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. 2011 Dec 20;8:91.
doi: 10.1186/1743-7075-8-91.

Effects of Dairy Consumption on SIRT1 and Mitochondrial Biogenesis in Adipocytes and Muscle Cells

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Free PMC article

Effects of Dairy Consumption on SIRT1 and Mitochondrial Biogenesis in Adipocytes and Muscle Cells

Antje Bruckbauer et al. Nutr Metab (Lond). .
Free PMC article

Abstract

Background: Recent data from this laboratory suggest that components of dairy foods may serve as activators of SIRT1 (Silent Information Regulator Transcript 1), and thereby participate in regulation of glucose and lipid metabolism. In this study, an ex-vivo/in-vitro approach was used to examine the integrated effects of dairy diets on SIRT1 activation in two key target tissues (adipose and muscle tissue).

Methods: Serum from overweight and obese subjects fed low or high dairy diets for 28 days was added to culture medium (similar to conditioned media) to treat cultured adipocytes and muscle cells for 48 hours.

Results: Treatment with high dairy group conditioned media resulted in 40% increased SIRT1 gene expression in both tissues (p < 0.01) and 13% increased enzyme activity in adipose tissue compared to baseline. This was associated with increased gene expression of peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α), nuclear respiratory factor 1 (NRF1), cytochrome oxidase c subunit 7 (Cox 7), NADH dehydrogenase and uncoupling protein 2 (UCP2) in adipocytes as well as uncoupling protein 3 (UCP3), NRF1 and Cox 7 in muscle cells (p < 0.05). Further, direct incubation of physiological concentrations of leucine and its metabolites α-Ketoisocaproic acid (KIC) and β-hydroxy-methylbuteric acid (HMB) with recombinant human SIRT1 enzyme resulted in 30 to 50% increase of SIRT1 activity (p < 0.05).

Conclusions: These data indicate that dairy consumption leads to systemic effects, which may promote mitochondrial biogenesis in key target tissues such as muscle and adipose tissue both by direct activation of SIRT1 as well as by SIRT1-independent pathways.

Figures

Figure 1
Figure 1
The ex-vivo/in-vitro Approach. 20 overweight or obese subjects were fed a low (soy) or high dairy diet for 28 days in a cross-over design. Blood from each intervention period was drawn at start (day 0), at day 7 and at the end (day 28) to provide serum to utilize in cell studies. The serum reflected the integrated systemic response to the diets and was then added to culture medium (as serum conditioned medium) to treat cultured human adipocytes and muscle cells, separately and in co-culture, for 48 hours in order to assess the integrated effects of dairy feeding on SIRT1 activation in two key target tissues.
Figure 2
Figure 2
The effects of serum treatment on SIRT1 activity (a) and SIRT1 gene expression (b) in human adipocytes. Cultured human adipocytes were incubated for 48 hours with human serum collected on day 0 (baseline), 7 or 28 after high dairy diet or soy-based control diet. Values are expressed as means of % change to baseline ± SE (n = 5 subjects/group). Differing letters above the bars denote significant differences between groups, p ≤ 0.05.
Figure 3
Figure 3
Effects of serum treatment on mitochondrial biogenesis in human adipocytes. Cultured human adipocytes were incubated for 48 hours with human serum collected on day 0 (baseline), 7 or 28 after high dairy diet or soy-based control diet. (a) Uncoupling protein 2 (UCP2) and (b) PGC-1α were significantly increased by dairy at day 7 compared to baseline and soy-based diet. Values are expressed as means of % change to baseline ± SE (n = 4 to 5 subjects/group). Gene expression data are normalized to 18S. Differing letters above the bars denote significant differences between groups, p ≤ 0.05.
Figure 4
Figure 4
Effects of serum treatment on mitochondrial component genes in human adipocytes. Cultured human adipocytes were incubated for 48 hours with human serum collected on day 0 (baseline), 7 or 28 after high dairy diet or soy-based control diet. (a) Cytochrome c oxidase subunit 7 (Cox 7c), (b) nuclear respiratory factor 1 (NRF1), and mitochondrial NADH dehydrogenase ((c) mitochondrial encoded subunit (MT-ND1) and (d) nuclear encoded subunit (NDUFA)) were significantly up-regulated after dairy feeding compared to baseline and soy diet. Values are expressed as means of % change to baseline ± SE (n = 4 to 5 subjects/group). Gene expression data are normalized to 18S. Differing letters above the bars denote significant differences between groups, p ≤ 0.05.
Figure 5
Figure 5
The effects of serum treatment on SIRT1 activity (a) and SIRT1 gene expression (b) in mouse skeletal muscle. Cultured C2C12 muscle cells were grown in co-culture with 3T3-L1 adipocytes and incubated for 48 hours with human serum collected on day 0 (baseline), 7 or 28 after high dairy diet or soy-based control diet. Values are expressed as means of % change to baseline ± SE (n = 6 subjects/group). Differing letters above the bars denote significant differences between groups, p ≤ 0.05.
Figure 6
Figure 6
Effects of serum treatment on mitochondrial biogenesis in mouse skeletal muscle cells. C2C12 muscle cells were grown in co-culture with 3T3-L1 adipocytes and incubated for 48 hours with human serum collected on day 0 (baseline), 7 or 28 after high dairy diet or soy-based control diet. (a) Cytochrome c oxidase subunit 7 (COX 7), (b) nuclear respiratory factor 1 (NRF1) and (c) UCP 3 were significantly up-regulated 28 days after dairy feeding compared to baseline and soy-based control. Values are expressed as means of % change to baseline ± SE (n = 6 subjects/group). Gene expression data are normalized to 18S. Differing letters above the bars denote significant differences between groups, p ≤ 0.05.
Figure 7
Figure 7
Direct effects of Leucine, β-Hydroxy-β-Methylbutyrate (HMB) and Ketoisocaproate (KIC) on SIRT1 activity. Recombinant human SIRT1 enzyme was incubated with Leucine, HMB and KIC for 45 min and fluorescence of deacetylated substrate was measured. Resveratrol and Suramin were used as positive and negative control, respectively. Valine was used as BCAA control. Data are expressed as means of % change of SIRT1 activity ± SE (n = 4, p ≤ 0.05).

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