Anja Mähler

Randomized comparison of reduced fat and reduced carbohydrate hypocaloric diets on intrahepatic fat in overweight and obese human subjects

Obesity‐related hepatic steatosis is a major risk factor for metabolic and cardiovascular disease. Fat reduced hypocaloric diets are able to relieve the liver from ectopically stored lipids. We hypothesized that the widely used low carbohydrate hypocaloric diets are similarly effective in this regard. A total of 170 overweight and obese, otherwise healthy subjects were randomized to either reduced carbohydrate (n = 84) or reduced fat (n = 86), total energy restricted diet (−30% of energy intake before diet) for 6 months. Body composition was estimated by bioimpedance analyses and abdominal fat distribution by magnetic resonance tomography. Subjects were also submitted to fat spectroscopy of liver and oral glucose tolerance testing. In all, 102 subjects completed the diet intervention with measurements of intrahepatic lipid content. Both hypocaloric diets decreased body weight, total body fat, visceral fat, and intrahepatic lipid content. Subjects with high baseline intrahepatic lipids (>5.56%) lost ≈7‐fold more intrahepatic lipids compared with those with low baseline values (<5.56%) irrespective of diet composition. In contrast, changes in visceral fat mass and insulin sensitivity were similar between subgroups, with low and high baseline intrahepatic lipids. Conclusion: A prolonged hypocaloric diet low in carbohydrates and high in fat has the same beneficial effects on intrahepatic lipid accumulation as the traditional low‐fat hypocaloric diet. The decrease in intrahepatic lipids appears to be independent of visceral fat loss and is not tightly coupled with changes in whole body insulin sensitivity during 6 months of an energy restricted diet. (HEPATOLOGY 2011)

Salt-responsive gut commensal modulates TH17 axis and disease

A Western lifestyle with high salt consumption can lead to hypertension and cardiovascular disease. High salt may additionally drive autoimmunity by inducing T helper 17 (TH17) cells, which can also contribute to hypertension. Induction of TH17 cells depends on gut microbiota; however, the effect of salt on the gut microbiome is unknown. Here we show that high salt intake affects the gut microbiome in mice, particularly by depleting Lactobacillus murinus. Consequently, treatment of mice with L. murinus prevented salt-induced aggravation of actively induced experimental autoimmune encephalomyelitis and salt-sensitive hypertension by modulating TH17 cells. In line with these findings, a moderate high-salt challenge in a pilot study in humans reduced intestinal survival of Lactobacillus spp., increased TH17 cells and increased blood pressure. Our results connect high salt intake to the gut–immune axis and highlight the gut microbiome as a potential therapeutic target to counteract salt-sensitive conditions.

Epigallocatechin-3-gallate: a useful, effective and safe clinical approach for targeted prevention and individualised treatment of neurological diseases?

Neurodegenerative disorders show an increasing prevalence in a number of highly developed countries. Often, these diseases require life-long treatment mostly with drugs which are costly and mostly accompanied by more or less serious side-effects. Their heterogeneous manifestation, severity and outcome pose the need for individualised treatment options. There is an intensive search for new strategies not only for treating but also for preventing these diseases. Green tea and green tea extracts seem to be such a promising and safe alternative. However, data regarding the beneficial effects and possible underlying mechanism, specifically in clinical trials, are rare and rather controversial or non-conclusive. This review outlines the existing evidence from preclinical studies (cell and tissue cultures and animal models) and clinical trials regarding preventive and therapeutic effects of epigallcatechin-3-gallate in neurodegenerative diseases and considers antioxidative vs. pro-oxidative properties of the tea catechin important for dosage recommendations.

Is Metabolic Flexibility Altered in Multiple Sclerosis Patients

Objectives Metabolic flexibility is defined as ability to adjust fuel oxidation to fuel availability. Multiple sclerosis (MS) results in reduced muscle strength and exercise intolerance. We tested the hypothesis that altered metabolic flexibility contributes to exercise intolerance in MS patients. Methods We studied 16 patients (all on glatiramer) and 16 matched healthy controls. Energy expenditure (EE), and carbohydrate (COX) and lipid oxidation (LOX) rates were determined by calorimetry, before and after an oral glucose load. We made measurements either at rest (canopy device) or during 40 min low-grade (0.5 W/kg) exercise (metabolic chamber). We also obtained plasma, and adipose tissue and skeletal muscle dialysate samples by microdialysis to study tissue-level metabolism under resting conditions. Results At rest, fasting and postprandial plasma glucose, insulin, and free fatty acid levels did not differ between patients and controls. Fasting and postprandial COX was higher and LOX lower in patients. In adipose, fasting and postprandial dialysate glucose, lactate, and glycerol levels were higher in patients vs. controls. In muscle, fasting and postprandial dialysate metabolite levels did not differ significantly between the groups. During exercise, EE did not differ between the groups. However, COX increased sharply over 20 min in patients, without reaching a steady state, followed by an immediate decrease within the next 20 min and fell even below basal levels after exercise in patients, compared to controls. Conclusions Glucose tolerance is not impaired in MS patients. At rest, there is no indication for metabolic inflexibility or mitochondrial dysfunction in skeletal muscle. The increased adipose tissue lipolytic activity might result from glatiramer treatment. Autonomic dysfunction might cause dysregulation of postprandial thermogenesis at rest and lipid mobilization during exercise.

