Macronutrients,minerals, vitamins and energy

Carbohydrates have the general formula C_n(H₂O)_n. Monosaccharides have between three and six carbon atoms and exist as chains or ring structures. As rings, they link with other monosaccharide rings. The major carbohydrate in humans is glucose, which is stored as glycogen: branching chains of glucose molecules. Fat (triglyceride), which makes up adipose tissue, consists of three fatty acids bonded to glycerol, but other lipids include phospholipids and steroids. Proteins are composed of chains of amino acids linked by amide bonds folded on each other to form protein structures. Vitamins and minerals are obtained from the diet and are required in varying quantities for a variety of metabolic processes. Energy is derived from the oxidation of carbohydrate, fat and protein. Energy expenditure and substrate oxidation can be calculated from oxygen consumption, carbon dioxide production and urinary nitrogen excretion.     

Macronutrients,minerals, vitamins and energy

Carbohydrates have the general formula C_n(H₂O)_n. Monosaccharides have between three and six carbon atoms and exist as chains or ring structures. As rings, they link with other monosaccharide rings. The major carbohydrate in humans is glucose, which is stored as glycogen: branching chains of glucose molecules. Fat (triglyceride), which makes up adipose tissue, consists of three fatty acids bonded to glycerol, but other lipids include phospholipids and steroids. Proteins are composed of chains of amino acids linked by amide bonds folded on each other to form protein structures. Vitamins and minerals are obtained from the diet and are required in varying quantities for a variety of metabolic processes. Energy is derived from the oxidation of carbohydrate, fat and protein. Energy expenditure and substrate oxidation can be calculated from oxygen consumption, carbon dioxide production and urinary nitrogen excretion.     

Macronutrients,minerals, vitamins and energy

Macronutrients comprise carbohydrates, fats and proteins and make up most of the body's soft tissue structure. Carbohydrates are organic molecules made of carbon, hydrogen and oxygen atoms. Fats are composed of carbon, hydrogen and oxygen, but the proportion of oxygen atoms to carbon and hydrogen is lower than in carbohydrates. Proteins are usually made up of more than 100 amino acids linked into chains by peptide bonds. Amino acids consist of an asymmetrical carbon atom with both an amino group (NH₂) and a carboxyl group (COOH) attached. Energy used for metabolic homeostasis, thermoregulation, physical activity and normal organ function is obtained from the oxidation of these macronutrients. Micronutrients (trace minerals and vitamins) are dietary components necessary to sustain health. Most trace minerals appear to function as cofactors for a number of enzymes. Vitamins have many roles in intermediary metabolism and in the specialized metabolism of specifc organs.     

Carbohydrate metabolism

Carbohydrate normally accounts for about 50% of total dietary energy intake, but the general recommendation is for an increased consumption of complex carbohydrates. After digestion and absorption, carbohydrate is metabolized to provide energy (4 kcal/g) or is stored in muscle and liver as glycogen. The body’s carbohydrate stores are normally about 400–500 g in the fed state. Six-carbon glucose molecules are degraded by a series of chemical reactions to three-carbon pyruvate by the reactions of glycolysis; pyruvate can be further metabolized to lactate. These reactions occur in the cell cytoplasm without the involvement of molecular oxygen, so are described as anaerobic. Pyruvate (and lactate) can be further oxidized to CO₂ and water by the reactions of the Krebs’ (tricarboxylic acid) cycle that occur in the mitochondria. Glucose is an essential fuel for the brain and for some other cells, notably red blood cells. Because body carbohydrate reserves are limited, and also because stored fatty acids cannot be converted to carbohydrate, the metabolism of carbohydrates in different tissues is tightly regulated. Some de novo synthesis of glucose is possible from non-carbohydrate sources, including glycerol and the carbon skeletons of some amino acids. Excess dietary carbohydrate is generally oxidized rather than stored.     

