Impact of body mass index on the severity of bexarotene-associated hypertriglyceridemia: A post hoc analysis of an open-labeled clinical study of combined bexarotene and phototherapy in Japanese patients with cutaneous T-cell lymphoma.

Bexarotene is an effective oral drug for the treatment of cutaneous T-cell lymphoma, but careful management is required due to its various side effects. In particular, hypertriglyceridemia often requires a reduction or even suspension of bexarotene therapy. The risk factors of bexarotene-associated severe hypertriglyceridemia are not clear. Here, we conducted a post hoc analysis of the data from our previous clinical trial, which confirmed the efficacy and safety of combined bexarotene and phototherapy, to evaluate the effect of body mass index on bexarotene-associated hypertriglyceridemia. Twenty-five subjects were divided into two subgroups: normal and underweight (body mass index [BMI] <25 kg/m2 group) and overweight and obese (BMI ≥25 kg/m2 group) patients. The overall incidence of hypertriglyceridemia was 81.3% (13/16) in the BMI <25 kg/m2 group and 88.9% (8/9) in the BMI ≥25 kg/m2 group. The incidence of grade ≥3 hypertriglyceridemia (≥500 mg/dL) was 7.7% (1/13) in the BMI <25 kg/m2 group and 7/8 (87.5%) in the BMI ≥25 kg/m2 group (P < 0.001). Consequently, dose reduction in the BMI ≥25 kg/m2 group was larger than that in the BMI <25 kg/m2 group. The bexarotene-induced change in the serum triglyceride concentration was significantly increased in cutaneous T-cell lymphoma patients with a higher body mass index (ρ = 0.508, P = 0.009). The area under the curve was 0.886 (95% confidence interval 0.748-1.000, P = 0.002). With a body mass index cut-off of 24.85 kg/m2 , the sensitivity and specificity for identifying grade ≥3 hypertriglyceridemia were 0.875 and 0.882, respectively. The present findings suggest that BMI ≥25 kg/m2 is a risk factor for bexarotene-associated severe hypertriglyceridemia, therefore overweight and obese patients treated with bexarotene should receive lipid-lowering drugs prophylactically. Further studies for optimizing the initial bexarotene dose in such patients are required.

Glutamine deficiency induces lipolysis in adipocytes.

Glutamine is the most abundant amino acid in the body, and adipose tissue is one of the glutamine-producing organs. Glutamine has important and unique metabolic functions; however, its effects in adipocytes are still unclear. 3T3-L1 adipocytes produced and secreted glutamine dependent on glutamine synthetase, but preadipocytes did not. The inhibition of glutamine synthetase by l-methionine sulfoximine (MSO) impaired the differentiation of preadipocytes to mature adipocytes, and this inhibitory effect of MSO was rescued by exogenous glutamine supplementation. Glutamine concentrations were low, and Atgl gene expression was high in epididymal white adipose tissues of fasting mice in vivo. In 3T3-L1 adipocytes, glutamine deprivation induced Atgl expression and increased glycerol concentration in culture medium. Atgl expression is regulated by FoxO1, and glutamine deprivation reduced FoxO1 phosphorylation (Ser256), indicating the activation of FoxO1. These results demonstrate that glutamine is necessary for the differentiation of preadipocytes and regulates lipolysis through FoxO1 in mature adipocytes.