spectroscopy.     

Fibrillin-2 is dispensable for peripheral nerve development,myelination and regeneration

The extracellular matrix of peripheral nerve is formed from a diverse set of macromolecules, including glycoproteins, collagens and proteoglycans. Recent studies using knockout animal models have demonstrated that individual components of the extracellular matrix play a vital role in peripheral nerve development and regeneration. In this study we identified fibrillin-1 and fibrillin-2, large modular structural glycoproteins, as components of the extracellular matrix of peripheral nerve. Previously it was found that fibrillin-2 null mice display joint contractures, suggesting a possible defect of the peripheral nervous system in these animals. Close examination of the peripheral nerves of fibrillin-2 deficient animals described here revealed some structural abnormalities in the perineurium, while general structure of the nerve and molecular composition of nerve extracellular matrix remained unchanged. We also found that in spite of the obvious motor function impairment, fibrillin-2 null mice failed to display changes of nerve conduction properties or nerve regeneration capacity. Based on the data obtained we can conclude that peripheral neuropathy should be excluded as the cause of the impairment of locomotory function and joint contractures observed in fibrillin-2 deficient animals.     

Eliminating accidental deviations to minimize generalization error and maximize replicability: Applications in connectomics and genomics

Replicability, the ability to replicate scientific findings, is a prerequisite for scientific discovery and clinical utility. Troublingly, we are in the midst of a replicability crisis. A key to replicability is that multiple measurements of the same item (e.g., experimental sample or clinical participant) under fixed experimental constraints are relatively similar to one another. Thus, statistics that quantify the relative contributions of accidental deviations—such as measurement error—as compared to systematic deviations—such as individual differences—are critical. We demonstrate that existing replicability statistics, such as intra-class correlation coefficient and fingerprinting, fail to adequately differentiate between accidental and systematic deviations in very simple settings. We therefore propose a novel statistic, discriminability, which quantifies the degree to which an individual’s samples are relatively similar to one another, without restricting the data to be univariate, Gaussian, or even Euclidean. Using this statistic, we introduce the possibility of optimizing experimental design via increasing discriminability and prove that optimizing discriminability improves performance bounds in subsequent inference tasks. In extensive simulated and real datasets (focusing on brain imaging and demonstrating on genomics), only optimizing data discriminability improves performance on all subsequent inference tasks for each dataset. We therefore suggest that designing experiments and analyses to optimize discriminability may be a crucial step in solving the replicability crisis, and more generally, mitigating accidental measurement error.     

Effectiveness of knowledge brokering and recommendation dissemination for influencing healthcare resource allocation decisions: A cluster randomised controlled implementation trial

BackgroundImplementing evidence into clinical practice is a key focus of healthcare improvements to reduce unwarranted variation. Dissemination of evidence-based recommendations and knowledge brokering have emerged as potential strategies to achieve evidence implementation by influencing resource allocation decisions. The aim of this study was to determine the effectiveness of these two research implementation strategies to facilitate evidence-informed healthcare management decisions for the provision of inpatient weekend allied health services.Methods and findingsThis multicentre, single-blinded (data collection and analysis), three-group parallel cluster randomised controlled trial with concealed allocation was conducted in Australian and New Zealand hospitals between February 2018 and January 2020. Clustering and randomisation took place at the organisation level where weekend allied health staffing decisions were made (e.g., network of hospitals or single hospital). Hospital wards were nested within these decision-making structures. Three conditions were compared over a 12-month period: (1) usual practice waitlist control; (2) dissemination of written evidence-based practice recommendations; and (3) access to a webinar-based knowledge broker in addition to the recommendations. The primary outcome was the alignment of weekend allied health provision with practice recommendations at the cluster and ward levels, addressing the adoption, penetration, and fidelity to the recommendations. The secondary outcome was mean hospital length of stay at the ward level. Outcomes were collected at baseline and 12 months later. A total of 45 clusters (n = 833 wards) were randomised to either control (n = 15), recommendation (n = 16), or knowledge broker (n = 14) conditions. Four (9%) did not provide follow-up data, and no adverse events were recorded. No significant effect was found with either implementation strategy for the primary outcome at the cluster level (recommendation versus control β 18.11 [95% CI −8,721.81 to 8,758.02] p = 0.997; knowledge broker versus control β 1.24 [95% CI −6,992.60 to 6,995.07] p = 1.000; recommendation versus knowledge broker β −9.12 [95% CI −3,878.39 to 3,860.16] p = 0.996) or ward level (recommendation versus control β 0.01 [95% CI 0.74 to 0.75] p = 0.983; knowledge broker versus control β −0.12 [95% CI −0.54 to 0.30] p = 0.581; recommendation versus knowledge broker β −0.19 [−1.04 to 0.65] p = 0.651). There was no significant effect between strategies for the secondary outcome at ward level (recommendation versus control β 2.19 [95% CI −1.36 to 5.74] p = 0.219; knowledge broker versus control β −0.55 [95% CI −1.16 to 0.06] p = 0.075; recommendation versus knowledge broker β −3.75 [95% CI −8.33 to 0.82] p = 0.102). None of the control or knowledge broker clusters transitioned to partial or full alignment with the recommendations. Three (20%) of the clusters who only received the written recommendations transitioned from nonalignment to partial alignment. Limitations include underpowering at the cluster level sample due to the grouping of multiple geographically distinct hospitals to avoid contamination.ConclusionsOwing to a lack of power at the cluster level, this trial was unable to identify a difference between the knowledge broker strategy and dissemination of recommendations compared with usual practice for the promotion of evidence-informed resource allocation to inpatient weekend allied health services. Future research is needed to determine the interactions between different implementation strategies and healthcare contexts when translating evidence into healthcare practice.Trial registrationAustralian New Zealand Clinical Trials Registry ACTRN12618000029291.

