Development of a Mouse Model of Metabolic Syndrome, Pulmonary Hypertension, and Heart Failure with Preserved Ejection Fraction.

Pulmonary hypertension (PH) associated with heart failure with preserved ejection fraction (PH-HFpEF; World Health Organization Group II) secondary to left ventricular (LV) diastolic dysfunction is the most frequent cause of PH. It is an increasingly recognized clinical complication of the metabolic syndrome. To date, no effective treatment has been identified, and no genetically modifiable mouse model is available for advancing our understanding for PH-HFpEF. To develop a mouse model of PH-HFpEF, we exposed 36 mouse strains to 20 weeks of high-fat diet (HFD), followed by systematic evaluation of right ventricular (RV) and LV pressure-volume analysis. The HFD induces obesity, glucose intolerance, insulin resistance, hyperlipidemia, as well as PH, in susceptible strains. We observed that certain mouse strains, such as AKR/J, NON/shiLtJ, and WSB/EiJ, developed hemodynamic signs of PH-HFpEF. Of the strains that develop PH-HFpEF, we selected AKR/J for further model validation, as it is known to be prone to HFD-induced metabolic syndrome and had low variability in hemodynamics. HFD-treated AKR/J mice demonstrate reproducibly higher RV systolic pressure compared with mice fed with regular diet, along with increased LV end-diastolic pressure, both RV and LV hypertrophy, glucose intolerance, and elevated HbA1c levels. Time course assessments showed that HFD significantly increased body weight, RV systolic pressure, LV end-diastolic pressure, biventricular hypertrophy, and HbA1c throughout the treatment period. Moreover, we also identified and validated 129S1/SvlmJ as a resistant mouse strain to HFD-induced PH-HFpEF. These studies validate an HFD/AKR/J mouse model of PH-HFpEF, which may offer a new avenue for testing potential mechanisms and treatments for this disease.

T cell-mediated hepatic inflammation modulates adiponectin levels in mice: role of tumor necrosis factor alpha.

Experimental T cell-mediated hepatitis induced by concanavalin A (ConA) results in the initiation of an inflammatory response and the production of cytokines. Adiponectin is an adipocytokine produced by adipose tissue that is involved in the reciprocal regulation of other cytokines, including tumor necrosis factor alpha (TNF-alpha). Concanavalin A administration to C57BL/6J mice reduced circulating levels of adiponectin, whereas leptin was markedly increased. Adiponectin messenger RNA expression in adipose tissue was also decreased; however, the expression of both the adiponectin receptors remained unchanged. Neutralization of TNF-alpha reduced ConA-induced liver damage, and this was associated with restored circulating levels of adiponectin. These findings indicate that inflammation-induced TNF-alpha is a critical mediator of adipose-tissue-derived adiponectin in vivo.

Regulation of T cell-mediated hepatic inflammation by adiponectin and leptin.

Concanavalin A-induced hepatotoxicity was compared in lipodystrophic aP2-nSREBP-1c transgenic mice (LD mice) lacking adipose tissue, obese leptin-deficient ob/ob mice, and lean wild-type (WT) mice. Serum leptin and adiponectin were low in LD mice, whereas ob/ob mice had undetectable leptin, but high adiponectin. Protection from hepatotoxicity was observed in ob/ob, but not in LD mice, despite low cytokine levels and reduced T cell activation and hepatic natural killer T cells in both groups. Administration of adiponectin protected LD mice from hepatotoxicity without altering cytokine levels. In contrast, administration of leptin heightened disease susceptibility by restoring cytokine production. Neutralization of TNF alpha protected LD mice from liver damage. Increased in vivo susceptibility to the hepatotoxic effect of TNF alpha was observed in LD mice. In vitro, adiponectin protected primary hepatocytes from TNF alpha-induced death, whereas leptin had no protective effect. In conclusion, although leptin increases susceptibility to hepatotoxicity by regulating cytokine production and T cell activation, adiponectin protects hepatocytes from TNF alpha-induced death.

In vitro mononuclear cell production of tumour necrosis factor-alpha and weight loss.

OBJECTIVE: Elevated tumour necrosis factor-alpha (TNF-alpha) production in adipose tissue has been associated with obesity. We investigated whether mononuclear cell production of TNF-alpha decreased with weight loss in an obese population. RESEARCH METHODS AND PROCEDURES: Seventeen obese patients with type 2 diabetes (BMI 32.5+/-0.9 kg/m(2)) and 33 obese, non-diabetic controls (BMI 31.2+/-0.5 kg/m(2)) underwent 12 weeks of 30% total energy restriction (6622+/-84 KJ per day). Every 4 weeks, weight and blood pressure were measured and fasting venous blood was analysed for lipid, glucose and insulin concentrations. At the beginning and end of energy restriction, mononuclear cells were isolated from whole blood and TNF-alpha production measured by ELSIA. RESULTS: TNF-alpha production was not associated with the degree of adiposity but was higher in diabetic subjects (P<0.04). There was a reduction after energy restriction (281+/-43 to 182+/-30 pg/ml, P<0.05) however the presence of type 2 diabetes did not influence the magnitude of this change. Plasma glucose and insulin levels decreased after weight loss in all subjects and weak correlations were found with TNF-alpha concentrations (r=0.3, P<0.05). CONCLUSIONS: We conclude that maximal production of TNF-alpha from mononuclear cells decreases with energy restriction and is weakly associated with plasma glucose and insulin concentrations in obese patients.

