Hyperbaric oxygen rapidly improves tissue-specific insulin sensitivity and mitochondrial capacity in humans with type 2 diabetes: a randomised placebo-controlled crossover trial.

AIMS/HYPOTHESIS: Hyperbaric oxygen (HBO) therapy may improve hyperglycaemia in humans with type 2 diabetes, but underlying mechanisms are unclear. Our objective was to examine the glucometabolic effects of HBO on whole-body glucose disposal in humans with type 2 diabetes. METHODS: In a randomised placebo-controlled crossover trial located at the German Diabetes Center, 12 male individuals with type 2 diabetes (age 18-75 years, BMI <35 kg/m2, HbA1c 42-75 mmol/mol [6-9%]), randomly allocated by one person, underwent 2-h HBO, once with 100% (240 kPa; HBO) and once with 21% oxygen (240 kPa; control, CON). Insulin sensitivity was assessed by hyperinsulinaemic-euglycaemic clamps with D-[6,6-2H2]glucose, hepatic and skeletal muscle energy metabolism were assessed by 1H/31P-magnetic resonance spectroscopy, while high-resolution respirometry measured skeletal muscle and white adipose tissue (WAT) mitochondrial capacity. All participants and people assessing the outcomes were blinded. RESULTS: HBO decreased fasting blood glucose by 19% and increased whole-body, hepatic and WAT insulin sensitivity about one-third (p<0.05 vs CON). Upon HBO, hepatic γ-ATP concentrations doubled, mitochondrial respiratory control doubled in skeletal muscle and tripled in WAT (p<0.05 vs CON). HBO increased myocellular insulin-stimulated serine-473/threonine-308 phosphorylation of Akt but decreased basal inhibitory serine-1101 phosphorylation of IRS-1 and endoplasmic reticulum stress (p<0.05 vs CON). CONCLUSIONS/INTERPRETATION: HBO-mediated improvement of insulin sensitivity likely results from decreased endoplasmic reticulum stress and increased mitochondrial capacity, possibly leading to low-dose reactive oxygen species-mediated mitohormesis in humans with type 2 diabetes. TRIAL REGISTRATION: ClinicalTrials.gov NCT04219215 FUNDING: German Federal Ministry of Health, German Federal Ministry of Education and Research, North-Rhine Westfalia Ministry of Culture and Science, European-Regional-Development-Fund, German-Research-Foundation (DFG), Schmutzler Stiftung.

Dietary palmitate and oleate differently modulate insulin sensitivity in human skeletal muscle.

AIMS/HYPOTHESIS: Energy-dense nutrition generally induces insulin resistance, but dietary composition may differently affect glucose metabolism. This study investigated initial effects of monounsaturated vs saturated lipid meals on basal and insulin-stimulated myocellular glucose metabolism and insulin signalling. METHODS: In a randomised crossover study, 16 lean metabolically healthy volunteers received single meals containing safflower oil (SAF), palm oil (PAL) or vehicle (VCL). Whole-body glucose metabolism was assessed from glucose disposal (Rd) before and during hyperinsulinaemic-euglycaemic clamps with D-[6,6-2H2]glucose. In serial skeletal muscle biopsies, subcellular lipid metabolites and insulin signalling were measured before and after meals. RESULTS: SAF and PAL raised plasma oleate, but only PAL significantly increased plasma palmitate concentrations. SAF and PAL increased myocellular diacylglycerol and activated protein kinase C (PKC) isoform θ (p < 0.05) but only PAL activated PKCɛ. Moreover, PAL led to increased myocellular ceramides along with stimulated PKCζ translocation (p < 0.05 vs SAF). During clamp, SAF and PAL both decreased insulin-stimulated Rd (p < 0.05 vs VCL), but non-oxidative glucose disposal was lower after PAL compared with SAF (p < 0.05). Muscle serine1101-phosphorylation of IRS-1 was increased upon SAF and PAL consumption (p < 0.05), whereas PAL decreased serine473-phosphorylation of Akt more than SAF (p < 0.05). CONCLUSIONS/INTERPRETATION: Lipid-induced myocellular insulin resistance is likely more pronounced with palmitate than with oleate and is associated with PKC isoforms activation and inhibitory insulin signalling. TRIAL REGISTRATION: ClinicalTrials.gov .NCT01736202. FUNDING: German Federal Ministry of Health, Ministry of Culture and Science of the State North Rhine-Westphalia, German Federal Ministry of Education and Research, European Regional Development Fund, German Research Foundation, German Center for Diabetes Research.

