Daniel J. Cuthbertson

Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscle

The nature of the deficit underlying age‐related muscle wasting remains controversial. To test whether it could be due to a poor anabolic response to dietary amino acids, we measured the rates of myofibrillar and sarcoplasmic muscle protein synthesis (MPS) in 44 healthy young and old men, of similar body build, after ingesting different amounts of essential amino acids (EAA). Basal rates of MPS were indistinguishable, but the elderly showed less anabolic sensitivity and responsiveness of MPS to EAA, possibly due to decreased intramuscular expression, and activation (phosphorylation) after EAA, of amino acid sensing/signaling proteins (mammalian target of rapamycin, mTOR; p70 S6 kinase, or p70S6k; eukaryotic initiation factor [eIF]4BP‐1; and eIF2B). The effects were independent of insulin signaling since plasma insulin was clamped at basal values. Associated with the anabolic deficits were marked increases in NFκB, the inflammation‐associated transcription factor. These results demonstrate first, EAA stimulate MPS independently of increased insulin availability; second, in the elderly, a deficit in MPS in the basal state is unlikely; and third, the decreased sensitivity and responsiveness of MPS to EAA, associated with decrements in the expression and activation of components of anabolic signaling pathways, are probably major contributors to the failure of muscle maintenance in the elderly. Countermeasures to maximize muscle maintenance should target these deficits.

Improved glycaemia correlates with liver fat reduction in obese, type 2 diabetes, patients given glucagon-like peptide-1 (GLP-1) receptor agonists.

Glucagon-like peptide-1 receptor agonists (GLP-1 RA) are effective for obese patients with type 2 diabetes mellitus (T2DM) because they concomitantly target obesity and dysglycaemia. Considering the high prevalence of non-alcoholic fatty liver disease (NAFLD) in patients with T2DM, we determined the impact of 6 months’ GLP-1 RA therapy on intrahepatic lipid (IHL) in obese, T2DM patients with hepatic steatosis, and evaluated the inter-relationship between changes in IHL with those in glycosylated haemoglobin (HbA1c), body weight, and volume of abdominal visceral and subcutaneous adipose tissue (VAT and SAT). We prospectively studied 25 (12 male) patients, age 50±10 years, BMI 38.4±5.6 kg/m2 (mean ± SD) with baseline IHL of 28.2% (16.5 to 43.1%) and HbA1c of 9.6% (7.9 to 10.7%) (median and interquartile range). Patients treated with metformin and sulphonylureas/DPP-IV inhibitors were given 6 months GLP-1 RA (exenatide, n = 19; liraglutide, n = 6). IHL was quantified by liver proton magnetic resonance spectroscopy (1H MRS) and VAT and SAT by whole body magnetic resonance imaging (MRI). Treatment was associated with mean weight loss of 5.0 kg (95% CI 3.5,6.5 kg), mean HbA1c reduction of 1·6% (17 mmol/mol) (0·8,2·4%) and a 42% relative reduction in IHL (−59.3, −16.5%). The relative reduction in IHL correlated with that in HbA1c (ρ = 0.49; p = 0.01) but was not significantly correlated with that in total body weight, VAT or SAT. The greatest IHL reduction occurred in individuals with highest pre-treatment levels. Mechanistic studies are needed to determine potential direct effects of GLP-1 RA on human liver lipid metabolism.

Polycystic Ovary Syndrome with Hyperandrogenism Is Characterized by an Increased Risk of Hepatic Steatosis Compared to Nonhyperandrogenic PCOS Phenotypes and Healthy Controls, Independent of Obesity and Insulin Resistance

CONTEXT Nonalcoholic fatty liver disease may be evident in women with polycystic ovary syndrome (PCOS), both conditions being associated with obesity and insulin resistance. However, few studies have accounted for the high prevalence of obesity in PCOS. OBJECTIVE The aim of this study was to determine whether PCOS is independently associated with hepatic steatosis, compared with healthy controls of similar age and body mass index (BMI), and whether steatosis is associated with hyperandrogenemia. DESIGN AND SETTING We conducted a cross-sectional, case-control study at two tertiary referral centers. PATIENTS Twenty-nine women with PCOS diagnosed by the Rotterdam criteria [aged 28 yr; 95% confidence interval (CI), 26-31; BMI, 33 kg/m2; 95% CI, 31-36] and 22 healthy controls (aged 29 yr; 95% CI, 28-31; BMI, 30 kg/m2; 95% CI, 28-33) were studied. METHODS Proton-magnetic resonance spectroscopy quantified hepatic and skeletal muscle fat; whole body magnetic resonance imaging quantified internal, visceral, and sc adipose tissue volumes. Differences were assessed between PCOS and controls using t tests, and between hyperandrogenic (HA) PCOS, PCOS with normal androgens (NA), and controls using analysis of covariance. RESULTS After statistical adjustment for BMI, HA-PCOS had significantly higher liver fat vs. NA-PCOS (3.7%; 95% CI, 0.6-13.1) and vs. controls (2.1%; 95% CI, 0.3-6.6). Similarly, after adjustment for homeostasis model assessment for insulin resistance, internal and visceral adipose tissue volumes, liver fat remained significantly greater in HA-PCOS compared to NA-PCOS and controls. CONCLUSION These data suggest that HA-PCOS is associated with hepatic steatosis, independent of obesity and insulin resistance.