-308 Nco I polymorphism of tumour necrosis factor alpha in overweight Caucasians.

We investigated whether a polymorphism in the promoter region of the TNFalpha gene (-308 A/G) is associated with reduced weight loss in obese Australian subjects on an energy restricted diet. 189 healthy subjects and 91 subjects with type II diabetes were genotyped for the -308 Nco I polymorphism using PCR-RFLP techniques. A subset of these subjects (211 females and 45 males), were placed on a 30% energy restricted diet (6200 kJ) for 12 weeks. Subjects were assessed every 2 weeks and changes in body weight, waist circumference and BMI were used as determinants of weight loss. Fasting plasma was analysed for glucose, insulin, lipids and free fatty acids. 64% of subjects were GG homozygotes, 31% were AG heterozygotes and 5% were AA homozygotes. There was no significant difference between the allele frequency in healthy subjects (0.21) and type 2 diabetic patients (0.24). The presence of the -308 A/G polymorphism did not significantly influence initial BMI, the amount of weight lost (GG, 8.1+/-0.65 kg, AG, 6.9+/-0.77 kg, AA, 7.6+/-0.12 kg), waist circumference or any metabolic variable. The AA variant at position -308 in the promoter region of the TNFalpha gene does not influence the amount of weight lost in overweight and obese men and women on a 30% energy restricted diet.

Survival for patients With HIV admitted to the ICU continues to improve in the current era of combination antiretroviral therapy.

BACKGROUND: The combination antiretroviral therapy (ART) era (1996 to the present) has been associated with improved survival among HIV-infected outpatients, but ICU data from 2000 to the present are limited. METHODS: We conducted a retrospective study of HIV-infected adults who had been admitted to the ICU at San Francisco General Hospital (from 2000 to 2004). The primary outcome was survival to hospital discharge. RESULTS: During the 5-year study period, there were 311 ICU admissions for 281 patients. Respiratory failure remained the most common indication for ICU admission (42% overall), but the proportion of patients with respiratory failure decreased each year from 52 to 34% (p = 0.02). Hospital survival ratios significantly increased during the 5-year period (p = 0.001). ART use at ICU admission was not associated with survival, but it was associated with higher CD4 cell counts, lower plasma HIV RNA levels, higher serum albumin levels, and lower proportions with AIDS-associated ICU admission diagnoses and with Pneumocystis pneumonia. In a multivariate analysis, a higher serum albumin level (adjusted odds ratio [AOR], 2.08; 95% confidence interval [CI], 1.41 to 3.06; p = 0.002) and the absence of mechanical ventilation (AOR, 6.11; 95% CI, 2.73 to 13.72; p < 0.001) were associated with survival. CONCLUSIONS: In this sixth in a series of consecutive studies started in 1981, we found that the epidemiology of ICU admission diagnoses continues to change. Our study also found that survival for critically ill HIV-infected patients continues to improve in the current era of ART. Although ART use was not associated with survival, it was associated with predictors that were associated with survival in a multivariate analysis.

Plasma alpha-melanocyte-stimulating hormone: sex differences and correlations with obesity.

Rodent experiments raise the possibility of a regulatory role of peripheral alpha-melanocyte-stimulating hormone (alpha-MSH) in obesity and metabolism, but human data on peripheral alpha-MSH levels remain fragmentary. Because of the possible relationship between alpha-MSH and obesity, we endeavored to test the hypothesis that higher levels of alpha-MSH in obese patients would correlate with leptin levels and with other markers of obesity. Sixty normal-weight to obese healthy men and women participated. Weight, measures of body composition, and diet diaries were obtained; fasting blood was analyzed for alpha-MSH, lipids, glucose, insulin, leptin, and adiponectin. To begin to understand the source of peripherally measured hormones, alpha-MSH was also measured in serum samples from 5 individuals with untreated Addison disease. Levels of alpha-MSH were higher in men vs women (10.1 +/- 4.3 vs 7.6 +/- 3.4 pmol/L, P = .019), and alpha-MSH levels were higher in patients with Addison disease vs controls (17.7 +/- 2.3 vs 8.7 +/- 0.52 pmol/L, P < .001). Measures of adiposity correlated with insulin and leptin in men and women, and with adiponectin in women. alpha-Melanocyte-stimulating hormone levels did not correlate significantly with any parameter of adiposity or diet composition. The elevated alpha-MSH levels in patients with untreated Addison disease suggest possible pituitary secretion of alpha-MSH to the periphery. The lack of correlation between peripheral alpha-MSH and parameters of adiposity suggests that endogenous plasma alpha-MSH levels are not a metric for body composition per se.