In a cluster randomized controlled implementation trial, Dr. Mitchell N Sarkies and colleagues examine the effectiveness of knowledge brokering and recommendation dissemination in influencing healthcare resource allocation decisions in Australia and New Zealand.     

Interleukin-6 gene expression is increased in insulin-resistant rat skeletal muscle following insulin stimulation

IL-6 expression in skeletal muscle is stimulated by contractions. We sought to examine whether hyperinsulinaemia increases IL-6 mRNA in skeletal muscle and whether any increase is modified in insulin resistant muscle. We hypothesized that intramuscular IL-6 mRNA would be increased in response to insulin, but such an affect would be unaffected by insulin resistance because the primary insulin sensitive signalling protein responsible for activating IL-6 functions normally in insulin resistant muscle. Transgenic rats over-expressing the gluconeogenic regulatory enzyme phosphoenolpyruvate carboxykinase (PEPCK) were studied. White gastrocnemius muscle samples were obtained under hyperinsulinaemic, euglycaemic clamp (4 mU kg(-1)min(-1) insulin, plasma glucose concentration 4-6 mmol L(-1)) and basal conditions in both PEPCK (basal n=4; insulin n=5) and wild-type (CON) (basal n=5; insulin n=4) rats, which were previously injected with a bolus of 2-[1-14C]deoxyglucose (2-DG) into the carotid artery. Muscle samples were assayed for 2-DG uptake and IL-6 mRNA. No differences in 2-DG uptake or IL-6 mRNA were observed when comparing groups under basal conditions. Under clamp conditions, 2-DG uptake was lower (P<0.05) in PEPCK compared with CON. Insulin stimulation in CON did not change IL-6 mRNA compared with basal levels. In contrast, there was an approximately 8-fold increase (P<0.05) in IL-6 mRNA in insulin-stimulated PEPCK compared with CON basal levels. Insulin stimulation increases IL-6 gene expression in insulin resistant, but not healthy, skeletal muscle, suggesting that IL-6 expression in skeletal muscle is sensitive to changes in insulin in circumstances of insulin resistance. It is likely that the differences observed when comparing healthy with insulin resistant muscle are due to the differential activation of insulin sensitive signalling proteins responsible for activating IL-6.     

Cholesterol gallstone formation in overweight mice establishes that obesity per se is not linked directly to cholelithiasis risk

The relationship between obesity and cholesterol cholelithiasis is not well understood at physiologic or genetic levels. To clarify whether obesity per se leads to increased prevalence of cholelithiasis, we examined cholesterol gallstone susceptibility in three polygenic (KK/H1J, NON/LtJ, NOD/LtJ) and five monogenic [carboxypeptidase E (Cpe (fat)), agouti yellow (A(y)), tubby (tub), leptin (Lep(ob)), leptin receptor (Lepr (db))] murine models of obesity during ingestion of a lithogenic diet containing dairy fat, cholesterol, and cholic acid. At 8 weeks on the diet, one strain of polygenic obese mice was resistant whereas the others revealed low or intermediate prevalence rates of cholelithiasis. Monogenic obese mice showed distinct patterns with either high or low gallstone prevalence rates depending upon the mutation. Dysfunction of the leptin axis, as evidenced by the Lep(ob) and the Lepr (db) mutations, markedly reduced gallstone formation in a genetically susceptible background strain, indicating that in mice with this genetic background, physiologic leptin homeostasis is a requisite for cholesterol cholelithogenesis. In contrast, the Cpe (fat) mutation enhanced the prevalence of cholelithiasis markedly when compared with the background strain. Since CPE converts many prohormones to hormones, a deficiency of biologically active cholecystokinin is a likely contributor to enhanced susceptibility to cholelithiasis through compromising gallbladder contractility and small intestinal motility. Because some murine models of obesity increased, whereas others decreased cholesterol gallstone susceptibility, we establish that cholesterol cholelithiasis in mice is not simply a secondary consequence of obesity per se. Rather, specific genes and distinct pathophysiological pathways are responsible for the shared susceptibility to both of these common diseases.