5-Aminoimidazole-4-Carboxamide 1-β-d-Ribofuranoside Acutely Stimulates Skeletal Muscle 2-Deoxyglucose Uptake in Healthy Men

Activation of AMP-activated protein kinase (AMPK) in rodent muscle by exercise, metformin, 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside (AICAR), and adiponectin increases glucose uptake. The aim of this study was to determine whether AICAR stimulates muscle glucose uptake in humans. We studied 29 healthy men (aged 26 ± 8 years, BMI 25 ± 4 kg/m2 [mean ± SD]). Rates of muscle 2-deoxyglucose (2DG) uptake were determined by measuring accumulation of total muscle 2DG (2DG and 2DG-6-phosphate) during a primed, continuous 2DG infusion. The effects of AICAR and exercise on muscle AMPK activity/phosphorylation and 2DG uptake were determined. Whole-body glucose disposal was compared before and during AICAR with the euglycemic-hyperinsulinemic clamp. Muscle 2DG uptake was linear over 9 h (R2 = 0.88 ± 0.09). After 3 h, 2DG uptake increased 2.1 ± 0.8- and 4.7 ± 1.7-fold in response to AICAR or bicycle exercise, respectively. AMPK α1 and α2 activity or AMPK phosphorylation was unchanged after 20 min or 3 h of AICAR, but AMPK phosphorylation significantly increased immediately and 3 h after bicycle exercise. AICAR significantly increased phosphorylation of extracellular signal–regulated kinase 1/2, but phosphorylation of β-acetyl-CoA carboxylase, glycogen synthase, and protein kinase B or insulin receptor substrate-1 level was unchanged. Mean whole-body glucose disposal increased by 7% with AICAR from 9.3 ± 0.6 to 10 ± 0.6 mg · kg−1 · min−1 (P < 0.05). In healthy people, AICAR acutely stimulates muscle 2DG uptake with a minor effect on whole-body glucose disposal.

Endothelial function measured using flow‐mediated dilation in polycystic ovary syndrome: a meta‐analysis of the observational studies

Women with polycystic ovary syndrome (PCOS) demonstrate an increased prevalence of cardiovascular disease (CVD) risk factors. Previous researchers have compared flow‐mediated dilation (FMD), an early marker of CVD, in women with and without PCOS. Evidence for a PCOS‐mediated reduction in FMD remains equivocal, potentially because of study differences in cohort‐matching and measurement approaches. The aims of this systematic review and meta‐analysis were to examine to what extent FMD is impaired in PCOS and to explore the influence of potential moderators of FMD reduction, such as age and BMI.

Obesity-related metabolic dysfunction in dogs: a comparison with human metabolic syndrome

BackgroundRecently, metabolic syndrome (MS) has gained attention in human metabolic medicine given its associations with development of type 2 diabetes mellitus and cardiovascular disease. Canine obesity is associated with the development of insulin resistance, dyslipidaemia, and mild hypertension, but the authors are not aware of any existing studies examining the existence or prevalence of MS in obese dogs.Thirty-five obese dogs were assessed before and after weight loss (median percentage loss 29%, range 10-44%). The diagnostic criteria of the International Diabetes Federation were modified in order to define canine obesity-related metabolic dysfunction (ORMD), which included a measure of adiposity (using a 9-point body condition score [BCS]), systolic blood pressure, fasting plasma cholesterol, plasma triglyceride, and fasting plasma glucose. By way of comparison, total body fat mass was measured by dual-energy X-ray absorptiometry, whilst total adiponectin, fasting insulin, and high-sensitivity C-reactive protein (hsCRP) were measured using validated assays.ResultsSystolic blood pressure (P = 0.008), cholesterol (P = 0.003), triglyceride (P = 0.018), and fasting insulin (P < 0.001) all decreased after weight loss, whilst plasma total adiponectin increased (P = 0.001). However, hsCRP did not change with weight loss. Prior to weight loss, 7 dogs were defined as having ORMD, and there was no difference in total fat mass between these dogs and those who did not meet the criteria for ORMD. However, plasma adiponectin concentration was less (P = 0.031), and plasma insulin concentration was greater (P = 0.030) in ORMD dogs.ConclusionsIn this study, approximately 20% of obese dogs suffer from ORMD, and this is characterized by hypoadiponectinaemia and hyperinsulinaemia. These studies can form the basis of further investigations to determine path genetic mechanisms and the health significance for dogs, in terms of disease associations and outcomes of weight loss.

