Dietary impact on fasting and stimulated GLP-1 secretion in different metabolic conditions - a narrative review.

Glucagon-like peptide 1 (GLP-1), a gastrointestinal peptide and central mediator of glucose metabolism, is secreted by L cells in the intestine in response to food intake. Postprandial secretion of GLP-1 is triggered by nutrient-sensing via transporters and G-protein-coupled receptors (GPCRs). GLP-1 secretion may be lower in adults with obesity/overweight (OW) or type 2 diabetes mellitus (T2DM) than in those with normal glucose tolerance (NGT), but these findings are inconsistent. Because of the actions of GLP-1 on stimulating insulin secretion and promoting weight loss, GLP-1 and its analogs are used in pharmacologic preparations for the treatment of T2DM. However, physiologically stimulated GLP-1 secretion through the diet might be a preventive or synergistic method for improving glucose metabolism in individuals who are OW, or have impaired glucose tolerance (IGT) or T2DM. This narrative review focuses on fasting and postprandial GLP-1 secretion in individuals with different metabolic conditions and degrees of glucose intolerance. Further, the influence of relevant diet-related factors (e.g., specific diets, meal composition, and size, phytochemical content, and gut microbiome) that could affect fasting and postprandial GLP-1 secretion are discussed. Some studies showed diminished glucose- or meal-stimulated GLP-1 response in participants with T2DM, IGT, or OW compared with those with NGT, whereas other studies have reported an elevated or unchanged GLP-1 response in T2DM or IGT. Meal composition, especially the relationship between macronutrients and interventions targeting the microbiome can impact postprandial GLP-1 secretion, although it is not clear which macronutrients are strong stimulants of GLP-1. Moreover, glucose tolerance, antidiabetic treatment, grade of overweight/obesity, and sex were important factors influencing GLP-1 secretion. The results presented in this review highlight the potential of nutritional and physiologic stimulation of GLP-1 secretion. Further research on fasting and postprandial GLP-1 concentrations and the resulting metabolic consequences under different metabolic conditions is needed.

Biomarkers of Alzheimer's disease and neurodegeneration in dried blood spots-A new collection method for remote settings.

BACKGROUND: We aimed to evaluate the precision of Alzheimer's disease (AD) and neurodegeneration biomarker measurements from venous dried plasma spots (DPSv enous) for the diagnosis and monitoring of neurodegenerative diseases in remote settings. METHODS: In a discovery (n = 154) and a validation cohort (n = 115), glial fibrillary acidic protein (GFAP); neurofilament light (NfL); amyloid beta (Aß) 40, Aß42; and phosphorylated tau (p-tau181 and p-tau217) were measured in paired DPSvenous and ethylenediaminetetraacetic acid plasma samples with single-molecule array. In the validation cohort, a subset of participants (n = 99) had cerebrospinal fluid (CSF) biomarkers. RESULTS: All DPSvenous and plasma analytes correlated significantly, except for Aß42. In the validation cohort, DPSvenous GFAP, NfL, p-tau181, and p-tau217 differed between CSF Aß-positive and -negative individuals and were associated with worsening cognition. DISCUSSION: Our data suggest that measuring blood biomarkers related to AD pathology and neurodegeneration from DPSvenous extends the utility of blood-based biomarkers to remote settings with simplified sampling conditions, storage, and logistics. HIGHLIGHTS: A wide array of biomarkers related to Alzheimer's disease (AD) and neurodegeneration were detectable in dried plasma spots (DPSvenous). DPSvenous biomarkers correlated with standard procedures and cognitive status. DPSvenous biomarkers had a good diagnostic accuracy discriminating amyloid status. Our findings show the potential interchangeability of DPSvenous and plasma sampling. DPSvenous may facilitate remote and temperature-independent sampling for AD biomarker measurement. Innovative tools for blood biomarker sampling may help recognizing the earliest changes of AD.

CSF p-tau205: a biomarker of tau pathology in Alzheimer's disease.