Targeted proteomic response to coffee consumption.

PURPOSE: Coffee is widely consumed and implicated in numerous health outcomes but the mechanisms by which coffee contributes to health is unclear. The purpose of this study was to test the effect of coffee drinking on candidate proteins involved in cardiovascular, immuno-oncological and neurological pathways. METHODS: We examined fasting serum samples collected from a previously reported single blinded, three-stage clinical trial. Forty-seven habitual coffee consumers refrained from drinking coffee for 1 month, consumed 4 cups of coffee/day in the second month and 8 cups/day in the third month. Samples collected after each coffee stage were analyzed using three multiplex proximity extension assays that, after quality control, measured a total of 247 proteins implicated in cardiovascular, immuno-oncological and neurological pathways and of which 59 were previously linked to coffee exposure. Repeated measures ANOVA was used to test the relationship between coffee treatment and each protein. RESULTS: Two neurology-related proteins including carboxypeptidase M (CPM) and neutral ceramidase (N-CDase or ASAH2), significantly increased after coffee intake (P < 0.05 and Q < 0.05). An additional 46 proteins were nominally associated with coffee intake (P < 0.05 and Q > 0.05); 9, 8 and 29 of these proteins related to cardiovascular, immuno-oncological and neurological pathways, respectively, and the levels of 41 increased with coffee intake. CONCLUSIONS: CPM and N-CDase levels increased in response to coffee intake. These proteins have not previously been linked to coffee and are thus novel markers of coffee response worthy of further study. CLINICAL TRIAL REGISTRY: http://www.isrctn.com/ISRCTN12547806.

Lipidomic Response to Coffee Consumption.

Coffee is widely consumed and contains many bioactive compounds, any of which may impact pathways related to disease development. Our objective was to identify individual lipid changes in response to coffee drinking. We profiled the lipidome of fasting serum samples collected from a previously reported single blinded, three-stage clinical trial. Forty-seven habitual coffee consumers refrained from drinking coffee for 1 month, consumed 4 cups of coffee/day in the second month and 8 cups/day in the third month. Samples collected after each coffee stage were subject to quantitative lipidomic profiling using ion-mobility spectrometry⁻mass spectrometry. A total of 853 lipid species mapping to 14 lipid classes were included for univariate analysis. Three lysophosphatidylcholine (LPC) species including LPC (20:4), LPC (22:1) and LPC (22:2), significantly decreased after coffee intake (p < 0.05 and q < 0.05). An additional 72 species mapping to the LPC, free fatty acid, phosphatidylcholine, cholesteryl ester and triacylglycerol classes of lipids were nominally associated with coffee intake (p < 0.05 and q > 0.05); 58 of these decreased after coffee intake. In conclusion, coffee intake leads to lower levels of specific LPC species with potential impacts on glycerophospholipid metabolism more generally.

Acute dietary fat intake initiates alterations in energy metabolism and insulin resistance.

BACKGROUND: Dietary intake of saturated fat is a likely contributor to nonalcoholic fatty liver disease (NAFLD) and insulin resistance, but the mechanisms that initiate these abnormalities in humans remain unclear. We examined the effects of a single oral saturated fat load on insulin sensitivity, hepatic glucose metabolism, and lipid metabolism in humans. Similarly, initiating mechanisms were examined after an equivalent challenge in mice. METHODS: Fourteen lean, healthy individuals randomly received either palm oil (PO) or vehicle (VCL). Hepatic metabolism was analyzed using in vivo 13C/31P/1H and ex vivo 2H magnetic resonance spectroscopy before and during hyperinsulinemic-euglycemic clamps with isotope dilution. Mice underwent identical clamp procedures and hepatic transcriptome analyses. RESULTS: PO administration decreased whole-body, hepatic, and adipose tissue insulin sensitivity by 25%, 15%, and 34%, respectively. Hepatic triglyceride and ATP content rose by 35% and 16%, respectively. Hepatic gluconeogenesis increased by 70%, and net glycogenolysis declined by 20%. Mouse transcriptomics revealed that PO differentially regulates predicted upstream regulators and pathways, including LPS, members of the TLR and PPAR families, NF-κB, and TNF-related weak inducer of apoptosis (TWEAK). CONCLUSION: Saturated fat ingestion rapidly increases hepatic lipid storage, energy metabolism, and insulin resistance. This is accompanied by regulation of hepatic gene expression and signaling that may contribute to development of NAFLD.REGISTRATION. ClinicalTrials.gov NCT01736202. FUNDING: Germany: Ministry of Innovation, Science, and Research North Rhine-Westfalia, German Federal Ministry of Health, Federal Ministry of Education and Research, German Center for Diabetes Research, German Research Foundation, and German Diabetes Association. Portugal: Portuguese Foundation for Science and Technology, FEDER - European Regional Development Fund, Portuguese Foundation for Science and Technology, and Rede Nacional de Ressonância Magnética Nuclear.

