Soybean diet alters the insulin-signaling pathway in the liver of rats recovering from early-life malnutrition

Abstract

Adult rats maintained with a soybean diet exhibited insulin resistance due, at least in part, to alterations in the early steps of the insulin signal transduction pathway.

Nutritional Recovery with a Soybean Diet after Weaning Reduces Lipogenesis but Induces Inflammation in the Liver in Adult Rats Exposed to Protein Restriction during Intrauterine Life and Lactation

“…In this study, rats recovered with the soybean diet showed low body weight and normalization of serum triacylglycerol concentrations, corroborating the well-known favorable effect of soy protein containing various levels of isoflavones on somatic parameters [ 39 , 40 ] and serum triacylglycerol levels [ 41 , 42 ]. However, contrary to the observations that soy protein reduces serum insulin levels [ 42 , 43 ], we verify here, as in previous studies [ 23 , 24 , 26 ], that the consumption of a soybean flour diet increased serum insulin concentrations. This effect may be attributable to genistein, which increases insulin secretion due to its ability to activate the cAMP-PKA pathway [ 26 ].…”

“…Thus, in this and in a previous study [ 37 ], the interplay between liver insulin resistance, which induces SREBP-1c overexpression, and other factors (e.g., genistein and soy protein) that suppress its expression resulted in no change in nSREBP-1c contents or SREBP-1c mRNA expression. An adequate explanation for the paradoxical association of liver insulin resistance with unmodified nSREBP-1c concentrations is the mild hyperinsulinemia and the euglycemia observed in our animals fed with soybean, as noted here and previously [ 24 ]. SREBP-1c expression has been shown to be stimulated by glucose and insulin and repressed by glucagon [ 9 , 10 , 48 ].…”

“…Interestingly, the repression of SREBP-1c expression by soy protein has been attributed to decreased insulin : glucagon ratios [ 21 ]. In our animals, we previously observed reduced insulin : glucagon ratios in LC and LL rats compared with LS rats [ 24 ]. In that prior study [ 24 ], we observed that both the LC and LL groups exhibited lower serum insulin concentrations, lower liver insulin resistance, and basal glucose concentrations that were similar to those of LS rats.…”

“…Interestingly, we observed that serum insulin concentrations were increased in animals reared on a soybean diet, but alterations occurred in the early steps of the hepatic insulin signal transduction pathway, indicating hepatic insulin resistance [ 23 , 24 ]. Moreover, the weight and lipid content of the white adipose tissue as well as the lipolysis rate by isoproterenol in white adipocytes were decreased in rats fed the soybean diet [ 25 ].…”

The Effect of Spirulina platensis versus Soybean on Insulin Resistance in HIV-Infected Patients: A Randomized Pilot Study

“…Most animal studies have shown an improvement in insulin sensitivity and other parameters of glucose homeostasis [22,31,32,33,34]. However, one recently published study showed that in rats recovering from early life malnutrition that were fed on a soybean diet, there was an alteration in the insulin signaling pathway, leading to an increase in insulin resistance [35]. In humans, early studies done in diabetics registered an improvement in glycemic control [36], but recently published studies have not shown any beneficial effects on indices of glucose homeostasis [21,37].…”