Fruktose vs. Glukose in der total parenteralen Ernährung kritisch kranker Patienten

Parenteral nutrition required following surgery or injury should not only meet post-aggression caloric requirements but also match the specific metabolic needs so as not to worsen the metabolic disruptions already present in this situation. The primary objective of parenteral nutrition is body protein maintenance or restoration by reduction of protein catabolism or promotion of protein synthesis or both. Whether all parenteral energy donors, i.e., glucose, fructose, other polyols, and lipid emulsions, are equally capable of achieving this objective continues to be a controversial issue. The objective of the present study was to answer the following questions: (1) Do glucose and fructose differ in their effects on the metabolic changes seen following surgery or injury, the changes in glucose metabolism in particular? (2) Can the observation of poorer glucose utilization in the presence of lipids be confirmed in ICU patients? Patients, materials and methods. A prospective, randomized clinical trial has been conducted in 20 aseptic surgical ICU patients to generate an objective database along these lines by performing a detailed analysis of the metabolic responses to different parenteral nutrition protocols. The effects of a glucose solution+lipid emulsion regimen vs fructose solution+lipid emulsion regimen on a number of carbohydrate and lipid metabolism variables were evaluated for an isocaloric (carbohydrates: 0.25?g/kg body weight/h; lipids: 0.166?g/kg body weight/h) and isonitrogenous (amino acids: 0.0625?g/kg body weight/h) total nutrient supply over a 10-h study period. Results. A significantly smaller rise in blood glucose concentrations (increase from baseline: glucose+lipids P<0.001 vs fructose+lipids n.s.) suggested that fructose had a small effect, if any at all, on glucose metabolism. Serum insulin activity showed significant differences as a function of carbohydrate regimen, i.e. infusion of fructose instead of glucose produced a less pronounced increase in insulin activity (increase from baseline: glucose+lipids P<0.001 vs fructose+lipids P<0.01). Impairment of glucose utilization by concomitant administration of lipids was observed neither in patients who first received glucose nor in those who first received fructose. Conclusions. As demonstrated, parenteral fructose, unlike parenteral glucose, has a significantly less adverse impact than glucose on the glucose balance, which is disrupted initially in the post-aggression state. In addition, the less pronounced increase in insulin activity during fructose infusion than during glucose infusion can be assumed to facilitate mobilization of endogenous lipid stores and lipid oxidation. Earlier workers pointed out that any rise in free fatty acid and ketone body concentrations in the serum produces inhibition of muscular glucose uptake and oxidation, and of glycolysis. These findings were recorded in a rat model and could not be confirmed in our post-aggression state patients receiving lipid doses commensurate with the usual clinical infusion rates. The serious complications that can result from hereditary fructose intolerance are completely avoidable if a careful patient history is taken before the first parenteral use of fructose. If the patient or family members and close friends, are simply asked whether he/she can tolerate fruit and sweet dishes, hereditary fructose intolerance can be ruled out beyond all reasonable doubt. Only in the extremely rare situations in which it is not possible to question either the patient or any significant other, a test dose will have to be administered to exclude fructose intolerance. The benefits of fructose-specific metabolic effects reported in the literature and corroborated by the results of our own study suggest that fructose is an important nutrient that contributes to metabolic stabilization, especially in the post-aggression phase and in septic patients. Hyperglycaemic states are largely prevented, and fewer patients require exogenous insulin, thus avoiding the frequently underestimated risk of hypoglycaemic states.     

Comparison of palmitic acid and glucose metabolism in the rabbit urinary bladder

This study was designed to investigate the relative importance of carbohydrate and fatty acids as substrates for energy production in the urinary bladder and to obtain information about the kinetics involved in the oxidation of glucose and a representative fatty acid by rabbit bladder incubated in vitro. Isolated strips of rabbit bladder body were incubated in the presence of various concentrations of ¹⁴C-glucose or ¹⁴C-palmitate for different periods of time up to 90 minutes. The rate of ¹⁴CO₂ generation was measured. In addition, the effect of bethanechol on both glucose and palmitic acid metabolism was determined. The results can be summarized as follows: (1) The oxidation of glucose showed a distinct lag period with time lasting for about 30 minutes. From 30 to 90 minutes the rate of ¹⁴C₂-palmitate was linear over the entire 90-minute period of incubation. (2) Experiments in which the concentration of glucose was varied showed saturation kinetics. From a Lineweaver-Burk plot a V_max of 0.645 umol/g/hr was obtained with a k_m of 2.30 mM. (3) Preincubation of tissues without substrate caused a significant increase in the rate of glucose oxidation. (4) The rate of oxidation of ¹⁴C-palmitate increased with concentration of the fatty acid. (5) A Lineweaver-Burk plot showed a V_max of 30.0 nmol/g/hr and a k_m of 2.50 mM. Addition of unlabeled glucose to tissues oxidizing ¹⁴C-palmitate had no effect on ¹⁴CO₂ production. Similarly, the addition of non-radioactive palmitate to tissues incubated with ¹⁴C-glucose did not decrease glucose oxidation. When both radioactive substrates were present the rates of oxidation were additive. (6) Although bethanechol stimulated glucose oxidation, the drug had no significant effect on palmitate metabolism.     