Effect of Low-Energy Diets Differing in Fiber, Red Meat, and Coffee Intake on Cardiac Autonomic Function in Obese Individuals With Type 2 Diabetes.

OBJECTIVE: The autonomic nervous system (ANS) regulates both the cardiovascular system and energy balance and is disturbed in diabetes and obesity. The effect of different approaches of caloric restriction on ANS function has not been assessed in individuals with diabetes. Thus, we sought to determine whether low-energy diets differing in fiber, red meat, and coffee intake exert differential effects on cardiac autonomic function. RESEARCH DESIGN AND METHODS: In this randomized parallel-group pilot trial, obese patients with type 2 diabetes were randomly allocated to consume either a diet high in cereal fiber, free of red meat, and high in coffee (n = 13) or a diet low in fiber, high in red meat, and coffee free (n = 15) over 8 weeks. Eight measures of heart rate variability (HRV) indicating vagal and/or sympathetic modulation over 3 h and inflammatory markers were determined during a hyperinsulinemic-euglycemic clamp. RESULTS: After 8 weeks, both dietary interventions resulted in a mean weight loss of 5-6 kg, a mean decline in heart rate of 4-6 bpm, and improvement in vagally mediated HRV. However, the changes in HRV parameters from baseline to 8 weeks did not differ between the groups. In the entire study cohort, incremental HRV from baseline to 8 weeks was associated with enhanced oxidative glucose utilization (P < 0.05), but not with insulin sensitivity and inflammatory markers. CONCLUSIONS: In obese patients with type 2 diabetes, energy restriction per se over 8 weeks contributed to improved cardiac vagal function in relation to improved oxidative glucose utilization. This preliminary finding should be verified in a confirmatory trial.

Low-energy diets differing in fibre, red meat and coffee intake equally improve insulin sensitivity in type 2 diabetes: a randomised feasibility trial.