Post-mortem staging of Alzheimer's disease (AD) neurofibrillary pathology is commonly performed by immunohistochemistry using AT8 antibody for phosphorylated tau (p-tau) at positions 202/205. Thus, quantification of p-tau205 and p-tau202 in cerebrospinal fluid (CSF) should be more reflective of neurofibrillary tangles in AD than other p-tau epitopes. We developed two novel Simoa immunoassays for CSF p-tau205 and p-tau202 and measured these phosphorylations in three independent cohorts encompassing the AD continuum, non-AD cases and cognitively unimpaired participants: a discovery cohort (n = 47), an unselected clinical cohort (n = 212) and a research cohort well-characterized by fluid and imaging biomarkers (n = 262). CSF p-tau205 increased progressively across the AD continuum, while CSF p-tau202 was increased only in AD and amyloid (Aß) and tau pathology positive (A+T+) cases (P < 0.01). In A+ cases, CSF p-tau205 and p-tau202 showed stronger associations with tau-PET (rSp205 = 0.67, rSp202 = 0.45) than Aß-PET (rSp205 = 0.40, rSp202 = 0.09). CSF p-tau205 increased gradually across tau-PET Braak stages (P < 0.01), whereas p-tau202 only increased in Braak V-VI (P < 0.0001). Both showed stronger regional associations with tau-PET than with Aß-PET, and CSF p-tau205 was significantly associated with Braak V-VI tau-PET regions. When assessing the contribution of Aß and tau pathologies (indexed by PET) to CSF p-tau205 and p-tau202 variance, tau pathology was found to be the most prominent contributor in both cases (CSF p-tau205: R2 = 69.7%; CSF p-tau202: R2 = 85.6%) Both biomarkers associated with brain atrophy measurements globally (rSp205 = - 0.36, rSp202 = - 0.33) and regionally, and correlated with cognition (rSp205 = - 0.38/- 0.40, rSp202 = - 0.20/- 0.29). In conclusion, we report the first high-throughput CSF p-tau205 immunoassay for the in vivo quantification of tau pathology in AD, and a potentially cost-effective alternative to tau-PET in clinical settings and clinical trials.

Cell Cycle Control by Optogenetically Regulated Cell Cycle Inhibitor Protein p21.

The progression through the cell cycle phases is driven by cyclin-dependent kinases and cyclins as their regulatory subunits. As nuclear protein, the cell cycle inhibitor p21/CDKN1A arrests the cell cycle at the growth phase G1 by inhibiting the activity of cyclin-dependent kinases. The G1 phase correlates with increased cell size and cellular productivity. Here, we applied an optogenetic approach to control the subcellular localization of p21 and its nuclear functions. To generate light-controllable p21, appropriate fusions with the blue light switch cryptochrome 2/CIBN and the AsLOV-based light-inducible nuclear localization signal, LINuS, were used. Both systems, p21-CRY2/CIB1 and p21-LINuS, increased the amounts of cells arrested in the G1 phase correlating with the increased cell-specific productivity of the reporter-protein-secreted alkaline phosphatase. Varying the intervals of blue LED light exposure and the light dose enable the fine-tuning of the systems. Light-controllable p21 implemented in producer cell lines could be applied to steer the uncoupling of cell proliferation and cell cycle arrest at the G1 phase optimizing the production of biotherapeutic proteins.

Levels of Alzheimer's disease blood biomarkers are altered after food intake-A pilot intervention study in healthy adults.

