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. 2022 Jun 28;14(7):1368.
doi: 10.3390/pharmaceutics14071368.

l-Arginine Induces White Adipose Tissue Browning-A New Pharmaceutical Alternative to Cold

Andjelika Kalezic  1 , Aleksandra Korac  2 , Bato Korac  1 , Aleksandra Jankovic  1
Affiliations

l-Arginine Induces White Adipose Tissue Browning-A New Pharmaceutical Alternative to Cold

Andjelika Kalezic et al. Pharmaceutics. .

Abstract

The beneficial effects of l-arginine supplementation in obesity and type II diabetes involve white adipose tissue (WAT) reduction and increased substrate oxidation. We aimed to test the potential of l-arginine to induce WAT browning. Therefore, the molecular basis of browning was investigated in retroperitoneal WAT (rpWAT) of rats exposed to cold or treated with 2.25% l-arginine for 1, 3, and 7 days. Compared to untreated control, levels of inducible nitric oxide (NO) synthase protein expression and NO signaling increased in both cold-exposed and l-arginine-treated groups. These increases coincided with the appearance of multilocular adipocytes and increased expression levels of uncoupling protein 1 (UCP1), thermogenic and beige adipocyte-specific genes (Cidea, Cd137, and Tmem26), mitochondriogenesis markers (peroxisome proliferator-activated receptor (PPAR)-γ coactivator-1α, mitochondrial DNA copy number), nuclear respiratory factor 1, PPARα and their respective downstream lipid oxidation enzymes after l-arginine treatment. Such browning phenotype in the l-arginine-treated group was concordant with end-course decreases in leptinaemia, rpWAT mass, and body weight. In conclusion, l-arginine mimics cold-mediated increases in NO signaling in rpWAT and induces molecular and structural fingerprints of rpWAT browning. The results endorse l-arginine as a pharmaceutical alternative to cold exposure, which could be of great interest in obesity and associated metabolic diseases.