AIMS/HYPOTHESIS: Epidemiological studies have found that a diet high in fibre and coffee, but low in red meat, reduces the risk for type 2 diabetes. We tested the hypothesis that these nutritional modifications differentially improve whole-body insulin sensitivity (primary outcome) and secretion. METHODS: Inclusion criteria were: age 18-69 years, BMI ≥ 30 kg/m(2), type 2 diabetes treated with diet, metformin or acarbose and known disease duration of ≤ 5 years. Exclusion criteria were: HbA1c >75 mmol/mol (9.0%), type 1 or secondary diabetes types and acute or chronic diseases including cancer. Patients taking any medication affecting the immune system or insulin sensitivity, other than metformin, were also excluded. Of 59 patients (randomised using randomisation blocks [four or six patients] with consecutive numbers), 37 (54% female) obese type 2 diabetic patients completed this controlled parallel-group 8-week low-energy dietary intervention. The participants consumed either a diet high in cereal fibre (whole grain wheat/rye: 30-50 g/day) and coffee (≥ 5 cups/day), and free of red meat (L-RISK, n = 17) or a diet low in fibre (≤ 10 g/day), coffee-free and high in red meat (≥ 150 g/day) diet (H-RISK, n = 20). Insulin sensitivity and secretion were assessed by hyperinsulinaemic-euglycaemic clamp and intravenous glucose tolerance tests with isotope dilution. Whole-body and organ fat contents were measured by magnetic resonance imaging and spectroscopy. RESULTS: Whole-body insulin sensitivity increased in both groups (mean [95% CI]) (H-RISK vs L-RISK: 0.8 [0.2, 1.4] vs 1.0 [0.4, 1.7]mg kg(-1) min(-1), p = 0.59), while body weight decreased (-4.8% [-6.1%, -3.5%] vs -4.6% [-6.0%, -3.3%], respectively). Hepatic insulin sensitivity remained unchanged, whereas hepatocellular lipid content fell in both groups (-7.0% [-9.6%, -4.5%] vs -6.7% [-9.5%, -3.9%]). Subcutaneous fat mass (-1,553 [-2,767, -340] cm(3) vs -751 [-2,047; 546] cm(3), respectively) visceral fat mass (-206 [-783, 371] cm(3) vs -241 [-856, 373] cm(3), respectively) and muscle fat content (-0.09% [-0.16%, -0.02%] vs -0.02% [-0.10%, 0.05%], respectively) decreased similarly. Insulin secretion remained unchanged, while the proinflammatory marker IL-18 decreased only after the L-RISK diet. CONCLUSIONS/INTERPRETATION: No evidence of a difference between both low-energy diets was identified. Thus, energy restriction per se seems to be key for improving insulin action in phases of active weight loss in obese type 2 diabetic patients, with a potential improvement of subclinical inflammation with the L-RISK diet. TRIAL REGISTRATION: Clinicaltrials.gov NCT01409330. FUNDING: This study was supported by the Ministry of Science and Research of the State of North Rhine-Westphalia (MIWF NRW), the German Federal Ministry of Health (BMG), the Federal Ministry for Research (BMBF) to the Center for Diabetes Research (DZD e.V.) and the Helmholtz Alliance Imaging and Curing Environmental Metabolic Diseases (ICEMED).

Sfrp5 correlates with insulin resistance and oxidative stress.

BACKGROUND: Secreted frizzled-related protein 5 (Sfrp5) has been described as novel adipokine in mice with insulin-sensitising and anti-inflammatory properties similar to adiponectin. The aim of this study was to compare serum concentrations and determinants of Sfrp5, its pro-inflammatory antagonist wingless-type MMTV integration site family member (Wnt)5a and adiponectin in humans and their regulation by coffee. MATERIAL AND METHODS: Serum concentrations of Sfrp5, Wnt5a and adiponectin were measured in 47 individuals who participated in a coffee intervention study. Associations with demographic, metabolic and immunological variables and regulation of serum levels by different amounts of daily coffee intake were analysed. RESULTS: At baseline, fasting serum Sfrp5 levels ranged between 96 and 4056 ng/mL. Sfrp5 was directly correlated with a surrogate of insulin resistance (homeostasis model assessment of insulin resistance/HOMA-IR; r = 0·32, P < 0·05) and with the oxidative stress markers 8-isoprostane (r = 0·44, P < 0·01) and nitrotyrosine (r = 0·52, P < 0·001). Adiponectin showed inverse correlations with several indices of insulin resistance (e.g. HOMA-IR, Stumvoll index; all P < 0·05) and a direct correlation with the anti-atherogenic apolipoprotein A-I (r = 0·56, P < 0·001). Coffee did not affect serum concentrations of Sfrp5. Serum Wnt5a concentrations were below the detection limit (0·02 ng/mL) in 81% of the study participants. CONCLUSIONS: In contrast to obese mouse models, serum Sfrp5 was directly related to HOMA-IR and oxidative stress in humans, but not with apolipoproteins, and thus, associations differed from those found for circulating adiponectin. These differences between Sfrp5 and adiponectin might be explained by differences in the investigated species.

Low levels of serum 25-hydroxyvitamin D are associated with increased risk of myocardial infarction, especially in women: results from the MONICA/KORA Augsburg case-cohort study.

