This article is available online at http://www.jlr.org However, data from studies conducted in rodents have shown that infusing palmitoleic acid (16:1n-7), which is normally produced in adipose tissue and the liver through lipogenesis, followed by desaturation of palmitic acid (16:0) by the stearoyl-CoA desaturase (SCD1) gene, augments skeletal muscle insulin signaling and increases insulin-mediated muscle glucose uptake ( 2 ). The importance of circulating palmitoleic acid in regulating insulin sensitivity in humans is unclear because of confl icting data from different studies, which have found that the percentage of palmitoleate in plasma FFA or lipids correlated directly with insulin sensitivity ( 3 ) or was greater in insulinresistant (IR) than insulin-sensitive (IS) subjects ( 4-8 ). Moreover, these studies did not measure absolute palmitoleate concentration, which provides a better assessment of palmitoleate availability to peripheral tissues, or palmitoleate within very low-density lipoprotein (VLDL), which may be an important contributor to tissue fatty acid delivery.The purpose of the present study was to determine whether impaired insulin-mediated skeletal muscle glucose uptake was associated with a decrease in plasma palmitoleic acid availability in obese people. Accordingly, we determined plasma free palmitoleic acid concentration, which is derived primarily from palmitoleate synthesized in adipose tissue, and palmitoleic acid content in VLDL, which is derived primarily from palmitoleate synthesized in the liver. Study subjects were specifi cally selected to be either IS or IR based on the increase in glucose uptake during a hyperinsulinemic-euglycemic clamp procedure. An increase in circulating free fatty acids (FFA) impairs insulin action in skeletal muscle and liver and likely contributes to the insulin resistance associated with obesity ( 1 ). DK-37948, UL1 RR-024992 (Clinical and Translational Science Award), DK 56341 (Nutrition and Obesity Research Center), and RR-00954 (Biomedical Mass Spectrometry Resource) Abbreviations: BMI, body mass index; BSA, body surface area; C t , threshold crossing; HISI, hepatic insulin sensitivity index; IR, insulin resistant; IS, insulin sensitive; Ra, rate of appearance; Rd, rate of disappearance; TG, triglyceride. This study was supported by National Institutes of Health Grants

Previous studies have suggested that children with neurofibromatosis type 1 (NF1) are shorter than their unaffected counterparts. Unfortunately, these reports did not consider other contributing factors that might also influence short stature. The purpose of the current study was to characterize the genetic influence of NF1 on the growth of children. Height data was measured and recorded for 170 patients, while parental measurements were obtained for 61 patients to calculate sex-corrected mid-parental target heights. Children with NF1 had population mean height and mid-parental height z-scores statistically different from the general population. Importantly, these differences were pronounced when neither parent had NF1, but were not significant when one of the parents had NF1. Moreover, height z-scores for children with NF1 were also statistically different than their unaffected siblings. Collectively, these data establish a clear effect of a germline NF1 gene mutation on stature in children with NF1.

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