RARgamma and TRbeta expressions are decreased in PBMC and SWAT of obese subjects in weight gain

PPAR-γ Gene Expression in Human Adipose Tissue Is Associated with Weight Loss After Sleeve Gastrectomy

BACKGROUND

The peroxisome proliferator-activated receptor (PPAR)-γ plays a key role in adipose tissue differentiation and fat metabolism. However, it is unclear which factors may regulate its expression and whether obese patients have changes in adipose tissue expression of PPAR-γor potential regulators such as miR-27. Thus, our aims were to analyze PPAR-γ and miR-27 expression in adipose tissue of obese patients, and to correlate their levels with clinical variables.

SUBJECTS AND METHODS

We included 43 morbidly obese subjects who underwent sleeve gastrectomy (31 of them completed 1-year follow-up) and 19 non-obese subjects. mRNA expression of PPAR-γ1 and PPAR-γ2, miR-27a, and miR-27b was measured by qPCR in visceral and subcutaneous adipose tissue. Clinical variables and serum adipokine and hormone levels were correlated with PPAR-γ and miR-27 expression. In addition, a systematic review of the literature regarding PPAR-γ expression in adipose tissue of obese patients was performed.

RESULTS

We found no differences in the expression of PPAR-γ and miR-27 in adipose tissue of obese patients vs. controls. The literature review revealed discrepant results regarding PPAR-γ expression in adipose tissue of obese patients. Of note, we described a significant negative correlation between pre-operative PPAR-γ1 expression in adipose tissue of obese patients and post-operative weight loss, potentially linked with insulin resistance markers.

CONCLUSION

PPAR-γ1 expression in adipose tissue is associated with weight loss after sleeve gastrectomy and may be used as a biomarker for response to surgery.

Loss of μ-crystallin causes PPARγ activation and obesity in high-fat diet-fed mice

The thyroid hormone-binding protein μ-crystallin (CRYM) mediates thyroid hormone action by sequestering triiodothyronine in the cytoplasm and regulating the intracellular concentration of thyroid hormone. As thyroid hormone action is closely associated with glycolipid metabolism, it has been proposed that CRYM may contribute to this process by reserving or releasing triiodothyronine in the cytoplasm. We aimed to clarify the relationship between CRYM and glycolipid metabolism by comparing wild-type and CRYM knockout mice fed a high-fat diet. Each group was provided a high-fat diet for 10 weeks, and then their body weight and fasting blood glucose levels were measured. Although no difference in body weight was observed between the two groups with normal diet, the treatment with a high-fat diet was found to induce obesity in the knockout mice. The knockout group displayed increased dietary intake, white adipose tissue, fat cell hypertrophy, and hyperglycemia in the intraperitoneal glucose tolerance test. In CRYM knockout mice, liver fat deposits were more pronounced than in the control group. Enhanced levels of PPARγ, which is known to cause fatty liver, and ACC1, which is a target gene for thyroid hormone and is involved in the fat synthesis, were also detected in the livers of CRYM knockout mice. These observations suggest that CRYM deficiency leads to obesity and lipogenesis, possibly in part through increasing the food intake of mice fed a high-fat diet.

Adipose tissue μ-crystallin is a thyroid hormone-binding protein associated with systemic insulin sensitivity

BACKGROUND

Circulating thyroid hormones have been described to be intrinsically associated with insulin sensitivity in healthy subjects. μ-Crystallin is a nicotinamide adenine dinucleotide phosphate-dependent thyroid hormone-binding protein that has been shown to bind T3 in the cytoplasm. We aimed to study μ-Crystallin expression in adipose tissue and in muscle in association with insulin action and thyroid function.

METHODS

μ-Crystallin gene expression was studied in 81 visceral and 75 sc adipose tissue samples and in 26 muscle samples from a cohort of subjects with a wide spectrum of adiposity (cohort 1). μ-Crystallin was also evaluated in 30 morbidly obese subjects in whom insulin action was evaluated using euglycemic clamp (cohort 2) and in 22 sc adipose tissue samples obtained before and after bariatric surgery-induced weight loss (cohort 3). μ-Crystallin was also evaluated during differentiation of human adipocytes. μ-Crystallin was overexpressed in human sc adipocytes using lentiviruses.

RESULTS

μ-Crystallin gene expression was 2.6- to 3-fold higher in sc vs visceral adipose tissue in direct association with the expression of thyroid hormone receptor α 1 in cohort 1 and cohort 2. Visceral, but not sc, adipose tissue μ-Crystallin was positively associated with the serum T3/T4 ratio in cohort 1 and with insulin sensitivity in cohort 2. In fact, μ-Crystallin gene expression was significantly decreased in visceral adipose tissue (-43%) and in muscle (-26%) in subjects with impaired fasting glucose and type 2 diabetes. Weight loss did not result in significant sc adipose tissue μ-Crystallin changes. μ-Crystallin overexpression led to increased insulin-induced (Ser473)Akt phosphorylation in sc adipocytes. During differentiation of adipocytes, μ-Crystallin gene expression decreased in both visceral (P = .006) and sc (P = .003) adipocytes from obese subjects.

CONCLUSION

Visceral, but not sc, adipose tissue μ-Crystallin is an adipose tissue factor linked to parameters of thyroid hormone action (T3/T4 ratio) and might mediate the interaction of thyroid function and insulin sensitivity.

Retinoids and nuclear retinoid receptors in white and brown adipose tissues: physiopathologic aspects

Vitamin A, ingested either as retinol or β-carotene from animal- or plant-derived foods respectively, is a nutrient essential for many biological functions such as embryonic development, vision, immune response, tissue remodeling, and metabolism. Its main active metabolite is all