Male FATZO mice spontaneously develop significant metabolic disease when compared to normal controls while maintaining hyperglycemia in the presence of high leptin levels and hyperinsulinemia.
Subsequently, in vitro studies in 3T3-L1 (white) and T37i (brown) adipocytes suggest that the increased leptin and adiponectin levels were mainly driven by the elevated insulin levels.
This led to metabolic consequences, with significant higher leptin levels and a trend towards hyperinsulinemia, indicating a phenotype resembling the metabolic syndrome.
In first-degree relatives normal glucose tolerant women, fasting hyperinsulinemia, independently of the presence of metabolic syndrome, is associated with elevated IL-6 and leptin levels, suggesting an increased cardiovascular risk.
Further, similar hypothalamic leptin transgene expression abrogated chronic hyperglycemia and hyperinsulinemia, the predisposing risk factors of the age and environmentally acquired diabetes type 2, and instituted euglycemia by independently activating relays that stimulate glucose metabolism and repress hyperinsulinemia and improve insulin sensitivity in the periphery.
Recently, we found that old male BN rats treated chronically with troglitazone, an insulin sensitizer, lowered high insulin and leptin levels, decreased body fat, and corrected the blunted food intake and body weight gain response to fasting without affecting basal ARC NPY gene expression.
This finding together with the positive association of chemerin and leptin with markers of insulin resistance, suggests that these adipokines and more especially chemerin and leptin accompanied by their adipose tissue expression could contribute to the increased insulin resistance and low grade inflammation that characterizes GDM-obese women.
Impaired appetite regulation, in terms of elevated insulin levels and decreased leptin levels, occurs in early psychosis, before antipsychotic treatment.
Liver-specific AlbCre+Cc1<sup>fl/fl</sup> mutants exhibited impaired insulin clearance and hyperinsulinemia at 2 months, followed by hepatic insulin resistance (assessed by hyperinsulinemic-euglycemic clamp analysis) and steatohepatitis at ~ 7 months of age, at which point visceral obesity and hyperphagia developed, in parallel to hyperleptinemia and blunted hypothalamic STAT3 phosphorylation in response to an intraperitoneal injection of leptin.
These results identify a novel molecular pathway by which leptin confers inhibitory action on insulin secretion, and impaired PP-1 inhibition by leptin may be involved in dysfunction of the adipoinsular axis during the development of hyperinsulinemia and type 2 diabetes mellitus.
To investigate the role of chronic hyperinsulinemia in the regulation of plasma leptin concentrations, we studied 13 patients with surgically confirmed insulinoma before and after tumor removal, along with 15 healthy control subjects matched for sex, age, and BMI.
This study demonstrates that targeted POMC gene delivery in the hypothalamus suppresses food intake and weight gain and reduces visceral adiposity and hyperinsulinemia in leptin-resistant obese Zucker rats.
Women with polycystic ovaries on ultrasound have increased insulin sensitivity and possible leptin resistance, which could predispose to future weight gain.