Glycerol: its metabolism and use as an intravenous energy source

Ensuring optimal lipid oxidation during physical activity in overweight and obese patients using a capillary glycerol sensor

AIM

To describe lipid oxidation during physical activity (PA) in overweight and obese patients using a real-time capillary glycerol sensor and to propose a personalized strategy to optimize lipolysis.

METHODS

Healthy adult volunteers with a BMI >25 kg/m2 were recruited. All participants performed 27 sessions of 30-min PA covering all possible combinations of exercises (low, moderate, high intensities) and pre-exercise meals (high-carbohydrate, high-fat, or fasting) with 3 replicates. Glycerol measurements were performed five times during each session: at T0, T20, T30, T45, and T60. The evolution of capillary glycerolemia during PA was modeled by a nonlinear mixed-effects model. We developed a personalized PA recommendation based on the first 2 glycerolemia measurements that indicates whether a change in activity type is preferable.

RESULTS

Thirteen patients were included in the study and 1232 capillary glycerolemia measurements were performed. Hyperglycemic and hyperlipidemic meals were associated with lower baseline glycerolemia (p < 0.0001 for both) compared to fasting. In contrast, the type of meal was not significantly associated with PA-induced lipolysis (p = 0.52 and p = 0.76 for high-carbohydrate and hyperlipidemic meal respectively). Compared with exercises done at low and moderate intensities, high intensity exercises were associated with a higher PA-induced lipolysis (p = 0.0002). Specific strength exercises were associated with a lower PA-induced lipolysis (p < 0.0001). The 2 initial glycerolemia measurements appeared to be a pertinent criterion which help the personalization of PA programs for such individuals (c-index 0.67).

CONCLUSION

The inter-individual lipolysis responses to PA and the availability of a real-time capillary blood glycerol sensor may enable the personalization of PA programs, thus promoting optimal lipolysis in subjects with overweight and obesity.

Metabolomic analysis reveals the metabolic disturbance in aortic dissection: Subtype difference and accurate diagnosis

BACKGROUND AND AIMS

Aortic dissection (AD), a severe clinical emergency with high mortality, is easily misdiagnosed as are other cardiovascular diseases. This study aimed at discovering plasma metabolic markers with the potential to diagnose AD and clarifying the metabolic differences between two subtypes of AD.

METHODS AND RESULTS

To facilitate the diagnosis of AD, we investigated the plasma metabolic profile by metabolomic approach. A total 482 human subjects were enrolled in the study: 80 patients with AD (50 with Stanford type A and 30 with Stanford type B), 198 coronary artery disease (CAD) patients, and 204 healthy individuals. Plasma samples were submitted to targeted metabolomic analysis. The partial least-squares discriminant analysis models were constructed to illustrate clear discrimination of AD patients with CAD patients and healthy control. Subsequently, the metabolites that were clinically relevant to the disturbances in AD were identified. Twenty metabolites induced the separation of AD patients and healthy control, 9 of which caused the separation of CAD patients and healthy control. There are 11 metabolites specifically down-regulated in AD group. Subgroup analysis showed that the levels of glycerol and uridine were dramatically lower in the plasma of patients with Stanford type A AD than those in the healthy control or Stanford type B AD groups.

CONCLUSION

This study characterized metabolomic profiles specifically associated with the pathogenesis and development of AD. The findings of this research may potentially lead to earlier diagnosis and treatment of AD.

DietSee: An on-hand, portable, strip-type biosensor for lipolysis monitoring via real-time amperometric determination of glycerol in blood

Glycerol is a clinical biomarker of lipolysis that is mainly produced by adipose tissues. Blood glycerol content increases in pathological conditions such as metabolic and cardiovascular diseases or cancer cachexia, but also in response to energetic stress such as physical exercise. Accurate glycerol monitoring is therefore important in a range of healthcare contexts. However, current methods available for the quantification of glycerol are expensive, time-consuming, and require the extraction of plasma from blood, from which blood glycerol content is then extrapolated. Here, we report the development of a new point-of-care glycerometer device, DietSee, based on a strip-type biosensor that enables the quantification of glycerol directly from whole blood in 6 s. The performance of the biosensor was first evaluated using buffer solutions and spiked human and mouse plasma samples, and its response was compared with that of the gold-standard colorimetric method. The results obtained using DietSee correlated strongly with those from the reference method and demonstrated a linear response to glycerol levels across a wide range of concentrations (40-750 μM) that were representative of those in the human body. Next, the biosensor was validated using spiked human blood samples over a range of 30-55% hematocrit; it also demonstrated a strong correlation with reference measurements under these conditions (R² = 0.97). In addition, the biosensor was only minimally affected by a variety of potential interferents (endogenous and exogenous) and was highly stable in storage (more than 2 years when strips were stored dry at 4 °C). Finally, we investigated the application of the biosensor to real-time monitoring of lipolysis and found that the DietSee is well adapted for this purpose in both human and mouse samples. To conclude, the novel DietSee glycerometer is a sensitive, selective, and rapid tool that enables characterization of the metabolic status of an individual by measuring the glycerol concentration from a single fingertip blood drop.

Glycerol Infusion Versus Mannitol for Cerebral Edema: A Systematic Review and Meta-analysis

PURPOSE

For the treatment of cerebral edema, the use of glycerol, an osmotic agent, as well as mannitol, is popular in Asia. However, the relative therapeutic benefit of glycerol remains unknown. The goal of this study was to investigate the comparative efficacy and safety of glycerol infusion versus mannitol infusion for cerebral edema.

METHODS

A systematic search was performed in PubMed, Cochrane Central Register of Controlled Trials, Web of Science, EMBASE, and Scopus for all eligible articles published before July 2020, with no restrictions on language. Two reviewers independently screened the articles, extracted data, and carefully assessed the quality of the evidence.