Left Ventricular Mass and Function With Reduced-Fat or Reduced-Carbohydrate Hypocaloric Diets in Overweight and Obese Subjects

In animals, carbohydrate and fat composition during dietary interventions influenced cardiac metabolism, structure, and function. Because reduced-carbohydrate and reduced-fat hypocaloric diets are commonly used in the treatment of obesity, we investigated whether these interventions differentially affect left ventricular mass, cardiac function, and blood pressure. We randomized 170 overweight and obese subjects (body mass index, 32.9±4.4; range, 26.5–45.4 kg/m2) to 6-month hypocaloric diets with either reduced carbohydrate intake or reduced fat intake. We obtained cardiac MRI and ambulatory blood pressure recordings over 24 hours before and after 6 months. Ninety subjects completing the intervention period had a full cardiac MRI data set. Subjects lost 7.3±4.0 kg (7.9±3.8%) with reduced-carbohydrate diet and 6.2±4.2 kg (6.7±4.4%) with reduced-fat diet (P<0.001 within each group; P=not significant between interventions). Caloric restriction led to similar significant decreases in left ventricular mass with low-carbohydrate diets (5.4±5.4 g) or low-fat diets (5.2±4.8 g; P<0.001 within each group; P=not significant between interventions). Systolic and diastolic left ventricular function did not change with either diet. The 24-hour systolic blood pressure decreased similarly with both interventions. Body weight change (&bgr;=0.33; P=0.02) and percentage of ingested n-3 polyunsaturated fatty acids (&bgr;=−0.27; P=0.03) predicted changes in left ventricular mass. In conclusion, weight loss induced by reduced-fat diets or reduced-carbohydrate diets similarly improved left ventricular mass in overweight and obese subjects over a 6-month period. However, n-3 polyunsaturated fatty acid ingestion may have an independent beneficial effect on left ventricular mass.

Tracking CNS and systemic sources of oxidative stress during the course of chronic neuroinflammation

The functional dynamics and cellular sources of oxidative stress are central to understanding MS pathogenesis but remain elusive, due to the lack of appropriate detection methods. Here we employ NAD(P)H fluorescence lifetime imaging to detect functional NADPH oxidases (NOX enzymes) in vivo to identify inflammatory monocytes, activated microglia, and astrocytes expressing NOX1 as major cellular sources of oxidative stress in the central nervous system of mice affected by experimental autoimmune encephalomyelitis (EAE). This directly affects neuronal function in vivo, indicated by sustained elevated neuronal calcium. The systemic involvement of oxidative stress is mirrored by overactivation of NOX enzymes in peripheral CD11b+ cells in later phases of both MS and EAE. This effect is antagonized by systemic intake of the NOX inhibitor and anti-oxidant epigallocatechin-3-gallate. Together, this persistent hyper-activation of oxidative enzymes suggests an “oxidative stress memory” both in the periphery and CNS compartments, in chronic neuroinflammation.

Increased catabolic activity in adipose tissue of patients with chronic heart failure

Patients with chronic heart failure (CHF) have an increased catabolic state that affects both muscle and adipose tissue (AT), and may ultimately result in cardiac cachexia. Increased plasma levels of ANP might contribute to increased lipid mobilization and oxidation in CHF. We tested the hypothesis that increased plasma ANP levels are associated with an increased catabolic (lipolytic) state of white AT in patients with CHF.

