Influence of membrane-bound tumor necrosis factor (TNF)-alpha on obesity and glucose metabolism

OBJECTIVES

To investigate the influence of transmembrane tumor necrosis factor (TNF)-alpha on adipose tissue development and insulin-mediated glucose metabolism.

METHODS AND RESULTS

TNF-alpha and lymphotoxin-alpha-deficient mice expressing non-cleavable transmembrane TNF-alpha (Tg-tmTNF-alpha) and TNF-alpha/lymphotoxin-alpha double knockout (control) mice were kept on high-fat diet for 15 weeks. The food intake and feeding efficiency of Tg-tmTNF-alpha mice were significantly higher compared with control mice. At the end of the study, Tg-tmTNF-alpha mice had a significantly higher total body weight, as well as subcutaneous and gonadal adipose tissue mass. Histological analysis revealed that the expression of Tg-tmTNF-alpha resulted in a significantly increased adipocyte area and blood vessel density. Plasma leptin levels correlated positively with adipose tissue mass. The plasma levels of total cholesterol and HDL-cholesterol were significantly increased and LDL-cholesterol levels significantly decreased in Tg-tmTNF-alpha mice. Fasting blood glucose and plasma insulin levels were not different between the two genotypes and intraperitoneal glucose and insulin tolerance tests did not show significant differences.

CONCLUSIONS

Transmembrane TNF-alpha enhances adipose tissue formation without altering insulin-mediated glucose metabolism in mice with nutritionally induced obesity.

[The effect of brimonidine on postoperative hypertonia after an extracapsular cataract extraction]

PURPOSE

We conducted a prospective study to determine the effect of topical administration of brimonidine tartrate 0.2% on postoperative intraocular pressure (IOP) spikes during the first 24 hours after an extracapsular cataract extraction.

MATERIAL AND METHODS

In a placebo-controlled study, we randomized 40 consecutive normotensive eyes undergoing extracapsular cataract surgery into two treatment modalities. Twenty eyes (group A) received placebo and 20 eyes (group B) were given brimonidine tartate 0.2% drops twice the day before and twice on the day of the operation. IOP was measured at baseline (prior to surgery) and then 4, 6, 12 and 24 hours postoperatively.

RESULTS

Mean postoperative IOP was higher in the placebo group than in the brimonidine group at every time point studied. In both groups, peak elevation of mean IOP was recorded 6 hours after surgery. At that time, mean IOP was significantly higher in the placebo group (36.2+/-4.0 mmHg) than in the brimonidine group (24.7+/-3.8 mmHg) (p<0.001). A gradual reduction in IOP followed, yet with significantly higher values than those found preoperatively, even 12 hours after surgery (p<0.001). It was only the brimonidine group that achieved a near-to-normal mean IOP 24 hours after surgery (p>0.05). Four of the placebo group patients compared to 1 of the brimonidine group patients had an IOP higher than 40 mmHg 6 hours after surgery and therefore received additional therapy.

CONCLUSION

Prophylactic treatment with brimonidine tartrate 0.2% drops twice a day for 2 days is effective in reducing IOP spikes throughout the first 24 hours after an extracapsular cataract extraction.

Differential expression of plasminogen activator inhibitor-1, tumor necrosis factor-alpha, TNF-alpha converting enzyme and ADAMTS family members in murine fat territories

Our objective was to investigate expression of A disintegrin and metalloproteinase (ADAM) and ADAM proteins with a thrombospondin (TS) motif (ADAMTS) family members in adipose tissue of lean and obese mice. Five-week-old male mice were kept on standard chow (SFD) or on high fat diet (HFD) for 15 weeks, and subcutaneous (SC) and gonadal (GON) adipose tissue, as well as mature adipocytes and stromal-vascular (S-V) cells were harvested. mRNA levels of plasminogen activator inhibitor-1 (PAI-1), tumor necrosis factor-alpha (TNF-alpha), ADAM-17 (TACE or TNF-alpha converting enzyme), ADAMTS-1 and ADAMTS-8 were quantified in isolated adipose tissues and cell fractions, and during differentiation of murine preadipocytes. The HFD resulted in a significantly enhanced weight of isolated SC and GON fat pads, and in enhanced blood levels of glucose, cholesterol and PAI-1. ADAM-17, TNF-alpha, PAI-1, ADAMTS-1 and ADAMTS-8 mRNA were detected in both SC and GON adipose tissue of lean mice (SFD). In SC adipose tissue of obese mice (HFD), the expression of ADAM-17 and PAI-1 was enhanced and that of ADAMTS-1 reduced, whereas in GON adipose tissue expression of TNF-alpha was enhanced and that of ADAMTS-8 reduced. In lean and obese mice, expression of ADAM-17, ADAMTS-1 and ADAMTS-8 was higher in the S-V cell fraction than in mature adipocytes. During differentiation of murine 3T3-F442A preadipocytes, expression of ADAM-17 and ADAMTS-1 remained virtually unaltered, whereas that of ADAMTS-8 decreased as adipocytes matured. Several ADAM and ADAMTS family members are expressed in adipose tissue and during differentiation of preadipocytes. Modulation of their expression upon development of obesity is adipose tissue-dependent.

Nutritionally induced obesity is attenuated in transgenic mice overexpressing plasminogen activator inhibitor-1

OBJECTIVE

The objective of this study was to investigate the role of plasminogen activator inhibitor-1 (PAI-1) in adipose tissue development in vivo.

METHODS AND RESULTS

Transgenic (Tg) mice overexpressing murine PAI-1 under control of the adipocyte promoter aP2 and wild-type (WT) controls were kept on standard food (SFD) or on high-fat diet (HFD) for 15 weeks. The body weight and the weight of the isolated subcutaneous and gonadal fat deposits of the Tg mice kept on the HFD were significantly lower than those of the WT mice. The number of adipocytes in the adipose tissue was similar for Tg and WT mice on the HFD, but adipocyte hypotrophy and a significantly lower ratio of stroma cells/adipocytes were observed in the Tg mice. A significant negative correlation (P<0.01) was observed between expression of preadipocyte factor-1, which blocks adipocyte differentiation, and adipose tissue weight. Fasting insulin and total cholesterol levels on the HFD were lower in Tg than in WT mice.

CONCLUSIONS

High circulating PAI-1 levels attenuate nutritionally induced obesity. This may be related to modifications in adipose tissue cellularity affecting weight and plasma metabolic parameters.