INTRODUCTION: Blood biomarkers accurately identify Alzheimer's disease (AD) pathophysiology and axonal injury. We investigated the influence of food intake on AD-related biomarkers in cognitively healthy, obese adults at high metabolic risk. METHODS: One-hundred eleven participants underwent repeated blood sampling during 3 h after a standardized meal (postprandial group, PG). For comparison, blood was sampled from a fasting subgroup over 3 h (fasting group, FG). Plasma neurofilament light (NfL), glial fibrillary acidic protein (GFAP), amyloid-beta (Aß) 42/40, phosphorylated tau (p-tau) 181 and 231, and total-tau were measured via single molecule array assays. RESULTS: Significant differences were found for NfL, GFAP, Aß42/40, p-tau181, and p-tau231 between FG and PG. The greatest change to baseline occurred for GFAP and p-tau181 (120 min postprandially, p < 0.0001). CONCLUSION: Our data suggest that AD-related biomarkers are altered by food intake. Further studies are needed to verify whether blood biomarker sampling should be performed in the fasting state. HIGHLIGHTS: Acute food intake alters plasma biomarkers of Alzheimer's disease in obese, otherwise healthy adults. We also found dynamic fluctuations in plasma biomarkers concentration in the fasting state suggesting physiological diurnal variations. Further investigations are highly needed to verify if biomarker measurements should be performed in the fasting state and at a standardized time of day to improve the diagnostic accuracy.

Acute Impact of Dietary Pattern and Walking on Postprandial Attention, Mood, and Satiety in Older Adults: A Randomized Crossover Trial.

Research suggests that attention, mood, and satiety can be influenced by meal composition and postprandial activity. The present study examined whether this hypothesis applies to persons with a risk phenotype for the development of cardiovascular/neurodegenerative diseases. A randomized crossover trial was conducted in subjects with metabolic syndrome traits (n = 26, 8 female, age 70 ± 5, BMI 30.3 ± 2.3 kg/m2). Each subject participated in four interventions: iso-energetic (4300 kJ) meals (Western diet high-fat, WD, and Mediterranean-type diet, MD) followed by either 30 min of moderate walking (4.6 ± 0.1 km/h) or rest. Attention, mood, satiety and plasma cortisol concentrations were measured at fasting and 1.5, 3.0, 4.5 h postprandially. Data were analyzed by linear mixed models. In all interventions, attention increased continuously in the postprandial period (time effect, P < 0.001). After WD, attention was lower after walking compared to resting (meal × activity effect, P < 0.05). Postprandial mood was generally "good" with no intervention effects. Postprandial satiety increased reaching maximum at 1.5 h after meal (time effect, P < 0.001) and was higher after MD compared to WD (meal effect, P < 0.001). In all interventions, plasma cortisol decreased similar to its diurnal variation (time effect, P < 0.001). In our subjects, meal composition had no relevant impact on attention and mood. After typical WD, resting instead of walking seems to have a more beneficial effect on postprandial attention. MD leads to a strong and long-lasting feeling of satiety, possibly resulting in reduced energy intake in the further course of the day and, thus, long-term effect on weight control.

Moderate Postmeal Walking Has No Beneficial Effects Over Resting on Postprandial Lipemia, Glycemia, Insulinemia, and Selected Oxidative and Inflammatory Parameters in Older Adults with a Cardiovascular Disease Risk Phenotype: A Randomized Crossover Trial.

