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1.  Deficiency of Insulin-Like Growth Factor-1 Receptor Confers Resistance to Oxidative Stress in C2C12 Myoblasts 
PLoS ONE  2013;8(5):e63838.
IGF-1 receptor (IGF-1R) signaling regulates cell growth, transformation and survival. Haploinsufficiency of the IGF-1R is reported to paradoxically confer resistance to oxidative stress in vivo and in cells cultured from Igf1r+/− mice. In order to determine whether IGF-1R deficiency directly confers resistance to oxidative stress in specific cell types, an siRNA-mediated approach was applied to reduce IGF-1R in C2C12 myoblasts, NIH3T3 fibroblasts and MC3T3-E1 osteoblasts. Treating the IGF-1R deficient myoblasts with H2O2 resulted in significantly higher phosphorylation of Akt as compared to cells having normal expression of IGF-1R. Similar results were obtained with UV treatment, another inducer of oxidative stress. This enhanced activation of Akt was associated with reduced level of cleaved caspase-3 and PARP. Moreover, in the IGF-1R knockdown myoblasts, phosphorylation of the Akt substrate Bad was enhanced after peroxide treatment. However, in NIH-3T3 fibroblasts and MC3T3-E1 osteoblasts, the loss of IGF-1R by siRNA directed knockdown was associated with reduced levels of phosphorylated Akt on treatment with H2O2 or UV as compared to control cells and these cells showed more apoptosis. These results suggest a novel mechanism of cell type specific differential regulation of resistance to oxidative stress induced apoptosis by reduced levels of IGF-1R.
PMCID: PMC3651254  PMID: 23675509
2.  High Fat Diet Induced Insulin Resistance and Glucose Intolerance is Gender-Specific in IGF-1R Heterozygous Mice 
Interactions between genes and environment play a critical role in the pathogenesis of Type 2 diabetes. Low birth weight, due to genetic and environmental variables affecting fetal growth, is associated with increased susceptibility to the development of type 2 diabetes and metabolic disorders in adulthood. Clinical studies have shown that polymorphisms in the Insulin-like growth factor 1 (IGF-1) gene or heterozygous mutations in IGF-1 and IGF-1 receptor (IGF-1R) genes, resulting in reduced IGF-1 action, are associated with low birth weight and post-natal growth. Mice lacking one of the IGF-1R alleles (Igf1r+/−) exhibit a 10% reduction in post-natal growth, and develop glucose intolerance and insulin resistance as they age. To investigate whether adverse environmental factors could accelerate the onset of the metabolic syndrome, we conducted a short duration intervention of high fat diet (HFD) feeding in male and female Igf1r+/− and wild-type (WT) control mice. The HFD resulted in insulin resistance, hyperglycemia, and impaired glucose tolerance in males of both genotypes whereas in females exacerbated diabetes was observed only in the Igf1r+/− genotype, thus suggesting a sexual dimorphism in the influence of obesity on the genetic predisposition to diabetes caused by reduced IGF-1 action.
PMCID: PMC3185216  PMID: 21910970
IGF-1; IGF-1R; Igf1r+/−; SGA; HFD; Type 2 diabetes
3.  Does Reduced IGF-1R Signaling in Igf1r+/− Mice Alter Aging? 
PLoS ONE  2011;6(11):e26891.
Mutations in insulin/IGF-1 signaling pathway have been shown to lead to increased longevity in various invertebrate models. Therefore, the effect of the haplo- insufficiency of the IGF-1 receptor (Igf1r+/−) on longevity/aging was evaluated in C57Bl/6 mice using rigorous criteria where lifespan and end-of-life pathology were measured under optimal husbandry conditions using large sample sizes. Igf1r+/− mice exhibited reductions in IGF-1 receptor levels and the activation of Akt by IGF-1, with no compensatory increases in serum IGF-1 or tissue IGF-1 mRNA levels, indicating that the Igf1r+/− mice show reduced IGF-1 signaling. Aged male, but not female Igf1r+/− mice were glucose intolerant, and both genders developed insulin resistance as they aged. Female, but not male Igf1r+/− mice survived longer than wild type mice after lethal paraquat and diquat exposure, and female Igf1r+/− mice also exhibited less diquat-induced liver damage. However, no significant difference between the lifespans of the male Igf1r+/− and wild type mice was observed; and the mean lifespan of the Igf1r+/− females was increased only slightly (less than 5%) compared to wild type mice. A comprehensive pathological analysis showed no significant difference in end-of-life pathological lesions between the Igf1r+/− and wild type mice. These data show that the Igf1r+/− mouse is not a model of increased longevity and delayed aging as predicted by invertebrate models with mutations in the insulin/IGF-1 signaling pathway.
PMCID: PMC3223158  PMID: 22132081
Indian Journal of Dermatology  2011;56(4):375-379.
Neurocutaneous syndromes (NCS) are a group of genetic disorders that produce a variety of developmental abnormalities of the skin along with an increased risk of neurological complications. Cutaneous manifestations usually appear early in life and progress with time, but neurological features generally present at a later age. There is a paucity of data regarding the evolution of skin lesions and their correlation with the central nervous system involvement in children.
The primary objective was to track the course of skin lesions in various forms of NCS in the pediatric age group. Our secondary aim was to assess whether there was any predictive value of the lesions in relation to the neurological manifestations.
Materials and Methods:
This prospective longitudinal study was conducted at a tertiary care pediatric dermatology referral clinic of the Institute of Child Health, Kolkata, West Bengal. Children between the age group 0 and 12 years were included in the study on the basis of standard diagnostic criteria for different NCS, during the period from March, 2000 to February, 2004, and each of the enrolled cases were followed up for a duration of six years.
The study population comprised of 67 children (35 boys, 32 girls).The mean age of presentation was 33.8±27.8 months (range 10 days to 111 months). The various forms of NCS observed was neurofibromatosis 1(NF1) (n=33), tuberous sclerosis complex (TSC) (n=23), Sturge Weber syndrome (n=6), ataxia telangiectasia (n=2), PHACE syndrome (n=1), incontinentia pigmenti (n=1), and hypomelanosis of Ito (n=1). The presentations were varied, ranging from predominantly cutaneous to primarily neurological, depending on the disease entity and age group concerned. There was a significant increase in the number of café au lait macules (CALMs) with time (P=0.0002) in NF1, unlike that of hypopigmented macules of TSC (P=0.15). Statistically, no relation was documented between the evolution of skin lesions and neurological manifestations in the major groups.
As NCS is not an uncommon disease in children, it is always necessary to find out the subtle neurological signs, whenever we observe any case with cutaneous markers suggestive of NCS. In addition, it is a must to do a detailed dermatological examination in a child with central nervous system involvement, in the pediatric population. However, the neurological course cannot be predicted from skin lesions.
PMCID: PMC3178997  PMID: 21965842
Neurocutaneous; neurofibromatosis; tuberous sclerosis

Results 1-4 (4)