Uric acid: Effects on serum and urine levels in patients receiving intravenous dextrose,fat, and/or amino acid solutions

Parenteral dextrose/amino acid solutions reduce serum uric acid levels when infused into patients. To elucidate the mechanism further, 53 patients with invasive bladder cancer were selected for study. Patients received either amino acids alone (n = 13), 5% dextrose + amino acids (n = 15), 5% dextrose in water (n = 13), 25% dextrose + amino acids (n = 7), or fat 10% + amino acids (n = 5). All patients received 2500 ml intravenously for 3 days preop and 3000 ml for at least 7 days postop containing 1.4 g AA/kg/day; after Day +7 oral intake was allowed. No patient had gout. Serial serum uric acid levels and daily 24-hr urine uric acid and creatinine levels were measured. There were no significant differences among intravenous groups in: mean patient age, percentage ideal body weight, duration of operation, operative blood loss, fluid-blood replacement, or serum and urine creatinine levels. Mean serum uric acid levels decreased postoperatively in all groups. The mean change in serum uric acid levels from Day ?3 to Day +7 was significantly different between the D5/AA group (2.3 ± 0.2 mg/dl) and the AA/H₂O group (1.1 ± 0.4 mg/dl) and between the D25/AA group (2.8 ± 0.6 mg/dl) and the AA/H₂O and D5W (1.4 ± 0.3 mg/dl) group. This significant change in mean serum uric acid levels with infusion of 5 and 25% dextrose with amino acids occurred without increased uricosuria compared to the other groups of patients.     

The fate of a glucose infusion in fasting and fed guinea pigs: Glucose oxidation rates and the distribution of glucose in liver,muscle, and adipose tissue

We have undertaken two studies in which normal guinea pigs (24 hr fasting or fed ad libitum) have been infused with exogenous glucose (55 μmole/kg·min) together with a primed constant infusion of [U-¹⁴C]glucose. In the first study (n = 10), the animals were sacrificed after a 2-hr glucose infusion. The carcasses were immediately homogenized and the distribution of the isotope determined. We found that 14.8 ± 2.5% of infused label appeared as ¹⁴CO₂ in the fasted animals. The remaining isotopic label (84.8 ± 2.3%) was recovered in the protein-free filtrate fraction of the carcass homogenate. In protein, glycogen, and fat, 6.6 ± 1.8, 1.2 ± 0.2 and 5.6 ± 0.7% were recovered respectively. In the fed animals, 25.0 ± 1.8% of infused label appeared as ¹⁴CO₂. Of the remaining isotopic label 77.9 ± 1.7% was recovered in the protein-free filtrate fraction of the carcass homogenate. In protein, glycogen, and fat, 10.9 ± 0.6, 1.1 ± 0.1, and 5.7 ± 0.5% were recovered respectively. In the second study (n = 18), both glucose kinetics and the fate of the infused glucose with respect to end product (glycogen, fat, or protein) in liver, muscle, and epididymal fat pads was determined during a 5-hr glucose infusion. Infused glucose (32.6 and 31.6%) was oxidized directly for energy in the fasted and fed animals, respectively. The fate of the remaining glucose that was not oxidized depended upon the nutritional state of the animal. In the depleted animals, glucose was directed predominantly toward hepatic glycogen, whereas in the fed animals the labeled glucose was recovered primarily in the peripheral fat.     

