Immunoglobulin G subclass levels and antibody responses to the 2009 influenza A (H1N1) monovalent vaccine among human immunodeficiency virus (HIV)-infected and HIV-uninfected adults.

Immunoglobulin (Ig)G levels are important for antibody vaccine responses and IgG subclass deficiencies have been associated with severe 2009 influenza A (H1N1) infections. Studies have demonstrated variations in immune responses to the H1N1 vaccine, but the aetiology of this is unknown. We determined the associations between pre-vaccination overall and influenza-specific IgG subclass levels and 2009 H1N1-specific antibody responses post-vaccination (robust versus poor at day 28) stratified by human immunodeficiency virus (HIV) status. Logistic regression models were utilized to evaluate whether pre-vaccination IgG subclass levels were associated with the antibody response generated post-vaccination. We evaluated 48 participants as part of a clinical study who were stratified by robust versus poor post-vaccination immune responses. Participants had a median age of 35 years; 92% were male and 44% were Caucasian. HIV-infected adults had a median CD4 count of 669 cells/mm(3) , and 79% were receiving highly active anti-retroviral therapy. HIV-infected participants were more likely to have IgG2 deficiency (<240 mg/dl) than HIV-uninfected individuals (62% versus 4%, P < 0·001). No association of pre-vaccination IgG subclass levels (total or influenza-specific) and the antibody response generated by HIN1 vaccination in either group was found. In summary, pre-vaccination IgG subclass levels did not correlate with the ability to develop robust antibody responses to the 2009 influenza A (H1N1) monovalent vaccine. IgG2 deficiencies were common among HIV-infected individuals but did not correlate with poor influenza vaccine responses. Further investigations into the aetiology of disparate vaccine responses are needed.

Influenza-like illness surveillance on the California-Mexico border, 2004-2009.

BACKGROUND: Since 2004, the Naval Health Research Center, with San Diego and Imperial counties, has collaborated with the US Centers for Disease Control and Prevention to conduct respiratory disease surveillance in the US-Mexico border region. In 2007, the Secretariat of Health, Mexico and the Institute of Public Health of Baja California joined the collaboration. OBJECTIVES: The identification of circulating respiratory pathogens in respiratory specimens from patients with influenza-like illness (ILI). METHODS: Demographic, symptom information and respiratory swabs were collected from enrollees who met the case definition for ILI. Specimens underwent PCR testing and culture in virology and bacteriology. RESULTS: From 2004 through 2009, 1855 persons were sampled. Overall, 36% of the participants had a pathogen identified. The most frequent pathogen was influenza (25%), with those aged 6-15 years the most frequently affected. In April 2009, a young female participant from Imperial County, California, was among the first documented cases of 2009 H1N1. Additional pathogens included influenza B, adenovirus, parainfluenza virus, respiratory syncytial virus, enterovirus, herpes simplex virus, Streptococcus pneumoniae, and Streptococcus pyogenes. CONCLUSIONS: The US-Mexico border is one of the busiest in the world, with a large number of daily crossings. Due to its traffic, this area is an ideal location for surveillance sites. We identified a pathogen in 36% of the specimens tested, with influenza A the most common pathogen. A number of other viral and bacterial respiratory pathogens were identified. An understanding of the incidence of respiratory pathogens in border populations is useful for development of regional vaccination and disease prevention responses.

Altered fluxes responsible for reduced hepatic glucose production and gluconeogenesis by exogenous glucose in rats.

