T lymphopaenia in relation to body mass index and TNF-alpha in human obesity: adequate weight reduction can be corrective.

OBJECTIVE: Although individuals with obesity are susceptible to infection, the underlying causes have not been fully identified. To investigate whether obesity affects immunity, we studied subjects with isolated obesity. DESIGN AND SUBJECTS: Thirty-four obese persons from our outpatient obesity clinic and 50 nonobese healthy control subjects were studied. The effects of weight reduction were evaluated in obese subjects on a very-low-energy diet. We examined blastogenic response, lymphocyte subsets, circulatory TNF-alpha, soluble TNF-alpha receptor 1, soluble TNF-alpha receptor 2, and in vitro TNF-alpha production in obesity. MEASUREMENTS: Lymphocyte subsets were analysed with flowcytometry. TNF-alpha and soluble TNF receptors levels were assayed using commercially available enzyme-linked immunosorbent assay kits. RESULTS: Blastogenic responses to phytohemagglutinin or concanavalin A of T cells, CD3(+), CD4(+), CD8(+), CD4(+)CD45RO(+), and TCR alpha beta T cells were significantly diminished in obese subjects. Strong negative correlations were observed between TCR alpha beta and body weight and BMI in obese subjects. Circulatory levels of TNF-alpha, soluble TNF-alpha receptors, and in vitro TNF-alpha production were significantly increased compared to nonobese subjects. In obese subjects, there were significant positive correlations between serum levels of TNF-alpha and waist-hip ratio, serum levels of soluble TNF-alpha receptor 1 and body weight, soluble TNF-alpha receptor 2 and BMI, and soluble TNF-alpha receptor 2 and waist-hip ratio. The T cell responses and previously reduced non-CD8 T cell subsets were increased significantly following weight reduction. CONCLUSIONS: Our results suggest that subsets of T cell populations and their function may be reduced in human obesity, and that this may be related, at least in part, to the elevated TNF-alpha production. Furthermore, this T cell dysfunction can be recovered by adequate weight reduction.

T lymphopenia in genetically obese-diabetic Wistar fatty rats: effects of body weight reduction on T cells.

Patients with long-standing diabetes may have a propensity for infection-related mortality. In this study, lymphocyte subsets, the proliferative response of splenocytes to mitogens, and circulating levels of tumor necrosis factor alpha (TNF-alpha) in genetically obese-diabetic Wistar fatty (fa/fa) rats (WF) were longitudinally compared versus lean (+/?) litters (WL). Moreover, the effects of weight reduction with voglibose treatment on immunity were evaluated (WFV and WLV). Body weight was significantly increased in WF compared with WL. Hyperglycemia and hyperlipidemia developed, respectively, 11 weeks and 5 weeks thereafter throughout the observation periods. Circulating T cells and T-cell subsets of WF were significantly reduced after 22 weeks. There were also significant decreases in CD4+ and CD8+ thymocytes and the proliferative response of splenocytes. Circulating levels of TNF-alpha were significantly increased in WF. Treatment with voglibose resulted in significantly reduced blood glucose, insulin, cholesterol, triglyceride, and body weight in WFV. After weight reduction, circulating T cells and T-cell subsets were increased and TNF-alpha was decreased significantly in WFV. Our results suggest that the number and function of T cells in WF may be reduced, which may be related at least in part to elevated TNF-alpha levels, although the role of the other factors such as glucose, insulin, cholesterol, and triglycerides on T-cell immunity should be further investigated.

T lymphopenia in obese diabetic (db/db) mice is non-selective and thymus independent.

Although C57BL/KsJ db/db mice, an animal model of non-insulin-dependent diabetes mellitus (NIDDM), develop T lymphopenia in association with the progression of NIDDM, the T lymphopenia has not been fully investigated. In this study, to elucidate how and why T lymphopenia develops in db/db mice, T-lymphocyte subsets in spleen and thymus were longitudinally examined by flow cytometry and the effects of thymectomy and dietary restriction on the development of T lymphopenia were evaluated. After 8 weeks of age, when obese diabetes progresses, T lymphopenia in both spleen and thymus developed and all T-lymphocyte subsets examined were similarly reduced compared to lean (-/X) littermates, indicating non-selective T lymphopenia in db/db mice. Thymectomy performed at 5 wk of age, when neither T lymphopenia nor NIDDM yet presents, had no significant effect on the development of T lymphopenia. Furthermore, pair feeding until 30 weeks of age produced normal body weight and normoglycemia with still marked hyperinsulinemia, but failed to correct T lymphopenia in db/db mice. In conclusion, our results suggest that T lymphopenia may develop non-selectively and independently of either thymic dysfunction or obese diabetes in db/db mice.

T lymphopenia in genetically obese rats.