Long-Lasting Improvements in Liver Fat and Metabolism Despite Body Weight Regain After Dietary Weight Loss

OBJECTIVE Weight loss reduces abdominal and intrahepatic fat, thereby improving metabolic and cardiovascular risk. Yet, many patients regain weight after successful diet-induced weight loss. Long-term changes in abdominal and liver fat, along with liver test results and insulin resistance, are not known. RESEARCH DESIGN AND METHODS We analyzed 50 overweight to obese subjects (46 ± 9 years of age; BMI, 32.5 ± 3.3 kg/m2; women, 77%) who had participated in a 6-month hypocaloric diet and were randomized to either reduced carbohydrates or reduced fat content. Before, directly after diet, and at an average of 24 (range, 17–36) months follow-up, we assessed body fat distribution by magnetic resonance imaging and markers of liver function and insulin resistance. RESULTS Body weight decreased with diet but had increased again at follow-up. Subjects also partially regained abdominal subcutaneous and visceral adipose tissue. In contrast, intrahepatic fat decreased with diet and remained reduced at follow-up (7.8 ± 9.8% [baseline], 4.5 ± 5.9% [6 months], and 4.7 ± 5.9% [follow-up]). Similar patterns were observed for markers of liver function, whole-body insulin sensitivity, and hepatic insulin resistance. Changes in intrahepatic fat und intrahepatic function were independent of macronutrient composition during intervention and were most effective in subjects with nonalcoholic fatty liver disease at baseline. CONCLUSIONS A 6-month hypocaloric diet induced improvements in hepatic fat, liver test results, and insulin resistance despite regaining of weight up to 2 years after the active intervention. Body weight and adiposity measurements may underestimate beneficial long-term effects of dietary interventions.

Metabolic response to epigallocatechin-3-gallate in relapsing-remitting multiple sclerosis: a randomized clinical trial

BACKGROUND Muscle weakness and fatigue are common symptoms in multiple sclerosis (MS). Green tea catechins such as (-)epigallocatechin-3-gallate (EGCG) are known to improve energy metabolism at rest and during exercise. OBJECTIVE We tested the hypothesis that EGCG improves energy metabolism and substrate utilization in patients with MS. DESIGN Eighteen patients (8 men) with relapsing-remitting MS (expanded disability status scale score <4.5, all receiving glatiramer acetate) participated in this randomized, double-blind, placebo-controlled, crossover trial at a clinical research center. All patients received EGCG (600 mg/d) and placebo over 12 wk (4-wk washout in between). After each intervention, fasting and postprandial energy expenditure (EE), as well as fat oxidation (FAOx) and carbohydrate oxidation (CHOx) rates, were measured either at rest or during 40 min of exercise (0.5 W/kg). At rest, blood samples and microdialysates from adipose tissue and skeletal muscle were also taken. RESULTS At rest, postprandial EE and CHOx, as well as adipose tissue perfusion and glucose supply, were significantly lower in men but higher in women receiving EGCG compared with placebo. During exercise, postprandial EE was lower after EGCG than after placebo, indicating an increased working efficiency (men > women). After placebo, exercise EE was mainly fueled by FAOx in both men and women. After EGCG, there was a shift to a higher and more stable CHOx during exercise in men but not in women. CONCLUSIONS Our data indicate that EGCG given to patients with MS over 12 wk improves muscle metabolism during moderate exercise to a greater extent in men than in women, possibly because of sex-specific effects on autonomic and endocrine control.

Differential response of the natriuretic peptide system to weight loss and exercise in overweight or obese patients.

Objective: Relative atrial natriuretic peptide (ANP) deficiency has been implicated in the pathogenesis of obesity-associated cardiovascular and metabolic disease. We tested the hypothesis that more than 5% body weight reduction through 6 months hypocaloric dieting alters ANP release at rest and more so during exercise in overweight or obese patients. Methods: Venous mid-regional pro-ANP concentration was assessed at rest and after incremental exhaustive exercise testing before and after weight reduction. We also measured natriuretic peptide receptor A and C mRNA expression in subcutaneous adipose tissue to gauge both ANP responsiveness and clearance mechanisms. Results: The average weight reduction of 9.1 ± 3.8 kg was associated with reductions in visceral and subcutaneous abdominal fat mass, liver fat content, insulin resistance, and ambulatory blood pressure. However, mid-regional pro-ANP plasma concentrations were unchanged with weight loss (51 ± 24 vs. 53 ± 24 pmol/l). Exercise elicited similar acute mid-regional pro-ANP increases before and after weight loss. Adipose tissue natriuretic peptide receptor type A mRNA expression remained unchanged, whereas natriuretic peptide receptor type C mRNA decreased with weight loss. Conclusions: We conclude that physical exercise acutely increases ANP release in obese patients, whereas modest diet-induced weight loss primarily affects ANP clearance mechanisms. Interventions combining weight loss and regular physical exercise may be particularly efficacious in reversing obesity-associated relative natriuretic peptide deficiency.