Evaluation of Candidate ''Kill or Cure'' Strategies to Treat MFN2-related Lipodystrophy

The R707W mutation in mitofusin 2, encoded by MFN2, causes a form of Multiple Symmetrical Lipomatosis (MFN2-MSL). This resembles sporadic, alcohol-associated MSL, combining loss of lower body adipose tissue with upper body adipose hyperplasia. Morbidity and sometimes mortality arise both from mechanical complications of head and neck adipose overgrowth, and metabolic complications. We reasoned that interventions that either mitigate the underlying cellular pathology, or that exacerbate it to induce selective death of hyperplastic adipose tissue may be beneficial. We thus assessed the effect of a metabolic or pharmacologic stressors or rapamycin in Mfn2R707W/R707W mice and or derived preadipocytes. 50mmol ethanol had little effect on WT or Mfn2R707W/R707W white preadipocytes, but increased mitochondrial content and blunted mitolysosome formation in Mfn2R707W/R707Wbrown preadipocytes. Daily consumption of 20% EtOH increased brown adipose tissue mass in female Mfn2R707W/R707W mice, and serum lactate in males. 200nM rapamycin - a candidate treatment - increased size and mitolysosome content of WT and Mfn2R707W/R707W white and brown preadipocytes, but these effects were blunted in Mfn2R707W/R707W cells. In male but not female Mfn2R707W/R707W mice, rapamycin reduced or reversed weight gain, reduced brown adipose mass, and increased serum Fgf21. Finally, a panel of other metabolic and pharmacological mitochondrial stressors solicited no selective death or ISR in Mfn2R707W/R707W preadipocytes. We conclude that ethanol mildly exacerbates MFN-MSL in mice, while rapamycin is tolerated. Lack of sensitisation to mitochondrial stressors implies that the MSL-inducing effect of MFN2 R707W may not be exerted through compromised oxidative phosphorylation.