Although obese animals are more susceptible to infection, the underlying causes are not fully known. In this study, long-term measurements were made of lymphocyte subsets in peripheral blood, spleen, and thymus in genetically obese Zucker (fa/fa) rats. Blastogenic response of splenocytes to mitogens was also examined. fa/fa rats developed obesity, hyperlipidemia, and hyperinsulinemia after 5 weeks of age. Flow cytometric analysis revealed that T cells in peripheral blood, spleen, and thymus were all reduced significantly in obese rats after 8 weeks of age compared to nonobese (Fa/-) littermates. All T-cell subsets examined, including CD4+ and CD8+ T cells, were similarly reduced in spleen and thymus as well as in peripheral blood with advance in age. In addition, proliferative responses of splenocytes to mitogens were significantly low in obese rats. These results indicate that long-term obesity may reduce the size of the T-cell pool and impair the responsiveness of splenocytes in rats.

Defective adenoassociated viral-mediated transfection of insulin gene by direct injection into liver parenchyma decreases blood glucose of diabetic mice.

The present study assessed the feasibility of transferring the insulin gene into liver cells of diabetic individuals using a defective adenoassociated viral (AAV) vehicle. AAV offers several advantages over other viral vectors, since this vehicle can facilitate transfection in vivo without cell division and without any viral coding sequences (thus minimizing inflammation). The rat insulin gene and lacZ were each packed into a defective AAV vehicle (AAV-INS and AAV-lacZ, respectively). Successful AAV-mediated transfection and expression of lacZ into hepatocytes in primary cell culture were demonstrated by chemiluminescent assay of beta-galactosidase. Similarly, AAV-mediated transfection and expression of the insulin gene into hepatocytes was demonstrated by immunocytochemistry and reverse-transcriptase polymerase chain reaction (RT-PCR). After AAV-mediated transfection of the insulin gene into hepatocytes, glucose in the medium was significantly reduced for up to 5 days. After direct injection of AAV-INS into liver parenchyma of diabetic mice, successful transfection was demonstrated by RT-PCR, and blood glucose was significantly decreased for at least 6 days. These studies suggest that the AAV vector may be used to transfer the insulin gene into liver cells in vitro and in vivo.

Genetic control of in vivo tumor necrosis factor production in mice.

We report on the genetic effect on in vivo production of tumor necrosis factor (TNF)-alpha induced by lipopolysaccharides (LPS) using various congenic mouse strains. B10.A, Bl0.A(3R), B10.AQR, B10.A(5R), and B10.S(7R) produced significantly high TNF-alpha compared with B10.BR, B10.S, C57BL/10, B10.A(2R), B10.A(4R), B10.G, B10.DA(80NS), and B10.RIII(71NS). This suggests that LPS-induced TNF-alpha production is genetically controlled by H-2. Mice with the same alleles on K, A, E, or S loci produced various (high or low) levels of TNF-alpha, thus indicating that regulatory genes are located outside these loci. All strains with H-2Dd produced significantly high levels of TNF-alpha, but strains with other alleles in the H-2D locus produced low levels. Thus, TNF-alpha production appears to be genetically linked to H-2D itself or H-2D linked genes and the allele d is linked to a high responder gene. This was the case with the A background. C3H/HeN (H-2k), however, showed a high TNF-alpha production, suggesting the presence of another controlling gene outside H-2. In addition, high TNF-alpha productivity was transmitted into F1 mice (B10.A X B10.BR) in a dominant fashion. Both LPS-stimulated and unstimulated TNF-alpha mRNA expression in splenic macrophages were enhanced in high responder strains. Thus, we conclude that TNF-alpha production is closely related to genes within or linked to the H-2D locus as well as others outside H-2.

Insufficient expression of Fas antigen on helper T cells in Behçet's disease.

AIMS: To investigate the lack of equilibrium in the regulatory mechanism of the immune system in Behçet's disease (BD), the expression of Fas antigen, an apoptosis related antigen, on peripheral blood lymphocytes from BD patients was analysed. METHODS: Twenty one BD patients were the subjects in this study. Ten healthy adults were examined as controls. Cell surface antigens of lymphocytes were analysed with flow cytometry. RESULTS: There was a significant (p < 0.01) difference in the proportion of CD4 positive cells with CD25 between BD patients with active uveoretinitis (27.6% (SD 8.4%)) and the controls (14.7% (2.3%)), but no significant difference in the proportion of CD4 or CD45RO positive cells with Fas. On the other hand, the proportion of CD8 positive cells with Fas was significantly (p < 0.01) higher in BD patients with active uveoretinitis (45.6% (11.6%)) than in those with inactive uveoretinitis (23.8% (8.1%)) or in the controls (24.4% (2.5%)). The proportion of CD19 positive cells with Fas was also significantly (p < 0.01) higher in BD patients with active uveoretinitis (13.0% (5.0%)) than in the controls (5.1% (2.1%)). CONCLUSION: The insufficient expression of Fas on activated CD4 positive T cells and its high expression on CD8 positive T cells seem to play an important role in the chronic inflammation in BD.