FINDINGS

Eight studies (6 clinical, 2 animal) were ultimately included in the qualitative analysis, and five were included in the quantitative analysis. Pooled analyses revealed nonsignificant differences in the successful control of cerebral edema (relative risk [RR], 0.97; 95% CI, 0.81-1.15). The combination therapy with glycerol led to a favorable trend in neurologic improvements. Regarding safety, glycerol was associated with a significantly lower risk of acute kidney injury (RR, 0.27; 95% CI, 0.11-0.69) and electrolyte disturbances (RR, 0.20; 95% CI, 0.06-0.64), as well as a lower possibility of rebound effects. No hemolysis was observed at the final follow-up.

IMPLICATIONS

Although the data are limited, compared with mannitol, glycerol shows a similar level of effectiveness, a more favorable safety profile, and promising neurologic improvement in individuals with cerebral edema. Additional research is needed to confirm these findings.

PROSPERO

CRD42020187702.

Effect of different human tissue processing techniques on SARS-CoV-2 inactivation-review

The safety of the tissue transplant recipient is a top priority for tissue banks, and the emergence of the new coronavirus SARS-CoV-2 has raised significant concerns about the risks of releasing tissue for clinical use. In the present study, we conducted a literature review about the potential infectivity of SARS-CoV-2 in different biological tissues and the influence of various tissue processing and sterilization procedures on viral inactivation. The search revealed that SARS-CoV-2 binds to the human angiotensin-converting enzyme receptor to penetrate human cells. These receptors are present in skin cells, musculoskeletal tissue, amniotic membranes, cardiovascular tissue and ocular tissues, including the cornea. In general, we found that coronaviruses are stable at low temperatures, and inactivated upon exposure to extreme heat and pH. Notably, gamma irradiation, which has already been employed to inactivate SARS and MERS, could be useful for sterilizing skin, amnion and musculoskeletal tissues against SARS-CoV-2. We conclude that due to the limited information about the effects of physical and chemical tissue processing methods on viral neutralization, rigorous donor screening is still essential for tissue transplant recipient safety.

The distinctive short-term response of late-pregnant prolific ewes to propylene glycol or glycerol drenching

Pregnancy toxemia is the most frequent metabolic disorder of ewes in late pregnancy. Although propylene glycol (PG) and glycerol (GLY) are common glucogenic supplements for treating pregnancy toxemia in ewes, the relative benefit of these 2 supplements is not entirely clear. Therefore, the objectives of the present study were to determine the changes during 24 h in key blood metabolites and insulin in response to PG or GLY drenching in prolific ewes. To this end, 36 multiparous late-pregnant Afec-Assaf ewes (∼132.4 d pregnant) bearing 2 to 4 fetuses, divided into 2 blocks (18 ewes in each block), with a blood β-hydroxybutyrate (BHB) concentration of 0.5 to 1.6 mmol/L were included. Ewes were divided into 3 groups (12 ewes each; 6 ewes in each experimental day), according to their BHB levels, expected litter size, body weight, and body condition score, and were drenched with the following: (1) control group (CTL), 55 mL of water; (2) PG, 106 mL of PG (100% PG, 448 calories); or (3) GLY, 108 mL of Koforin 80 (80% GL; 448 calories). Blood samples were taken before drenching and every hour after drenching for 24 h. Plasma concentration of glucose, BHB, nonesterified fatty acids, lactate, glycerol, and insulin were determined. Because there were no effects of treatments after 12 h in the first block, the data were analyzed for 12 h after drenching rather than 24 h. The plasma glucose concentration during the first 5 h after drenching was the highest in the GLY, BHB concentration was the lowest in the PG, and the nonesterified fatty acid levels were lower in the PG compared with the CTL ewes during the first 5 h after drenching. However, glucose concentration was higher in the PG ewes at 9, 11, and 12 h after drenching than in CTL or GLY ewes. The mean lactate concentration in plasma for 12 h was 2.5- and 1.9-fold higher in the PG compared with the CTL and GLY ewes, respectively, and except at 11 h after drenching, it was significantly higher at each time point. The insulin concentration was higher in the GLY than in both other groups at 2 to 5 h after drenching. These results suggest that during the first few hours after drenching the effect of PG was more effective in reducing the BHB concentration, whereas the GLY effect was more effective in enhancing glucose concentration. The increased concentration in lactate following PG treatment suggests that the PG contribution to gluconeogenesis is mediated through its metabolism to lactate. In contrast, the lack of an effect on lactate, and the faster increase in blood glucose in response to GLY suggest that GLY has a more advanced entry point to gluconeogenesis, which influences the immediate response in enhancing the glucose blood concentration.

Mining the effect of the neonicotinoids imidacloprid and clothianidin on the chemical homeostasis and energy equilibrium of primary mouse neural stem/progenitor cells using metabolomics

The projection of plant protection products' (PPPs) toxicity to non-target organisms at early stages of their development is challenging and demanding. Recent developments in bioanalytics, however, have facilitated the study of fluctuations in the metabolism of biological systems in response to treatments with bioactives and the discovery of corresponding toxicity biomarkers. Neonicotinoids are improved insecticides that target nicotinic acetylocholine receptors (nAChR) in insects which are similar to mammals. Nonetheless, they have sparked controversy due to effects on non-target organisms. Within this context, mammalian cell cultures represent ideal systems for the development of robust models for the dissection of PPPs' toxicity. Thus, we have investigated the toxicity of imidacloprid, clothianidin, and their mixture on primary mouse (Mus musculus) neural stem/progenitor (NSPCs) and mouse neuroblastoma-derived Neuro-2a (N2a) cells, and the undergoing metabolic changes applying metabolomics. Results revealed that NSPCs, which in vitro resemble those that reside in the postnatal and adult central nervous system, are five to seven-fold more sensitive than N2a to the applied insecticides. The energy equilibrium of NSPCs was substantially altered, as it is indicated by fluctuations of metabolites involved in energy production (e.g. glucose, lactate), Krebs cycle intermediates, and fatty acids, which are important components of cell membranes. Such evidence plausibly suggests a switch of cells' energy-producing mechanism to the direct metabolism of glucose to lactate in response to insecticides. The developed pipeline could be further exploited in the discovery of unintended effects of PPPs at early steps of development and for regulatory purposes.

