Circulating and adipose tissue gene expression of zinc-alpha2-glycoprotein in obesity: its relationship with adipokine and lipolytic gene markers in subcutaneous and visceral fat

CONTEXT

Zinc-alpha2-glycoprotein (ZAG) is a soluble protein similar to the class I major histocompatibility complex heavy chain, which has been implicated in lipid catabolism. We hypothesized that ZAG mRNA expression in adipose tissue may be linked with lipolytic and adipokine gene expression and have a close relationship with clinical phenotype.

OBJECTIVES

The objective of the study was to analyze ZAG gene expression in human adipose tissue from lean and obese subjects. ZAG circulating plasma levels and its relationship with cardiometabolic risk factors were also studied.

DESIGN

Seventy-three Caucasian (43 male and 30 female) subjects were included. Plasma and adipose tissue [sc (SAT) and visceral (VAT)] from the same patient were studied. mRNA of PPARgamma, hormone-sensitive lipase (HSL), adipose triglyceride lipase, adiponectin, omentin, visfatin, and ZAG were quantified. Plasma concentrations of ZAG were determined with ELISA.

RESULTS

ZAG plasma levels showed a negative correlation with insulin (r = -0.39; P = 0.008) and the homeostasis model assessment for insulin resistance index (r = -0.36; P = 0.016). No differences in ZAG circulating levels according to body mass index classification were observed. ZAG expression in SAT was significantly reduced in overweight and obese individuals compared with lean subjects (P < 0.001 and P = 0.007, respectively). ZAG mRNA expression in both SAT and VAT depots were negatively correlated with many clinical and metabolic cardiovascular risk factors. After multiple linear regression analysis, SAT ZAG was mainly predicted by adiponectin mRNA expression (B = 0.993; P < 0.0001) and plasma triglyceride levels (B = -0.565; P = 0.006). VAT ZAG expression was predicted by adiponectin expression (B = 0.449; P < 0.0001), and HSL VAT expression (B = 0.180; P = 0.023).

CONCLUSIONS

The present study provides evidence of a role of ZAG gene in adipose tissue metabolism, with a close association with adiponectin gene expression in sc and visceral fat.

Adipose tissue expression of the glycerol channel aquaporin-7 gene is altered in severe obesity but not in type 2 diabetes

CONTEXT

Aquaporin-7 is required for efflux of glycerol from adipocytes and influences whole-body glucose homeostasis in animal studies.

OBJECTIVE

Our objective was to test the hypothesis that AQP7 gene expression levels may be affected by presence of obesity and type 2 diabetes in humans.

DESIGN

The obesity study cohort consisted of 12 lean, 22 nonseverely obese, and 13 severely obese subjects. The type 2 diabetes study cohort consisted of 17 lean and 39 obese type 2 diabetic patients. Circulating levels of plasma soluble proteins monocyte chemoattractant protein-1, TNF receptors 1 and 2, and IL-6 and glycerol were measured. The sc adipose tissue gene expression of AQP7, MCP-1, IL-6, TNFalpha, PPARgamma, and SREBP1c genes was measured by real-time PCR. AQP7 gene mutation analysis was performed.

RESULTS

Severely obese women showed lower AQP7 expression levels compared with lean and nonseverely obese (P < 0.001). Moreover, circulating glycerol concentration was lower in severely obese subjects, but no correlation with AQP7 adipose tissue expression was observed. AQP7 expression was negatively related with proinflammatory genes (for monocyte chemoattractant protein-1, r = -0.203 and P = 0.044; for TNFalpha, r = -0.209 and P = 0.036). Concerning adipogenic factors, AQP7 expression levels were found to be positively determined by PPARgamma mRNA expression levels (r = 0.265; P = 0.012). AQP7 expression did not show differences regarding the presence of type 2 diabetes.

CONCLUSION

Expression of AQP7 is down-regulated in women with severe obesity. The expression of this glycerol channel is not affected by type 2 diabetes.

