Should Carbohydrate Intake Be More Liberal during Oral and Enteral Nutrition in Type 2 Diabetic Patients?

Carbohydrate (CHO) intake in oral and enteral nutrition is regularly reduced in nutritional support of older patients due to the high prevalence of diabetes (usually type 2-T2DM) in this age group. However, CHO shortage can lead to the lack of building blocks necessary for tissue regeneration and other anabolic processes. Moreover, low CHO intake decreases CHO oxidation and can increase insulin resistance. The aim of our current study was to determine the extent to which an increased intake of a rapidly digestible carbohydrate-maltodextrin-affects blood glucose levels monitored continuously for one week in patients with and without T2DM. Twenty-one patients (14 T2DM and seven without diabetes) were studied for two weeks. During the first week, patients with T2DM received standard diabetic nutrition (250 g CHO per day) and patients without diabetes received a standard diet (350 g of CHO per day). During the second week, the daily CHO intake was increased to 400 in T2DM and 500 g in nondiabetic patients by addition of 150 g maltodextrin divided into three equal doses of 50 g and given immediately after the main meal. Plasma glucose level was monitored continually with the help of a subcutaneous sensor during both weeks. The increased CHO intake led to transient postprandial increase of glucose levels in T2DM patients. This rise was more manifest during the first three days of CHO intake, and then the postprandial peak hyperglycemia was blunted. During the night's fasting period, the glucose levels were not influenced by maltodextrin. Supplementation of additional CHO did not influence the percentual range of high glucose level and decreased a risk of hypoglycaemia. No change in T2DM treatment was indicated. The results confirm our assumption that increased CHO intake as an alternative to CHO restriction in type 2 diabetic patients during oral and enteral nutritional support is safe.

Mitochondrial Respiration of Platelets: Comparison of Isolation Methods

Multiple non-aggregatory functions of human platelets (PLT) are widely acknowledged, yet their functional examination is limited mainly due to a lack of standardized isolation and analytic methods. Platelet apheresis (PA) is an established clinical method for PLT isolation aiming at the treatment of bleeding diathesis in severe thrombocytopenia. On the other hand, density gradient centrifugation (DC) is an isolation method applied in research for the analysis of the mitochondrial metabolic profile of oxidative phosphorylation (OXPHOS) in PLT obtained from small samples of human blood. We studied PLT obtained from 29 healthy donors by high-resolution respirometry for comparison of PA and DC isolates. ROUTINE respiration and electron transfer capacity of living PLT isolated by PA were significantly higher than in the DC group, whereas plasma membrane permeabilization resulted in a 57% decrease of succinate oxidation in PA compared to DC. These differences were eliminated after washing the PA platelets with phosphate buffer containing 10 mmol·L⁻¹ ethylene glycol-bis (2-aminoethyl ether)-N,N,N′,N′-tetra-acetic acid, suggesting that several components, particularly Ca²⁺ and fuel substrates, were carried over into the respiratory assay from the serum in PA. A simple washing step was sufficient to enable functional mitochondrial analysis in subsamples obtained from PA. The combination of the standard clinical PA isolation procedure with PLT quality control and routine mitochondrial OXPHOS diagnostics meets an acute clinical demand in biomedical research of patients suffering from thrombocytopenia and metabolic diseases.

The predominant role of glucose as a building block and precursor of reducing equivalents

PURPOSE OF REVIEW

Stores of glucose (Glc) in our body are small compared with protein and lipid. Therefore, at times of famines or trauma/disease-related starvation, glucose utilization must be limited only to pathways that can only run with glucose carbon as substrate. We will try to outline how insulin resistance drives these pathways and inhibits glucose oxidation in the stressed organism.

RECENT FINDINGS

Glc is a basic substrate for a variety of other biomolecules like nucleic acids, amino acids, proteoglycans, mucopolysaccharides and lipids. It is essential for the formation of reducing equivalents, indispensable for anabolic, antioxidative, regulatory and immune processes. As a result, a continuous Glc turnover/cycle is essential to secure at all times the Glc requirements for nonoxidative pathways mentioned above but then requires introduction of extra glucose or other intermediates into the cycle. The production of ATP through complete Glc oxidation occurs only when Glc intake is higher than required for its nonoxidative metabolism. Insulin resistance and decreased Glc oxidation indicate that requirements of Glc for anabolic pathways are high.

SUMMARY

Glc is an important building block for anabolic reactions and substrate for reducing equivalents formation. Insulin resistance prevents irreversible Glc oxidation and stimulates Glc production during stress or growth. Glc is only oxidized when intake is in excess of its anabolic requirements.

The Impact of Glucose-Based or Lipid-Based Total Parenteral Nutrition on the Free Fatty Acids Profile in Critically Ill Patients

Introduction: Our study aim was to assess how the macronutrient intake during total parenteral nutrition (TPN) modulates plasma total free fatty acids (FFAs) levels and individual fatty acids in critically ill patients. Method: Adult patients aged 18–80, admitted to the intensive care unit (ICU), who were indicated for TPN, with an expected duration of more than three days, were included in the study. Isoenergetic and isonitrogenous TPN solutions were given with a major non-protein energy source, which was glucose (group G) or glucose and lipid emulsions (Smof lipid; group L). Blood samples were collected on days 0, 1, 3, 6, 9, 14, and 28. Results: A significant decrease (p < 0.001) in total FFAs occurred in both groups with a bigger decrease in group G (p < 0.001) from day 0 (0.41 ± 0.19 mmol∙L⁻¹) to day 28 (0.10 ± 0.07 mmol∙L⁻¹). Increased palmitooleic acid and decreased linoleic and docosahexaenoic acids, with a trend of increased mead acid to arachidonic acid ratio, on day 28 were observed in group G in comparison with group L. Group G had an insignificant increase in leptin with no differences in the concentrations of vitamin E, triacylglycerides, and plasminogen activator inhibitor-1. Conclusion: Decreased plasma FFA in critically ill patients who receive TPN may result from increased insulin sensitivity with a better effect in group G, owing to higher insulin and glucose dosing and no lipid emulsions. It is advisable to include a lipid emulsion at the latest from three weeks of TPN to prevent essential fatty acid deficiency.

