Comparison of Hormones, Lipoproteins and Substrates in Blood Plasma in a C57bl6 Mouse Strain after Starvation and a High Fat Diet

Metabolic syndrome, the complex of conditions that put humans to risk for coronary heart disease and type-2 diabetes, is increasingly common in Western countries. In North America, it is estimated that over 50 million American people or 20% of the US population are affected.

In addition, the numbers of cases are also increasing in Europe.Obesity is a strong factor involved in metabolic syndrome, and some researchers claim metabolic syndrome is in itself closely linked to the metabolic derangement called insulin resistance in humans.

Early signals of emerging obesity might be found in the blood, which functions as the body’s transport medium by carrying nutrients, lipids and waste products between cells.

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Paracrine Insulin-like Growth Factor Binding Protein-3 Acts as Pro-apoptotic Factor for Leydig cells in the Rat Testis

Insulin-like growth factors (IGFs) are involved in cell metabolism, growth, differentiation, and survival in most organs, including those of the reproductive axis. The activities of these factors are regulated by a family of six high affinity-binding proteins (IGFBP-1–6), which determine IGF bioavailability in circulating fluids and the cellular environment.

IGFBP-3 is the most abundant circulating IGF-binding protein and mediates IGF independent actions on cell survival and apoptosis. In the testis, IGFs and IGFBPs are localized in the same cells that express LH and FSH receptors. IGFBP-2 and -3 are the most abundant IGFBPs in this organ and large amounts of IGFBP-3 are produced by Sertoli and Leydig cells. Both FSH and (Bu)2cAMP markedly lower IGFBP-3 levels in Sertoli cells and this binding protein can either inhibit or enhance the effects on Leydig cells steroidogenesis depending on the surrounding conditions.

The involvement of IGFBP-3 in steroidogenesis, development, and tumor growth in the testis is poorly understood. Previous investigations have revealed that IGFBP-3, -4, and -2 are predominantly expressed by Leydig cells. It has been proposed that IGFBP-3 also potentiates the inhibitory effects of cytokines on steroidogenesis. Both IGFBP-3 and -4 have been reported to be down-regulated in testicular seminomas, allowing more rapid tumor growth.

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