Receptor of ghrelin is expressed in cutaneous neurofibromas of individuals with neurofibromatosis 1

Cutaneous Neurofibroma Heterogeneity: Factors that Influence Tumor Burden in Neurofibromatosis Type 1

Neurofibromatosis type 1 is one of the most common genetic disorders of the nervous system and predisposes patients to develop benign and malignant tumors. Cutaneous neurofibromas (cNFs) are NF1-associated benign tumors that affect nearly 100% of patients with NF1. cNFs dramatically reduce patients' QOL owing to their unaesthetic appearance, physical discomfort, and corresponding psychological burden. There is currently no effective drug therapy option, and treatment is restricted to surgical removal. One of the greatest hurdles for cNF management is the variability of clinical expressivity in NF1, resulting in intrapatient and interpatient cNF tumor burden heterogeneity, that is, the variability in the presentation and evolution of these tumors. There is growing evidence that a wide array of factors are involved in the regulation of cNF heterogeneity. Understanding the mechanisms underlying this heterogeneity of cNF at the molecular, cellular, and environmental levels can facilitate the development of innovative and personalized treatment regimens.

Ghrelin Represses Thymic Stromal Lymphopoietin Gene Expression through Activation of Glucocorticoid Receptor and Protein Kinase C Delta in Inflamed Skin Keratinocytes

Ghrelin, a peptide hormone secreted from enteroendocrine cells of the gastrointestinal tract, has anti-inflammatory activity in skin diseases, including dermatitis and psoriasis. However, the molecular mechanism underlying the beneficial effect of ghrelin on skin inflammation is not clear. In this study, we found that ghrelin alleviates atopic dermatitis (AD)-phenotypes through suppression of thymic stromal lymphopoietin (TSLP) gene activation. Knockdown or antagonist treatment of growth hormone secretagogue receptor 1a (GHSR1a), the receptor for ghrelin, suppressed ghrelin-induced alleviation of AD-like phenotypes and suppression of TSLP gene activation. We further found that ghrelin induces activation of the glucocorticoid receptor (GR), leading to the binding of GR with histone deacetylase 3 (HDAC3) and nuclear receptor corepressor (NCoR) NCoR corepressor to negative glucocorticoid response element (nGRE) on the TSLP gene promoter. In addition, ghrelin-induced protein kinase C δ (PKCδ)-mediated phosphorylation of p300 at serine 89 (S89), which decreased the acetylation and DNA binding activity of nuclear factor- κB (NF-κB) p65 to the TSLP gene promoter. Knockdown of PKCδ abolished ghrelin-induced suppression of TSLP gene activation. Our study suggests that ghrelin may help to reduce skin inflammation through GR and PKCδ-p300-NF-κB-mediated suppression of TSLP gene activation.

Attribution of Ghrelin to Cancer; Attempts to Unravel an Apparent Controversy

Ghrelin is an endogenous peptide hormone mainly produced in the stomach. It has been known to regulate energy homeostasis, stimulate secretion of growth hormone, and mediate many other physiologic effects. Various effects attributed to ghrelin contribute to many aspects of cancer development and progression. Accordingly, a large body of evidence has emerged about the association of ghrelin with several types of cancer in scales of cell-line, animal, and human studies. However, existing data are controversial. This controversy occurs in two main domains: one is the controversial results in local effects of ghrelin on different types of human cancer cell-lines; the second is the apparent disagreement in the results of in-vitro and clinical studies that investigated ghrelin association to one type of cancer. These inconsistencies have hampered the indications to consider ghrelin as a potential tumor biomarker or therapeutic agent in cancer patients. Previous studies have reviewed different parts of current literature about the ghrelin-cancer relationship. Although they have highlighted these controversial results in various ways, no specific recommendations have been given to address it. In this study, we comprehensively reviewed in-vitro, in-vivo, and clinical studies and attempted to use the following approaches to unravel the inconsistencies detected: (a) to distinguish local and systemic effects of ghrelin in interpreting its summary clinical role in each cancer; (b) scrutinizing factors that regulate local effects of ghrelin and could justify different effects of ghrelin on different cancer cell-lines. These approaches could have notable implications for future in-vitro and clinical studies.