The net release of glucose from the liver, or hepatic glucose production (HGP), and apparent gluconeogenesis (GNG) are reduced by exogenous glucose. We investigated the changes in metabolic fluxes responsible. Flux through the hepatic GNG pathway was quantified by mass isotopomer distribution analysis (MIDA) from [2-13C]glycerol. Unidirectional flux across hepatic glucose-6-phosphatase (G-6-Pase), or total hepatic glucose output (THGO), and hepatic glucose cycling (HGC) were also measured by using glucuronate (GlcUA) to correct for glucose 6-phosphate (G-6-P) labeling. Infusion of glucose (15-30 mg.kg-1.min-1 iv) to 24 h-fasted rats caused two important metabolic alterations. First was a significant increase in hepatic glucose uptake and HGC: > 60% of THGO was from HGC. Second, although flux through hepatic G-6-P increased (from 15.7 to 17.7-22.7 mg.kg-1.min-1), the partitioning of G-6-P flux changed markedly [from 30-35% to 55-60% entering UDP-glucose (UDP-Glc), P < 0.01]. Total flux through the GNG pathway remained active during intravenous glucose, but increased partitioning into UDP-Glc lowered GNG flux plasma glucose by 50%. In summary, the suppression of HGP and GNG flux into glucose is not primarily due to reduced carbon flow through hepatic G-6-Pase or the hepatic GNG pathway. THGO persists, but hepatic G-6-P is derived increasingly from plasma glucose, and flow through GNG persists, but the partitioning coefficient of G-6-P into UDP-Glc doubles. These adjustments permit net HGP to fall despite increased total production of hepatic G-6-P during administration of glucose.

Effects of dietary n-3 fatty acid supplementation in men with weight loss associated with the acquired immune deficiency syndrome: Relation to indices of cytokine production.

Cytokines may be involved in weight loss and disturbances of metabolism associated with human immunodeficiency virus (HIV) infection. Dietary n-3 fatty acids reduce the production of interleukin-1 (IL-1) and tumor necrosis factor (TNF) by peripheral blood mononuclear cells (PBMC) in normal humans and prevent IL-1 and TNF anorexia in animals. Accordingly, we studied the nutritional and metabolic effects of a 10-week trial of dietary fish oil (MaxEPA 18 g/day) in men with weight loss due to acquired immune deficiency syndrome (AIDS). Twenty men were enrolled, and 16 completed the 10-week supplementation period. Prior weight loss was 13.7 +/- 1.8 kg(17.4 +/- 1.6% body weight, means +/- SE). Food intake, body composition, blood chemistries, serum cytokine concentrations, in vitro production of IL-1 and TNF by PBMC, and clinical course were followed. A subset of subjects (n=12) underwent stable isotope infusions to measure de novo hepatic lipogenesis (DNL), an in vivo metabolic index that is influenced by cytokine presence and has previously been found to be elevated in AIDS. An unsupplemented group of men with AIDS wasting (10.4 +/- 2.4 kg weight loss, 13.1 +/- 2.2% body weight) was monitored for 10 weeks as controls. Baseline food intake (2,395 +/- 177 kcal/day and 95.1 +/- 7.2 g protein/day), body weight, percent fat, and fat-free mass were unchanged over the 10-week supplementation period. Serum triglycerides were reduced in hypertriglyceridemic subjects, confirming compliance with fish oil supplementation and suggesting that their hypertriglyceridemia was at least in part due to overproduction. Serum TNF and IL-1 were undetectable before or after fish oil supplementation. Serum interferon alpha (IFN) was measurable but did not change. In vitro production of IL-1 and TNF by PBMC was markedly reduced both at baseline and after fish oil supplementation in this population, even in the presence of new AIDS complications, compared with normal controls. The metabolic measurement DNL fell and weight was gained (2.1 +/- 1.3 kg) in subjects who did not develop new AIDS-related complications, but further increases in DNL and further weight loss were observed in subjects who developed a new AIDS complication (p<0.05 for interaction between new complication and change in DNL). No changes in body weight, food intake, serum triglycerides, serum cytokines, or DNL were observed in the unsupplemented group. We conclude that fish oil is a weak anticytokine agent that is unable to overcome the metabolic and nutritional consequences of acute AIDS-related complications but may exert a clinical anticytokine effect in stable AIDS patients. Cytokine production by PBMC is not a useful or reliable marker of in vivo cytokine activity in AIDS patients with weight loss. In contrast, an integrative functional index that is sensitive to cytokine presence in tissues (hepatic DNL) correlated with clinical response. These findings are relevant to the design of future studies of more potent anticytokine agents, such as thalidomide.

