Liver-specific loss of long chain acyl-CoA synthetase-1 decreases triacylglycerol synthesis and beta-oxidation and alters phospholipid fatty acid composition.

In mammals, a family of five acyl-CoA synthetases (ACSLs), each the product of a separate gene, activates long chain fatty acids to form acyl-CoAs. Because the ACSL isoforms have overlapping preferences for fatty acid chain length and saturation and are expressed in many of the same tissues, the individual function of each isoform has remained uncertain. Thus, we constructed a mouse model with a liver-specific knock-out of ACSL1, a major ACSL isoform in liver. Eliminating ACSL1 in liver resulted in a 50% decrease in total hepatic ACSL activity and a 25-35% decrease in long chain acyl-CoA content. Although the content of triacylglycerol was unchanged in Acsl1(L)(-/-) liver after mice were fed either low or high fat diets, in isolated primary hepatocytes the absence of ACSL1 diminished the incorporation of [(14)C]oleate into triacylglycerol. Further, small but consistent increases were observed in the percentage of 16:0 in phosphatidylcholine and phosphatidylethanolamine and of 18:1 in phosphatidylethanolamine and lysophosphatidylcholine, whereas concomitant decreases were seen in 18:0 in phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and lysophosphatidylcholine. In addition, decreases in long chain acylcarnitine content and diminished production of acid-soluble metabolites from [(14)C]oleate suggested that hepatic ACSL1 is important for mitochondrial beta-oxidation of long chain fatty acids. Because the Acsl1(L)(-/-) mice were not protected from developing either high fat diet-induced hepatic steatosis or insulin resistance, our study suggests that lowering the content of hepatic acyl-CoA without a concomitant decrease in triacylglycerol and other lipid intermediates is insufficient to protect against hepatic insulin resistance.

The antibody response to influenza vaccination is not impaired in type 2 diabetics.

BACKGROUND: Diabetics are considered to be at high risk for complications from influenza infection and type 2 diabetes is a significant comorbidity of obesity. Obesity is an independent risk factor for complications from infection with influenza. Annual vaccination is considered the best strategy for protecting against influenza infection and it's complications. Our previous study reported intact antibody responses 30 days post vaccination in an obese population. This study was designed to determine the antibody response to influenza vaccination in type 2 diabetics. METHODS: Subjects enrolled were 18 or older without immunosuppressive diseases or taking immunosuppressive medications. A pre-vaccination blood draw was taken at time of enrollment, the subjects received the influenza vaccine and returned 28-32 days later for a post-vaccination blood draw. Height and weight were also obtained at the first visit and BMI was calculated. Antibody levels to the vaccine were determined by both ELISA and hemagglutination inhibition (HAI) assays. RESULTS: As reported in our previous work, obesity positively correlates with the influenza antibody response (p=0.02), while age was negatively correlated with antibody response (p<0.001). In both year 1 and year 2 of our study there was no significant difference in the percentage of the type 2 diabetic subjects classified as seroprotected or a responder to the influenza vaccine compared to the non-diabetic subjects. CONCLUSIONS: These data are important because they demonstrate that diabetics, considered a high risk group during influenza season, are able to mount an antibody response to influenza vaccination that may protect them from influenza infection.

Overweight and obese adult humans have a defective cellular immune response to pandemic H1N1 influenza A virus.

OBJECTIVE: Obese adults have a greater risk of morbidity and mortality from infection with pandemic H1N1 influenza A virus (pH1N1). The objective of the present study was to elucidate the specific mechanisms by which obesity and overweight impact the cellular immune response to pH1N1. DESIGN AND METHODS: Peripheral blood mononuclear cells from healthy weight, overweight, and obese individuals were stimulated ex vivo with live pH1N1 and then markers of activation and function were measured using flow cytometry and cytokine secretion was measured using cytometric bead array assays. RESULTS: CD4(+) and CD8(+) T cells from overweight and obese individuals expressed lower levels of CD69, CD28, CD40 ligand, and interleukin-12 receptor, as well as, produced lower levels of interferon-γ and granzyme B, compared with healthy weight individuals, suggesting deficiencies in activation and function are indicated. Dendritic cells from the three groups expressed similar levels of major histocompatibility complex-II, CD40, CD80, and CD86, as well as, produced similar levels of interleukin-12. CONCLUSIONS: The defects in CD4(+) and CD8(+) T cells may contribute to the increased morbidity and mortality from pH1N1 in obese individuals. These data also provide evidence that both overweight and obesity cause impairments in immune function.