Analysis of energy utilization and body composition in kidney,bladder, and adrenal cancer patients

ObjectiveTo investigate resting energy expenditure (REE) and body composition and the relationship between substrate utilization and energy expenditure in urologic cancer patients.Patients and methodsMeasured resting energy expenditure (mREE) was detected by indirect calorimetry in 122 urologic cancer patients and 131 control subjects. Extracellular fluid (ECF), intracellular fluid (ICF), and total water (TW) were measured by bioelectrical impedance appliance. Fat oxidation rate (F-O), carbohydrate oxidation rate, fat mass (FM), and fat free mass (FFM) were further determined.ResultsCompared with the controls, cancer patients showed significantly elevated mREE and mREE/FFM (P = 0.049; P < 0.001). Of all the cancer patients, 50% (n = 61) were hypermetabolic, 43.4% (n = 53) normometabolic, and 6.6% (n = 8) hypometabolic, whereas 35.1% (n = 46) of the controls were hypermetabolic, 56.5% (n = 74) normometabolic, and 8.4% (n = 11) hypometabolic. REE was correlated to substrate oxidation rate (R² = 0.710). Cancer patients exhibited no significant difference in FM, FM/body weight (BW) and FFM, compared with controls. Cancer patients presented no significant difference in TW compared with controls (P = 0.791), but they had increased ECF (P < 0.001) and decreased ICF (P < 0.001).ConclusionAberrations in substrate utilization may contribute to the elevated energy expenditure in urologic cancer patients. Cancer type and pathologic stage are influential factors of REE.     

Adaptation of β-Cell and Endothelial Function to Carbohydrate Loading: Influence of Insulin Resistance

High-carbohydrate diets have been associated with β-cell strain, dyslipidemia, and endothelial dysfunction. We examined how β-cell and endothelial function adapt to carbohydrate overloading and the influence of insulin resistance. On sequential days in randomized order, nondiabetic subjects (classified as insulin-sensitive [IS] [n = 64] or insulin-resistant [IR] [n = 79] by euglycemic clamp) received four mixed meals over 14 h with either standard (300 kcal) or double carbohydrate content. β-Cell function was reconstructed by mathematical modeling; brachial artery flow-mediated dilation (FMD) was measured before and after each meal. Compared with IS, IR subjects showed higher glycemia and insulin hypersecretion due to greater β-cell glucose and rate sensitivity; potentiation of insulin secretion, however, was impaired. Circulating free fatty acids (FFAs) were less suppressed in IR than IS subjects. Baseline FMD was reduced in IR, and postprandial FMD attenuation occurred after each meal, particularly with high carbohydrate, similarly in IR and IS. Throughout the two study days, higher FFA levels were significantly associated with lower (incretin-induced) potentiation and impaired FMD. In nondiabetic individuals, enhanced glucose sensitivity and potentiation upregulate the insulin secretory response to carbohydrate overloading. With insulin resistance, this adaptation is impaired. Defective suppression of endogenous FFA is one common link between impaired potentiation and vascular endothelial dysfunction.     