Gluconeogenesis and intrahepatic triose phosphate flux in response to fasting or substrate loads. Application of the mass isotopomer distribution analysis technique with testing of assumptions and potential problems.

We measured gluconeogenesis (GNG) in rats by mass isotopomer distribution analysis, which allows enrichment of the true biosynthetic precursor pool (hepatic cytosolic triose phosphates) to be determined. Fractional GNG from infused [3-13C]lactate, [1-13C]lactate, and [2-13C]glycerol was 88 +/- 2, 89 +/- 3, and 87 +/- 2%, respectively, after 48 h of fasting. [2-13C]Glycerol was the most efficient label and allowed measurement of rate of appearance of intrahepatic triose phosphate (Ra triose-P), by dilution. IV fructose (10-15 mg/kg/min) increased absolute GNG by 81-147%. Ra triose-P increased proportionately, but endogenous Ra triose-P was almost completely suppressed, suggesting feedback control. Interestingly, 15-17% of fructose was directly converted to glucose without entering hepatic triose-P. IV glucose reduced GNG and Ra triose-P. 24-h fasting reduced hepatic glucose production by half, but absolute GNG was unchanged due to increased fractional GNG (51-87%). Reduced hepatic glucose production was entirely due to decreased glycogen input, from 7.3 +/- 1.8 to 1.1 +/- 0.2 mg/kg/min. Ra triose-P fell during fasting, but efficiency of triose-P disposal into GNG increased, maintaining GNG constant. Secreted glucuronyl conjugates and plasma glucose results correlated closely. In summary, GNG and intrahepatic triose-P flux can be measured by mass isotopomer distribution analysis with [2-13C]glycerol.

Metabolic interactions between surplus dietary energy intake and cigarette smoking or its cessation.

Cigarette smoking (CS) alters lipid metabolism and is associated clinically with an atherogenic lipid profile. We recently showed that, under controlled eucaloric dietary conditions, CS stimulates lipolysis without increasing oxidation of fat and that cessation of CS does not result in a rebound tendency to synthesize or store fat. We asked here whether the ad libitum intake of surplus dietary energy interacts with the metabolic effects of CS or its cessation. Eight male heavy smokers were allowed ad libitum food intake in a metabolic ward, 1 wk in CS phase and 1 wk in non-CS phase, followed by 4 wk of outpatient non-CS and a repeat 7-day study. De novo hepatic lipogenesis (DNL), lipolysis, substrate cycling of free fatty acids (FFA), hepatic glucose production, and energy expenditure were measured by using a multiple stable-isotope infusion protocol and indirect calorimetry. Surplus dietary energy intake (> 150% of predicted energy needs) occurred in five of eight subjects (2 subjs > 5,500 kcal/day, 3 subjs > 4,000 kcal/day) with weight gain of 1-4 kg/wk, but with no difference between CS and non-CS phases. Acute CS significantly increased (P < 0.05) serum FFA concentrations (58%), FFA flux (63%), and glycerol flux (36%); nonsignificantly increased extra-adipocyte (hepatic) esterification of FFA (125%, P = 0.10) and resting energy expenditure (4.1%, P = 0.22); and did not change adipocyte reesterification of FFA or whole body oxidation of fat. Basal metabolic parameters (after overnight abstention from CS) did not differ between phases. Fractional DNL correlated significantly with excess energy intake (r2 = 0.39) and with percentage of total energy needs provided by carbohydrate (r2 = 0.47). The absence or presence of CS did not affect the increase in fractional DNL in subjects with excess energy intake, however. We conclude that cessation of CS does not result in a rebound tendency to synthesis or storage of fat, even in the presence of positive short-term energy balance, contrary to previous suggestions. Moreover, stimulation of lipolysis by CS does not increase oxidation of fat and thereby protect against fat deposition under conditions of surplus energy intake. The prevention of weight gain after cessation of CS, whether or not nicotine is provided, should focus on energy balance (calorigenesis as well as intake) rather than specific alterations in lipid metabolism.