Keywords: browning; l-arginine; nitric oxide; obesity.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Induction of l-arginine/NO pathway in rpWAT of cold-exposed rats and the effects of 2.25% l-arginine supplementation. Protein expression analysis of endothelial NO synthase (eNOS), inducible NO synthase (iNOS), arginases I and II, nuclear factor-erythroid factor 2-related factor 2 (Nrf2), and 3-nitrotyrosine (3-NT)-modified proteins (represented by two-immunoreactive bands, at 35 and 55 KDa) during 1, 3, and 7 days of cold exposure and l-arginine treatment (a) and their corresponding blots (b). Each band is representative of six pooled samples per group. Protein content is expressed relative to control acclimated to room temperature (100%). Experiments were repeated in triplicate. Data were quantified as described in the Methods. (c) Detection of nitric oxide (NO) levels in the mature adipocytes stimulated by l-arginine (300 µM) for 30 min, at 37 °C, previously isolated from rpWAT of untreated (control), cold-exposed, and l-arginine (2.25%)-treated rats for 7 days (n = 9, 3 per group, in three technical replicates per group). Data represent the mean ± SEM. * Compared to control, * p < 0.05, ** p < 0.01 and *** p < 0.001.
Figure 2
Figure 2
l-arginine reduces body weight gain and retroperitoneal white adipose tissue (rpWAT) mass. Body weight gain, adiposity index, and relative rpWAT mass of untreated (control) and l-arginine-treated rats; 2.5-month-old rats were randomly assigned to receive drinking water or 2.25% l-arginine∙HCl in drinking water for 7 days. * Comparison with control; (n = 6–8 per group); * p < 0.05; ** p < 0.01.
Figure 3
Figure 3
l-arginine increases fatty acid turnover in retroperitoneal white adipose tissue (rpWAT). Protein content of hormone sensitive lipase (HSL), adipose triglyceride lipase (ATGL), and monoacylglycerol O-acyltransferase 1 (MGAT1) in rpWAT of rats receiving either drinking water or 2.25% l-arginine∙HCl in drinking water for 1, 3, and 7 days, determined by Western blot. The signals from representative Western blots are shown (a). Data obtained after quantification of specific bands and expressed as % of the control group taken as 100% represent the mean ± SEM (b). Each band is representative of six pooled samples per group. Experiments were repeated in triplicate. Data were quantified as described in the Methods. * Comparison between control and l-arginine-treated group; * p < 0.05, ** p < 0.01, *** p < 0.001.
Figure 4
Figure 4
Peroxisome proliferator-activated receptor-gamma coactivator—1α (PGC-1α) gene expression and mitochondrial DNA copy number (MCN) level increase in retroperitoneal white adipose tissue (rpWAT) upon 1 and 7 days of 2.25% l-arginine∙HCl treatment. * Comparison with control (n = 6 per group); ** p < 0.01, *** p < 0.001.
Figure 5
Figure 5
Protein content of nuclear respiratory factor 1 (NRF1), peroxisome proliferator-activated receptor-α (PPARα), carnitine palmitoyltransferase 1 (CPT1), and acyl-CoA dehydrogenase medium chain (ACADM) in retroperitoneal white adipose tissue (rpWAT) of rats receiving either drinking water or 2.25% l-arginine∙HCl in drinking water for 1, 3, and 7 days. Data obtained after quantification of specific bands and expressed as % of the control group taken as 100% represent the mean ± SEM (a). Each band is representative of six pooled samples per group (b). Experiments were repeated in triplicate. Data were quantified as described in the Methods. * Comparison between control and l-arginine-treated group; * p < 0.05, ** p < 0.01, *** p < 0.001.
Figure 6
Figure 6
UCP1 protein expression level and tissue expression pattern in control, cold-exposed, and l-arginine-treated rats. Analysis of UCP1 protein expression after 1, 3, and 7 days of l-arginine treatment (a). Maximum induction of UCP1 was observed on day 3 of l-arginine treatment. Protein content is expressed relative to control rats (100%). Data represent the mean ± SEM. * Compared to control, * p < 0.05, *** p < 0.001. Experiments were repeated in triplicate. Data were quantified as described in the Methods. Analysis on the morphological level (H&E) indicates the simultaneous appearance of sporadic islets of multilocular cells selectively in retroperitoneal white adipose tissue (rpWAT) of l-arginine-treated rats (b). Inset, enlarged area of multilocular cells. Scale bars, 200 μm. Immunohistochemical staining for UCP1 (b, lower panel) showed that, compared with very weak UCP1-immunopositive adipocytes in the control, stronger UCP1-immunopositivity characterized adipocytes in rpWAT of rats exposed to cold and treated with l-arginine for 3 days. Moreover, highly positive UCP1-positive multilocular adipocytes appear only in the l-arginine-treated group of rats. Scale bars, 50 μm.
Figure 7
Figure 7
The l-arginine treatment induces gene expression of thermogenic beige adipocyte markers cell death-inducing DFFA like effector A (Cidea), Tmem26, and Cd137 and protein levels of proliferation marker proliferating cell nuclear antigen (PCNA) in rat retroperitoneal white adipose tissue (rpWAT). Adipose tissue gene expression (mean ± SEM of normalized ratios with 18S) of Cidea, Tmem26, and Cd137 in rats treated with 2.25% l-arginine∙HCl for 1 and 7 days is upregulated by l-arginine, as compared to the control group (a). Also, PCNA protein levels after 1, 3, and 7 days of l-arginine treatment were analyzed in rpWAT by Western blot, as presented in the Material and Methods section. The protein content is expressed relative to control rats (100%) (b), and the respective bands are presented (c). Data represent the mean ± SEM. * Compared to control, ** p < 0.01, *** p < 0.001. Experiments were repeated in triplicate.
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References

    1. Sakers A., De Siqueira M.K., Seale P., Villanueva C.J. Adipose-tissue plasticity in health and disease. Cell. 2022;185:419–446. doi: 10.1016/j.cell.2021.12.016. - DOI - PubMed
    1. Jankovic A., Golic I., Markelic M., Stancic A., Otasevic V., Buzadzic B., Korac A., Korac B. Two key temporally distinguishable molecular and cellular components of white adipose tissue browning during cold acclimation. J. Physiol. 2015;593:3267–3280. doi: 10.1113/JP270805. - DOI - PMC - PubMed
    1. Nedergaard J., Golozoubova V., Matthias A., Asadi A., Jacobsson A., Cannon B. UCP1: The only protein able to mediate adaptive non-shivering thermogenesis and metabolic inefficiency. Biochim. Biophys. Acta Bioenerg. 2001;1504:82–106. doi: 10.1016/S0005-2728(00)00247-4. - DOI - PubMed
    1. Ricquier D. Uncoupling protein 1 of brown adipocytes, the only uncoupler: A historical perspective. Front. Endocrinol. 2011;2:85. doi: 10.3389/fendo.2011.00085. - DOI - PMC - PubMed
    1. Flachs P., Rossmeisl M., Kuda O., Kopecky J. Stimulation of mitochondrial oxidative capacity in white fat independent of UCP1: A key to lean phenotype. Biochim. Biophys. Acta Mol. Cell Biol. Lipids. 2013;1831:986–1003. doi: 10.1016/j.bbalip.2013.02.003. - DOI - PubMed

Grants and funding

This research was financially supported by the Science Fund of the Republic of Serbia, PROMIS, #6066747, WARMED and the Ministry of Education, Science and Technological Development of the Republic of Serbia, grant number 451-03-68/2022-14/200007.
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