No abstract

We have deduced the entire 1,370-amino-acid sequence of the human insulin receptor precursor from a single complementary DNA clone. The precursor starts with a 27-amino-acid signal sequence, followed by the receptor alpha-subunit, a precursor processing enzyme cleavage site, then the beta-subunit containing a single 23-amino-acid transmembrane sequence. There are sequence homologies to human epidermal growth factor receptor and the members of the src family of oncogene products.

The expression of leptin, the ob gene product, is increased in adipose tissue in response to feeding and energy repletion, while leptin expression decreases during fasting. Infusion of leptin decreases food intake. Because adipose tissue gene expression is regulated by cytokines induced during infection and because infection is associated with anorexia, we tested whether induction of leptin might occur during the host response to infection. Administration of endotoxin (LPS), a model for gram negative infections, induces profound anorexia and weight loss in hamsters. In fasted animals, LPS increased the expression of leptin mRNA in adipose tissue to levels similar to fed control animals. There is a strong inverse correlation between mRNA levels of leptin and subsequent food intake. TNF and IL-1, mediators of the host response to LPS, also induced anorexia and increased levels of leptin mRNA in adipose tissue. As assessed by immunoprecipitation and Western blotting, circulating leptin protein is regulated by LPS and cytokines in parallel to regulation of adipose tissue leptin mRNA. Induction of leptin during the host response to infection may contribute to the anorexia of infection. (J. Clin. Invest. 1996. 97:2152-2157.)

Objective Despite widespread highly active antiretroviral therapy use, HIV disease remains associated with increased risk of kidney disease. Whether tenofovir use is associated with higher risk of kidney disease is controversial. Design We evaluated the association of cumulative and ever exposure to tenofovir on kidney outcomes in 10,841 HIV-infected patients from the Veterans Health Administration who initiated antiretroviral therapy from 1997-2007. Methods Cox proportional hazards and marginal structural models evaluated associations between tenofovir and time to first occurrence of 1) proteinuria (two consecutive urine dipstick measurements ≥30mg/dL), 2) rapid decline in kidney function (≥3ml/min/1.73m2 annual decline), and 3) CKD (estimated glomerular filtration rate <60ml/min/1.73m2). Results Median follow-up ranged from 3.9 years (proteinuria) to 5.5 years (CKD), during which 3400 proteinuria, 3078 rapid decline, and 533 CKD events occurred. After multivariable adjustment, each year of exposure to tenofovir was associated with 34% increased risk of proteinuria (95%CI 25-45%, p<0.0001), 11% increased risk of rapid decline (3-18%, p=0.0033), and 33% increased risk of CKD (18-51%; p<0.0001). Pre-existing renal risk factors did not appear to worsen the effects of tenofovir. Other ARVs showed weaker or inconsistent associations with kidney disease events. Among those who discontinued tenofovir use, risk of kidney disease events did not appear to decrease during follow-up. Conclusions Tenofovir exposure was independently associated with increased risk for three types of kidney disease events, and did not appear to be reversible. Because subtle kidney function decline affects long-term morbidity and mortality, the balance between efficacy and probable adverse effects requires further study.

The disruption of the cutaneous permeability barrier results in metabolic events that ultimately restore barrier function. These include increased epidermal sterol, fatty acid, and sphingolipid synthesis, as well as increased epidermal DNA synthesis. Because tumor necrosis factor (TNF) and other cytokines are known products of keratinocytes and have been shown to modulate lipid and DNA synthesis in other systems, their levels were examined in two acute models and one chronic model of barrier perturbation in hairless mice. Acute barrier disruption with acetone results in a 72% increase in epidermal TNF 2.5 h after treatment, as determined by Western blotting. Furthermore, epidermal TNF mRNA was elevated ninefold over controls 2.5 h after acetone treatment. This elevation in TNF mRNA was maximal at 1 h after acetone, and decreased to control levels by 8 h. After tape stripping, a second acute model of barrier disruption that avoids application of potentially toxic chemicals, TNF mRNA was elevated fivefold over controls at 2.5 h. Moreover, the mRNA levels for epidermal IL-1 alpha, IL-1 beta, and granulocyte macrophage-colony-stimulating factor (GM-CSF) also were elevated several-fold over controls, after either acetone treatment or tape stripping, but their kinetics differed. GM-CSF mRNA reached a maximal level at 1 h after acetone, while IL-1 alpha and IL-1 beta were maximal at 4 h after treatment. In contrast, mRNAs encoding IL-6 and IFN gamma were not detected either in control murine epidermis or in samples obtained at various times after tape stripping or acetone treatment. The relationship of the cytokine response to barrier function is further strengthened by results obtained in essential fatty acid deficient mice. In this chronic model of barrier perturbation mRNA levels for epidermal TNF, IL-1 alpha, IL-1 beta, and GM-CSF were each elevated several-fold over controls. These results suggest that epidermal cytokine production is increased after barrier disruption and may play a role in restoring the cutaneous permeability barrier. (J. Clin. Invest. 1992. 90:482-487.) Key words: tumor necrosis factor.interleukin-1 * granulocyte macrophage-colony-stimulating factor * essential fatty acid deficiency Introduction The stratum corneum provides the cutaneous permeability