Trehalose as an alternative to glycerol as a glassing agent for in vivo DNP MRI

PURPOSE

In dynamic nuclear polarization (DNP), the solution needs to form a glass to attain significant levels of polarization in reasonable time periods. Molecules that do not form glasses by themselves are often mixed with glass forming excipients. Although glassing agents are often essential in DNP studies, they have the potential to perturb the metabolic measurements that are being studied. Glycerol, the glassing agent of choice for in vivo DNP studies, is effective in reducing ice crystal formation during freezing, but is rapidly metabolized, potentially altering the redox and adenosine triphosphate balance of the system.

METHODS

DNP buildup curves of ¹³ C urea and alanine with OX063 in the presence of trehalose, glycerol, and other polyol excipients were measured as a function of concentration. T₁ and T_m relaxation times for OX063 in the presence of trehalose were measured by EPR.

RESULTS

Approximately 15-20 wt% trehalose gives a glass that polarizes samples more rapidly than the commonly used 60%-wt formulation of glycerol and yields similar polarization levels within clinically relevant timeframes.

CONCLUSIONS

Trehalose may be an attractive biologically inert alternative to glycerol for situations where there may be concerns about glycerol's glucogenic potential and possible alteration of the adenosine triphosphate/adenosine diphosphate and redox balance.

Safety Assessment of Glycerin as Used in Cosmetics

This is a safety assessment of glycerin as used in cosmetics. Glycerin functions as a denaturant, fragrance ingredient, hair conditioning agent, humectant, oral care agent, oral health-care drug, skin protectant, skin conditioning agent-humectant, and viscosity-decreasing agent. The Cosmetic Ingredient Review Expert Panel (Panel) reviewed relevant animal and human data. The Panel concluded that glycerin is safe as a cosmetic ingredient in the practices of use and concentration described in this safety assessment.

Anemia in infancy is associated with alterations in systemic metabolism and microbial structure and function in a sex-specific manner: an observational study

Background

Anemia is a term that describes low hemoglobin concentrations and can result from micronutrient deficiencies, infection, or low birth weight. Early-life anemia, particularly iron-deficiency anemia (IDA) is associated with several negative metabolic, developmental, and cognitive outcomes, some of which persist into adulthood.

Objective

The aim of this study was to investigate alterations in systemic metabolism and fecal microbial diversity and functionality associated with anemia and IDA in male and female infants from Iquitos, Peru.

Design

Cross-sectional stool and serum samples were collected from 95 infants (53 boys and 42 girls) at 12 mo of age. The fecal microbiome was assessed by using 16S ribosomal RNA gene sequencing, and the fecal and serum metabolomes were quantified using 1H-nuclear magnetic resonance.

Results

The prevalence of anemia was 64%, with a greater proportion of anemia in male infants attributed to iron deficiency. Metabolically, anemia was associated with decreased concentrations of tricarboxylic acid cycle metabolites in both sexes (males: succinate, P = 0.031; females: fumarate, P = 0.028). In addition, anemic male infants exhibited significantly lower serum concentrations of several amino acids compared with nonanemic male infants. Although no specific structural or functional differences in the microbiota were observed with anemia in general, likely due the heterogeneity of its etiology, IDA affected the microbiome both structurally and functionally. Specifically, the abundance of butyrate-producing bacteria was lower in IDA subjects of both sexes than in nonanemic, non-iron-deficient subjects of the same sex (females: Butyricicoccus, P = 0.041; males: Coprococcus, P = 0.010; Roseburia, P = 0.027). IDA male infants had higher concentrations of 4-hydroxyphenyllactate (P < 0.001) and putrescine (P = 0.042) than those without IDA, whereas IDA female infants exhibited higher concentrations of leucine (P = 0.011) and valine (P = 0.003).

Conclusions

Sexually dimorphic differences associated with anemia and IDA are suggestive of greater mitochondrial dysfunction and oxidative stress in male infants compared with female infants, and alterations in microbial structure and function may further contribute. Differences in metabolic pathways associated with anemia and IDA in each sex point to potential mechanisms for the associated lasting cognitive deficits. This trial is registered at clinicaltrials.gov as NCT03377777.

Glycerol metabolism and its implication in virulence in Mycoplasma

Glycerol and glycerol-containing compounds such as lipids belong to the most abundant organic compounds that may serve as nutrient for many bacteria. For the cell wall-less bacteria of the genus Mycoplasma, glycerol derived from phospholipids of their human or animal hosts is the major source of carbon and energy. The lipids are first degraded by lipases, and the resulting glycerophosphodiesters are transported into the cell and cleaved to release glycerol-3-phosphate. Alternatively, free glycerol can be transported, and then become phosphorylated. The oxidation of glycerol-3-phosphate in Mycoplasma spp. as well as in related firmicutes involves a hydrogen peroxide-generating glycerol-3-phosphate oxidase. This enzyme is a key player in the virulence of Mycoplasma spp. as the produced hydrogen peroxide is one of the major virulence factors of these bacteria. In this review, the different components involved in the utilization of lipids and glycerol in Mycoplasma pneumoniae and related bacteria are discussed.