Effects of cigarette smoking and its cessation on lipid metabolism and energy expenditure in heavy smokers.

The relationship between thermogenic and potentially atherogenic effects of cigarette smoking (CS) and its cessation was investigated. Heavy smokers (n = 7, serum cotinine > 200 ng/ml, > 20 cigarettes/d) were maintained on isoenergetic, constant diets for 2 wk, 1 wk with and 1 wk without CS. Stable isotope infusions with indirect calorimetry were performed on day 7 of each phase, after an overnight fast. CS after overnight abstention increased resting energy expenditure by 5% (not significant vs. non-CS phase; P = 0.18). CS increased the flux of FFA by 77%, flux of glycerol by 82%, and serum FFA concentrations by 73% (P < 0.02 for each), but did not significantly affect fat oxidation. Hepatic reesterification of FFA increased more than threefold (P < 0.03) and adipocyte recycling increased nonsignificantly (P = 0.10). CS-induced lipid substrate cycles represented only 15% (estimated 11 kcal/d) of observed changes in energy expenditure. De novo hepatic lipogenesis was low (< 1-2 g/d) and unaffected by either acute CS or its chronic cessation. Hepatic glucose production was not affected by CS, despite increased serum glycerol and FFA fluxes. Cessation of CS caused no rebound effects on basal metabolic fluxes. In conclusion, a metabolic mechanism for the atherogenic effects of CS on serum lipids (increased hepatic reesterification of FFA) has been documented. Increased entry of FFA accounts for CS-induced increases in serum FFA concentrations. The thermogenic effect of CS is small or absent in heavy smokers while the potentially atherogenic effect is maintained, and cessation of CS does not induce a rebound lipogenic milieu that specifically favors accrual of body fat in the absence of increased food intake.

Quantification of menstrual and diurnal periodicities in rates of cholesterol and fat synthesis in humans.

The mass isotopomer distribution analysis (MIDA) technique is applied here in men and menstruating women to quantify periodicities in the biosynthesis of serum cholesterol and very low density lipoprotein (VLDL)-palmitate. The isotopic enrichment of the true biosynthetic precursor (intracellular acetyl-CoA) during oral or intravenous administration of sodium[1-13C]- or [2-13C]acetate was calculated from mass isotopomer fractional abundances in free cholesterol and VLDL-palmitate, determined by gas chromatography-mass spectrometry (GC-MS). To convert fractional into absolute cholesterol synthesis rates, decay rate constants of plasma cholesterol were determined from the die-away curves of endogenously labeled high-mass isotopomers. Oral [13C]acetate was a 3-4 times more efficient means of labeling the precursor pool for VLDL-palmitate than was intravenous [13C]acetate, consistent with a splanchnic site of VLDL-fatty acid synthesis, whereas the precursor for free cholesterol had an intermediate enrichment, suggesting a contribution from extra-splanchnic tissues as well. Endogenous synthesis of serum cholesterol was 8-11 mg/kg per day (an estimated 65-75% of input into serum cholesterol); it was 1.5- to 3-fold higher at night than during the day (37-49 mg/h at night compared to 9-23 mg/h during the day) and did not vary over the menstrual cycle (608-697 mg/day). In contrast, endogenous synthesis of fatty acids made a relatively minor contribution to body fat pools (1/10-1/20) of input into VLDL-palmitate) compared to dietary fat intake; it was greater in the day-time, and was influenced by menstrual cycle (3-fold elevated in the follicular phase compared to the luteal phase), and body composition (higher in obese men than normal weight men, r2 = 0.59 for lipogenesis vs. body mass index). Factors responsible for periodicities in endogenous lipid synthesis can be studied in humans using this approach.

Measurement of endogenous synthesis of plasma cholesterol in rats and humans using MIDA.