Augmented production of tumor necrosis factor-alpha in obese mice.

Non-insulin-dependent diabetes mellitus develops in obesity. The insulin resistance of this disease may be mediated by tumor necrosis factor-alpha (TNF-alpha). In particular, the TNF-alpha derived from adipose tissues might be involved in the induction of peripheral insulin resistance in rodent models of obesity. In general, monocytes/macrophages have been considered as the major source of TNF-alpha. This study was designed to examine the potential production of TNF-alpha from monocyte/macrophages in obese mice. In obese (ob/ob) and obese diabetic (db/db) mice, both of which are known to have severe insulin resistance, unstimulated serum bioactivity of TNF-alpha was significantly higher than that in lean control mice. Spontaneous TNF-alpha mRNA expression in splenic macrophages was also enhanced in obese mice, but not in monosodium-L-glutamate (MST)-induced obese mice which have no insulin resistance. In addition, both ob/ob and db/db mice produce more TNF-alpha than lean mice upon in vivo lipopolysaccharide (LPS) stimulation. The LPS-induced increase in serum TNF-alpha activity was not observed in MSG-induced obese mice. Taken together, it is postulated that TNF-alpha produced by monocytes/macrophages may also play an important role in the genesis of insulin resistance in obesity. Further study is needed to reveal the mechanism of enhanced TNF-alpha production in obese states and its possible etiologic relevance to obesity.

Wistar fatty rat is obese and spontaneously hypertensive.

The purpose of this study was to determine whether genetically obese Wistar fatty rats have higher blood pressure than their lean littermates and if so to elucidate the mechanism of this obesity-related hypertension. We measured blood glucose and plasma insulin levels, blood pressure, and catecholamine and sodium excretions in age-matched female Wistar fatty and lean rats. After 12 weeks of age, the body weight of Wistar fatty rats was significantly greater than that of their lean counterparts. Fasting blood glucose and plasma insulin concentrations were higher in the fatty than the lean rats throughout the observation period (8 to 24 weeks of age). Systolic blood pressure of fatty rats measured by the tail-cuff method was similar to that of lean rats at 8 weeks of age (135 +/- 2 [mean +/- SEM] versus 134 +/- 3 mm Hg) but significantly higher at 16 (158 +/- 2 versus 136 +/- 3 mm Hg, P < .01) and 24 (166 +/- 5 versus 142 +/- 2 mm Hg, P < .01) weeks of age. Urinary norepinephrine excretion was significantly increased in the fatty rats at both 16 (1755 +/- 173 versus 977 +/- 128 ng/24 h, P < .05) and 24 (1907 +/- 283 versus 737 +/- 173 ng/24 h, P < .01) weeks of age. The ratio of urinary norepinephrine excretion to body weight was also significantly increased in the fatty rats. These results show that with increasing body weight Wistar fatty rats develop hypertension, which may be attributable to an increased sympathetic nerve activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Impaired immunity in obesity: suppressed but reversible lymphocyte responsiveness.

Although obese people have been reported to have a higher incidence of infections and some types of cancer, the immunocompetence of obese subjects remains poorly understood. To investigate whether obesity affects immunity, we studied obese subjects (BMI > 30 kg/m2) whose health was uncomplicated by any other disorder, including hyperglycemia. We compared mitogen-induced blastogenic response of peripheral blood lymphocytes in 34 obese subjects (mean +/- s.e. BMI: 38.4 +/- 2.0 kg/m2) and 35 non-obese controls (BMI: 21.3 +/- 0.4 kg/m2) who were matched for age and sex. The effects of weight reduction were also evaluated in 19 obese persons (BMI: 36.4 +/- 1.8 kg/m2) on a very low calorie diet. Mean (+/- s.e.) intracellular incorporation of [3H]-thymidine, on stimulation of T lymphocytes with either phytohaemagglutinin (PHA) or concanavalin A (Con A), and B lymphocytes with pokeweed mitogen, was significantly diminished in obese subjects compared to non-obese controls (47552 +/- 6917 vs. 83720 +/- 6252 cpm, P < 0.001; 30301 +/- 6018 vs. 45942 +/- 3723 cpm, P < 0.05; 13669 +/- 2971 vs. 23735 +/- 2048 cpm, P < 0.01, respectively). After weight reduction (BMI: 27.8 +/- 1.2 kg/m2), the mean T lymphocyte responses to PHA and Con A were increased significantly vs. baseline (98404 +/- 2444 vs. 50337 +/- 9516 cpm, P < 0.05 and 69523 +/- 15480 vs. 36695 +/- 8006 cpm, P < 0.05, respectively). Depressed blastogenesis of B lymphocytes was also augmented but was not statistically significant. The results suggest that obese subjects have underlying immune impairment in responsiveness of lymphocytes and that these impairments are reversible with adequate weight reduction.