Comparison of Mitochondrial Incubation Media for Measurement of Respiration and Hydrogen Peroxide Production

High-Resolution FluoRespirometry is a well-established and versatile approach to study mitochondrial oxygen uptake amperometrically in combination with measurement of fluorescence signals. One of the most frequently applied fluorescent dyes is Amplex UltraRed for monitoring rates of hydrogen peroxide production. Selection of an appropriate mitochondrial respiration medium is of crucial importance, the primary role of which is to support and preserve optimum mitochondrial function. For harmonization of results in a common database, we compared respiration and H₂O₂ production of permeabilized HEK 293T cells measured in MiR05 (sucrose and K-lactobionate), Buffer Z (K-MES and KCl), MiR07 (combination of MiR05 and Buffer Z), and MiRK03 (KCl). Respiration in a simple substrate-uncoupler-inhibitor titration protocol was identical in MiR05, Buffer Z, and MiR07, whereas oxygen fluxes detected with MiRK03 were consistently lower in all coupling and electron transfer-pathway states. H₂O₂ production rates were comparable in all four media, while assay sensitivity was comparatively low with MiR05 and MiR07 and higher but declining over time in the other two media. Stability of assay sensitivity over experimental time was highest in MiR05 but slightly less in MiR07. Taken together, MiR05 and Buffer Z yield comparable results on respiration and H₂O₂ production. Despite the lower sensitivity, MiR05 was selected as the medium of choice for FluoRespirometry due to the highest stability of the sensitivity or calibration constant observed in experiments over periods of up to 2 h.

The effect of alpha-tocopheryl succinate on succinate respiration in rat liver mitochondria

We compared the effect of alpha-tocopheryl succinate (TOS) on succinate-dependent respiration in rat liver mitochondria, homogenate and permeabilized hepatocytes in both a coupled and uncoupled state. In isolated mitochondria, a significant inhibitory effect was observed at a concentration of 5 microM, in liver homogenate at 25 microM and in permeabilized hepatocytes at 50 microM. The inhibitory effect of TOS on succinate respiration in an uncoupled state was less pronounced than in a coupled state in all the experimental models tested. When the concentration dependence of the TOS inhibitory effect was tested, the most sensitive in both states were isolated mitochondria; the most resistant were permeabilized hepatocytes.

The effect of D-galactosamine on lean and steatotic rat hepatocytes in primary culture

The aim of our work was to compare the effect of D-galactosamine (GalN) on primary cultures of lean and steatotic rat hepatocytes isolated from intact and fatty liver, respectively. GalN caused more severe injury to steatotic hepatocytes than to lean cells as documented by lactate dehydrogenase leakage. Necrotic mode of cell death strongly prevails over apoptosis since we did not observe any significant increase in activities of caspase 3, 8 and 9 in any group of hepatocytes treated with GalN. Reactive oxygen species (ROS) formation and lipid peroxidation were elevated in a dose-dependent manner by GalN and were significantly more pronounced in fatty hepatocytes. A decrease in the percentage of hepatocytes with energized mitochondria was observed from 30 mM and 10 mM GalN in lean and steatotic hepatocytes, respectively. Our results undoubtedly indicate that steatotic hepatocytes exert higher sensitivity to the toxic effect of GalN. This sensitivity may be caused by more intensive GalN-induced ROS production and lipid peroxidation and by higher susceptibility of mitochondria to loss of mitochondrial membrane potential in steatotic hepatocytes. In our experimental arrangement, apoptosis does not seem to participate considerably on hepatotoxic action of GalN in either group of hepatocytes.

Comparison of acetaminophen toxicity in primary hepatocytes isolated from transgenic mice with different appolipoprotein E alleles

The nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor, important for combating electrophilic and oxidative stress in the liver and other organs. This encompasses detoxification of hepatotoxic drugs, including acetaminophen (APAP). Recently, an association between apolipoprotein E (ApoE) genotype and Nrf2 expression was described. We compared the toxicity of APAP on primary culture hepatocytes isolated from transgenic mice carrying two different human ApoE alleles and wild-type controls. The cells were exposed to APAP in concentrations from 0.5 to 4 mM for up to 24 hours. APAP led to a dose-dependent hepatotoxicity from 1 mM after 16 h exposure in all mice tested. The toxicity was higher in hepatocytes isolated from both transgenic strains than in wild-type controls and most pronounced in ApoE3 mice. Concurrently, there was a decline in mitochondrial membrane potential, especially in ApoE3 hepatocytes. The formation of reactive oxygen species was increased after 24 hours with 2.5 mM APAP in hepatocytes of all strains tested, with the highest increase being in the ApoE3 genotype. The activity of caspases 3 and 7 did not differ among groups and was minimal after 24 hour incubation with 4 mM APAP. We observed higher lipid accumulation in hepatocytes isolated from both transgenic strains than in wild-type controls. The expression of Nrf2-dependent genes was higher in ApoE3 than in ApoE4 hepatocytes and some of these genes were induced by APAP treatment. In conclusion, transgenic mice with ApoE4 and ApoE3 alleles displayed higher susceptibility to acute APAP toxicity in vitro than wild-type mice. Of the two transgenic genotypes tested, ApoE3 allele carriers were more prone to injury.