Adipose tissue transplantation improves metabolic, behavioural and histological parameters in leptin-deficient mice

Leptin is an important adipokine involved in the regulation of food intake and energy homeostasis. In the absence of leptin or its functional receptors, rodents and humans develop a variety of metabolic dysfunctions, including decreased energy expenditure, severe insulin resistance, diabetes, dyslipidaemia and increased body weight. Leptin also has several extra-hypothalamic effects, and its neurogenic actions regulate anxiety and depression-like behaviours. Moreover, leptin deficiency leads to the development of steatohepatitis, lung fibrosis and can impair iron metabolism. Daily exogenous subcutaneous leptin injections improve insulin sensitivity and several metabolic abnormalities associated with leptin deficiency in animals and humans, but novel curative and permanent therapies must be developed. In this study, a novel technique to normalise the phenotype of leptin-deficient ob/ob mice through white adipose tissue (WAT) transplantation has been applied. Perigonadal WAT was harvested from congenic NZegTg+/ Lep+/+ mice, which express nuclear enhanced green fluorescent protein (EGFP) at very high levels in all cells. Approximately 2 g of WAT were subcutaneously transplanted into the dorsal area of 7- to 12-week-old leptin-deficient mice (ob/ob -/-). A 22-week post-surgical follow-up study was conducted on transplanted and sham-operated mice. The follow-up study included weight monitoring, intraperitoneal glucose tolerance tests (IPGTTs), and behavioural assessments through open-field tests. At the completion of the observational study, mice were sacrificed and blood was collected for measurements of plasma leptin and insulin levels, by enzyme-linked immunosorbent assay (ELISA). Tissues including liver, lung and spleen were collected for histological analyses. For the detection of EGFP-expressing cells originated from the transplanted WAT, acetone fixed cryosections was used for fluorescent microscopy. The presence of those cells was confirmed by real-time PCR. We observed that the transplantation of perigonadal adipose tissue from leptin-sufficient, EGFP-expressing mice was able to determine significant weight loss, which was correlated with leptin levels. Moreover, significant decreases of mean glucose levels and insulin resistance were obtained. The WAT transplantation determined a decrease in anxiety-like behaviour according to the results obtained from the open-field tests. In addition, the procedure prevented histological changes associated with leptin deficiency and severe obesity in liver, lung, and spleen. EGFP-expressing cells were observed in those tissues by fluorescent microscopy and confirmed by real-time PCR. The series of experiments confirmed that transplantation of perigonadal adipose tissue from leptin-sufficient mice into the dorsal area of leptin-deficient mice leads to significant improvements in metabolic, behavioural and histological parameters. The techniques employed in this study, as well as the results obtained from it, will be useful for the development of larger animal studies, with a longer follow-up period, and with the use of other cells or tissues, such as mesenchymal or induced pluripotent stem cells. -- provided by Candidate