Margot Umpleby

Increased hepatic secretion of very-low-density-lipoprotein apolipoprotein B-100 in heterozygous familial hypercholesterolaemia: a stable isotope study

We have measured the hepatic secretion of very-low-density-lipoprotein apolipoprotein B-100 (VLDL apo B) in 6 patients with heterozygous familial hypercholesterolaemia (FH) (4 males, 2 females, age 47.0 +/- 2.7 years (mean +/- S.E.M.), weight 71.0 +/- 5.3 kg) and 6 normocholesterolaemic subjects matched for age, weight and sex (4 males, 2 females, age 47.5 +/- 3.1 years, weight 70.0 +/- 4.4 kg) using a stable isotope method. Each subject received a primed, constant infusion of [I-13C]leucine and isotopic enrichment of VLDL apo B was determined using gas-chromatography mass-spectrometry (GCMS). Mean plasma low-density-lipoprotein (LDL) cholesterol and apo B concentrations in the FH group were more than twice that in the control group (FH, 8.5 +/- 0.5 mmol/l vs. controls, 3.3 +/- 0.2 mmol/l, P < 0.001; and FH, 2.0 +/- 0.1 g/l vs. controls, 1.0 +/- 0.04 g/l, P < 0.0001, respectively). Plasma triglyceride (TG) and high-density-lipoprotein (HDL) cholesterol concentrations were not significantly different between the two groups. Although the fractional secretion rates of VLDL apo B were similar (FH, 14.3 +/- 3.6 pools/day vs. controls, 11.6 +/- 1.7 pools/day, P = 0.53), VLDL apo B pool size and VLDL apo B absolute secretion rates (ASR) were significantly higher in the FH group (FH, 234.2 +/- 27.8 mg vs. controls, 66.3 +/- 13.5 mg, P < 0.001; and FH, 51.4 +/- 17.9 mg/kg per day vs. controls, 9.4 +/- 1.1 mg/kg per day, P < 0.02, respectively). We conclude that FH is associated with increased hepatic secretion of VLDL apo B and that this may contribute to the elevated concentration of LDL-cholesterol. The findings are also consistent with the hypothesis that in FH increased hepatic cholesterol availability (due to increased uptake of LDL-cholesterol via the receptor-independent pathway) stimulates hepatic secretion of VLDL apo B.

rhIGF-I Administration Reduces Insulin Requirements, Decreases Growth Hormone Secretion, and Improves the Lipid Profile in Adults With IDDM

IDDM is associated with elevated circulating levels of growth hormone (GH) and reduced insulin-like growth factor I (IGF-I). GH antagonizes the action of insulin-increasing insulin requirements in IDDM. The effects of subcutaneously administered rhIGF-I on glycemie control, insulin requirements, and GH secretion were studied in eight adults with IDDM. Patients received either placebo or rhIGF-I (50 pg/kg b.i.d.) for 19 days in a randomized, double-blind, parallel-design, placebo-controlled trial. Overnight GH, plasma glucose, free insulin, IGF-I, fructosamine, and lipid profiles were assessed during this period. rhIGF-I therapy increased IGF-I concentration from 117.1 ± 14.2 (mean ± SE) ng/ml (baseline) to 310.5 ± 40.6 and 257.1 ± 41.2 ng/ml on day 5 (P < 0.01 vs. baseline) and day 20 (P < 0.01 vs. baseline), respectively. After 19 days of rhIGF-I treatment, fructosamine concentrations were unchanged compared with baseline (439 ± 32 vs. 429 ± 35 μmol/l, day –1 vs. day 20, respectively), yet insulin requirements were decreased by ∼45% (0.67 ± 0.08 vs. 0.36 ± 0.07 U · kg−1 · day−1, day –1 vs. day 19, respectively, P < 0.005). After 4 days of rhIGF-I therapy, there was a decrease in free insulin levels (8.38 ± 1.47 vs. 4.98 ± 0.84 mU/l, P < 0.05), mean overnight GH concentration (12.6 ± 3.3 vs. 3.8 ± 2.1 mU/l, P = 0.05), and total cholesterol and triglycerides (4.68 ± 0.31 vs. 4.25 ± 0.35 mmol/l, P < 0.05, 1.27 ± 0.19 vs. 0.95 ± 0.21 mmol/l, P < 0.001, respectively). There was no change in any variable in the placebo-treated patients. This study demonstrates that subcutaneous administration of rhIGF-I decreases insulin requirements and improves the plasma lipid profile while maintaining glycemie control in adults with IDDM. The excess nocturnal release of GH, characteristic of IDDM, is also decreased by rhIGF-I therapy. Exogenous rhIGF-I therapy may have a role in the treatment of adults with IDDM, particularly in the setting of abnormal lipids and a high insulin requirement.