Palatability, digestibility, and metabolizable energy of dietary glycerol in adult cats

Glycerol is a humectant, which reduces water activity when added to the diet. This property seems to offer dietary benefits, specifically in high-moisture diets for cats, where some humectants cannot be used. According to the U.S. Food and Drug Administration, glycerol is generally recognized as sustenance safe (GRAS). It is suggested that cats are able to metabolize glycerol and use it as an energy source without compromising health. Three experiments were conducted to evaluate the following characteristics of glycerol in the diet for cats: 1) a preference test, 2) digestibility, ME, and fecal and urinary characteristics, and 3) postprandial plasma glycemia. Twelve healthy adult female cats were randomly distributed among 4 treatments consisting of a basal diet (4,090 kcal ME/kg DM, 32% CP, 11% fat, 2.3% crude fiber, and 7.0% ash) and 3 diets with varying percentages of glycerol, made by replacing the basal diet with 2.5, 5.0, and 10.0% purified glycerol (99.5%). The inclusion of glycerol proportionally reduced ( < 0.05) water activity in the diets. The preference test was conducted by observing the contrast between the basal diet and the 5.0% and 10% glycerol diets. Cats did not show a preference for any diet in particular ( > 0.05). The digestibility assays showed that increasing dietary glycerol levels did not affect food intake or the apparent total tract digestibility of macronutrients and energy ( > 0.05). The inclusion of glycerol in the diets did not alter the stool moisture, fecal score, or urine volume. However, glycerol was detected in urine when it was incorporated into the diet at 10%. Glycemia increased up to 900 min following the first meal after the fasting period with no difference between treatments, even when the means were adjusted for food intake. The blood glucose area under the curve also showed no significant difference between treatments ( > 0.05). Cats accepted glycerol under the conditions of the study, and its nutritional value was determined as it has been done for other species. The ME of glycerol for adult cats was estimated to be 3,185 kcal/kg DM. Supplementing the diets of the cats with 10% glycerol may exceed their capacity to metabolize glycerol, possibly leading to urinary excretions.

Substrate Metabolism and Insulin Sensitivity During Fasting in Obese Human Subjects: Impact of GH Blockade

CONTEXT

Insulin resistance and metabolic inflexibility are features of obesity and are amplified by fasting. Growth hormone (GH) secretion increases during fasting and GH causes insulin resistance.

OBJECTIVE

To study the metabolic effects of GH blockade during fasting in obese subjects.

SUBJECTS AND METHODS

Nine obese males were studied thrice in a randomized design: (1) after an overnight fast (control), (2) after 72 hour fasting (fasting), and (3) after 72 hour fasting with GH blockade (pegvisomant) [fasting plus GH antagonist (GHA)]. Each study day consisted of a 4-hour basal period followed by a 2-hour hyperinsulinemic, euglycemic clamp combined with indirect calorimetry, assessment of glucose and palmitate turnover, and muscle and fat biopsies.

RESULTS

GH levels increased with fasting (P < 0.01), and the fasting-induced reduction of serum insulin-like growth factor I was enhanced by GHA (P < 0.05). Fasting increased lipolysis and lipid oxidation independent of GHA, but fasting plus GHA caused a more pronounced suppression of lipid intermediates in response to hyperinsulinemic, euglycemic clamp. Fasting-induced insulin resistance was abrogated by GHA (P < 0.01) primarily due to reduced endogenous glucose production (P = 0.003). Fasting plus GHA also caused elevated glycerol levels and reduced levels of counterregulatory hormones. Fasting significantly reduced the expression of antilipolytic signals in adipose tissue independent of GHA.

CONCLUSIONS

Suppression of GH activity during fasting in obese subjects reverses insulin resistance and amplifies insulin-stimulated suppression of lipid intermediates, indicating that GH is an important regulator of substrate metabolism, insulin sensitivity, and metabolic flexibility also in obese subjects.

Re-evaluation of glycerol (E 422) as a food additive

The ANS Panel provides a scientific opinion re‐evaluating the safety of glycerol (E 422) used as a food additive. In 1981, the Scientific Committee on Food (SCF) endorsed the conclusion from the Joint FAO/WHO Expert Committee on Food Additives (JECFA) in 1976 of ‘acceptable daily intake (ADI) for man not specified’. The Panel concluded that glycerol has low acute toxicity and that local irritating effects of glycerol in the gastrointestinal tract reported in some gavage studies was likely due to hygroscopic and osmotic effects of glycerol. Glycerol did not raise concern with respect to genotoxicity and was of no concern with regard to carcinogenicity. Reproductive and prenatal developmental studies were limited to conclude on reproductive toxicity but no dose‐related adverse effects were reported. None of the animal studies available identified an adverse effect for glycerol. The Panel conservatively estimated the lowest oral dose of glycerol required for therapeutic effect to be 125 mg/kg bw per hour and noted that infants and toddlers can be exposed to that dose by drinking less than the volume of one can (330 mL) of a flavoured drink. The Panel concluded that there is no need for a numerical ADI and no safety concern regarding the use of glycerol (E 422) as a food additive at the refined exposure assessment for the reported uses. The Panel also concluded that the manufacturing process of glycerol should not allow the production of a food additive, which contains genotoxic and carcinogenic residuals at a level which would result in a margin of exposure below 10,000. The Panel recommended modification of the EU specifications for E 422. The Panel also recommended that more information on uses and use levels and analytical data should be made available to the Panel.