Human bone collagen synthesis is a rapid, nutritionally modulated process

We developed a direct assay of human bone collagen synthesis using [13C] or [15N] proline and applied it to determine the effects of feeding in young healthy men. Surprisingly, postabsorptive bone collagen synthesis is not sluggish, being ∼0.07%/h more rapid than that of muscle protein, and capable of being stimulated within 4 h of intravenous feeding by 66 ± 13%.

Peptide receptor radionuclide therapy with 90Y-DOTATATE/90Y-DOTATOC in patients with progressive metastatic neuroendocrine tumours: assessment of response, survival and toxicity

Background:Peptide receptor radionuclide therapy (PRRT) is an established treatment for patients with metastatic neuroendocrine tumours (NETs), although which factors are associated with an improved overall survival (OS) remains unclear. The primary aim of this study is to determine to what extent a radiological response to 90Y-DOTATOC/90Y-DOTATATE PRRT is associated with an improved OS. The association of biochemical and clinical response to OS were assessed as secondary outcome measures.Methods:A retrospective analysis was conducted on 57 patients: radiological response was classified using RECIST criteria, biochemical response was classified using WHO criteria and clinical response was assessed subjectively. Responses were recorded as positive response (PR), stable disease (SD) or progressive disease (PD), and survival analysed.Results:Radiological response was achieved in 71.5% (24.5% PR, 47% SD) and was associated with a greater OS (51 and 56 months, respectively), compared with PD (18 months). A biochemical or clinical response post PRRT were not associated with a statistically significant improvement in OS. However, when combined with radiological response a survival benefit was observed according to the number of outcomes (radiological, biochemical, clinical), in which a response was observed. Mild haematological toxicity was common, renal toxicity was rare.Conclusion:In patients with progressive metastatic NETs receiving 90Y-DOTATOC/90Y-DOTATATE PRRT, a radiological response with either a PR or a SD post therapy confers a significant OS benefit.

Presentation, management and outcomes in acute pituitary apoplexy: a large single-centre experience from the United Kingdom

To study the presentation, management and outcomes and to apply retrospectively the Pituitary Apoplexy Score (PAS) (United Kingdom (UK) guidelines for management of apoplexy) to a large, single‐centre series of patients with acute pituitary apoplexy.

External validation of the fatty liver index and lipid accumulation product indices, using 1H-magnetic resonance spectroscopy, to identify hepatic steatosis in healthy controls and obese, insulin-resistant individuals

BACKGROUND AND AIMS Simple clinical algorithms including the fatty liver index (FLI) and lipid accumulation product (LAP) have been developed as surrogate markers for non-alcoholic fatty liver disease (NAFLD), constructed using (semi-quantitative) ultrasonography. This study aimed to validate FLI and LAP as measures of hepatic steatosis, as determined quantitatively by proton magnetic resonance spectroscopy (1H-MRS). METHODS Data were collected from 168 patients with NAFLD and 168 controls who had undergone clinical, biochemical and anthropometric assessment. Values of FLI and LAP were determined and assessed both as predictors of the presence of hepatic steatosis (liver fat>5.5%) and of actual liver fat content, as measured by 1H-MRS. The discriminative ability of FLI and LAP was estimated using the area under the receiver operator characteristic curve (AUROC). As FLI can also be interpreted as a predictive probability of hepatic steatosis, we assessed how well calibrated it was in our cohort. Linear regression with prediction intervals was used to assess the ability of FLI and LAP to predict liver fat content. Further validation was provided in 54 patients with type 2 diabetes mellitus. RESULTS FLI, LAP and alanine transferase discriminated between patients with and without steatosis with an AUROC of 0.79 (IQR=0.74, 0.84), 0.78 (IQR=0.72, 0.83) and 0.83 (IQR=0.79, 0.88) respectively although could not quantitatively predict liver fat. Additionally, the algorithms accurately matched the observed percentages of patients with hepatic steatosis in our cohort. CONCLUSIONS FLI and LAP may be used to identify patients with hepatic steatosis clinically or for research purposes but could not predict liver fat content.