Simvastatin decreases the hepatic secretion of very‐low‐density lipoprotein apolipoprotein B‐100 in heterozygous familial hypercholesterolaemia: pathophysiological and therapeutic implications

Abstract. We studied six patients with heterozygous familial hypercholesterolaemia (FH) before and after 8 weeks of treatment with simvastatin (40 mg day‐1), an inhibitor of 3‐hydroxy‐3‐methyl‐glutaryl‐Coenzyme A. Simvastatin decreased plasma low‐density lipoprotein (LDL) cholesterol by 43% (P= 0.002), triglycerides by 27% (P= 0.05) and mevalonic acid (a measure of in vivo cholesterol synthesis) by 20% (P= 0.002); high‐density lipoprotein cholesterol increased by 17% (P= 0.02). The hepatic secretion rate of very‐low‐density lipoprotein apolipoprotein B‐100 (VLDL apoB) was measured directly using a primed, constant intravenous infusion of l‐[13C]‐leucine with monitoring of the isotopic enrichment of apoB by gas chromatography‐mass spectrometry; fractional secretion rate (FSR) was derived using a mono‐exponential function. Simvastatin decreased the FSR, ASR and pool size of VLDL apoB by 17% (14.3 (SEM 3.6)) vs. (11.9 (SEM 3.5) pools day‐1, P= 0.10), 83% (51.4 (SEM 17.9) vs. (8.6 (SEM 1.4), P= 0.007mgkg‐1day‐1) and 65% (234.2 (SEM 30.4) vs. 82.6 (SEM 24.0)mg, P= 0.02), respectively. The change in the ASR of VLDL apoB was significantly correlated with the change in plasma LDL cholesterol concentration (P= 0.04), but not with the change of triglyceride or mevalonic acid. We conclude that the hepatic secretion of VLDL apoB in FH is decreased by simvastatin, which may partly explain the fall in plasma cholesterol. This effect does not appear to be directly related to the inhibition of cholesterol synthesis and may be due to decreased hepatic delivery of cholesterol esters via the LDL receptor‐independent pathway, but these mechanisms require further investigation.

Metabolically healthy and unhealthy obesity: differential effects on myocardial function according to metabolic syndrome, rather than obesity

Background:The term ‘metabolically healthy obese (MHO)’ is distinguished using body mass index (BMI), yet BMI is a poor index of adiposity. Some epidemiological data suggest that MHO carries a lower risk of cardiovascular disease (CVD) or mortality than being normal weight yet metabolically unhealthy.Objectives:We aimed to undertake a detailed phenotyping of individuals with MHO by using imaging techniques to examine ectopic fat (visceral and liver fat deposition) and myocardial function. We hypothesised that metabolically unhealthy individuals (irrespective of BMI) would have adverse levels of ectopic fat and myocardial dysfunction compared with MHO individuals.Subjects:Individuals were categorised as non-obese or obese (BMI ⩾30 kg m−2) and as metabolically healthy or unhealthy according to the presence or absence of metabolic syndrome.Methods:Sixty-seven individuals (mean±s.d.: age 49±11 years) underwent measurement of (i) visceral, subcutaneous and liver fat using magnetic resonance imaging and proton magnetic resonance spectroscopy, (ii) components of metabolic syndrome, (iii) cardiorespiratory fitness and (iv) indices of systolic and diastolic function using tissue Doppler echocardiography.Results:Cardiorespiratory fitness was similar between all groups; abdominal and visceral fat was highest in the obese groups. Compared with age- and BMI-matched metabolically healthy counterparts, the unhealthy (lean or obese) individuals had higher liver fat and decreased early diastolic strain rate, early diastolic tissue velocity and systolic strain indicative of subclinical systolic and diastolic dysfunction. The magnitude of dysfunction correlated with the number of components of metabolic syndrome but not with BMI or with the degree of ectopic (visceral or liver) fat deposition.Conclusions:Myocardial dysfunction appears to be related to poor metabolic health rather than simply BMI or fat mass. These data may partly explain the epidemiological evidence on CVD risk relating to the different obesity phenotypes.