Addition of crude glycerin to pig diets: sow and litter performance, and metabolic and feed intake regulating hormones

The continued growth in biofuel production has led to a search for alternative value-added applications of its main by-product, crude glycerin. The surplus glycerin production and a higher cost of feedstuffs have increased the emphasis on evaluating its nutritive value for animal feeding. The aim of this research was to evaluate the effect of the dietary addition of crude glycerin on sow and litter performance, and to determine the serum concentrations of hormones related to energy metabolism and feed intake in sows during gestation and lactation. A total of 63 sows were assigned randomly to one of three dietary treatments, containing 0, 3 or 6% crude glycerin (G0, G3 and G6, respectively) added to a barley-soybean meal-based diet. During gestation, none of the dietary treatments had an effect on performance, while during lactation, glycerin-fed sows consumed less feed than those fed the control diet (3.8 v. 4.2kg DM/day; P=0.007). Although lactating sows fed the G3 diet had a higher BW loss than those fed the control diet (���20.6 v. ���8.7 kg; P=0.002), this difference was not reflected in litter performance. In gestation, the inclusion of glycerin did not affect blood concentrations of insulin or cortisol. However, pregnant sows fed diets supplemented with glycerin showed lower concentrations of acyl-ghrelin and higher concentrations of leptin (���55 and +68%, respectively; P<0.001). In lactating sows, there were no differences between dietary treatments for any of the hormones measured. Pre-prandial acyl-ghrelin concentrations were positively correlated with cortisol concentrations during gestation (r=0.81; P=0.001) and lactation (r=0.61; P=0.015). In conclusion, the inclusion of up to 6% crude glycerin did not affect the performance of sows during the gestation period; however it had a negative effect on the feed intake and weight loss of lactating sows. Moreover, further research is needed to elucidate the potential relationship between glycerin inclusion levels in the diet and the serum concentrations of hormones related to feed intake and energy balance control.

Retrospective evaluation of ProcalAmine administration in a population of hospitalized ICU dogs: 36 cases (2010-2013)

OBJECTIVE

To describe the use of ProcalAmine as a source of parenteral nutrition in hospitalized dogs and to report complications possibly referable to its use.

DESIGN

Retrospective study.

SETTINGS

Private veterinary teaching hospital.

ANIMALS

Thirty-six dogs hospitalized in ICU receiving ProcalAmine between October 2010 and March 2013.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The most common underlying disease process in this population of dogs was trauma (n = 8). Median duration of administration was 4 days and median resting energy requirement provided via ProcalAmine was 33%. ProcalAmine was administered via central catheters in 86% of cases and via peripheral catheters in 14% of cases. The overall mechanical complication rate was 19%. Metabolic complications possibly associated with ProcalAmine administration were documented in 12/36 dogs. Hyponatremia was most commonly identified (n = 6) followed by hyperglycemia (n = 4), hypochloremia (n = 2), azotemia (n = 2), metabolic alkalosis (n = 2), hyperchloremia (n = 1), and metabolic acidosis (n = 1).

CONCLUSION

ProcalAmine appears to be relatively safe and a viable option for parenteral nutrition in ill and injured dogs. Due to the potential for electrolyte derangements and other metabolic complications, daily monitoring of these parameters is advisable.

Qualidade da carne de suínos com uso de glicerina na alimentação

O objetivo deste trabalho foi avaliar os efeitos do fornecimento de diferentes níveis de glicerina na alimentação sobre a qualidade da carne de suínos em terminação. Foram utilizados 30 machos castrados e 30 fêmeas que apresentaram peso inicial de 79,3±4,0kg. Utilizou-se delineamento em blocos casualizados (peso inicial) em esquema fatorial 2 × 4 + 2, sendo duas categorias sexuais (macho castrado e fêmea), quatro níveis de glicerina bruta (50, 100, 150 e 200g/kg) e dois grupos controle (macho castrado e fêmea alimentados com dieta sem glicerina), totalizando dez tratamentos com seis repetições e a unidade experimental representada por um animal. Após o abate, foram realizadas as análises físico-químicas e centesimais dos músculos Longissimus dorsi (lombo) e Semimembranosus (pernil) do lado esquerdo das carcaças. Os resultados mostraram interação entre os níveis de glicerina e sexo para a intensidade de vermelho e cinzas no pernil. Observou-se que, nos corte do lombo, o pH final dos machos castrados foi maior do que o das fêmeas suínas. Os resultados indicaram que suínos machos castrados apresentaram maior teor de extrato etéreo no pernil e no lombo quando comparados às fêmeas. No pernil, o teor de cinzas das fêmeas suínas foi superior ao dos machos castrados. Entretanto, no lombo, não se verificou influência dos níveis de glicerina sobre a composição centesimal. Contudo, apesar de o uso da glicerina ter ocasionado modificação na cor vermelha e teor de cinzas no pernil de machos castrados, de forma geral não provocou mudanças relevantes sobre as características físico-químicas e centesimais da carne de suínos, podendo ser utilizada até o nível de 200g/kg na alimentação desses animais.

Randomized Controlled Study of Glycerol Versus Dextrose in Postoperative Hypocaloric Peripheral Parenteral Nutrition

The aim of this study was to use glycerol and dextrose in hypocaloric peripheral parenteral nutrition (HPNN) and investigate their effects on postoperative metabolic and nutritional responses. Thirty patients who had undergone major gastrointestinal surgery were examined in a prospective randomized study. The study period extended from the day before operation to postoperative day 7. Fifteen patients (intervention group) received 1.2 g amino acids, 1.2 g glycerol, and 0.5 g fat emulsion/kg/day (approximately 15 kcal/kg/day). The other 15 patients (control group) received 1.2 g amino acids, 1.5 g dextrose, and 0.5 g fat emulsion/kg/day (approximately 15 kcal/kg/day). After 7 days of study, both groups were found to have a decrease in body weight, mid-arm circumference, triceps skin fold, serum albumin, and transferrin and prealbumin levels, but an increase in serum cholesterol and triglyceride levels. However, the differences between them were not significant. Improvements in nitrogen balance were observed in the intervention group (p = .035). These data suggest that advantages favoring the administration of glycerol instead of dextrose in hypocaloric parenteral nutrition could hardly be found in our investigation, except that better nitrogen equilibrium is maintained. Nonetheless, the peripheral intravenously administered ProcalAmine with fat emulsion has been well tolerated and safe for these patients, as well as more convenient for clinical use.