Expression of TWEAK and its receptor Fn14 in human subcutaneous adipose tissue. Relationship with other inflammatory cytokines in obesity

TWEAK, a cytokine of the TNF family, has been found to be expressed under different inflammatory conditions but no data is available concerning the expression of this cytokine and its receptor (Fn14) in human obesity. In the present work we have evaluated the expression of many pro-inflammatory TNF system cytokines (TNF-alpha, TWEAK and their respective receptors, TNFR1, TNFR2 and Fn14) in human adipose tissue of 84 subjects some with different degree of obesity and type 2 diabetes, and its relation with inflammation by also measuring the expression of macrophage marker CD68. We detected expression of TWEAK and Fn14 in isolated mature adipocytes and in the stromovascular fraction. Additionally, we found that LPS upregulates the expression of both genes on THP-1 human monocytic cell line. TWEAK was expressed in adipose tissue of all studied subjects with no differences between obesity group, and was associated with Fn14 expression in morbid obese, mainly in women with type 2 diabetes. The data obtained here also showed that TNF-alpha and TNFR2 mRNAs were significantly more expressed in subcutaneous adipose tissue of subjects with morbid obesity compared to obese and non-obese subjects. In contrast, TNFR1 gene expression was negatively associated with BMI. Our results suggest that the expression of TNF-derived pro-inflammatory cytokines are increased in severe obesity, where macrophage infiltrate could modulate the inflammatory environment through activation of its receptors.

[Comparison of 2 methods of evaluation of food and nutrient intake: 24-hour recall and semiquantitative frequency questionnaire]

BACKGROUND

Methods of dietary collection at an individual level include various procedures with different estimates of food, energy and nutrients intakes. The aim of this study was to compare two dietary methods widely used in nutritional epidemiology: a 24-hour recall and a semiquantitative food frequency questionnaire.

METHODS

One hundred and fifty-five people selected at random from the population of the Valle de Arán (Lérida, Spain) were surveyed. Nutritional intake information was obtained from both methods.

RESULTS

The frequency method overestimated all the nutrient intakes only before adjustment by energy intake, except for cholesterol. After adjustment by energy intake estimations from both questionnaires were very similar; the percentages of energy supplied by proteins, fatty acids and carbohydrates were very similar, too; the polyunsaturated/monounsaturated fatty acid ratios, were almost the same. Results show a level of correlation between the questionnaires that ranges from 0.81 to 0.23. Nutrients that showed the highest crude correlation between both questionnaires were alcohol, energy, carbohydrates, sodium and iodine (R > or = 0.7) while vitamins C, B1, B6, B12, and A, niacine, folic acid, iron, phosphorus and potassium showed the lowest (R < or = 0.5). Energy adjusted correlations were quite different to unadjusted ones particularly for lipids, monounsaturated fatty acids, carbohydrates, fiber, cholesterol, zinc and sodium, for which a lower coefficient was calculated after adjustment, and vitamins B2, B6, C, D and potassium, for which a higher coefficient was estimated after energy adjustment.

CONCLUSIONS

Both methods make similar assessments when adjusting for caloric intake, but food frequency questionnaire tends to overestimate food consumption.

Course of subepithelial corneal haze over 18 months after photorefractive keratectomy for myopia [corrected]

This study of 285 myopic eyes treated with photorefractive keratectomy (PRK), with a maximum follow up of 18 months, was designed to analyze the clinical subepithelial significance of corneal haze after excimer laser PRK. The treatment parameters included an ablation zone diameter from 3.6 to 5 mm, ablation rate from 0.22 to 0.25 micron pulse, fluence of 180 mJ/cm2, and frequency of 10 Hz. All patients used a standard topical corticosteroid regimen. A statistical analysis of the subjective haze grading showed a maximum at 3 months (mean grading, 1.03) and a decrease to 0.38 at 18 months. Haze is statistically greater with higher amounts of treatment (p = .003 between 2.00 D and 3.00 D groups, p = .0002 between 2.00 D and 6.00 D groups). In males (p = .0004), and in ablations less than 4.5 mm diameter (p = .0002) but no difference was found related to age. The overall frequency of clinically significant haze was 11.5% with a mean age of 35.1 years and a mean attempted correction of -5.71 D. This frequency increased to 24% in the 6.20 D to 9.90 D group and 38.6% in the 4.4 mm and less group, and it decreased to 8.6% in the 1.00 D to 6.00 D group and 6.6% in the 4.5 and 5 mm group. All patients with significant haze gave a history of discontinued use of corticosteroids. We suggest there exists a significant haze risk group in which the absence of steroid or discontinuation of corticosteroids will lead to significant haze.