In their in vitro study, Hyun et al. examined the effect of fibroin, the basic silk protein, on 3T3-L1 adipocyte cells; Three different forms were used silk protein, hydrolyzate, and fractions. As a result of the study, they observed that it has more than one effect on adipocyte metabolism. To mention one or two of these effects, it has been demonstrated that fibroin increases insulin-sensitive glucose uptake in 3T3-L1 adipocytes versus physiological insulin concentration. In addition, it blocked the development of insulin resistance against chronic insulin exposure. To summarize; Silk protein hydrolyzate has been reported to increase glucose metabolism and insulin sensitivity in adipocytes, prevent beta-cell death caused by glucotoxicity, and increase beta-cell function.
In addition, silk protein hydrolyzate has been shown to increase insulin-stimulated glucose uptake by regulating the glucose transport pathway and reduce fat accumulation through inhibition of the main transcription factors of adipogenesis. It is stated that silk protein hydrolyzate directly affects the regulation of leptin, reduces fat accumulation and is associated with an increase in GLUT4 expression.
Another study showed that sericin extracted from silk cocoon significantly lowered blood glucose levels and protected the nervous system against diabetes mellitus. In this study, type 2 diabetes mellitus was developed in rats by intraperitoneal injection of 25 mg/kg streptozotocin for three consecutive days and rats were treated with sericin for 35 days. After treatment, it was determined that blood glucose levels in diabetic rats decreased significantly, insulin-like growth factor-1 level and growth hormone receptor expression in the hippocampus increased significantly. Experimental findings show that sericin ameliorates growth hormone/insulin-like growth factor 1 axis disorders to alleviate hippocampal damage in diabetic rats.
Silk fibroin hydrolysates exert an anti-diabetic effect by increasing pancreatic β-cell mass in C57BL/KsJ-db/db mice.
ın a study investigating the anti-hyperglycemic and anti-hyperlipidemic effects of silk protein hydrolysates, the antidiabetic effects of silk protein hydrolysates for four weeks were evaluated in vivo in C57BL/KsJ-db/db mice. As a result of the study, it was determined that silk protein hydrolyzate E5K6 increased insulin secretion activity by inducing beta cell activity in pancreatic cells (Park et al.).
Silk protein also has physiological effects such as hypocholesterolomic effect. In a study investigating the effects of silk protein on body weight and lipid metabolism in different fibroin / sericin compositions in high-fat fed mice; animals were fed a high-fat diet with fibroin only and half supplemented with fibroin/sericine for 6 weeks. Compared to the high-fat diet, mice fed silk protein had reduced body weight and improved lipid profile. As the amount of sericin in the diet increased, the HDL-cholesterol level increased, while the amount of body fat, triglyceride and total plasma cholesterol levels, atherogenic index and free fatty acid levels tended to decrease. This hypolipidemic effect was partly due to increased fecal lipid excretion, inhibition of lipogenesis and regulation of adipokine production. These findings suggest that silk protein, especially sericin, may be beneficial in preventing high-fat diet-induced hyperlipidemia and obesity (Lee et al.).
On the other hand, the blood pressure lowering effect of fibroin has been demonstrated in experimental studies (Park et al.). In conclusion, this study was planned and carried out due to the lack of studies showing the active biological effects of silkworm proteins. The hypothesis of the study is to determine whether the consumption of silk protein has an effect on some biochemical parameters, body weight, and feed and water consumption, and if so, with which amount consumption.