Hypothalamic protein kinase C regulates glucose production

OBJECTIVE—A selective rise in hypothalamic lipid metabolism and the subsequent activation of SUR1/Kir6.2 ATP-sensitive K⁺ (K_ATP) channels inhibit hepatic glucose production. The mechanisms that link the ability of hypothalamic lipid metabolism to the activation of K_ATP channels remain unknown.RESEARCH DESIGN AND METHODS—To examine whether hypothalamic protein kinase C (PKC) mediates the ability of central nervous system lipids to activate K_ATP channels and regulate glucose production in normal rodents, we first activated hypothalamic PKC in the absence or presence of K_ATP channel inhibition. We then inhibited hypothalamic PKC in the presence of lipids. Tracer-dilution methodology in combination with the pancreatic clamp technique was used to assess the effect of hypothalamic administrations on glucose metabolism in vivo.RESULTS—We first reported that direct activation of hypothalamic PKC via direct hypothalamic delivery of PKC activator 1-oleoyl-2-acetyl-sn-glycerol (OAG) suppressed glucose production. Coadministration of hypothalamic PKC-δ inhibitor rottlerin with OAG prevented the ability of OAG to activate PKC-δ and lower glucose production. Furthermore, hypothalamic dominant-negative Kir6.2 expression or the delivery of the K_ATP channel blocker glibenclamide abolished the glucose production-lowering effects of OAG. Finally, inhibition of hypothalamic PKC eliminated the ability of lipids to lower glucose production.CONCLUSIONS—These studies indicate that hypothalamic PKC activation is sufficient and necessary for lowering glucose production.The hypothalamus senses nutrients and hormones to regulate energy and glucose homeostasis (1–9), but the associated central nervous system (CNS) sensing mechanisms remain unclear. A selective increase in long-chain fatty acyl-coenzyme A (LCFA-CoA) level in the hypothalamus leads to the activation of SUR1/Kir6.2-containing ATP-sensitive K⁺ (K_ATP) channels and lowers glucose production (10). In contrast, an elevation of LCFA-CoA level in the liver actually increases glucose production during hyperinsulinemia (1). These observations led us to hypothesize that lipid-sensing mechanisms share similar biochemical (i.e., LCFA-CoA accumulation) but have opposing physiological mechanisms (i.e., glucose production regulation) in operation (1).In the peripheral tissues such as the liver and muscle, an elevation of lipids (especially the long-chain fatty acids [LCFAs]) activates the novel isoforms of protein kinase C (PKC) (i.e., -δ, -ɛ, and -θ) to induce insulin resistance during hyperinsulinemic-euglycemic clamps (11–16). Although novel isoforms of PKC (especially -δ and -ɛ) are expressed in the brain (17), it is currently unknown whether LCFAs activate hypothalamic, novel isoforms of PKC to regulate glucose production. It has been reported that activation of PKC leads to phosphorylation of the conserved threonine residue (T180) in the pore-forming subunit Kir6.2 of the K_ATP channels in the pancreatic β-cells (18). These channels are expressed in both β-cells and neurons (18,19), and direct activation of the hypothalamic K_ATP channels has been shown to lower glucose production (19). Both the PKC-induced K_ATP channel activation (18) and hypothalamic K_ATP channels’ regulation of glucose production (19) are blocked by pretreatment with the K_ATP channel blocker glibenclamide (18,19). It is possible that the mechanism of activation of K_ATP channels in the β-cells by PKC is also found in the hypothalamus.Based on these independent yet parallel findings, we tested the hypothesis that activation of hypothalamic PKC is sufficient and necessary for CNS lipid-sensing mechanisms to lower glucose production and regulate glucose homeostasis (Fig. 1A).Open in a separate windowFIG. 1.Hypothalamic PKC activation lowers glucose production. A: Working hypothesis: lipids activate hypothalamic PKC to phosphorylate and activate the hypothalamic Kir6.2/SUR1-containing K_ATP channels to lower glucose production. Direct MBH administration of PKC activator OAG increased glucose infusion rate (B) and lowered glucose production (C) during the clamps. MBH OAG coinfused with general PKC inhibitor BIM (n = 5), specific PKC-δ inhibitor Rot (n = 6), or K_ATP channel blocker glibenclamide (n = 5) or in MBH DN Kir6.2 AAA-injected rats (n = 5) failed to increase glucose infusion rate (B) and lower glucose production (C). D: Glucose uptake was comparable in all groups. MBH vehicle (VEH) (n = 6) consisted of MBH saline (n = 3) and MBH 5% DMSO (n = 3). MBH OAG (n = 7) consisted of MBH OAG in normal rats (n = 4) and in MBH GFP-injected rats (n = 3). *P < 0.001 (ANOVA) and P < 0.01 vs. other individual groups.     

Multiple laser pulses in conjunction with an optical clearing agent to improve the curative effect of cutaneous vascular lesions