BACKGROUND: Research suggests that postprandial events, as risk factors for cardiovascular diseases (CVDs), are influenced by meal composition and exercise. OBJECTIVES: We investigated the effect of walking versus rest on postprandial metabolic, inflammatory, and oxidative events following the consumption of test meals reflecting 2 different dietary patterns in older adults with an increased CVD risk. METHODS: A randomized crossover trial was conducted in 26 men and women (aged 70 ± 5 y; BMI 30.3 ± 2.3 kg/m2). Each adult participated in 4 treatments combining 1 of 2 iso-energetic (4300 kJ) meals [Western diet high-fat meal (WD): total fat, 59.4 g; saturated fatty acids, 32.0 g, dietary fiber, 4.2 g; or Mediterranean-type diet meal (MD): total fat, 40.1 g; saturated fatty acids, 5.1 g; dietary fiber, 14.5 g] with 30 min walking (4.6 ± 0.1 km/h) or rest. Primary (serum triglycerides) and secondary [serum nonesterified fatty acids (NEFAs); parameters of glucose metabolism, inflammation, endothelial activation, oxidation; blood pressure/heart rate] outcomes were measured at fasting and 1.5, 3.0, and 4.5 h postprandially. Data were analyzed by linear mixed models. RESULTS: Triglycerides were higher after the WD than after the MD [AUC in mmol/L × min: Western diet high-fat meal plus postprandial walking (WD-W), 218 ± 15.2; Western diet high-fat meal plus postprandial resting (WD-R), 207 ± 12.6; Mediterranean-type diet meal plus postprandial walking (MD-W), 139 ± 9.83; Mediterranean-type diet meal plus postprandial resting (MD-R), 149 ± 8.15; P  < 0.001]. No meal or activity effect was observed for NEFAs based on AUC data (WD-W, -43.5 ± 7.08; WD-R, -49.2 ± 6.94; MD-W, -48.0 ± 11.6; MD-R, -67.6 ± 7.58). Plasma glucose was higher after the MD than after the WD (WD-W, 222 ± 34.9; WD-R, 177 ± 32.8; MD-W, 314 ± 44.4; MD-R, 275 ± 57.8; P  < 0.001), as was serum insulin (AUC in nmol/L × min: WD-W, 82.0 ± 10.3; WD-R, 88.6 ± 12.8; MD-W, 129 ± 14.7; MD-R, 138 ± 20.5; P < 0.001). Plasma IL-6 was higher after walking than after resting (AUC in pg/mL × min: WD-W, 72.0 ± 34.0; WD-R, 14.3 ± 38.8; MD-W, 70.8 ± 39.4; MD-R, 5.60 ± 26.0; P < 0.05). Plasma vitamin C was higher after the MD than after the WD (P < 0.001) and after walking than after resting (P < 0.05; AUC in mg/L × min: WD-W, -305 ± 59.6; WD-R, -396 ± 84.0; MD-W, 113 ± 56.4; MD-R, -44.5 ± 48.1). We observed no meal or activity effects on parameters of oxidation and endothelial adhesion molecules. Our data revealed no significant meal × activity effects on all outcomes. CONCLUSIONS: In older adults with an increased CVD risk, the MD was associated with superior effects on several postprandial parameters (e.g., triglycerides), in comparison to the WD. Data revealed no relevant differences regarding the effects of postmeal walking and resting. None of the 4 treatments can be rated as superior regarding their acute effects on the shown postprandial metabolic, oxidative, and inflammatory parameters. The trial was registered at German Clinical Trials Register (DRKS; http://www.germanctr.de and http://www.drks.de) under identifier DRKS00012409.

Elevated systemic monocyte chemoattractrant protein-1 in hepatic steatosis without significant hepatic inflammation.

Non-alcoholic fatty liver disease (NAFLD) is strongly associated with obesity and the metabolic syndrome. It encompasses a clinico-pathologic spectrum of conditions ranging from simple steatosis to nonalcoholic steatohepatitis (NASH). The latter develops upon pro-inflammatory cell infiltration and is widely considered as the first relevant pathophysiological step in NAFLD-progression. The chemokine monocyte chemoattractant protein 1 (MCP-1) plays an important role in the progression of hepatic inflammation and fibrosis, and both increased hepatic expression and circulating serum levels have been described in NASH. Here, we aimed to investigate MCP-1 expression in simple hepatic steatosis. Upon feeding a high-fat diet mice developed hepatic steatosis in the absence of significant hepatic inflammation, but elevated hepatic MCP-1 expression compared to control mice fed a standard chow. Interestingly, high-fat diet fed mice had significantly higher MCP-1 serum levels, and MCP-1 mRNA expression was significantly increased in visceral adipose tissue. Furthermore, MCP-1 serum levels were also elevated in patients with ultrasound-diagnosed NAFLD and correlated with the body-mass index and fasting glucose. In conclusion, our data indicate both the liver and adipose tissue as cellular sources of elevated circulating MCP-1 levels already in the early phase of hepatic steatosis. Since MCP-1 derived from visceral adipose tissue reaches the liver via portal circulation at high concentrations it may significantly contribute to the progression of simple steatosis to NASH.