CONTEXT AND OBJECTIVE: A growing body of evidence suggests that vitamin D deficiency may adversely affect the cardiovascular system. Therefore, we thought to prospectively assess the association between serum 25-hydroxyvitamin D, the most commonly used index of vitamin D status, and incident coronary heart disease. DESIGN, SETTING, AND PATIENTS: We measured serum levels of 25[OH]D in 1783 healthy middle-aged subjects (964 men, 819 women) in the population-based Monitoring of Trends and Determinants in Cardiovascular Disease/Cooperative Health Research in the Region of Augsburg studies. A total of 298 coronary heart disease cases were identified over a mean follow-up period of 11 yr. RESULTS: After adjustment for age, survey, and season of blood sampling, the hazard ratio (HR) and 95% confidence interval comparing tertile extremes of serum levels of 25[OH]D was 0.32 (0.16-0.65) (P for trend = 0.001) in women and 0.56 (0.38-0.82) (P for trend = 0.005) in men. Further adjustment for traditional cardiovascular risk factors slightly attenuated the association in women [HR 0.39 (0.18-0.84); P for trend = 0.013], whereas it became nonsignificant in men [HR 0.76 (0.49-1.17); P for trend = 0.215]. After additional adjustment for C-reactive protein, IL-6, soluble intercellular adhesion molecule-1, and interferon-γ-inducible protein-10, the association still remained significant in women [HR 0.42 (0.19-0.93); P for trend = 0.028], and it was further reduced in men [HR 0.84 (0.52-1.35); P for trend = 0.461]. CONCLUSION: Our findings suggest that higher vitamin D levels are associated with decreased risk of coronary heart disease. This effect is more pronounced in women than in men. Further clinical and experimental studies are needed to investigate the sex differences and whether vitamin D supplementation could contribute to the prevention of coronary heart disease.

Effects of coffee consumption on subclinical inflammation and other risk factors for type 2 diabetes: a clinical trial.

BACKGROUND: Coffee consumption is associated with a decreased risk of type 2 diabetes. Suggested mechanisms underlying the association have included attenuation of subclinical inflammation and a reduction in oxidative stress. OBJECTIVE: The aim was to investigate the effects of daily coffee consumption on biomarkers of coffee intake, subclinical inflammation, oxidative stress, glucose, and lipid metabolism. DESIGN: Habitual coffee drinkers (n = 47) refrained for 1 mo from coffee drinking; in the second month they consumed 4 cups of filtered coffee/d and in the third month 8 cups of filtered coffee/d (150 mL/cup). Blood samples were analyzed by gas chromatography-mass spectrometry, bead-based multiplex technology, enzyme-linked immunosorbent assay, or immunonephelometry. RESULTS: Coffee consumption led to an increase in coffee-derived compounds, mainly serum caffeine, chlorogenic acid, and caffeic acid metabolites. Significant changes were also observed for serum concentrations of interleukin-18, 8-isoprostane, and adiponectin (medians: -8%, -16%, and 6%, respectively; consumption of 8 compared with 0 cups coffee/d). Serum concentrations of total cholesterol, HDL cholesterol, and apolipoprotein A-I increased significantly by 12%, 7%, and 4%, respectively, whereas the ratios of LDL to HDL cholesterol and of apolipoprotein B to apolipoprotein A-I decreased significantly by 8% and 9%, respectively (8 compared with 0 cups coffee/d). No changes were seen for markers of glucose metabolism in an oral-glucose-tolerance test. CONCLUSIONS: Coffee consumption appears to have beneficial effects on subclinical inflammation and HDL cholesterol, whereas no changes in glucose metabolism were found in our study. Furthermore, many coffee-derived methylxanthines and caffeic acid metabolites appear to be useful as biomarkers of coffee intake.

Combined activation of innate and T cell immunity for recognizing immunomodulatory properties of therapeutic agents.

Complex syndromes such as atherosclerosis and type 2 diabetes are disorders that are associated with inflammatory processes involving innate and adaptive immunity. Emerging knowledge about the pathological consequences of immune imbalances in a wide range of disease settings is expected to help to identify novel therapeutic targets. However, current test systems for immunomodulatory drugs tend to be too simplistic, as they rely only on cells of the innate- or the adaptive-immune system, or they are complex, in vivo models, which are not suitable for screening purposes. Using a modified mixed lymphocyte culture (MMLC) assay for combined analysis of innate and adaptive immunity, we show that this assay is very sensitive for the presence of low concentrations of immunomodulatory agents. Low-dose lipopolysaccharide stimulation of cells from two unrelated donors yields a strong cytokine response including interleukin (IL)-12 and IL-18, which induce interferon-gamma as a potential analysis parameter. As the MMLC assay is based on the mutual interaction of cells of the innate and adaptive immunity, it enables the monitoring of cytokine release under almost physiological conditions and might be of interest for the characterization of known and novel drugs concerning their immunomodulatory potency.