Kristin Halvorsen Hortemo

• Brandtzæg, Karianne Haga; Lippe, Charlotte von der; Almdahl, Ina S.; Rossow, Anvor Søvde; Falk, Ragnhild S. & Gjersvik, Petter [Show all 8 contributors for this article] (2026). Quality of Life, Mental Health and Executive Function in Individuals with Basal Cell Naevus Syndrome. Acta Dermato-Venereologica. ISSN 0001-5555. 106. doi: 10.2340/actadv.v106.adv-2026-0335. Full text in Research Archive Show summary

  Basal cell naevus syndrome (BCNS) is a rare genetic disorder characteriszed by multiple basal cell carcinomas, as well as different extracutaneous tumours, cysts and abnormalities. Research on health-related quality of life (HRQoL) and mental health in BCNS is limited. This cross-sectional study included 62 individuals ≥18 years diagnosed with BCNS. Clinical and genetic data were collected, and five5 validated questionnaires were used to assess self-reported HRQoL, psychological distress, fatigue, pain and everyday executive functioning. Median regression analyses were conducted to identify factors associated with HRQoL. Independent samples t-tests and one proportion z-tests were conducted to compare the BCNS group with the general population. Individuals with BCNS reported lower HRQoL compared with the general population. Elevated anxiety symptoms were observed in 14 individuals (24%). The proportion of individuals reporting everyday executive deficits was higher in the BCNS group compared with the general population. Engagement in employment or higher education was associated with better physical and mental HRQoL, whereas symptoms of anxiety and everyday executive deficits were associated with reduced mental HRQoL. Findings highlight mental health challenges in BCNS. Routine screening for anxiety and executive functioning is suggested as essential steps in identifying those at risk and provideproviding timely psychological support.

• Brandtzæg, Karianne Haga; Lippe, Charlotte von der; Vestengen, Ingvild Kibsgaard; Holtan, Josephine Prener; Winge, Mona Irene & Rustad, Cecilie F. [Show all 11 contributors for this article] (2025). Clinical and genetic findings in 103 individuals in Norway with basal cell naevus syndrome. British Journal of Dermatology. ISSN 0007-0963. doi: 10.1093/bjd/ljaf413. Full text in Research Archive Show summary

  Background Basal cell naevus syndrome (BCNS) is a rare autosomal dominant condition characterized by early onset and multiple basal cell carcinomas (BCCs), skeletal and ocular abnormalities, and extracutaneous tumours and cysts. In most cases, BCNS is caused by a pathogenic variant in the tumour suppressor gene PTCH1. Pathogenic variants in SUFU account for a minority of cases. No clear genotype–phenotype associations between different PTCH1 variants have been established. Objectives To identify all individuals with BCNS in Norway, characterize their clinical and genetic profiles, and investigate possible genotype–phenotype associations. Methods In this cross-sectional study, we approached all individuals with BCNS registered at the Department of Dermatology at Oslo University Hospital and two national resource centres for rare medical conditions. Dermatologists, dentists and geneticists across Norway were contacted in order to identify additional individuals with BCNS. Data were collected from structured interviews, whole-body physical examinations, electronic medical records, radiographic imaging and molecular genetic analyses. Results We identified 109 individuals with BCNS, indicating a national prevalence of BCNS of at least 1.9 per 100 000, of whom 103 agreed to be included. Clinical findings confirmed the considerable phenotypic variation in BCNS, including BCC in 61 individuals (median number of BCCs 48, range 1–1025), odontogenic keratocysts in 72 (median number of odontogenic keratocysts 5, range 1–30) and a wide spectrum of ocular and skeletal abnormalities in 43 and 98 individuals, respectively. This study is the first to report the prevalence estimates of autism (4%) and epilepsy (7%), as well as intracranial lesions associated with epilepsy, in BCNS. Genetic analyses identified a pathogenic or probable pathogenic PTCH1 variant in 93 individuals, while 5 individuals had variants of uncertain clinical significance. Twenty-one of the pathogenic PTCH1 variants were novel. None of the individuals with PTCH1 variants in exon 1, all belonging to the same family, exhibited BCCs, odontogenic keratocysts or palmoplantar pitting. Conclusions This study expands the number of pathogenic PTCH1 variants, elucidates important clinical aspects in BCNS and reveals novel insight to genotype–phenotype associations, providing new implications for management and follow-up.

