OBJECTIVETo assess the efficacy of curcumin in delaying development of type 2 diabetes mellitus (T2DM) in the prediabetic population.RESEARCH DESIGN AND METHODSThis randomized, double-blinded, placebo- controlled trial included subjects (n = 240) with criteria of prediabetes. All subjects were randomly assigned to receive either curcumin or placebo capsules for 9 months. To assess the T2DM progression after curcumin treatments and to determine the number of subjects progressing to T2DM, changes in β-cell functions (homeostasis model assessment [HOMA]-β, C-peptide, and proinsulin/insulin), insulin resistance (HOMA-IR), anti-inflammatory cytokine (adiponectin), and other parameters were monitored at the baseline and at 3-, 6-, and 9-month visits during the course of intervention.RESULTSAfter 9 months of treatment, 16.4% of subjects in the placebo group were diagnosed with T2DM, whereas none were diagnosed with T2DM in the curcumin-treated group. In addition, the curcumin-treated group showed a better overall function of β-cells, with higher HOMA-β (61.58 vs. 48.72; P < 0.01) and lower C-peptide (1.7 vs. 2.17; P < 0.05). The curcumin-treated group showed a lower level of HOMA-IR (3.22 vs. 4.04; P < 0.001) and higher adiponectin (22.46 vs. 18.45; P < 0.05) when compared with the placebo group.CONCLUSIONSA 9-month curcumin intervention in a prediabetic population significantly lowered the number of prediabetic individuals who eventually developed T2DM. In addition, the curcumin treatment appeared to improve overall function of β-cells, with very minor adverse effects. Therefore, this study demonstrated that the curcumin intervention in a prediabetic population may be beneficial.

Cyclin D1 is a component of the core cell cycle machinery1. Abnormally high levels of cyclin D1 are detected in many human cancer types2. To elucidate the molecular functions of cyclin D1 in human cancers, here we performed a proteomic screen for cyclin D1 protein partners in several types of human tumors. Analyses of cyclin D1-interactors revealed a network of DNA repair proteins, including RAD51, a recombinase that drives the homologous recombination process3. We found that cyclin D1 directly binds RAD51, and that cyclin D1-RAD51 interaction is induced by radiation. Like RAD51, cyclin D1 is recruited to DNA damage sites in a BRCA2-dependent fashion. Reduction of cyclin D1 levels in human cancer cells impaired recruitment of RAD51 to damaged DNA, impeded the homologous recombination-mediated DNA repair, and increased sensitivity of cells to radiation in vitro and in vivo. This effect was seen in cancer cells lacking the retinoblastoma protein, which do not require D-cyclins for proliferation4, 5. These findings reveal an unexpected function of a core cell cycle protein in DNA repair and suggest that targeting cyclin D1 may be beneficial also in retinoblastoma-negative cancers which are currently thought to be oblivious to cyclin D1 inhibition.

Cyclin D1 belongs to the core cell cycle machinery, and it is frequently overexpressed in human cancers 1,2 . The full repertoire of cyclin D1 functions in normal development and in oncogenesis is currently unclear. Here we developed FLAG-and HA-tagged cyclin D1 knock-in mouse strains that allowed high-throughput mass spectrometry approach to search for cyclin D1-binding proteins in different mouse organs. In addition to cell cycle partners, we observed several proteins involved in transcription. Genome-wide location (ChIP-chip) analyses revealed that during mouse development cyclin D1 occupies promoters of abundantly expressed genes. In particular, we found that in developing mouse retinas -an organ that critically requires cyclin D1 function 3,4 -cyclin D1 binds the upstream regulatory region of the Notch1 gene where it serves to recruit CBP histone acetyltransferase. Genetic ablation of cyclin D1 resulted in decreased CBP recruitment, decreased histone acetylation of the Notch1 promoter region, and led to decreased levels of the Notch transcript and protein in cyclin D1-null retinas. Transduction of an activated allele of Notch1 into cyclin D1 −/− retinas increased proliferation of retinal progenitor cells, indicating that upregulating Notch1 signaling alleviates the phenotype of cyclin D1-deficiency. These studies reveal that in addition to its well-established cell cycle roles, cyclin D1 plays an in vivo transcriptional function in mouseCorrespondence and request for materials should be addressed to P.S. (Peter_Sicinski@dfci.harvard.edu). * These authors contributed equally to this work. 8 Current address: Stanford University School of Medicine, Stanford, CA 94305, USA.Supplementary Information is linked to the online version of the paper at www.nature.com/nature Author Contributions F.B. and PS designed the study, analyzed the data and wrote the manuscript. F.B. performed the experiments with the help of co-authors as detailed below. S.J. performed protein purifications. J.E.E. performed and together with S.P.G. Author InformationThe complete ChIP-chip and expression datasets have been submitted to the online data repository GEO, record GSE13636 (http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?token=zvuhbiaakuwumxa&acc=GSE13636). Reprints and permissions information is available at www.nature.com/reprints. NIH Public Access Author ManuscriptNature. Author manuscript; available in PMC 2010 September 22. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript development. Our approach, which we term "genetic-proteomic" can be used to study the in vivo function of essentially any protein.To study the molecular functions of cyclin D1 during development and in cancer formation, we generated knock-in mouse strains in which tandem (FLAG-and HA-) tags were inserted into the endogenous cyclin D1 locus through homologous recombination in embryonal stem cells. Tags were introduced into N-terminus of cyclin D1 (D1 Ntag allele) or into C-terminus (D1 Ctag ) and homozygous D1 Ntag/Ntag and D1 C...