Interaction between Testosterone and Growth Hormone on Whole-Body Protein Anabolism Occurs in the Liver

CONTEXT GH and testosterone both exert protein-anabolic effects and may act synergistically. Liver and muscle are major sites of protein metabolism. OBJECTIVE Our objective was to determine whether the site of GH and testosterone interaction on protein metabolism is primarily hepatic or extrahepatic. DESIGN In this open-label randomized crossover study, the impact on whole-body protein metabolism of oral (solely hepatic testosterone exposure) and transdermal (systemic testosterone exposure) testosterone replacement in the presence or absence of GH was compared. PATIENTS AND INTERVENTION Eleven hypopituitary men with GH and testosterone deficiency were randomized to 2-wk treatments with transdermal testosterone (10 mg) or oral testosterone (40 mg), with or without GH replacement (0.6 mg/d). The dose of testosterone administered orally achieves physiological portal testosterone concentrations without spillover into the systemic circulation. MAIN OUTCOME MEASURES Whole-body leucine turnover was measured, from which leucine rate of appearance (LRa), an index of protein breakdown, and leucine oxidation (Lox), a measure of irreversible protein loss, were estimated at the end of each treatment. RESULTS In the absence of GH, neither transdermal nor oral testosterone affected LRa or Lox. GH therapy significantly increased LRa, an effect equally reduced by transdermal and oral testosterone administration. GH replacement alone did not significantly change Lox, whereas addition of testosterone treatment reduced Lox, with the effect not significantly different between transdermal and oral testosterone. CONCLUSIONS In the doses used, testosterone stimulates protein anabolism by reducing protein breakdown and oxidation only in the presence of GH. Because the net effect on protein metabolism during GH therapy is not different between systemic and solely hepatic testosterone administration, we conclude that the liver is the primary site of this hormonal interaction.

Oral low-dose testosterone administration induces whole-body protein anabolism in postmenopausal women: a novel liver-targeted therapy.

OBJECTIVE In hypopituitary men, oral delivery of unesterified testosterone in doses that result in a solely hepatic androgen effect enhances protein anabolism during GH treatment. In this study, we aimed to determine whether liver-targeted androgen supplementation induces protein anabolism in GH-replete normal women. DESIGN Eight healthy postmenopausal women received 2-week treatment with oral testosterone at a dose of 40 mg/day (crystalline testosterone USP). This dose increases portal concentrations of testosterone, exerting androgenic effects on the liver without a spillover into the systemic circulation. OUTCOME MEASURES The outcome measures were whole-body leucine turnover, from which leucine rate of appearance (LRa, an index of protein breakdown) and leucine oxidation (Lox, a measure of irreversible protein loss) were estimated, energy expenditure and substrate utilization. We measured the concentration of liver transaminases as well as of testosterone, SHBG and IGF1. RESULTS Testosterone treatment significantly reduced LRa by 7.1 ± 2.5% and Lox by 14.6 ± 4.5% (P<0.05). The concentration of liver transaminases did not change significantly, while that of serum SHBG fell within the normal range by 16.8 ± 4.0% and that of IGF1 increased by 18.4 ± 7.7% (P<0.05). The concentration of peripheral testosterone increased from 0.4 ± 0.1 to 1.1 ± 0.2 nmol/l (P<0.05), without exceeding the upper normal limit. There was no change in energy expenditure and fat and carbohydrate utilization. CONCLUSIONS Hepatic exposure to unesterified testosterone by oral delivery stimulates protein anabolism by reducing protein breakdown and oxidation without inducing systemic androgen excess in women. We conclude that a small oral dose of unesterified testosterone holds promise as a simple novel treatment of protein catabolism and muscle wasting.