Port-wine stain (PWS) birthmark is a congenital microvascular malformation of the skin. A 1064-nm Nd:YAG laser can achieve a deeper treatment, but the weak absorption by blood limits its clinical application. Multiple laser pulses (MLPs) are a potential solution to enhance the curative effect of a Nd:YAG laser. To reduce the pulse number (p_n) required for the thermal destruction of the blood vessel, the effect of glucose in conjunction with MLP was investigated. In vivo experiments were performed on a dorsal skin chamber model. Different concentrations (20, 25, 30, and 40%) of glucose were applied to the sub-dermal side of the hamster skin before laser irradiation. Identical vessels with diameters of 200?±?30 and 110?±?20 μm were chosen as representatives of typical PWS vessels. Instant thermal responses of the blood vessel were recorded by a high-speed camera. The required p_n for blood vessel damage was compared with that without glucose pretreatment. Results showed that the use of glucose with a concentration of 20% combined with MLP Nd:YAG laser to damage blood vessels is more appropriate because severe hemorrhage or carbonization easily appeared in blood vessels at higher glucose concentration of 25, 30, and 40%. When 20% glycerol is pretreated on the sub-dermal hamster skin, the required p_n for blood vessel damage can be significantly decreased for different power densities. For example, p_n can be reduced by 40% when the power density is 57 J/cm². In addition, generation of cavitation and bubbles in blood vessels is difficult upon pretreatment with glucose. The combination of glucose with MLP Nd:YAG laser could be an effective protocol for reducing the p_n required for blood vessel damage. Randomized controlled trial (RCT) and human trials will be conducted in the future.     

Common variants in the adiponectin gene (ADIPOQ) associated with plasma adiponectin levels, type 2 diabetes, and diabetes-related quantitative traits: the Framingham Offspring Study

OBJECTIVE— Variants in ADIPOQ have been inconsistently associated with adiponectin levels or diabetes. Using comprehensive linkage disequilibrium mapping, we genotyped single nucleotide polymorphisms (SNPs) in ADIPOQ to evaluate the association of common variants with adiponectin levels and risk of diabetes.RESEARCH DESIGN AND METHODS— Participants in the Framingham Offspring Study (n = 2,543, 53% women) were measured for glycemic phenotypes and incident diabetes over 28 years of follow-up; adiponectin levels were quantified at exam 7. We genotyped 22 tag SNPs that captured common (minor allele frequency >0.05) variation at r² > 0.8 across ADIPOQ plus 20 kb 5′ and 10 kb 3′ of the gene. We used linear mixed effects models to test additive associations of each SNP with adiponectin levels and glycemic phenotypes. Hazard ratios (HRs) for incident diabetes were estimated using an adjusted Cox proportional hazards model.RESULTS— Two promoter SNPs in strong linkage disequilibrium with each other (r² = 0.80) were associated with adiponectin levels (rs17300539; P_nominal [P_n] = 2.6 × 10⁻⁸; P_empiric [P_e] = 0.0005 and rs822387; P_n = 3.8 × 10⁻⁵; P_e = 0.001). A 3′-untranslated region (3′UTR) SNP (rs6773957) was associated with adiponectin levels (P_n = 4.4 × 10⁻⁴; P_e = 0.005). A nonsynonymous coding SNP (rs17366743, Y111H) was confirmed to be associated with diabetes incidence (HR 1.94 [95% CI 1.16–3.25] for the minor C allele; P_n = 0.01) and with higher mean fasting glucose over 28 years of follow-up (P_n = 0.0004; P_e = 0.004). No other significant associations were found with other adiposity and metabolic phenotypes.CONCLUSIONS— Adiponectin levels are associated with SNPs in two different regulatory regions (5′ promoter and 3′UTR), whereas diabetes incidence and time-averaged fasting glucose are associated with a missense SNP of ADIPOQ.Adiponectin is an adipokine produced by adipocytes that has drawn attention over the past few years for its potential role in diabetes physiology (1). Adiponectin is believed to have anti-inflammatory and insulin-sensitizing properties. High levels of circulating adiponectin have been associated with lower diabetes incidence in many prospective studies (1).Adiponectin is encoded by the gene ADIPOQ located in the chromosomal region 3q27. ADIPOQ spans 16 kb and contains three exons. Previous genome-wide linkage scans have identified 3q27 as a susceptibility locus for diabetes (2,3). Various single nucleotide polymorphisms (SNPs) in ADIPOQ have been reported to be associated with adiponectin levels and/or diabetes but with inconsistent results. A recent comprehensive review (4) showed that a few ADIPOQ SNPs were associated with adiponectin levels and insulin resistance, but none was consistently associated with diabetes or with adiposity as measured by BMI. As underlined by Menzaghi et al. (4), the lack of consistent findings emphasizes the need for comprehensive characterization of the genetic variation in and around the ADIPOQ gene. They also emphasized the need to address the issue that some ADIPOQ SNPs seem to be associated with adiponectin levels, whereas others seem to be associated with insulin resistance and diabetes-related metabolic traits.With this background in mind, we conducted a fine-mapping study of ADIPOQ, including regulatory regions upstream and downstream of the gene. We studied participants of the Framingham Offspring Study (FOS), a large representative community-based sample that has been followed prospectively for cardiovascular risk factors, including intermediate metabolic traits and diabetes. Our goals were to confirm the associations of SNPs reported previously, to identify SNPs that might have stronger adiponectin or diabetes association signals than those reported, and to seek new associations with adiponectin levels or diabetes incidence using comprehensive characterization of the gene and detailed metabolic phenotyping over a long follow-up, in a large population sample to ensure adequate power.     