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Skin is the largest human organ. Skin continually reconstructs itself to ensure its viability, integrity, and ability to provide protection for the body. Some areas of skin are continuously exposed to a variety of environmental stressors that can inflict direct and indirect damage to skin cell DNA. Skin homeostasis is maintained by mesenchymal stem cells in inner layer dermis and epidermal stem cells (ESCs) in the outer layer epidermis. Reduction of skin stem cell number and function has been linked to impaired skin homeostasis (e.g., skin premature aging and skin cancers). Skin stem cells, with self-renewal capability and multipotency, are frequently affected by environment. Ultraviolet radiation (UVR), a major cause of stem cell DNA damage, can contribute to depletion of stem cells (ESCs and mesenchymal stem cells) and damage of stem cell niche, eventually leading to photoinduced skin aging. In this review, we discuss the role of UV-induced DNA damage and oxidative stress in the skin stem cell aging in order to gain insights into the pathogenesis and develop a way to reduce photoaging of skin cells.

The human CCND1 gene, encoding a cell cycle protein cyclin D1, is one of the most frequently amplified genes in human cancers. Cyclin D1 activates cyclin dependent kinases CDK4 and CDK6 and drives cell proliferation. Beyond the cell cycle role, the full repertoire of cyclin D1 functions in cancer cells is still unclear. Emerging evidence indicates that cyclin D1 may play a role in DNA damage response. In this review we discuss observations linking cyclin D1 to DNA damage repair, and we summarize our recent findings, which demonstrate cyclin D1 function in homologous recombination-mediated DNA repair.

Responses of melanocytes (MC) to ultraviolet (UV) irradiation can be influenced by their neighbouring keratinocytes (KC). We investigated the role of Nrf2 in regulating paracrine effects of KC on UVB-induced MC responses through phosphorylation of MAPKs in association with oxidative stress in primary human MC cocultured with primary human KC using a transwell co-culture system and small-interfering RNA-mediated silencing of Nrf2 (siNrf2). The mechanisms by which Nrf2 modulated paracrine factors including α-melanocyte-stimulating hormone (α-MSH) and paracrine effects of KC on UVB-mediated apoptosis were also assessed. Our findings showed that co-culture of MC with siNrf2-transfected KC enhanced UVB-mediated cyclobutane pyrimidine dimer (CPD) formation, apoptosis and oxidant formation, together with phosphorylation of ERK, JNK and p38 in MC. Treatment of MC with conditioned medium (CM) from Nrf2-depleted KC also increased UVB-mediated MC damage, suggesting that KC modulated UVB-mediated MC responses via paracrine effects. Additionally, depletion of Nrf2 in KC suppressed UVB-induced α-MSH levels as early as 30 min post-irradiation, although pretreatment with N-acetylcysteine (NAC) elevated its levels in CM from siNrf2-transfected KC. Furthermore, NAC reversed the effect of CM from Nrf2-depleted KC on UVB-induced apoptosis and inflammatory response in MC. Our study demonstrates for the first time that KC provided a rescue effect on UVB-mediated MC damage, although depletion of Nrf2 in KC reversed its protective effects on MC in a paracrine fashion in association with elevation of ROS levels and activation of MAPK pathways in MC. Nrf2 may indirectly regulate the paracrine effects of KC probably by affecting levels of the paracrine factor α-MSH via a ROS-dependent mechanism.

Without exposure to any DNA-damaging agents, non-dividing eukaryotic cells carry endogenous DNA double-strand breaks (EDSBs), or Replication-Independent (RIND)-EDSBs. In human cells, RIND-EDSBs are enriched in the methylated heterochromatic areas of the genome and are repaired by an ATM-dependent non-homologous end-joining pathway (NHEJ). Here, we showed that Saccharomyces cerevisiae similarly possess RIND-EDSBs. Various levels of EDSBs were detected during different phases of the cell cycle, including G0. Using a collection of mutant yeast strains, we investigated various DNA metabolic and DNA repair pathways that might be involved in the maintenance of RIND-EDSB levels. We found that the RIND-EDSB levels increased significantly in yeast strains lacking proteins involved in NHEJ DNA repair and in suppression of heterochromatin formation. RIND-EDSB levels were also upregulated when genes encoding histone deacetylase, endonucleases, topoisomerase, and DNA repair regulators were deleted. In contrast, RIND-EDSB levels were downregulated in the mutants that lack chromatin-condensing proteins, such as the high-mobility group box proteins, and Sir2. Likewise, RIND-EDSB levels were also decreased in human cells lacking HMGB1. Therefore, we conclude that the genomic levels of RIND-EDSBs are evolutionally conserved, dynamically regulated, and may be influenced by genome topology, chromatin structure, and the efficiency of DNA repair systems.