Nitrogen-corrected apparent metabolizable energy value of crude glycerol for laying hens

An experiment was conducted with laying hens to determine the AME(n) value of crude glycerol, a coproduct of biodiesel production. Crude glycerol (87% glycerol, 9% water, 0.03% methanol, 1.26% Na, and 3,625 kcal/kg of gross energy) was obtained from a commercial biodiesel production facility (Ag Processing Inc., Sergeant Bluff, IA). A total of forty-eight 40-wk-old laying hens (Hy-Line W-36) were placed in metabolic cages (2 hens/ cage) and given free access to the experimental diets. A corn and soybean meal-based basal diet (18% CP, 2,875 kcal/kg of AME(n), 4.51% Ca, 0.51% nonphytate P) was formulated with 15% glucose.H(2)O and 1% Celite. Four dietary treatments were created by substituting 0, 5, 10, or 15% crude glycerol for glucose.H(2)O (3,640 kcal/kg of AME(n)). After 7 d of dietary adaptation, excreta were collected twice daily for 3 d, freeze-dried, and analyzed for contents of DM, Kjeldahl N, acid-insoluble ash, and gross energy. Egg production was recorded daily, and eggs were collected on d 7 and 8 of the experiment for calculation of egg mass (egg production x egg weight). Feed consumption was measured over the 10-d experimental period. Egg-production data were analyzed by ANOVA with 4 treatments and 6 replications in a completely randomized experimental design. The AME(n) value of crude glycerol was estimated as the slope of the linear relationship between the inclusion rate of dietary crude glycerol and the glucose-corrected AME(n) value of the experimental diets. No significant treatment effects (P > 0.1) were apparent for egg-production rate (93.0%), egg weight (56.1 g), egg mass (52.2 g/d), or feed consumption (104 g/d). Linear regression analysis (P < 0.001, r(2) = 0.92, n = 24) revealed that the AME(n) value of the crude glycerol used in this study was 3,805 +/- 238 kcal/kg (mean +/- SEM; as-is basis) for laying hens.

Evaluation of nonglucose carbohydrates in parenteral nutrition for diabetic patients

OBJECTIVE

There is little information on the advantages of nonglucose carbohydrates in total parenteral nutrition (TPN) for diabetic patients. The aim of this study is to evaluate glycemic control and insulin requirements in diabetic patients who received TPN with different sources of carbohydrates, and to determine whether insulin requirements are different when septic and non-septic diabetic patients are studied.

MATERIALS AND METHODS

One-hundred and thirty-eight patients were randomly divided into two groups receiving either glucose (G), n=71, or glucose-fructose-xylitol 2:1:1 (GFX), n=67. There were no differences between the demographic or anthropometric characteristics of the groups, nor between the patients with diabetes mellitus type 1 and type 2, nor the initial TPN composition. Acceptable glycemic control was considered when glycemia reached <200 mg/dl.

RESULTS

Glycemic control was attained in 79.7% of patients (74.6 vs 85.1%), in the same period of treatment. At the end of treatment, insulin requirements were not different (45+/-19 vs 45+/-26 UI/day) in both groups, while similar amounts of carbohydrates (191+/-36 vs 187+/-45 g/day) were infused. The ratio insulin/body weight and insulin/carbohydrates were equal in both groups. In the GFX group nonseptic and septic patients needed less and more insulin, respectively, than their counterparts in the G group. No major adverse events related to carbohydrate infusions were observed.

CONCLUSIONS

Either G or GFX could be used in TPN for diabetic patients, providing glycemic control in most cases with similar insulin requirements. GFX mixtures were slightly more beneficial to attain glycemic control in nonseptic patients, but septic diabetic patients had higher insulin needs in this group.

Oxidation of [(13)C]glycerol ingested along with glucose during prolonged exercise

The respective oxidation of glycerol and glucose (0.36 g/kg each) ingested simultaneously immediately before exercise (120 min at 68 +/- 2% maximal oxygen uptake) was measured in six subjects using (13)C labeling. Indirect respiratory calorimetry corrected for protein and glycerol oxidation was used to evaluate the effect of glucose + glycerol ingestion on the oxidation of glucose and fat. Over the last 80 min of exercise, 10.0 +/- 0.8 g of exogenous glycerol were oxidized (43% of the load), while exogenous glucose oxidation was 21% higher (12.1 +/- 0.7 g or 52% of the load). However, because the energy potential of glycerol is 18% higher than that of glucose (4.57 vs. 3.87 kcal/g), the contribution of both exogenous substrates to the energy yield was similar (4.0-4.1%). Total glucose and fat oxidation were similar in the placebo (144.4 +/- 13.0 and 60.5 +/- 4.2 g, respectively) and the glucose + glycerol (135.2 +/- 12.0 and 59.4 +/- 6.5 g, respectively) trials, whereas endogenous glucose oxidation was significantly lower than in the placebo trial (123.7 +/- 11.7 vs. 144.4 +/- 13.0 g). These results indicate that exogenous glycerol can be oxidized during prolonged exercise, presumably following conversion into glucose in the liver, although direct oxidation in peripheral tissues cannot be ruled out.