Mangiferin Stimulates Carbohydrate Oxidation and Protects Against Metabolic Disorders Induced by High-Fat Diets

Excessive dietary fat intake causes systemic metabolic toxicity, manifested in weight gain, hyperglycemia, and insulin resistance. In addition, carbohydrate utilization as a fuel is substantially inhibited. Correction or reversal of these effects during high-fat diet (HFD) intake is of exceptional interest in light of widespread occurrence of diet-associated metabolic disorders in global human populations. Here we report that mangiferin (MGF), a natural compound (the predominant constituent of Mangifera indica extract from the plant that produces mango), protected against HFD-induced weight gain, increased aerobic mitochondrial capacity and thermogenesis, and improved glucose and insulin profiles. To obtain mechanistic insight into the basis for these effects, we determined that mice exposed to an HFD combined with MGF exhibited a substantial shift in respiratory quotient from fatty acid toward carbohydrate utilization. MGF treatment significantly increased glucose oxidation in muscle of HFD-fed mice without changing fatty acid oxidation. These results indicate that MGF redirects fuel utilization toward carbohydrates. In cultured C2C12 myotubes, MGF increased glucose and pyruvate oxidation and ATP production without affecting fatty acid oxidation, confirming in vivo and ex vivo effects. Furthermore, MGF inhibited anaerobic metabolism of pyruvate to lactate but enhanced pyruvate oxidation. A key target of MGF appears to be pyruvate dehydrogenase, determined to be activated by MGF in a variety of assays. These findings underscore the therapeutic potential of activation of carbohydrate utilization in correction of metabolic syndrome and highlight the potential of MGF to serve as a model compound that can elicit fuel-switching effects.     

In Vivo Identification,Survival, and Functional Efficacy of Transplanted Hepatocytes in Acute Liver Failure Mice Model by FISH Using Y-Chromosome Probe

Hepatocyte transplantation has excited much interest in lending temporary metabolic support to a failing liver following acute liver injury. The exact site from which they act and the clinical, biochemical, and histological changes in the recipient body following hepatocyte transplantation is yet to be worked out. The present study is an attempt to delineate location and function of transplanted hepatocytes and also the overall survival of these cells with a fluorescent in situ hybridization (FISH) technique using a Y-chromosome–specific probe in a carbon tetrachloride (CCl₄)-induced mice model of fulminant hepatic failure. Fifty-five syngenic adult Swiss female mice of approximately the same age and body weight were divided into three groups. Group-1 (n = 15), which received mineral oil, served as a negative control. Group-II (n = 15) received CCl₄ (3 mL/kg) 40% vol/vol in mineral oil, by gavage served as positive control for hepatic failure. Group-III (n = 25) received intrasplenic transplantation of syngenic single cell suspension of hepatocytes in Hanks medium, after 30 h of CCl₄ administration. Male Swiss adult mice (n = 15) served as donors of hepatocytes. The overall survival of animals in groups I to III was 100, 0, and 70%, respectively, by 2 wk of the study period. Transplanted hepatocytes were identified by Periodic Acid Schiff (PAS) staining and confirmed with a FISH technique using the Y-chromosome probe. The majority of exogenously transplanted hepatocytes were found in the liver and spleen sections even after 1 wk of hepatocyte transplantation. Transplanted cells were mostly found to be translocated into the sinusoids of the liver. Transplanted hepatocytes were found to be beneficial as a temporary liver support in a failing liver, significantly improving the survival of the animals. In the present study, the FISH technique was used to unequivocally distinguish the transplanted cells from the host, and thus describes a model for studying the distribution and survival of the transplanted cells.     