Lipid accumulation impairs adiponectin-mediated induction of activin A by increasing TGFbeta in primary human hepatocytes.

Fatty liver is commonly detected in obesity and has been identified as a risk factor for the progression of hepatic fibrosis in a wide range of liver diseases. Transforming growth factor beta (TGFß) and activin A, both members of the TGFß superfamiliy, are central regulators in liver fibrosis and regeneration, and the effect of hepatocyte lipid accumulation on the release of these proteins was studied. Primary human hepatocytes (PHH) were incubated with palmitic acid or oleic acid to increase lipid storage. Whereas activin A and its natural inhibitor follistatin were not affected, TGFß was 2-fold increased. The hepatoprotective adipokine adiponectin dose-dependently induced activin A while lowering follistatin but did not alter TGFß. Activin A was markedly reduced in hepatocyte cell lines compared to PHH and was not induced upon adiponectin incubation demonstrating significant differences of primary and transformed cells. In free fatty acid (FFA)-incubated PHH adiponectin-mediated induction of activin A was impaired. Inhibition of TGFß receptors ALK4/5 and blockage of SMAD3 phosphorylation rescued activin A synthesis in FFA and in TGFß incubated cells suggesting that FFA inhibit adiponectin activity by inducing TGFß. To evaluate whether serum levels of activin A and its antagonist are altered in patients with hepatic steatosis, both proteins were measured in the serum of patients with sonographically diagnosed fatty liver and age- and BMI-matched controls. Systemic adiponectin was significantly reduced in patients with fatty liver but activin A and follistatin were not altered. In summary the current data demonstrate that lipid accumulation in hepatocytes induces TGFß which impairs adiponectin bioactivity, and thereby may contribute to liver injury.

Prevalence of ultrasound-diagnosed non-alcoholic fatty liver disease in a hospital cohort and its association with anthropometric, biochemical and sonographic characteristics.

UNLABELLED: Non-alcoholic fatty liver disease (NAFLD) is considered as the most common liver disease in Western countries with still rising prevalence due to a lifestyle favoring the development of the metabolic syndrome. AIM: To investigate the prevalence of ultrasound-diagnosed NAFLD in patients with referral for sonographic examination of the abdomen, and to determine risk factors. METHODS: After exclusion of patients with known liver disease or risk factors for secondary NAFLD, a total of 155 arbitrarily selected patients (mean age 53.6±17.4 years; 52.6% male) from the interdisciplinary ultrasound department of a German University Hospital were included in this prospective study. Each patient underwent a standardized ultrasound, anthropometric and biochemical examination. RESULTS: The prevalence of ultrasound-diagnosed NAFLD was 40.0%. NAFLD-patients had significantly higher body mass index (BMI) and waist-to-hip ratio, higher rates of reported hypertension and diabetes mellitus, and lower HDL cholesterol serum levels. Furthermore, NAFLD-patients revealed significantly higher serum ALT levels (23.2±22.1 U/l vs. 15.0±8.2 U/l; p=0.001), lower AST/ALT ratio (1.76±0.79 vs. 2.11±0.94; p=0.019), and notably, decreased flow in the portal vein (22.9±6.3 cm/s vs. 26.7±10.5 cm/s; p=0.011). Multivariate analysis revealed BMI (odds ratio (OR): 14.05; 95% Confidence interval (CI): 3.3-59.8), AST/ALT ratio (OR: 0.39; CI: 0.18-0.82), and HDL-C (OR: 4.33; CI: 1.6-11.9) as independent risk factors. CONCLUSIONS: Ultrasound-diagnosed NAFLD is frequent in patients with referral for ultrasound examination of the abdomen, and our findings further support that NAFLD is the hepatic manifestation of the metabolic syndrome with obesity being the most important risk factor.