Circulating Pancreatic Polypeptide Concentrations Predict Visceral and Liver Fat Content

Context and objective: No current biomarker can reliably predict visceral and liver fat content, both of which are risk factors for cardiovascular disease. Vagal tone has been suggested to influence regional fat deposition. Pancreatic polypeptide (PP) is secreted from the endocrine pancreas under vagal control. We investigated the utility of PP in predicting visceral and liver fat. Patients and Methods: Fasting plasma PP concentrations were measured in 104 overweight and obese subjects (46 men and 58 women). In the same subjects, total and regional adipose tissue, including total visceral adipose tissue (VAT) and total subcutaneous adipose tissue (TSAT), were measured using whole-body magnetic resonance imaging. Intrahepatocellular lipid content (IHCL) was quantified by proton magnetic resonance spectroscopy. Results: Fasting plasma PP concentrations positively and significantly correlated with both VAT (r = 0.57, P < .001) and IHCL (r = 0.51, P < .001), but not with TSAT (r = 0.02, P = .88). Fasting PP concentrations independently predicted VAT after controlling for age and sex. Fasting PP concentrations independently predicted IHCL after controlling for age, sex, body mass index (BMI), waist-to-hip ratio, homeostatic model assessment 2-insulin resistance, (HOMA2-IR) and serum concentrations of triglyceride (TG), total cholesterol (TC), and alanine aminotransferase (ALT). Fasting PP concentrations were associated with serum ALT, TG, TC, low- and high-density lipoprotein cholesterol, and blood pressure (P < .05). These associations were mediated by IHCL and/or VAT. Fasting PP and HOMA2-IR were independently significantly associated with hepatic steatosis (P < .01). Conclusions: Pancreatic polypeptide is a novel predictor of visceral and liver fat content, and thus a potential biomarker for cardiovascular risk stratification and targeted treatment of patients with ectopic fat deposition.

Evaluation of fatty acid status in children of different nationalities

The fatty acid status of an individual can be estimated from the fatty acid composition of cellular or plasma lipid fractions, reflecting both dietary intake and metabolic processes. For example, the odd chain fatty acids 15:0 and 17:0 are not synthesised de novo in humans and reflect dairy intake. The long chain n-3 polyunsaturated fatty acids (PUFA) 20:5n-3 and 22:6n-3 are either obtained through the diet or, to a substantially lesser extent, through synthesis from 18 carbon precursors. 20:5n-3 plus 22:6n-3 are associated with health benefits such that the proportion of these PUFA in cellular phospholipids (PLs) is considered to be important for neurological function. Buccal cell PL fatty acid composition can be obtained through non-invasive sampling and can be useful for gaining insight into dietary intake and fatty acid status. The present study aimed to assess the relative intake of dietary fatty acids in children from different countries, using buccal cell PL fatty acid composition. Buccal cells were collected from children aged 11–12 years, participating in the finals of the Danone Nations Cup, held at the University of Surrey in 2013. The event is an annual international soccer tournament for school-aged children, involving teams from 32 different nations. We obtained samples from 99 children (all boys) from 10 countries during the tournament, using a rinse and spit technique and analysed the PL fatty acid composition by GC-MS (Figs 1–3). Differences between countries were assessed using ANOVA (with Welch’s test for non-parametric data).

Individuals with moderately raised liver fat show a greater increase in liver fat in response to a high sugar diet

Liver fat has been associated with the development of cardio-metabolic risk, and linked to a high intake of dietary sugars. To investigate these associations further, we examined the effects of two, 12 week diets, high and low in sugars, on the percentage of liver fat, and the influence of the initial percentage of liver fat. The dietary intervention used a randomised, cross-over design, and was conducted in a free-living setting with men (aged 40–65, n = 17) at increased cardio-metabolic risk according to the previously described ‘RISCK’ Study protocol. Percentage liver fat was measured before and after each diet by magnetic resonance spectroscopy. The high and low sugar diets, that delivered 27% and 9% energy as sugar, with starch to sugar ratios of 1:1 and 3:1, were accompanied by a consistent increase and decrease in liver fat, respectively. These changes resulted in a significant difference in the percentage of liver fat between the two diets (post-diet medians: 7.3% versus 2.2%, p<0.05). Individuals with a moderate increase in their percentage of liver fat at baseline (>4.2%), showed a significantly greater increase in liver fat after the high sugar diet relative to the low sugar diet.