We used the mass isotopomer distribution analysis (MIDA) technique to measure endogenous synthesis of plasma cholesterol in vivo in rats and normal human subjects. Sodium [1-13C]- or [2-13C]acetate was infused, and plasma free cholesterol was analyzed by gas chromatography-mass spectrometry. Frequencies of mass isotopomers M0-M4 (mass-to-charge ratio 368-372) were quantified. The enrichment of the true precursor for cholesterol synthesis (acetyl-coenzyme A in contributing tissues) was determined using the MIDA method. This technique remains mathematically valid even if more than one tissue contributes to circulating free cholesterol. The fractional contribution (f) from endogenous synthesis to free cholesterol in normal women (n = 5) was 2.48 +/- 0.39% after 7 h in the postabsorptive state and 1.27 +/- 0.41% after 8 h of refeeding. In ad libitum-fed rats (n = 12), f was 2.89 +/- 0.44% after 12 h, whereas administration of recombinant tumor necrosis factor increased this value fourfold. Next, the rate constant (k) for removal of labeled free cholesterol from plasma was calculated. Higher masses (M2-M4) were followed to avoid the problem of persistent label incorporation. During the 60 h after cessation of [13C]acetate infusions, k was 0.02490 +/- 0.00298/h in humans. Using these values of k and f, absolute cholesterogenesis was 568 +/- 55 mg/day in normal women (follicular menstrual phase), similar to prior estimates based on whole body sterol balances. Women also exhibited a diurnal variation for endogenous cholesterol synthesis (34.6 +/- 5.4 mg/h nighttime vs. 15.9 +/- 5.2 mg/h daytime) consistent with current knowledge about rhythms in cholesterogenesis. Checks on the model were internally consistent (e.g., comparisons among different isotopomers for calculating precursor enrichment). We conclude that fractional and absolute endogenous cholesterol synthesis can be measured using stable isotopes in vivo by the MIDA technique.

Mechanisms of fructose-induced hypertriglyceridaemia in the rat. Activation of hepatic pyruvate dehydrogenase through inhibition of pyruvate dehydrogenase kinase.

1. The effects of purified diets containing 70% glucose or 70% fructose on the activation state of hepatic pyruvate dehydrogenase (PDHa), activity of mitochondrial PDH kinase, plasma triacylglycerols (TG) and hepatic lipogenesis de novo in rats were measured. 2. Plasma TG were significantly increased in the fructose-fed compared with the glucose-fed group (125 +/- 45 mg/dl versus 57 +/- 19 mg/dl; P less than 0.002) after 3-5 weeks on the diet despite less daily food intake. 3. Hepatic PDHa in fructose-fed rats was 144% of the value in glucose-fed rats (15.4 +/- 1.2% versus 10.7 +/- 0.5%; P less than 0.002), whereas cardiac muscle PDHa was not different (45.5 +/- 6.6% versus 41.0 +/- 7.8%). 4. Intrinsic hepatic PDH kinase activity was decreased to 34% of glucose-fed values by fructose feeding (-k = 3.56 +/- 0.39 versus 10.41 +/- 1.85 min-1; P less than 0.005). 5. The fractional contribution to very-low-density-lipoprotein palmitate from hepatic lipogenesis de novo, measured by a stable-isotope mass-spectrometric method, was 10.49 +/- 2.42% (n = 8) in fructose-fed rats versus 5.55 +/- 1.38% (n = 9) in glucose-fed rats (P less than 0.05), and 2.66 +/- 2.39% (n = 3) in chow-fed rats (P less than 0.05 versus fructose-fed group). The absolute contribution to circulating TG from lipogenesis de novo was also significantly higher in the fructose-fed than in the glucose-fed group (14.9 +/- 5.1 mg/dl versus 2.9 +/- 0.6 mg/dl; P less than 0.05) 6. Portal insulin concentrations were significantly higher in the fructose-fed rats (206 +/- 49 mu-units/ml versus 81 +/- 15 mu-units/ml; P less than 0.05). 7. In conclusion, dietary fructose appears to have a specific activating effect on hepatic PDH, mediated at least in part by inhibition of PDH kinase. These results are consistent with increased flux through hepatic PDH and synthesis of new fat, not just increased re-esterification of non-esterified fatty acids.