Feasibility of an air motor-driven centrifugal blood-pumping system

The use of cardiopulmonary bypass (CPB) is extending out of the cardiac surgery operating room into new venues. The long-term goal of this project is the development of a completely disposable temporary-use CPB system that could be economically distributed to all of the units where it might be needed. Centrifugal blood pumps have demonstrated successful and widespread use. However, they are not as widely available as might be desired because they require a large and expensive console. An inexpensive, small, lightweight, disposable unit, in contrast, could be widely distributed for emergency care of patients and would be logistically practical for patient transportation between the presenting institution and a major cardiac care facility equipped for definitive treatment. An air motor might be an approach to such a device. The current research project underway at the University of Akron in conjunction with the Cleveland Clinic Foundation has focused on the following key feasibility issues: air consumption, air motor noise, and sealing the rotating shaft. Prototypes have been constructed from commercially available vane and turbine motors. Early studies have demonstrated favorable results with regard to air consumption and shaft sealing and directions for handling air motor noise.

Glycerol metabolism in patients with alcohol-induced liver cirrhosis

The clearance rate of glycerol has been found to be impaired in alcoholic liver disease. However it remains unclear, if this can be ascribed to a defect of hepatic gluconeogenesis. Thus, the purpose of this work was to investigate glycerol clearance and hepatic glucose production in patients with liver cirrhosis. 13 patients with alcohol-induced Child B cirrhosis and 8 healthy volunteers were studied. Rates of appearance (R(a)) of glycerol, glucose and alanine were determined using stable isotope techniques. In addition indocyanine green clearance (ICGC) and plasma substrate concentrations were measured. Clearance rates were calculated as R(a) divided by the corresponding substrate concentration. R(a) of glycerol in patients was not different from controls, but glycerol clearance was significantly reduced (29 +/- 3 vs. 41 +/- 4 ml/kg/min). No differences in R(a) of glucose and alanine and corresponding plasma concentrations were observed. ICGC in patients was about 35% lower than reference values. Diminished glycerol clearance in patients with liver cirrhosis was not due to impaired hepatic gluconeogenesis. Since glycerol is almost completely extracted by the liver decreased glycerol clearance possibly simply reflected compromised liver perfusion as seen by reduced ICGC.

Hemodynamic, respiratory, and metabolic effects of medium-chain triglyceride-enriched lipid emulsions following valvular heart surgery

STUDY

A lipid emulsion containing 10 percent medium-chain triglycerides (MCT) and 10 percent long-chain triglycerides (LCT) was infused at a rate of 1 ml/kg/h (3.3 mg/kg/min) for 2 h, in 12 patients (2 males, 10 females; mean age, 54 +/- 3 (SEM) years; range, 34 to 67 years) 24 h after open-heart surgery (mitral valve replacement).

METHODS

Hemodynamic factors (pulmonary and radial artery indwelling catheters), oxygen and carbon dioxide partial pressures, oxygen saturation, oxygen delivery and consumption, and intrapulmonary shunt fraction were obtained before, during, and after lipid infusion (for 2 h), at 30-s intervals, along with some metabolic indexes (triglycerides, free fatty acids, glucose, insulin, lactate, acetoacetate).

RESULTS

No statistically significant changes in heart rate, cardiac index, systemic and pulmonary pressures and resistances, central venous and pulmonary capillary pressures, or arterial oxygen partial pressure were observed during infusion. Arterial carbon dioxide partial pressure values were constantly reduced throughout and after the end of lipid infusion, as compared with baseline values, while oxygen consumption was increased significantly without any change in oxygen delivery. No adverse effects on intrapulmonary shunt fraction were observed. Statistically significant increases of triglycerides, free fatty acids, acetoacetate and insulin (peak values at end of the lipid infusion) were found in comparison with baseline values. Plasma glucose increased significantly during lipid infusion and remained higher than baseline values until the end of the study. Lactate levels were unchanged except for a slight decrease at the end of the study, without any derangement of acid-base equilibrium. Neither arrhythmias nor adverse clinical reactions were observed as a consequence of lipid infusion.

CONCLUSIONS

Fat emulsions containing both MCT and LCT, when given at 3.3 mg/kg/min for 120 min following valvular heart surgery, do not exert negative cardiopulmonary effects, and could represent a source of rapidly metabolized substrates.

Metabolic clearance of a fat emulsion containing medium-chain triglycerides in cirrhotic patients

Medium-chain triglycerides (MCTs) may be advantageous in cirrhotic patients, but data on the clearing capacity are lacking. Intravenous fat tolerance test (IVFTT) was performed on 28 cirrhotic patients (Child's A, n = 9; Child's B, n = 13; Child's C, n = 6) to determine the clearance rate of Lipofundin MCT 20%, which contains a physical mixture of MCT and long-chain triglycerides (LCT). The mean fractional elimination rate (k2) of MCT/LCT physical blend in the cirrhotic patients (7.72%/min) was comparable with that of the healthy control subjects (n = 9, k2 = 5.43%/min). Significantly higher serum free fatty acid (FFA) levels were found in the cirrhotic patients during IVFTT. The difference could be accounted for by their higher basal levels. In all patients, serum FFA concentrations returned to basal value at the end of 1 hour. Prompt appearance of glycerol and beta-hydroxybutyrate was seen during IVFTT, indicating that hydrolysis of triglycerides and release of ketone bodies from the liver were rapid. It was concluded that the ability to eliminate MCT/LCT physical blend was not impaired in the cirrhotic patients.

Issues in Contemporary Drug Delivery: Part V: Total Parenteral Nutrition

Objective:

To provide an overview of common compounding and administration guidelines for total parenteral nutrition (TPN). The compatibility of various drug products with TPN preparations is also discussed.