• Hortemo, Kristin Halvorsen; Lunde, Per Kristian; Anonsen, Jan Haug; Kvaløy, Heidi; Munkvik, Morten & Rehn, Tommy Aune [Show all 10 contributors for this article] (2016). Exercise training increases protein O-GlcNAcylation in rat skeletal muscle. Physiological Reports. 4(18), p. e12896–e12896. doi: 10.14814/phy2.12896. Full text in Research Archive Show summary

  Protein O‐GlcNAcylation has emerged as an important intracellular signaling system with both physiological and pathophysiological functions, but the role of protein O‐GlcNAcylation in skeletal muscle remains elusive. In this study, we tested the hypothesis that protein O‐GlcNAcylation is a dynamic signaling system in skeletal muscle in exercise and disease. Immunoblotting showed different protein O‐GlcNAcylation pattern in the prototypical slow twitch soleus muscle compared to fast twitch EDL from rats, with greater O‐GlcNAcylation level in soleus associated with higher expression of the modulating enzymes O‐GlcNAc transferase (OGT), O‐GlcNAcase (OGA), and glutamine fructose‐6‐phosphate amidotransferase isoforms 1 and 2 (GFAT1, GFAT2). Six weeks of exercise training by treadmill running, but not an acute exercise bout, increased protein O‐GlcNAcylation in rat soleus and EDL. There was a striking increase in O‐GlcNAcylation of cytoplasmic proteins ~50 kDa in size that judged from mass spectrometry analysis could represent O‐GlcNAcylation of one or more key metabolic enzymes. This suggests that cytoplasmic O‐GlcNAc signaling is part of the training response. In contrast to exercise training, postinfarction heart failure (HF) in rats and humans did not affect skeletal muscle O‐GlcNAcylation level, indicating that aberrant O‐GlcNAcylation cannot explain the skeletal muscle dysfunction in HF. Human skeletal muscle displayed extensive protein O‐GlcNAcylation that by large mirrored the fiber‐type‐related O‐GlcNAcylation pattern in rats, suggesting O‐GlcNAcylation as an important signaling system also in human skeletal muscle.

• Hortemo, Kristin Halvorsen; Aronsen, Jan Magnus; Lunde, Ida Gjervold; Sjaastad, Ivar; Lunde, Per Kristian & Sejersted, Ole M (2015). Exhausting treadmill running causes dephosphorylation of sMLC2 and reduced level of myofilament MLCK2 in slow twitch rat soleus muscle. Physiological Reports. 3(2). doi: 10.14814/phy2.12285. Full text in Research Archive Show summary

  Myosin light chain 2 (MLC2) is a small protein in the myosin complex, regulating muscle contractile function by modulating Ca2+ sensitivity of myofilaments. MLC2 can be modified by phosphorylation and O-GlcNAcylation, two reversible and dynamic posttranslational modifications. The slow isoform of MLC2 (sMLC2) is dephosphorylated in soleus muscle during in situ loaded shortening contractions, which correlates with reduction in shortening capacity. Here, we hypothesize that exhausting in vivo treadmill running induces dephosphorylation of MLC2 in slow twitch soleus, but not in fast twitch EDL muscle, and that there are reciprocal changes in MLC2 O-GlcNAcylation. At rest, both phosphorylation and O-GlcNAcylation of MLC2 were lower in slow than fast twitch muscles. One bout of exhausting treadmill running induced dephosphorylation of sMLC2 in soleus, paralleled by reduced levels of the kinase MLCK2 associated to myofilaments, suggesting that the acute reduction in phosphorylation is mediated by dissociation of MLCK2 from myofilaments. O-GlcNAcylation of MLC2 did not change significantly, and seems of limited importance in the regulation of MLC2 phosphorylation during in vivo running. After 6 weeks of treadmill running, the dephosphorylation of sMLC2 persisted in soleus along with reduction in MLCK2 both in myofilament- and total protein fraction. In EDL on the contrary, phosphorylation of MLC2 was not altered after one exercise bout or after 6 weeks of treadmill running. Thus, in contrast to fast twitch muscle, MLC2 dephosphorylation occurs in slow twitch muscle during in vivo exercise and may be linked to reduced myofilament-associated MLCK2 and reduced shortening capacity.

• Hortemo, Kristin Halvorsen; Munkvik, Morten; Lunde, Per Kristian & Sejersted, Ole M (2013). Multiple Causes of Fatigue during Shortening Contractions in Rat Slow Twitch Skeletal Muscle. PLOS ONE. 8(8). doi: 10.1371/journal.pone.0071700. Full text in Research Archive Show summary

  Fatigue in muscles that shorten might have other causes than fatigue during isometric contractions, since both cross-bridge cycling and energy demand are different in the two exercise modes. While isometric contractions are extensively studied, the causes of fatigue in shortening contractions are poorly mapped. Here, we investigate fatigue mechanisms during shortening contractions in slow twitch skeletal muscle in near physiological conditions. Fatigue was induced in rat soleus muscles with maintained blood supply by in situ shortening contractions at 37°C. Muscles were stimulated repeatedly (1 s on/off at 30 Hz) for 15 min against a constant load, allowing the muscle to shorten and perform work. Fatigue and subsequent recovery was examined at 20 s, 100 s and 15 min exercise. The effects of prior exercise were investigated in a second exercise bout. Fatigue developed in three distinct phases. During the first 20 s the regulatory protein Myosin Light Chain-2 (slow isoform, MLC-2s) was rapidly dephosphorylated in parallel with reduced rate of force development and reduced shortening. In the second phase there was degradation of high-energy phosphates and accumulation of lactate, and these changes were related to slowing of muscle relengthening and relaxation, culminating at 100 s exercise. Slowing of relaxation was also associated with increased leak of calcium from the SR. During the third phase of exercise there was restoration of high-energy phosphates and elimination of lactate, and the slowing of relaxation disappeared, whereas dephosphorylation of MLC-2s and reduced shortening prevailed. Prior exercise improved relaxation parameters in a subsequent exercise bout, and we propose that this effect is a result of less accumulation of lactate due to more rapid onset of oxidative metabolism. The correlation between dephosphorylation of MLC-2s and reduced shortening was confirmed in various experimental settings, and we suggest MLC-2s as an important regulator of muscle shortening. Copyright 2013 Hortemo et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License.

