Anabolism, effect of insulin

The anabolic effects of somatropin are mediated by somatomedins or insulin-like growth factors. Somatropin is a synthetic polypeptide identical to the natural occurring growth hormone which stimulates longitudinal growth. Only preparations made with recombinant DNA technology are used nowadays. They can consist of 191 amino acids as growth hormone itself or 192 amino acids with one extra methionine. Somatropin is employed in the treatment... 

In addition, there are numerous effects of insulin, generally anabolic, not mediated through its well-known effects on glucose transport. For example, in muscle, insulin decreases glycogenolysis and proteolysis. Lipolysis is inhibited by insulin in adipocytes. The effect of insulin on hepatic tissue is to promote increased glycogen production and protein synthesis and to inhibit glycogenolysis, proteolysis, lipolysis, and gluconeogenesis (Fig. 10-1). 

The protein-anabolic and protein-sparing actions of GH require the metabolic effects of insulin, glucagon, cortisol, and thyroid hormone in the unstressed individual. These actions depend on fine-tuned control of GH release, which is achieved mainly by substrate feedback to the hypothalamus (Figure 31-5). 

Table 11.2 Selected genes whose rate of transcription is altered by binding of insulin to its receptor. In virtually all instances, the ultimate effect is to promote anabolic events characteristic of insulin action. Two-dimensional gel electrophoresis has also pinpointed dozens of proteins of unknown function whose cellular level is altered by insulin...

Figure 12.17 Sites at which insulin stimulates protein synthesis in a muscle. The sites are indicated by 0. Insulin has its anabolic effect on protein synthesis in muscle by affecb ng six processes or reactions (i) it inhibits protein degradab on in the muscle (ii) it sb mulates amino acid transport from the blood into the muscle (iii) it stimulates the inib ab on-reacb on of the pathway for protein synthesis, i.e. formab on of the complex (tRNA-amino acid-mRNA-ribosomal RNA) (iv) it increases the rate of mRNA synthesis, and therefore the number of mRNA molecules (v) it stimulates ribosomal RNA synthesis (vi) it sb mulates elongabon of the pepbde (see Chapter 20).

Il.f.l.1. Insulins. Insulin is the most effective of diabetes medications. Insulin has profound effects on carbohydrate, protein, fat metabolism and electrolytes. It has anabolic and anticatabolic actions. In a state of insulin deficiency, glycogenesis, glucose transport, protein synthesis, triglyceride synthesis, LPL activity in adipose tissue, cellular potassium uptake all decrease on the other hand, gluconeogene-sis, glycogenolysis, protein degradation, ketogene-sis, lipolysis increase. 

Mechanism of Action. Few data are available that describe the effects of anabolic steroids on protein metabolism even fewer data exist for assessment of direct effects of anabolic steroids on lipid metabolism in growing ruminants. The lack of any consistent change in somatotropin, prolactin, insulin, or other metabolic hormones (qv) in a total of 15 studies has been noted (1,38). 

Most athletes have heard of IGF-1 (Insulin like growth factor-1) and the amazing anabolic effects it has been reported to have upon protein based tissue such as muscle. Des (1-3) IGF-1 is over 10 times (1000%) more anabolic than IGF-1. Now that is amazing ... 

Urea, the end product of nitrogen metabolism, accumulates rapidly in ARF. Most patients with ARF have a primary stressful illness that results in ureagenesis, and thus protein breakdown is markedly accelerated. Protein catabolism in ARF may be stimulated as the result of insulin resistance, metabolic acidosis, circulating proteases and inflammatory mediators, and the effects of uremic toxins. The mechanism may be direct, via modulation of protein synthesis, or indirect, by inhibiting the action of anabolic hormones. ... 

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