Increased resting metabolism in neurofibromatosis type 1

BACKGROUND & AIMS

Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disease that is characterized by neurocutaneous changes with multisystem involvement. A previous study with adults with NF1 revealed that changes in total energy expenditure were related to food consumption and body composition. Resting energy expenditure (REE), a measure of energy that the body expends to maintain vital functions, has not been assessed in NF1 populations. This study aimed to assess REE in individuals with NF1 using indirect calorimetry (IC) and evaluate its correlation with body composition and muscle strength.

METHODS

Twenty-six adults with NF1 (14 men) aged 18-45 years underwent IC for assessing REE, respiratory quotient (RQ), and substrate utilization. Body composition was assessed by dual energy X-ray absorptiometry. Weight, height, and waist circumference (WC) were also measured. Maximum muscular strength (Smax) was measured by handgrip test using a dynamometer. Patients in the NF1 group were compared to 26 healthy controls in the control group, who were matched by sex, age, body mass index (BMI), and physical activity level.

RESULTS

There were no differences in weight, WC, fat mass, and body fat percentage (BFP). Appendicular lean mass (ALM) adjusted by BMI (ALM_BMI) (0.828 ± 0.161 versus 0.743 ± 0.190; P = 0.048) and Smax (37.5 ± 10.6 versus 31.1 ± 12.2; P = 0.035) was lower in the NF1 group than in the control group. No differences in body composition, strength, and anthropometric parameters were observed in men, but women with NF1 presented lower body surface area (BSA), lean body mass (LBM), ALM, ALM_BMI, and Smax. REE adjusted by weight, LBM, or ALM was higher in the NF1 group than in the control group (medians, 21.9 versus 26.3, P = 0.046; 36.5 versus 41.1, P = 0.012; and 82.3 versus 92.4, P = 0.006, respectively), and these differences were observed only among women. RQ was lower in the NF1 group than in the control group (0.9 ± 0.1 versus 0.8 ± 0.1; P = 0.008), revealing that individuals with NF1 oxidized more lipids and fewer carbohydrates than controls. REE correlated negatively with BFP and positively with weight, height, BMI, WC, BSA, LBM, ALM, ALM_BMI, bone mineral content, and Smax.

CONCLUSIONS

Individuals with NF1, particularly women, presented with increased REE (adjusted by weight, LBM, or ALM) and lower RQ compared to healthy controls. These findings were associated with lower ALM_BMI and Smax, possibly indicating premature sarcopenia in this population. Further investigation concerning energy metabolism in NF1 and gender differences may be helpful in explaining underlying mechanisms of these changes.

Prevalence and clinicopathological characteristics of lipomatous neurofibromas in neurofibromatosis 1: An investigation of 229 cutaneous neurofibromas and a systematic review of the literature

BACKGROUND

Lipomatous neurofibroma (Lnf) is a histopathological variant with adipocytes noted among cells of cutaneous neurofibromas. We aimed to investigate the prevalence and clinicopathological features of Lnfs of neurofibromatosis 1 (NF1)-associated cutaneous neurofibromas and to review the literature systematically. We also evaluated the expression of leptin (a hormone involved in lipid metabolism) in neurofibromas to better understand the pathogenesis of Lnfs.

METHODS

A prospective histologic study was conducted on 229 cutaneous neurofibromas from 85 NF1 individuals. Leptin expression was immunohistochemically evaluated in 111 cutaneous neurofibromas. To systematically review the literature, two authors independently performed literature searches without year restriction.

RESULTS

Forty (17.5%) neurofibromas were lipomatous. Lnfs were significantly larger lesions and associated with females. Eighteen (7.9%) of all neurofibromas had multinucleated floret-like giant cells, and these were associated with Lnfs. All neurofibromas expressed leptin. We systematically reviewed 13 articles. Three large studies investigated Lnfs mainly in sporadic neurofibromas and suggested that 0.3% to 8.0% of tumors (NF1 and sporadic) are Lnfs.

CONCLUSION

In NF1, Lnfs are common, mainly in larger tumors and women. All cutaneous NF1-neurofibromas express leptin. It is unknown if the expression of leptin accounts for the lipomatous variant, but it may have a role in the pathogenesis of cutaneous neurofibroma.