• Dutka, Travis L; Verburg, Esther; Larkins, Noni; Hortemo, Kristin Halvorsen; Lunde, Per Kristian & Sejersted, Ole M [Show all 7 contributors for this article] (2012). ROS-Mediated Decline in Maximum Ca2+-Activated Force in Rat Skeletal Muscle Fibers following In Vitro and In Vivo Stimulation. PLOS ONE. 7(5), p. e35226–e35226. doi: 10.1371/journal.pone.0035226. Full text in Research Archive
• Wanichawan, Pimthanya; Louch, William Edward; Hortemo, Kristin Halvorsen; Austbø, Bjørg; Lunde, Per Kristian & Scott, John D. [Show all 8 contributors for this article] (2011). Full-length cardiac Na+/Ca2+ exchanger 1 protein is not phosphorylated by protein kinase A. American Journal of Physiology - Cell Physiology. 300(5), p. C989–C997. doi: 10.1152/ajpcell.00196.2010. Full text in Research Archive

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• Dhondup, Yangchen; Hortemo, Kristin Halvorsen; Krogh, Carl Fredrik Von & Rizvi, Syed Mohammad Husain (2022). En mann i 40-årene med utslett og hallusinasjoner. Tidsskrift for Den norske legeforening (Tidsskriftet). ISSN 0029-2001. 142(9). doi: 10.4045/tidsskr.21.0634. Full text in Research Archive
• Hortemo, Kristin Halvorsen; Aronsen, Jan Magnus; Sjaastad, Ivar; Lunde, Per Kristian & Sejersted, Ole M (2014). Phospho-GlcNAc modulation of MLC2 is different in slow- and fast twitch muscle during treadmill running. Full text in Research Archive
• Hortemo, Kristin Halvorsen; Sejersted, Ole M & Lunde, Per Kristian (2011). Dynamic skeletal muscle exercise and fatigue development in post infarction heart failure rats and effect of warm-up. Full text in Research Archive
• Hortemo, Kristin Halvorsen; Sejersted, Ole M & Lunde, Per Kristian (2011). Dynamic skeletal muscle exercise and fatigue development in post infarction heart failure rats and effect of warm-up. Biophysical Journal. ISSN 0006-3495. 100(3), p. 287a–287a. Full text in Research Archive
• Hortemo, Kristin Halvorsen; Sejersted, Ole M & Lunde, Per Kristian (2011). Dynamic skeletal muscle exercise and fatigue development in post infarction heart failure rats and effect of warm-up. Biophysical Journal. ISSN 0006-3495. 100, p. 287a–287a. Full text in Research Archive
• Hortemo, Kristin Halvorsen; Munkvik, Morten; Lunde, Per Kristian & Sejersted, Ole M (2009). Recovery of contractile properties and MLC2 phosphorylation in rat soleus muscles druing fatigue from shortening contractions in healthy and heart failure rats. Full text in Research Archive
• Hortemo, Kristin Halvorsen; Munkvik, Morten; Lunde, Per Kristian & Sejersted, Ole M (2009). Improved exercise performance following recovery from fatigue and in heart failure rats. Full text in Research Archive
• Hortemo, Kristin Halvorsen; Munkvik, Morten; Lunde, Per Kristian & Sejersted, Ole M (2009). Recovery of contractile properties and MLC2 phosphorylation in rat soleus muscles druing fatigue from shortening contractions in healthy and heart failure rats. Full text in Research Archive
• Hortemo, Kristin Halvorsen; Munkvik, Morten; Lunde, Per Kristian & Sejersted, Ole M (2008). MLC2 phosphorylation in slow twitch skeletal muscle during different types of exercise. Full text in Research Archive
• Verburg, Esther; Sjåland, Cecilie; Hortemo, Kristin Halvorsen; Munkvik, Morten; Aronsen, Jon magnus & Sejersted, Ole M [Show all 7 contributors for this article] (2008). Increased skeletal muscle fatigability in heart failure is counteracted by an increase sensitivity of the contractile proteins. Acta Physiologica Sinica. ISSN 0371-0874. 60, p. 191–191. Full text in Research Archive
• Hortemo, Kristin Halvorsen (2016). Fatigue mechanisms of shortening skeletal muscle: Protein phosphorylation and O-GlcNAcylation with emphasis on regulatory myosin light chain (MLC2). Universitetet i Oslo. Full text in Research Archive

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