Data Sources:

References were selected from published bibliographies of specialized nutrition and drug-nutrient interaction articles, package inserts and manufacturer's information, and specific topic searches in MEDLINE computerized database (English language, through 1989).

Study Selection:

Studies that investigated stability were selected preferentially to those studying compatibility alone; when stability data were not available, compatibility studies were included. Studies using products marketed in the US were chosen preferentially to those using European products; studies and case reports using human subjects were selected in preference to animal studies. Sixty percent of the initially identified studies were selected for inclusion.

Data Extraction:

Studies were reviewed by the authors for internal consistency and statistical validity.

Data Synthesis:

Intravenous solutions can be manufactured to meet various nutritional specifications. As additional nutrients and drugs are incorporated, the risk of incompatibility and instability of the admixture increases. Stability data are relatively sparse, leading to a dependence on compatibility studies for decision making.

Conclusions:

A wide variety of TPN formulations can be compounded to meet the individual needs of patients of all ages and assorted disease states. Addition of specific drugs to the TPN preparation may improve the efficiency of drug delivery and improve overall therapeutic response. Care must be taken, however, to ensure that incompatible compounds are not combined in a single TPN preparation.

Brain oedema and intracranial hypertension treatment by GLIAS

The authors present their results regarding the use of a buffered solution of glycerol 30%-sodium ascorbate 20% (GLIAS) for the treatment of brain oedema and intracranial hypertension. GLIAS was perfused intravenously in 80 patients with several types of brain oedema. In every patients serum and urinary osmolarity, diuresis, main blood and urine parameters, and ICP were monitored. Following GLIAS infusion an increase in plasma osmolarity was observed, changing the average basal value plus 13.4% after 15 min., 10.5% after 30'. At the same time there was a reduction of ICP and improvement in cerebral compliance. In each case there was a decrease in intracranial hypertension and brain oedema without significant collateral effects.

13C-NMR study of glycerol metabolism in rabbit renal cells of proximal convoluted tubules

Perchloric acid extracts of rabbit renal proximal convoluted tubular cells (PCT) incubated with [2-13C]glycerol and [1,3-13C]glycerol were investigated by 13C-NMR spectroscopy. These 13C-NMR spectra enabled us to determine cell metabolic pathways of glycerol in PCT cells. The main percentage of 13C-label, arising from 13C-enriched glycerol, was found in glucose, lactate, glutamine and glutamate. So far it can be concluded that glycerol is a suitable substrate for PCT cells and is involved in gluconeogenesis and glycolysis as well in the Krebs cycle intermediates. Label exchange and label enrichment in 13C-labelled glucose, arising from [2-13C]glycerol and [1,3-13C]glycerol, is explained by label scrambling through the pentose shunt and a label exchange in the triose phosphate pool. From relative enrichments it is estimated that the ratio of the pyruvate kinase flux to the gluconeogenetic flux is 0.97:1 and that the ratio of pyruvate carboxylase activity relative to pyruvate dehydrogenase activity is 2.0:1. Our results show that 13C-NMR spectroscopy, using 13C-labelled substrates, is a powerful tool for the examination of renal metabolism.

A key to the literature of total parenteral nutrition: update 1987

This comprehensive bibliography is intended to enhance the education of the practitioner, student, and academician in the area of parenteral nutrition. This bibliography is not all-inclusive but serves as an update from the original published in 1983. Of particular note in this work is the addition of topics that reflect a growing interest in medical specialties with regard to patient nutritional status and support.

Double-blind study of glycerol vs glucose in parenteral nutrition of postsurgical insulin-treated diabetic patients

Twenty-five insulin-treated diabetic patients were randomly assigned postoperatively to 5 days of intravenous infusions of ProcalAmine (3% amino acids, 3% glycerol, and electrolytes) or FreAmineIII + dextrose and electrolytes. The solutions were given isocalorically and isonitrogenously. Insulin was adjusted to keep glycemia at the level of 150-200 mg/dl. The ProcalAmine group by the 5th day had plasma glucose of 158 +/- 25 mg/dl and required 1.20 +/- 0.10 U/hr insulin. The FreAmine + dextrose group had plasma glucose of 169 +/- 53 mg/dl and required 2.28 +/- 0.13 U/hr. At all time points postsurgically, the ProcalAmine group required less insulin.

Cancer cachexia and the rate of whole body lipolysis in man

While malnutrition attending cancer cachexia may be associated with variable losses of body fat, lipid metabolism has been only minimally studied. To clarify potential aberrations of lipid metabolism in weight losing cancer patients, the whole body rate of lipolysis was determined in 9 cancer patients in the postabsorptive state and compared to that in 5 normal subjects. A primed-three stage infusion of glycerol was used to measure plasma glycerol clearance and turnover. A positive correlation between glycerol turnover and plasma concentration was demonstrated in both cancer patients (r = 0.72) and in normal subjects (r = 0.81). Glycerol turnover rate in cancer patients (2.05 +/- 0.14 mumol X kg-1 X min-1) was not different from that in normals (2.31 +/- 0.50); while glycerol clearance in cancer patients (1.72 +/- 0.13 L/min) was significantly lower (P less than 0.025) by 32% than that in normals. This study demonstrates that the whole body lipolytic rate in cancer patients is not different from healthy normals. As a consequence, the loss of body fat in patients with cancer cachexia may be due to a reduced rate of lipogenesis rather than augmented lipolysis as is observed in nonmalignant malnutrition, starvation, or injury.

Intravenous feeding--a review of aspects of current practice

This review summarises the present state of knowledge of energy and nitrogen requirements of hospital patients requiring intravenous feeding. It also addresses electrolyte, inorganic element and vitamin intakes, and examines possible differences in requirements in some special circumstances. It is concluded that most of the patients could be fed using one of a small number of standard regimens.