Steatosis has emerged as a histologic finding of importance to the progression of hepatitis C virus (HCV)-associated liver disease. However, most studies of HCV-associated steatosis have excluded alcohol drinkers and individuals with diabetes and thus have not addressed the relative contribution of known causes of steatosis to liver injury in HCV-associated disease. To address this issue, we studied 297 consecutive patients with HCV who met inclusion criteria. Alcohol consumption, demographics, and serologic tests were correlated with degrees of steatosis and fibrosis on liver biopsy. Liver biopsy specimens were also examined for evidence of significant alcohol or nonalcoholic steatohepatitis (NASH) injury. In univariate analysis, steatosis correlated with type 2 diabetes mellitus (P ‫؍‬ .005) and body mass index (BMI) (P ‫؍‬ .0001) but not with the intensity of alcohol intake (in grams per day). In multivariate analysis, BMI (P ‫؍‬ .0002) and genotype 3a infection (P ‫؍‬ .02) were independent predictors of steatosis. When patients with risk factors for NASH were excluded, genotype 3a infection was the only independent predictor of steatosis. Steatosis (P ‫؍‬ .04) and inflammation (P < .0001) scores on liver biopsy were the only independent predictors of fibrosis. Significant alcohol or NASH injury was found in only 6% of biopsy specimens. In conclusion, steatosis in HCV infection is associated with risk factors for NASH, particularly obesity, rather than alcohol consumption. (HEPATOLOGY 2002;36:729-736.)

Leptin is a 16 kDa protein mainly produced by adipose tissue in proportion to adipose tissue mass. Originally thought to be a satiety factor, leptin is a pleiotropic molecule. In addition to playing a role in energy regulation, leptin also regulates endocrine and immune functions. Both the structure of leptin and that of its receptor suggest that leptin might be classified as a cytokine. The secondary structure of leptin has similarities to the long-chain helical cytokines family, which includes interleukin 6 (IL-6), IL-11, CNTF, and LIF, and the leptin receptor is homologous to the gp-130 signal-transducing subunit of the IL-6-type cytokine receptors. Leptin plays a role in innate and acquired immunity. Leptin levels increase acutely during infection and inflammation, and may represent a protective component of the host response to inflammation. More important, leptin deficiency increases susceptibility to infectious and inflammatory stimuli and is associated with dysregulation of cytokine production. Leptin deficiency also causes a defect in hematopoiesis. Leptin regulates T cells responses, polarizing Th cells toward a Th1 phenotype. Low leptin levels occurring during starvation mediate the neuroendocrine and immune dysfunction of starvation.

Infection causes disturbances in lipid metabolism that may be mediated by cytokines. Therefore we studied plasma lipids, lipoproteins, triglyceride (TG) metabolism, and serum cytokines in three groups: patients with the acquired immunodeficiency syndrome (AIDS) without active secondary infection, patients with evidence of human immunodeficiency virus infection but without clinical AIDS (HIV+), and controls. Plasma TGs and FFA were increased in AIDS, while plasma cholesterol, high density lipoprotein (HDL) cholesterol, apolipoprotein-A-1 (Apo-A-1), low density lipoprotein (LDL) cholesterol, and Apo-B-100 levels were decreased. Increased TG levels in AIDS were primarily due to increases in very low density lipoprotein of normal composition; in addition, LDL and HDL were TG enriched. In HIV+, TGs and FFA were not increased, but total cholesterol, HDL cholesterol, Apo-A-1, and Apo-B-100 were significantly decreased. Interferon-alpha (IFN alpha) and C-reactive protein levels were increased in AIDS, but tumor necrosis factor and haptoglobin levels were not. There was a significant correlation between plasma TGs and IFN alpha levels (r = 0.477; P less than 0.01), but not between TGs and tumor necrosis factor, C-reactive protein, haptoglobin, or P-24 antigen. In addition, there was no relationship between circulating IFN alpha levels and plasma cholesterol, HDL cholesterol, Apo-A-1, LDL cholesterol, Apo-B-100, or FFA. TG clearance time and postheparin lipase were significantly decreased in AIDS and HIV+. There was a strong correlation between serum IFN alpha levels and TG clearance time in AIDS and HIV+ (r = 0.783; P less than 0.001). In summary, decreases in cholesterol and cholesterol containing lipoproteins (including HDL) in both AIDS and HIV+ precede the appearance of hypertriglyceridemia and are not related to IFN alpha or TG levels. Our data raise the possibility that with development of AIDS, subsequent increases in IFN alpha may contribute to increases in plasma TG levels in part by decreasing the clearance of TG.