The crystal sheaths from bivalve hinge ligaments

Summary The aragonite crystals in the molluscan bivalve hinge ligament are surrounded by an organic sheath which is distinct from the remainder of the ligament matrix.Methods have been developed to isolate these sheathed crystals from the ligaments ofSpisula solidissima andMercenaria mercenaria employing a papain digestion of the matrix protein. The sheathed crystals fromSpisula have a CaCO₃/protein ratio of 11.1 and those fromMercenaria a ratio of 29.6. The sheathed crystals and the empty crystal sheaths have been examined by electron microscopy for structural integrity.The sheath proteins exhibit much smaller proportions of the amino acids glycine and methionine than the hinge ligaments. These are characteristic amino acids of high concentration in the hinge ligaments of both species. The concentrations of acidic and basic amino acids are increased about two fold in the sheaths over those of the ligaments. Otherwise there is little similarity in the amino acid composition of the sheaths in the two species. However, SDS electrophoresis shows the sheaths of both to contain a major protein component with a molecular weight of about 25,000. The sheath protein from theMercenaria ligament contains about 5% carbohydrate and that ofSpisula sheaths less than 1% carbohydrate.     

Compartmentalized Acyl-CoA Metabolism in Skeletal Muscle Regulates Systemic Glucose Homeostasis

The impaired capacity of skeletal muscle to switch between the oxidation of fatty acid (FA) and glucose is linked to disordered metabolic homeostasis. To understand how muscle FA oxidation affects systemic glucose, we studied mice with a skeletal muscle–specific deficiency of long-chain acyl-CoA synthetase (ACSL)1. ACSL1 deficiency caused a 91% loss of ACSL-specific activity and a 60–85% decrease in muscle FA oxidation. Acsl1^M−/− mice were more insulin sensitive, and, during an overnight fast, their respiratory exchange ratio was higher, indicating greater glucose use. During endurance exercise, Acsl1^M−/− mice ran only 48% as far as controls. At the time that Acsl1^M−/− mice were exhausted but control mice continued to run, liver and muscle glycogen and triacylglycerol stores were similar in both genotypes; however, plasma glucose concentrations in Acsl1^M−/− mice were ∼40 mg/dL, whereas glucose concentrations in controls were ∼90 mg/dL. Excess use of glucose and the likely use of amino acids for fuel within muscle depleted glucose reserves and diminished substrate availability for hepatic gluconeogenesis. Surprisingly, the content of muscle acyl-CoA at exhaustion was markedly elevated, indicating that acyl-CoAs synthesized by other ACSL isoforms were not available for β-oxidation. This compartmentalization of acyl-CoAs resulted in both an excessive glucose requirement and severely compromised systemic glucose homeostasis.     

The effect of CO2 pneumoperitoneum on the growth of a solid colon carcinoma in rats

Background: In order to investigate the effect of carbon dioxide (CO₂) pneumoperitoneum on solid colon carcinomas, we used a colon anastomosis tumor model in 30 male syngeneic WAG rats, which were divided, at random into three groups. Methods: In all rats, 10⁶ CC531 S colon carcinoma cells were injected as an enema into the colon. Subsequently, a transection and a reanastomosis of the colon descendens was performed via laparotomy. After 2 weeks, group 1 (n= 10) was anesthetized as an anesthesia control group. Group 2 (n= 10) had a laparotomy that was closed after 20 min. In group 3 (n= 10), a CO₂ pneumoperitoneum of ≤6 mmHg was created and maintained during 20 min. After 2 weeks, all rats were killed, and total tumor weight and volume was measured. Results: At necroscopy tumor growth was found in 16 rats (group 1: six; group 2: five; group 3: five). No difference in tumor growth (weight or volume) was found between the three groups. Conclusion: In our solid colon carcinoma model, CO₂ pneumoperitoneum did not enhance tumor growth.