In vitro and in vivo effects of IGF-I on adiposity in HIV-associated metabolic disease: a pilot study.

BACKGROUND AND AIMS: We tested the effects of recombinant insulin-like growth factor-I (IGF-I) in an adipocyte model of HIV lipodystrophy and in an open label study on body composition and metabolism in patients with HIV lipodystrophy. METHODS: The effects of IGF-I on ritonavir-induced adipocyte cell death were studied in vitro. We assessed lipid accumulation, IGF signaling, apoptosis, and gene expression. We conducted a 24-week open label trial of recombinant IGF-I in ten adults with HIV associated lipoatrophy. Laboratory assessments included glucose, insulin, lipids, and IGF-I. At weeks 0 and 24, body composition studies were performed including skinfold measurement, dual-energy x-ray absorptiometry, and computed tomography of the abdomen and thigh. RESULTS: In vitro, ritonavir increased delipidation and apoptosis of adipocytes, whereas co-treatment with IGF-I attenuated the effect. In the clinical study, subcutaneous adipose tissue did not increase in patients after treatment with IGF-I; however, there was a decrease in the proportion of abdominal fat (39.8 ± 7% vs. 34.6 ± 7%, p = 0.007). IGF-I levels increased with treatment (143 ± 28 µg/L at week 0 vs. 453 ± 212 µg/L at week 24, p = 0.002), whereas IGFBP-3 levels declined (3.554 ± 1.146 mg/L vs. 3.235 ± 1.151 mg/L, p = 0.02). Insulin at week 12 decreased significantly (90.1 ± 39.8 pmol/L vs. 33.2 ± 19.6 pmol/L, p = 0.002). There was a nonsignificant decrease in visceral adipose tissue (155.2 ± 68 cm² at week 0 vs. 140.6 ± 70 cm² at week 24, p = 0.08). CONCLUSIONS: Use of recombinant IGF-I may lower fasting insulin and abdominal fat in patients with lipoatrophy associated with HIV infection. Further evaluation of this agent for treatment of HIV-associated lipodystrophy may be warranted.

Bacterial colonization leads to the colonic secretion of RELMbeta/FIZZ2, a novel goblet cell-specific protein.

BACKGROUND & AIMS: Goblet cells are highly polarized exocrine cells found throughout the small and large intestine that have a characteristic morphology due to the accumulation of apical secretory granules. These granules contain proteins that play important physiologic roles in cellular protection, barrier function, and proliferation. A limited number of intestinal goblet cell-specific proteins have been identified. In this study, we investigate the expression and regulation of RELMbeta, a novel colon-specific gene. METHODS: The regulation of RELMbeta messenger RNA expression was determined in LS174T, Caco-2, and HT-29 cell lines in response to stimulation with interleukin 13 and lipopolysaccharide. Quantitative reverse-transcription polymerase chain reaction, immunoblots, and immunohistochemistry were used to examine the expression of RELMbeta in BALB/c and C.B17.SCID mice housed in conventional, germ-free, and gnotobiotic environments. RESULTS: Messenger RNA for RELMbeta is restricted to the undifferentiated, proliferating colonic epithelium. Immunohistochemistry shows that this protein is expressed in goblet cells located primarily in the distal half of the colon and cecum with lower levels detectable in the proximal colon. High levels of RELMbeta can be detected in the stool of mice and humans, where it exists as a homodimer under nonreducing conditions. Interestingly, the secretion of RELMbeta is dramatically reduced in germ-free mice. Furthermore, introduction of germ-free mice into a conventional environment results in enhanced expression and robust secretion of RELMbeta within 48 hours. CONCLUSIONS: These studies define a new goblet cell-specific protein and provide the first evidence that colon-specific gene expression can be regulated by colonization with normal enteric bacteria.

RELMbeta/FIZZ2 is a goblet cell-specific immune-effector molecule in the gastrointestinal tract.

Gastrointestinal (GI) nematode infections are an important public health and economic concern. Experimental studies have shown that resistance to infection requires CD4(+) T helper type 2 (Th2) cytokine responses characterized by the production of IL-4 and IL-13. However, despite >30 years of research, it is unclear how the immune system mediates the expulsion of worms from the GI tract. Here, we demonstrate that a recently described intestinal goblet cell-specific protein, RELMbeta/FIZZ2, is induced after exposure to three phylogenetically distinct GI nematode pathogens. Maximal expression of RELMbeta was coincident with the production of Th2 cytokines and host protective immunity, whereas production of the Th1 cytokine, IFN-gamma, inhibited RELMbeta expression and led to chronic infection. Furthermore, whereas induction of RELMbeta was equivalent in nematode-infected wild-type and IL-4-deficient mice, IL-4 receptor-deficient mice showed minimal RELMbeta induction and developed persistent infections, demonstrating a direct role for IL-13 in optimal expression of RELMbeta. Finally, we show that RELMbeta binds to components of the nematode chemosensory apparatus and inhibits chemotaxic function of a parasitic nematode in vitro. Together, these results suggest that intestinal goblet cell-derived RELMbeta may be a novel Th2 cytokine-induced immune-effector molecule in resistance to GI nematode infection.

The IL-27 receptor (WSX-1) is an inhibitor of innate and adaptive elements of type 2 immunity.

Although previous studies have investigated the role of IL-27/WSX-1 interactions in the regulation of Th1 responses, little is known about their role in regulating Th2-type responses. Studies presented in this work identify a direct role for IL-27/WSX-1 interactions in the negative regulation of type 2 responses independent of effects on type 1 cytokines. WSX-1-/- mice infected with the gastrointestinal helminth Trichuris muris displayed accelerated expulsion of parasites and the development of exaggerated goblet cell hyperplasia and mastocytosis in the gut due to increased production of Th2 cytokines. Enhanced mast cell activity in the absence of WSX-1 was consistent with the ability of wild-type mast cells to express this receptor. In addition, IL-27 directly suppressed CD4+ T cell proliferation and Th2 cytokine production. Together, these studies identify a novel role for IL-27/WSX-1 in limiting innate and adaptive components of type 2 immunity at mucosal sites.