Influence of Aging and Calorie Restriction on Protein Metabolism and microRNA Expression.
Margolis, Lee.
2017
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Abstract: Modulation in
the expression of microRNA (miRNA), which are small non-coding RNA that regulate gene
expression, has been identified as a potential mechanism controlling age-associated
declines in skeletal muscle mass. Recently, miRNA have also been identified to be stable
analytes present in circulation (c-miRNA), with alterations in c-miRNA expression
profiles suggested to reflect ... read morethe underlying physiological state of skeletal muscle. The
potential for c-miRNA to provide insight into physiological adaptations within skeletal
muscle makes them a promising noninvasive marker to assess mechanisms regulating muscle
mass. Three investigations were conducted to assess the influence of aging and dietary
manipulation on expression of miRNA in circulation and skeletal muscle to determine the
functional implications to alterations in miRNA expression profiles. The first
investigation sought to determine the influence of aging on c-miRNA expression at rest
and following acute resistance exercise in 18 younger (22 ± 1 yrs, n = 9) and older
(74 ± 2 yrs, n = 9) male volunteers. Primary findings revealed that fasting c-miRNA
expression profiles were significantly (P < 0.05) predictive of aging, with
miR-19b-3p, miR-206 and miR-486 distinguishing between age groups. Following resistance
exercise, principal component analysis revealed a divergent response in expression of 10
c-miRNA. Using Ingenuity Pathway Analysis to test c-miRNA-to-mRNA interactions in
skeletal muscle, it was found that the response of c-miRNA to exercise was indicative of
an anabolic response in younger but not older participants. These findings were
corroborated with a positive association (P < 0.05) observed with the phosphorylation
status of p-AktSer473 and p-70S6K1Thr389 and expression of miR-19a-3p, miR-19b-3p,
miR-20a-5p, miR-26b-5p, miR-143-3p, and miR-195-5p. These data provide evidence that
alterations of c-miRNA expression with aging may be reflective of underlying molecular
mechanisms resulting in age-associated declines in skeletal muscle mass. The second
investigation examined the relationship of circulating muscle specific microRNA
(c-myomiR; miR-1-3p, miR-133a-3p, miR-133b, miR-206) to whole-body protein synthesis
following 28 days of calorie restriction (CR) in 16 older (64 ± 2 yrs) overweight
(28.5 ± 1.2 kg·m-2) males. Following CR, overall expression of c-myomiR
increased (P < 0.05) compared to weight maintenance values, with c-myomiR inversely
associated (r = -0.70, P < 0.05) with whole-body protein synthesis. Confirming these
results, in vitro CR of C2C12 myotubes reduced protein synthesis 2.1 ± 0.2 fold,
while myomiR expression in medium increased 2.9 ± 0.1 fold compared to controls.
Results from in vivo and in vitro analysis suggest that increased expression of c-myomiR
reflects lower rates of protein synthesis following CR. The final investigation assessed
the influence of prolonged (16-wks) 40% CR consuming adequate (10%) or high (32%)
protein milk-based diets on skeletal muscle mTORC1 signaling and expression of
associated miRNA in 12-wk old male Sprague Dawley rats. Independent of dietary protein
intake, CR resulted in lower (P < 0.05) muscle protein content, as well as
phosphorylation and total Akt, mTOR, rpS6 and p70S6K compared to AL. Despite
downregulations in mTORC1 signaling following CR, associated miRNA expression was not
altered by either energy or protein intake. Overall, results from these studies suggest
that aging results in modulations in c-miRNA profiles that may be further exacerbated by
CR, as c-myomiR were upregulated following short-term CR and inversely associated with
protein synthesis.
Thesis (Ph.D.)--Tufts University, 2017.
Submitted to the Dept. of Biochemical and Molecular Nutrition.
Advisor: Roger Fielding.
Committee: Donato Rivas, James McClung, and Stefan Pasiakos.
Keywords: Molecular biology, and Nutrition.read less - ID:
- 4x51hw360
- Component ID:
- tufts:20432
- To Cite:
- DCA Citation Guide EndNote
