Familial hypobetalipoproteinemia (FH ), a syndrome characterized by low plasma cholesterol levels, is caused by mutations in the apo-B gene that interfere with the synthesis of apo-B100. FH  mutations frequently lead to the synthesis of a truncated form of apo-B, which typically is present in plasma at Ͻ 5% of the levels of apo-B100. Although many FH  mutations have been characterized, the basic mechanisms causing the low plasma levels of truncated apo-B variants have not been defined. We used gene targeting to create a mutant allele that exclusively yields a truncated apo-B, apo-B83. In mice heterozygous for the Apob 83 allele, plasma levels and the size and density distribution of apo-B83-containing lipoproteins were strikingly similar to those observed in humans with FH  and an apo-B83 mutation. Analysis of mice carrying the Apob 83 mutation revealed two mechanisms for the low plasma levels of apo-B83. First, Apob 83 mRNA levels and apo-B83 secretion were reduced 76 and 72%, respectively. Second, apo-B83 was removed rapidly from the plasma, compared with apo-B100. This mouse model provides a new level of understanding of FH  and adds new insights into apo-B metabolism.
Introduction Gender-affirming mastectomy (GAM) is the most commonly performed gender-affirming surgery. Unfortunately, many areas of sexual health for transmasculine people are understudied. In particular, there are few studies that assess how chest and nipple stimulation, or lack of sensation, affect the sexual health and satisfaction of trans patients after GAM. Objective This study aims to 1) assess the importance of chest and nipple stimulation for trans patients before any chest surgery, 2) evaluate how GAM affects patients’ sexual health postoperatively, and 3) investigate how chest and nipple sensation change after GAM. Methods This is a prospective study performed at one institution. All participants are patients recruited at their GAM consultation or follow-up appointment. Pre-operative and post-operative surveys were developed based on previous validated Patient Reported Quality of Life Survey with multiple rounds of editing by two gender affirming surgeons. Surveys were distributed through Qualtrics (Qualtrics XM, Seattle, Washington). Results Since July 2021, 144 unique surveys (45 unique pre-operative and 99 unique post-operative) have been completed. The three most common gender identities are man (43%), non-binary (25%), and transgender man (9%). Eighty-four to 89% of pre-operative patients reported being able to sense normal pressure, light touch, and temperature on their chests. Sixty-two percent of preoperative patients were not concerned about potential loss of nipple sensation after surgery. Compared to their sensation before top surgery, 43 – 65% of post-operative patients reported they had decreased sensation of normal pressure, light touch, and temperature on their chests and nipples. Regarding sexual satisfaction levels, 76% of pre-operative patients reported that nipple stimulation is sometimes, rarely, or never involved in their sexual activities. Seventy-six percent of preoperative patients also stated that nipple and chest stimulation is slightly important or not at all important to their sexual activity. Compared to their sexual health pre-operatively, 59% of post-operative patients reported that the importance of their nipple and chest stimulation stayed the same, is little less, or much less important to their sexual life after the operation. After surgery, 40% of patients thought their sexual satisfaction was much or a little better. Less than 1% of patients reported that their sexual satisfaction was much worse. One hundred percent of post-operative patients were satisfied having undergone GAM and agreed that top surgery had changed their life for the better. Conclusions Sexual health of patients undergoing GAM has rarely been studied before. This study shows that nipple stimulation for the majority of top surgery patients is not heavily involved in their sexual activities and may actually decrease after surgery. Although most patients report decreased sensation postoperatively, patients’ overall sexual satisfaction does not change and for some may even improve after surgery. GAM can immensely improve quality of life while preserving or even improving patients’ sexual health. Disclosure No
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